Melatonin receptor agonist ramelteon alleviates experimental acute ocular inflammation via HIF-1Α/VEGF/E-NOS signaling.

Abstract

Ramelteon (RML) is a potent, selective agonist of the high-affinity melatonin receptor 1 and 2 receptors. In addition, RML is known to have antioxidant and anti-inflammatory effects. In this study, we aimed to investigate the effects of RML on HIF-1α, VEGF and e-NOS signaling pathway in a rat model of endotoxin-induced uveitis (EIU). Twenty-eight Wistar albino rats were divided into 4 groups as controls, lypopolysaccharide (LPS) group (5 mg/kg i.p.), LPS + RML group (5 mg/kg i.p and 8 mg/kg orally, respectively) and RML group (8 mg/kg orally). EIU was induced by a single intraperitoneal LPS injection. Histopathological and genetical analyses were performed. In histopathological analysis, LPS caused mild anterior uveitis characterized by increased surface area of iris leaflets and ciliary body due to edema, mild to moderate congestion, and inflammatory infiltrate 6 h following the injection. The pathological findings were reduced by RML. Higher inflammation levels seen in LPS group were significantly reduced in LPS + RML group. Also, HIF-1 α, eNOS and VEGF expressions increased in LPS and decreased in LPS + RML group. RML treatment reversed the changes in the HIF-1α /eNOS/ VEGF signaling pathway in LPS-induced uveitis in rats, preventing the progression of the damage and showed positive effects.