Effects of Antrodia camphorata extracts on the viability, apoptosis, [Ca2+]i, and MAPKs phosphorylation of OC2 human oral cancer cells.

The effect of Antrodia camphorata (AC) on human oral cancer cells has not been explored. This study examined the effect of AC on the viability, apoptosis, mitogen-activated protein kinases (MAPKs) phosphorylation and Ca2+ regulation of OC2 human oral cancer cells. AC at a concentration of 25 microM induced an increase in cell viability, but AC at concentrations > or = 50 microg/ml decreased viability in a concentration-dependent manner. AC at concentrations of 100-200 microg/ml induced apoptosis in a concentration-dependent manner as demonstrated by propidium iodide staining. AC (25 microg/ml) did not alter basal [Ca2+]i, but decreased the [Ca2+]i increases induced by ATP, bradykinin, histamine and thapsigargin. ATP, bradykinin, and histamine increased cell viability whereas thapsigargin decreased it. AC (25 microg/ml) pretreatment failed to alter ATP-induced increase in viability, potentiated bradykinin-induced increase in viability, decreased histamine-induced increase in viability and reversed thapsigargin-induced decrease in viability. Immunoblotting suggested that AC induced phosphorylation of ERK and JNK MAPKs, but not p38 MAPK. Collectively, for OC2 cells, AC exerted multiple effects on their viability and [Ca2+]i, induced their ERK and JNK MAPK phosphorylation, and probably evoked their apoptosis.

Ketoconazole-induced JNK phosphorylation and subsequent cell death via apoptosis in human osteosarcoma cells.

This study examined the effect of ketoconazole on viability, apoptosis, mitogen-activated protein kinases (MAPKs) and Ca(2+) levels in MG63 osteosarcoma cells. Ketoconazole at 20-200 microM decreased cell viability via apoptosis as demonstrated by propidium iodide staining and activation of caspase-3. Immunoblotting suggested that ketoconazole induced phosphorylation of ERK and JNK, but not p38, MAPKs. Ketoconazole-induced cell death and apoptosis were partially reversed by the selective JNK inhibitor SP600125, but not by the selective ERK inhibitor PD98059, suggesting that ketoconazole's cytotoxic action was via JNK, but not via ERK and p38 MAPKs. Ketoconazole at a concentration of 100 microM induced [Ca(2+)](i) increases. Chelation of intracellular Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) totally inhibited ketoconazole-induced [Ca(2+)](i) increases without reversing ketoconazole-induced cell death. Collectively, in MG63 cells, ketoconazole induced cell death and apoptosis via evoking JNK phosphorylation in a Ca(2+)-independent manner.

Cadmium-induced cytosolic Ca2+ elevation and subsequent apoptosis in renal tubular cells.

Cadmium (Cd2+) is an industrial and environmental metal. The effect of Cd2+ on intracellular free-Ca2+ levels ([Ca2+](i)) and viability in Madin Darby canine kidney cells was explored. Cd2+increased [Ca2+](i) in a concentration-dependent manner with an EC50 of 85 microM. Cd2+-induced Mn2+ entry demonstrated Ca2+ influx. Removal of extracellular Ca2+ decreased the [Ca2+](i) signal by 60%. The [Ca2+](i) signal was inhibited by La3+ but not by L-type Ca2+ channel blockers. In Ca2+-free medium, Cd2+-induced [Ca2+]i signal was abolished by pre-treatment with 1 microM thapsigargin (an endoplasmic reticulum Ca2+pump inhibitor) and 2 microM carbonylcyanide m-chlorophenylhydrazone (CCCP; a mitochondrial uncoupler). Cd2+-induced Ca2+ release was not altered by inhibition of phospholipase C. At concentrations between 10 and 100 microM, Cd2+killed cells in a concentration-dependent manner. The cytotoxic effect of 100 microM Cd2+was reversed by pre-chelating cytosolic Ca2+with BAPTA. Cd2+-induced apoptosis was demonstrated by propidium iodide. Collectively, this study shows that Cd2+ induced a [Ca2+](i) increase in Madin Darby canine kidney cells via evoking Ca2+ entry through non-selective Ca2+ channels, and releasing stored Ca2+ from endoplasmic reticulum and mitochondria in a phospholipase C-independent manner.

Effect of MK-886 on Ca2+ level and viability in PC3 human prostate cancer cells.

