Senotherapeutics: Targeting senescence in idiopathic pulmonary fibrosis

Mitochondrial dynamics in pulmonary disease: Implications for the potential therapeutics

Mitochondria are dynamic organelles that continuously undergo fusion/fission to maintain normal cell physiological activities and energy metabolism. When mitochondrial dynamics is unbalanced, mitochondrial homeostasis is broken, thus damaging mitochondrial function. Accumulating evidence demonstrates that impairment in mitochondrial dynamics leads to lung tissue injury and pulmonary disease progression in a variety of disease models, including inflammatory responses, apoptosis, and barrier breakdown, and that the role of mitochondrial dynamics varies among pulmonary diseases. These findings suggest that modulation of mitochondrial dynamics may be considered as a valid therapeutic strategy in pulmonary diseases. In this review, we discuss the current evidence on the role of mitochondrial dynamics in pulmonary diseases, with a particular focus on its underlying mechanisms in the development of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD), asthma, pulmonary fibrosis (PF), pulmonary arterial hypertension (PAH), lung cancer and bronchopulmonary dysplasia (BPD), and outline effective drugs targeting mitochondrial dynamics-related proteins, highlighting the great potential of targeting mitochondrial dynamics in the treatment of pulmonary disease.

Quercetin influences intestinal dysbacteriosis and delays alveolar epithelial cell senescence by regulating PTEN/PI3K/AKT signaling in pulmonary fibrosis

Pulmonary fibrosis is a chronic and progressive lung disease with high mortality. This study aims to explore the protective mechanism of quercetin against pulmonary fibrosis regarding cell senescence and gut microbiota. Rats were intratracheally injected with bleomycin (BLM) to establish a pulmonary fibrosis rat model. RLE-6TN cells were stimulated with BLM to build the model of alveolar epithelial cell senescence, and RLE-6TN-derived conditional medium (CM) was harvested to further culture fibroblasts. Histopathological changes were assessed by H&E and Masson staining. α-SMA expression was assessed by immunofluorescence assay. Senescence-associated β-galactosidase (SA-β-gal) staining and senescence-associated secretory phenotype (SASP) cytokine assay were conducted to assess cellular senescence. Gut microbiota was analyzed by 16S rRNA gene sequencing. The fibrosis-, senescence-, and PTEN/PI3K/AKT signaling-related proteins were examined by western blot. In BLM-induced pulmonary fibrosis rats, quercetin exerted its protective effects by reducing histological injury and collagen deposition, lessening cellular senescence, and regulating gut microbiota. In BLM-induced alveolar epithelial cell senescence, quercetin inhibited senescence, lessened SASP cytokine secretion of alveolar epithelial cells, and further ameliorated collagen deposition in fibroblasts. In addition, quercetin might exert its functional effects by regulating the PTEN/PI3K/AKT signaling pathway. Moreover, quercetin regulated intestinal dysbacteriosis in BLM-induced pulmonary fibrosis rats, especially boosting the abundance of Akkermansia. To conclude, our findings provide an in-depth understanding of the potential mechanism behind the protective role of quercetin against pulmonary fibrosis.

Fibroblast senescence-associated extracellular matrix promotes heterogeneous lung niche

Senescent cell accumulation in the pulmonary niche is associated with heightened susceptibility to age-related disease, tissue alterations, and ultimately a decline in lung function. Our current knowledge of senescent cell-extracellular matrix (ECM) dynamics is limited, and our understanding of how senescent cells influence spatial ECM architecture changes over time is incomplete. Herein is the design of an in vitro model of senescence-associated extracellular matrix (SA-ECM) remodeling using a senescent lung fibroblast-derived matrix that captures the spatiotemporal dynamics of an evolving senescent ECM architecture. Multiphoton second-harmonic generation microscopy was utilized to examine the spatial and temporal dynamics of fibroblast SA-ECM remodeling, which revealed a biphasic process that established a disordered and heterogeneous architecture. Additionally, we observed that inhibition of transforming growth factor-β signaling during SA-ECM remodeling led to improved local collagen fiber organization. Finally, we examined patient samples diagnosed with pulmonary fibrosis to further tie our results of the in vitro model to clinical outcomes. Moreover, we observed that the senescence marker p16 is correlated with local collagen fiber disorder. By elucidating the temporal dynamics of SA-ECM remodeling, we provide further insight on the role of senescent cells and their contributions to pathological ECM remodeling.

A pipeline for senolytics

There is intense interest in identifying compounds that selectively kill senescent cells, termed senolytics, for ameliorating age-related comorbidities. However, screening for senolytic compounds currently relies on primary cells or cell lines where senescence is induced in vitro. Given the complexity of senescent cells across tissues and diseases, this approach may not target the senescent cells that develop under specific conditions in vivo. In this issue of the JCI, Lee et al. describe a pipeline for high-throughput drug screening of senolytic compounds where senescence was induced in vivo and identify the HSP90 inhibitor XL888 as a candidate senolytic to treat idiopathic pulmonary fibrosis.

Tetrandrine alleviates pulmonary fibrosis by inhibiting alveolar epithelial cell senescence through PINK1/Parkin-mediated mitophagy

Idiopathic pulmonary fibrosis (IPF) is a fatal and insidious interstitial lung disease. So far, there are no effective drugs for preventing the disease process. Cellular senescence plays a critical role in the development of IPF, with the senescence and insufficient mitophagy of alveolar epithelial cells being implicated in its pathogenesis. Tetrandrine is a natural alkaloid which is now produced synthetically. It was known that the tetrandrine has anti-fibrotic effects, but the efficacy and mechanisms are still not well evaluated. Here, we reveal the roles of tetrandrine on AECs senescence and the antifibrotic effects by using a bleomycin challenged mouse model of pulmonary fibrosis and a bleomycin-stimulated mouse alveolar epithelial cell line (MLE-12). We performed the β-galactosidase staining, immunohistochemistry and fluorescence to assess senescence in MLE-12 cells. The mitophagy levels were detected by co-localization of LC3 and COVIX. Our findings indicate that tetrandrine suppressed bleomycin-induced fibroblast activation and ultimately blocked the increase of collagen deposition in mouse model lung tissue. It has significantly inhibited the bleomycin-induced senescence and senescence-associated secretory phenotype (SASP) in alveolar epithelial cells (AECs). Mechanistically, tetrandrine suppressed the decrease of mitochondrial autophagy-related protein expression to rescue the bleomycin-stimulated impaired mitophagy in MLE-12 cells. We revealed that knockdown the putative kinase 1 (PINK1) gene by a short interfering RNA (siRNA) could abolish the ability of tetrandrine and reverse the MLE-12 cells senescence, which indicated the mitophagy of MLE-12 cells is PINK1 dependent. Our data suggest the tetrandrine could be a novel and effective drug candidate for lung fibrosis and senescence-related fibrotic diseases.

An in vivo screening platform identifies senolytic compounds that target p16INK4a+ fibroblasts in lung fibrosis

The appearance of senescent cells in age-related diseases has spurred the search for compounds that can target senescent cells in tissues, termed senolytics. However, a major caveat with current senolytic screens is the use of cell lines as targets where senescence is induced in vitro, which does not necessarily reflect the identity and function of pathogenic senescent cells in vivo. Here, we developed a new pipeline leveraging a fluorescent murine reporter that allows for isolation and quantification of p16Ink4a+ cells in diseased tissues. By high-throughput screening in vitro, precision-cut lung slice (PCLS) screening ex vivo, and phenotypic screening in vivo, we identified a HSP90 inhibitor, XL888, as a potent senolytic in tissue fibrosis. XL888 treatment eliminated pathogenic p16Ink4a+ fibroblasts in a murine model of lung fibrosis and reduced fibrotic burden. Finally, XL888 preferentially targeted p16INK4a-hi human lung fibroblasts isolated from patients with idiopathic pulmonary fibrosis (IPF), and reduced p16INK4a+ fibroblasts from IPF PCLS ex vivo. This study provides proof of concept for a platform where p16INK4a+ cells are directly isolated from diseased tissues to identify compounds with in vivo and ex vivo efficacy in mice and humans, respectively, and provides a senolytic screening platform for other age-related diseases.

