Toll-like receptors in the pathogenesis of pulmonary fibrosis

Pachymic Acid Protects Against Bleomycin-Induced Pulmonary Fibrosis by Suppressing Fibrotic, Inflammatory, and Oxidative Stress Pathways in Mice

Pachymic acid (PA), a natural extract from Poria cocos (Schw.) Wolf, possesses anti-inflammatory and anti-oxidative properties. However, it is still unknown whether PA can protect against bleomycin (BLM)-induced pulmonary fibrosis (PF). In this study, we investigated the effects of PA in mice administered BLM. Our results showed that PA significantly improved lung damage and pathological manifestations. Additionally, PA reduced the levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-α, while increasing the level of IL-10. PA also decreased the levels of hydroxyproline and malondialdehyde, and increased the activities of superoxide dismutase and glutathione peroxidase in lung tissue. Furthermore, PA inhibited the increases in pyrin domain-containing protein 3 (NLRP3), ASC, IL-1β, P20, and TXNIP induced by BLM. In conclusion, our study demonstrated the protective effects of PA against BLM-induced PF in mice by suppressing fibrotic, inflammatory, and oxidative stress pathways.

Macrophage-derived exosomal HMGB3 regulates silica-induced pulmonary inflammation by promoting M1 macrophage polarization and recruitment

BACKGROUND

Chronic inflammation and fibrosis are characteristics of silicosis, and the inflammatory mediators involved in silicosis have not been fully elucidated. Recently, macrophage-derived exosomes have been reported to be inflammatory modulators, but their role in silicosis has not been explored. The purpose of the present study was to investigate the role of macrophage-derived exosomal high mobility group box 3 (HMGB3) in silica-induced pulmonary inflammation.

METHODS

The induction of the inflammatory response and the recruitment of monocytes/macrophages were evaluated by immunofluorescence, flow cytometry and transwell assays. The expression of inflammatory cytokines was examined by RT-PCR and ELISA, and the signalling pathways involved were examined by western blot analysis.

RESULTS

HMGB3 expression was increased in exosomes derived from silica-exposed macrophages. Exosomal HMGB3 significantly upregulated the expression of inflammatory cytokines, activated the STAT3/MAPK (ERK1/2 and p38)/NF-κB pathways in monocytes/macrophages, and promoted the migration of these cells by CCR2.

CONCLUSIONS

Exosomal HMGB3 is a proinflammatory modulator of silica-induced inflammation that promotes the inflammatory response and recruitment of monocytes/macrophages by regulating the activation of the STAT3/MAPK/NF-κB/CCR2 pathways.

Emerging delivery approaches for targeted pulmonary fibrosis treatment

Pulmonary fibrosis (PF) is a progressive, and life-threatening interstitial lung disease which causes scarring in the lung parenchyma and thereby affects architecture and functioning of lung. It is an irreversible damage to lung functioning which is related to epithelial cell injury, immense accumulation of immune cells and inflammatory cytokines, and irregular recruitment of extracellular matrix. The inflammatory cytokines trigger the differentiation of fibroblasts into activated fibroblasts, also known as myofibroblasts, which further increase the production and deposition of collagen at the injury sites in the lung. Despite the significant morbidity and mortality associated with PF, there is no available treatment that efficiently and effectively treats the disease by reversing their underlying pathologies. In recent years, many therapeutic regimens, for instance, rho kinase inhibitors, Smad signaling pathway inhibitors, p38, BCL-xL/ BCL-2 and JNK pathway inhibitors, have been found to be potent and effective in treating PF, in preclinical stages. However, due to non-selectivity and non-specificity, the therapeutic molecules also result in toxicity mediated severe side effects. Hence, this review demonstrates recent advances on PF pathology, mechanism and targets related to PF, development of various drug delivery systems based on small molecules, RNAs, oligonucleotides, peptides, antibodies, exosomes, and stem cells for the treatment of PF and the progress of various therapeutic treatments in clinical trials to advance PF treatment.

Monocytes and macrophages: emerging mechanisms and novel therapeutic targets in pulmonary fibrosis

Pulmonary fibrosis results from a plethora of abnormal pathogenetic events. In idiopathic pulmonary fibrosis (IPF), inhalational, environmental, or occupational exposures in genetically and epigenetically predisposed individuals trigger recurrent cycles of alveolar epithelial cell injury, activation of coagulation pathways, chemoattraction, and differentiation of monocytes into monocyte-derived alveolar macrophages (Mo-AMs). When these events happen intermittently and repeatedly throughout the individual's life cycle, the wound repair process becomes aberrant leading to bronchiolization of distal air spaces, fibroblast accumulation, extracellular matrix deposition, and loss of the alveolar-capillary architecture. The role of immune dysregulation in IPF pathogenesis and progression has been underscored in the past mainly after the disappointing results of immunosuppressant use in IPF patients; however, recent reports highlighting the prognostic and mechanistic roles of monocytes and Mo-AMs revived the interest in immune dysregulation in IPF. In this review, we will discuss the role of these cells in the onset and progression of IPF, as well as potential targeted therapies.

[YKL-40 Promotes the Expression of Inflammatory Factors in Type Ⅱ Alveolar Epithelial Cell Model of A549 Cell Line]

Objective

YKL-40, also known as chitinase-3-like-1 (CHI3L1), is a human cartilage glycoprotein-39, with its N-terminus consisting of tyrosine (Y), lysine (K), and leucine (L), hence the name YKL-40. In this study, we explored whether YKL-40 could promote the expression of inflammatory factors in type Ⅱ alveolar epithelial cells.

Methods

A549 cells were cultured in vitro with interleukin (IL)-1β (20 ng/mL), IL-6 (20 ng/mL), tumor necrosis factor-alpha (TNF-α) (20 ng/mL), and interferon-gamma (IFN-γ) (20 ng/mL). The expression of YKL-40 transcription was determined by RT-qPCR. A549 cells were cultured with IL-1β at 5, 10, and 20 ng/mL and the expression of YKL-40 protein was determined by Western blot. A549 cells were cultured with recombinant YKL-40 protein at 0, 100, 500, and 1 000 ng/mL and the expression levels of IL-6 and IL-8 were measured by RT-qPCR. Three pairs of small interfering RNAs targeting YKL-40 (si- YKL-40-1/2/3) and the negative control (NC) were designed and used to transfect A549 cells, respectively, and the expression of YKL-40 was determined by RT-qPCR and Western blot. si- YKL-40-3 was screened out for subsequent experiments. In A549 cells, si- YKL-40-3 and si-NC were transfected and, then, IL-1β (20 ng/mL) was added in for culturing. The expression of YKL-40, IL-6, and IL-8 was determined by RT-qPCR and the expression of multiple factors in the supernatant was measured with the QAH-INF-1 kit.

Results

RT-qPCR results showed that IL-1β could up-regulate YKL-40 protein transcription level compared with that of the control group and the difference was statistically significant ( P<0.01), but IL-6, TNF-α, and IFN-γ could not up-regulate YKL-40 protein transcription level. Western blot results showed that IL-1β (20 ng/mL) could significantly promote the expression of YKL-40 and, compared with that of the control group, the differences showed by groups treated with different concentrations of IL-1β were all statistical significant ( P<0.01). After adding human recombinant YKL-40 protein to A549 cells, the results showed that the expression of inflammatory factors IL-6 and IL-8 was significantly increased and the difference was statistically significant compared with that of the control group ( P<0.05). After the expression of YKL-40 was decreased by si- YKL-40-3 transfection, the expression of IL-6 ( P<0.05), IL-8 ( P<0.05), and other inflammatory factors was inhibited compared with that of the control group.

Conclusion

YKL-40 can promote the expression and secretion of IL-6, IL-8, and other acute inflammatory factors in A549 cell line, a type Ⅱ alveolar epithelial cell model, thus aggravating the inflammatory response. Targeted inhibition of YKL-40 expression may effectively inhibit inflammatory response.

