Purpose: To determine whether P7C3-A20, a proneurogenic neuroprotective agent, can protect the retinal ganglion cells (RGCs) of rats from optic nerve crushing.
Methods: The left optic nerve of 67 rats was crushed, and 5.0 mg/kg/day of P7C3-A20 (crush-P7C3) or its vehicle (crush-placebo) was injected intraperitoneally for 3 days from one day prior to the crushing. The protective effects were determined by the number of Tuj-1-stained RGCs and by the ratio of the mRNA levels of BAX/Bcl-2 on day 7. The levels of NAD and NAD-related genes were also determined.
Results: The density of RGCs was 2009.4 ± 57.7 cells/mm2 in the sham controls; it was significantly lower in the crush-placebo group at 979.7 ± 144.3 cells/mm2 (P < 0.0001). The neuroprotective effects of P7C3-A20 was demonstrated by the significantly higher density of 1266.0 ± 193.1 cells/mm2 than in the crush-placebo group (P = 0.01, Scheffe). After crushing the optic nerve the BAX/Bcl-2 ratio was higher in the optic nerves and retina, application of P7C3-A20 significantly reduced this ratio. P7C3-A20 significantly increased the NAD level in the untouched optic nerves from 1.36 ± 0.05 to 1.59 ± 0.10 nmol/mg protein (P = 0.02, t test). Crushing the optic nerve decreased the level to 1.27 ± 0.21 nmol/mg protein and P7C3-A20 preserved the level at 1.43 ± 0.10 nmol/mg protein. Crushing the optic nerve decreased the mRNA levels of Nampt and Sirt-1 in the optic nerves, while P7C3-A20 significantly restored the levels.
Conclusions: P7C3-A20 can protect RGCs from optic nerve crushing possibly through preserving the NAD levels in the optic nerves.
Keywords: NAD; NAMPT; Optic nerve crush; P7C3; SIRT-1.