LPS exacerbates functional and inflammatory responses to ovalbumin and decreases sensitivity to inhaled fluticasone propionate in a guinea pig model of asthma

Endotoxin Is Inactivated by Ethylene Oxide, Gamma, Electron Beam, and Steam Sterilization

The effect of sterilization on bacterial endotoxin is receiving greater attention within the medical device industry. Contributing factors to this increased attention include the growing popularity of transferring devices among sterilization modalities and the focus on aspects of microbiological quality other than sterilization. This systematic review examined the effects of sterilization on bacterial endotoxin, with attention drawn to industry standards and regulations to elucidate whether such documents are aligned with published data. In summary, numerous experiments have shown a reduction in pyrogenicity and/or limulus amebocyte lysate reactivity of endotoxin following sterilization, whereas a number of publications and industry standards have claimed (without data or references) that sterilization does not inactivate endotoxin. The results of this review would be useful for device manufacturers when selecting a sterilization modality or deciding whether to test for endotoxin pre- vs poststerilization, as well as for standards developers and regulators in aligning standards and regulations with peer-reviewed data.

Neutrophil activation and NETosis are the predominant drivers of airway inflammation in an OVA/CFA/LPS induced murine model

Background

Asthma is one of the most common chronic diseases that affects more than 300 million people worldwide. Though most asthma can be well controlled, individuals with severe asthma experience recurrent exacerbations and impose a substantial economic burden on healthcare system. Neutrophil inflammation often occurs in patients with severe asthma who have poor response to glucocorticoids, increasing the difficulty of clinical treatment.

Methods

We established several neutrophil-dominated allergic asthma mouse models, and analyzed the airway hyperresponsiveness, airway inflammation and lung pathological changes. Neutrophil extracellular traps (NETs) formation was analyzed using confocal microscopy and western blot.

Results

We found that the ovalbumin (OVA)/complete Freund’s adjuvant (CFA)/low-dose lipopolysaccharide (LPS)-induced mouse model best recapitulated the complex alterations in the airways of human severe asthmatic patients. We also observed OVA/CFA/LPS-exposed mice produced large quantities of neutrophil extracellular traps (NETs) in lung tissue and bone marrow neutrophils. Furthermore, we found that reducing the production of NETs or increasing the degradation of NETs can reduce airway inflammation and airway hyperresponsiveness.

Conclusion

Our findings identify a novel mouse model of neutrophilic asthma. We have also identified NETs play a significant role in neutrophilic asthma models and contribute to neutrophilic asthma pathogenesis. NETs may serve as a promising therapeutic target for neutrophilic asthma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02209-0.

Coadministration of Stigmasterol and Dexamethasone (STIG+DEX) Modulates Steroid-Resistant Asthma

Airway inflammation in asthma is managed with anti-inflammatory steroids such as dexamethasone (DEX). However, about 20% of asthmatics do not respond to this therapy and are classified as steroid-resistant. Currently, no effective therapy is available for steroid-resistant asthma. This work therefore evaluated the effect of a plant sterol, stigmasterol (STIG), and stigmasterol-dexamethasone combination (STIG+DEX) in LPS-ovalbumin-induced steroid-resistant asthma in Guinea pigs. To do this, the effect of drugs on inflammatory features such as airway hyperreactivity and histopathology of lung tissue was evaluated. Additionally, the possible pathway of drug action was assessed by measuring events such neutrophil levels, oxidative and nitrative stress, and histone deacetylase 2 (HDAC2) and interleukin 17 (IL-17) levels. STIG alone did not affect inflammatory features, although it caused some changes in the molecular events associated with steroid-resistant asthma. However, STIG+DEX caused significant modulation of inflammatory features by protecting against destruction of lung tissue. The modulation of inflammatory features was associated with significant inhibition of neutrophilia and oxidative and nitrative stress, decrease in HDAC2, and increase in IL-17 levels that are usually associated with steroid-resistant asthma. Our findings show that although STIG and DEX individually do not protect against steroid-resistant asthma, their coadministration results in significant modulation of inflammatory features and the associated molecular events that lead to steroid-resistant asthma.

Isoorientin ameliorates OVA-induced asthma in a murine model of asthma

Allergic asthma which is induced by ovalbumin (OVA) is a chronic airway inflammation disease. Isoorientin (Iso) is a natural C-glucosyl flavone with many biological properties. We aimed to evaluate the effectiveness of Iso on OVA-induced allergic asthma. A total of 30 C57BL/6 mice were randomly divided into five groups: control group, OVA group, Dex (dexamethasone, 10 mg/kg) group, low-dose Iso group (Iso-L, 25 mg/kg), and high-dose Iso group (Iso-H, 50 mg/kg). The serum and bronchoalveolar lavage fluid (BALF) were collected for biochemical parameters, the lung tissue was collected for hematoxylin-eosin (H&E) staining, immunohistochemistry (IHC), and western blot. The levels of IL-4, IL-5, IL-13, malondialdehyde (MDA), NO, and reactive oxygen species (ROS) in Iso-L and Iso-H groups were significantly lower than that in model group (p < 0.05). Simultaneously, the levels of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity were higher than that in model group (p < 0.05). Iso significantly ameliorated airway hyperresponsiveness. Meanwhile, H&E staining revealed that mice treated with Iso resulted in the ameliorated inflammatory cell infiltration and a reduction in interstitial thickening. The nuclear factor erythroid 2-like 2 (Nrf2) and HO-1 protein expression in Iso-L and Iso-H groups were enhanced over that in model group, while p-NF-κB-p65 and p-IκB-α protein expression was decreased (p < 0.05). Our research indicated that Iso alleviated the OVA-induced allergic asthma, and this effect can be explained by the modulation of Nrf2/HO-1 and NF-κB signaling pathway; thus, the results providing a therapeutic rationale for the treatment of Iso on allergic asthma.

