Newer developments in idiopathic pulmonary fibrosis in the era of anti-fibrotic medications

Hypermethylation of PPARG-encoding gene promoter mediates fine particulate matter-induced pulmonary fibrosis by regulating the HMGB1/NLRP3 axis

The inflammatory response induced by fine particulate matter (PM2.5), a common class of air pollutants, is an important trigger for the development of pulmonary fibrosis. However, the specific mechanisms responsible for this phenomenon are yet to be fully understood. To investigate the mechanisms behind the onset and progression of lung fibrosis owing to PM2.5 exposure, both rats and human bronchial epithelial cells were subjected to varying concentrations of PM2.5. The involvement of the PPARG/HMGB1/NLRP3 signaling pathway in developing lung fibrosis caused by PM2.5 was validated through the utilization of a PPARG agonist (rosiglitazone), a PPARG inhibitor (GW9662), and an HMGB1 inhibitor (glycyrrhizin). These outcomes highlighted the downregulation of PPARG expression and activation of the HMGB1/NLRP3 signaling pathway triggered by PM2.5, thereby eliciting inflammatory responses and promoting pulmonary fibrosis. Additionally, PM2.5 exposure-induced DNA hypermethylation of PPARG-encoding gene promoter downregulated PPARG expression. Moreover, the DNA methyltransferase inhibitor 5-azacytidine mitigated the hypermethylation of the PPARG-encoding gene promoter triggered by PM2.5. In conclusion, the HMGB1/NLRP3 signaling pathway was activated in pulmonary fibrosis triggered by PM2.5 through the hypermethylation of the PPARG-encoding gene promoter.

N6-methyladenosine mediates Nrf2 protein expression involved in PM2.5-induced pulmonary fibrosis

It has been reported that particulate matter with an aerodynamic diameter of <2.5 µm (PM2.5) could induce epithelial-mesenchymal transition (EMT)- and extracellular matrix (ECM)-related pulmonary fibrosis (PF). The transcription factor Nrf2 alleviated PM2.5-induced PF by antagonizing oxidative stress. The N⁶-methyladenosine (m⁶A) modification plays a significant role in the stress response. However, the effect of m⁶A modification on the mechanisms of Nrf2-mediated defense against PM2.5-induced PF remained unknown. Here, we explored the role and the underlying molecular mechanisms of m⁶A methylation of Nrf2 mRNA in PM2.5-induced PF. We established filtered air (FA), unfiltered air (UA), and concentrated PM2.5 air (CA) group mice model and 0, 50, and 100 μg/mL PM2.5-treated 16HBE cell models. The extent of lung fibrosis in mice and fibrosis indicators were detected by histopathological analysis, immunohistochemical staining and western blotting. The molecular mechanism of m⁶A-modified Nrf2 was demonstrated by m⁶A-methylated RNA immunoprecipitation (MeRIP), RNA immunoprecipitation (RIP), qRT-PCR and T3 ligase-based PCR. Our data showed that PM2.5 exposure for 16 weeks could induce pulmonary fibrosis and activate Nrf2 signaling pathway. m⁶A methyltransferase METTL3 was upregulated after PM2.5 treatment in vivo and in vitro. Moreover, METTL3 mediated m⁶A modification of Nrf2 mRNA and promoted Nrf2 translation in mice and 16HBE cells after PM2.5 exposure. Mechanistically, three m⁶A-modified sites (1317, 1376 and 935; numbered relative to the first nucleotide of 3'UTR) of Nrf2 mRNA were identified in PM2.5-treatment 16HBE cells. Furthermore, the m⁶A binding proteins YTHDF1/IGF2BP1 promoted Nrf2 translation by binding to m⁶A residues of Nrf2 mRNA. Our results revealed the mechanism of m⁶A mediated Nrf2 signaling pathway against oxidative stress, which affected the development of PM2.5-induced PF.

