Abrogation of store-operated Ca2+ entry protects against crystal-induced ER stress in human proximal tubular cells

Control (noncrystal) CaP, CaOx, and CaP？+？CaOx (mixed) crystals were introduced into HK2 cells for 24？h. Crystal internalization effects on [Ca2+]i mobilization in GPCR-activated HK2 cells were measured by Ca2+ imaging. Mean fluorescent traces of Fura-2 loaded HK2 cells bathed in Ca2+-free solution and then 2.0？mM Ca2+ and neomycin CaSR activation were obtained for a Control; b CaP; c CaOx; and d Mixed crystals. Representative bar diagrams depict (e) peak [Ca2+]i release; f [Ca2+]i rise; and g percent reduction Ca2+ entry. Two-tailed t-test was used for statistical comparison in (e–g). Statistically significant differences are indicated (mean？±？SEM) from four different experiments. Levels of significance are indicated as *p？<？0.05; **p？<？0.01 as shown in the bar diagram