2 Mechanisms of Vascular Disease

Mechanisms of Vascular Disease: A Reference Book for Vascular Specialists

Robert Fitridge The University of Adelaide, The Queen Elizabeth Hospital, Woodville, Australia Matthew Thompson St George’s Hospital Medical School, London, UK

Published in Adelaide by

The University of Adelaide, Barr Smith Press Barr Smith Library The University of Adelaide South Australia 5005 [email protected] www.adelaide.edu.au/press

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© The Contributors 2011

This book is copyright. Apart from any fair dealing for the purposes of private study, research, criticism or review as permitted under the Copyright Act, no part may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior written permission. Address all inquiries to the Director at the above address.

This CIP cataloguing for this work is as follows;

Mechanisms of vascular disease : a reference book for vascular surgeons / Robert Fitridge, Matthew Thompson, [editors].

1. Blood vessels, Diseases. 2. Blood vessels‚ Surgery.

I. Fitridge, Robert II. Thompson, M. M.

For the full Cataloguing-in-Publication data please contact National Library of Australia: [email protected]

ISBN (paperback) 978-0-9871718-2-5

Book design: Midland Typesetters Cover design: Emma Spoehr, based on a diagram by Dave Heinrich of the Medical Illustration and Media Unit, Flinders Medical Centre Paperback edition printed by Griffin Press, South Australia Table of Contents

Contributors vii target 201 Detailed Contents xi Sandeep Prabhu, Rahul Sharma, Karlheinz Peter (Melbourne, Australia) 1. Endothelium 1 12. Pathogenesis of aortic aneurysms 227 Paul Kerr, Raymond Tam, Jonathan Golledge, Guo-Ping Shi, Frances Plane (Calgary, Canada) Paul Norman (Townsville & Perth, 2. Vascular smooth muscle structure and Australia; Boston, USA) function 13 13. Pharmacological treatment of David Wilson (Adelaide, Australia) aneurysms 247 3. Atherosclerosis 25 Matthew Thompson, Janet Powell Gillian Cockerill, Qingbo Xu (London, UK) (London, UK) 14. Aortic dissection and connective tissue 4. Mechanisms of plaque rupture 43 disorders 255 Ian Loftus (London, UK) Mark Hamilton (Adelaide, Australia) 5. Current and emerging therapies in 15. Biomarkers in vascular disease 277 atheroprotection 79 Ian Nordon, Robert Hinchliffe Stephen Nicholls, Rishi Puri (London, UK) (Cleveland, USA) 16. Pathophysiology and principles 6. Molecular approaches to of management of vasculitis and revascularisation in peripheral vascular Raynaud’s phenomenon 295 disease 103 Martin Veller (Johannesburg, Greg McMahon, Mark McCarthy South Africa) (Leicester, UK) 17. SIRS, sepsis and multiorgan 7. Biology of restenosis and targets for failure 315 intervention 115 Vishwanath Biradar, John Moran Richard Kenagy (Seattle, USA) (Adelaide, Australia) 8. Vascular arterial haemodynamics 153 18. Pathophysiology of reperfusion Michael Lawrence-Brown, Kurt injury 331 Liffman, James Semmens, Ilija Prue Cowled, Robert Fitridge Sutalo (Melbourne & Perth, Australia) (Adelaide, Australia) 9. Physiological haemostasis 177 19. Compartment syndrome 351 Simon McRae (Adelaide, Australia) Edward Choke, Robert Sayers, 10. Hypercoagulable states 189 Matthew Bown (Leicester, UK) Simon McRae (Adelaide, Australia) 20. Pathophysiology of pain 375 11. Platelets in the pathogenesis of vascular Stephan Schug, Helen Daly, disease and their role as a therapeutic Kathryn Stannard (Perth, Australia) v vi Mechanisms of Vascular Disease

21. Postamputation pain 389 26. Pathophysiology and principles of Stephan Schug, Gail Gillespie management of the diabetic foot 475 (Perth, Australia) David Armstrong, Timothy Fisher, 22. Treatment of neuropathic pain 401 Brian Lepow, Matthew White, Stephan Schug, Kathryn Stannard Joseph Mills (Tucson, USA) (Perth, Australia) 27. Lymphoedema – Principles, genetics 23. Principles of wound healing 423 and pathophysiology 497 Gregory Schultz, Gloria Chin, Matt Waltham (London, UK) Lyle Moldawer, Robert Diegelmann 28. Graft materials past and future 511 (Florida, USA) Mital Desai, George Hamilton 24. Pathophysiology and principles of (London, UK) varicose veins 451 29. Pathophysiology of vascular graft Andrew Bradbury (Birmingham, UK) infections 537 25. Chronic venous insufficiency and leg Mauro Vicaretti (Sydney, Australia) ulceration: Principles and vascular biology 459 Index 549 Michael Stacey (Perth, Australia) List of Contributors

David G Armstrong Prue Cowled The University of Arizona Department of Surgery Southern Arizona Limb Salvage Alliance University of Adelaide Tucson, AZ The Queen Elizabeth Hospital USA Woodville, SA Australia Vishwanath Biradar Intensive Care Unit Helen Daly The Queen Elizabeth Hospital Royal Perth Hospital Woodville, SA Perth, WA Australia Australia

Matthew Bown Mital Desai Department of Vascular Surgery University Department of Vascular Surgery Royal Free Hospital University of Leicester University College Leicester London UK UK

Andrew W Bradbury Robert F Diegelmann University Department of Vascular Surgery Department of Biochemistry Birmingham Heartlands Hospital Medical College of Virginia Birmingham Richmond, VA UK USA

Edward Choke Timothy K Fisher Department of Vascular Surgery Rashid Centre for Diabetes and Research University of Leicester Sheikh Khalifa Hospital Leicester Ajmon UK UAE

Gillian Cockerill Robert A Fitridge Department of Clinical Sciences Department of Surgery St George’s Hospital Medical School University of Adelaide London The Queen Elizabeth Hospital UK Woodville, SA Australia

vii viii Mechanisms of Vascular Disease

Gail Gillespie Michael MD Lawrence-Brown Royal Perth Hospital Curtin Health Innovation Research Perth, WA Institute Australia Curtin University Perth, WA Jonathan Golledge Australia Vascular Biology Unit School of Medicine & Dentistry Brian Lepow James Cook University The University of Arizona Townsville, QLD Department of Surgery Australia Southern Arizona Limb Salvage Alliance Tucson, AZ USA George Hamilton University Department of Vascular Surgery Kurt Liffman Royal Free Hospital CSIRO Material Science & Engineering University College and School of Mathematical Sciences London Monash University UK Melbourne, Vic Australia Mark Hamilton Department of Surgery Ian Loftus University of Adelaide Department of Vascular Surgery The Queen Elizabeth Hospital St George’s Hospital Woodville, SA London Australia UK

Robert J Hinchliffe Mark J McCarthy St George’s Vascular Institiute Department of Surgery and Cardiovascular St George’s Hospital Sciences London University of Leicester UK Leicester UK Richard D Kenagy Department of Surgery Greg S McMahon University of Washington Department of Surgery and Cardiovascular Seattle, WA Sciences USA University of Leicester Leicester Paul Kerr UK Department of Pharmacology University of Alberta Simon McRae Alberta Adult Haemophilia Treatment Centre Canada SA Pathology Adelaide, SA Australia List of Contributors ix

Joseph L Mills Janet T Powell The University of Arizona Imperial College Southern Arizona Limb Salvage Alliance London Tucson, AZ UK USA Sandeep Prabhu Lyle Moldawer Baker IDI Heart & Diabetes Institute Department of Surgery Alfred Hospital University of Florida Melbourne, Vic Gainesville, FL Australia USA Rishi Puri John L Moran The Heart and Vascular Institute Faculty of Health Sciences Cleveland Clinic University of Adelaide Cleveland, OH The Queen Elizabeth Hospital USA Woodville, SA Australia Stephan A Schug Stephen Nicholls Royal Perth Hospital The Heart and Vascular Institute Perth, WA Cleveland Clinic Australia Cleveland, OH USA Gregory S Schultz Department of Obstetrics and Gynaecology Ian M Nordon University of Florida St George’s Vascular Institiute Gainesville, FL St George’s Hospital USA London UK Rahul Sharma Baker IDI Heart & Diabetes Institute Paul E Norman Alfred Hospital School of Surgery Melbourne, Vic University of WA Australia Fremantle, WA Australia Guo-Ping Shi Department of Cardiovascular Medicine Karlheinz Peter Brigham & Women’s Hospital Baker IDI Heart & Diabetes Institute Harvard Medical School Melbourne, Vic Boston, MA Australia USA

Frances Plane Michael Stacey Department of Pharmacology University Department of Surgery University of Alberta Fremantle Hospital Alberta Fremantle, WA Canada Australia x Mechanisms of Vascular Disease

