Master Autophagy Regulator Transcription Factor EB Regulates Cigarette Smoke-Induced Autophagy Impairment and Chronic Obstructive Pulmonary Disease-Emphysema Pathogenesis

Premature senescence is regulated by crosstalk among TFEB, the autophagy lysosomal pathway and ROS derived from damaged mitochondria in NaAsO2-exposed auditory cells

Age-related hearing loss (ARHL) is one of the most prevalent types of sensory decline in a superaging society. Although various studies have focused on the effect of oxidative stress on the inner ear as an inducer of ARHL, there are no effective preventive approaches for ARHL. Recent studies have suggested that oxidative stress-induced DNA damage responses (oxidative DDRs) drive cochlear cell senescence and contribute to accelerated ARHL, and autophagy could function as a defense mechanism against cellular senescence in auditory cells. However, the underlying mechanism remains unclear. Sodium arsenite (NaAsO2) is a unique oxidative stress inducer associated with reactive oxygen species (ROS) that causes high-tone hearing loss similar to ARHL. Transcription factor EB (TFEB) functions as a master regulator of the autophagy‒lysosome pathway (ALP), which is a potential target during aging and the pathogenesis of various age-related diseases. Here, we focused on the function of TFEB and the impact of intracellular ROS as a potential target for ARHL treatment in a NaAsO2-induced auditory premature senescence model. Our results suggested that short exposure to NaAsO2 leads to DNA damage, lysosomal damage and mitochondrial damage in auditory cells, triggering temporary signals for TFEB transport into the nucleus and, as a result, causing insufficient autophagic flux and declines in lysosomal function and biogenesis and mitochondrial quality. Then, intracellular ROS derived from damaged mitochondria play a role as a second messenger to induce premature senescence in auditory cells. These findings suggest that TFEB activation via transport into the nucleus contributes to anti-senescence activity in auditory cells and represents a new therapeutic target for ARHL. We have revealed the potential function of TFEB as a master regulator of the induction of oxidative stress-induced premature senescence and the senescence-associated secretion phenotype (SASP) in auditory cells, which regulates ALP and controls mitochondrial quality through ROS production.

Circadian clock genes REV-ERBα regulates the secretion of IL-1β in deciduous tooth pulp stem cells by regulating autophagy in the process of physiological root resorption of deciduous teeth

Physiological root resorption is a common occurrence during the development of deciduous teeth in children. Previous research has shown that the regulation of the inflammatory microenvironment through autophagy in DDPSCs is a significant factor in this process. However, it remains unclear why there are variations in the autophagic status of DDPSCs at different stages of physiological root resorption. To address this gap in knowledge, this study examines the relationship between the circadian clock of DDPSCs, the autophagic status, and the periodicity of masticatory behavior. Samples were collected from deciduous teeth at various stages of physiological root resorption, and DDPSCs were isolated and cultured for analysis. The results indicate that the circadian rhythm of important autophagy genes, such as Beclin-1 and LC3, and the clock gene REV-ERBα in DDPSCs, disappears under mechanical stress. Additionally, the study found that REV-ERBα can regulate Beclin-1 and LC3. Evidence suggests that mechanical stress is a trigger for the regulation of autophagy via REV-ERBα. Overall, this study highlights the importance of mechanical stress in regulating autophagy of DDPSCs via REV-ERBα, which affects the formation of the inflammatory microenvironment and plays a critical role in physiological root resorption in deciduous teeth.

The role of lysosomes in airborne particulate matter-induced pulmonary toxicity

An investigation of the potential role of lysosomes in airborne particulate matter (APM) induced health risks is essential to fully comprehend the pathogenic mechanisms of respiratory diseases. It is commonly accepted that APM-induced lung injury is caused by oxidative stress, inflammatory responses, and DNA damage. In addition, there exists abundant evidence that changes in lysosomal function are essential for cellular adaptation to a variety of particulate stimuli. This review emphasizes that disruption of the lysosomal structure/function is a key step in the cellular metabolic imbalance induced by APMs. After being ingested by cells, most particles are localized within lysosomes. Thus, lysosomes become the primary locus where APMs accumulate, and here they undergo degradation and release toxic components. Recent studies have provided incontrovertible evidence that a wide variety of APMs interfere with the normal function of lysosomes. After being stimulated by APMs, lysosome rupture leads to a loss of lysosomal acidic conditions and the inactivation of proteolytic enzymes, promoting an inflammatory response by activating the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome. Moreover, APMs interfere with autophagosome production or block autophagic flux, resulting in autophagy dysfunction. Additionally, APMs disrupt the normal function of lysosomes in iron metabolism, leading to disruption on iron homeostasis. Therefore, understanding the impacts of APM exposure from the perspective of lysosomes will provide new insights into the detrimental consequences of air pollution.

PSAT1 promotes autophagy to resist insufficient autophagy caused by cigarette smoke extract in human airway epithelial cells

The inhaling of cigarette smoke (CS) causes damage to airway epithelial cells, which is related to chronic obstructive pulmonary disease (COPD). It has been established that CS induces autophagy, but it is still unclear whether excessive or insufficient autophagy results in cell death. This study discovered that CS significantly elevates PSAT1 expression in bronchial epithelial cells. Further studies using autophagy inhibitor, RNA interference, RT-qPCR, western blot, and CCK-8 assay in 16-HBE cells have confirmed that autophagy is temporarily initiated by cigarette smoke extract (CSE), but insufficient autophagy leads to cell death. PSAT1 induced by CSE promotes autophagy and resists insufficient autophagy caused by CSE through Akt/mTOR pathway in human bronchial epithelial cells, playing a protective role.

The Mechanisms of Resistin-Like Molecule-β-Mediated Airway Inflammation in Chronic Obstructive Pulmonary Disease via Autophagy

Background

The role of irreversible airway inflammatory damage in chronic obstructive pulmonary disease (COPD) progression is evident. Autophagy is an essential process in the cellular material metabolic cycle, and a family of resistant vegetative molecules may be involved in the COPD autophagic process. In this study, we investigated the mechanism of resistin-like molecule β (RELMβ) in COPD smoking-induced autophagy.

Methods

Firstly, the expression differences of RELMβ and autophagy markers between COPD and control groups were analyzed in the Gene Expression Omnibus (GEO) datasets and clinical specimens. Secondly, in vitro and in vivo experiments were conducted using immunoblotting, immunofluorescence, immunohistochemistry, and other methods to investigate the mechanism by which RELMβ promotes airway inflammation through autophagy in a cigarette smoke extract-induced 16HBE cell inflammation model and a cigarette smoke-induced COPD-like mouse model. In addition, immunoprecipitation was used to analyze the binding of RELMβ to the membrane protein TLR4.

Results

The expression of RELMβ and autophagy genes p62 and LC3B in lung tissue of COPD patients was significantly increased. RELMβ can mediate the activation of autophagy in 16HBE cells, and through autophagy, it increases the expression of inflammatory cytokines in a cigarette smoke extract-induced 16HBE cell inflammation model. RELMβ promotes cigarette smoke-induced COPD-like mouse airway inflammation through autophagy, and RELMβ can mediate signal transduction through the cell membrane receptor TLR4.

Conclusion

The RELMβ binds to TLR4 to encourage signal transduction and that RELMβ can promote inflammation in smoky COPD lungs through autophagy.

Autophagy/Mitophagy in Airway Diseases: Impact of Oxidative Stress on Epithelial Cells

Autophagy is the key process by which the cell degrades parts of itself within the lysosomes. It maintains cell survival and homeostasis by removing molecules (particularly proteins), subcellular organelles, damaged cytoplasmic macromolecules, and by recycling the degradation products. The selective removal or degradation of mitochondria is a particular type of autophagy called mitophagy. Various forms of cellular stress (oxidative stress (OS), hypoxia, pathogen infections) affect autophagy by inducing free radicals and reactive oxygen species (ROS) formation to promote the antioxidant response. Dysfunctional mechanisms of autophagy have been found in different respiratory diseases such as chronic obstructive lung disease (COPD) and asthma, involving epithelial cells. Several existing clinically approved drugs may modulate autophagy to varying extents. However, these drugs are nonspecific and not currently utilized to manipulate autophagy in airway diseases. In this review, we provide an overview of different autophagic pathways with particular attention on the dysfunctional mechanisms of autophagy in the epithelial cells during asthma and COPD. Our aim is to further deepen and disclose the research in this direction to stimulate the develop of new and selective drugs to regulate autophagy for asthma and COPD treatment.

