Dust induces lung fibrosis through dysregulated DNA methylation

Pneumoconiosis among artisanal miners in Chunya district, Mbeya, Tanzania

This case series sheds light on the pulmonary diseases afflicting artisanal gold miners in Chunya district, Mbeya, Tanzania. We present 3 cases from a group of 21 miners. The patients, ranging in age and mining exposure, exhibited symptoms of severe pulmonary conditions, including pneumoconiosis, pulmonary hypertension and Cor pulmonale, attributed to prolonged exposure to dust and inadequate protective measures in mining environments. These cases underscore the urgent need for enhanced occupational health standards and preventive strategies in artisanal mining communities.

DNA methylation modification in Idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and irreversible interstitial lung disease with a prognosis worse than lung cancer. It is a fatal lung disease with largely unknown etiology and pathogenesis, and no effective therapeutic drugs render its treatment largely unsuccessful. With continuous in-depth research efforts, the epigenetic mechanisms in IPF pathogenesis have been further discovered and concerned. As a widely studied mechanism of epigenetic modification, DNA methylation is primarily facilitated by DNA methyltransferases (DNMTs), resulting in the addition of a methyl group to the fifth carbon position of the cytosine base, leading to the formation of 5-methylcytosine (5-mC). Dysregulation of DNA methylation is intricately associated with the advancement of respiratory disorders. Recently, the role of DNA methylation in IPF pathogenesis has also received considerable attention. DNA methylation patterns include methylation modification and demethylation modification and regulate a range of essential biological functions through gene expression regulation. The Ten-Eleven-Translocation (TET) family of DNA dioxygenases is crucial in facilitating active DNA demethylation through the enzymatic conversion of the modified genomic base 5-mC to 5-hydroxymethylcytosine (5-hmC). TET2, a member of TET proteins, is involved in lung inflammation, and its protein expression is downregulated in the lungs and alveolar epithelial type II cells of IPF patients. This review summarizes the current knowledge of pathologic features and DNA methylation mechanisms of pulmonary fibrosis, focusing on the critical roles of abnormal DNA methylation patterns, DNMTs, and TET proteins in impacting IPF pathogenesis. Researching DNA methylation will enchance comprehension of the fundamental mechanisms involved in IPF pathology and provide novel diagnostic biomarkers and therapeutic targets for pulmonary fibrosis based on the studies involving epigenetic mechanisms.

Zinc Iodide Dimethyl Sulfoxide Reduces Collagen Deposition by Increased Matrix Metalloproteinase-2 Expression and Activity in Lung Fibroblasts

Chronic inflammatory lung diseases are characterized by disease-specific extracellular matrix accumulation resulting from an imbalance of matrix metalloproteinases (MMPs) and their inhibitors. Zinc is essential for the function of MMPs, and zinc deficiency has been associated with enhanced tissue remodeling. This study assessed if zinc iodide (ZnI) supplementation through dimethyl sulfoxide (DMSO) modifies the action of MMPs in isolated human lung fibroblasts. The expression and activity of two gelatinases, MMP-2 and MMP-9, were determined by gelatin zymography and enzyme-linked immuno-sorbent assay (ELISA). Collagen degradation was determined by cell-based ELISAs. Collagen type I and fibronectin deposition was stimulated by human recombinant tumor growth factor β1 (TGF-β1). Untreated fibroblasts secreted MMP-2 but only minute amounts of MMP-9. TGF-β1 (5 ng/mL) reduced MMP-2 secretion, but stimulated collagen type I and fibronectin deposition. All the effects of TGF-β1 were significantly reduced in cells treated with ZnI-DMSO over 24 h, while ZnI and DMSO alone had a lower reducing effect. ZnI-DMSO alone did not increase MMP secretion but enhanced the ratio of active to inactive of MMP-2. ZnI alone had a lower enhancing effect than ZnI-DMSO on MMP activity. Furthermore, MMP-2 activity was increased by ZnI-DMSO and ZnI in the absence of cells. Soluble collagen type I increased in the medium of ZnI-DMSO- and ZnI-treated cells. Blocking MMP activity counteracted all the effects of ZnI-DMSO. Conclusion: The data suggest that the combination of ZnI with DMSO reduces fibrotic processes by increasing the degradation of collagen type I by up-regulating the activity of gelatinases. Thus, the combination of ZnI with DMSO might be considered for treatment of fibrotic disorders of the lung. DMSO supported the beneficial effects of ZnI.

