The role of viral and bacterial infections in the pathogenesis of IPF: a systematic review and meta-analysis

Platelet Activating Factor Receptor and Intercellular Adhesion Molecule-1 Expression Increases in the Small Airway Epithelium and Parenchyma of Patients with Idiopathic Pulmonary Fibrosis: Implications for Microbial Pathogenesis

Background: Idiopathic pulmonary fibrosis (IPF) is an irreversible lung fibrotic disorder of unknown cause. It has been reported that bacterial and viral co-infections exacerbate disease pathogenesis. These pathogens use adhesion molecules such as platelet activating factor receptor (PAFR) and intercellular adhesion molecule-1 (ICAM-1) to gain cellular entry, causing infections. Methods: Immunohistochemical staining was carried out for lung resections from IPF patients (n = 11) and normal controls (n = 12). The quantification of PAFR and ICAM-1 expression is presented as a percentage in the small airway epithelium. Also, type 2 pneumocytes and alveolar macrophages were counted as cells per mm2 of the parenchymal area and presented as a percentage. All image analysis was done using Image Pro Plus 7.0 software. Results: PAFR expression significantly increased in the small airway epithelium (p < 0.0001), type 2 pneumocytes (p < 0.0001) and alveolar macrophages (p < 0.0001) compared to normal controls. Similar trend was observed for ICAM-1 expression in the small airway epithelium (p < 0.0001), type 2 pneumocytes (p < 0.0001) and alveolar macrophages (p < 0.0001) compared to normal controls. Furthermore, the proportion of positively expressed type 2 pneumocytes and alveolar macrophages was higher in IPF than in normal control. Conclusions: This is the first study to show PAFR and ICAM-1 expression in small airway epithelium, type 2 pneumocytes and alveolar macrophages in IPF. These findings could help intervene microbial impact and facilitate management of disease pathogenesis.

The Impact of Occupational Exposures on the Risk of Idiopathic Pulmonary Fibrosis: A Systematic Review and Meta-Analysis

Rationale: Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic pulmonary disorder of unknown etiology that is characterized by a usual interstitial pneumonia pattern. Previous meta-analyses have reported associations between occupational exposures and IPF, but higher-quality studies have been published in recent years, doubling the number of studied patients. Objectives: To provide a contemporary and comprehensive assessment of the relationship between occupational exposures and IPF. Methods: We searched PubMed, Embase, and Web of Science through July 2023 to identify all publications on occupational exposure and IPF. We conducted a meta-analysis of the occupational burden, odds ratio (OR), and population attributable fraction (PAF) of exposures. Five exposure categories were analyzed: vapors, gas, dust, and fumes (VGDF); metal dust; wood dust; silica dust; and agricultural dust. A comprehensive bias assessment was performed. The study protocol was registered in the International Prospective Register of Systematic Reviews (identifier CRD42021267808). Results: Our search identified 23,942 publications. Sixteen publications contained relative risks needed to calculate pooled ORs and PAFs, and 12 additional publications reported an occupational burden within a case series. The proportion of cases with occupational exposures to VGDF was 44% (95% confidence interval [CI], 36-53%), with a range of 8-17% within more specific exposure categories. The pooled OR was increased for VGDF at 1.8 (95% CI, 1.3-2.4), with a pooled PAF of 21% (95% CI, 15-28%). ORs and PAFs, respectively, were found to be 1.6 and 7% for metal dust, 1.6 and 3% for wood dust, 1.8 and 14% for agricultural dust, and 1.8 and 4% for silica dust. The pooled ORs and PAFs within specific exposure categories ranged from 1.6 to 1.8 and from 4% to 14%, respectively. We identified some publication bias, but it was not sufficient to diminish the association between occupational exposures and IPF based on sensitivity analysis and bias assessment. Conclusions: Our findings indicate that 21% of IPF cases (or approximately one in five) could be prevented by removal of occupational exposure (alongside a pooled OR of 1.8). Additionally, 44% of patients with IPF report occupational exposure to VGDF. This meta-analysis suggests that a considerable number of cases of IPF are attributable to inhaled occupational exposures and warrant increased consideration in the clinical care of patients and future prevention efforts.

