Appraising the causal role of smoking in idiopathic pulmonary fibrosis: a Mendelian randomization study

Genetics and Genomics of Pulmonary Fibrosis: Charting the Molecular Landscape and Shaping Precision Medicine

Recent genetic and genomic advancements have elucidated the complex etiology of idiopathic pulmonary fibrosis (IPF) and other progressive fibrotic interstitial lung diseases (ILDs), emphasizing the contribution of heritable factors. This state-of-the-art review synthesizes evidence on significant genetic contributors to pulmonary fibrosis (PF), including rare genetic variants and common SNPs. The MUC5B promoter variant is unusual, a common SNP that markedly elevates the risk of early and established PF. We address the utility of genetic variation in enhancing understanding of disease pathogenesis and clinical phenotypes, improving disease definitions, and informing prognosis and treatment response. Critical research gaps are highlighted, particularly the underrepresentation of non-European ancestries in PF genetic studies and the exploration of PF phenotypes beyond usual interstitial pneumonia/IPF. We discuss the role of telomere length, often critically short in PF, and its link to progression and mortality, underscoring the genetic complexity involving telomere biology genes (TERT, TERC) and others like SFTPC and MUC5B. In addition, we address the potential of gene-by-environment interactions to modulate disease manifestation, advocating for precision medicine in PF. Insights from gene expression profiling studies and multiomic analyses highlight the promise for understanding disease pathogenesis and offer new approaches to clinical care, therapeutic drug development, and biomarker discovery. Finally, we discuss the ethical, legal, and social implications of genomic research and therapies in PF, stressing the need for sound practices and informed clinical genetic discussions. Looking forward, we advocate for comprehensive genetic testing panels and polygenic risk scores to improve the management of PF and related ILDs across diverse populations.

Genetics of chronic respiratory disease

Chronic respiratory diseases, such as chronic obstructive pulmonary disease (COPD), asthma and interstitial lung diseases are frequently occurring disorders with a polygenic basis that account for a large global burden of morbidity and mortality. Recent large-scale genetic epidemiology studies have identified associations between genetic variation and individual respiratory diseases and linked specific genetic variants to quantitative traits related to lung function. These associations have improved our understanding of the genetic basis and mechanisms underlying common lung diseases. Moreover, examining the overlap between genetic associations of different respiratory conditions, along with evidence for gene-environment interactions, has yielded additional biological insights into affected molecular pathways. This genetic information could inform the assessment of respiratory disease risk and contribute to stratified treatment approaches.

Context-specific eQTLs reveal causal genes underlying shared genetic architecture of critically ill COVID-19 and idiopathic pulmonary fibrosis

Most genetic variants identified through genome-wide association studies (GWAS) are suspected to be regulatory in nature, but only a small fraction colocalize with expression quantitative trait loci (eQTLs, variants associated with expression of a gene). Therefore, it is hypothesized but largely untested that integration of disease GWAS with context-specific eQTLs will reveal the underlying genes driving disease associations. We used colocalization and transcriptomic analyses to identify shared genetic variants and likely causal genes associated with critically ill COVID-19 and idiopathic pulmonary fibrosis. We first identified five genome-wide significant variants associated with both diseases. Four of the variants did not demonstrate clear colocalization between GWAS and healthy lung eQTL signals. Instead, two of the four variants colocalized only in cell-type and disease-specific eQTL datasets. These analyses pointed to higher ATP11A expression from the C allele of rs12585036, in monocytes and in lung tissue from primarily smokers, which increased risk of IPF and decreased risk of critically ill COVID-19. We also found lower DPP9 expression (and higher methylation at a specific CpG) from the G allele of rs12610495, acting in fibroblasts and in IPF lungs, and increased risk of IPF and critically ill COVID-19. We further found differential expression of the identified causal genes in diseased lungs when compared to non-diseased lungs, specifically in epithelial and immune cell types. These findings highlight the power of integrating GWAS, context-specific eQTLs, and transcriptomics of diseased tissue to harness human genetic variation to identify causal genes and where they function during multiple diseases.

