Autophagy inhibitor 3-methyladenine protects against endothelial cell barrier dysfunction in acute lung injury

Risk factors of using late-autophagy inhibitors: Aspects to consider when combined with anticancer therapies

Cancer resistance to therapy is still an unsolved scientific and clinical problem. In 2022, the hallmarks of cancer have been expanded to include four new features, including cellular senescence. Therapy-induced senescence (TIS) is a stressor-based response to conventional treatment methods, e.g. chemo- and radiotherapy, but also to non-conventional targeted therapies. Since TIS reinforces resistance in cancers, new strategies for sensitizing cancer cells to therapy are being adopted. These include macroautophagy as a potential target for inhibition due to its potential cytoprotective role in many cancers. The mechanism of late-stage autophagy inhibitors is based on blockage of autophagolysosome formation or an increase in lysosomal pH, resulting in disrupted cargo degradation. Such inhibitors are relevant candidates for increasing anticancer therapy effectiveness. In particular, 4-aminoquoline derivatives: chloroquine/hydroxychloroquine (CQ/HCQ) have been tested in multiple clinical trials in combination with senescence-inducing anti-cancer drugs. In this review, we summarize the properties of selected late-autophagy inhibitors and their role in the regulation of autophagy and senescent cell phenotype in vitro and in vivo models of cancer as well as treatment response in clinical trials on oncological patients. Additionally, we point out that, although these compounds increase the effectiveness of treatment in some cases, their practical usage might be hindered due to systemic toxicity, hypoxic environment, dose- ant time-dependent inhibitory effects, as well as a possible contribution to escaping from TIS.

Effect of Nano-selenium on Biological Mechanism of Goblet Cells of the Small Intestine Within Laying Hen

Dietary selenium intake within the normal physiological range is critical for various supporting biological functions. However, the effect of nano-selenium on biological mechanism of goblet cells associated with autophagy is largely unknown.The purpose of this study was to investigate the effect of nano-selenium on the mucosal immune-defense mechanism of goblet cells (GCs) in the small intestine of laying hens.The autophagy was determined by using specific markers. Nano-selenium-treated group of immunohistochemistry (IHC), immunofluorescence (IF), and western blotting (WB) results indicated the strong positive immune signaling of microtubule-associated light chain (LC3) within the mucosal surface of the small intestine. However, weak expression of LC3 was observed in the 3-methyladenine autophagy inhibitor (3-MA) group. IHC and IF staining results showed the opposite tendency for LC3 of sequestosome 1 (P62/SQSTM1). P62/SQSTM1 showed strong positive immune signaling within the mucosal surface of the small intestine of the 3-MAgroup, and weak immune signaling of P62/SQSTM1 in the nano-selenium-treated group. Moreover, pinpointing autophagy was involved in the mucosal production and enrichment of mucosal immunity of the GCs. The morphology and ultrastructure evidence showed that the mucus secretion of GCs was significantly increased after nano-selenium treatment confirmed by light and transmission electron microscopy. Besides that, immunostaining of IHC, IF and WB showed that autophagy enhanced the secretion of Mucin2 (Muc2) protein in nano-selenium-treated group. This work illustrates that the nano-selenium particle might enhance the mucosal immune-defense mechanism via the protective role of GCs for intestinal homeostasis through autophagy.

MLKL Protects Pulmonary Endothelial Cells in Acute Lung Injury

The role of autophagy in pulmonary microvascular endothelial cells (PMVECs) is controversial in LPS-induced acute lung injury (ALI). Mixed lineage kinase domain-like pseudokinase (MLKL) has recently been reported to maintain cell survival by facilitating autophagic flux in response to starvation rather than its well-recognized role in necroptosis. Using a mouse PMVEC and LPS-induced ALI model, we showed that in PMVECs, MLKL was phosphorylated (p-MLKL) and autophagic flux was accelerated at the early stage of LPS stimulation (1-3 h), manifested by increases in concentrations of lipidated MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3 β; LC3-II), decreases in concentrations of SQSTM1/p62 (sequestosome 1), and fusion of the autophagosome and lysosome by pHluorin-mKate2-human LC3 assay, which were all reversed by either MLKL inhibitor or siRNA MLKL. In mice, the inhibition of MLKL increased vascular permeability and aggravated mouse ALI upon 3-hour LPS stimulation. The p-MLKL induced by short-term LPS formed multimers to facilitate the closure of the phagophore by HaloTag-LC3 autophagosome completion assay. The charged multivesicular body protein 2A (CHMP2A) is essential in the process of phagophore closure into the nascent autophagosome. In agreement with the p-MLKL change, CHMP2A concentrations markedly increased during 1-3-hour LPS stimulation. CHMP2A knockdown blocked autophagic flux upon LPS stimulation, whereas CHMP2A overexpression boosted autophagic flux and attenuated mouse ALI even in the presence of MLKL inhibitor. We propose that the activated MLKL induced by short-term LPS facilitates autophagic flux by accelerating the closure of the phagophore via CHMP2A, thus protecting PMVECs and alleviating LPS-induced ALI.

Capsaicin Attenuates LPS-Induced Acute Lung Injury by Inhibiting Inflammation and Autophagy Through Regulation of the TRPV1/AKT Pathway

Purpose

Acute lung injury (ALI) is a severe pulmonary disease characterized by damage to the alveoli and pulmonary blood vessels, leading to severe impairment of lung function. Studies on the effect of capsaicin (8-methyl-N-geranyl-6-nonamide, CAP) on lipopolysaccharide (LPS)-induced ALI in bronchial epithelial cells transformed with Ad12-SV40 2B (BEAS-2B) are still limited. This study aimed to investigate the effect and specific mechanism by which CAP improves LPS-induced ALI.

Methods

The present study investigated the effect of CAP and the potential underlying mechanisms in LPS-induced ALI in vitro and vivo via RNA sequencing, Western blotting (WB), quantitative real-time reverse transcription PCR (qRT‒PCR), enzyme-linked immunosorbent assay (ELISA), and transmission electron microscopy (TEM). The TRPV1 inhibitor AMG9810 and the AKT agonist SC79 were used to confirm the protective effect of the TRPV1/AKT axis against ALI. The autophagy agonist rapamycin (Rapa) and the autophagy inhibitors 3-methyladenine (3-MA) and bafilomycin A1 (Baf-A1) were used to clarify the characteristics of LPS-induced autophagy.

Results

Our findings demonstrated that CAP effectively suppressed inflammation and autophagy in LPS-induced ALI, both in vivo and in vitro. This mechanism involves regulation by the TRPV1/AKT signaling pathway. By activating TRPV1, CAP reduces the expression of P-AKT, thereby exerting its anti-inflammatory and inhibitory effects on pro-death autophagy. Furthermore, prior administration of CAP provided substantial protection to mice against ALI induced by LPS, reduced the lung wet/dry ratio, decreased proinflammatory cytokine expression, and downregulated LC3 expression.

Conclusion

Taken together, our results indicate that CAP protects against LPS-induced ALI by inhibiting inflammatory responses and autophagic death through the TRPV1/AKT signaling pathway, presenting a novel strategy for ALI therapy.

Vitamin D3 improved hypoxia-induced lung injury by inhibiting the complement and coagulation cascade and autophagy pathway

BACKGROUND

Pulmonary metabolic dysfunction can cause lung tissue injury. There is still no ideal drug to protect against hypoxia-induced lung injury, therefore, the development of new drugs to prevent and treat hypoxia-induced lung injury is urgently needed. We aimed to explore the ameliorative effects and molecular mechanisms of vitamin D3 (VD3) on hypoxia-induced lung tissue injury.

METHODS

Sprague-Dawley (SD) rats were randomly divided into three groups: normoxia, hypoxia, and hypoxia + VD3. The rat model of hypoxia was established by placing the rats in a hypobaric chamber. The degree of lung injury was determined using hematoxylin and eosin (H&E) staining, lung water content, and lung permeability index. Transcriptome data were subjected to differential gene expression and pathway analyses. In vitro, type II alveolar epithelial cells were co-cultured with hepatocytes and then exposed to hypoxic conditions for 24 h. For VD3 treatment, the cells were treated with low and high concentrations of VD3.

RESULTS

Transcriptome and KEGG analyses revealed that VD3 affects the complement and coagulation cascade pathways in hypoxia-induced rats, and the genes enriched in this pathway were Fgb/Fga/LOC100910418. Hypoxia can cause increases in lung edema, inflammation, and lung permeability disruption, which are attenuated by VD3 treatment. VD3 weakened the complement and coagulation cascade in the lung and liver of hypoxia-induced rats, characterized by lower expression of fibrinogen alpha chain (Fga), fibrinogen beta chain (Fgb), protease-activated receptor 1 (PAR1), protease-activated receptor 3 (PAR3), protease-activated receptor 4 (PAR4), complement (C) 3, C3a, and C5. In addition, VD3 improved hypoxic-induced type II alveolar epithelial cell damage and inflammation by inhibiting the complement and coagulation cascades. Furthermore, VD3 inhibited hypoxia-induced autophagy in vivo and in vitro, which was abolished by the mitophagy inducer, carbonyl cyanide-m-chlorophenylhydrazone (CCCP).

