亚低温通过p38MAPK信号通路调控CPR大鼠脑组织AQP4表达并减轻脑水肿

Mild hypothermia regulates aquaporin 4 expression in brain tissue of rats with cardiopulmonary resuscitation and reduces brain edema through p38 mitogen-activated protein kinase signaling pathway

目的探讨p38丝裂素活化蛋白激酶(p38MAPK)信号通路在亚低温降低心肺复苏(CPR)大鼠脑组织水通道蛋白4(AQP4)表达中的作用。方法按随机数字表法将48只健康雄性SD大鼠分为假手术组、常温组和亚低温组,每组16只。采用窒息法建立大鼠心搏骤停心肺复苏(CPR)模型;假手术组仅行动静脉置管、气管插管。亚低温组在自主循环恢复(ROSC)后0.5h给予亚低温治疗(维持食道温度在32~34℃);常温组则置于室温下治疗(维持食道温度在36~38℃)。各组均于ROSC6h取脑组织,采用苏木素-伊红(HE)染色观察脑组织病理学改变;采用干-湿比重法测定脑组织含水量;采用蛋白质免疫印迹试验(Western Blot)测定脑组织磷酸化p38丝裂素活化蛋白激酶(p-p38MAPK)、p38MAPK及AQP4蛋白表达。结果与假手术组比较,常温组脑组织神经细胞体积缩小,胞质疏松,核固缩,凋亡小体形成,脑组织含水量增加〔(83.64±2.53)%比(77.95±0.94)%,P<0.05〕,脑组织p-p38MAPK、p38MAPK、AQP4蛋白表达均明显升高(p38MAPK/β-actin:1.010±0.217比0.427±0.090,p-p38MAPK/p38MAPK:0.451±0.172比0.191±0.141,AQP4/β-actin:3.129±0.754比1.598±0.464,均P<0.05)。与常温组比较,亚低温组神经细胞坏死程度减轻,脑组织含水量明显降低〔(80.49±2.05)%比(83.64±2.53)%,P<0.05〕,脑组织p38MAPK、p-p38MAPK和AQP4表达明显降低(p38MAPK/β-actin:0.590±0.162比1.010±0.217,p-p38MAPK/p38MAPK:0.298±0.076比0.451±0.172,AQP4/β-actin:2.061±0.340比3.129±0.754,均P<0.05)。结论亚低温可能通过p38MAPK信号通路调控CPR大鼠脑组织AQP4表达,并减轻脑水肿,从而发挥脑保护作用。

Objective To investigate the role of p38 mitogen-activated protein kinase (p38MAPK) signaling pathway in the expression of aquaporin 4 (AQP4) in brain tissue of rats with cardiopulmonary resuscitation (CPR) during mild hypothermia. Methods Forty-eight healthy male Sprague-Dawley (SD) rats were divided into sham operation group, normal temperature group and mild hypothermia group according to random number table method, with 16 in each group. The rat model of cardiac arrest-cardiopulmonary resuscitation (CPR) was established by asphyxia method. The sham operation group only experienced venous catheterization and tracheal intubation. The mild hypothermia group was treated with hypothermia 0.5 hours after restore of spontaneous circulation (ROSC, maintaining esophageal temperature at 32-34℃);the normal temperature group was treated at room temperature after ROSC (maintaining esophageal temperature at 36-38℃). Brain tissue was harvested at 6 hours after ROSC, and histopathological changes were observed by hematoxylin-eosin (HE) staining. The water content of brain tissue was determined by dry-wet specific gravity method. The protein expressions of phosphorylation of p38 mitogen-activated protein kinase (p-p38MAPK), p38MAPK and AQP4 in brain tissue were determined by Western Blot. Results Compared with the sham operation group, the nerve cells in the normal temperature group were reduced in size, cytoplasmic loosening, nuclear pyknosis, and in apoptotic body formation, water content of brain tissue was significantly increased [(83.64±2.53)% vs.(77.95±0.94)%, P < 0.05], the protein expressions of p-p38MAPK, p38MAPK, AQP4 were significantly increased (p38MAPK/β-actin: 1.010±0.217 vs. 0.427±0.090, p-p38MAPK/p38MAPK: 0.451±0.172 vs. 0.191±0.141, AQP4/β-actin: 3.129±0.754 vs. 1.598±0.464, all P < 0.05). Compared with the normal temperature group, the degree of necrosis of nerve cells in the mild hypothermia group was reduced, the water content of brain tissue was significantly decreased [(80.49±2.05)% vs.(83.64±2.53)%, P < 0.05], the protein expression of p38MAPK, p-p38MAPK and AQP4 in brain tissue were significantly decreased (p38MAPK/β-actin: 0.590±0.162 vs. 1.010±0.217, p-p38MAPK/p38MAPK: 0.298±0.076 vs. 0.451±0.172, AQP4/β-actin: 2.061±0.340 vs. 3.129±0.754, all P < 0.05). Conclusion Mild hypothermia may regulate the expression of AQP4 in brain tissue of CPR rats through p38MAPK signaling pathway, and reduce brain edema, thereby exerting brain protection.