Mendelian randomization reveals no correlations between herpesvirus infection and idiopathic pulmonary fibrosis

BACKGROUND

Previous studies have found that the persistence of herpesvirus significantly increases the risk of idiopathic pulmonary fibrosis (IPF), but it is unclear whether this effect is causal. We conducted a two-sample Mendelian randomization (MR) study to evaluate the causal relationship between three herpesvirus infections and IPF.

METHODS

We used genome-wide association studies (GWAS) data from three independent datasets, including FinnGen cohort, Milieu Intérieur cohort, and 23andMe cohort, to screen for instrumental variables (IVs) of herpesvirus infection or herpesvirus-related immunoglobulin G (IgG) levels. Outcome dataset came from the largest meta-analysis of IPF susceptibility currently available.

RESULTS

In the FinnGen cohort, genetically predicted Epstein-Barr virus (EBV) (OR = 1.105, 95%CI: 0.897-1.149, p = 0.815), cytomegalovirus (CMV) (OR = 1.073, 95%CI: 0.926-1.244, p = 0.302) and herpes simplex (HSV) infection (OR = 0.906, 95%CI: 0.753-1.097, p = 0.298) were not associated with the risk of IPF. In the Milieu Intérieur cohort, we found no correlations between herpesvirus-related IgG EBV nuclear antigen-1 (EBNA1) (OR = 0.968, 95%CI: 0.782-1.198, p = 0.764), EBV viral capsid antigen (VCA) (OR = 1.061, 95CI%: 0.811-1.387, p = 0.665), CMV (OR = 1.108, 95CI%: 0.944-1.314, p = 0.240), HSV-1 (OR = 1.154, 95%CI: 0.684-1.945, p = 0.592) and HSV-2 (OR = 0.915, 95%CI: 0.793-1.056, p = 0.225) and IPF risk. Moreover, in the 23andMe cohort, no evidence of associations between mononucleosis (OR = 1.042, 95%CI: 0.709-1.532, p = 0.832) and cold scores (OR = 0.906, 95%CI: 0.603-1.362, p = 0.635) and IPF were found. Sensitivity analysis confirmed the robustness of our results.

CONCLUSIONS

This study provides preliminary evidence that EBV, CMV, and HSV herpesviruses, and herpesviruses-related IgG levels, are not causally linked to IPF. Further MR analysis will be necessary when stronger instrument variables and GWAS with larger sample sizes become available.

In vitro co-culture studies and the crucial role of fibroblast-immune cell crosstalk in IPF pathogenesis

IPF is a fatal lung disease characterized by intensive remodeling of lung tissue leading to respiratory failure. The remodeling in IPF lungs is largely characterized by uncontrolled fibrosis. Fibroblasts and their contractile phenotype the myofibroblast are the main cell types responsible for typical wound healing responses, however in IPF, these responses are aberrant and result in the overactivation of fibroblasts which contributes to the inelasticity of the lung leading to a decrease in lung function. The specific mechanisms behind IPF pathogenesis have been elusive, but recently the innate and adaptive immunity have been implicated in the fibrotic processes of the disease. In connection with this, several in vitro co-culture models have been used to investigate the specific interactions occurring between fibroblasts and immune cells and how this contributes to the pathobiology of IPF. In this review, we discuss the in vitro models that have been used to examine the abnormal interactions between fibroblasts and cells of the innate and adaptive immune system, and how these contribute to the fibrotic processes in the lungs of IPF patients.

Progress in understanding and treating idiopathic pulmonary fibrosis: recent insights and emerging therapies

Idiopathic pulmonary fibrosis (IPF) is a long-lasting, continuously advancing, and irrevocable interstitial lung disorder with an obscure origin and inadequately comprehended pathological mechanisms. Despite the intricate and uncharted causes and pathways of IPF, the scholarly consensus upholds that the transformation of fibroblasts into myofibroblasts-instigated by injury to the alveolar epithelial cells-and the disproportionate accumulation of extracellular matrix (ECM) components, such as collagen, are integral to IPF's progression. The introduction of two novel anti-fibrotic medications, pirfenidone and nintedanib, have exhibited efficacy in decelerating the ongoing degradation of lung function, lessening hospitalization risk, and postponing exacerbations among IPF patients. Nonetheless, these pharmacological interventions do not present a definitive solution to IPF, positioning lung transplantation as the solitary potential curative measure in contemporary medical practice. A host of innovative therapeutic strategies are presently under rigorous scrutiny. This comprehensive review encapsulates the recent advancements in IPF research, spanning from diagnosis and etiology to pathological mechanisms, and introduces a discussion on nascent therapeutic methodologies currently in the pipeline.

