Abstract：
Fibrosis is characterized by excessive deposition of extracellular matrix proteins, particularly collagen, caused by myofibroblasts in response to chronic inflammation. Although G protein-coupled receptors (GPCRs) are among the targets of current antifibrotic drugs, no drug has yet been approved to stop fibrosis progression. Herein, we aimed to identify GPCRs with profibrotic effects. In gene expression analysis of mouse lungs with induced fibrosis, eight GPCRs were identified, showing a >2-fold increase in mRNA expression after fibrosis induction. Among them, we focused on Gpr176 owing to its significant correlation with a myofibroblast marker α-smooth muscle actin (αSMA), the profibrotic factor transforming growth factor β1 (TGFβ1), and collagen in a human lung gene expression database. Similar to the lung fibrosis model, increased Gpr176 expression was also observed in other organs affected by fibrosis, including the kidney, liver, and heart, suggesting its role in fibrosis across various organs. Furthermore, fibroblasts abundantly expressed Gpr176 compared to alveolar epithelial cells, endothelial cells, and macrophages in the fibrotic lung. GPR176 expression was unaffected by TGFβ1 stimulation in rat renal fibroblast NRK-49 cells, whereas knockdown of Gpr176 by siRNA reduced TGFβ1-induced expression of αSMA, fibronectin, and collagen as well as Smad2 phosphorylation. This suggested that Gpr176 regulates fibroblast activation. Consequently, Gpr176 acts in a profibrotic manner, and inhibiting its activity could potentially prevent myofibroblast differentiation and improve fibrosis. Developing a GPR176 inverse agonist or allosteric modulator is a promising therapeutic approach for fibrosis.
摘要：
纤维化的特征是细胞外基质蛋白的过度沉积，特别是胶原蛋白，由肌成纤维细胞引起的慢性炎症反应。尽管G蛋白偶联受体（GPCRs）是目前抗纤维化药物的靶标之一，目前还没有药物被批准阻止纤维化进展.在这里，我们旨在鉴定具有促纤维化作用的GPCRs。在诱导纤维化的小鼠肺的基因表达分析中，确定了8个GPCR，显示纤维化诱导后mRNA表达增加>2倍。其中,我们专注于Gpr176，因为它与肌成纤维细胞标记α-平滑肌肌动蛋白（αSMA）显着相关，促纤维化因子转化生长因子β1（TGFβ1），和人肺基因表达数据库中的胶原蛋白。类似于肺纤维化模型，在受纤维化影响的其他器官中也观察到Gpr176表达增加，包括肾脏,肝脏,和心，表明它在各种器官的纤维化中的作用。此外，与肺泡上皮细胞相比，成纤维细胞大量表达Gpr176，内皮细胞，和纤维化肺中的巨噬细胞。在大鼠肾成纤维细胞NRK-49细胞中，GPR176的表达不受TGFβ1刺激的影响，而通过siRNA敲除Gpr176降低TGFβ1诱导的αSMA表达，纤连蛋白,和胶原蛋白以及Smad2磷酸化。这表明Gpr176调节成纤维细胞活化。因此,Gpr176以促纤维化的方式起作用，抑制其活性可能阻止肌成纤维细胞分化并改善纤维化。开发GPR176反向激动剂或变构调节剂是一种有前途的纤维化治疗方法。
