Neonatal chlamydial infection induces mixed T-cell responses that drive allergic airway disease

Deficiency in platelet 12-lipoxygenase exacerbates inflammation and disease severity during SARS-CoV-2 infection

Platelets, known for maintaining blood balance, also participate in antimicrobial defense. Upon severeacute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, platelets become hyperactivated, releasing molecules such as cytokines, granule contents, and bioactive lipids. The key effector biolipids produced by platelets include 12-hydroxyeicosatetraenoic acid (12-HETE) and 12-hydroxyeicosatrienoic acid (12-HETrE), produced by 12-lipoxygenase (12-LOX), and prostaglandins and thromboxane, produced by cyclooxygenase-1. While prostaglandin E2 and thromboxane B2 were previously associated with lung inflammation in severe COVID-19, the role of platelet 12-LOX in SARS-CoV-2 infection remains unclear. Using mice deficient for platelets' 12-LOX, we report that SARS-CoV-2 infection resulted in higher lung inflammation characterized by histopathological tissue analysis, increased leukocyte infiltrates, and cytokine production relative to wild-type mice. In addition, distinct platelet and lung transcriptomic changes, including alterations in NOD-like receptor (NLR) family pyrin domain-containing 1 (NLRP1) inflammasome-related gene expression, were observed. Mass spectrometry lipidomic analysis in 12-LOX-deficient-infected mice revealed significant changes in bioactive lipid content, including reduced levels of 12-HETrE that inversely correlated with disease severity. Finally, platelet 12-LOX deficiency was associated with increased morbidity and lower survival rates relative to wild type (WT) mice. Overall, this study highlights the complex interplay between 12-LOX-related lipid metabolism and inflammatory responses during SARS-CoV-2 infection. The findings provide valuable insights into potential therapeutic targets aimed at mitigating severe outcomes, emphasizing the pivotal role of platelet enzymes in the host response to viral infections.

Female sex hormones and the oral contraceptive pill modulate asthma severity through GLUT-1

Females are disproportionately affected by asthma. An increased understanding of how female sex hormones influence key pathophysiological processes that underpin asthma may identify new, more effective asthma therapies, particularly for females with severe, poorly controlled asthma. We assessed the effects of oral ethinylestradiol/levonorgestrel (representing OCP use) and depot-medroxyprogesterone acetate (DMPA) and estradiol injections on key features of experimental asthma, and determined their effects on glucose transporter-1 (GLUT-1). The effects of OCP use on clinical asthma outcomes, and the relationships between estrogen receptors and type 2 (T2), non-T2, and GLUT-1 responses, in clinical asthma were also determined. OCP and DMPA reduce T2 responses, disease features, and lung expression of GLUT-1, whereas estradiol increases lung expression of GLUT-1, and results in severe, corticosteroid-insensitive, neutrophil-enriched disease, in experimental asthma. OCP use is associated with reduced T2 cytokine and GLUT-1 responses in clinical asthma. GLUT-1 expression is increased in sputum of severe asthmatics, and positively correlates with estrogen receptor expression and both T2 and non-T2 inflammatory responses. Significantly, OCP or GLUT-1 inhibition protects against obesity-associated or estradiol-induced, severe, experimental asthma, respectively. Together, these data show how female sex hormones and the OCP likely modulate asthma severity by modifying GLUT-1 responses in the airways.

Selective phosphodiesterase 4 inhibitor roflumilast reduces inflammation and lung injury in models of betacoronavirus infection in mice

OBJECTIVE

We aimed to understand the potential therapeutic and anti-inflammatory effects of the phosphodiesterase-4 (PDE4) inhibitor roflumilast in models of pulmonary infection caused by betacoronaviruses.

METHODS

Mice were infected intranasally with murine hepatitis virus (MHV-3) or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Roflumilast was given to MHV-3-infected mice therapeutically at doses of 1 mg/kg or 10 mg/kg, or prophylactically at 10 mg/kg. In SARS-CoV-2-infected mice, roflumilast was given therapeutically at a dose of 10 mg/kg. Lung histopathology, chemokines (CXCL-1 and CCL2), cytokines (IL-1β, IL-6, TNF, IFN-γ, IL-10 and TGFβ), neutrophil immunohistochemical staining (Ly6G+ cells), macrophage immunofluorescence staining (F4/80+ cells), viral titration plaque assay, real-time PCR virus detection, and blood cell counts were examined.

RESULTS

Therapeutic treatment with roflumilast at 10 mg/kg reduced lung injury in SARS-CoV-2 or MHV-3-infected mice without compromising viral clearance. In MHV-3-infected mice, reduced lung injury was associated with decreased chemokines levels, prevention of neutrophil aggregates and reduced macrophage accumulation in the lung tissue. However, the prophylactic treatment strategy with roflumilast increased lung injury in MHV-3-infected mice.

CONCLUSION

Our findings indicate that therapeutic treatment with roflumilast reduced lung injury in MHV-3 and SARS-CoV-2 lung infections. Given the protection induced by roflumilast in inflammation, PDE4 targeting could be a promising therapeutic avenue worth exploring following severe viral infections of the lung.

Immune checkpoints are suppressed during pregnancy following influenza A virus infection

Influenza A virus (IAV) infection is a major health risk during pregnancy. Although vaccination and antiviral agents are widely used and reduce IAV-induced symptoms, they are not sufficient to control IAV infections in pregnancy, especially during pandemics. Respiratory viruses like IAV exploit immune alterations that occur during pregnancy, including the upregulation of immune checkpoint proteins (ICPs) like programmed death ligand-1 (PDL1), programmed cell death receptor 1 (PD1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA4). We hypothesize that blocking expression of PDL1 on innate immune cells will improve maternal immunity following IAV infection. We used murine models of IAV infection during pregnancy with and without treatment with the immune checkpoint inhibitor (ICI), a-PDL1. Pregnant and nonpregnant mice were infected with mouse-adapted IAV (A/PR/8) and assessed at 3 days post infection (3 dpi). Lung cells were analyzed using flow cytometry. Lung mRNA expression of inflammatory and antiviral markers and histology was measured. Protein concentrations of inflammatory and antiviral markers, as well as viral titers were measured from lung bronchiolar lavage fluid (BALF). Lung function was also assessed. Following IAV infection, immune cells from pregnant mice had significant increases in the ICPs, PDL1, PD1, and CTLA4. a-PDL1 treatment effectively suppressed these ICPs and increased the activation marker, CD86. a-PDL1 treatment also reduced lung inflammatory cell infiltration and viral titers, increased antiviral responses, and improved lung function. Overall, IAV infection in pregnancy activates key inhibitory ICPs, leading to worsened disease outcomes. a-PDL1 treatment during IAV infection in pregnancy is an effective method to reduce ICP expression and improve overall immune cell responses.NEW & NOTEWORTHY Influenza infection worsens disease outcomes during pregnancy; however, treatment with anti-PDL1 can restore immune function during pregnancy.

Maternal thirdhand exposure to e-cigarette vapor alters lung and bone marrow immune cell responses in offspring in the absence or presence of influenza infection

There is increasing evidence that thirdhand exposure to e-cigarette vapor (e-vapor) can have detrimental effects on the lungs. However, whether maternal exposure during pregnancy results in harmful changes to the offspring is unknown. Using two different e-cigarette settings (low vs. high power), BALB/c mice were subjected to thirdhand e-vapor (e-vapor deposited onto towels, towels changed daily) in the absence or presence of nicotine, before, during, and after pregnancy. Male adult offspring were then infected with mouse-adapted influenza A virus (A/PR/8/34 H1N1; Flu) and lung and bone marrow immune cell responses were assessed 7 days postinfection. Maternal thirdhand exposure to low-power (MLP) or high-power (MHP) e-vapor with nicotine (MLP + NIC and MHP + NIC, respectively) increased the percentage of lung immune cells and neutrophils in the bone marrow. Interestingly, Flu-infected offspring from MLP + NIC and MHP + NIC groups had lower percentages of lung alveolar macrophages and more pronounced increases in neutrophils in the bone marrow, when compared with offspring from MSham Flu controls. Flu infection also decreased the percentage of lung CD4+ T cells and increased the percentage of lung CD8+ T cells, irrespective of maternal exposure (MLP -/+ NIC and MHP -/+ NIC). Significantly, both MLP + NIC and MHP + NIC resulted in blunted activation of lung CD4+ T cells, but only MLP + NIC caused blunted activation of lung CD8+ T cells. Together, we show for the first time that maternal thirdhand exposure to e-vapor results in significant, long-lived effects on lung and bone marrow immune cell responses in offspring at baseline and response to Flu infection.NEW & NOTEWORTHY Maternal exposure to environmental residues of e-cigarette use has significant effects on immune cell responses in the lungs and bone marrow of offspring at both baseline and in response to influenza A virus (Flu) infection.