Inflammation-Associated Lung Tissue Remodeling and Fibrosis in Morphine-Dependent SIV-Infected Macaques

With the advent of antiretroviral therapy, improved survival of people with HIV (PWH) is accompanied with increased prevalence of HIV-associated comorbidities. Chronic lung anomalies are recognized as one of the most devastating sequelae in PWH. The limited available data describing the lung complications in PWH with a history of opioid abuse warrants more research to better define the course of disease pathogenesis. The current study was conducted to investigate the progression of lung tissue remodeling in a morphine (Mor)-exposed rhesus macaque model of SIV infection. Pathologic features of lung remodeling, including histopathologic changes, oxidative stress, inflammation, and proliferation of fibroblasts, were investigated in archival lung tissues of SIVmac-251/macaque model with or without Mor dependence. Lungs of Mor-exposed, SIV-infected macaques exhibited significant fibrotic changes and collagen deposition in the alveolar and the bronchiolar region. There was increased oxidative stress, profibrotic transforming growth factor-β, fibroblast proliferation and trans-differentiation, epithelial-mesenchymal transition, and matrix degradation in SIV-infected macaques, which was further exacerbated in the lungs of Mor-exposed macaques. Interestingly, there was decreased inflammation-associated remodeling in Mor-dependent SIV-infected macaques compared with SIV-infected macaques that did not receive Mor. Thus, the current findings suggest that SIV independently induces fibrotic changes in macaque lungs, which is further aggravated by Mor.

Role of circulatory miRNA-21 and associated signaling pathways in the pathogenesis of pulmonary fibrosis among individuals recovered after COVID-19 infection

Introduction

Currently pulmonary fibrosis in post-COVID individuals represents a crucial milieu of investigation due to long-term associated complications and worse clinical outcome. Lack of studies in Indian population confers a crucial need for elucidating possible targets and mechanisms to explore better management and outcome. Hence, this study aimed to explore the role of circulating miRNA-21 in patients from South India after COVID-19 recovery, while targeting TGF-β signaling pathway involved in the development of pulmonary fibrosis.

Methods

This prospective, single centre, hospital-based study enrolled a total of 50 participants in the age group of 50 to 60 years including 25 non-infected controls and 25 patients who were recovered after 3–6 months of COVID-19 infection and presented radiological pulmonary abnormalities. Quantification of miRNA-21 and selected gene transcripts (TGF-β, Col1A2, Col3A1, and α-SMA) was performed in plasma samples of both patients and controls.

Results

Significantly increased expression levels of miRNA-21 was observed in patient samples compared to controls (4.50 ± 1.03 vs 12.60 ± 3.52, p < 0.0001) with 72.10% sensitivity and 80.10% specificity. Further, significantly increased levels of central fibrosis regulatory gene transcript TGF-β (0.56 ± 0.27 vs 1.83 ± 0.98), two crucial collagen transcripts Col1A2 (0.62 ± 0.19 vs 1.56 ± 1.00) and Col3A1 (0.61 ± 0.27 vs 1.54 ± 0.89), and α-SMA (0.46 ± 0.17 vs 1.20 ± 0.78) was observed in patients compared to controls. Western-blot analysis also showed almost similar observations at proteins levels.

Conclusion

Circulating miRNA-21 may provide crucial insights for elucidating TGF-β mediated pulmonary remodeling involved in the fibrosis development and achieve better clinical outcome for post-COVID patients after recovery, in real-time with high diagnostic accuracy.

Colchicine Is a Weapon for Managing the Heart Disease Among Interstitial Lung Disease With Viral Infection: Have We Found the Holy Grail?

