Induction of S100A11 calcium-binding protein in renal tubular epithelial cells during the formation of calcium oxalate crystals.

Acute kidney injuries and renal dysfunction caused by ethylene glycol poisoning are often associated with nephrolithiasis. Calcium oxalate (CaOx) crystal formation is considered one of the most common events at the early stage of nephrolithiasis. The aim of this study is to investigate molecular mechanisms underlying CaOx crystal formation on renal tubular epithelial cells in vitro. We applied oxalate or potassium oxalate (final concentrations, 200-1200 µM) in the medium culturing NRK-52E rat proximal tubular epithelial cells. Cell death was observed with levels of oxalate or potassium oxalate above 800 µM 48 hr after addition. Crystals, mainly consisting of CaOx as confirmed by polarized light microscopy, were detected on cells treated with 800 µM oxalate or potassium oxalate. Transcriptome analysis showed that a gene (S100A11-like) belonging to the S100 family, which consists of homologous Ca-binding proteins, many of which can form complexes with annexin family proteins, was the gene most upregulated by 800 µM oxalate. Immunoblot as well as immunocytochemical analysis indicated not only upregulation but also alteration of intracellular localization of S100A11. The same altered pattern of localization was also observed for annexin A2, which has been shown to be involved in the formation of CaOx crystals. This study presents the possibility that, in addition to annexin family proteins, S100 family proteins might be involved in the regulation of CaOx crystal formation and/or other events associated with crystal formation.