Inhibiting Endothelial SMS2 Alleviates Atherosclerosis by Blocking Endothelial‑Mesenchymal Transition Through Boosted Fatty Acid Oxidation

BACKGROUND: Endothelial-to-mesenchymal transition (EndMTE) is implicated in atherosclerosis by contributing to endothelial dysfunction (ED). SMS2 (sphingomyelin synthase 2), a key enzyme in sphingomyelin synthesis, plays a significant role in both ED and atherosclerosis. Nonetheless, the precise mechanisms of SMS2-associated ED, and its potential modulation via EndMT remain unexplored in the context of ED and atherosclerosis progression. METHODS: To investigate this, we inhibited SMS2 activity using the inhibitor Ly93 and performed RNA sequencing on human umbilical vein endothelial cells. Furthermore, we validated the potential mechanisms of EndMT in human umbilical vein endothelial cells, Apo E −/− mice, and human atherosclerotic plaques. RESULTS: SMS2 inhibition suppressed EndMT by blocking the Wnt/β-catenin pathway. This blockade attenuated PPARγ (peroxisome proliferator-activated receptor gamma) ubiquitination-mediated degradation via PPARγ-β-catenin interaction, ultimately reducing CPT1A expression and fatty acid oxidation. In vivo, endothelial cell-specific overexpression of SMS2 in ApoE −/− mice enhances atherosclerosis, and SMS2 positively correlates with Wnt/β-catenin, EndMT, and ED, but inversely correlates with PPARγ activity and fatty acid oxidation. Furthermore, in the unstable atherosclerosis plaques of humans, the expression of SMS2 in endothelial cells is significantly higher compared with that in stable plaques. The relationship between SMS2 and Wnt/β-catenin, EndMT, ED, PPARγ, and fatty acid oxidation aligns with the aforementioned findings. CONCLUSIONS: SMS2 can activate the Wnt/β-catenin pathway, which is inversely correlated with the activity of PPARγ and fatty acid oxidation. This process facilitates EndMT and ED, ultimately contributing to the initiation and development of atherosclerosis. These findings suggest that inhibition of endothelial SMS2 activity with Ly93 could be beneficial for the treatment of atherosclerosis.