Ex vivo–expanded human regulatory T cells enhance cholesterol efflux and PON1 expression in oxLDL-exposed macrophages

Lipid-driven chronic inflammation is a primary driver of atherosclerosis progression. Enhancing the anti-inflammatory response by bolstering regulatory T cell (Treg) numbers or improving their function, holds promise for therapeutic control of the disease. We and others have previously demonstrated in clinical trials the safety and potential efficacy of adoptive Treg transfer in restoring immunological balance. This study investigates the capability of ex vivo expanded regulatory T cells to counterbalance pro-inflammatory signals and lipid accumulation in primary macrophages, thereby contrasting plaque formation and atherosclerosis progression. To test this hypothesis, freshly isolated Tregs were ex vivo expanded into a clinical grade cell product before co-culturing with monocyte-derived M2-like macrophages. Macrophages were exposed to oxidised low-density lipoprotein (oxLDL) and co-cultured alone or in the presence of Tregs. Changes in macrophage phenotype, gene expression profile and functional properties such as the capacity to regulate the accumulation of cholesterol were analysed by flow cytometry, RNA sequencing and western blotting. In the co-culture system, the study demonstrated a significant reduction in both pro-inflammatory effects of oxLDL and accumulation of modified cholesterol in macrophages when Tregs were present. We identified that Tregs through the transferring of cAMP into macrophages, could potentiate the ABCA1-mediated cholesterol efflux pathway, and crucially, elevate the anti-atherogenic activity by inducing Paraoxonase-1 expression. The findings suggest a novel atheroprotective role for Tregs which supports the potential development of new experimental therapies for cardiovascular disease. By influencing macrophage function and cholesterol accumulation, Tregs present a promising avenue for mitigating atherosclerosis.