Hallmarks of the ageing lung

Redox Dysregulation in Aging and COPD: Role of NOX Enzymes and Implications for Antioxidant Strategies

With a rapidly growing elderly human population, the incidence of age-related lung diseases such as chronic obstructive pulmonary disease (COPD) continues to rise. It is widely believed that reactive oxygen species (ROS) play an important role in ageing and in age-related disease, and approaches of antioxidant supplementation have been touted as useful strategies to mitigate age-related disease progression, although success of such strategies has been very limited to date. Involvement of ROS in ageing is largely attributed to mitochondrial dysfunction and impaired adaptive antioxidant responses. NADPH oxidase (NOX) enzymes represent an important enzyme family that generates ROS in a regulated fashion for purposes of oxidative host defense and redox-based signalling, however, the associations of NOX enzymes with lung ageing or age-related lung disease have to date only been minimally addressed. The present review will focus on our current understanding of the impact of ageing on NOX biology and its consequences for age-related lung disease, particularly COPD, and will also discuss the implications of altered NOX biology for current and future antioxidant-based strategies aimed at treating these diseases.

Molecular programs of fibrotic change in aging human lung

Lung fibrosis is increasingly detected with aging and has been associated with poor outcomes in acute lung injury or infection. However, the molecular programs driving this pro-fibrotic evolution are unclear. Here we profile distal lung samples from healthy human donors across the lifespan. Gene expression profiling by bulk RNAseq reveals both increasing cellular senescence and pro-fibrotic pathway activation with age. Quantitation of telomere length shows progressive shortening with age, which is associated with DNA damage foci and cellular senescence. Cell type deconvolution analysis of the RNAseq data indicates a progressive loss of lung epithelial cells and an increasing proportion of fibroblasts with age. Consistent with this pro-fibrotic profile, second harmonic imaging of aged lungs demonstrates increased density of interstitial collagen as well as decreased alveolar expansion and surfactant secretion. In this work, we reveal the transcriptional and structural features of fibrosis and associated functional impairment in normal lung aging.

Upregulation of Human Endogenous Retroviruses in Bronchoalveolar Lavage Fluid of COVID-19 Patients

Severe COVID-19 pneumonia has been associated with the development of intense inflammatory responses during the course of infections with SARS-CoV-2. Given that human endogenous retroviruses (HERVs) are known to be activated during and participate in inflammatory processes, we examined whether HERV dysregulation signatures are present in COVID-19 patients. By comparing transcriptomes of bronchoalveolar lavage fluid (BALF) of COVID-19 patients and healthy controls, and peripheral blood monocytes (PBMCs) from patients and controls, we have shown that HERVs are intensely dysregulated in BALF of COVID-19 patients compared to those in BALF of healthy control patients but not in PBMCs. In particular, upregulation in the expression of specific HERV families was detected in BALF samples of COVID-19 patients, with HERV-FRD being the most highly upregulated family among the families analyzed. In addition, we compared the expression of HERVs in human bronchial epithelial cells (HBECs) without and after senescence induction in an oncogene-induced senescence model in order to quantitatively measure changes in the expression of HERVs in bronchial cells during the process of cellular senescence. This apparent difference of HERV dysregulation between PBMCs and BALF warrants further studies in the involvement of HERVs in inflammatory pathogenetic mechanisms as well as exploration of HERVs as potential biomarkers for disease progression. Furthermore, the increase in the expression of HERVs in senescent HBECs in comparison to that in noninduced HBECs provides a potential link for increased COVID-19 severity and mortality in aged populations.

IMPORTANCE SARS-CoV-2 emerged in late 2019 in China, causing a global pandemic. Severe COVID-19 is characterized by intensive inflammatory responses, and older age is an important risk factor for unfavorable outcomes. HERVs are remnants of ancient infections whose expression is upregulated in multiple conditions, including cancer and inflammation, and their expression is increased with increasing age. The significance of this work is that we were able to recognize dysregulated expression of endogenous retroviral elements in BALF samples but not in PBMCs of COVID-19 patients. At the same time, we were able to identify upregulated expression of multiple HERV families in senescence-induced HBECs in comparison to that in noninduced HBECs, a fact that could possibly explain the differences in disease severity among age groups. These results indicate that HERV expression might play a pathophysiological role in local inflammatory pathways in lungs afflicted by SARS-CoV-2 and their expression could be a potential therapeutic target.

Redox Regulation in Aging Lungs and Therapeutic Implications of Antioxidants in COPD

Mammals, including humans, are aerobic organisms with a mature respiratory system to intake oxygen as a vital source of cellular energy. Despite the essentiality of reactive oxygen species (ROS) as byproducts of aerobic metabolism for cellular homeostasis, excessive ROS contribute to the development of a wide spectrum of pathological conditions, including chronic lung diseases such as COPD. In particular, epithelial cells in the respiratory system are directly exposed to and challenged by exogenous ROS, including ozone and cigarette smoke, which results in detrimental oxidative stress in the lungs. In addition, the dysfunction of redox regulation due to cellular aging accelerates COPD pathogenesis, such as inflammation, protease anti-protease imbalance and cellular apoptosis. Therefore, various drugs targeting oxidative stress-associated pathways, such as thioredoxin and N-acetylcysteine, have been developed for COPD treatment to precisely regulate the redox system. In this review, we present the current understanding of the roles of redox regulation in the respiratory system and COPD pathogenesis. We address the insufficiency of current COPD treatment as antioxidants and discuss future directions in COPD therapeutics targeting oxidative stress while avoiding side effects such as tumorigenesis.

Association between previous lung diseases and lung cancer risk: a systematic review and meta-analysis

Previous lung diseases (PLD) are known risk factors for lung cancer. However, it remains unclear how the association varies by lung cancer subtype and socio-demographic characteristics. We conducted a systematic literature search in three electronic databases from the inception of each database up until 13 January 2021. A total of 73 studies (18 cohort and 55 case-control studies) consisting of 97,322 cases and 7,761,702 controls were included. Heterogeneity was assessed using the I 2 statistic. Based on the heterogeneity, either the fixed-effects or random-effects model was used to estimate the pooled summary estimate (PSE) and 95% confidence interval (CI) for the association between PLD and lung cancer risk. A history of asthma, chronic bronchitis, emphysema, pneumonia, tuberculosis, and COPD was associated with higher lung cancer risk, with a history of COPD and emphysema having at least two-fold relative risk. A history of hay fever was associated with lower lung cancer risk (PSE= 0.66, 95% CI= 0.54-0.81), even among ever-smokers (PSE= 0.55, 95% CI= 0.41-0.73). Older individuals with a history of asthma, chronic bronchitis, emphysema, COPD, or tuberculosis were associated with higher lung cancer risk. Individuals with a diagnosis of asthma, emphysema, or pneumonia within 1 to 10 years prior to lung cancer diagnosis were associated with higher lung cancer risk. Among ever-smokers, a history of COPD or emphysema have at least two-fold relative risk of lung cancer. PLD was associated with higher risk of lung cancer. Individuals with PLD should be closely monitored and prioritised for lung cancer screening.

