The acute respiratory distress syndrome: from mechanism to translation

Knockdown of lncRNA MALAT1 Alleviates LPS-Induced Acute Lung Injury via Inhibiting Apoptosis Through the miR-194-5p/FOXP2 Axis

Purpose

We aimed to identify and verify the key genes and lncRNAs associated with acute lung injury (ALI) and explore the pathogenesis of ALI. Research showed that lower expression of the lncRNA metastasis-associated lung carcinoma transcript 1 (MALAT1) alleviates lung injury induced by lipopolysaccharide (LPS). Nevertheless, the mechanisms of MALAT1 on cellular apoptosis remain unclear in LPS-stimulated ALI. We investigated the mechanism of MALAT1 in modulating the apoptosis of LPS-induced human pulmonary alveolar epithelial cells (HPAEpiC).

Methods

Differentially expressed lncRNAs between the ALI samples and normal controls were identified using gene expression profiles. ALI-related genes were determined by the overlap of differentially expressed genes (DEGs), genes correlated with lung, genes correlated with key lncRNAs, and genes sharing significantly high proportions of microRNA targets with MALAT1. Quantitative real-time PCR (qPCR) was applied to detect the expression of MALAT1, microRNA (miR)-194-5p, and forkhead box P2 (FOXP2) mRNA in 1 μg/ml LPS-treated HPAEpiC. MALAT1 knockdown vectors, miR-194-5p inhibitors, and ov-FOXP2 were constructed and used to transfect HPAEpiC. The influence of MALAT1 knockdown on LPS-induced HPAEpiC proliferation and apoptosis via the miR-194-5p/FOXP2 axis was determined using Cell counting kit-8 (CCK-8) assay, flow cytometry, and Western blotting analysis, respectively. The interactions between MALAT1, miR-194-5p, and FOXP2 were verified using dual-luciferase reporter gene assay.

Results

We identified a key lncRNA (MALAT1) and three key genes (EYA1, WNT5A, and FOXP2) that are closely correlated with the pathogenesis of ALI. LPS stimulation promoted MALAT1 expression and apoptosis and also inhibited HPAEpiC viability. MALAT1 knockdown significantly improved viability and suppressed the apoptosis of LPS-stimulated HPAEpiC. Moreover, MALAT1 directly targeted miR-194-5p, a downregulated miRNA in LPS-stimulated HPAEpiC, when FOXP2 was overexpressed. MALAT1 knockdown led to the overexpression of miR-194-5p and restrained FOXP2 expression. Furthermore, inhibition of miR-194-5p exerted a rescue effect on MALAT1 knockdown of FOXP2, whereas the overexpression of FOXP2 reversed the effect of MALAT1 knockdown on viability and apoptosis of LPS-stimulated HPAEpiC.

Conclusion

Our results demonstrated that MALAT1 knockdown alleviated HPAEpiC apoptosis by competitively binding to miR-194-5p and then elevating the inhibitory effect on its target FOXP2. These data provide a novel insight into the role of MALAT1 in the progression of ALI and potential diagnostic and therapeutic strategies for ALI patients.

Proinflammatory cytokines and ARDS pulmonary edema fluid induce CD40 on human mesenchymal stromal cells-A potential mechanism for immune modulation

Human mesenchymal stem/stromal cells (hMSCs) are a promising therapy for acute respiratory distress syndrome (ARDS) and other inflammatory conditions. While considerable research has focused on paracrine effects and mitochondrial transfer that improve lung fluid balance, hMSCs are well known to have immunomodulatory properties as well. Some of these immunomodulatory properties have been related to previously reported paracrine effectors such as indoleamine-2,3-dioxygenase (IDO), but these effects cannot fully account for cell-contact dependent immunomodulation. Here, we report that CD40 is upregulated on hMSCs under the same conditions previously reported to induce IDO. Further, CD40 transcription is also upregulated on hMSCs by ARDS pulmonary edema fluid but not by hydrostatic pulmonary edema fluid. Transcription of CD40, as well as paracrine effectors TSG6 and PTGS2 remained significantly upregulated for at least 12 hours after withdrawal of cytokine stimulation. Finally, induction of this immune phenotype altered the transdifferentiation of hMSCs, one of their hallmark properties. CD40 may play an important role in the immunomodulatory effects of hMSCs in ARDS and inflammation.

The pathophysiology of SARS-CoV-2: A suggested model and therapeutic approach

In this paper, a model is proposed of the pathophysiological processes of COVID-19 starting from the infection of human type II alveolar epithelial cells (pneumocytes) by SARS-CoV-2 and culminating in the development of ARDS. The innate immune response to infection of type II alveolar epithelial cells leads both to their death by apoptosis and pyroptosis and to alveolar macrophage activation. Activated macrophages secrete proinflammatory cytokines and chemokines and tend to polarise into the inflammatory M1 phenotype. These changes are associated with activation of vascular endothelial cells and thence the recruitment of highly toxic neutrophils and inflammatory activated platelets into the alveolar space. Activated vascular endothelial cells become a source of proinflammatory cytokines and reactive oxygen species (ROS) and contribute to the development of coagulopathy, systemic sepsis, a cytokine storm and ARDS. Pulmonary activated platelets are also an important source of proinflammatory cytokines and ROS, as well as exacerbating pulmonary neutrophil-mediated inflammatory responses and contributing to systemic sepsis by binding to neutrophils to form platelet-neutrophil complexes (PNCs). PNC formation increases neutrophil recruitment, activation priming and extraversion of these immune cells into inflamed pulmonary tissue, thereby contributing to ARDS. Sequestered PNCs cause the development of a procoagulant and proinflammatory environment. The contribution to ARDS of increased extracellular histone levels, circulating mitochondrial DNA, the chromatin protein HMGB1, decreased neutrophil apoptosis, impaired macrophage efferocytosis, the cytokine storm, the toll-like receptor radical cycle, pyroptosis, necroinflammation, lymphopenia and a high Th17 to regulatory T lymphocyte ratio are detailed.

Soluble cluster of differentiation 74 regulates lung inflammation through the nuclear factor-κB signaling pathway

The soluble form of the migration inhibitory factor receptor cluster of differentiation 74 (sCD74) has previously been shown to be elevated during the development of acute lung injury (ALI) in mice. However, the biological role of increased sCD74 in ALI remans poorly understood. Synthesized recombinant sCD74 protein was administered to mice intratracheally. Pro-inflammatory genes in lung tissue and the inflammatory factors in bronchoalveolar lavage fluid (BALF) were analyzed using RT-PCR and ELISA, respectively. Additionally, RAW264.7, A549, and human umbilical vein endothelial cells (HUVEC) were treated with sCD74, and the resulting pro-inflammatory factor protein and gene expression levels were analyzed in the supernatants and cell lysates. Meanwhile, the level of nuclear factor (NF)-κB components in cell lysates after stimulating macrophages with sCD74 was also assessed. After administration of 0.5 mg/kg body weight sCD74 to mice, the expression of Tnfa, Mip2, and Il6 increased in lung tissues after 2 h by 2.1-, 3.4-, and 2.8-fold, respectively. Moreover, the BALF concentrations of TNF-α and MIP-2 reached maximal levels of 560 and 107 pg/mL at 8 h compared to those in the saline group, respectively. Similarly, TNFA, MIP2, and IL6 expression increased by 4.0-, 11.8-, and 2.6-fold, respectively, 2 h after stimulating macrophages with 1000 ng/mL sCD74. The levels of phospho-IκB and phospho-p65 were also significantly increased in the cytoplasm and nucleus of macrophages following sCD74 stimulation. Taken together, these results suggest that sCD74 is a critical cellular factor involved in the lung acute inflammatory response through nuclear factor-κB signaling.

