Inhibition of ultraviolet B-mediated activation of nuclear factor kappaB in normal human epidermal keratinocytes by green tea Constituent (-)-epigallocatechin-3-gallate.
Epigallocatechin-3-gallate (EGCG), the major constituent of green tea, possesses significant anti-inflammatory and cancer chemopreventive properties. Studies have shown the photochemopreventive effects of green tea and EGCG in cell culture, animal models, and human skin. The molecular mechanism(s) of photochemopreventive effects of EGCG are incompletely understood. We recently showed that EGCG treatment of the normal human epidermal keratinocytes (NHEK) inhibits ultraviolet (UV)B-mediated activation of the mitogen-activated protein kinase (MAPK) pathway. In this study, we evaluated the effect of EGCG on UVB-mediated modulation of the nuclear factor kappa B (NF-kappaB) pathway, which is known to play a critical role in a variety of physiological functions and is involved in inflammation and development of cancer. Immunoblot analysis demonstrated that the treatment of NHEK with EGCG (10-40 microM) for 24 h resulted in a significant inhibition of UVB (40 mJ/cm(2))-mediated degradation and phosphorylation of IkappaBalpha and activation of IKKalpha, in a dose-dependent manner. UVB-mediated degradation and phosphorylation of IkappaBalpha and activation of IKKalpha was also observed in a time-dependent protocol (15 and 30 min, 1, 2, 3, 6, 12 h post-UVB exposure). Employing immunoblot analysis, enzyme-linked immunosorbent assay, and gel shift assay, we demonstrate that EGCG treatment of the cells resulted in a significant dose- and time-dependent inhibition of UVB-mediated activation and nuclear translocation of a NF-kappaB/p65. Our data suggest that EGCG protects against the adverse effects of UV radiation via modulations in NF-kappaB pathway, and provide a molecular basis for the photochemopreventive effect of EGCG.
Afaq
Farrukh
F
Department of Dermatology, University of Wisconsin, Madison, WI 53706, USA.
Adhami
Vaqar M
VM
Ahmad
Nihal
N
Mukhtar
Hasan
H
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D003593:Cytoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D000078404:Epidermal Cells; D006801:Humans; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins / Q000378:metabolism; D015603:Keratinocytes / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000528:radiation effects; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000528:radiation effects; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000528:radiation effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D013662:Tea / Q000737:chemistry*; D051996:Transcription Factor RelA; D014158:Transcription, Genetic / Q000187:drug effects* / Q000528:radiation effects; D014466:Ultraviolet Rays
D016588:Anticarcinogenic Agents; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D011837:Radiation-Protective Agents; D013662:Tea; D051996:Transcription Factor RelA; D000072000:NF-KappaB Inhibitor alpha; D002392:Catechin; C045651:epigallocatechin gallate; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human