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Contents

xi

8.3

Adipokines

136

8.3.1

Leptin

137

8.3.2

Adiponectin

139

8.3.3

Resistin

139

8.3.4

Visfatin

140

8.3.5

Plasminogen Activator Inhibitor

140

8.3.6

Interleukin-6

141

8.3.7

Transforming Growth Factor-b1

141

8.4

Conclusions

142

References

142

Chapter 9 Astrocyte Signaling in Neurological Disorders

149

A. R. Jayakumar and M. D. Norenberg

9.1

Introduction

149

9.1.1

Structure and Function of Astrocytes

149

9.1.2

Responses of Astrocytes to Injury

151

9.2 Intracellular Signaling System in Reactive Astrocytes

155

9.2.1

Oxidative/Nitrosative Stress (ONS)

155

9.2.2

Protein Kinase C (PKC)

156

9.2.3

Phosphatidylinositol 3-Kinases (PI3K)

156

9.2.4

Mitogen-activated Protein Kinases (MAPKs)

156

9.2.5

Signal Transducer and Activator

of Transcription 3 (STAT3)

157

9.2.6

Nuclear Factor Kappa B (NF-kB)

158

9.3 Signaling Systems in Astrocyte Swelling

158

9.3.1

Oxidative/Nitrosative Stress (ONS)

159

9.3.2

Cytokines

159

Signaling Kinases

160

9.3.3

Protein Kinase C (PKC)

160

9.3.4

Phosphatidylinositol 3-Kinase (PI3K)

160

9.3.5

Protein Kinase G (PKG)

160

9.3.6

Mitogen-activated Protein Kinases (MAPKs)

161

Transcription Factors

161

9.3.7

Signal Transducer and Activator

of Transcription 3 (STAT3)

161

9.3.8

Nuclear Factor Kappa B (NF-kB)

161

9.3.9

p53

162

Swelling E ectors

162

9.3.10

Ion Channels/Transporters/Exchangers

162

9.3.11

Aquaporin-4 (AQP-4)

163

9.4

Conclusions and Perspectives

163

Acknowledgements

165

References

165


xii

Contents

Chapter 10 DNA, Nuclear Cell Signaling and Neurodegeneration

175

James D. Adams, Jr., Ph.D.

