Bronchial lesions of mouse model of asthma are preceded by immune complex vasculitis and induced bronchial associated lymphoid tissue (iBALT)

The contribution of the WNT pathway to the therapeutic effects of montelukast in experimental murine airway inflammation induced by ovalbumin and lipopolysaccharide

The wingless/integrase-1 (WNT) pathway involved in the pathogenesis of inflammatory airway diseases has recently generated considerable research interest. Montelukast, a leukotriene receptor antagonist, provides therapeutic benefits in allergic asthma involving eosinophils. We aimed to investigate the role of the WNT pathway in the therapeutic actions of montelukast (MT) in a mixed type of allergic-acute airway inflammation model induced by ovalbumin (OVA) and lipopolysaccharide (LPS) in mice. Female mice were sensitized with intraperitoneal OVA-Al(OH)3 administration in the initiation phase and intranasal OVA followed by LPS administration in the challenge phase. The mice were divided into eight groups: control, asthmatic, and control/asthmatic treated with XAV939 (inhibitor of the canonical WNT pathway), LGK-974 (inhibitor of the secretion of WNT ligands), or MT at different doses. The inhibition of the WNT pathway prevented tracheal 5-HT and bradykinin hyperreactivity, while only the inhibition of the canonical WNT pathway partially reduced 5-HT and bradykinin contractions compared to the inflammation group. Therefore, MT treatment hindered 5-HT and bradykinin hyperreactivity associated with airway inflammation. Furthermore, MT prevented the increases in the phosphorylated GSK-3β and WNT5A levels, which had been induced by airway inflammation, in a dose-dependent manner. Conversely, the MT application caused a further increase in the fibronectin levels, while there was no significant alteration in the phosphorylation of the Smad-2 levels in the isolated lungs of the mice. The MT treatment reversed the increase in the mRNA expression levels of interleukin-17A. An increase in eosinophil and neutrophil counts was observed in bronchoalveolar lavage fluid samples obtained from the mice in the inflammation group, which was hampered by the MT treatment. The inhibition of the WNT pathway did not alter inflammatory cytokine expression or cell infiltration. The WNT pathway mediated the therapeutic effects of MT due to the inhibition of GSK-3β phosphorylation as well as the reduction of WNT5A levels in a murine airway inflammation model.

Similarities and differences in kinetic characteristics of airways inflammation, formation of inducible bronchial-associated lymphoid tissue and remodeling between young and old murine asthma surrogates induced with house dust mite

Elderly asthmatics have higher morbidity and mortality compared with those of youngers. It has been shown that there are also some differences in clinic phenomena between young and elderly asthmatics, however, there is lack of the kinetic comparisons of the changes in the development of asthma between two populations. To better understand the specific pathophysiological manifestations in older patients with asthma, we dynamically and parallelly compared pathophysiological changes in the airways and lung tissues between young and old murine asthma surrogates based on sensitization and challenge with house dust mite (HDM). Murine models were established in young (6-8-week-old) and old (16-17-month-old) female wild-type C57BL/6 mice. Our data showed that repetitive HDM exposure induced relatively low type 2 immune responses (airway hyperresponsiveness, eosinophils recruitment, expression of type 2 cytokines, mucus secretion, serum HDM specific immunoglobulin E (IgE) and IgG) in old mice. However, the type 3 immune responses (neutrophils infiltration and IL-17A expression) were enhanced in old HDM exposed mice, which sustained longer and higher than that of young mice. Notably, the relatively weakened allergic inflammation characteristics might be associated with lower numbers of CD20⁺ B cells and IgE⁺ cells in the iBALTs in old mice compared with those in young mice. Our data suggest that aging might compromise the ability to induce type 2 immune responses, but enhance type 3 immune responses upon repetitive HDM challenge, which might cause relevant phenomena in old experimental mice and might even be applicable to elderly patients with asthma in the clinic.

