Epigallocatechin-3-gallate partially restored redox homeostasis in arsenite-stressed keratinocytes.

ABSTRACT

Arsenite (AsIII) is known for inducing severe oxidative stress and skin carcinogenesis. Contrastingly, phytochemical, epigallocatechin-3-gallate (EGCG) combats toxic insults. Our study focused on the effect of EGCG on redox status of AsIII-stressed normal human keratinocytes, HaCaT cells. EGCG (50 µm) increased the cell viability by 29% in AsIII (50 µm) insulted HaCaT cells but exhibited pro-oxidant activity by elevated expression of the oxidative stress markers. EGCG was effective not only in reducing AsIII-induced nuclear expression of Nrf2 and Nrf2Ser40 but also in increasing nuclear expression of Keap1 both at protein and mRNA level. EGCG did not have similar effects on all Nrf2 downstream targets. EGCG elevated expression of HO-1 and γ-GCL,showed no change in MRP1 but decreased superoxide dismutase, NAD(P)H dehydrogenase quinone 1 and glutathione S transferase activity in AsIII-treated HaCaT cells. EGCG along with AsIII caused decreased phosphorylation of Nrf2 at ser40 residue, which might have facilitated Keap1-mediated nuclear export and degradation of Nrf2 and paved the pro-survival signal for AsIII-insulted HaCaT cells. In conclusion, it might be indicated that EGCG in spite of inducing the pro-oxidant effect was effective in increasing the viability of AsIII-treated HaCaT cells by partially restoring the Nrf2/Keap1-mediated signaling axis.