Safrole-Induced Ca²⁺Mobilization and Cytotoxicity in Human PC3 Prostate Cancer Cells

Abstract

The effect of the carcinogen safrole on intracellular Ca2+ mobilization and on viability of human PC3 prostate cancer cells was examined. Cytosolic free Ca2+ levels ([Ca2+]i) were measured by using fura-2 as a probe. Safrole at concentrations above 10 microM increased [Ca2+]i in a concentration-dependent manner with an EC50 value of 350 microM. The Ca2+ signal was reduced by more than half after removing extracellular Ca2+ but was unaffected by nifedipine, nicardipine, nimodipine, diltiazem, or verapamil. In Ca2+-free medium, after treatment with 650 microM safrole, 1 microM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor) failed to release Ca2+. Neither inhibition of phospholipase C with U73122 nor modulation of protein kinase C activity affected safrole-induced Ca2+ release. Overnight incubation with 0.65-65 microM safrole did not affect cell viability, but incubation with 325-625 microM safrole decreased viability. Collectively, the data suggest that in PC3 cells, safrole induced a [Ca2+]i increase by causing Ca2+ release from the endoplasmic reticulum in a phospholipase C- and protein kinase C-independent fashion, and by inducing Ca2+ influx. Safrole can decrease cell viability in a concentration-dependent manner.

Effect of MK‐886 on Ca2+ Level and Viability in PC3 Human Prostate Cancer Cells

“…Previous studies showed that the endoplasmic reticulum is a major Ca 2+ store in most cells [19–21]. Fig.…”

“…Regarding the Ca 2+ stores involved in MK‐886‐induced Ca 2+ release, our data show that the thapsigargin‐sensitive stores overlapped with MK‐886‐sensitive stores because depletion of the endoplasmic reticulum with thapsigargin fully prevented MK‐886 from releasing more store Ca 2+ , and conversely, MK‐886 pre‐treatment completely depleted thapsigargin‐sensitive stores. Previous studies also have shown that thapsigargin‐sensitive endoplasmic reticulum Ca 2+ store is the dominant store in PC3 cells, by using other agonists such as desipramine [19] and safrole [20]. Furthermore, it seems that phospholipase C‐dependent pathways did not play a role in MK‐886‐induced Ca 2+ release, because the response was not altered by suppressing phospholipase C activity.…”

Effect of celecoxib on Ca2+handling and viability in human prostate cancer cells (PC3)

“…Previous reports have shown that the endoplasmic reticulum (ER) is the major Ca 2+ store in PC3 cells (Chang et al, 2006(Chang et al, , 2008. Figure 4A shows that treatment with 30 μM of celecoxib for 440 seconds induced a [Ca 2+ ] i rise of 52 ± 2 nM, followed by a decay to near baseline.…”

“…The inositol 1,4,5-trisphosphate (IP3)-sensitive Ca 2+ store is an important Ca 2+ store that releases Ca 2+ into the cytosol when cells are stimulated by endogenous ligands, such as histamine (Lee et al, 2001). But, exogenous ligands can release Ca 2+ from inositol IP3insensitive stores (Chang et al, 2006(Chang et al, , 2008.…”

“…PC3 cells have characteristics similar to human prostate cells and have been used as a model for research on the human prostate (Rodan et al, 1983). Many endogenous and exogenous reagents can stimulate PC3 cells by evoking a [Ca 2+ ] i rise, such as desipramine (Chang et al, 2008), safrole (Chang et al, 2006), and histamine (Lee et al, 2001). The inositol 1,4,5-trisphosphate (IP3)-sensitive Ca 2+ store is an important Ca 2+ store that releases Ca 2+ into the cytosol when cells are stimulated by endogenous ligands, such as histamine (Lee et al, 2001).…”