The hoverfly and the wasp: A critique of the hallmarks of aging as a paradigm

With the goal of representing common denominators of aging in different organisms López-Otín et al. in 2013 described nine hallmarks of aging. Since then, this representation has become a major reference point for the biogerontology field. The template for the hallmarks of aging account originated from landmark papers by Hanahan and Weinberg (2000, 2011) defining first six and later ten hallmarks of cancer. Here we assess the strengths and weaknesses of the hallmarks of aging account. As a checklist of diverse major foci of current aging research, it has provided a useful shared overview for biogerontology during a time of transition in the field. It also seems useful in applied biogerontology, to identify interventions (e.g. drugs) that impact multiple symptomatic features of aging. However, while the hallmarks of cancer provide a paradigmatic account of the causes of cancer with profound explanatory power, the hallmarks of aging do not. A worry is that as a non-paradigm the hallmarks of aging have obscured the urgent need to define a genuine paradigm, one that can provide a useful basis for understanding the mechanistic causes of the diverse aging pathologies. We argue that biogerontology must look and move beyond the hallmarks to understand the process of aging.

Citrus alkaline extracts prevent endoplasmic reticulum stress in type II alveolar epithelial cells to ameliorate pulmonary fibrosis via the ATF3/PINK1 pathway

BACKGROUND

Idiopathic pulmonary fibrosis is a chronic, progressive, fibrotic disease. Although the pathogenesis remains unclear, the effect of endoplasmic reticulum (ER) stress in type II alveolar epithelial cells (AEC IIs) is increasingly thought to be a critical mechanism.

PURPOSE

We investigated the effects of citrus alkaline extracts (CAE) on AEC IIs and elucidated the underlying mechanism for their possible use in ameliorating pulmonary fibrosis (PF).

METHODS

A bleomycin-induced mouse model of PF, and an in vitro tunicamycin (TM) -induced ER stress model in A549 cells were successfully established. Accumulation of collagen in lung tissues in vivo was assessed using histological analysis and western blotting. The expression levels of the ER-stress marker BiP and other related proteins were assessed by western blotting and immunofluorescence staining. Mitochondrial membrane potential was assessed to evaluate mitochondrial homeostasis.

RESULTS

CAE mitigated collagen deposition to ameliorate PF in vivo. CAE suppressed the bleomycin or TM-induced increases in ER-stress biomarker, BiP, and PERK pathway proteins, resulting in a decrease in ER stress in mouse lung tissues and A549 cells, respectively. Additionally, CAE treatment suppressed the bleomycin or TM-induced increase in the ER-stress downstream proteins, activating ATF3 and increased the levels of PINK1 in AEC IIs, both in vivo and in vitro. The reduced mitochondrial homeostasis induced by TM was restored by CAE-treatment in A549 cells. Furthermore, conditioned media from TM-treated A549 cells increased collagen deposition in MRC5 cells mainly via TGF-β1. The increased collagen deposition was not seen using conditioned media from CAE-treated A549 cells.

CONCLUSION

These results provide novel insights into the potential mechanism of CAE in inhibiting ER stress in AEC IIs, and suggests that it has great potential to ameliorate PF via the ATF3/PINK1 pathway.

Comparative analysis of the bronchoalveolar microbiome in Portuguese patients with different chronic lung disorders

The lung is inhabited by a diverse microbiome that originates from the oropharynx by a mechanism of micro-aspiration. Its bacterial biomass is usually low; however, this condition shifts in lung cancer (LC), chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD). These chronic lung disorders (CLD) may coexist in the same patient as comorbidities and share common risk factors, among which the microbiome is included. We characterized the microbiome of 106 bronchoalveolar lavages. Samples were initially subdivided into cancer and non-cancer and high-throughput sequenced for the 16S rRNA gene. Additionally, we used a cohort of 25 CLD patients where crossed comorbidities were excluded. Firmicutes, Proteobacteria and Bacteroidetes were the most prevalent phyla independently of the analyzed group. Streptococcus and Prevotella were associated with LC and Haemophilus was enhanced in COPD versus ILD. Although no significant discrepancies in microbial diversity were observed between cancer and non-cancer samples, statistical tests suggested a gradient across CLD where COPD and ILD displayed the highest and lowest alpha diversities, respectively. Moreover, COPD and ILD were separated in two clusters by the unweighted UniFrac distance (P value = 0.0068). Our results support the association of Streptoccocus and Prevotella with LC and of Haemophilus with COPD, and advocate for specific CLD signatures.

Time-resolved proteomic profiling of cigarette smoke-induced experimental chronic obstructive pulmonary disease

BACKGROUND AND OBJECTIVE

Chronic obstructive pulmonary disease (COPD) is the third leading cause of illness and death worldwide. Current treatments aim to control symptoms with none able to reverse disease or stop its progression. We explored the major molecular changes in COPD pathogenesis.

METHODS

We employed quantitative label-based proteomics to map the changes in the lung tissue proteome of cigarette smoke-induced experimental COPD that is induced over 8 weeks and progresses over 12 weeks.

RESULTS

Quantification of 7324 proteins enabled the tracking of changes to the proteome. Alterations in protein expression profiles occurred in the induction phase, with 18 and 16 protein changes at 4- and 6-week time points, compared to age-matched controls, respectively. Strikingly, 269 proteins had altered expression after 8 weeks when the hallmark pathological features of human COPD emerge, but this dropped to 27 changes at 12 weeks with disease progression. Differentially expressed proteins were validated using other mouse and human COPD bronchial biopsy samples. Major changes in RNA biosynthesis (heterogeneous nuclear ribonucleoproteins C1/C2 [HNRNPC] and RNA-binding protein Musashi homologue 2 [MSI2]) and modulators of inflammatory responses (S100A1) were notable. Mitochondrial dysfunction and changes in oxidative stress proteins also occurred.

CONCLUSION

We provide a detailed proteomic profile, identifying proteins associated with the pathogenesis and disease progression of COPD establishing a platform to develop effective new treatment strategies.

Spirometry: A practical lifespan predictor of global health and chronic respiratory and non-respiratory diseases

OBJECTIVES

1. To review and discuss available evidence supporting that spirometry is an overlooked global health marker, that could be used regularly through the lifespan to monitor human health and predict risk of chronic respiratory and other chronic non-communicable diseases (NCDs). 2. To discuss the challenges and opportunities that this proposal faces.Summary of key data. First, spirometry is essential to assess and monitor respiratory health. Second, spirometry adds prognostic value to other well-accepted health markers used in clinical practice, such as blood pressure, body mass index, glucose and blood lipids, by identifying individuals at risk, not only of respiratory diseases, but also of other NCDs, particularly cardiovascular and metabolic disorders.

CONCLUSION

Although we acknowledge that research gaps still exist, we propose that spirometry assessed during childhood, adolescence and early and late adulthood can be a reproducible, non-invasive, safe and affordable global health marker to identify individuals in the general population at risk of respiratory and non-respiratory NCDs. In this context, spirometry may act as the caged canaries that miners used to carry into mines to alert them of dangerous accumulations of gases, thus providing an early warning and save lives.