CONCLUSION

VD3 alleviated hypoxia-induced pulmonary edema by inhibiting the complement and coagulation cascades and autophagy pathways.

Liensinine alleviates LPS-induced acute lung injury by blocking autophagic flux via PI3K/AKT/mTOR signaling pathway

Acute lung injury (ALI) is a major pathological problem characterized by severe inflammatory reactions and is a critical disease with high clinical morbidity and mortality. Liensinine, a major isoquinoline alkaloid, is extracted from the green embryos of mature Nelumbonaceae seeds. It has been reported to have an inhibitory effect on tumors. However, the effects of liensinine on ALI have not been reported to-date. The aim of this study was to explore the inhibitory effects of liensinine on lipopolysaccharide (LPS)-induced ALI and its possible mechanism. We found that liensinine significantly reduced LPS-induced ALI and reduced the production of inflammatory factors IL-6, IL-8, and TNF-α. In addition, liensinine blocked autophagic flux and increased the number of autophagosomes by upregulating LC3-II/I and p62 protein levels. More importantly, pretreatment with the early stages autophagy inhibitor 3-Methyladenine (3-MA) can reverse the inhibitory effects of liensinine on the secretion of inflammatory factors in ALI. The PI3K/AKT/mTOR pathway is involved in LPS-induced autophagy regulated by liensinine in ALI. In summary, this study suggests that liensinine inhibits the production of inflammatory factors in LPS-induced ALI by regulating autophagy via the PI3K/AKT/mTOR pathway, which may provide a new therapeutic strategy to alleviate ALI.

Spleen Tyrosine Kinase phosphorylates VE-cadherin to cause endothelial barrier disruption in acute lung injury

Increased endothelial cell (EC) permeability is a cardinal feature of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Tyrosine phosphorylation of VE-cadherin is a key determinant of EC barrier disruption. However, the identity and role of tyrosine kinases in this context are incompletely understood. Here we report that Spleen Tyrosine Kinase (Syk) is a key mediator of EC barrier disruption and lung vascular leak in sepsis. Inhibition of Syk by pharmacological or genetic approaches, each reduced thrombin-induced EC permeability. Mechanistically, Syk associates with and phosphorylates VE-cadherin to cause EC permeability. To study the causal role of endothelial Syk in sepsis-induced ALI, we used a remarkably efficient and cost-effective approach based on gene transfer to generate EC-ablated Syk mice. These mice were protected against sepsis-induced loss of VE-cadherin and inflammatory lung injury. Notably, the administration of Syk inhibitor R788 (fostamatinib); currently in phase II clinical trial for the treatment of COVID-19, mitigated lung injury and mortality in mice with sepsis. These data identify Syk as a novel kinase for VE-cadherin and a druggable target against ALI in sepsis.

Phthalate derivative DEHP disturbs the antiproliferative effect of camptothecin in human lung cancer cells by attenuating DNA damage and activating Akt/NF-κB signaling pathway

Plasticizers/phthalates play a facilitating role in the development of cancer and help the tumor to grow and metastasize. Camptothecin (CPT) and its derivatives are known to have anticancer properties of inhibiting cell growth, promoting cell apoptosis, and increasing autophagy. Therefore, in this study, we investigated whether the presence of di(2-ethylhexyl) phthalate (DEHP) could hinder apoptosis and autophagy caused by CPT in non-small cell lung cancer (NSCLC) cells. We found that DEHP interferes with CPT-induced apoptosis and autophagy and increases the prosurvival pathway by reducing the DNA damage marker γ-H2AX and activating the Akt and NF-κB pathways. Furthermore, we also confirmed that combining DEHP with 3-MA has additive effects in inhibiting autophagy and apoptosis in NSCLC cells. Taken together, our findings show that DEHP could affect CPT-induced anticancer treatment and provide evidence to show that DEHP induces chemoresistance in CPT-based chemotherapy.

WWOX activates autophagy to alleviate lipopolysaccharide-induced acute lung injury by regulating mTOR

Acute lung injury (ALI) is characterized by acute systemic inflammatory responses that may lead to severe acute respiratory distress syndrome (ARDS). The clinical course of ALI/ARDS is variable; however, it has been reported that lipopolysaccharides (LPS) play a role in its development. The fragile chromosomal site gene WWOX is highly sensitive to genotoxic stress induced by environmental exposure and is an important candidate gene for exposure-related lung disease research. However, the expression of WWOX and its role in LPS-induced ALI still remain unidentified. This study investigated the expression of WWOX in mouse lung and epithelial cells and explored the role of WWOX in LPS-induced ALI model in vitro and in vivo. In addition, we explored one of the possible mechanisms by which WWOX alleviates ALI from the perspective of autophagy. Here, we observed that LPS stimulation reduced the expression of WWOX and the autophagy marker microtubule-associated protein 1 light chain 3β-II (MAP1LC3B/LC3B) in mouse lung epithelial and human epithelial (H292) cells. Overexpression of WWOX led to the activation of autophagy and inhibited inflammatory responses in LPS-induced ALI cells and mouse model. More importantly, we found that WWOX interacts with mechanistic target of rapamycin [serine/threonine kinase] (mTOR) and regulates mTOR and ULK-1 signaling-mediated autophagy. Thus, reduced WWOX levels were associated with LPS-induced ALI. WWOX can activate autophagy in lung epithelial cells and protect against LPS-induced ALI, which is partly related to the mTOR-ULK1 signaling pathway.

Pretreatment with 3-methyladenine ameliorated Pseudomonas aeruginosa-induced acute pneumonia by inhibiting cell death of neutrophils in a mouse infection model

Pseudomonas aeruginosa is one of the leading causes of nosocomial infections worldwide. Clinical isolates that are resistant to multiple antimicrobials make it intractable. The interactions between P. aeruginosa and host cell death have multiple effects on bacterial clearance and inflammation; however, the potential intervention effects remain to be defined. Herein, we demonstrated that intravenous administration of 3-methyladenine before, but not after, P. aeruginosa infection enhanced autophagy-independent survival, which was accompanied by a decrease in the bacterial load, alleviation of pathology and reduction in inflammatory cytokines, in an acute pneumonia mouse model. Interestingly, these beneficial effects were not dependent on neutrophil recruitment or phagocytosis, but on the enhanced killing capacity induced by inhibiting the cell death of 3-MA pretreated neutrophils. These findings demonstrate a novel protective role of 3-MA pretreatment in P. aeruginosa-induced acute pneumonia.

Research Progress on Autophagy Regulation by Active Ingredients of Traditional Chinese Medicine in the Treatment of Acute Lung Injury

Autophagy is a highly conserved process that maintains cell stability in eukaryotes, participates in the turnover of intracellular substances to maintain cell function, helps to resist pathogen invasion, and improves cell tolerance to environmental changes. Autophagy has been observed in many diseases, and the symptoms of these diseases are significantly improved by regulating autophagy. Autophagy is also involved in the development of lung diseases. Studies have shown that autophagy may play a beneficial or harmful role in acute lung injury (ALI), and ALI has been treated with traditional Chinese medicine designed to promote or inhibit autophagy. In this paper, the molecular mechanism and common pathways regulating autophagy and the relationship between autophagy and ALI are introduced, and the active ingredients of traditional Chinese medicine that improve ALI symptoms by regulating autophagy are summarized.

TM9SF1 knockdown decreases inflammation by enhancing autophagy in a mouse model of acute lung injury

TM9SF1 is a member of the TM9SF (Transmembrane 9 Superfamily Member) family, which usually has a long N-terminal extracellular region and nine transmembrane domains. TM9SF1's biological function and mechanisms in inflammation are yet unknown. Tm9sf1 was shown to be upregulated in the lung tissues of mice suffering from LPS-induced acute lung injury (ALI). Tm9sf1 knockout mice were studied, and it was shown that Tm9sf1 knockout significantly alleviated LPS-induced ALI, as evidenced by higher survival rate, improved pulmonary vascular permeability, decreased inflammatory cell infiltration, and downregulated inflammatory cytokines. TM9SF1 was also demonstrated to be a negative regulator of autophagy in the LPS-induced ALI model in vitro and in vivo. The autophagy inhibitor 3-MA could counteract the beneficial effects of Tm9sf1 knockout on ALI. Therefore, we discover for the first time the role and mechanism of TM9SF1 in LPS-induced ALI and establish a relationship between TM9SF1 regulated autophagy and ALI progression, which may provide novel targets for the treatment of ALI.

circEXOC5 promotes acute lung injury through the PTBP1/Skp2/Runx2 axis to activate autophagy

To understand the pathogenesis of acute lung injury (ALI), we focused on circEXOC5, a significantly up-regulated circular RNA in ALI. Using the in vivo cecal ligation and puncture (CLP)-induced ALI mouse model and in vitro LPS-challenged mouse pulmonary microvascular endothelial cell (MPVEC) model, we examined the impacts of knockdown circEXOC5 on lung injury, inflammation, and autophagy. The regulation between circEXOC5, polypyrimidine tract-binding protein 1 (PTBP1), S-phase kinase-associated protein 2 (Skp2), and Runt-related transcription factor 2 (Runx2) was investigated by combining RNA immunoprecipitation, qRT-PCR, mRNA stability, and ubiquitination assays. The significance of PTBP1 in circEXOC5-induced ALI phenotypes was examined both in vitro and in vivo. circEXOC5 was up-regulated and associated with increased inflammation and activated autophagy in cecal ligation and puncture-induced ALI lung tissues and LPS-challenged MPVECs. Through the interaction with PTBP1, circEXOC5 accelerated Skp2 mRNA decay, an E3 ubiquitin ligase for Runx2, and therefore increased Runx2 expression. Functionally, overexpressing PTBP1 reversed shcircEXOC5-inhibited ALI, inflammation, or autophagy. The signaling cascade circEXOC5/PTBP1/Skp2/Runx2, by essentially regulating inflammation and autophagy in MPVECs, aggravates sepsis-induced ALI.

