-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 diindolylmethane, a natural compound derived from indole-3-carbinol in cruciferous vegetables, on cytosolic Ca(2+) concentrations ([Ca(2+)](i)) and viability in HA59T human hepatoma cells is unclear. This study explored whether diindolylmethane changed [Ca(2+)](i) in HA59T cells. The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)](i). Diindolylmethane at concentrations of 1-50 μM evoked a [Ca(2+)](i) rise in a concentration-dependent manner. The signal was reduced by removing Ca(2+). Diindolylmethane-induced Ca(2+) influx was not inhibited by nifedipine, econazole, SK&F96365, and protein kinase C modulators but was inhibited by aristolochic acid. In Ca(2+)-free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitors thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) inhibited or abolished diindolylmethane-induced [Ca(2+)](i) rise. Incubation with diindolylmethane 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 10-75 μM, diindolylmethane killed cells in a concentration-dependent manner. The cytotoxic effect of diindolylmethane was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. Propidium iodide staining data suggest that diindolylmethane (25-50 μM) induced apoptosis in a concentration-dependent manner. Collectively, in HA59T cells, diindolylmethane induced a [Ca(2+)](i) rise by causing phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) influx via phospholipase A(2)-sensitive channels. Diindolylmethane induced cell death that may involve apoptosis.

Effect of the carcinogen thapsigargin on human prostate cancer cells is unclear. This study examined if thapsigargin altered basal [Ca²⁺](i) levels in suspended PC3 human prostate cancer cells by using fura-2 as a Ca²⁺-sensitive fluorescent probe. Thapsigargin at concentrations between 10 nM and 10 µM increased [Ca²⁺](i) in a concentration-dependent fashion. The Ca²⁺ signal was reduced partly by removing extracellular Ca²⁺ indicating that Ca²⁺ entry and release both contributed to the [Ca²⁺](i) rise. This Ca²⁺ influx was inhibited by suppression of phospholipase A2, but not by inhibition of store-operated Ca²⁺ channels or by modulation of protein kinase C activity. In Ca²⁺-free medium, pretreatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-(t-butyl)-1,4-hydroquinone (BHQ) nearly abolished thapsigargin-induced Ca²⁺ release. Conversely, pretreatment with thapsigargin greatly reduced BHQ-induced [Ca²⁺](i) rise, suggesting that thapsigargin released Ca²⁺ from the endoplasmic reticulum. Inhibition of phospholipase C did not change thapsigargin-induced [Ca²⁺](i) rise. At concentrations of 1-10 µM, thapsigargin induced cell death that was partly reversed by chelation of Ca²⁺ with BAPTA/AM. Annexin V/propidium iodide staining data suggest that apoptosis was partly responsible for thapsigargin-induced cell death. Together, in PC3 human prostate cancer cells, thapsigargin induced [Ca²⁺](i) rises by causing phospholipase C-independent Ca²⁺ release from the endoplasmic reticulum and Ca²⁺ influx via phospholipase A2-sensitive Ca²⁺ channels. Thapsigargin also induced cell death via Ca²⁺-dependent pathways and Ca²⁺-independent apoptotic pathways.

The effect of the insecticide methoxychlor on the physiology of oral cells is unknown. This study aimed to explore the effect of methoxychlor on cytosolic Ca 2+ concentrations ([Ca 2+ ] i ) in human oral cancer cells (OC2) by using the Ca 2+ -sensitive fluorescent dye fura-2. Methoxychlor at 5-20 lM increased [Ca 2+ ] i in a concentration-dependent manner. The signal was reduced by 70% by removing extracellular Ca 2+. Methoxychlor-induced Ca 2+ entry was not affected by nifedipine, econazole, SK&F96365 and protein kinase C modulators but was inhibited by the phospholipase A2 inhibitor aristolochic acid. In Ca Methoxychlor ( fig. 1) is a broad-spectrum chlorinated insecticide, which is an organochlorine derivative of dichlorodiphenyl-trichloroethane (DDT) but with a much lower toxicity. Methoxychlor has become a substitute for the banned DDT and is commonly used in the USA to control insects on agricultural crops, livestock, animal feeds and household pets [1]. Because of work, chemical application and food ingestion, human beings as well as wildlife species are easily exposed to methoxychlor [2]. Methoxychlor acts as a proestrogen, and metabolism of this chemical by liver microsomes produces mono-, bis-, tris-hydroxy and catechol-M, which are oestrogenic in nature. The most active oestrogenic form is 2,2-bis(p-hydroxyphenyl)-1,1,1-trichloroethane (HPTE) [3]. Recent findings have revealed that methoxychlor reduces fertility in male rats [4] and decreases the ability of ovarian cells to synthesize and secrete hormones in female rats [5]. Such adverse effects found in the male and female rat reproductive systems have not been shown in human beings.Methoxychlor is shown to increase cytosolic Ca ] i trigger key cellular functions such as contraction of myofilaments, secretion of hormones and neurotransmitters and modulation of metabolism [7,8]. Ca 2+ also has a major function in triggering mitotic division in some cell types (e.g. T lymphocytes and of oocytes) and conversely in the regulation of cell death [9]. Evidence shows that Ca 2+ release from the endoplasmic reticulum and capa- ] i that form Ca 2+ spikes and waves [7].Programmed cell death (apoptosis) is an essential mechanism to eliminate unwanted cells during the development and homoeostasis of multicellular organisms. This extremely well-organized process involves DNA fragmentation,