Pirfenidone in Idiopathic Pulmonary Fibrosis: Real-World Observation on Efficacy and Safety, Focus on Patients Undergoing Antithrombotic and Anticoagulant

Idiopathic pulmonary fibrosis (IPF) is a rare and progressive interstitial lung disease characterized by irreversible distortion of lung architecture and subsequent loss of pulmonary function. Pirfenidone is an antifibrotic agent associated with increased progression-free survival and overall survival rates, but it carries multiple side effects. The aim of the study was to examine the efficacy and safety profile of pirfenidone in a real-life context, with a focus on the concomitant use of antithrombotic and/or anticoagulant treatments. The clinical and functional data (forced vital capacity [FVC], forced expiratory volume in 1 s [FEV1], diffusing lung capacity for carbon monoxide [DLCO], and 6 min walking test distance [6MWD]) of all IPF patients treated with pirfenidone and referred to our two centers between 2019 and 2022 were retrospectively analyzed at baseline, 6 and 12 months after the start of treatment. A total of 55 IPF subjects undergoing pirfenidone treatment were included in the analysis (45.5% females, median [IQR] age at disease onset 68.0 [10.0] years, median [IQR] age at baseline 69.0 [10.8] years). Compared to baseline, at 12 months, FVC (86.0% vs. 80.0%; p = 0.023) and DLCO (44.0% vs. 40.0%; p = 0.002) were significantly reduced, while FEV1 (p = 0.304) and 6MWD (p = 0.276) remained stable; no significant change was recorded at 6 months. Most of the reported adverse events were mild or moderate. Gastrointestinal intolerance (9.1%) was the main cause of treatment discontinuation. A total of 5% of patients reported at least one minor bleeding event, although all episodes occurred in those receiving concomitant antithrombotic or anticoagulant. Overall, this real-life experience confirms the efficacy and safety profile of pirfenidone in the case of the concomitant use of antithrombotic and/or anticoagulant drugs.

The association of maternal smoking around birth with chronic respiratory diseases in adult offspring: A Mendelian randomization study

INTRODUCTION

Maternal smoking during pregnancy disturbs fetal lung development, and induces in their offspring childhood respiratory diseases. Whether it has a continued impact on offspring adult lung health and exerts a casual effect of chronic respiratory diseases (CRDs), remains uncertain. We seek to determine the causal relationships between maternal smoking around birth and offspring adult CRDs, using summary data from previously described cohorts.

METHODS

Mendelian randomization (MR) study was used to analyze the genome-wide associations of maternal smoking around birth and offspring adult CRDs, including respiratory insufficiency, chronic obstructive pulmonary disease (COPD), related respiratory insufficiency, emphysema, COPD, COPD hospital admissions, early onset of COPD, later onset of COPD, asthma, idiopathic pulmonary fibrosis (IPF), lung cancer (LC), small cell lung carcinoma (SCLC), and lung squamous cell carcinoma (LUSC).

RESULTS

After removing single-nucleotide polymorphisms (SNPs) associated with smoking by the offspring, maternal smoking around birth was associated with increased risk of offspring adult respiratory diseases (OR=1.14; 95% CI: 1.013-1.284; p=0.030), respiratory insufficiency (OR=2.413; 95% CI: 1.039-5.603; p=0.040), COPD (OR=1.14; 95% CI: 1.013-1.284; p=0.003), and asthma (OR=1.336; 95% CI: 1.161-1.538; p<0.001). Besides, maternal smoking during pregnancy was associated with a greater risk of LUSC (OR=1.229; 95% CI: 0.992-1.523; p=0.059) than the risk of IPF (OR=1.001; 95% CI: 0.999-1.003; p=0.224), LC (OR=1.203; 95% CI: 0.964-1.501; p=0.103), or SCLC (OR=1.11; 95% CI: 0.77-1.601; p=0.577).

