摘要
目的 探讨诱导型一氧化氮合酶 (iNOS)抑制剂S 甲基异硫脲 (S methylisourea ,SMT)对脂多糖(lipopolysaccharide ,LPS)诱导多巴胺 (DA)能神经元变性的保护作用及其机制。 方法 4 8只大鼠随机分成 4组(n =12 ) :磷酸缓冲液 (PBS)对照组、LPS组、生理盐水治疗对照组和SMT治疗组 ;此 4组又各分成 1,7d两个亚组。立体定向注射 5 μgLPS致大鼠脑黑质建立PD炎症模型 ,采用化学比色法检测 1d亚组黑质内NO释放量以及iNOS活性改变 ;RT PCR检测iNOSmRNA的表达 ;酪氨酸羟化酶 (tyrosinehydroxylase ,TH)免疫组织化学染色观察 7d亚组黑质DA能神经元的损伤情况。结果 与PBS对照组相比 ,LPS注入黑质导致TH阳性细胞数下降至 35 % (P <0 .0 5 ) ;同时黑质内NO含量 ,iNOS活性及iNOSmRNA表达明显增高 ;SMT治疗组NO释放量 ,iN OS活性及iNOSmRNA表达显著降低 (P <0 .0 1) ;TH阳性细胞数亦明显增多 ,达 70 % (P <0 .0 5 ) ,生理盐水治疗组对此无明显改善。结论 iNOS上调是LPS诱导DA能神经元变性机制中重要的因素之一 。
Objective To explore the mechanism related to S-methylisourea (SMT) protective effect against the degeneration of dopaminergic neurons induced by intranigral injection of lipopolysaccharide (LPS). Methods Forty-eight female Sprague-Dawley rats were randomly divided into four groups(n=12):PBS group; LPS group; saline solution treatment group and SMT treatment group. Each group was divided into 1 d and 7 d subgroups. The Parkinson’s model was established by intranigral injection of LPS. NO production and inducible nitric oxide synthase (iNOS) activity in the Substantia nigra (SN) were examined one day later by chemicalcolorimetry; the expression of iNOS mRNA was measured with RT-PCR; the damage of the substantial nigral DA neurons was assessed by using tyrosine-hydroxylse (TH) immunohistochemical staining 7 d later. Results Compared with PBS control group, TH-positive neurons in the SN decreased by 65%, and production of NO, activity of iNOS and iNOS mRNA were upregulated post injection of LPS(P<0.01). SMT significantly inhibited NO production, iNOS activity, iNOS mRNA, and increased the TH-positive neurons in the SN compared with saline treatment group(P<0.01).Conclusion The up-regulation of iNOS may be a crucial mechanism in LPS-induced DA neurons degeneration; SMT attenuated the neurotoxicity of LPS and inhibited iNOS mRNA expression.
基金
国家自然科学基金资助(30170334)
2002年国家教委博士点基金资助(20020487065)