Regulation of Cellular Senescence Is Independent from Profibrotic Fibroblast-Deposited ECM

Idiopathic pulmonary fibrosis (IPF) is a devastating lung disease with poor survival. Age is a major risk factor, and both alveolar epithelial cells and lung fibroblasts in this disease exhibit features of cellular senescence, a hallmark of ageing. Accumulation of fibrotic extracellular matrix (ECM) is a core feature of IPF and is likely to affect cell function. We hypothesize that aberrant ECM deposition augments fibroblast senescence, creating a perpetuating cycle favouring disease progression. In this study, primary lung fibroblasts were cultured on control and IPF-derived ECM from fibroblasts pretreated with or without profibrotic and prosenescent stimuli, and markers of senescence, fibrosis-associated gene expression and secretion of cytokines were measured. Untreated ECM derived from control or IPF fibroblasts had no effect on the main marker of senescence p16^Ink4a and p21^Waf1/Cip1. However, the expression of alpha smooth muscle actin (ACTA2) and proteoglycan decorin (DCN) increased in response to IPF-derived ECM. Production of the proinflammatory cytokines C-X-C Motif Chemokine Ligand 8 (CXCL8) by lung fibroblasts was upregulated in response to senescent and profibrotic-derived ECM. Finally, the profibrotic cytokines transforming growth factor β1 (TGF-β1) and connective tissue growth factor (CTGF) were upregulated in response to both senescent- and profibrotic-derived ECM. In summary, ECM deposited by IPF fibroblasts does not induce cellular senescence, while there is upregulation of proinflammatory and profibrotic cytokines and differentiation into a myofibroblast phenotype in response to senescent- and profibrotic-derived ECM, which may contribute to progression of fibrosis in IPF.

Frailty in patients with interstitial lung disease

PURPOSE OF REVIEW

The incidence of age-related diseases such as interstitial lung disease (ILD) is rising, and the importance of multimorbidity and accumulation of health deficits in patients with chronic lung diseases is increasingly recognized. There are multiple relationships between aging and ILD on a demographic and a biological level. Frailty conceptualizes the decline of a patient's physiological reserves and complements the chronological and biological aspects of aging.

RECENT FINDINGS

Frailty affects more than 50% of patients with ILD, with respiratory impairment, accelerated biological aging, comorbidities, medication adverse effects, and social factors collectively playing important roles. Frailty is an independent risk factor for adverse health outcomes such as hospitalizations and early mortality, including before and after lung transplant. Given the multicomponent determinants of frailty, programs such as pulmonary rehabilitation are promising strategies for managing this complex issue.

SUMMARY

Frailty is a common risk factor for adverse outcomes in patients with ILD. The multiple pathways leading to frailty are not completely understood, and further studies are needed to determine the optimal tools for assessment and to develop strategies to prevent and counteract frailty in the aging ILD population.

Myofibroblast fate plasticity in tissue repair and fibrosis: Deactivation, apoptosis, senescence and reprogramming

In response to tissue injury, fibroblasts differentiate into professional repair cells called myofibroblasts, which orchestrate many aspects of the normal tissue repair programme including synthesis, deposition and contraction of extracellular matrix proteins, leading to wound closure. Successful tissue repair responses involve termination of myofibroblast activities in order to prevent pathologic fibrotic scarring. Here, we discuss the cellular and molecular mechanisms limiting myofibroblast activities during physiological tissue repair, including myofibroblast deactivation, apoptosis, reprogramming and immune clearance of senescent myofibroblasts. In addition, we summarize pathological mechanisms leading to myofibroblast persistence and survival, a hallmark of fibrotic diseases. Finally, we discuss emerging anti-fibrotic therapies aimed at targeting myofibroblast fate such as senolytics, gene therapy, cellular immunotherapy and CAR-T cells.

MUC16 Is Overexpressed in Idiopathic Pulmonary Fibrosis and Induces Fibrotic Responses Mediated by Transforming Growth Factor-β1 Canonical Pathway

Several transmembrane mucins have demonstrated that they contribute intracellularly to induce fibrotic processes. The extracellular domain of MUC16 is considered as a biomarker for disease progression and death in IPF patients. However, there is no evidence regarding the signalling capabilities of MUC16 that contribute to IPF development. Here, we demonstrate that MUC16 was overexpressed in the lung tissue of IPF patients (n = 20) compared with healthy subjects (n = 17) and localised in fibroblasts and hyperplastic alveolar type II cells. Repression of MUC16 expression by siRNA-MUC16 transfection inhibited the TGF-β1-induced fibrotic processes such as mesenchymal/ myofibroblast transformations of alveolar type II A549 cells and lung fibroblasts, as well as fibroblast proliferation. SiRNA-MUC16 transfection also decreased the TGF-β1-induced SMAD3 phosphorylation, thus inhibiting the Smad Binding Element activation. Immunoprecipitation assays and confocal immunofluorescence showed the formation of a protein complex between MUC16/p-SMAD3 in the cell membrane after TGF-β1 stimulation. This study shows that MUC16 is overexpressed in IPF and collaborates with the TGF-β1 canonical pathway to induce fibrotic processes. Therefore, direct or indirect targeting of MUC16 could be a potential drug target for human IPF.

Epigenetics and pulmonary diseases in the horizon of precision medicine: a review

Epigenetic mechanisms represent potential molecular routes which could bridge the gap between genetic background and environmental risk factors contributing to the pathogenesis of pulmonary diseases. In patients with COPD, asthma and pulmonary arterial hypertension (PAH), there is emerging evidence of aberrant epigenetic marks, mainly including DNA methylation and histone modifications which directly mediate reversible modifications to the DNA without affecting the genomic sequence. Post-translational events and microRNAs can be also regulated epigenetically and potentially participate in disease pathogenesis. Thus, novel pathogenic mechanisms and putative biomarkers may be detectable in peripheral blood, sputum, nasal and buccal swabs or lung tissue. Besides, DNA methylation plays an important role during the early phases of fetal development and may be impacted by environmental exposures, ultimately influencing an individual's susceptibility to COPD, asthma and PAH later in life. With the advances in omics platforms and the application of computational biology tools, modelling the epigenetic variability in a network framework, rather than as single molecular defects, provides insights into the possible molecular pathways underlying the pathogenesis of COPD, asthma and PAH. Epigenetic modifications may have clinical applications as noninvasive biomarkers of pulmonary diseases. Moreover, combining molecular assays with network analysis of epigenomic data may aid in clarifying the multistage transition from a "pre-disease" to "disease" state, with the goal of improving primary prevention of lung diseases and its subsequent clinical management.We describe epigenetic mechanisms known to be associated with pulmonary diseases and discuss how network analysis could improve our understanding of lung diseases.

Regenerative Medicine and the Hope for a Cure

Current therapeutic strategies have succeeded in slowing down the progression of idiopathic pulmonary fibrosis (IPF). Emerging evidence highlights IPF as a disease of aging and impaired regeneration. Novel antiaging and regenerative medicine approaches hold promise to be able to reverse disease and might present hope for a cure. Research focusing on a deeper understanding of lung stem cell populations and how these are regulated and altered in fibrotic disease continues to drive the field, and accompanied by earlier diagnosis, the adaptation of clinically relevant models and readouts for regeneration of diseased lung, ultimately paves the way for translation into clinics.

Early Changes and Indicators Characterizing Lung Aging in Neonatal Chronic Lung Disease

Infants suffering from neonatal chronic lung disease, i.e., bronchopulmonary dysplasia, are facing long-term consequences determined by individual genetic background, presence of infections, and postnatal treatment strategies such as mechanical ventilation and oxygen toxicity. The adverse effects provoked by these measures include inflammatory processes, oxidative stress, altered growth factor signaling, and remodeling of the extracellular matrix. Both, acute and long-term consequences are determined by the capacity of the immature lung to respond to the challenges outlined above. The subsequent impairment of lung growth translates into an altered trajectory of lung function later in life. Here, knowledge about second and third hit events provoked through environmental insults are of specific importance when advocating lifestyle recommendations to this patient population. A profound exchange between the different health care professionals involved is urgently needed and needs to consider disease origin while future monitoring and treatment strategies are developed.