A Proteomics Investigation of Cigarette Smoke Exposed Wistar Rats Revealed Improved Anti-Inflammatory Effects of the Cysteamine Nanoemulsions Delivered via Inhalation

Cigarette smoking is the major cause of chronic inflammatory diseases such as chronic obstructive pulmonary disease (COPD). It is paramount to develop pharmacological interventions and delivery strategies against the cigarette smoke (CS) associated oxidative stress in COPD. This study in Wistar rats examined cysteamine in nanoemulsions to counteract the CS distressed microenvironment. In vivo, 28 days of CS and 15 days of cysteamine nanoemulsions treatment starting on 29th day consisting of oral and inhalation routes were established in Wistar rats. In addition, we conducted inflammatory and epithelial-to-mesenchymal transition (EMT) studies in vitro in human bronchial epithelial cell lines (BEAS2B) using 5% CS extract. Inflammatory and anti-inflammatory markers, such as tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, IL-1β, IL-8, IL-10, and IL-13, have been quantified in bronchoalveolar lavage fluid (BALF) to evaluate the effects of the cysteamine nanoemulsions in normalizing the diseased condition. Histopathological analysis of the alveoli and the trachea showed the distorted, lung parenchyma and ciliated epithelial barrier, respectively. To obtain mechanistic insights into the CS COPD rat model, "shotgun" proteomics of the lung tissues have been carried out using high-resolution mass spectrometry wherein genes such as ABI1, PPP3CA, PSMA2, FBLN5, ACTG1, CSNK2A1, and ECM1 exhibited significant differences across all the groups. Pathway analysis showed autophagy, signaling by receptor tyrosine kinase, cytokine signaling in immune system, extracellular matrix organization, and hemostasis, as the major contributing pathways across all the studied groups. This work offers new preclinical findings on how cysteamine taken orally or inhaled can combat CS-induced oxidative stress.

Peroxinredoxin 6 reduction accelerates cigarette smoke extract‑induced senescence by regulating autophagy in BEAS‑2B cells

Cigarette smoke (CS)-induced accelerated senescence and insufficient autophagy has been implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Peroxiredoxin (PRDX) 6 is a protein with prevalent antioxidant capacity. Previous studies indicate that PRDX6 could activate autophagy and alleviate senescence in other diseases. The present study investigated whether PRDX6-regulated autophagy was involved in the regulation of CS extract (CSE)-induced BEAS-2B cell senescence via the knockdown of PRDX6 expression. Furthermore, the present study evaluated the mRNA levels of PRDX6, autophagy and senescence-associated genes in the small airway epithelium from patients with COPD by analyzing the GSE20257 dataset from the Gene Expression Omnibus database. The results demonstrated that CSE reduced PRDX6 expression levels and transiently induced the activation of autophagy, followed by the accelerated senescence of BEAS-2B cells. Knockdown of PRDX6 induced autophagy degradation and accelerated senescence in CSE-treated BEAS-2B cells. Furthermore, autophagy inhibition by 3-Methyladenine increased P16 and P21 expression levels, while autophagy activation by rapamycin reduced P16 and P21 expression levels in CSE-treated BEAS-2B cells. The GSE20257 dataset revealed that patients with COPD had lower PRDX6, sirtuin (SIRT) 1 and SIRT6 mRNA levels, and higher P62 and P16 mRNA levels compared with non-smokers. P62 mRNA was significantly correlated with P16, P21 and SIRT1, which indicated that insufficient autophagic clearance of damaged proteins could be involved in accelerated cell senescence in COPD. In conclusion, the present study demonstrated a novel protective role for PRDX6 in COPD. Furthermore, a reduction in PRDX6 could accelerate senescence by inducing autophagy impairment in CSE-treated BEAS-2B cells.

CircRNA_0026344 via miR-21 is involved in cigarette smoke-induced autophagy and apoptosis of alveolar epithelial cells in emphysema

Cigarette smoke (CS), a main source of indoor air pollution, is a primary risk factor for emphysema, and aberrant cellular autophagy is related to the pathogenesis of emphysema. Circular RNAs (circRNAs) affect the expression of mRNAs via acting as microRNA (miRNA) sponges, but their role in emphysema progression is not established. In the present investigation, CS, acting on alveolar epithelial cells, caused higher levels of miR-21, p-ERK, and cleaved-caspase 3 and led to lower levels of circRNA_0026344 and PTEN, which induced autophagy and apoptosis. miR-21 suppressed the expression of PTEN, which was involved in the regulation of autophagy and apoptosis. Further, in alveolar epithelial cells, overexpression of circRNA_0026344 blocked cigarette smoke extract (CSE)-induced autophagy and apoptosis, but this blockage was reversed by upregulation of miR-21 with a mimic. These results demonstrated that, in alveolar epithelial cells, CS decreases circRNA_0026344 levels, which sponge miR-21 to inhibit the miR-21 target, PTEN, which, in turn, activates ERK and thereby promotes autophagy and apoptosis, leading to emphysema. Thus, for emphysema, circRNA_0026344 regulates the PTEN/ERK axis by sponging miR-21, which is associated with the CS-induced autophagy and apoptosis of alveolar epithelial cells. In sum, the present investigation identifies a novel mechanism for CS-induced emphysema and provides information useful for the diagnosis and treatment of CS-induced emphysema.

Drugs against metabolic diseases as potential senotherapeutics for aging-related respiratory diseases

Recent advances in aging research have provided novel insights for the development of senotherapy, which utilizes cellular senescence as a therapeutic target. Cellular senescence is involved in the pathogenesis of various chronic diseases, including metabolic and respiratory diseases. Senotherapy is a potential therapeutic strategy for aging-related pathologies. Senotherapy can be classified into senolytics (induce cell death in senescent cells) and senomorphics (ameliorate the adverse effects of senescent cells represented by the senescence-associated secretory phenotype). Although the precise mechanism has not been elucidated, various drugs against metabolic diseases may function as senotherapeutics, which has piqued the interest of the scientific community. Cellular senescence is involved in the pathogenesis of chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF), which are aging-related respiratory diseases. Large-scale observational studies have reported that several drugs, such as metformin and statins, may ameliorate the progression of COPD and IPF. Recent studies have reported that drugs against metabolic diseases may exert a pharmacological effect on aging-related respiratory diseases that can be different from their original effect on metabolic diseases. However, high non-physiological concentrations are needed to determine the efficacy of these drugs under experimental conditions. Inhalation therapy may increase the local concentration of drugs in the lungs without exerting systemic adverse effects. Thus, the clinical application of drugs against metabolic diseases, especially through an inhalation treatment modality, can be a novel therapeutic approach for aging-related respiratory diseases. This review summarizes and discusses accumulating evidence on the mechanisms of aging, as well as on cellular senescence and senotherapeutics, including drugs against metabolic diseases. We propose a developmental strategy for a senotherapeutic approach for aging-related respiratory diseases with a special focus on COPD and IPF.

Impaired autophagy flux by lncRNA NEAT1 is critical for inflammation factors production in human periodontal ligament stem cells with nicotine treatment

BACKGROUND AND OBJECTIVES

Periodontitis is the top reason for tooth loss, and smoking significantly increases severe periodontitis risk. Defective autophagy has been reported to play a vital role in periodontitis. This study aimed to elucidate the relationship between autophagy and inflammation factors production in nicotine-treated periodontal ligament stem cells (PDLSCs) and the underlying mechanism.

METHODS

In this study, transmission electron microscopy, immunofluorescence, and the mCherry-GFP-LC3 plasmid were used to study autophagy flux. The gene levels of inflammation factors and long noncoding RNA nuclear paraspeckle assembly transcript 1 (lncRNA NEAT1) were detected by quantitative real-time PCR (qRT-PCR). Western blot was performed to assess the protein levels of autophagic markers and α7 nicotinic acetylcholine receptor (α7nAChR).

RESULTS

We found that nicotine impaired autophagosome-lysosome fusion and lysosome functions to block autophagy flux, contributing to inflammatory factors production in nicotine-treated PDLSCs. Moreover, nicotine upregulated NEAT1 by activating α7nAChR. NEAT1 decreased autophagy flux by downregulating syntaxin 17 (STX17).

CONCLUSION

Our data indicate that NEAT1-decreased autophagy flux is pivotal for inflammation factors production in nicotine-treated PDLSCs.

Cigarette smoke extract-induced inflammatory response via inhibition of the TFEB-mediated autophagy in NR8383 cells

Objective: Chronic pulmonary inflammation caused by long-term smoking is the core pathology of COPD. Alveolar macrophages (AMs) are involved in the pulmonary inflammation of COPD. The accumulation of damaged materials caused by impaired autophagy triggers inflammatory response in macrophages. As a key transcription regulator, transcription factor EB (TFEB) activates the transcription of target genes related autophagy and lysosome by binding to promoters, whereas it is unclarified for the relationship between inflammatory response induced by cigarette smoke extract (CSE) and TFEB-mediated autophagy. Thus, we investigated the role of TFEB-mediated autophagy in inflammatory response induced by CSE in NR8383 cells, and to explore its potential mechanism. Methods: Based on cell viability and autophagy, cells treated with 20% concentration of CSE for 24 h were selected for further studies. Cells were divided into control group, chloroquine (CQ, the autophagy inhibitor) group, CSE group, CSE + rapamycin (the autophagy inducer) group and CSE + fisetin (the TFEB inducer) group. The levels of tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and IL-6 in supernatant were detected by ELISA kits. The protein expressions were tested by western blot. The intensity of fluorescence of Lysosome-associated membrane protein 1 (LAMP1) and TFEB was detected by immunofluorescence. Lyso-Tracker Red staining was applied to detect the lysosome environment. Results: CSE inhibited the cell viability, increased the contents of TNF-α, IL-1β, IL-6, the ratio of LC3II/I, and the level of P62 protein. Besides, CSE decreased the fluorescence intensity of LAMP1 protein and Lyso-Tracker Red staining, as well as the ratio of nucleus/cytosol of TFEB protein. Activating autophagy with rapamycin alleviated CSE-induced inflammatory response. The activation of TFEB via fisetin alleviated CSE-induced autophagy impairment and lysosomal dysfunction, thus alleviated inflammatory response in NR8383 cells. Conclusion: CSE-induced inflammatory response in NR8383 cells, which may be related to the inhibition of TFEB-mediated autophagy.