Ilija D Sutalo Matt Waltham CSIRO Material Science & Engineering Academic Department of Surgery and Curtin Health Innovation St Thomas’ Hospital Research Instutute London Curtin University UK Highett, Vic Matthew L White Raymond Tam Vascular and Endovascular Surgery Department of Pharmacology University of Arizona University of Alberta Tucson, AZ Alberta USA Canada David P Wilson Matthew Thompson School of Medical Sciences St Georges Hospital Medical School Discipline of Physiology London University of Adelaide UK Adelaide SA Australia Martin Veller Department of Surgery Qingbo Xu University of Witwatersrand Department of Cardiology Johannesburg Kings College South Africa University of London UK Mauro Vicaretti Department of Vascular Surgery Westmead Hospital Westmead, NSW Australia Detailed Contents

Chapter 1 – Endothelium Smooth muscle proliferation and vascular remodeling 20 Paul Kerr, Raymond Tam, Frances Plane Summary 22 Introduction 1 References Endothelium-dependent regulation of vascular tone 2 Angiogenesis 7 Chapter 3 – Atherosclerosis Haemostasis 8 Gillian Cockerill, Qingbo Xu Inflammation 9 Introduction 25 Conclusions 10 Atherosclerotic lesions 26 References Fatty streaks Plaque or atheroma Chapter 2 – Vascular Hypercholesterolemia and oxidised-LDL Smooth Muscle Structure 27 and Function High-density lipoproteins role in atheroprotection 28 David Wilson Hypertension and biomechanical stress Introduction 13 29 Smooth muscle (vascular) structure Biomechanical stress-induced cell death Cytoskeleton 14 30 Contractile myofilament Biomechanical stress and inflammation Functional regulation of vascular smooth 31 muscle: Neuronal, hormonal, receptor Biomechanical stress-induced smooth mediated 15 muscle cell proliferation 32 Smooth muscle function 17 Infections and heat shock proteins Myofilament basis of smooth muscle Infections contraction and relaxation Heat shock proteins 33 Smooth muscle contraction and Infections and HSP expression relaxation 18 Infections, sHSP and innate immuntiy Ion channels important in the regulation 34 of smooth muscle function Immune responses 36 Regulation of cellular Ca2+ MHC class II antigens and T cells Sources of cytosolic Ca2+ entry 19 Oxidised LDL as a candidate antigen Potassium channels HSP60 as a candidate antigen 37 Endothelial regulation of smooth muscle B2-gylcoprotein Ib as a candidate antigen vasodilatation 20 Inflammation xi xii Mechanisms of Vascular Disease

C-reactive protein 38 Stephen Nicholls, Rishi Puri CD40/CD40L Background 79 Summary and perspectives 39 Pathology References Risk factor modification 80 Statins, LDL lowering and C-reactive Chapter 4 – Mechansims of protein Plaque Rupture The complexity of HDL 84 The controversy of trigylcerides 87 Ian Loftus Hypertension Introduction 43 Risk factor modification in the diabetic Evidence for the ‘plaque rupture theory’ patient 89 44 Glycaemic control Coronary circulation Global risk factor reduction in diabetics Cerebral circulation 91 The role of individual components of the The metabolic syndrome 92 arterial wall Future targets 93 The endothelium 45 Conclusion The lipid core 47 References 94 The cap of the plaque 49 Smooth muscle cells and collagen production 50 Chapter 6 – Molecular Macrophages and collagen degradation approaches to 51 revascularisation in The vessel lumen 56 peripheral vascular disease The role of angiogenesis in plaque rupture Greg S McMahon, Mark J McCarthy The role of infectious agents in plaque rupture 57 Introduction 103 Risk prediction of plaque instability 58 Mechanisms of vascular growth Imaging Vasculogenesis Blood markers 59 Angiogenesis 104 Therapy aimed at plaque stabilisation Neovessel maturation 105 HMG Co-A reductase inhibitors 60 Microvascular network maturation 106 MMP inhibition Arteriogenesis Tissue inhibitors of metalloproteinases Therapeutic induction of vascular growth (TIMPs) 61 107 Synthetic MMP inhibitors Delivery of molecular activators of Doxycycline vascular growth ACE inhibitors Angiogenic activators 108 Summary 62 Arteriogenic activators 109 References 63 Clinical trials for angiogenic therapy of peripheral vascular disease Chapter 5 – Current and Conclusions 110 emerging therapies in References atheroprotection Detailed Contents xiii

Chapter 7 – Biology of Laplace’s law of wall of tension 154 restenosis and targets for Newtonian fluid 155 intervention Non-Newtonian fluid Poiseuille flow 158 Richard Kenagy Bernoulli’s equation Introduction 115 Young’s modulus and pulsatile flow 159 Mechanisms of restenosis Mass conversion 161 Thrombosis 116 Reynold’s number Remodelling Arterial dissection, collateral circulation Intimal hyperplasia 123 and competing flows 163 Sequence of events after injury Shear stress and pressure 164 Origin of intimal cells 125 Forces on graft systems 165 Inflammation 126 Case 1 – The cylindrical graft 168 Role of ECM production 127 Case 2 – The windsock graft The contribution of specific factors to Case 3 – The curved graft 169 restenosis Case 4 – The symmetric bifurcated graft Growth factors/cytokines Computational modelling 170 Inhibitors 128 Recent development and future directions Coagulation and fibrinolytic factors 129 171 Matrix metalloproteinases Conclusions 172 Extracellular matrix/receptors References 173 Targets for intervention 130 Intracellular signalling molecules mTOR and microtubules Chapter 9 – Physiological Transcription factors haemostasis miRNA 131 Simon McRae Inflammation targets Brachytherapy Introduction 177 Extracellular targets and cell-based Primary haemostasis therapies Platelets Angiotensin pathway Platelet adhesion Cell-based therapies 132 Platelet activation and shape change Differential effects on endothelium and 179 SMCs Platelet aggregation 180 Delivery devices Interactions between primary and Prevention versus reversal of restenosis secondary haemostasis 181 Conclusions 133 Secondary haemostasis References 134 The coagulation cascade 182 Initiation 183 Amplification Chapter 8 – Vascular Propagation 184 arterial haemodynamics Normal inhibitors of coagulation Michael Lawrence Brown, Kurt Liffman, Fibrinolysis 185 James Semmens, Ilija Sutalo Conclusions 186 References Introduction 153 xiv Mechanisms of Vascular Disease

Chapter 10 – vascular disease and their Hypercoagulable states role as a therapeutic target Simon McRae Sandeep Prabhu, Rahul Sharma, Introduction 189 Karlheinz Peter Classification of thrombophilia Inherited thrombophilia 190 Introduction 201 Type 1 conditions Platelet function – Adhesion and Antithrombin deficiency activation Protein C and Protein S deficiency Platelet adhesion 202 Type 2 conditions 191 Platelet activation 203 Factor V Leiden Mediators of platelet activation and The prothrombin (G20210A) gene ‘outside in’ signalling mutation Thrombin and collagen 204 FVL/PGM compound heterozygotes Adenosine diphosphate (ADP) Other inherited conditions Thromboxane A2 (TXA2) Acquired thrombophilia 192 Adrenaline 206 Antiphospholipid antibodies Second messenger systems 207 Heparin induced thrombocytopenia Physiological consequences of platelet Myeloproliferative disorders 193 activation Potential reasons for performing The GP IIb/IIIa receptor and ‘inside- thrombophilia testing out’ signalling Patients with venous thrombosis and Granule exocytosis 208 their relatives Activation-induced conformational Providing an understanding of the change of platelets aetiology of a thrombotic event Platelets and atherosclerosis 209 Determining risk of recurrence and Role of platelets in the initiation of the therefore optimal duration of atherosclerosis anticoagulation 194 Role of the platelets in the progression of Determining the need for primary the atherosclerosis prophylaxis in asymptomatic Role of platelets in vulnerable plaques and family members 195 plaque rupture Making decisions regarding the use of Current and future anti-platelet agents the oral contraceptive pill 196 Determining the need for 210 thromboprophylaxis during Aspirin (salicylic acid) pregnancy Thienopyridines 211 Patients with arterial thrombosis Clopidogrel Potential detrimental effects of Prasugrel 213 thrombophilia testing 197 Ticlopidine Conclusion Ticagrelor References GPIIb/IIIa Antagonists Other anti-platelet agents and promising new deleopments 214 Chapter 11 – Platelets Platelet function testing 215 in the pathogenesis of Light-transmission aggregometry Detailed Contents xv

