Mouse Lung Research Articles

Alcohol Activates Cannabinoid Receptor 1 and 2 in a Model of Pathogen Induced Pulmonary Inflammation

Alcohol use disorder (AUD) is defined as patterns of alcohol misuse and affects over 30 million people in the US. AUD is a systemic disease with the epidemiology of acute lung injury and excessive alcohol use established in the literature. However, the distinct mechanisms by which alcohol induces the risk of pulmonary inflammation are less clear. A compelling body of evidence shows that cannabinoid receptors (CB1R and CB2R) play a relevant role in AUD. For this study, we investigated the role of CBR signaling in pulmonary immune activation. Using a human macrophage cell line, we evaluated the expression of CBR1 and CBR2 after cells were exposed to EtOH, +/- cannabinoid agonists and antagonists by flow cytometry. We also evaluated the expression of cannabinoid receptors from the lungs of adolescent mice exposed to acute binge EtOH +/- cannabinoid agonists and antagonists at both resting state and after microbial challenge via western blot, rt-PCR, cytokine analysis, and histology. Our results suggest that EtOH exposure modulates the expression of CBR1 and CBR2. Second, EtOH may contribute to the release of DAMPs and other proinflammatory cytokines, Finally, microbial challenge induces pulmonary inflammation in acute binge EtOH-exposed mice, and this observed immune activation may be CBR-dependent. We have shown that adolescent binge drinking primes the lung to subsequent microbial infection in adulthood and this response can be mitigated with cannabinoid antagonists. These novel findings may provide a framework for developing potential novel therapeutics in AUD research.

Silibinin Induces Both Apoptosis and Necroptosis with Potential Anti-tumor Efficacy in Lung Cancer.

Lung cancer incidence is steadily on the rise, posing a growing threat to human health. The search for therapeutic drugs from natural active substance and elucidating their mechanism have been the focus of anti-tumor research. In our work, Silibinin (SiL) was chosen as a possible substance that could inhibit lung cancer. and its effects on inducing tumor cell death have been studied. CCK-8 analysis and morphological observation were used to assess the cytotoxic impacts of SiL on lung cancer cells in vitro. The alterations in mitochondrial membrane potential (MMP) and apoptosis rate of cells were detected by flow cytometry. The level of lactate dehydrogenase (LDH) release out of cells was measured. The expression changes of apoptosis or necroptosis-related proteins were detected using western blotting. Protein interactions among RIPK1, RIPK3 and MLKL were analyzed using the co-immunoprecipitation technique. In vivo, SiL was evaluated for its antitumor effects using LLC tumor-bearing mice with mouse lung cancer. With an increased dose of SiL, the proliferation ability of A549 cells was considerably inhibited, and the accompanying cell morphology changed. The results of flow cytometry showed that after SiL treatment, MMP levels decreased, and the proportion of cells undergoing apoptosis increased. The proteins associated with apoptosis were upregulated and activated. The amount of LDH released from the cells increased following SiL treatment, accompanied by augmented expression and phosphorylation levels of necroptosis-related proteins. The co-IP assay further confirmed necrosome formation induced by SiL. Furthermore, Necrosulfonamide (an MLKL inhibitor) increased the apoptotic rate of SiL-treated cells and aggravated the cytotoxic effect of SiL, indicating that necroptosis blockade could switch cell death to apoptosis and increase the inhibitory effect of SiL on A549 cells. In LLC-bearing mice, gastric administration of SiL significantly inhibited tumor growth. This study helped clarify the anti-tumor mechanism of SiL against lung cancer, elucidating its role in dual induction of apoptosis and necroptosis. In particular, necroptosis blockade could switch cell death to apoptosis and increase the inhibitory effect of SiL. Our work provided an experimental basis for the research on cell death induced by SiL and revealed its possible applications for improving the management of lung cancer.</p>.