Transcription factor-mediated signaling pathways' contribution to the pathology of acute lung injury and acute respiratory distress syndrome

The 2019 novel coronavirus (2019-nCoV) is still spreading rapidly around the world, and one cause of lethality for patients infected with 2019-nCoV is acute respiratory distress syndrome (ARDS). ARDS is a severe syndrome of acute lung injury (ALI) that is predominantly triggered by inflammation and results in a sudden loss of, or damage to, kidney function. Emerging studies reveal that multiple transcription factor-associated signaling pathways are activated in the pathology of ALI/ARDS. Of these pathways, the activation of NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells), AP-1 (activator protein 1), IRFs (interferon regulatory factors), STATs (signal transducer and activator of transcription), Wnt/β-catenin-TCF/LEF (T-cell factor/lymphoid enhancer-binding factor), and CtBP2 (C-Terminal binding protein 2)-associated transcriptional complex contributes to ALI/ARDS pathology through diverse mechanisms, such as inducing proinflammatory cytokine levels and mediating macrophage polarization. In this review, we present an updated summary of the mechanisms underlying these signaling activations and regulations, as well as their contribution to the pathogenesis of ALI/ARDS. We aim to develop a better understanding of how ALI/ARDS occurs and improve ALI/ARDS therapy.

Intermedin alleviates the inflammatory response and stabilizes the endothelial barrier in LPS-induced ARDS through the PI3K/Akt/eNOS signaling pathway

Inflammatory storms and endothelial barrier dysfunction are the central pathophysiological features of acute respiratory distress syndrome (ARDS). Intermedin (IMD), a member of the calcitonin gene-related peptide (CGRP) family, has been reported to alleviate inflammation and protect endothelial cell (EC) integrity. However, the effects of IMD on ARDS have not been clearly elucidated. In the present study, clinical ARDS data were used to explore the relationship between serum IMD levels and disease severity and prognosis, and we then established a model to predict the possibility of hospital survival. Mouse models of ARDS and LPS-challenged endothelial cells were used to analyze the protective effect and underlying mechanism of IMD. We found that in patients with ARDS, increased serum IMD levels were associated with reduced disease severity and increased rates of hospital survival. IMD alleviated the LPS-induced inflammatory response by decreasing proinflammatory cytokines, NF-κB p65 expression and NF-κB p65 nuclear translocation. In addition, IMD stabilized the endothelial barrier by repairing adherens junctions (AJs), cytoskeleton and capillary leakage. IMD exerted protective effects against ARDS on pulmonary endothelial cells, at least partly, through PI3K/Akt/eNOS signaling, while IMD's anti-inflammation effect was mediated through an eNOS-independent mechanism. Our study may provide new therapeutic insight for ARDS treatment.

Immune checkpoint blockade: releasing the breaks or a protective barrier to COVID-19 severe acute respiratory syndrome?

The rapid emergence of COVID-19 has sent shockwaves through healthcare systems globally, with cancer patients at increased risk. The interplay of the virus and host immune system has been implicated in the development of ARDS. Immunotherapy agents have the potential to adversely potentiate this phenomenon, requiring careful real-world observation.

The Monocyte-Derived Exosomal CLMAT3 Activates the CtBP2-p300-NF-κB Transcriptional Complex to Induce Proinflammatory Cytokines in ALI

Monocytes and macrophages are the two major cell types involved in innate immunity. Exosomes act as signaling molecules to regulate cell-to-cell communication by releasing proteins, mRNAs, microRNAs (miRNAs), and long noncoding RNAs (lncRNAs). However, it is still unclear whether monocyte-derived exosomes are involved in the communication between monocytes and macrophages. In this study, we analyzed the differentially expressed lncRNA profiles in monocytes isolated from blood samples of healthy controls and acute lung injury (ALI) patients. We focused our study on investigating the signaling downstream of CLMAT3 (colorectal liver metastasis-associated transcript 3), a lncRNA that regulated proinflammatory cytokine genes. We revealed that CLMAT3 specifically targeted CtBP2 (C-terminal binding protein 2) and repressed its expression. Elevated CtBP2 acted as a coactivator to assemble a transcriptional complex with histone acetyltransferase p300 and NF-κB (nuclear factor κB) subunits. In vitro coculture and in vivo injection of ALI monocyte-derived exosomes increased the production of proinflammatory cytokines. Importantly, the administration of two CtBP2 inhibitors, NSC95397 and MTOB, could significantly reverse CtBP2-mediated transactivation. Collectively, our results support a model in which monocyte-derived exosomal CLMAT3 activates the CtBP2-p300-NF-κB complex to induce proinflammatory cytokines, thus contributing to the pathogenesis of ALI.

Vitamin D in COVID - 19: Dousing the fire or averting the storm? - A perspective from the Asia-Pacific

COVID-19, the acute respiratory tract infection (RTI) caused by the Coronavirus, Sars-CoV-2, has swept around the world. No country has been spared from its onslaught. Treatments that can reduce the risk of infection and mortality from the disease are desperately needed. Though high quality randomized controlled trials are lacking, some observational and interventional studies that explore the link between vitamin D and RTIs exist. Vitamin D modulates both innate as well as adaptive immunity and may potentially prevent or mitigate the complications associated with RTIs. Evidence linking vitamin D to COVID-19 include that the outbreak occurred in winter in the northern hemisphere at a time when vitamin D levels are lowest in resident populations, that blacks and minority ethnic individuals who are known to have lower levels of vitamin D appear to be disproportionately affected and have more severe complications from the disease, that vitamin D deficiency has been shown to contribute to acute respiratory distress syndrome and that case fatality rates increase with age and in populations with comorbid conditions such as diabetes, hypertension, and cardiovascular disease, all of which are associated with lower vitamin D levels. This narrative review summarizes the current knowledge about the epidemiology and pathophysiology of COVID-19, the evidence linking vitamin D and RTIs, especially COVID-19, the mechanistic reasons behind the possible protective effect of vitamin D in COVID-19, and the evidence with regard to vitamin D supplementation in RTIs. It concludes with some recommendations regarding supplementation of vitamin D in patients with COVID-19.

Use of Anti-Interleukin-6 Receptor Monoclonal Antibody in Drug-Induced Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a disorder that involves the activation of alveolar macrophages triggering the innate immune system. The parenchymal lung injury seen in ARDS is a result of many proinflammatory elevations including interleukin-6. There remains no effective standard of care of ARDS, and current treatments at this time currently do not target the immunological mechanisms or pathways involved. Treatments involving this pathway should be further investigated as targeted treatment. We discuss a case of a patient with multiple myeloma who was hospitalized with drug-induced ARDS who had a rapid response to an anti-interleukin-6 monoclonal antibody.

The Role of Deubiquitinating Enzymes in Acute Lung Injury and Acute Respiratory Distress Syndrome

Acute lung injury and acute respiratory distress syndrome (ALI/ARDS) are characterized by an inflammatory response, alveolar edema, and hypoxemia. ARDS occurs most often in the settings of pneumonia, sepsis, aspiration of gastric contents, or severe trauma. The prevalence of ARDS is approximately 10% in patients of intensive care. There is no effective remedy with mortality high at 30-40%. Most functional proteins are dynamic and stringently governed by ubiquitin proteasomal degradation. Protein ubiquitination is reversible, the covalently attached monoubiquitin or polyubiquitin moieties within the targeted protein can be removed by a group of enzymes called deubiquitinating enzymes (DUBs). Deubiquitination plays an important role in the pathobiology of ALI/ARDS as it regulates proteins critical in engagement of the alveolo-capillary barrier and in the inflammatory response. In this review, we provide an overview of how DUBs emerge in pathogen-induced pulmonary inflammation and related aspects in ALI/ARDS. Better understanding of deubiquitination-relatedsignaling may lead to novel therapeutic approaches by targeting specific elements of the deubiquitination pathways.

Carnosine and Lung Disease

Carnosine (β-alanyl-L-histidine) is a small dipeptide with numerous activities, including antioxidant effects, metal ion chelation, proton buffering capacity, and inhibitory effects on protein carbonylation and glycation. Carnosine has been mostly studied in organs where it is abundant, including skeletal muscle, cerebral cortex, kidney, spleen, and plasma. Recently, the effect of supplementation with carnosine has been studied in organs with low levels of carnosine, such as the lung, in animal models of influenza virus or lipopolysaccharide-induced acute lung injury and pulmonary fibrosis. Among the known protective effects of carnosine, its antioxidant effect has attracted increasing attention for potential use in treating lung disease. In this review, we describe the in vitro and in vivo biological and physiological actions of carnosine. We also report our recent study and discuss the roles of carnosine or its related compounds in organs where carnosine is present in only small amounts (especially the lung) and its protective mechanisms.

