Nonylphenol‐induced cytosolic Ca2+ elevation and death in renal tubular cells

Abstract

AbstractNonylphenol is an environmental endocrine disrupter. The effect of nonylphenol on intracellular free Ca2+ levels ([Ca2+]i) and viability in Madin‐Darby canine kidney (MDCK) cells was explored. Nonylphenol increased [Ca2+]i in a concentration‐dependent manner (EC50∼0.8 μM). Nonylphenol‐induced Mn2+ entry demonstrated Ca2+ influx and removal of extracellular Ca2+ partly decreased the [Ca2+]i rise. The [Ca2+]i rise was inhibited by the protein kinase C activator, phorbol 13‐myristate acetate (PMA) but not by L‐type Ca2+ channel blockers. In Ca2+‐free medium, nonylphenol‐induced [Ca2+]i rise was partly inhibited by pretreatment with 1 μM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor). Conversely, nonylphenol pretreatment abolished thapsigargin‐induced Ca2+ release. Nonylphenol‐induced Ca2+ release was unaltered by inhibition of phospholipase C. At concentrations of 5–100 μM, nonylphenol killed cells in a concentration‐dependent manner. The cytotoxic effect of 100 μM nonylphenol was not affected by preventing [Ca2+]i rises with BAPTA/AM. Collectively, this study shows that nonylphenol induced [Ca2+]i increase in MDCK cells via evoking Ca2+ entry through protein kinase C‐regulated Ca2+ channels, and releasing Ca2+ from endoplasmic reticulum and other stores in a phospholipase C‐independent manner. Nonylphenol also killed cells in a Ca2+‐independent fashion. Drug Dev Res, 2009. © 2009 Wiley‐Liss, Inc.