PEDF upregulated in Ngfr-positive cells suppresses proliferation of pulmonary artery smooth muscle cells

Abstract Background Pulmonary arterial hypertension (PAH) is a disease with poor prognosis that causes right heart failure due to progressive pulmonary artery remodeling. Although existing pulmonary vasodilators contribute to pulmonary artery reverse remodeling by reducing share stress, the development of therapeutic agents that directly target pulmonary vascular remodeling is desired. Nerve growth factor receptor (Ngfr) is involved in the inflammatory reaction and repair process of damaged tissues. We have previously reported that Ngfr-positive cells are increased in the peripheral blood (PB) of PAH patients and are associated with disease progression. We also found that Ngfr inhibited the pathogenetic progression of pulmonary hypertension in a model of hypoxia-induced pulmonary hypertension. However, it remains unclear how Ngfr positive cells are involved in the pathology of PAH. Purpose In this study, we investigate how Ngfr-positive cells affect the pathogenesis of PAH. Methods &amp; Results To evaluate the localization of Ngfr-positive cells in lung tissue, WT mice (C57BL/6) transplanted with bone marrow (BM) of GFP-Tg mice were kept under hypoxia for 3 weeks to create hypoxia-induced pulmonary hypertension (PH) model. Immunostaining of lung tissue sections indicated that double positive cells (Ngfr+GFP+) were present in the interstitial tissue around the small pulmonary artery. To examine the cellular characteristics of Ngfr-positive cells, RNA sequencing of Ngfr-positive and Ngfr-negative cells in PB was performed. Significantly 78 genes were upregulated in Ngfr-positive cells, including 11 secreted proteins. Among these, we focused on pigment epithelium-derived factor (PEDF), a secreted protein involved in angiogenesis. PEDF mRNA expression was decreased in the lung of Ngfr-KO mice compared to WT mice. We next examined the effect of PEDF on pulmonary artery smooth muscle cells (PASMCs). Platelet-derived growth factor (PDGF)-induced cell proliferation of PASMC was inhibited by PEDF stimulation. Furthermore, PEDF stimulation significantly inhibited PDGF-induced mRNA expressions of TNF and MMP9 in PASMCs. Conclusion In this study, we show that PEDF expression is upregulated in Ngfr-positive cells and that PEDF inhibits PDGF-induced hPASMC proliferation, suggesting that NGFR-positive cells may suppress pulmonary vascular remodeling through PEDF-mediated paracrine effects. PEDF might be a new therapeutic target for PH.

S-RBD-modified and miR-486-5p-engineered exosomes derived from mesenchymal stem cells suppress ferroptosis and alleviate radiation-induced lung injury and long-term pulmonary fibrosis

BackgroundRadiation-induced lung injury (RILI) is associated with alveolar epithelial cell death and secondary fibrosis in injured lung. Mesenchymal stem cell (MSC)-derived exosomes have regenerative effect against lung injury and the potential to intervene of RILI. However, their intervention efficacy is limited because they lack lung targeting characters and do not carry sufficient specific effectors. SARS-CoV-2 spike glycoprotein (SARS-CoV-2-S-RBD) binds angiotensin-converting enzyme 2 (ACE2) receptor and mediates interaction with host cells. MiR-486-5p is a multifunctional miRNA with angiogenic and antifibrotic potential and acts as an effector in MSC-derived exosomes. Ferroptosis is a form of cell death associated with radiation injury, its roles and mechanisms in RILI remain unclear. In this study, we developed an engineered MSC-derived exosomes with SARS-CoV-2-S-RBD- and miR-486-5p- modification and investigated their intervention effects on RIPF and action mechanisms via suppression of epithelial cell ferroptosis.ResultsAdenovirus-mediated gene modification led to miR-486-5p overexpression in human umbilical cord MSC exosomes (p < 0.05), thereby constructing miR-486-5p engineered MSC exosomes (miR-486-MSC-Exo). MiR-486-MSC-Exo promoted the proliferation and migration of irradiated mouse lung epithelial (MLE-12) cells in vitro and inhibited RILI in vivo (all p < 0.05). MiR-486-MSC-Exo suppressed ferroptosis in MLE-12 cells, and an in vitro assay revealed that the expression of fibrosis-related genes is up-regulated following ferroptosis (both p < 0.05). MiR-486-MSC-Exo reversed the up-regulated expression of fibrosis-related genes induced by TGF-β1 in vitro and improved pathological fibrosis in RIPF mice in vivo (all p < 0.05). SARS-CoV-2-S-RBD-modified and miR-486-5p-engineered MSC exosomes (miR-486-RBD-MSC-Exo) were also constructed, and the distribution of DiR dye-labeled miR-486-RBD-MSC-Exo in hACE2CKI/CKI Sftpc-Cre+ mice demonstrated long-term retention in the lung (p < 0.05). MiR-486-RBD-MSC-Exo significantly improved the survival rate and pathological changes in hACE2CKI/CKI Sftpc-Cre+ RIPF mice (all p < 0.05). Furthermore, miR-486-MSC-Exo exerted anti-fibrotic effects via targeted SMAD2 inhibition and Akt phosphorylation activation (p < 0.05).ConclusionsEngineered MSC exosomes with SARS-CoV-2-S-RBD- and miR-486-5p-modification were developed. MiR-486-RBD-MSC-Exo suppressed ferroptosis and fibrosis of MLE-12 cells in vitro, and alleviated RILI and long-term RIPF in ACE2 humanized mice in vivo. MiR-486-MSC-Exo exerted anti-fibrotic effects via SMAD2 inhibition and Akt activation. This study provides a potential approach for RIPF intervention.Graphical

