金属基质蛋白酶9在抗肾小球基底膜病发病机制中的作用

Anti-glomerular basement membrane (GBM) disease is an autoimmune disorder characterized by rapidly progressive glomerulonephritis and a high risk for alveolar hemorrhage. It has been regarded as a prototypical example of autoantibody-mediated disease with a well documented autoantigen, which has been identified as the non-collagenous domain (NC1) of α3 chain of type IV collagen [α3(IV)NC1]. However, it is still unknown why the immune tolerance to GBM is broken during the pathogenesis of the disease. MMP 9 is an effective enzyme to degrade the type IV collagen and liberate NC1 domains of α3 chain into the circulation, which is called tumstatin. Previous studies in animal models suggest that MMP-9 may be involved in the glomerular injury during the early stage of anti-GBM disease. We speculate that high activity levels of MMP 9 in anti-GBM patients may generate high levels of tumstatin and thus break the immune tolerance to α3(IV)NC1. In this study, we will exam the level and activity of MMP 9 in anti-GBM patients, as well as its expression in glomeruli. The expression of MMP 9 in glomeruli and the level of circulating tumstatin will be investigated in anti-GBM rat mode during different stage of the disease in order to find out the correlation between them.

抗GBM病的发病过程中，人体为何会打破免疫耐受，产生针对α3(IV)NC1的自身抗体/自身反应性的淋巴细胞，至今仍不明确。MMP-9 可以降解GBM的IV型胶原，产生游离的α3(IV)NC1即tumstatin。既往动物实验表明MMP-9参与了抗GBM病的早期发病过程，但机制尚不明确。我们推测抗GBM病发病过程中可能存在MMP-9的表达水平或活性异常，使GBM过度降解，暴露了GBM上隐匿的抗原位点，并使循环中的tumstatin水平异常，从而打破了人体的免疫耐受。本课题将利用ELISA的方法及明胶酶谱法研究抗GBM病患者循环中MMP-9的水平及活性；利用免疫组化的方法检测抗GBM病患者肾组织上MMP-9的表达水平及分布。同时，本课题将利用本实验室现有的抗GBM病大鼠模型，研究在抗GBM病发病过程中，大鼠体内MMP-9的表达或活性是否存在异常，明确其与循环中tumstatin水平之间的关系。

金属基质蛋白酶9（MMP-9） 可以降解GBM的IV型胶原，产生游离的α3(IV).NC1，既往动物实验表明MMP-9参与了抗GBM病的早期发病过程，但机制尚不明确。本课题利用ELISA的方法检测了抗GBM病患者循环中MMP-9的水平及.活性，发现其确实高于正常对照，但与其他肾脏疾病组相比并没有显著差异，因此推测该酶在抗GBM病中水平和活性的变化可能不具有疾病特异性。我们前期研究发现α3(IV)NC1上第127-148位氨基酸P14可能是抗GBM病的致病性的抗原决定簇，我们证实了它是抗GBM病患者T、B细胞共同识别的抗原表位，利用氨基酸替换明确了其上B细胞识别的关键氨基酸，并且利用该肽段免疫Wistar-kyto大鼠成功诱发了抗GBM肾炎，为进一步研究该病的发病机制及免疫治疗提供了平台。