Response of renal tubular cells to differential types and doses of calcium oxalate crystals: Integrative proteome network analysis and functional investigations

We have previously identified changes in the cellular proteome of renal tubular cells induced by low-dose (100 μg/mL) and high-dose (1000 μg/mL) calcium oxalate monohydrate (COM) and dihydrate (COD) crystals. However, the functional significance of such expression data remained unclear. In this study, we performed comparative analyses and functional investigations of four proteomic datasets to define potential mechanisms by which renal tubular cells responded to differential crystal types and doses. The data showed that high-dose induced greater changes than low-dose, whereas COM induced more changes than COD. Luciferin–luciferase ATP assay revealed increased intracellular ATP level by high-dose of both COM and COD. OxyBlot assay and Western blotting showed accumulated intracellular oxidized proteins but decreased ubiquitinated proteins by high-dose of both crystals. Flow cytometric analysis of cell death showed that high-dose of both crystals, particularly COM, significantly increased cell death. Also, crystal adhesion assay showed higher degree of cell–crystal adhesion in high-dose and COM when compared to low-dose and COD, respectively. Finally, pretreatment of epigallocatechin-3-gallate revealed a protective effect on COM/COD crystals-induced oxidative stress and cell-crystal adhesion. Collectively, these data may provide a better understanding of cellular responses of renal tubular cells to COM/COD crystals in kidney stone disease.