Invasive Aspergillosis as an Under-recognized Superinfection in COVID-19

Pulmonary aspergillosis has been increasingly reported following severe respiratory viral infections. Millions have been infected by SARS-CoV-2, placing large numbers of patients at-risk for COVID-19 associated pulmonary aspergillosis (CAPA). Prompt recognition of this syndrome and is paramount to improve outcomes.

The α7 nicotinic acetylcholine receptor agonist, GTS-21, attenuates hyperoxia-induced acute inflammatory lung injury by alleviating the accumulation of HMGB1 in the airways and the circulation

Background

Oxygen therapy, using supraphysiological concentrations of oxygen (hyperoxia), is routinely administered to patients who require respiratory support including mechanical ventilation (MV). However, prolonged exposure to hyperoxia results in acute lung injury (ALI) and accumulation of high mobility group box 1 (HMGB1) in the airways. We previously showed that airway HMGB1 mediates hyperoxia-induced lung injury in a mouse model of ALI. Cholinergic signaling through the α7 nicotinic acetylcholine receptor (α7nAChR) attenuates several inflammatory conditions. The aim of this study was to determine whether 3–(2,4 dimethoxy-benzylidene)-anabaseine dihydrochloride, GTS-21, an α7nAChR partial agonist, inhibits hyperoxia-induced HMGB1 accumulation in the airways and circulation, and consequently attenuates inflammatory lung injury.

Methods

Mice were exposed to hyperoxia (≥99% O₂) for 3 days and treated concurrently with GTS-21 (0.04, 0.4 and 4 mg/kg, i.p.) or the control vehicle, saline.

Results

The systemic administration of GTS-21 (4 mg/kg) significantly decreased levels of HMGB1 in the airways and the serum. Moreover, GTS-21 (4 mg/kg) significantly reduced hyperoxia-induced acute inflammatory lung injury, as indicated by the decreased total protein content in the airways, reduced infiltration of inflammatory monocytes/macrophages and neutrophils into the lung tissue and airways, and improved lung injury histopathology.

Conclusions

Our results indicate that GTS-21 can attenuate hyperoxia-induced ALI by inhibiting extracellular HMGB1-mediated inflammatory responses. This suggests that the α7nAChR represents a potential pharmacological target for the treatment regimen of oxidative inflammatory lung injury in patients receiving oxygen therapy.

The Role of TRPV4 in Regulating Innate Immune Cell Function in Lung Inflammation

Ion channels/pumps are essential regulators of innate immune cell function. Macrophages have been increasingly recognized to have phenotypic plasticity and location-specific functions in the lung. Transient receptor potential vanilloid 4 (TRPV4) function in lung injury has been shown to be stimulus- and cell-type specific. In the current review, we discuss the importance of TRPV4 in macrophages and its role in phagocytosis and cytokine secretion in acute lung injury/acute respiratory distress syndrome (ARDS). Furthermore, TRPV4 controls a MAPK molecular switch from predominately c-Jun N-terminal kinase, JNK activation, to that of p38 activation, that mediates phagocytosis and cytokine secretion in a matrix stiffness-dependent manner. Expanding knowledge regarding the downstream mechanisms by which TRPV4 acts to tailor macrophage function in pulmonary inflammatory diseases will allow for formulation of novel therapeutics.

S-allylmercaptocysteine inhibits mucin overexpression and inflammation via MAPKs and PI3K-Akt signaling pathways in acute respiratory distress syndrome

Cytokine storm is an important cause of acute respiratory distress syndrome and multiple organ failure. Excessive secretion and accumulation of mucins on the surface of airway cause airway obstruction and exacerbate lung infections. MUC5AC and MUC5B are the main secreted mucins and overexpressed in various inflammatory responses. S-allylmercaptocysteine, a water-soluble organic sulfur compound extracted from garlic, has anti-inflammatory and anti-oxidative effects for various pulmonary diseases. The aim of this work was to investigate the therapeutic effects of SAMC on mucin overproduction and inflammation in 16HBE cells and LPS-induced ARDS mice. Results show that SAMC treatment ameliorated inflammatory cell infiltration and lung histopathological changes in the LPS-induced ARDS mice. SAMC also inhibited the expressions of MUC5AC and MUC5B, decreased the production of pro-inflammatory markers (IL-6, TNF-α, CD86 and IL-12) and increased the production of anti-inflammatory markers (IL-10, CD206 and TGF-β). These results confirm that SAMC had potential beneficial effects on suppressed hyperinflammation and mucin overexpression. Furthermore, SAMC exerted the therapeutic effects through the inhibition of phosphorylation of MAPKs and PI3K-Akt signaling pathways in the 16HBE cells and mice. Overall, our results demonstrate the effects of SAMC on the LPS-induced mucin overproduction and inflammation both in the 16HBE cells and mice.

Suppressed nuclear factor-kappa B alleviates lipopolysaccharide-induced acute lung injury through downregulation of CXCR4 mediated by microRNA-194

Acute lung injury (ALI) is a highly lethal pulmonary disease that causes edema, hypoxemia and respiratory failure. Recent evidence indicates that nuclear factor-kappa B (NF-κB) plays a crucial role in ALI development. However, the regulatory mechanism of NF-κB on ALI remains enigmatic. In this study, we investigated potential molecular mechanism of NF-κB on ALI induced by lipopolysaccharide (LPS). BALB/c mice were subjected to intratracheal spraying of LPS to generate an ALI mode, with the activity of NF-κB in mice tissues being detected by enzyme linked immunosorbent assay (ELISA), and the number of inflammatory cells in bronchoalveolar lavage fluid being counted. Then, the macrophage cell line RAW264.7 exposed to LPS were treated with ammonium pyrrolidinedithiocarbamate (PDTC) (inhibitor of NF-κB), miR-194 mimic, or oe-chemokine receptor type 4 (CXCR4) separately or in combination. After that, ELISA and reverse transcription quantitative polymerase chain reaction (RT-qPCR) were used to detect the expression level of IL-1β, IL-6, TNF-α, miR-194 and CXCR4, respectively. In addition, the targeting relationship between miR-194 and CXCR4 was verified by dual-luciferase reporter gene assay. The dry/wet ratio of lung and the MPO activity were also measured to assess the inflammatory response in mice. Activation of NF-κB down-regulated the miR-194 expression in LPS-induced ALI. Overexpression of miR-194 alleviated LPS-induced ALI and reduced the expression of inflammatory factors IL-1β, IL-6 and TNF-α via targeting CXCR4. In LPS-induced ALI, NF-κB mediates the CXCR4 expression by inhibiting the expression of miR-194, thus promoting the inflammatory injury of lung.

Developing Novel Host-Based Therapies Targeting Microbicidal Responses in Macrophages and Neutrophils to Combat Bacterial Antimicrobial Resistance

Antimicrobial therapy has provided the main component of chemotherapy against bacterial pathogens. The effectiveness of this strategy has, however, been increasingly challenged by the emergence of antimicrobial resistance which now threatens the sustained utility of this approach. Humans and animals are constantly exposed to bacteria and have developed effective strategies to control pathogens involving innate and adaptive immune responses. Impaired pathogen handling by the innate immune system is a key determinant of susceptibility to bacterial infection. However, the essential components of this response, specifically those which are amenable to re-calibration to improve host defense, remain elusive despite extensive research. We provide a mini-review focusing on therapeutic targeting of microbicidal responses in macrophages and neutrophils to de-stress reliance on antimicrobial therapy. We highlight pre-clinical and clinical data pointing toward potential targets and therapies. We suggest that developing focused host-directed therapeutic strategies to enhance "pauci-inflammatory" microbial killing in myeloid phagocytes that maximizes pathogen clearance while minimizing the harmful consequences of the inflammatory response merits particular attention. We also suggest the importance of One Health approaches in developing host-based approaches through model development and comparative medicine in informing our understanding of how to deliver this strategy.

MicroRNA: Potential biomarker and target of therapy in acute lung injury

MicroRNAs (miRNAs) are small noncoding RNAs stretching over 18-22 nucleotides and considered to be modifiers of many respiratory diseases. They are highly evolutionary conserved and have been implicated in several biological processes, including cell proliferation, apoptosis, differentiation, among others. Acute lung injury (ALI) is a fatal disease commonly caused by direct or indirect injury factors and has a high mortality rate in intensive care unit. Changes in expression of several types of miRNAs have been reported in patients with ALI. Some miRNAs suppress cellular injury and accelerate the recovery of ALI by targeting specific molecules and decreasing excessive immune response. For this reason, miRNAs are proposed as potential biomarkers for ALI and as therapeutic targets for this disease. This review summarizes current evidence supporting the role of miRNAs in ALI.