Whole blood aggregometry 217 response 249 VerifyNow® Assay Non-steroidal anti-inflammatories Flow cytometry 218 Matrix metalloproteinase (MMP) References inhibition Anti-chlamydial therapy 250 Drugs acting on the renin/angiotensin axis Chapter 12 – Pathogenesis HMG Co-A reductase inhibitors 251 of aortic aneurysms The future – Data from recent Jonathan Golledge, Guo-Ping Shi, experimental studies Paul E Norman References Introduction 227 Differences between thoracic and Chapter 14 – abdominal aortic aneurysms 228 Pathophysiology of Aortic Summary of current theories and stages of Dissection and Connective AAA evolution Tissue Disorders Atherosclerosis and AAA Mark Hamilton Immune mechanisms in AAA 229 Extracellular matrix dysfunction 232 Introduction 255 Infection 233 Embryology of thoracic aorta and arch Biomechanical forces vessels Angiogenesis Haemodynamics of thoracic compared to Intra-luminal thrombus abdominal aorta 257 Extracellular matrix proteolysis 234 Sizes of normal aorta Genetics 236 Classification of aortic syndromes Acute/Chronic AAA rupture 237 DeBakey classification of class 1 Biomechanical factors in aneurysms dissection – Type 1, 2, and 3 rupture Stanford classification 258 The role of enzymes in AAA rupture European task force Role of intraluminal thrombus in Pathogenesis of thoracic aortic dissection aneurysm rupture 238 Classical thoracic aortic dissection (class 1 Future research dissection) 260 References Intramural haematoma (class 2 aortic dissection) 261 Chapter 13 – Penetrating aortic ulcer (class 4 aortic Pharmacological dissection) 262 treatment of aneurysms Complications of acute aortic syndromes 263 Matthew Thompson, Janet T Powell Visceral ischaemia /malperfusion Background 247 syndromes Screening programmes Fate of the false lumen Pathophysiology 248 Aneurysmal degeneration and rupture Therapeutic strategies 264 Beta blockade Connective tissue disorders and acute Modification of the inflammatory aortic syndromes xvi Mechanisms of Vascular Disease

Marfan syndrome Chapter 16 – Fibrillin and Marfan syndrome 265 Pathophysiology and The role of transforming growth factor principles of management beta in development of the vascular of vasculitis and Raynaud’s system in health and disease 266 phenomenon Ehlers-Danlos syndrome 267 Diagnosis of Ehlers-Danlos syndrome Martin Veller 268 Vasculitides 295 Loeys-Deitz syndrome 270 Introduction Familial thoracic aortic aneurysm disease Classification of vasculitides 296 271 Clinical presentation of vasculitides Bicuspid aortic valve 273 Investigations of vasculitides Turners Syndrome Principles of treatment of vasculitides Summary 274 297 Reference list The vasculitides of specific interest to vascular surgeons 298 Giant cell arteritis Chapter 15 – Biomarkers in Takayasu’s arteritis 299 vascular disease Thromboangitis obliterans (Buerger’s Ian M Nordon, Robert J Hinchliffe disease) 300 Introduction 277 Behcet’s disease 301 What is a biomarker? Polyarteritis nodosa 302 Types of biomarkers Vasculitides secondary to connective A classical clinical example 278 tissue diseases 303 Potential value of biomarkers in vascular Systemic lupus erythematosus (SLE) disease 279 Antiphospholipid antibody syndrome Biomarker discovery steps 280 (APS) 304 AAA biomarkers Rheumatoid arthritis 305 Circulating extracellular matrix markers Scleroderma 281 Infective vasculitides 306 Matrix-degrading enzymes 283 Human immunodeficiency virus (HIV) Proteins associated with thrombosis Pathophysiology and principles of Markers of inflammation 284 Raynaud’s phenomenon 307 Biomarkers of AAA rupture 285 Prevalence of Raynaud’s phenomenon Biomarkers following endovascular repair 308 Inflammation 287 Clinical findings in Raynaud’s Lipid accumulation phenomenon 309 Apoptosis Diagnosis of Raynaud’s phenomenon Thrombosis Prognosis 310 Proteolysis 288 Treatment Challenges in biomarkers discovery Recommendations 311 Future work References 312 Conclusion 289 References Chapter 17 – SIRS, sepsis and Detailed Contents xvii mug ltior an failure Eicosanoids 334 Nitric Oxide 335 Vishwanath Biradar, John Moran Endothelin 336 Epidemiology 315 Cytokines Historical perspectives and definition 316 Neutrophil and endothelial interactions Risk factors for sepsis 317 338 Causative agents Complement activation 340 Pathophysiology of sepsis Tissue destruction 341 innate immunity and toll-like receptors Proteases and metalloproteinases (TLRs) 319 Apoptotic cell death during ischaemia- Proinflammatory response reperfusion injury Coagulation cascade No-reflow phenomenon 342 Multiorgan dysfunction syndrome Therapeutic approaches to IRI (MODS) 320 Ischaemic preconditioning Epithelial and endothelial dysfunction Ischaemic post-conditioning 343 Immune suppression and apoptosis Conditioning effects of volatile Sepsis, circulatory failure and organ anaesthetics dysfunction Pharmacological treatments 344 Management 322 Summary 345 Steroids 323 References Recombinant human activated protein C (rhAPC) 324 Chapter 19 – Compartment Glucose control 325 Syndrome Renal replacement therapy 3-hydroxy-3-methylglutaryl-coenzyme Edward Choke, Robert Sayers, Matthew reductase inhibitors (HMG-CoA) Bown 326 Definition 351 Other adjuvant therapies in sepsis Acute limb compartment syndrome Cytokines and anticytokine therapies Incidence Pooled immunoglobulin (IVIG) Anatomy/physiology 352 Acute respiratory distress syndrome Aetiology/pathophysiology (ARDS) 327 Clinical presentation 354 References Investigation 355 Treatment 357 Chapter 18 – Complication of LCS 359 Pathophysiology of Outcome 360 reperfusion injury Acute abdominal compartment syndrome Incidence 361 Prue Cowled, Rob Fitridge Aetiology Introduction 331 Pathological effects of raised intra- Ischaemia abdominal pressure 362 ATP and mitochondrial function Clinical presentation 363 Gene expression during ischaemia 332 Investigation Reperfusion 333 Treatment 364 Reactive oxygen species Complications of surgical decompression xviii Mechanisms of Vascular Disease

Outcome 367 Peripheral neuropathies References 368 Central neuropathies 385 References Chapter 20 – Pathophysiology of Pain Chapter 21 – Post-amputation pain Stephan Schug, Helen Daly, Kathryn Stannard Stephan Schug, Gail Gillespie Introduction 375 Introduction 389 Peripheral mechanisms Classification and incidence of post- Nociception/transduction amputation pain syndromes Conduction 376 Stump pain Spinal cord mechanisms Phantom sensation 390 Ascending systems 377 Phantom limb pain Descending control Pathophysiology of post-amputation pain Pain modulation 378 syndromes Peripheral sensation Peripheral factors Central sensitisation in the dorsal horn Spinal factors 391 Neuropathic pain 379 Supraspinal factors Mechanisms of neuropathic pain Current pathophysiological model of post- Peripheral mechanisms amputation pain syndromes 392 Prevention of post-amputation pain Spontaneous ectopic discharge Perioperative lumbar epidural blockade Altered gene expression Peripheral nerve blockade 393 Spared sensory neurons NMDA antagonists Involvement of the sympathetic nervous Evaluation of the patient with post- system 380 amputation pain syndromes Collateral sprouting Examination Effects of bradykinin Therapy of post-amputation pain Central mechanisms syndromes 394 Wind up Calcitonin Central sensitization 381 Ketamine Central disinhibition Analgesic and Co-analgesic compounds Expansion in receptive field size Opioids 395 (recuruitment) Gabapentin Immediate early gene expression Clonazepam Anatomical re-organisation of the spinal Lidocaine cord Carbamazepine Contribution of glial cells to pain Tricyclic antidepressants (TCA) conditions 382 Selective serotonin reuptake inhibitors Symptoms of neuropathic pain Baclofen Stimulus-dependent pain Capsaicin Stimulus-independent pain 383 Symptomatic treatment of pain Sympathetically maintained pain (SMP) components 396 Neuropathic pain syndromes Neuropharmacological therapies Detailed Contents xix

Invasive therapies Phenytoin Electroconvulsive therapy (ECT) Lamotrigene Nerve blockade Recommendations for clinical use of Spinal cord stimulation anticonvulsants as analgesics Implantable intrathecal delivery systems Local anaesthetics and antiarrhythmics Dorsal root entry zone (DREZ) lesions 409 Psychological therapy 397 Mechanism of action Future aims Lignocaine References Mexiletine Recommendations for clinical use of lignocaine and mexiletine in Chapter 22 – Treatment of neuropathic pain neuropathic pain N-methyl-D-aspartate-receptor Stephan Schug, Kathryn Stannard antagonists (NMDA) Ketamine 410 Introduction 401 Other NMDA antagonists Principles of treatment Miscellaneous compounds for systemic Pharmacological treatment 402 use Opioids Clonidine Recommendations for clinical use of Efficacy opioids Baclofen Tramadol Levodopa 411 Mechanism of action Cannabinoids Efficacy 403 Topical treatments Adverse effects Lignocaine 5% medicated plaster Recommendations for clinical use of Capsaicin 412 tramadol in neuropathic pain Mechanism of action Antidepressants Efficacy Tricyclic antidepressants (TCAs) Non-pharmacological therapy Mechanism of action 404 Transcutaneous electrical nerve Adverse effects stimulation (TENS) Selective serotonin re-uptake inhibitors Spinal cord stimulation (SCS) 413 (SSRIs) Sympathetic nerve blocks Serotonin/Noradrenaline reuptake Neurosurgical destructive techniques inhibitors (SNRIs) 405 Cognitive behavious therapy Recommendations for clinical use of References 414 antidepressants as analgesics Anticonvulsants Mechanism of action 406 Chapter 23 – Principles of Individual medications wound healing Clonazepam Gregory Schultz, Gloria Chin, Gabapentin Lyle Moldawer, Robert Diegelmann Pregabalin 407 Carbamazepine Introduction 423 Sodium valproate 408 Phases of acute wound healing Haemostasis xx Mechanisms of Vascular Disease

