Hori Y, Katoh T, Hirakata M, Joki N, Kaname S, Fukagawa M, Okuda T, Ohashi H, Fujita T, Miyazono K, Kurokawa K
1st Department of Internal Medicine, University of Tokyo School of Medicine, Japan.
Kidney Int. 1998 Jun;53(6):1616-25. doi: 10.1046/j.1523-1755.1998.00908.x.
Transforming growth factor-beta (TGF-beta) is usually secreted as a large latent complex associated with latent TGF-beta binding protein-1 (LTBP-1), which is known to bind to extracellular matrix (ECM) components. Although the LTBP-ECM interaction has been suggested to play a role in the activation and biological action of TGF-beta, the precise mechanism is still unclear. In glomerular hypertension mesangial cells are believed to perceive the increased cyclic strain and we have recently reported that cyclic mechanical stretch in vitro enhances the expression of ECM components via an autocrine/paracrine secretion of TGF-beta in cultured rat mesangial cells. Therefore, in this study we examined the role of LTBP-1 in the stretch-induced, TGF-beta-mediated ECM expression. Mesangial cells expressed mRNA for short and long forms of LTBP-1 (LTBP-1S and LTBP-1L, respectively). Mesangial cells were subjected to cyclic stretch to provide a maximal elongation of 20% at a rate of 60 cycles/min for 24 to 36 hours in the presence of polyclonal antibody raised against human LTBP-1 or synthetic oligopeptides corresponding to the N-terminal portions of human LTBP-1, which may work as competitive inhibitors against the LTBP-ECM association. Both anti-LTBP-1 antibody (Ab39) and synthetic oligopeptides inhibited the stretch-induced mRNA expression of type I collagen and fibronectin in a dose-dependent manner, but the inhibition by Ab39 or the oligopeptides was recovered by adding recombinant TGF-beta. Ab39 or the oligopeptides did not change the effect of exogenously added TGF-beta, such as growth-inhibition in mink lung epithelial cells. These results suggest that mesangial cells secrete TGF-beta as a large latent complex, and the LTBP-ECM interaction may be a pivotal step in TGF-beta action and ECM accumulation, providing a new therapeutic strategy against progression of glomerulosclerosis and other fibrotic diseases.
转化生长因子-β（TGF-β）通常以与潜伏性TGF-β结合蛋白-1（LTBP-1）相关的大潜伏复合物形式分泌，已知LTBP-1可与细胞外基质（ECM）成分结合。尽管有人提出LTBP-ECM相互作用在TGF-β的激活和生物学作用中发挥作用，但其确切机制仍不清楚。在肾小球高压中，系膜细胞被认为能感知增加的周期性应变，并且我们最近报道，体外周期性机械拉伸通过培养的大鼠系膜细胞中TGF-β的自分泌/旁分泌分泌增强了ECM成分的表达。因此，在本研究中，我们研究了LTBP-1在拉伸诱导的、TGF-β介导的ECM表达中的作用。系膜细胞表达短型和长型LTBP-1的mRNA（分别为LTBP-1S和LTBP-1L）。在存在针对人LTBP-1的多克隆抗体或对应于人LTBP-1 N端部分的合成寡肽（其可能作为LTBP-ECM结合的竞争性抑制剂）的情况下，对系膜细胞进行周期性拉伸，以60次循环/分钟的速率提供20%的最大伸长率，持续24至36小时。抗LTBP-1抗体（Ab39）和合成寡肽均以剂量依赖方式抑制拉伸诱导的I型胶原和纤连蛋白的mRNA表达，但通过添加重组TGF-β可恢复Ab39或寡肽的抑制作用。Ab39或寡肽不改变外源性添加的TGF-β的作用，如对貂肺上皮细胞的生长抑制作用。这些结果表明，系膜细胞以大潜伏复合物形式分泌TGF-β，并且LTBP-ECM相互作用可能是TGF-β作用和ECM积累的关键步骤，为对抗肾小球硬化和其他纤维化疾病的进展提供了新的治疗策略。
