大黄酚对局灶性脑缺血再灌注小鼠Beclin1及Bax的作用

目的 研究大黄酚（chrysophanol，CHR）对短暂性局灶性脑缺血再灌注小鼠缺血半暗带区自噬蛋白Beclin1及缺血侧大脑半球促凋亡蛋白Bax水平的影响，探究CHR对脑缺血再灌注损伤的保护机制。方法 将18只健康C57BL/B6雄性小鼠按数字表法随机分为3组：假手术（Sham）组、大脑中动脉梗死（middle cerebral artery occlusion，MCAO）组、CHR组（自造模当天至再灌注后14 d每天按0.1 mg/kg腹腔注射CHR），每组6只。按照线栓法制作小鼠右侧大脑中动脉缺血45 min再灌注模型。再灌注14 d时将小鼠处死后，迅速断头、取脑，应用免疫荧光染色法检测脑组织冰冻切片缺血半暗带区自噬Beclin1水平，Western blotting法检测缺血侧脑组织Bax蛋白水平。结果 1） Sham组小鼠脑内偶见Beclin1阳性细胞。MCAO组小鼠脑缺血半暗带区Beclin1表达水平比Sham组显著升高（P<0.05）。给予CHR治疗的脑缺血再灌注小鼠半暗带区Beclin1的表达水平比MCAO组显著减少（P<0.05）。2）在脑缺血半暗带区，Beclin1与神经元标志物NeuN共定位。3） MCAO组小鼠缺血侧脑组织Bax蛋白水平比Sham组明显升高（P<0.05）。CHR组小鼠缺血侧脑组织Bax蛋白水平比MCAO组显著减少（P<0.05）。结论 CHR可能通过抑制Bax蛋白表达水平，减少Beclin1蛋白产生，减轻神经元凋亡，避免自噬过度激活，从而对脑缺血再灌注损伤发挥长期神经保护作用。

Effects of chrysophanol on Beclin1 and Bax protein expressions in mice with focal cerebral ischemia/reperfusion injury

Objective To study the protective effect mechanism of chrysophanol (CHR) on focal cerebral ischemia/reperfusion mice by regulating the expressions of autophagy-related protein Beclin1 and apoptosis-related protein Bax. Methods A total of 18 male C57BL/B6 mice were randomly (random number) divided into three groups:Sham group (n=6), middle cerebral artery occlusion (MCAO)/perfusion (MCAO group, n=6), and CHR group (n=6). The right MCAO for 45 min was induced by thread embolism and the reperfusion lasted for 14 days. CHR in dose of 0.1 mg/kg was intraperitoneally injected in CHR group mice once a day. On 14 d after reperfusion, the brain tissue was obtained. The positive expressions of autophagy-related protein Beclin1 in the brain ischemic penumbra were observed with immunofluorescent staining. The level of apoptosis-related protein Bax in ischemic brain tissue sections was determined by Western blotting. Results 1) There was little Beclin1 positive cells in Sham group. Compared with Sham group, the number of Beclin1 positive cells in the penumbra of MCAO group obviously increased on 14 d after reperfusion (P<0.05). Compared with MCAO group, the number of positive cells of Beclin1 decreased significantly in the penumbra of CHR group on 14 d after reperfusion (P<0.05). 2) The Beclin1 positive cells were co-localized with NeuN, a general neuronal marker, in the brain ischemic penumbra. 3) Bax protein level was upregulated in the brains of MCAO mice on 14 d after reperfusion. CHR treatment decreased Bax protein level in the ischemic tissue compared with MCAO group (P<0.05). Conclusion CHR may reduce neuronal apoptosis and alleviate excessive activation of autophagy by inhibiting the production of Bax protein and reducing the production of Beclin1 protein, and thus exerts long-term neuroprotective effects on cerebral ischemia-reperfusion injury.