Embelin Alleviates Severe Airway Inflammation in OVA-LPS-Induced Rat Model of Allergic Asthma

BACKGROUND

Asthma is a chronic lung disease, which causes wheezing, tightness in the chest, shortness of breath and coughing. In the wake of coronavirus disease 2019 (COVID-19), which affect the lungs, asthma patients are at high risk. Embelin, a natural benzoquinone obtained mainly from Embelia ribes Burm, has excellent biological properties, including protection against acute asthma. However, since asthma is a chronic and multi-factorial inflammatory disease, asthma conferred by a single allergen in an animal may not be clinically significant. Therefore, the purpose of the current study was to evaluate the effectiveness of embelin against ovalbumin (OVA)-lipopolysaccharide (LPS)-induced severe airway inflammation in experimental animals and to investigate the plausible mechanism of action.

METHODS

Rats (n=36) were divided into six groups. Group I served as a normal control. Groups II-VI were sensitised with severe allergens (OVA and LPS) on day 7, 14 and 21, followed by OVA and LPS challenge for 30 min three times/week for 3 weeks. Group II acted as an asthmatic disease control and received only vehicle. On the other hand, groups III-V received embelin (12.5, 25 and 50 mg/kg, P.O. respectively) while group VI received a standard dexamethasone (2.5 mg/kg, P.O.) for 15 days from day 27. Lung function parameters, including the respiratory rate, tidal volume and airflow rate were measured at the end of the experiment (day 42). The total and differential counts of leukocytes in the blood and bronchoalveolar fluid (BALF) were calculated. Th2-mediated serum pro-inflammatory cytokines such as interleukin (IL)-4, IL-5 and IL-13 levels were analyzed. At the end of the study protocol, the lung tissues were removed for a histopathology study. Additionally, a molecular docking simulation on embelin and standard dexamethasone was applied to support the in vivo findings.

RESULTS

Significant inhibition of eosinophils, neutrophils, lymphocytes and monocytes in the blood and the BALF was seen in the groups, which received embelin (25 and 50 mg/kg) and dexamethasone (2.5 mg/kg). Moreover, the lung function parameters were normalised by embelin (25 and 50 mg/kg) treatment significantly. The lung histopathological changes confirmed the protective effect of embelin against severe airway inflammation. The docking findings indicated good binding efficacy of embelin to IL-13.

CONCLUSION

Overall, our findings indicate that embelin can alleviate severe airway inflammation in OVA-LPS-induced model of allergic asthma occurring by suppression of Th2-mediated immune response. Due to its promising anti-asthmatic effect, it is recommended that embelin should be investigated in clinical trials against asthma. It should also be further explored against COVID-19 or COVID-like diseases due to its ameliorative effects on cytokines and immune cell infiltration.

Galectin-1 secreted by bone marrow-derived mesenchymal stem cells mediates anti-inflammatory responses in acute airway disease

The hallmarks of allergic airway disease (AAD) include infiltration of inflammatory cells into the bronchoalveolar space. Bone marrow derived mesenchymal stem cells (BMSCs) show anti-inflammatory properties in AAD. In addition, galectin-1 (Gal-1) is a lectin significantly upregulated upon inflammation and is also known to mediate potential anti-inflammatory responses. We hypothesized that BMSCs regulated inflammatory responses by secretion of Gal-1 during AAD pathogenesis. BMSCs were isolated from murine femurs and tibiae and adoptively transferred into an ovalbumin-induced AAD mouse model. Knockdown of Gal-1 in BMSCs was performed using shRNA. Flow cytometry, ELISAs, and immunohistology were performed to analyze inflammatory responses in mice, and a Transwell system was used to establish an in vitro co-culture system of lung epithelial cells (MLE-12) and BMSCs. Administration of BMSCs significantly upregulated Gal-1 expression upon inflammation and decreased infiltration of inflammatory cells and secretion of proinflammatory cytokines in vivo. In addition, we showed that this function was mediated by reduced activation of the MAPK p38 signaling pathway. Similar observations were found using an in vitro lipopolysaccharide-induced model when MLE-12 cells were co-cultured with BMSCs. Gal-1 secretion by BMSCs alleviated inflammatory responses observed in AAD and hence provides a promising therapeutic alternative to AAD patients insensitive to conventional drug treatments.