3-[1-(p-chlorobenzyl)-5-(isopropyl)-3-tert-butylthioindol-2-yl]-2, 2-dimethylpropanoic acid (MK-886) is widely used for inhibition of leucotriene synthesis in in vitro studies, however, many of its other effects have been reported. The present study investigated the effect of MK-886 on cytosolic-free Ca(2+) concentrations ([Ca(2+)](i)) and viability in human PC3 prostate cancer cells. [Ca(2+)](i) in suspended cells was measured by using fura-2. MK-886 at concentrations of 1 microM and above increased [Ca(2+)](i) in a concentration-dependent manner with an EC(50) value of 20 microM. The Ca(2+) signal was reduced partly by removing extracellular Ca(2+). MK-886 evoked Mn(2+) quenching of fura-2 fluorescence, implicating Ca(2+) entry. MK-886-induced Ca(2+) influx was inhibited by store-operated Ca(2+) entry inhibitors nifedipine, econazole and SKF96365. In Ca(2+)-free medium, after pre-treatment with 10 microM MK-886, 1 microM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor)-induced [Ca(2+)](i) rises were abolished; and conversely, thapsigargin pre-treatment abolished MK-886-induced [Ca(2+)](i) rises. Inhibition of phospholipase C with U73122 did not alter MK-886-induced [Ca(2+)](i) rises. MK-886 at concentrations of 1-100 microM concentration-dependently decreased cell viability with an IC(50) value of 60 microM. The cytotoxic effect of MK-886 was not inhibited by pre-chelating cytosolic Ca(2+) with BAPTA/AM. Together, in PC3 cells, MK-886 induced [Ca(2+)](i) rises by causing phospholipase C-independent Ca(2+) release from the endoplasmic reticulum; and Ca(2+) influx via store-operated Ca(2+) channels. Independently, MK-886 was cytotoxic to cells in a Ca(2+)-independent manner.

Desipramine-induced Ca-independent apoptosis in Mg63 human osteosarcoma cells: dependence on P38 mitogen-activated protein kinase-regulated activation of caspase 3.

1. It has been shown that the antidepressant desipramine is able to induce increases in [Ca(2+)](i) and cell death in MG63 human osteosacroma cells, but whether apoptosis is involved is unclear. In the present study, the effect of desipramine on apoptosis and the underlying mechanisms were explored. It was demonstrated that desipramine induced cell death in a concentration- and time-dependent manner. 2. Cells treated with 100-800 mmol/L desipramine showed typical apoptotic features, including an increase in sub-diploid nuclei and activation of caspase 3, indicating that these cells underwent apoptosis. Immunoblotting revealed that 100 mmol/L desipramine activated extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). Although pretreatment of cells with 20 mmol/L PD98059 (an ERK inhibitor) or 20 mmol/L SP600125 (an inhibitor of JNK) did not inhibit cell death, the addition of 20 mmol/L SB203580 (a p38 MAPK inhibitor) partially rescued cells from apoptosis. Desipramine-induced caspase 3 activation required p38 MAPK activation. 3. Pretreatment of cells with BAPTA/AM (20 mmol/L) to prevent desipramine-induced increases in [Ca(2+)](i) did not protect cells from death. 4. The results of the present study suggest that, in MG63 human osteosarcoma cells, desipramine causes Ca(2+)-independent apoptosis by inducing p38 MAPK-associated activation of caspase 3.

Tamoxifen-induced [Ca2+]i rise and apoptosis in corneal epithelial cells.

The effect of tamoxifen on cytosolic free Ca2+ concentrations ([Ca2+]i) and viability has not been explored in corneal epithelial cells. This study examined whether tamoxifen altered [Ca2+]i and viability in SIRC corneal epithelial cells. Tamoxifen at concentrations > or = 1 microM increased [Ca2+]i in a concentration-dependent manner with an EC50 value of 6 microM. The Ca2+ signal was reduced substantially by removing extracellular Ca2+. Tamoxifen induced Mn2+ quench of fura-2 fluorescence implicating Ca2+ influx. The Ca2+ influx was insensitive to Ca2+ entry inhibitors and protein kinase C modulators. After pretreatment with thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor), tamoxifen-induced [Ca2+]i rises were abolished; conversely, tamoxifen pretreatment abolished thapsigargin-induced [Ca2+]i rises. Inhibition of phospholipase C with U73122 did not change the [Ca2+]i rises. At concentrations of 5-30 microM, tamoxifen killed cells in a concentration-dependent manner. The cytotoxic effect of 15 microM tamoxifen was not reversed by prechelating cytosolic Ca2+ with BAPTA/AM. Apoptosis was induced by 5-30 microM tamoxifen. Tamoxifen (30 microM did not induce production of reactive oxygen species (ROS). Collectively, in SIRC cells, tamoxifen induced [Ca2+]i rises by causing Ca2+ release from the endoplasmic reticulum in a phospholipase C-independent manner, and Ca2+ influx via unknown pathways. Tamoxifen-caused cytotoxicity was partly mediated by a Ca2+-independent apoptotic pathway.

