Fisher Amanda J, Cipolla Ellyse, Varre Ananya, Gu Hongmei, Mickler Elizabeth A, Vittal Ragini
Department of Medicine, Division of Pulmonary and Critical Care Medicine, Indiana University School of Medicine, Indianapolis, Indiana.
Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of Michigan, Ann Arbor, USA.
Cell Mol Med Open Access. 2017;3(3). doi: 10.21767/2573-5365.100037. Epub 2017 Nov 22.
While our previous studies suggest that limiting bleomycin-induced complement activation suppresses TGF-β signaling, the specific hierarchical interactions between TGF-β and complement in lung fibrosis are unclear. Herein, we investigated the mechanisms underlying TGF-β-induced complement activation in the pathogenesis of lung fibrosis. C57-BL6 mice were given intratracheal instillations of adenoviral vectors overexpressing TGF-β (Ad-TGFβ) or the firefly gene-luciferase (Ad-Luc; control). Two weeks later, mice with fibrotic lungs were instilled RNAi specific to receptors for or - or , and sacrificed at day 28. Histopathological analyses revealed that genetic silencing of or arrested the progression of TGF-β-induced lung fibrosis, collagen deposition and content (hydroxyproline, /2); and significantly suppressed local complement activation. With genetic silencing of either or , in Ad-TGFβ-injured lungs: we detected the recovery of Smad7 (TGF-β inhibitor) and diminished local release of DAF (membrane-bound complement inhibitor); : TGF-β-mediated loss of DAF was prevented. Conversely, blockade of the TGF-β receptor prevented -mediated loss of DAF in both normal primary human alveolar and small airway epithelial cells. Of the 52 miRNAs analyzed as part of the Affymetrix array, normal primary human SAECs exposed to , or TGF-β caused discrete and overlapping miRNA regulation related to epithelial proliferation or apoptosis (miR-891A, miR-4442, miR-548, miR-4633), cellular contractility (miR-1197) and lung fibrosis (miR-21, miR-200C, miR-31HG, miR-503). Our studies present potential mechanisms by which TGF-β activates complement and promotes lung fibrosis.
虽然我们之前的研究表明，限制博来霉素诱导的补体激活可抑制转化生长因子-β（TGF-β）信号传导，但TGF-β与补体在肺纤维化中的具体层级相互作用尚不清楚。在此，我们研究了TGF-β诱导的补体激活在肺纤维化发病机制中的潜在机制。给C57-BL6小鼠气管内滴注过表达TGF-β的腺病毒载体（Ad-TGFβ）或萤火虫基因荧光素酶（Ad-Luc；对照）。两周后，对患有肺纤维化的小鼠滴注针对C3或C5或C5a受体的RNA干扰剂，并在第28天处死。组织病理学分析显示，C3或C5基因沉默可阻止TGF-β诱导的肺纤维化、胶原蛋白沉积和含量（羟脯氨酸，μg/mg）的进展；并显著抑制局部补体激活。在Ad-TGFβ损伤的肺中，C3或C5基因沉默后：我们检测到Smad7（TGF-β抑制剂）的恢复以及衰变加速因子（DAF，膜结合补体抑制剂）局部释放的减少；TGF-β介导的DAF丢失得到预防。相反，在正常原代人肺泡和小气道上皮细胞中，阻断TGF-β受体可预防C5a介导的DAF丢失。作为Affymetrix阵列分析一部分的52种微小RNA中，暴露于C3、C5或TGF-β的正常原代人小气道上皮细胞导致与上皮增殖或凋亡（miR-891A、miR-4442、miR-548、miR-4633）、细胞收缩性（miR-1197）和肺纤维化（miR-21、miR-200C、miR-31HG、miR-503）相关的离散且重叠的微小RNA调节。我们的研究揭示了TGF-β激活补体并促进肺纤维化的潜在机制。
