Metformin attenuates lung fibrosis development via NOX4 suppression

Abstract

BackgroundAccumulation of profibrotic myofibroblasts in fibroblastic foci (FF) is a crucial process for development of fibrosis during idiopathic pulmonary fibrosis (IPF) pathogenesis, and transforming growth factor (TGF)-β plays a key regulatory role in myofibroblast differentiation. Reactive oxygen species (ROS) has been proposed to be involved in the mechanism for TGF-β-induced myofibroblast differentiation. Metformin is a biguanide antidiabetic medication and its pharmacological action is mediated through the activation of AMP-activated protein kinase (AMPK), which regulates not only energy homeostasis but also stress responses, including ROS. Therefore, we sought to investigate the inhibitory role of metformin in lung fibrosis development via modulating TGF-β signaling.MethodsTGF-β-induced myofibroblast differentiation in lung fibroblasts (LF) was used for in vitro models. The anti-fibrotic role of metfromin was examined in a bleomycin (BLM)-induced lung fibrosis model.ResultsWe found that TGF-β-induced myofibroblast differentiation was clearly inhibited by metformin treatment in LF. Metformin-mediated activation of AMPK was responsible for inhibiting TGF-β-induced NOX4 expression. NOX4 knockdown and N-acetylcysteine (NAC) treatment illustrated that NOX4-derived ROS generation was critical for TGF-β-induced SMAD phosphorylation and myofibroblast differentiation. BLM treatment induced development of lung fibrosis with concomitantly enhanced NOX4 expression and SMAD phosphorylation, which was efficiently inhibited by metformin. Increased NOX4 expression levels were also observed in FF of IPF lungs and LF isolated from IPF patients.ConclusionsThese findings suggest that metformin can be a promising anti-fibrotic modality of treatment for IPF affected by TGF-β.

Metformin Does Not Affect Clinically Relevant Outcomes in Patients with Idiopathic Pulmonary Fibrosis

“…Metformin was found to reduce radiological and histological signs of fibrosis, inflammatory cell infiltration, and alterations to alveolar structures, resulting in cellprotective effects from radiation-induced pulmonary injury in a mouse model [34]. In addition, 2 studies in bleomycin-induced lung fibrosis mouse models have shown that metformin exerts antifibrotic and anti-inflammatory effects [26,35]. The first study showed that metformin inhibited TGF-β-induced myofibroblast differentiation in lung fibroblasts via activation of AMPK [26].…”

“…In addition, 2 studies in bleomycin-induced lung fibrosis mouse models have shown that metformin exerts antifibrotic and anti-inflammatory effects [26,35]. The first study showed that metformin inhibited TGF-β-induced myofibroblast differentiation in lung fibroblasts via activation of AMPK [26]. In the other study, metformin was also shown to inhibit TGF-β-induced myofibroblast differentiation, thereby reducing the proportion of inflammatory cells in bronchoalveolar lavage fluid and reducing inflammation on histological examination of the lung tissue [35].…”

“…Preclinical studies have suggested that metformin has antifibrotic and anti-inflammatory effects [23][24][25]. Metformin has been found to attenuate lung fibrosis by inhibiting transforming growth factor-beta (TGF-β) via adenosine monophosphate-activated protein kinase (AMPK) activation [26,27].…”

Transcription Factor NRF2 as a Therapeutic Target for Chronic Diseases: A Systems Medicine Approach

“…In fact, SFN reduces hepatic glucose production and improves glucose control in patients with T2DM (Axelsson et al, 2017). Interestingly, some evidence suggests that metformin may be effective in preventing other nonglycemic pathophenotypes of the NRF2 diseasome, including cardiovascular (Nesti and Natali, 2017), respiratory (Sato et al, 2016), digestive (Bauer and Duca, 2016), neurodegenerative (Markowicz-Piasecka et al, 2017), autoimmune (Schuiveling et al, 2017), and neoplastic (Heckman-Stoddard et al, 2017) disorders. The mechanism of action of metformin is not completely clear, but it involves inhibition of mitochondrial complex I, thus increasing the AMP/ATP ratio (El-Mir et al, 2000;Owen et al, 2000) and leading to activation of the energy sensor AMPK (Hardie, 2004;Rena et al, 2017).…”

Metformin in Idiopathic Pulmonary Fibrosis “Seeking the Holy-Grail through Drug-Repositioning”

“…The study rationale was based on: (1) epidemiological data linking diabetes with IPF development and progression (knowledge of disease phenotypes and comorbidities) [5] and (2) pre-clinical evidence showing that metformin may exert anti-fibrotic properties through regulation of cellular bioenergetics and autophagy via activation of AMP-activated protein kinase in experimental models of lung fibrosis (knowledge of drug and disease mechanisms) [6][7][8]. Authors report that metformin users were mostly males (85 vs. 73%) and had increased prevalence of metabolic profile as assessed by the coexistence of diabetes, hypercholesterolemia, and hypertension compared to non-metformin users (99 vs. 12%).…”