Therapeutic Targeting of NF-κB in Acute Lung Injury: A Double-Edged Sword

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a devastating disease that can be caused by a variety of conditions including pneumonia, sepsis, trauma, and most recently, COVID-19. Although our understanding of the mechanisms of ALI/ARDS pathogenesis and resolution has considerably increased in recent years, the mortality rate remains unacceptably high (~40%), primarily due to the lack of effective therapies for ALI/ARDS. Dysregulated inflammation, as characterized by massive infiltration of polymorphonuclear leukocytes (PMNs) into the airspace and the associated damage of the capillary-alveolar barrier leading to pulmonary edema and hypoxemia, is a major hallmark of ALI/ARDS. Endothelial cells (ECs), the inner lining of blood vessels, are important cellular orchestrators of PMN infiltration in the lung. Nuclear factor-kappa B (NF-κB) plays an essential role in rendering the endothelium permissive for PMN adhesion and transmigration to reach the inflammatory site. Thus, targeting NF-κB in the endothelium provides an attractive approach to mitigate PMN-mediated vascular injury, not only in ALI/ARDS, but in other inflammatory diseases as well in which EC dysfunction is a major pathogenic mechanism. This review discusses the role and regulation of NF-κB in the context of EC inflammation and evaluates the potential and problems of targeting it as a therapy for ALI/ARDS.

Effects of 3-methyladenine, an autophagy inhibitor, on the elevated blood pressure and arterial dysfunction of angiotensin II-induced hypertensive mice

Autophagy is an intracellular degradation system that disassembles cytoplasmic components through autophagosomes fused with lysosomes. Recently, it has been reported that autophagy is associated with cardiovascular diseases, including pulmonary hypertension, atherosclerosis, and myocardial ischemia. However, the involvement of autophagy in hypertension is not well understood. In the present study, we hypothesized that excessive autophagy contributes to the dysfunction of mesenteric arteries in angiotensin II (Ang II)-induced hypertensive mice. Treatment of an autophagy inhibitor, 3-methyladenine (3-MA), reduced the elevated blood pressure and wall thickness, and improved endothelium-dependent relaxation in mesenteric arteries of Ang II-treated mice. The expression levels of autophagy markers, beclin1 and LC3 II, were significantly increased by Ang II infusion, which was reduced by treatment of 3-MA. Furthermore, treatment of 3-MA induced vasodilation in the mesenteric resistance arteries pre-contracted with U46619 or phenylephrine, which was dependent on endothelium. Interestingly, nitric oxide production and phosphorylated endothelial nitric oxide synthase (p-eNOS) at S1177 in the mesenteric arteries of Ang II-treated mice were increased by treatment with 3-MA. In HUVECs, p-eNOS was reduced by Ang II, which was increased by treatment of 3-MA. 3-MA had direct vasodilatory effect on the pre-contracted mesenteric arteries. In cultured vascular smooth muscle cells (VSMCs), Ang II induced increase in beclin1 and LC3 II and decrease in p62, which was reversed by treatment of 3-MA. These results suggest that autophagy inhibition exerts beneficial effects on the dysfunction of mesenteric arteries in hypertension.

Pulmonary delivery of resveratrol-β-cyclodextrin inclusion complexes for the prevention of zinc chloride smoke-induced acute lung injury

Smoke bombs are often used in military/fire training, which can produce a large amount of zinc chloride (ZnCl₂) smoke. Inhalation of ZnCl₂ smoke usually causes acute lung injury (ALI) that would likely develop to acute respiratory distress syndrome (ARDS). However, there is no effective prevention or treatment strategy for the smoke-induced ALI. Resveratrol (RES) is a natural polyphenol with good anti-inflammatory and anti-apoptotic activities, but its low solubility, stability, and bioavailability restrict its clinical application. In this study, an inhalable RES formulation composed of RES-β-cyclodextrin inclusion complexes (RES-β-CD) was prepared for the prevention of ZnCl₂ smoke-induced ALI. RES-β-CD powders had a small mass median aerodynamic diameter of 3.61 μm and a high fine particle fraction of 38.84%, suitable for pulmonary inhalation. RES-β-CD exhibited low BEAS-2B cytotoxicity. Pulmonary delivery of RES-β-CD to mice remarkably prevented the smoke-induced ALI with downregulation of TNF-α, IL-1β, STAT3, and GATA3, and upregulation of T-bet and Foxp3. RES-β-CD protected the respiratory function, percutaneous oxygen saturation, physical activity, lung capillary integrity, and lung liquid balance, alleviating inflammation and apoptosis. Pulmonary delivery of the positive drug, budesonide (BUD), also alleviated the smoke-induced ALI by reduction of inflammation and cell apoptosis. RES-β-CD exhibited the regulation of the Th1/Th2 and Treg/Th17 balances, while BUD did not show any effect on immune balances. In conclusion, pulmonary delivery of RES-β-CD is a promising anti-inflammatory and anti-apoptosis strategy for the prevention of ZnCl₂ smoke-induced ALI by direct lung drug distribution and regulation of immune balance.

Knockout of GGPPS1 restrains rab37-mediated autophagy in response to ventilator-induced lung injury

Mechanical ventilation may cause ventilator-induced lung injury (VILI) in patients requiring ventilator support. Inhibition of autophagy is an important approach to ameliorate VILI as it always enhances lung injury after exposure to various stress agents. This study aimed to further reveal the potential mechanisms underlying the effects of geranylgeranyl diphosphate synthase large subunit 1 (GGPPS1) knockout and autophagy in VILI using C57BL/6 mice with lung-specific GGPPS1 knockout that were subjected to mechanical ventilation. The results demonstrate that GGPPS1 knockout mice exhibit significantly attenuated VILI based on the histologic score, the lung wet-to-dry ratio, total protein levels, neutrophils in bronchoalveolar lavage fluid, and reduced levels of inflammatory cytokines. Importantly, the expression levels of autophagy markers were obviously decreased in GGPPS1 knockout mice compared with wild-type mice. The inhibitory effects of GGPPS1 knockout on autophagy were further confirmed by measuring the ultrastructural change of lung tissues under transmission electron microscopy. In addition, knockdown of GGPPS1 in RAW264.7 cells reduced cyclic stretch-induced inflammation and autophagy. The benefits of GGPPS1 knockout for VILI can be partially eliminated through treatment with rapamycin. Further analysis revealed that Rab37 was significantly downregulated in GGPPS1 knockout mice after mechanical ventilation, while it was highly expressed in the control group. Simultaneously, Rab37 overexpression significantly enhances autophagy in cells that are treated with cyclin stretch, including GGPPS1 knockout cells. Collectively, our results indicate that GGPPS1 knockout results in reduced expression of Rab37 proteins, further restraining autophagy and VILI.

Ferrostatin-1 and 3-Methyladenine Ameliorate Ferroptosis in OVA-Induced Asthma Model and in IL-13-Challenged BEAS-2B Cells

Ferroptosis was reported to be involved in the occurrence and development of asthma. However, the potential mechanism underlying the role of ferroptosis in asthma remains unclear. In this study, we established the mouse asthma model following the ovalbumin (OVA) method in C57BL/6 mice and the cell model with IL-13 induction in bronchial epithelial cells (BEAS-2B cells). Treatment of ferrostatin-1 (Ferr-1) and 3-methyladenine (3-MA) decreased iron deposition in IL-13-induced BEAS-2B cells and lung tissues of asthma mice, opposite to that in bronchoalveolar lavage fluid (BALF). Meanwhile, excessive lipid peroxidation asthma model in vivo and in vitro was alleviated by Ferr-1 or 3-MA treatment. In addition, Ferr-1 and 3-MA inhibited the expression of LC-3 in these cells and lung tissues of mice. Moreover, Ferr-1 and 3-MA also suppressed the production of inflammatory cytokines (IL-1β, IL-6, and TNF-α) and oxidative stress factors (ROS and MDA), while promoting the level of SOD, in vivo and in vitro. Furthermore, application of Ferr-1 exhibited a greater inhibitory effect on iron release and lipid peroxidation in IL-13-induced BEAS-2B cells and asthma mice than 3-MA, accompanied with a weaker effect on ferritinophagy than 3-MA. Collectively, Ferr-1 and 3-MA ameliorated asthma in vivo and in vitro through inhibiting ferroptosis, providing a new strategy for the clinical treatment of asthma.