Collagen Biosynthesis, Processing, and Maturation in Lung Ageing

In addition to providing a macromolecular scaffold, the extracellular matrix (ECM) is a critical regulator of cell function by virtue of specific physical, biochemical, and mechanical properties. Collagen is the main ECM component and hence plays an essential role in the pathogenesis and progression of chronic lung disease. It is well-established that many chronic lung diseases, e.g., chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF) primarily manifest in the elderly, suggesting increased susceptibility of the aged lung or accumulated alterations in lung structure over time that favour disease. Here, we review the main steps of collagen biosynthesis, processing, and turnover and summarise what is currently known about alterations upon lung ageing, including changes in collagen composition, modification, and crosslinking. Recent proteomic data on mouse lung ageing indicates that, while the ER-resident machinery of collagen biosynthesis, modification and triple helix formation appears largely unchanged, there are specific changes in levels of type IV and type VI as well as the two fibril-associated collagens with interrupted triple helices (FACIT), namely type XIV and type XVI collagens. In addition, levels of the extracellular collagen crosslinking enzyme lysyl oxidase are decreased, indicating less enzymatically mediated collagen crosslinking upon ageing. The latter contrasts with the ageing-associated increase in collagen crosslinking by advanced glycation endproducts (AGEs), a result of spontaneous reactions of protein amino groups with reactive carbonyls, e.g., from monosaccharides or reactive dicarbonyls like methylglyoxal. Given the slow turnover of extracellular collagen such modifications accumulate even more in ageing tissues. In summary, the collective evidence points mainly toward age-induced alterations in collagen composition and drastic changes in the molecular nature of collagen crosslinks. Future work addressing the consequences of these changes may provide important clues for prevention of lung disease and for lung bioengineering and ultimately pave the way to novel targeted approaches in lung regenerative medicine.

Long-term tobacco exposure and immunosenescence: Paradoxical effects on T-cells telomere length and telomerase activity

Immunosenescence are alterations on immune system that occurs throughout an individual life. The main characteristic of this process is replicative senescence, evaluated by telomere shortening. Several factors implicate on telomere shortening, such as smoking. In this study, we evaluated the influence of smoking and Chronic Obstructive Pulmonary Disease (COPD) on cytokines, telomere length and telomerase activity. Blood samples were collected from subjects aged over 60 years old: Healthy (never smokers), Smokers (smoking for over 30 years) and COPDs (ex-smokers for ≥15 years). A young group was included as control. PBMCs were cultured for assessment of telomerase activity using RT-PCR, and cytokines secretion flow cytometry. CD4+ and CD8+ purified lymphocytes were used to assess telomere length using FlowFISH. We observed that COPD patients have accelerated telomere shortening. Paradoxically, smokers without lung damage showed preserved telomere length, suggesting that tobacco smoking may affect regulatory mechanisms, such as telomerase. Telomerase activity showed diminished activity in COPDs, while Smokers showed increased activity compared to COPDs and Healthy groups. Extracellular environment reflected this unbalance, indicated by an anti-inflammatory profile in Smokers, while COPDs showed an inflammatory prone profile. Further studies focusing on telomeric maintenance may unveil mechanisms that are associated with cancer under long-term smoking.

Implications for Extracellular Matrix Interactions With Human Lung Basal Stem Cells in Lung Development, Disease, and Airway Modeling

The extracellular matrix (ECM) is not simply a quiescent scaffold. This three-dimensional network of extracellular macromolecules provides structural, mechanical, and biochemical support for the cells of the lung. Throughout life, the ECM forms a critical component of the pulmonary stem cell niche. Basal cells (BCs), the primary stem cells of the airways capable of differentiating to all luminal cell types, reside in close proximity to the basolateral ECM. Studying BC-ECM interactions is important for the development of therapies for chronic lung diseases in which ECM alterations are accompanied by an apparent loss of the lung's regenerative capacity. The complexity and importance of the native ECM in the regulation of BCs is highlighted as we have yet to create an in vitro culture model that is capable of supporting the long-term expansion of multipotent BCs. The interactions between the pulmonary ECM and BCs are, therefore, a vital component for understanding the mechanisms regulating BC stemness during health and disease. If we are able to replicate these interactions in airway models, we could significantly improve our ability to maintain basal cell stemness ex vivo for use in in vitro models and with prospects for cellular therapies. Furthermore, successful, and sustained airway regeneration in an aged or diseased lung by small molecules, novel compounds or via cellular therapy will rely upon both manipulation of the airway stem cells and their immediate niche within the lung. This review will focus on the current understanding of how the pulmonary ECM regulates the basal stem cell function, how this relationship changes in chronic disease, and how replicating native conditions poses challenges for ex vivo cell culture.

Downregulation of DUOX1 function contributes to aging-related impairment of innate airway injury responses and accelerated senile emphysema

Aging is associated with a gradual loss of lung function due to increased cellular senescence, decreased regenerative capacity, and impaired innate host defense. One important aspect of innate airway epithelial host defense to nonmicrobial triggers is the secretion of alarmins such as IL-33 and activation of type 2 inflammation, which were previously found to depend on activation of the NADPH oxidase (NOX) homolog DUOX1, and redox-dependent signaling pathways that promote alarmin secretion. Here, we demonstrate that normal aging of C57BL/6J mice resulted in markedly decreased lung innate epithelial type 2 responses to exogenous triggers such as the airborne allergen Dermatophagoides pteronyssinus, which was associated with marked downregulation of DUOX1, as well as DUOX1-mediated redox-dependent signaling. DUOX1 deficiency was also found to accelerate age-related airspace enlargement and decline in lung function but did not consistently affect other features of lung aging such as senescence-associated inflammation. Intriguingly, observations of age-related DUOX1 downregulation and enhanced airspace enlargement due to DUOX1 deficiency in C57BL/6J mice, which lack a functional mitochondrial nicotinamide nucleotide transhydrogenase (NNT), were much less dramatic in C57BL/6NJ mice with normal NNT function, although the latter mice also displayed impaired innate epithelial injury responses with advancing age. Overall, our findings indicate a marked aging-dependent decline in (DUOX1-dependent) innate airway injury responses to external nonmicrobial triggers, but the impact of aging on DUOX1 downregulation and its significance for age-related senile emphysema development was variable between different C57BL6 substrains, possibly related to metabolic alterations due to differences in NNT function.

Glutathione S-transferases and their implications in the lung diseases asthma and chronic obstructive pulmonary disease: Early life susceptibility?

Our lungs are exposed daily to airborne pollutants, particulate matter, pathogens as well as lung allergens and irritants. Exposure to these substances can lead to inflammatory responses and may induce endogenous oxidant production, which can cause chronic inflammation, tissue damage and remodeling. Notably, the development of asthma and Chronic Obstructive Pulmonary Disease (COPD) is linked to the aforementioned irritants. Some inhaled foreign chemical compounds are rapidly absorbed and processed by phase I and II enzyme systems critical in the detoxification of xenobiotics including the glutathione-conjugating enzymes Glutathione S-transferases (GSTs). GSTs, and in particular genetic variants of GSTs that alter their activities, have been found to be implicated in the susceptibility to and progression of these lung diseases. Beyond their roles in phase II metabolism, evidence suggests that GSTs are also important mediators of normal lung growth. Therefore, the contribution of GSTs to the development of lung diseases in adults may already start in utero, and continues through infancy, childhood, and adult life. GSTs are also known to scavenge oxidants and affect signaling pathways by protein-protein interaction. Moreover, GSTs regulate reversible oxidative post-translational modifications of proteins, known as protein S-glutathionylation. Therefore, GSTs display an array of functions that impact the pathogenesis of asthma and COPD.

