Effects of glycated type IV collagen on extracellular matrix components synthesis in rat mesangial cells

最近的研究表明，肾小球蛋白糖基化增加在糖尿病肾病的发病机制中起着重要作用。IV型胶原是肾小球细胞外基质的主要成分之一，由于其较长的半衰期，似乎是蛋白质糖化的主要靶点。糖尿病肾病以系膜基质堆积为特征。系膜基质的积聚是由于基质成分的增加或基质降解的减少而发生的，最近的研究表明转化生长因子-β在系膜基质的积聚中起着突出的作用。为了阐明IV型胶原在肾小球硬化发展中的作用，我们研究了IV型胶原体外糖基化对大鼠肾小球系膜细胞基质成分、基质降解酶和转化生长因子-β基因表达的影响。新增总账…随着IV型胶原与膜细胞的结合增多，α1(I)胶原基因表达水平呈时间依赖性增加，48h达到最大值。添加糖化的IV型胶原还导致α1(IV)胶原和纤维连接蛋白的mRNA水平增加。添加糖化的IV型胶原不影响条件培养液中明胶酶的分解活性。糖基化的IV型胶原对基质金属蛋白酶-2的mRNA表达水平也没有明显影响。糖化的IV型胶原在24小时后诱导转化生长因子-βmRNA水平升高，这先于α1(I)胶原mRNA水平的升高。与抗转化生长因子-β中和抗体共同孵育后，糖化Coll IV诱导的α1(I)胶原基因表达水平显著降低。瞬时转染α1(I)胶原启动子-荧光素酶的系膜细胞，加入糖化的IV型胶原后，启动子活性显著增加。这些结果表明，糖化的IV型胶原通过转录激活诱导系膜细胞基质成分基因的表达，这种作用部分是通过诱导转化生长因子-β的表达来实现的。较少

Recent studies have indicated that increased glycation in glomerular proteins plays an important role in the pathogenesis of diabetic nephropathy. Type IV collagen, one of major components of glomerular extracellular matrix, appears to be a predominant targets for protein glycation because of its long half life. Diabetic nephropathy is characterized by the accumulation of mesangial matrix. Accumulation of mesangial matrix occurs as the result of an increase in production of matrix components or a decrease in matrix degradation, and recent studies indicates a preeminent role for TGF-beta in the accumulation of mesangial matrix. To clarify the role of accumulation of glacycated type IV collagen in the development of glmerular sclerosis, we investigated that the effects of in vitro glycation of type IV collagen on the gene expression of matrix components, matrix-degrading enzyme, and TGF-beta in rat mesangial cells.Type IV collagen was glycated with incubation with glucose. Addition of gl … More ycated type IV collagen to meangial cells caused time dependent increase in the alpha1(I) collagen mRNA levels with maximal increases occurring at 48 hr. Addition of glycated type IV collagen also led to increases in mRNA levels for alpha1(IV) collagen and fibronectin. Gelatinolytic activity in conditioned media was not affected by the addition of glycated type IV collagen. The mRNA levels for matrix metalloproteinase-2 also did not show significant change by the glycated type IV collagen. Glycated type IV collagen induced increase in TGF-beta mRNA levels after 24 hr, which preceded the increase in alpha1(I) collagen mRNA levels. Increase in alpha1(I) collagen mRNA levels induced by glycated coll IV was significantly decreased by the co-incubation with anti-TGF-beta neutralizing antibody. Transient transfections of mesangial cells with alpha1(I) collagen promoter-luciferase constructs showed significant increase in promoter activity by the addition of glycated type IV collagen.These results indicated that glycated type IV collagen induces matrix components gene expression through transcriptional activation in mensangial cells and these effects are mediated in part by the induction of TGF-beta expression. Less