Dynamics of IL-4 and IL-13 expression in the airways of sheep following allergen challenge

Evaluation of a translational swine model of respiratory hypersensitivity induced by exposure to Phleum pratense pollen allergens

Introduction

Asthma is a disease characterized by chronic inflammation of the airway mucosa that causes tissue remodeling and a reversible decrease in airflow. The causative agent of asthma is still unknown; however, several studies have shown that environmental factors such as allergens present in pollens are involved. This project's objective was to develop and evaluate a model of respiratory hypersensitivity in Vietnamese minipigs, which is closer in many aspects to humans than rodents, using Phleum pratense allergenic pollen extract.

Methods

In this hypersensitivity model, human-like signs were observed during a challenge with the allergens. Intradermal and passive anaphylaxis tests confirmed that specific IgE mediated the response.

Results

Significant changes in lung tissue remodeling, high levels of serum allergen-specific IgA, IgG, and to a lesser extent IgE were found in the sensitized pigs, which could favor tolerance and pathogenesis. However, since chronic pathology did not develop, elevated levels of cytokines were not proven.

Discussion

This work demonstrated that the immunization protocol in this experimental model can induce a type I respiratory hypersensitivity-like response mediated by antigen-specific IgE, with pathophysiological similarities to those of humans and prospective for translational basic and applied research.

Lipidomic profiling of amniotic fluid reveals aberrant fetal lung development and fetal growth disrupted by lipid disorders during gestational asthma

This study aimed to investigate how maternal asthma during pregnancy disrupts fetal lung development by altering lipid metabolism in the amniotic fluid, which is crucial for fetal development. A pregnancy-induced asthma model was established in female rats using house dust mite (HDM) as a common allergen. The fetuses were divided into four groups based on whether the mother and fetus were exposed to the allergen: PBS+PBS, PBS+HDM, HDM+PBS, and HDM+HDM. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was employed to analyze changes in the lipid profile of the amniotic fluid and bronchoalveolar lavage fluid (BALF). Principal component analysis (PCA) and ChemRICH methods were used to explore the potential relationship between lipid metabolism abnormalities and impaired fetal lung development. The results indicate that maternal asthma exacerbates asthma-related inflammatory markers in fetuses, leading to pathological changes in the lungs and elevated levels of cytokines IL-5, IL-13, and IgE. Additionally, 18 differential lipids, primarily oxygenated lipids, were identified in the amniotic fluid after modeling, suggesting an enhanced oxidative stress environment for the fetus. This environment causes metabolic disturbances in various lipid groups in fetal lungs, with the HDM+HDM group showing significant abnormalities in lipids critical for lung development, including phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and fatty acids (FA). In conclusion, gestational asthma can reshape the lipid profile in the amniotic fluid and BALF, significantly disrupting fetal growth and lung development. Restoring normal lipid metabolism in the amniotic fluid and fetal lungs may offer a potential therapeutic approach to managing aberrant fetal lung development in asthmatic mothers.

Angiotensinergic effect of β-Caryophyllene on Lipopolysaccharide- induced systemic inflammation

Renin-Angiotensin System (RAS) is a peptidergic system, canonically known for its role in blood pressure regulation. Furthermore, a non-canonical RAS regulates pathophysiological phenomena, such as inflammation since it consists of two main axes: the pro-inflammatory renin/(pro)renin receptor ((P)RR) axis, and the anti-inflammatory angiotensin-converting enzyme 2 (ACE2)/Angiotensin-(1-7) (Ang-(1-7))/Mas Receptor (MasR) axis. Few phytochemicals have shown to exert angiotensinergic and anti-inflammatory effects through some of these axes; nevertheless, anti-inflammatory drugs, such as phytocannabinoids have not been studied regarding this subject. Among phytocannabinoids, β-Caryophyllene stands out as a dietary phytocannabinoid with antiphlogistic activity that possess a unique sesquiterpenoid structure. Although its cannabinergic effect has been studied, its angiotensinergic effect reminds underexplored. This study aims to explore the angiotensinergic effect of β-Caryophyllene on inflammation and stress at a systemic level. After intranasal Lipopolysaccharide (LPS) installation and oral treatment with β-Caryophyllene, the concentration and activity of key RAS elements in the serum, such as Renin, ACE2 and Ang-(1-7), along with the stress hormone corticosterone and pro/anti-inflammatory cytokines, were measured in mice serum. The results show that β-Caryophyllene treatment modified RAS levels by increasing Renin and Ang-(1-7), alongside the reduction of pro-inflammatory cytokines and corticosterone levels. These results indicate that β-Caryophyllene exhibits angiotensinergic activity in favor of anti-inflammation.