E3 Ubiquitin Ligase Smurf1 Regulates the Inflammatory Response in Macrophages and Attenuates Hepatic Damage during Betacoronavirus Infection

The E3 ubiquitin ligase Smurf1 catalyzes the ubiquitination and proteasomal degradation of several protein substrates related to inflammatory responses and antiviral signaling. This study investigated the role of Smurf1 in modulating inflammation induced by Betacoronavirus infection. Bone marrow-derived macrophages (BMDMs) from C57BL/6 (wild-type) or Smurf1-deficient (Smurf1-/-) mice were infected with MHV-A59 to evaluate the inflammatory response in vitro. Smurf1 was found to be required to downregulate the macrophage production of pro-inflammatory mediators, including TNF, and CXCL1; to control viral release from infected cells; and to increase cell viability. To assess the impact of Smurf 1 in vivo, we evaluated the infection of mice with MHV-A59 through the intranasal route. Smurf1-/- mice infected with a lethal inoculum of MHV-A59 succumbed earlier to infection. Intranasal inoculation with a 10-fold lower dose of MHV-A59 resulted in hematological parameter alterations in Smurf1-/- mice suggestive of exacerbated systemic inflammation. In the lung parenchyma, Smurf1 expression was essential to promote viral clearance, downregulating IFN-β mRNA and controlling the inflammatory profile of macrophages and neutrophils. Conversely, Smurf1 did not affect IFN-β mRNA regulation in the liver, but it was required to increase TNF and iNOS expression in neutrophils and decrease TNF expression in macrophages. In addition, Smurf1-/- mice exhibited augmented liver injuries, accompanied by high serum levels of alanine aminotransferase (ALT). These findings suggest that Smurf1 plays a critical role in regulating the inflammatory response in macrophages and attenuating systemic inflammation during Betacoronavirus infection.

Neonatal Chlamydia muridarum respiratory infection causes neuroinflammation within the brainstem during the early postnatal period

Respiratory infections are one of the most common causes of illness and morbidity in neonates worldwide. In the acute phase infections are known to cause wide-spread peripheral inflammation. However, the inflammatory consequences to the critical neural control centres for respiration have not been explored. Utilising a well characterised model of neonatal respiratory infection, we investigated acute responses within the medulla oblongata which contains key respiratory regions. Neonatal mice were intranasally inoculated within 24 h of birth, with either Chlamydia muridarum or sham-infected, and tissue collected on postnatal day 15, the peak of peripheral inflammation. A key finding of this study is that, while the periphery appeared to show no sex-specific effects of a neonatal respiratory infection, sex had a significant impact on the inflammatory response of the medulla oblongata. There was a distinct sex-specific response in the medulla coincident with peak of peripheral inflammation, with females demonstrating an upregulation of anti-inflammatory cytokines and males showing very few changes. Microglia also demonstrated sex-specificity with the morphology of females and males differing based upon the nuclei. Astrocytes showed limited changes during the acute response to neonatal infection. These data highlight the strong sex-specific impact of a respiratory infection can have on the medulla in the acute inflammatory phase.

The glycosaminoglycan-binding chemokine fragment CXCL9(74-103) reduces inflammation and tissue damage in mouse models of coronavirus infection

Introduction

Pulmonary diseases represent a significant burden to patients and the healthcare system and are one of the leading causes of mortality worldwide. Particularly, the COVID-19 pandemic has had a profound global impact, affecting public health, economies, and daily life. While the peak of the crisis has subsided, the global number of reported COVID-19 cases remains significantly high, according to medical agencies around the world. Furthermore, despite the success of vaccines in reducing the number of deaths caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), there remains a gap in the treatment of the disease, especially in addressing uncontrolled inflammation. The massive recruitment of leukocytes to lung tissue and alveoli is a hallmark factor in COVID-19, being essential for effectively responding to the pulmonary insult but also linked to inflammation and lung damage. In this context, mice models are a crucial tool, offering valuable insights into both the pathogenesis of the disease and potential therapeutic approaches.

Methods

Here, we investigated the anti-inflammatory effect of the glycosaminoglycan (GAG)-binding chemokine fragment CXCL9(74-103), a molecule that potentially decreases neutrophil transmigration by competing with chemokines for GAG-binding sites, in two models of pneumonia caused by coronavirus infection.

Results

In a murine model of betacoronavirus MHV-3 infection, the treatment with CXCL9(74-103) decreased the accumulation of total leukocytes, mainly neutrophils, to the alveolar space and improved several parameters of lung dysfunction 3 days after infection. Additionally, this treatment also reduced the lung damage. In the SARS-CoV-2 model in K18-hACE2-mice, CXCL9(74-103) significantly improved the clinical manifestations of the disease, reducing pulmonary damage and decreasing viral titers in the lungs.

Discussion

These findings indicate that CXCL9(74-103) resulted in highly favorable outcomes in controlling pneumonia caused by coronavirus, as it effectively diminishes the clinical consequences of the infections and reduces both local and systemic inflammation.

Pyrogallol protects against influenza A virus-triggered lethal lung injury by activating the Nrf2-PPAR-γ-HO-1 signaling axis

Pyrogallol, a natural polyphenol compound (1,2,3-trihydroxybenzene), has shown efficacy in the therapeutic treatment of disorders associated with inflammation. Nevertheless, the mechanisms underlying the protective properties of pyrogallol against influenza A virus infection are not yet established. We established in this study that pyrogallol effectively alleviated H1N1 influenza A virus-induced lung injury and reduced mortality. Treatment with pyrogallol was found to promote the expression and nuclear translocation of nuclear factor erythroid-2-related factor 2 (Nrf2) and peroxisome proliferator-activated receptor gamma (PPAR-γ). Notably, the activation of Nrf2 by pyrogallol was involved in elevating the expression of PPAR-γ, both of which act synergistically to enhance heme oxygenase-1 (HO-1) synthesis. Blocking HO-1 by zinc protoporphyrin (ZnPP) reduced the suppressive impact of pyrogallol on H1N1 virus-mediated aberrant retinoic acid-inducible gene-I-nuclear factor kappa B (RIG-I-NF-κB) signaling, which thus abolished the dampening effects of pyrogallol on excessive proinflammatory mediators and cell death (including apoptosis, necrosis, and ferroptosis). Furthermore, the HO-1-independent inactivation of janus kinase 1/signal transducers and activators of transcription (JAK1/STATs) and the HO-1-dependent RIG-I-augmented STAT1/2 activation were both abrogated by pyrogallol, resulting in suppression of the enhanced transcriptional activity of interferon-stimulated gene factor 3 (ISGF3) complexes, thus prominently inhibiting the amplification of the H1N1 virus-induced proinflammatory reaction and apoptosis in interferon-beta (IFN-β)-sensitized cells. The study provides evidence that pyrogallol alleviates excessive proinflammatory responses and abnormal cell death via HO-1 induction, suggesting it could be a potential agent for treating influenza.

Platelet-activating factor and protease-activated receptor 2 cooperate to promote neutrophil recruitment and lung inflammation through nuclear factor-kappa B transactivation

Although it is well established that platelet-activated receptor (PAF) and protease-activated receptor 2 (PAR2) play a pivotal role in the pathophysiology of lung and airway inflammatory diseases, a role for a PAR2-PAFR cooperation in lung inflammation has not been investigated. Here, we investigated the role of PAR2 in PAF-induced lung inflammation and neutrophil recruitment in lungs of BALB/c mice. Mice were pretreated with the PAR2 antagonist ENMD1068, PAF receptor (PAFR) antagonist WEB2086, or aprotinin prior to intranasal instillation of carbamyl-PAF (C-PAF) or the PAR2 agonist peptide SLIGRL-NH2 (PAR2-AP). Leukocyte infiltration in bronchoalveolar lavage fluid (BALF), C-X-C motif ligand 1 (CXCL)1 and CXCL2 chemokines, myeloperoxidase (MPO), and N-acetyl-glycosaminidase (NAG) levels in BALF, or lung inflammation were evaluated. Intracellular calcium signaling, PAFR/PAR2 physical interaction, and the expression of PAR2 and nuclear factor-kappa B (NF-КB, p65) transcription factor were investigated in RAW 264.7 cells stimulated with C-PAF in the presence or absence of ENMD1068. C-PAF- or PAR2-AP-induced neutrophil recruitment into lungs was inhibited in mice pretreated with ENMD1068 and aprotinin or WEB2086, respectively. PAR2 blockade impaired C-PAF-induced neutrophil rolling and adhesion, lung inflammation, and production of MPO, NAG, CXCL1, and CXCL2 production in lungs of mice. PAFR activation reduced PAR2 expression and physical interaction of PAR2 and PAFR; co-activation is required for PAFR/PAR2 physical interaction. PAR2 blockade impaired C-PAF-induced calcium signal and NF-κB p65 translocation in RAW 264.7 murine macrophages. This study provides the first evidence for a cooperation between PAFR and PAR2 mediating neutrophil recruitment, lung inflammation, and macrophage activation.

Gut microbiota from patients with COVID-19 cause alterations in mice that resemble post-COVID symptoms

Long-term sequelae of coronavirus disease (COVID)-19 are frequent and of major concern. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection affects the host gut microbiota, which is linked to disease severity in patients with COVID-19. Here, we report that the gut microbiota of post-COVID subjects had a remarkable predominance of Enterobacteriaceae strains with an antibiotic-resistant phenotype compared to healthy controls. Additionally, short-chain fatty acid (SCFA) levels were reduced in feces. Fecal transplantation from post-COVID subjects to germ-free mice led to lung inflammation and worse outcomes during pulmonary infection by multidrug-resistant Klebsiella pneumoniae. transplanted mice also exhibited poor cognitive performance. Overall, we show prolonged impacts of SARS-CoV-2 infection on the gut microbiota that persist after subjects have cleared the virus. Together, these data demonstrate that the gut microbiota can directly contribute to post-COVID sequelae, suggesting that it may be a potential therapeutic target.