Burden of silica-attributed pneumoconiosis and tracheal, bronchus & lung cancer for global and countries in the national program for the elimination of silicosis, 1990-2019: a comparative study

BACKGROUND

In industries worldwide, crystalline silica is pervasive and poses risks of pneumoconiosis and respiratory malignancies, with the latter being a knowledge gap in disease burden research that this study aims to address. By integrating both diseases, we also seek to provide an in-depth depiction of the silica-attributed disease burden.

METHODS

Data from the Global Burden of Disease 2019 were extracted to analyze the disease burden due to silica exposure. The trends of age-standardized mortality rate (ASMR) and age-standardized DALY rate (ASDR) from 1990 to 2019, as well as the age-specific number and rate of deaths and disability-adjusted life years (DALYs) in 1990 and 2019, were presented using GraphPad Prism software. The average annual percentage changes (AAPCs) on ASMR and ASDR were calculated using joinpoint regression models.

RESULTS

The global trends of disease burden due to silica exposure from 1990 to 2019 showed a significant decrease, with AAPCs on ASMR and ASDR of -1.22 (-1.38, -1.06) and - 1.18 (-1.30, -1.05), respectively. Vietnam was an exception with an unprecedented climb in ASMR and ASDR in general over the years. The age-specific deaths and DALYs mainly peaked in the age group 60-64. In comparison to 1990, the number of deaths and DALYs became higher after 45 years old in 2019, while their rates stayed consistently lower in 2019. Males experienced an elevated age-specific burden than females. China's general age-standardized burden of pneumoconiosis and tracheal, bronchus & lung (TBL) cancer ranked at the forefront, along with the highest burden of pneumoconiosis in Chilean males and South African females, as well as the prominent burden of TBL cancer in Turkish males, Thai females, and overall Vietnamese. The age-specific burden of TBL cancer surpassed that of pneumoconiosis, and a delay was presented in the pneumoconiosis pinnacle burden compared to the TBL cancer. Besides, the burden of pneumoconiosis indicated a sluggish growth trend with advancing age.

CONCLUSION

Our research highlights the cruciality of continuous enhancements in occupational health legislation for countries seriously suffering from industrial silica pollution and the necessity of prioritizing preventive measures for male workers and elderly retirees.

Epigenetic hallmarks in pulmonary fibrosis: New advances and perspectives

Epigenetics indicates that certain phenotypes of an organism can undergo heritable changes in the absence of changes in the genetic DNA sequence. Many studies have shown that epigenetic patterns play an important role in the lung and lung diseases. Pulmonary fibrosis (PF) is also a type of lung disease. PF is an end-stage change of a large group of lung diseases, characterized by fibroblast proliferation and massive accumulation of extracellular matrix, accompanied by inflammatory injury and histological destruction, that is, structural abnormalities caused by abnormal repair of normal alveolar tissue. It causes loss of lung function in patients with multiple complex diseases, leading to respiratory failure and subsequent death. However, current treatment options for IPF are very limited and no drugs have been shown to significantly prolong the survival of patients. Therefore, based on a systematic understanding of the disease mechanisms of PF, this review integrates the role of epigenetics in the development and course of PF, describes preventive and potential therapeutic targets for PF, and provides a theoretical basis for further exploration of the mechanisms of PF.

Potential Effect of Combined Exposure of Crystalline Silica Dust and Cigarette Smoking on the Incidence of Silicosis among Chinese Male Stone Processing Workers: A Cross-Sectional Study

Background: Silicosis is a progressive and irreversible disease primarily caused by exposure to crystalline silica dust and, to a lesser extent, cigarette smoking. However, further research is needed to validate the potential combined effect of these risk factors on the increased incidence of the disease. Methods: A total of 1688 male workers employed at a Chinese stone processing plant between 1 January 1999 and 31 December 2019, were included in the study. Cumulative exposure to industrial crystalline silica dust and packyears of smoking were collected through health surveillance, and odds ratios (ORs) with 95% confidence intervals (CIs) for silicotic changes due to industrial silica exposure and cigarette smoking were estimated using logistic regression models. Results: Among all participants, a significant exposure-response relationship was observed between long-term exposure to industrial silica dust and radiographic findings resembling silicosis (OR 1.74, 95% CI 1.25 to 2.41). However, among middle-aged workers, a weak and statistically insignificant relationship was found between prolonged cigarette smoking and X-ray evidence of lung silicosis (OR 1.59, 95% CI 1.00 to 2.53). Furthermore, significant combined effects, exceeding the additive models, were identified in each age group and employment sector (relative risk due to interaction 0.51, 95% CI 0.08 to 3.42). Conclusions: It is critically important to implement effective dust removal measures and tobacco control strategies in order to enhance respiratory health among employees across all age groups in the stone processing industry.