Asthma: The Use of Animal Models and Their Translational Utility

Asthma is characterized by chronic lower airway inflammation that results in airway remodeling, which can lead to a permanent decrease in lung function. The pathophysiology driving the development of asthma is complex and heterogenous. Animal models have been and continue to be essential for the discovery of molecular pathways driving the pathophysiology of asthma and novel therapeutic approaches. Animal models of asthma may be induced or naturally occurring. Species used to study asthma include mouse, rat, guinea pig, cat, dog, sheep, horse, and nonhuman primate. Some of the aspects to consider when evaluating any of these asthma models are cost, labor, reagent availability, regulatory burden, relevance to natural disease in humans, type of lower airway inflammation, biological samples available for testing, and ultimately whether the model can answer the research question(s). This review aims to discuss the animal models most available for asthma investigation, with an emphasis on describing the inciting antigen/allergen, inflammatory response induced, and its translation to human asthma.

KCa3.1 differentially regulates trachea and bronchi epithelial gene expression in a chronic-asthma mouse model

Ion channels are potentially exploitable as pharmacological targets to treat asthma. This study evaluated the role of KCa3.1 channels, encoded by Kcnn4, in regulating the gene expression of mouse airway epithelium and the development of asthma traits. We used the ovalbumin (OVA) challenge as an asthma model in wild type and Kcnn4^-/- mice, performed histological analysis, and measured serum IgE to evaluate asthma traits. We analyzed gene expression of isolated epithelial cells of trachea or bronchi using mRNA sequencing and gene ontology and performed Ussing chamber experiments in mouse trachea to evaluate anion secretion. Gene expression of epithelial cells from mouse airways differed between trachea and bronchi, indicating regional differences in the inflammatory and transepithelial transport properties of proximal and distal airways. We found that Kcnn4 silencing reduced mast cell numbers, mucus, and collagen in the airways, and reduced the amount of epithelial anion secretion in the OVA-challenged animals. Additionally, gene expression was differentially modified in the trachea and bronchi, with Kcnn4 genetic silencing significantly altering the expression of genes involved in the TNF pathway, supporting the potential of KCa3.1 as a therapeutic target for asthma.

Aberrant Th2 Immune Responses Are Associated With a Reduced Frequency of IL-35-Induced Regulatory T Cells After Allergen Exposure in Patients With Allergic Asthma

PURPOSE

Allergen exposure induces aberrant T helper (Th) 2 immune responses in patients with allergic asthma, but not in sensitized asymptomatic and nonallergic subjects. Interleukin (IL)-35-induced regulatory T (iTr35) cells are a new subset of regulatory T cells with immunoregulatory properties. These cells can significantly suppress Th2 responses in seasonal allergic rhinitis. However, it remains unknown whether iTr35 cells are involved in the immunoregulation of allergic asthmatic individuals after specific allergen exposure.

METHODS

The iTr35 cell frequency in peripheral blood mononuclear cells (PBMCs) was measured in patients with allergic asthma as well as in asymptomatic and healthy subjects. The difference in naïve CD4⁺ T cell conversion to iTr35 cells in vitro during allergen stimulation was also investigated. The effects of iTr35 cells on naïve CD4⁺ T cell differentiation into Th2 cells, CD4⁺CD25^- T (Teff) cell proliferation and Th2 cytokine production in vitro were assessed.