Inflammation 426 Varicose veins 453 Neutrophils 427 Valvular abnormalities Macrophages 428 Muscle pump failure 455 Proliferative phase 429 Venous recirculation Fibroblast migration 430 Recurrent varicose veins Collagen and extracellular matrix New varicose veins production Persistent varicose veins Angiogenesis 431 True recurrent varicose veins 456 Granulation 432 Cellular and molecular biology of varicose Epithelialization veins Remodelling 433 Conclusion 457 Summary of acute wound healing 435 References Comparison of acute and chronic wounds Normal and pathological responses to injury Chapter 25 – Chronic Biochemical differences in the molecular venous insufficiency and environments of healing and chronic leg ulceration: Principles wounds 436 and vascular biology Biological differences in the response of Michael Stacey chronic wound cells to growth factors Definitions 459 439 Chronic venous insuffiency From bench to bedside Leg ulceration Role of endocrine hormones in the Assessment of cause of leg ulceration regulation of wound healing 460 Molecular basis of chronic non-healing Epidemiology 461 wounds Pathophysiology Chronic venous stasis ulcers 441 Venous abnormality Pressure ulcers Effect of ambulatory venous hypertension Future concepts for the treatment of on the tissues in the leg 463 chronic wounds 442 Influence of venous disease on the wound Bacterial biofilms in chronic wounds healing process 465 443 Genetic associations with venous Conclusion 445 ulceration 466 References Assessment of venous function 467 Treatment of venous ulceration Chapter 24 – Compression therapy Pathophysiology and Dressings 468 principles of management Surgery of varicose veins Prevention of venous ulcer recurrence 470 Andrew Bradbury Sclerotherapy and other techniques to Introduction 451 obliterate surface and perforating veins Anatomy Other therapies 471 Histology 452 References Physiology Detailed Contents xxi

Chapter 26 – Chapter 27 – Lymphoedema Pathophysiology and – Principles, genetics and principles of management pathophysiology of the diabetic foot Matt Waltham David Armstrong, Timothy Fisher, Brian Introduction 497 Lepow, Matthew White, Joseph Mills Classification of lymphoedema Introduction 475 Classification of primary lymphoedema Pathophysiology of the diabetic foot 476 498 Neuropathy The genetics of lymphangiogensis in Structural abnormalities/gait primary lymphoedema 500 abnormalities Milroy’s disease Angiopathy 478 Lymphoedema – distichiasis syndrome Diagnosis 501 History and rapid visual screening Hypotrichosis – lymphoedema – Neurological examination 479 telangiectasia syndrome 502 Monofilament testing Meige disease (primary non-syndromic Vibration testing lymphoedema) Dermatologic examination 480 Other primary lymphoedema disorders Anatomy of occlusive disease – vascular 503 examination Structure and development of the Prediction of wound healing: assessment lymphatic circulation of perfusion 481 Clinical aspects of lymphoedema 505 Arterial imaging Summary Soft tissue imaging 482 References Classification systems 483 Diabetes mellitus foot risk classification University of Texas wound classification Chapter 28 – Graft system materials past and future Clinical problems and principles of Mital Desai, George Hamilton management 484 Ulceration The pathophysiology of graft healing 511 Epidemiology and risk factors The peri-anastomotic area Offloading Healing of prosthetic grafts 512 Non-vascular surgical treatment 485 The healing process of the anastomosis Class I – Elective 486 Graft porosity and permeability Class II – Prophylactic Physical properties of prosthetic materials Class III – Curative 514 Class IV – Emergency (urgent) Tubular compliance Post-operative management Anastomotic compliance mismatch Infections 487 The compliance hypothesis of graft failure Charcot arthopathy Synthetic grafts 515 Prevention 490 Newer developments of Dacron grafts Conclusion 492 Modifications and newer developments of References PTFE grafts 517 Polyurethane grafts xxii Mechanisms of Vascular Disease

Newer developments of polyurethane Chapter 29 – vascular grafts 518 Pathophysiology of Biological vascular grafts 519 vascular graft infections Newer developments of biological Mauro Vicaretti vascular grafts 520 Prosthetic graft modifications Introduction 537 Modifications to reduce graft infection Natural history of prosthetic vascular graft Modifications to improve patency 521 infections Nanocomposite grafts Mechanism of graft contamination at Endothelial cell seeding 522 operation 538 Single stage seeding Pathogenesis of graft infections Two stage seeding Bacteriology of vascular graft infections Vascular tissue engineering Investigations for detection of prosthetic Non-degradable polymer and cell seeding graft infections 539 523 History and physical examination Bioresorbable and biodegradable polymers Laboratory investigations Combined bioresorbable and tissue Diagnostic imaging 540 engineered grafts 524 Management of prosthetic graft infections Mechanical conditioning of seeded Prevention vascular cells Reduction of prosthetic vascular graft Alternative scaffolds infection with rifampicin bonded Tissue-engineered grafts 525 gelatin sealed Dacron 541 Graft materials for aortic endografts 526 Established infection The future Antibiotic therapy References 527 Operative management Conclusion 542 References Acknowledgements

The Editors gratefully acknowledge the outstanding contributions of each Author involved in this reference book. We would also like to acknowledge the invaluable efforts of Ms Sheona Page who has worked tirelessly on this project. We would also like to thank Prue Cowled PhD and Ms Cayley Wright for their assistance.

xxiii Abbreviation List

a1-PI a1-protease inhibitor

5-HT 5-Hydroxytryptamine/Serotonin

AAA Abdominal aortic aneurysm

AAS Acute aortic syndrome

AAV Adeno-associated viruses

ACE Angiotensin converting enzyme

ACS Acute coronary syndrome

ACS Abdominal compartment syndrome

ACTH Adrenocorticotropic hormone

ADAMTS A disintegrin and metalloproteinase with thrombospondin motifs

ADP Adenosine diphosphate

AIDS Acquired immune deficiency syndrome

ALI Acute lung injury

AMP Adenosine monophosphate

AMPA α-amino-3 hydroxy-5-methylisoxazole

ANA Anti-nuclear antibody

ANCA Anti-neutrophil cytoplasmic antibody

AOD Aortic occlusive disease

AP1 Activated protein 1

APC Activated protein C

APC Antigen presenting cell

APLAS Antiphospholipid antibody syndrome

ApoAI Apolipoprotein AI

ApoE Apolipoprotein E

APS Antiphospholipid antibody syndrome

APTT Activated partial thromboplastin time

xxiv Abbreviation List xxv

ARDS Acute respiratory distress syndrome

AT Antithrombin

ATP Adenosine triphosphate

AVP Ambulatory venous thrombosis b2-GPI b2-glycoprotein Ib bFGF Basic fibroblast growth factor

BKCa Large conductance calcium activated potassium channel

BMPs Bone morphogenetic proteins

BMS Bare metal stent

CAD Coronary artery disease

CaM Calmodulin

CAM Cell adhesion molecule cAMP Cyclic adenosine monophosphate

CCK Cholecystokinin cGMP Cyclic guanine monophosphate

CD Cluster of differentiation

CD40L Cluster of differentiation 40 ligand

CEA Carotid endarterectomy

CETP Cholesteryl ester transfer protein

CFD Computational fluid dynamics

CG Cationized gelatin

CGRP Calcitonic gene regulated peptide

CHD Coronary heart disease

CI Confidence interval

CIMT Carotid intimal-media thickness c-JNK c-Jun N-terminal kinase

CK-MB Creatinine kinase (Myocardial specific)

CNCP Chronic noncancer pain cNOS Constitutive nitric oxygen synthase enzyme

COX-1 Cyclooxygenase-1

COX-2 Cyclooxygenase-2

CROW Charcot restraint orthotic walker

CRRT Continuous renal replacement therapy xxvi Mechanisms of Vascular Disease

CRP C-reactive protein

CRPS Complex regional pain syndromes

CT Computational tomography

CTA Computed tomographic angiography

CTD Connective tissue disorders

CTGF Connective tissue growth factor

CYP Cytochrome P450

CVD Cardiovascular disease

CVI Chronic venous insufficiency

DAG Diacylglycerol

DES Drug-eluting stent

DRG Dorsal root ganglion

DNA Deoxyribonucleic acid

DSA Digital subtraction arteriography

DTS Dense tubular system

DVT Deep vein thrombosis

EC Endothelial cell

ECM Extracellular matrix

EDCF Endothelium-derived contracting factor

EDH Endothelium-dependent hyperpolarisation

EDS Ehlers-Danlos syndrome

EET Epoxyeicosatrienoic acids

ELAM-1 Endothelial-leukocyte adhesion molecule-1

ELG Endoluminal grafts

ELISA Enzyme linked immunosorbent assay

EK Equilibrium potential

EM Membrane potential

eNOS Endothelial nitric oxide synthase enzyme

EPC Endothelial progenitor cells

EPCR Endothelial protein C receptor

ePTFE Expanded polytetrafluoroethylene

ERK Extracellular signal-regulated kinase

ESR Erythrocyte sedimentation rate Abbreviation List xxvii

ET Essential thrombocytosis

ET-1 Endothelin 1

EVAR Endovascular aortic aneurysm repair

EVLA Endovenous LASER ablation

FDA Food and drug administration

FDPs Fibrin degradation products (soluble)