Different Levels of Autophagy Activity in Mesenchymal Stem Cells Are Involved in the Progression of Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is an age-related lung interstitial disease that occurs predominantly in people over 65 years of age and for which there is a lack of effective therapeutic agents. It has demonstrated that mesenchymal stem cells (MSCs) including alveolar epithelial cells (AECs) can perform repair functions. However, MSCs lose their repair functions due to their distinctive aging characteristics, eventually leading to the progression of IPF. Recent breakthroughs have revealed that the degree of autophagic activity influences the renewal and aging of MSCs and determines the prognosis of IPF. Autophagy is a lysosome-dependent pathway that mediates the degradation and recycling of intracellular material and is an efficient way to renew the nonnuclear (cytoplasmic) part of eukaryotic cells, which is essential for maintaining cellular homeostasis and is a potential target for regulating MSCs function. Therefore, this review focuses on the changes in autophagic activity of MSCs, clarifies the relationship between autophagy and health status of MSCs and the effect of autophagic activity on MSCs senescence and IPF, providing a theoretical basis for promoting the clinical application of MSCs.

Cutaneous Redox Senescence

Our current understanding of skin cell senescence involves the role of environmental stressors (UV, O3, cigarette smoke, particulate matter, etc.), lifestyle (diet, exercise, etc.) as well as genetic factors (metabolic changes, hormonal, etc.). The common mechanism of action of these stressors is the disturbance of cellular redox balance characterized by increased free radicals and reactive oxygen species (ROS), and when these overload the intrinsic antioxidant defense system, it can lead to an oxidative stress cellular condition. The main redox mechanisms that activate cellular senescence in the skin involve (1) the oxidative damage of telomeres causing their shortening; (2) the oxidation of proteomes and DNA damage; (3) an a in lysosomal mass through the increased activity of resident enzymes such as senescence-associated β-galactosidase (SA-β-gal) as well as other proteins that are products of lysosomal activity; (4) and the increased expression of SASP, in particular pro-inflammatory cytokines transcriptionally regulated by NF-κB. However, the main targets of ROS on the skin are the proteome (oxi-proteome), followed by telomeres, nucleic acids (DNAs), lipids, proteins, and cytoplasmic organelles. As a result, cell cycle arrest pathways, lipid peroxidation, increased lysosomal content and dysfunctional mitochondria, and SASP synthesis occur. Furthermore, oxidative stress in skin cells increases the activity of p16INK4A and p53 as inhibitors of Rb and CDks, which are important for maintaining the cell cycle. p53 also promotes the inactivation of mTOR-mediated autophagic and apoptotic pathways, leading to senescence. However, these markers alone cannot establish the state of cellular senescence, and multiple analyses are encouraged for confirmation. An updated and more comprehensive approach to investigating skin senescence should include further assays of ox-inflammatory molecular pathways that can consolidate the understanding of cutaneous redox senescence.

Researching New Drug Combinations with Senolytic Activity Using Senescent Human Lung Fibroblasts MRC-5 Cell Line

Therapeutically targeting senescent cells seems to be an interesting perspective in treating chronic lung diseases, which are often associated with human aging. The combination of the drug dasatinib and the polyphenol quercetin is used in clinical trials as a senolytic, and the first results point to the relief of physical dysfunction in patients with idiopathic pulmonary fibrosis. In this work, we tested new combinations of drugs and polyphenols, looking for senolytic activity using human lung fibroblasts (MRC-5 cell line) with induced senescence. We researched drugs, such as azithromycin, rapamycin, metformin, FK-506, aspirin, and dasatinib combined with nine natural polyphenols, namely caffeic acid, chlorogenic acid, ellagic acid, ferulic acid, gallic acid, epicatechin, hesperidin, quercetin, and resveratrol. We found new effective senolytic combinations with dasatinib and ellagic acid and dasatinib and resveratrol. Both drug combinations increased apoptosis, reduced BCL-2 expression, and increased caspase activity in senescent MRC-5 cells. Ellagic acid senolytic activity was more potent than quercetin, and resveratrol counteracted inflammatory cytokine release during senolysis in vitro. In conclusion, dasatinib and ellagic acid and dasatinib and resveratrol present in vitro senolytic potential like that observed for the combination in clinical trials of dasatinib and quercetin, and maybe they could be future alternatives in the senotherapeutic field.

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.

Total alkaloids of bulbus of Fritillaria cirrhosa alleviate bleomycin-induced inflammation and pulmonary fibrosis in rats by inhibiting TGF-β and NF-κB signaling pathway

Background

Bulbus of Fritillaria cirrhosa is a medicinal and edible plant that has the functions of clearing away heat and moisturizing the lungs, resolving phlegm, and relieving coughs. Its ethanol extract has been proven to have a therapeutic effect on lung diseases. Pulmonary fibrosis is a respiratory disease that forms scars in lung tissue, leading to severe respiratory problems. However, the therapeutic effect of total alkaloids of bulbus of Fritillaria cirrhosa (BFC-TA) on pulmonary fibrosis has not been confirmed.

Objective

This study aimed to investigate the therapeutic effect of total alkaloids of Fritillaria cirrhosa on pulmonary fibrosis rat model and explore its potential mechanism.

Design

The total alkaloids in the bulbus of Fritillaria cirrhosa were purified using cation exchange resin. The alkaloids contained in the BFC-TA were identified, and the concentration of alkaloids was determined by High Performance Liquid Chromatography-Diode Array Detector-Evaporative Light Scattering Detector (HPLC-DAD-ELSD). Bleomycin (BLM) (5.0 mg/kg) was instilled into the trachea of 60 rats to establish a pulmonary fibrosis model. After 7 days, BFC-TA (34.2, 68.4, and 136.8 mg/kg) was administered continuously for 21 days. During this period, the body weight changes of the rats were measured, the levels of hydroxyproline (HYP) and inflammatory factors were measured in the collected serum, and the histological analysis of the lung tissue was performed by staining technology. Western blotting and quantitative Polymerase Chain Reaction (qPCR) were used to assess the protein and gene composition of inflammation and transforming growth factor-β (TGF-β) signaling pathways.

Results

Nine main components (Peimisine, Imperialine-3-β-D-glucoside, Yibeinoside A, Imperialine, Peiminine, Isopeimine, Hupehenine, Delavinone, Ebeiedinone) were determined by HPLC-DAD-ELSD, and the contents of Peimisine, Imperialine-3-β-D-glucoside and Imperialine were determined. BFC-TA (34.2, 68.4, and 136.8 mg/kg) reduced the levels of pro-inflammatory factors, increased the levels of anti-inflammatory factors, dose-dependently improved the morphology of lung tissue. And during epithelial-mesenchymal transition process, BFC-TA dose-dependently reduced the expression of E-cadherin, dose-dependently increased the expression of Fibronectin. In addition, Western blot analysis and qPCR results showed that inhibiting NF-κB and TGF-β-related signaling pathways effectively slowed down the occurrence of BLM-induced pulmonary fibrosis in rats. And the therapeutic effect of BFC-TA (136.8 mg/kg) is better than that of pirfenidon (PFD) (150 mg/kg).

Conclusion

BFC-TA effectively alleviates the progression of the BLM-induced pulmonary fibrosis rat model by regulating the inflammatory response in the lungs and the expression of the TGF-β signaling pathway.