Potential stem cell-Conditioned medium and their derived exosomes versus omeprazole in treatment of experimental model of gastric ulcer

Gastric ulcer is a common frequent clinical problem affecting all age and gender. This work aims to compare between the therapeutic effects of stem cell derived exosomes, stem cells conditioned medium and omeprazole on the healing of gastric ulcer model. Fifty rats were, assigned into 5 groups; control, gastric ulcer, omeprazole-treated, conditioned medium- treated, and exosomes-treated groups. Gastric ulcer was induced by aspirin dissolved in 1% carboxymethyl cellulose at a daily dose of 200 mg/kg for 5 consecutive days. Stomach specimens were obtained for histological, biochemical, and immunohistochemical assessments. The gastric ulcer group revealed widening of the fundic glands lumen containing, exfoliated dead cells. There was a remarkable distortion of the normal histological structure of the gastric mucosa with surface lining epithelial cell sloughing, vascular congestion and inflammatory cell infiltration. Both exosomes and conditioned medium treatments ameliorated almost all of the histopathological changes. Interestingly, the healing effect of exosomes was greater because it restored the histological architecture of gastric mucosa to nearly normal. In conclusion, this work may pave the future for using stem cell derived exosomes as a more convenient and effective adjuvant therapy in gastric ulcer.

PRMT5 in T Cells Drives Th17 Responses, Mixed Granulocytic Inflammation, and Severe Allergic Airway Inflammation

Severe asthma is characterized by steroid insensitivity and poor symptom control and is responsible for most asthma-related hospital costs. Therapeutic options remain limited, in part due to limited understanding of mechanisms driving severe asthma. Increased arginine methylation, catalyzed by protein arginine methyltransferases (PRMTs), is increased in human asthmatic lungs. In this study, we show that PRMT5 drives allergic airway inflammation in a mouse model reproducing multiple aspects of human severe asthma. We find that PRMT5 is required in CD4⁺ T cells for chronic steroid-insensitive severe lung inflammation, with selective T cell deletion of PRMT5 robustly suppressing eosinophilic and neutrophilic lung inflammation, pathology, airway remodeling, and hyperresponsiveness. Mechanistically, we observed high pulmonary sterol metabolic activity, retinoic acid-related orphan receptor γt (RORγt), and Th17 responses, with PRMT5-dependent increases in RORγt's agonist desmosterol. Our work demonstrates that T cell PRMT5 drives severe allergic lung inflammation and has potential implications for the pathogenesis and therapeutic targeting of severe asthma.

Corticosteroid insensitivity persists in the absence of STAT1 signaling in severe allergic airway inflammation

Corticosteroid insensitivity in asthma limits the ability to effectively manage severe asthma, which is characterized by persistent airway inflammation, airway hyperresponsiveness (AHR), and airflow obstruction despite corticosteroid treatment. Recent reports indicate that corticosteroid insensitivity is associated with increased interferon-γ (IFN-γ) levels and T-helper (Th) 1 lymphocyte infiltration in severe asthma. Signal transducer and activator of transcription 1 (STAT1) activation by IFN-γ is a key signaling pathway in Th1 inflammation; however, its role in the context of severe allergic airway inflammation and corticosteroid sensitivity remains unclear. In this study, we challenged wild-type (WT) and Stat1^-/- mice with mixed allergens (MA) augmented with c-di-GMP [bis-(3'-5')-cyclic dimeric guanosine monophosphate], an inducer of Th1 cell infiltration with increased eosinophils, neutrophils, Th1, Th2, and Th17 cells. Compared with WT mice, Stat1^-/- had reduced neutrophils, Th1, and Th17 cell infiltration. To evaluate corticosteroid sensitivity, mice were treated with either vehicle, 1 or 3 mg/kg fluticasone propionate (FP). Corticosteroids significantly reduced eosinophil infiltration and cytokine levels in both c-di-GMP + MA-challenged WT and Stat1^-/- mice. However, histological and functional analyses show that corticosteroids did not reduce airway inflammation, epithelial mucous cell abundance, airway smooth muscle mass, and AHR in c-di-GMP + MA-challenged WT or Stat1^-/- mice. Collectively, our data suggest that increased Th1 inflammation is associated with a decrease in corticosteroid sensitivity. However, increased airway pathology and AHR persist in the absence of STAT1 indicate corticosteroid insensitivity in structural airway cells is a STAT1 independent process.