FGF Fibroblast growth factor

FGF-2 Fibroblast growth factor 2

FMN Flavin mononucleotide

FVL Factor V Leiden

GABA Gamma-aminobutyric acid

GABA B Gamma-aminobutyric acid subtype B

G-CSF Granulocyte colony stimulating factor

GMCSF Granulocyte-macrophage colony stimulating factor

GP Glycoprotein

GPCR G-protein coupled receptor

GSV Great saphenous vein

HDL High density lipoprotein

HDL-C High density lipoprotein cholesterol

HIF Hypoxia inducible factor

HIT Heparin induced thrombocytopenia

HIV Human immunodeficiency virus

HLA Human leukocyte antigen

HMG Co-A Hydroxymethylglutaryl coenzyme-A

HMW High molecular weight

HPETE Hydroperoxyeicosatetraenoic acid

HETE Hydroxyeicosatetraenoic acids

HR Hazard ratio hsCRP High-sensitive C-reactive protein

HSP Heat shock protein

HUV Human umbilical vein

IAH Intra-abdominal hypertension xxviii Mechanisms of Vascular Disease

IAP Intra-abdominal pressure

IAPP Intra-abdominal perfusion pressure

ICAM-1 Inter-cellular adhesion molecule-1

ICAM-2 Inter-cellular adhesion molecule-2

ICP Intra-compartmental pressure

ICU Intensive care unit

IFN Interferon

IGF-1 Insulin-like growth factor-1

IHD Ischemic heart disease

IL Interleukin

IL-1 Interleukin-1

IL-1α Interleukin-1 alpha

IL1-β Interleukin-1 beta

IL-6 Interleukin-6

IL-8 Interleukin-8

ILT Intraluminal thrombus

IKCa Intermediate conductance calcium-activated potassium channels

IMH Intramural haematoma

IMP Inosine monophosphate

iNOS Inducible nitric oxide synthase enzyme

IP(3) 1,4,5-inositol triphosphate

IRI Ischemia reperfusion injury

IVIG Intravenous pooled immunoglobulin

IVUS Intravascular ultrasound

KGF Keratinocyte growth factor

KGF-2 Keratinocyte growth factor-2

LAP Latency associated peptide

LCS Limb compartment syndrome

LDL Low density lipoprotein

LDS Loeys-Dietz syndrome

LLC Large latent complex

LEC Lymphatic endothelial cells Abbreviation List xxix

LFA-1 Lymphocyte function-associated antigen-1

LO Lipoxygenase

LOX Lysyl oxidase

LOPS Loss of protective sensation

LPA Lysophosphatidic acid

LPS Lipopolysaccharide

LTA Lipoteichoic acid

LTGFBP Latent TGF binding protein

MAC-1 Macrophage-1 antigen

MAPK Mitogen activated protein kinase

MCP-1 Monocyte chemoattractant protein-1

M-CSF Macrophage-colony stimulating factor

MFS Marfan syndrome

MHC Major histocompatibility

MI Myocardial infarction

MIP-1 Macrophage inflammatory protein-1

MLC20 Myosin light chain20

MLCK Myosin light chain kinase

MLCP Myosin light chain phosphatase

MMP Matrix metalloproteinase

MODS Multiple organ dysfunction syndrome

MRA Magnetic resonance angiography

MRI Magnetic resonance imaging mRNA Messenger RNA

MRSA Methicillin resistant Staphylococcus aureus

MRSE Methicillin resistant Staphylococcus epidermidis

MRTA Magnetic resonance tomographic angiography

MTHFR Methylenetetrahydrofolate reductase

MT-MMP Membrane-type MMP

MVPS Mitral valve prolapse syndrome

NADPH Nicotinamide adenine dinucleotide phosphate

NGF Nerve growth factor xxx Mechanisms of Vascular Disease

NFκB Nuclear factor kappa B

NiTi Nitinol

NJP Non-junctional perforators

NMDA N-methyl-D-aspartate

NNH Number needed to harm

NNT Number needed to treat

NO Nitric oxide

NOS Nitric oxide synthase enzyme

NSAID Non-steroidal anti-inflammatory drug

NV Neovascularisation

OCP Oestrogen/progesterone contraceptive pill

OPN Osteopontin

OPG Osteoprotegerin

OR Odds ratio

OxLDL Oxidised low density lipoprotein

PAD Peripheral arterial disease

PAF Platelet activating factor

PAI Plasminogen activator inhibitor

PAI-1 Plasminogen activator inhibitor-1

PAR Protease activated receptor

PAR-1 Protease activated receptor-1

PAR-4 Protease activated receptor-4

PAU Penetrating aortic ulcer

PC Protein C

PCA Poly (carbonate-urea) urethane

PCI Percutaneous coronary intervention (angioplasty)

PCWP Pulmonary capillary wedge pressure

PDGF Platelet-derived growth factor

PDGFb Platelet-derived growth factor-b

PDS Polydioxanone

PECAM-1 Platelet-endothelial cell adhesion molecule-1

PEDF Pigment epithelium-derived factor

PES Paclitaxel-eluting stent Abbreviation List xxxi

PET Positron emission tomography

PF4 Platelet factor 4

PGI2 Prostacyclin

PGG2 Prostaglandin G2

PGH2 Prostaglandin H2

PGEI2/PGI2 Prostaglandin I2

PGN Peptidoglycan

PHN Postherpetic neuropathy

PHZ Para-anastomotic hyper-compliant zone

PI3K Phosphatidylinositol 3-kinase

PIP2 Phosphatidylinositol 4,5-bisphosphate

PLC Phospholipase C

PLOD Procollagen lysyl hydroxylase

PMCA Plasma membrane Ca2+ APTases

PMN Polymorphonuclear leukocyte

POSS Polyhedral oligomeric silsesquioxanes

PPAR Peroxisomal proliferation activating receptor

PPI Proton pump inhibitor

PRV Polycythaemia rubra vera

PS Protein S

PSGL-1 P-selectin glycoprotein ligand-1

PT Prothombin time

PTCA Percutaneous coronary angioplasty

PTFE Polytetrafluoroethylene

PTS Post-thrombotic syndrome

PUFA Polyunsaturated fatty acid

PVI Primary valvular incompetence rAAA Ruptured AAA

Rac Ras activated cell adhesion molecule

RANTES Regulated upon activation, normal T cell expressed and secreted

RAS Renin angiotensin system

RCT Randomised controlled trial xxxii Mechanisms of Vascular Disease

RF Rheumatoid factor

RFA Radiofrequency ablation

rhAPC Recombinant human activated protein C

RNA Ribonucleic acid

ROS Reactive oxygen species

RR Relative risk

RSD Reflex sympathetic dystrophy

S1P Sphingosine-1-phosphate

SAPK Stress-activated protein kinase

SCF Stem cell factor

SCS Spinal cord stimulation

ScvO2 Superior vena cava venous oxygen saturation

SDF-1 Stromal-cell-derived factor-1

SERCA Sarco/endoplasmic reticulum CaATPases

SEP Serum elastin peptides

SES Sirolimus-eluting stent

SEPS Subfascial endoscopic perforator surgery

SFA Superficial femoral artery

SFJ Sapheno-femoral junction

SIRS Systemic inflammatory response syndrome

SKCa Small conductance calcium-activated potassium channels

SLE Systemic lupus erythematosus

SMA Smooth muscle alpha actin

SMC Smooth muscle cell

SMP Sympathetically maintained pain

SNARE Soluble N-ethylmaleimide-sensitive factor activating protein receptors

SNP Single nucleotide polymorphisms

SNRI Serotonin/Noradrenaline reuptake inhibitors

SPJ Sapheno-popliteal junction

SPP Skin perfusion pressure

SR Sarcoplasmic reticulum

SSRIs Selective serotonin re-uptake inhibitors

SSV Small saphenous vein Abbreviation List xxxiii

SVT Superficial thrombophlebitis

STIM1 Stromal interacting molecule 1

TaCE TNFa converting enzyme

TAAD Thoracic aortic aneurysm disease

TAD Thoracic aortic dissection

TAFI Thrombin-activatable fibrinolysis inhibitor

Tc-99 MDP Technetium-99 methylene diphosphonate

TCA Tricyclic antidepressant

TCC Total contact cast

TCR T-cell receptor

TENS Transcutaneous electrical nerve stimulation

TF Tissue factor

TFPI Tissue factor pathway inhibitor

TGF Transforming growth factor

TGF-α Transforming growth factor-alpha

TGF-β Transforming growth factor-beta

TGL Triglycerides

Th T helper

TIA Transient ischemic attack

TIMP Tissue inhibitors of metalloproteinase

TLR Toll-like receptors

TNF Tumour necrosis factor

TNF-α Tumour necrosis factor-alpha tPA Tissue-type plasminogen activator

TRP Transient receptor potential

TRPC Transmembrane receptor potential canonical

TRPV1 Transmembrane receptor potential Vanilloid-type

TXA2 Thromboxane A2 uPA Urokinase

UT University of Texas

VCAM Vascular cell adhesion molecule

VCAM-1 Vascular cell adhesion molecule-1

VEGF Vascular endothelial growth factor xxxiv Mechanisms of Vascular Disease

VEGF-R Vascular endothelial growth factor receptor

VIP Vasoactive intestinal peptide

VLA-1 Very late activating antigen-1

VOCC Voltage operated calcium channels

VPT Vibratory perception threshold

VSMC Vascular smooth muscle cells

VTE Venous thromboembolism

VV Varicose veins

vWF von Willebrand factor

XO Xanthine oxidase 2 • Vascular Smooth Muscle Structure and Function David P Wilson

