Role of wild-type estrogen receptor-β in mitochondrial cytoprotection of cultured normal male and female human lens epithelial cells

The influence of sexual category as a modifier of cellular function is underinvestigated. Whether sex differences affect estrogen-mediated mitochondrial cytoprotection was determined using cell cultures of normal human lens epithelia (nHLE) from postmortem male and female donors. Experimental indicators assessed included differences in estrogen receptor-beta (ER beta) isoform expression, receptor localization in mitochondria, and estrogen-mediated prevention of loss of mitochondrial membrane potential using the potentiometric fluorescent compound JC-1 after nHLE were exposed to peroxide. The impact of wild-type ER beta (wtER beta 1) was also assessed using wtER beta 1 siRNA to suppress expression. A triple-primer PCR assay was employed to determine the proportional distribution of the receptor isoforms (wtER beta 1, -beta 2, and -beta 5) from the total ER beta message pool in male and female cell cultures. Irrespective of sex, nHLE express wtER beta 1 and the ER beta 2 and ER beta 5 splice variants in similar ratios. Confocal microscopy and immunofluorescence revealed localization of the wild-type receptor in peripheral mitochondrial arrays and perinuclear mitochondria as well as nuclear staining in both cell populations. The ER beta 2 and ER beta 5 isoforms were distributed primarily in the nucleus and cytosol, respectively; no association with the mitochondria was detected. Both male and female nHLE treated with E-2 (1 mu M) displayed similar levels of protection against peroxide-induced oxidative stress. In conjunction with acute oxidative insult, RNA suppression of wtER beta 1 elicited the collapse of mitochondrial membrane potential and markedly diminished the otherwise protective effects of E2. Thus, whereas the estrogen-mediated prevention of mitochondrial membrane permeability transition is sex independent, the mechanism of estrogen-induced mitochondrial cytoprotection is wtER beta 1 dependent.