Premature lung aging and cellular senescence in the pathogenesis of idiopathic pulmonary fibrosis and COPD/emphysema

Convergent evolution of senescent fibroblasts in fibrosis and cancer with aging

Aging is associated with stereotyped changes in the tissue microenvironment that increase susceptibility to diseases of the elderly, including organ fibrosis and cancer. From a tissue perspective, fibrosis and cancer can both be viewed as non-healing wounds with pathogenic activation of tissue repair pathways in the stroma. If fibrosis and cancer represent an example of the convergent evolution of maladaptive stromal responses in distinct pathologies, what are the analogous cell types that might emerge in both diseases that share similarities in identity and function? In this review, we explore how senescent fibroblasts form a nexus that connects the aging organ with both fibrosis and cancer. The advent of single cell sequencing, coupled with improved detection of cell types with senescent traits in vivo, have allowed us to identify senescent fibroblasts with similar identities in both fibrosis and cancer that share pro-fibrotic programs. In addition to their ability to reorganize the extracellular matrix in diseased states, these pro-fibrotic senescent fibroblasts can also promote epithelial reprogramming and immune rewiring, which drive disease progression in fibrosis and cancer. Finally, the identification of common pathogenic cell types in fibrosis and cancer also presents a therapeutic opportunity to target both diseases with a shared approach.

Can salivary and skin microbiome become a biodetector for aging-associated diseases? Current insights and future perspectives

Growth and aging are fundamental elements of human development. Aging is defined by a decrease in physiological activities and higher illness vulnerability. Affected by lifestyle, environmental, and hereditary elements, aging results in disorders including cardiovascular, musculoskeletal, and neurological diseases, which accounted for 16.1 million worldwide deaths in 2019. Stress-induced cellular senescence, caused by DNA damage, can reduce tissue regeneration and repair, promoting aging. The root cause of many age-related disorders is inflammation, encouraged by the senescence-associated secretory phenotype (SASP). Aging's metabolic changes and declining immune systems raise illness risk via promoting microbiome diversity. Stable, individual-specific skin and oral microbiomes are essential for both health and disease since dysbiosis is linked with periodontitis and eczema. Present from birth to death, the human microbiome, under the influence of diet and lifestyle, interacts symbiotically with the body. Poor dental health has been linked to Alzheimer's and Parkinson's diseases since oral microorganisms and systemic diseases have important interactions. Emphasizing the importance of microbiome health across the lifetime, this study reviews the understanding of the microbiome's role in aging-related diseases that can direct novel diagnosis and treatment approaches.

HHIP's Dynamic Role in Epithelial Wound Healing Reveals a Potential Mechanism of COPD Susceptibility

A genetic variant near HHIP has been consistently identified as associated with increased risk for Chronic Obstructive Pulmonary Disease (COPD), the third leading cause of death worldwide. However HHIP's role in COPD pathogenesis remains elusive. Canonically, HHIP is a negative regulator of the hedgehog pathway and downstream GLI1 and GLI2 activation. The hedgehog pathway plays an important role in wound healing, specifically in activating transcription factors that drive the epithelial mesenchymal transition (EMT), which in its intermediate state (partial EMT) is necessary for the collective movement of cells closing the wound. Herein, we propose a mechanism to explain HHIP's role in faulty epithelial wound healing, which could contribute to the development of emphysema, a key feature of COPD. Using two different Boolean models compiled from the literature, we show dysfunctional HHIP results in a lack of negative feedback on GLI, triggering a full EMT, where cells become mesenchymal and do not properly close the wound. We validate these Boolean models with experimental evidence gathered from published scientific literature. We also experimentally test if low HHIP expression is associated with EMT at the edge of wounds by using a scratch assay in a human lung epithelial cell line. Finally, we show evidence supporting our hypothesis in bulk and single cell RNA-Seq data from different COPD cohorts. Overall, our analyses suggest that aberrant wound healing due to dysfunctional HHIP, combined with chronic epithelial damage through cigarette smoke exposure, may be a primary cause of COPD-associated emphysema.

Aging in chronic lung disease: Will anti-aging therapy be the key to the cure?

Chronic lung disease is the third leading cause of death globally, imposing huge burden of death, disability and healthcare costs. However, traditional pharmacotherapy has relatively limited effects in improving the cure rate and reducing the mortality of chronic lung disease. Thus, new treatments are urgently needed for the prevention and treatment of chronic lung disease. It is particularly noteworthy that, multiple aging-related phenotypes were involved in the occurrence and development of chronic lung disease, such as blocked proliferation, telomere attrition, mitochondrial dysfunction, epigenetic alterations, altered nutrient perception, stem cell exhaustion, chronic inflammation, etc. Consequently, senescent cells induce a series of pathological changes in the lung, such as immune dysfunction, airway remodeling, oxidative stress and regenerative dysfunction, which is a critical issue that needs special attention in chronic lung diseases. Therefore, anti-aging interventions may bring new insights into the treatment of chronic lung diseases. In this review, we elaborate the involvement of aging in chronic lung disease and further discuss the application and prospects of anti-aging therapy.

Effect of physical activity in lymphocytes senescence burden in patients with COPD

Chronic obstructive pulmonary disease (COPD) is regarded as an accelerated-age disease in which chronic inflammation, maladaptive immune responses, and senescence cell burden coexist. Accordingly, cellular senescence has emerged as a potential mechanism involved in COPD pathophysiology. In this study, 25 stable patients with COPD underwent a daily physical activity promotion program for 6 mo. We reported that increase of physical activity was related to a reduction of the senescent cell burden in circulating lymphocytes of patients with COPD. Senescent T-lymphocyte population, characterized by absence of surface expression of CD28, was reduced after physical activity intervention, and the reduction was associated to the increase of physical activity level. In addition, the mRNA expression of cyclin-dependent kinase inhibitors, a hallmark of cell senescence, was reduced and, in accordance, the proliferative capacity of lymphocytes was improved postintervention. Moreover, we observed an increase in functionality in T cells from patients after intervention, including improved markers of activation, enhanced cytotoxicity, and altered cytokine secretions in response to viral challenge. Lastly, physical activity intervention reduced the potential of lymphocytes' secretome to induce senescence in human primary fibroblasts. In conclusion, our study provides, for the first time, evidence of the potential of physical activity intervention in patients with COPD to reduce the senescent burden in circulating immune cells.NEW & NOTEWORTHY For the first time, we identified in patients with COPD a relation between physical activity intervention with respiratory function improvement and cellular senescence burden in lymphocytes that improved the T cell functionality and proliferative capacity of patients. In addition, our experiments highlight the possible impact of T-cell senescence in other cell types which could be related to some of the clinical lung complications observed in COPD.

The cGAS-STING pathway in COPD: targeting its role and therapeutic potential

Chronic obstructive pulmonary disease(COPD) is a gradually worsening and fatal heterogeneous lung disease characterized by airflow limitation and increasingly decline in lung function. Currently, it is one of the leading causes of death worldwide. The consistent feature of COPD is airway inflammation. Several inflammatory factors are known to be involved in COPD pathogenesis; however, anti-inflammatory therapy is not the first-line treatment for COPD. Although bronchodilators, corticosteroids and roflumilast could improve airflow and control symptoms, they could not reverse the disease. The cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) signaling pathway plays an important novel role in the immune system and has been confirmed to be a key mediator of inflammation during infection, cellular stress, and tissue damage. Recent studies have emphasized that abnormal activation of cGAS-STING contributes to COPD, providing a direction for new treatments that we urgently need to develop. Here, we focused on the cGAS-STING pathway, providing insight into its molecular mechanism and summarizing the current knowledge on the role of the cGAS-STING pathway in COPD. Moreover, we explored antagonists of cGAS and STING to identify potential therapeutic strategies for COPD that target the cGAS-STING pathway.

Lipid Deficiency Contributes to Impaired Alveolar Progenitor Cell Function in Aging and Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is an aging-associated interstitial lung disease resulting from repeated epithelial injury and inadequate epithelial repair. Alveolar type II cells (AEC2s) are progenitor cells that maintain epithelial homeostasis and repair the lung after injury. In the current study, we assessed lipid metabolism in AEC2s from human lungs of patients with IPF and healthy donors, as well as AEC2s from bleomycin-injured young and old mice. Through single-cell RNA sequencing, we observed that lipid metabolism-related genes were downregulated in IPF AEC2s and bleomycin-injured mouse AEC2s. Aging aggravated this decrease and hindered recovery of lipid metabolism gene expression in AEC2s after bleomycin injury. Pathway analyses revealed downregulation of genes related to lipid biosynthesis and fatty acid β-oxidation in AEC2s from IPF lungs and bleomycin-injured, old mouse lungs compared with the respective controls. We confirmed decreased cellular lipid content in AEC2s from IPF lungs and bleomycin-injured, old mouse lungs using immunofluorescence staining and flow cytometry. Futhermore, we show that lipid metabolism was associated with AEC2 progenitor function. Lipid supplementation and PPARγ (peroxisome proliferator activated receptor γ) activation promoted progenitor renewal capacity of both human and mouse AEC2s in three-dimensional organoid cultures. Lipid supplementation also increased AEC2 proliferation and expression of SFTPC in AEC2s. In summary, we identified a lipid metabolism deficiency in AEC2s from lungs of patients with IPF and bleomycin-injured old mice. Restoration of lipid metabolism homeostasis in AEC2s might promote AEC2 progenitor function and offer new opportunities for therapeutic approaches to IPF.