Precision medicine advances in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a highly heterogeneous, unpredictable and ultimately lethal chronic lung disease. Over the last decade, two anti-fibrotic agents have been shown to slow disease progression, however, both drugs are administered uniformly with minimal consideration of disease severity and inter-individual molecular, genetic, and genomic differences. Advances in biological understanding of disease endotyping and the emergence of precision medicine have shown that "a one-size-fits-all approach" to the management of chronic lung diseases is no longer appropriate. While precision medicine approaches have revolutionized the management of other diseases such as lung cancer and asthma, the implementation of precision medicine in IPF clinical practice remains an unmet need despite several reports demonstrating a large number of diagnostic, prognostic and theragnostic biomarker candidates in IPF. This review article aims to summarize our current knowledge of precision medicine in IPF and highlight barriers to translate these research findings into clinical practice.

The alcohol extracts of Sceptridium ternatum (Thunb.) Lyon exert anti-pulmonary fibrosis effect through targeting SETDB1/STAT3/p-STAT3 signaling

ETHNOPHARMACOLOGICAL RELEVANCE

Pulmonary fibrosis (PF) is a pathological process of irreversible scarring of lung tissues, with limited treatment means. Sceptridium ternatum (Thunb.) Lyon (STE) is a traditional Chinese herbal medicine that has a traditional use in relieving cough and asthma, resolving phlegm, clearing heat, and detoxicating in China. However, its role in PF has not been reported.

AIM OF THE STUDY

This study aims to investigate the protective role of STE in PF and the underlying mechanisms.

MATERIALS AND METHODS

Sprague-Dawley (SD) rats were divided into control group, PF model group, positive drug (pirfenidone) group and STE group. After 28 days of STE administration in bleomycin (BLM)-induced PF rats, living Nuclear Magnetic Resonance Imaging (NMRI) was used to observe the structural changes of lung tissues. H&E and Masson's trichrome staining were used to observe PF-associated pathological alteration, and immunohistochemistry (IHC) staining, western blotting, and qRT-PCR were used to detect the expression of PF-related marker proteins in the lung tissues. ELISA was used to detect PF-associated biochemical criteria in the lung tissue homogenates. The proteomics technology was used to screen the different proteins. Co-immunoprecipitation, western blotting, and IHC staining were used to confirm the underlying targets of STE as well as its downstream signaling. UPLC-Triple-TOF/MS assay was used to explore the effective components in the alcohol extracts of STE. Autodock vina was used to detect the potential binding between the above effective components and SETDB1.

RESULTS

STE prevented PF by inhibiting the activation of lung fibroblasts and ECM deposition in BLM-induced PF rats. Mechanism analyses demonstrated that STE could inhibit the up-regulation of SETDB1 induced by BLM and TGF-β1, which further blocked the binding of SETDB1 and STAT3 as well as the phosphorylation of STAT3, ultimately preventing the activation and proliferation of lung fibroblasts.

CONCLUSION

STE played a preventive role in PF by targeting the SETBD1/STAT3/p-STAT3 pathway, which may be a potential therapeutic agent for PF.

Oxy210, a Semi-Synthetic Oxysterol, Inhibits Profibrotic Signaling in Cellular Models of Lung and Kidney Fibrosis

Oxy210, a semi-synthetic oxysterol derivative, displays cell-selective inhibition of Hedgehog (Hh) and transforming growth factor beta (TGF-β) signaling in epithelial cells, fibroblasts, and macrophages as well as antifibrotic and anti-inflammatory efficacy in models of liver fibrosis. In the present report, we examine the effects of Oxy210 in cellular models of lung and kidney fibrosis, such as human lung fibroblast cell lines IMR-90, derived from healthy lung tissue, and LL97A, derived from an idiopathic pulmonary fibrosis (IPF) patient. In addition, we examine the effects of Oxy210 in primary human renal fibroblasts, pericytes, mesangial cells, and renal tubular epithelial cells, known for their involvement in chronic kidney disease (CKD) and kidney fibrosis. We demonstrate in fibroblasts that the expression of several profibrotic TGF-β target genes, including fibronectin (FN), collagen 1A1 (COL1A1), and connective tissue growth factor (CTGF) are inhibited by Oxy210, both at the basal level and following TGF-β stimulation in a statistically significant manner. The inhibition of COL1A1 gene expression translated directly to significantly reduced COL1A1 protein expression. In human primary small airway epithelial cells (HSAECs) and renal tubular epithelial cells, Oxy210 significantly inhibited TGF-β target gene expression associated with epithelial-mesenchymal transition (EMT). Oxy210 also inhibited the proliferation of fibroblasts, pericytes, and mesangial cells in a dose-dependent and statistically significant manner.

Ephedrine alleviates bleomycin-induced pulmonary fibrosis by inhibiting epithelial-mesenchymal transition and restraining NF-κB signaling

Pulmonary fibrosis is a lethal and progressive pulmonary disorder in human beings. Ephedrine is a compound isolated from Ephedra and plays a regulatory role in inflammatory response. This study focused on the anti-pulmonary fibrosis effect of ephedrine and its potential molecular mechanism. After a mouse model of pulmonary fibrosis was established through bleomycin (BLM) induction, the survival percentage, body weight, and pulmonary index were measured. Hematoxylin-eosin staining and Masson's trichrome staining for lung tissues were performed to observe the pathological alterations. The viability of lung epithelial BEAS-2B cells, intracellular production of reactive oxygen species, and the levels of pro-inflammatory cytokines were examined by cell counting kit-8 assays, 2',7'-dichlorofluorescein diacetate (DCF-DA) staining, and enzyme-linked immunosorbent assay, respectively. Immunofluorescence staining was performed to determine E-cadherin and vimentin expression after BLM or ephedrine treatment. The mRNA and protein levels of cytokeratin-8, E-cadherin, α-SMA, and vimentin were subjected to quantitative polymerase chain reaction and immunoblotting. Experimental results revealed that ephedrine treatment rescued the repressive impact of BLM on BEAS-2B cell viability, and ephedrine inhibited BLM-induced overproduction of reactive oxygen species and inflammatory response in BEAS-2B cells. Additionally, ephedrine suppressed epithelial-mesenchymal transition (EMT) process stimulated by BLM treatment, as demonstrated by the reduced α-SMA and vimentin levels together with the increased cytokeratin-8 and E-cadherin levels in BLM + Ephedrine group. In addition, ephedrine inhibited NF-κB and activated Nrf-2 signaling in BLM-treated BEAS-2B cells. Moreover, ephedrine ameliorated pulmonary fibrosis in BLM-induced mice and improved the survival of model mice. In conclusion, ephedrine attenuates BLM-evoked pulmonary fibrosis by repressing EMT process via blocking NF-κB signaling and activating Nrf-2 signaling, suggesting that ephedrine might become a potential anti-pulmonary fibrosis agent in the future.

An optimized herbal combination for the treatment of liver fibrosis: Hub genes, bioactive ingredients, and molecular mechanisms

ETHNOPHARMACOLOGICAL RELEVANCE

Liver fibrosis is a chronic liver disease that can lead to cirrhosis, liver failure, and hepatocellular carcinoma, and it is associated with long-term adverse outcomes and mortality. As a primary resource for complementary and alternative medicine, traditional Chinese medicine (TCM) has accumulated a large number of effective formulas for the treatment of liver fibrosis in clinical practice. However, studies on how to systematically optimize TCM formulas are still lacking.

AIM OF THE REVIEW

To provide a methodological reference for the systematic optimization of TCM formulae against liver fibrosis and explored the underlying molecular mechanisms; To provide an efficient method for searching for lead compounds from natural sources and developing from herbal medicines; To enable clinicians and patients to make more reasonable choices and promote the effective treatment toward those patients with liver fibrosis.

MATERIALS AND METHODS

TCM formulas related to treating liver fibrosis were collected from the Web of Science, PubMed, the China National Knowledge Infrastructure (CNKI), Wan Fang, and the Chinese Scientific Journals Database (VIP). Furthermore, the TCM compatibility patterns were mined using association analysis. The core TCM combinations were found by designing an optimized formulas algorithm. Finally, the hub target proteins, potential molecular mechanisms, and active compounds were explored through integrative pharmacology and docking-based inverse virtual screening (IVS) approaches.

