Mitochondrial superoxide dismutase activation with 17 β-estradiol-treated human lens epithelial cells

PURPOSE 17 beta-estradiol (17beta-E(2)) protects human lens epithelial cells against oxidative stress by preserving mitochondrial function in part via the non-genomic rapid activation of prosurvival signal transduction pathways. The study described herein examined whether 17beta-E(2) also elicits genomic protection by influencing the expression (and activity) of mitochondrial-associated manganese superoxide dismutase (MnSOD) as a possible parallel mechanism by which 17beta-E(2) protects against oxidative stress. METHODS Virally-transformed human lens epithelial cells (HLE-B3) were pre-incubated with 17beta-E(2), and mRNA or protein lysates were collected over a time course ranging from 90 min to 24 h. Positive expression of lens epithelial cell MnSOD mRNA was determined by semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR), and its levels were monitored by real-time PCR up to 24 h after 17beta-E(2) administration. Western blot analysis was used to examine the pattern of protein expression as influenced by 17beta-E(2) treatment. MnSOD activity as influenced by 17beta-E(2) was determined by measuring enzymatic activity. RESULTS A significant rapid increase in the activity of MnSOD was observed with HLE-B3 cells by 90 min post-bolus addition of 17beta-E(2), which returned to control level by 240 min. Neither an increase in MnSOD mRNA nor in protein expression was detected up through 24 h. CONCLUSIONS These data demonstrate that 17beta-E(2) rapidly and transiently increases the activity of MnSOD but influences neither its mRNA expression nor its protein expression. The results suggest that (estrogen-activated) MnSOD plays an important role against mitochondrial oxidative stress by diminishing reactive oxygen species, thus promoting cell survival.