Aging and aging-related diseases: from molecular mechanisms to interventions and treatments

Aging is a gradual and irreversible pathophysiological process. It presents with declines in tissue and cell functions and significant increases in the risks of various aging-related diseases, including neurodegenerative diseases, cardiovascular diseases, metabolic diseases, musculoskeletal diseases, and immune system diseases. Although the development of modern medicine has promoted human health and greatly extended life expectancy, with the aging of society, a variety of chronic diseases have gradually become the most important causes of disability and death in elderly individuals. Current research on aging focuses on elucidating how various endogenous and exogenous stresses (such as genomic instability, telomere dysfunction, epigenetic alterations, loss of proteostasis, compromise of autophagy, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication, deregulated nutrient sensing) participate in the regulation of aging. Furthermore, thorough research on the pathogenesis of aging to identify interventions that promote health and longevity (such as caloric restriction, microbiota transplantation, and nutritional intervention) and clinical treatment methods for aging-related diseases (depletion of senescent cells, stem cell therapy, antioxidative and anti-inflammatory treatments, and hormone replacement therapy) could decrease the incidence and development of aging-related diseases and in turn promote healthy aging and longevity.

Unravelling the Therapeutic Potential of Nano-Delivered Functional Foods in Chronic Respiratory Diseases

Chronic inflammation of the respiratory tract is one of the most concerning public health issues, as it can lead to chronic respiratory diseases (CRDs), some of which are more detrimental than others. Chronic respiratory diseases include chronic obstructive pulmonary disease (COPD), asthma, lung cancer, and pulmonary fibrosis. The conventional drug therapies for the management and treatment of CRDs only address the symptoms and fail to reverse or recover the chronic-inflammation-mediated structural and functional damage of the respiratory tract. In addition, the low efficacy and adverse effects of these drugs have directed the attention of researchers towards nutraceuticals in search of potential treatment strategies that can not only ameliorate CRD symptoms but also can repair and reverse inflammatory damage. Hence, there is a growing interest toward investigating the medicinal benefits of nutraceuticals, such as rutin, curcumin, zerumbone, and others. Nutraceuticals carry many nutritional and therapeutic properties, including anti-inflammatory, antioxidant, anticancer, antidiabetic, and anti-obesity properties, and usually do not have as many adverse effects, as they are naturally sourced. Recently, the use of nanoparticles has also been increasingly studied for the nano drug delivery of these nutraceuticals. The discrete size of nanoparticles holds great potential for the level of permeability that can be achieved when transporting these nutraceutical compounds. This review is aimed to provide an understanding of the use of nutraceuticals in combination with nanoparticles against CRDs and their mechanisms involved in slowing down or reversing the progression of CRDs by inhibiting pro-inflammatory signaling pathways.

The Multifaceted Roles of Autophagy in Infectious, Obstructive, and Malignant Airway Diseases

Autophagy is a highly conserved dynamic process by which cells deliver their contents to lysosomes for degradation, thus ensuring cell homeostasis. In response to environmental stress, the induction of autophagy is crucial for cell survival. The dysregulation of this degradative process has been implicated in a wide range of pathologies, including lung diseases, representing a relevant potential target with significant clinical outcomes. During lung disease progression and infections, autophagy may exert both protective and harmful effects on cells. In this review, we will explore the implications of autophagy and its selective forms in several lung infections, such as SARS-CoV-2, Respiratory Syncytial Virus (RSV) and Mycobacterium tuberculosis (Mtb) infections, and different lung diseases such as Cystic Fibrosis (CF), Chronic Obstructive Pulmonary Disease (COPD), and Malignant Mesothelioma (MM).

Toll-Like Receptor 4 Exacerbates Mycoplasma pneumoniaevia Promoting Transcription Factor EB-Mediated Autophagy

Mycoplasma pneumoniae (M. pneumoniae) is the most common cause of community-acquired pneumonia. Toll-like receptors (TLRs) play an essential role in pneumonia. The purpose of this study was to investigate the roles of TLR4 in M. pneumoniae. Mice were administrated with 100 μl (1 × 107 ccu/ml) of M. pneumoniae. HE staining was applied for histological analysis. The protein expression was determined by western blot. The cytokine level was detected by ELISA. The results showed that TLR4-deficient mice were protected from M. pneumoniae. However, downregulation of TLR4 inhibited inflammatory response and autophagy. Moreover, transcription factor EB (TFEB) participated in M. pneumoniae-induced inflammatory response and autophagy, while knockdown of TLR4 downregulated TFEB and its nuclear translocation.

Particulate matter in COPD pathogenesis: an overview

Chronic obstructive pulmonary disease (COPD) is a progressive lung disorder with substantial patient burden and leading cause of death globally. Cigarette smoke remains to be the most recognised causative factor behind COPD pathogenesis. Given the alarming increase in prevalence of COPD amongst non-smokers in recent past, a potential role of air pollution particularly particulate matter (PM) in COPD development has gained much attention of the scientists. Indeed, several epidemiological studies indicate strong correlation between airborne PM and COPD incidence/exacerbations. PM-induced oxidative stress seems to be the major player in orchestrating COPD inflammatory cycle but the exact molecular mechanism(s) behind such a process are still poorly understood. This may be due to the complexity of multiple molecular pathways involved. Oxidative stress-linked mitochondrial dysfunction and autophagy have also gained importance and have been the focus of recent studies regarding COPD pathogenesis. Accordingly, the present review is aimed at understanding the key molecular players behind PM-mediated COPD pathogenesis through analysis of various experimental studies supported by epidemiological data to identify relevant preventive/therapeutic targets in the area.

The Link between Circadian Clock Genes and Autophagy in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD), a progressive respiratory disease, is characterized by the alveolar epithelium injury and persistent airway inflammation. It is documented that oscillation and dysregulated expression of circadian clock genes, like Bmal1, Per1, and Per2, involved in COPD pathogenies, including chronic inflammation and imbalanced autophagy level, and targeting the associations of circadian rhythm and autophagy is promising strategies in the management and treatment of COPD. Herein, we reviewed the mechanisms of the circadian clock and the unbalance of the autophagic level in COPD, as well as the link between the two, so as to provide further theoretical bases for the study on the pathogenesis of COPD.

Cellular senescence-an aging hallmark in chronic obstructive pulmonary disease pathogenesis

Chronic obstructive pulmonary disease (COPD),¹ a representative aging-related pulmonary disorder, is mainly caused by cigarette smoke (CS) exposure. Age is one of the most important risk factors for COPD development, and increased cellular senescence in tissues and organs is a component of aging. CS exposure can induce cellular senescence, as characterized by irreversible growth arrest and aberrant cytokine secretion of the senescence-associated secretory phenotype; thus, accumulation of senescent cells is widely implicated in COPD pathogenesis. CS-induced oxidative modifications to cellular components may be causally linked to accelerated cellular senescence, especially during accumulation of damaged macromolecules. Autophagy is a conserved mechanism whereby cytoplasmic components are sent for lysosomal degradation to maintain proteostasis. Autophagy diminishes with age, and loss of proteostasis is one of the hallmarks of aging. We have reported the involvement of insufficient autophagy in regulating CS-induced cellular senescence with respect to COPD pathogenesis. However, the role of autophagy in COPD pathogenesis can vary based on levels of cell stress and type of selective autophagy because excessive activation of autophagy can be responsible for inducing regulated cell death. Senotherapies targeting cellular senescence may be effective COPD treatments. Autophagy activation could be a promising sonotherapeutic approach, but the optimal modality of autophagy activation should be examined in future studies.

