Anti-fibrotic effects of nintedanib on lung fibroblasts derived from patients with Progressive Fibrosing Interstitial Lung Diseases (PF-ILDs)

The tyrosine kinase inhibitor nintedanib has been recently approved for the treatment of Interstitial Lung Diseases (ILDs) that manifest a progressive fibrosis phenotype other than Idiopathic pulmonary Fibrosis (IPF). Nintedanib reduces the development of lung fibrosis in various animal models resembling features of PF-ILD and in vitro, it inhibits the fibrosing phenotype of human lung fibroblasts (HLFs) isolated from patients with IPF. To get insight on the cellular and molecular mechanisms that drive the clinical efficiency of nintedanib in patients with non-IPF PF-ILD, we investigated its effects on the fibrosing functions of HLFs derived from patients with PF-hypersensitivity pneumonitis (PF-HP, n = 7), PF-sarcoidosis (n = 5) and pleuroparenchymal fibroelastosis (PPFE, n = 4). HLFs were treated with nintedanib (10 nM-1 μM) and then stimulated with PDGF-BB (25-50 ng/ml) or TGF-β1 (1 ng/ml) for 24-72 h to assess proliferation and migration or differentiation. At nanomolar concentrations, nintedanib reduced the levels of PDGF receptor and ERK1/2 phosphorylation, the proliferation and the migration of PF-HP, PF-sarcoidosis and PPFE HLFs stimulated with PDGF-BB. Moreover, nintedanib also attenuates the myofibroblastic differentiation driven by TGF-β1 but only when it is used at 1 μM. The drug reduced the phosphorylation of SMAD2/3 and decreased the induction of collagen, fibronectin and α-smooth muscle actin expression induced by TGF-β1. In conclusion, our results demonstrate that nintedanib counteracts fundamental fibrosing functions of lung fibroblasts derived from patients with PF-HP, PF-sarcoidosis and PPFE, at concentrations previously reported to inhibit control and IPF HLFs. Such effects may contribute to its clinical benefit in patients suffering from these irreversible ILDs.

TRPM7 restrains plasmin activity and promotes transforming growth factor-β1 signaling in primary human lung fibroblasts

Sustained exposure of the lung to various environmental or occupational toxins may eventually lead to pulmonary fibrosis, a devastating disease with no cure. Pulmonary fibrosis is characterized by excessive deposition of extracellular matrix (ECM) proteins such as fibronectin and collagens. The peptidase plasmin degrades the ECM, but protein levels of the plasmin activator inhibitor-1 (PAI-1) are increased in fibrotic lung tissue, thereby dampening plasmin activity. Transforming growth factor-β1 (TGF-β1)-induced activation of SMAD transcription factors promotes ECM deposition by enhancing collagen, fibronectin and PAI-1 levels in pulmonary fibroblasts. Hence, counteracting TGF-β1-induced signaling is a promising approach for the therapy of pulmonary fibrosis. Transient receptor potential cation channel subfamily M Member 7 (TRPM7) supports TGF-β1-promoted SMAD signaling in T-lymphocytes and the progression of fibrosis in kidney and heart. Thus, we investigated possible effects of TRPM7 on plasmin activity, ECM levels and TGF-β1 signaling in primary human pulmonary fibroblasts (pHPF). We found that two structurally unrelated TRPM7 blockers enhanced plasmin activity and reduced fibronectin or PAI-1 protein levels in pHPF under basal conditions. Further, TRPM7 blockade strongly inhibited fibronectin and collagen deposition induced by sustained TGF-β1 stimulation. In line with these data, inhibition of TRPM7 activity diminished TGF-β1-triggered phosphorylation of SMAD-2, SMAD-3/4-dependent reporter activation and PAI-1 mRNA levels. Overall, we uncover TRPM7 as a novel supporter of TGF-β1 signaling in pHPF and propose TRPM7 blockers as new candidates to control excessive ECM levels under pathophysiological conditions conducive to pulmonary fibrosis.

Arsenic trioxide inhibits the functions of lung fibroblasts derived from patients with idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic and fatal interstitial lung disease. Currently, no treatment can block or reverse the development of lung fibrosis in patients suffering from IPF. Recent studies indicate that arsenic trioxide (ATO), a safe, effective anti-cancer pro-oxidant drug, prevents the differentiation of normal human lung fibroblasts (NHLFs) in vitro and reduces experimental pulmonary fibrosis in vivo. In this context, we investigated the anti-fibrotic effects of ATO on the main fibrosis functions of human lung fibroblasts (HLFs) isolated from patients with IPF. IPF and non-IPF (control) HLFs were incubated with 0.01-1 μM ATO and stimulated with pro-fibrotic factors (PDGF-BB or TGF-β1). We measured their rates of proliferation, migration and differentiation and the cell stress response triggered by ATO. ATO did not affect cell viability but strongly inhibited the proliferation and migration of PDGF-BB-stimulated IPF and control HLFs. ATO also prevented myofibroblastic differentiation, as assessed by the expression of α-smooth muscle actin (α-SMA) and collagen-1, and the phosphorylation of SMAD2/3 in TGF-β1-stimulated HLFs. These antifibrotic effects were associated with increased expression of the transcription factor NRF2 and its target genes NQO1 and HMOX1. Genetic silencing of NRF2 inhibited the ATO-induced cell stress response but did not prevent the ATO-dependent inhibition of α-SMA expression in TGF-β1-stimulated HLFs. The results demonstrate that ATO, at concentrations similar to exposure in blood plasma of ATO-treated cancer patients, counteracted pro-fibrotic activities of HLFs from IPF patients. We propose to consider ATO for clinical exploration to define the therapeutic potential in patients with IPF.