Molecular Physiology of Vascular Function Research Group, Discipline of Physiology, University of Adelaide, South Australia

INTRODUCTION SMOOTH MUSCLE (VASCULAR) STRUCTURE Smooth muscle has an important role in regulating the function of a variety of hollow Vascular smooth muscle cells have classically organ systems including the: vasculature, been envisaged as fusiform cells, on average airways, gastrointestinal tract, uterus and 200 microns long × 5 microns in diameter, reproductive tract, bladder and urethra and with a large central nucleus surrounded by several other systems. Smooth muscle has an abundant array of endoplasmic reticulum two fundamental roles: 1) to alter the shape and golgi apparatus, with the cytosol and of an organ and 2) to withstand the force of plasma membrane tapering toward the poles. an internal load presented to that organ. In Although the dimensions of the vascular order to achieve these fundamental objectives smooth muscle cell narrow toward their ends smooth muscles have developed mechanisms there is clear evidence that the end-to-end of mechanical coupling, which enable the junctions coupling smooth muscle cells are development of powerful and coordinated complex and contain a significant number contractions at a relatively low energy cost. For of membrane invaginations to provide example, smooth muscle in the gastrointestinal increased surface area for both mechanical tract must undergo intermittent but coordin­ tight junctions and electrical coupling via ated phasic contractions to propel the bolus gap junctions (Figure 2.1). Vascular smooth of food through the alimentary canal. muscle cells do not contain the complex Whereas in the airways and vasculature the t-tubule/sarcoplasmic reticulum system smooth muscle is more often in various states common to striated muscles, but rather they of tonic contraction, but can be dynamically contain a significant number of invaginations regulated to relax or contract in response to along the plasma membrane called caveolae, specific neuro-hormonal and haemodynamic which serve a similar, albeit less developed role signals. In keeping with the aims of this to increase the cellular surface: volume ratio. text, this chapter will focus on the principle These specialized caveolae further provide mechanisms through which vascular smooth a unique plasma membrane environment, muscle functions. which enables clustering of specific groups

13 14 Mechanisms of Vascular Disease

Figure 2.1: Highlights the fusiform shape of typical smooth muscle cells and the patterned array of actin myosin myofilaments across the cell. Smooth muscle cells have invaginations along their length to provide increased surface area for mechanical coupling via tight junctions and electrical coupling through Gap junctions. Dense bodies are thought to be similar to Z-disks found in striated muscle. of ion channels and receptors important in that function to provide static support cellular signal transduction. to the cell and to enable motor protein In contractile vascular smooth muscle the mediated transport of cytosolic cargo and endoplasmic reticulum has been modified for chromosomal segregation during mitosis. to enable Ca2+ release and reuptake and has The actin cytoskeleton and elements of therefore been termed sarcoplasmic reticulum. the actin contractile myofilament are also In smooth muscle cells the sarcoplasmic generated from the polymerization of reticulum/endoplasmic reticulum (SR/ER) globular monomeric actin to form polymeric complex comprises about 5% of the total actin filaments. This process is dynamically cell volume, with a considerable amount regulated even within the time scale of of rough endoplasmic reticulum and golgi contractile processes, i.e., as the smooth apparatus adjacent to the nucleus, which muscle slowly shortens it can actually reflects the significant capacity that smooth synthesise and extend the length of the actin muscle has for protein synthesis and secretion. filaments. The fact that vascular smooth muscle has a fundamental role in mediating pressure and CONTRACTILE MYOFILAMENT flow in the vasculature is reflected in the abundance of cytoskeletal and contractile The structure of the smooth muscle acto­ proteins expressed. myosin array is similar to striated muscle with several important differences: CYTOSKELETON 1. there is no troponin complex in smooth As with all eukaryotic cells the cytoskeleton is muscle comprised of a network of many and various 2. contraction is regulated by Ca2+ filamentous proteins, often formed by the calmodulin-dependent myosin light polymerization of monomeric subunits. chain kinase (MLCK) mediated For example, monomers of alpha and beta phosphorylation of the regulatory light tubulin self assemble into microtubules chains of myosin, which enables actin Vascular Smooth Muscle Structure and Function 15

myosin interaction and cross bridge responsible for the Ca2+ calmodulin mediated

cycling phosphorylation of LC20 is actin associated 3. in the absence of Ca2+ and calmodulin while MLCP which removes the phosphoryl

(CaM), caldesmon interacts with groups from LC20 is associated with myosin. actomyosin inhibiting the activity of (Figure 2.3) myosin ATPase 4. the activity of myosin light chain FUNCTIONAL REGULATION OF phosphatase (MLCP) directly causes VASCULAR SMOOTH MUSCLE: the dephosphorylation of myosin LC 20 NEURONAL, HORMONAL, leading to relaxation RECEPTOR MEDIATED 5. the actin: myosin ratio is higher in smooth muscle averaging 15:1 in Smooth muscle from all hollow organs vascular smooth muscle in comparison including blood vessels have been somewhat to 6:1 in skeletal or cardiac muscle. artificially categorized into either single There are no intercalated disks or unit smooth muscle or multiunit smooth z-disks, however, dense bodies in smooth muscle, when in reality they should likely be muscle are thought to be analogous to considered as a combination of both types. z-disks (Figure 2.2). Nevertheless, historically, multiunit smooth muscle has been considered to be regulated There are a variety of intermediate filament primarily through autonomic sympathetic proteins but desmin and vimentin are innervations, which release neurotransmitters particularly abundant in smooth muscle. In from varicosities along the axon, rather than fact, desmin has been shown to be upregulated specifically coupling to individual cells. in several myopathies and during smooth Consequently, neurotransmitters are required muscle hypertrophy. As indicated once to diffuse anywhere from 5-100 nm to the globular actin polymerizes into filaments adjacent smooth muscle membrane in order they coil to form mature filamentous actin to activate their receptors. The activation that then combines with tropomyosin to of sympathetic nerves therefore causes form a large actin-tropomyosin filament membrane depolarization and activation of which together is arranged in side polar voltage dependent ion channels, the most arrays with myosin II filaments (Figure 2.1). prominent of which are the clinically relevant The myosin II thick filaments are composed voltage operated Ca2+ channels (VOCC) of of two 200kDa heavy chains, two 17kDa the Cav1.2 family, also known as the long light chains and two phosphorylatable acting L-type Ca2+ channels. Due to the regulatory myosin light chains (LC20). The mechanism of membrane depolarization, this two heavy chains coil together forming a form of cellular activation has been termed 155nm rod, while the globular head contains electromechanical coupling. In contrast, the motor domain consisting of light chains single unit smooth muscles have very little and Mg2+ ATPase activity and the actin innervation and are primarily activated binding domain. The myosin is arranged in by autocrine and paracrine hormones, an anti parallel array that enables the myosin including noradrenalin, adrenalin, and motors, on the heads of myosin molecules, angiotensin II, all of which function through to draw actin polymers along its length and G-protein coupled membrane receptors. effect shortening of the cell, so-called cross Receptor acti­vation either triggers sarcoplasmic bridge cycling (Figure 2.2). MLCK, which is reticulum-mediated Ca2+ release or membrane 16 Mechanisms of Vascular Disease

Figure 2.2: Illustrates the patterned array of actin and myosin in smooth muscle in both cross section and the longitudinal axis. Following phosphorylation of the light chains of myosin, actin and myosin interact followed by the synchronous sliding of actin across the myosin. The movement of actin filaments toward the center of the cell is driven by the Mg2+ ATPase activity in the myosin heads and results in cell shortening or development of tension.