RESULTS

We found that the herbs for reinforcing deficiency, activating blood, removing blood stasis, and clearing heat were the basis of TCM formulae patterns. Furthermore, the combination of Salviae Miltiorrhizae (Salvia miltiorrhiza Bunge; Chinese salvia/Danshen), Astragali Radix (Astragalus membranaceus (Fisch.) Bunge; Astragalus/Huangqi), and Radix Bupleuri (Bupleurum chinense DC.; Bupleurum/Chaihu) was identified as core groups. A total of six targets (TNF, STAT3, EGFR, IL2, ICAM1, PTGS2) play a pivotal role in TCM-mediated liver fibrosis inhibition. (-)-Cryptotanshinone, Tanshinaldehyde, Ononin, Thymol, Daidzein, and Formononetin were identified as active compounds in TCM. And mechanistically, TCM could affect the development of liver fibrosis by regulating inflammation, immunity, angiogenesis, antioxidants, and involvement in TNF, MicroRNAs, Jak-STAT, NF-kappa B, and C-type lectin receptors (CLRs) signaling pathways. Molecular docking results showed that key components had good potential to bind to the target genes.

CONCLUSION

In summary, this study provides a methodological reference for the systematic optimization of TCM formulae and exploration of underlying molecular mechanisms.

CFD simulation of porous microsphere particles in the airways of pulmonary fibrosis

BACKGROUND AND OBJECTIVE

Pulmonary fibrosis (PF) is a chronic progressive disease with an extremely high mortality rate and is a complication of COVID-19. Inhalable microspheres have been increasingly used in the treatment of lung diseases such as PF in recent years. Compared to the direct inhalation of drugs, a larger particle size is required to ensure the sustained release of microspheres. However, the clinical symptoms of PF may lead to the easier deposition of microspheres in the upper respiratory tract. Therefore, it is necessary to understand the effects of PF on the deposition of microspheres in the respiratory tract.

METHODS

In this study, airway models with different degrees of PF in humans and mice were established, and the transport and deposition of microspheres in the airway were simulated using computational fluid dynamics.

RESULTS

The simulation results showed that PF increases microsphere deposition in the upper respiratory tract and decreases bronchial deposition in both humans and mice. Porous microspheres with low density can ensure deposition in the lower respiratory tract and larger particle size. In healthy and PF humans, porous microspheres of 10 µm with densities of 700 and 400 kg/m³ were deposited most in the bronchi. Unlike in humans, microspheres larger than 4 µm are completely deposited in the upper respiratory tract of mice owing to their high inhalation velocity. For healthy and PF mice, microspheres of 6 µm with densities of and 100 kg/m³ are recommended.

CONCLUSIONS

The results showed that with the exacerbation of PF, it is more difficult for microsphere particles to deposit in the subsequent airway. In addition, there were significant differences in the deposition patterns among the different species. Therefore, it is necessary to process specific microspheres from different individuals. Our study can guide the processing of microspheres and achieve differentiated drug delivery in different subjects to maximize therapeutic effects.

Identification and validation of autophagy-related gene expression for predicting prognosis in patients with idiopathic pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and fatal fibrotic pulmonary disease with unknow etiology. Owing to lack of reliable prognostic biomarkers and effective treatment measures, patients with IPF usually exhibit poor prognosis. The aim of this study is to establish a risk score prognostic model for predicting the prognosis of patients with IPF based on autophagy-related genes.

Methods

The GSE70866 dataset was obtained from the gene expression omnibus (GEO) database. The autophagy-related genes were collected from the Molecular Signatures Database (MSigDB). Gene enrichment analysis for differentially expressed genes (DEGs) was performed to explore the function of DEGs. Univariate, least absolute shrinkage and selection operator (LASSO), as well as multivariate Cox regression analyses were conducted to identify a multi-gene prognostic model. Receiver operating characteristic (ROC) curve was applied to assess the prediction accuracy of the model. The expression of genes screened from the prognostic model was validated in clinical samples and human lung fibroblasts by qPCR and western blot assays.

Results

Among the 514 autophagy-related genes, a total of 165 genes were identified as DEGs. These DEGs were enriched in autophagy-related processes and pathways. Based on the univariate, LASSO, and multivariate Cox regression analyses, two genes (MET and SH3BP4) were included for establishing the risk score prognostic model. According to the median value of the risk score, patients with IPF were stratified into high-risk and low-risk groups. Patients in high-risk group had shorter overall survival (OS) than low-risk group in both training and test cohorts. Multivariate regression analysis indicated that prognostic model can act as an independent prognostic indicator for IPF. ROC curve analysis confirmed the reliable predictive value of prognostic model. In the validation experiments, upregulated MET expression and downregulated SH3BP4 expression were observed in IPF lung tissues and TGF-β1-activated human lung fibroblasts, which is consistent with results from microarray data analysis.

Conclusion

These findings indicated that the risk score prognostic model based on two autophagy-related genes can effectively predict the prognosis of patients with IPF.

Study on the molecular mechanisms of tetrandrine against pulmonary fibrosis based on network pharmacology, molecular docking and experimental verification

Aims

This study aims to screen the potential targets of tetrandrine (Tet) against pulmonary fibrosis (PF) based on network pharmacological analysis, molecular docking and experimental verification.

Main methods

The network pharmacology methods were employed to predict targets, construct Tet-PF-intersection target-pathway networks, and screen the candidate targets. The molecular docking was performed using AutoDockTools1.5.6. TGF-β1-induced human lung adenocarcinoma A549 cells were used as an in vitro experimental verification model, taking dexamethasone (Dex) as the positive control, to verify the effects of Tet on the mRNA expression of the candidate targets.

Key findings

Six candidate targets were predicted based on network pharmacology and molecular docking, namely PIK3CA, PDPK1, RAC1, PTK2, KDR, and RPS6KB1. The experimental verification results showed that Dex and Tet presented quite different pharmacological effects. Specifically, compared with the model group, both Dex and Tet (5 μΜ) significantly increased the mRNA expression of PIK3CA and KDR (P < 0.001). Dex up-regulated the mRNA expression of PDPK1 and RAC1, while Tet (1.25 μΜ) down-regulated (P < 0.001). Dex up-regulated the mRNA expression of PTK2, but Tet had no effect. Dex down-regulated RPS6KB1 mRNA expression, while Tet (5 μΜ) up-regulated (P < 0.01).

Significance

Combined with the results of theoretical calculation and experimental verification, and considering the roles of these targets in the pathogenesis of PF, Tet might antagonize PF by acting on PDPK1 and RAC1. The results of this study will provide scientific reference for the prevention and clinical diagnosis and treatment of PF.

Ameliorative Effects of Arctigenin on Pulmonary Fibrosis Induced by Bleomycin via the Antioxidant Activity

In this study, we evaluated the in vivo effect of arctigenin (ATG) on bleomycin-induced pulmonary fibrosis in mice and assessed the role of antioxidant activity. Hematoxylin and eosin (H&E) staining, the results of Masson's trichrome, and Sirius red staining showed that bleomycin induced obvious pathological changes and collagen deposition in the lung tissue of mice, which were effectively inhibited by ATG. Specifically, based on immunohistochemistry and western blot results, ATG inhibited the expression of fibrosis markers, such as collagen, fibronectin, and α-SMA. Moreover, ATG regulated reactive oxygen species (ROS), superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione (GSH) in the lung tissue of pulmonary fibrosis mice and reduced the pressure of oxidative stress. ATG also regulated the TGF-β-induced expression of p-Akt, confirming that ATG can inhibit fibrosis through antioxidant activity modulation.

