Nogo-B attenuates vascular calcification by activating NRF2-SLC7A11 to enhance antioxidant defense

Vascular calcification (VC), characterized by abnormal calcium salts buildup in blood vessels, greatly raises the risk of adverse cardiovascular events. However, the mechanisms behind VC are not fully understood. Nogo-B, a member of the reticulon family, has been implicated in various pathological processes including intimal neovascularization, obesity, and metabolic-associated fatty liver disease. Yet, its role in VC has not been explored.

VC was induced in C57BL/6J mice and smooth muscle cell (SMC)-specific Nogo knockout mice (Nogo^SMKO) using nicotine and vitamin D₃ (VD₃). An ex vivo osteogenic model employing human arteries and an in vitro osteogenic model using human aortic smooth muscle cells (HASMCs) were both created under high phosphate conditions. Nogo-B expression was significantly downregulated in calcified human and mouse aortas, as well as in high phosphate-treated HASMCs. Additionally, SMC-specific knockout of Nogo-B exacerbated VC. Conversely, overexpressing Nogo-B suppressed osteogenic differentiation of HASMCs. Mechanistically, Nogo-B inhibited VC by upregulating the expression of the amino acid transporter SLC7A11. Nogo-B strongly interacts with SLC7A11 and promotes recruitment of the deubiquitinating enzyme OTU domain-containing ubiquitin aldehyde-binding protein 1 (OTUB1), thereby preventing K63-linked ubiquitination of SLC7A11 at K30. Furthermore, Nogo-B-mediated upregulation of SLC7A11 boosted intracellular glutathione (GSH) synthesis, which activated NRF2. NRF2 functions as a transcriptional enhancer of SLC7A11. Ultimately, Nogo-B activated antioxidant defense and alleviated oxidative stress to suppress vascular calcification.

This study identifies Nogo-B as a novel regulator of VC. Nogo-B stabilizes the SLC7A11 protein by modulating OTUB1-mediated deubiquitination and enhances the GSH/NRF2 signaling axis, thereby promoting glutathione synthesis, reducing oxidative stress, and inhibiting the osteogenic differentiation of VSMCs and VC progression.