Paeonol alleviates atherosclerosis by inhibiting CD8+ T-cell activation via targeting the SYK/NFATc1 signaling pathway in ApoE-/- mice.

Moutan Cortex, a traditional Chinese medicine, has been used to treat cardiovascular diseases. Paeonol (Pae), a key bioactive compound, is responsible for its anti-atherosclerotic effects. Although CD8+ T-cell activation drives atherosclerosis, Pae's role in this process remains unclear. We investigated whether Pae inhibits atherosclerosis by targeting the spleen tyrosine kinase (SYK)/nuclear factor of activated T-cells c1 (NFATc1) pathway, thereby reducing CD8+ T-cell activation and attenuating vascular endothelial cell injury. High-fat diet-fed apolipoprotein E-deficient (ApoE-/-) mice received Pae or simvastatin for 4 weeks. Atherosclerotic plaque formation was assessed by hematoxylin-eosin staining, and CD8+ T-cell activation, SYK/NFATc1 signaling, and cytotoxic mediators were analyzed by immunofluorescence, Western blot, and enzyme-linked immunosorbent assay. Pae-SYK interaction was studied by co-immunoprecipitation, cellular thermal shift assay, and molecular dynamics. Mechanisms were validated in vitro using primary CD8+ T-cells and human umbilical vein endothelial cells. Pae attenuated plaque formation and T-cell activation in ApoE-/- mice. SYK, upregulated in atherosclerotic aortas, was directly targeted by Pae. Pae inhibited SYK phosphorylation; blocked NFATc1 nuclear translocation; and downregulated perforin, granzyme B, tumor necrosis factor-α, and interferon-γ in activated CD8+ T-cells. SYK overexpression abolished these effects. Pae also reduced vascular endothelial cell injury induced by CD8+ T-cell-conditioned medium. SYK in CD8+ T-cells represents a potential therapeutic target for atherosclerosis. Pae inhibits atherosclerosis by blocking the SYK/NFATc1 pathway to reduce cytotoxic mediator release and prevent vascular endothelial cell injury.