Neuronatin Influences Endothelial Homeostasis and Atherosclerosis via ER-Mitochondria Interactions.

BACKGROUND: Atherosclerosis (AS) is driven by endothelial dysfunction, lipid dysregulation, and inflammation, yet its molecular mechanisms remain incompletely understood. Neuronatin (NNAT), an endoplasmic reticulum (ER)-associated protein, has an unclear role in AS. ER-mitochondria contact sites have been implicated in endothelial cell function. This study aimed to investigate the role of NNAT and its association with ER-mitochondria interactions in AS. METHODS: NNAT expression was analyzed in human AS datasets and in ApoE -/- mice fed a Western-type diet (WD). NNAT-deficient and double-knockout mice were evaluated for plaque burden, lipid accumulation, and vascular inflammation. Human umbilical vein endothelial cells (HUVECs) treated with oxidized LDL (oxLDL) were used to assess NNAT's effects on endothelial function, lipid metabolism, and ER-mitochondria-related features. RESULTS: NNAT expression was markedly reduced in human AS lesions and in WD-fed ApoE -/- mice. Loss of NNAT accelerated plaque formation, lipid deposition, and vascular inflammation. In HUVECs, oxLDL suppressed NNAT, inducing endothelial dysfunction, cholesterol accumulation, reactive oxygen species generation, and altered ER-mitochondria interactions. NNAT overexpression restored nitric oxide production, attenuated adhesion molecule expression and NF-κB activation, and improved lipid homeostasis. These effects were associated with improved ER-mitochondria contact and mitochondrial function. Disruption of ER-mitochondria interactions markedly attenuated the protective effects of NNAT, suggesting that ER-mitochondria interactions contributes to NNAT-associated endothelial effects. CONCLUSION: NNAT is associated with endothelial homeostasis and attenuation of AS progression, potentially involving ER-mitochondria interactions. NNAT deficiency aggravates atherosclerotic phenotypes, highlighting its potential relevance in cardiovascular disease.