5-Aza-2′-Deoxycytidine (5-Aza-dC, Decitabine) Inhibits Collagen Type I and III Expression in TGF-β1-Treated Equine Endometrial Fibroblasts

Endometrosis negatively affects endometrial function and fertility in mares, due to excessive deposition of type I (COL1) and type III (COL3) collagens. The pro-fibrotic transforming growth factor (TGF-β1) induces myofibroblast differentiation, characterized by α-smooth muscle actin (α-SMA) expression, and collagen synthesis. In humans, fibrosis has been linked to epigenetic mechanisms. To the best of our knowledge, this has not been described in mare endometrium. Therefore, this study aimed to investigate the in vitro epigenetic regulation in TGF-β1-treated mare endometrial fibroblasts and the use of 5-aza-2′-deoxycytidine (5-aza-dC), an epigenetic modifier, as a putative treatment option for endometrial fibrosis. Methods and Results: The in vitro effects of TGF-β1 and of 5-aza-dC on DNA methyltransferases (DNMT1, DNMT3A, and DNMT3B), COL1A1, COL3A1, and α-SMA transcripts were analyzed in endometrial fibroblasts, and COL1 and COL3 secretion in a co-culture medium. TGF-β1 upregulated DNMT3A transcripts and collagen secretion. In TGF-β1-treated endometrial fibroblasts, DNA methylation inhibitor 5-aza-dC decreased collagen transcripts and secretion, but not α-SMA transcripts. Conclusion: These findings suggest a possible role of epigenetic mechanisms during equine endometrial fibrogenesis. The in vitro effect of 5-aza-dC on collagen reduction in TGF-β1-treated fibroblasts highlights this epigenetic involvement. This may pave the way to different therapeutic approaches for endometrosis.

IL-27 induces autophagy through regulation of the DNMT1/lncRNA MEG3/ERK/p38 axis to reduce pulmonary fibrosis

PURPOSE

Previous studies have shown that interleukin-27 (IL-27) can reduce bleomycin (BLM)-induced pulmonary fibrosis (PF). However, the underlying mechanism by which IL-27 attenuates PF is not fully clear.

METHODS

In this research, we used BLM to construct a PF mouse model, and MRC-5 cells stimulated by transforming growth factor-β1 (TGF-β1) were used to construct a PF model in vitro. The lung tissue status was observed by Masson and hematoxylin and eosin (HE) staining. To detect gene expression, RT‒qPCR was used. The protein levels were detected by western blotting and immunofluorescence staining. EdU and ELISA were used to detect cell proliferation viability and hydroxyproline (HYP) content, respectively.

RESULTS

Aberrant IL-27 expression was observed in BLM-induced mouse lung tissues, and the use of IL-27 attenuated mouse lung tissue fibrosis. TGF-β1 induced autophagy inhibition in MRC-5 cells, and IL-27 alleviated MRC-5 cell fibrosis by activating autophagy. The mechanism is inhibition of DNA methyltransferase 1 (DNMT1)-mediated lncRNA MEG3 methylation and ERK/p38 signaling pathway activation. Overexpression of DNMT1, knockdown of lncRNA MEG3, autophagy inhibitor or ERK/p38 signaling pathway inhibitors reversed the positive effect of IL-27 in a lung fibrosis model in vitro.

CONCLUSION

In conclusion, our study shows that IL-27 upregulates MEG3 expression through inhibition of DNMT1-mediated lncRNA MEG3 promoter methylation, which in turn inhibits ERK/p38 signaling pathway-induced autophagy and attenuates BLM-induced PF, providing a contribution to the elucidation of the potential mechanisms by which IL-27 attenuates PF.