Targeting Growth Factor and Cytokine Pathways to Treat Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic interstitial lung disease of unknown origin that usually results in death from secondary respiratory failure within 2–5 years of diagnosis. Recent studies have identified key roles of cytokine and growth factor pathways in the pathogenesis of IPF. Although there have been numerous clinical trials of drugs investigating their efficacy in the treatment of IPF, only Pirfenidone and Nintedanib have been approved by the FDA. However, they have some major limitations, such as insufficient efficacy, undesired side effects and poor pharmacokinetic properties. To give more insights into the discovery of potential targets for the treatment of IPF, this review provides an overview of cytokines, growth factors and their signaling pathways in IPF, which have important implications for fully exploiting the therapeutic potential of targeting cytokine and growth factor pathways. Advances in the field of cytokine and growth factor pathways will help slow disease progression, prolong life, and improve the quality of life for IPF patients in the future.

NecroX-5 ameliorates bleomycin-induced pulmonary fibrosis via inhibiting NLRP3-mediated epithelial-mesenchymal transition

Background

Pulmonary fibrosis is a progressive and usually lethal pulmonary disease. Despite considerable research efforts, no effective therapeutic strategy for pulmonary fibrosis has been developed. NecroX-5 has been reported to possess anti-inflammatory, anti-oxidative and anti-tumor activities. In the present study, we aimed to determine whether NecroX-5 exhibits antifibrotic property in bleomycin (BLM)-induced pulmonary fibrosis.

Results

We found that pre-treatment with NecroX-5 alleviated inflammatory response, reduced oxidative stress, inhibited epithelial–mesenchymal transition (EMT), and ameliorated pulmonary fibrosis in vivo and in vitro. Our data further indicated that NecroX-5 substantially reduced activation of NLRP3 inflammasome and TGF-β1/Smad2/3 signaling in vivo and in vitro. Additionally, NLRP3 overexpression significantly reversed the protective effects of NecroX-5 in lung epithelial cells exposed to BLM.

Conclusions

Overall, our results demonstrate the potent antifibrotic properties of NecroX-5 and its therapeutic potential for pulmonary fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02044-3.

Oxy210, a Semi-Synthetic Oxysterol, Exerts Anti-Inflammatory Effects in Macrophages via Inhibition of Toll-like Receptor (TLR) 4 and TLR2 Signaling and Modulation of Macrophage Polarization

Inflammatory responses by the innate and adaptive immune systems protect against infections and are essential to health and survival. Many diseases including atherosclerosis, osteoarthritis, rheumatoid arthritis, psoriasis, and obesity involve persistent chronic inflammation. Currently available anti-inflammatory agents, including non-steroidal anti-inflammatory drugs, steroids, and biologics, are often unsafe for chronic use due to adverse effects. The development of effective non-toxic anti-inflammatory agents for chronic use remains an important research arena. We previously reported that oral administration of Oxy210, a semi-synthetic oxysterol, ameliorates non-alcoholic steatohepatitis (NASH) induced by a high-fat diet in APOE*3-Leiden.CETP humanized mouse model of NASH and inhibits expression of hepatic and circulating levels of inflammatory cytokines. Here, we show that Oxy210 also inhibits diet-induced white adipose tissue inflammation in APOE*3-Leiden.CETP mice, evidenced by the inhibition of adipose tissue expression of IL-6, MCP-1, and CD68 macrophage marker. Oxy210 and related analogs exhibit anti-inflammatory effects in macrophages treated with lipopolysaccharide in vitro, mediated through inhibition of toll-like receptor 4 (TLR4), TLR2, and AP-1 signaling, independent of cyclooxygenase enzymes or steroid receptors. The anti-inflammatory effects of Oxy210 are correlated with the inhibition of macrophage polarization. We propose that Oxy210 and its structural analogs may be attractive candidates for future therapeutic development for targeting inflammatory diseases.

Peripheral blood circular RNA hsa_circ_0058493 as a potential novel biomarker for silicosis and idiopathic pulmonary fibrosis

Existing studies reported that some circular RNAs (circRNAs) play vital roles in the development of pulmonary fibrosis. However, few studies explored the biomarker potential of circRNAs for pulmonary fibrosis based on population data. Therefore, we aimed to identify peripheral blood circRNAs as potential biomarkers for diagnosing silicosis and idiopathic pulmonary fibrosis (IPF). In brief, an RNA-seq screening based on 4 silicosis cases and 4 controls was initially performed. Differentially expressed circRNAs were combined with the human serum circRNA dataset to identify overlapping serum-detectable circRNAs, followed by validation using the GEO dataset (3 IPF cases and 3 controls) and subsequent qRT-PCR, including 84 additional individuals. Following the above steps, 243 differentially expressed circRNAs were identified during the screening stage, with fold changes ≥ 1.5 and P < 0.05. Of note, the human serum circRNA dataset encompassed 28 of 243 circRNAs. GEO (GSE102660) validation revealed two highly expressed circRNAs (P < 0.05) in the IPF case group. Furthermore, at the enlarged sample validation stage, hsa_circ_0058493 was highly expressed in both silicosis and IPF cases (silicosis: P = 1.16 × 10^-6; IPF: P = 7.46 × 10^-5). Additionally, hsa_circ_0058493 expression was significantly increased in MRC-5 cells upon TGF-β1 treatment, while hsa_circ_0058493 knockdown inhibited the expression of fibrotic molecules by affecting the epithelial-mesenchymal transition process. These shreds of evidence indicated that hsa_circ_0058493 might serve as a novel biomarker for diagnosing silicosis and IPF.

Indole-Based Small Molecules as Potential Therapeutic Agents for the Treatment of Fibrosis

Indole alkaloids are widely distributed in nature and have been particularly studied because of their diverse biological activities, such as anti-inflammatory, anti-tumor, anti-bacterial, and anti-oxidant activities. Many kinds of indole alkaloids have been applied to clinical practice, proving that indole alkaloids are beneficial scaffolds and occupy a crucial position in the development of novel agents. Fibrosis is an end-stage pathological condition of most chronic inflammatory diseases and is characterized by excessive deposition of fibrous connective tissue components, ultimately resulting in organ dysfunction and even failure with significant morbidity and mortality. Indole alkaloids and indole derivatives can alleviate pulmonary, myocardial, renal, liver, and islet fibrosis through the suppression of inflammatory response, oxidative stress, TGF-β/Smad pathway, and other signaling pathways. Natural indole alkaloids, such as isorhynchophylline, evodiamine, conophylline, indirubin, rutaecarpine, yohimbine, and vincristine, are reportedly effective in organ fibrosis treatment. In brief, indole alkaloids with a wide range of pharmacological bioactivities are important candidate drugs for organ fibrosis treatment. The present review discusses the potential of natural indole alkaloids, semi-synthetic indole alkaloids, synthetic indole derivatives, and indole-contained metabolites in organ fibrosis treatment.

The journey of SARS-CoV-2 in human hosts: a review of immune responses, immunosuppression, and their consequences

Coronavirus disease 2019 (COVID-19) is a highly infectious viral disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Laboratory findings from a significant number of patients with COVID-19 indicate the occurrence of leukocytopenia, specifically lymphocytopenia. Moreover, infected patients can experience contrasting outcomes depending on lymphocytopenia status. Patients with resolved lymphocytopenia are more likely to recover, whereas critically ill patients with signs of unresolved lymphocytopenia develop severe complications, sometimes culminating in death. Why immunodepression manifests in patients with COVID-19 remains unclear. Therefore, the evaluation of clinical symptoms and laboratory findings from infected patients is critical for understanding the disease course and its consequences. In this review, we take a logical approach to unravel the reasons for immunodepression in patients with COVID-19. Following the footprints of the virus within host tissues, from entry to exit, we extrapolate the mechanisms underlying the phenomenon of immunodepression.