Background

This study investigated the effect of colchicine use on the risks of heart disease (HD), pericarditis, endocarditis, myocarditis, cardiomyopathy, cardiac arrhythmia, and cardiac failure in patients having interstitial lung disease (ILD) with virus infection (ILD cohort).

Methods

We retrospectively enrolled ILD cohort between 2000 and 2013 from the Longitudinal Health Insurance Database and divided them into colchicine users (n = 12,253) and colchicine non-users (n = 12,253) through propensity score matching. The event of interest was the diagnosis of HD. The incidence of HD was analyzed using multivariate Cox proportional hazards models between colchicine users and the comparison cohort after adjustment for age, sex, medication, comorbidities, and index date based on the time-dependent analysis.

Results

Colchicine users had a significantly lower risk of HD (aHR = 0.87, 95% confidence interval (CI]) = 0.82–0.92) than did the colchicine non-user. For colchicine non-users as the reference, the aHR (95% CI) of the patients who received colchicine of 2–7, 8–30, 31–150, and &gt; 150 days were 0.89 (0.81–0.98), 0.84 (0.76–0.94), 090 (0.80–0.99), and 0.83 (0.74–0.93), respectively; regardless of duration use, the lower risk of HD persisted in colchicine users. The cumulative incidence of HD in colchicine users was significantly lower than that in the colchicine non-users (log-rank p &lt; 0.001).

Conclusion

The addition of short-term or long-term colchicine to standard medical therapy may have benefits to prevent the HD among the ILD patients concurrent with a virus infection or comorbidities even in elderly patients.

Hydroxychloroquine on the Pulmonary Vascular Diseases in Interstitial Lung Disease: Immunologic Effects, and Virus Interplay

To investigate the effects of hydroxychloroquine (HCQ) drug use on the risk of pulmonary vascular disease (PVD) in an interstitial lung disease cohort (ILD cohort, ILD+ virus infection), we retrospectively enrolled the ILD cohort with HCQ (HCQ users, N = 4703) and the ILD cohort without HCQ (non-HCQ users, N = 4703) by time-dependence after propensity score matching. Cox models were used to analyze the risk of PVD. We calculated the adjusted hazard ratios (aHRs) and their 95% confidence intervals (CIs) for PVD after adjusting for sex, age, comorbidities, index date and immunosuppressants, such as steroids, etc. Compared with the HCQ nonusers, in HCQ users, the aHRs (95% CIs) for PVD were (2.24 (1.42, 3.54)), and the women’s aHRs for PVD were (2.54, (1.49, 4.35)). The aHRs based on the days of HCQ use for PVD of 28−30 days, 31−120 days, and >120 days were (1.27 (0.81, 1.99)), (3.00 (1.81, 4.87)) and (3.83 (2.46, 5.97)), respectively. The medium or long-term use of HCQ or young women receiving HCQ were associated with a higher aHR for PVD in the ILD cohort. These findings indicated interplay of the primary immunologic effect of ILD, comorbidities, women, age and virus in the HCQ users.

Gut Microbiome and Organ Fibrosis

Fibrosis is a pathological process associated with most chronic inflammatory diseases. It is defined by an excessive deposition of extracellular matrix proteins and can affect nearly every tissue and organ system in the body. Fibroproliferative diseases, such as intestinal fibrosis, liver cirrhosis, progressive kidney disease and cardiovascular disease, often lead to severe organ damage and are a leading cause of morbidity and mortality worldwide, for which there are currently no effective therapies available. In the past decade, a growing body of evidence has highlighted the gut microbiome as a major player in the regulation of the innate and adaptive immune system, with severe implications in the pathogenesis of multiple immune-mediated disorders. Gut microbiota dysbiosis has been associated with the development and progression of fibrotic processes in various organs and is predicted to be a potential therapeutic target for fibrosis management. In this review we summarize the state of the art concerning the crosstalk between intestinal microbiota and organ fibrosis, address the relevance of diet in different fibrotic diseases and discuss gut microbiome-targeted therapeutic approaches that are current being explored.

