Barhoumi Rola, Burghardt Robert C, Qian Yongchang, Tiffany-Castiglioni Evelyn
Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843-4458, USA.
Brain Res. 2007 May 11;1145:11-8. doi: 10.1016/j.brainres.2007.01.118. Epub 2007 Feb 2.
The effects of propofol, a short-acting general anesthetic, upon cell growth and Ca(2+) signaling in a human astrocytic cell line were examined. Exposure of cells to graded concentrations of propofol resulted in a dose-dependent decrease in cell number with an inhibitory concentration of cell viability (IC50) of 31.7+/-1.2 microM. To evaluate the changes in intracellular Ca(2+) homeostasis induced by propofol, cytoplasmic and mitochondrial Ca(2+) were measured by fluorescence imaging. Mitochondrial Ca(2+) increased while cytoplasmic Ca(2+) decreased significantly at a propofol concentration lower than the IC50 (10 microM for 24 h, 1 microM for 72 h). In addition, propofol diminished the Ca(2+) response induced by fetal bovine serum (FBS). To determine the source of Ca(2+) alterations induced by propofol, pharmacologic agents targeting intracellular Ca(2+) homeostasis mechanisms were used. Nifedipine, an L-type Ca(2+) channel blocker, decreased FBS-induced Ca(2+) response of control cells to a level similar to propofol treated cells. However, diazoxide (a K(+)-ATP channel opener) administered 1 h before FBS addition restored the FBS response in propofol treated cells to a level similar to control. In addition, diazoxide increased mitochondrial Ca(2+) in control cells to a level comparable to propofol treated cells suggesting activation of these channels by propofol treatment. Addition of 1 muM RU-360 (a selective blocker of the mitochondrial Ca(2+) uniporter) for 30 min prior to propofol treatment restored mitochondrial and cytoplasmic Ca(2+) to control levels. These data suggest that voltage operated Ca(2+) channels, mitochondrial Ca(2+) and K(+)-ATP channels may be targets of propofol action in astrocytes.
研究了短效全身麻醉药丙泊酚对人星形胶质细胞系细胞生长和Ca(2+)信号传导的影响。将细胞暴露于不同浓度的丙泊酚中，细胞数量呈剂量依赖性减少，细胞活力抑制浓度（IC50）为31.7±1.2微摩尔。为评估丙泊酚诱导的细胞内Ca(2+)稳态变化，通过荧光成像测量细胞质和线粒体Ca(2+)。在丙泊酚浓度低于IC50时（10微摩尔作用24小时，1微摩尔作用72小时），线粒体Ca(2+)增加而细胞质Ca(2+)显著降低。此外，丙泊酚减弱了胎牛血清（FBS）诱导的Ca(2+)反应。为确定丙泊酚诱导的Ca(2+)改变的来源，使用了针对细胞内Ca(2+)稳态机制的药物。硝苯地平，一种L型Ca(2+)通道阻滞剂，将FBS诱导的对照细胞Ca(2+)反应降低到与丙泊酚处理细胞相似的水平。然而，在添加FBS前1小时给予二氮嗪（一种K(+)-ATP通道开放剂）可将丙泊酚处理细胞中的FBS反应恢复到与对照相似的水平。此外，二氮嗪使对照细胞中的线粒体Ca(2+)增加到与丙泊酚处理细胞相当的水平，表明丙泊酚处理激活了这些通道。在丙泊酚处理前30分钟添加1微摩尔RU-360（线粒体Ca(2+)单向转运体的选择性阻滞剂）可使线粒体和细胞质Ca(2+)恢复到对照水平。这些数据表明，电压门控Ca(2+)通道、线粒体Ca(2+)和K(+)-ATP通道可能是丙泊酚在星形胶质细胞中的作用靶点。