Polyhexamethylene Guanidine Phosphate Induces Restrictive Ventilation Defect and Alters Lung Resistance and Compliance in Mice

Polyhexamethylene guanidine phosphate (PHMG-p), a major ingredient of humidifier disinfectants, is known to induce inflammation, interstitial pneumonitis, and fibrosis in the lungs. While its histopathologic toxicities have been studied in rodents, research on pulmonary function test (PFT) changes following PHMG-p exposure is limited. This study aimed to investigate the acute and chronic effects, as well as the dose and time response, of PHMG-p on the lungs in mice using PFT and histopathologic examinations. In the single instillation model, mice received PHMG-p and were sacrificed at 2, 4, and 8 weeks. In the five-time instillation model, PHMG-p was administered five times at one-week intervals, and mice were sacrificed 10 weeks after the first instillation. Results showed that PHMG-p exposure reduced lung volume, increased resistance, and decreased compliance, indicating a restrictive ventilation defect. Histopathologic examination showed increases in lung inflammation and fibrosis scores. Changes in several lung volume and compliance parameters, as well as histopathology, were dose-dependent. Lung resistance and compliance parameters had significant correlations with lung inflammation and fibrosis scores. PHMG-p exposure in mice resulted in a restrictive ventilation defect with altered lung resistance and compliance, along with histopathologic lung inflammation and fibrosis.

The protective effect and immunomodulatory ability of orally administrated Lacticaseibacillus rhamnosus GG against Mycoplasma pneumoniae infection in BALB/c mice.

Mycoplasma pneumoniae represents one of the significant etiologies of community-acquired pneumonia in pediatric patients. However, clinical treatment of M. pneumoniae infection in children has encountered challenges due to the escalating resistance to quinolones. Numerous studies have highlighted the potential of probiotic lactobacillus administration in boosting immune responses to bacterial and viral respiratory infections. In this study, the protective efficacy of pre-oral administration of Lacticaseibacillus rhamnosus GG (LGG), Limosilactobacillus reuteri F275, Lactiplantibacillus plantarum NCIMB 8826, L. plantarum S1 or L. plantarum S2 was evaluated in the BALB/c mice model; it was observed that among these five strains of lactobacillus, the supplementation of LGG exhibited the most significant protective effect against M. pneumoniae infection. Moreover, when administered orally, both live LGG and heat-inactivated LGG have demonstrated efficacy in reducing the burden of M. pneumoniae in the lungs and alleviating pulmonary inflammation. Oral supplementation with LGG resulted in the inhibition of neutrophil recruitment into the lungs and increased recruitment of alveolar macrophages in M. pneumoniae-infected mice. Additionally, LGG supplementation led to increased production of IL-10 and secretory IgA (sIgA), while suppressing the levels of IL-1β, IL-6, IL-17A, and TNF-α in the lungs of mice infected with M. pneumoniae. The data suggests that supplementation with LGG can modulate immune responses, decrease pathogen load, and alleviate inflammatory injury in the lungs of M. pneumoniae-infected mice.

Parishin Alleviates Pulmonary Fibrosis by Reducing CD38 Levels in Naturally Aging Mice.

