No abstract

-free medium, pre-treatment with the endoplasmic reticulum Ca 2+ pump inhibitor thapsigargin or 2,5-di-(t-butyl)-1,4-hydroquinone nearly abolished sertraline-induced Ca ] i rises by causing phospholipase C-dependent Ca 2+ release from the endoplasmic reticulum and via multiple Ca 2+ influx pathways that involve store-operated Ca 2+ channels. Sertraline also induced apoptosis that was not triggered by [Ca 2+ ] i rise.

The effect of the natural product diindolylmethane on cytosolic Ca(2+) concentrations ([Ca(2+)](i)) and viability in PC3 human prostate cancer cells was explored. The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)](i). Diindolylmethane at concentrations of 20-50 µM induced [Ca(2+)](i) rise in a concentration-dependent manner. The response was reduced partly by removing Ca(2+). Diindolylmethane-evoked Ca(2+) entry was suppressed by nifedipine, econazole, SK&F96365, protein kinase C modulators and aristolochic acid. In the absence of extracellular Ca(2+), incubation with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) inhibited or abolished diindolylmethane-induced [Ca(2+)](i) rise. Incubation with diindolylmethane also inhibited thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C with U73122 reduced diindolylmethane-induced [Ca(2+)](i) rise. At concentrations of 50-100 µM, diindolylmethane killed cells in a concentration-dependent manner. This cytotoxic effect was not altered by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Annexin V/PI staining data implicate that diindolylmethane (50 and 100 µM) induced apoptosis in a concentration-dependent manner. In conclusion, diindolylmethane induced a [Ca(2+)](i) rise in PC3 cells by evoking phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via phospholipase A(2)-sensitive store-operated Ca(2+) channels. Diindolylmethane caused cell death in which apoptosis may participate.

Celecoxib has been shown to have an antitumor effect in previous studies, but the mechanisms are unclear. Ca(2+) is a key second messenger in most cells. The effect of celecoxib on cytosolic free Ca(2+) concentrations ([Ca(2+)](i)) in human suspended PC3 prostate cancer cells was explored by using fura-2 as a fluorescent dye. Celecoxib at concentrations between 5 and 30 μM increased [Ca(2+)](i) in a concentration-dependent manner. The Ca(2+) signal was reduced partly by removing extracellular Ca(2+). Celecoxib-induced Ca(2+) influx was not blocked by L-type Ca(2+) entry inhibitors or protein kinase C/A modulators [phorbol 12-myristate 13-acetate (PMA), GF109203X, H-89], but was inhibited by the phospholipase A(2) inhibitor, aristolochic acid. In Ca(2+)-free medium, 30 μM of celecoxib failed to induce a [Ca(2+)](i) rise after pretreatment with thapsigargin (an endoplasmic reticulum [ER] Ca(2+) pump inhibitor). Conversely, pretreatment with celecoxib inhibited thapsigargin-induced Ca(2+) release. Inhibition of phospholipase C with U73122 did not change celecoxib-induced [Ca(2+)](i) rises. Celecoxib induced slight cell death in a concentration-dependent manner, which was enhanced by chelating cytosolic Ca(2+) with BAPTA. Collectively, in PC3 cells, celecoxib induced [Ca(2+)](i) rises by causing phospholipase C-independent Ca(2+) release from the ER and Ca(2+) influx via non-L-type, phospholipase A(2)-regulated Ca(2+) channels. These data may contribute to the understanding of the effect of celecoxib on prostate cancer cells.

The effect of the natural product 3,3¢-diindolylmethane (DIM) on cytosolic Ca 2+ concentrations ([Ca 2+ ] i ) and viability in MG63 human osteosarcoma cells was explored. The Ca 2+ -sensitive fluorescent dye fura-2 was applied to measure [Ca 2+ ] i . DIM at concentrations of 40-80 lM induced a [Ca 2+ ] i rise in a concentration-dependent manner. . DIM and its derivatives induce apoptosis in pancreatic cancer cells through endoplasmic reticulum stress [12]. Extended treatment with physiological concentrations of DIM results in gene expression alteration, growth inhibition and apoptosis of cancer cells in vitro [13,14]. In prostate cancer cells, DIM was shown to regulate oestrogen metabolism and acts as an antiandrogen [15] by decreasing the adverse effects of oestrogen [16], and DIM is shown to possess potential efficacy in the prevention of prostate cancer development [17]. Regulation of FOXO3a ⁄ b-catenin ⁄ GSK-3b signalling by DIM was found to contribute to inhibition of cell proliferation and induction of apoptosis in prostate cancer cells [18]. The effect of DIM on bone cells is less obvious except that DIM was shown to attenuate experimental arthritis and osteoclastogenesis [19]. Ca 2+ is a pivotal second messenger in a diversity of biolog- ] i and viability in human osteoblasts. The MG63 human osteosarcoma cell was a useful system for osteoblast research. In this cell, it has been shown that ketoconazole induces JNK phosphorylation and subsequent