(-)-Epicatechin-3-gallate, a Green Tea Polyphenol Is a Potent Agent Against UVB-induced Damage in HaCaT Keratinocytes

Abstract

(-)-Epicatechin-3-gallate (ECG) is a polyphenolic compound similar to (-)-epigallocatechin-3-gallate (EGCG) which is abundant in green tea. Numerous workers have proposed that EGCG protects epidermal cells against UVB-induced damage. However, little has been known about whether ECG protects keratinocytes against UVB-induced damage. We decided to investigate the protective effects and underlying mechanisms of ECG on UVB-induced damage. Cell viability was determined by the MTT assay. Activation of ERK1/2, p38 and JNK was analyzed by Western blotting. Intracellular H₂O₂ production and DNA content was analyzed by flow cytometry. Lipid peroxidation was assayed by colorimetry. In our study, we found that ECG dose-dependently attenuated UVB-induced keratinocyte death. Moreover, ECG markedly inhibited UVB-induced cell membrane lipid peroxidation and H₂O₂ generation in keratinocytes, suggesting that ECG can act as a free radical scavenger when keratinocytes were photodamaged. In parallel, H₂O₂-induced the activation of ERK1/2, p38 and JNK in keratinocytes could be inhibited by ECG. UVB-induced pre-G1 arrest leading to apoptotic changes of keratinocytes were blocked by ECG. Taken together, we provide here evidence that ECG protects keratinocytes from UVB-induced photodamage and H₂O₂-induced oxidative stress, possibly through inhibition of the activation of ERK1/2, p38 and JNK and/or scavenging of free radicals.