Anticachectic regulator analysis reveals Perp-dependent antitumorigenic properties of 3-methyladenine in pancreatic cancer

Approximately 80% of pancreatic cancer patients suffer from cachexia, and one-third die due to cachexia-related complications such as respiratory failure and cardiac arrest. Although there has been considerable research into cachexia mechanisms and interventions, there are, to date, no FDA-approved therapies. A major contributing factor for the lack of therapy options could be the failure of animal models to accurately recapitulate the human condition. In this study, we generated an aged model of pancreatic cancer cachexia to compare cachexia progression in young versus aged tumor-bearing mice. Comparative skeletal muscle transcriptome analyses identified 3-methyladenine (3-MA) as a candidate antiwasting compound. In vitro analyses confirmed antiwasting capacity, while in vivo analysis revealed potent antitumor effects. Transcriptome analyses of 3-MA-treated tumor cells implicated Perp as a 3-MA target gene. We subsequently (a) observed significantly higher expression of Perp in cancer cell lines compared with control cells, (b) noted a survival disadvantage associated with elevated Perp, and (c) found that 3-MA-associated Perp reduction inhibited tumor cell growth. Finally, we have provided in vivo evidence that survival benefits conferred by 3-MA administration are independent of its effect on tumor progression. Taken together, we report a mechanism linking 3-MA to Perp inhibition, and we further implicate Perp as a tumor-promoting factor in pancreatic cancer.

Argonaute-2 protects the neurovascular unit from damage caused by systemic inflammation

BACKGROUND

The brain vasculature plays a pivotal role in the inflammatory process by modulating the interaction between blood cells and the neurovascular unit. Argonaute-2 (Ago2) has been suggested as essential for endothelial survival but its role in the brain vasculature or in the endothelial-glial crosstalk has not been addressed. Thus, our aim was to clarify the significance of Ago2 in the inflammatory responses elicited by these cell types.

METHODS

Mouse primary cultures of brain endothelial cells, astrocytes and microglia were used to evaluate cellular responses to the modulation of Ago2. Exposure of microglia to endothelial cell-conditioned media was used to assess the potential for in vivo studies. Adult mice were injected intraperitoneally with lipopolysaccharide (LPS) (2 mg/kg) followed by three daily intraperitoneal injections of Ago2 (0.4 nM) to assess markers of endothelial disruption, glial reactivity and neuronal function.

RESULTS

Herein, we demonstrated that LPS activation disturbed the integrity of adherens junctions and downregulated Ago2 in primary brain endothelial cells. Exogenous treatment recovered intracellular Ago2 above control levels and recuperated vascular endothelial-cadherin expression, while downregulating LPS-induced nitric oxide release. Primary astrocytes did not show a significant change in Ago2 levels or response to the modulation of the Ago2 system, although endogenous Ago2 was shown to be critical in the maintenance of tumor necrosis factor-α basal levels. LPS-activated primary microglia overexpressed Ago2, and Ago2 silencing contained the inflammatory response to some extent, preventing interleukin-6 and nitric oxide release. Moreover, the secretome of Ago2-modulated brain endothelial cells had a protective effect over microglia. The intraperitoneal injection of LPS impaired blood-brain barrier and neuronal function, while triggering inflammation, and the subsequent systemic administration of Ago2 reduced or normalized endothelial, glial and neuronal markers of LPS damage. This outcome likely resulted from the direct action of Ago2 over the brain endothelium, which reestablished glial and neuronal function.

CONCLUSIONS

Ago2 could be regarded as a putative therapeutic agent, or target, in the recuperation of the neurovascular unit in inflammatory conditions.

Essential Role of Rho-Associated Kinase in ABO Immune Complex-Mediated Endothelial Barrier Disruption

ABO immune complexes (ABO-IC) formed by ABO-incompatible antigen-antibody interaction are associated with hemolysis and platelet destruction in patients transfused with ABO-nonidentical blood products. However, the effects of ABO-IC on endothelial cells (EC) are unclear. ABO-IC were formed in vitro from normal donor-derived plasma and serum. Human pulmonary artery EC (HPAEC) were cultured and treated with media, ABO-identical and –non-identical plasma, and ABO-IC. EC barrier integrity was evaluated using transendothelial electrical resistance (TEER), scanning electron microscopy (SEM), vascular endothelial (VE)-cadherin and phalloidin staining, and Rho-associated Kinase (ROCK) inhibitor treatment. TEER revealed significant/irreversible barrier disruption within 1–2 h of exposure to ABO non-identical plasma and ABO-IC; this occurred independently of EC ABO type. Treatment with ABO-IC resulted in decreased VE-cadherin staining and increased phalloidin staining in a time-dependent manner, suggesting that the resultant increased EC barrier permeability is secondary to actin stress fiber formation and loss of cell surface VE-cadherin. Inhibition of ROCK was effective in protecting against IC-induced barrier disruption even two hours after ABO-IC exposure. ABO-IC causes increased EC barrier permeability by decreasing cell surface VE-cadherin and promoting stress fiber formation, which is preventable by inhibiting ROCK activation to protect against EC contraction and gap formation.

Positive regulation of TFEB and mitophagy by PGC-1α to alleviate LPS-induced acute lung injury in rats

AIM OF THE STUDY

Acute lung injury (ALI) exhibits the features of noncardiogenic pulmonary edema and acute inflammatory process, and it also displays significant morbidity and mortality rates. This work focused on identifying how overexpression of PPARγ coactivator 1α (PGC-1α) positively regulated TFEB and mitophagy for resisting the lipopolysaccharide (LPS)-mediated ALI.

MATERIALS AND METHODS

The levels of autophagic proteins and inflammatory factors in LPS-induced ALI rats and primary type II alveolar epithelial cells were measured, respectively. Lung wet/dry ratios were calculated. Protein co-immunoprecipitation of PGC-1α and TFEB was detected. To explore the interaction between TFEB and PGC-1α, a luciferase reporter assay was conducted.

RESULTS

The results showed that overexpression of PGC-1α decreases IL-1 and IL-6 but increases IL-10 in LPS-mediated ALI rats and type II alveolar epithelial cells (P < 0.05). Overexpression of PGC-1α can reduce lung edema in LPS-mediated ALI rats (P < 0.05). Overexpression of PGC-1α upregulates mitophagy-related proteins, such as TFEB, LC3B, Beclin, and LAMP1, and improves mitophagy in LPS-induced ALI. Protein immunoprecipitation indicated that TFEB and PGC-1α are interacting proteins. The luciferase reporter assay demonstrated that PGC-1α positively regulated TFEB in the LPS-induced primary type II alveolar epithelial cells.

CONCLUSION

PGC-1α protects LPS-induced ALI by decreasing inflammation and alleviating lung edema. The mechanism might be positive regulation of TFEB directly and then upregulation of mitophagy in LPS-induced ALI.

FUNDC1 Regulates Autophagy by Inhibiting ROS-NLRP3 Signaling to Avoid Apoptosis in the Lung in a Lipopolysaccharide-Induced Mouse Model

ABSTRACT

The incidence and mortality of acute respiratory distress syndrome (ARDS) are high, but the relevant mechanism for this disorder remains unclear. Autophagy plays an important role in the development of ARDS. The mitochondrial outer membrane protein FUNDC1 is involved in hypoxia-mediated mitochondrial autophagy, which may contribute to ARDS development. This study explored whether FUNDC1 regulates autophagy by inhibiting ROS-NLRP3 signaling to avoid apoptosis in the lung in a lipopolysaccharide-induced mouse model. In this study, FUNDC1 knockout mice were constructed, and a lipopolysaccharide-induced mouse model was generated. HE staining of pathological sections from the lung, wet/dry lung measurements, myeloperoxidase concentration/neutrophil counts in BALF and survival time of mice were examined to determine the effect of modeling. The release of cytokines (TNF-α, IL-1β, IL-6, and IL-10) in response to LPS in the BALF and plasma was assessed using ELISA. The effects of oxidative stress (malondialdehyde, superoxide dismutase, catalase, glutathione peroxidase) in lung tissue in response to LPS were detected by biochemical analysis. Oxidative stress damage was validated by iNOS staining, and apoptosis was assessed by TUNEL staining after LPS. Finally, the expression of autophagy-associated proteins and inflammasome-associated proteins in lung tissue after LPS intervention was analyzed by western blot. We found that wild-type control, FUNDC1 knockout control, lipopolysaccharide-induced wild-type, and FUNDC1 knockout mouse models were used to investigate whether FUNDC1-mediated autophagy is involved in lung injury and its possible molecular mechanisms. Compared with the normal control group, lung tissue FUNDC1 and LC3 II increased and p62/SQSTM1 decreased after LPS intervention, and increased ROS levels led to a decrease in corresponding antioxidant enzymes along with an increased inflammatory response and apoptosis. Levels of autophagy in lipopolysaccharide-induced mice deficient in FUNDC1 were significantly decreased, but the expression of ROS and inflammatory factors in lung tissue was more severe than in lipopolysaccharide-induced wild-type mice, and the survival rate was significantly decreased. Western blot analysis showed that autophagy was significantly inhibited in the FUNDC1 KO+LPS group, and there was a significant increase in NLRP3, caspase-1, IL-1β, and ASC compared with the lipopolysaccharide-induced wild-type group. In summary, lipopolysaccharide-induced wild-type mice exhibit ROS-dependent activation of autophagy, and knocking out FUNDC1 promotes inflammasome activation and exacerbates lung injury.

