Oral Administration of Piperine Ameliorates Experimental Autoimmune Uveitis

This study aimed to evaluate the impact of piperine on experimental autoimmune uveitis (EAU). EAU was induced by immunization with interphotoreceptor retinoid-binding protein emulsified in complete Freund adjuvant. Starting from day 8 post-induction, Lewis rats were given piperine (0, 20, 40, and 80 mg/kg-P.O.) or prednisolone (10 mg/kg-P.O.) for 18 consecutive days. The 80 mg/kg dose of piperine demonstrated superior regression of clinical symptoms, increased nitric oxide levels, and enhanced IDO activity in eye homogenates compared to other doses. The 40 and 80 mg/kg doses of piperine were more effective in promoting weight gain in EAU rats than the 20 mg/kg dose. EAU rats treated with 80 mg/kg piperine showed more favorable mRNA expression of IL-10 and TGF-β in their eyes than other treatment groups. The interventions led to a significant decrease in mRNA ratios of T-bet/GATA-3, RORγt/T-bet, RORγt/Foxp3, and RORγt/GATA-3 in the eyes of EAU rats compared to untreated EAU rats. Specifically, EAU rats treated with 80 mg/kg piperine exhibited a greater reduction in the mRNA ratio of RORγt/Foxp3 expression compared to other treatment groups. Overall, oral administration of piperine may offer potential for clinical application in uveitis.