IP3 R attenuates oxidative stress and inflammation damage in smoking-induced COPD by promoting autophagy

Tobacco smoking is one of the most important risk factors for chronic obstructive pulmonary disease (COPD). However, the most critical genes and proteins remain poorly understood. Therefore, we aimed to investigate these hub genes and proteins in tobacco smoke-induced COPD, together with the potential mechanism(s). Differentially expressed genes (DEGs) were analysed between smokers and patients with COPD. mRNA expression and protein expression of IP3 R were confirmed in patients with COPD and extracted smoke solution (ESS)-treated human bronchial epithelial (HBE) cells. Moreover, expression of oxidative stress, inflammatory cytokines and/or autophagy-related protein was tested when IP3 R was silenced or overexpressed in ESS-treated and/or 3-MA-treated cells. A total of 30 DEGs were obtained between patients with COPD and smoker samples. IP3 R was identified as one of the key targets in tobacco smoke-induced COPD. In addition, IP3 R was significantly decreased in patients with COPD and ESS-treated cells. Loss of IP3 R statistically increased expression of oxidative stress and inflammatory cytokines in ESS-treated HBE cells, and overexpression of IP3 R reversed the above functions. Furthermore, the autophagy-related proteins (Atg5, LC3 and Beclin1) were statistically decreased, and p62 was increased by silencing of IP3 R cells, while overexpression of IP3 R showed contrary results. Additionally, we detected that administration of 3-MA significantly reversed the protective effects of IP3 R overexpression on ESS-induced oxidative stress and inflammatory injury. Our results suggest that IP3 R might exert a protective role against ESS-induced oxidative stress and inflammation damage in HBE cells. These protective effects might be associated with promoting autophagy.

Impaired TRIM16-Mediated Lysophagy in Chronic Obstructive Pulmonary Disease Pathogenesis

Insufficient autophagic degradation has been implicated in accelerated cellular senescence during chronic obstructive pulmonary disease (COPD) pathogenesis. Aging-linked and cigarette smoke (CS)-induced functional deterioration of lysosomes may be associated with impaired autophagy. Lysosomal membrane permeabilization (LMP) is indicative of damaged lysosomes. Galectin-3 and tripartite motif protein (TRIM) 16 play a cooperative role in recognizing LMP and inducing lysophagy, a lysosome-selective autophagy, to maintain lysosome function. In this study, we sought to examine the role of TRIM16-mediated lysophagy in regulating CS-induced LMP and cellular senescence during COPD pathogenesis by using human bronchial epithelial cells and lung tissues. CS extract (CSE) induced lysosomal damage via LMP, as detected by galectin-3 accumulation. Autophagy was responsible for modulating LMP and lysosome function during CSE exposure. TRIM16 was involved in CSE-induced lysophagy, with impaired lysophagy associated with lysosomal dysfunction and accelerated cellular senescence. Airway epithelial cells in COPD lungs showed an increase in lipofuscin, aggresome and galectin-3 puncta, reflecting accumulation of lysosomal damage with concomitantly reduced TRIM16 expression levels. Human bronchial epithelial cells isolated from COPD patients showed reduced TRIM16 but increased galectin-3, and a negative correlation between TRIM16 and galectin-3 protein levels was demonstrated. Damaged lysosomes with LMP are accumulated in epithelial cells in COPD lungs, which can be at least partly attributed to impaired TRIM16-mediated lysophagy. Increased LMP in lung epithelial cells may be responsible for COPD pathogenesis through the enhancement of cellular senescence.

The aging lung: Physiology, disease, and immunity

The population is aging at a rate never seen before in human history. As the number of elderly adults grows, it is imperative we expand our understanding of the underpinnings of aging biology. Human lungs are composed of a unique panoply of cell types that face ongoing chemical, mechanical, biological, immunological, and xenobiotic stress over a lifetime. Yet, we do not fully appreciate the mechanistic drivers of lung aging and why age increases the risk of parenchymal lung disease, fatal respiratory infection, and primary lung cancer. Here, we review the molecular and cellular aspects of lung aging, local stress response pathways, and how the aging process predisposes to the pathogenesis of pulmonary disease. We place these insights into context of the COVID-19 pandemic and discuss how innate and adaptive immunity within the lung is altered with age.

Autophagy Promotes Cigarette Smoke-Initiated and Elastin-Driven Bronchitis-Like Airway Inflammation in Mice

Cigarette smoke (CS)-induced macrophage activation and airway epithelial injury are both critical for the development of chronic obstructive pulmonary disease (COPD), while the eventual functions of autophagy in these processes remain controversial. We have recently developed a novel COPD mouse model which is based on the autoimmune response sensitized by CS and facilitated by elastin. In the current study, we therefore utilized this model to investigate the roles of autophagy in different stages of the development of bronchitis-like airway inflammation. Autophagic markers were increased in airway epithelium and lung tissues, and Becn+/- or Lc3b-/- mice exhibited reduced neutrophilic airway inflammation and mucus hyperproduction in this COPD mouse model. Moreover, treatment of an autophagic inhibitor 3-methyladenine (3-MA) either during CS-initiated sensitization or during elastin provocation significantly inhibited the bronchitis-like phenotypes in mice. Short CS exposure rapidly induced expression of matrix metallopeptidase 12 (MMP12) in alveolar macrophages, and treatment of doxycycline, a pan metalloproteinase inhibitor, during CS exposure effectively attenuated the ensuing elastin-induced airway inflammation in mice. CS extract triggered MMP12 expression in cultured macrophages, which was attenuated by autophagy impairment (Becn+/- or Lc3b-/-) or inhibition (3-MA or Spautin-1). These data, taken together, demonstrate that autophagy mediates both the CS-initiated MMP12 activation in macrophages and subsequent airway epithelial injury, eventually contributing to development COPD-like airway inflammation. This study reemphasizes that inhibition of autophagy as a novel therapeutic strategy for CS-induced COPD.

FSTL1 aggravates cigarette smoke-induced airway inflammation and airway remodeling by regulating autophagy

BACKGROUND

Cigarette smoke (CS) is a major risk factor for Chronic Obstructive Pulmonary Disease (COPD). Follistatin-like protein 1 (FSTL1), a critical factor during embryogenesis particularly in respiratory lung development, is a novel mediator related to inflammation and tissue remodeling. We tried to investigate the role of FSTL1 in CS-induced autophagy dysregulation, airway inflammation and remodeling.

METHODS

Serum and lung specimens were obtained from COPD patients and controls. Adult female wild-type (WT) mice, FSTL1^± mice and FSTL1^flox/+ mice were exposed to room air or chronic CS. Additionally, 3-methyladenine (3-MA), an inhibitor of autophagy, was applied in CS-exposed WT mice. The lung tissues and serum from patients and murine models were tested for FSTL1 and autophagy-associated protein expression by ELISA, western blotting and immunohistochemical. Autophagosome were observed using electron microscope technology. LTB4, IL-8 and TNF-α in bronchoalveolar lavage fluid of mice were examined using ELISA. Airway remodeling and lung function were also assessed.

RESULTS

Both FSTL1 and autophagy biomarkers increased in COPD patients and CS-exposed WT mice. Autophagy activation was upregulated in CS-exposed mice accompanied by airway remodeling and airway inflammation. FSTL1^± mice showed a lower level of CS-induced autophagy compared with the control mice. FSTL1^± mice can also resist CS-induced inflammatory response, airway remodeling and impaired lung function. CS-exposed WT mice with 3-MA pretreatment have a similar manifestation with CS-exposed FSTL1^± mice.

CONCLUSIONS

FSTL1 promotes CS-induced COPD by modulating autophagy, therefore targeting FSTL1 and autophagy may shed light on treating cigarette smoke-induced COPD.

The ER Stress/UPR Axis in Chronic Obstructive Pulmonary Disease and Idiopathic Pulmonary Fibrosis

Cellular protein homeostasis in the lungs is constantly disrupted by recurrent exposure to various external and internal stressors, which may cause considerable protein secretion pressure on the endoplasmic reticulum (ER), resulting in the survival and differentiation of these cell types to meet the increased functional demands. Cells are able to induce a highly conserved adaptive mechanism, known as the unfolded protein response (UPR), to manage such stresses. UPR dysregulation and ER stress are involved in numerous human illnesses, such as metabolic syndrome, fibrotic diseases, and neurodegeneration, and cancer. Therefore, effective and specific compounds targeting the UPR pathway are being considered as potential therapies. This review focuses on the impact of both external and internal stressors on the ER in idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD) and discusses the role of the UPR signaling pathway activation in the control of cellular damage and specifically highlights the potential involvement of non-coding RNAs in COPD. Summaries of pathogenic mechanisms associated with the ER stress/UPR axis contributing to IPF and COPD, and promising pharmacological intervention strategies, are also presented.