Parishin, a natural compound, has demonstrated significant potential in mitigating age-related phenotypes and improving outcomes in age-associated diseases. Given that aging is a major risk factor for numerous chronic conditions, including pulmonary fibrosis, we investigated parishin's effects on cellular senescence and lung health. In our study, we treated mouse lung epithelial cells with parishin and observed a reduction in cellular senescence markers alongside an upregulation of sirtuin 1 (SIRT1). Building on these in vitro findings, we administered parishin to naturally aged mice. The treatment resulted in decreased pulmonary fibrosis and reduced DNA damage in lung tissue. Notably, we found that parishin treatment led to a reduction in Cluster of differentiation 38 (CD38) levels, concomitant with an increase in SIRT1 expression. These findings indicate that parishin may enhance lung function in aged mice, suggesting its potential as a therapeutic agent for treating age-related pulmonary disorders.

L-arginine, aminoguanidine and mesenchymal stem cells reduce the level of endoplasmic reticulum stress markers and D-dimer in the lungs of mice with antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by damage to the intima of the microcirculatory blood vessels as a result of the formation of autoimmune antibodies to phospholipids of cell membranes. Recent data indicate a possible link between the occurrence of autoimmune diseases and endoplasmic reticulum stress, impaired nitric oxide availability, high plasma D-dimer level. The aim of the study was to estimate the effect of nitric oxide synthesis modulators L-arginine and aminoguanidine, and mesenchymal stem cells on the level of inositol-requiring enzyme-1a (IRE-1a), glucose-regulated protein 78 (GRP-78) as ER stress markers, and the level of D-dimer in the lung tissue of female BALB/c line mice with experimental APS induced with cardiolipin administration. 30 experimental animals were divided into five groups: 1 – control animals; 2 – mice with APS; 3 – mice with APS, injected intraperitoneally with L-arginine hydrochloride (25 mg/kg) and aminoguanidine (10 mg/kg); 4 – mice with APS, injected intraperitoneally with stem cells (5×106/kg); 5 – mice with APS, injected with L-arginine hydrochloride, aminoguanidine and stem cells in combination. After 10 days post APS formation animals were removed from the experiment, proteins were extracted from the lung tissue and their level was determined with Western blotting. It was established that in group with APS the levels of IRE-1, GRP-78 and D-dimer were substantially increased as compared to the control group. After separate administration of both arginine with aminoguanidine and MSC, as well as with their combined use, the level of IRE-1, GRP-78 and D-dimer decreased compared to the indices in animals with induced APS. The obtained data indicated that this effect is probably due to the reduction of ER stress through iNOS inhibition and the anti-inflammatory action of MSCs. Keywords: aminoguanidine, antiphospholipid syndrome, D-dimer, endoplasmic reticulume stress, GRP-78, IRE-1, L-arginine, lung, mesenchymal stem cells

Preliminary proteomic analysis of mouse lung tissue treated with cyclophosphamide and Venetin-1

Cyclophosphamide (CPAm) is a widely used chemotherapeutic agent that exhibits potent anti-cancer properties but is often associated with debilitating side effects. Despite its efficacy, the management of CPAm-induced toxicities remains a significant clinical challenge. There has been growing interest in exploring complementary and alternative therapies to mitigate these adverse effects in recent years, and this may be a chance for the earthworm-derived preparation, Venetin-1. Its rich composition of bioactive compounds has demonstrated promising pharmacological properties, including anti-inflammatory, antioxidant, and immunomodulatory effects. These properties suggest its potential to counteract various systemic toxicities induced by CPAm. We conducted a comprehensive study to investigate the effect of Venetin-1 on cyclophosphamide-induced toxicity. Mice were administered CPAm for four days, followed by application of the earthworm preparation in two doses (50 mg/kg and 100 mg/kg b.w). Importantly, the preparation did not cause any side effects in all mice, ensuring the safety of the intervention. We then determined global changes in the proteome using proteomics and quantitative SWATH-MS analysis, which is a robust and reliable method. This allowed us to identify up- and downregulated proteins in each studied group, providing valuable insights into the mechanism of action of Venetin-1. As shown by the results, Venetin-1 had a significant effect on the proteome of mouse lung tissue. It was possible to determine quantitative changes in 400 proteins, and the analysis after administration of Venetin-1 showed a change in the global proteomic profile from upregulated to down-regulated. The stimulating properties of the preparation concerning the complement system were also confirmed in a separate validation experiment. Venetin-1 shows promise in reducing the harmful effects of cyclophosphamide on lung tissue. It encourages tissue regeneration, reduces inflammation, supports autophagy, and boosts the immune system. However, more research is needed to thoroughly elucidate and describe the benefits of Venetin-1.