Traditional Medicinal Plants Conferring Protection Against Ovalbumin-Induced Asthma in Experimental Animals: A Review

Asthma is a chronic inflammatory disease of the respiratory tract in which the numerous immune cells, including eosinophils, neutrophils, macrophages, T-lymphocytes, mast cells and epithelial lining play key roles. The numerous anti-asthmatic drugs are available in modern medicine to treat asthma, but they have several disadvantages, including side effects and the cost variations, which compromise treatment compliance. The literature review reveals that traditional herbal medicines have good potential as alternative treatment and management for asthma. However, communities hesitated to use the traditional herbal medicines due to lack of established mechanism of action about their anti-asthmatic potential. The present review aimed to summarise the information stated in the literature about the potential effect of traditional medicinal plants (TMPs) conferring protection against ovalbumin (OVA)-induced asthma model. The literature search was conducted in database like PubMed, Scopus, Google Scholar and ScienceDirect. After screening through the literature from 2011 to date, a total of 27 medicinal plants and two polyherbal extracts have been reported to be used as traditional herbal medicines and also utilised to be tested against OVA-induced asthma, were included. We found them to be an important alternative source of treatment for asthma, since some have comparable efficacies with drugs commonly used in the modern system against asthma. All the reported medicinal plants confirmed their traditional use against asthma or its related inflammation. The present review provides faith in traditional information and also offers new insight into the potential of natural products against asthma.

LPS decreases CFTR open probability and mucociliary transport through generation of reactive oxygen species

Lipopolysaccharide (LPS) serves as the interface between gram-negative bacteria (GNB) and the innate immune response in respiratory epithelial cells (REC). Herein, we describe a novel biological role of LPS that permits GNB to persist in the respiratory tract through inducing CFTR and mucociliary dysfunction. LPS reduced cystic fibrosis transmembrane conductance regulater (CFTR)-mediated short-circuit current in mammalian REC in Ussing chambers and nearly abrogated CFTR single channel activity (defined as forskolin-activated Cl^- currents) in patch clamp studies, effects of which were blocked with toll-like receptor (TLR)-4 inhibitor. Unitary conductance and single-channel amplitude of CFTR were unaffected, but open probability and number of active channels were markedly decreased. LPS increased cytoplasmic and mitochondrial reactive oxygen species resulting in CFTR carbonylation. All effects of exposure were eliminated when reduced glutathione was added in the medium along with LPS. Functional microanatomy parameters, including mucociliary transport, in human sinonasal epithelial cells in vitro were also decreased, but restored with co-incubation with glutathione or TLR-4 inhibitor. In vivo measurements, following application of LPS in the nasal cavities showed significant decreases in transepithelial Cl^- secretion as measured by nasal potential difference (NPD) – an effect that was nullified with glutathione and TLR-4 inhibitor. These data provide definitive evidence that LPS-generated reactive intermediates downregulate CFTR function in vitro and in vivo which results in cystic fibrosis-type disease. Findings have implications for therapeutic approaches intent on stimulating Cl^- secretion and/or reducing oxidative stress to decrease the sequelae of GNB airway colonization and infection.

Oral Formulation of Angiotensin-(1-7) Promotes Therapeutic Actions in a Model of Eosinophilic and Neutrophilic Asthma

The presence of eosinophils and neutrophils in the lungs of asthmatic patients is associated with the severity of the disease and resistance to corticosteroids. Thus, defective resolution of eosinophilic and neutrophilic inflammation is importantly related to exacerbation of asthma. In this study, we investigated a therapeutic action of angiotensin-(1-7) (Ang-(1-7)) in a model of asthma induced by ovalbumin (OVA) and lipopolysaccharide (LPS). Balb-c mice were sensitized and challenged with OVA. Twenty-three hours after the last OVA challenge, experimental groups received LPS, and 1 h and 7 h later, mice were treated with oral formulation of Ang-(1-7). On the next day, 45 h after the last challenge with OVA, mice were subjected to a test of motor and exploratory behavior; 3 h later, lung function was evaluated, and bronchoalveolar lavage fluid (BALF) and lungs were collected. Motor and exploratory activities were lower in OVA + LPS-challenged mice. Treatment with Ang-(1-7) improved these behaviors, normalized lung function, and reduced eosinophil, neutrophil, myeloperoxidase (MPO), eosinophilic peroxidase (EPO), and ERK1/2 phosphorylation (p-ERK1/2) in the lungs. In addition, Ang-(1-7) decreased the deposition of mucus and extracellular matrix in the airways. These results extended those of previous studies by demonstrating that oral administration of Ang-(1-7) at the peak of pulmonary inflammation can be valuable for the treatment of neutrophil- and eosinophil-mediated asthma. Therefore, these findings potentially provide a new drug to reverse the natural history of the disease, unlike the current standards of care that manage the disease symptoms at best.