TLR7 promotes smoke-induced experimental lung damage through the activity of mast cell tryptase

Toll-like receptor 7 (TLR7) is known for eliciting immunity against single-stranded RNA viruses, and is increased in both human and cigarette smoke (CS)-induced, experimental chronic obstructive pulmonary disease (COPD). Here we show that the severity of CS-induced emphysema and COPD is reduced in TLR7-deficient mice, while inhalation of imiquimod, a TLR7-agonist, induces emphysema without CS exposure. This imiquimod-induced emphysema is reduced in mice deficient in mast cell protease-6, or when wild-type mice are treated with the mast cell stabilizer, cromolyn. Furthermore, therapeutic treatment with anti-TLR7 monoclonal antibody suppresses CS-induced emphysema, experimental COPD and accumulation of pulmonary mast cells in mice. Lastly, TLR7 mRNA is increased in pre-existing datasets from patients with COPD, while TLR7+ mast cells are increased in COPD lungs and associated with severity of COPD. Our results thus support roles for TLR7 in mediating emphysema and COPD through mast cell activity, and may implicate TLR7 as a potential therapeutic target.

A 5-Lipoxygenase Inhibitor, Zileuton, Modulates Host Immune Responses and Improves Lung Function in a Model of Severe Acute Respiratory Syndrome (SARS) Induced by Betacoronavirus

Exacerbated inflammatory responses are a hallmark of severe coronavirus disease 2019 (COVID-19). Zileuton (Zi) is a selective inhibitor of 5-lipoxygenase, an enzyme involved in the production of several inflammatory/pro-resolving lipid mediators. Herein, we investigated the effect of Zi treatment in a severe acute respiratory syndrome (SARS) model. Mouse hepatitis virus (MHV)3-infected mice treated with Zi significantly improved the clinical score, weight loss, cardiopulmonary function, and survival rates compared with infected untreated animals. The protection observed in Zi-treated mice was associated with a lower inflammatory score, reduced dendritic cell-producing tumor necrosis factor (TNF), and increased neutrophil-producing interleukin (IL)-10 in the lungs three days after infection (dpi). At 5 dpi, the lungs of treated mice showed an increase in Th2-, Treg CD4+-, and Treg CD8+-producing IL-10 and reduced Th1 infiltrating cells. Furthermore, similar results were found upon Zi treatment after SARS-CoV-2 infection in transgenic mice expressing the human angiotensin I-converting enzyme 2 (ACE2) receptor driven by the cytokeratin-18 (K18) gene promoter (K18-hACE2), significantly improving the clinical score, weight loss, and lung inflammatory score compared with untreated animals. Our data suggest that Zi protects against developing severe lung disease during SARS induced by betacoronavirus without affecting the host's capacity to deal with infection.

Inhibition of γ-glutamyl transferase suppresses airway hyperresponsiveness and airway inflammation in a mouse model of steroid resistant asthma exacerbation

Introduction

Despite recent advances, there are limited treatments available for acute asthma exacerbations. Here, we investigated the therapeutic potential of GGsTop, a γ-glutamyl transferase inhibitor, on the disease with a murine model of asthma exacerbation.

Methods

GGsTop was administered to mice that received lipopolysaccharide (LPS) and ovalbumin (OVA) challenges. Airway hyperresponsiveness (AHR), lung histology, mucus hypersecretion, and collagen deposition were analyzed to evaluate the hallmark features of asthma exacerbation. The level of proinflammatory cytokines and glutathione were determined with/without GGsTop. The transcription profiles were also examined.

Results

GGsTop attenuates hallmark features of the disease with a murine model of LPS and OVA driven asthma exacerbation. Airway hyperresponsiveness (AHR), mucus hypersecretion, collagen deposition, and expression of inflammatory cytokines were dramatically inhibited by GGsTop treatment. Additionally, GGsTop restored the level of glutathione. Using RNA-sequencing and pathway analysis, we demonstrated that the activation of LPS/NFκB signaling pathway in airway was downregulated by GGsTop. Interestingly, further analysis revealed that GGsTop significantly inhibited not only IFNγ responses but also the expression of glucocorticoid-associated molecules, implicating that GGsTop profoundly attenuates inflammatory pathways.

Conclusions

Our study suggests that GGsTop is a viable treatment for asthma exacerbation by broadly inhibiting the activation of multiple inflammatory pathways.

Chronic ethanol exposure impairs alveolar leukocyte infiltration during pneumococcal pneumonia, leading to an increased bacterial burden despite increased CXCL1 and nitric oxide levels

Ethanol abuse is a risk factor for the development of pneumonia caused by Streptococcus pneumoniae, a critical pathogen for public health. The aim of this article was to investigate the inflammatory mechanisms involved in pneumococcal pneumonia that may be associated with chronic ethanol exposure. Male C57BL6/J-Unib mice were exposed to 20% (v/v) ethanol for twelve weeks and intranasally infected with 5x10⁴ CFU of S. pneumoniae. Twenty-four hours after infection, lungs, bronchoalveolar lavage and blood samples were obtained to assess the consequences of chronic ethanol exposure during infection. Alcohol-fed mice showed increased production of nitric oxide and CXCL1 in alveoli and plasma during pneumococcal pneumonia. Beside this, ethanol-treated mice exhibited a decrease in leukocyte infiltration into the alveoli and reduced frequency of severe lung inflammation, which was associated with an increase in bacterial load. Curiously, no changes were observed in survival after infection. Taken together, these results demonstrate that chronic ethanol exposure alters the inflammatory response during S. pneumoniae lung infection in mice with a reduction in the inflammatory infiltrate even in the presence of higher levels of the chemoattractant CXCL1.

Diosmetin alleviates benzo[a]pyrene-exacerbated H1N1 influenza virus-induced acute lung injury and dysregulation of inflammation through modulation of the PPAR-γ-NF-κB/P38 MAPK signaling axis

The severity of a viral respiratory illness was greatly exacerbated after exposure to a contaminant containing benzo[a]pyrene (B[a]P). Flavonoid-rich fruit intake has gained intense interest due to their health-promoting benefits for viral respiratory diseases, including influenza viruses. In our study, diosmetin (3',5,7-trihydroxy-4'-methoxyflavone), a naturally occurring hydroxylated methoxyflavone that is abundant in Citrus fruits, was explored for its effects on B[a]P-exacerbated H1N1 influenza virus-mediated inflammation and lung injury. Initially, in vivo results demonstrated that diosmetin protected against H1N1 virus-elicited acute lung injury. Simultaneously, H1N1 virus or B[a]P-stimulated A549 cells treated with diosmetin inhibited NF-κB and P-P38 activation, resulting in suppression of pro-inflammatory cytokines and apoptosis. Interestingly, diosmetin obviously promoted the expression of PPAR-γ as well as nuclear translocation of PPAR-γ, whereas, PPAR-γ inhibition by GW9662 weakened the inhibitory effects of diosmetin on H1N1 virus or B[a]P-mediated activation of NF-κB and P-P38, elevated expression of pro-inflammatory mediators as well as apoptosis. Furthermore, it was surprising to discover that mice exposed to both B[a]P and H1N1 viruses contributed to exacerbated acute lung injury, which were significantly ameliorated by diosmetin administration. In vitro studies showed that A549 cells with the combination of B[a]P and H1N1 virus augmented NF-κB and P-P38 activation, accompanied by higher levels of pro-inflammatory mediators and apoptosis, all of which were also significantly reduced by diosmetin treatment. Repressing PPAR-γ abrogated the inhibitory effects of diosmetin on B[a]P-exacerbated H1N1 virus-mediated NF-κB and P-P38 activation, inflammation, and apoptosis in A549 cells. Our findings suggest that diosmetin protected against B[a]P-exacerbated H1N1 virus-mediated lung injury by suppressing the exacerbation of NF-κB and P38 kinase activation in a PPAR-γ-dependent manner, suggesting potential benefits for B[a]P-exacerbated influenza-related illness therapeutics.

Tim-3 blockade enhances the clearance of Chlamydia psittaci in the lung by promoting a cell-mediated immune response

Chlamydia psittaci is remarkable at disrupting immunity and thus poses a great risk to the animal industry and public health. Immune inhibitory molecule upregulation and the accumulation of specialized cells play key roles in chlamydial clearance. It is clear that the T-cell immunoglobulin and mucin domain protein 3 receptor (Tim-3) can regulate effector T cells in infectious disease. However, the immunomodulatory effect of Tim-3 in C. psittaci infection remains unknown. Thus, the expression of Tim-3 in effector T cells and its immune regulatory function during C. psittaci infection were investigated. The level of Tim-3 on CD4⁺ and CD8⁺ T cells was meaningfully higher in C. psittaci-infected mice. Blockade of Tim-3 signaling by anti-Tim-3 antibody showed accelerated C. psittaci clearance and less pathological changes in the lung than isotype immunoglobulin treatment. Furthermore, treatment with anti-Tim-3 antibody greatly enhanced the levels of IFN-γ and interleukin (IL)-22/IL-17, which were correlated with an improved Th1- and Th17-mediated immune response, and decreased IL-10, which were related with a decreased Treg immune response. In conclusion, Tim-3 expression in effector T cells negatively regulates Th1 and Th17 immune responses against C. psittaci respiratory infection.