Apelin-13-Mediated AMPK ameliorates endothelial barrier dysfunction in acute lung injury mice via improvement of mitochondrial function and autophagy

Maintaining the pulmonary endothelial barrier that prevents the exudation of inflammatory factors and proteins is the key to the treatment of acute lung injury (ALI). Apelin-13 plays an important role in vascular diseases; however, the protective effects of Apelin-13 on ALI with pulmonary endothelial barrier are unknown. Therefore, mice and human umbilical vein endothelial cells (HUVECs) were injured by LPS following Apelin-13 administration. ALI mice showed reduced pulmonary vascular permeability, adhesion junction, mitochondrial function, mitochondrial biogenesis, and autophagy compared to the control group. Apelin-13 administration in ALI mice ameliorated LPS-induced lung injury, pulmonary vascular permeability, mitochondrial function, and promoted autophagic flux in mice and HUVECs. However, the effect of Apelin-13 was reduced after AMPK inhibition using Compound C. These data suggest that Apelin-13 ameliorates pulmonary vascular permeability in mice with ALI induced by LPS, which may be related to enhanced phosphorylation of AMPK to regulate mitochondrial function and autophagy.

Sitagliptin activates the p62-Keap1-Nrf2 signalling pathway to alleviate oxidative stress and excessive autophagy in severe acute pancreatitis-related acute lung injury

Acute lung injury (ALI) is a complication of severe acute pancreatitis (SAP). Sitagliptin (SIT) is a DPP4 inhibitor that exerts anti-inflammatory and antioxidant effects; however, its mechanism of action in SAP-ALI remains unclear. In this study, we investigated the effects of SIT on SAP-ALI and the specific pathways involved in SAP-induced lung inflammation, including oxidative stress, autophagy, and p62-Kelch-like ECH-associated protein 1 (Keap1)-NF-E2-related factor 2 (Nrf2) signalling pathways. Nrf2 knockout (Nrf2-/-) and wild-type (WT) mice were pre-treated with SIT (100 mg/kg), followed by caerulein and lipopolysaccharide (LPS) administration to induce pancreatic and lung injury. BEAS-2B cells were transfected with siRNA-Nrf2 and treated with LPS, and the changes in inflammation, reactive oxygen species (ROS) levels, and autophagy were measured. SIT reduced histological damage, oedema, and myeloperoxidase activity in the lung, decreased the expression of pro-inflammatory cytokines, and inhibited excessive autophagy and ROS production via the activation of the p62-Keap1-Nrf2 signalling pathway and promotion of the nuclear translocation of Nrf2. In Nrf2-knockout mice, the anti-inflammatory effect of SIT was reduced, resulting in ROS accumulation and excessive autophagy. In BEAS-2B cells, LPS induced ROS production and activated autophagy, further enhanced by Nrf2 knockdown. This study demonstrates that SIT reduces SAP-ALI-associated oxidative stress and excessive autophagy through the p62-Keap1-Nrf2 signalling pathway and nuclear translocation of Nrf2, suggesting its therapeutic potential in SAP-ALI.

lncRNA-SNHG14 Plays a Role in Acute Lung Injury Induced by Lipopolysaccharide through Regulating Autophagy via miR-223-3p/Foxo3a

lncRNAs play important roles in lipopolysaccharide- (LPS-) induced acute lung injury. But the mechanism still needs further research. In the present study, we investigate the functional role of the lncRNA-SNHG14/miR-223-3p/Foxo3a pathway in LPS-induced ALI and tried to confirm its regulatory effect on autophagy. Transcriptomic profile changes were identified by RNA-seq in LPS-treated alveolar type II epithelial cells. The expression changes of lncRNA-SNHG14/miR-223-3p/Foxo3a were confirmed using qRT-PCR and west blot. The binding relationship of lncRNA-SNHG14/miR-223-3p/and miR-223-3p/Foxo3a was verified using dual-luciferase reporter, RNA immunoprecipitation, and RNA pull-down assays. Using gain-of-function or loss-of-function approaches, the effect of lncRNA-SNHG14/miR-223-3p/Foxo3a was investigated in LPS-induced acute lung injury mice model and in vitro. Increasing of lncRNA-SNHG14 and Foxo3a with reducing miR-223-3p was found in LPS-treated A549 cells and lung tissue collected from the LPS-induced ALI model. lncRNA-SNHG14 inhibited miR-223-3p but promoted Foxo3a expression as a ceRNA. Artificially changes of lncRNA-SNHG14/miR-223-3p/Foxo3a pathway promoted or protected cell injury from LPS in vivo and in vitro. Autophagy activity could be influenced by lncRNA-SNHG14/miR-223-3p/Foxo3a pathway in cells with or without LPS treatment. In conclusion, aberrant expression changes of lncRNA-SNHG14 participated alveolar type II epithelial cell injury and acute lung injury induced by LPS through regulating autophagy. One underlying mechanism is that lncRNA-SNHG14 regulated autophagy by controlling miR-223-3p/Foxo3a as a ceRNA. It suggested that lncRNA-SNHG14 may serve as a potential therapeutic target for patients with sepsis-induced ALI.

Hydrogen alleviates cell damage and acute lung injury in sepsis via PINK1/Parkin-mediated mitophagy

BACKGROUND

Multiple organ failure (MOF) is the main cause of early death in septic shock. Lungs are among the organs that are affected in MOF, resulting in acute lung injury. Inflammation is an important factor that causes immune cell dysfunction in the pathogenesis of sepsis. Autophagy is involved in the process of inflammation and also occurs in response to cell and tissue injury in several diseases. We previously demonstrated that hydrogen alleviated the inflammation-induced cell injury and organ damage in septic mice.

AIM

The focus of the present study was to elucidate whether mitophagy mediates the inflammatory response or oxidative injury in sepsis in vitro and in vivo. Furthermore, we evaluated the role of mitophagy in the protective effects of hydrogen against cell injury or organ dysfunction in sepsis.

METHOD

RAW 264.7 macrophages induced by lipopolysaccharide (LPS) were used as an in vitro model for inflammation, and cecal ligation and puncture (CLP)-induced acute lung injury mice were used as an in vivo model for sepsis. The key protein associated with mitophagy, PTEN-induced putative kinase 1 (PINK1), was knocked down by PINK1 shRNA transfection in RAW 264.7 macrophages or mice.

RESULTS

Hydrogen ameliorated cell injury and enhanced mitophagy in macrophages stimulated by LPS. PINK1 was required for the mitigation of the cell impairment in LPS-stimulated macrophages by hydrogen treatment. PINK1 knockdown abrogated the beneficial effects of hydrogen on mitophagy in LPS-stimulated macrophages. Hydrogen inhibited acute lung injury in CLP mice via activation of PINK1-mediated mitophagy.

CONCLUSION

These results suggest that PINK1-mediated mitophagy plays a key role in the protective effects of hydrogen against cell injury in LPS-induced inflammation and CLP-induced acute lung injury.

Phosphodiesterase 10A Is a Key Mediator of Lung Inflammation

Cyclic nucleotides cAMP and cGMP are important regulators of immune cell functions. Phosphodiesterases (PDEs) hydrolyze cAMP and/or cGMP and, thus, play crucial roles in cyclic nucleotide homeostasis. Abnormal alterations of PDE expression have been implicated in several diseases. To understand the function of PDEs in macrophages, we screened for all PDE genes in both peritoneal and alveolar macrophages from C57BL/6J mice and found that PDE4B and PDE10A are highly induced by LPS. A number of PDE4 inhibitors have been used clinically for the treatment of inflammatory lung diseases. However, the role of PDE10A in inflammation is still poorly understood. We therefore investigated the role of PDE10A in macrophage inflammatory response in vitro and acute lung inflammation in vivo. We found that LPS induces a sustained PDE10A expression in macrophages, which is different from a transient induction by PDE4B. PDE10A inhibition blocked LPS-induced MCP-1 expression, but not TNF-α, whereas PDE4B inhibition blocked LPS-induced TNF-α expression, but not MCP-1. In addition, PDE10A inhibition or deficiency decreased LPS-induced HIF-1α protein expression and subsequently suppressed MCP-1 expression. In vivo, PDE10A expression was also elevated in lung tissue after LPS exposure. Global PDE10A knockout or systemic administration of the PDE10A inhibitor TP-10 in mice significantly suppressed inflammatory molecule levels in the lung tissue and bronchoalveolar lavage fluid as well as inflammatory cell infiltration. These findings show that PDE10A plays a critical role in lung inflammation by promoting the activation of resident macrophages and infiltration of neutrophils.