The bronchus-associated-lymphoid tissue (BALT) an unique lymphoid organ in man and animals

The development structure and number of bronchus-associated lymphoid tissue (BALT) will be described in many different animals (like chicken, rabbit, mouse, rat, farm animals and particular the pig, monkey) and these data compared to healthy man and in human diseases. The term induced BALT should not be used because it is a tertiary lymphoid structure, which lacks the contact to a bronchus and does not consist of the important area (dome area) which is essential for antigen uptake of microbial stimuli, which are essential in the development of BALT. Mycoplasma seems to play a critical role as shown in pigs but there not been documented in other species like rabbits. More studies have to be performed in health and disease (e.g. in apes) to document the structural and functional basis to use BALT as an entry site for vaccination protocols.

Tespa1 plays a role in the modulation of airway hyperreactivity through the IL-4/STAT6 pathway

BACKGROUND

Thymocyte-expressed, positive selection-associated 1 (Tespa1) is a critical signaling molecule in thymocyte development. This study aimed to investigate the regulatory effect of Tespa1 on mast cells in the pathogenesis of asthma and its relationship with the interleukin (IL)-4/signal transducers and activators of transcription 6 (STAT6) signaling pathway.

METHODS

Tespa1 mRNA expression analysis and IgE levels were carried out using the induced sputum of 33 adults with stable asthma and 36 healthy controls. Tespa1-knockout mice (Tespa1-/-, KO) and C57BL/6 background (wild-type, WT) mice were sensitized and treated with ovalbumin (OVA) to establish an asthma model. Pathological changes, number and activity of mast cells, and changes in activation of the IL-4/STAT6 pathway in lung tissue were detected. The changes of tryptase expression and STAT6 activation after mast cell gene knockout were analyzed in vitro. The changes of enzyme expression and STAT6 activation after mast cell gene knockout were analyzed in vitro. The association between the Tespa1 and p-STAT6 was analyzed by co-immunoprecipitation method.

RESULTS

Compared with the healthy controls, Tespa1 expression was decreased, and IgE levels were elevated in the sputum of asthmatic patients. Animal experiments showed that Tespa1-/- mice exhibited more severe inflammation, higher quantity of goblet cells and mast cells in the bronchium, and greater expression of mast cell tryptase, which is induced by ovalbumin, than WT mice. And IL-4, IL-13, phospho-Janus kinase 1, and p-STAT6 expressions presented a higher increase in the Tespa1-/- mouse model than in the WT mouse model. Further in vitro studies confirmed that IL-4 could more significantly promote tryptase and p-STAT6 activities in Tespa1-/- mast cells than their WT counterparts. Correlation analysis results showed a negative correlation between Tespa1 and p-STAT6. Co-immunoprecipitation results demonstrated an association between Tespa1 and p-STAT6.

CONCLUSIONS

Altogether, our results indicate that Tespa1 can negatively regulate mast cell activity, and this event is related to the mast cell IL-4/STAT6 signaling pathway and could be therapeutically exploited to treat asthma attacks.

Role of chemical composition and redox modification of poorly soluble nanomaterials on their ability to enhance allergic airway sensitisation in mice

BACKGROUND

Engineered nanoparticles (NPs) have been shown to enhance allergic airways disease in mice. However, the influence of the different physicochemical properties of these particles on their adjuvant properties is largely unknown. Here we investigate the effects of chemical composition and redox activity of poorly soluble NPs on their adjuvant potency in a mouse model of airway hypersensitivity.