Cell Proliferation and Apoptosis-Key Players in the Lung Aging Process

Currently, the global lifespan has increased, resulting in a higher proportion of the population over 65 years. Changes that occur in the lung during aging increase the risk of developing acute and chronic lung diseases, such as acute respiratory distress syndrome, chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, and lung cancer. During normal tissue homeostasis, cell proliferation and apoptosis create a dynamic balance that constitutes the physiological cell turnover. In basal conditions, the lungs have a low rate of cell turnover compared to other organs. During aging, changes in the rate of cell turnover in the lung are observed. In this work, we review the literature that evaluates the role of molecules involved in cell proliferation and apoptosis in lung aging and in the development of age-related lung diseases. The list of molecules that regulate cell proliferation, apoptosis, or both processes in lung aging includes TNC, FOXM1, DNA-PKcs, MicroRNAs, BCL-W, BCL-XL, TCF21, p16, NOX4, NRF2, MDM4, RPIA, DHEA, and MMP28. However, despite the studies carried out to date, the complete signaling pathways that regulate cell turnover in lung aging are still unknown. More research is needed to understand the changes that lead to the development of age-related lung diseases.

SIRT1: An Intermediator of Key Pathways Regulating Pulmonary Diseases

Silent information regulator type-1 (SIRT1), a nicotinamide adenine dinucleotide+-dependent deacetylase, is a member of the sirtuins family and has unique protein deacetylase activity. SIRT1 participates in physiological as well as pathophysiological processes by targeting a wide range of protein substrates and signalings. In this review, we described the latest progress of SIRT1 in pulmonary diseases. We have introduced the basic information and summarized the prominent role of SIRT1 in several lung diseases, such as acute lung injury, acute respiratory distress syndrome, chronic obstructive pulmonary disease, lung cancer, and aging-related diseases.

Alveolar epithelial cells of lung fibrosis patients are susceptible to severe virus-induced injury

Patients with pulmonary fibrosis (PF) often experience exacerbations of their disease, characterised by a rapid, severe deterioration in lung function that is associated with high mortality. Whilst the pathobiology of such exacerbations is poorly understood, virus infection is a trigger. The present study investigated virus-induced injury responses of alveolar and bronchial epithelial cells (AECs and BECs, respectively) from patients with PF and age-matched controls (Ctrls). Air-liquid interface (ALI) cultures of AECs, comprising type I and II pneumocytes or BECs were inoculated with influenza A virus (H1N1) at 0.1 multiplicity of infection (MOI). Levels of interleukin-6 (IL-6), IL-36γ and IL-1β were elevated in cultures of AECs from PF patients (PF-AECs, n = 8-11), being markedly higher than Ctrl-AECs (n = 5-6), 48 h post inoculation (pi) (P<0.05); despite no difference in H1N1 RNA copy numbers 24 h pi. Furthermore, the virus-induced inflammatory responses of PF-AECs were greater than BECs (from either PF patients or controls), even though viral loads in the BECs were overall 2- to 3-fold higher than AECs. Baseline levels of the senescence and DNA damage markers, nuclear p21, p16 and H2AXγ were also significantly higher in PF-AECs than Ctrl-AECs and further elevated post-infection. Senescence induction using etoposide augmented virus-induced injuries in AECs (but not viral load), whereas selected senotherapeutics (rapamycin and mitoTEMPO) were protective. The present study provides evidence that senescence increases the susceptibility of AECs from PF patients to severe virus-induced injury and suggests targeting senescence may provide an alternative option to prevent or treat the exacerbations that worsen the underlying disease.

HHIP protein interactions in lung cells provide insight into COPD pathogenesis

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide. The primary causes of COPD are environmental, including cigarette smoking; however, genetic susceptibility also contributes to COPD risk. Genome-Wide Association Studies (GWASes) have revealed more than 80 genetic loci associated with COPD, leading to the identification of multiple COPD GWAS genes. However, the biological relationships between the identified COPD susceptibility genes are largely unknown. Genes associated with a complex disease are often in close network proximity, i.e. their protein products often interact directly with each other and/or similar proteins. In this study, we use affinity purification mass spectrometry (AP-MS) to identify protein interactions with HHIP , a well-established COPD GWAS gene which is part of the sonic hedgehog pathway, in two disease-relevant lung cell lines (IMR90 and 16HBE). To better understand the network neighborhood of HHIP , its proximity to the protein products of other COPD GWAS genes, and its functional role in COPD pathogenesis, we create HUBRIS, a protein-protein interaction network compiled from 8 publicly available databases. We identified both common and cell type-specific protein-protein interactors of HHIP. We find that our newly identified interactions shorten the network distance between HHIP and the protein products of several COPD GWAS genes, including DSP, MFAP2, TET2 , and FBLN5 . These new shorter paths include proteins that are encoded by genes involved in extracellular matrix and tissue organization. We found and validated interactions to proteins that provide new insights into COPD pathobiology, including CAVIN1 (IMR90) and TP53 (16HBE). The newly discovered HHIP interactions with CAVIN1 and TP53 implicate HHIP in response to oxidative stress.

Biomarkers of chronic airflow limitation and COPD identified by mass spectrometry

Rationale

COPD affects 300 million people worldwide and is the third leading cause of death according to World Health Organization global health estimates. Early symptoms are subtle, and so COPD is often diagnosed at an advanced stage. Thus, there is an unmet need for biomarkers that can identify individuals at early stages of the disease before clinical symptoms have manifested. To date, few biomarkers are available for clinical diagnostic use in COPD.

Methods

We evaluated a panel of serum biomarkers related to inflammation and infection for their ability to discriminate between 77 subjects with chronic airflow limitation (CAL) and 142 subjects with COPD, versus 150 healthy subjects (divided into two control groups that were matched with regards to age, gender and smoking to CAL and COPD). Healthy subjects and CAL were from Burden of Obstructive Lung Disease (BOLD), a population-based study. CAL was defined by post-bronchodilatory forced expiratory volume in 1 s/forced vital capacity ratio <0.7 in the BOLD population. COPD subjects were from Tools for Identifying Exacerbations (TIE), a COPD patient cohort. Quantification of 100 biomarker candidates was done by liquid chromatography-tandem mass spectrometry.

Results

Several protein-derived peptides were upregulated in CAL, compared to controls; most notably peptides representing histidine-rich glycoprotein (HRG), α1-acid glycoprotein (AGP1), α1-antitrypsin (α1AT) and fibronectin. Out of these, HRG-, AGP1- and α1AT-specific peptides were also elevated in the COPD cohort.

Conclusion

HRG, AGP1 and α1AT biomarkers distinguish subjects with CAL and COPD from healthy controls. HRG and AGP1 represent novel findings.

The Plastic Interplay between Lung Regeneration Phenomena and Fibrotic Evolution: Current Challenges and Novel Therapeutic Perspectives

Interstitial lung diseases (ILDs) are a heterogeneous group of pulmonary disorders characterized by variable degrees of inflammation, interstitial thickening, and fibrosis leading to distortion of the pulmonary architecture and gas exchange impairment. Among them, idiopathic pulmonary fibrosis (IPF) displays the worst prognosis. The only therapeutic options consist of the two antifibrotic drugs, pirfenidone and nintedanib, which limit fibrosis progression but do not reverse the lung damage. The shift of the pathogenetic paradigm from inflammatory disease to epithelium-derived disease has definitively established the primary role of type II alveolar cells, which lose their epithelial phenotype and acquire a mesenchymal phenotype with production of collagen and extracellular matrix (EMC) deposition. Some predisposing environmental and genetic factors (e.g., smoke, pollution, gastroesophageal reflux, variants of telomere and surfactant genes) leading to accelerated senescence set a pro-fibrogentic microenvironment and contribute to the loss of regenerative properties of type II epithelial cells in response to pathogenic noxae. This review provides a complete overview of the different pathogenetic mechanisms leading to the development of IPF. Then, we summarize the currently approved therapies and the main clinical trials ongoing. Finally, we explore the potentialities offered by agents not only interfering with the processes of fibrosis but also restoring the physiological properties of alveolar regeneration, with a particular focus on potentialities and concerns about cell therapies based on mesenchymal stem cells (MSCs), whose anti-inflammatory and immunomodulant properties have been exploited in other fibrotic diseases, such as graft versus host disease (GVHD) and COVID-19-related ARDS.

p38 MAPK signaling in chronic obstructive pulmonary disease pathogenesis and inhibitor therapeutics

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is characterized by persistent respiratory symptoms and airflow limitation due to airway and/or alveolar remodeling. Although the abnormalities are primarily prompted by chronic exposure to inhaled irritants, maladjusted and self-reinforcing immune responses are significant contributors to the development and progression of the disease. The p38 isoforms are regarded as pivotal hub proteins that regulate immune and inflammatory responses in both healthy and disease states. As a result, their inhibition has been the subject of numerous recent studies exploring their therapeutic potential in COPD.