Increased expression of Cathepsin C in airway epithelia exacerbates airway remodeling in asthma.

Airway remodeling is a critical factor determining the pathogenesis and treatment sensitivity of severe asthma (SA) or uncontrolled asthma (UA). The activation of epithelial-mesenchymal trophic units (EMTUs) regulated by airway epithelial cells (AECs) has been proven to induce airway remodeling directly. However, the triggers for EMTU activation and the underlying mechanism of airway remodeling are not fully elucidated. Here, we screened the differentially expressed gene Cathepsin C (CTSC)/dipeptidyl peptidase 1 (DPP-1) in epithelia of SA and UA patients using RNA sequencing data and further verified the increased expression of CTSC in induced sputum of asthma patients which was positively correlated with the severity and airway remodeling. Moreover, direct instillation of exogenous CTSC induced airway remodeling. Genetic inhibition of CTSC suppressed EMTU activation and airway remodeling in two asthma models with airway remodeling. Mechanistically, increased secretion of CTSC from AECs induced EMTU activation through p38-mediated pathway, further inducing airway remodeling. Meanwhile, inhibition of CTSC also reduced the infiltration of inflammatory cells and the production of inflammatory factors in the lungs of asthmatic mice. Consequently, targeting CTSC with compound AZD7986 protected against airway inflammation, EMTU activation and remodeling in asthma model. Based on the dual effects of CTSC on airway inflammation and remodeling, CTSC is a potential biomarker and therapeutic target for SA or UA.

RT-qPCR Analysis of Inflammatory & Apoptotic Factors-Related Gene Expression in ZIKV-Infected IFNAR1-/- Mice.

ZIKV was a mosquito-borne neglected tropical pathogen until it spread into the Pacific and South America, followed by large human outbreaks related to congenital abnormalities in neonates and neurological disorders in adults. The following study used the C57BL/6 IFNAR1 receptor knockout (IFN AR1-/-) mouse model to understand the role of selected cytokines and apoptotic factors in the pathogenicity of ZIKV strain PRVABC59. Mice infected with 102 particles of Zika viruses died until 9days post infection. The brain, spleen, and lung were collected from intramuscularly infected mice on day 6 post infection (pi) to quantify the mRNA expression of targeted cytokines and apoptosis-mediated factors by RT-qPCR. Upregulation of IL-6, IL-17α, IFN-α, and IFN-β were found in the brain and lung of infected mice. IFN-γ was also significantly upregulated in the infected brain and spleen. The collective findings from our study indicate that a strong immune response was developed against ZIKV PRVABC59 in the infected mice brain.

α4 Nicotinic Acetylcholine Receptors in Lipopolysaccharide-Related Lung Inflammation

Sepsis remains an important healthcare challenge. The lungs are often affected in sepsis, resulting in acute lung injury characterized by inflammation. Mechanisms involving lipopolysaccharide (LPS) stimulation of toll-like receptor (TLR) signaling with induction of proinflammatory pathways have been implicated in this process. To date, however, studies targeting these pathways have failed to improve outcomes. We have found that LPS may also promote lung injury through the activation of α4 nicotinic acetylcholine receptors (α4 nAChRs) in immune cells. We observed increased expression of α4 nAChRs in human THP-1 monocytic cells exposed to LPS (100 ng/mL, 24 h). We also observed that LPS stimulated the expression of other relevant genes, including tumor necrosis factor-α, interleukin-1β, plasminogen activator inhibitor-1, the solute carrier family 7 member 11, extracellular superoxide dismutase, and transforming growth factor-β1. Of interest, dihydro-β-erythroidine hydrobromide (DHβE), a specific chemical inhibitor of α4 nAChRs, inhibited the LPS-induced expression of these genes. We generated mice with a global knockout mutation of the α4 nAChR subunit in the C57BL/6 background using CRISPR/Cas9 technology. The lungs of these LPS-treated animals demonstrated a reduction in the expression of the above-mentioned genes when compared with the lungs of wild-type animals. In support of the role of oxidative stress, we observed that LPS induced expression of the cystine transporter Slc7a11 in both THP-1 cells and in wild-type mouse lungs. The effects of LPS on THP-1 cells were blocked by the thiol antioxidant N-acetylcysteine and mimicked by redox stress. Importantly, the induction of IL-1β by redox stress was inhibited by the α4 nAChR inhibitor DHβE. Finally, we showed that LPS stimulated calcium influx in THP-1 cells, which was blocked by the α4 nAChR inhibitor. Our observations suggest that LPS promotes lung injury by stimulating redox stress, which activates α4 nAChR signaling and drives proinflammatory cytokine expression.