Coal dust nanoparticles induced pulmonary fibrosis by promoting inflammation and epithelial-mesenchymal transition via the NF-κB/NLRP3 pathway driven by IGF1/ROS-mediated AKT/GSK3β signals

Pneumoconiosis is the most common and serious disease among coal miners. In earlier work on this subject, we documented that coal dust (CD) nanoparticles (CD-NPs) induced pulmonary fibrosis (PF) more profoundly than did CD micron particles (CD-MPs), but the mechanism has not been thoroughly studied. Based on the GEO database, jveen, STRING, and Cytoscape tools were used to screen hub genes regulating PF. Particle size distribution of CD were analyzed with Malvern nanoparticle size potentiometer. Combining 8 computational methods, we found that IGF1, POSTN, MMP7, ASPN, and CXCL14 may act as hub genes regulating PF. Based on the high score of IGF1 and its important regulatory role in various tissue fibrosis, we selected it as the target gene in this study. Activation of the IGF1/IGF1R axis promoted CD-NPs-induced PF, and inhibition of the axis activation had the opposite effect in vitro and in vivo. Furthermore, activation of the IGF1/IGF1R axis induced generation of reactive oxygen species (ROS) to promote epithelial-mesenchymal transition (EMT) in alveolar epithelial cells (AECs) to accelerate PF. High-throughput gene sequencing based on lung tissue suggested that cytokine-cytokine receptor interaction and the NF-kB signaling pathway play a key role in PF. Also, ROS induced inflammation and EMT by the activation of the NF-kB/NLRP3 axis to accelerate PF. ROS can induce the activation of AKT/GSK3β signaling, and inhibition of it can inhibit ROS-induced inflammation and EMT by the NF-kB/NLRP3 axis, thereby inhibiting PF. CD-NPs induced PF by promoting inflammation and EMT via the NF-κB/NLRP3 pathway driven by IGF1/ROS-mediated AKT/GSK3β signals. This study provides a valuable experimental basis for the prevention and treatment of coal workers' pneumoconiosis. Illustration of the overall research idea of this study: IGF1 stimulates coal dust nanoparticles induced pulmonary fibrosis by promoting inflammation and EMT via the NF-κB/NLRP3 pathway driven by ROS-mediated AKT/GSK3β signals.

The emerging role of epigenetic regulation in the progression of silicosis

Silicosis is one of the most severe occupational diseases worldwide and is characterized by silicon nodules and diffuse pulmonary fibrosis. However, specific treatments for silicosis are still lacking at present. Therefore, elucidating the pathogenesis of silicosis plays a significant guiding role for its treatment and prevention. The occurrence and development of silicosis are accompanied by many regulatory mechanisms, including epigenetic regulation. The main epigenetic regulatory mechanisms of silicosis include DNA methylation, non-coding RNA (ncRNA), and histone modifications. In recent years, the expression and regulation of genes related to silicosis have been explored at epigenetic level to reveal its pathogenesis further, and the identification of aberrant epigenetic markers provides new biomarkers for prediction and diagnosis of silicosis. Here, we summarize the studies on the role of epigenetic changes in the pathogenesis of silicosis to give some clues for finding specific therapeutic targets for silicosis.

Sputum Microbiota in Coal Workers Diagnosed with Pneumoconiosis as Revealed by 16S rRNA Gene Sequencing

Coal worker’s pneumoconiosis (CWP) is an occupationally induced progressive fibrotic lung disease. This irreversible but preventable disease currently affects millions across the world, mainly in countries with developed coal mining industries. Here, we report a pilot study that explores the sputum microbiome as a potential non-invasive bacterial biomarker of CWP status. Sputum samples were collected from 35 former and active coal miners diagnosed with CWP and 35 healthy controls. Sequencing of bacterial 16S rRNA genes was used to study the taxonomic composition of the respiratory microbiome. There was no difference in alpha diversity between CWP and controls. The structure of bacterial communities in sputum samples (β diversity) differed significantly between cases and controls (pseudo-F = 3.61; p = 0.004). A significant increase in the abundance of Streptococcus (25.12 ± 11.37 vs. 16.85 ± 11.35%; p = 0.0003) was detected in samples from CWP subjects as compared to controls. The increased representation of Streptococcus in sputum from CWP patients was associated only with the presence of occupational pulmonary fibrosis, but did not depend on age, and did not differ between former and current miners. The study shows, for the first time, that the sputum microbiota of CWP subjects differs from that of controls. The results of our present exploratory study warrant further investigations on a larger cohort.