Regulation of epithelial transitional states in murine and human pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive scarring disease arising from impaired regeneration of the alveolar epithelium after injury. During regeneration, type 2 alveolar epithelial cells (AEC2s) assume a transitional state that upregulates multiple keratins and ultimately differentiate into AEC1s. In IPF, transitional AECs accumulate with ineffectual AEC1 differentiation. However, whether and how transitional cells cause fibrosis, whether keratins regulate transitional cell accumulation and fibrosis, and why transitional AECs and fibrosis resolve in mouse models but accumulate in IPF are unclear. Here, we show that human keratin 8 (KRT8) genetic variants were associated with IPF. Krt8-/- mice were protected from fibrosis and accumulation of the transitional state. Keratin 8 (K8) regulated the expression of macrophage chemokines and macrophage recruitment. Profibrotic macrophages and myofibroblasts promoted the accumulation of transitional AECs, establishing a K8-dependent positive feedback loop driving fibrogenesis. Finally, rare murine transitional AECs were highly senescent and basaloid and may not differentiate into AEC1s, recapitulating the aberrant basaloid state in human IPF. We conclude that transitional AECs induced and were maintained by fibrosis in a K8-dependent manner; in mice, most transitional cells and fibrosis resolved, whereas in human IPF, transitional AECs evolved into an aberrant basaloid state that persisted with progressive fibrosis.

Death-seq identifies regulators of cell death and senolytic therapies

Selectively ablating damaged cells is an evolving therapeutic approach for age-related disease. Current methods for genome-wide screens to identify genes whose deletion might promote the death of damaged or senescent cells are generally underpowered because of the short timescales of cell death as well as the difficulty of scaling non-dividing cells. Here, we establish "Death-seq," a positive-selection CRISPR screen optimized to identify enhancers and mechanisms of cell death. Our screens identified synergistic enhancers of cell death induced by the known senolytic ABT-263. The screen also identified inducers of cell death and senescent cell clearance in models of age-related diseases by a related compound, ABT-199, which alone is not senolytic but exhibits less toxicity than ABT-263. Death-seq enables the systematic screening of cell death pathways to uncover molecular mechanisms of regulated cell death subroutines and identifies drug targets for the treatment of diverse pathological states such as senescence, cancer, and fibrosis.

Novel approaches to target fibroblast mechanotransduction in fibroproliferative diseases

The ability of cells to sense and respond to changes in mechanical environment is vital in conditions of organ injury when the architecture of normal tissues is disturbed or lost. Among the various cellular players that respond to injury, fibroblasts take center stage in re-establishing tissue integrity by secreting and organizing extracellular matrix into stabilizing scar tissue. Activation, activity, survival, and death of scar-forming fibroblasts are tightly controlled by mechanical environment and proper mechanotransduction ensures that fibroblast activities cease after completion of the tissue repair process. Conversely, dysregulated mechanotransduction often results in fibroblast over-activation or persistence beyond the state of normal repair. The resulting pathological accumulation of extracellular matrix is called fibrosis, a condition that has been associated with over 40% of all deaths in the industrialized countries. Consequently, elements in fibroblast mechanotransduction are scrutinized for their suitability as anti-fibrotic therapeutic targets. We review the current knowledge on mechanically relevant factors in the fibroblast extracellular environment, cell-matrix and cell-cell adhesion structures, stretch-activated membrane channels, stress-regulated cytoskeletal structures, and co-transcription factors. We critically discuss the targetability of these elements in therapeutic approaches and their progress in pre-clinical and/or clinical trials to treat organ fibrosis.

Pulmonary inflammation and fibroblast immunoregulation: from bench to bedside

In recent years, there has been an explosion of interest in how fibroblasts initiate, sustain, and resolve inflammation across disease states. Fibroblasts contain heterogeneous subsets with diverse functionality. The phenotypes of these populations vary depending on their spatial distribution within the tissue and the immunopathologic cues contributing to disease progression. In addition to their roles in structurally supporting organs and remodeling tissue, fibroblasts mediate critical interactions with diverse immune cells. These interactions have important implications for defining mechanisms of disease and identifying potential therapeutic targets. Fibroblasts in the respiratory tract, in particular, determine the severity and outcome of numerous acute and chronic lung diseases, including asthma, chronic obstructive pulmonary disease, acute respiratory distress syndrome, and idiopathic pulmonary fibrosis. Here, we review recent studies defining the spatiotemporal identity of the lung-derived fibroblasts and the mechanisms by which these subsets regulate immune responses to insult exposures and highlight past, current, and future therapeutic targets with relevance to fibroblast biology in the context of acute and chronic human respiratory diseases. This perspective highlights the importance of tissue context in defining fibroblast-immune crosstalk and paves the way for identifying therapeutic approaches to benefit patients with acute and chronic pulmonary disorders.

The aged extracellular matrix and the profibrotic role of senescence-associated secretory phenotype

Idiopathic pulmonary fibrosis (IPF) is an irreversible and fatal lung disease that is primarily found in the elderly population, and several studies have demonstrated that aging is the major risk factor for IPF. IPF is characterized by the presence of apoptosis-resistant, senescent fibroblasts that generate an excessively stiff extracellular matrix (ECM). The ECM profoundly affects cellular functions and tissue homeostasis, and an aberrant ECM is closely associated with the development of lung fibrosis. Aging progressively alters ECM components and is associated with the accumulation of senescent cells that promote age-related tissue dysfunction through the expression of factors linked to a senescence-associated secretary phenotype (SASP). There is growing evidence that SASP factors affect various cell behaviors and influence ECM turnover in lung tissue through autocrine and/or paracrine signaling mechanisms. Since life expectancy is increasing worldwide, it is important to elucidate how aging affects ECM dynamics and turnover via SASP and thereby promotes lung fibrosis. In this review, we will focus on the molecular properties of SASP and its regulatory mechanisms. Furthermore, the pathophysiological process of ECM remodeling by SASP factors and the influence of an altered ECM from aged lungs on the development of lung fibrosis will be highlighted. Finally, recent attempts to target ECM alteration and senescent cells to modulate fibrosis will be introduced.NEW & NOTEWORTHY Aging is the most prominent nonmodifiable risk factor for various human diseases including Idiopathic pulmonary fibrosis. Aging progressively alters extracellular matrix components and is associated with the accumulation of senescent cells that promote age-related tissue dysfunction. In this review, we will discuss the pathological impact of aging and senescence on lung fibrosis via senescence-associated secretary phenotype factors and potential therapeutic approaches to limit the progression of lung fibrosis.

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

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

Inhibition of tyrosine kinase Fgr prevents radiation-induced pulmonary fibrosis (RIPF)

Cellular senescence is involved in the development of pulmonary fibrosis as well as in lung tissue repair and regeneration. Therefore, a strategy of removal of senescent cells by senolytic drugs may not produce the desired therapeutic result. Previously we reported that tyrosine kinase Fgr is upregulated in ionizing irradiation-induced senescent cells. Inhibition of Fgr reduces the production of profibrotic proteins by radiation-induced senescent cells in vitro; however, a mechanistic relationship between senescent cells and radiation-induced pulmonary fibrosis (RIPF) has not been established. We now report that senescent cells from the lungs of mice with RIPF, release profibrotic proteins for target cells and secrete chemotactic proteins for marrow cells. The Fgr inhibitor TL02-59, reduces this release of profibrotic chemokines from the lungs of RIPF mice, without reducing numbers of senescent cells. In vitro studies demonstrated that TL02-59 abrogates the upregulation of profibrotic genes in target cells in transwell cultures. Also, protein arrays using lung fibroblasts demonstrated that TL02-59 inhibits the production of chemokines involved in the migration of macrophages to the lung. In thoracic-irradiated mice, TL02-59 prevents RIPF, significantly reduces levels of expression of fibrotic gene products, and significantly reduces the recruitment of CD11b+ macrophages to the lungs. Bronchoalveolar lavage (BAL) cells from RIPF mice show increased Fgr and other senescent cell markers including p16. In human idiopathic pulmonary fibrosis (IPF) and in RIPF, Fgr, and other senescent cell biomarkers are increased. In both mouse and human RIPF, there is an accumulation of Fgr-positive proinflammatory CD11b+ macrophages in the lungs. Thus, elevated levels of Fgr in lung senescent cells upregulate profibrotic gene products, and chemokines that might be responsible for macrophage infiltration into lungs. The detection of Fgr in senescent cells that are obtained from BAL during the development of RIPF may help predict the onset and facilitate the delivery of medical countermeasures.