MAIN BODY

We performed a systematic search based on the PRISMA guidelines to find relevant studies about P38 signaling in COPD patients. We searched the PubMed and Google Scholar databases and used "P38" AND "COPD" Mesh Terms. We applied the following inclusion criteria: (1) human, animal, ex vivo and in vitro studies; (2) original research articles; (3) published in English; and (4) focused on P38 signaling in COPD pathogenesis, progression, or treatment. We screened the titles and abstracts of the retrieved studies and assessed the full texts of the eligible studies for quality and relevance. We extracted the following data from each study: authors, year, country, sample size, study design, cell type, intervention, outcome, and main findings. We classified the studies according to the role of different cells and treatments in P38 signaling in COPD.

CONCLUSION

While targeting p38 MAPK has demonstrated some therapeutic potential in COPD, its efficacy is limited. Nevertheless, combining p38 MAPK inhibitors with other anti-inflammatory steroids appears to be a promising treatment choice. Clinical trials testing various p38 MAPK inhibitors have produced mixed results, with some showing improvement in lung function and reduction in exacerbations in COPD patients. Despite these mixed results, research on p38 MAPK inhibitors is still a major area of study to develop new and more effective therapies for COPD. As our understanding of COPD evolves, we may gain a better understanding of how to utilize p38 MAPK inhibitors to treat this disease. Video Abstract.

Cellular senescence and ophthalmic diseases: narrative review

PURPOSE

Cellular senescence is a state of permanent growth arrest whereby a cell reaches its replicative limit. However, senescence can also be triggered prematurely in certain stressors including radiation, oxidative stress, and chemotherapy. This stress-induced senescence has been studied in the context of promoting inflammation, tumor development, and several chronic degenerative diseases of aging. Emerging research has elucidated the role of senescence in various ocular diseases.

METHODS

The literature search was performed using PubMed with using the query (senescence OR aging) AND (eye disease OR ocular disease OR ophthalmic disease OR cornea OR glaucoma OR cataract OR retina) on October 20th, 2022. No time restriction was proposed. Articles were excluded if they were not referenced in English.

RESULTS

Overall, 51 articles regarding senescence and ocular diseases were found and summarized in this study. Several signaling pathways have been implicated in the development of senescence. Currently, senescence has been linked to various corneal and retinal pathologies, as well as cataract and glaucoma. Given the number of pathologies, senolytics, which are small molecules with the ability to selective targeting of senescent cells, can be used as therapeutic or prophylactic agents.

CONCLUSIONS

Senescence has been shown to underlie the pathogenesis of numerous ocular diseases. The overall literature on senescence and ocular disease is growing rapidly. There is an ongoing debate whether or not cellular senescence detected in experiments contributes in a significant way to diseases. Research on understanding the mechanism of senescence from ocular cells and tissues is just beginning. Multiple animal models are required to test potential senolytics. Currently, no studies exist to date which have demonstrated the benefits of senolytic therapies in human studies.

Sohlh2 promotes pulmonary fibrosis via repression of p62/Keap1/Nrf2 mediated anti-oxidative signaling pathway

Disturbance in the redox balance of alveolar epithelial cells (AECs) was considered as a causal factor for pulmonary fibrosis. The regulatory mechanisms of redox hemostasis in the development of pulmonary fibrosis remain largely unknown. Using a type II AEC-specific Sohlh2 conditional knock-in (CKI) mouse model, we found that Sohlh2, a basic HLH transcription factor, accelerated age-related pulmonary fibrosis. High-fat diet (HFD) resulted in a tremendous increase in lung inflammation and fibrotic changes in the lung tissues of Sohlh2 CKI mice. Sohlh2 overexpression led to a significant rise of intracellular ROS and apoptosis in the lung, mouse primary AECIIs, and human A549 cells, which was attenuated by ROS inhibitor (NAC). Sohlh2 enhanced oxidative stress via repressing p62/Keap1/Nrf2 mediated anti-oxidative signaling pathway. p62, a direct target of Sohlh2, mediated Sohlh2 effects on ROS generation and apoptosis in A549 cells. Hence, our findings elucidate a pivotal mechanism underlying oxidative stress-induced pulmonary fibrosis, providing a framework for aging-related disorder interventions.

Lung inflammation and interstitial fibrosis by targeted alveolar epithelial type I cell death

Introduction

The pathogenesis of chronic lung diseases is multifaceted with a major role of recurrent micro-injuries of the epithelium. While several reports clearly indicated a prominent role for surfactant-producing alveolar epithelial type 2 (AT2) cells, the contribution of gas exchange-permissive alveolar epithelial type 1 (AT1) cells has not been addressed yet. Here, we investigated whether repeated injury of AT1 cells leads to inflammation and interstitial fibrosis.

Methods

We chose an inducible model of AT1 cell depletion following local diphtheria toxin (DT) administration using an iDTR flox/flox (idTRfl/fl) X Aquaporin 5CRE (Aqp5CRE) transgenic mouse strain.

Results

We investigated repeated doses and intervals of DT to induce cell death of AT1 cells causing inflammation and interstitial fibrosis. We found that repeated DT administrations at 1ng in iDTRfl/fl X Aqp5CRE mice cause AT1 cell death leading to inflammation, increased tissue repair markers and interstitial pulmonary fibrosis.

Discussion

Together, we demonstrate that depletion of AT1 cells using repeated injury represents a novel approach to investigate chronic lung inflammatory diseases and to identify new therapeutic targets.

CSE reduces OTUD4 triggering lung epithelial cell apoptosis via PAI-1 degradation

Ovarian tumor family deubiquitinase 4 (OTUD4), a member of the OTU deubiquitinating enzyme, is implicated to decrease in cancer to regulate cell apoptosis. However, the role of OTUD4 in cigarette smoke induced epithelial cell apoptosis and its mechanism have not been elucidated. In this study, we showed that OTUD4 protein reduced in CSE treated mice and airway epithelial cells. OTUD4 silence aggravated cell apoptosis and emphysematous change in the lung tissue of cigarette smoke extract (CSE) treated mice. Additionally, restoration of OTUD4 in the lung of mice alleviated CSE induced apoptosis and emphysematous morphology change. The effect of OTUD4 on cell apoptosis was also confirmed in vitro. Through protein profile screening, we identified that OTUD4 may interact with plasminogen activator inhibitor 1(PAI-1). We further confirmed that OTUD4 interacted with PAI-1 for de-ubiquitination and inhibiting CSE induced PAI-1 degradation. Furthermore, the protective role of OTUD4 in airway epithelial cells apoptosis was blocked by PAI-1 deactivation. Taken together, our data suggest that OTUD4 regulates cigarette smoke (CS)-triggered airway epithelial cell apoptosis via modulating PAI-1 degradation. Targeting OUTD4/PAI-1 signaling might potentially provide a therapeutic target against the lung cell apoptosis in cigarette smoke (CS)-induced emphysema.

Senescence-associated alterations in the extracellular matrix: deciphering their role in the regulation of cellular function

The extracellular matrix (ECM) is a dynamic structural network that provides a physical scaffolding, as well as biochemical factors that maintain normal tissue homeostasis and thus its disruption is implicated in many pathological conditions. On the other hand, senescent cells express a particular secretory phenotype, affecting the composition and organization of the surrounding ECM and modulating their microenvironment. As accumulation of senescent cells may be linked to the manifestation of several age-related conditions, senescence-associated ECM alterations may serve as targets for novel anti-aging treatment modalities. Here, we will review characteristic changes in the ECM elicited by cellular senescence and we will discuss the complex interplay between ECM and senescent cells, in relation to normal aging and selected age-associated pathologies.

