细胞凋亡在脊髓小脑性共济失调3型发病机制中的作用

Role of cell apoptosis in the molecular pathogenesis of spinocerebellar ataxia type 3

目的研究细胞凋亡在脊髓小脑性共济失调3型(SCA3)分子发病机制中的作用。方法将带有SCA3正常与突变基因的增强型绿色荧光蛋白真核表达载体(pEGFP)转染大鼠肾上腺嗜铬细胞瘤(PC12)细胞,采用丫啶橙(AO)染色及电镜观察细胞凋亡的发生情况,免疫荧光检测转染后24h、72h、120h半胱氨酸天门冬氨酸酶3、8(caspase3、8)在细胞核内的分布及其与核内包涵体(INIs)共定位的情况;缺口末端标记(TUNEL)法观察正常基因组与突变基因组以及突变基因组在给予广谱caspase阻断剂zVAD-fmk(100μmol/L)后细胞凋亡的变化。结果随着转染后时间的延长,突变基因组细胞发生了明显的凋亡,caspase3、caspase8核内与INIs共定位。正常组与突变组TUNEL阳性细胞数有明显差异并有显著性意义(P<0.01),突变组在给予zVAD-fmk后细胞凋亡明显减轻,差异有显著性意义(P<0.01)。结论细胞凋亡在SCA3发病机制中起重要的作用,抑制凋亡通路可以减少细胞死亡,推测对凋亡环节的干预有可能成为SCA3治疗的靶点。

Objective To study the role of cell apoptosis in the molecular pathogenesis of spinocerebellar ataxia type 3 （SCA3）. Methods Plasmid-enhanced green fluorescent protein （pEGFP） including normal or mutant SCA3 gene was transfected into PC12 cells. Apoptosis was observed by AO-staining and electron microscope. The locations of caspase3 and caspase8 in cell nucleus and their co-locations with intranuclear inclusions （INIs） were observed by immunocytochemistry after transfection of 24 h, 72 h, and 120 h. The difference of cell apoptosis was studied with TUNEL between the normal and mutant SCA3 gene group and the mutant gene group before and after giving the caspases inhibitor zVAD-fmk （100 μmol/L） by TUNEL. Results Apoptosis was obvious in the mutant SCA3 gene group after transfection. Caspase3 and caspase8 co-localized with INIs and gave off dense fluorescence. The quantity difference of TUNEL positive cells was significant （P〈0.01） between the normal and mutant SCA3 gene group. So was it between the mutant gene group before and after giving zVAD-fmk. Conclusion The cell apoptosis plays an important role in the molecular pathogenesis of SCA3. Inhibition of caspases mitigates the cell death greatly. And the interference of cell apoptosis would be one way of SCA3 therapy.