Immunology of the eye
Inflammation has a potential role in the initial stages of diabetic retinopathy involving ischemia/reperfusion (I/R)-induced retinal damage. We studied the possibility that therapeutic use of α-MSH, a potent anti-inflammatory neuropeptide, could reduce retinal damage caused by I/R. Ischemia was induced in C57BL/6 mice via anterior chamber cannulation and elevating intraocular pressure to 90-100 mmHg for 90 minutes. The treatment group was immediately given 5μg of α-MSH intraperitoneally, and on day 2 and 7 the eyes were enucleated and prepared for histological analysis. Retinal survivability was gauged via retinal ganglion cell (RGC) count density, and clinical histological scoring for the severity of inflammation and retinal damage. Visual analysis demonstrated evident increases in infiltration, retinal folding, and retinal layer loss. The damage in untreated mice worsened with time and was ameliorated by α-MSH treatment with significantly lower clinical scores in the α-MSH treated mice on day 2 (0.9 ± 0.65, P < 0.05), but not on day 7. Untreated mice had significantly fewer RGCs on day 2 (43 ± 9 cells/mm) and day 7 (28 ± 4 cells/mm) compared to retinas of healthy mice (78 ± 5 cells/mm). RGC survival was significantly higher in the α-MSH treated mice on day 2 (63 ± 14 cells/mm, P = 0.02), but not on day 7 (40 ± 14 cells/mm) compared to the untreated mice. The results demonstrate that α-MSH-therapy has the ability to reduce I/R-induced retinal damage. The results suggest that suppressing inflammation early in diabetic retinopathy can minimize damage to the retina.