PAI-1 Regulation of p53 Expression and Senescence in Type II Alveolar Epithelial Cells

Cellular senescence contributes importantly to aging and aging-related diseases, including idiopathic pulmonary fibrosis (IPF). Alveolar epithelial type II (ATII) cells are progenitors of alveolar epithelium, and ATII cell senescence is evident in IPF. Previous studies from this lab have shown that increased expression of plasminogen activator inhibitor 1 (PAI-1), a serine protease inhibitor, promotes ATII cell senescence through inducing p53, a master cell cycle repressor, and activating p53-p21-pRb cell cycle repression pathway. In this study, we further show that PAI-1 binds to proteasome components and inhibits proteasome activity and p53 degradation in human lung epithelial A549 cells and primary mouse ATII cells. This is associated with a senescence phenotype of these cells, manifested as increased p53 and p21 expression, decreased phosphorylated retinoblastoma protein (pRb), and increased senescence-associated beta-galactose (SA-β-gal) activity. Moreover, we find that, although overexpression of wild-type PAI-1 (wtPAI-1) or a secretion-deficient, mature form of PAI-1 (sdPAI-1) alone induces ATII cell senescence (increases SA-β-gal activity), only wtPAI-1 induces p53, suggesting that the premature form of PAI-1 is required for the interaction with the proteasome. In summary, our data indicate that PAI-1 can bind to proteasome components and thus inhibit proteasome activity and p53 degradation in ATII cells. As p53 is a master cell cycle repressor and PAI-1 expression is increased in many senescent cells, the results from this study will have a significant impact not only on ATII cell senescence/lung fibrosis but also on the senescence of other types of cells in different diseases.

Senescence of alveolar epithelial progenitor cells: a critical driver of lung fibrosis

Pulmonary fibrosis comprises a range of chronic interstitial lung diseases (ILDs) that impose a significant burden on patients and public health. Among these, idiopathic pulmonary fibrosis (IPF), a disease of aging, is the most common and most severe form of ILD and is treated largely by lung transplantation. The lack of effective treatments to stop or reverse lung fibrosis-in fact, fibrosis in most organs-has sparked the need to understand causative mechanisms with the goal of identifying critical points for potential therapeutic intervention. Findings from many groups have indicated that repeated injury to the alveolar epithelium-where gas exchange occurs-leads to stem cell exhaustion and impaired alveolar repair that, in turn, triggers the onset and progression of fibrosis. Cellular senescence of alveolar epithelial progenitors is a critical cause of stemness failure. Hence, senescence impairs repair and thus contributes significantly to fibrosis. In this review, we discuss recent evidence indicating that senescence of epithelial progenitor cells impairs alveolar homeostasis and repair creating a profibrotic environment. Moreover, we discuss the impact of senescent alveolar epithelial progenitors, alveolar type 2 (AT2) cells, and AT2-derived transitional epithelial cells in fibrosis. Emerging evidence indicates that transitional epithelial cells are prone to senescence and, hence, are a new player involved in senescence-associated lung fibrosis. Understanding the complex interplay of cell types and cellular regulatory factors contributing to alveolar epithelial progenitor senescence will be crucial to developing targeted therapies to mitigate their downstream profibrotic sequelae and to promote normal alveolar repair.NEW & NOTEWORTHY With an aging population, lung fibrotic diseases are becoming a global health burden. Dysfunctional repair of the alveolar epithelium is a key causative process that initiates lung fibrosis. Normal alveolar regeneration relies on functional progenitor cells; however, the senescence of these cells, which increases with age, hinders their ability to contribute to repair. Here, we discuss studies on the control and consequence of progenitor cell senescence in fibrosis and opportunities for research.

PAI-1 regulates AT2-mediated re-alveolarization and ion permeability

BACKGROUND

Acute lung injury is characterized by overwhelmingly elevated PAI-1 in both lung edema fluid and the circulating system. The role of increased PAI-1, encoded by Serpine1 gene, in the regeneration of injured lung epithelium has not been understood completely. This study aimed to investigate the role of Serpine1 in the regulation of alveolar type 2 epithelial cell (AT2) fate in a humanized mouse line carrying diseased mutants (Serpine1^Tg).

METHODS

Wild-type (wt) and Serpine1^Tg AT2 cells were either cultured as monolayers or 3D alveolospheres. Colony-forming assay and total surface area of organoids were analyzed. AT1 and AT2 cells in organoids were counted by immunohistochemistry and fluorescence-activated cell sorting (FACS). To test the potential effects of elevated PAI-1 on the permeability in the epithelial monolayers, we digitized the biophysical properties of polarized AT2 monolayers grown at the air-liquid interface.

RESULTS

A significant reduction in total AT2 cells harvested in Serpine1^Tg mice was observed compared with wt controls. AT2 cells harvested from Serpine1^Tg mice reduced significantly over the wt controls. Spheroids formed by Serpine1^Tg AT2 cells were lesser than wt control. Similarly, the corresponding surface area, a readout of re-alveolarization of injured epithelium, was markedly reduced in Serpine1^Tg organoids. FACS analysis revealed a significant suppression in the number of AT2 cells, in particular, the CD44⁺ subpopulation, in Serpine1^Tg organoids. A lesser ratio of AT1:AT2 cells in Serpine1^Tg organoids was observed compared with wt cultures. There was a significant increase in transepithelial resistance but not amiloride inhibition.

CONCLUSIONS

Our study suggests elevated PAI-1 in injured lungs downregulates alveolar epithelial regeneration by reducing the AT2 self-renewal, particularly in the CD44⁺ cells.

Adipokines in interstitial lung diseases

Interstitial lung diseases (ILD) are a heterogenic group of respiratory diseases with complex pathogenesis. A growing number of evidence suggests role of adipose tissue and it's hormones (adipokines) in pathogenesis of various disorders, including lung tissue diseases. The aim of this study was to assess the concentrations of selected adipokines and their receptors (apelin, adiponectin, chemerin, chemerin receptor - CMKLR1) in patients with IPF (idiopathic pulmonary fibrosis) and sarcoidosis in comparison to healthy controls. We found changes in adipokines concentrations in ILD. Adiponectin concentrations were higher in all respiratory diseases patients in comparison to healthy controls. Apelin concentration in ILD patients was higher then those in healthy subjects. The trend of chemerin and CMKLR1 concentrations were similar, with highest concentrations seen in sarcoidosis. The study shows a difference of adipokines concentrations between patients with ILD and healthy controls. Adipokines are a potential marker and therapeutic target in patients with IPF and sarcoidosis.

Reciprocal interactions between alveolar progenitor dysfunction and aging promote lung fibrosis

Aging is a critical risk factor in idiopathic pulmonary fibrosis (IPF). Dysfunction and loss of type 2 alveolar epithelial cells (AEC2s) with failed regeneration is a seminal causal event in the pathogenesis of IPF, although the precise mechanisms for their regenerative failure and demise remain unclear. To systematically examine the genomic program changes of AEC2s in aging and after lung injury, we performed unbiased single-cell RNA-seq analyses of lung epithelial cells from uninjured or bleomycin-injured young and old mice, as well as from lungs of IPF patients and healthy donors. We identified three AEC2 subsets based on their gene signatures. Subset AEC2-1 mainly exist in uninjured lungs, while subsets AEC2-2 and AEC2-3 emerged in injured lungs and increased with aging. Functionally, AEC2 subsets are correlated with progenitor cell renewal. Aging enhanced the expression of the genes related to inflammation, stress responses, senescence, and apoptosis. Interestingly, lung injury increased aging-related gene expression in AEC2s even in young mice. The synergistic effects of aging and injury contributed to impaired AEC2 recovery in aged mouse lungs after injury. In addition, we also identified three subsets of AEC2s from human lungs that formed three similar subsets to mouse AEC2s. IPF AEC2s showed a similar genomic signature to AEC2 subsets from bleomycin-injured old mouse lungs. Taken together, we identified synergistic effects of aging and AEC2 injury in transcriptomic and functional analyses that promoted fibrosis. This study provides new insights into the interactions between aging and lung injury with interesting overlap with diseased IPF AEC2 cells.

The role of Sirtuin 1 and its activators in age-related lung disease

Aging is a major driving factor in lung diseases. Age-related lung disease is associated with downregulated expression of SIRT1, an NAD⁺-dependent deacetylase that regulates inflammation and stress resistance. SIRT1 acts by inducing the deacetylation of various substrates and regulates several mechanisms that relate to lung aging, such as genomic instability, lung stem cell exhaustion, mitochondrial dysfunction, telomere shortening, and immune senescence. Chinese herbal medicines have many biological activities, exerting anti-inflammatory, anti-oxidation, anti-tumor, and immune regulatory effects. Recent studies have confirmed that many Chinese herbs have the effect of activating SIRT1. Therefore, we reviewed the mechanism of SIRT1 in age-related lung disease and explored the potential roles of Chinese herbs as SIRT1 activators in the treatment of age-related lung disease.

