The Neuroprotective Effect of Carnosine (β-Alanyl-L-Histidine) on Retinal Ganglion Cell Following Ischemia-Reperfusion Injury

Purpose: To investigate whether carnosine can increase retinal ganglion cell (RGC) survival in ischemic mouse retina. Methods: Retinal ischemia was induced by constant elevation of intraocular pressure (100-110mmHg) for 60 min in C57BL/6 J mice pretreated with carnosine (1000 mg/kg) or saline. Hypoxia inducing factor-1 alpha (HIF-1 alpha), glial fibrillary acidic protein (GFAP), and dynamin-related protein-1 (Drp-1) expressions were assessed at 6, 12, and 24 h after retinal ischemia. Bax and Bcl-2 expressions were also analyzed at 12 h after retinal ischemia. RGC survival was assessed by retrograde FluoroGold labeling at 2 weeks after retinal ischemia. Results: The expression of HIF-1 alpha, GFAP, and Drp-1 was increased within 24 h after ischemic injury. Carnosine treatment effectively decreased the elevated expression of HIF-1 alpha, GFAP, and Drp-1 in ischemic mouse retina. In ischemic retina treated with carnosine, Bax expression was decreased, whereas Bcl-2 expression was increased compared with ischemic retina treated with saline. Carnosine treatment also protected against RGC loss in ischemia mouse retina. Conclusions: Our findings showed that carnosine treatment significantly decreased RGC loss through decreased expression of HIF-1 alpha, GFAP, Drp-1, and Bax, and increased expression of Bcl-2 in ischemic mouse retina. We suggest that carnosine can be an effective endogenous neuroprotective molecule in the prevention of RGC loss in ischemic retina.