Extracellular Vesicles Derived from Adipose Mesenchymal Stem Cells Alleviate PM2.5-Induced Lung Injury and Pulmonary Fibrosis

Background

Exposure to PM2.5 (fine particulate matter ≤2.5 μm in aerodynamic diameter) in air increases the risk of lung injury and pulmonary fibrosis (PF). Extracellular vesicles (EVs) derived from adipose mesenchymal stem cells (ADSCs) have been identified as a potential treatment based on the proteins or RNAs delivery and immunomodulatory properties. Here, we assessed the protective effects and mechanisms of ADSCs-EVs on PM2.5-induced lung injury or PF.

Material/Methods

Rats (male, 6 weeks old) were exposed to PBS or PM2.5 (1.5 mg/kg/day) for 3 days a week for 4 weeks. ADSCs-EVs were extracted by ultracentrifugation. PBS and ADSCs-EVs were administrated through intratracheal instillation. After the end of exposure, the rats were anesthetized and killed. Lung tissues with different treatments were collected for Western blot analysis and HE, IHC, and IF staining analysis. Cells exposed to PM2.5 or “PM2.5+ADSCs-EVs” in vitro were also collected for further Western blotting, qRT-PCR, and IF staining evaluation.

Results

The results indicated that the initial response of lungs exposed to PM2.5 was lung injury with oxidative stress and inflammation. Long-term PM2.5 exposure resulted in obvious PF in rats. Treatment with ADSCs-EVs decreased PM2.5-induced apoptosis and necrosis in type II alveolar epithelial cells and alleviated lung injury and PF in rats. ADSCs-EVs suppressed reactive oxygen species (ROS) levels and inflammation induced by PM2.5. Furthermore, ADSCs-EVs inhibited TGF-βRI by transferring let-7d-5p and further mitigated PF.

Conclusions

Our results suggest that EVs derived from ADSCs can alleviate PM2.5-induced lung injury and PF.

First-in-human high-cumulative-dose stem cell therapy in idiopathic pulmonary fibrosis with rapid lung function decline

Previous phase I studies demonstrated safety and some beneficial effects of mesenchymal stem cells (MSCs) in patients with mild to moderate idiopathic pulmonary fibrosis (IPF). The aim of our study was to evaluate the safety, tolerability, and efficacy of a high cumulative dose of bone marrow MSCs in patients with rapid progressive course of severe to moderate IPF. Twenty patients with forced ventilation capacity (FVC) ≥40% and diffusing capacity of the lung for carbon monoxide (DLCO) ≥20% with a decline of both >10% over the previous 12 months were randomized into two groups: one group received two intravenous doses of allogeneic MSCs (2 × 10⁸ cells) every 3 months, and the second group received a placebo. A total amount of 1.6 × 10⁹ MSCs had been administered to each patient after the study completion. There were no significant adverse effects after administration of MSCs in any patients. In the group of MSC therapy, we observed significantly better improvement for the 6‐minute walk distance in 13 weeks, for DLCO in 26 weeks, and for FVC in 39 weeks compared with placebo. FVC for 12 months in the MSCs therapy group increased by 7.8% from baseline, whereas it declined by 5.9% in the placebo group. We did not find differences between the groups in mortality (two patients died in each group) or any changes in the high‐resolution computed tomography fibrosis score. In patients with IPF and a rapid pulmonary function decline, therapy with high doses of allogeneic MSCs is a safe and promising method to reduce disease progression.

New therapeutic strategies for IPF: Based on the "phagocytosis-secretion-immunization" network regulation mechanism of pulmonary macrophages

Pulmonary fibrosis is a chronic and progressive interstitial lung disease of known and unknown etiology. Over the past decades, macrophages have been recognized to play a significant role in IPF pathogenesis. According to their anatomical loci, macrophages can be divided to alveolar macrophages (AMs) subtypes and interstitial macrophages subtypes (IMs) with different responsibility in the damage defense response. Depending on diverse chemokines and cytokines in local microenvironments, macrophages can be induced and polarized to either classically activated (M1) or alternatively activated (M2) phenotypes in different stages of immunity. Therefore, we hypothesize that there is a "phagocytosis-secretion-immunization" network regulation of pulmonary macrophages related to a number of chemokines and cytokines. In this paper, we summarize and discuss the role of chemokines and cytokines involved in the "phagocytosis-secretion-immunization" network regulation mechanism of pulmonary macrophages, pointing toward novel therapeutic approaches based on the network target regulation in the field. Therapeutic strategies focused on modifying the chemokines, cytokines and the network are promising for the pharmacotherapy of IPF. Some Traditional Chinese medicines may have more superiorities in delaying the progression of pulmonary fibrosis for their multi-target activities of this network regulation.