Alveolar epithelial cells are competent producers of interstitial extracellular matrix with disease relevant plasticity in a human in vitro 3D model

Alveolar epithelial cells (AEC) have been implicated in pathological remodelling. We examined the capacity of AEC to produce extracellular matrix (ECM) and thereby directly contribute towards remodelling in chronic lung diseases. Cryopreserved type 2 AEC (AEC2) from healthy lungs and chronic obstructive pulmonary disease (COPD) afflicted lungs were cultured in decellularized healthy human lung slices for 13 days. Healthy-derived AEC2 were treated with transforming growth factor ß1 (TGF-β1) to evaluate the plasticity of their ECM production. Evaluation of phenotypic markers and expression of matrisome genes and proteins were evaluated by RNA-sequencing, mass spectrometry and immunohistochemistry. The AEC2 displayed an AEC marker profile similar to freshly isolated AEC2 throughout the 13-day culture period. COPD-derived AECs proliferated as healthy AECs with few differences in gene and protein expression while retaining increased expression of disease marker HLA-A. The AEC2 expressed basement membrane components and a complex set of interstitial ECM proteins. TGF-β1 stimuli induced a significant change in interstitial ECM production from AEC2 without loss of specific AEC marker expression. This study reveals a previously unexplored potential of AEC to directly contribute to ECM turnover by producing interstitial ECM proteins, motivating a re-evaluation of the role of AEC2 in pathological lung remodelling.

Advances in cellular senescence in idiopathic pulmonary fibrosis (Review)

Idiopathic pulmonary fibrosis (IPF) is a progressive, irreversible and fatal interstitial lung disease of unknown cause, with a median survival of 2-3 years. Its pathogenesis is unclear and there is currently no effective treatment for IPF. Approximately two-thirds of patients with IPF are >60 years old, with a mean age of 66 years, suggesting a link between aging and IPF. However, the mechanism by which aging promotes development of PF remains unclear. Senescence of alveolar epithelial cells and lung fibroblasts (LFs) and their senescence-associated secretion phenotype (SASP) may be involved in the occurrence and development of IPF. The present review focus on senescence of LFs and epithelial and stem cells, as well as SASP, the activation of profibrotic signaling pathways and potential treatments for pathogenesis of IPF.

Modeling of Respiratory Diseases Evolving with Fibrosis from Organoids Derived from Human Pluripotent Stem Cells

Respiratory disease is one of the leading causes of morbidity and mortality worldwide. There is no cure for most diseases, which are treated symptomatically. Hence, new strategies are required to deepen the understanding of the disease and development of therapeutic strategies. The advent of stem cell and organoid technology has enabled the development of human pluripotent stem cell lines and adequate differentiation protocols for developing both airways and lung organoids in different formats. These novel human-pluripotent-stem-cell-derived organoids have enabled relatively accurate disease modeling. Idiopathic pulmonary fibrosis is a fatal and debilitating disease that exhibits prototypical fibrotic features that may be, to some extent, extrapolated to other conditions. Thus, respiratory diseases such as cystic fibrosis, chronic obstructive pulmonary disease, or the one caused by SARS-CoV-2 may reflect some fibrotic aspects reminiscent of those present in idiopathic pulmonary fibrosis. Modeling of fibrosis of the airways and the lung is a real challenge due to the large number of epithelial cells involved and interaction with other cell types of mesenchymal origin. This review will focus on the status of respiratory disease modeling from human-pluripotent-stem-cell-derived organoids, which are being used to model several representative respiratory diseases, such as idiopathic pulmonary fibrosis, cystic fibrosis, chronic obstructive pulmonary disease, and COVID-19.

The telomerase activator TA-65 protects from cigarette smoke-induced small airway remodeling in mice through extra-telomeric effects

Small airway remodeling (SAR) is a key phenomenon of airflow obstruction in smokers, leading to chronic obstructive pulmonary disease (COPD). SAR results in an increased thickness of small airway walls, with a combination of peribronchiolar fibrosis with increased fibrous tissue and accumulation of mesenchymal and epithelial cells. SAR pathogenesis is still unclear but recent data suggest that alterations in telomerase activity could represent a possible underlying mechanism of SAR. Our study was dedicated to identify a potential protective role of TA-65, a pharmacological telomerase activator, in a cigarette smoke (CS) model of SAR in mice, and to further precise if extra-telomeric effects of telomerase, involving oxidative stress modulation, could explain it. C57BL/6J mice were daily exposed to air or CS during 4 weeks with or without a concomitant administration of TA-65 starting 7 days before CS exposure. Morphological analyses were performed, and mucus production, myofibroblast differentiation, collagen deposition, as well as transforming growth factor-β1 (TGF-β1) expression in the small airway walls were examined. In addition, the effects of TA-65 treatment on TGF-β expression, fibroblast-to-myofibroblast differentiation, reactive oxygen species (ROS) production and catalase expression and activity were evaluated in primary cultures of pulmonary fibroblasts and/or mouse embryonic fibroblasts in vitro. Exposure to CS during 4 weeks induced SAR in mice, characterized by small airway walls thickening and peribronchiolar fibrosis (increased deposition of collagen, expression of α-SMA in small airway walls), without mucus overproduction. Treatment of mice with TA-65 protected them from CS-induced SAR. This effect was associated with the prevention of CS-induced TGF-β expression in vivo, the blockade of TGF-β-induced myofibroblast differentiation, and the reduction of TGF-β-induced ROS production that correlates with an increase of catalase expression and activity. Our findings demonstrate that telomerase is a critical player of SAR, probably through extra-telomeric anti-oxidant effects, and therefore provide new insights in the understanding and treatment of COPD pathogenesis.

The miR-15b-Smurf2-HSP27 axis promotes pulmonary fibrosis

BACKGROUND

Heat shock protein 27 (HSP27) is overexpressed during pulmonary fibrosis (PF) and exacerbates PF; however, the upregulation of HSP27 during PF and the therapeutic strategy of HSP27 inhibition is not well elucidated.

METHODS

We have developed a mouse model simulating clinical stereotactic body radiotherapy (SBRT) with focal irradiation and validated the induction of RIPF. HSP25 (murine form of HSP27) transgenic (TG) and LLC1-derived orthotropic lung tumor models were also used. Lung tissues of patients with RIPF and idiopathic pulmonary fibrosis, and lung tissues from various fibrotic mouse models, as well as appropriated cell line systems were used. Public available gene expression datasets were used for therapeutic response rate analysis. A synthetic small molecule HSP27 inhibitor, J2 was also used.

RESULTS

HSP27 expression with its phosphorylated form (pHSP27) increased during PF. Decreased mRNA expression of SMAD-specific E3 ubiquitin-protein ligase 2 (Smurf2), which is involved in ubiquitin degradation of HSP27, was responsible for the increased expression of pHSP27. In addition, increased expression of miRNA15b was identified with decreased expression of Smurf2 mRNA in PF models. Inverse correlation between pHSP27 and Smurf2 was observed in the lung tissues of PF animals, an irradiated orthotropic lung cancer models, and PF tissues from patients. Moreover, a HSP27 inhibitor cross-linked with HSP27 protein to ameliorate PF, which was more effective when targeting the epithelial to mesenchymal transition (EMT) stage of PF.

CONCLUSIONS

Our findings identify upregulation mechanisms of HSP27 during PF and provide a therapeutic strategy for HSP27 inhibition for overcoming PF.

Epithelial Endoplasmic Reticulum Stress Enhances the Risk of Muc5b-associated Lung Fibrosis

The gain-of-function minor allele of the MUC5B (mucin 5B, oligomeric mucus/gel-forming) promoter (rs35705950) is the strongest risk factor for idiopathic pulmonary fibrosis (IPF), a devastating fibrotic lung disease that leads to progressive respiratory failure in adults. We have previously demonstrated that Muc5b overexpression in mice worsens lung fibrosis after bleomycin exposure and have hypothesized that excess Muc5b promotes endoplasmic reticulum (ER) stress and apoptosis, stimulating fibrotic lung injury. Here, we report that ER stress pathway members ATF4 (activating transcription factor 4) and ATF6 coexpress with MUC5B in epithelia of the distal IPF airway and honeycomb cyst and that this is more pronounced in carriers of the gain-of-function MUC5B promoter variant. Similarly, in mice exposed to bleomycin, Muc5b expression is temporally associated with markers of ER stress. Using bulk and single-cell RNA sequencing in bleomycin-exposed mice, we found that pathologic ER stress-associated transcripts Atf4 and Ddit3 (DNA damage inducible transcript 3) were elevated in alveolar epithelia of SFTPC-Muc5b transgenic (SFTPC-Muc5bTg) mice relative to wild-type (WT) mice. Activation of the ER stress response inhibits protein translation for most genes by phosphorylation of Eif2α (eukaryotic translation initiation factor 2 alpha), which prevents guanine exchange by Eif2B and facilitates translation of Atf4. The integrated stress response inhibitor (ISRIB) facilitates interaction of phosphorylated Eif2α with Eif2B, overcoming translation inhibition associated with ER stress and reducing Atf4. We found that a single dose of ISRIB diminished Atf4 translation in SFTPC-Muc5bTg mice after bleomycin injury. Moreover, ISRIB resolved the exaggerated fibrotic response of SFTPC-Muc5bTg mice to bleomycin. In summary, we demonstrate that MUC5B and Muc5b expression is associated with pathologic ER stress and that restoration of normal translation with a single dose of ISRIB promotes lung repair in bleomycin-injured Muc5b-overexpressing mice.