Cold ischemia time alters cell-type specific senescence leading to loss of cellular integrity in mouse lungs

Purpose: Ischemia-reperfusion injury (IRI) is a major challenge in lung transplantation often causing graft dysfunction and chronic airway illnesses in recipients. To prevent potential transplant related complications, strict guidelines were put in place to choose viable donor lungs with minimal risk of IRI. These regulations deem most of the donor organs unfit for transplant which then are donated for research to understand the mechanisms of health and diseases in human. However, resected organs that are being transported undergo cold ischemia that can negatively affect the tissue architecture and other cellular functions under study. Thus, it is important to assess how cold ischemia time (CIT) affects the physiological mechanism. In this respect, we are interested in studying how CIT affects cellular senescence in normal aging and various pulmonary pathologies. We thus hypothesized that prolonged CIT exhibits cell-type specific changes in lung cellular senescence in mice. Methods: Lung lobes from C57BL/6J (n = 5–8) mice were harvested and stored in UW Belzer cold storage solution for 0, 4-, 9-, 12-, 24-, and 48-h CIT. Lung cellular senescence was determined using fluorescence (C12FdG) assay and co-immunolabelling was performed to identify changes in individual cell types. Results: We found a rapid decline in the overall lung cellular senescence after 4-h of CIT in our study. Co-immunolabelling revealed the endothelial cells to be most affected by cold ischemia, demonstrating significant decrease in the endothelial cell senescence immediately after harvest. Annexin V-PI staining further revealed a prominent increase in the number of necrotic cells at 4-h CIT, thus suggesting that most of the cells undergo cell death within a few hours of cold ischemic injury. Conclusions: We thus concluded that CIT significantly lowers the cellular senescence in lung tissues and must be considered as a confounding factor for mechanistic studies in the future.

Impact of Curcumin on the IL-17A-Mediated p53-Fibrinolytic System: Mouse Proteomics and Integrated Human Fibrosis scRNAseq Insights.

Acute lung injury (ALI) is primarily driven by an intense inflammation in the alveolar epithelium. Key to this is the pro-inflammatory cytokine, Interleukin 17 (IL-17), which influences pulmonary immunity and modifies p53 function. The direct role of IL-17A in p53-fibrinolytic system is still unclear, it is important to evaluate this mechanism to regulate the ALI progression to idiopathic pulmonary fibrosis (IPF). C57BL/6 mice, exposed to recombinant IL-17A protein and treated with curcumin, provided insight into IL-17A mechanisms and curcumin's potential for modulating early pulmonary fibrosis stages. A diverse methodology, including proteomics, single-cell RNA sequencing (scRNA-seq) integration, molecular, and Schroedinger approach were utilized. In silico approaches facilitated the potential interactions between curcumin, IL-17A, and apoptosis-related proteins. A notable surge in the expression levels of IL-17A, p53, and fibrinolytic components such as Plasminogen Activator Inhibitor-1 (PAI-I) was discerned upon the IL17A exposure in mouse lungs. Furthermore, the enrichment of pathways and differential expression of proteins underscored the significance of IL-17A in governing downstream regulatory pathways such as inflammation, NF-kappaB signaling, Mitogen-Activated Protein Kinases (MAPK), p53, oxidative phosphorylation, JAK-STAT, and apoptosis. The integration of scRNA-seq data from 20 IPF and 10 control lung specimens emphasized the importance of IL-17A mediated downstream regulation in PF patients. A potent immuno-pharmacotherapeutic agent, curcumin, demonstrated a substantial capacity to modulate the lung pathology and molecular changes induced by IL-17A in mouse lungs. Human IPF single cell data integration confirmed the effects of IL-17A mediated fibrinolytic components in ALI to IPF progression.

Monocyte-regulated interleukin 12 production drives clearance of Staphylococcus aureus.