Back to the future: re-establishing guinea pig in vivo asthma models

Research using animal models of asthma is currently dominated by mouse models. This has been driven by the comprehensive knowledge on inflammatory and immune reactions in mice, as well as tools to produce genetically modified mice. Many of the identified therapeutic targets influencing airway hyper-responsiveness and inflammation in mouse models, have however been disappointing when tested clinically in asthma. It is therefore a great need for new animal models that more closely resemble human asthma. The guinea pig has for decades been used in asthma research and a comprehensive table of different protocols for asthma models is presented. The studies have primarily been focused on the pharmacological aspects of the disease, where the guinea pig undoubtedly is superior to mice. Further reasons are the anatomical and physiological similarities between human and guinea pig airways compared with that of the mouse, especially with respect to airway branching, neurophysiology, pulmonary circulation and smooth muscle distribution, as well as mast cell localization and mediator secretion. Lack of reagents and specific molecular tools to study inflammatory and immunological reactions in the guinea pig has however greatly diminished its use in asthma research. The aim in this position paper is to review and summarize what we know about different aspects of the use of guinea pig in vivo models for asthma research. The associated aim is to highlight the unmet needs that have to be addressed in the future.

LPS aggravates lung inflammation induced by RSV by promoting the ERK-MMP-12 signaling pathway in mice

Background

RSV can lead to persistent airway inflammation and airway hyperresponsiveness (AHR), and is intimately associated with childhood recurrent wheezing and asthma, but the underlying mechanisms remain unclear. Lipopolysaccharide (LPS) is also implicated in the onset and exacerbation of asthma. However, whether inhalation of LPS can boost airway inflammation induced by RSV is not clear. In this study, we utilized an LPS- and RSV-superinfected mouse model to explore underlying pathogenesis.

Methods

Mice were infected with RSV on day 0 and inoculated with LPS from day 35 to day 41, samples were collected on day 42. Inflammatory cells, lung histopathology and AHR were measured. Cytokines were detected by ELISA and ERK, JNK, p38 was determined by western blot. MMP408, PD98059, SP600125 and SB203580 were used to inhibit MMP-12, ERK, JNK and p38 respectively.

Results

LPS exposure superimposed on RSV-infected lungs could lead to more vigorous cellular influx, lung structures damage, augmented AHR and higher MMP-12 levels. Inhibition of MMP-12 or ERK signaling pathway in vivo both diminished LPS-driven airway inflammation and AHR.

Conclusions

Exposure to LPS in RSV-infected mice is associated with enhanced increases in ERK-MMP-12 expression that translates into increased lung inflammation and AHR. These findings contribute novel information to the field investigating the onset of post-RSV bronchiolitis recurrent wheezing as a result of LPS exposure.

Caspase-11 promotes allergic airway inflammation

Activated caspase-1 and caspase-11 induce inflammatory cell death in a process termed pyroptosis. Here we show that Prostaglandin E₂ (PGE₂) inhibits caspase-11-dependent pyroptosis in murine and human macrophages. PGE₂ suppreses caspase-11 expression in murine and human macrophages and in the airways of mice with allergic inflammation. Remarkably, caspase-11-deficient mice are strongly resistant to developing experimental allergic airway inflammation, where PGE₂ is known to be protective. Expression of caspase-11 is elevated in the lung of wild type mice with allergic airway inflammation. Blocking PGE₂ production with indomethacin enhances, whereas the prostaglandin E₁ analog misoprostol inhibits lung caspase-11 expression. Finally, alveolar macrophages from asthma patients exhibit increased expression of caspase-4, a human homologue of caspase-11. Our findings identify PGE₂ as a negative regulator of caspase-11-driven pyroptosis and implicate caspase-4/11 as a critical contributor to allergic airway inflammation, with implications for pathophysiology of asthma.

Caspase 11 activation involves transcriptional upregulation and proteolytic cleavage. Here the authors show that prostaglandin E₂ prevents caspase-11-mediated pyroptosis, blocking caspase-11 mRNA and protein upregulation in macrophages and in vivo, and that mice lacking caspase-11 are strongly protected from allergic airway inflammation.

Effects of Dietary Fat Sources during Late Gestation on Colostrum Quality and Mammary Gland Inflammation in Lipopolysaccharide-Challenged Sows

Simple Summary

In the present study, late gestating sows were challenged with lipopolysaccharide (LPS) endotoxin, which can impair the immune system of mammary gland cells and result in an inflammatory response. Additionally, the LPS-treated sows were fed 3% soybean oil (SO), 3% coconut oil (CO) or 3% fish oil (FO) diets and were used to study the effect of fat sources on the colostrum quality and mammary gland inflammation of sows exposed to immune challenge. The results show that FO inclusion exerted anti-inflammatory effects in mammary glands and counteracted the LPS-induced damaged colostrum synthesis and pro-inflammatory response when compared to CO diets. These findings suggest that fatty acid profiles of different oil types in late gestation differentially affect metabolic health in sows, but a longer period of FO supplementation to sows is needed to determine a positive effect on piglets.

Abstract

This study aimed to investigate the effects of maternal lipopolysaccharide (LPS) challenge and dietary fat sources on colostrum quality and inflammatory response in sows. Sixty Landrace × Yorkshire sows were randomly assigned to three dietary treatments supplemented with 3% soybean oil (SO), 3% coconut oil (CO) or 3% fish oil (FO), respectively, from Day 90 of gestation until parturition. On Day 112 of gestation, half the sows from each dietary treatment were challenged with LPS (10 μg/kg BW) or saline. The results showed that maternal LPS challenge decreased colostrum yield and dry matter content. A similar pattern of changes was observed for body weight gain and colostrum intake in piglets from LPS-challenged sows. Maternal LPS challenge increased the levels of tumor necrosis factor α (TNFα), interleukin 1β (IL1β) and IL6 in colostum, and the mRNA abundance of IL6, IL1β and TNFα and the phosphorylation level of p65 in mammary glands. However, the responses of these variables to LPS treatment were lower in sows fed a FO diet. In conclusion, maternal immune challenge reduced the growth performance of piglets by decreasing colostrum yield and intake by piglets, and dietary supplementation with FO in sows attenuates the LPS-induced inflammatory response in mammary glands.

