L-deprenyl protects injured retinal precursor cells in vitro

We evaluated the ability of L-deprenyl, a monoamine oxidase-B inhibitor (MAO-B), to preserve the viability of serum-deprived immortalized retinal precursor cells in vitro. We serum-deprived rat neural retinal ganglion cells immortalized by an incompetent retro virus. We instilled L-deprenyl in concentrations ranging from 0.01 to 100 μM. After 72 hours we performed a cell count of the L-deprenyl cultures and the control (no L-deprenyl instilled) with a hemocytometer and flow cytometry. We used transmission electron microscopy, DNA gel electrophoresis, and flow cytometry to determine the mechanism of cell death. This study showed that all five concentrations of L-deprenyl statistically increased the survival rate of immortalized retinal precursor cells at 72 hours in the serum-deprived medium (P = 0.01, ANOVA test). Ten μM and higher appeared to provide the greatest immortalized retinal precursor cell survival (12.7 x 10^-4 cells) compared to the control (5.8 x 10^-4 cells). Flow cytometry also demonstrated a higher percentage of surviving cells at 10 μM (80%) and 100 μM (76%) than with the control (58%) (P = 0.0017, χ² test). Transmission electron microscopy, DNA electrophoresis, and flow cytometry showed that the mode of cell death was by apoptosis. This study suggests that L-deprenyl may be worthy of further investigation as a neuroprotective agent to treat chronic open-angle glaucoma.