An update on current and emerging drug treatments for idiopathic pulmonary fibrosis

INTRODUCTION

Idiopathic Pulmonary Fibrosis (IPF) is a progressive and devastating lung disease, characterized by progressive lung scarring.

AREAS COVERED

Prior to antifibrotic therapy (pirfenidone and nintedanib), there was no validated pharmaceutical therapy for IPF. Both antifibrotics can slow disease progression, however, IPF remains a detrimental disease with poor prognosis and treated survival rates of less than 7 years from diagnosis. Despite their effect the disease remains non-reversible and progressing whilst their side effect profile is often challenging. Treatment of comorbidities is also crucial. In this review, we discuss the current pharmacological management as well as management of comorbidities and symptoms. We also reviewed clinicaltrials.gov and summarised all the mid to late stage clinical trials (phase II and III) registered in IPF over the last 7 years and discuss the most promising drugs in clinical development.

EXPERT OPINION

Future for IPF management will need to focus on current unresolved issues. First a primary pathogenetic pathway has not been clearly identified. Future management may involve a combination of brushstroke approach with antifibrotics with targeted treatments for specific pathways in patient subsets following an 'oncological' approach. Another unmet need is management of exacerbations, which are deathly in most cases as well as either treating or preventing lung cancer.

Early events marking lung fibroblast transition to profibrotic state in idiopathic pulmonary fibrosis

BACKGROUND

Idiopathic Pulmonary Fibrosis (IPF) is an age-associated progressive lung disease with accumulation of scar tissue impairing gas exchange. Previous high-throughput studies elucidated the role of cellular heterogeneity and molecular pathways in advanced disease. However, critical pathogenic pathways occurring in the transition of fibroblasts from normal to profibrotic have been largely overlooked.

METHODS

We used single cell transcriptomics (scRNA-seq) from lungs of healthy controls and IPF patients (lower and upper lobes). We identified fibroblast subclusters, genes and pathways associated with early disease. Immunofluorescence assays validated the role of MOXD1 early in fibrosis.

RESULTS

We identified four distinct fibroblast subgroups, including one marking the normal-to-profibrotic state transition. Our results show for the first time that global downregulation of ribosomal proteins and significant upregulation of the majority of copper-binding proteins, including MOXD1, mark the IPF transition. We find no significant differences in gene expression in IPF upper and lower lobe samples, which were selected to have low and high degree of fibrosis, respectively.

CONCLUSIONS

Early events during IPF onset in fibroblasts include dysregulation of ribosomal and copper-binding proteins. Fibroblasts in early stage IPF may have already acquired a profibrotic phenotype while hallmarks of advanced disease, including fibroblast foci and honeycomb formation, are still not evident. The new transitional fibroblasts we discover could prove very important for studying the role of fibroblast plasticity in disease progression and help develop early diagnosis tools and therapeutic interventions targeting earlier disease states.

Senolytics dasatinib and quercetin in idiopathic pulmonary fibrosis: results of a phase I, single-blind, single-center, randomized, placebo-controlled pilot trial on feasibility and tolerability

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is an age-related, chronic, irreversible fibrotic lung disease. IPF is associated with increased senescent cells burden, which may be alleviated with administration of senescent cell targeting drugs termed 'senolytics'. We previously conducted an open-label single-arm pilot study of the senolytic combination of dasatinib and quercetin (D + Q) in patients with IPF but lack of control group limited interpretation and next-stage trial planning. The primary objective of this confirmatory randomized placebo-controlled pilot trial (RCT; NCT02874989) was to report adverse events with D + Q and inform study feasibility for future efficacy trials.

METHODS

Twelve participants with IPF aged >50 years were blinded and randomized at a 1:1 ratio to either receive three weeks of D + Q (D: 100 mg/d and Q: 1250 mg/d, three consecutive days per week) or matching placebo.

FINDINGS

All participants completed the scheduled drug dosing regimen (108/108 doses) and planned assessments (60/60). While the placebo arm reported fewer overall non-serious AEs (65 vs 22), there were no serious adverse events related to D + Q. Most AEs in the D + Q arm are common in IPF patients or anticipated side effects of D. Sleep disturbances and anxiety were disproportionately represented in the D + Q arm (4/6 vs 0/6). Frailty, pulmonary, or physical function were explored before and after intermittent D + Q; though under-powered to evaluate change, these measures do not appear to differ meaningfully between groups.

INTERPRETATION

Intermittently-dosed D + Q in patients with IPF is feasible and generally well-tolerated. Further prospective studies, such as a larger RCT, are needed to confirm the safety and efficacy of D + Q in patients with IPF.

FUNDING

This work was supported by National Institutes of Health grants R33AG61456 (JLK, TT), Robert and Arlene Kogod (JLK, TT), the Connor Fund (JLK, TT), Robert J. and Theresa W. Ryan (JLK, TT), and the Noaber Foundation (JLK, TT) San Antonio Claude D. Pepper Older Americans Independence Center's (OAIC)Pilot/Exploratory Studies Core (PESC) Grant (AMN, NM); NIHK01 AG059837 (JNJ), P30 AG021332 (SBK, JNJ); NIHR37 AG013925 (JLK), the Connor Group (JLK), Glenn/AFAR BIG Award (JLK), Robert J. and Theresa W. Ryan (JLK), and the Noaber and Ted Nash Long Life Foundations (JLK).

Cellular rejuvenation: molecular mechanisms and potential therapeutic interventions for diseases

The ageing process is a systemic decline from cellular dysfunction to organ degeneration, with more predisposition to deteriorated disorders. Rejuvenation refers to giving aged cells or organisms more youthful characteristics through various techniques, such as cellular reprogramming and epigenetic regulation. The great leaps in cellular rejuvenation prove that ageing is not a one-way street, and many rejuvenative interventions have emerged to delay and even reverse the ageing process. Defining the mechanism by which roadblocks and signaling inputs influence complex ageing programs is essential for understanding and developing rejuvenative strategies. Here, we discuss the intrinsic and extrinsic factors that counteract cell rejuvenation, and the targeted cells and core mechanisms involved in this process. Then, we critically summarize the latest advances in state-of-art strategies of cellular rejuvenation. Various rejuvenation methods also provide insights for treating specific ageing-related diseases, including cellular reprogramming, the removal of senescence cells (SCs) and suppression of senescence-associated secretory phenotype (SASP), metabolic manipulation, stem cells-associated therapy, dietary restriction, immune rejuvenation and heterochronic transplantation, etc. The potential applications of rejuvenation therapy also extend to cancer treatment. Finally, we analyze in detail the therapeutic opportunities and challenges of rejuvenation technology. Deciphering rejuvenation interventions will provide further insights into anti-ageing and ageing-related disease treatment in clinical settings.