Selenomethionine mitigate PM2.5-induced cellular senescence in the lung via attenuating inflammatory response mediated by cGAS/STING/NF-κB pathway

Particulate matter 2.5 (PM2.5) is a widely known atmospheric pollutant which can induce the aging-related pulmonary diseases such as acute respiratory distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD) and interstitial pulmonary fibrosis (IPF). In recent years, with the increasing atmospheric pollution, airborne fine PM2.5, which is an integral part of air pollutants, has become a thorny problem. Hence, this study focused on the effect of PM2.5 on cellular senescence in the lung, identifying which inflammatory pathway mediated PM2.5-induced cellular senescence and how to play a protective role against this issue. Our data suggested that PM2.5 induced time- and concentration-dependent increasement in the senescence of A549 cells. Using an inhibitor of cGAS (PF-06928215) and an inhibitor of NF-κB (BAY 11-7082), it was revealed that PM2.5-induced senescence was regulated by inflammatory response, which was closely related to the cGAS/STING/NF-κB pathway activated by DNA damage. Moreover, our study also showed that the pretreatment with selenomethionine (Se-Met) could inhibit inflammatory response and prevent cellular senescence by hindering cGAS/STING/NF-κB pathway in A549 cells exposed to PM2.5. Furthermore, in vivo C57BL/6J mice model demonstrated that aging of mouse lung tissue caused by PM2.5 was attenuated by decreasing cGAS expression after Se-Met treatment. Our findings indicated that selenium made a defense capability for PM2.5-induced cellular senescence in the lung, which provided a novel insight for resisting the harm of PM2.5 to human health.

Does senescence play a role in age-related macular degeneration?

Advanced age is the most established risk factor for developing age-related macular degeneration (AMD), one of the leading causes of visual impairment in the elderly, in Western and developed countries. Similarly, after middle age, there is an exponential increase in pathologic molecular and cellular events that can induce senescence, traditionally defined as an irreversible loss of the cells' ability to divide and most recently reported to also occur in select post-mitotic and terminally differentiated cells, such as neurons. Together these facts raise the question as to whether or not cellular senescence, may play a role in the development of AMD. A number of studies have reported the effect of ocular-relevant inducers of senescence using primarily in vitro models of poorly polarized, actively dividing retinal pigment epithelial (RPE) cell lines. However, in interpretating the data, the fidelity of these culture models to the RPE in vivo, must be considered. Fewer studies have explored the presence and/or impact of senescent cells in in vivo models that present with phenotypic features of AMD, leaving this an open field for further investigation. The goal of this review is to discuss current thoughts on the potential role of senescence in AMD development and progression, with consideration of the model systems used and their relevance to human disease.

Resveratrol attenuates cigarette smoke extract induced cellular senescence in human airway epithelial cells by regulating the miR-34a/SIRT1/NF-κB pathway

Chronic obstructive pulmonary disease (COPD) is characterized by accelerated lung aging. Smoking is the critical risk factor for COPD. Cellular senescence of airway epithelial cells is the cytological basis of accelerated lung aging in COPD, and the regulation of microRNAs (miRNAs) is the central epigenetic mechanism of cellular senescence. Resveratrol (Res) is a polyphenol with anti-aging properties. This study investigated whether Res attenuates cigarette smoke extract (CSE)-induced cellular senescence in human airway epithelial cells (BEAS-2B) through the miR-34a/SIRT1/nuclear factor-kappaB (NF-κB) pathway. BEAS-2B cells were treated with Res, CSE and transfected with miR-34a-5p mimics. Cellular senescence was evaluated by senescence -related β-galactosidase (SA-β-gal) staining and expression of senescence-related genes (p16, p21, and p53). The expressions of miR-34a-5p, SIRT1, and NF-κB p65 were examined using quantitative real time polymerase chain reaction and western blotting. The senescence-associated secretory phenotype (SASP) cytokines (IL-1β, IL-6, IL-8, TNF-α) were assessed by enzyme-linked immunosorbent assay. The binding between miR-34a-5p and SIRT1 was confirmed by dual-luciferase reporter assay. The results showed that CSE dose-dependently decreased cell viability and elevated cellular senescence, characterized by increased SA-β-gal staining and senescence-related gene expressions (p16, p21, and p53). Further, CSE dose-dependently increased the expression of miR-34a-5p and SASP cytokines (IL-1β, IL-6, IL-8, TNF-α) in BEAS-2B cells. Pretreatment with Res inhibited CSE-induced cellular senescence and secretion of SASP cytokines (IL-1β, IL-6, IL-8, TNF-α) in a dose-dependent manner. Moreover, Res reversed the CSE-induced down-regulation of SIRT1 and up-regulation of miR-34a-5p and NF-κB p65. SIRT1 is a target of miR-34a-5p. Overexpression of miR-34a-5p via transfection with miR-34a-5p mimic in BEAS-2B cells attenuated the inhibitory effect of Res on cellular senescence, accompanied by reversing the expression of SIRT1 and NF-κB p65. In conclusion, Res attenuated CSE-induced cellular senescence in BEAS-2B cells by regulating the miR-34a/SIRT1/NF-κB pathway, which may provide a new approach for COPD treatment.

Senescent AECⅡ and the implication for idiopathic pulmonary fibrosis treatment

Idiopathic pulmonary fibrosis (IPF) is a chronic and lethal lung disease with limited treatment options. The onset of IPF increases with age, indicating that aging is a major risk factor for IPF. Among the hallmarks of aging, cellular senescence is the primordial driver and primary etiological factor for tissue and organ aging, and an independent risk factor for the progression of IPF. In this review, we focus on the senescence of alveolar type II epithelial cells (AECIIs) and systematically summarize abnormal changes in signal pathways and biological process and implications of senescent AECIIs during IPF progression. Meanwhile, we objectively analyze current medications targeting the elimination of senescent cells or restoration of vitality such as senolytics, senomorphics, autophagy regulators, and stem cell therapy. Finally, we dialectically discuss the feasibility and limitation of targeting senescent AECIIs for IPF treatment. We hope that the understanding will provide new insights to the development of senescent AECII-based approaches for the prevention and mitigation of IPF.

Endoplasmic Reticulum Stress in Chronic Obstructive Pulmonary Disease: Mechanisms and Future Perspectives

The endoplasmic reticulum (ER) is an integral organelle for maintaining protein homeostasis. Multiple factors can disrupt protein folding in the lumen of the ER, triggering ER stress and activating the unfolded protein response (UPR), which interrelates with various damage mechanisms, such as inflammation, apoptosis, and autophagy. Numerous studies have linked ER stress and UPR to the progression of chronic obstructive pulmonary disease (COPD). This review focuses on the mechanisms of other cellular processes triggered by UPR and summarizes drug intervention strategies targeting the UPR pathway in COPD to explore new therapeutic approaches and preventive measures for COPD.

Highway to heal: Influence of altered extracellular matrix on infiltrating immune cells during acute and chronic lung diseases

Environmental insults including respiratory infections, in combination with genetic predisposition, may lead to lung diseases such as chronic obstructive pulmonary disease, lung fibrosis, asthma, and acute respiratory distress syndrome. Common characteristics of these diseases are infiltration and activation of inflammatory cells and abnormal extracellular matrix (ECM) turnover, leading to tissue damage and impairments in lung function. The ECM provides three-dimensional (3D) architectural support to the lung and crucial biochemical and biophysical cues to the cells, directing cellular processes. As immune cells travel to reach any site of injury, they encounter the composition and various mechanical features of the ECM. Emerging evidence demonstrates the crucial role played by the local environment in recruiting immune cells and their function in lung diseases. Moreover, recent developments in the field have elucidated considerable differences in responses of immune cells in two-dimensional versus 3D modeling systems. Examining the effect of individual parameters of the ECM to study their effect independently and collectively in a 3D microenvironment will help in better understanding disease pathobiology. In this article, we discuss the importance of investigating cellular migration and recent advances in this field. Moreover, we summarize changes in the ECM in lung diseases and the potential impacts on infiltrating immune cell migration in these diseases. There has been compelling progress in this field that encourages further developments, such as advanced in vitro 3D modeling using native ECM-based models, patient-derived materials, and bioprinting. We conclude with an overview of these state-of-the-art methodologies, followed by a discussion on developing novel and innovative models and the practical challenges envisaged in implementing and utilizing these systems.