Pivotal role of endothelial cell autophagy in sepsis

Sepsis is a fatal organ dysfunction resulting from a disordered host response to infection. Endothelial cells (ECs) are usually the primary targets of inflammatory mediators in sepsis; damage to ECs plays a pivotal part in vital organ failure. In recent studies, autophagy was suggested to play a critical role in the ECs injury although the mechanisms by which ECs are injured in sepsis are not well elucidated. Autophagy is a highly conserved catabolic process that includes sequestrating plasma contents and transporting cargo to lysosomes for recycling the vital substrates required for metabolism. This pathway also counteracts microbial invasion to balance and retain homeostasis, especially during sepsis. Increasing evidence indicates that autophagy is closely associated with endothelial function. The role of autophagy in sepsis may or may not be favorable depending upon conditions. In the present review, the current knowledge of autophagy in the process of sepsis and its influence on ECs was evaluated. In addition, the potential of targeting EC autophagy for clinical treatment of sepsis was discussed.

Deciphering the Role of the Coagulation Cascade and Autophagy in Cancer-Related Thrombosis and Metastasis

Thrombotic complications are the second leading cause of death among oncology patients worldwide. Enhanced thrombogenesis has multiple origins and may result from a deregulation of megakaryocyte platelet production in the bone marrow, the synthesis of coagulation factors in the liver, and coagulation factor signaling upon cancer and the tumor microenvironment (TME). While a hypercoagulable state has been attributed to factors such as thrombocytosis, enhanced platelet aggregation and Tissue Factor (TF) expression on cancer cells, further reports have suggested that coagulation factors can enhance metastasis through increased endothelial-cancer cell adhesion and enhanced endothelial cell activation. Autophagy is highly associated with cancer survival as a double-edged sword, as can both inhibit and promote cancer progression. In this review, we shall dissect the crosstalk between the coagulation cascade and autophagic pathway and its possible role in metastasis and cancer-associated thrombosis formation. The signaling of the coagulation cascade through the autophagic pathway within the hematopoietic stem cells, the endothelial cell and the cancer cell are discussed. Relevant to the coagulation cascade, we also examine the role of autophagy-related pathways in cancer treatment. In this review, we aim to bring to light possible new areas of cancer investigation and elucidate strategies for future therapeutic intervention.

Autophagy, Unfolded Protein Response and Lung Disease

Acute Respiratory Distress Syndrome is a severe disorder affecting thousands of individuals worldwide. The available medical countermeasures do not sufficiently suppress the unacceptable high mortality rates associated with those in need. Thus, intense efforts aim to delineate the function of the lung endothelium, so to deliver new therapeutic approaches against this disease. The present manuscript attempts to shed light on the interrelations between the unfolded protein response and autophagy towards lung disease, to deliver a new line of possible therapeutic approaches against the ferocious Acute Respiratory Distress Syndrome.

Autophagy inhibition protects from alveolar barrier dysfunction in LPS-induced ALI mice by targeting alveolar epithelial cells

OBJECTIVE

The aim of this study was to investigate whether autophagy is enhanced in alveolar epithelial cells as well as its role in alveolar barrier function of in lipopolysaccharide (LPS)-induced ALI mice.

MATERIALS AND METHODS

Autophagy inhibitors, including 3-methyladenine (3-MA) and chloroquine (CLQ), and LPS were intraperitoneally administered to mice. Histological evaluation and confocal microscopy, Western blot, transmission electron microscopy, and ELISA were performed for analysis. First, the mouse model of ALI was established. Then, autophagy level changes in the mouse lung as well as the effects of autophagy inhibition on indirect ALI and alveolar epithelial barrier function induced by LPS were assessed. Finally, pro-inflammatory factors in BALF from ALI mice after autophagy inhibition by 3-MA or CLQ administration were detected.

RESULTS

The experimental animal model of LPS-induced ALI had the expected features. In addition, autophagy in alveolar epithelial cells in ALI mice was enhanced. Furthermore, autophagy in alveolar epithelial cells promoted alveolar epithelial barrier dysfunction in LPS-induced ALI. Finally, autophagy inhibition resulted in reduced LPS-induced lung tissue inflammation.

CONCLUSION

These findings suggest that autophagy inhibition protects from alveolar barrier dysfunction in LPS-induced ALI mice by targeting alveolar epithelial cells.

Autophagy protein ATG7 is a critical regulator of endothelial cell inflammation and permeability

Endothelial cell (EC) inflammation and permeability are critical pathogenic mechanisms in many inflammatory conditions including acute lung injury. In this study, we investigated the role of ATG7, an essential autophagy regulator with no autophagy-unrelated functions, in the mechanism of EC inflammation and permeability. Knockdown of ATG7 using si-RNA significantly attenuated thrombin-induced expression of proinflammatory molecules such as IL-6, MCP-1, ICAM-1 and VCAM-1. Mechanistic study implicated reduced NF-κB activity in the inhibition of EC inflammation in ATG7-silenced cells. Moreover, depletion of ATG7 markedly reduced the binding of RelA/p65 to DNA in the nucleus. Surprisingly, the thrombin-induced degradation of IκBα in the cytosol was not affected in ATG7-depleted cells, suggesting a defect in the translocation of released RelA/p65 to the nucleus in these cells. This is likely due to suppression of thrombin-induced phosphorylation and thereby inactivation of Cofilin1, an actin-depolymerizing protein, in ATG7-depleted cells. Actin stress fiber dynamics are required for thrombin-induced translocation of RelA/p65 to the nucleus, and indeed our results showed that ATG7 silencing inhibited this response via inactivation of Cofilin1. ATG7 silencing also reduced thrombin-mediated EC permeability by inhibiting the disassembly of VE-cadherin at adherens junctions. Together, these data uncover a novel function of ATG7 in mediating EC inflammation and permeability, and provide a mechanistic basis for the linkage between autophagy and EC dysfunction.

House Dust Mite Specific Antibodies induce Neutrophilic Inflammation in the Heart

Rationale: Inflammatory heart disorders are among the causes of human death. The causative factors of heart inflammation are to be further elucidated. House dust mite (HDM)-derived protein antigens are involved in the pathogenesis of many human diseases. This study aims to investigate the role of HDM-specific autoantibodies in the pathogenesis of heart inflammation.

Methods: Human heart tissue samples were obtained from surgically removed hearts in heart transplantation. The interaction of the heart tissues with HDM-specific antibodies was assessed by pertinent immune analysis. The role of HDM-specific autoantibodies in the induction of heart inflammation was assessed with a murine model.

Results: HDM-specific IgG (mIgG) was detected in the serum of patients with myocarditis (Mcd); the mIgG titers were positively correlated with the neutrophil counts in the heart tissues. The mIgG specifically bound to keratin-10 (KRT10) in heart vascular endothelial cells and the heart tissue protein extracts. The amounts of C3a, C5a and C5b-9 were increased in the mouse heart tissues after exposing to mIgG. In the presence of the complement-containing serum, mIgG bound cardiovascular epithelial monolayers to impair the barrier functions. Administration of mIgG or HDM induced the Mcd-like inflammation in the heart, in which neutrophils were the dominant cellular components in the infiltration of inflammatory cells.

Conclusions: Mcd patients with neutrophilic inflammation in the heart had higher serum levels of mIgG. The mIgG bound heart endothelial cells to impair the endothelial barrier functions and induce neutrophilic inflammation in the heart.

The Glycoprotein and Nucleocapsid Protein of Hantaviruses Manipulate Autophagy Flux to Restrain Host Innate Immune Responses

Hantavirus infection, which causes severe zoonotic diseases with high mortality in humans, has become a global public health concern. Here, we demonstrate that Hantaan virus (HTNV), the prevalent prototype of the hantavirus in Asia, can restrain innate immune responses by manipulating host autophagy flux. HTNV induces complete mitophagy at the early stage of infection but incomplete autophagy at the late stage, and these responses involve the viral glycoprotein (Gn) and nucleocapsid protein (NP), respectively. Gn translocates to mitochondria and interacts with TUFM, recruiting LC3B and promoting mitophagy. Gn-induced mitophagy inhibits type I interferon (IFN) responses by degrading MAVS. Additionally, we found that NP competes with Gn for binding to LC3B, which inhibits Gn-mediated autophagosome formation, and interacts with SNAP29, which prevents autophagosome-lysosome fusion. Thus, NP disturbs the autophagic degradation of Gn. These findings highlight how hantaviruses repurpose host autophagy and evade innate immune responses for their life cycle and pathogenesis.