Sanglifehrin A mitigates multi-organ fibrosis in vivo by inducing secretion of the collagen chaperone cyclophilin B

Pathological deposition and crosslinking of collagen type I by activated myofibroblasts drives progressive tissue fibrosis. Therapies that inhibit collagen synthesis by myofibroblasts have clinical potential as anti-fibrotic agents. Lysine hydroxylation by the prolyl-3-hydroxylase complex, comprised of cartilage associated protein, prolyl 3-hydroxylase 1, and cyclophilin B, is essential for collagen type I crosslinking and formation of stable fibers. Here, we identify the collagen chaperone cyclophilin B as a major cellular target of the macrocyclic natural product sanglifehrin A (SfA) using photo-affinity labeling and chemical proteomics. Our studies reveal a unique mechanism of action in which SfA binding to cyclophilin B in the endoplasmic reticulum (ER) induces the secretion of cyclophilin B to the extracellular space, preventing TGF-β1-activated myofibroblasts from synthesizing collagen type I in vitro without inhibiting collagen type I mRNA transcription or inducing ER stress. In addition, SfA prevents collagen type I secretion without affecting myofibroblast contractility or TGF-β1 signaling. In vivo, we provide chemical, molecular, functional, and translational evidence that SfA mitigates the development of lung and skin fibrosis in mouse models by inducing cyclophilin B secretion, thereby inhibiting collagen synthesis from fibrotic fibroblasts in vivo . Consistent with these findings in preclinical models, SfA reduces collagen type I secretion from fibrotic human lung fibroblasts and precision cut lung slices from patients with idiopathic pulmonary fibrosis, a fatal fibrotic lung disease with limited therapeutic options. Our results identify the primary liganded target of SfA in cells, the collagen chaperone cyclophilin B, as a new mechanistic target for the treatment of organ fibrosis.

N-acetylcysteine delayed cadmium-induced chronic kidney injury by activating the sirtuin 1-P53 signaling pathway

With the development of modern industrial civilization, cadmium (Cd), a known nephrotoxic metal, has become a growing public safety issue due to its ability to induce various types of kidney disease. Maladaptive proximal tubule repair is a significant cause of Cd-induced chronic kidney disease (CKD), which is characterized by premature senescence and pro-fibrosis. Previously, we demonstrated that cadmium causes DNA damage and cycle arrest in renal tubular epithelial cells, which may be relevant to premature senescence regulated by sirtuin 1 (SIRT1). In this study, in vivo and in vitro studies were conducted to elucidate the role of SIRT1-mediated premature renal senescence in Cd-induced CKD. As oxidative stress is a significant cause of aging, we evaluated whether N-acetylcysteine (NAC) would inhibit Cd-induced premature aging and dysfunction in rat renal tubular epithelial cells. Cadmium induced premature renal senescence and fibrosis, and NAC inhibited premature renal senescence and fibrosis through the SIRT1-P53 pathway and delayed CKD progression. Overall, the results suggested that the SIRT1-P53 pathway mediates oxidative stress, premature renal senescence, and renal fibrosis during cadmium exposure, which may be a potential therapeutic target for Cd-induced CKD.

The Role of Myofibroblasts in Physiological and Pathological Tissue Repair

Myofibroblasts are the construction workers of wound healing and repair damaged tissues by producing and organizing collagen/extracellular matrix (ECM) into scar tissue. Scar tissue effectively and quickly restores the mechanical integrity of lost tissue architecture but comes at the price of lost tissue functionality. Fibrotic diseases caused by excessive or persistent myofibroblast activity can lead to organ failure. This review defines myofibroblast terminology, phenotypic characteristics, and functions. We will focus on the central role of the cell, ECM, and tissue mechanics in regulating tissue repair by controlling myofibroblast action. Additionally, we will discuss how therapies based on mechanical intervention potentially ameliorate wound healing outcomes. Although myofibroblast physiology and pathology affect all organs, we will emphasize cutaneous wound healing and hypertrophic scarring as paradigms for normal tissue repair versus fibrosis. A central message of this review is that myofibroblasts can be activated from multiple cell sources, varying with local environment and type of injury, to either restore tissue integrity and organ function or create an inappropriate mechanical environment.

Preparation and physicochemical characterization of N-succinyl chitosan-coated liposomes for oral delivery of grape seed extract and evaluation of its effect on pulmonary fibrosis induced by bleomycin in rats

Objectives

This study aimed to develop an oral succinyl chitosan-coated liposomal formulation containing grape seed extract and assess its therapeutic efficacy in rats with bleomycin-induced pulmonary fibrosis.

Materials and Methods

N-succinyl chitosan was synthesized, and the liposomal formulations were prepared and characterized regarding phenolic content assay and morphology. Size, zeta potential, in vitro drug release, and stability. Pulmonary fibrosis was induced by intratracheal bleomycin injection, and hydroxyproline measurements, lung weight, animal body weight, as well as histopathological studies were performed.

Results

Succinyl chitosan increases the physical stability of the formulation, especially in acidic conditions. Drug release studies revealed that 66.27% of the loaded drug was released from CF2 in an acidic medium in 2 hr, but 92.31% of the drug was released in 8 hr in a pH=7 medium. An in vivo study demonstrated that rats exposed to bleomycin significantly lost weight, while those treated with CF2 (400 mg/kg) partially regained weight. Bleomycin treatment increased the mean lung weight and the amount of hydroxyproline in the lungs; these values were significantly decreased in the group treated with 400 mg/kg CF2 (P<0.05). Histopathological examination confirmed that treatment with 400 mg/kg CF2 improved lung fibrosis.

Conclusion

In rats, oral administration of N-succinyl chitosan-coated liposomes containing grape seed extract at the 400 mg/kg dose ameliorates bleomycin-induced pulmonary fibrosis.

Pim-1 kinase is a positive feedback regulator of the senescent lung fibroblast inflammatory secretome

Cellular senescence is emerging as a driver of idiopathic pulmonary fibrosis (IPF), a progressive and fatal disease with limited effective therapies. The senescence-associated secretory phenotype (SASP), involving the release of inflammatory cytokines and profibrotic growth factors by senescent cells, is thought to be a product of multiple cell types in IPF, including lung fibroblasts. NF-κB is a master regulator of the SASP, and its activity depends on the phosphorylation of p65/RelA. The purpose of this study was to assess the role of Pim-1 kinase as a driver of NF-κB-induced production of inflammatory cytokines from low-passage IPF fibroblast cultures displaying markers of senescence. Our results demonstrate that Pim-1 kinase phosphorylates p65/RelA, activating NF-κB activity and enhancing IL-6 production, which in turn amplifies the expression of PIM1, generating a positive feedback loop. In addition, targeting Pim-1 kinase with a small molecule inhibitor dramatically inhibited the expression of a broad array of cytokines and chemokines in IPF-derived fibroblasts. Furthermore, we provide evidence that Pim-1 overexpression in low-passage human lung fibroblasts is sufficient to drive premature senescence, in vitro. These findings highlight the therapeutic potential of targeting Pim-1 kinase to reprogram the secretome of senescent fibroblasts and halt IPF progression.

Systematic Analysis Strategy Based on Network Pharmacology to Investigate the Potential Mechanism of Fritillaria thunbergii Miq. against Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a long-term, distressing, and age-related interstitial lung disease characterized by a complicated etiology and irreversible progression. Fritillaria thunbergii Miq. (Zhe Beimu, ZBM) is frequently used for its heat-clearing and phlegm-resolving properties in herbal compounds for the treatment of IPF. However, the specific mechanisms underlying the effects of ZBM against IPF have not yet been reported. In this study, we applied a systematic analysis strategy based on network pharmacology to explore the probable core targets and major pathways of ZBM against IPF. In addition, molecular docking simulation and quantitative real-time polymerase chain reaction (qRT-PCR) were performed to preliminarily investigate the possible mechanisms underlying the therapeutic effects of ZBM on IPF. We collected a total of 86 components of ZBM and used network pharmacology analysis to screen nine presumptive targets of ZBM against IPF. The molecular-docking results indicated that the components of ZBM exhibited good binding activity with presumptive targets. The qRT-PCR results also suggested that ZBM may partly alleviate IPF by regulating the expression of presumptive targets. This study laid the foundation for further clinical applications of ZBM and the development of IPF-related therapeutic products.

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.