Figure 2.3: Illustrates the major pathways by which Ca2+ enters the cytosol, areas highlighted in blue indicate mechanisms by which Ca2+ exits that cell. Ca2+ entry activates Ca2+ CaM-dependent myosin light chain kinase leading to phosphorylation of myosin, leading to actin myosin interaction and contraction. Myosin phosphatase dephosphorylates myosin uncoupling actin-myosin favouring vasorelaxation. Various G-protein coupled receptors are capable of activating PKC/CPI-17 or RhoA/Rho kinases pathways which are capable of inhibiting myosin phosphatase further favouring vasoconstriction. Vascular Smooth Muscle Structure and Function 17 depolarization through the activation of relationship is considerably more variable ion channels which may include VOCC. than that for skeletal or cardiac muscle, but Consequently this form of activation has appears to be directly related to the degree been termed pharmacomechanical coupling. of phosphorylation of the regulatory light Experimental evidence also exists to suggest chains of myosin. The broader range of that like striated muscle, extracellular Ca2+ optimal resting length amongst smooth entry in smooth muscle can also activate SR muscle may reflect the dynamic changes in Ca2+ release into the cytosol, so called Ca2+ load that exist within the vasculature and of induced Ca2+ release, although this appears the high actin:myosin ratio in smooth muscle to be a less common mechanism of Ca2+ relative to striated muscle. Interestingly, at entry. Once activated, single unit smooth the onset of stretch or pressurization smooth muscle cells tends to contract in synchrony muscle responds via activation of stretch with neighbouring smooth cells, which are receptors (TREK and TRAK) that induce coupled through gap junctions. Gap junctions Ca2+ entry and consequent smooth muscle are composed of 6 connexin proteins, which shortening, which directly offsets increased are transmembrane spanning proteins which vascular wall stress. This is the important assemble to form a barrel-shaped connexon mechanism governing the phenomenon of or hemichannel in the plasma membrane. autoregulation. It is important to note that When two hemichannels from adjacent although gastrointestinal smooth muscle cells assemble they form a functional gap appears relatively unaffected by significant junction that enables the movement of ions stretch, more that 25% stretch often destroys (electrical coupling) and small molecules the contractile properties of vascular smooth between adjacent cells (Figure 2.1). Evidence muscle. indicates that at least some of the vascular smooth muscle cells in most vascular beds MYOFILAMENT BASIS OF are electrically coupled via gap junctions and SMOOTH MUSCLE may even be coupled to the endothelium in CONTRACTION AND a similar manner. RELAXATION Motility studies using isolated actin and SMOOTH MUSCLE FUNCTION myosin proteins have identified that the duty As with other muscle types smooth muscle cycle of the myosin head power stroke is functions best when at its optimal resting 7-11 nm. Perhaps more important than the length L0, which provides the ideal balance stroke length of the myosin is the activity of of actin-myosin interaction and muscle the myosin ATPase, which along with Ca2+/ shortening. Vascular smooth muscle cells CaM and the activation state of myosin that are stretched beyond L0 have less than light chain kinase and myosin light chain optimal overlap of actomyosin crossbridges phosphatase, determines the extent and the and thus are unable to maintain or generate rate of contraction of the vascular smooth maximum force. In contrast, smooth muscle (Figure 2.3). Smooth muscle myosin muscle that is over shortened experiences ATPase hydrolyses ATP at a rate of ~0.16 increased internal resistance due to internal moles ATP/mol myosin/second, which is friction generated from having too many several orders of magnitude slower than slowly cycling cross bridges. However, in the skeletal muscle myosin ATPase which smooth muscle the optimal length tension hydrolyses ~10-20 moles ATP/mol myosin/ 18 Mechanisms of Vascular Disease second. In part the slower ATPase rate of vasodilatation. However, myosin associated, the myosin head accounts for the vastly myosin light chain phosphatase (MLCP), slower contraction rates of vascular smooth is responsible for the dephosphorylation muscle compared with striated muscles. of myosin LC20 and the consequent loss In addition, there are a variety of different of smooth muscle acto-myosin interaction isoforms of smooth muscle myosin II which and the attenuation of cross bridge cycling when differentially expressed will increase (Figure 2.3). It is important to recognize that, or decrease the maximum rate of smooth simple removal of extracellular Ca2+ only muscle contraction. For example, so called stops the phosphorylation of LC20 and does foetal isoforms of smooth muscle myosin II not provide an explanation for subsequent have a slower rate of contraction. In addition, smooth muscle relaxation since the LC20 these “foetal” isoforms have been shown to be remains phosphorylated. This also partially upregulated during extended hypoxia, and explains why Ca2+ channel blockers are less during phenotypic remodelling of smooth effective in attenuating pre-existing vascular muscle from a contractile to synthetic or spasm as opposed to preventing spasm. proliferative phenotype.

ION CHANNELS IMPORTANT IN Smooth muscle contraction and THE REGULATION OF SMOOTH relaxation MUSCLE FUNCTION As mentioned, unlike cardiac and skeletal Regulation of cellular Ca2+ muscle, smooth muscle does not contain troponin and therefore is not subject to There are vast arrays of ion channels, troponin mediated regulation of contraction. pumps, transporters and exchangers that are Smooth muscle contraction makes use important in regulating ionic balance and of another Ca2+ binding protein called smooth muscle membrane potential. Perhaps calmodulin (CaM), which when bound the best know are the electrogenic 3Na+/2K+ with Ca2+ mediates the activation of the ATPase and the voltage gated L-type Ca2+ actin bound myofilament enzyme, myosin channels but includes: Na+/Ca2+ exchangers, light chain kinase (MLCK), which in turn plasma membrane Ca2+ ATPases (PMCA), phosphorylates the regulatory light chains which provide routes to extrude Ca2+ from of myosin (LC20). Phosphorylation of the the cytosol into the extracellular space, 2+ myosin LC20 is a critical step in smooth muscle whereas the sarcoplasmic reticulum Ca contraction which causes a conformational ATPases (SERCA) are important in removing change in the myosin head enabling the Ca2+ from the cytosol back into the SR. In interaction of myosin with actin, cross bridge contrast, when the SR becomes depleted of cycling, and contraction. Removal of cytosolic Ca2+, Ca2+ sensor proteins in the SR termed Ca2+ occurs through the activation of energy stromal interacting molecule 1 (STIM1) dependent plasma membrane Ca2+ ATPases translocate to the plasma membrane and (PMCA), Na+/Ca2+ exchangers and sarco/ activate an ion channel called Orai1 which endoplasmic reticulum CaATPases (SERCA) enables refilling of SR Ca2+ stores. In addition, (Figure 2.3). However, since MLCK- a great deal of recent research has focused mediated phosphorylation of the serine 19 on the non-selective cation channels of the of myosin LC20 generates a covalent bond, transmembrane receptor potential canonical simply removing Ca2+ does not directly cause (TRPC) family that are thought be involved Vascular Smooth Muscle Structure and Function 19 in regulating Na+ and Ca2+ entry. Finally a variety of non-selective cation channels have series of potassium channels are involved in the capacity to conduct a variety of ions either re or hyperpolarisation of the plasma including Ca2+ and Na+ into the smooth membrane and thereby have therapeutic muscle cell but due to their low conductance potential in limiting extracellular Ca2+ entry are currently thought to be more important through voltage operated Ca2+ channels and in regulating membrane potential and thereby limiting vasoconstriction. subsequent activation of plasma membrane VDCC (Figure 2.3). Sources of cytosolic Ca2+ entry Potassium channels Within the smooth muscle cell, Ca2+ enters the cytosol from the extracellular space The insulin-dependent electrogenic 3Na+/ or from the intracellular endoplasmic 2K+ ATPase is important in establishing reticulum, which in muscle cells is termed the resting membrane potential (EM) of the the sarcoplasmic reticulum (SR). Within vascular smooth muscle cell. However, muscle the sarcoplasmic reticulum has the activation states of several types of K+ become variously modified to affect Ca2+ channels in smooth muscle are also important release into the cytoplasm. Typically agents in effecting membrane depolarization and that activate the ryanodyne receptor such as hyperpolarisation and consequent smooth caffeine or phospholipase C (PLC) derived muscle contraction and relaxation, respectively. inositol 1, 4, 5 tris phosphate (IP3) which The inward rectifier KIR channels become activates the IP3 receptors (which are ion activated when the membrane becomes channels) in the SR cause Ca2+ to be released hyper­polarized and beyond the equilibrium 2+ into the cytosol. Ca entering the smooth potential for potassium (EK) they transport muscle cell from the extracellular space does more K+ ions from the extracellular space into so through non-selective cation channels or the cell thereby offsetting or rectifying the selective Ca2+ channels, which may or may hyperpolarizing stimulus. However, there are not be gated by voltage. To date the most few if any physiological conditions in which 2+ important source of extracellular Ca entry EM is more negative than EK, consequently, in vascular smooth muscle is mediated by the even the KIR channels conduct a small outward voltage dependent Ca2+ channels (VDCC). hyperpolarizing K+ current, and therefore The primary VDCC are the long lasting Ca2+ along with the 3Na+/2K+ ATPase may be channel, so called L-type or Cav1.2 channels, important in mediating smooth muscle tone. which are the clinical targets of the L-type The KV family of potassium channels as the channel blockers the dihydropryidines, name suggests are activated by depolarization phenylalkamines, benzothiazapenes. More and thus are thought to be an important recent evidence indicates that a second class control mechanism to hyperpolarize the of VDCC, the transient or T-type Ca2+ smooth muscle cell following neural or channels also known as the Cav3.X family hormonal-mediated depolarization. Agonists may be important in mediating Ca2+ entry in including histamine acting through the the microvasculature. As the name suggests H1 receptor have been shown to block the

VDCC are activated by a depolarization 4-aminopyridine sensitive KV channels in of the plasma membrane, which increases coronary arteries. 2+ the open probability and overall Ca Physiologically KATP channels are activated conductance into the cell. In addition, a by agents including, adenosine, calcitonin gene 20 Mechanisms of Vascular Disease

regulated peptide (CGRP) and vasoactive endothelin-1, serotonin and thromboxane A2. intestinal peptide (VIP). The activation of Many GPCRs exhibit divergent subcellular

