Resveratrol is a natural compound that affects cellular calcium (Ca2+) homeostasis and viability in different cells. This study examined the effect of resveratrol on cytosolic free Ca2+ concentrations ([Ca2+]i) and viability in OC2 human oral cancer cells. The Ca2+-sensitive fluorescent dye fura-2 was used to measure [Ca2+]i, and water-soluble tetrazolium-1 was used to measure viability. Resveratrol evoked concentration-dependent increase in [Ca2+]i. The response was reduced by removing extracellular Ca2+. Resveratrol also caused manganese-induced fura-2 fluorescence quench. Resveratrol-evoked Ca2+ entry was inhibited by nifedipine and the protein kinase C (PKC) inhibitor GF109203X but was not altered by econazole, SKF96365, and the PKC activator phorbol 12-myristate 13 acetate. In Ca2+-free medium, treatment with the endoplasmic reticulum Ca2+ pump inhibitor 2,5-di- tert-butylhydroquinone (BHQ) abolished resveratrol-evoked [Ca2+]i rise. Conversely, treatment with resveratrol inhibited BHQ-evoked [Ca2+]i rise. Inhibition of phospholipase C (PLC) with U73122 abolished resveratrol-evoked [Ca2+]i rise. At 20–100 μM, resveratrol decreased cell viability, which was not affected by chelating cytosolic Ca2+with 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid-acetoxymethyl ester. Annexin V-fluorescein isothiocyanate staining data suggest that resveratrol at 20–40 μM induced apoptosis in a concentration-dependent manner. Collectively, in OC2 cells, resveratrol induced [Ca2+]i rise by evoking PLC-dependent Ca2+ release from the endoplasmic reticulum and by causing Ca2+ entry via nifedipine-sensitive, PKC-regulated mechanisms. Resveratrol also caused Ca2+-independent apoptosis.

The effect of the natural product diindolylmethane (DIM) on cytosolic Ca(2+) concentrations ([Ca(2+)]i) and viability in MDCK renal tubular cells was explored. The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)]i. DIM at concentrations 1-50 μM induced a [Ca(2+)]i rise in a concentration-dependent manner. The response was reduced partly by removing Ca(2+). DIM induced Mn(2+) influx leading to quenching of fura-2 fluorescence. DIM-evoked Ca(2+) entry was suppressed by nifedipine, econazole, SK&F96365 and protein kinase C modulators. In the absence of extracellular Ca(2+), incubation with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin (TG) or 2,5-di-tert-butylhydroquinone (BHQ) greatly inhibited DIM-induced [Ca(2+)]i rise. Incubation with DIM abolished TG or BHQ-induced [Ca(2+)]i rise. Inhibition of phospholipase C with U73122 reduced DIM-induced [Ca(2+)]i rise by 50%. At 1, 10, 40 and 50 μM, DIM slightly enhanced cell proliferation. The effect of 50 μM DIM was reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. In sum, in MDCK cells, DIM induced a [Ca(2+)]i rise by evoking phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via protein kinase C-sensitive store-operated Ca(2+) channels. DIM did not induce cell death.

ABSTRACT. Isoflurane can induce widespread cytotoxicity. We hypothesized that isoflurane induces apoptosis partly by causing excessive calcium release from the endoplasmic reticulum (ER) via direct activation of inositol 1,4,5-trisphosphate receptors (IP 3 R). Rat pheochromocytoma cells cultured for seven days with nerve growth factor were divided into four groups: control group (C), IP 3 R antagonist group (X), isoflurane group (I) and isoflurane + IP 3 R antagonist group (I+X). Groups I and I+X were treated with 1 MAC isoflurane for 12 h. Groups X and I+X were pretreated with IP 3 R antagonist. Annexin V/PI apoptosis and TUNEL assays were performed to evaluate cell apoptosis. TEM was used to observe changes in cell ultrastructure. Changes in ] i increased in groups I and I+X (P < 0.05). Compared to group C, IP 3 R mRNA expression was lower in group X and higher in group I (P < 0.05). Compared to group X, cell apoptosis rate, [Ca 2+ ] i and IP 3 R mRNA expression increased in groups I and I+X (P < 0.05). Compared to group I, cell apoptosis rate, [Ca 2+ ] i and IP 3 R mRNA expression decreased in group I+X (P < 0.05). These results suggest that exposure to 1 MAC isoflurane for 12 h causes excessive calcium release partly by direct activation of IP 3 R on the ER membrane and triggers cell apoptosis.

ABSTRACT. SNX-2112 is a potential molecular targeted therapeutic drug against esophageal cancer (EC). However, its exact mechanism of action remains to be explained. The aim of this study was to investigate the effect of SNX-2112 on excision repair cross-complementing 1 (ERCC1), epidermal growth factor receptor (EGFR), and p53, to elucidate the mechanism of action of SNX-2112 on EC. Fresh tumor sections were surgically obtained from 65 patients with EC, and the expression of ERCC1, EGFR, and p53 was determined by immunohistochemical staining. Furthermore, the effect of SNX-2112 (0.2 µM) on the proliferation of EC-9706 cells and the expression of ERCC1, EGFR, and p53 in these cells were analyzed by a cell proliferation assay and western blot, respectively. We observed a significant decrease and increase in ERCC1 (P = 0.001) and p53 (P = 0.043) expression, respectively, and no significant difference in EGFR (P = 0.59) expression, with the TNM stage of EC, which suggested that ERCC1 and p53 could be potential markers for the TNM stage of EC. We also observed a significant increase in ERCC1 expression, and decrease in p53 and EGFR expression, in EC-9706 cells treated with SNX-2112 (P < 0.05), indicating the regulation of EC by SNX-2112. Furthermore, SNX-2112 treatment induced a significant decrease in the proliferation of EC-9706, which confirmed the function of SNX-2112. In summary, SNX-2112 inhibits the proliferation of EC cells by regulating the expression of ERCC1, EGFR, and p53.