BIOCHEMICAL PHARMACOLOGY Preface (1St Edition 2012)
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MICHAEL PALMER ALICE CHAN THORSTEN DIECKMANN JOHN HONEK BIOCHEMICAL PHARMACOLOGY Preface (1st edition 2012) Those who have taken upon them to lay down the law of nature as a thing already searched out and understood, . have therein done philosophy and the sciences great injury. For as they have been successful in inducing belief, so they have been effective in quenching and stopping inquiry. Francis Bacon This book aims to explain the biochemical principles of drug action, to students of bio- chemistry and of related scientific disciplines, at the advanced undergraduate or beginning graduate level. For each drug that we discuss, we cover the biochemical concepts needed to understand its function. We explain some of the experimental methods used to investigate drugs and their receptors, along with examples of the evidence that these methods provide. Clinical and physiological aspects are outlined where this seems useful to appreciate the significance of a drug’s action. Finally, we have tried to heed Bacon’s advice and point out some of the open questions that will need to be solved by future researchers. In selecting the topics for a teaching text, one has to balance breadth and depth. We chose to forgo comprehensive coverage in favor of treating selected drugs in some more detail. Therefore, many drugs that are important in clinical medicine are not covered here. Similarly, topics from fundamental biochemistry are limited to the context required for the chosen example drugs. While such limited treatment of biochemistry may seem natural, it is important to realize that it will miss out on recent discoveries that may provide the foundations for future drugs; the biochemistry of today is the pharmacology of tomorrow. This point is well illustrated in Chapter 13, contributed by Thorsten Dieckmann, which discusses emerging applications of ribonucleic acids as drugs and drug targets. Among the other chapters, the first five are devoted to general principles of drug action. Chapters 6–12 discuss a number of mostly proven drugs, but also some experimental ones, grouped along biochemical and pathophysiological lines. Chapter 14, by Alice Chan, covers drug delivery, and chapter 15, by John Honek, discusses drug discovery. While these ii Preface topics are not strictly part of pharmacology, they provide valuable context for this subject nevertheless. The book has evolved from courses taught at the University of Waterloo that met with lively interest among our students. We envision that the book may be useful in similar course offerings at other institutions. We would love to hear from our readers and appreciate any corrections and suggestions for improvement. Update January 2017: The above preface appeared in the first edition of this book, which was published by Wiley in 2012. Wiley has since agreed to revert the rights to the book to us, and my co-authors have agreed to let me release this electronic version for free. In this initial updated version, some minor errors have been corrected, and most figures have been updated to colored versions that also appear in the accompanying slides and lecture notes. Moreover, a glossary has been added. I plan to update and maintain this online version in the future. Therefore, if you find errors or shortcomings, a message pointing them out would be appreciated. Copyright notice: This book has been made freely available, but it is not in the public domain. No part of it may be reproduced without written consent from the authors, except as follows: • You may download and/or print a copy for your personal use. • If you are an instructor and use this book in teaching your class, you may distribute electronic copies free of charge to your students. You may also distribute printed copies to them for free; or you may charge a fee, but only to cover the costs of printing, without any surcharge. • You may use individual images or short excerpts in keeping with general fair use con- siderations. Examples are inclusion of one or several figures in a thesis, scientific paper, or conference poster. In any such use, proper attribution must be made. It is not permitted to post this book on a publicly accessible web server. Exempt from this restriction are websites which can be accessed only by the students of a class that use it as teaching material. Exempt from all above restrictions are several images that have been obtained from third parties. The origin of all such figures is specified in the respective figure captions. While these figures were here used with written permission, you should contact the owners directly regarding any questions pertaining to your intended reuse. iii Acknowledgments First and foremost, I would like to thank my coauthors. I