Immunosenescence, Inflammaging, and Lung Senescence in Asthma in the Elderly

Prevalence of asthma in older adults is growing along with increasing global life expectancy. Due to poor clinical consequences such as high mortality, advancement in understanding the pathophysiology of asthma in older patients has been sought to provide prompt treatment for them. Age-related alterations of functions in the immune system and lung parenchyma occur throughout life. Alterations with advancing age are promoted by various stimuli, including pathobionts, fungi, viruses, pollutants, and damage-associated molecular patterns derived from impaired cells, abandoned cell debris, and senescent cells. Age-related changes in the innate and adaptive immune response, termed immunosenescence, includes impairment of phagocytosis and antigen presentation, enhancement of proinflammatory mediator generation, and production of senescence-associated secretory phenotype. Immnunosenescence could promote inflammaging (chronic low-grade inflammation) and contribute to late-onset adult asthma and asthma in the elderly, along with age-related pulmonary disease, such as chronic obstructive pulmonary disease and pulmonary fibrosis, due to lung parenchyma senescence. Aged patients with asthma exhibit local and systemic type 2 and non-type 2 inflammation, associated with clinical manifestations. Here, we discuss immunosenescence’s contribution to the immune response and the combination of type 2 inflammation and inflammaging in asthma in the elderly and present an overview of age-related features in the immune system and lung structure.

Clinical, radiological and pathological findings in patients with persistent lung disease following SARS-CoV-2 infection

Some patients experience pulmonary sequelae after SARS-CoV-2 infection, ranging from self-limited abnormalities to major lung diseases. Morphological analysis of lung tissue may help our understanding of pathogenic mechanisms and help to provide consistent personalised management. The aim of this study was to ascertain morphological and immunomolecular features of lung tissue. Transbronchial lung cryobiopsy was carried out in patients with persistent symptoms and computed tomography suggestive of residual lung disease after recovery from SARS-CoV-2 infection. 164 patients were referred for suspected pulmonary sequelae after COVID-19; 10 patients with >5% parenchymal lung disease underwent lung biopsy. The histological pattern of lung disease was not homogeneous and three different case clusters could be identified, which was mirrored by their clinical and radiological features. Cluster 1 ("chronic fibrosing") was characterised by post-infection progression of pre-existing interstitial pneumonias. Cluster 2 ("acute/subacute injury") was characterised by different types and grades of lung injury, ranging from organising pneumonia and fibrosing nonspecific interstitial pneumonia to diffuse alveolar damage. Cluster 3 ("vascular changes") was characterised by diffuse vascular increase, dilatation and distortion (capillaries and venules) within otherwise normal parenchyma. Clusters 2 and 3 had immunophenotypical changes similar to those observed in early/mild COVID-19 pneumonias (abnormal expression of STAT3 in hyperplastic pneumocytes and PD-L1, IDO and STAT3 in endothelial cells). This is the first study correlating histological/immunohistochemical patterns with clinical and radiological pictures of patients with post-COVID lung disease. Different phenotypes with potentially different underlying pathogenic mechanisms have been identified.

Syndrome of Combined Pulmonary Fibrosis and Emphysema: An Official ATS/ERS/JRS/ALAT Research Statement

Background: The presence of emphysema is relatively common in patients with fibrotic interstitial lung disease. This has been designated combined pulmonary fibrosis and emphysema (CPFE). The lack of consensus over definitions and diagnostic criteria has limited CPFE research. Goals: The objectives of this task force were to review the terminology, definition, characteristics, pathophysiology, and research priorities of CPFE and to explore whether CPFE is a syndrome. Methods: This research statement was developed by a committee including 19 pulmonologists, 5 radiologists, 3 pathologists, 2 methodologists, and 2 patient representatives. The final document was supported by a focused systematic review that identified and summarized all recent publications related to CPFE. Results: This task force identified that patients with CPFE are predominantly male, with a history of smoking, severe dyspnea, relatively preserved airflow rates and lung volumes on spirometry, severely impaired DlCO, exertional hypoxemia, frequent pulmonary hypertension, and a dismal prognosis. The committee proposes to identify CPFE as a syndrome, given the clustering of pulmonary fibrosis and emphysema, shared pathogenetic pathways, unique considerations related to disease progression, increased risk of complications (pulmonary hypertension, lung cancer, and/or mortality), and implications for clinical trial design. There are varying features of interstitial lung disease and emphysema in CPFE. The committee offers a research definition and classification criteria and proposes that studies on CPFE include a comprehensive description of radiologic and, when available, pathological patterns, including some recently described patterns such as smoking-related interstitial fibrosis. Conclusions: This statement delineates the syndrome of CPFE and highlights research priorities.

COVID-19 lung disease shares driver AT2 cytopathic features with Idiopathic pulmonary fibrosis

BACKGROUND

In the aftermath of Covid-19, some patients develop a fibrotic lung disease, i.e., post-COVID-19 lung disease (PCLD), for which we currently lack insights into pathogenesis, disease models, or treatment options.

METHODS

Using an AI-guided approach, we analyzed > 1000 human lung transcriptomic datasets associated with various lung conditions using two viral pandemic signatures (ViP and sViP) and one covid lung-derived signature. Upon identifying similarities between COVID-19 and idiopathic pulmonary fibrosis (IPF), we subsequently dissected the basis for such similarity from molecular, cytopathic, and immunologic perspectives using a panel of IPF-specific gene signatures, alongside signatures of alveolar type II (AT2) cytopathies and of prognostic monocyte-driven processes that are known drivers of IPF. Transcriptome-derived findings were used to construct protein-protein interaction (PPI) network to identify the major triggers of AT2 dysfunction. Key findings were validated in hamster and human adult lung organoid (ALO) pre-clinical models of COVID-19 using immunohistochemistry and qPCR.

FINDINGS

COVID-19 resembles IPF at a fundamental level; it recapitulates the gene expression patterns (ViP and IPF signatures), cytokine storm (IL15-centric), and the AT2 cytopathic changes, e.g., injury, DNA damage, arrest in a transient, damage-induced progenitor state, and senescence-associated secretory phenotype (SASP). These immunocytopathic features were induced in pre-clinical COVID models (ALO and hamster) and reversed with effective anti-CoV-2 therapeutics in hamsters. PPI-network analyses pinpointed ER stress as one of the shared early triggers of both diseases, and IHC studies validated the same in the lungs of deceased subjects with COVID-19 and SARS-CoV-2-challenged hamster lungs. Lungs from tg-mice, in which ER stress is induced specifically in the AT2 cells, faithfully recapitulate the host immune response and alveolar cytopathic changes that are induced by SARS-CoV-2.

INTERPRETATION

Like IPF, COVID-19 may be driven by injury-induced ER stress that culminates into progenitor state arrest and SASP in AT2 cells. The ViP signatures in monocytes may be key determinants of prognosis. The insights, signatures, disease models identified here are likely to spur the development of therapies for patients with IPF and other fibrotic interstitial lung diseases.

FUNDING

This work was supported by the National Institutes for Health grants R01- GM138385 and AI155696 and funding from the Tobacco-Related disease Research Program (R01RG3780).

COVID-19 lung disease shares driver AT2 cytopathic features with Idiopathic pulmonary fibrosis

Background

In the aftermath of Covid-19, some patients develop a fibrotic lung disease, i.e., p ost- C OVID-19 l ung d isease (PCLD), for which we currently lack insights into pathogenesis, disease models, or treatment options.

Method

Using an AI-guided approach, we analyzed > 1000 human lung transcriptomic datasets associated with various lung conditions using two viral pandemic signatures (ViP and sViP) and one covid lung-derived signature. Upon identifying similarities between COVID-19 and idiopathic pulmonary fibrosis (IPF), we subsequently dissected the basis for such similarity from molecular, cytopathic, and immunologic perspectives using a panel of IPF-specific gene signatures, alongside signatures of alveolar type II (AT2) cytopathies and of prognostic monocyte-driven processes that are known drivers of IPF. Transcriptome-derived findings were used to construct protein-protein interaction (PPI) network to identify the major triggers of AT2 dysfunction. Key findings were validated in hamster and human adult lung organoid (ALO) pre-clinical models of COVID-19 using immunohistochemistry and qPCR.