Absence of CCR2 Promotes Proliferation of Alveolar Macrophages That Control Lung Inflammation in Acute Respiratory Distress Syndrome in Mice

Acute respiratory distress syndrome (ARDS) consists of uncontrolled inflammation that causes hypoxemia and reduced lung compliance. Since it is a complex process, not all details have been elucidated yet. In a well-controlled experimental murine model of lipopolysaccharide (LPS)-induced ARDS, the activity and viability of macrophages and neutrophils dictate the beginning and end phases of lung inflammation. C-C chemokine receptor type 2 (CCR2) is a critical chemokine receptor that mediates monocyte/macrophage activation and recruitment to the tissues. Here, we used CCR2-deficient mice to explore mechanisms that control lung inflammation in LPS-induced ARDS. CCR2−/− mice presented higher total numbers of pulmonary leukocytes at the peak of inflammation as compared to CCR2+/+ mice, mainly by enhanced influx of neutrophils, whereas we observed two to six-fold lower monocyte or interstitial macrophage numbers in the CCR2−/−. Nevertheless, the time needed to control the inflammation was comparable between CCR2+/+ and CCR2−/−. Interestingly, CCR2−/− mice presented higher numbers and increased proliferative rates of alveolar macrophages from day 3, with a more pronounced M2 profile, associated with transforming growth factor (TGF)-β and C-C chemokine ligand (CCL)22 production, decreased inducible nitric oxide synthase (Nos2), interleukin (IL)-1β and IL-12b mRNA expression and increased mannose receptor type 1 (Mrc1) mRNA and CD206 protein expression. Depletion of alveolar macrophages significantly delayed recovery from the inflammatory insult. Thus, our work shows that the lower number of infiltrating monocytes in CCR2−/− is partially compensated by increased proliferation of resident alveolar macrophages during the inflammation control of experimental ARDS.

Loss of SP-A in the Lung Exacerbates Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a devastating and common chronic lung disease that is pathologically characterized by the destruction of lung architecture and the accumulation of extracellular matrix in the lung. Previous studies have shown an association between lung surfactant protein (SP) and the pathogenesis of IPF, as demonstrated by mutations and the altered expression of SP in patients with IPF. However, the role of SP in the development of lung fibrosis is poorly understood. In this study, the role of surfactant protein A (SP-A) was explored in experimental lung fibrosis induced with a low or high dose of bleomycin (BLM) and CRISPR/Cas9-mediated genetic deletion of SP-A. Our results showed that lung SP-A deficiency in mice promoted the development of fibrotic damage and exacerbated inflammatory responses to the BLM challenge. In vitro experiments with murine lung epithelial LA-4 cells demonstrated that in response to transforming growth factor-β1 (TGF-β1), LA-4 cells had a decreased protein expression of SP-A. Furthermore, exogenous SP administration to LA-4 cells inhibited the TGF-β1-induced upregulation of fibrotic markers. Overall, these findings suggest a novel antifibrotic mechanism of SP-A in the development of lung fibrosis, which indicates the therapeutic potential of the lung SP-A in preventing the development of IPF.

Itaconate and itaconate derivatives target JAK1 to suppress alternative activation of macrophages

The Krebs cycle-derived metabolite itaconate and its derivatives suppress the inflammatory response in pro-inflammatory "M1" macrophages. However, alternatively activated "M2" macrophages can take up itaconate. We therefore examined the effect of itaconate and 4-octyl itaconate (OI) on M2 macrophage activation. We demonstrate that itaconate and OI inhibit M2 polarization and metabolic remodeling. Examination of IL-4 signaling revealed inhibition of JAK1 and STAT6 phosphorylation by both itaconate and OI. JAK1 activation was also inhibited by OI in response to IL-13, interferon-β, and interferon-γ in macrophages and in T helper 2 (Th2) cells. Importantly, JAK1 was directly modified by itaconate derivatives at multiple residues, including cysteines 715, 816, 943, and 1130. Itaconate and OI also inhibited JAK1 kinase activity. Finally, OI treatment suppressed M2 macrophage polarization and JAK1 phosphorylation in vivo. We therefore identify itaconate and OI as JAK1 inhibitors, suggesting a new strategy to inhibit JAK1 in M2 macrophage-driven diseases.

Proteomic Analysis Reveals a Novel Therapeutic Strategy Using Fludarabine for Steroid-Resistant Asthma Exacerbation

Virus-induced asthma exacerbation is a health burden worldwide and lacks effective treatment. To better understand the disease pathogenesis and find novel therapeutic targets, we established a mouse model of steroid (dexamethasone (DEX)) resistant asthma exacerbation using ovalbumin (OVA) and influenza virus (FLU) infection. Using liquid chromatography-tandem mass spectrometry (LC-MC/MS), we performed a shotgun proteomics assay coupled with label-free quantification to define all dysregulated proteins in the lung proteome of asthmatic mice. Compared to control, 71, 89, and 30 proteins were found significantly upregulated by at least two-fold (p-value ≤ 0.05) in OVA-, OVA/FLU-, and OVA/FLU/DEX-treated mice, respectively. We then applied a Z-score transformed hierarchical clustering analysis and Ingenuity Pathway Analysis (IPA) to highlight the key inflammation pathways underlying the disease. Within all these upregulated proteins, 64 proteins were uniquely highly expressed in OVA/FLU mice compared to OVA mice; and 11 proteins were DEX-refractory. IPA assay revealed two of the most enriched pathways associated with these over-expressed protein clusters were those associated with MHC class I (MHC-I) antigen-presentation and interferon (IFN) signaling. Within these pathways, signal-transducer-and-activator-of-transcription-1 (STAT1) protein was identified as the most significantly changed protein contributing to the pathogenesis of exacerbation and the underlying steroid resistance based on the label-free quantification; and this was further confirmed by both Parallel Reaction Monitoring (PRM) proteomics assay and western blots. Further, the pharmacological drug Fludarabine decreased STAT1 expression, restored the responsiveness of OVA/FLU mice to DEX and markedly suppressed disease severity. Taken together, this study describes the proteomic profile underpinning molecular mechanisms of FLU-induced asthma exacerbation and identifies STAT1 as a potential therapeutic target, more importantly, we provided a novel therapeutic strategy that may be clinically translated into practice.

Natural Killer Cells Regulate Pulmonary Macrophages Polarization in Host Defense Against Chlamydial Respiratory Infection

NK cells and pulmonary macrophages both are important components of innate immunity. The interaction between NK cells and pulmonary macrophages during chlamydial infection is poorly understood. In this study, we explored the effect of NK cells on regulation of pulmonary macrophage function during chlamydial respiratory infection. We found that NK depletion led to polarization of pulmonary macrophages from M1 to M2 phenotype, and it is related to reduced miR-155 expression in lung macrophage. Using adoptive transfer approach, we found that the recipients receiving lung macrophages isolated from C. muridarum-infected NK-cell-depleted mice exhibited an increased bacterial load and severe inflammation in the lung upon chlamydial challenge infection when compared with the recipients of lung macrophages from infected isotype control antibody treated mice. Herein, the effects of NK cells on macrophage polarization were examined in vitro. We found that NK cells from chlamydial-infected mice (iNK) significantly induced M1 polarization compared to that from uninfected mice (uNK). Inhibition of miR-155 expression in macrophages reduced M1 polarization induced by iNK, while miR-155 over-expression enhanced it. Furthermore, neutralization of IFN-γ in the coculture system decreased the expression of miR-155 by macrophages, and resulted in weakened M1 polarization. The data indicates that NK cells promote M1 polarization through up-regulation of miR-155 in macrophages by producing IFN-γ during chlamydial infection, and NK-regulated macrophage polarization is functionally relevant to host defense against the infection.

Single-cell RNA transcriptomic analysis identifies Creb5 and CD11b-DCs as regulator of asthma exacerbations

Immune responses that result in asthma exacerbation are associated with allergen or viral exposure. Identification of common immune factors will be beneficial for the development of uniformed targeted therapy. We employed a House Dust Mite (HDM) mouse model of asthma and challenged allergic HDM mice with allergens (HDM, cockroach extract (CRE)) or respiratory syncytial virus (RSV). Purified lung immune cells underwent high-dimensional single-cell RNA deep sequencing (scRNA-seq) to generate an RNA transcriptome. Gene silencing with siRNA was employed to confirm the efficacy of scRNA-seq analysis. scRNA-seq UMAP analysis portrayed an array of cell markers within individual immune clusters. SCENIC R analysis showed an increase in regulon number and activity in CD11b^- DC cells. Analysis of conserved regulon factors further identified Creb5 as a shared regulon between the exacerbation groups. Creb5 siRNAs attenuated HDM, CRE or RSV-induced asthma exacerbation. scRNA-seq multidimensional analysis of immune clusters identified gene pathways that were conserved between the exacerbation groups. We propose that these analyses provide a strong framework that could be used to identify specific therapeutic targets in multifaceted pathologies.