Construction of prediction model of inflammation related genes in idiopathic pulmonary fibrosis and its correlation with immune microenvironment

BACKGROUND

The role of inflammation in the formation of idiopathic pulmonary fibrosis (IPF) has gained a lot of attention recently. However, the involvement of genes related to inflammation and immune exchange environment status in the prognosis of IPF remains to be further clarified. The objective of this research is to establish a new model for the prediction of the overall survival (OS) rate of inflammation-related IPF.

METHODS

Gene Expression Omnibus (GEO) was employed to obtain the three expression microarrays of IPF, including two from alveolar lavage fluid cells and one from peripheral blood mononuclear cells. To construct the risk assessment model of inflammation-linked genes, least absolute shrinkage and selection operator (lasso), univariate cox and multivariate stepwise regression, and random forest method were used. The proportion of immune cell infiltration was evaluated by single sample Gene Set Enrichment Analysis (ssGSEA) algorithm.

RESULTS

The value of genes linked with inflammation in the prognosis of IPF was analyzed, and a four-genes risk model was constructed, including tpbg, Myc, ffar2, and CCL2. It was highlighted by Kaplan Meier (K-M) survival analysis that patients with high-risk scores had worse overall survival time in all training and validation sets, and univariate and multivariate analysis highlighted that it has the potential to act as an independent risk indicator for poor prognosis. ROC analysis showed that the prediction efficiency of 1-, 3-, and 5-year OS time in the training set reached 0.784, 0.835, and 0.921, respectively. Immune infiltration analysis showed that Myeloid-Derived Suppressor Cells (MDSC), macrophages, regulatory T cells, cd4+ t cells, neutrophils, and dendritic cells were more infiltrated in the high-risk group than in the low-risk group.

CONCLUSION

Inflammation-related genes can be well used to evaluate the IPF prognosis and impart a new idea for the treatment and follow-up management of IPF patients.

Pulmonary fibrosis from molecular mechanisms to therapeutic interventions: lessons from post-COVID-19 patients

Pulmonary fibrosis (PF) is characterised by several grades of chronic inflammation and collagen deposition in the interalveolar space and is a hallmark of interstitial lung diseases (ILDs). Recently, infectious agents have emerged as driving causes for PF development; however, the role of viral/bacterial infections in the initiation and propagation of PF is still debated. In this context, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for the current coronavirus disease 2019 (COVID-19) pandemic, has been associated with acute respiratory distress syndrome (ARDS) and PF development. Although the infection by SARS-CoV-2 can be eradicated in most cases, the development of fibrotic lesions cannot be precluded; furthermore, whether these lesions are stable or progressive fibrotic events is still unknown. Herein, an overview of the main molecular mechanisms driving the fibrotic process together with the currently approved and newly proposed therapeutic solutions was given. Then, the most recent data that emerged from post-COVID-19 patients was discussed, in order to compare PF and COVID-19-dependent PF, highlighting shared and specific mechanisms. A better understanding of PF aetiology is certainly needed, also to develop effective therapeutic strategies and COVID-19 pathology is offering one more chance to do it. Overall, the work reported here could help to define new approaches for therapeutic intervention in the diversity of the ILD spectrum.

The Crucial Role of NLRP3 Inflammasome in Viral Infection-Associated Fibrosing Interstitial Lung Diseases

Idiopathic pulmonary fibrosis (IPF), one of the most common fibrosing interstitial lung diseases (ILD), is a chronic-age-related respiratory disease that rises from repeated micro-injury of the alveolar epithelium. Environmental influences, intrinsic factors, genetic and epigenetic risk factors that lead to chronic inflammation might be implicated in the development of IPF. The exact triggers that initiate the fibrotic response in IPF remain enigmatic, but there is now increasing evidence supporting the role of chronic exposure of viral infection. During viral infection, activation of the NLRP3 inflammasome by integrating multiple cellular and molecular signaling implicates robust inflammation, fibroblast proliferation, activation of myofibroblast, matrix deposition, and aberrant epithelial-mesenchymal function. Overall, the crosstalk of the NLRP3 inflammasome and viruses can activate immune responses and inflammasome-associated molecules in the development, progression, and exacerbation of IPF.