RESULTS

NPs of roughly similar sizes with different chemical composition and redox activity, including CeO₂, Zr-doped CeO₂, Co₃O₄, Fe-doped Co₃O₄(using Fe₂O₃ or Fe₃O₄) and TiO₂ NPs, all showed adjuvant activity. OVA induced immune responses following intranasal exposure of BALB/c mice to 0.02% OVA in combination with 200 μg NPs during sensitization (on day 1, 3, 6 and 8) and 0.5% OVA only during challenge (day 22, 23 and 24) were more pronounced compared to the same OVA treatment regime without NPs. Changes in OVA-specific IgE and IgG1 plasma levels, differential cell count and cytokines in bronchoalveolar lavage fluid (BALF), and histopathological detection of mucosa cell metaplasia and eosinophil density in the conducting airways were observed. Adjuvant activity of the CeO₂ NPs was primarily mediated via the Th2 response, while that of the Co₃O₄ NPs was characterised by no or less marked increases in IgE plasma levels, BALF IL-4 and IL-5 concentrations and percentages of eosinophils in BALF and more pronounced increases in BALF IL-6 concentrations and percentages of lymphocytes in BALF. Co-exposure to Co₃O₄ NPs with OVA and subsequent OVA challenge also induced perivascular and peribronchiolar lymphoid cell accumulation and formation of ectopic lymphoid tissue in lungs. Responses to OVA combined with various NPs were not affected by the amount of doping or redox activity of the NPs.

CONCLUSIONS

The findings indicate that chemical composition of NPs influences both the relative potency of NPs to exacerbate allergic airway sensitization and the type of immune response. However, no relation between the acellular redox activity and the observed adjuvant activity of the different NPs was found. Further research is needed to pinpoint the precise physiological properties of NPs and biological mechanisms determining adjuvant activity in order to facilitate a safe-by-design approach to NP development.

Chronic exposure to non-eruptive volcanic activity as cause of bronchiolar histomorphological alteration and inflammation in mice

It is estimated that 10% of the worldwide population lives in the vicinity of an active volcano. However, volcanogenic air pollution studies are still outnumbered when compared with anthropogenic air pollution studies, representing an unknown risk to human populations inhabiting volcanic areas worldwide. This study was carried out in the Azorean archipelago of Portugal, in areas with active non-eruptive volcanism. The hydrothermal emissions within the volcanic complex of Furnas (São Miguel Island) are responsible for the emission of nearly 1000 tons of CO₂ per day, along with H₂S, the radioactive gas - radon, among others. Besides the gaseous emissions, metals (e.g., Hg, Cd, Al, Ni) and particulate matter are also released into the environment. We test the hypothesis that chronic exposure to volcanogenic air pollution alters the histomorphology of the bronchioles and terminal bronchioles, using the house mouse, Mus musculus, as bioindicator species. Mus musculus were live-captured at three different locations: two villages with active volcanism and a village without any type of volcanic activity (reference site). The histomorphology of the bronchioles (diameter, epithelium thickness, smooth muscle layer thickness, submucosa thickness and the histological evaluation of the peribronchiolar inflammation) and of the terminal bronchioles (epithelium thickness and classification) were evaluated. Mice chronically exposed to volcanogenic air pollution presented bronchioles with increased epithelial thickness, increased smooth muscle layer, increased submucosa thickness and increased peribronchiolar inflammation. Similarly, terminal bronchioles presented structural alterations consistent with bronchodysplasia. For the first time we demonstrate that chronic exposure to non-eruptive volcanically active environments causes inflammation and histomorphological alterations in mice lower airways consistent with asthma and chronic bronchitis. These results reveal that chronic exposure to non-eruptive volcanic activity represents a risk factor that can affect the health of the respiratory system of humans inhabiting hydrothermal areas.