Complex interplay between autophagy and oxidative stress in the development of pulmonary disease

The autophagic pathway involves the encapsulation of substrates in double-membraned vesicles, which are subsequently delivered to the lysosome for enzymatic degradation and recycling of metabolic precursors. Autophagy is a major cellular defense against oxidative stress, or related conditions that cause accumulation of damaged proteins or organelles. Selective forms of autophagy can maintain organelle populations or remove aggregated proteins. Dysregulation of redox homeostasis under pathological conditions results in excessive generation of reactive oxygen species (ROS), leading to oxidative stress and the associated oxidative damage of cellular components. Accumulating evidence indicates that autophagy is necessary to maintain redox homeostasis. ROS activates autophagy, which facilitates cellular adaptation and diminishes oxidative damage by degrading and recycling intracellular damaged macromolecules and dysfunctional organelles. The cellular responses triggered by oxidative stress include the altered regulation of signaling pathways that culminate in the regulation of autophagy. Current research suggests a central role for autophagy as a mammalian oxidative stress response and its interrelationship to other stress defense systems. Altered autophagy phenotypes have been observed in lung diseases such as chronic obstructive lung disease, acute lung injury, cystic fibrosis, idiopathic pulmonary fibrosis, and pulmonary arterial hypertension, and asthma. Understanding the mechanisms by which ROS regulate autophagy will provide novel therapeutic targets for lung diseases. This review highlights our current understanding on the interplay between ROS and autophagy in the development of pulmonary disease.

Autophagy Augmentation to Alleviate Immune Response Dysfunction, and Resolve Respiratory and COVID-19 Exacerbations

The preservation of cellular homeostasis requires the synthesis of new proteins (proteostasis) and organelles, and the effective removal of misfolded or impaired proteins and cellular debris. This cellular homeostasis involves two key proteostasis mechanisms, the ubiquitin proteasome system and the autophagy–lysosome pathway. These catabolic pathways have been known to be involved in respiratory exacerbations and the pathogenesis of various lung diseases, such as chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), idiopathic pulmonary fibrosis (IPF), acute lung injury (ALI), acute respiratory distress syndrome (ARDS), and coronavirus disease-2019 (COVID-19). Briefly, proteostasis and autophagy processes are known to decline over time with age, cigarette or biomass smoke exposure, and/or influenced by underlying genetic factors, resulting in the accumulation of misfolded proteins and cellular debris, elevating apoptosis and cellular senescence, and initiating the pathogenesis of acute or chronic lung disease. Moreover, autophagic dysfunction results in an impaired microbial clearance, post-bacterial and/or viral infection(s) which contribute to the initiation of acute and recurrent respiratory exacerbations as well as the progression of chronic obstructive and restrictive lung diseases. In addition, the autophagic dysfunction-mediated cystic fibrosis transmembrane conductance regulator (CFTR) immune response impairment further exacerbates the lung disease. Recent studies demonstrate the therapeutic potential of novel autophagy augmentation strategies, in alleviating the pathogenesis of chronic obstructive or restrictive lung diseases and exacerbations such as those commonly seen in COPD, CF, ALI/ARDS and COVID-19.

SIRT1 is a key regulatory target for the treatment of the endoplasmic reticulum stress-related organ damage

Endoplasmic reticulum (ER) stress is an evolutionarily conserved adaptive response that contributes to deal with the misfolded or unfolded protein in the lumen of the ER and restore the ER homeostasis. However, excessive and prolonged ER stress can trigger the cell-death signaling pathway which causes cell death, usually in the form of apoptosis. It is generally accepted that inappropriate cellular apoptosis and a series of the subsequent inflammatory response and oxidative stress can cause disturbance of normal physiological functions and organ damage. A lot of evidence shows that the excessive activation of the ER stress contributes to the pathogenesis of many kinds of diseases and inhibiting the inappropriate stress is of great significance for maintaining the normal physiological function. In recent years, Sirtuin1 (SIRT1) has become a research hotspot on ER stress. As a master regulator of ER stress, increasing evidence suggests that SIRT1 plays a positive role in a variety of ER stress-induced organ damage via multiple mechanisms, including inhibiting cellular apoptosis and promoting autophagy. Furthermore, a lot of factors have shown effective regulation of SIRT1, which indicates the feasibility of treating SIRT1 as a target for the treatment of ER stress-related diseases. We summarize and reveal the molecular mechanisms underlying the protective effect of SIRT1 in multiple ER stress-mediated organ damage in this review. We also summed up the possible adjustment mechanism of SIRT1, which provides a theoretical basis for the treatment of ER stress-related diseases.

Shared mechanisms of multimorbidity in COPD, atherosclerosis and type-2 diabetes: the neutrophil as a potential inflammatory target

Multimorbidity is increasingly common and current healthcare strategies are not always aligned to treat this complex burden of disease. COPD, type-2 diabetes mellitus (T2D) and cardiovascular disease, especially atherosclerosis, occur more frequently together than expected, even when risk factors such as smoking, obesity, inactivity and poverty are considered. This supports the possibility of unifying mechanisms that contribute to the pathogenesis or progression of each condition.Neutrophilic inflammation is causally associated with COPD, and increasingly recognised in the pathogenesis of atherosclerosis and T2D, potentially forming an aetiological link between conditions. This link might reflect an overspill of inflammation from one affected organ into the systemic circulation, exposing all organs to an increased milieu of proinflammatory cytokines. Additionally, increasing evidence supports the involvement of other processes in chronic disease pathogenesis, such as cellular senescence or changes in cellular phenotypes.This review explores the current scientific evidence for inflammation, cellular ageing and cellular processes, such as reactive oxygen species production and phenotypic changes in the pathogenesis of COPD, T2D and atherosclerosis; highlighting common mechanisms shared across these diseases. We identify emerging therapeutic approaches that target these areas, but also where more work is still required to improve our understanding of the underlying cellular biology in a multimorbid disease setting.

Mitochondrial Dysfunction as a Pathogenic Mediator of Chronic Obstructive Pulmonary Disease and Idiopathic Pulmonary Fibrosis

The mechanisms underlying the pathogenesis of chronic lung diseases, including chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis, remain incompletely understood. Mitochondria are vital cellular organelles crucial for energy generation, the maintenance of cellular metabolism, calcium homeostasis, intracellular signaling, and the regulation of cell death programs. Emerging evidence suggests that mitochondrial dysfunction plays a cardinal role in the initiation and progression of many human diseases, including chronic lung diseases. Upregulation of the autophagy program, a cellular adaptive mechanism for protein and organelle turnover, can occur in response to injury and may have a cell type-specific impact on the progression of disease. The selective autophagy subtype specific for mitochondria (mitophagy), regulated by PINK1 (phosphatase and tensin homolog-induced putative kinase 1), is a cellular response to accumulation of depolarized or injured mitochondria. Autophagy and mitophagy may be associated with either cellular protection or propagation of injury in a cell type-specific manner, and they may also be associated with modulation of cell death pathways. Genetic studies in mouse models have revealed opposing roles for PINK1 and/or mitophagy in the propagation of emphysema and fibrosis, whereas human studies have shown altered regulation of PINK1 in both idiopathic pulmonary fibrosis and COPD. We have also recently identified a role for mitophagy in regulating the cellular necroptosis program, with implications in COPD pathogenesis. Damage-associated molecular patterns released from injured mitochondria and/or necrotic cells may promote proinflammatory and profibrotic responses. In this review, we explore current experimental evidence for mitochondrial dysfunction as a key determinant in the pathogenesis of chronic lung diseases.

Curcumin ameliorates chronic obstructive pulmonary disease by modulating autophagy and endoplasmic reticulum stress through regulation of SIRT1 in a rat model

Objectives

The ability of curcumin to activate SIRT1 and thereby promote autophagy and inhibit endoplasmic reticulum stress (ERS) in chronic obstructive pulmonary disease (COPD) remains unclear. We investigated the relationship between curcumin and SIRT1 activation in relation to autophagy and ERS in COPD.

Methods

We developed a rat COPD model by cigarette smoke exposure, and divided the rats into control, COPD, COPD + low-dose curcumin (50 mg/kg), COPD + medium-dose curcumin (100 mg/kg), COPD + high-dose curcumin (150 mg/kg), and COPD + high-dose curcumin + sirtinol (2 mM, 30 μL/kg) groups. Apoptosis was detected by TUNEL assay. SIRT1 gene and protein expression, and protein expression of autophagy-related genes LC3-I, LC3-II, and Beclin1, and ERS-related genes CHOP and GRP78 were measured by reverse transcription-polymerase chain reaction and western blot.

Results

SIRT1, LC3-I, LC3-II, and Beclin1 expression were significantly decreased and CHOP and GRP78 were enhanced in COPD compared with control rats. Curcumin increased the expression of SIRT1, LC3-I, LC3-II, and Beclin1 and decreased the expression of CHOP and GRP78 in COPD rats. The alleviating effects of curcumin on COPD in the SIRT1-inhibition group were reversed by suppressing LC3-I, LC3-II, and Beclin1 and increasing CHOP and GRP78.

Conclusion

Curcumin might alleviate COPD by promoting autophagy and inhibiting ERS through SIRT1 activation.

Therapeutic potential of BLT1 antagonist for COPD: involvement of inducing autophagy and ameliorating inflammation

Purpose

Leukotriene B4 (LTB4) is a major pro-inflammatory mediator that leads to the persistence of chronic inflammation in chronic obstructive pulmonary disease (COPD). The purpose of this study was to evaluate therapeutic potential of BLT1 antagonist for cigarette smoke (CS)-induced COPD and to explore the underlying mechanism.

