活性氧和ERK1/2信号通路在缺氧大鼠肺动脉平滑肌细胞增殖和凋亡中的作用

目的：研究缺氧状态下大鼠肺动脉平滑肌细胞（PASMCs）内活性氧（ROS）水平的变化，ROS对细胞外信号调节激酶（ERK）1/2蛋白表达的影响以及ROS和ERK1/2在PASMCs增殖和凋亡关系失衡中的作用。方法: 原代培养正常大鼠PASMCs，选用第2-3代用于实验。分别在常氧及缺氧条件下用ROS清除剂tiron、ERK1/2抑制剂PD98059进行分组干预。通过NBT还原法和DCFH-DA荧光探针检测细胞内ROS，免疫荧光法检测磷酸化- ERK1/2（p-ERK1/2）蛋白表达，MTT比色法和增殖细胞核抗原（PCNA）蛋白的免疫细胞化学法检测细胞增殖，原位末端标记法（TUNEL）检测细胞凋亡。结果: (1)缺氧组细胞内ROS水平明显高于对照组（P<0.01）；(2)缺氧组的增殖活性与对照组相比显著增高（P<0.01），而凋亡率显著降低（P<0.01），使用tiron后能明显抑制缺氧诱导的细胞增殖（P<0.05），而凋亡率却明显升高（P<0.01）；(3)缺氧组p-ERK1/2蛋白表达显著高于对照组（P<0.01），使用tiron后缺氧诱导的p-ERK1/2表达被显著抑制（P<0.01）；(4)使用PD98059也能明显抑制缺氧诱导的细胞增殖（P<0.05），而凋亡率也明显升高（P<0.01），缺氧下同时使用PD98059和tiron与单用tiron相比，对细胞增殖和凋亡的影响均无明显差异（P>0.05）。结论: 缺氧时PASMCs中生成增多的ROS通过活化下游ERK1/2信号通路，促进PASMCs增殖并抑制凋亡，从而在缺氧性肺动脉重建过程中发挥重要作用。

Role of reactive oxygen species and ERK1/2 signaling pathway in proliferation and apoptosis of hypoxic rat pulmonary arterial smooth muscle cells

AIM:To investigate the change of reactive oxygen species (ROS) production in hypoxic pulmonary arterial smooth muscle cells (PASMCs) of rats, the effect of ROS on the expression of extracellular signal-regulated kinase (ERK)1/2 protein, and the role of ROS and ERK1/2 in the imbalance between proliferation and apoptosis of PASMCs.METHODS: Primary cultures of PASMCs were established and cells between passages 2 to 3 were used for experiments. PASMCs were treated with tiron, a membrane permeable ROS scavenger, and PD98059, an ERK1/2 inhibitor, under normoxia or hypoxia condition. The ROS production was measured by DCFH-DA and NBT reduction. The expression of phosphorylated-ERK1/2 (p-ERK1/2) protein was detected by immunofluorescence. Cell proliferation was examined by MTT colorimetric assay and the expression of PCNA. Cell apoptosis was detected by TUNEL.RESULTS: (1)Compared with control group, the ROS levels in hypoxia group were significantly increased (P<0.01). (2) In hypoxia group, the proliferative capacity was higher and the apoptosis index was lower than those in control group (P<0.01). Tiron significantly attenuated hypoxia-induced cell proliferation (P<0.05) and also significantly raised the apoptosis index in hypoxia cells (P<0.01). (3) The expression of p-ERK1/2 in hypoxia group were higher than that in control group (P<0.01), which were significantly suppressed by tiron (P<0.01)．(4) PD98059 significantly attenuated hypoxia-induced cell proliferation (P<0.05) and also significantly raised the apoptosis index in hypoxia cells (P<0.01). The proliferative capacity and apoptosis index was similar in hypoxia+tiron+PD98059 group to those in hypoxia+tiron group (P>0.05).CONCLUSION:The hypoxia-mediated increase in PASMCs proliferation and the decrease in PASMCs apoptosis are related to the overproduction of intracellular ROS through downstream activation of ERK1/2. ROS and ERK1/2 play important roles in the hypoxic remodeling of pulmonary artery.