Huang Jong-Khing, Huang Chun-Jen, Chen Wei-Chuan, Liu Shiuh-Inn, Hsu Shu-Shong, Chang Hong-Tai, Tseng Li-Ling, Chou Chiang-Ting, Chang Chih-Hung, Jan Chung-Ren
Department of Surgery, Kaohsiung Veterans General Hospital, Kaohsiung, 813, Taiwan.
Naunyn Schmiedebergs Arch Pharmacol. 2005 Jul;372(1):88-94. doi: 10.1007/s00210-005-1086-y. Epub 2005 Aug 4.
The effect of the carcinogen safrole on intracellular Ca2+ movement and cell proliferation has not been explored previously. The present study examined whether safrole could alter Ca2+ handling and growth in human oral cancer OC2 cells. Cytosolic free Ca2+ levels ([Ca2+]i) in populations of cells were measured using fura-2 as a fluorescent Ca2+ probe. Safrole at a concentration of 325 microM started to increase [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced by 40% by removing extracellular Ca2+, and was decreased by 39% by nifedipine but not by verapamil or diltiazem. In Ca2+-free medium, after pretreatment with 650 microM safrole, 1 microM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor) barely induced a [Ca2+]i rise; in contrast, addition of safrole after thapsigargin treatment induced a small [Ca2+]i rise. Neither inhibition of phospholipase C with 2 microM U73122 nor modulation of protein kinase C activity affected safrole-induced Ca2+ release. Overnight incubation with 1 microM safrole did not alter cell proliferation, but incubation with 10-1000 microM safrole increased cell proliferation by 60+/-10%. This increase was not reversed by pre-chelating Ca2+ with 10 microM of the Ca2+ chelator BAPTA. Collectively, the data suggest that in human oral cancer cells, safrole induced a [Ca2+]i rise by causing release of stored Ca2+ from the endoplasmic reticulum in a phospholipase C- and protein kinase C-independent fashion and by inducing Ca2+ influx via nifedipine-sensitive Ca2+ entry. Furthermore, safrole can enhance cell growth in a Ca2+-independent manner.
致癌物质黄樟素对细胞内钙离子移动和细胞增殖的影响此前尚未得到研究。本研究检测了黄樟素是否会改变人口腔癌细胞OC2中的钙离子处理和生长情况。使用fura-2作为荧光钙离子探针来测量细胞群体中的胞质游离钙离子水平（[Ca2+]i）。浓度为325微摩尔的黄樟素开始以浓度依赖的方式增加[Ca2+]i。去除细胞外钙离子后，钙离子信号降低了40%，硝苯地平使其降低了39%，但维拉帕米或地尔硫䓬没有使其降低。在无钙培养基中，用650微摩尔黄樟素预处理后，1微摩尔毒胡萝卜素（一种内质网钙离子泵抑制剂）几乎未诱导[Ca2+]i升高；相反，在毒胡萝卜素处理后添加黄樟素诱导了较小的[Ca2+]i升高。用2微摩尔U73122抑制磷脂酶C或调节蛋白激酶C活性均不影响黄樟素诱导的钙离子释放。用1微摩尔黄樟素过夜孵育不会改变细胞增殖，但用10 - 1000微摩尔黄樟素孵育会使细胞增殖增加60±10%。用10微摩尔钙离子螯合剂BAPTA预先螯合钙离子并不能逆转这种增加。总体而言，数据表明在人口腔癌细胞中，黄樟素通过以磷脂酶C和蛋白激酶C非依赖的方式从内质网释放储存的钙离子以及通过诱导经硝苯地平敏感的钙离子内流来诱导[Ca2+]i升高。此外，黄樟素可以以钙离子非依赖的方式增强细胞生长。
