Tada H, Isogai S
2nd Department of Internal Medicine, Toho University School of Medicine, Tokyo, Japan.
Nephron. 1998;79(1):38-43. doi: 10.1159/000044989.
Thrombospondin (TSP) is a multifunctional glycoprotein that is synthesized by a variety of cells including mesangial cells (MCs). To clarify the effect of TSP on the pathogenesis of diabetic nephropathy, we studied the effect of glucose concentrations on TSP synthesis in cultured human MCs. Thereafter, the effects of TSP on the activation of transforming growth factor beta (TGF-beta) and fibronectin production were investigated in MCs. Incubating MCs with elevated glucose levels for 6 days resulted in an increase in TSP synthesis, measured by an enzyme-linked immunosorbent assay, both in culture media and cell layers. Treatment of MCs with TSP (final concentrations 1 and 5 microg/ml) for 24 h resulted in an increase (1.3- and 2.1-fold, respectively) in active TGF-beta, which was determined with an enzyme-linked immunosorbent assay using TGF-beta-soluble receptor type II, in the culture media without having any effect on the production of total TGF-beta. Exposure of MCs to TSP caused enhancement of fibronectin production in both media and cell layers in a TSP dose-dependent manner with the maximum at a TSP concentration of 1 microg/ml. The TSP-induced increase in fibronectin production from MCs was completely prevented by concomitant treatment with 10 microg/ml anti-TGF-beta neutralizing antibody. These results indicate that the TSP production is promoted by a high ambient glucose concentration in human MCs and that TSP, in turn, causes an increase in fibronectin production via activation of TGF-beta.
血小板反应蛋白（TSP）是一种多功能糖蛋白，由包括系膜细胞（MCs）在内的多种细胞合成。为了阐明TSP在糖尿病肾病发病机制中的作用，我们研究了葡萄糖浓度对培养的人MCs中TSP合成的影响。此后，在MCs中研究了TSP对转化生长因子β（TGF-β）激活和纤连蛋白产生的影响。将MCs置于高糖水平下培养6天，通过酶联免疫吸附测定法测量，培养基和细胞层中的TSP合成均增加。用TSP（终浓度1和5μg/ml）处理MCs 24小时，导致培养基中活性TGF-β增加（分别为1.3倍和2.1倍），这是使用II型TGF-β可溶性受体通过酶联免疫吸附测定法测定的，而对总TGF-β的产生没有任何影响。MCs暴露于TSP会导致培养基和细胞层中的纤连蛋白产生以TSP剂量依赖性方式增强，在TSP浓度为1μg/ml时达到最大值。用10μg/ml抗TGF-β中和抗体同时处理可完全阻止TSP诱导的MCs纤连蛋白产生增加。这些结果表明，高环境葡萄糖浓度可促进人MCs中TSP的产生，而TSP反过来又通过激活TGF-β导致纤连蛋白产生增加。