In this review we will provide an overview of the specific functions of each class of mammalian cytosolic GSTs. This is followed by a comprehensive analysis of their expression profiles in the lung in healthy subjects, as well as alterations that have been described in (epithelial cells of) asthmatics and COPD patients. Particular emphasis is placed on the emerging evidence of the regulatory properties of GSTs beyond detoxification and their contribution to (un)healthy lungs throughout life. By providing a more thorough understanding, tailored therapeutic strategies can be designed to affect specific functions of particular GSTs.

The Stress of Lung Aging: Endoplasmic Reticulum and Senescence Tête-à-Tête

Beyond the structural changes, features including the dysregulation of endoplasmic reticulum (ER) stress response and increased senescence characterize the lung aging. ER stress response and senescence have been reported to be induced by factors like cigarette smoke. Therefore, deciphering the mechanisms underlying ER and senescent pathways interaction has become a challenge. In this review we highlight the known and unknown regarding ER stress response and senescence and their cross talk in aged lung.

Relationship between handgrip strength and lung function in adults: a systematic review

Handgrip strength (HGS) is a functional test that has been directly associated with lung function in some healthy populations; however, inconsistent findings have been reported for populations with chronic diseases. The aim of this study was to identify the relationship between HGS and lung function in both healthy and unhealthy adults. A systematic search was conducted using six databases from their earliest inception to February 29, 2020. Two authors reviewed and assessed methodological quality of eligible studies using the Crowe Critical Appraisal Tool (CCAT). Twenty-five studies met the inclusion criteria with 8 and 17 studies examining healthy and unhealthy populations, respectively. Reported average methodological quality of all included studies using the CCAT was 38-85% with most rated as Good to Excellent. Despite the use of heterogeneous equipment and protocols during HGS and lung function assessments, significant positive and moderate correlations and/or regression coefficients were reported for healthy populations consistently. Conversely, the reported relationships between HGS and lung function for unhealthy counterparts were variable. Handgrip strength was significantly associated with lung function in most healthy adults. Future robust studies are needed to confirm the suitability of HGS to assess lung function for healthy and unhealthy adults.

Cystic Fibrosis Lung Disease in the Aging Population

The demographics of the population with cystic fibrosis (CF) is continuously changing, with nowadays adults outnumbering children and a median predicted survival of over 40 years. This leads to the challenge of treating an aging CF population, while previous research has largely focused on pediatric and adolescent patients. Chronic inflammation is not only a hallmark of CF lung disease, but also of the aging process. However, very little is known about the effects of an accelerated aging pathology in CF lungs. Several chronic lung disease pathologies show signs of chronic inflammation with accelerated aging, also termed “inflammaging”; the most notable being chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF). In these disease entities, accelerated aging has been implicated in the pathogenesis via interference with tissue repair mechanisms, alterations of the immune system leading to impaired defense against pulmonary infections and induction of a chronic pro-inflammatory state. In addition, CF lungs have been shown to exhibit increased expression of senescence markers. Sustained airway inflammation also leads to the degradation and increased turnover of cystic fibrosis transmembrane regulator (CFTR). This further reduces CFTR function and may prevent the novel CFTR modulator therapies from developing their full efficacy. Therefore, novel therapies targeting aging processes in CF lungs could be promising. This review summarizes the current research on CF in an aging population focusing on accelerated aging in the context of chronic airway inflammation and therapy implications.

Telomerase treatment prevents lung profibrotic pathologies associated with physiological aging

Short/dysfunctional telomeres are at the origin of idiopathic pulmonary fibrosis (IPF) in patients mutant for telomere maintenance genes. However, it remains unknown whether physiological aging leads to short telomeres in the lung, thus leading to IPF with aging. Here, we find that physiological aging in wild-type mice leads to telomere shortening and a reduced proliferative potential of alveolar type II cells and club cells, increased cellular senescence and DNA damage, increased fibroblast activation and collagen deposits, and impaired lung biophysics, suggestive of a fibrosis-like pathology. Treatment of both wild-type and telomerase-deficient mice with telomerase gene therapy prevented the onset of lung profibrotic pathologies. These findings suggest that short telomeres associated with physiological aging are at the origin of IPF and that a potential treatment for IPF based on telomerase activation would be of interest not only for patients with telomerase mutations but also for sporadic cases of IPF associated with physiological aging.

Reactive oxygen species modulators in pulmonary medicine

Adapted to effectively capture oxygen from inhaled air and deliver it to all other parts of the body, the lungs constitute the organ with the largest surface area. This makes the lungs more susceptible to airborne pathogens and pollutants that mediate pathologies through generation of reactive oxygen species (ROS). One pathological consequence of excessive levels of ROS production is pulmonary diseases that account for a large number of mortality and morbidity in the world. Of the various mechanisms involved in pulmonary disease pathogenesis, mitochondrial dysfunction takes prominent importance. Herein, we briefly describe the significance of oxidative stress caused by ROS in pulmonary diseases and some possible therapeutic strategies.

Liproxstatin-1 alleviates bleomycin-induced alveolar epithelial cells injury and mice pulmonary fibrosis via attenuating inflammation, reshaping redox equilibrium, and suppressing ROS/p53/α-SMA pathway

With undetermined etiology and limited treatment option, idiopathic pulmonary fibrosis (IPF) an age related disease is extremely lethal. Persistent injury of epithelial cells, abnormal activation of fibroblasts/myofibroblasts, and superabundant deposition of extracellular matrix protein pathologically characterize IPF. Redox imbalance is reported to play a vital role in both IPF development and senescence. This study aim to investigate whether and how Liproxstatin-1 (Lip-1), a strong lipid autoxidation inhibitor, regulates bleomycin (BLM) induced pulmonary fibrosis both in vivo and in vitro. It's demonstrated that Lip-1 exerted a potent anti-fibrotic function in BLM-induced mice pulmonary fibrosis via alleviating inflammatory, reshaping redox equilibrium, and ameliorating collagen deposition. Lip-1 reduced the level of reactive oxygen species (ROS) and methane dicarboxylic aldehyde (MDA), promoted the expression of glutathione (GSH), catalase (CAT), and total superoxide dismutase (T-SOD) after BLM treatment. Moreover, in vitro experiments verified that Lip-1 protected A549 cells from BLM-induced injury and fibrosis. Lip-1 seemed to attenuate BLM-induced fibrosis by targeting ROS/p53/α-SMA signaling both in vivo and in vitro. In summary, this study demonstrates that Lip-1 administration performs a protective role in against pulmonary fibrosis and lights up the potential of Lip-1 treatment for patient with IPF in future.