Immunological association of inducible bronchus-associated lymphoid tissue organogenesis in Ag85B-rHPIV2 vaccine-induced anti-tuberculosis mucosal immune responses in mice

We previously reported that Ag85B-expressing human parainfluenza type 2 virus (Ag85B-rHPIV2) was effective as a nasal vaccine against tuberculosis in mice; however, the mechanism by which it induces an immune response remains to be investigated. In the present study, we found that organogenesis of inducible bronchus-associated lymphoid tissue (iBALT) played a role in the induction of antigen-specific T cells and IgA antibody responses in the lung of mice intra-nasally administered Ag85B-rHPIV2. We found that expression of Ag85B was dispensable for the development of iBALT, suggesting that HPIV2 acted as an iBALT-inducing vector. When iBALT organogenesis was disrupted in Ag85B-rHPIV2-immunized mice, either by neutralization of the lymphotoxin pathway or depletion of CD11b⁺ cells, Ag85B-specific immune responses (i.e. IFN γ-producing T cells and IgA antibody) were diminished in the lung. Furthermore, we found that immunization with Ag85B-rHPIV2 induced neutrophil and eosinophil infiltration temporally after the immunization in the lung. Thus, our results show that iBALT organogenesis contributes to the induction of antigen-specific immune responses by Ag85B-rHPIV2 and that Ag85B-rHPIV2 provokes its immune responses without inducing long-lasting inflammation.

Role of iBALT in Respiratory Immunity

Pulmonary respiration inevitably exposes the mucosal surface of the lung to potentially noxious stimuli, including pathogens, allergens, and particulates, each of which can trigger pulmonary damage and inflammation. As inflammation resolves, B and T lymphocytes often aggregate around large bronchi to form inducible Bronchus-Associated Lymphoid Tissue (iBALT). iBALT formation can be initiated by a diverse array of molecular pathways that converge on the activation and differentiation of chemokine-expressing stromal cells that serve as the scaffolding for iBALT and facilitate the recruitment, retention, and organization of leukocytes. Like conventional lymphoid organs, iBALT recruits naïve lymphocytes from the blood, exposes them to local antigens, in this case from the airways, and supports their activation and differentiation into effector cells. The activity of iBALT is demonstrably beneficial for the clearance of respiratory pathogens; however, it is less clear whether it dampens or exacerbates inflammatory responses to non-infectious agents. Here, we review the evidence regarding the role of iBALT in pulmonary immunity and propose that the final outcome depends on the context of the disease.

Impaired airway mucociliary function reduces antigen-specific IgA immune response to immunization with a claudin-4-targeting nasal vaccine in mice

Vaccine delivery is an essential element for the development of mucosal vaccine, but it remains to be investigated how physical barriers such as mucus and cilia affect vaccine delivery efficacy. Previously, we reported that C-terminal fragment of Clostridium perfringens enterotoxin (C-CPE) targeted claudin-4, which is expressed by the epithelium associated with nasopharynx-associated lymphoid tissue (NALT), and could be effective as a nasal vaccine delivery. Mice lacking tubulin tyrosine ligase-like family, member 1 (Ttll1-KO mice) showed mucus accumulation in nasal cavity due to the impaired motility of respiratory cilia. Ttll1-KO mice nasally immunized with C-CPE fused to pneumococcal surface protein A (PspA-C-CPE) showed reduced PspA-specific nasal IgA responses, impaired germinal center formation, and decreased germinal center B-cells and follicular helper T cells in the NALT. Although there was no change in the expression of claudin-4 in the NALT epithelium in Ttll1-KO mice, the epithelium was covered by a dense mucus that prevented the binding of PspA-C-CPE to NALT. However, administration of expectorant N-acetylcysteine removed the mucus and rescued the PspA-specific nasal IgA response. These results show that the accumulation of mucus caused by impaired respiratory cilia function is an interfering factor in the C-CPE-based claudin-4-targeting nasal vaccine.

Sentinels of the Type 2 Immune Response

Type 2 immune responses have evolved to sense and respond to large, non-replicating infections or non-microbial noxious compounds in tissues. The development of these responses therefore depends upon highly coordinated and tightly regulated tissue-residing cellular sensors and responders. Multiple exposure to type 2 helper T cell (Th2)-inducing stimuli further enhances both the diversity and potency of the response. This review discusses advances in our understanding of the interacting cellular subsets that comprise both primary and secondary type 2 responses. Current knowledge regarding type 2 immune responses in the lung are initially presented and are then contrasted with what is known about the small intestine. The studies described portray an immune response that depends upon well-organized tissue structures, and suggest their modulation as a therapeutic strategy.