Materials and methods

In vitro, autophagy proteins were determined by Western blotting in RAW264.7 macrophages treated with U75302 (BLT1 antagonist) or autophagy inhibitor in cigarette smoke extract-induced inflammation. In vivo, C57BL/6J mice were randomly divided into three groups: Control group, CS group and CS+U75302 group. After 12-week exposure, histological analysis and lung function tests were performed to evaluate the inflammatory infiltration and emphysema. The expression of inflammatory cytokines was measured by real-time PCR and enzyme-linked immunosorbent assay. Immunohistochemical analysis and Western blotting detected the expression of autophagy-related proteins. Transmission electron microscopy (TEM) showed the alterations of autophagosomes and lysosomes.

Results

Lower levels of inflammatory factors and autophagy markers were detected in U75302-treated cells and mice after CS exposure than control. In vitro, LC3 mRNA expression was elevated when treated with U75302. Autophagy inhibition resulted in augmented inflammatory response and autophagy proteins even with U75302 treatment. Furthermore, BLT1 antagonist decreased the number of lysosomes and autophagosomes in alveolar macrophages of mice and potentially enhanced the expression of transcriptional activation of transcription factor-EB (TFEB) in vitro and vivo.

Conclusion

Insufficient autophagy of macrophages was associated with LTB4-mediated inflammation in CS-exposure models. BLT1 antagonist ameliorated inflammatory response through inducing autophagy.

The plant flavonoid, fisetin alleviates cigarette smoke-induced oxidative stress, and inflammation in Wistar rat lungs

In the present study, we tested the antioxidant and anti-inflammatory potential of the plant flavonoid, fisetin against cigarette smoke-induced oxidative stress, and inflammation in rat lungs. Male Wistar rats were chronically exposed to cigarette smoke (CS) with or without administration of fisetin. Fisetin administration to CS-exposed rats resulted in a significant reduction in neutrophils and macrophages in bronchoalveolar lavage fluid as well as malondialdehyde, 3-nitrotyrosine, 8-isoprostane, tumor necrosis factor-alpha, interleukin-1beta, granulocyte macrophage-colony stimulating factor, interleukin-4, and interleukin-10 levels in lung tissues compared to those in CS-exposed rats not treated with fisetin. Fisetin also significantly augmented lung hemoxinase-1, glutathione peroxidase-2, reduced glutathione, superoxide dismutase, nitric oxide, and nuclear factor erythroid 2-related factor (Nrf2) levels in CS-exposed rats. In addition, a marked reversal in CS-induced histopathological changes was noted in fisetin-treated rats. Collectively, these data demonstrate the potential of fisetin to blunt CS-induced oxidative stress and inflammation in the lung and to prevent tissue damage via the Nrf2-mediated upregulation of antioxidant gene expression. PRACTICAL APPLICATIONS: In the present study, we found that the plant flavonoid, fisetin significantly abrogated the oxidative stress, inflammation, and tissue damage induced by cigarette smoke, a powerful pro-oxidant in rat lungs. Additionally, fisetin markedly reversed cigarette smoke-induced increases in neutrophil and macrophage cell populations in bronchoalveolar lavage fluid. These findings are particularly significant considering the association of cigarette smoking with increased oxidative stress and inflammation, which are central to the pathologies of a wide variety of chronic diseases including chronic obstructive pulmonary disease, cancer, and cardiovascular diseases. Therefore, the present work underscores the beneficial effects of the regular consumption of plant-based foods with medicinal properties for the effective prevention of these chronic diseases.

Accelerated lung aging and chronic obstructive pulmonary disease

INTRODUCTION

The prevalence of chronic obstructive pulmonary disease (COPD) increases exponentially with aging. Its pathogenesis, however, is not well known and aside from smoking cessation, there are no disease-modifying treatments for this disease. Areas covered: COPD is associated with accelerating aging and aging-related diseases. In this review, we will discuss the hallmarks of aging including genomic instability, telomere attrition, epigenetic alteration, loss of proteostasis, mitochondrial dysfunction, deregulated nutrient sensing, cellular senescence, stem cell exhaustion, and altered intercellular communication, which may be involved in COPD pathogenesis. Expert commentary: COPD and the aging process share similar molecular and cellular changes. Aging-related molecular pathways may represent novel therapeutic targets and biomarkers for COPD.

Novel cystamine-core dendrimer-formulation rescues ΔF508-CFTR and inhibits Pseudomonas aeruginosa infection by augmenting autophagy

BACKGROUND

Cystic fibrosis (CF) is challenged with pathophysiological barriers for effective airway drug-delivery. Hence, we standardized the therapeutic efficacy of the novel dendrimer-based autophagy-inducing anti-oxidant drug, cysteamine.

RESEARCH DESIGN AND METHODS

Human primary-CF epithelial-cells, CFBE41o-cells were used to standardize the efficacy of the dendrimer-cystamine in correcting impaired-autophagy, rescuing ΔF508-CFTR and Pseudomonas-aeruginosa (Pa) infection.

RESULTS

We first designed a novel cystamine-core dendrimer formulation (G4-CYS) that significantly increases membrane-ΔF508CFTR expression in CFBE41o-cells (p < 0.05) by forming its reduced-form cysteamine, in vivo. Additionally, G4-CYS treatment corrects ΔF508-CFTR-mediated impaired-autophagy as observed by a significant decrease (p < 0.05) in Ub-LC3-positive aggresome-bodies. Next, we verified that in non-permeabilized CFBE41o-cells, G4-CYS significantly (p < 0.05) induces ΔF508-CFTR's forward-trafficking to the plasma membrane. Furthermore, cysteamine's known antibacterial and anti-biofilm properties against Pa were enhanced as our findings demonstrate that both G4-CYS and its control DAB-core dendrimer, G4-DAB, exhibited significant (p < 0.05) bactericidal-activity against Pa. We also found that both G4-CYS and G4-DAB exhibit marked mucolytic-activity against porcine-mucus (p < 0.05). Finally, we demonstrate that G4-CYS not only corrects the autophagy-impairment by rescuing ΔF508-CFTR in CFBE41o-cells but also corrects the intrinsic phagocytosis defect (p < 0.05).

CONCLUSIONS

Overall, our data demonstrates the efficacy of novel cystamine-dendrimer formulation in rescuing ΔF508-CFTR to the plasma membrane and inhibiting Pa bacterial-infection by augmenting autophagy.

Protective Features of Autophagy in Pulmonary Infection and Inflammatory Diseases

Autophagy is a highly conserved catabolic process involving autolysosomal degradation of cellular components, including protein aggregates, damaged organelles (such as mitochondria, endoplasmic reticulum, and others), as well as various pathogens. Thus, the autophagy pathway represents a major adaptive response for the maintenance of cellular and tissue homeostasis in response to numerous cellular stressors. A growing body of evidence suggests that autophagy is closely associated with diverse human diseases. Specifically, acute lung injury (ALI) and inflammatory responses caused by bacterial infection or xenobiotic inhalation (e.g., chlorine and cigarette smoke) have been reported to involve a spectrum of alterations in autophagy phenotypes. The role of autophagy in pulmonary infection and inflammatory diseases could be protective or harmful dependent on the conditions. In this review, we describe recent advances regarding the protective features of autophagy in pulmonary diseases, with a focus on ALI, idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD), tuberculosis, pulmonary arterial hypertension (PAH) and cystic fibrosis.

Autophagy augmentation alleviates cigarette smoke-induced CFTR-dysfunction, ceramide-accumulation and COPD-emphysema pathogenesis

In this study, we aimed to investigate precise mechanism(s) of sphingolipid-imbalance and resulting ceramide-accumulation in COPD-emphysema. Where, human and murine emphysema lung tissues or human bronchial epithelial cells (Beas2b) were used for experimental analysis. We found that lungs of smokers and COPD-subjects with increasing emphysema severity demonstrate sphingolipid-imbalance, resulting in significant ceramide-accumulation and increased ceramide/sphingosine ratio, as compared to non-emphysema/non-smoker controls. Next, we found a substantial increase in emphysema chronicity-related ceramide-accumulation in murine (C57BL/6) lungs, while sphingosine levels only slightly increased. In accordance, the expression of the acid ceramidase decreased after CS-exposure. Moreover, CS-induced (sub-chronic) ceramide-accumulation was significantly (p < 0.05) reduced by treatment with TFEB/autophagy-inducing drug, gemfibrozil (GEM), suggesting that autophagy regulates CS-induced ceramide-accumulation. Next, we validated experimentally that autophagy/lipophagy-induction using an anti-oxidant, cysteamine, significantly (p < 0.05) reduces CS-extract (CSE)-mediated intracellular-ceramide-accumulation in p62 + aggresome-bodies. In addition to intracellular-accumulation, we found that CSE also induces membrane-ceramide-accumulation by ROS-dependent acid-sphingomyelinase (ASM) activation and plasma-membrane translocation, which was significantly controlled (p < 0.05) by cysteamine (an anti-oxidant) and amitriptyline (AMT, an inhibitor of ASM). Cysteamine-mediated and CSE-induced membrane-ceramide regulation was nullified by CFTR-inhibitor-172, demonstrating that CFTR controls redox impaired-autophagy dependent membrane-ceramide accumulation. In summary, our data shows that CS-mediated autophagy/lipophagy-dysfunction results in intracellular-ceramide-accumulation, while acquired CFTR-dysfunction-induced ASM causes membrane ceramide-accumulation. Thus, CS-exposure alters the sphingolipid-rheostat leading to the increased membrane- and intracellular- ceramide-accumulation inducing COPD-emphysema pathogenesis that is alleviated by treatment with cysteamine, a potent anti-oxidant with CFTR/autophagy-augmenting properties.