Citrus Alkaline Extracts Inhibit Senescence of A549 Cells to Alleviate Pulmonary Fibrosis via the β-Catenin/P53 Pathway

BACKGROUND Idiopathic pulmonary fibrosis (IPF) is a disease related to aging, which has become increasingly prevalent as the population has aged. However, there remains no effective treatment for the disease. Alveolar epithelial type II cell (AEC II) senescence plays an important role in the occurrence and development of IPF. Therefore, enhancing our understanding of aging AEC IIs might facilitate the development of a new therapeutic strategy for the prevention and treatment of IPF. The aim of this study was to investigate the effect of citrus alkaline extracts (CAE) on senescence in A549 cells and elucidate the mechanism by which CAE function. MATERIAL AND METHODS Adriamycin RD (ARD) induces the senescence of A549 cells. Relevant indicators were identified following administration of 3 concentrations of CAE (50 μg/mL, 100 μg/mL, and 200 μg/mL) to A549 cells. RESULTS CAE inhibited senescence in ARD-induced A549 cells. It inhibited p16, p21, p53, and a senescence-associated secretory phenotype, and reduced expression of the senescence-related positive cells of ß-galactosidase. Further study revealed that activation of the ß-catenin signaling pathway is closely associated with p53. CAE inhibited senescence in A549 cells via the ß-catenin/p53 pathway. Further, inhibition of b-catenin was associated with reduced expression levels of p53 and p21, and the anti-aging effects of CAE were enhanced. When expression of p53 was inhibited, expression levels of ß-catenin also tended to decrease. CONCLUSIONS In summary, our study showed that CAE can inhibit aging in A549 cells to alleviate pulmonary fibrosis, and thus limit the secretion of the extracellular matrix and collagen in lung fibroblasts.

Dysbiosis, malnutrition and enhanced gut-lung axis contribute to age-related respiratory diseases

Older people are at an increased risk of developing respiratory diseases such as chronic obstructive pulmonary diseases, asthma, idiopathic pulmonary fibrosis or lung infections. Susceptibility to these diseases is partly due to the intrinsic ageing process, characterized by genomic, cellular and metabolic hallmarks and immunosenescence, and is associated with changes in the intestinal microbiota. Importantly, in the lungs, ageing is also associated with a dysbiosis and loss of resilience of the resident microbiota and alterations of the gut-lung axis. Notably, as malnutrition is often observed in the elderly, nutrition is one of the most accessible modifiable factors affecting both senescence and microbiota. This article reviews the changes affecting the lung and its resident microbiota during ageing, as well as the interconnections between malnutrition, senescence, microbiota, gut-lung axis and respiratory health. As the communication along the gut-lung axis becomes more permissive with ageing, this review also explores the evidence that the gut and lung microbiota are key players in the maintenance of healthy lungs, and as such, are potential targets for nutrition-based preventive strategies against lung disease in elderly populations.

The effects of BMMSC treatment on lung tissue degeneration in elderly macaques

BACKGROUND

Age-associated lung tissue degeneration is a risk factor for lung injury and exacerbated lung disease. It is also the main risk factor for chronic lung diseases (such as COPD, idiopathic pulmonary fibrosis, cancer, among others). So, it is particularly important to find new anti-aging treatments.

METHODS

We systematically screened and evaluated elderly senile multiple organ dysfunction macaque models to determine whether BMMSCs inhibited lung tissue degeneration.

RESULTS

The average alveolar area, mean linear intercept (MLI), and fibrosis area in the elderly macaque models were significantly larger than in young rhesus monkeys (p < 0.05), while the capillary density around the alveoli was significantly low than in young macaque models (p < 0.05). Intravenous infusion of BMMSCs reduced the degree of pulmonary fibrosis, increased the density of capillaries around the alveoli (p < 0.05), and the number of type II alveolar epithelium in elderly macaques (p < 0.05). In addition, the infusion reduced lung tissue ROS levels, systemic and lung tissue inflammatory levels, and Treg cell ratio in elderly macaque models (p < 0.05). Indirect co-cultivation revealed that BMMSCs suppressed the expression of senescence-associated genes, ROS levels, apoptosis rate of aging type II alveolar epithelial cells (A549 cells), and enhanced their proliferation (p < 0.05).

CONCLUSIONS

BMMSC treatment inhibited age-associated lung tissue degeneration.

Healing after COVID-19: are survivors at risk for pulmonary fibrosis?

The novel SARS-CoV-2 coronavirus, which is responsible for COVID-19 disease, was first reported in Wuhan, China, in December of 2019. The virus rapidly spread, and the World Health Organization declared a pandemic by March 2020. With millions of confirmed cases worldwide, there is growing concern and considerable debate regarding the potential for coronavirus infection to contribute to an appreciable burden of chronic respiratory symptoms or fibrotic disease among recovered individuals. Because the first case of COVID-19 was documented less than one year ago, data regarding long-term clinical outcomes are not yet available, and predictions for long-term outcome are speculative at best. However, due to the staggering number of cases and the severity of disease in many individuals, there is a critical need to consider the potential long-term implications of COVID-19. This review examines current basic and clinical data regarding fibrogenic mechanisms of viral injury in the context of SARS-CoV-2. Several intersecting mechanisms between coronavirus infection and fibrotic pathways are discussed to highlight factors and processes that may be targetable to improve patient outcome. Reports of post-infection sequelae from previous coronavirus outbreaks are presented toward the goal of improved recognition of potential contributing risk factors for fibrotic disease.

[Aging of the lungs and immune system as hellmark in the pathogenesis of idiopathic pulmonary fibrosis and COVID-19]

Idiopathic pulmonary fibrosis (IPF) does not occur in younger persons. Therefore, it is not surprising that the nine hallmarks of biological aging can all be found in the pathomechanism of IPF. In this respect the homeostasis of cellular protein synthesis, degradation and recycling becomes unbalanced, which causes a dysregulation of repair mechanisms in the case of lung damage. Severve acute respiratory syndrome coronarvius type 2 (SARS-CoV-2) infections may also predominantyl seen in aged persons. In this situation cellular aging of the lungs also plays a role but additionally, the aging of the immune system is also of great importance. Immunosenescence is associated with a loss of naïve T‑cells. Moreover, there are gender-specific differences with a loss of B‑cells only in men but not in women, which partly explains the more severe course of COVID-19 pneumonia in older men.

An antioxidant suppressed lung cellular senescence and enhanced pulmonary function in aged mice

Oxidative stress is one of the major causes of cellular senescence in mammalian cells. The excess amount of reactive oxygen species generated by oxygen metabolism is pathogenic and facilitates tissue aging. Lung tissue is more susceptible to oxidative stress than other organs because it is directly exposed to environmental stresses. The aging of lung tissues increases the risk of chronic diseases. Senescent cells accumulate in tissues during aging and contribute to aging-associated morbidity; however, the roles of cellular senescence in lung aging and diseases have not yet been elucidated in detail. To clarify the physiological role of oxidative stress-induced cellular senescence in aging-associated declines in pulmonary function, we herein investigated the effects of the antioxidant N-acetyl-L-cysteine (NAC) on lung cellular senescence and aging in mice. The administration of NAC to 1-year-old mice reduced the expression of senescence-associated genes in lung tissue. Pulmonary function and lung morphology were partly restored in mice administered NAC. Collectively, these results suggest that oxidative stress is a major inducer of cellular senescence in vivo and that the control of oxidative stress may prevent lung aging and diseases.