An experimental model of asthma in rats using ovalbumin and lipopolysaccharide allergens

Asthma is chronic and multi-factorial inflammatory disease hence single allergen induced asthma in an animal is not identical to clinical asthma. Therefore, we developed a novel experimental model of asthma in rats using ovalbumin (OVA) and lipopolysaccharide (LPS) allergens. Rats were divided into four groups; normal (NC), OVA, LPS, and OVA-LPS treated. Rats were sensitized with OVA (100 μg/kg, adsorbed in 100 mg/mL aluminum hydroxide, i.p.), LPS (10 μg/kg, i.p.) and both (OVA-LPS) on 7^th, 14^th, 21^st days and was followed by challenge with OVA (1%w/v), LPS (1%w/v), OVA (0.5%w/v) and LPS (0.5%w/v) for 30 min thrice/week for three weeks in the OVA, LPS and OVA-LPS groups, respectively. On 41 day, lung function parameters (respiration rate, tidal volume, and airflow rate), total and differential leukocytes count in the blood as well as BALf and inflammatory cytokines (IL-4, IL-5, and IL-13) in serum were measured. Histology of lungs was performed.

The results suggested that the tidal volume and airflow rate were significantly decreased while respiration rate, total and differential leukocytes count in blood as well as BALf and serum cytokines level were significantly increased in the OVA-LPS as compared to NC, OVA, and LPS.

In conclusion, the combination of OVA and LPS induced phenotypes of severe asthma with eosinophilic, neutrophilic and lymphocytic inflammation.

An anti-asthmatic activity of natural Toll-like receptor-4 antagonist in OVA-LPS-induced asthmatic rats

Toll-like receptor-4 (TLR4) is a key component of the innate immune system and activation of TLR4 signaling has a significant role in the pathogenesis of asthma. Therefore, our objective was to identify the natural TLR4 antagonist and evaluate its activity in experimentally induced asthma. Soya lecithin origin phosphatidylcholine (soya PC) was identified as a natural TLR4 antagonist by computational study. Based on the computational study, TLR4 antagonist activity of soya PC was confirmed in in vitro lipopolysaccharide (LPS)-induced neutrophil adhesion assay. In the in vivo study, rats were sensitized with ovalbumin (OVA) (100 μg/kg, i.p.) on the 7th, 14th and 21st days and challenged intranasally with OVA (100 μg/100 μL) and LPS (10 ng/100 μL), 4 days/wk for 3 weeks. At the end of the experiment, we performed lung function parameters (respiratory rate, tidal volume, airflow rate), inflammatory cytokines (interleukin [IL]-4, IL-5, IL-13), total and differential leukocytes in blood as well as bronchoalveolar lavage fluid (BALf) and histological examinations. The computational study indicated that TLR4 antagonist activity of soya PC is due to linoleic acid (18:2) fatty acid chain. Soya PC significantly suppressed the LPS-induced neutrophil adhesion in a concentration-dependent manner to 1 μg/mL. The treatment of soya PC (5 and 10 mg/kg, 18 days, i.p.) significantly improved the lung function parameters, total and differential leukocyte counts in blood and BALf in asthmatic rats. This efficacy of soya PC was in extent similar to dexamethasone (2.5 mg/kg, 18 days, i.p.). However, soya PC was superior to dexamethasone in terms of benefits. The protective action of soya PC may be due to TLR4 antagonist activity and linoleic acid composition.

Dual Role of Toll-like Receptors in Human and Experimental Asthma Models

Asthma is a chronic airway inflammatory disease that is influenced by the interplay between genetic factors and exposure to environmental allergens, microbes, or microbial products where toll-like receptors (TLRs) play a pivotal role. TLRs recognize a wide range of microbial or endogenous molecules as well as airborne environmental allergens and act as adjuvants that influence positively or negatively allergic sensitization. TLRs are qualitatively and differentially expressed on hematopoietic and non-hematopoietic stromal or structural airway cells that when activated by TLRs agonists exert an immune-modulatory role in asthma development. Therefore, understanding mechanisms and pathways by which TLRs orchestrate asthma outcomes may offer new strategies to control the disease. Here, we aim to review and critically discuss the role of TLRs in human asthma and murine models of allergic airway inflammation, highlighting the complexity of TLRs function in development, exacerbation, or control of airway allergic inflammation.