Autophagy in exposure to environmental chemicals

Autophagy is a catabolic pathway, which breaks down old and damaged cytoplasmic material into basic biomolecules through lysosome-mediated digestion thereby recycling cellular material. In this way, autophagy prevents the accumulation of damaged cellular components inside cells and reduces metabolic stress and toxicity. The basal level of autophagy is generally low but essential for maintaining the turnover of proteins and other molecules. The level is, however, increased in response to various stress conditions including chemical stress. This elevation in autophagy is intended to restore energy balance and improve cell survival in stress conditions. However, aberrant and/or deficient autophagy may also be involved in the aggravation of chemical-caused insults. Thus, the overall role of autophagy in chemical-induced toxicity is complex and only a limited number of environmental chemicals have been studied from this point of view. Autophagy is associated with many of the chemical-caused cytotoxic mechanisms, including mitochondrial dysfunction, DNA damage, oxidative stress, changes in the endoplasmic reticulum, impairment of lysosomal functions, and inflammation. This mini-review describes autophagy and its involvement in the responses to some common environmental exposures including airborne particulate matter, nanoparticles and tobacco smoke as well as to some common single environmental chemicals.

Cell Death in the Lung: The Apoptosis-Necroptosis Axis

Regulated cell death is a major mechanism to eliminate damaged, infected, or superfluous cells. Previously, apoptosis was thought to be the only regulated cell death mechanism; however, new modalities of caspase-independent regulated cell death have been identified, including necroptosis, pyroptosis, and autophagic cell death. As an understanding of the cellular mechanisms that mediate regulated cell death continues to grow, there is increasing evidence that these pathways are implicated in the pathogenesis of many pulmonary disorders. This review summarizes our understanding of regulated cell death as it pertains to the pathogenesis of chronic obstructive pulmonary disease, asthma, idiopathic pulmonary fibrosis, acute respiratory distress syndrome, and pulmonary arterial hypertension.

Enhancing TFEB-Mediated Cellular Degradation Pathways by the mTORC1 Inhibitor Quercetin

Signaling pathways mediated by the mechanistic target of rapamycin (mTOR) play key roles in aging and age-related diseases. As a downstream protein of mTOR, transcription factor EB (TFEB) controls lysosome biogenesis and cellular trafficking, processes that are essential for the functions of phagocytic cells like the retinal pigment epithelium (RPE). In the current study, we show that a naturally occurring polyphenolic compound, quercetin, promoted TFEB nuclear translocation and enhanced its transcriptional activity in cultured RPE cells. Activated TFEB facilitated degradation of phagocytosed photoreceptor outer segments. Quercetin is a direct inhibitor of mTOR but did not influence the activity of Akt at the tested concentration range. Our data suggest that the dietary compound quercetin can have beneficial roles in neuronal tissues by improving the functions of the TFEB-lysosome axis and enhancing the capacities of cellular degradation and self-renewal.

Correlation between autophagy levels in peripheral blood mononuclear cells and clinical parameters in patients with chronic obstructive pulmonary disease

Autophagy serves a role in the pathogenesis of chronic inflammatory diseases. The aim of the present study was to compare the autophagy levels in the peripheral blood mononuclear cells (PBMCs) of patients with chronic obstructive pulmonary disease (COPD) and healthy individuals and to assess the association between autophagy and the clinical parameters of COPD. Samples of peripheral blood from 20 patients with stable COPD and 20 healthy controls were collected. PBMCs were harvested using Ficoll density gradient centrifugation. Levels of the autophagy‑associated proteins ubiquitin‑binding protein p62 (p62), microtubule‑associated proteins 1A/1B light chain 3A (LC3I/II) and beclin‑1 in PBMCs were detected by western blotting. Enzyme‑linked immunosorbent assay kits were used to detect the serum concentrations of interleukin (IL)‑6, IL‑8 and tumor necrosis factor (TNF)‑α. Associations between the levels of autophagy and forced expiratory volume in 1 sec % predicted (FEV1%) and pro‑inflammatory factors were assessed. Western blotting demonstrated that the protein expression of p62 was decreased, but LC3II/I and beclin‑1 levels increased in patients with COPD compared with healthy controls. Serum levels of IL‑6, IL‑8 and TNF‑α were increased in patients with COPD. The extent of PBMC autophagy was negatively correlated with FEV1% predicted, but positively correlated with levels of pro‑inflammatory cytokines. The levels of autophagy in PBMCs in patients with COPD were increased and were negatively correlated with FEV1% predicted and positively correlated with circulating levels of pro‑inflammatory cytokines. Autophagy may serve a role as a biomarker of the severity of COPD or as a therapeutic target for treatment of COPD.

Autophagy and inflammation in chronic respiratory disease

Persistent inflammation within the respiratory tract underlies the pathogenesis of numerous chronic pulmonary diseases including chronic obstructive pulmonary disease, asthma and pulmonary fibrosis. Chronic inflammation in the lung may arise from a combination of genetic susceptibility and environmental influences, including exposure to microbes, particles from the atmosphere, irritants, pollutants, allergens, and toxic molecules. To this end, an immediate, strong, and highly regulated inflammatory defense mechanism is needed for the successful maintenance of homeostasis within the respiratory system. Macroautophagy/autophagy plays an essential role in the inflammatory response of the lung to infection and stress. At baseline, autophagy may be critical for inhibiting spontaneous pulmonary inflammation and fundamental for the response of pulmonary leukocytes to infection; however, when not regulated, persistent or inefficient autophagy may be detrimental to lung epithelial cells, promoting lung injury. This perspective will discuss the role of autophagy in driving and regulating inflammatory responses of the lung in chronic lung diseases with a focus on potential avenues for therapeutic targeting. Abbreviations AR allergic rhinitis AM alveolar macrophage ATG autophagy-related CF cystic fibrosis CFTR cystic fibrosis transmembrane conductance regulator COPD chronic obstructive pulmonary disease CS cigarette smoke CSE cigarette smoke extract DC dendritic cell IH intermittent hypoxia IPF idiopathic pulmonary fibrosis ILD interstitial lung disease MAP1LC3B microtubule associated protein 1 light chain 3 beta MTB Mycobacterium tuberculosis MTOR mechanistic target of rapamycin kinase NET neutrophil extracellular traps OSA obstructive sleep apnea PAH pulmonary arterial hypertension PH pulmonary hypertension ROS reactive oxygen species TGFB1 transforming growth factor beta 1 TNF tumor necrosis factor.

Inhibition of histone-deacetylase activity rescues inflammatory cystic fibrosis lung disease by modulating innate and adaptive immune responses

Background

Chronic lung disease resulting from dysfunctional cystic fibrosis transmembrane conductance regulator (CFTR) and NFκB-mediated neutrophilic-inflammation forms the basis of CF-related mortality. Here we aimed to evaluate if HDAC inhibition controls Pseudomonas-aeruginosa-lipopolysaccharide (Pa-LPS) induced airway inflammation and CF-lung disease.

Methods

For in vitro experiments, HEK293-cells were transfected with IL-8 or NFκB-firefly luciferase, and SV40-renilla- luciferase reporter constructs or ΔF508-CFTR-pCEP, followed by treatment with suberoylanilide hydroxamic acid (SAHA), Trichostatin-A (TSA) and/or TNFα. For murine studies, Cftr^+/+ or Cftr^−/− mice (n = 3) were injected/instilled with Pa-LPS and/or treated with SAHA or vehicle control. The progression of lung disease was monitored by quantifying changes in inflammatory markers (NFκB), cytokines (IL-6/IL-10), neutrophil activity (MPO, myeloperoxidase and/or NIMP-R14) and T-reg numbers.

Results

SAHA treatment significantly (p < 0.05) suppresses TNFα-induced NFκB and IL-8 reporter activities in HEK293-cells. Moreover, SAHA, Tubacin (selective HDAC6-inhibitor) or HDAC6-shRNAs controls CSE-induced ER-stress activities (p < 0.05). In addition, SAHA restores trafficking of misfolded-ΔF508-CFTR, by inducing protein levels of both B and C forms of CFTR. Murine studies using Cftr^+/+ or Cftr^−/− mice verified that SAHA controls Pa-LPS induced IL-6 levels, and neutrophil (MPO levels and/or NIMP-R14), NFκB-(inflammation) and Nrf2 (oxidative-stress marker) activities, while promoting FoxP3⁺ T-reg activity.