RESULTS

Significantly reduced iTr35 cell frequencies and IL-35 expression levels were found in asthmatic patients with Derp1 allergy compared with asymptomatic and healthy subjects. Moreover, the circulating iTr35 cell proportion and IL-35 expression level in asthmatic patients gradually decreased with disease severity. Patients with allergic asthma had reduced transformation of naïve CD4⁺ T cells into iTr35 cells and IL-35 production after allergen exposure compared with asymptomatic and healthy subjects. Most importantly, iTr35 cells inhibited allergen-driven differentiation of naïve CD4⁺ T cells into Th2 cells, Teff cell proliferation and Th2 cytokine production in an IL-35-dependent manner.

CONCLUSIONS

The results of our study suggest that iTr35 cells may play an important role in preventing Th2 responses to allergens by secreting IL-35 and that iTr35 cells may be a potential new immune regulator of allergic asthma.

Serum levels of epithelial-derived mediators and interleukin-4/interleukin-13 signaling after bronchial challenge with Dermatophagoides pteronyssinus in patients with allergic asthma

Allergens are the main trigger that enhances airway type 2 inflammation, and the epithelium is the first line of defense that reacts to its exposure. Therefore, epithelial-derived mediators, such as interleukin (IL)-25, IL-33, thymic stromal lymphopoietin (TSLP) and ezrin, may play a role as alarmins in IL-4/IL-13 signaling in allergic asthma (AA). We investigated the serum levels of IL-25, IL-33, TSLP, ezrin, IL-4 and IL-13, after bronchial challenge with Dermatophagoides pteronyssinus in patients with AA. We examined 18 subjects: nine steroid-free stable patients with AA sensitized to D. pteronyssinus and nine non-atopic healthy subjects (HS). Bronchial allergen challenge was performed using inhaled D. pteronyssinus allergen. IL-4, IL-13, IL-25, IL-33, TSLP and ezrin levels in serum were measured by ELISA at two time points - before and 24 hours after bronchial allergen challenge. The serum levels of IL-25, TSLP and ezrin did not differ between AA and HS groups at baseline. However, after allergen exposure, significant increases in serum levels of IL-25, TSLP and ezrin were observed only in patients with AA. The serum level of IL-33 at baseline was significantly higher in the AA group compared with HS, but the allergen challenge did not provoke an increase of this cytokine in any group. IL-4 and IL-13 levels were significantly higher at baseline in the AA group compared with HS and, after allergen exposure, were significantly increased in the AA group, with no effect on HS. Thus, the epithelial-derived mediators IL-25, TSLP and ezrin, via IL4/IL13 signaling, enhance type 2 inflammation after bronchial challenge with D. pteronyssinus in AA.

Maternal allergic asthma during pregnancy alters fetal lung and immune development in sheep: potential mechanisms for programming asthma and allergy

KEY POINTS

Experimental maternal allergic asthma in sheep provides an experimental model in which to test impacts on progeny. Fetuses from allergic asthmatic ewes had fewer surfactant-producing cells in lungs. A greater proportion of lymphocytes from thymus were CD44 positive in fetuses from allergic asthmatic ewes than in controls. These changes to fetal development might contribute to poor neonatal lung function and increased risk of allergy seen in offspring of pregnancies complicated by asthma.

ABSTRACT

Asthma is prevalent in pregnancy and increases the risk of disease in offspring, including neonatal respiratory distress and childhood asthma and allergy, but the mechanisms are not understood. We hypothesized that fetal lung structure and immune phenotype in late gestation fetal sheep would be impaired in our sheep model of maternal allergic asthma during pregnancy. Singleton-bearing ewes were either sensitized before pregnancy to house dust mite (HDM, allergic, n = 7) or were non-allergic (control, n = 5). The ewes were subsequently subjected to repeated airway challenges with HDM (allergic group) or saline (control group) throughout gestation. Tissues were collected at 140 ± 1 days gestational age (term, ∼147 days). The density of type II alveolar epithelial cells (surfactant protein C-immunostained) in the lungs was 30% lower in fetuses from allergic ewes than in controls (P < 0.001), but tissue-to-air space ratio and numbers of leucocytes and macrophages were not different between groups. The proportion of CD44⁺ lymphocytes in the fetal thymus was 3.5-fold higher in fetuses from allergic ewes than in control ewes (P = 0.043). Fewer surfactant-producing type II alveolar epithelial cells may contribute to the increased risk of neonatal respiratory distress in infants of asthmatic mothers, suggesting that interventions to promote lung maturation could improve their neonatal outcomes. If the elevated lymphocyte expression of CD44 persists postnatally, this would confer greater susceptibility to allergic diseases in progeny of asthmatic mothers, consistent with observations in humans. Further experiments are needed to evaluate postnatal phenotypes of progeny and investigate potential interventions.

