High Glucose Enhances oxLDL-Induced Apoptosis in Human Renal Proximal Tubular Epithelial Cells Largely via Inducing Lectin-Like ox-LDL Receptor-1

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BACKGROUND: High blood glucose is characteristic of diabetic nephropathy (DN). Both lectin-like ox-LDL receptor-1 (LOX-1) and renal tubular epithelial cells apoptosis reportedly are important for the pathogenesis and progression of DN. In this study, we explored the regulatory effects of high glucose on the expression of LOX-1 and its impact on oxLDL-induced apoptosis in human renal proximal tubular epithelial cells (HRPTEpCs). METHODS: Primary HRPTEpCs were treated with high glucose with or without concurrent treatment with selective p38 mitogen-activated protein kinase (MAPK) inhibitor PD169316 or lentiviral knockdown of LOX-1. HRPTEpCs cultured in normal glucose concentration (5.5 mmol/l) was used as a control. RESULTS AND CONCLUSION: High glucose concentration dependency increased the expression of LOX-1, which led to increased ox-LDL binding in HRPTEpCs. In addition, high glucose upregulated the LOX-1 gene promoter activity but not its mRNA stability in HRPTEpCs; the effect was abolished by PD169316. Furthermore, high glucose markedly enhanced oxLDL-induced apoptosis in HRPTEpCs, which was largely abolished by knockdown of LOX-1. This study demonstrates that high glucose induces the expression of LOX-1 at the gene promoter/transcription level mainly by a p38 MAPK-dependent mechanism, which enhances oxLDL-induced apoptosis in renal tubular epithelial cells. It adds new insights into the molecular mechanisms underlying DN.

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