Regulation of Catecholamine Release from the Adrenal Medulla Under the Physiological Stress Response
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REGULATION OF CATECHOLAMINE RELEASE FROM THE ADRENAL MEDULLA UNDER THE PHYSIOLOGICAL STRESS RESPONSE BY BARBARA A. KURI Submitted in partial fulfillment of the requirements For the degree of Doctor of Philosophy Dissertation Adviser: Dr. Corey Smith Department of Physiology and Biophysics CASE WESTERN RESERVE UNIVERSITY January 2010 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the thesis/dissertation of ______________________________________________________ candidate for the ________________________________degree *. (signed)_______________________________________________ (chair of the committee) ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ (date) _______________________ *We also certify that written approval has been obtained for any proprietary material contained therein. TABLE OF CONTENTS Table of Contents ii List of Figures iv Acknowledgements vi List of Abbreviations vii Abstract ix Chapter 1: Adrenal Medulla Contribution to Release of Catecholamine Under Stress 1.1 The Adrenal Gland 2 1.2 Stress 7 1.3 Regulation of Catecholamine Release 11 1.4 Cellular Mechanisms Regulating Exocytosis in Chromaffin 18 Cells 1.5 Methods Used to Study Catecholamine Release in Adrenal 22 Chromaffin Cells 1.6 Summary Statement of Thesis Project 32 Chapter 2: Increased Secretory Capacity of Mouse Adrenal Chromaffin Cells by Chronic Intermittent Hypoxia: A Role for Protein Kinase C 2.1 Introduction 36 2.2 Materials and Methods 38 2.3 Results 42 2.4 Discussion 53 ii Chapter 3: PACAP Regulates Immediate Catecholamine Release from Adrenal Chromaffin Cells in an Activity Dependent Manner through a Protein Kinase C Dependent Pathway 3.1 Introduction 57 3.2 Materials and Methods 61 3.3 Results 67 3.4 Discussion 91 Chapter 4: Discussion and Future Directions 4.1 PKC 95 4.2 Sodium Calcium Exchange 102 4.3 T-type Calcium Channels 112 2+ 4.4 IP3 Release of Ca from Internal Stores 112 4.5 Epac 113 4.6 Overall Conclusion 114 4.7 Future Directions 116 Work Cited 123 iii LIST OF FIGURES Figure 1.1 The biosynthesis of catecholamine 6 Figure 1.2 PACAP is an activator of adenylate cyclase and a potent 16 secretagogue Figure 1.3 Capacitance recordings provide a high resolution measure of 26 quantal catecholamine release Figure 1.4 Carbon fiber amperometry quantitatively measures 29 catecholamine release Figure 2.1 Intermittent hypoxia leads to an increased RRP 44 Figure 2.2 Continuous hypoxia does not lead to an increased RRP 46 Figure 2.3 Superoxide dismutase mimetic blocks the CIH-dependent 48 increase in RRP Figure 2.4 The CIH-d4-mediated increase in the RRP is due to an 51 increased PKC phosphorylation Figure 3.1 PACAP stimulation of adrenal chromaffin cells results in an 70 immediate and robust release of catecholamine Figure 3.2 PACAP evokes catecholamine release under elevated 73 sympathetic input Figure 3.3 PACAP-dependent secretion is dependent on extracellular 77 Ca2+ and blocked by PLC and PKC inhibition Figure 3.4 PACAP-dependent Ca2+ signals are dependent on 78 extracellular Ca2+ and blocked by PLC and PKC inhibition Figure 3.5 Ni2+ -sensitive Ca2+ currents in adrenal tissue slices 82 iv Figure 3.6 PACAP-dependent catecholamine secretion is blocked by 85 benzamil, voltage clamp and extracellular Ni2+ Figure 3.7 PACAP-dependent Ca2+ signals are blocked by benzamil, 86 voltage clamp and extracellular Ni2+ Figure 3.8 Epac stimulation elicits nickel-sensitive catecholamine 88 secretion Figure 3.9 Summary diagram for the proposed PACAP signaling 90 pathway Figure 4.1 Phosphorylated Protein Kinase Cδ is found in mouse 99 adrenal medullary tissue Figure 4.2 PACAP knockout mice fail to elicit a secretory response 120 under burst-mode stress stimulation Figure 4.3 PACAP knockout mice express the PACR-1 receptor 121 Figure 4.4 PACAP knockout mice respond to exogenous PACAP 122 v Acknowledgements I would like to thank, first and foremost, my advisor Dr. Corey Smith for his support both professionally and personally. I would like to thank my committee members; Dr Cathleen Carlin, Dr. Carole Liedtke, Dr. Andrea Romani, Dr. Steve Jones, and Dr. Thomas Dick for their guidance and support. Additionally, I would like to thank my lab-mates Dr. Shyue-An Chan, Dr. Bryan Doreian, and Jackie Hill for their support, technical assistance, personal support and friendship. Finally, I would like to thank my family and friends for their unending support. vi List of Abbreviations A Adrenaline Ach Acetylcholine ACTH Adrenocorticotropic Hormone ANOVA Analysis of Variance Cm Capacitance CA Catecholamine CaM Kinase Calmodulin Dependent Protein Kinase cAMP Cyclic Adenosine