Serum/glucocorticoid-regulated kinase 1 regulates vascular inflammation in atherosclerosis

Endothelial and macrophage inflammation and sterol transport play an important role in atherogenesis. Serum/glucocorticoid-regulated kinase 1 (SGK1) is a member of the serine/threonine kinase family sharing approximately 54% identity with Akt. It has been implicated in smooth muscle cell calcification and macrophage inflammation during atherosclerosis; however, the role of SGK1 in endothelial dysfunction and endothelial or macrophage lipid metabolism is less characterized. In this study, we intraperitoneally injected high-cholesterol diet-fed male ApoE-knockout mice with the SGK1 inhibitor EMD638683 (10 mg/kg) every other day for 2 weeks, followed by histopathological and transcriptome analysis of the atherosclerotic lesion. To study the SGK1-associated mechanism in vascular inflammation in vitro, SGK1 silencing was performed in primary human umbilical vein endothelial cells (HUVECs), followed by treatment with pro-inflammatory cytokines. In THP-1-differentiated macrophages, SGK1 silencing followed by treatment with lipopolysaccharides was used. We showed that ApoE-knockout mice treated with EMD638683 show reduced atherosclerotic plaque area and attenuated endothelial and macrophage inflammation. Further transcriptome analysis of thoracic aortae showed that SGK1 inhibition downregulated inflammation and lipid metabolism-associated genes. In vitro, interleukin-1β treatment induces SGK1 phosphorylation. SGK1 inhibitor or siRNA reduced endothelial inflammation induced by pro-inflammatory cytokine treatments in HUVECs through nuclear factor κ light chain enhancer of activated B cell (NF-κB) signaling. In THP-1-differentiated macrophages, SGK1 inhibition or knockdown by siRNA is associated with reduced levels of pro-inflammatory cytokines, NF-κB, and sterol regulatory element binding protein 1 (SREBP1) pathway activation, following lipopolysaccharide treatment. SREBP1 inhibition by fatostatin or siRNA reduced p65 phosphorylation. In conclusion, the inhibition of SGK1 has been shown to reduce atherosclerotic plaque area and attenuate endothelial and macrophage inflammation in ApoE-knockout mice via NF-κB and SREBP1 signaling. These results not only contribute to our understanding of the complex interplay between vascular inflammation and lipid metabolism but also hold promise for the development of novel therapeutic strategies for atherosclerosis.