Anti-Atherogenic Actions of Pomegranate Polyphenol Punicalagin and Its Metabolites: In Vitro Effects on Vascular Cells and In Vivo Atheroprotection by Urolithin A via Anti-Inflammatory and Plaque-Stabilising Mechanisms

Nutraceuticals are emerging as promising agents for the prevention and treatment of atherosclerosis, particularly in light of the limitations associated with current pharmacotherapies. Pomegranate-derived polyphenols, especially punicalagin (PC), possess multiple cardioprotective properties. However, their direct biological effects are constrained by poor absorption and low bioavailability. Instead, many of their actions are mediated by gut microbiota-derived metabolites known as urolithins. Despite this, the roles of PC and its metabolites in atherosclerosis remain inadequately defined. The objective of this study was to investigate the anti-atherogenic effects and underlying mechanisms of PC and its major metabolites-ellagic acid and urolithins A, B, C, and D-using in vitro and in vivo approaches. In vitro, these compounds broadly inhibited key pro-atherogenic processes in macrophages and endothelial cells, including reactive oxygen species production and inflammatory gene expression, with notable metabolite-specific differences. Urolithin A (UA), identified as the most effective compound, was further evaluated in LDL receptor-deficient mice fed a high-fat diet. UA supplementation improved peripheral blood immune cell profile, reduced atherosclerotic plaque burden and inflammation, and enhanced markers of plaque stability. RNA sequencing of the thoracic aorta revealed key molecular pathways underlying the protective actions of UA. Collectively, these findings highlight the therapeutic potential of PC-derived metabolites, particularly UA, in combating atherosclerosis and support the need for future human clinical studies.