Naringenin: A Promising Therapeutic Agent against Organ Fibrosis

Fibrosis is the final common pathology of most chronic diseases as seen in the heart, liver, lung, kidney, and skin and contributes to nearly half of death in the developed countries. Fibrosis, or scarring, is mainly characterized by the transdifferentiation of fibroblasts into myofibroblasts and the excessive accumulation of extracellular matrix (ECM) secreted by myofibroblasts. Despite immense efforts made in the field of organ fibrosis over the past decades and considerable understanding of the occurrence and development of fibrosis gained, there is still lack of an effective treatment for fibrotic diseases. Therefore, identifying a new therapeutic strategy against organ fibrosis is an unmet clinical need. Naringenin, a flavonoid that occurs naturally in citrus fruits, has been found to confer a wide range of pharmacological effects including antioxidant, anti-inflammatory, and anticancer benefits and thus potentially exerting preventive and curative effects on numerous diseases. In addition, emerging evidence has revealed that naringenin can prevent the pathogenesis of fibrosis in vivo and in vitro via the regulation of various pathways that involved signaling molecules such as transforming growth factor-β1/small mother against decapentaplegic protein 3 (TGF-β1/Smad3), mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt), sirtuin1 (SIRT1), nuclear factor-kappa B (NF-κB), or reactive oxygen species (ROS). Targeting these profibrotic pathways by naringenin could potentially become a novel therapeutic approach for the management of fibrotic disorders. In this review, we present a comprehensive summary of the antifibrotic roles of naringenin in vivo and in vitro and their underlying mechanisms of action. As a food derived compound, naringenin may serve as a promising drug candidate for the treatment of fibrotic disorders.

Regulation of TLR4 signaling through the TRAF6/sNASP axis by reversible phosphorylation mediated by CK2 and PP4

Recognition of invading pathogens by Toll-like receptors (TLRs) activates innate immunity through signaling pathways that involved multiple protein kinases and phosphatases. We previously demonstrated that somatic nuclear autoantigenic sperm protein (sNASP) binds to TNF receptor-associated factor 6 (TRAF6) in the resting state. Upon TLR4 activation, a signaling complex consisting of TRAF6, sNASP, interleukin (IL)-1 receptor-associated kinase 4, and casein kinase 2 (CK2) is formed. CK2 then phosphorylates sNASP to release phospho-sNASP (p-sNASP) from TRAF6, initiating downstream signaling pathways. Here, we showed that protein phosphatase 4 (PP4) is the specific sNASP phosphatase that negatively regulates TLR4-induced TRAF6 activation and its downstream signaling pathway. Mechanistically, PP4 is directly recruited by phosphorylated sNASP to dephosphorylate p-sNASP to terminate TRAF6 activation. Ectopic expression of PP4 specifically inhibited sNASP-dependent proinflammatory cytokine production and downstream signaling following bacterial lipopolysaccharide (LPS) treatment, whereas silencing PP4 had the opposite effect. Primary macrophages and mice infected with recombinant adenovirus carrying a gene encoding PP4 (Ad-PP4) showed significant reduction in IL-6 and TNF-α production. Survival of Ad-PP4-infected mice was markedly increased due to a better ability to clear bacteria in a sepsis model. These results indicate that the serine/threonine phosphatase PP4 functions as a negative regulator of innate immunity by regulating the binding of sNASP to TRAF6.

The impact of airborne endotoxin exposure on rheumatoid arthritis-related joint damage, autoantigen expression, autoimmunity, and lung disease

Airborne biohazards are risk factors in the development and severity of rheumatoid arthritis (RA) and RA-associated lung disease, yet the mechanisms explaining this relationship remain unclear. Lipopolysaccharide (LPS, endotoxin) is a ubiquitous inflammatory agent in numerous environmental and occupational air pollutant settings recognized to induce airway inflammation. Combining repetitive LPS inhalation exposures with the collagen induced arthritis (CIA) model, DBA1/J mice were assigned to either: sham (saline injection/saline inhalation), CIA (CIA/saline), LPS (saline/LPS 100 ng inhalation), or CIA + LPS for 5 weeks. Serum anti-citrullinated (CIT) protein antibody (ACPA) and anti-malondialdehyde-acetaldehyde (MAA) antibodies were strikingly potentiated with co-exposure (CIA + LPS). CIT- and MAA-modified lung proteins were increased with co-exposure and co-localized across treatment groups. Inhaled LPS exacerbated arthritis with CIA + LPS > LPS > CIA versus sham. Periarticular bone loss was demonstrated in CIA and CIA + LPS but not in LPS alone. LPS induced airway inflammation and neutrophil infiltrates were reduced with co-exposure (CIA + LPS). Potentially signaling transition to pro-fibrotic processes, there were increased infiltrates of activated CD11c+CD11b+ macrophages and transitioning CD11c+CD11bint monocyte-macrophage populations with CIA + LPS. Moreover, several lung remodeling proteins including fibronectin and matrix metalloproteinases as well as complement C5a were potentiated with CIA + LPS compared to other treatment groups. IL-33 concentrations in lung homogenates were enhanced with CIA + LPS with IL-33 lung staining driven by LPS. IL-33 expression was also significantly increased in lung tissues from patients with RA-associated lung disease (N = 8) versus controls (N = 7). These findings suggest that patients with RA may be more susceptible to developing interstitial lung disease following airborne biohazard exposures enriched in LPS.

The interplay of DAMPs, TLR4, and proinflammatory cytokines in pulmonary fibrosis

Pulmonary fibrosis is a chronic debilitating condition characterized by progressive deposition of connective tissue, leading to a steady restriction of lung elasticity, a decline in lung function, and a median survival of 4.5 years. The leading causes of pulmonary fibrosis are inhalation of foreign particles (such as silicosis and pneumoconiosis), infections (such as post COVID-19), autoimmune diseases (such as systemic autoimmune diseases of the connective tissue), and idiopathic pulmonary fibrosis. The therapeutics currently available for pulmonary fibrosis only modestly slow the progression of the disease. This review is centered on the interplay of damage-associated molecular pattern (DAMP) molecules, Toll-like receptor 4 (TLR4), and inflammatory cytokines (such as TNF-α, IL-1β, and IL-17) as they contribute to the pathogenesis of pulmonary fibrosis, and the possible avenues to develop effective therapeutics that disrupt this interplay.

Molecular Biomarkers in Idiopathic Pulmonary Fibrosis: State of the Art and Future Directions

Idiopathic pulmonary fibrosis (IPF), the most lethal form of interstitial pneumonia of unknown cause, is associated with a specific radiological and histopathological pattern (the so-called "usual interstitial pneumonia" pattern) and has a median survival estimated to be between 3 and 5 years after diagnosis. However, evidence shows that IPF has different clinical phenotypes, which are characterized by a variable disease course over time. At present, the natural history of IPF is unpredictable for individual patients, although some genetic factors and circulating biomarkers have been associated with different prognoses. Since in its early stages, IPF may be asymptomatic, leading to a delayed diagnosis. Two drugs, pirfenidone and nintedanib, have been shown to modify the disease course by slowing down the decline in lung function. It is also known that 5-10% of the IPF patients may be affected by episodes of acute and often fatal decline. The acute worsening of disease is sometimes attributed to identifiable conditions, such as pneumonia or heart failure; but many of these events occur without an identifiable cause. These idiopathic acute worsenings are termed acute exacerbations of IPF. To date, clinical biomarkers, diagnostic, prognostic, and theranostic, are not well characterized. However, they could become useful tools helping facilitate diagnoses, monitoring disease progression and treatment efficacy. The aim of this review is to cover molecular mechanisms underlying IPF and research into new clinical biomarkers, to be utilized in diagnosis and prognosis, even in patients treated with antifibrotic drugs.

