RESUMEN
Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease characterized by progressive interstitial scarification. A hallmark morphological lesion is the accumulation of myofibroblasts or fibrotic lung fibroblasts (FL-fibroblasts) in areas called fibroblastic foci. We previously demonstrated that the expression of both urokinase-type plasminogen activator (uPA) and the uPA receptor are elevated in FL-fibroblasts from the lungs of patients with IPF. FL-fibroblasts isolated from human IPF lungs and from mice with bleomycin-induced pulmonary fibrosis showed an increased rate of proliferation compared with normal lung fibroblasts (NL-fibroblasts) derived from histologically "normal" lung. Basal expression of plasminogen activator inhibitor-1 (PAI-1) in human and murine FL-fibroblasts was reduced, whereas collagen-I and α-smooth muscle actin were markedly elevated. Conversely, alveolar type II epithelial cells surrounding the fibrotic foci in situ, as well as those isolated from IPF lungs, showed increased activation of caspase-3 and PAI-1 with a parallel reduction in uPA expression. Transduction of an adenovirus PAI-1 cDNA construct (Ad-PAI-1) suppressed expression of uPA and collagen-I and attenuated proliferation in FL-fibroblasts. On the contrary, inhibition of basal PAI-1 in NL-fibroblasts increased collagen-I and α-smooth muscle actin. Fibroblasts isolated from PAI-1-deficient mice without lung injury also showed increased collagen-I and uPA. These changes were associated with increased Akt/phosphatase and tensin homolog proliferation/survival signals in FL-fibroblasts, which were reversed by transduction with Ad-PAI-1. This study defines a new role of PAI-1 in the control of fibroblast activation and expansion and its role in the pathogenesis of fibrosing lung disease and, in particular, IPF.
Asunto(s)
Células Epiteliales/metabolismo , Fibroblastos/metabolismo , Fibrosis Pulmonar Idiopática/metabolismo , Inhibidor 1 de Activador Plasminogénico/metabolismo , Alveolos Pulmonares/metabolismo , Actinas/genética , Actinas/metabolismo , Animales , Apoptosis/genética , Bleomicina , Western Blotting , Proliferación Celular/genética , Células Cultivadas , Colágeno Tipo I/genética , Colágeno Tipo I/metabolismo , Células Epiteliales/patología , Fibroblastos/patología , Expresión Génica , Fibrosis Pulmonar Idiopática/genética , Fibrosis Pulmonar Idiopática/patología , Ratones Endogámicos C57BL , Ratones Noqueados , Microscopía Confocal , Músculo Liso/metabolismo , Inhibidor 1 de Activador Plasminogénico/genética , Alveolos Pulmonares/patología , Fibrosis Pulmonar/inducido químicamente , Fibrosis Pulmonar/genética , Fibrosis Pulmonar/metabolismo , Receptores del Activador de Plasminógeno Tipo Uroquinasa/genética , Receptores del Activador de Plasminógeno Tipo Uroquinasa/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Activador de Plasminógeno de Tipo Uroquinasa/genética , Activador de Plasminógeno de Tipo Uroquinasa/metabolismoRESUMEN
Idiopathic pulmonary fibrosis (IPF) is a life-threatening disease resulting from dysregulated repair responses to lung injury. Excessive extracellular matrix deposition by expanding myofibroblasts and fibrotic lung fibroblasts (fLfs) has been implicated in the pathogenesis of PF, including IPF. We explored fLfs' microRNA-34a (miR-34a) expression from IPF tissues. Basal miR-34a levels were decreased with reduced binding of p53 to the promoter DNA and 3'UTR mRNA sequences. Overexpression of miR-34a in fLfs increased p53, PAI-1, and reduced pro-fibrogenic markers. The regulatory effects of miR-34a were altered by modifying the p53 expression. Precursor-miR-34a lung transduction reduced bleomycin-induced PF in wild-type mice. fLfs treated with caveolin-1 scaffolding domain peptide (CSP) or its fragment, CSP7, restored miR-34a, p53, and PAI-1. CSP/CSP7 reduced PDGFR-ß and pro-fibrogenic markers, which was abolished in fLfs following blockade of miR-34a expression. These peptides failed to resolve PF in mice lacking miR-34a in fLfs, indicating miR-34a-p53-feedback induction required for anti-fibrotic effects.