VEGF Triggers Transient Induction of Autophagy in Endothelial Cells via AMPKα1

AMP-activated protein kinase (AMPK) is activated by vascular endothelial growth factor (VEGF) in endothelial cells and it is significantly involved in VEGF-induced angiogenesis. This study investigates whether the VEGF/AMPK pathway regulates autophagy in endothelial cells and whether this is linked to its pro-angiogenic role. We show that VEGF leads to AMPKα1-dependent phosphorylation of Unc-51-like kinase 1 (ULK1) at its serine residue 556 and to the subsequent phosphorylation of the ULK1 substrate ATG14. This triggers initiation of autophagy as shown by phosphorylation of ATG16L1 and conjugation of the microtubule-associated protein light chain 3B, which indicates autophagosome formation; this is followed by increased autophagic flux measured in the presence of bafilomycin A1 and by reduced expression of the autophagy substrate p62. VEGF-induced autophagy is transient and probably terminated by mechanistic target of rapamycin (mTOR), which is activated by VEGF in a delayed manner. We show that functional autophagy is required for VEGF-induced angiogenesis and may have specific functions in addition to maintaining homeostasis. In line with this, inhibition of autophagy impaired VEGF-mediated formation of the Notch intracellular domain, a critical regulator of angiogenesis. Our study characterizes autophagy induction as a pro-angiogenic function of the VEGF/AMPK pathway and suggests that timely activation of autophagy-initiating pathways may help to initiate angiogenesis.

Endosomes and Autophagy: Regulators of Pulmonary Endothelial Cell Homeostasis in Health and Disease

Significance: Alterations in oxidant/antioxidant balance injure pulmonary endothelial cells and are important in the pathogenesis of lung diseases, such as Acute Respiratory Distress Syndrome (ARDS), ischemia/reperfusion injury, pulmonary arterial hypertension (PAH), and emphysema. Recent Advances: The endosomal and autophagic pathways regulate cell homeostasis. Both pathways support recycling or degradation of macromolecules or organelles, targeted to endosomes or lysosomes, respectively. Thus, both processes promote cell survival. However, with environmental stress or injury, imbalance in endosomal and autophagic pathways may enhance macromolecular or organelle degradation, diminish biosynthetic processes, and cause cell death. Critical Issues: While the role of autophagy in cellular homeostasis in pulmonary disease has been investigated, the role of the endosome in the lung vasculature is less known. Furthermore, autophagy can either decrease or exacerbate endothelial injury, depending upon inciting insult and disease process. Future Directions: Diseases affecting the pulmonary endothelium, such as emphysema, ARDS, and PAH, are linked to altered endosomal or autophagic processing, leading to enhanced degradation of macromolecules and potential cell death. Efforts to target this imbalance have yielded limited success as treatments for lung injuries, which may be due to the complexity of both processes. It is possible that endosomal trafficking proteins, such as Rab GTPases and late endosomal/lysosomal adaptor, MAPK and MTOR activator 1, may be novel therapeutic targets. While endocytosis or autophagy have been linked to improved function of the pulmonary endothelium in vitro and in vivo, further studies are needed to identify targets for modulating cellular homeostasis in the lung.

Recent advances in our understanding of the mechanisms of lung alveolarization and bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common cause of morbidity and mortality in preterm infants. A key histopathological feature of BPD is stunted late lung development, where the process of alveolarization-the generation of alveolar gas exchange units-is impeded, through mechanisms that remain largely unclear. As such, there is interest in the clarification both of the pathomechanisms at play in affected lungs, and the mechanisms of de novo alveoli generation in healthy, developing lungs. A better understanding of normal and pathological alveolarization might reveal opportunities for improved medical management of affected infants. Furthermore, disturbances to the alveolar architecture are a key histopathological feature of several adult chronic lung diseases, including emphysema and fibrosis, and it is envisaged that knowledge about the mechanisms of alveologenesis might facilitate regeneration of healthy lung parenchyma in affected patients. To this end, recent efforts have interrogated clinical data, developed new-and refined existing-in vivo and in vitro models of BPD, have applied new microscopic and radiographic approaches, and have developed advanced cell-culture approaches, including organoid generation. Advances have also been made in the development of other methodologies, including single-cell analysis, metabolomics, lipidomics, and proteomics, as well as the generation and use of complex mouse genetics tools. The objective of this review is to present advances made in our understanding of the mechanisms of lung alveolarization and BPD over the period 1 January 2017-30 June 2019, a period that spans the 50th anniversary of the original clinical description of BPD in preterm infants.

Ubiquitin-based modifications in endothelial cell-cell contact and inflammation

Endothelial cell-cell contacts are essential for vascular integrity and physiology, protecting tissues and organs from edema and uncontrolled invasion of inflammatory cells. The vascular endothelial barrier is dynamic, but its integrity is preserved through a tight control at different levels. Inflammatory cytokines and G-protein-coupled receptor agonists, such as histamine, reduce endothelial integrity and increase vascular leakage. This is due to elevated myosin-based contractility, in conjunction with phosphorylation of proteins at cell-cell contacts. Conversely, reducing contractility stabilizes or even increases endothelial junctional integrity. Rho GTPases are key regulators of such cytoskeletal dynamics and endothelial cell-cell contacts. In addition to signaling-induced regulation, the expression of junctional proteins, such as occludin, claudins and vascular endothelial cadherin, also controls endothelial barrier function. There is increasing evidence that, in addition to protein phosphorylation, ubiquitylation (also known as ubiquitination) is an important and dynamic post-translational modification that regulates Rho GTPases, junctional proteins and, consequently, endothelial barrier function. In this Review, we discuss the emerging role of ubiquitylation and deubiquitylation events in endothelial integrity and inflammation. The picture that emerges is one of increasing complexity, which is both fascinating and promising given the clinical relevance of vascular integrity in the control of inflammation, and of tissue and organ damage.

Critical role of autophagy regulator Beclin1 in endothelial cell inflammation and barrier disruption

Recent studies have implicated autophagy in several inflammatory diseases involving aberrant endothelial cell (EC) responses, such as acute lung injury (ALI). However, the mechanistic basis for a role of autophagy in EC inflammation and permeability remain poorly understood. In this study, we impaired autophagy by silencing the essential Beclin1 autophagy gene in human pulmonary artery EC. This resulted in reduced expression of proinflammatory genes in response to thrombin, a procoagulant and proinflammatory mediator whose concentration is elevated in many diseases including sepsis and ALI. These (Beclin1-depleted) cells also displayed a marked decrease in NF-κB activity secondary to impaired DNA binding of RelA/p65 in the nucleus, but exhibited normal IκBα degradation in the cytosol. Further analysis showed that Beclin1 knockdown was associated with impaired RelA/p65 translocation to the nucleus. Additionally, Beclin1 knockdown attenuated thrombin-induced phosphorylation of RelA/p65 at Ser536, a critical event necessary for the transcriptional activity of RelA/p65. Beclin1 silencing also protected against thrombin-induced EC barrier disruption by preventing the loss of VE-cadherin at adherens junctions. Moreover, Beclin1 knockdown reduced thrombin-induced phosphorylation/inactivation of actin depolymerizing protein Cofilin1 and thereby actin stress fiber formation required for EC permeability as well as RelA/p65 nuclear translocation. Together, these data identify Beclin1 as a novel mechanistic link between autophagy and EC dysfunction (inflammation and permeability).

Lycorine Derivative LY-55 Inhibits EV71 and CVA16 Replication Through Downregulating Autophagy

Hand, foot, and mouth disease (HFMD) is a global health concern, especially in the Asia-Pacific region. HFMD caused by Enterovirus 71 (EV71) and Coxsackievirus A16 (CVA16) infection is usually self-limited but occasionally leads to severe pulmonary edema, neurological complications, and even death. Unfortunately, no effective drugs are currently available in clinical practice for the prevention and treatment of HFMD. Thus, anti-HFMD drugs must be urgently developed. A previous study had reported that lycorine could inhibit EV71 replication. In the present study, we found that LY-55, a lycorine derivative, inhibited the replication of EV71 and CVA16 in vitro and provided partial protection to mice from EV71 infection, as indicated by the decreased viral load and protein expression levels in muscles, clinical scores, and increased survival rates of infected mice. Mechanistically, LY-55 was not directly viricidal. Instead, the LY-55-mediated inhibition of EV71 and CVA16 was found to be mechanistically possible, at least in part, through downregulating autophagy, which plays an important role for EV71 and CVA16 replication. These findings suggest that LY-55 could be a potential lead or supplement for the development of anti-HFMD agents in the future.

Antibiotics induced intestinal tight junction barrier dysfunction is associated with microbiota dysbiosis, activated NLRP3 inflammasome and autophagy

Tight junction barrier is critical to intestinal homeostasis. Applying antibiotics to treat infections is common in clinical practice, which may affect intestinal microbiota. Intestinal microbiota dysbiosis is involved in the occurrence of some gastrointestinal diseases. Therefore, this study was aimed to investigate the influence of antibiotics on intestinal tight junction barrier and the possible underlying mechanisms. Healthy adult female C57BL/6 mice were treated with a broad-spectrum antibiotic cocktail for 14 days. 16S rDNA Illumina sequencing and headspace gas chromatography-mass spectrometry (HS-GC/MS) were respectively used to analyze microbial community and to detect short-chain fatty acids (SCFAs) contents. In vivo intestinal paracellular permeability to fluorescein isothiocyanate-dextran (FITC-dextran) was measured. Protein expression was determined by immunoblotting. Immunofluoresence was applied to observe the distributions of ZO-1, LC3B and ASC. Antibiotics remarkably altered intestinal microbiota composition in healthy mice, accompanying reduced SCFAs' concentrations. In addition, the intestinal tight junction barrier was disrupted by antibiotic treatment, as evidenced by increased intestinal paracellular permeability to FITC-dextran, decreased tight junction protein expressions, and disrupted ZO-1 morphology. Furthermore, NLRP3 inflammasome and autophagy were activated by antibiotic treatment. In conclusion, intestinal epithelial tight junction barrier dysfunction induced by antibiotics is associated with intestinal microbiota dysbiosis, activated NLRP3 inflammasome and autophagy in mice.