Preterm umbilical cord blood derived mesenchymal stem/stromal cells protect preterm white matter brain development against hypoxia-ischemia

INTRODUCTION

Preterm infants are at high risk for white matter injury and subsequent neurodevelopmental impairments. Mesenchymal stem/stromal cells (MSC) have anti-inflammatory/immunomodulatory actions and are of interest for neural repair in adults and newborns. This study examined the neuroprotective effects of allogeneic MSC, derived from preterm umbilical cord blood (UCB), in a preterm sheep model of white matter injury.

METHODS

Quad-lineage differentiation, clonogenicity and self-renewal ability of UCB-derived MSC were confirmed. Chronically instrumented fetal sheep (0.7 gestation) received either 25 min hypoxia-ischemia (HI) to induce preterm brain injury, or sham-HI. Ten million MSC, or saline, were administered iv to fetuses at 12 h after HI. Fetal brains were collected 10d after HI for histopathology and immunocytochemistry.

RESULTS

HI induced white matter injury, as indicated by a reduction in CNPase-positive myelin fiber density. HI also induced microglial activation (Iba-1) in the periventricular white matter and internal capsule (P < .05 vs control). MSC administration following HI preserved myelination (P < .05), modified microglial activation, and promoted macrophage migration (CD163) and cell proliferation (Ki-67) within cerebral white matter (P < .05). Cerebral CXCL10 concentration was increased following MSC administration (P < .05), which was likely associated with macrophage migration and cell proliferation within the preterm brain. Additionally, MSC administration reduced systemic pro-inflammatory cytokine TNFα at 3d post-HI (P < .05).

CONCLUSIONS

UCB-derived MSC therapy preserved white matter brain structure following preterm HI, mediated by a suppression of microglial activation, promotion of macrophage migration and acceleration of self-repair within the preterm brain. UCB-derived MSC are neuroprotective, acting via peripheral and cerebral anti-inflammatory and immunomodulatory mechanisms.

Lymphatic cannulation models in sheep: Recent advances for immunological and biomedical research

Lymphatic cannulation models are useful tools for studying the immunobiology of the lymphatic system and the immunopathology of specific tissues in diseases. Sheep cannulations have been used extensively, as models for human physiology, fetal and neonatal development, human diseases, and for studies of ruminant pathobiology. The development of new and improved cannulation techniques in recent years has meant that difficult to access sites, such as mucosal associated tissues, are now more readily available to researchers. This review highlights the new approaches to cannulation and how these, in combination with advanced omics technologies, will direct future research using the sheep model.

Animal models of asthma: utility and limitations

Clinical studies in asthma are not able to clear up all aspects of disease pathophysiology. Animal models have been developed to better understand these mechanisms and to evaluate both safety and efficacy of therapies before starting clinical trials. Several species of animals have been used in experimental models of asthma, such as Drosophila, rats, guinea pigs, cats, dogs, pigs, primates and equines. However, the most common species studied in the last two decades is mice, particularly BALB/c. Animal models of asthma try to mimic the pathophysiology of human disease. They classically include two phases: sensitization and challenge. Sensitization is traditionally performed by intraperitoneal and subcutaneous routes, but intranasal instillation of allergens has been increasingly used because human asthma is induced by inhalation of allergens. Challenges with allergens are performed through aerosol, intranasal or intratracheal instillation. However, few studies have compared different routes of sensitization and challenge. The causative allergen is another important issue in developing a good animal model. Despite being more traditional and leading to intense inflammation, ovalbumin has been replaced by aeroallergens, such as house dust mites, to use the allergens that cause human disease. Finally, researchers should define outcomes to be evaluated, such as serum-specific antibodies, airway hyperresponsiveness, inflammation and remodeling. The present review analyzes the animal models of asthma, assessing differences between species, allergens and routes of allergen administration.