Blomia tropicalis-Specific TCR Transgenic Th2 Cells Induce Inducible BALT and Severe Asthma in Mice by an IL-4/IL-13-Dependent Mechanism

Previous studies have highlighted the importance of lung-draining lymph nodes in the respiratory allergic immune response, whereas the lung parenchymal immune system has been largely neglected. We describe a new in vivo model of respiratory sensitization to Blomia tropicalis, the principal asthma allergen in the tropics, in which the immune response is focused on the lung parenchyma by transfer of Th2 cells from a novel TCR transgenic mouse, specific for the major B. tropicalis allergen Blo t 5, that targets the lung rather than the draining lymph nodes. Transfer of highly polarized transgenic CD4 effector Th2 cells, termed BT-II, followed by repeated inhalation of Blo t 5 expands these cells in the lung >100-fold, and subsequent Blo t 5 challenge induced decreased body temperature, reduction in movement, and a fall in specific lung compliance unseen in conventional mouse asthma models following a physiological allergen challenge. These mice exhibit lung eosinophilia; smooth muscle cell, collagen, and goblet cell hyperplasia; hyper IgE syndrome; mucus plugging; and extensive inducible BALT. In addition, there is a fall in total lung volume and forced expiratory volume at 100 ms. These pathophysiological changes were substantially reduced and, in some cases, completely abolished by administration of neutralizing mAbs specific for IL-4 and IL-13 on weeks 1, 2, and 3. This IL-4/IL-13-dependent inducible BALT model will be useful for investigating the pathophysiological mechanisms that underlie asthma and the development of more effective drugs for treating severe asthma.

Isolation of vascular smooth muscle antigen-reactive CD4(+)αβTh1 clones that induce pulmonary vasculitis in MRL/Mp-Fas(+/+) mice

Here, we established CD4(+)αβTh1 clones specific for rat vascular smooth muscle antigen (VSMAg) that induced vasculitis lesions in the lungs of MRL/Mp-Fas(+/+) mice following adoptive transfer. Six different T cell clones, MV1b1 (Vβ1), MV1b4 (Vβ4), MV1b8.3 (Vβ8.3), MV1b61 (Vβ6), MV1b62 (Vβ6), and MV1b63 (Vβ6), were isolated from the MV1 T cell line from the regional lymph nodes of immunized MRL/Mp-Fas(+/+) mice; the three (Vβ6) clones had unique CDR3 amino acid sequences. Following stimulation with VSMAg-pulsed antigen presenting cells, MV1b61 and MV1b62 failed to secrete interferon-γ and tumor necrosis factor-α, although the other four clones secreted high levels of both cytokines. In adoptive transfer experiments, MV1b61 and MV1b62 did not induce organ involvement including pulmonary vasculitis. In contrast, MV1b1, MV1b4, MV1b8.3, and MV1b63 induced perivascular mononuclear cell infiltration in pulmonary small arteries. These clones may provide useful tools for investigating the underlying mechanisms of vasculitis syndromes and for developing therapeutic strategies.

Immunopathology of Experimental Models of Syphilis, Influenza, and Asthma

The introduction of immunopathologic reaction classification in the 1960s led to a major advance in understanding immune effector mechanisms and how lesions of immunopathologic diseases developed. In this article, immunopathologic mechanisms are presented for experimental models of syphilis, influenza, and asthma. The chancre of syphilis is a delayed hypersensitivity skin reaction that is initiated by sensitized T cells that activate macrophages to phagocytose and kill the infecting organism, Treponema pallidum, in interstitial tissues. The primary immune effector mechanism in experimental influenza is T-cell-mediated cytotoxicity that kills infected epithelial cells, bronchial lining cells, and Type-II pneumocytes, in a manner similar to viral exanthema. The bronchial lesions of the experimental model of asthma in mice are preceded by an immune complex vasculitis and not an immunoglobulin E-mediated mast cell mechanism.