Staphylococcus aureus is a versatile bacterium responsible for conditions ranging from mild skin and soft-tissue infections to serious disorders such as pneumonia and sepsis. Monocytes play a role in protection against pathogens by migrating to inflamed tissues and differentiating into macrophages but their specific role in the context of S. aureus pulmonary infection has not been fully elucidated. Using a CCR2-DTR transgenic mouse model we demonstrate that over the course of infection monocyte depletion resulted in worse airway clearance of S. aureus. The bronchoalveolar lavage fluid (BALF) of CCR2-DTR mice after S. aureus infection displayed significant decreases in interleukin-12 (IL-12), IFN-γ, IP-10, MIG and RANTES, all IFN-γ regulated, compared to wild-type (WT) infected controls. NK cells were identified as the main producers of IFN-γ, but both NK cells and IFN-γ were dispensable for clearance. We demonstrated through cytokine production and RNA-seq analysis that IL-12 and IL-12 regulated genes are strongly induced in monocytes upon S. aureus infection. Administration of IL-12 during infection restored the bacterial burdens in the BALF and lungs of monocyte-depleted CCR2-DTR mice to the levels of WT mice, independent of IFN-γ. In the absence of monocytes, alveolar macrophages are the primary phagocytic cells, and IL-12 influences their capacity to produce reactive oxygen species and clear S. aureus. These results show that production of IL-12 contributes to the control of S. aureus via its influence on alveolar macrophage function.

Update on the immunological mechanisms of primary graft dysfunction and chronic lung allograft dysfunction.

Primary graft dysfunction (PGD) and chronic lung allograft dysfunction (CLAD) are the leading causes of graft loss in lung transplant recipients. The development of mouse lung transplant models has allowed for the genetic dissection of cellular and molecular pathways that prevent graft survival. This review provides an overview into recent mechanistic insights into PGD and CLAD. Mouse orthotopic lung transplant models and investigations of human lung transplant recipeints have revealed new molecular and cellular targets that promote PGD and CLAD. Donor and recipient-derived innate immune cells promote PGD and CLAD. PGD is driven by communication between classical monocytes and tissue-resident nonclassical monocytes activating alveolar macrophages to release chemokines that recruit neutrophils. Products of cell damage trigger neutrophil NET release, which together with NK cells, antibodies and complement, that further promote PGD. The development of CLAD involves circuits that activate B cells, CD8+ T cells, classical monocytes, and eosinophils. Effective targeted management of PGD and CLAD in lung transplant recipient to improve their long-term outcome remains a critical unmet need. Current mechanistic studies and therapeutic studies in mouse models and humans identify new possibilities for prevention and treatment.

Intestinal microbiome dysbiosis increases Mycobacteria pulmonary colonization in mice by regulating the Nos2-associated pathways

Increasing researches reveal gut microbiota was associated with the development of tuberculosis (TB). How to prevent or reduce Mycobacterium tuberculosis colonization in the lungs is a key measure to prevent TB. However, the data on gut microbiota preventing Mycobacterium colonization in the lungs were scarce. Here, we established the clindamycin-inducing intestinal microbiome dysbiosis and fecal microbial transplantation models in mice to identify gut microbiota’s effect on Mycobacterium’s colonization in the mouse lungs and explore its potential mechanisms. The results showed that clindamycin treatment altered the diversity and composition of the intestinal bacterial and fungal microbiome, weakened the trans-kingdom network interactions between bacteria and fungi, and induced gut microbiome dysbiosis in the mice. Gut microbiota dysbiosis increases intestinal permeability and enhances the susceptibility of Mycobacterium colonization in the lungs of mice. The potential mechanisms were gut microbiota dysbiosis altered the lung transcriptome and increased Nos2 expression through the ‘gut–lung axis’. Nos2 high expression disrupts the intracellular antimicrobial and anti-inflammatory environment by increasing the concentration of nitric oxide, decreasing the levels of reactive oxygen species and Defb1 in the cells, and promoting Mycobacteria colonization in the lungs of mice. The present study raises a potential strategy for reducing the risks of Mycobacteria infections and transmission by regulating the gut microbiome balance.

Lung and liver editing by lipid nanoparticle delivery of a stable CRISPR-Cas9 ribonucleoprotein.