Role of cellular senescence in the pathogenesis of systemic sclerosis

PURPOSE OF REVIEW

Systemic sclerosis (SSc) is a chronic rheumatic disease that is characterized by immune activation, vasculopathy and fibrosis of the skin and internal organs. It has been proposed that premature onset of ageing pathways and associated senescent changes in cells contribute to the clinical and pathological features of SSc. The aim of this review is to critically review recent insights into the involvement of cellular senescence in SSc.

RECENT FINDINGS

Cellular senescence plays a critical role in SSc pathogenesis, particularly involving endothelial cells and fibroblasts. Immunosenescence could also contribute to SSc pathogenesis by direct alteration of cellular functions or indirect promotion of defective immune surveillance. Molecular studies have shed some light on how cellular senescence contributes to fibrosis. Recent and planned proof-of-concept trials using senotherapeutics showed promising results in fibrotic diseases, including SSc.

SUMMARY

There is increasing evidence implicating cellular senescence in SSc. The mechanisms underlying premature cellular senescence in SSc, and its potential role in pathogenesis, merit further investigation. Emerging drugs targeting senescence-related pathways might be potential therapeutic options for SSc.

Yiqi Huayu decoction alleviates bleomycin-induced pulmonary fibrosis in rats by inhibiting senescence

Overview: In treating pulmonary fibrosis (PF), traditional Chinese medicine (TCM) has received much attention, but its mechanism is unclear. The pharmacological mechanisms of TCM can be explored through network pharmacology. However, due to its virtual screening properties, it still needs to be verified by in vitro or in vivo experiments. Therefore, we investigated the anti-PF mechanism of Yiqi Huayu Decoction (YHD) by combining network pharmacology with in vivo experiments.

Methods: Firstly, we used classical bleomycin (BLM)-induced rat model of PF and administrated fibrotic rats with YHD (low-, medium-, and high-dose). We comprehensively assessed the treatment effect of YHD according to body weight, lung coefficient, lung function, and histopathologic examination. Second, we predict the potential targets by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) combined with network pharmacology. In brief, we obtained the chemical ingredients of YHD based on the UHPLC-MS/MS and TCMSP database. We collected drug targets from TCMSP, HERB, and Swiss target prediction databases based on active ingredients. Disease targets were acquired from drug libraries, Genecards, HERB, and TTD databases. The intersecting targets of drugs and disease were screened out. The STRING database can obtain protein-protein interaction (PPI) networks and hub target proteins. Molecular Complex Detection (MCODE) clustering analysis combined with enrichment analysis can explore the possible biological mechanisms of YHD. Enrichment analyses were conducted through the R package and the David database, including the Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology (GO), and Reactome. Then, we further validated the target genes and target proteins predicted by network pharmacology. Protein and gene expression detection by immunohistochemistry, Western blot (WB), and real-time quantitative PCR (rt-qPCR).

Results: The results showed that high-dose YHD effectively attenuated BLM-induced lung injury and fibrosis in rats, as evidenced by improved lung function, relief of inflammatory response, and reduced collagen deposition. We screened nine core targets and cellular senescence pathways by UHPLC-MS/MS analysis and network pharmacology. We subsequently validated key targets of cellular senescence signaling pathways. WB and rt-qPCR indicated that high-dose YHD decreased protein and gene expression of senescence-related markers, including p53 (TP53), p21 (CDKN1A), and p16 (CDKN2A). Increased reactive oxygen species (ROS) are upstream triggers of the senescence program. The senescence-associated secretory phenotypes (SASPs), containing interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), and transforming growth factor-β1 (TGF-β1), can further exacerbate the progression of senescence. High-dose YHD inhibited ROS production in lung tissue and consistently reduced the SASPs expression in serum.

Conclusion: Our study suggests that YHD improves lung pathological injury and lung function in PF rats. This protective effect may be related to the ability of YHD to inhibit cellular senescence.

Research Progress in the Molecular Mechanisms, Therapeutic Targets, and Drug Development of Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease. Recent studies have identified the key role of crosstalk between dysregulated epithelial cells, mesenchymal, immune, and endothelial cells in IPF. In addition, genetic mutations and environmental factors (e.g., smoking) have also been associated with the development of IPF. With the recent development of sequencing technology, epigenetics, as an intermediate link between gene expression and environmental impacts, has also been reported to be implicated in pulmonary fibrosis. Although the etiology of IPF is unknown, many novel therapeutic targets and agents have emerged from clinical trials for IPF treatment in the past years, and the successful launch of pirfenidone and nintedanib has demonstrated the promising future of anti-IPF therapy. Therefore, we aimed to gain an in-depth understanding of the underlying molecular mechanisms and pathogenic factors of IPF, which would be helpful for the diagnosis of IPF, the development of anti-fibrotic drugs, and improving the prognosis of patients with IPF. In this study, we summarized the pathogenic mechanism, therapeutic targets and clinical trials from the perspective of multiple cell types, gene mutations, epigenetic and environmental factors.

Targeting Histone Deacetylases in Idiopathic Pulmonary Fibrosis: A Future Therapeutic Option

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease with limited therapeutic options, and there is a huge unmet need for new therapies. A growing body of evidence suggests that the histone deacetylase (HDAC) family of transcriptional corepressors has emerged as crucial mediators of IPF pathogenesis. HDACs deacetylate histones and result in chromatin condensation and epigenetic repression of gene transcription. HDACs also catalyse the deacetylation of many non-histone proteins, including transcription factors, thus also leading to changes in the transcriptome and cellular signalling. Increased HDAC expression is associated with cell proliferation, cell growth and anti-apoptosis and is, thus, a salient feature of many cancers. In IPF, induction and abnormal upregulation of Class I and Class II HDAC enzymes in myofibroblast foci, as well as aberrant bronchiolar epithelium, is an eminent observation, whereas type-II alveolar epithelial cells (AECII) of IPF lungs indicate a significant depletion of many HDACs. We thus suggest that the significant imbalance of HDAC activity in IPF lungs, with a “cancer-like” increase in fibroblastic and bronchial cells versus a lack in AECII, promotes and perpetuates fibrosis. This review focuses on the mechanisms by which Class I and Class II HDACs mediate fibrogenesis and on the mechanisms by which various HDAC inhibitors reverse the deregulated epigenetic responses in IPF, supporting HDAC inhibition as promising IPF therapy.

Mammalian Neuraminidases in Immune-Mediated Diseases: Mucins and Beyond

Mammalian neuraminidases (NEUs), also known as sialidases, are enzymes that cleave off the terminal neuraminic, or sialic, acid resides from the carbohydrate moieties of glycolipids and glycoproteins. A rapidly growing body of literature indicates that in addition to their metabolic functions, NEUs also regulate the activity of their glycoprotein targets. The simple post-translational modification of NEU protein targets-removal of the highly electronegative sialic acid-affects protein folding, alters protein interactions with their ligands, and exposes or covers proteolytic sites. Through such effects, NEUs regulate the downstream processes in which their glycoprotein targets participate. A major target of desialylation by NEUs are mucins (MUCs), and such post-translational modification contributes to regulation of disease processes. In this review, we focus on the regulatory roles of NEU-modified MUCs as coordinators of disease pathogenesis in fibrotic, inflammatory, infectious, and autoimmune diseases. Special attention is placed on the most abundant and best studied NEU1, and its recently discovered important target, mucin-1 (MUC1). The role of the NEU1 - MUC1 axis in disease pathogenesis is discussed, along with regulatory contributions from other MUCs and other pathophysiologically important NEU targets.