Effects of Anti-IL-17 on Inflammation, Remodeling, and Oxidative Stress in an Experimental Model of Asthma Exacerbated by LPS

Inflammation plays a central role in the development of asthma, which is considered an allergic disease with a classic Th2 inflammatory profile. However, cytokine IL-17 has been examined to better understand the pathophysiology of this disease. Severe asthmatic patients experience frequent exacerbations, leading to infection, and subsequently show altered levels of inflammation that are unlikely to be due to the Th2 immune response alone. This study estimates the effects of anti-IL-17 therapy in the pulmonary parenchyma in a murine asthma model exacerbated by LPS. BALB/c mice were sensitized with intraperitoneal ovalbumin and repeatedly exposed to inhalation with ovalbumin, followed by treatment with or without anti-IL-17. Twenty-four hours prior to the end of the 29-day experimental protocol, the two groups received LPS (0.1 mg/ml intratracheal OVA-LPS and OVA-LPS IL-17). We subsequently evaluated bronchoalveolar lavage fluid, performed a lung tissue morphometric analysis, and measured IL-6 gene expression. OVA-LPS-treated animals treated with anti-IL-17 showed decreased pulmonary inflammation, edema, oxidative stress, and extracellular matrix remodeling compared to the non-treated OVA and OVA-LPS groups (p < 0.05). The anti-IL-17 treatment also decreased the numbers of dendritic cells, FOXP3, NF-κB, and Rho kinase 1- and 2-positive cells compared to the non-treated OVA and OVA-LPS groups (p < 0.05). In conclusion, these data suggest that inhibition of IL-17 is a promising therapeutic avenue, even in exacerbated asthmatic patients, and significantly contributes to the control of Th1/Th2/Th17 inflammation, chemokine expression, extracellular matrix remodeling, and oxidative stress in a murine experimental asthma model exacerbated by LPS.

The Interactive Roles of Lipopolysaccharides and dsRNA/Viruses on Respiratory Epithelial Cells and Dendritic Cells in Allergic Respiratory Disorders: The Hygiene Hypothesis

The original hygiene hypothesis declares "more infections in early childhood protect against later atopy". According to the hygiene hypothesis, the increased incidence of allergic disorders in developed countries is explained by the decrease of infections. Epithelial cells and dendritic cells play key roles in bridging the innate and adaptive immune systems. Among the various pattern-recognition receptor systems of epithelial cells and dendritic cells, including toll-like receptors (TLRs), nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) and others, TLRs are the key systems of immune response regulation. In humans, TLRs consist of TLR1 to TLR10. They regulate cellular responses through engagement with TLR ligands, e.g., lipopolysaccharides (LPS) acts through TLR4 and dsRNA acts through TLR3, but there are certain common components between these two TLR pathways. dsRNA activates epithelial cells and dendritic cells in different directions, resulting in allergy-related Th2-skewing tendency in epithelial cells, and Th1-skewing tendency in dendritic cells. The Th2-skewing effect by stimulation of dsRNA on epithelial cells could be suppressed by the presence of LPS above some threshold. When LPS level decreases, the Th2-skewing effect increases. It may be via these interrelated networks and related factors that LPS modifies the allergic responses and provides a plausible mechanism of the hygiene hypothesis. Several hygiene hypothesis-related phenomena, seemingly conflicting, are also discussed in this review, along with their proposed mechanisms.

Route of Administration Affects Corticosteroid Sensitivity of a Combined Ovalbumin and Lipopolysaccharide Model of Asthma Exacerbation in Guinea Pigs

Lipopolysaccharide (LPS) contributes to asthma exacerbations and development of inhaled corticosteroid insensitivity. Complete resistance to systemic corticosteroids is rare, and most patients lie on a continuum of steroid responsiveness. This study aimed to examine the sensitivity of combined ovalbumin- (Ova) and LPS-induced functional and inflammatory responses to inhaled and systemic corticosteroid in conscious guinea pigs to test the hypothesis that the route of administration affects sensitivity. Guinea pigs were sensitized to Ova and challenged with inhaled Ova alone or combined with LPS. Airway function was determined by measuring specific airway conductance via whole-body plethysmography. Airway hyper-responsiveness to histamine was determined before and 24 hours post-Ova challenge. Airway inflammation and underlying mechanisms were determined from bronchoalveolar lavage cell counts and lung tissue cytokines. Vehicle or dexamethasone was administered by once-daily i.p. injection (5, 10, or 20 mg/kg) or twice-daily inhalation (4 or 20 mg/ml) for 6 days before Ova challenge or Ova with LPS. LPS exacerbated Ova-induced responses, elongating early asthmatic responses (EAR), prolonging histamine bronchoconstriction, and further elevating airway inflammation. Intraperitoneal dexamethasone (20 mg/kg) significantly reduced the elongated EAR and airway inflammation but not the increased bronchoconstriction to histamine. In contrast, inhaled dexamethasone (20 mg/ml), which inhibited responses to Ova alone, did not significantly reduce functional and inflammatory responses to combined Ova and LPS. Combined Ova and LPS–induced functional and inflammatory responses are insensitive to inhaled, but they are only partially sensitive to systemic, dexamethasone. This finding suggests that the route of corticosteroid administration may be important in determining corticosteroid sensitivity of asthmatic responses.

