Reactive oxygen species mediated calcium oxalate crystal-induced expression of MCP-1 in HK-2 cells

Under severe hyperoxaluric conditions calcium oxalate crystals often deposit in the renal interstitium and produce localized inflammation. We have proposed that renal epithelial cells exposed to CaOx crystals produce chemoattractants such as monocyte chemoattractant protein-1 (MCP-1). MCP-1 synthesis is mediated by reactive oxygen species (ROS). HK-2 cells of human renal epithelial line were exposed to CaOx crystals for different lengths of time. The culture media was tested for cell injury marker LDH, and subjected to enzyme-linked immunosorbent assay to determine the secretion of MCP-1 protein. Cell expression of MCP-1 was assessed by Western blot analysis. Gene expression was determined by reverse transcriptase-polymerase chain reaction. The data clearly showed that the HK-2 cells express MCP-1 gene and protein. The MCP-1 mRNA expression was increased following exposure to CaOx crystals, which was reduced upon treatment with free radical scavengers, catalase and superoxide dismutase. Results indicate that CaOx crystals strongly induce MCP-1 synthesis and secretion by the HK-2 cells and production is mediated by intracellular ROS production. Based on these and other data, antioxidant therapy and blockade of rennin-angiotensin system may prove beneficial for the prevention of end stage renal disease caused by hyperoxaluria and CaOx crystal deposition.