Functional Role of SUV39H1 in Human Renal Tubular Epithelial Cells Under High-glucose Ambiance

SUV39H1, the histone methyltransferase (HMTase) of histone H3 lysine 9 trimethylation (H3K9me3), is a known transcriptional repressor of inflammatory genes. The effect of SUV39H1 on inflammatory gene promoters under high-glucose stimulation in vascular smooth muscle cells (VSMCs), macrophages, and cardiomyocytes has been studied, but how SUV39H1 functions in renal tubules under diabetic conditions is unclear. Renal biopsy specimens of ten diabetic nephropathy (DN) subjects and seven non-DN minimal change diseases (MCD) subjects were collected. SUV39H1, IL-6, and MCP-1 expression in renal tissues were measured using immunohistochemical, while SUV39H1, H3K9me3, IL-6, and MCP-1 in human proximal tubular epithelial cells (HK-2) under varying glucose conditions were assayed by Western blot and ELISA. SUV39H1 was overexpressed in HK-2 cells; the regulation of SUV39H1 and H3K9me3 on NF-κB, IL-6, MCP-1, caspase 3, and apoptosis was measured. SUV39H1 was expressed more in diabetic human renal tubules. HK-2 cells with high glucose up-regulated IL-6 and MCP-1 in a dose- and time-dependent manner, and SUV39H1 expression was reduced with greater glucose and prolonged stimulation. Expression of H3K9me3 was synchronized with SUV39H1. Moreover, overexpression of SUV39H1 in high glucose environment was accompanied with increased H3K9me3 and decreased inflammation and apoptosis. SUV39H1 dysregulation may be involved in DN progression. Overexpression of SUV39H1 may reduce renal inflammation and apoptosis via epigenetic modulation, thus plays a protective role in DN.