Lipid nanoparticle (LNP) delivery of clustered regularly interspaced short palindromic repeat (CRISPR) ribonucleoproteins (RNPs) could enable high-efficiency, low-toxicity and scalable in vivo genome editing if efficacious RNP-LNP complexes can be reliably produced. Here we engineer a thermostable Cas9 from Geobacillus stearothermophilus (GeoCas9) to generate iGeoCas9 variants capable of >100× more genome editing of cells and organs compared with the native GeoCas9 enzyme. Furthermore, iGeoCas9 RNP-LNP complexes edit a variety of cell types and induce homology-directed repair in cells receiving codelivered single-stranded DNA templates. Using tissue-selective LNP formulations, we observe genome-editing levels of 16‒37% in the liver and lungs of reporter mice that receive single intravenous injections of iGeoCas9 RNP-LNPs. In addition, iGeoCas9 RNPs complexed to biodegradable LNPs edit the disease-causing SFTPC gene in lung tissue with 19% average efficiency, representing a major improvement over genome-editing levels observed previously using viral or nonviral delivery strategies. These results show that thermostable Cas9 RNP-LNP complexes can expand the therapeutic potential of genome editing.

Endothelial ENaC-α Restrains Oxidative Stress in Lung Capillaries in Murine Pneumococcal Pneumonia-associated Acute Lung Injury.

Infection of lung endothelial cells with pneumococci activates the superoxide-generating enzyme NADPH oxidase 2 (NOX2), involving the pneumococcal virulence factor pneumolysin (PLY). Excessive NOX2 activity disturbs capillary barriers, but its global inhibition can impair bactericidal phagocyte activity during pneumococcal pneumonia. Depletion of the α subunit of the epithelial sodium channel (ENaC) in pulmonary endothelial cells increases expression and PMA-induced activity of NOX2. Direct ENaC activation by TIP peptide improves capillary barrier function -measured by electrical cell substrate impedance sensing in endothelial monolayers and by Evans Blue Dye incorporation in mouse lungs- following infection with pneumococci. PLY-induced hyperpermeability in HL-MVEC monolayers is abrogated by both NOX2 inhibitor gp91dstat and TIP peptide. Endothelial NOX2 expression is assessed by increased surface membrane presence of phosphorylated p47phox subunit (Western blotting) in vitro and by co-localization of CD31 and gp91phox in mouse lung slices using DuoLink, whereas NOX2-generated superoxide is measured by chemiluminescence. TIP peptide blunts PMA-induced NOX2 activity in cells expressing ENaC-α, but not in neutrophils, which lack ENaC. Conditional endothelial ENaC-α KO (enENaC-α KO) mice develop increased capillary leak upon i.t. instillation with PLY or pneumococci, compared to wild type (wt) animals. TIP peptide diminishes capillary leak in Sp-infected wt mice, without significantly increasing lung bacterial load. Lung slices from Sp-infected enENaC-α KO mice have a significantly increased endothelial NOX2 expression, as compared to infected CRE mice. In conclusion, endothelial ENaC may represent a novel therapeutic target to reduce NOX2-mediated oxidative stress and capillary leak in ARDS, without impairing host defense.

The metalloproteinase ADAM10 sheds angiotensin-converting enzyme (ACE) from the pulmonary endothelium as a soluble, functionally active convertase.

The renin-angiotensin-aldosterone system (RAAS) plays a critical role in the regulation of blood pressure and fluid balance, with angiotensin-converting enzyme (ACE) being a key transmembrane enzyme that converts angiotensin I to angiotensin II. Hence, ACE activity is an important drug target in cardiovascular pathologies such as hypertension. Our study demonstrates that human pulmonary microvascular endothelial cells (HPMECs) are an important source of proteolytically released ACE. The proteolytic release of transmembrane proteins, a process known as ectodomain shedding, is facilitated by membrane proteases called sheddases. By knockout and inhibition studies, we identified ADAM10 (A disintegrin and metalloprotease 10) as a primary sheddase responsible for ACE release in HEK293 cells. The function of ADAM10 as primary, constitutive sheddase of ACE was confirmed in HPMECs. Moreover, we demonstrated the physiological relevance of ADAM10 for ACE shedding in exvivo precision cut lung slices (PCLS) from human and mouse lungs. Notably, ADAM17 activity is not directly involved in ACE shedding but indirectly by regulating ACE mRNA and protein levels, leading to increased ADAM10-mediated ACE shedding. Importantly, soluble ACE generated by shedding is enzymatically active and can thereby participate in systemic RAAS functions. Taken together, our findings highlight the critical role of ADAM10 (directly) and ADAM17 (indirectly) in ACE shedding and RAAS modulation.