Effect of calmidazolium on [Ca2+]i and viability in human hepatoma cells.

The effect of calmidazolium on cytosolic free Ca2+ concentrations ([Ca2+]i) and viability has not been explored in human hepatoma cells. This study examined whether calmidazolium altered [Ca2+]i and caused cell death in HA59T cells. [Ca2+]i and cell viability were measured using the fluorescent dyes fura-2 and WST-1, respectively. Calmidazolium at concentrations > or =1 microM increased [Ca2+]i in a concentration-dependent manner with an EC50 value of 1.5 microM. The Ca2+ signal was reduced partly by removing extracellular Ca2+. Calmidazolium induced Mn2+ quench of fura-2 fluorescence implicating Ca2+ influx. The Ca2+ influx was insensitive to L-type Ca2+ entry blockers, but was inhibited partly by enhancing or inhibiting protein kinase C activity. In Ca2+-free medium, after pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor), calmidazolium-induced [Ca2+]i rises were largely inhibited; and conversely, calmidazolium pretreatment totally suppressed thapsigargin-induced [Ca2+]i rises. Inhibition of phospholipase C with 2 microM U73122 did not change calmidazolium-induced [Ca2+]i rises. At concentrations between 1 and 15 microM, calmidazolium induced apoptosis-mediated cell death. Collectively, in HA59T hepatoma cells, calmidazolium induced [Ca2+]i rises by causing Ca2+ release from the endoplasmic reticulum in a phospholipase C-independent manner, and Ca2+ influx via protein kinase C-regulated Ca2+ entry pathway. Calmidazolium caused cytotoxicity via apoptosis.

Econazole-evoked [Ca2+]i rise and non-Ca2+-triggered cell death in rabbit corneal epithelial cells (SIRC).

The effects of econazole, an antifungal drug applied for treatment of keratitis and mycotic corneal ulcer, on cytosolic-free Ca(2+) concentrations ([Ca(2+)](i)) and viability of corneal cells was examined by using SIRC rabbit corneal epithelial cells as model. [Ca(2+)](i) and cell viability were measured by using the fluorescent dyes fura-2 and WST-1, respectively. Econazole at concentrations > or = 1 microM increased [Ca(2+)](i) in a concentration-dependent manner. The Ca(2+) signal was reduced partly by removing extracellular Ca(2+). The econazole-induced Ca(2+) influx was insensitive to L-type Ca(2+) channel blockers and protein kinase C modulators. In Ca(2+)-free medium, after pretreatment with 20 microM econazole, [Ca(2+)](i) rises induced by 1 microM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor) were abolished. Conversely, thapsigargin pretreatment also abolished econazole-induced [Ca(2+)](i) rises. Inhibition of phospholipase C with 2 microM U73122 did not change econazole-induced [Ca(2+)](i) rises. At concentrations between 10 and 80 microM, econazole killed cells in a concentration-dependent manner. The cytotoxic effect of 20 microM econazole was not reversed by prechelating cytosolic Ca(2+) with BAPTA. This shows that in SIRC cells econazole induces [Ca(2+)](i) rises by causing Ca(2+) release from the endoplasmic reticulum and Ca(2+) influx from unknown pathways. Econazole-caused cytotoxicity was independent from a preceding [Ca(2+)](i) rise.

Mechanism of paroxetine-induced cell death in renal tubular cells.

Paroxetine belongs to the family of selective serotonin reuptake inhibitors. Much research has been performed on the in vitro effect of paroxetine; however, the effect of paroxetine on Madin-Darby canine kidney renal tubular cells is unknown. The present study was aimed at exploring how paroxetine affects viability and to examine the underlying mechanisms. Paroxetine (15-200 microM) was shown to reduce cell viability via inducing apoptosis in a concentration-dependent manner. Paroxetine-induced cytotoxicity and apoptosis were not changed by the p38 mitogen-activated protein kinase inhibitor SB203580 and the c-Jun NH2-terminal kinase inhibitor SP600125, but was potentiated by the extracellular signal-regulated kinase inhibitor PD98059; inhibited by GF 109203X, a protein kinase C inhibitor; and potentiated by phorbol 12-myristate 13-acetate, a protein kinase C activator. Paroxetine induced [Ca2+](i) rises; however, pre-treatment with 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl)ester, a Ca2+ chelator, to prevent 20 microM paroxetine-induced [Ca2+](i) rises did not protect cells from death. H-89 (a protein kinase A inhibitor) and U73122 (a phospholipase C inhibitor) failed to alter paroxetine-induced cell death. The results suggest that in Madin-Darby canine kidney cells, paroxetine caused protein kinase C-dependent, Ca2+-independent apoptosis which was potentiated by inhibition of the extracellular signal-regulated kinase pathway.