The methyl-CpG-binding domain 2 facilitates pulmonary fibrosis by orchestrating fibroblast to myofibroblast differentiation

Although DNA methylation has been recognized in the pathogenesis of idiopathic pulmonary fibrosis (IPF), the exact mechanisms, however, are yet to be fully addressed. Herein, we demonstrated that lungs originated from IPF patients and mice after bleomycin (BLM)-induced pulmonary fibrosis are characterized by the altered DNA methylation along with overexpression of methyl-CpG-binding domain 2 (MBD2) in myofibroblasts, a reader responsible for interpreting DNA methylome-encoded information. Specifically, depletion of Mbd2 in fibroblasts or myofibroblasts protected mice from BLM-induced pulmonary fibrosis coupled with a significant reduction of fibroblast differentiation. Mechanistically, TGF-β1 induced a positive feedback regulatory loop between transforming growth factor-β receptor I (TβRI), Smad3 and Mbd2, and erythroid differentiation regulator 1 (Erdr1). TGF-β1 induced fibroblasts to undergo a global DNA hypermethylation along with Mbd2 overexpression in a TβRI/Smad3 dependent manner, and Mbd2 selectively bound to the methylated CpG DNA within the Erdr1 promoter to repress its expression, through which it enhances TGF-β/Smads signaling to promote fibroblast differentiating into myofibroblast and exacerbate pulmonary fibrosis. Therefore, enhancing Erdr1 expression strikingly reversed established pulmonary fibrosis. Collectively, our data support that strategies aimed at silencing Mbd2 or increasing Erdr1 could be viable therapeutic approaches for prevention and treatment of pulmonary fibrosis in clinical settings.

Epigenetic Changes and Functions in Pneumoconiosis

Pneumoconiosis is one of the most common occupational diseases in the world, and specific treatment methods of pneumoconiosis are lacking at present, so it carries great social and economic burdens. Pneumoconiosis, coronavirus disease 2019, and idiopathic pulmonary fibrosis all have similar typical pathological changes-pulmonary fibrosis. Pulmonary fibrosis is a chronic lung disease characterized by excessive deposition of the extracellular matrix and remodeling of the lung tissue structure. Clarifying the pathogenesis of pneumoconiosis plays an important guiding role in its treatment. The occurrence and development of pneumoconiosis are accompanied by epigenetic factors (e.g., DNA methylation and noncoding RNA) changes, which in turn can promote or inhibit the process of pneumoconiosis. Here, we summarize epigenetic changes and functions in the several kinds of evidence classification (epidemiological investigation, in vivo, and in vitro experiments) and main types of cells (macrophages, fibroblasts, and alveolar epithelial cells) to provide some clues for finding specific therapeutic targets for pneumoconiosis and even for pulmonary fibrosis.

Idiopathic Pulmonary Fibrosis: An Update on Pathogenesis

Idiopathic pulmonary fibrosis (IPF) is a progressive, lethal fibrotic lung disease that occurs primarily in middle-aged and elderly adults. It is a major cause of morbidity and mortality. With an increase in life expectancy, the economic burden of IPF is expected to continuously rise in the near future. Although the exact pathophysiological mechanisms underlying IPF remain not known. Significant progress has been made in our understanding of the pathogenesis of this devastating disease in last decade. The current paradigm assumes that IPF results from sustained or repetitive lung epithelial injury and subsequent activation of fibroblasts and myofibroblast differentiation. Persistent myofibroblast phenotype contributes to excessive deposition of the extracellular matrix (ECM) and aberrant lung repair, leading to tissue scar formation, distortion of the alveolar structure, and irreversible loss of lung function. Treatments of patients with IPF by pirfenidone and nintedanib have shown significant reduction of lung function decline and slowing of disease progression in patients with IPF. However, these drugs do not cure the disease. In this review, we discuss recent advances on the pathogenesis of IPF and highlight the development of novel therapeutic strategies against the disease.

Cellular response of lung fibroblasts and epithelial cells to particulate matter10 treatment examined via comparative transcriptome analysis

Particulate matter (PM) can be categorized by particle size (PM₁₀, PM_2.5 and PM_1.0), which is an important factor affecting the biological response. Exposure to PM in the air (dust, smoke, dirt and biological contaminants) is clearly associated with lung disease (lung cancer, pneumonia and asthma). Although PM primarily affects lung epithelial cells, the specific response of related cell types to PM remains to be elucidated. The present study performed Gene Ontology (GO) analysis programs (Clustering GO and Database for Annotation, Visualization and Integrated Discovery) on differentially expressed genes in lung epithelial cells (WI‑38 VA‑13) and fibroblasts (WI‑38) following treatment with PM₁₀ and evaluated the cell‑specific biological responses related to cell proliferation, apoptosis, adhesion and extracellular matrix production. The results suggested that short‑ or long‑term exposure to PM may affect cell condition and may consequently be related to several human diseases, including lung cancer and cardiopulmonary disease.