A microRNA-21-mediated SATB1/S100A9/NF-κB axis promotes chronic obstructive pulmonary disease pathogenesis

[Figure: see text].

A Biosafety Level 2 Mouse Model for Studying Betacoronavirus-Induced Acute Lung Damage and Systemic Manifestations

The emergence of life-threatening zoonotic diseases caused by betacoronaviruses, including the ongoing coronavirus disease 19 (COVID-19) pandemic, has highlighted the need for developing preclinical models mirroring respiratory and systemic pathophysiological manifestations seen in infected humans. Here, we showed that C57BL/6J wild-type mice intranasally inoculated with the murine betacoronavirus murine hepatitis coronavirus 3 (MHV-3) develop a robust inflammatory response leading to acute lung injuries, including alveolar edema, hemorrhage, and fibrin thrombi. Although such histopathological changes seemed to resolve as the infection advanced, they efficiently impaired respiratory function, as the infected mice displayed restricted lung distention and increased respiratory frequency and ventilation. Following respiratory manifestation, the MHV-3 infection became systemic, and a high virus burden could be detected in multiple organs along with morphological changes. The systemic manifestation of MHV-3 infection was also marked by a sharp drop in the number of circulating platelets and lymphocytes, besides the augmented concentration of the proinflammatory cytokines interleukin 1 beta (IL-1β), IL-6, IL-12, gamma interferon (IFN-γ), and tumor necrosis factor (TNF), thereby mirroring some clinical features observed in moderate and severe cases of COVID-19. Importantly, both respiratory and systemic changes triggered by MHV-3 infection were greatly prevented by blocking TNF signaling, either via genetic or pharmacologic approaches. In line with this, TNF blockage also diminished the infection-mediated release of proinflammatory cytokines and virus replication of human epithelial lung cells infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Collectively, results show that MHV-3 respiratory infection leads to a large range of clinical manifestations in mice and may constitute an attractive, lower-cost, biosafety level 2 (BSL2) in vivo platform for evaluating the respiratory and multiorgan involvement of betacoronavirus infections. IMPORTANCE Mouse models have long been used as valuable in vivo platforms to investigate the pathogenesis of viral infections and effective countermeasures. The natural resistance of mice to the novel betacoronavirus SARS-CoV-2, the causative agent of COVID-19, has launched a race toward the characterization of SARS-CoV-2 infection in other animals (e.g., hamsters, cats, ferrets, bats, and monkeys), as well as adaptation of the mouse model, by modifying either the host or the virus. In the present study, we utilized a natural pathogen of mice, MHV, as a prototype to model betacoronavirus-induced acute lung injure and multiorgan involvement under biosafety level 2 conditions. We showed that C57BL/6J mice intranasally inoculated with MHV-3 develops severe disease, which includes acute lung damage and respiratory distress that precede systemic inflammation and death. Accordingly, the proposed animal model may provide a useful tool for studies regarding betacoronavirus respiratory infection and related diseases.

IL-17A is a common and critical driver of impaired lung function and immunopathology induced by influenza virus, rhinovirus and respiratory syncytial virus

BACKGROUND AND OBJECTIVE

Influenza virus (FLU), rhinovirus (RV) and respiratory syncytial virus (RSV) are the most common acute respiratory infections worldwide. Infection can cause severe health outcomes, while therapeutic options are limited, primarily relieving symptoms without attenuating the development of lesions or impaired lung function. We therefore examined the inflammatory response to these infections with the intent to identify common components that are critical drivers of immunopathogenesis and thus represent potential therapeutic targets.

METHODS

BALB/c mice were infected with FLU, RV or RSV, and lung function, airway inflammation and immunohistopathology were measured over a 10-day period. Anti-IL-17A mAb was administered to determine the impact of attenuating this cytokine's function on the development and severity of disease.

RESULTS

All three viruses induced severe airway constriction and inflammation at 2 days post-infection (dpi). However, only FLU induced prolonged inflammation till 10 dpi. Increased IL-17A expression was correlated with the alterations in lung function and its persistence. Neutralization of IL-17A did not affect the viral replication but led to the resolution of airway hyperresponsiveness. Furthermore, anti-IL-17A treatment resulted in reduced infiltration of neutrophils (in RV- and FLU-infected mice at 2 dpi) and lymphocytes (in RSV-infected mice at 2 dpi and FLU-infected mice at 10 dpi), and attenuated the severity of immunopathology.

CONCLUSION

IL-17A is a common pathogenic molecule regulating disease induced by three prevalent respiratory viruses. Targeting the IL-17A pathway may provide a unified approach to the treatment of these respiratory infections alleviating both inflammation-induced lesions and difficulties in breathing.

Inhibition of β-Catenin/CREB Binding Protein Signaling Attenuates House Dust Mite-Induced Goblet Cell Metaplasia in Mice

Excessive mucus production is a major feature of allergic asthma. Disruption of epithelial junctions by allergens such as house dust mite (HDM) results in the activation of β-catenin signaling, which has been reported to stimulate goblet cell differentiation. β-catenin interacts with various co-activators including CREB binding protein (CBP) and p300, thereby regulating the expression of genes involved in cell proliferation and differentiation, respectively. We specifically investigated the role of the β-catenin/CBP signaling pathway in goblet cell metaplasia in a HDM-induced allergic airway disease model in mice using ICG-001, a small molecule inhibitor that blocks the binding of CBP to β-catenin. Female 6- 8-week-old BALB/c mice were sensitized to HDM/saline on days 0, 1, and 2, followed by intranasal challenge with HDM/saline with or without subcutaneous ICG-001/vehicle treatment from days 14 to 17, and samples harvested 24 h after the last challenge/treatment. Differential inflammatory cells in bronchoalveolar lavage (BAL) fluid were enumerated. Alcian blue (AB)/Periodic acid–Schiff (PAS) staining was used to identify goblet cells/mucus production, and airway hyperresponsiveness (AHR) was assessed using invasive plethysmography. Exposure to HDM induced airway inflammation, goblet cell metaplasia and increased AHR, with increased airway resistance in response to the non-specific spasmogen methacholine. Inhibition of the β-catenin/CBP pathway using treatment with ICG-001 significantly attenuated the HDM-induced goblet cell metaplasia and infiltration of macrophages, but had no effect on eosinophils, neutrophils, lymphocytes or AHR. Increased β-catenin/CBP signaling may promote HDM-induced goblet cell metaplasia in mice.

Time-resolved proteomic profiling of cigarette smoke-induced experimental chronic obstructive pulmonary disease

BACKGROUND AND OBJECTIVE

Chronic obstructive pulmonary disease (COPD) is the third leading cause of illness and death worldwide. Current treatments aim to control symptoms with none able to reverse disease or stop its progression. We explored the major molecular changes in COPD pathogenesis.

METHODS

We employed quantitative label-based proteomics to map the changes in the lung tissue proteome of cigarette smoke-induced experimental COPD that is induced over 8 weeks and progresses over 12 weeks.

RESULTS

Quantification of 7324 proteins enabled the tracking of changes to the proteome. Alterations in protein expression profiles occurred in the induction phase, with 18 and 16 protein changes at 4- and 6-week time points, compared to age-matched controls, respectively. Strikingly, 269 proteins had altered expression after 8 weeks when the hallmark pathological features of human COPD emerge, but this dropped to 27 changes at 12 weeks with disease progression. Differentially expressed proteins were validated using other mouse and human COPD bronchial biopsy samples. Major changes in RNA biosynthesis (heterogeneous nuclear ribonucleoproteins C1/C2 [HNRNPC] and RNA-binding protein Musashi homologue 2 [MSI2]) and modulators of inflammatory responses (S100A1) were notable. Mitochondrial dysfunction and changes in oxidative stress proteins also occurred.

CONCLUSION

We provide a detailed proteomic profile, identifying proteins associated with the pathogenesis and disease progression of COPD establishing a platform to develop effective new treatment strategies.

Concomitant experimental coinfection by Plasmodium berghei NK65-NY and Ascaris suum downregulates the Ascaris-specific immune response and potentiates Ascaris-associated lung pathology

Background

Ascariasis and malaria are highly prevalent parasitic diseases in tropical regions and often have overlapping endemic areas, contributing to high morbidity and mortality rates in areas with poor sanitary conditions. Several studies have previously aimed to correlate the effects of Ascaris-Plasmodium coinfections but have obtained contradictory and inconclusive results. Therefore, the present study aimed to investigate parasitological and immunopathological aspects of the lung during murine experimental concomitant coinfection by Plasmodium berghei and Ascaris suum during larvae ascariasis.

Methods

C57BL/6J mice were inoculated with 1 × 10⁴P. berghei strain NK65-NY-infected red blood cells (iRBCs) intraperitoneally and/or 2500 embryonated eggs of A. suum by oral gavage. P. berghei parasitaemia, morbidity and the survival rate were assessed. On the seventh day postinfection (dpi), A. suum lung burden analysis; bronchoalveolar lavage (BAL); histopathology; NAG, MPO and EPO activity measurements; haematological analysis; and respiratory mechanics analysis were performed. The concentrations of interleukin (IL)-1β, IL-12/IL-23p40, IL-6, IL-4, IL-33, IL-13, IL-5, IL-10, IL-17A, IFN-γ, TNF and TGF-β were assayed by sandwich ELISA.