The circadian protein BMAL1 in myeloid cells is a negative regulator of allergic asthma

Our body clock drives rhythms in the expression of genes that have a 24-h periodicity. The transcription factor BMAL1 is a crucial component of the molecular clock. A number of physiological processes, including immune function, are modulated by the circadian clock. Asthma, a disease with very strong clinical evidence demonstrating regulation by circadian variation, is of particular relevance to circadian control of immunity. Airway hypersensitivity and asthma attacks are more common at night in humans. The molecular basis for this is unknown, and there is no model of asthma in animals with genetic distortion of the molecular clock. We used mice lacking BMAL1 in myeloid cells (BMAL1-LysM-/-) to determine the role of BMAL1 in allergic asthma. Using the ovalbumin model of allergic asthma, we demonstrated markedly increased asthma features, such as increased lung inflammation, demonstrated by drastically higher numbers of eosinophils and increased IL-5 levels in the lung and serum, in BMAL1-LysM-/- mice. In vitro studies demonstrated increased proinflammatory chemokine and mannose receptor expression in IL-4- as well as LPS-treated macrophages from BMAL1-LysM-/- mice compared with wild-type controls. This suggests that Bmal1 is a potent negative regulator in myeloid cells in the context of allergic asthma. Our findings might explain the increase in asthma incidents during the night, when BMAL1 expression is low.

Defining the inflammatory signature of human lung explant tissue in the presence and absence of glucocorticoid

Background: Airway inflammation is a feature of many respiratory diseases and there is a need for newer, more effective anti-inflammatory compounds. The aim of this study was to develop an ex vivo human lung explant model which can be used to help study the mechanisms underlying inflammatory responses and which can provide a tool to aid drug discovery for inflammatory respiratory diseases such as asthma and COPD.

Method: Parenchymal lung tissue from 6 individual donors was dissected and cultured with two pro-inflammatory stimuli, lipopolysaccharide (LPS) (1 µg/ml) and interleukin-1 beta (IL-1β) (10 ng/ml) in the presence or absence of dexamethasone (1 µM).  Inflammatory responses were assessed using Luminex analysis of tissue culture supernatants to measure levels of 21 chemokines, growth factors and cytokines.

Results: A robust and reproducible inflammatory signal was detected across all donors for 12 of the analytes measured following LPS stimulation with a modest fold increase (<2-fold) in levels of CCL22, IL-4, and IL-2; increases of 2-4-fold in levels of CXCL8, VEGF and IL-6 and increases >4-fold in CCL3, CCL4, GM-CSF, IL-10, TNF-α and IL-1β.  The inflammatory signal induced by IL-1β stimulation was less than that observed with LPS but resulted in elevated levels of 7 analytes (CXCL8, CCL3, CCL4, GM-CSF, IL-6, IL-10 and TNF-α).  The inflammatory responses induced by both stimulations was supressed by dexamethasone for the majority of analytes.

Conclusions: These data provide proof of concept that this ex vivo human lung explant model is responsive to inflammatory signals and could be used to investigate the anti-inflammatory effects of existing and novel compounds.  In addition this model could be used to help define the mechanisms and pathways involved in development of inflammatory airway disease.

Abbreviations: COPD: Chronic Obstructive Pulmonary Disease; ICS: inhaled corticosteroids; LPS: lipopolysaccharide; IL-1β: interleukin-1 beta; PSF: penicillin, streptomycin and fungizone

Bufalin Inhibits the Inflammatory Effects in Asthmatic Mice through the Suppression of Nuclear Factor-Kappa B Activity

Asthma is an inflammatory airway disease characterized by increased infiltration of inflammatory cells into the airways and poor respiratory function. Bufalin is one of the biological ingredients obtained from Chansu. Bufalin was found to possess various pharmacological properties including anti-inflammatory activities. However, the effect of bufalin treatment on asthma has not yet been reported. Therefore, this study aimed to investigate the inhibitory effect of bufalin on asthmatic response in a murine model. A mouse asthma model was developed by ovalbumin (OVA) sensitization and challenge in the BALB/c mice. OVA-specific serum IgE and the levels of interleukin (IL)-4, IL-5, and IL-13 in bronchoalveolar lavage fluid (BALF) were determined by an enzyme-linked immunosorbent assay. Recruitment of inflammatory cells into BALF or lung tissues, and goblet cell hyperplasia were evaluated by histological staining. The expression levels of inhibitory subunit of nuclear factor-kappa B (NF-κB) alpha (IκBα) and phosphorylated p65 protein were measured by Western blot analyses. The results demonstrated that bufalin (5 and 10 mg/kg) markedly attenuated hyperresponsiveness, and strongly suppressed the OVA-induced increases of total inflammatory cells including macrophages, eosinophils, lymphocytes, and neutrophils in BALF. The levels of IL-4, IL-5, and IL-13 in BALF and OVA-specific IgE in serum were significantly reduced by bufalin. Histological staining of lung tissues showed that bufalin reduced inflammatory cell infiltration and goblet cell hyperplasia. The results of Western blotting indicated that bufalin suppressed the IκBα degradation from NF-κB, and reduced the level of phosphorylated p65 protein in the lung tissues. These data suggest that bufalin can exert its anti-inflammatory effects possibly through the inhibition of the NF-κB activity.

