Effect of NPC-14686 (Fmoc-L-homophenylalanine) on intracellular Ca2+ levels in human hepatoma cells

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.

NPC-14686 (Fmoc-l-homophenylalanine)-induced CaCa2+ increases and death in human prostate cancer cells

The effect of NPC-14686, a potential anti-inflammatory drug, on cytosolic free Ca2+ levels ([Ca2+]i) and growth in PC3 human prostate cancer cells was examined by using fura-2 as a fluorescent Ca2+ indicator and WST-1 as a fluorescent growth dye. NPC-14686 at concentrations above 10 microM increased [Ca2+]i in a concentration-dependent manner with an EC50 value of 100 microM. NPC-14686-induced Ca2+ influx was confirmed by Mn2+ quench of fura-2 fluorescence. The Ca2+ signal was also reduced by removing extracellular Ca2+. Pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor) to deplete the endoplasmic reticulum Ca2+ nearly abolished 200 microM NPC-14686-induced Ca2+ release; and conversely pretreatment with NPC-14686 completely inhibited thapsigargin-induced Ca2+ release. The Ca2+ release induced by 200 microM NPC-14686 was not affected by inhibiting phospholipase C with 2 microM U73122. Overnight treatment with 1-500 microM NPC-14686 decreased cell viability in a concentration-dependent manner. These findings suggest that in human PC3 prostate cancer cells, NPC-14686 increases [Ca2+]i by evoking extracellular Ca2+ influx and releasing intracellular Ca2+ from the endoplasmic reticulum via a phospholiase C-independent manner. NPC-14686 may be cytotoxic to prostate cancer cells.