The Prognostic Value of Integrated Analysis of Inflammation and Hypoxia-Related Genes in Idiopathic Pulmonary Fibrosis

Currently, the aetiology and pathogenesis of idiopathic pulmonary fibrosis (IPF) are still largely unclear. Moreover, patients with IPF exhibit a considerable difference in clinical presentation, treatment, and prognosis. Optimal biomarkers or models for IPF prognosis are lacking. Therefore, this study quantified the levels of various hallmarks using a single-sample gene set enrichment analysis algorithm. The hazard ration was calculated using Univariate Cox regression analysis based on the transcriptomic profile of bronchoalveolar lavage cells and clinical survival information. Afterwards, weighted Gene Co-expression Network Analysis was performed to construct a network between gene expression, inflammation response, and hypoxia. Subsequently, univariate Cox, random forest, and multivariate Cox regressions were applied to develop a robust inflammation and hypoxia-related gene signature for predicting clinical outcomes in patients with IPF. Furthermore, a nomogram was constructed to calculate risk assessment. The inflammation response and hypoxia were identified as latent risk factors for patients with IPF. Five genes, including HS3ST1, WFDC2, SPP1, TFPI, and CDC42EP2, were identified that formed the inflammation-hypoxia-related gene signature. Kaplan-Meier plotter showed that the patients with high-risk scores had a worse prognosis than those with low-risk scores in training and validation cohorts. The time-dependent concordance index and the receiver operating characteristic analysis revealed that the risk model could accurately predict the clinical outcome of patients with IPF. Therefore, this study contributes to elucidating the role of inflammation and hypoxia in IPF, which can aid in assessing individual prognosis and personalised treatment decisions.

Lung-Targeted Delivery of Dimethyl Fumarate Promotes the Reversal of Age-Dependent Established Lung Fibrosis

Idiopathic pulmonary fibrosis (IPF), a severe and deadly form of lung fibrosis, is widely regarded as a disease of aging. We previously demonstrated that aged mice with persistent lung fibrosis and IPF lung myofibroblasts exhibit deficient Nrf2-mediated antioxidant responses. Tecfidera is an orally administered FDA-approved drug for the treatment of multiple sclerosis, where the active pharmaceutical ingredient is dimethyl fumarate (DMF), an active Nrf2 activator. However, no studies have evaluated the efficacy of DMF for age-associated persistent lung fibrosis. Here, we demonstrate that in IPF lung fibroblasts, DMF treatment inhibited both TGF-β-mediated pro-fibrotic phenotypes and led to a reversal of established pro-fibrotic phenotypes. We also evaluated the pre-clinical efficacy of lung-targeted (inhaled) vs. systemic (oral) delivery of DMF in an aging murine model of bleomycin-induced persistent lung fibrosis. DMF or vehicle was administered daily to aged mice by oral gavage or intranasal delivery from 3-6 weeks post-injury when mice exhibited non-resolving lung fibrosis. In contrast to systemic (oral) delivery, only lung-targeted (inhaled) delivery of DMF restored lung Nrf2 expression levels, reduced lung oxidative stress, and promoted the resolution of age-dependent established fibrosis. This is the first study to demonstrate the efficacy of lung-targeted DMF delivery to promote the resolution of age-dependent established lung fibrosis.

Idiopathic Pulmonary Fibrosis: An Update on Pathogenesis

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

Multipotent stromal cells: One name, multiple identities

Multipotent stromal cells (MSCs) are vital for development, maintenance, function, and regeneration of most tissues. They can differentiate along multiple connective lineages, but unlike most other stem/progenitor cells, they carry out various other functions while maintaining their developmental potential. MSCs function as damage sensors, respond to injury by fostering regeneration through secretion of trophic factors as well as extracellular matrix (ECM) molecules, and contribute to fibrotic reparative processes when regeneration fails. Tissue-specific MSC identity, fate(s), and function(s) are being resolved through fate mapping coupled with single cell "omics," providing unparalleled insights into the secret lives of tissue-resident MSCs.

Iron oxide nanoparticles augment the intercellular mitochondrial transfer-mediated therapy

The transfer of mitochondria between cells has recently been revealed as a spontaneous way to protect the injured cells. However, the utilization of this natural transfer process for disease treatment is so far limited by its unsatisfactory transfer efficiency and selectivity. Here, we demonstrate that iron oxide nanoparticles (IONPs) can augment the intercellular mitochondrial transfer from human mesenchymal stem cells (hMSCs) selectively to diseased cells, owing to the enhanced formation of connexin 43–containing gap junctional channels triggered by ionized IONPs. In a mouse model of pulmonary fibrosis, the IONP-engineered hMSCs achieve a remarkable mitigation of fibrotic progression because of the promoted intercellular mitochondrial transfer, with no serious safety issues identified. The present study reports a potential method of using IONPs to enable hMSCs for efficient and safe transfer of mitochondria to diseased cells to restore mitochondrial bioenergetics.

Leveraging ageing models of pulmonary fibrosis: the efficacy of nintedanib in ageing

Nintedanib is one of two US Food and Drug Administration (FDA)-approved treatments for idiopathic pulmonary fibrosis (IPF). The clinical efficacy of nintedanib for inhibiting the progression of lung fibrosis is well-established [1]. However, although nintedanib is overwhelmingly prescribed to elderly patients, the impact of ageing on its efficacy is difficult to discern from clinical data due to the magnitude of confounding variables that exist among human subjects (genetics, gender, comorbidities, disease stage at the onset of treatment, etc.). A recent post hoc meta-analysis of five IPF clinical trials suggested that the effect of nintedanib in reducing the rate of forced vital capacity decline is consistent across patients with age (patients >75 versus patients <75 years of age) [2]. However, it is important to note that the average age of IPF diagnosis is 66 years and the average patient ages in these cohorts were 78 (>75) versus 64 (<75) years. Further, one could argue that patients in both cohorts represent the elderly population. This study highlights the complexity of evaluating the impact of ageing on efficacy in a clinical setting. To date, all pre-clinical efficacy studies with nintedanib have been performed in young animals. We therefore sought to determine whether ageing impacts the efficacy of nintedanib for inhibiting the development of lung fibrosis. Bleomycin-induced lung injury in young (2 month) and aged (18 month) mice was followed by treatment with nintedanib or vehicle from day 10–21 (figure 1a), using a previously described protocol [3]. We previously demonstrated in this injury model that the severity of lung fibrosis is identical in young and aged mice, in terms of the net increase in total lung collagen following injury [4]. Although some prior studies have reported seemingly contradictory results, indicating increased severity of fibrosis in aged mice [5, 6], this discrepancy could be attributed to increased baseline levels of collagen in aged mice and the methodology/analyses used for fibrosis assessment, as the net increase in collagen appear to be similar in both young and aged mice [5, 6]. In line with our previous findings, both young and aged vehicle-treated mice demonstrated similar levels of fibrosis severity and a similar decline in lung function at 3 weeks post-injury (figure 1b–d, g–h). Also consistent with numerous prior reports [7, 8], we found that in young mice, nintedanib demonstrated efficacy for inhibiting the development of fibrosis (figure 1b–g) and led to improved lung function (figure 1h). Interestingly, nintedanib also significantly inhibited the development of lung fibrosis in aged mice, to a similar extent as young cohorts (figure 1b–g). Although nintedanib treatment resulted in lung functional improvement to a similar extent in both young (49%) and aged (57%) mice (figure 1h), results did not reach statistical significance in aged mice. Of note, there is less than 47% power to detect mean differences between the aged-vehicle and aged-nintedanib groups given the observed effect and sample sizes of aged mice; the trending p-value of 0.06 is displayed to provide a better understanding of the results. No significant differences in survival rate were observed between nintedanib- versus vehicle-treated groups for both young (68% versus 72%, respectively) and aged mice (83% versus 76%, respectively) during this treatment period (day 10–21). Overall, these data indicate that ageing does not impact the efficacy of nintedanib in terms of its ability to inhibit the development of de novo lung fibrosis.

