||Thimerosal is a mercury-containing component found in many vaccine preparations and used as a preservative. It causes Ca2+ movement across cell membrane in different cells that may be mediated via effects on different receptors and ion channels.|
A rise in intracellular free Ca2+ concentrations ([Ca2+]i) is a key signal for many pathophysiological processes in cells, including apoptosis and necrosis. Thimerosal increases [Ca2+]i in different cell types. The mechanisms underlying thimerosal-induced Ca2+ signal vary with cell types.
The present study evaluated the effects of thimerosal on [Ca2+]i in human prostate cancer cells (PC3). WST-1 reduction assays and propidium iodide-staining assays were used to determine cell viability and apoptosis in the presence of thimerosal. The experimental results may be helpful to understand the pahrmocological and toxicological effects of thimerosal on cells from important organs.
Results showed that thimerosal (10–200μM) increased [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced partly by removing extracellular Ca2+. Thimerosal-induced Ca2+ influx was inhibited by econazole, SKF963656, the phospholipase A2 inhibitor aristolochic acid, and protein kinase C modulators [phorbol 12-myristate 13-acetate (PMA) and GF109203X]. In Ca2+-free medium, a 200-mM thimerosal-induced [Ca2+]i rise was partly inhibited after pretreatment with 2,5-di-tert-butylhydroquinone (BHQ) (an endoplasmic reticulum Ca2+ pump inhibitor). Thimerosal at 1–7μM induced cell death in a concentration-dependent manner that was not reversed when cytosolic Ca2+ was chelated with 1,2-bis(2-aminophenoxy)ethane-N,N,N’,N’-tetraacetic acid (BAPTA). Propidium iodide staining suggests that apoptosis played a role in the death.
Collectively, in PC3 cells, thimerosal induced [Ca2+]i rise by causing Ca2+ release from the endoplasmic reticulum and Ca2+ influx via store-operated Ca2+ channels in a manner regulated by protein kinase C and phospholipase A2. Thimerosal also induced cell death in a Ca2+-independent apoptotic manner.