MCU介导的线粒体Ca2+稳态失调参与模拟失重引起的大鼠脑动脉平滑肌细胞凋亡

目的 观察线粒体钙单向转运体（mitochondrial Ca2+ uniporter, MCU）在模拟失重引起大鼠脑动脉平滑肌细胞凋亡中的作用。 方法 采用尾吊大鼠方法建立模拟失重模型，实验大鼠分为对照（Control, CON）组和尾吊（tail suspension, SUS）组。造模成功后，分离脑动脉血管，取病理切片行TUNEL染色及细胞色素C免疫荧光染色检测平滑肌细胞凋亡水平，蛋白免疫印迹实验检测凋亡相关蛋白及MCU蛋白表达水平，最后急性分离脑动脉平滑肌细胞，分别采用Rhod-2 AM、mitoSOX染色检测细胞线粒体内Ca2+水平和活性氧簇（reactive oxygen species，ROS）水平。 结果 与对照组比较，尾吊组模拟失重大鼠基底动脉平滑肌细胞TUNEL阳性率显著增加（P < 0.05），细胞色素C入核率显著增加（P < 0.05），促凋亡蛋白cleaved caspas-9、cleaved caspas-3、Bax表达显著增加（P < 0.05），抑制凋亡蛋白Bcl-2显著降低（P < 0.05）；同时，MCU蛋白表达水平下调（P < 0.05）；此外，尾吊组大鼠脑动脉平滑肌细胞线粒体内Ca2+浓度下降（P < 0.05）及ROS水平增加（P < 0.05）。 结论 模拟失重引起大鼠脑动脉平滑肌细胞凋亡，同时MCU表达降低，提示MCU可能参与了模拟失重引起的脑动脉平滑肌细胞凋亡这一病理过程。

MCU mediated dysregulation of mitochondrial Ca2+ homeostasis is involved in apoptosis of cerebral arterial smooth muscle cells induced by simulated microgravity in rats

AIM To investigate the effects of mitochondrial Ca2+ uniporter (MCU) on the apoptosis of cerebral arterial smooth muscle cells induced by simulated microgravity. METHODS Hindlimb unloading tail suspension was performed in rats to simulate the effect of weightlessness on vascular system. The experimental animals were divided into a control group (CON) and a tail suspension group (SUS). After the SUS model was successfully established, apoptosis of cerebral arterial smooth muscle cells was assessed by TUNEL staining and cytochrome cimmunofluorescence staining, and protein expressions of Bcl-2 and Bax and cleaved Caspase-3 and Caspase-9 in cerebral arteries were detected by Western blot. Rhod-2 AM and mitoSOX were used to detect the levels of mitochondrial Ca2+ and reactive oxygen species (ROS), respectively. RESULTS Simulated microgravity enhanced the apoptosis of cerebral artery smooth muscle cells (P < 0.05) and the expression of MCU was down-regulated (P < 0.05). In addition, the mitochondrial Ca2+ decreased (P < 0.05) and ROS levels increased (P < 0.05) in cerebral artery smooth muscle cells isolated from SUS rats. CONCLUSION Down-regulation of MCU expression in cerebral artery of rats leads to the decrease of mitochondrial Ca2+ level and the increase of ROS level, which participate in the apoptosis of cerebral artery smooth muscle cells induced by simulated weightlessness.