Although nintedanib is overwhelmingly prescribed to elderly patients, this is the first study to demonstrate that ageing does not impact the efficacy of nintedanib. This study sheds light on the utility of aged animal models in pulmonary fibrosis.https://bit.ly/3zA9RC5

The dual distinct role of telomerase in repression of senescence and myofibroblast differentiation

Many aging related diseases such as cancer implicate the myofibroblast in disease progression. Furthermore genesis of the myofibroblast is associated with manifestation of cellular senescence of unclear significance. In this study we investigated the role of a common regulator, namely telomerase reverse transcriptase (TERT), in order to evaluate the potential significance of this association between both processes. We analyzed the effects of TERT overexpression or deficiency on expression of CDKN2A and ACTA2 as indicators of senescence and differentiation, respectively. We assess binding of TERT or YB-1, a repressor of both genes, to their promoters. TERT repressed both CDKN2A and ACTA2 expression, and abolished stress-induced expression of both genes. Conversely, TERT deficiency enhanced their expression. Altering CDKN2A expression had no effect on ACTA2 expression. Both TERT and YB-1 were shown to bind the CDKN2A promoter but only YB-1 was shown to bind the ACTA2 promoter. TERT overexpression inhibited CDKN2A promoter activity while stimulating YB-1 expression and activation to repress ACTA2 gene. TERT repressed myofibroblast differentiation and senescence via distinct mechanisms. The latter was associated with TERT binding to the CDKN2A promoter, but not to the ACTA2 promoter, which may require interaction with co-factors such as YB-1.

Cellular Senescence in Lung Fibrosis

Fibrosing interstitial lung diseases (ILDs) are chronic and ultimately fatal age-related lung diseases characterized by the progressive and irreversible accumulation of scar tissue in the lung parenchyma. Over the past years, significant progress has been made in our incomplete understanding of the pathobiology underlying fibrosing ILDs, in particular in relation to diverse age-related processes and cell perturbations that seem to lead to maladaptation to stress and susceptibility to lung fibrosis. Growing evidence suggests that a specific biological phenomenon known as cellular senescence plays an important role in the initiation and progression of pulmonary fibrosis. Cellular senescence is defined as a cell fate decision caused by the accumulation of unrepairable cellular damage and is characterized by an abundant pro-inflammatory and pro-fibrotic secretome. The senescence response has been widely recognized as a beneficial physiological mechanism during development and in tumour suppression. However, recent evidence strengthens the idea that it also drives degenerative processes such as lung fibrosis, most likely by promoting molecular and cellular changes in chronic fibrosing processes. Here, we review how cellular senescence may contribute to lung fibrosis pathobiology, and we highlight current and emerging therapeutic approaches to treat fibrosing ILDs by targeting cellular senescence.

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.

Repairing damaged lungs using regenerative therapy

There is an urgent need for better treatment of lung diseases that are a major cause of morbidity and mortality worldwide. This urgency is illustrated by the current COVID-19 health crisis. Moderate-to-extensive lung injury characterizes several lung diseases, and not only therapies that reduce such lung injury are needed but also those that regenerate lung tissue and repair existing lung injury. At present, such therapies are not available, but as a result of a rapid increase in our understanding of lung development and repair, lung regenerative therapies are on the horizon. Here, we discuss existing targets for treatment, as well as novel strategies for development of pharmacological and cell therapy-based regenerative treatment for a variety of lung diseases and clinical studies. We discuss how both patient-relevant in vitro disease models using innovative culture techniques and other advanced new technologies aid in the development of pulmonary regenerative medicine.

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.

A story of fibers and stress: Matrix-embedded signals for fibroblast activation in the skin

Our skin is continuously exposed to mechanical challenge, including shear, stretch, and compression. The extracellular matrix of the dermis is perfectly suited to resist these challenges and maintain integrity of normal skin even upon large strains. Fibroblasts are the key cells that interpret mechanical and chemical cues in their environment to turnover matrix and maintain homeostasis in the skin of healthy adults. Upon tissue injury, fibroblasts and an exclusive selection of other cells become activated into myofibroblasts with the task to restore skin integrity by forming structurally imperfect but mechanically stable scar tissue. Failure of myofibroblasts to terminate their actions after successful repair or upon chronic inflammation results in dysregulated myofibroblast activities which can lead to hypertrophic scarring and/or skin fibrosis. After providing an overview on the major fibrillar matrix components in normal skin, we will interrogate the various origins of fibroblasts and myofibroblasts in the skin. We then examine the role of the matrix as signaling hub and how fibroblasts respond to mechanical matrix cues to restore order in the confusing environment of a healing wound.

The inflammatory speech of fibroblasts

Activation of fibroblasts is a key event during normal tissue repair after injury and the dysregulated repair processes that result in organ fibrosis. To most researchers, fibroblasts are rather unremarkable spindle-shaped cells embedded in the fibrous collagen matrix of connective tissues and/or deemed useful to perform mechanistic studies with adherent cells in culture. For more than a century, fibroblasts escaped thorough classification due to the lack of specific markers and were treated as the leftovers after all other cells have been identified from a tissue sample. With novel cell lineage tracing and single cell transcriptomics tools, bona fide fibroblasts emerge as only one heterogeneous sub-population of a much larger group of partly overlapping cell types, including mesenchymal stromal cells, fibro-adipogenic progenitor cells, pericytes, and/or perivascular cells. All these cells are activated to contribute to tissue repair after injury and/or chronic inflammation. "Activation" can entail various functions, such as enhanced proliferation, migration, instruction of inflammatory cells, secretion of extracellular matrix proteins and organizing enzymes, and acquisition of a contractile myofibroblast phenotype. We provide our view on the fibroblastic cell types and activation states playing a role during physiological and pathological repair and their crosstalk with inflammatory macrophages. Inflammation and fibrosis of the articular synovium during rheumatoid arthritis and osteoarthritis are used as specific examples to discuss inflammatory fibroblast phenotypes. Ultimately, delineating the precursors and functional roles of activated fibroblastic cells will contribute to better and more specific intervention strategies to treat fibroproliferative and fibrocontractive disorders.

Nogo-B promotes epithelial-mesenchymal transition in lung fibrosis via PERK branch of the endoplasmic reticulum stress pathway

Background

Idiopathic pulmonary fibrosis (IPF) is a fatal chronic pulmonary fibrosis disease and pathological mechanisms of fibrogenesis in IPF are still to be elucidated. Here, we investigated the potential role of Nogo-B in pulmonary fibrogenesis.

Methods

A mouse model of pulmonary fibrosis was established by intratracheal injection of bleomycin (BLM). Lung epithelial cells MLE-12 and TC-1 JHU-1 were cultured for TGF-β treatment. The extent of lung fibrosis was evaluated using hematoxylin and eosin (HE) staining and Masson staining in model mice and Nogo-B knockout mice. The protein levels of Nogo-B, endoplasmic reticulum stress (ERS) sensors including PERK, IRE1α, ATF6 and epithelial-mesenchymal transition (EMT) markers including E-cadherin and N-cadherin, vimentin were assayed by Western blotting respectively after Nogo-B knockdown or overexpression with lentivirus. Enzyme-linked immunosorbent assay (ELISA) was used to evaluate cytokine levels of TGF-β, TNF-α, IL-1β, IL-6 and IL-10 in bronchoalveolar lavage fluid (BALF).

Results

Nogo-B expression was up-regulated in lung tissues of fibrosis model mice and alveolar epithelial cells. Nogo-B knockdown significantly attenuated lung fibrogenesis, downregulated the levels of inflammatory cytokines, inhibited EMT as well as decreased the level of phosphor-PERK/PERK but not the levels of phosphor-IRE1α/IRE1α and c-ATF6. Additionally, a potential efficacy of PERK blockade was demonstrated in improving the extent of lung fibrosis in model mice.

Conclusions

This study discovered that involvement of Nogo-B in pulmonary fibrogenesis was associated with the PERK branch of ERS pathway and EMT. Nogo-B could be considered as a potential therapeutic target for the treatment of IPF.