Aqueous humor and iris ciliary body cell culture supernatants upregulate BCL-2 and downregulate Bax gene expression and suppress apoptosis in corneal endothelial cells

Purpose. To assess the effects of aqueous humor (AH) and supernatants from iris/ciliary body (I/CB) cell cultures on Bcl-2 and Bax gene expression and apoptosis in corneal endothelial cells. Methods. Human and mouse corneal endothelial cells were cultured in the presence of either 50% AH or 50% I/CB cell conditioned culture supernatants and assessed for apoptosis by flow cytometry. Expression of Bcl-2 and Bax genes was determined by northern blot analysis of mRNA from cultured corneal endothelial cells. Results. Apoptosis of NZB mouse and human corneal endothelial cells was reduced over the three-day observation period by 42% to 55% in cells propagated in medium containing AH and by 25% in medium containing I/CB conditioned culture medium. Bcl-2 mRNA expression was increased by 100% and 790% in human corneal endothelial cells exposed to AH and I/CB conditioned culture medium respectively. By contrast, Bax gene expression was reduced by 40% in cells cultured in the presence of AH. Conclusions. The inability of corneal endothelial cells to undergo mitosis jeopardizes cornea function under conditions which lead to programmed cell death. AH contains one or more factors that stimulate expression of at least one gene (Bcl-2) that inhibits apoptosis while downregulating a gene (Bax) that promotes programmed cell death.