LPS Cooperates with Poly-L-Arginine to Promote IL-6 and IL-8 Release via the JNK Signaling Pathway in NCI-H292 Cells

Objective. Herein, we aimed to study the mechanism whereby poly-L-arginine (PLA) and lipopolysaccharide (LPS) can synergistically induce the release of interleukin-6 (IL-6) and IL-8 in NCI-H292 cells. Methods. NCI-H292 cells were divided into control, PLA, LPS, and PLA+LPS groups. At various time points, the phosphorylation of JNK in each group was measured by western blotting. Additionally, the productions of IL-6 and IL-8 were assessed using an enzyme-linked immunosorbent assay (ELISA). The effects of SP600125, an inhibitor of the JNK pathway, on the increase of p-JNK, IL-6, and IL-8 were also studied. Results. Our results showed that either PLA or LPS treatment alone can significantly increase the phosphorylation level of JNK in NCI-H292 cells. Of interest was the combined use of PLA and LPS that has a synergistic effect on the phosphorylation of JNK, as well as synergistically inducing the release of IL-6 and IL-8 in NCI-H292 cells. Furthermore, SP600125 significantly inhibited the activation of JNK signal, as well as reducing the productions of IL-6 and IL-8 in response to PLA+LPS stimulation. Conclusions. The JNK signaling pathway contributes to the release of IL-6 and IL-8, which is stimulated by the synergistic actions of PLA+LPS in NCI-H292 cells.

Andrographolide Restores Steroid Sensitivity To Block Lipopolysaccharide/IFN-γ-Induced IL-27 and Airway Hyperresponsiveness in Mice

LPS and IFN-γ alone or in combination have been implicated in the development of steroid resistance. Combined LPS/IFN-γ strongly upregulates IL-27 production, which has been linked to steroid-resistant airway hyperresponsiveness (AHR). Andrographolide, a bioactive molecule isolated from the plant Andrographis paniculata, has demonstrated anti-inflammatory and antioxidant properties. The present study investigated whether andrographolide could restore steroid sensitivity to block LPS/IFN-γ-induced IL-27 production and AHR via its antioxidative property. The mouse macrophage cell line Raw 264.7, mouse primary lung monocytes/macrophages, and BALB/c mice were treated with LPS/IFN-γ, in the presence and absence of dexamethasone and/or andrographolide. Levels of IL-27 in vitro and in vivo were examined and mouse AHR was assessed. Dexamethasone alone failed to inhibit LPS/IFN-γ-induced IL-27 production and AHR in mice. Andrographolide significantly restored the suppressive effect of dexamethasone on LPS/IFN-γ-induced IL-27 mRNA and protein levels in the macrophage cell line and primary lung monocytes/macrophages, mouse bronchoalveolar lavage fluid and lung tissues, and AHR in mice. LPS/IFN-γ markedly reduced the nuclear level of histone deacetylase (HDAC)2, an essential epigenetic enzyme that mediates steroid anti-inflammatory action. LPS/IFN-γ also decreased total HDAC activity but increased the total histone acetyltransferase/HDAC activity ratio in mouse lungs. Andrographolide significantly restored nuclear HDAC2 protein levels and total HDAC activity, and it diminished the total histone acetyltransferase/HDAC activity ratio in mouse lungs exposed to LPS/IFN-γ, possibly via suppression of PI3K/Akt/HDAC2 phosphorylation, and upregulation of the antioxidant transcription factor NF erythroid-2-related factor 2 level and DNA binding activity. Our data suggest that andrographolide may have therapeutic value in resensitizing steroid action in respiratory disorders such as asthma.

Assessment of the Mechanistic Role of Cinnarizine in Modulating Experimentally-Induced Bronchial Asthma in Rats

BACKGROUND/AIMS

Calcium influx, inflammatory infiltration, cytokine production, immunoglobulin E activation and oxidative stress play coordinated roles in bronchial asthma pathogenesis. We aim to assess the protective effect of cinnarizine against experimentally induced bronchial asthma.

METHODS

Bronchial asthma was induced by ovalbumin sensitization and challenge. Rats were allocated into a normal control, an asthma control, a dexamethasone (standard) treatment, and 2 cinnarizine treatment groups. The respiratory functions tidal volume (TV) and peak expiratory flow rate (PEFR), the inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-5 (IL-5) in lung tissue, the allergic immunoglobulin IgE in serum, the absolute eosinophil count (AEC) in bronchoalveolar lavage fluid (BALF), as well as the oxidative and nitrosative markers glutathione reduced (GSH) and superoxide dismutase (SOD) in lung tissue and nitric oxide end products (NOx) in BALF were assessed, followed by a histopathological study.

RESULTS

Cinnarizine administration significantly restored TV, PEFR, TNF-α, IL-5, IgE, AEC, GSH, SOD and NOx values back to normal levels, and significantly decreased perivascular and peribronchiolar inflammatory scores.

CONCLUSION

Cinnarizine may protect against experimental bronchial asthma. Suppressant effect of cinnarizine on pro-inflammatory cytokines release, IgE antibody production, eosinophil infiltration as well as oxidative and nitrosative stress may explain its anti-asthmatic potential.