enjoyed our collaboration and discussions, and I feel that their chapters strengthen this book substantially. Jonathan Rose of John Wiley & Sons suggested the idea for this book and saw it through to the end. I am grateful for his friendly advice and for his patience when at times the pace of my progress resembled Achilles’ race with the tortoise. Alice Chan, Michael Peinecke, Eric Brefo-Mensah, Kate Wood and Bruce Reed read parts of the manuscript and gave suggestions for improvement. Mike Chong pointed out several errors that were corrected in this updated version. Finally, I thank my wife, Shenhui Lang, for the encouragement, understanding and support she showed me during this work. M. P. iv Contents 1 Introduction 1 1.1 Origin and preparation of drugs ........................... 3 1.2 Drugs and drug targets ................................. 4 1.3 Resemblance of drug molecules and physiological receptor ligands . 7 1.4 Strategies of drug discovery and development ................... 11 2 Pharmacodynamics 15 2.1 Molecular features of drug–receptor interaction . 15 2.2 Theory of drug–receptor binding ........................... 17 2.3 Dose-effect relationships in signaling cascades . 25 2.4 Potency and efficacy ................................... 28 2.5 Beneficial and toxic drug effects ........................... 28 2.6 Appendix .......................................... 30 2.7 Study questions ...................................... 35 3 Pharmacokinetics 37 3.1 Anatomical barriers to drug transport ........................ 38 3.2 Solute transport across cell membranes ....................... 40 3.3 Drug application ..................................... 49 3.4 Drug distribution ..................................... 53 3.5 Drug elimination via the kidneys ........................... 56 3.6 Quantitative experimental methods in pharmacokinetics . 64 3.7 Study questions ...................................... 65 4 Drug metabolism 67 4.1 Overview: Possible functional outcomes of drug metabolism . 68 4.2 Phase I and phase II reactions ............................. 70 4.3 Cytochrome P450 ..................................... 71 4.4 Reductive drug metabolism .............................. 74 4.5 Conjugation reactions .................................. 75 v Contents 4.6 Enzyme induction .................................... 83 4.7 Metabolism-related toxicity as a therapeutic target . 84 4.8 Study questions ...................................... 85 5 G protein-coupled receptors 86 5.1 Overview .......................................... 86 5.2 GPCR structure ...................................... 87 5.3 Structural GPCR families ................................ 88 5.4 Activation of GPCRs ................................... 89 5.5 GPCR dimerization and oligomerization ...................... 95 5.6 G proteins ......................................... 97 5.7 GPCR phosphorylation, endocytosis, and G protein-independent signaling . 101 5.8 Appendix .......................................... 102 5.9 Study questions ...................................... 106 6 Pharmacology of cell excitation 108 6.1 Ions, pumps, and channels ............................... 110 6.2 ATP-driven active ion transport ............................ 113 6.3 Voltage-gated channels and the action potential . 113 6.4 Channels controlled by intracellular ligands . 116 6.5 Transient receptor potential (TRP) channels . 118 6.6 Voltage-gated channels of nerve cells as drug targets . 118 6.7 Synaptic transmission .................................. 125 6.8 Pharmacology of individual transmitters . 134 6.9 Appendix .......................................... 152 6.10 Study questions ...................................... 159 7 Hormones 160 7.1 Hormone receptors ................................... 160 7.2 The hypothalamus and the pituitary gland . 162 7.3 Thyroid gland hormones ................................ 167 7.4 Steroid hormones .................................... 172 7.5 Endocrine control of bone mineralization . 180 7.6 Study questions ...................................... 186 8 Pharmacology of nitric oxide 187 8.1 Characterization of nitric oxide as a biological signaling molecule . 187 8.2 Nitric oxide synthase and its isoforms . 188 8.3 Biochemical mechanisms of NO signaling . 191 8.4 The biological function of iNOS ............................ 196 8.5 NO-releasing drugs .................................... 197 8.6 NOS inhibitors ...................................... 200 vi Contents 8.7 Phosphodiesterase inhibitors ............................. 201 8.8 Study questions ...................................... 201 9 Eicosanoid mediators and related drugs 202 9.1 Biosynthesis of eicosanoids .............................. 204 9.2 The cyclooxygenase reaction .............................. 205 9.3 Cyclooxygenase isoforms