KATP channels and hyperpolarization medi­ signalling mechanisms and there is increasing ated vasodilatation is thought to be due in evidence for diversity of subcellular signalling part to activation of adenylyl cyclase and amongst vascular beds (Figure 2.3). For subsequent cAMP dependent activation of example, angiotensin II can be generated protein kinase A. More recent evidence has both locally within smooth muscle cells and also indicated that KATP channels become systemically through the renin angiotensin activated in a protein kinase C-dependent system (RAS). In smooth muscle the manner. However, perhaps more important is type I AngII receptors are prototypical the fact that cytosolic ATP and ADP function G-protein coupled receptors which couple to close and open KATP channels, respectively. through Gq11. Similarly endothelin-1 can This explains part of the mechanism be generated locally via endothelial cells, underlying the finding that vasculature in inflammatory cells or renal sources. Like ischemic tissue, containing high ADP: ATP Ang II, endothelin-1 makes use of Gq11 in levels extrude K+ in an effort to hyperpolarize smooth muscle to activate PLC, releasing the membrane and effect vasodilatation. diacylglycerol (DAG) activating non selective Both experimentally and clinically the cation channels which facilitates membrane so-called vasodilatory K+ channel openers depolarization and subsequent extracellular including pinacidil, cromakalim, diazoxide, Ca2+ entry through VGCC. In addition, and minoxidil activate KATP channels. the activation of PLC generates IP3 causing Interestingly the antidiabetic sulfonylurea SR-mediated Ca2+ release. DAG can also drugs, including glibenclamide actually activate PKC leading to the phosphorylation inhibit KATP channels, enabling membrane of CPI-17 which specifically inhibits myosin depolarization and activation of VOCC in phosphatase, favouring phosphorylation of pancreatic beta cells enabling insulin release. the LC20 of myosin and vasoconstriction Consequently overuse of sulfonourea drugs (Figure 2.3). However, in contrast to AngII, may therefore interfere with the efficacy endothelin-1 also activates G13 coupled of vascular K+ channel openers or directly receptors activating the RhoA/ Rho associated contribute to vasoconstriction. kinase which leads to a direct inhibitory The large conductance Ca2+ activated phosphorylation of myosin phosphatase, potassium channels (BKCa) channels are also again favouring contraction (Figure 2.3). voltage sensitive but the smaller conductance smK channels are less sensitive to voltage. Ca ENDOTHELIAL REGULATION This family of K+ channels are activated by OF SMOOTH MUSCLE increases in cytosolic Ca2+ which occurs after VASODILATATION agonist stimulation, membrane depolarization or stretch/pressure-dependent activation of Nitric oxide is a potent vasodilator generated Ca2+ entry and therefore is involved in that in the endothelium which has many and arm of the myogenic mechanism involved in varied effects in the vasculature including hyperpolarization. attenuating: platelet adhesion and aggre­ G protein coupled receptors (GPCRs) gation, cellular proliferation, and vaso­ transduce­ signals from the autonomic nervous constriction. A common theme underlying system and hormonal stimuli including brady­ the influence of nitric oxide is activation kinin, noradrenalin, adrenaline, angiotensin II, of guanylyl cyclase, formation of cGMP, Vascular Smooth Muscle Structure and Function 21 activation of protein kinase G and con­ density of the Golgi apparatus. So called sequent activation of K+ channels effect­ synthetic vascular smooth muscle cells are ing K+ removal from the cell leading to therefore able to undergo very active protein membrane hyperpolarization and con­ and DNA synthesis, cell division, and in sequent inactivation of VDCC favoring pathological settings are capable of taking up low intracellular Ca2+ and vasorelaxation. large amounts of oxidized and nonoxidized Cyclooxygenase activation in endothelial lipids which can contribute to lipid loading of cells also leads to generation of prostaglandin vascular smooth muscle cells and the formation

PGI2 which leads to receptor mediated of so-called foam cells in the vascular wall. As activation of adenylyl cyclase, generation of the name foam cell suggests, under microscopic cAMP, subsequent activation of PKA and examination lipid laden smooth muscle cells inhibition of K+ channels (Figure 2.4). appear much like foam. Synthetic vascular smooth muscle cells also secrete, external to the cell, a great deal of extracellular matrix SMOOTH MUSCLE including the proteins; collagen I, III, IV, PROLIFERATION AND VASCULAR and the proteoglycans, perlican, hyaluronan, REMODELLING laminin. Proliferative smooth muscle cells also In the normal adult vascular wall most secrete or associate with the membrane surface vascular smooth muscle cells subserve a several, matrix metalloproteinases (MMPs) contractile function to directly modulate and their corres­ponding tissue inhibitors of vaso­constriction and vasodilatation. However, matrix metalloproteases (TIMPs) to enable during development, following injury or in correct repair and remodelling of growing or the presence of growth factors and mitogens, damaged vessels. Evidence exists that a chronic including inflammatory cytokines and excess of inflammatory cytokines and growth oxidized lipids, vascular smooth muscle can factors can cause dysregulation of both undergo phenotypic modulation. Vascular MMPs and TIMPs which can contribute smooth muscle phenotypic modulation to inappropriate vascular remodelling. This involves a partial down regulation of the remodelling plays a significant role in the proteins that activate the contractile apparatus progression of vascular stenosis, restenosis in favour of the synthetic and proliferative following mechanical interventions, the cellular machinery i.e., the cell increases progression of unstable atheroma, and the abundance of; endoplasmic reticulum, aneurysmal dissection and rupture. ribosomes for protein synthesis and the

Figure 2.4: outlines the major influences of prostaglandin I2 and nitric oxide (NO) in regulating the activation state of various K+ channels leading to hyperpolarization of smooth muscle cells and vasodilatation. 22 Mechanisms of Vascular Disease

At this point it is worth noting that of myosin phosphatase are also important proliferative smooth muscle cells have an targets for future therapeutic development. attenuated response to vasoconstrictors and vasodilators, probably due to the down REFERENCES regulation of the contractile apparatus and certain elements of the subcellular signalling Biochemistry of Smooth Muscle machinery that is involved in vasoconstriction. contraction: Ed M Barany: 1996 However, many of the ligands that normally Academic Press Inc. lead to vasoconstriction, for example, Hill MA, Davis MJ, Meininger GA, noradrenalin, angiotensin II and endothelin Potocnik SJ & Murphy TV (2006). also function to promote smooth muscle Arteriolar myogenic signalling proliferation both in the context of cellular mechanisms: Implications for local hypertrophy and hyperplasia. Platelet derived vascular function. Clin Hemorheol growth factor (PDGF), is a potent smooth Microcirc 34, 67–79. muscle cell mitogen and growth stimulant Morgan KG & Gangopadhyay SG (2001). and contributes to normal vessel repair while Invited review: Cross-bridge regulation chronically elevated levels, for example, by thin filament-associated proteins. generated from unstable thrombus, can J Appl Physiol 91, 953–962. contribute to proliferative vascular disorders. Somlyo, A. P. and Somlyo, A. V. (2003) Interestingly nitric oxide, in addition to Ca2+sensitivity of smooth muscle and functioning as a potent vasodilator also nonmuscle myosin II: modulated limits smooth muscle hyperplasia and hyper­ by G proteins, kinases and myosin trophy, probably by limiting intracellular phosphatase. Physiol. Rev 83, Ca2+ and associated Ca2+dependent vascular 1325–1358 proliferation. Dimopoulos S, Semba S, Kitazawa K, Eto M, Kitazawa T (2007). Ca2+- dependent rapid Ca2+sensitization of SUMMARY contraction in arterial smooth muscle. It is clear from the preceding that there is a Circ Res 100, 121–129. dynamic interplay between cellular Ca2+ entry WierWG & Morgan KG (2003). from the extracellular space mediated by α1-Adrenergic signaling mechanisms membrane depolarization and the activation in contraction of resistance arteries. of voltage dependent Ca2+ channels. Rev Physiol Biochem Pharmacol 150, Extracellular Ca2+ entry can be offset by the 91–139. activation of K+ channels through either Wilson, D. P., Sutherland, C. and endothelial nitric oxide-cGMP/PKG- or Walsh, M. P. (2002) Ca2+activation of PGI2-cAMP/PKA-dependent mechanisms, smooth muscle contraction. Evidence both of which function to limit smooth for the involvement of calmodulin muscle contraction and proliferation. that is bound to the Triton insoluble However, the simple fact that L-type Ca2+ fraction even in the absence of Ca2+. channel blockers and nitric oxide treatment J. Biol. Chem 277, 2186–2192 are limited in their ability to effectively Wilson DP, Susnjar M, Kiss E, manage several disorders of hypercontractility Sutherland C &Walsh MP (2005). suggests that the additional mechanisms Thromboxane A2-induced contraction including; SR Ca2+ release and regulation of rat caudal arterial smooth muscle Vascular Smooth Muscle Structure and Function 23 involves activation of Ca2+ entry and MYPT1 at Thr-855, but not Thr-697. Ca2+sensitization: Rho-associated Biochem J 389, 763–774. kinase-mediated phosphorylation of