The cognitive consequences of the COVID-19 epidemic: collateral damage?

Recovery from coronavirus disease 2019 (COVID-19) will be principally defined in terms of remission from respiratory symptoms; however, both clinical and animal studies have shown that coronaviruses may spread to the nervous system. A systematic search on previous viral epidemics revealed that while there has been relatively little research in this area, clinical studies have commonly reported neurological disorders and cognitive difficulties. Little is known with regard to their incidence, duration or underlying neural basis. The hippocampus appears to be particularly vulnerable to coronavirus infections, thus increasing the probability of post-infection memory impairment, and acceleration of neurodegenerative disorders such as Alzheimer's disease. Future knowledge of the impact of COVID-19, from epidemiological studies and clinical practice, will be needed to develop future screening and treatment programmes to minimize the long-term cognitive consequences of COVID-19.

Aloin suppresses lipopolysaccharide-induced acute lung injury by inhibiting NLRP3/NF-κB via activation of SIRT1 in mice

OBJECTIVE

The purpose of this study was to explore the protective effects and potential mechanisms of aloin on lipopolysaccharide (LPS)-induced acute lung injury (ALI).

METHODS

Mice were pretreatment with aloin 1 h before LPS administration. The number of inflammatory cells and the levels of TNF-α and IL-1β was detected. The lung histopathological changes, wet/dry ratio, MPO activity, GSH, MDA, SOD, and the expression of NF-κB and NLRP3 inflammasome were measured.

RESULTS

The results showed that aloin significantly inhibited the number of total cells, neutrophils, and macrophages, as well as the levels of TNF-α and IL-1β in BALF induced by LPS. In addition, pretreatment with aloin also inhibited LPS-induced lung histopathological injuries, lung wet/dry ratio, MPO activity, and MDA content. The levels of GSH and SOD were decreased by LPS and treatment of aloin could increase the levels of GSH and SOD. To study the protective mechanisms of alion on LPS-induced ALI, the expression of SIRT1, NF-κB and NLRP3 inflammasome were tested. We found that aloin significantly inhibited the activation of NF-κB and NLRP3 inflammasome in ALI induced by LPS. Meanwhile, aloin was found to increase the expression of SIRT1 and inhibition of SIRT1 by EX-527 reversed the protective effects of aloin.

CONCLUSIONS

These results suggest that aloin exerts its protective effects on LPS-induced ALI by activation SIRT1, which subsequently results in the suppression of NF-κB and NLRP3 inflammasome.

The Society for Immunotherapy of Cancer perspective on regulation of interleukin-6 signaling in COVID-19-related systemic inflammatory response

The pandemic caused by the novel coronavirus SARS-CoV-2 has placed an unprecedented burden on healthcare systems around the world. In patients who experience severe disease, acute respiratory distress is often accompanied by a pathological immune reaction, sometimes referred to as 'cytokine storm'. One hallmark feature of the profound inflammatory state seen in patients with COVID-19 who succumb to pneumonia and hypoxia is marked elevation of serum cytokines, especially interferon gamma, tumor necrosis factor alpha, interleukin 17 (IL-17), interleukin 8 (IL-8) and interleukin 6 (IL-6). Initial experience from the outbreaks in Italy, China and the USA has anecdotally demonstrated improved outcomes for critically ill patients with COVID-19 with the administration of cytokine-modulatory therapies, especially anti-IL-6 agents. Although ongoing trials are investigating anti-IL-6 therapies, access to these therapies is a concern, especially as the numbers of cases worldwide continue to climb. An immunology-informed approach may help identify alternative agents to modulate the pathological inflammation seen in patients with COVID-19. Drawing on extensive experience administering these and other immune-modulating therapies, the Society for Immunotherapy of Cancer offers this perspective on potential alternatives to anti-IL-6 that may also warrant consideration for management of the systemic inflammatory response and pulmonary compromise that can be seen in patients with severe COVID-19.

Increased mortality of acute respiratory distress syndrome was associated with high levels of plasma phenylalanine

Background

There is a dearth of drug therapies available for the treatment of acute respiratory distress syndrome (ARDS). Certain metabolites play a key role in ARDS and could serve as potential targets for developing therapies against this respiratory disorder. The present study was designed to determine such “functional metabolites” in ARDS using metabolomics and in vivo experiments in a mouse model.

Methods

Metabolomic profiles of blood plasma from 42 ARDS patients and 28 healthy controls were captured using Ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) assay. Univariate and multivariate statistical analysis were performed on metabolomic profiles from blood plasma of ARDS patients and healthy controls to screen for “functional metabolites”, which were determined by variable importance in projection (VIP) scores and P value. Pathway analysis of all the metabolites was performed. The mouse model of ARDS was established to investigate the role of “functional metabolites” in the lung injury and mortality caused by the respiratory disorder.

Results

The metabolomic profiles of patients with ARDS were significantly different from healthy controls, difference was also observed between metabolomic profiles of the non-survivors and the survivors among the ARDS patient pool. Levels of Phenylalanine, D-Phenylalanine and Phenylacetylglutamine were significantly increased in non-survivors compared to the survivors of ARDS. Phenylalanine metabolism was the most notably altered pathway between the non-survivors and survivors of ARDS patients. In vivo animal experiments demonstrated that high levels of Phenylalanine might be associated with the severer lung injury and increased mortality of ARDS.

Conclusion

Increased mortality of acute respiratory distress syndrome was associated with high levels of plasma Phenylalanine.

Trial registration

Chinese Clinical Trial Registry, ChiCTR1800015930. Registered 29 April 2018, http://www.chictr.org.cn/edit.aspx?pid=25609&htm=4

Codon Usage and Phenotypic Divergences of SARS-CoV-2 Genes

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which first occurred in Wuhan (China) in December of 2019, causes a severe acute respiratory illness with a high mortality rate, and has spread around the world. To gain an understanding of the evolution of the newly emerging SARS-CoV-2, we herein analyzed the codon usage pattern of SARS-CoV-2. For this purpose, we compared the codon usage of SARS-CoV-2 with that of other viruses belonging to the subfamily of Orthocoronavirinae. We found that SARS-CoV-2 has a high AU content that strongly influences its codon usage, which appears to be better adapted to the human host. We also studied the evolutionary pressures that influence the codon usage of five conserved coronavirus genes encoding the viral replicase, spike, envelope, membrane and nucleocapsid proteins. We found different patterns of both mutational bias and natural selection that affect the codon usage of these genes. Moreover, we show here that the two integral membrane proteins (matrix and envelope) tend to evolve slowly by accumulating nucleotide mutations on their corresponding genes. Conversely, genes encoding nucleocapsid (N), viral replicase and spike proteins (S), although they are regarded as are important targets for the development of vaccines and antiviral drugs, tend to evolve faster in comparison to the two genes mentioned above. Overall, our results suggest that the higher divergence observed for the latter three genes could represent a significant barrier in the development of antiviral therapeutics against SARS-CoV-2.

Novel coronavirus disease (COVID-19) in children

Coronavirus disease (COVID-19) was firstly reported at the end of 2019. The disease rapidly spread all around the world in a few months and was declared a worldwide pandemic by WHO in March 2020. By April 9, there were 1,436,198 confirmed COVID-19 cases in the world, nearly with 6% mortality rate. This novel infectious disease causes respiratory tract illness that may generally occur as mild upper respiratory tract disease or pneumonia. In older patients and/or patients with underlying conditions, it may result in acute respiratory distress syndrome, multi organ failure and even death. According to the current literature, children account approximately for 1%–5% of diagnosed COVID-19 cases. Generally, COVID-19 seems to be a less severe disease for children than adults. Approximately 90% of pediatric patients are diagnosed as asymptomatic, mild, or moderate disease. However, up to 6.7% of cases may be severe. Severe illness is generally seen in patients smaller than 1 year of age and patients who have underlying disesases. The epidemiological and clinical patterns of COVID-19 and treatment approaches in pediatric patients still remain unclear although many pediatric reports are published. This review aims to summarize the current epidemics, clinical presentations, diagnosis, and treatment of COVID-19 in pediatric patients.