Conclusion

In summary, SAHA-mediated HDAC inhibition modulates innate and adaptive immune responses involved in pathogenesis and progression of inflammatory CF-lung disease.

Electronic supplementary material

The online version of this article (10.1186/s12931-017-0705-8) contains supplementary material, which is available to authorized users.

Cigarette Smoke Exposure Inhibits Bacterial Killing via TFEB-Mediated Autophagy Impairment and Resulting Phagocytosis Defect

INTRODUCTION

Cigarette smoke (CS) exposure is the leading risk factor for COPD-emphysema pathogenesis. A common characteristic of COPD is impaired phagocytosis that causes frequent exacerbations in patients leading to increased morbidity. However, the underlying mechanism is unclear. Hence, we investigated if CS exposure causes autophagy impairment as a mechanism for diminished bacterial clearance via phagocytosis by utilizing murine macrophages (RAW264.7 cells) and Pseudomonas aeruginosa (PA01-GFP) as an experimental model.

METHODS

Briefly, RAW cells were treated with cigarette smoke extract (CSE), chloroquine (autophagy inhibitor), TFEB-shRNA, CFTR(inh)-172, and/or fisetin prior to bacterial infection for functional analysis.

RESULTS

Bacterial clearance of PA01-GFP was significantly impaired while its survival was promoted by CSE (p < 0.01), autophagy inhibition (p < 0.05; p < 0.01), TFEB knockdown (p < 0.01; p < 0.001), and inhibition of CFTR function (p < 0.001; p < 0.01) in comparison to the control group(s) that was significantly recovered by autophagy-inducing antioxidant drug, fisetin, treatment (p < 0.05; p < 0.01; and p < 0.001). Moreover, investigations into other pharmacological properties of fisetin show that it has significant mucolytic and bactericidal activities (p < 0.01; p < 0.001), which warrants further investigation.

CONCLUSIONS

Our data suggests that CS-mediated autophagy impairment as a critical mechanism involved in the resulting phagocytic defect, as well as the therapeutic potential of autophagy-inducing drugs in restoring is CS-impaired phagocytosis.

Augmentation of S-Nitrosoglutathione Controls Cigarette Smoke-Induced Inflammatory-Oxidative Stress and Chronic Obstructive Pulmonary Disease-Emphysema Pathogenesis by Restoring Cystic Fibrosis Transmembrane Conductance Regulator Function

AIMS

Cigarette smoke (CS)-mediated acquired cystic fibrosis transmembrane conductance regulator (CFTR)-dysfunction, autophagy-impairment, and resulting inflammatory-oxidative/nitrosative stress leads to chronic obstructive pulmonary disease (COPD)-emphysema pathogenesis. Moreover, nitric oxide (NO) signaling regulates lung function decline, and low serum NO levels that correlates with COPD severity. Hence, we aim to evaluate here the effects and mechanism(s) of S-nitrosoglutathione (GSNO) augmentation in regulating inflammatory-oxidative stress and COPD-emphysema pathogenesis.

RESULTS

Our data shows that cystic fibrosis transmembrane conductance regulator (CFTR) colocalizes with aggresome bodies in the lungs of COPD subjects with increasing emphysema severity (Global Initiative for Chronic Obstructive Lung Disease [GOLD] I - IV) compared to nonemphysema controls (GOLD 0). We further demonstrate that treatment with GSNO or S-nitrosoglutathione reductase (GSNOR)-inhibitor (N6022) significantly inhibits cigarette smoke extract (CSE; 5%)-induced decrease in membrane CFTR expression by rescuing it from ubiquitin (Ub)-positive aggresome bodies (p < 0.05). Moreover, GSNO restoration significantly (p < 0.05) decreases CSE-induced reactive oxygen species (ROS) activation and autophagy impairment (decreased accumulation of ubiquitinated proteins in the insoluble protein fractions and restoration of autophagy flux). In addition, GSNO augmentation inhibits protein misfolding as CSE-induced colocalization of ubiquitinated proteins and LC3B (in autophagy bodies) is significantly reduced by GSNO/N6022 treatment. We verified using the preclinical COPD-emphysema murine model that chronic CS (Ch-CS)-induced inflammation (interleukin [IL]-6/IL-1β levels), aggresome formation (perinuclear coexpression/colocalization of ubiquitinated proteins [Ub] and p62 [impaired autophagy marker], and CFTR), oxidative/nitrosative stress (p-Nrf2, inducible nitric oxide synthase [iNOS], and 3-nitrotyrosine expression), apoptosis (caspase-3/7 activity), and alveolar airspace enlargement (Lm) are significantly (p < 0.05) alleviated by augmenting airway GSNO levels. As a proof of concept, we demonstrate that GSNO augmentation suppresses Ch-CS-induced perinuclear CFTR protein accumulation (p < 0.05), which restores both acquired CFTR dysfunction and autophagy impairment, seen in COPD-emphysema subjects.

INNOVATION

GSNO augmentation alleviates CS-induced acquired CFTR dysfunction and resulting autophagy impairment.

CONCLUSION

Overall, we found that augmenting GSNO levels controls COPD-emphysema pathogenesis by reducing CS-induced acquired CFTR dysfunction and resulting autophagy impairment and chronic inflammatory-oxidative stress. Antioxid. Redox Signal. 27, 433-451.

Cigarette smoke induced autophagy-impairment regulates AMD pathogenesis mechanisms in ARPE-19 cells

Age related macular degeneration (AMD) is one of the leading causes of blindness. Genetics, environmental insult, and age-related factors all play a key role in altering proteostasis, the homeostatic process regulating protein synthesis, degradation and processing. These factors also play a role in the pathogenesis of AMD and it has been well established that cigarette smoking (CS) initiates AMD pathogenic mechanisms. The primary goal of this study is to elucidate whether CS can induce proteostasis/autophagy-impairment in retinal pigment epithelial (RPE) cells. In our preliminary analysis, it was found that cigarette smoke extract (CSE) induces accumulation of ubiquitinated proteins in the insoluble protein fraction (p < 0.01), which was subsequently mitigated through cysteamine (p < 0.01) or fisetin (p < 0.05) treatment. Further, it was verified that these CSE induced ubiquitinated proteins accumulated in the peri-nuclear spaces (p<0.05) that were cleared- off with cysteamine (p < 0.05) or fisetin (p < 0.05). Moreover, CSE-induced aggresome-formation (LC3B-GFP and Ub-RFP co-localization) and autophagy-flux impairment was significantly (p<0.01) mitigated by cysteamine (p<0.05) or fisetin (p<0.05) treatment, indicating the restoration of CSE-mediated autophagy-impairment. CSE treatment was also found to induce intracellular reactive oxygen species (ROS, p < 0.001) while impacting cell viability (p < 0.001), which was quantified using CMH2DCFDA-dye (ROS) and MTS (proliferation) or propodium iodide staining (cell viability) assays, respectively. Moreover, cysteamine and fisetin treatment ameliorated CS-mediated ROS production (p < 0.05) and diminished cell viability (p < 0.05). Lastly, CSE was found to induce cellular senescence (p < 0.001), which was significantly ameliorated by cysteamine (p < 0.001) or fisetin (p < 0.001). In conclusion, our study indicates that CS induced proteostasis/autophagy-impairment regulates mechanisms associated with AMD pathogenesis. Moreover, autophagy-inducing drugs such as cysteamine or fisetin can ameliorate AMD pathogenesis mechanisms that warrant further investigation in pre-clinical murine models.

Augmenting autophagy for prognosis based intervention of COPD-pathophysiology

Chronic obstructive pulmonary disease (COPD) is foremost among the non-reversible fatal ailments where exposure to tobacco/biomass-smoke and aging are the major risk factors for the initiation and progression of the obstructive lung disease. The role of smoke-induced inflammatory-oxidative stress, apoptosis and cellular senescence in driving the alveolar damage that mediates the emphysema progression and severe lung function decline is apparent, although the central mechanism that regulates these processes was unknown. To fill in this gap in knowledge, the central role of proteostasis and autophagy in regulating chronic lung disease causing mechanisms has been recently described. Recent studies demonstrate that cigarette/nicotine exposure induces proteostasis/autophagy-impairment that leads to perinuclear accumulation of polyubiquitinated proteins as aggresome-bodies, indicative of emphysema severity. In support of this concept, autophagy inducing FDA-approved anti-oxidant drugs control tobacco-smoke induced inflammatory-oxidative stress, apoptosis, cellular senescence and COPD-emphysema progression in variety of preclinical models. Hence, we propose that precise and early detection of aggresome-pathology can allow the timely assessment of disease severity in COPD-emphysema subjects for prognosis-based intervention. While intervention with autophagy-inducing drugs is anticipated to reduce alveolar damage and lung function decline, resulting in a decrease in the current mortality rates in COPD-emphysema subjects.