The aging transcriptome and cellular landscape of the human lung in relation to SARS-CoV-2

Age is a major risk factor for severe coronavirus disease-2019 (COVID-19). Here, we interrogate the transcriptional features and cellular landscape of the aging human lung. By intersecting these age-associated changes with experimental data on SARS-CoV-2, we identify several factors that may contribute to the heightened severity of COVID-19 in older populations. The aging lung is transcriptionally characterized by increased cell adhesion and stress responses, with reduced mitochondria and cellular replication. Deconvolution analysis reveals that the proportions of alveolar type 2 cells, proliferating basal cells, goblet cells, and proliferating natural killer/T cells decrease with age, whereas alveolar fibroblasts, pericytes, airway smooth muscle cells, endothelial cells and IGSF21+ dendritic cells increase with age. Several age-associated genes directly interact with the SARS-CoV-2 proteome. Age-associated genes are also dysregulated by SARS-CoV-2 infection in vitro and in patients with severe COVID-19. These analyses illuminate avenues for further studies on the relationship between age and COVID-19.

WNT Signalling in Lung Physiology and Pathology

The main physiological function of the lung is gas exchange, mediated at the interface between the alveoli and the pulmonary microcapillary network and facilitated by conducting airway structures that regulate the transport of these gases from and to the alveoli. Exposure to microbial and environmental factors such as allergens, viruses, air pollution, and smoke contributes to the development of chronic lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and lung cancer. Respiratory diseases as a cluster are the commonest cause of chronic disease and of hospitalization in children and are among the three most common causes of morbidity and mortality in the adult population worldwide. Many of these chronic respiratory diseases are associated with inflammation and structural remodelling of the airways and/or alveolar tissues. They can often only be treated symptomatically with no disease-modifying therapies that normalize the pathological tissue destruction driven by inflammation and remodelling. In search for novel therapeutic strategies for these diseases, several lines of evidence revealed the WNT pathway as an emerging target for regenerative strategies in the lung. WNT proteins, their receptors, and signalling effectors have central regulatory roles under (patho)physiological conditions underpinning lung function and (chronic) lung diseases and we summarize these roles and discuss how pharmacological targeting of the WNT pathway may be utilized for the treatment of chronic lung diseases.

Non-coding RNAs as Regulators of Cellular Senescence in Idiopathic Pulmonary Fibrosis and Chronic Obstructive Pulmonary Disease

Cellular senescence is a cell fate implicated in the pathogenesis of idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD). Cellular senescence occurs in response to cellular stressors such as oxidative stress, DNA damage, telomere shortening, and mitochondrial dysfunction. Whether these stresses induce cellular senescence or an alternative cell fate depends on the type and magnitude of cellular stress, but also on intrinsic factors regulating the cellular stress response. Non-coding RNAs, including both microRNAs and long non-coding RNAs, are key regulators of cellular stress responses and susceptibility to cellular senescence. In this review, we will discuss cellular mechanisms that contribute to senescence in IPF and COPD and highlight recent advances in our understanding of how these processes are influenced by non-coding RNAs. We will also discuss the potential therapeutic role for targeting non-coding RNAs to treat these chronic lung diseases.

Fisetin Alleviated Bleomycin-Induced Pulmonary Fibrosis Partly by Rescuing Alveolar Epithelial Cells From Senescence

Idiopathic pulmonary fibrosis is an aging-associated disease, satisfactory therapies are not yet available. Accelerated senescence of alveolar epithelial cells plays an important part in Idiopathic pulmonary fibrosis pathogenesis. Fisetin (FIS) is a natural non-toxic flavonoid, which has many pharmacological functions. However, the role of FIS in pulmonary fibrosis has not been established. In this study, we found that FIS treatment apparently alleviated BLM-induced weight loss, inflammatory cells infiltration, inflammatory factors expression, collagen deposition and alveolar epithelial cell senescence, along with AMPK activation and the down regulation of NF-κB and TGF-β/Smad3 in vivo. In vitro, FIS administration significantly inhibited the senescence of alveolar epithelial cells and senescence-associated secretory phenotype, followed by reduced transdifferentiation of fibroblasts to myofibroblasts as well as collagen deposition in fibroblasts, which was blocked by an AMPK inhibitor, Compound C. Together, these results suggest that FIS can alleviate the development of BLM-induced pulmonary fibrosis, which is related to the inhibition of TGF-β/Smad3 signaling and the reduction of alveolar epithelium cell senescence by regulating AMPK/NF-κB signaling pathway. FIS may be a promising candidate for patients with pulmonary fibrosis.

COPD-derived fibroblasts secrete higher levels of senescence-associated secretory phenotype proteins

COPD-derived fibroblasts have increased cellular senescence. Senescent cell accumulation can induce tissue dysfunction by their senescence-associated secretory phenotype (SASP). We aimed to determine the SASP of senescent fibroblasts and COPD-derived lung fibroblasts, including severe, early-onset (SEO)-COPD. SASP protein secretion was measured after paraquat-induced senescence in lung fibroblasts using Olink Proteomics and compared between (SEO-)COPD-derived and control-derived fibroblasts. We identified 124 SASP proteins of senescent lung fibroblasts, of which 42 were secreted at higher levels by COPD-derived fibroblasts and 35 by SEO-COPD-derived fibroblasts compared with controls. Interestingly, the (SEO-)COPD-associated SASP included proteins involved in chronic inflammation, which may contribute to (SEO-)COPD pathogenesis.

A glitch in the matrix: Age-dependent changes in the extracellular matrix facilitate common sites of metastasis

People over 55 years old represent the majority of cancer patients and suffer from increased metastatic burden compared to the younger patient population. As the aging population increases globally, it is prudent to understand how the intrinsic aging process contributes to cancer progression. As we age, we incur aberrant changes in the extracellular matrix (ECM) of our organs, which contribute to numerous pathologies, including cancer. Notably, the lung, liver, and bone represent the most common sites of distal metastasis for all cancer types. In this review, we describe how age-dependent changes in the ECM of these organs influence cancer progression. Further, we outline how these alterations prime the premetastatic niche and why these may help explain the disparity in outcome for older cancer patients.

Idiopathic Pulmonary Fibrosis in Elderly Patients: Analysis of the INSIGHTS-IPF Observational Study

Background: An association between idiopathic pulmonary fibrosis (IPF) and advancing age is suspected since IPF occurs primarily in patients over 60 years of age. Though, little is known about the disease in the elderly. The aim of this study was to characterize elderly IPF patients using data from the longitudinal, German-wide INSIGHTS-IPF registry. Methods: Patients were grouped into elderly (≥75 years) and nonelderly IPF (<75 years) at the time of enrollment into the study. Baseline clinical characteristics, comorbidities, health related quality of life (HRQoL), medical therapy and survival were compared between age groups. Effects of antifibrotic therapy on forced vital capacity (FVC) were analyzed over 24 months. Results: Of 1,009 patients, 350 (34.7%) were ≥75 years old. Elderly IPF patients compared to younger patients had a higher number of comorbidities (3.6 ± 2.5 vs. 2.8 ± 2.3; p < 0.001). The mean ± SD EQ-5D score (0.64 ± 0.21 vs. 0.69 ± 0.21; p = 0.005), and the overall WHO-5 score (13.1 ± 5.9 vs. 14.3 ± 6.0; p = 0.015) were significantly lower while the UCSD-SOBQ (52.6 ± 31.2 vs. 45.5 ± 31.2; p = 0.030) was significantly higher in elderly patients, indicating a more impaired HRQoL and more breathlessness. At baseline, 55.4% of elderly and 56.8% of nonelderly patients with IPF were treated with antifibrotic therapy (p = 0.687). For FVC decline after initiation of antifibrotic therapy, there was neither a significant difference between age groups at the different time points over 24 months (beta: 0.41; 95%-CI: -0.98 to 1.81; p = 0.563) nor over the whole course of time (beta: -0.05; 95%-CI: -0.20 to 0.09; p = 0.478). All-cause mortality was higher in elderly patients (49.1 vs. 37.9%; HR 1.65; 95%-CI 1.36-2.00; p < 0.001). Antifibrotic therapy was associated with improved survival in IPF patients, independent from age (<75 years: beta 0.76; 95%-CI: 0.59-0.99; p = 0.049; ≥75 years: beta 0.71; 95%-CI: 0.51-0.98; p = 0.043). Conclusion: In real life, a significant proportion of IPF patients are ≥75 years old, characterized by higher number of comorbidities and global reduced HRQoL. However, the effect of an antifibrotic therapy was similar between age groups and associated with a survival benefit emphasizing the importance for an early antifibrotic therapy in IPF, independent from age.