Effects of antrodia camphorata on viability, apoptosis, and [Ca2+]i in PC3 human prostate cancer cells.

Antrodia camphorata (AC) has been used as a health supplement in Asia to control different cancers; however, the cellular mechanisms of its effects are unclear. The effect of AC on cultured human prostate cancer cells (PC3) has not been explored. This study examined the effect of AC on viability, apoptosis, mitogen-activated protein kinases (MAPKs) phosphorylation and Ca2+ handling in PC3 cells. AC at concentrations of 5-50 microg/ml did not affect cell viability, but at 100-200 microg/ml decreased viability and induced apoptosis in a concentration-dependent manner. AC at concentrations of 25-200 microg/ml did not alter basal [Ca2+]i, but at a concentration of 25 microg/ml decreased the [Ca2+]i increases induced by ATP, bradykinin, histamine and thapsigargin. ATP, bradykinin and histamine increased cell viability whereas thapsigargin decreased it. AC (25 microg/ml) pretreatment inhibited ATP-, bradykinin-, and histamine-induced enhancement on viability, but reversed thapsigargin-induced cytotoxicity. Immunoblotting showed that AC (200 microg/ml) did not induce the phosphorylation of ERK, JNK, and p38 MAPKs. Collectively, in PC3 cells, AC exerted multiple effects on viability and [Ca2+]i, caused apoptosis via pathways unrelated to [Ca2+]i signal and phosphorylation of ERK, JNK and p38 MAPKs.

Desipramine-induced apoptosis in human PC3 prostate cancer cells: activation of JNK kinase and caspase-3 pathways and a protective role of [Ca2+]i elevation.

The antidepressant desipramine has been shown to induce a rise in cytosolic Ca2+ levels ([Ca2+]i) and cytotoxicity in human PC3 prostate cancer cells, but the mechanisms underlying its cytotoxic effect is unclear. Cell viability was examined by WST-1 assays. Apoptosis was assessed by propidium iodide staining and an increase in caspase-3 activation. Phosphorylation of protein kinases was analyzed by immunoblotting. Desipramine caused cell death via apoptosis in a concentration-dependent manner. Immunoblotting data revealed that desipramine activated the phosphorylation of c-Jun NH2-terminal kinase (JNK), but not extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK). SP600125 (a selective JNK inhibitor) partially prevented cells from apoptosis. Pretreatment with BAPTA/AM, a Ca2+ chelator, to prevent desipramine-induced [Ca2+]i rises worsened desipramine-induced cytotoxicity. Immunoblotting data suggest that BAPTA/AM pretreatment enhanced desipramine-evoked JNK phosphorylation and caspase-3 cleavage. The results suggest that in PC3 cells, desipramine caused apoptosis via inducing JNK-associated caspase-3 activation, and [Ca2+]i rises may slow down or alleviate desipramine-induced cytotoxicity.

Diethylstilbestrol-induced estrogen receptor-dependent [Ca2+]i rises and apoptosis in Chinese hamster ovary (CHO) cells.

