Allicin Mitigates Diabetic Retinopathy in Rats by Activating Phosphatase and Tensin Homolog-induced Kinase 1/Parkin-mitophagy and Inhibiting Oxidative Stress-mediated NOD-like Receptor Family Pyrin Domain Containing 3 Inflammasome

Diabetic retinopathy (DR) is one of the significant disabling outcomes of diabetes mellitus characterized by retinal microvascular damage, inflammation, and neuronal dysfunction. Allicin (Alc), a natural compound found in garlic, has garnered attention for its antioxidant and anti-inflammatory properties, positioning it as a potential therapeutic agent for DR. The aim of the present study was to investigate the therapeutic efficacy of Alc in DR management and elucidate its underlying mechanisms of action. We established a DR model in male Sprague-Dawley rats (n = 50, 200-250 g, 12 weeks old) using a high-fat diet for 8 weeks plus a low dose of streptozotocin administered at the start of the 4th week. The diabetic (Diab) animals were administered Alc (16 mg/kg/day, orally), either alone or in combination with mitochondrial division inhibitor-1 (Mdivi-1) as a mitophagy inhibitor, starting 28 days before tissue sampling. We evaluated histopathological changes, metabolic abnormalities associated with type 2 diabetes mellitus (T2DM), the expression of proteins regulating pyroptosis (NOD-like receptor family pyrin domain containing 3, cleaved-caspase 1, and gasdermin D-N terminal) and mitophagy (phosphatase and tensin homolog-induced kinase 1 [PINK1] and Parkin), as well as the levels of oxidative stress mediators and proinflammatory cytokines. Alc treatment effectively ameliorated histopathological changes and metabolic abnormalities associated with T2DM. It downregulated pyroptosis-related proteins, upregulated mitophagy-related proteins, reduced proinflammatory cytokine levels, and attenuated oxidative stress. Treatment with Mdivi-1 suppressed the beneficial effects of Alc. Our findings highlight the therapeutic potential of Alc in managing DR by targeting multiple pathophysiological pathways, including pyroptosis, inflammation, and oxidative stress. The observed antipyroptotic effects of Alc were partially mediated by the activation of the PINK1/parkin-mediated mitophagy pathway. Additional studies are necessary to thoroughly understand the therapeutic mechanisms of Alc and its viability as a treatment choice for DR.