CONCLUSIONS

In this MR analysis, maternal smoking around birth caused a strong risk factor for the offspring to develop lung problems and CRDs in adulthood. The policy related to smoking cessation for mothers during pregnancy should be encouraged.

Emerging roles of ferroptosis in pulmonary fibrosis: current perspectives, opportunities and challenges

Pulmonary fibrosis (PF) is a chronic interstitial lung disorder characterized by abnormal myofibroblast activation, accumulation of extracellular matrix (ECM), and thickening of fibrotic alveolar walls, resulting in deteriorated lung function. PF is initiated by dysregulated wound healing processes triggered by factors such as excessive inflammation, oxidative stress, and coronavirus disease (COVID-19). Despite advancements in understanding the disease's pathogenesis, effective preventive and therapeutic interventions are currently lacking. Ferroptosis, an iron-dependent regulated cell death (RCD) mechanism involving lipid peroxidation and glutathione (GSH) depletion, exhibits unique features distinct from other RCD forms (e.g., apoptosis, necrosis, and pyroptosis). Imbalance between reactive oxygen species (ROS) production and detoxification leads to ferroptosis, causing cellular dysfunction through lipid peroxidation, protein modifications, and DNA damage. Emerging evidence points to the crucial role of ferroptosis in PF progression, driving macrophage polarization, fibroblast proliferation, and ECM deposition, ultimately contributing to alveolar cell death and lung tissue scarring. This review provides a comprehensive overview of the latest findings on the involvement and signaling mechanisms of ferroptosis in PF pathogenesis, emphasizing potential novel anti-fibrotic therapeutic approaches targeting ferroptosis for PF management.

Mendelian randomization analysis suggests no causal influence of gastroesophageal reflux disease on the susceptibility and prognosis of idiopathic pulmonary fibrosis

BACKGROUND

The relationship between gastroesophageal reflux disease (GERD) and the susceptibility as well as the prognosis of idiopathic pulmonary fibrosis (IPF) has been previously suggested, with the potential confounding factor of smoking not adequately addressed. In light of this, we conducted a Mendelian randomization (MR) study to investigate the causal effects of GERD on the susceptibility and prognosis of IPF while excluding smoking.

METHODS

We chose GERD as the exposure variable and employed genome-wide association data to examine its association with susceptibility, forced vital capacity (FVC), diffusing capacity of the lung for carbon monoxide (DLco), and transplant-free survival (TFS) in patients with IPF as the outcome variables. MR analyses were performed using the inverse variance weighted (IVW) method, and sensitivity analyses were conducted using the MR-PRESSO outlier test, Cochran's Q test, MR-Egger intercept test, and leave-one-out sensitivity analysis. Additionally, to mitigate the potential effects of smoking on our MR estimates, we conducted a multivariable MR (MVMR) analysis by adjusting for smoking.

RESULTS

The univariable MR analysis demonstrated no causal effect of GERD on FVC (βIVW = 26.63, SE = 48.23, P = 0.581), DLco (βIVW = 0.12, SE = 0.12, P = 0.319), and TFS (HRIVW = 0.87, 95% CI = 0.56 to 1.35, P = 0.533) in patients with IPF. Furthermore, sensitivity analysis revealed no evidence of heterogeneity, horizontal pleiotropy, or outlier single nucleotide polymorphisms. The MVMR analysis showed no causal effect of GERD on susceptibility to IPF after adjusting for smoking (ORIVW = 1.30, 95% CI = 0.93 to 1.68, P = 0.071). These findings were consistent in the replication cohort.

CONCLUSIONS

The link between GERD and its potential impact on susceptibility to IPF may not be of a direct causal nature and could be influenced by factors such as smoking. Our findings did not reveal any evidence of a causal relationship between GERD and the FVC, DLco, and TFS of patients with IPF.