The effect of the synthetic estrogen diethylstilbestrol (DES) on cytosolic free Ca2+ concentrations ([Ca2+]i) and cell viability was explored in Chinese hamster ovary (CHO-K1). [Ca2+]i and cell viability were measured by using the fluorescent dyes fura-2 and WST-1, respectively. DES at concentrations>or=1 proportional, variant increased [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced partly by removing extracellular Ca2+. In Ca2+-free medium, after pretreatment with 50 proportional, variant DES, 1 proportional, variant thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor)-induced [Ca2+]i rises were abolished. Conversely, thapsigargin pretreatment abolished DES-induced [Ca2+]i rises. Inhibition of phospholipase C with U73122 did not alter DES-induced [Ca2+]i rises. At a concentration of 5 proportional, variant, DES increased cell viability. At concentrations of 100-200 microM, DES decreased viability in a concentration-dependent manner. The effect of 5 and 100 microM DES on viability was partly reversed by prechelating cytosolic Ca2+ with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N' -tetraacetic acid (BAPTA). DES-induced cell death was induced via apoptosis as demonstrated by propidium iodide staining. DES (100 microM)-induced [Ca2+]i rises were largely inhibited by pretreatment with the estrogen receptor antagonist ICI-182,780 (100 microM). ICI-182,780 did not affect 5 microM DES-induced increase in viability but partly reversed 100 microM DES-induced cell death. Collectively, in CHO-K1 cells, DES induced [Ca2+]i rises by stimulating estrogen receptors leading to Ca2+ release from the endoplasmic reticulum in a phospholipase C-independent manner, and Ca2+ influx. DES-caused cytotoxicity was mediated by an estrogen receptor- and Ca2+-dependent pathway.

Mechanisms of AM404-induced [Ca(2+)](i) rise and death in human osteosarcoma cells.

The effect of N-(4-hydroxyphenyl) arachidonoyl-ethanolamide (AM404), a drug commonly used to inhibit the anandamide transporter, on intracellular free Ca2+ levels ([Ca2+]i) and viability was studied in human MG63 osteosarcoma cells using the fluorescent dyes fura-2 and WST-1, respectively. AM404 at concentrations > or = 5 microM increased [Ca2+]i in a concentration-dependent manner with an EC50 value of 60 microM. The Ca2+ signal was reduced partly by removing extracellular Ca2+. AM404 induced Mn2+ quench of fura-2 fluorescence implicating Ca2+ influx. The Ca2+ influx was sensitive to La3+, Ni2+, nifedipine and verapamil. In Ca2+-free medium, after pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor), AM404-induced [Ca2+]i rise was abolished; and conversely, AM404 pretreatment totally inhibited thapsigargin-induced [Ca2+]i rise. Inhibition of phospholipase C with U73122 did not change AM404-induced [Ca2+]i rise. At concentrations between 10 and 200 microM, AM404 killed cells in a concentration-dependent manner presumably by inducing apoptotic cell death. The cytotoxic effect of 50 microM AM404 was partly reversed by prechelating cytosolic Ca2+ with BAPTA/AM. Collectively, in MG63 cells, AM404 induced [Ca2+]i rise by causing Ca2+ release from the endoplasmic reticulum in a phospholipase C-independent manner, and Ca2+ influx via L-type Ca2+ channels. AM404 caused cytotoxicity which was possibly mediated by apoptosis.

Tamoxifen-induced [Ca2+]i rises and Ca2+-independent cell death in human oral cancer cells.

The purpose of this study was to explore the effect of tamoxifen on cytosolic free Ca(2+) concentrations ([Ca(2+)](i)) and cell viability in OC2 human oral cancer cells. [Ca(2+)](i) and cell viability were measured by using the fluorescent dyes fura-2 and WST-1, respectively. Tamoxifen at concentrations above 2 microM increased [Ca(2+)](i) in a concentration-dependent manner. The Ca(2+) signal was reduced partly by removing extracellular Ca(2+). The tamoxifen-induced Ca(2+) influx was sensitive to blockade of L-type Ca(2+) channel blockers but insensitive to the estrogen receptor antagonist ICI 182,780 and protein kinase C modulators. In Ca(2+)-free medium, after pretreatment with 1 muM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor), tamoxifen-induced [Ca(2+)](i) rises were substantially inhibited; and conversely, tamoxifen pretreatment inhibited a part of thapsigargin-induced [Ca(2+)](i) rises. Inhibition of phospholipase C with 2 microM U73122 did not change tamoxifen-induced [Ca(2+)](i) rises. At concentrations between 10 and 50 microM tamoxifen killed cells in a concentration-dependent manner. The cytotoxic effect of 23 microM tamoxifen was not reversed by prechelating cytosolic Ca(2+) with BAPTA. Collectively, in OC2 cells, tamoxifen induced [Ca(2+)](i) rises, in a nongenomic manner, by causing Ca(2+) release from the endoplasmic reticulum, and Ca(2+) influx from L-type Ca(2+) channels. Furthermore, tamoxifen-caused cytotoxicity was not via a preceding [Ca(2+)](i) rise.

Mechanisms of carvedilol-induced [Ca2+] i rises and death in human hepatoma cells.