Interstitial Lung Disease in Connective Tissue Disease: A Common Lesion With Heterogeneous Mechanisms and Treatment Considerations

Connective tissue disease (CTD) related interstitial lung disease (CTD-ILD) is one of the leading causes of morbidity and mortality of CTD. Clinically, CTD-ILD is highly heterogenous and involves rheumatic immunity and multiple manifestations of respiratory complications affecting the airways, vessels, lung parenchyma, pleura, and respiratory muscles. The major pathological features of CTD are chronic inflammation of blood vessels and connective tissues, which can affect any organ leading to multi-system damage. The human lung is particularly vulnerable to such damage because anatomically it is abundant with collagen and blood vessels. The complex etiology of CTD-ILD includes genetic risks, epigenetic changes, and dysregulated immunity, which interact leading to disease under various ill-defined environmental triggers. CTD-ILD exhibits a broad spectra of clinical manifestations: from asymptomatic to severe dyspnea; from single-organ respiratory system involvement to multi-organ involvement. The disease course is also featured by remissions and relapses. It can range from stability or slow progression over several years to rapid deterioration. It can also present clinically as highly progressive from the initial onset of disease. Currently, the diagnosis of CTD-ILD is primarily based on distinct pathology subtype(s), imaging, as well as related CTD and autoantibodies profiles. Meticulous comprehensive clinical and laboratory assessment to improve the diagnostic process and management strategies are much needed. In this review, we focus on examining the pathogenesis of CTD-ILD with respect to genetics, environmental factors, and immunological factors. We also discuss the current state of knowledge and elaborate on the clinical characteristics of CTD-ILD, distinct pathohistological subtypes, imaging features, and related autoantibodies. Furthermore, we comment on the identification of high-risk patients and address how to stratify patients for precision medicine management approaches.

The Epithelial-Immune Crosstalk in Pulmonary Fibrosis

Interactions between the lung epithelium and the immune system involve a tight regulation to prevent inappropriate reactions and have been connected to several pulmonary diseases. Although the distal lung epithelium and local immunity have been implicated in the pathogenesis and disease course of idiopathic pulmonary fibrosis (IPF), consequences of their abnormal interplay remain less well known. Recent data suggests a two-way process, as illustrated by the influence of epithelial-derived periplakin on the immune landscape or the effect of macrophage-derived IL-17B on epithelial cells. Additionally, damage associated molecular patterns (DAMPs), released by damaged or dying (epithelial) cells, are augmented in IPF. Next to “sterile inflammation”, pathogen-associated molecular patterns (PAMPs) are increased in IPF and have been linked with lung fibrosis, while outer membrane vesicles from bacteria are able to influence epithelial-macrophage crosstalk. Finally, the advent of high-throughput technologies such as microbiome-sequencing has allowed for the identification of a disease-specific microbial environment. In this review, we propose to discuss how the interplays between the altered distal airway and alveolar epithelium, the lung microbiome and immune cells may shape a pro-fibrotic environment. More specifically, it will highlight DAMPs-PAMPs pathways and the specificities of the IPF lung microbiome while discussing recent elements suggesting abnormal mucosal immunity in pulmonary fibrosis.

Rheumatoid arthritis related interstitial lung disease

INTRODUCTION

Interstitial lung disease (ILD) represents a frequent extra-articular manifestation of rheumatoid arthritis (RA) deeply impacting both quality of life and overall prognosis. Areas covered: A literature search was performed including PubMed, Embase, Scopus, and Web of Science. Many retrospective studies investigated the possible risk factors for RA-related ILD (RA-ILD), aiming to identify patients at risk. Among them, males, smokers, positivity of anti-citrullinated peptide antibodies have been associated with RA-ILD, such as some genetic haplotypes. Usual interstitial pneumonia is the histologic and radiologic pattern most frequently observed, followed by nonspecific interstitial pneumonia. Since lung involvement can represent the RA onset, an early differential diagnosis with idiopathic interstitial pneumonia can be difficult or sometimes impossible. High-resolution computed tomography represents the gold standard for ILD diagnosis, while multidisciplinary discussion should be required to assess disease staging, severity and progression.  Expert opinion: Management of RA-ILD patients is challenging due to the lack of evidence-based data regarding both assessment and treatment. Moreover, the high variability of clinical presentation and evolution makes it difficult to establish the correct therapeutic strategy. Currently, multidisciplinary approach, including at least rheumatologists, pulmonologists, and radiologists, is desirable to define therapy and follow-up strategies.

Genetic Risk Factors for Idiopathic Pulmonary Fibrosis: Insights into Immunopathogenesis

Idiopathic pulmonary fibrosis is an etiologically complex interstitial lung disease characterized by progressive scarring of the lungs with a subsequent decline in lung function. While much of the pathogenesis of IPF still remains unclear, it is now understood that genetic variation accounts for at least one-third of the risk of developing the disease. The single-most validated and most significant risk factor, genetic or otherwise, is a gain-of-function promoter variant in the MUC5B gene. While the functional impact of these IPF risk variants at the cellular and tissue levels are areas of active investigation, there is a growing body of evidence that these genetic variants may influence disease pathogenesis through modulation of innate immune processes.

Inhibiting TGF-[Formula: see text] 1-Mediated Cellular Processes as an Effective Strategy for the Treatment of Pulmonary Fibrosis with Chinese Herbal Medicines

Pulmonary fibrosis (PF) is a chronic and irreversible interstitial lung disease that even threatens the lives of some patients infected with COVID-19. PF is a multicellular pathological process, including the initial injuries of epithelial cells, recruitment of inflammatory cells, epithelial-mesenchymal transition, activation and differentiation of fibroblasts, etc. TGF-[Formula: see text]1 acts as a key effect factor that participates in these cellular processes of PF. Recently, much attention was paid to inhibiting TGF-[Formula: see text]1 mediated cell processes in the treatment of PF with Chinese herbal medicines (CHM), an important part of traditional Chinese medicine. Here, this review first summarized the effects of TGF-[Formula: see text]1 in different cellular processes of PF. Then, this review summarized the recent research on CHM (compounds, multi-components, single medicines and prescriptions) to directly and/or indirectly inhibit TGF-[Formula: see text]1 signaling (TLRs, PPARs, micrRNA, etc.) in PF. Most of the research focused on CHM natural compounds, including but not limited to alkaloids, flavonoids, phenols and terpenes. After review, the research perspectives of CHM on TGF-[Formula: see text]1 inhibition in PF were further discussed. This review hopes that revealing the inhibiting effects of CHM on TGF-[Formula: see text]1-mediated cellular processes of PF can promote CHM to be better understood and utilized, thus transforming the therapeutic activities of CHM into practice.

Mangiferin and organ fibrosis: A mini review

Fibrosis is the end stage of many chronic diseases, which results in organ function failure and high mortality. Mangiferin is a major constituent in mango and other 16 plants, and has been shown a variety of pharmacological effects, such as antioxidant, antibacterial, anti-tumor, anti-inflammation. The emerging evidence has shown that mangiferin can improve renal interstitial fibrosis, pulmonary fibrosis, myocardial fibrosis and hepatic fibrosis through the inhibition of inflammation, oxidative stress and fibrogenesis effects, indicating that mangiferin is promising therapeutic choice for organ fibrosis. The aim of this review is to summarize the therapeutic effects of mangiferin on fibrosis of various organs and the underlying mechanisms.

Pathogenesis and treatment of idiopathic and rheumatoid arthritis-related interstitial pneumonia. The possible lesson from COVID-19 pneumonia

INTRODUCTION

Main clinical manifestations of SARS-CoV-2 infection are characterized by fever, dyspnea, and interstitial pneumonia, frequently evolving in acute respiratory distress syndrome (ARDS).

AREAS COVERED

Features of coronavirus disease 2019 (COVID-19) presents some common points with interstitial lung disease (ILD) both idiopathic and related to rheumatoid arthritis (RA), typically characterized by a chronic progression over time and possibly complicated by acute exacerbation (AE). The study of common pathogenetic mechanisms, such as the involvement of toll-like receptor 4, could contribute to the knowledge and treatment of idiopathic and RA-ILD. Moreover, hyperinflammation, mainly characterized by increase of effector T-cells and inflammatory cytokines, and activation of coagulation cascade, observed in COVID-19 related ARDS have been already shown in patients with AE of idiopathic and RA-ILD. A literature search was performed in PubMed, Embase, Scopus, and Web of Science, together with a manual search in COVID-resource centers of the main journals.