Results

Animals coinfected with P. berghei and A. suum show decreased production of type 1, 2, and 17 and regulatory cytokines; low leukocyte recruitment in the tissue; increased cellularity in the circulation; and low levels of NAG, MPO and EPO activity that lead to an increase in larvae migration, as shown by the decrease in larvae recovered in the lung parenchyma and increase in larvae recovered in the airway. This situation leads to severe airway haemorrhage and, consequently, an impairment respiratory function that leads to high morbidity and early mortality.

Conclusions

This study demonstrates that the Ascaris-Plasmodium interaction is harmful to the host and suggests that this coinfection may potentiate Ascaris-associated pathology by dampening the Ascaris-specific immune response, resulting in the early death of affected animals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03824-w.

Necroptosis Signalling Promotes Inflammation, Airway Remodelling and Emphysema in COPD

RATIONALE

Necroptosis, mediated by RIPK3 and MLKL, is a form of regulated necrosis that can drive tissue inflammation and destruction, however its contribution to COPD pathogenesis is poorly understood.

OBJECTIVES

To determine the role of necroptosis in COPD.

METHODS

Levels of RIPK3, MLKL and activated phospho-MLKL were measured in lung tissues of COPD patients and non-COPD controls. Necroptosis-related mRNA and proteins and cell death were examined in the lungs and pulmonary macrophages of mice with cigarette smoke (CS)-induced experimental COPD. The responses of Ripk3- and Mlkl-deficient (-/-) mice to CS exposure were compared to wild-type mice. Combined inhibition of apoptosis (pan-caspase inhibitor qVD-OPh) and necroptosis (Mlkl-/- mice) was assessed.

MEASUREMENTS AND MAIN RESULTS

Protein levels of MLKL and pMLKL but not RIPK3 were increased in lung tissues of COPD patients compared to never smokers or smoker non-COPD controls. Necroptosis-related mRNA and protein levels were increased in lung tissue and macrophages in CS-exposed mice/experimental COPD. Ripk3 or Mlkl deletion prevented airway inflammation in response to acute CS-exposure. Ripk3 deficiency reduced airway inflammation and remodelling and development of emphysematous pathology following chronic CS-exposure. Mlkl deletion and qVD-OPh treatment reduced chronic CS-induced airway inflammation, but only Mlkl deletion prevented airway remodelling and emphysema. Ripk3 or Mlkl deletion and qVD-OPh treatment reduced CS-induced lung cell death.

CONCLUSIONS

Necroptosis is induced by CS exposure and increased in COPD patient lungs and experimental COPD. Inhibiting necroptosis attenuates CS-induced airway inflammation, airway remodelling and emphysema. Targeted inhibition of necroptosis is a potential therapeutic strategy in COPD.

Gut Dysbiosis during Influenza Contributes to Pulmonary Pneumococcal Superinfection through Altered Short-Chain Fatty Acid Production

Secondary bacterial infections often complicate viral respiratory infections. We hypothesize that perturbation of the gut microbiota during influenza A virus (IAV) infection might favor respiratory bacterial superinfection. Sublethal infection with influenza transiently alters the composition and fermentative activity of the gut microbiota in mice. These changes are attributed in part to reduced food consumption. Fecal transfer experiments demonstrate that the IAV-conditioned microbiota compromises lung defenses against pneumococcal infection. In mechanistic terms, reduced production of the predominant short-chain fatty acid (SCFA) acetate affects the bactericidal activity of alveolar macrophages. Following treatment with acetate, mice colonized with the IAV-conditioned microbiota display reduced bacterial loads. In the context of influenza infection, acetate supplementation reduces, in a free fatty acid receptor 2 (FFAR2)-dependent manner, local and systemic bacterial loads. This translates into reduced lung pathology and improved survival rates of double-infected mice. Lastly, pharmacological activation of the SCFA receptor FFAR2 during influenza reduces bacterial superinfection.

Chlamydia muridarum Can Invade the Central Nervous System via the Olfactory and Trigeminal Nerves and Infect Peripheral Nerve Glial Cells

Chlamydia pneumoniae can infect the brain and has been linked to late-onset dementia. Chlamydia muridarum, which infects mice, is often used to model human chlamydial infections. While it has been suggested to be also important for modelling brain infection, nervous system infection by C. muridarum has not been reported in the literature. C. pneumoniae has been shown to infect the olfactory bulb in mice after intranasal inoculation, and has therefore been suggested to invade the brain via the olfactory nerve; however, nerve infection has not been shown to date. Another path by which certain bacteria can reach the brain is via the trigeminal nerve, but it remains unknown whether Chlamydia species can infect this nerve. Other bacteria that can invade the brain via the olfactory and/or trigeminal nerve can do so rapidly, however, whether Chlamydia spp. can reach the brain earlier than one-week post inoculation remains unknown. In the current study, we showed that C. muridarum can within 48 h invade the brain via the olfactory nerve, in addition to infecting the trigeminal nerve. We also cultured the glial cells of the olfactory and trigeminal nerves and showed that C. muridarum readily infected the cells, constituting a possible cellular mechanism explaining how the bacteria can invade the nerves without being eliminated by glial immune functions. Further, we demonstrated that olfactory and trigeminal glia differed in their responses to C. muridarum, with olfactory glia showing less infection and stronger immune response than trigeminal glia.

A monoclonal antibody to Siglec-8 suppresses non-allergic airway inflammation and inhibits IgE-independent mast cell activation

In addition to their well characterized role in mediating IgE-dependent allergic diseases, aberrant accumulation and activation of mast cells (MCs) is associated with many non-allergic inflammatory diseases, whereby their activation is likely triggered by non-IgE stimuli (e.g., IL-33). Siglec-8 is an inhibitory receptor expressed on MCs and eosinophils that has been shown to inhibit IgE-mediated MC responses and reduce allergic inflammation upon ligation with a monoclonal antibody (mAb). Herein, we evaluated the effects of an anti-Siglec-8 mAb (anti-S8) in non-allergic disease models of experimental cigarette-smoke-induced chronic obstructive pulmonary disease and bleomycin-induced lung injury in Siglec-8 transgenic mice. Therapeutic treatment with anti-S8 inhibited MC activation and reduced recruitment of immune cells, airway inflammation, and lung fibrosis. Similarly, using a model of MC-dependent, IL-33-induced inflammation, anti-S8 treatment suppressed neutrophil influx, and cytokine production through MC inhibition. Transcriptomic profiling of MCs further demonstrated anti-S8-mediated downregulation of MC signaling pathways induced by IL-33, including TNF signaling via NF-κB. Collectively, these findings demonstrate that ligating Siglec-8 with an antibody reduces non-allergic inflammation and inhibits IgE-independent MC activation, supporting the evaluation of an anti-Siglec-8 mAb as a therapeutic approach in both allergic and non-allergic inflammatory diseases in which MCs play a role.

Human β-defensin-2 suppresses key features of asthma in murine models of allergic airways disease

BACKGROUND

Asthma is an airway inflammatory disease and a major health problem worldwide. Anti-inflammatory steroids and bronchodilators are the gold-standard therapy for asthma. However, they do not prevent the development of the disease, and critically, a subset of asthmatics are resistant to steroid therapy.

OBJECTIVE

To elucidate the therapeutic potential of human β-defensins (hBD), such as hBD2 mild to moderate and severe asthma.

METHODS

We investigated the role of hBD2 in a steroid-sensitive, house dust mite-induced allergic airways disease (AAD) model and a steroid-insensitive model combining ovalbumin-induced AAD with C muridarum (Cmu) respiratory infection.

RESULTS

In both models, we demonstrated that therapeutic intranasal application of hBD2 significantly reduced the influx of inflammatory cells into the bronchoalveolar lavage fluid. Furthermore, key type 2 asthma-related cytokines IL-9 and IL-13, as well as additional immunomodulating cytokines, were significantly decreased after administration of hBD2 in the steroid-sensitive model. The suppression of inflammation was associated with improvements in airway physiology and treatment also suppressed airway hyper-responsiveness (AHR) in terms of airway resistance and compliance to methacholine challenge.

CONCLUSIONS AND CLINICAL RELEVANCE

These data indicate that hBD2 reduces the hallmark features and has potential as a new therapeutic agent in allergic and especially steroid-resistant asthma.

[Inhibition of CD96 enhances interferon-γ secretion by natural killer cells to alleviate lung injury in mice with pulmonary Chlamydia muridarum infection]

OBJECTIVE

To assess the effect of neutralizing CD96 on natural killer (NK) cell functions in mice with pulmonary Chlamydia muridarum infection and explore the possible mechanism.