The significance of disseminated intravascular coagulation on multiple organ dysfunction during the early stage of acute respiratory distress syndrome

BACKGROUND

Multiple organ dysfunction syndrome (MODS) is a predominant cause of death in acute respiratory distress syndrome (ARDS). Disseminated intravascular coagulation (DIC) is recognized as a syndrome that frequently develops MODS. To test the hypothesis that DIC scores are useful for predicting MODS development and that DIC is associated with MODS, we retrospectively analyzed the data of a prospective, multicenter study on ARDS.

METHODS

Patients who met the Berlin definition of ARDS were included. DIC scores as well as the disease severity and the development of MODS on the day of the diagnosis of ARDS (day 0) and day 3 were evaluated. The primary and secondary outcomes were the development of MODS and the hospital mortality.

RESULTS

In the 129 eligible patients, the prevalence of DIC was 45.7% (59/129). DIC patients were more seriously ill and exhibited a higher prevalence of MODS on days 0 and 3 than non-DIC patients. The DIC scores on day 0 detected the development of MODS with good area under the receiver operating characteristic curve (0.714, p<.001). DIC on day 0 was significantly associated with MODS on days 0 and 3 (odds ratio 1.53 and 1.34, respectively). Patients with persistent DIC from days 0 to 3 had higher rates of both MODS on day 3 (p=.035) and hospital mortality (p=.031) than the other patients.

CONCLUSIONS

DIC scores were able to predict MODS, and DIC was associated with MODS during the early stage of ARDS. Persistent DIC may also have role in this association.

Activation of Alpha-7 Nicotinic Acetylcholine Receptors (α7nAchR) Promotes the Protective Autophagy in LPS-Induced Acute Lung Injury (ALI) In Vitro and In Vivo

The release of inflammatory cytokines and chemokines and autophagy has been reported to be involved in the pathogenic mechanism of acute lung injury (ALI). Reportedly, alpha-7 nicotinic acetylcholine receptors (α7nAchR) might play a protective role in LPS-induced ALI. In the current research, we established LPS-induced ALI model in mice and α7nAchR agonist PNU-282987 improved LPS-induced injury. In MH-S cells, LPS stimulation inhibited, whereas α7nAchR agonist PNU-282987 enhanced the autophagy. α7nAchR agonist PNU-282987 protected MH-S cells from LPS-induced inflammation by reducing the concentrations of IL-6, TNF-α, and IL-1β. Finally, LPS stimulation dramatically inhibited MH-S cell viability but enhanced cell apoptosis, whereas PNU-282987 treatment exerted opposite effects; α7nAchR might regulate the cellular homeostasis via affecting the crosstalk between the autophagy and apoptosis in MH-S cells; in other words, α7nAChR agonist enhances MH-S cell autophagy and inhibits MH-S cell apoptosis. In conclusion, α7nAchR promote the protective autophagy in LPS-induced ALI model in mice and MH-S cells. The application of α7nAchR agonist is considered a potent target for LPS-induced ALI, which needs further clinical investigation.

Suppression of NLRP3 Inflammasome by Erythropoietin via the EPOR/JAK2/STAT3 Pathway Contributes to Attenuation of Acute Lung Injury in Mice

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common and devastating clinical disorders with high mortality and no specific therapy. An excessive inflammatory response results in the progression of ALI/ARDS, and the NLRP3 inflammasome is a key participant in inflammation. Erythropoietin (EPO), which is clinically used for anemia, reportedly exerts pleiotropic effects in ALI. However, whether EPO could protect against lipopolysaccharide (LPS)-induced ALI by regulating the NLRP3 inflammasome and its underlying mechanisms remain poorly elucidated. This study aimed to explore whether the therapeutic effects of EPO rely on the suppression of the NLRP3 inflammasome and the specific mechanisms in an LPS-induced ALI mouse model. ALI was induced in C57BL/6 mice by intraperitoneal (i.p.) injection of LPS (15 mg/kg). EPO was administered intraperitoneally at 5 U/g after LPS challenge. The mice were sacrificed 8 h later. Our findings indicated that application of EPO markedly diminished LPS-induced lung injury by restoring histopathological changes, lessened lung wet/dry (W/D) ratio, protein concentrations in bronchoalveolar lavage fluid (BALF) and myeloperoxidase (MPO) levels. Meanwhile, EPO evidently decreased interleukin-1β (IL-1β) and interleukin-18 (IL-18) secretion, the expression of NLRP3 inflammasome components including pro-IL-1β, NLRP3, and cleaved caspase-1 as well as phosphorylation of nuclear factor-κB (NF-κB) p65, which may be associated with activation of EPO receptor (EPOR), phosphorylation of Janus-tyrosine kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3). However, all the beneficial effects of EPO on ALI and modulation NLRP3 inflammasome were remarkably abrogated by the inhibition of EPOR/JAK2/STAT3 pathway and knockout (KO) of NLRP3 gene. Taken together, this study indicates that EPO can effectively attenuate LPS-induced lung injury in mice by suppressing the NLRP3 inflammasome, which is dependent upon activation of EPOR/JAK2/STAT3 signaling and inhibition of the NF-κB pathway.

Characterization of pulmonary immune responses to hyperoxia by high-dimensional mass cytometry analyses

Prolonged exposure to hyperoxia has deleterious effects on the lung, provoking both inflammation and alveolar injury. The elements of hyperoxic injury, which result in high rates of lethality in experimental models, are thought to include multicellular immune responses. To characterize these alterations in immune cell populations, we performed time-of-flight mass cytometry (CyTOF) analysis of CD45-expressing immune cells in whole lung parenchyma and the bronchoalveolar space of mice, exposed to 48 hours of hyperoxia together with normoxic controls. At the tested time point, hyperoxia exposure resulted in decreased abundance of immunoregulatory populations (regulatory B cells, myeloid regulatory cells) in lung parenchyma and markedly decreased proliferation rates of myeloid regulatory cells, monocytes and alveolar macrophages. Additionally, hyperoxia caused a shift in the phenotype of alveolar macrophages, increasing proportion of cells with elevated CD68, CD44, CD11c, PD-L1, and CD205 expression levels. These changes occurred in the absence of histologically evident alveolar damage and abundance of neutrophils in the parenchyma or alveolar space did not change at these time points. Collectively, these findings demonstrate that pulmonary response to hyperoxia involves marked changes in specific subsets of myeloid and lymphoid populations. These findings have important implications for therapeutic targeting in acute lung injury.

Inhibition of the endoplasmic reticulum (ER) stress-associated IRE-1/XBP-1 pathway alleviates acute lung injury via modulation of macrophage activation

Background

Both endoplasmic reticulum (ER) stress and macrophage diversity contribute to inflammatory processes in lung injury. However, the interaction between ER stress and macrophage M1/M2 imbalance in lung inflammation remains unclear. The present study, thus, aimed to evaluate the role of ER stress-mediated macrophage phenotype changes in lipopolysaccharide (LPS)-induced acute lung injury (ALI).

Methods

Lung inflammation and injury were examined in a murine model of LPS-induced ALI with or without ER stress inhibitors. Alveolar macrophage (AM) polarization was determined by flow cytometry. Bone marrow-derived macrophages (BMDMs) were treated with either an ER stress inducer, inhibitor, or an IRE-1 endonuclease inhibitor before being polarized to an M1 and M2 phenotype. The macrophage polarization status was examined via RT-PCR and flow cytometry.

Results

Our results indicated that ER stress and IRE-1/XBP-1 signaling are activated in LPS-induced ALI. Furthermore, we observed that AM polarizes to an inflammatory phenotype upon exposure to LPS in the induction phase and an anti-inflammatory phenotype in the resolution phase of lung inflammation. Inhibition of ER stress attenuated the pathophysiological features of LPS-induced lung inflammation/injury, as evidenced by a decrease in bronchoalveolar lavage (BAL) protein levels, the number of inflammatory cells, and the expression level of inflammatory mediators. In addition, the ER stress inducer promoted M1 polarization and the switch from M2 to M1 in BMDMs, whereas inhibition of ER stress and XBP-1 splicing suppressed M1 but did not promote M2, both in vivo and in vitro.