EXPERT OPINION

Despite the uncertainty about pathogenetic aspects about COVID-19- pneumonia, it could be a possible model for other forms of ILD and AE. The great amount of data from studies on COVID-19 could be helpful in proposing safe therapeutic approaches for RA-ILD, in understanding pathogenesis of usual interstitial pneumonia and to develop new therapeutic strategies for AE.

Prominence of IL6, IGF, TLR, and Bioenergetics Pathway Perturbation in Lung Tissues of Scleroderma Patients With Pulmonary Fibrosis

Scleroderma-associated pulmonary fibrosis (SSc-PF) and idiopathic pulmonary fibrosis (IPF) are two of many chronic fibroproliferative diseases that are responsible for nearly 45% of all deaths in developed countries. While sharing several pathobiological characteristics, they also have very distinct features. Currently no effective anti-fibrotic treatments exist that can halt the progression of PF or reverse it. Our goal is to uncover potential gene targets for the development of anti-fibrotic therapies efficacious in both diseases, and those specific to SSc-PF, by identifying universal pathways and molecules driving fibrosis in SSc-PF and IPF tissues as well as those unique to SSc-PF. Using DNA microarray data, a meta-analysis of the differentially expressed (DE) genes in SSc-PF and IPF lung tissues (diseased vs. normal) was performed followed by a full systems level analysis of the common and unique transcriptomic signatures obtained. Protein-protein interaction networks were generated to identify hub proteins and explore the data using the centrality principle. Our results suggest that therapeutic strategies targeting IL6 trans-signaling, IGFBP2, IGFL2, and the coagulation cascade may be efficacious in both SSc-PF and IPF. Further, our data suggest that the expression of matrikine-producing collagens is also perturbed in PF. Lastly, an overall perturbation of bioenergetics, specifically between glycolysis and fatty acid metabolism, was uncovered in SSc-PF. Our findings provide insights into potential targets for the development of anti-fibrotic therapies that could be effective in both IPF and SSc-PF.

Molecular regulation of TLR signaling in health and disease: mechano-regulation of macrophages and TLR signaling

Immune cells encounter tissues with vastly different biochemical and physical characteristics. Much of the research emphasis has focused on the role of cytokines and chemokines in regulating immune cell function, but the role of the physical microenvironment has received considerably less attention. The tissue mechanics, or stiffness, of healthy tissues varies dramatically from soft adipose tissue and brain to stiff cartilage and bone. Tissue mechanics also change due to fibrosis and with diseases such as atherosclerosis or cancer. The process by which cells sense and respond to their physical microenvironment is called mechanotransduction. Here we review mechanotransduction in immunologically important diseases and how physical characteristics of tissues regulate immune cell function, with a specific emphasis on mechanoregulation of macrophages and TLR signaling.

SP-A and TLR4 localization in lung tissue of SM-exposed patients

INTRODUCTION

Long-term pulmonary complications are one of the major long-term consequences of sulfur mustard (SM) exposure. Toll-like receptor 4 (TLR4) involves in the pathogenesis of several pulmonary disorders. Surfactant protein-A (SP-A) regulates LPS-induced TLR4 localization and activation responses. However, the intensity and significance of TLR4 and SP-A expression by lung cells in SM-exposed patients is not clear.

METHODS

The gene expression of TLR4 (through real-time PCR) and TLR4 and SP-A positive cells and alveolar type II cells, as SP-A producers, (using IHC) were assessed in formalin fixed paraffin embedded (FFPE) specimens from SM-exposed (n = 17), and non-SM exposed individuals (n = 12).

RESULTS

TLR4 gene expression did not change between study groups. However, its cell surface presentation was significantly reduced in SM-exposed patients and particularly in which with constrictive bronchiolitis compared with the control group (P < 0.001 and P = 0.002, respectively). Frequency of alveolar type II cells was lower in the case group rather than the control group while the number of SP-A positive cells did not alter.

CONCLUSIONS

These findings suggest that reduced TLR4 cell surface presentation may have anti-inflammatory function and SP-A may have a critical role in regulation of inflammatory responses in SM-exposed patients. Further investigation on other possible mechanisms involved in TLR4 internalization maybe help to illustrate the modulatory or inflammatory activity of TLR4 in these patients.

Biologic Treatments in Interstitial Lung Diseases

Interstitial lung diseases (ILD) represent a group of heterogeneous parenchymal lung disorders with complex pathophysiology, characterized by different clinical and radiological patterns, ultimately leading to pulmonary fibrosis. A considerable proportion of these disease entities present with no effective treatment, as current therapeutic regimens only slow down disease progression, thus leaving patients, at best case, with considerable functional disability. Biologic therapies have emerged and are being investigated in patients with different forms of ILD. Unfortunately, their safety profile has raised many concerns, as evidence shows that they might cause or exacerbate ILD status in a subgroup of patients. This review article aims to summarize the current state of knowledge on their role in patients with ILD and highlight future perspectives.

Mangiferin attenuates bleomycin-induced pulmonary fibrosis in mice through inhibiting TLR4/p65 and TGF-β1/Smad2/3 pathway

Objectives

Investigating the antipulmonary fibrosis effect of mangiferin from Mangifera indica and the possible molecular mechanism.

Methods

In vivo, bleomycin (BLM)-induced pulmonary fibrosis experimental model was used for evaluating antipulmonary fibrosis effect of mangiferin. Histopathologic examination and collagen deposition were investigated by HE and Masson staining as well as detecting the content of hydroxyproline. The expression of transforming growth factor-β1 (TGF-β1), α-smooth muscle actin (α-SMA), TLR4 and p-P65 in lung tissue was analysed through immunofluorescence. Leucocytes and inflammatory cytokines including IL-1β, IL-6, TNF-α and MCP-1 in bronchoalveolar lavage fluid were detected by cell counting and enzyme-linked immunosorbent assay. In vitro, TGF-β1-induced A549 epithelial–mesenchymal transition (EMT) cell model was used for investigating the possible molecular mechanism. Reactive oxygen species (ROS) generation was detected by DCFH-DA assay. Expression of all proteins was examined by Western blot.

Key findings

Oral administration of mangiferin could attenuate the severity of BLM-induced pulmonary fibrosis through increasing the survival rate, improving histopathological lesion and body weight loss as well as decreasing pulmonary index visibly. Pulmonary hydroxyproline content, TGF-β1, and α-SMA levels were reduced significantly. The molecular mechanism of mangiferin for inhibiting pulmonary fibrosis is that it could obviously inhibit the occurrence of inflammation and the secretion of inflammatory cytokine through inhibiting activation of TLR4 and phosphorylation of p65. Meanwhile, EMT process was suppressed obviously by mangiferin through blocking the phosphorylation of Smad2/3 and reducing MMP-9 expression. Besides, mangiferin could significantly inhibit the process of oxidant stress through downregulating the intracellular ROS generation.

Conclusions

Mangiferin attenuates BLM-induced pulmonary fibrosis in mice through inhibiting TLR4/p65 and TGF-β1/Smad2/3 pathway.

Topographic distribution of idiopathic pulmonary fibrosis: a hybrid physics- and agent-based model

OBJECTIVE

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal disease characterized by excessive deposition of collagen and associated stiffening of lung tissue. While it is known that inflammation and dysfunction of fibroblasts are involved in disease development, it remains poorly understood how cells and their microenvironment interact to produce a characteristic subpleural pattern of high and low tissue density variations, called honeycombing, on CT images of patients with IPF. Since the pleura is stiffer than the parenchyma, we hypothesized that local stiffness of the underlying extracellular matrix can influence fibroblast activation and consequently the deposition of collagen, which in turn influences tissue stiffness in a positive feedback loop.

APPROACH

We tested this hypothesis by developing a hybrid physics-based/agent-based computational model in which aberrant fibroblast activation is induced when cells migrate on stiff tissue. This activation then feeds back on itself via the altered mechanical environment that it creates by depositing collagen.

