RESPONSE OF LENS EPITHELIAL-CELLS TO HYDROGEN-PEROXIDE STRESS AND THEPROTECTIVE EFFECT OF CALORIC RESTRICTION

Hydrogen peroxide (H2O2) has been reported to be present at significan t levels in the lens and aqueous humor in some cataract patients and s uggested as a possible source of chronically inflicted damage to lens epithelial (LE) cells. We measured H2O2 effects on bovine and mouse LE cells and determined whether LE cells from old calorically restricted mice were more resistant to H2O2-induced cellular damage than those o f same age ad libitum fed (AL) mice. Bovine lens epithelial cells were exposed to H2O2 at 40 or 400 mu M for 2 h and then allowed to recover from the stress. The cells were assayed for DNA damage, DNA synthesis , cell viability, cell morphology, response to growth stimuli, and pro liferation potential. Hydrogen peroxide-treated cells showed an increa sed DNA unwinding 50% greater than that for untreated controls. These DNA strand breaks appeared to be almost completely rejoined by 30 min following removal of the cells from a 2 h exposure. The 40 mu M exposu re did not produce a significantly lower DNA synthesis rate than the c ontrol, it responded to growth factor stimuli, and it replicated as di d the control cells after removal of H2O2. The 400 mu M H2O2 severely affected DNA synthesis and replication, as shown by increased cell siz e and by markedly reduced clonal cell growth. The cells did not respon d to growth stimulation by serum or growth factors and lost irreversib ly the capacity to proliferate. The responses of LE cells from old adl ib diet (AL) and calorically restricted (CR) mice to H2O2 were signifi cantly different. Exposure of LE cells to 20, 40, or 100 mu M H2O2 for 1 h induces a significant loss of cellular proliferation in cells fro m old AL mice. LE cells from long-term CR mice of the same strain and age were more resistant to oxidative damage at all three concentration s of H2O2 than those of both old and young AL mice and showed a signif icantly higher proliferation potential following treatment. It is conc luded that CR results in superior resistance to reactive oxygen radica ls in the lens epithelium. (C) 1998 Academic Press.