Human bcl-2 gene attenuates the ability of rabbit lens epithelial cells against H2O2-induced apoptosis through down-regulation of the alpha B-crystallin gene

It is well established that the proto-oncogene, bcl-2, can prevent apoptosi s induced by a variety of factors. Regarding the mechanism by which BCL-2 p revents cell death, one theory suggests that it acts by protecting cells fr om oxidative stress. In the lens system, oxidative stress-induced apoptosis is implicated in cataractogenesis. To explore the possibility of anti-apop totic gene therapy development for cataract prevention and also to further test the anti-oxidative stress theory of BCL-2 action, we have introduced t he human bcl-2 gene into an immortalized rabbit lens epithelial cell line, N/N1003A. The stable expression clones of both vector- and bcl-2-transfecte d cells have been established. Treatment of the two cell lines With H2O2 re vealed that bcl-2-transfected cells were less capable of detoxifying H2O2 t han the control cells. Moreover, bcl-2-transfected cells are more susceptib le to H2O2-induced apoptosis. To explore why bcl-2-transfected cells have r educed resistance to H2O2-induced apoptosis, we examined the expression pat terns of several relevant genes and found that expression of the alphaB-cry stallin gene was distinctly downregulated in bcl-2-transfected cells compar ed with that in vector-transfected cells. This down-regulation was specific because a substantial inhibition of BCL-2 expression through antisense bcl -2 RNA significantly restored the level of alphaB-crystallin and, moreover, enhanced the ability of the bcl-2-transfected cells against H2O2-induced a poptosis. Introduction of a mouse alphaB-crystallin gene into bcl-2-transfe cted cells also counteracted the BCL-2 effects. Down-regulation of alphaB-c rystallin gene was largely derived from changed lens epithelial cell-derive d growth factor activity. Besides, alphaB-crystallin prevents apoptosis thr ough interaction with procaspase-3 and partially processed procaspase-3 to prevent caspase-3 activation. Together, our results reveal that BCL-2 can r egulate gene expression in rabbit lens epithelial cells. Through down-regul ation of the alphaB-crystallin gene, BCL-2 attenuates the ability of rabbit lens epithelial cells against H2O2-induced apoptosis.