Exacerbation of Ventilation-Induced Lung Injury and Inflammation in Preterm Lambs by High-Dose Nanoparticles

Mechanical ventilation of preterm neonates causes lung inflammation and injury, with potential life-long consequences. Inert 50-nm polystyrene nanoparticles (PS50G) reduce allergic inflammation in the lungs of adult mice. We aimed to confirm the anti-inflammatory effects of PS50G in a sheep asthma model, and investigate the effects of prophylactic administration of PS50G on ventilation-induced lung injury (VILI) in preterm lambs. We assessed lung inflammatory cell infiltration, with and without PS50G, after airway allergen challenge in ewes sensitised to house dust mite. Preterm lambs (0.83 gestation) were delivered by caesarean section for immediate tissue collection (n = 5) or ventilation either with (n = 6) or without (n = 5) prophylactic intra-tracheal administration of PS50G nanoparticles (3% in 2 ml). Ventilation was continued for a total of 2 h before tissue collection for histological and biomolecular assessment of lung injury and inflammation. In ewes with experimental asthma, PS50G decreased eosinophilic infiltration of the lungs. Ventilated preterm lambs showed molecular and histological signs of lung injury and inflammation, which were exacerbated in lambs that received PSG50G. PS50G treatment decreased established inflammation in the lungs of asthmatic sheep. However, prophylactic administration of PSG50 exacerbated ventilation-induced lung injury and lung inflammation in preterm lambs.

Interleukins and large domestic animals, a bibliometric analysis

Interleukins have been well described in mice and humans. In large domestic animals the situation is drastically different and there is still a need for further researches aiming at identifying all the homologous interleukins and comparing their functions among species. We performed here a bibliometric analysis of all interleukins described in the literature in various large animal species to identify what is known so far and to underline where there is a need for new studies. Using indicators such as H index but also M quotient, A index, G index, GH ratio, and HG index we ranked 39 interleukins identified so far in bovine, caprine, equine, ovine, and porcine, the main large domestic animals. Indexes and ratio under investigations were higher for IL1, IL2, IL4, IL5, IL6, IL8, IL10, IL12, and IL18 than for other interleukins, particularly in bovine and porcine species and to a certain extent in equine species. Recently discovered interleukins presented low values for the different indexes, quotient, and ratio. Even some “old” interleukins showed low values highlighting the need for further developments in comparative immunology. For instance an interleukin such as IL4 demonstrated variation in its functions between species. In conclusion, this study provides the first bibliometric analysis dedicated to large domestic animal interleukins and underlines the need for more studies to fully determine the structure and the functions of interleukins in other mammal species.

Human amnion epithelial cells modulate the inflammatory response to ventilation in preterm lambs

Ventilation of preterm neonates causes pulmonary inflammation that can contribute to lung injury, propagate systemically and result in long-term disease. Modulation of this initial response may reduce lung injury and its sequelae. We aimed to determine the effect of human amnion epithelial cells (hAECs) on immune activation and lung injury in preterm neonatal lambs. Preterm lambs received intratracheal hAECs (90x106) or vehicle, prior to 2 h of mechanical ventilation. Within 5 min of ventilation onset, lambs also received intravenous hAECs (90x106) or vehicle. Lung histology, bronchoalveolar lavage (BAL) cell phenotypes, and cytokine profiles were examined after 2 h of ventilation, and in unventilated controls. Histological indices of lung injury were higher than control, in vehicle-treated ventilated lambs but not in hAEC-treated ventilated lambs. Ventilation-induced pulmonary leukocyte recruitment was greater in hAEC-treated lambs than in vehicle-treated lambs. Lung IL-1β and IL-6 mRNA expression was higher in vehicle- and hAEC-treated ventilated lambs than in controls but IL-8 mRNA levels were greater than control only in vehicle-treated ventilated lambs. Numbers of CD44+ and CD21+ lymphocytes and macrophages from the lungs were altered in vehicle- and hAEC-treated ventilated lambs. Numbers of CD8+ macrophages were lower in hAEC-treated ventilated lambs than in vehicle-treated ventilated lambs. Indices of systemic inflammation were not different between vehicle- and hAEC-treated lambs. Human amnion epithelial cells modulate the pulmonary inflammatory response to ventilation in preterm lambs, and reduce acute lung injury. Immunomodulatory effects of hAECs reduce lung injury in preterm neonates and may protect against longer-term respiratory disease.