DNA methylation in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD), a complex disease with polygenetic tendency, is one of the most important health problems in the world. Recently, in the study of the pathogenesis of the COPD, epigenetic changes caused by environmental factors, such as DNA methylation, started to attract more attention than genetic factors. In this review, we discuss the main features of DNA methylation, such as DNA methyltransferases and the methylation sites that modulate the DNA methylation level, and their roles in COPD progression. Finally, to promote new ideas for the prevention and treatment of COPD, we focus on the potential of DNA methylation as a COPD therapeutic target.

Association between MeCP2 and Smad7 in the pathogenesis and development of pathological scars

To explore the relationship between methylated binding protein 2 (MeCP2) and mothers against decapentaplegic homolog 7 (Smad7) in the pathogenesis and development of pathological scars. Immunohistochemistry, Western blot and real-time polymerase chain reaction (RT-PCR) were used to detect the expression of MeCP2 in different types of human scars and hypertrophic scars at different growth times. The methylation status of Smad7 gene promoter in different scar tissues was determined by methylation-specific PCR. After transfection with MeCP2-siRNA (small interfering RNA) in human keloid fibroblasts, MTT assay was used to assess the proliferation activity of keloid fibroblasts, while RT-PCR and Western blot assays were used to detect the expression levels of MeCP2, transforming growth factor-β1 (TGF-β1), α-smooth muscle actin (α-SMA), phospho-Smad2 (p-Smad2) and Smad7. MeCP2 was mainly expressed in the nucleus of fibroblasts. The mRNA and protein levels of MeCP2 were significantly higher in keloids than in hypertrophic scars, normal scars and normal skin (p<.05). The expression level of MeCP2 in hypertrophic scars during the growth period of <6 months was markedly higher than that of >6 months (p<.05). The methylation level of Smad7 was significantly higher in keloids compared to normal skin. After MeCP2 silencing, the proliferation rate of human keloid fibroblasts was decreased, the mRNA and protein levels of Smad7 were increased, and the expression levels of TGF-β1, α-SMA and p-Smad2 were decreased (p<.05). MeCP2 and Smad7 play an important role in formation of pathological scars. During keloid formation, MeCP2 weakens the inhibitory effect of Smad7 on p-Smad2/3 by downregulating the expression of Smad7, which in turn promotes fibrosis and scar hyperplasia.

More than a Genetic Code: Epigenetics of Lung Fibrosis

At the end of the last century, genetic studies reported that genetic information is not transmitted solely by DNA, but is also transmitted by other mechanisms, named as epigenetics. The well-described epigenetic mechanisms include DNA methylation, biochemical modifications of histones, and microRNAs. The role of altered epigenetics in the biology of various fibrotic diseases is well-established, and recent advances demonstrate its importance in the pathogenesis of pulmonary fibrosis-predominantly referring to idiopathic pulmonary fibrosis, the most lethal of the interstitial lung diseases. The deficiency in effective medications suggests an urgent need to better understand the underlying pathobiology. This review summarizes the current knowledge concerning epigenetic changes in pulmonary fibrosis and associations of these changes with several cellular pathways of known significance in its pathogenesis. It also designates the most promising substances for further research that may bring us closer to new therapeutic options.

Senescence in Pulmonary Fibrosis: Between Aging and Exposure

To date, chronic pulmonary pathologies represent the third leading cause of death in the elderly population. Evidence-based projections suggest that >65 (years old) individuals will account for approximately a quarter of the world population before the turn of the century. Genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication, are described as the nine “hallmarks” that govern cellular fitness. Any deviation from the normal pattern initiates a complex cascade of events culminating to a disease state. This blueprint, originally employed to describe aberrant changes in cancer cells, can be also used to describe aging and fibrosis. Pulmonary fibrosis (PF) is the result of a progressive decline in injury resolution processes stemming from endogenous (physiological decline or somatic mutations) or exogenous stress. Environmental, dietary or occupational exposure accelerates the pathogenesis of a senescent phenotype based on (1) window of exposure; (2) dose, duration, recurrence; and (3) cells type being targeted. As the lung ages, the threshold to generate an irreversibly senescent phenotype is lowered. However, we do not have sufficient knowledge to make accurate predictions. In this review, we provide an assessment of the literature that interrogates lung epithelial, mesenchymal, and immune senescence at the intersection of aging, environmental exposure and pulmonary fibrosis.