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.

Chronic Obstructive Pulmonary Disease Pathogenesis

Chronic obstructive pulmonary disease (COPD) has been traditionally considered a self-inflicted disease caused by tobacco smoking. Current available evidence, however, indicates that the pathogenesis of COPD needs to consider the dynamic and cumulative nature of a series of environment (including smoking plus other exposures)-host interactions that eventually determine lung development, maintenance, repair, and aging. By doing so, these factors modulate the trajectory of lung function of the individual through life and the odds of developing COPD through different routes, which likely represent different forms of the disease that require different preventive and therapeutic strategies.

Aging-related changes in the gene expression profile of human lungs

Aging is a multifactorial process that leads to molecular and cellular changes, contributing to the susceptibility of most lung diseases. However, the molecular and genetic mechanism of lung aging remains poorly understood. Here, we performed RNA-seq transcriptome analysis of the lung tissues of 68 subjects and analyzed their gene expression profile to evaluate candidate genes related to lung aging. The subjects were classified into two groups (Younger group and Older group) based on their age. Lung tissues were obtained from surgically resected specimens, processed, and analyzed with RNA-seq. The median age of the subjects was 45 years in the Younger group and 74 years in the Older group. Around 71% and 53% of the subjects were female in the Younger and Older groups, respectively. After gene quality control and filtering, differentially expressed gene analysis showed that MAP3K15, CHRM2, and GALNT13 were upregulated in the Younger group, whereas COL17A1 and EDA2R were upregulated in the Older group. Multivariate analysis with adjustment for covariates showed that EDA2R was a risk factor for lung aging. Our study identified differences in the gene expression of the lungs of older subjects compared with younger subjects. These findings may have implications in lung aging.

Lung regeneration: implications of the diseased niche and ageing

Most chronic and acute lung diseases have no cure, leaving lung transplantation as the only option. Recent work has improved our understanding of the endogenous regenerative capacity of the lung and has helped identification of different progenitor cell populations, as well as exploration into inducing endogenous regeneration through pharmaceutical or biological therapies. Additionally, alternative approaches that aim at replacing lung progenitor cells and their progeny through cell therapy, or whole lung tissue through bioengineering approaches, have gained increasing attention. Although impressive progress has been made, efforts at regenerating functional lung tissue are still ineffective. Chronic and acute lung diseases are most prevalent in the elderly and alterations in progenitor cells with ageing, along with an increased inflammatory milieu, present major roadblocks for regeneration. Multiple cellular mechanisms, such as cellular senescence and mitochondrial dysfunction, are aberrantly regulated in the aged and diseased lung, which impairs regeneration. Existing as well as new human in vitro models are being developed, improved and adapted in order to study potential mechanisms of lung regeneration in different contexts. This review summarises recent advances in understanding endogenous as well as exogenous regeneration and the development of in vitro models for studying regenerative mechanisms.

E-Liquid Containing a Mixture of Coconut, Vanilla, and Cookie Flavors Causes Cellular Senescence and Dysregulated Repair in Pulmonary Fibroblasts: Implications on Premature Aging

Electronic cigarette (e-cig) usage has risen dramatically worldwide over the past decade. While they are touted as a safe alternative to cigarettes, recent studies indicate that high levels of nicotine and flavoring chemicals present in e-cigs may still cause adverse health effects. We hypothesized that an e-liquid containing a mixture of tobacco, coconut, vanilla, and cookie flavors would induce senescence and disrupt wound healing processes in pulmonary fibroblasts. To test this hypothesis, we exposed pulmonary fibroblasts (HFL-1) to e-liquid at varying doses and assessed cytotoxicity, inflammation, senescence, and myofibroblast differentiation. We found that e-liquid exposure caused cytotoxicity, which was accompanied by an increase in IL-8 release in the conditioned media. E-liquid exposure resulted in elevated senescence-associated beta-galactosidase (SA-β-gal) activity. Transforming growth factor-β1 (TGF-β1) induced myofibroblast differentiation was inhibited by e-liquid exposure, resulting in decreased α-smooth muscle actin and fibronectin protein levels. Together, our data suggest that an e-liquid containing a mixture of flavors induces inflammation, senescence and dysregulated wound healing responses.

Small airway loss in the physiologically ageing lung: a cross-sectional study in unused donor lungs

BACKGROUND

Physiological lung ageing is associated with a gradual decline in dynamic lung volumes and a progressive increase in residual volume due to diminished elastic recoil of the lung, loss of alveolar tissue, and lower chest wall compliance. However, the effects of ageing on the small airways (ie, airways <2·0 mm in diameter) remain largely unknown. By using a combination of ex-vivo conventional CT (resolution 1 mm), whole lung micro-CT (resolution 150 μm), and micro-CT of extracted cores (resolution 10 μm), we aimed to provide a multiresolution assessment of the small airways in lung ageing in a large cohort of never smokers.

METHODS

For this cross-sectional study, we included donor lungs collected from 32 deceased never-smoking donors (age range 16-83 years). Ex-vivo CT and whole lung high-resolution CT (micro-CT) were used to determine total airway numbers, stratified by airway diameter. Micro-CT was used to assess the number, length, and diameter of terminal bronchioles (ie, the last generation of conducting airways); mean linear intercept; and surface density in four lung tissue cores from each lung, extracted using a uniform sampling approach. Regression β coefficients are calculated using linear regression and polynomial models.

FINDINGS

Ex-vivo CT analysis showed an age-dependent decrease in the number of airways of diameter 2·0 mm to less than 2·5 mm (β coefficient per decade -0·119, 95% CI -0·193 to -0·045; R²=0·29) and especially in airways smaller than 2·0 mm in diameter (-0·158, -0·233 to -0·084; R²=0·47), between 30 and 80 years of age, but not of the larger (≥2·5 mm) diameter airways (-0·00781, -0·04409 to 0·02848; R²=0·0007). In micro-CT analysis of small airways, the total number of terminal bronchioles per lung increased until the age of 30 years, after which an almost linear decline in the number of terminal bronchioles was observed (β coefficient per decade -2035, 95% CI -2818 to -1252; R²=0·55), accompanied by a non-significant increase in alveolar airspace size (6·44, -0·57 to 13·45, R²=0·10). Moreover, this decrease in terminal bronchioles was associated with the age-related decline of pulmonary function predicted by healthy reference values.

INTERPRETATION

Loss of terminal bronchioles is an important structural component of age-related decline in pulmonary function of healthy, non-smoking individuals.

FUNDING

Research Foundation-Flanders, KU Leuven, Parker B Francis Foundation, UGent, Canadian Institutes for Health.