METHODS

Male BALB/c mice were randomly divided into infection group (Cm group), anti-CD96 treatment group (anti-CD96 group) and control group (n=5). In the former two groups, C. muridarum was inoculated via intranasal administration to establish mouse models of pulmonary C. muridarum infection, and the mice in the control group received intranasal administration of the inhalation buffer. In anti-CD96 group, the mice were injected with anti-CD96 antibody intraperitoneally at the dose of 250 μg every 3 days after the infection; the mice in Cm group received intraperitoneal injections of saline. The body weight of the mice was recorded daily. The mice were sacrificed 5 days after C. muridarum infection, and CD96 expression was detected by quantitative real-time PCR and Western blotting. HE staining and pathological scores were used to evaluate pneumonia of the mice. The inclusion body forming units (IFUs) were detected in the lung tissue homogenates to assess lung tissue chlamydia load. Flow cytometry and ELISA were used to assess the capacity of the lung NK cells to produce interferon-γ (IFN-γ) and regulate macrophages and Th1 cells.

RESULTS

C. muridarum infection inhibited CD96 expression in NK cells of the mice. Compared with those in Cm group, the mice in antiCD96 mice showed significantly milder lung inflammation (P < 0.05) and reduced chlamydia load in the lung tissue (P < 0.05). Neutralizing CD96 with anti-CD96 significantly enhanced IFN-γ secretion by the NK cells (P < 0.05) and augmented the immunoregulatory effect of the NK cells shown by enhanced responses of the lung macrophages (P < 0.05) and Th1 cells (P < 0.05).

CONCLUSIONS

Inhibition of CD96 alleviates pneumonia in C. muridarum-infected mice possibly by enhancing IFN-γ secretion by NK cells and augmenting the immunoregulatory effect of the NK cells on innate and adaptive immunity.

Vaccination with ADCC activating HA peptide epitopes provides partial protection from influenza infection

Influenza-specific antibody dependent cellular cytotoxicity (ADCC) antibodies have a broad cross reactivity and potential as an immune correlate for universal vaccines. Peptide-mapping for ADCC reactivity of H1-HA and H7-HA proteins from human serum samples identified high ADCC-inducing peptides in both the HA1 and HA2 regions. Vaccination of mice with single ADCC-peptides induced ADCC activity leading to partial protection from lethal influenza challenge, with increased survival, reduced viral loads, and reduced activation of NK cells in the lungs. Targeted vaccination strategies to elicit ADCC responses may provide an approach for universal vaccines.

Emerging therapeutic targets and preclinical models for severe asthma

INTRODUCTION

Asthma is a heterogeneous disease with complex multifactorial causes. It is possible to subclassify asthma into different phenotypes that have distinct immunological features. Eosinophilic asthma is a well-known phenotype of severe asthma; however, a large body of clinical and experimental evidence strongly associates persistent airway inflammation, including the accumulation of neutrophils in the bronchial mucosa, and resistance to corticosteroid therapy and non-Type-2 immune responses with severe asthma. Importantly, mainstay therapies are often ineffective in severe asthma and effective alternatives are urgently needed.

AREAS COVERED

Here, we discussed recently developed mouse models of severe asthma that recapitulates key features of the disease in humans. We also provide findings from clinically relevant experimental models that have identified potential therapeutic targets for severe asthma. The most relevant publications on the topic of interest were selected from PubMed.

EXPERT COMMENTARY

Increasing the understanding of disease-causing mechanisms in severe asthma may lead to the identification of novel therapeutic targets and the development of more effective therapies. Intense research interest into investigating the pathophysiological mechanisms of severe asthma has driven the development and interrogation of a myriad of mouse models that aim to replicate hallmark features of severe asthma in humans.

A role for mast cells and mast cell tryptase in driving neutrophil recruitment in LPS-induced lung inflammation via protease-activated receptor 2 in mice

OBJECTIVE

This study aims to investigate the role of protease-activated receptor (PAR) 2 and mast cell (MC) tryptase in LPS-induced lung inflammation and neutrophil recruitment in the lungs of C57BL/6 mice.

METHODS

C57BL/6 mice were pretreated with the PAR2 antagonist ENMD-1068, compound 48/80 or aprotinin prior to intranasal instillation of MC tryptase or LPS. Blood leukocytes, C-X-C motif chemokine ligand (CXCL) 1 production leukocytes recovered from bronchoalveolar lavage fluid (BALF), and histopathological analysis of the lung were evaluated 4 h later. Furthermore, we performed experiments to determine intracellular calcium signaling in RAW 264.7 cells stimulated with LPS in the presence or absence of a protease inhibitor cocktail or ENMD-1068 and evaluated PAR2 expression in the lungs of LPS-treated mice.

RESULTS

Pharmacological blockade of PAR2 or inhibition of proteases reduced neutrophils recovered in BALF and LPS-induced calcium signaling. PAR2 blockade impaired LPS-induced lung inflammation, PAR2 expression in the lung and CXCL1 release in BALF, and increased circulating blood neutrophils. Intranasal instillation of MC tryptase increased the number of neutrophils recovered in BALF, and MC depletion with compound 48/80 impaired LPS-induced neutrophil migration.

CONCLUSION

Our study provides, for the first time, evidence of a pivotal role for MCs and MC tryptase in neutrophil migration, lung inflammation and macrophage activation triggered by LPS, by a mechanism dependent on PAR2 activation.

NK Cells Contribute to Protective Memory T Cell Mediated Immunity to Chlamydia muridarum Infection

We previously reported that NK cells can promote type 1 T cell immune response that is essential for protection to a primary infection of Chlamydia muridarum. In this study, we have investigated the contribution of NK cells to memory T cells associated immunity during chlamydial infection. We have found that NK cell depletion led to impaired production of IFN-γ by memory T cells upon re-stimulation with chlamydial antigens in vitro. Mice with depleted NK cells also exhibited reduced type 1 T cell recall responses, with increased production of IL-4 from CD4⁺ T cells and a lower level of Chlamydia-specific IgG2a titers compared to control mice. In addition, Tregs response was significantly increased in mice with NK cell depletion. Moreover, NK cell-depleted mice showed an increased bacterial loads and more severe inflammatory pathological changes than control mice. These findings indicate that NK cells contribute to protective memory T cell associated immunity to chlamydial re-infection through modulating the cytokine pattern of T cell and inhibition of Tregs response.

Critical role for iron accumulation in the pathogenesis of fibrotic lung disease

Increased iron levels and dysregulated iron homeostasis, or both, occur in several lung diseases. Here, the effects of iron accumulation on the pathogenesis of pulmonary fibrosis and associated lung function decline was investigated using a combination of murine models of iron overload and bleomycin-induced pulmonary fibrosis, primary human lung fibroblasts treated with iron, and histological samples from patients with or without idiopathic pulmonary fibrosis (IPF). Iron levels are significantly increased in iron overloaded transferrin receptor 2 (Tfr2) mutant mice and homeostatic iron regulator (Hfe) gene-deficient mice and this is associated with increases in airway fibrosis and reduced lung function. Furthermore, fibrosis and lung function decline are associated with pulmonary iron accumulation in bleomycin-induced pulmonary fibrosis. In addition, we show that iron accumulation is increased in lung sections from patients with IPF and that human lung fibroblasts show greater proliferation and cytokine and extracellular matrix responses when exposed to increased iron levels. Significantly, we show that intranasal treatment with the iron chelator, deferoxamine (DFO), from the time when pulmonary iron levels accumulate, prevents airway fibrosis and decline in lung function in experimental pulmonary fibrosis. Pulmonary fibrosis is associated with an increase in Tfr1⁺ macrophages that display altered phenotype in disease, and DFO treatment modified the abundance of these cells. These experimental and clinical data demonstrate that increased accumulation of pulmonary iron plays a key role in the pathogenesis of pulmonary fibrosis and lung function decline. Furthermore, these data highlight the potential for the therapeutic targeting of increased pulmonary iron in the treatment of fibrotic lung diseases such as IPF. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Assessment of evidence for or against contributions of Chlamydia pneumoniae infections to Alzheimer's disease etiology

Alzheimer's disease, the most common form of dementia, was first formally described in 1907 yet its etiology has remained elusive. Recent proposals that Aβ peptide may be part of the brain immune response have revived longstanding contention about the possibility of causal relationships between brain pathogens and Alzheimer's disease. Research has focused on infectious pathogens that may colonize the brain such as herpes simplex type I. Some researchers have proposed the respiratory bacteria Chlamydia pneumoniae may also be implicated in Alzheimer's disease, however this remains controversial. This review aims to provide a balanced overview of the current evidence and its limitations and future approaches that may resolve controversies. We discuss the evidence from in vitro, animal and human studies proposed to implicate Chlamydia pneumoniae in Alzheimer's disease and other neurological conditions, the potential mechanisms by which the bacterium may contribute to pathogenesis and limitations of previous studies that may explain the inconsistencies in the literature.

Cellular mechanisms underlying steroid-resistant asthma

Severe steroid-resistant asthma is clinically important, as patients with this form of the disease do not respond to mainstay corticosteroid therapies. The heterogeneity of this form of asthma and poor understanding of the pathological mechanisms involved hinder the identification of therapeutic targets and the development of more effective therapies. A major limiting factor in the understanding of severe steroid-resistant asthma is the existence of multiple endotypes represented by different immunological and inflammatory phenotypes, particularly in adults. Several clinical and experimental studies have revealed associations between specific respiratory infections and steroid-resistant asthma in adults. Here, we discuss recent findings from other authors as well as our own studies that have developed novel experimental models for interrogating the association between respiratory infections and severe steroid-resistant asthma. These models have enabled the identification of new therapies using macrolides, as well as several novel disease mechanisms, including the microRNA-21/phosphoinositide 3-kinase/histone deacetylase 2 axis and NLRP3 inflammasomes, and highlight the potential of these mechanisms as therapeutic targets.