Preterm white matter brain injury is prevented by early administration of umbilical cord blood cells

Infants born very preterm are at high risk for neurological deficits including cerebral palsy. In this study we assessed the neuroprotective effects of umbilical cord blood cells (UCBCs) and optimal administration timing in a fetal sheep model of preterm brain injury. 50 million allogeneic UCBCs were intravenously administered to fetal sheep (0.7 gestation) at 12h or 5d after acute hypoxia-ischemia (HI) induced by umbilical cord occlusion. The fetal brains were collected at 10d after HI. HI (n=7) was associated with reduced number of oligodendrocytes (Olig2+) and myelin density (CNPase+), and increased density of activated microglia (Iba-1+) in cerebral white matter compared to control fetuses (P<0.05). UCBCs administered at 12h, but not 5d after HI, significantly protected white matter structures and suppressed cerebral inflammation. Activated microglial density showed a correlation with decreasing oligodendrocyte number (P<0.001). HI caused cell death (TUNEL+) in the internal capsule and cell proliferation (Ki-67+) in the subventricular zone compared to control (P<0.05), while UCBCs at 12h or 5d ameliorated these effects. Additionally, UCBCs at 12h induced a significant systemic increase in interleukin-10 at 10d, and reduced oxidative stress (malondialdehyde) following HI (P<0.05). UCBC administration at 12h after HI reduces preterm white matter injury, via anti-inflammatory and antioxidant actions.

Variability of the Sheep Lung Microbiota

Sequencing technologies have recently facilitated the characterization of bacterial communities present in lungs during health and disease. However, there is currently a dearth of information concerning the variability of such data in health both between and within subjects. This study seeks to examine such variability using healthy adult sheep as our model system. Protected specimen brush samples were collected from three spatially disparate segmental bronchi of six adult sheep (age, 20 months) on three occasions (day 0, 1 month, and 3 months). To further explore the spatial variability of the microbiotas, more-extensive brushing samples (n = 16) and a throat swab were taken from a separate sheep. The V2 and V3 hypervariable regions of the bacterial 16S rRNA genes were amplified and sequenced via Illumina MiSeq. DNA sequences were analyzed using the mothur software package. Quantitative PCR was performed to quantify total bacterial DNA. Some sheep lungs contained dramatically different bacterial communities at different sampling sites, whereas in others, airway microbiotas appeared similar across the lung. In our spatial variability study, we observed clustering related to the depth within the lung from which samples were taken. Lung depth refers to increasing distance from the glottis, progressing in a caudal direction. We conclude that both host influence and local factors have impacts on the composition of the sheep lung microbiota.

IMPORTANCE

Until recently, it was assumed that the lungs were a sterile environment which was colonized by microbes only during disease. However, recent studies using sequencing technologies have found that there is a small population of bacteria which exists in the lung during health, referred to as the "lung microbiota." In this study, we characterize the variability of the lung microbiotas of healthy sheep. Sheep not only are economically important animals but also are often used as large animal models of human respiratory disease. We conclude that, while host influence does play a role in dictating the types of microbes which colonize the airways, it is clear that local factors also play an important role in this regard. Understanding the nature and influence of these factors will be key to understanding the variability in, and functional relevance of, the lung microbiota.