chapter  31
18 Pages

Photoprotection by Green Tea Polyphenols

Introduction 640

Green Tea Polyphenols and Photoprotection 641

Photoprotective Effects of Green Tea Polyphenols in Skin Cancer 642

Green Tea Polyphenols and the Different Stages of Photocarcinogenesis 643

Photoprotective Effects of Green Tea Polyphenols on the Acute

UV-Induced Sunburn Response 644

Photoprotective Effects of Green Tea Polyphenols on Photoaging 645

Protective Effects of Green Tea Polyphenols in UV-Induced

Immunosuppression 646

Mechanisms of Action of Green Tea Polyphenols 647

Cellular Effects 647

Apoptosis 647

Proliferation of Keratinocytes 647

Inflammatory Cell Infiltration 647

Molecular Effects 648

DNA Damage 648

Reactive Oxygen Intermediates 648

Proteasome Activation 649

Biochemical Activities 649

Conclusions 650

Acknowledgments 651

References 651

INTRODUCTION

The relationship that humans have with sun exposure is delicately balanced

between the positive effects that this form of radiant energy provides and the

negative aspects that overexposure engenders. The benefits of sun exposure

include its positive psychological actions, the role it plays in vitamin D metab-

olism, and the value it has as a therapeutic agent in cutaneous and systemic

disease. The adverse consequences of overexposure include acute UV-induced

erythema (i.e., a sunburn), nonmelanoma skin cancer (cutaneous squamous cell

and basal cell carcinoma), melanoma, photoaging of the skin, and UV-induced

immunosuppression.