10.1

Adipokines, Toxic Lipids and the Aging Brain

175

10.1.1 Toxic Lifestyles, Adipokines and Toxic Lipids

176

10.1.2 Ceramide Toxicity in the Brain

177

10.1.3 Endocannabinoids, Ceramide and Amyloidb

177

10.2

The Blood-Brain Barrier as a Target

for Neurodegenerative Conditions

178

10.2.1 Visfatin and the Blood-Brain Barrier

178

10.3

Oxygen Radicals, Hydrogen Peroxide and Cell Death

179

10.4

Gene Transcription and DNA Damage

183

10.5

Conclusions

184

References

184

Chapter 11 G Protein-Coupled Receptors: Conformational

‘‘Gatekeepers’’ of Transmembrane Signal Transduction

and Diversification

188

Ravinder Abrol and William A. Goddard III, FRSC

11.1

Introduction

188

11.2

Cellular Signaling

190

11.2.1

Types of Signaling

190

11.2.2 Membrane Proteins in Signaling

191

11.3

G Protein-Coupled Receptors

192

11.3.1

Structure of GPCRs

193

11.3.2 GPCR Activation: Conformation Driven

Functional Selectivity

203

11.3.3 Functional Control of GPCRs by Ligands

217

11.3.4 Challenges in GPCR Targeted Drug Design

221

11.4

Summary and Looking Ahead

223

Acknowledgements

224

References

225

Chapter 12 Phytochemicals as Modulators of Signaling in Inflammation

230

Lori Klaidman

12.1

Introduction

230

12.2

Overview of the Inflammatory Cascade

231

12.3

Overview of NF-kB

232

12.4

PPARg and LXRs Regulate NF-kB

233

12.5

Natural Products and Phytochemical

Inhibitors of NF-kB

235

12.5.1

Anthocyanins

235

12.5.2

Gallates

236


Contents

xiii

12.5.3

Quercetin

237

12.5.4

Isoflavones

237

12.5.5

Piperine

238

12.5.6

Gingerol

239

12.5.7

Curcumin

239

12.5.8

Guggulsterone

240

12.6

Agonists of PPARg that Reciprocally Inhibit NF-kB

241

12.6.1

Phytanic Acid

241

12.6.2

Dehydroabietic Acid

241

12.6.3

Geraniol

242

12.7

Agonists of LXR that Reciprocally Inhibit NF-kB

242

12.7.1

Stigmasterol

242

12.7.2

b-Sitosterol

243

12.7.3

Ergosterol

243

12.8

Conclusion

243

References

244

Chapter 13 Intracellular Signaling Pathways in Parkinson’s Disease

247

Monica Sanchez Contreras and Fernando Cardozo-Pelaez

13.1

Introduction

247

13.2

Selective Dopaminergic Neuronal Death

248

13.3

Signaling Pathways Involved in Selective

Dopaminergic Neuronal Death

254

13.3.1 Initiators and Signaling Molecules

254

13.3.2 Signal Transducers, Intracellular Messengers

and Upstream Elements

261

13.3.3

Intracellular Signaling Cascades

263

13.3.4 Potentially Involved Intracellular Signaling

Components

266

13.3.5 E ector Pathways and Final E ects

267

13.4

Conclusions

270

References

271

Subject Index

283



CHAPTER 1

Extracellular and Intracellular Signaling – a New Approach to Diseases and Treatments

JAMES DAVID ADAMS, JR.,*a ERIC J. LIENa AND KEITH PARKERb

a Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, 1985 Zonal Avenue,

Los Angeles, CA, USA 90089; b Department of Pharmaceutical Sciences (MPH102) BMED, School of Pharmacy and Allied Health Sciences, Skaggs Building, Missoula, MT, USA 59812-1552

1.1 Introduction

1.1.1Linear Model of Drug Receptor Interactions

The body and mind depend on a variety of receptors and endogenous, extracellular ligands in order to maintain health. In the past, a simplistic, linear model of ligand receptor binding has been used with great success for drug development.

Ligand þ Receptor ! Ligand-Receptor complex ! Effect

ð1:1Þ

This model has led to a simplistic, linear model of disease where one aberrant gene produces one abnormal protein leading to the induction of one disease. It is now clear that the body does not function according to these linear models.

RSC Drug Discovery Series No. 10 Extracellular and Intracellular Signaling

Edited by James D. Adams, Jr. and Keith K. Parker r Royal Society of Chemistry 2011

Published by the Royal Society of Chemistry, www.rsc.org

1

2

Chapter 1

Instead, the body makes use of a complex interacting system of intracellular matrices, called signal transduction networks, in order to maintain health. Proper health depends on maintaining the proper balance of these intracellular signal transduction networks. Most of us are born healthy and could stay healthy, if we knew how. Many economically important diseases are not caused by single gene aberrations, but are caused by lifestyle changes that alter many genes and the balance of signal transduction networks.

1.1.2Matrix Model of Drug Receptor Interactions

fCalcium mechanismsg

fPhospholipasesg Ligand-Receptor complex fProtein kinasesg ! Effect

fNAD mechanismsg

(1.2)

The model above is intended to show that matrix division and matrix multiplication lead to drug e ects. For instance, phospholipase mechanisms liberate active lipids that may multiply the e ects of a drug receptor interaction. This is synergism. However, protein kinase mechanisms that phosphorylate proteins, may decrease, or divide, the e ects of a drug receptor interaction. This is dysynergism. For each ligand receptor interaction there may be synergism and dysynergism by many signal transduction networks (only four are shown) that are involved in processing the interaction and producing the e ect. Equation (1.2) is simplified since many receptors can exist in active and inactive states, or states of altered activity. Ligand binding may have di erent e ects depending on the state of the receptor at binding.

There are many endogenous, extracelllular ligands, made in the body, that produce e ects upon receptor binding. These extracellular ligands, such as the adipokines and the cytokines, modify the balance of normal intracellular signal transduction networks in order to maintain health or cause disease. Drugs tend to mimic these endogenous ligands, in terms of chemical structure and receptor interactions. It is likely that only a minority of the endogenous ligands are currently known. Many more will be discovered in the future. Endogenous ligands include lipoxins, prostaglandins, endocannabinoids, enkephalins, endorphins, adipokines, cytokines, hormones, neurotransmitters and many others. Many of these endogenous ligands are produced locally, act locally and have short half-lives. This makes them superior to drugs that must penetrate to the site of action and persist until the e ect is attained. Drugs are usually designed to have half-lives of about 24 hours so that patients can take them daily, or on a convenient schedule. The long residence time of drugs in the body increases the risk of toxicity.

In general, for each receptor in the body there is at least one endogenous agonist and one antagonist. Therefore, health depends on the balance of