Conclusions

Our results demonstrated that inhibition of the ER stress-associated IRE-1/XBP-1 signaling pathway suppresses M1 polarization and ameliorates LPS-induced lung injury. This indicates that the interaction between ER stress and macrophage polarization might be a novel therapeutic target for endotoxin-induced lung inflammatory disorders.

The IL1β-HER2-CLDN18/CLDN4 axis mediates lung barrier damage in ARDS

Objective: The high mortality rate associated with acute respiratory distress syndrome (ARDS) is a major challenge for intensive care units. In the present study, we applied bioinformatics and animal models to identify core genes and potential corresponding pathways in ARDS.

Results: Using bioinformatics analysis, IL-1β was identified as the core gene of ARDS. Cell experiments showed that up-regulation of IL-1β downregulates claudin18 to promote lung barrier function damage by regulating the IL-1β-HER2/HER3 axis, further promoting the development of ARDS. This was validated in the animal models.

Conclusion: IL-1β promotes the development of ARDS by regulating the IL-1β-HER2/HER3 axis. These findings deepen the understanding of the pathological mechanisms of ARDS.

Methods: Transcription data sets related to ARDS were subjected to differential expression gene analysis, functional enrichment analysis, and receiver operating characteristic curve analysis and, so as to identify core genes in ARDS. Cell experiments were used to further explore the effects of core genes on lung barrier function damage. Animal models were applied to validate the effects of core gene in mediating biological signal pathways in ARDS.

Toll-like Receptor 8 Stability Is Regulated by Ring Finger 216 in Response to Circulating MicroRNAs

TLR8 (Toll-like receptor 8) is an intracellular pattern recognition receptor that senses RNA in endosomes to initiate innate immune signaling through NF-κB, and mechanisms regulating TLR8 protein abundance are not completely understood. Protein degradation is a cellular process controlling protein concentrations, accomplished largely through ubiquitin transfer directed by E3 ligase proteins to substrates. In the present study, we show that TLR8 has a short half-life in THP-1 monocytes (∼1 h) and that TLR8 is ubiquitinated and degraded in the proteasome. Treatment with the TLR8 agonist R848 causes rapid depletion of TLR8 concentrations at early time points, an effect blocked by proteasomal inhibition. We show a novel role for RNF216 (ring finger protein 216), an E3 ligase that targets TLR8 for ubiquitination and degradation. RNF216 overexpression reduces TLR8 concentrations, whereas RNF216 knockdown stabilizes TLR8. We describe a potential role for TLR8 activation by circulating RNA ligands in humans with acute respiratory distress syndrome (ARDS): Plasma and extracted RNA fractions from subjects with ARDS activated TLR8 in vitro. MicroRNA (miRNA) expression profiling revealed several circulating miRNAs from subjects with ARDS. miRNA mimics promoted TLR8 proteasomal degradation in THP-1 cells. These data show that TLR8 proteasomal disposal through RNF216 in response to RNA ligands regulates TLR8 cellular concentrations and may have implications for innate immune signaling. In addition, TLR8 activation by circulating RNA ligands may be a previously underrecognized stimulus contributing to excessive innate immune signaling characteristic of ARDS.

TRPV4 Protects the Lung from Bacterial Pneumonia via MAPK Molecular Pathway Switching

Mechanical cell-matrix interactions can drive the innate immune responses to infection; however, the molecular underpinnings of these responses remain elusive. This study was undertaken to understand the molecular mechanism by which the mechanosensitive cation channel, transient receptor potential vanilloid 4 (TRPV4), alters the in vivo response to lung infection. For the first time, to our knowledge, we show that TRPV4 protects the lung from injury upon intratracheal Pseudomonas aeruginosa in mice. TRPV4 functions to enhance macrophage bacterial clearance and downregulate proinflammatory cytokine secretion. TRPV4 mediates these effects through a novel mechanism of molecular switching of LPS signaling from predominant activation of the MAPK, JNK, to that of p38. This is accomplished through the activation of the master regulator of inflammation, dual-specificity phosphatase 1. Further, TRPV4's modulation of the LPS signal is mechanosensitive in that both upstream activation of p38 and its downstream biological consequences depend on pathophysiological range extracellular matrix stiffness. We further show the importance of TRPV4 on LPS-induced activation of macrophages from healthy human controls. These data are the first, to our knowledge, to demonstrate new roles for macrophage TRPV4 in regulating innate immunity in a mechanosensitive manner through the modulation of dual-specificity phosphatase 1 expression to mediate MAPK activation switching.

Genetically modified mesenchymal stem cell therapy for acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a devastating hypoxemic respiratory failure, characterized by disruption of the alveolar-capillary membrane barrier. Current management for ARDS remains supportive, including lung-protective ventilation and a conservative fluid strategy. Mesenchymal stem cells (MSCs) have emerged as a potentially attractive candidate for the management of ARDS through facilitating lung tissue regeneration and repair by releasing paracrine soluble factors. Over the last decade, a variety of strategies have emerged to optimize MSC-based therapy. Among these, the strategy using genetically modified MSCs has received increased attention recently due to its distinct advantage, in conferring incremental migratory capacity and, enhancing the anti-inflammatory, immunomodulatory, angiogenic, and antifibrotic effects of these cells in numerous preclinical ARDS models, which may in turn provide additional benefits in the management of ARDS. Here, we provide an overview of recent studies testing the efficacy of genetically modified MSCs using preclinical models of ARDS.

A cross-sectional study of acute cor pulmonale in acute respiratory distress syndrome patients in China

BACKGROUND

Increased right ventricle afterload during acute respiratory distress syndrome (ARDS) may induce acute cor pulmonale (ACP), which is associated with a poor clinical outcome. Echocardiography is now considered as a rapid and non-invasive tool for diagnosis of ACP. The aims of this study were to investigate the morbidity and mortality rates of ACP in ARDS patients in intensive care units (ICUs) across the mainland of China and to determine the severity and prognosis of ACP in ARDS patients through an ultrasound protocol (TRIP). And the association between ACP related factors and the ICU mortality will be revealed.

METHODS

This study is a multicenter and cross-sectional study in China which will include ICU participants when diagnosed as ARDS. The ultrasound protocol, known as the TRIP, is proposed as severity assessment for ACP, which includes tricuspid regurgitation velocity (T), right ventricular size (R), inferior vena cava diameter fluctuation (I), and pulmonary regurgitation velocity (P). The 28-day mortality, ICU/hospital mortality, the length of stay in ICU, mechanical ventilation days, hemodynamic parameters and lab parameters of liver function and kidney function are all recorded.

DISCUSSION

This large-scale study would give a sufficient epidemic investigation of ACP in ARDS patients in China. In addition, with the TRIP protocol, we expect that we could stratify ACP with more echocardiography parameters.

TRIAL REGISTRATION

NCT03827863, https://clinicaltrials.gov/ct2/show/NCT03827863.

Respiratory parameters and acute kidney injury in acute respiratory distress syndrome: a causal inference study

Background

Assess the respiratory-related parameters associated with subsequent severe acute kidney injury in mechanically ventilated patients with acute respiratory distress syndrome (ARDS).

Methods

Retrospective cohort, analyzing a large public database-Multiparameter Intelligent Monitoring in Intensive Care-III. Adult patients with at least 48 h of mechanical ventilation (MV), under volume controlled ventilation and an oxygenation index less than 300 mmHg were included.

Results

A total of 1,142 patients had complete data and were included in the final analyses. According to a causal directed acyclic graph (DAG) that included respiratory system compliance (C_rs), tidal volume (Vt), driving pressure (ΔP), plateau pressure (P_Plat), PEEP, PaO₂ and PaCO₂ as possible exposures related to severe AKI, only C_rs and PEEP levels had significant causal association with severe acute kidney injury (AKI) (OR 0.90, 95% CI: 0.84-0.94 for each 5-mL/cmH₂O reduction in C_rs; OR, 1.05 95% CI: 1.03-1.10 for each 1-cmH₂O increase of PEEP). Using mediation analysis, we examined whether any mechanical ventilation, blood gas or hemodynamic parameters could explain the effects of C_sr on AKI. Only PEEP mediated the significant but small effect (less than 5%) of C_sr on severe AKI. The effects of PEEP, in turn, were not mediated by any other evaluated parameter. Several sensitivity analyses with (I) need of renal replacement therapy (RRT) as an alternative outcome and (II) only patients with Vt <8 mL/kg, confirmed our main findings. In trying to validate our DAG assumptions, we confirmed that only ΔP was associated with mortality but not with severe AKI.