MAIN RESULTS

The model produces power law distributions of both low- and high-attenuation area clusters and predicts the development of honeycombing only when mechanical rupture is allowed to take place in highly strained normal tissue surrounded by stiff fibrotic tissue. These predictions compare well with histologic data computed from CT images of patients with IPF.

SIGNIFICANCE

We conclude that the clinical manifestation of subpleural honeycombing in IPF may result from fibroblasts entering into a positive feedback loop induced by the abnormally high tissue stiffness near the pleura.

Mesenchymal Stem Cells for the Treatment of Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is an inexorably progressive lung disease of unknown origin. Prognosis is poor, with limited treatment options available, and the median survival remains just 3-5 years. Despite the use of pirfenidone and nintedanib for the treatment of IPF, curative therapies remain elusive and mortality remains high. Regenerative medicine and the use of cell-based therapies has recently emerged as a potential option for various diseases. Promising results of preclinical studies using mesenchymal stem cells (MSCs) suggest that they may represent a potential therapeutic option for the treatment of chronic lung diseases including IPF. Encouraging results of Phase 1 studies of MSCs various have reduced safety concerns. Nonetheless, there is still a pressing need for exploratory biomarkers and interval end-points in the context of MSCs investigation. This review intends to summarize the current state of knowledge for stem cells in the experimental and clinical setting of IPF, present important safety and efficacy issues, highlight future challenges and address the need for large, multicenter clinical trials coupled with realistic end-points, including biomarkers, to assess treatment efficacy.

Safety and efficacy of nintedanib in idiopathic pulmonary fibrosis: A real-life observational study in Greece

BACKGROUND

Nintedanib represents an antifibrotic compound able to slow down disease progression of patients with idiopathic pulmonary fibrosis (IPF).

OBJECTIVE

To investigate the safety and efficacy of nintedanib in patients with IPF in a real-life setting.

METHODS

This was a multicentre, retrospective, observational, real-life study for patients with IPF receiving nintedanib between October 2014 and October 2016.

RESULTS

We identified 94 patients with IPF receiving nintedanib (72 males, mean age±SD: 73.8 ± 7.5, mean%FVC±SD = 68.1 ± 18.3, mean%DLCo±SD = 44.4 ± 14.5). Diarrhea (n = 52, 55.3%) was the most commonly reported adverse event. Twenty patients (21.2%) had to permanently discontinue nintedanib due to severe adverse events. In the 6-months follow-up, median decline in %FVC predicted and %DLCO predicted were 1.36 (95%Cl: 0 to 2.97) and 4.00 (95%Cl: 2.01 to 6.20), respectively, when deaths were censored and excluded from the analysis. At 12 months, mean%FVC±SD and mean%DLCo±SD were 64.5 ± 19.1 and 43.7 ± 15.4, respectively. With regards to mortality, 17 patients (18.1%) died over a study period of 730 days.

CONCLUSION

Nintedanib demonstrated an acceptable safety and efficacy profile in our real-world observational study. Prospective observational studies in the context of registries that collect well-defined supporting data over time are sorely needed to answer residual questions on drug's performance.

Metabolic Disorders in Chronic Lung Diseases

Chronic lung diseases represent complex diseases with gradually increasing incidence, characterized by significant medical and financial burden for both patients and relatives. Their increasing incidence and complexity render a comprehensive, multidisciplinary, and personalized approach critically important. This approach includes the assessment of comorbid conditions including metabolic dysfunctions. Several lines of evidence show that metabolic comorbidities, including diabetes mellitus, dyslipidemia, osteoporosis, vitamin D deficiency, and thyroid dysfunction have a significant impact on symptoms, quality of life, management, economic burden, and disease mortality. Most recently, novel pathogenetic pathways and potential therapeutic targets have been identified through large-scale studies of metabolites, called metabolomics. This review article aims to summarize the current state of knowledge on the prevalence of metabolic comorbidities in chronic lung diseases, highlight their impact on disease clinical course, delineate mechanistic links, and report future perspectives on the role of metabolites as disease modifiers and therapeutic targets.

Longitudinal "Real-World" Outcomes of Pirfenidone in Idiopathic Pulmonary Fibrosis in Greece

Background

Pirfenidone is an antifibrotic compound able to slow down disease progression in patients with idiopathic pulmonary fibrosis (IPF).

Objective

To investigate the safety and efficacy of pirfenidone in patients with IPF in a real-life setting.

Methods

This was a multicenter, retrospective, real-life, observational study for patients with IPF receiving pirfenidone.

Results

We identified 92 patients with IPF receiving pirfenidone. Eighty patients (70 males and 10 females, mean age ± SD: 68.1 + 7.5, mean %FVC ± SD = 74.9 ± 17.2, mean %DL_CO ± SD = 48.1 ± 16.9) were included in the analysis. Skin-related (25%) and gastrointestinal (17.5%) adverse events were the most common and led to drug discontinuation in 22.5% of cases. The majority (87%) of patients experienced side effects during the first 6 months of treatment. At 36 months, changes in %FVC and %DL_CO were -9.25 ± 16.34 and -9.26 ± 15.26, respectively. At 6, 12, and 24 months after treatment initiation (n = 80, 60, and 26), 18, 15, and 5 patients (22.5, 25, and 19.2%) experienced significant (>10%) and 11, 3, and 3 patients (13.8, 5, and 11.5%) experienced marginal (5-10%) %FVC improvement; and 13, 6, and 1 patient (16.2, 10, and 3.9%) experienced marginal (-5 to -10%) and 20, 21, and 8 patients (25, 35, and 30.8%) experienced significant decline (<-10%) in %FVCpred. Median survival was 851 days, and 41 patients died during the study period.

Conclusion

Pirfenidone demonstrated an acceptable safety and therapeutic profile in patients with IPF on a longitudinal basis. Prospective observational registries are urgently needed to provide a real-world view of outcomes of pirfenidone in clinical practice.

Potential contribution of alveolar epithelial type I cells to pulmonary fibrosis

Pulmonary fibrosis (PF) is characterized by inflammation and fibrosis of the interstitium and destruction of alveolar histoarchitecture ultimately leading to a fatal impairment of lung function. Different concepts describe either a dominant role of inflammatory pathways or a disturbed remodeling of resident cells of the lung parenchyma during fibrogenesis. Further, a combination of both the mechanisms has been postulated. The present review emphasizes the particular involvement of alveolar epithelial type I cells in all these processes, their contribution to innate immune/inflammatory functions and maintenance of proper alveolar barrier functions. Amongst the different inflammatory and repair events the purinergic receptor P2X7, an ATP-gated cationic channel that regulates not only apoptosis, necrosis, autophagy, and NLPR3 inflammosome activation, but also the turnover of diverse tight junction (TJ) and water channel proteins, seems to be essential for the stability of alveolar barrier integrity and for the interaction with protective factors during lung injury.

Extracellular matrix remodeling in idiopathic pulmonary fibrosis. It is the 'bed' that counts and not 'the sleepers'

INTRODUCTION

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive interstitial lung disease characterized by irreversible fibrosis. Current disease pathogenesis assumes an aberrant wound healing process in response to repetitive injurious stimuli leading to apoptosis of epithelial cells, activation of fibroblasts and accumulation of extracellular matrix (ECM). Particularly, lung ECM is a highly dynamic structure that lies at the core of several physiological and developmental pathways. The scope of this review article is to summarize current knowledge on the role of ECM in the pathogenesis of IPF, unravel novel mechanistic data and identify future more effective therapeutic targets. Areas covered: The exact mechanisms through which lung microenvironment activates fibroblasts and inflammatory cells, regulates profibrotic signaling cascades through growth factors, integrins and degradation enzymes ultimately leading to excessive matrix deposition are discussed. Furthermore, the potential therapeutic usefulness of specific inhibitors of matrix deposition or activators of matrix degradation pathways are also presented. Expert commentary: With a gradually increasing worldwide incidence IPF still present a major challenge in clinical research due to its unknown etiopathogenesis and current ineffective treatment approaches. Today, there is an amenable need for more effective therapeutic targets and ECM components may represent one.