17β-estradiol stimulates MAPK signaling pathway in human lens epithelial cell cultures preventing collapse of mitochondrial membrane potential during acute oxidative stress

摘要

17β-estradiol (17β-E_2) protects against H_2O_2-mediated depletion of intracellular ATP and lessens the degree of depolarization of mitochondrial membrane potential (△Ψ _m) in cultured lens epithelial cells consequential to oxidative insult. We now report that 17β-E_2 acts as a positive regulator of the survival signal transduction pathway, MAPK which, in turn, acts to stabilize △Ψ _m, in effect, attenuating the extent of depolarization of mitochondrial membrane potential in the face of acuteoxidative stress. The SV-40 viral transformed human cell line, HLE-B3 was treated with 17β-E_2 over a time course of 60 min and phosphorylation of ERK1/2 was analyzed by Western blot. ERK1/2 was phosphorylated within 5-15 min in the presence of 17β-E_2. Cell cultures were exposed to the MEK1/2 inhibitor, UO126, subsequent to H_2O_2 ± 17β-E_2 treatment and the △Ψ _m examined using JC-1, a potentiometric dye which serves as an indicator for the state of mitochondrial membrane potential. UO126 treatment attenuated ERK1/2 phosphorylation irrespective of whether estradiol was administered. Mitochondrial membrane depolarization resulting from H_2O_2 stress was substantially greater in the presence of UO126. The greater the extent of depolarization, theless effective 173-E_2 treatment was in checking mitochondrial membrane depolarization, indicating that the relative degree of ERK phosphorylation influences mitochondrial stability with oxidative insult. The data support a positive correlation between17β-E_2 stimulation of ERK1/2 phosphorylation and mitochondrial stabilization that would otherwise cause a complete collapse of △Ψ _m.