Conclusions

C_rs and PEEP are the only respiratory-related variables with a direct causal association in severe AKI. No mechanical ventilator or blood gas parameter mediated the effects of C_rs. Approaches reducing Vt and/or ΔP in ARDS can have limited effect on renal protection.

A study on the protective effects of CpG oligodeoxynucleotide-induced mucosal immunity against lung injury in a mouse acute respiratory distress syndrome model

This study aims to determine the feasibility of using oligodeoxynucleotides with unmethylated cytosine-guanine dinucleotide sequences (CpG ODN) as an immunity protection strategy for a mouse model of acute respiratory distress syndrome (ARDS). This is a prospective laboratory animal investigation. Twenty-week-old BALB/c mice in Animal research laboratory were randomized into groups. An ARDS model was induced in mice using lipopolysaccharides (LPSs). CpG ODN was intranasally and transrectally immunized before or after the 3rd and 7th days of establishing the ARDS model. Mice were euthanized on Day 7 after the second immunization. Then, retroorbital bleeding was carried out and the chest was rapidly opened to collect the trachea and tissues from both lungs for testing. CpG ODN significantly improved the pathologic impairment in mice lung, especially after the intranasal administration of 50 μg. This resulted in the least severe lung tissue injury. Furthermore, interleukin-6 (IL-6) and IL-8 concentrations were lower, which was second to mice treated with the rectal administration of 20 µg CpG ODN. In contrast, the nasal and rectal administration of CpG ODN in BALB/c mice before LPS immunization did not appear to exhibit any significant protective effects. The intranasal administration of CpG ODN may be a potential treatment approach to ARDS. More studies are needed to further determine the protective mechanism of CpG ODN.

Carnosic acid protects against lipopolysaccharide-induced acute lung injury in mice

Acute respiratory distress syndrome is a well-known inflammatory disease associated with high rates of morbidity and mortality due to a lack of effective treatment methods. Carnosic acid (CA) is a phenolic diterpene compound that serves a central role in cytoprotective responses to inflammation. In the present study, the protective mechanism of CA on acute lung injury (ALI) induced by lipopolysaccharide (LPS) was investigated. Mice were randomly assigned to the following five groups: Control group, LPS group, and LPS plus CA groups (at 10, 20 and 40 mg/kg doses). Following pre-treatment with vehicle or CA, ALI was induced by the administration of LPS. At 6 h after LPS treatment, mice were sacrificed and lung tissues were harvested for histologic analysis and the determination of wet-to-dry ratio, myeloperoxidase activity and toll-like receptor 4 (TLR4) and NF-κB expression. Additionally, the levels of interleukin (IL)-1β, IL-6 and tumor necrosis factor-α (TNF-α) were determined in bronchoalveolar lavage fluid (BALF) and lung tissues, as well as the rate of apoptosis of the isolated neutrophils from BALF. The alleviation of LPS-induced ALI by CA was confirmed by histologic results and a reduction in the wet-to-dry ratio of lung tissues. Additionally, CA was revealed to significantly suppress the inhibitory effect of LPS on neutrophil apoptosis and the promoting effects of LPS on IL-1β, IL-6, TNF-α, TLR4 and NF-κB expression, and NF-κB phosphorylation. The current results indicated that CA protects against LPS-induced ALI via a mechanism that inhibits inflammation.

Interleukin 17 (IL-17) manipulates mouse bone marrow- derived neutrophils in response to acute lung inflammation

Interleukin 17 (IL-17) mediates neutrophil migration to the lungs during acute inflammation, potentially leading to lung tissue damage. In the present study, we evaluated whether IL-17 could facilitate certain neutrophil functions in a mouse model. Mice were divided into four groups and intranasally challenged with PBS (1 = Control), Influenza A (H1N1) and Klebsiella pneumoniae (2 = Mix), Influenza A alone (3 = Flu), or K. pneumoniae (4 = KP) alone. Bone marrow, BAL cells, and lung specimens were collected seven days post-challenge for analysis. Mice in the Flu group showed the highest mortality rate. Neutrophils were the prominent cell type in BAL from Mix and KP, whereas lymphocytes were most numerous in Flu. Lesions in the lungs revealed considerably damage in the Mix, Flu, and KP groups. Isolated bone marrow-derived neutrophils were in vitro primed with mouse recombinant IL-17A protein (rIL-17A) followed by various functional assays. The reactive oxygen species (ROS) levels in rIL-17A primed cells showed significant elevations in all groups. Phagocytosis and bacterial destruction showed no significant difference between (+) or (-) rIL-17A groups. The formation of neutrophil extracellular traps (NETs) in rIL-17A-primed neutrophils showed elevated NET production. We next monitored expressions of genes in neutrophils. IL-17A mRNA expression was significantly increased in Mix and Flu; IL-1β mRNA only significantly increased in Flu, and IL-17RA showed constitutive expressions in all groups. In summary, neutrophils may cause tissue damage during lung inflammation through specific functions influenced by IL-17.

Inhibition of myeloid differentiation factor 2 by baicalein protects against acute lung injury

BACKGROUND

ALI/ARDS is characterized by severe hypoxemic respiratory failure attributed to inflammatory tissue injury. There are no treatment modalities able to prevent/reverse the dire pathological sequelae in these patients. Evidence links the inflammatory lung injury to uncontrolled activation of the immune signaling complex, TLR4-MD2 (Toll-like receptor-myeloid differentiation factor 2). Baicalein, a natural flavonoid, is reported to have robust anti-inflammatory properties, but its inhibition mechanism remains unclear.

HYPOTHESIS/PURPOSE

This study investigated the protective mechanisms of baicalein on ALI/ARDS.

METHODS

We used two experimental mouse models of LPS-induced ALI, pulmonary infection model (intratracheal LPS), and systemic infection model (intravenous LPS). Blood, BALF, lung and liver tissues were analyzed using routine methods. In vitro studies using peritoneal mouse macrophages or recombinant proteins were designed to elucidate inhibition mechanisms of baicalein.

RESULTS

Our critical new findings revealed that Baicalein was an MD2 inhibitor, directly bound to MD2, effectively suppressing TLR4-MD2 activation and the subsequent MAPK and NF-κB signaling. The inhibited MD2 prevented development of inflammatory tissue injury and improved survival. The importance of MD2 in the inflammatory injury in ALI was corroborated by data obtained from MD2^-/- mice, which did not develop the characteristic LPS-induced lung tissue damage. Thus, the findings indicated that MD2 was critical for development of ALI, functioning as an early upstream signal driving the progression of inflammatory injury.

CONCLUSION

Baicalein, as a direct and selective MD2 inhibitor, inhibited the early upstream TLR4-MD2 signaling and is a promising therapeutic agent for the treatment of ALI/ARDS.

Enhanced Anti-inflammatory Activity of Peptide-Gold Nanoparticle Hybrids upon Cigarette Smoke Extract Modification through TLR Inhibition and Autophagy Induction

Overwhelming uncontrolled inflammation is the hallmark of pathophysiological features of many acute and chronic inflammatory diseases, such as sepsis and allergy and autoimmune disorders. It is important to develop potent pharmacological interventions to effectively control such detrimental inflammatory reactions in these diseases. Recently, we have developed a special class of peptide-gold nanoparticle hybrid system that can inhibit Toll-like receptor 4 (TLR4) signal transduction pathways and decrease its downstream inflammatory responses. Herein, we serendipitously discovered that a tiny amount of cigarette smoke extract (CSE, 1%) was able to significantly enhance the inhibitory activity of the hybrids on TLR4-mediated inflammatory responses. Mechanistically, it was found that active components in CSE were able to adsorb onto the hybrids and largely increased their cellular uptake in THP-1 cell-derived macrophages. Such high cellular uptake not only enhanced the inhibition on the endosomal acidification required for TLR4 activation but also contributed to autophagy induction and subsequent antioxidant protein expression. Consequently, this duel action strengthened the anti-inflammatory activity of the hybrids in cells and in an acute lung injury (ALI) mouse model. This work aids our fundamental understanding of nanoparticles regulating the innate immune responses. It also provides a new way to design potent anti-inflammatory nanotherapeutics for inflammatory diseases such as ALI.