Findings

COVID-19 resembles IPF at a fundamental level; it recapitulates the gene expression patterns (ViP and IPF signatures), cytokine storm (IL15-centric), and the AT2 cytopathic changes, e.g., injury, DNA damage, arrest in a transient, damage-induced progenitor state, and senescence-associated secretory phenotype (SASP). These immunocytopathic features were induced in pre-clinical COVID models (ALO and hamster) and reversed with effective anti-CoV-2 therapeutics in hamsters. PPI-network analyses pinpointed ER stress as one of the shared early triggers of both diseases, and IHC studies validated the same in the lungs of deceased subjects with COVID-19 and SARS-CoV-2-challenged hamster lungs. Lungs from tg - mice, in which ER stress is induced specifically in the AT2 cells, faithfully recapitulate the host immune response and alveolar cytopathic changes that are induced by SARS-CoV-2.

Interpretation

Like IPF, COVID-19 may be driven by injury-induced ER stress that culminates into progenitor state arrest and SASP in AT2 cells. The ViP signatures in monocytes may be key determinants of prognosis. The insights, signatures, disease models identified here are likely to spur the development of therapies for patients with IPF and other fibrotic interstitial lung diseases.

Funding

This work was supported by the National Institutes for Health grants R01-GM138385 and AI155696 and funding from the Tobacco-Related disease Research Program (R01RG3780).

One Sentence Summary

Severe COVID-19 triggers cellular processes seen in fibrosing Interstitial Lung Disease.

RESEARCH IN CONTEXT

Evidence before this study: In its aftermath, the COVID-19 pandemic has left many survivors, almost a third of those who recovered, with a mysterious long-haul form of the disease which culminates in a fibrotic form of interstitial lung disease (post-COVID-19 ILD). Post-COVID-19 ILD remains a largely unknown entity. Currently, we lack insights into the core cytopathic features that drive this condition.Added value of this study: Using an AI-guided approach, which involves the use of sets of gene signatures, protein-protein network analysis, and a hamster model of COVID-19, we have revealed here that COVID-19 -lung fibrosis resembles IPF, the most common form of ILD, at a fundamental levelâ€"showing similar gene expression patterns in the lungs and blood, and dysfunctional AT2 processes (ER stress, telomere instability, progenitor cell arrest, and senescence). These findings are insightful because AT2 cells are known to contain an elegant quality control network to respond to intrinsic or extrinsic stress; a failure of such quality control results in diverse cellular phenotypes, of which ER stress appears to be a point of convergence, which appears to be sufficient to drive downstream fibrotic remodeling in the lung.Implications of all the available evidence: Because unbiased computational methods identified the shared fundamental aspects of gene expression and cellular processes between COVID-19 and IPF, the impact of our findings is likely to go beyond COVID-19 or any viral pandemic. The insights, tools (disease models, gene signatures, and biomarkers), and mechanisms identified here are likely to spur the development of therapies for patients with IPF and, other fibrotic interstitial lung diseases, all of whom have limited or no treatment options. To dissect the validated prognostic biomarkers to assess and track the risk of pulmonary fibrosis and develop therapeutics to halt fibrogenic progression.

Altered pharmacology and toxicology during ageing: implications for lung disease

PURPOSE OF REVIEW

Drug use in elderly people is high compared to younger people. Simultaneously, elderly are at greater risk when exposed to environmental substances. It is puzzling therefore, that ageing, as a variable in pharmacological and toxicological processes is not investigated in more depth. Moreover, recent data suggest that molecular manifestations of the ageing process also hallmark the pathogenesis of chronic lung diseases, which may impact pharmacology and toxicology.

RECENT FINDINGS

In particular, absorption, distribution, metabolism and excretion (ADME) processes of drugs and toxins alter because of ageing. Polypharmacy, which is quite usual with increasing age, increases the risk of drug-drug interactions. Individual differences in combination of drugs use in conjunction with individual variations in drug metabolizing enzymes can influence lung function.

SUMMARY

Exploring exposure throughout life (i.e. during ageing) to potential triggers, including polypharmacy, may avoid lung disease or unexplained cases of lung damage. Understanding of the ageing process further unravels critical features of chronic lung disease and helps to define new protective targets and therapies. Optimizing resilience can be key in pharmacology and toxicology and helps in maintaining healthy lungs for a longer period.

Aging and Susceptibility to Pulmonary Disease

The lungs are continually subjected to noxious and inert substances, are immunologically active, and are in a constant state of damage and repair. This makes the pulmonary system particularly vulnerable to diseases of aging. Aging can be understood as random molecular damage that is unrepaired and accumulates over time, resulting in cellular defects and tissue dysfunction. The breakdown of cellular mechanisms, including stem cell exhaustion, genomic instability, telomere attrition, epigenetic alteration, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, altered intercellular communication, and changes in the extracellular matrix is thought to advance the aging process itself. Chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and cancers illustrate a pathologic breakdown in these mechanisms beyond normal aging. The immune system becomes less effective with advancing age. There is a low-level state of chronic inflammation termed inflammaging which is thought to be driven by immunosenescence, the changes in the innate and adaptive immune systems with advancing age that lead to dysregulation and decreased effectiveness of the immune system. These processes of aging lead to expected changes in the form and function of the respiratory system, most notably a loss of lung elasticity, decrease in respiratory muscle strength, increase in ventilation-perfusion mismatching, and stiffening of the vasculature. The astute clinician is aware of these expected findings and does not often attribute dyspnea to aging alone. Maintaining a low threshold to investigate for comorbid disease and understanding how pulmonary disease presents differently in the elderly than in younger adults can improve clinical outcomes. © 2022 American Physiological Society. Compr Physiol 12:3509-3522, 2022.

Effects of Hypocalcemic Vitamin D Analogs in the Expression of DNA Damage Induced in Minilungs from hESCs: Implications for Lung Fibrosis

In our previous work, we evaluated the therapeutic effects of 1α,25-Dihydroxyvitamin D₃, the biologically active form of vitamin D, in the context of bleomycin-induced lung fibrosis. Contrary to the expected, vitamin D supplementation increased the DNA damage expression and cellular senescence in alveolar epithelial type II cells and aggravated the overall lung pathology induced in mice by bleomycin. These effects were probably due to an alteration in the cellular DNA double-strand breaks’ repair capability. In the present work, we have evaluated the effects of two hypocalcemic vitamin D analogs (calcipotriol and paricalcitol) in the expression of DNA damage in the context of minilungs derived from human embryonic stem cells and in the cell line A549.

Emerging role of exosomes in the pathology of chronic obstructive pulmonary diseases; destructive and therapeutic properties

Chronic obstructive pulmonary disease (COPD) is known as the third leading cause of human death globally. Enhanced chronic inflammation and pathological remodeling are the main consequences of COPD, leading to decreased life span. Histological and molecular investigations revealed that prominent immune cell infiltration and release of several cytokines contribute to progressive chronic remodeling. Recent investigations have revealed that exosomes belonging to extracellular vesicles are involved in the pathogenesis of COPD. It has been elucidated that exosomes secreted from immune cells are eligible to carry numerous pro-inflammatory factors exacerbating the pathological conditions. Here, in this review article, we have summarized various and reliable information about the negative role of immune cell-derived exosomes in the remodeling of pulmonary tissue and airways destruction in COPD patients.

Senescent macrophages alter fibroblast fibrogenesis in response to SARS-CoV-2 infection

SARS-CoV-2 has, since its emergence in 2019, become a global pandemic. Disease outcomes are worsened in older patients who are infected. The causes for this is multifactorial, but one potential cause for this disparity is increased rates of cellular senescence in older individuals, particularly in immune cells. Cellular senescence, the accumulation of factors resulting in cell growth arrest and apoptosis resistance, increases as individuals age. In immune cells, senescence is associated with increased inflammation, and alterations in immune response. We utilized a co-culture system consisting of senescent or non-senescent macrophages directly cultured with fibroblasts, and infected with SARS-CoV-2. We assessed the expression of collagen and fibronectin, important molecules in the extracellular matrix, as well as a number of fibrogenic factors. We observed that infection with SARS-CoV-2 induced collagen production in co-cultures with senescent, but not non-senescent macrophages. Fibronectin expression was decreased in both co-culture conditions. While significant results were not observed, concentrations of other fibrogenic molecules were consistent with the collagen results. These data demonstrate that senescence in macrophages alters the production of fibrotic molecules from fibroblasts in a SARS-CoV-2 infection model. As collagen and fibronectin expression are generally directly correlated, this suggests that senescence dysregulates fibrogenesis in response to infection with SARS-CoV-2. There is a need to further investigate the mechanisms for these changes.