雄激素对新生大鼠缺氧缺血脑损伤的保护作用及机制研究(英文)

Protection of androgen against hypoxic-ischemic brain damage in neonatal rats and possible mechanisms

摘要:

目的：雄激素对缺氧缺血后脑损伤有神经保护作用,但其作用机制尚不完全清楚。该研究探讨雄激素对缺氧缺血性脑损伤(HIBD)的保护作用及其可能的机制。方法：64只7日龄SD大鼠随机分为假手术组、HIBD对照组和雄激素干预组。通过结扎左颈总动脉和吸入8%氧气和92%氮气的混合气体制备新生鼠HIBD模型。假手术组仅做颈正中切口,游离左颈总动脉,不结扎,不行低氧处理。雄激素干预组在模型制成后即刻注射丙酸睾丸酮(25mg/kg)。缺氧缺血(HI)后6h、24h、72h、7d取脑组织制作石蜡切片,用免疫组化法观察Bcl-2和Bax蛋白在各组大鼠皮质和海马表达的动态变化。HI后6h、24h、48h断头取脑制作脑匀浆,测定SOD活性和MDA含量。结果：假手术组大鼠左脑的皮质及海马可见少量Bcl-2蛋白和Bax蛋白免疫阳性细胞表达,与HIBD对照组和雄激素干预组比较差异均有显著性意义(P<0.01)。雄激素干预组HI后6h、24h、72hBcl-2蛋白在皮层和海马的表达水平明显高于HIBD对照组(P<0.05或0.01)。雄激素干预组Bax蛋白的表达水平在HI后24h显著低于HIBD对照组(P<0.05),其他时间点两组Bax蛋白的表达无明显差别。与假手术组比较,HIBD对照组HI后6h大鼠脑组织中SOD活性明显降低,MDA含量明显增加(P<0.05)。HIBD对照组HI后24hSOD活性降至最低值,MDA含量升至最高。雄激素干预增加了SOD活性,雄激素干预组HI后6h、24h、48hSOD活性均明显高于HIBD对照组,差异有显著性意义(P<0.05或0.01)。雄激素干预亦导致了脑组织中MDA含量降低,雄激素干预组HI后6h、24hMDA含量均明显低于HIBD对照组,差异有显著性意义(分别P<0.05、P<0.01)。结论：雄激素发挥脑保护作用可能通过上调Bcl-2蛋白、下调Bax蛋白表达以及通过减少抗氧化剂的消耗和抑制氧自由基的生成,从而减轻缺氧缺血后神经细胞的损伤。

Abstract:

OBJECTIVE: Some research has shown that androgen has a neuroprotection against hypoxia-ischemia brain damage (HIBD). However, the relevant mechanism has not been fully elucidated. This study aimed to explore the neuroprotection of androgen against HIBD in neonatal rats and the possible mechanism. METHODS: Sixty-four seven-day-old Sprague-Dawley (SD) rats were randomly assigned into three groups: Sham-operation, HIBD and Androgen. The HIBD model was induced by ligation of the left carotid common artery along with hypoxia exposure in neonatal rats from the latter two groups. The Sham-operation group was not subjected to hypoxia-ischemia (HI). The Androgen intervention group received an injection of testosterone propionate (25 mg/kg) immediately after HIBD. Bcl-2 and Bax protein expressions in the cortex and hippocampal CA region were detected by immunohistochemical method at 6, 24 and 72 hrs and at 7 days after HI. The contents of SOD and MDA in the brain tissue homogenate were measured by the thiobarbituric acid (TBA) method and the xanthine oxidase luminescence method respectively at 6, 24 and 48 hrs after HI. RESULTS: There were few Bcl-2 and Bax immune positive cells in the cortex or hippocampus in the left hemisphere in the Sham-operation group at 6 hrs after operation. This was significantly different from the HIBD control and Androgen intervention groups(P< 0.01). The expression of Bcl-2 protein in the cortex and hippocampus of the Androgen intervention group was significantly higher than that of the HIBD control group at 6, 24 and 72 hrs after HI (P<0.05 or 0.01). The expression of Bax protein in the cortex and hippocampus of the Androgen intervention group was significantly lower than that of the HIBD control group at 24 hrs after HI (P﹤0.05).The SOD content in the brain tissue homogenate of the HIBD control group was significantly reduced, in contrast, the MDA content in the brain tissue homogenate of the HIBD control group increased significantly at 6 hrs after HI compared with the Sham-operation group (P<0.05). The SOD content was reduced to a nadir and the MDA content increased to a peak at 24 hrs after HI in the HIBD control group. Androgen intervention increased significantly the SOD activity at 6,24 and 48 hrs after HI and decreased significantly the MDA content at 6 and 24 hrs after HI as compared with the HIBD control group(P<0.05 or 0.01). CONCLUSIONS: The neuroprotection of androgen against neonatal HIBD is produced possibly through an increase of Bcl-2 protein expression and a reduction in Bax protein expression, thus decreasing neuronal apoptosis after HI.There may also be a reduction in the consumption of antioxidant and an inhibition of the formation of oxidant free radicals to alleviate neuronal damage following HI.