Lipopolysaccharide induces steroid-resistant exacerbations in a mouse model of allergic airway disease collectively through IL-13 and pulmonary macrophage activation

BACKGROUND

Acute exacerbations of asthma represent a major burden of disease and are often caused by respiratory infections. Viral infections are recognized as significant triggers of exacerbations; however, less is understood about the how microbial bioproducts such as the endotoxin (lipopolysaccharide (LPS)) trigger episodes. Indeed, increased levels of LPS have been linked to asthma onset, severity and steroid resistance.

OBJECTIVE

The goal of this study was to identify mechanisms underlying bacterial-induced exacerbations by employing LPS as a surrogate for infection.

METHODS

We developed a mouse model of LPS-induced exacerbation on the background of pre-existing type-2 allergic airway disease (AAD).

RESULTS

LPS-induced exacerbation was characterized by steroid-resistant airway hyperresponsiveness (AHR) and an exaggerated inflammatory response distinguished by increased numbers of infiltrating neutrophils/macrophages and elevated production of lung inflammatory cytokines, including TNFα, IFNγ, IL-27 and MCP-1. Expression of the type-2 associated inflammatory factors such as IL-5 and IL-13 were elevated in AAD but not altered by LPS exposure. Furthermore, AHR and airway inflammation were no longer suppressed by corticosteroid (dexamethasone) treatment after LPS exposure. Depletion of pulmonary macrophages by administration of 2-chloroadenosine into the lungs suppressed AHR and reduced IL-13, TNFα and IFNγ expression. Blocking IL-13 function, through either IL-13-deficiency or administration of specific blocking antibodies, also suppressed AHR and airway inflammation.

CONCLUSIONS & CLINICAL RELEVANCE

We present evidence that IL-13 and innate immune pathways (in particular pulmonary macrophages) contribute to LPS-induced exacerbation of pre-existing AAD and provide insight into the complex molecular processes potentially underlying microbial-induced exacerbations.

Microbiome-focused asthma management strategies

Asthma is a common, heterogeneous and serious disease with high prevalence globally. Poorly controlled, steroid-resistant asthma is particularly important as there are no effective therapies and it exerts substantial healthcare and societal burden. The role of microbiomes, particularly in chronic diseases has generated considerable interest in recent times. Existing evidence clearly demonstrates an association between asthma initiation and the microbiome, both respiratory and gastro-intestinal, although its' roles are poorly understood when assessing the asthma progression or heterogeneity (i.e. phenotypes/endotypes) across different geographical locations. Moreover, modulating microbiomes could be preventive and/or therapeutic in patients with asthma warrants urgent attention. Here, we review recent advances in assessing the role of microbiomes in asthma and present the challenges associated with the potential therapeutic utility of modifying microbiomes in management.

IL-22 and its receptors are increased in human and experimental COPD and contribute to pathogenesis

Chronic obstructive pulmonary disease (COPD) is the third leading cause of morbidity and death globally. The lack of effective treatments results from an incomplete understanding of the underlying mechanisms driving COPD pathogenesis.Interleukin (IL)-22 has been implicated in airway inflammation and is increased in COPD patients. However, its roles in the pathogenesis of COPD is poorly understood. Here, we investigated the role of IL-22 in human COPD and in cigarette smoke (CS)-induced experimental COPD.IL-22 and IL-22 receptor mRNA expression and protein levels were increased in COPD patients compared to healthy smoking or non-smoking controls. IL-22 and IL-22 receptor levels were increased in the lungs of mice with experimental COPD compared to controls and the cellular source of IL-22 included CD4+ T-helper cells, γδ T-cells, natural killer T-cells and group 3 innate lymphoid cells. CS-induced pulmonary neutrophils were reduced in IL-22-deficient (Il22 -/-) mice. CS-induced airway remodelling and emphysema-like alveolar enlargement did not occur in Il22 -/- mice. Il22 -/- mice had improved lung function in terms of airway resistance, total lung capacity, inspiratory capacity, forced vital capacity and compliance.These data highlight important roles for IL-22 and its receptors in human COPD and CS-induced experimental COPD.

Lung development and emerging roles for type 2 immunity

Lung development is a complex process mediated through the interaction of multiple cell types, factors and mediators. In mice, it starts as early as embryonic day 9 and continues into early adulthood. The process can be separated into five different developmental stages: embryonic, pseudoglandular, canalicular, saccular, and alveolar. Whilst lung bud formation and branching morphogenesis have been studied extensively, the mechanisms of alveolarisation are incompletely understood. Aberrant lung development can lead to deleterious consequences for respiratory health such as bronchopulmonary dysplasia (BPD), a disease primarily affecting preterm neonates, which is characterised by increased pulmonary inflammation and disturbed alveolarisation. While the deleterious effects of type 1-mediated inflammatory responses on lung development have been well established, the role of type 2 responses in postnatal lung development remains poorly understood. Recent studies indicate that type 2-associated immune cells, such as group 2 innate lymphoid cells and alveolar macrophages, are increased in number during postnatal alveolarisation. Here, we present the current state of understanding of the postnatal stages of lung development and the key cell types and mediators known to be involved. We also provide an overview of how stem cells are involved in lung development and regeneration, and the negative influences of respiratory infections. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Neonatal Streptococcus pneumoniae Pneumonia Induces an Aberrant Airway Smooth Muscle Phenotype and AHR in Mice Model

Our previous study showed that neonatal S. pneumoniae infection aggravated airway inflammation and airway hyperresponsiveness (AHR) in an OVA-induced allergic asthma model. As airway smooth muscle (ASM) plays a pivotal role in AHR development, we aim to investigate the effects of neonatal S. pneumoniae pneumonia on ASM structure and AHR development. Non-lethal neonatal pneumonia was established by intranasally infecting 1-week-old BALB/C mice with the S. pneumoniae strain D39. Five weeks after infection, the lungs were collected to assess the levels of α-SMA and the contractile proteins of ASM. Our results indicate that neonatal S. pneumoniae pneumonia significantly increased adulthood lung α-SMA and SMMHC proteins production and aggravated airway inflammatory cells infiltration and cytokines release. In addition, the neonatal S. pneumoniae pneumonia group had significantly higher Penh values compared to the uninfected controls. These data suggest that neonatal S. pneumoniae pneumonia promoted an aberrant ASM phenotype and AHR development in mice model.

Inhalation of the prodrug PI3K inhibitor CL27c improves lung function in asthma and fibrosis

PI3K activation plays a central role in the development of pulmonary inflammation and tissue remodeling. PI3K inhibitors may thus offer an improved therapeutic opportunity to treat non-resolving lung inflammation but their action is limited by unwanted on-target systemic toxicity. Here we present CL27c, a prodrug pan-PI3K inhibitor designed for local therapy, and investigate whether inhaled CL27c is effective in asthma and pulmonary fibrosis. Mice inhaling CL27c show reduced insulin-evoked Akt phosphorylation in lungs, but no change in other tissues and no increase in blood glycaemia, in line with a local action. In murine models of acute or glucocorticoid-resistant neutrophilic asthma, inhaled CL27c reduces inflammation and improves lung function. Finally, inhaled CL27c administered in a therapeutic setting protects from bleomycin-induced lung fibrosis, ultimately leading to significantly improved survival. Therefore, local delivery of a pan-PI3K inhibitor prodrug reduces systemic on-target side effects but effectively treats asthma and irreversible pulmonary fibrosis.

Activation of PI3K plays a role in pulmonary inflammation. Here, the authors develop a drug inhibitor of PI3K, and show that it inhibits lung inflammation and damage in mouse models of asthma and lung fibrosis.

A standardized herbal extract PM014 ameliorates pulmonary fibrosis by suppressing the TGF-β1 pathway

Idiopathic pulmonary fibrosis (IPF) is a devastating and common chronic lung disease pathologically characterized by loss of epithelial cells and activation of fibroblasts and myofibroblasts. The etiology of IPF remains unclear and the disease pathology is poorly understood with no known efficacious therapy. PM014 is an herbal extract that has been shown to have beneficial effects in pulmonary diseases, which are likely to exert anti-inflammatory bioactions. In the present study, we observed that bleomycin (BLM) caused increased inflammatory infiltration as well as collagen deposition in lungs of mice on day 14 after treatment. Administration of PM014 suppressed BLM-induced inflammatory responses and fibrotic changes in dose-dependent manner in mice. Additionally, we provided in vitro evidence suggesting that PM014 inhibited TGF-β1-induced epithelial-mesenchymal transition (EMT) and fibroblast activation in alveolar epithelial cells and human lung fibroblasts from healthy donor and IPF patients. PM014 appeared to target TGF-β1 signaling via Smad-dependent pathways and p38 mitogen-activated protein kinases (MAPKs) pathways. Taken together, our data suggest that PM014 administration exerts a protective effect against lung fibrosis and highlight PM014 as a viable treatment option that may bring benefits to patient with IPF.