Oxalate upregulates expression of IL-2Rβ and activates IL-2R signaling in HK-2 cells, a line of human renal epithelial cells

The role of inflammation in oxalate-induced nephrolithiasis is debated. Our gene expression study indicated an increase in interleukin-2 receptor beta (IL-2R beta) mRNA in response to oxalate (Koul S, Khandrika L, Meacham RB, Koul HK. PLoS ONE 7: e43886, 2012). Herein, we evaluated IL-2R beta expression and its downstream signaling pathway in HK-2 cells in an effort to understand the mechanisms of oxalate nephrotoxicity. HK-2 cells were exposed to oxalate for various time points in the presence or absence of SB203580, a specific p38 MAPK inhibitor. Gene expression data were analyzed by Ingenuity Pathway Analysis software. mRNA expression was quantitated via real-time PCR, and changes in protein expression/kinase activation were analyzed by Western blotting. Exposure of HK-2 cells to oxalate resulted in increased transcription of IL-2R beta mRNA and increased protein levels. Oxalate treatment also activated the IL-2R beta signaling pathway (JAK1/STAT5 phosphorylation). Moreover, the increase in IL-2R beta protein was dependent upon p38 MAPK activity. These results suggest that oxalate-induced activation of the IL-2R beta pathway may lead to a plethora of cellular changes, the most common of which is the induction of inflammation. These results suggest a central role for the p38 MAPK pathway in mediating the effects of oxalate in renal cells, and additional studies may provide the key to unlocking novel biochemical targets in stone disease.