Green tea polyphenol epigallocatechin-3-gallate inhibits the expression of nitric oxide synthase and generation of nitric oxide induced by ultraviolet B in HaCaT cells.
BACKGROUND
Nitic oxide (NO) has been implicated in the pathogenesis of various inflammatory diseases, including sunburn and pigmentation induced by ultraviolet irradiation. Epigallocatechin-3-gallate (EGCG) is the major effective component in green tea and can protect skin from ultraviolet-induced damage. The purpose of this study was to investigate the protective mechanisms of EGCG on inducible nitric oxide synthase (iNOS) expression and NO generation by ultraviolet B (UVB) irradiation in HaCaT cells.


METHODS
HaCaT cells were irradiated with UVB 30 mJ/cm 2 and pretreated with EGCG at varying concentrations. The iNOS mRNA was detected by reverse transcriptase polymerase chain reaction (RT-PCR) and NO production was quantified by spectrophotometric method. The expression of NF-kappaB P65 was measured by immunofluorescence cytochemistry staining.


RESULTS
The expression of iNOS mRNA and generation of NO in HaCaT cells were increased by UVB irradiation. EGCG down regulated the UVB-induced iNOS mRNA synthesis and NO generation in a dose dependent manner. The UVB-induced ctivation and translocation of NF-kappaB were also down regulated by EGCG treatment in HaCaT cells (P < 0.01).


CONCLUSIONS
Green tea derived-EGCG can inhibit and down regulate the UVB-induced activation and translocation of NF-kappaB, expression of iNOS mRNA and generation of NO respectively, indicating EGCG may play a protective role from UVB-induced skin damage.
Song
Xiu-zu
XZ
Department of Dermatology, Third Hospital of Hangzhou, Hangzhou 310009, China. songxiuzu@sina.com
Bi
Zhi-gang
ZG
Xu
Ai-e
AE
D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002478:Cells, Cultured; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism / Q000528:radiation effects*; D009569:Nitric Oxide / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics*; D021381:Protein Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000032:analysis; D013662:Tea; D051996:Transcription Factor RelA / Q000378:metabolism; D014466:Ultraviolet Rays / Q000009:adverse effects*
D012333:RNA, Messenger; D013662:Tea; D051996:Transcription Factor RelA; D009569:Nitric Oxide; D002392:Catechin; C045651:epigallocatechin gallate; D052247:Nitric Oxide Synthase Type II