Independent Clinical Factors Relevant to Prognosis of Patients with Idiopathic Pulmonary Fibrosis

Background

The prognosis of idiopathic pulmonary fibrosis (IPF) is the worst among all interstitial lung diseases, and is related to the disease itself. Comorbidities or complications can worsen IPF. We assessed the effect of comorbidities on the survival of IPF patients. A retrospective review of patients with IPF was completed.

Material/Methods

Information on demographic features, clinical examination, and comorbidities at baseline were obtained. Then, median, 1-year, and 5-year survival was calculated. A total of 380 patients with IPF admitted to Beijing Chao-Yang Hospital from 1 April 2002 to 31 March 2015 were followed up until December 2016.

Results

Of these 380 patients, 71.9% died during the study period. Median survival was 2.25 years and overall 5-year survival was 28.5%. Also, 86.3% of patients were males. A total of 248 cases underwent lung function tests, and 178 patients underwent bronchoalveolar lavage (BAL). Multivariate analyses showed that forced expiratory volume in 1 second/forced vital capacity (FVC), diffusing capacity of the lungs for carbon monoxide percent predicted, FVC% predicted, the number of macrophages, neutrophils, and lymphocytes in BAL fluid, pulmonary hypertension, hypoxemia, and hydropower disorder were independent prognostic indicators of IPF, GAP gender (G), age (A), and 2 pulmonary physiological parameters (P) model can help to predict prognosis of IPF.

Conclusions

Spirometry, GAP model, and BAL are helpful to forecast the prognosis of IPF. IPF patients also suffering from pulmonary arterial hypertension, hypoxemia, and hydropower disorder have a poor prognosis.

PM2.5 induced pulmonary fibrosis in vivo and in vitro

Epidemiological studies have revealed positive correlation between particulate matter with an aerodynamic diameter of < 2.5 µm (PM_2.5) and pulmonary fibrosis (PF). As etiology and pathogenesis of PF have not been fully elucidated, this study was to investigate the potential mechanism by which PM_2.5 exposure adversely induced PF in vivo and in vitro. In the present study, 6-week-old C57/BL6J mice were intranasally administrated with PM_2.5 (100 μg/day) for 4 weeks. Micro-CT and hematoxylin-eosin (HE) staining analysis showed that lung inflammation and incipient fibrosis symptoms were induced after PM_2.5 exposure. The expression of Transforming growth factor-β1 (TGF-β1), α-Smooth muscle actin (α-SMA), and Collagen type I (COL1) in mice lung was increased. Upregulation of TGF-β1 in mice serum was also detected by ELISA after exposure to PM_2.5. Moreover, chronic PM_2.5 exposure on human bronchial epithelial cell line BEAS-2B cells led to activation of TGF-β1/SMAD3 pathway, TGF-β1 excretion and epithelial-mesenchymal transition (EMT), while PM_2.5 also triggered the activation of TGF-β1/SMAD3 pathway, TGF-β1 excretion as well as differentiation of human pulmonary fibroblast cell line HFL-1 cells, and TGF-β1 production in mouse macrophage cell line RAW264.7 cells. Furthermore, cell culture medium of PM_2.5-treated BEAS-2B and RAW264.7 cells could both activate TGF-β1/SMAD3 signaling, α-SMA and COL1 upregulation in HFL-1 cells. Therefore, we concluded that PM_2.5 could induce PF by targeting pulmonary epithelium, macrophages and fibroblasts, suggesting that PM_2.5 was a potent initiator of PF.