Molecular analysis of type IV collagen accumulation in diabetic nephropathy

肾小球系膜扩张被认为是糖尿病肾病的主要病变。病变是由各种基质蛋白，特别是IV型胶原蛋白的积累引起的。因此，了解IV型胶原如何在系膜区积累，对于明确糖尿病肾病的发病机制具有重要意义。我们之前发表的研究表明，高浓度葡萄糖通过代谢作用增加肾小球系膜细胞IV型胶原蛋白的产生。为了研究葡萄糖增加IV型胶原生成的机制，我们在培养的大鼠系膜细胞中分析了IV型胶原生成与高浓度葡萄糖代谢后果之间的联系。高浓度葡萄糖引起蛋白激酶C （PKC）和丝裂原相关蛋白激酶（MAP）的显著活化。各种血管活性物质，能够激活PKC和MAP激酶，被观察到刺激IV型胶原的产生。然而，在高糖条件下培养的系膜细胞中，用VI (alpha_1) cDNA northern blotting未检测到IV型胶原mRNA水平的变化。在这些实验中，负责降解IV型胶原蛋白的MMP-2和-9的mrna都没有改变。由此可见，葡萄糖可能激活PKC和MAP激酶，进而刺激IV型胶原的产生，这可能与糖尿病肾小球中IV型胶原的积累有关。

The mesangial expansion in glomerulis considered to be a cardinal lesion of diabetic nephropathy. The lesion is caused by the accumulation of various matrix proteins, especially of type IV collagen. So, it is important to know how type IV collagen accumulate in mesangial area in order to clarify the pathogenesis of diabetic nephropathy.We have previous published that high concentration of glucose increases type IV collagen production in glomerular mesangial cells via its metabolic effect. In an attempt to investigate the mehanism why glucose increases type IV collagen production, the linkage between type IV collagen production and metabolic consequences to high concentration of glucose was analyzed in rat cultured mesangial cells. High concentration of glucose caused significant activation of protein kinase C (PKC) as well as of mitogen-associated protein (MAP) kinase. Various vasoactive substances, which are able to activate PKC and MAP kinase, are observed to stimulate type IV collagen production. However, any change in mRNA level for type IV collagen was not detected by northern blotting using VI (alpha_1) cDNA in mesangial cells cultured under high glucose condition. mRNAs for MMP-2 and -9, which were responsible for degrading type IV cllagen were neither changed in those experiments.It is concluded from these results that glucose may activate PKC and MAP kinase, and may in turn stimulate type IV collagen production, which might be associated with the accumulation of type IV collagen in diabetic glomeruli.