The effect of the cardiovascular drug carvedilol on cytosolic free Ca2+ concentrations ([Ca2+]i) and viability has not been explored in human hepatoma cells. This study examined whether carvedilol altered [Ca2+]i and caused cell death in HA59T cells. [Ca2+]i and cell viability were measured using the fluorescent dyes fura-2 and WST-1, respectively. Carvedilol at concentrations >or=1 microM increased [Ca2+]i in a concentration-dependent manner with an EC50 value of 20 microM. The Ca2+ signal was reduced partly by removing extracellular Ca2+. Carvedilol induced Mn2+ quench of fura-2 fluorescence, implicating Ca2+ influx. The Ca2+ influx was sensitive to La3+, econazole, nifedipine, and SKF96365. In Ca2+-free medium, after pretreatment with 1 muM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor), carvedilol-induced [Ca2+]i rises were abolished; and conversely, carvedilol pretreatment inhibited a major part of thapsigargin-induced [Ca2+]i rises. Inhibition of phospholipase C with 2 microM U73122 did not change carvedilol-induced [Ca2+]i rises. At concentrations between 1 and 50 microM, carvedilol killed cells in a concentration-dependent manner. The cytotoxic effect of 1 microM (but not 30 microM) carvedilol was fully reversed by prechelating cytosolic Ca2+ with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Apoptosis was induced by 30 (but not 1) microM carvedilol. Collectively, in HA59T hepatoma cells, carvedilol induced [Ca2+]i rises by causing Ca2+ release from the endoplasmic reticulum in a phospholipase-C-independent manner and Ca2+ influx via store-operated Ca2+ channels. Carvedilol-caused cytotoxicity was mediated by Ca2+ and apoptosis in a concentration-dependent manner.

Ketoconazole-evoked [Ca2+]i rises and non-Ca2+-triggered cell death in rabbit corneal epithelial cells (SIRC).

The effect of ketoconazole on cytosolic free Ca2+ concentrations ([Ca2+]i) and proliferation has not been explored in corneal cells. This study examined whether ketoconazole alters Ca2+ levels and causes cell death in SIRC rabbit corneal epithelial cells. [Ca2+]i and cell viability were measured by using the fluorescent dyes fura-2 and WST-1, respectively. Ketoconazole at concentrations of 5 microM and above increased [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced partly by removing extracellular Ca2+. The ketoconazole-induced Ca2+ influx was insensitive to L-type Ca2+ channel blockers and protein kinase C modulators. In Ca2+-free medium, after pretreatment with 50 microM ketoconazole, thapsigargin-(1 microM)-induced [Ca2+]i rises were abolished; conversely, thapsigargin pretreatment nearly abolished ketoconazole-induced [Ca2+]i rises. Inhibition of phospholipase C with 2 microM U73122 did not change ketoconazole-induced [Ca2+]i rises. At concentrations between 5 and 100 microM, ketoconazole killed cells in a concentration-dependent manner. The cytotoxic effect of 50 microM ketoconazole was not reversed by prechelating cytosolic Ca2+ with BAPTA. In summary, in corneal cells, ketoconazole-induced [Ca2+]i rises by causing Ca2+ release from the endoplasmic reticulum and Ca2+ influx from unknown pathways. Furthermore, the cytotoxicity induced by ketoconazole was not caused via a preceding [Ca2+]i rise.

Thimerosal-induced apoptosis in human SCM1 gastric cancer cells: activation of p38 MAP kinase and caspase-3 pathways without involvement of [Ca2+]i elevation.

Thimerosal is a mercury-containing preservative in some vaccines. The effect of thimerosal on human gastric cancer cells is unknown. This study shows that in cultured human gastric cancer cells (SCM1), thimerosal reduced cell viability in a concentration- and time-dependent manner. Thimerosal caused apoptosis as assessed by propidium iodide-stained cells and caspase-3 activation. Although immunoblotting data revealed that thimerosal could activate the phosphorylation of extracellular signal-regulated kinase, c-Jun NH2-terminal protein kinase, and p38 mitogen-activated protein kinase (p38 MAPK), only SB203580 (a p38 MAPK inhibitor) partially prevented cells from apoptosis. Thimerosal also induced [Ca2+](i) increases via Ca2+ influx from the extracellular space. However, pretreatment with (bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetate)/AM, a Ca2+ chelator, to prevent thimerosal-induced [Ca2+](i) increases did not protect cells from death. The results suggest that in SCM1 cells, thimerosal caused Ca2+-independent apoptosis via phosphorylating p38 MAPK resulting in caspase-3 activation.