Deprenyl increases cell survival and decreases apoptosis in rat retinal cultures following trophic withdrawal

Purpose: Apoptotic death of retinal ganglion cells (RGC) have been demonstrated after axotomy and in experimental models of glaucoma. Retrograde loss of trophic support may be responsible for the observed neuronal death. (-)-Deprenyl, a monoamine oxidase (MAO) inhibitor, increased RGC survival after optic nerve crush (Buys et al., 1994). We examined whether (-)-deprenyl would increase cell survival and/or reduce apoptosis in rat retinal cell cultures following the removal of trophic support. Nflgtbods: Primary cultures of mixed rat retinal cells were grown to confluency in partially defined media plus NGF (10ng/ml)and5% serum. Removal of NGF and serum was used to induce apoptosis. The effect of (-)-deprenyl on cell survival were examined after trophic withdrawal. Cell viability was determined. Nuclear DNA cleavage, a characteristic feature of apoptosis, was detected using in situ 3' end labelling. Results: Our results indicate that (-)-deprenyl increased cell survival in a dose-dependent fashion and at a concentration which was too low to inhibit MAO. Removal of trophic support caused a decrease in cell numbers from 6.75x 104! 1.22 to 2.49 x Kr±0.18 (P<0.05). Addition of (-)-deprenyl (109Mand 10" M) in the minus serum/NGF group increased the number of cells at 24 hours to 4.89 x 104 ±0.48 (P<0.05) and 6.69 x 104 ±0.66 (P<0.01) respectively. Additionally, 10"9 M (-)-deprenyl decreased the number of apoptotic nuclei from 2.47 x 104 + 0.08 to 0.07 x 104 ±0.02 (n=4). When the cell cycle blocker cyclo-hexamide (35nM) was given concommitandy with (-)-deprenyl (109 M and 10~n M), there was a 1.3 fold (P<0.05) and 2.26 fold (P<0.01) decrease in cell survival respectively. Conclusions: We conclude that (-)-deprenyl increases the survival of rat retinal cells by preventing apoptosis. The process requires protein synthesis.