Different intensity of autophagy regulate interleukin-33 to control the uncontrolled inflammation of acute lung injury

OBJECTIVES

Cytokines participate in the progression of acute respiratory distress syndrome (ARDS), and uncontrolled inflammation is a central issue of acute lung injury (ALI). Interleukin (IL)-33 is a nuclear protein that has been reported to have a proinflammatory role in ARDS. Studies have shown that excessive autophagy may lead to the increased mortality of patients with ARDS, while several investigations indicated that IL-33 and autophagy interact with one another. The present study sought to clarify the relation between autophagy and IL-33's proinflammatory role in ARDS.

METHODS

We built a lipopolysaccharide (LPS)-induced lung injury mouse model. To study the relationship between IL-33 and autophagy, mice were pretreated with rapamycin (RAPA; a promoter of autophagy) and 3-methyladenine (3-MA; an inhibitor of autophagy) prior to LPS administration. The expression of IL-33 in serum and bronchoalveolar lavage fluid (BALF) was measured. Immunohistochemistry of IL-33 in lung tissue was examined. Th1,Th2 cytokines/chemokine levels in serum and BALF were tested. Further, the severity of lung injury was evaluated. And the nuclear factor-kappa B (NF-κB)'s nuclear translocation in lung tissue was detected.

RESULTS

In comparison with the control group, the levels of IL-33 in serum and BALF were increased after LPS injection. Th1 cytokines/chemokine levels were significantly increased in serum and BALF, while Th2 cytokine levels changed only a little. The levels of IL-33 in serum and BALF of the RAPA group was significantly increased after LPS was injected as compared with the LPS group; additionally, the levels of IL-33 in serum and BALF of the 3-MA group was significantly reduced after LPS was injected as compared with the LPS group, and that lung injury was ameliorated after 3-MA pretreatment. Th1 cytokines and chemokines in both serum and BALF were also decreased in the 3-MA group. Furthermore, we found that the nuclear translocation of NF-κB increased after LPS administration, and NF-κB's nuclear translocation was significantly increased in comparison with the LPS group after RAPA pretreatment. In contrast, NF-κB's nuclear translocation decreased after 3-MA pretreatment as compared with the LPS group.

CONCLUSIONS

These findings showed that autophagy might regulate IL-33 by activating or inhibiting NF-κB to control the uncontrolled inflammation of acute lung injury.

Role of Endoplasmic Reticulum Stress-Autophagy Axis in Severe Burn-Induced Intestinal Tight Junction Barrier Dysfunction in Mice

Severe burn injury induces intestinal barrier dysfunction; however, the underlying mechanisms remain elusive. Our previous studies have shown that the intestinal epithelial tight junction (TJ) barrier dysfunction is associated with both endoplasmic reticulum (ER) stress and autophagy in severely burned mice, but the precise role of ER stress and autophagy in the burn-induced intestinal TJ barrier dysfunction needs to be determined. In this study, female C57/BL6 mice were assigned randomly to either sham burn or 30% total body surface area (TBSA) full-thickness burn. The effects of ER stress and autophagy on the intestinal epithelial TJ barrier were validated by inducing or inhibiting both ER stress and autophagy in mice treated with sham burn or burn injury. The intestinal permeability, expression, and localization of TJ proteins, ER stress, and autophagy were assessed by physiological, morphological, and biochemical analyses. The results showed that inducing ER stress with tunicamycin or thapsigargin caused the activation of autophagy, the increase of intestinal permeability, as well as the reduction and reorganization of TJ proteins in the sham-burned mice, and aggravated the burn-induced activation of autophagy, increase of intestinal permeability, as well as the reduction and reorganization of TJ proteins. In contrast, inhibiting ER stress with 4-phenylbutyrate alleviated the burn-induced activation of autophagy, increase of intestinal permeability, as well as the reduction and reorganization of TJ proteins. In addition, inducing autophagy with rapamycin resulted in the increase of intestinal permeability, as well as the reduction and reorganization of TJ proteins in the sham-burned mice, and aggravated the burn-induced increase of intestinal permeability as well as the reduction and reorganization of TJ proteins. However, inhibiting autophagy with 3-methyladenine attenuated the burn-induced increase of intestinal permeability, as well as the reduction and reorganization TJ proteins. It is suggested that the ER stress-autophagy axis contributes to the intestinal epithelial TJ barrier dysfunction after severe burn injury.

Hydrogen-rich saline ameliorated LPS-induced acute lung injury via autophagy inhibition through the ROS/AMPK/mTOR pathway in mice

IMPACT STATEMENT

Acute lung injury (ALI), a common complication of many serious health issues, such as serious infection, burns, and shock, is one of the most common critical illnesses in clinical practice with a high mortality rate of 30-40%. There are still short of effective prevention and treatment measures. Evidence is growing that hydrogen-rich saline (HRS) may be an effective drug for the prevention and treatment of ALI. However, the mechanisms involved in have not been clearly understood. In this study, we investigated the underling mechanisms by focusing on autophagy regulation. The results showed that HRS ameliorated lipopolysaccharide-induced ALI in mice by inhibiting autophagy over-activation through ROS/AMPK/mTOR pathway. HRS may be a new therapeutic strategy for ALI prevention and treatment in the future.

Ursodeoxycholic acid stimulates alveolar fluid clearance in LPS-induced pulmonary edema via ALX/cAMP/PI3K pathway

This study aims to examine the impact of ursodeoxycholic acid (UDCA) on pulmonary edema and explore the underlying molecular mechanisms. The effects of UDCA on pulmonary edema were assessed through hematoxylin and eosin (H&E) staining, lung dry/wet (W/D) ratio, TNF-α/IL-1β levels of bronchoalveolar lavage fluid (BALF), protein expression of epithelial sodium channel (ENaC), and Na⁺ /K⁺ -ATPase. Besides, the detailed mechanisms were explored in primary rat alveolar type (AT) II epithelial cells by determining the effects of BOC-2 (ALX [lipoxin A4 receptor] inhibitor), Rp-cAMP (cAMP inhibitor), LY294002 (PI3K inhibitor), and H89 (PKA inhibitor) on the therapeutic effects of UDCA against lipopolysaccharide (LPS)-induced changes. Histological examination suggested that LPS-induced lung injury was obviously attenuated by UDCA. BALF TNF-α/IL-1β levels and lung W/D ratios were decreased by UDCA in LPS model rats. UDCA stimulated alveolar fluid clearance (AFC) though the upregulation of ENaC and Na⁺ /K⁺ -ATPase. BOC-2, Rp-cAMP, and LY294002 largely suppressed the therapeutic effects of UDCA. Significant attenuation of pulmonary edema and lung inflammation was revealed in LPS-challenged rats after the UDCA treatment. The therapeutic efficacy of UDCA against LPS was mainly achieved through the ALX/cAMP/PI3K pathway. Our results suggested that UDCA might be a potential drug for the treatment of pulmonary edema induced by LPS.

Selective Inactivation of Intracellular BiP/GRP78 Attenuates Endothelial Inflammation and Permeability in Acute Lung Injury

The role of Endoplasmic Reticulum Chaperone and Signaling Regulator BiP/GRP78 in acute inflammatory injury, particularly in the context of lung endothelium, is poorly defined. In his study, we monitored the effect of SubAB, a holoenzyme that cleaves and specifically inactivates BiP/GRP78 and its inactive mutant SubAA272B on lung inflammatory injury in an aerosolized LPS inhalation mouse model of acute lung injury (ALI). Analysis of lung homogenates and bronchoalveolar lavage (BAL) fluid showed that LPS-induced lung inflammation and injury were significantly inhibited in SubAB- but not in SubAA272B-treated mice. SubAB-treated mice were also protected from LPS-induced decrease in lung compliance. Gene transfer of dominant negative mutant of BiP in the lung endothelium protected against LPS-induced lung inflammatory responses. Consistent with this, stimulation of endothelial cells (EC) with thrombin caused an increase in BiP/GRP78 levels and inhibition of ER stress with 4-phenylbutyric acid (4-PBA) prevented this response as well as increase in VCAM-1, ICAM-1, IL-6, and IL-8 levels. Importantly, thrombin-induced Ca2+ signaling and EC permeability were also prevented upon BiP/GRP78 inactivation. The above EC responses are mediated by intracellular BiP/GRP78 and not by cell surface BiP/GRP78. Together, these data identify intracellular BiP/GRP78 as a novel regulator of endothelial dysfunction associated with ALI.

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.