Galloyl-Hexahydroxydiphenoyl (HHDP)-Glucose Isolated From Punica granatum L. Leaves Protects Against Lipopolysaccharide (LPS)-Induced Acute Lung Injury in BALB/c Mice

The hydroalcoholic extract and ethyl acetate fraction of Punica granatum leaves have been known to exhibit anti-inflammatory activities. In this study, we investigated the therapeutic effects of galloyl-hexahydroxydiphenoyl (HHDP)-glucose isolated from pomegranate leaves on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice. Male BALB/c mice were treated with different doses of galloyl-HHDP-glucose (5, 50, and 100 mg/Kg) or dexamethasone at 5 mg/Kg (per os) 6 h after intra-tracheal instillation of LPS. Vehicle-treated mice were used as controls. Twenty-four hours after LPS challenge, bronchoalveolar lavage fluid (BALF), and lung samples were collected for analyses. They were evaluated by monitoring the expression of NF-κB, JNK, and cytokine genes and proteins, as well as cell migration and lung function. All doses of galloyl-HHDP-glucose inhibited LPS-induced JNK and NF-κB activation. Likewise, the galloyl-HHDP-glucose-treated animals presented reduced expression of the TNF-α, IL-6, and IL-1β genes in the lungs and reduced TNF-α, IL-6, IL-1β, and IL-8 protein levels when compared with the vehicle-treated LPS-challenged mice. In addition, the ALI mice treated with galloyl-HHDP-glucose also presented reduced lung inflammatory cell accumulation, especially that of neutrophils, in their BALF and lungs. In addition, galloyl-HHDP-glucose treatment markedly ameliorated the LPS-induced pulmonary mechanism complications and attenuated weight loss. Overall, we showed for the first time that galloyl-HHDP-glucose protects against ALI, and may be useful for treating ALI and other inflammatory disorders.

LL-37 Exacerbates Local Inflammation in Sepsis-Induced Acute Lung Injury by Preventing Mitochondrial DNA (mtDNA) Degradation-Induced Autophagy

Background

Recent studies have proved that autophagy dysfunction in proinflammatory cells is involved in tissue damage and an excessive inflammatory response in sepsis. In the present study, we identified that the human antimicrobial peptide LL-37 facilitates resistance to DNase II-induced mitochondrial DNA (mtDNA) degradation and subsequent autophagy.

Material/Methods

We found higher serum levels of LL-37 in patients with severe sepsis compared to that in patients with mild sepsis. Neutrophils isolated from mice with sepsis after treatment with Cramp-mtDNA produced an excess of proinflammatory cytokines, including IL-1β, IL-6, IL-8, MMP-8, and TNF-α. Cramp-mtDNA in the lung samples from model animals with sepsis was detected by immunohistochemical staining.

Results

Exogenous delivery of Cramp-mtDNA complex significantly exacerbated lung inflammation but the antibody against Cramp-mtDNA attenuated the excessive inflammatory response in LPS-induced acute lung injury. The expression of proinflammatory cytokines in lungs was upregulated and downregulated after treatment with the complex and antibody, respectively. LC-3 expression in 16HBE cells increased after LPS induction, irrespective of stimulation with LL-37.

Conclusions

These data show that LL-37 treatment worsens local inflammation in sepsis-induced acute lung injury by preventing mtDNA degradation-induced autophagy.

Phage Therapy of Pneumonia Is Not Associated with an Overstimulation of the Inflammatory Response Compared to Antibiotic Treatment in Mice

Supported by years of clinical use in some countries and more recently by literature on experimental models, as well as its compassionate use in Europe and in the United States, bacteriophage (phage) therapy is providing a solution for difficult-to-treat bacterial infections. However, studies of the impact of such treatments on the host remain scarce. Murine acute pneumonia initiated by intranasal instillation of two pathogenic strains of Escherichia coli (536 and LM33) was treated by two specific bacteriophages (536_P1 and LM33_P1; intranasal) or antibiotics (ceftriaxone, cefoxitin, or imipenem-cilastatin; intraperitoneal). Healthy mice also received phages alone. The severity of pulmonary edema, acute inflammatory cytokine concentration (blood and lung homogenates), complete blood counts, and bacterial and bacteriophage counts were determined at early (≤12 h) and late (≥20 h) time points. The efficacy of bacteriophage to decrease bacterial load was faster than with antibiotics, but the two displayed similar endpoints. Bacteriophage treatment was not associated with overinflammation but in contrast tended to lower inflammation and provided a faster correction of blood cell count abnormalities than did antibiotics. In the absence of bacterial infection, bacteriophage 536_P1 promoted a weak increase in the production of antiviral cytokines (gamma interferon [IFN-γ] and interleukin-12 [IL-12]) and chemokines in the lungs but not in the blood. However, such variations were no longer observed when bacteriophage 536_P1 was administered to treat infected animals. The rapid lysis of bacteria by bacteriophages in vivo does not increase the innate inflammatory response compared to that with antibiotic treatment.

Staphylococcal phosphatidylinositol-specific phospholipase C potentiates lung injury via complement sensitisation

Staphylococcus aureus is frequently isolated from patients with community-acquired pneumonia and acute respiratory distress syndrome (ARDS). ARDS is associated with staphylococcal phosphatidylinositol-specific phospholipase C (PI-PLC); however, the role of PI-PLC in the pathogenesis and progression of ARDS remains unknown. Here, we showed that recombinant staphylococcal PI-PLC possesses enzyme activity that causes shedding of glycosylphosphatidylinositol-anchored CD55 and CD59 from human umbilical vein endothelial cell surfaces and triggers cell lysis via complement activity. Intranasal infection with PI-PLC-positive S. aureus resulted in greater neutrophil infiltration and increased pulmonary oedema compared with a plc-isogenic mutant. Although indistinguishable proinflammatory genes were induced, the wild-type strain activated higher levels of C5a in lung tissue accompanied by elevated albumin instillation and increased lactate dehydrogenase release in bronchoalveolar lavage fluid compared with the plc^- mutant. Following treatment with cobra venom factor to deplete complement, the wild-type strain with PI-PLC showed a reduced ability to trigger pulmonary permeability and tissue damage. PI-PLC-positive S. aureus induced the formation of membrane attack complex, mainly on type II pneumocytes, and reduced the level of CD55/CD59, indicating the importance of complement regulation in pulmonary injury. In conclusion, S. aureus PI-PLC sensitised tissue to complement activation leading to more severe tissue damage, increased pulmonary oedema, and ARDS progression.

Peripheral Circulating Exosome-Mediated Delivery of miR-155 as a Novel Mechanism for Acute Lung Inflammation

Emerging evidence has revealed that excessive activation of macrophages may result in an adverse lung inflammation involved in sepsis-related acute lung injury (ALI). However, it has never been clearly identified whether peripheral circulating serum exosomes participate in the pathogenesis of sepsis-related ALI. Therefore, the purposes of our study were to investigate the effect of serum exosomes on macrophage activation and elucidate a novel mechanism underlying sepsis-related ALI. Here we found that exosomes were abundant in the peripheral blood from ALI mice and selectively loaded microRNAs (miRNAs), such as miR-155. In vivo experiments revealed that intravenous injection of serum exosomes harvested from ALI mice, but not control mice, increased the number of M1 macrophages in the lung, and it caused lung inflammation in naive mice. In vitro, we demonstrated that serum exosomes from ALI mice delivered miR-155 to macrophages, stimulated nuclear factor κB (NF-κB) activation, and induced the production of tumor necrosis factor alpha (TNF-α) and interleukin (IL)-6. Furthermore, we also showed that serum exosome-derived miR-155 promoted macrophage proliferation and inflammation by targeting SHIP1 and SOCS1, respectively. Collectively, our data suggest the important role of circulating exosomes secreted into peripheral blood as a key mediator of septic lung injury via exosome-shuttling miR-155.