Monophosphoate CH Continuous Hypoxia CIH Chronic Intermittent Hypoxia DAG Diacylglycerol DBH Dopamine P-hydroxylase Epac Exchange Proteins Activated Directly by cAMP FURA-2 AM Fura-2-acetoxymethyl ester GIRK G-protein Coupled Inward Rectifying K+ Channel GPCR G-protein Coupled Receptor HVA High Voltage Activated Ca2+ Channels IHC Immunihistochemistry IP3 Inositol1,4,5 trisphosphate LVA Low Voltage Activated Ca2+ Channels MnTMPyP manganese (III) tetrakis (1-methyl-4-pyridyl) porphyrin pentachloride NA Noradrenaline vii nAChR Nicotinic Acetylcholine Receptor NCX Sodium Calcium Exchanger PACAP Pituitary Adenylate Cyclase Activating Peptide PACR-1 PACAP Receptor- 1 PFA Paraformaldehyde PKA Protein Kinase A PKC Protein Kinase C PLC Phospholipase C PMA phorbol 12-myristate 13-acetate PNMT Phenylethanolamine N-methyltransferase ROS Reactive Oxygen Species RRP Readily Releasable Pool TBARS Thiobarbituric Acid Reactive Substances TRP Transient Receptor Potential Cation Channels TSH Thyroid Stimulating hormone TTX Tetrodotoxin VIP Vasointestinal peptide XIP Endogenous Exchanger Inhibitory Region viii Regulation of Catecholamine Release from the Adrenal Medulla Under the Physiological Stress Response Abstract by BARBARA A. KURI Release of catecholamine from the adrenal glands is a highly regulated process. The chromaffin cells of the adrenal medulla are the parenchymal cells of the adrenal gland and are capable of releasing catecholamine (adrenaline and noradrenaline) and neuroactive peptides into the circulation. Under autonomic nervous control, the innervating splanchnic nerve directs the release of catecholamine. In this study, we show how chronic intermittent hypoxia (CIH), a common form of metabolic stress, affects the release of catecholamine from the adrenal chromaffin cells, in situ. Using electrophysiological capacitance recording techniques we show that exposure to CIH results in an increase of the amount of catecholamine available for release, upon a given stimulus, through the recruitment of catecholamine containing granules to the readily releasable pool. We show that this is possible through the generation of reactive oxygen species (ROS) and subsequent activation of protein kinase C (PKC). To further address the regulation of catecholamine release under sympathetic stimulation we developed a bipolar stimulation protocol that mimics stimulation frequencies ix at rest and under burst mode stress firing. Using an in situ adrenal gland slice preparation we show that there is an activity dependent regulation of catecholamine release involving pituitary adenylate cyclase activating peptide (PACAP) which is released from the splanchnic nerve under conditions mimicking the burst mode stress firing. We show that PACAP acts through a novel mechanistic pathway that is independent of the conventional sympathetic cholinergic pathway. This characteristic of PACAP makes it an ideal neurotransmitter under high intensity, burst mode sympathetic firing, in that it does not desensitize like the cholinergic pathway. We show that PACAP acts through a G-protein coupled receptor to activate phospholipase C (PLC) which in turn activates PKC. Activation of PKC plays a role in increasing the activity of the sodium calcium exchanger (NCX) in the forward direction to depolarize the cell membrane to potentials that increase the open probability of a Ni2+ sensitive, low voltage activated Ca2+ channel. It is the influx of Ca2+ through this channel to generate the Ca2+ dependent release of catecholamine. x Chapter 1: Adrenal Medulla Contribution to Release of Catecholamine Under Stress 1.1 The Adrenal Gland The adrenal gland is the primary peripheral endocrine gland in the sympathetic stress response. The parenchymal cells of the adrenal medulla are the chromaffin cells [1]. Belonging to the paraneuron family, chromaffin cells of the adrenal medulla are of neural crest origin, capable of eliciting action potentials, and secrete catecholamines under appropriate stimulation [1-3]. Formed during the early stages of development, there are two separate precursors migrate suprarenally and eventually differentiate to make up the adrenal gland. The outer layer of the adrenal gland is derived from mesoderm tissue and becomes the adrenal cortex [4]. The adrenal cortical cells, are not excitable, are not of neural crest origin but, are secretory and responsible for the production and release of glucocorticoids: aldosterone, cortisol and androgens [4]. The cortex comprises approximately 90% of the total adrenal gland mass. The remaining 10% of the adrenal gland is comprised of the fore mentioned chromaffin cells. The adrenal medulla is derived of sympathetic ganglion cells from the neural crest during development. After