Macrophage-Targeted Sod2 mRNA Nanotherapy Reduces Mitochondrial Oxidative Stress and Stabilizes Vulnerable Atherosclerotic Plaques.

BACKGROUND: Mitochondrial oxidative stress contributes to atherosclerotic plaque progression and instability, yet no therapies directly target mitochondrial redox imbalance. Superoxide dismutase 2 (SOD2), the primary mitochondrial antioxidant enzyme, has been linked to increased plaque vulnerability when its expression is reduced. METHODS AND RESULTS: We evaluated whether targeted restoration of SOD2 in plaque macrophages using p5RHH-based mRNA nanoparticles modulates mitochondrial oxidative stress and plaque phenotype. In primary monocytes from Sod2+/- mice, p5:Sod2 nanoparticles restored SOD2 expression, reduced mitochondrial superoxide, and improved mitochondrial respiratory capacity. Transcriptomic profiling identified changes in inflammatory and metabolic pathways consistent with altered myeloid activation states. In Apoe-/- mice with advanced carotid atherosclerosis, systemically delivered p5:Sod2 nanoparticles preferentially accumulated in plaque macrophages and increased their SOD2 protein expression by approximately 1.6-fold, as quantified by flow cytometry. Treatment reduced mitochondrial, but not total cellular, reactive oxygen species without affecting plasma lipids or plaque size. However, p5:Sod2 treatment reduced plaque lipid content, decreased macrophage-rich core regions, increased collagen and ACTA2+ fibrous cap cells, reduced intraplaque hemorrhage markers, and lowered plaque vulnerability index by 30%. These changes were accompanied by reduced lesional expression of IL1β, IL6, MMP2, and MMP9 and decreased circulating inflammatory cytokines. Flow cytometry showed shifts in plaque macrophages, with fewer inflammatory/stress-associated clusters and more remodeling/repair-associated subsets. CONCLUSIONS: Targeted SOD2 overexpression in plaque macrophages reduces mitochondrial oxidative stress and promotes transcriptional and matrix remodeling-associated changes consistent with plaque stabilization without affecting overall lesion burden. These findings support mitochondrial redox modulation as an immunometabolic strategy to reduce plaque vulnerability.