Blockade of the NLRP3/Caspase-1 Axis Ameliorates Airway Neutrophilic Inflammation in a Toluene Diisocyanate-Induced Murine Asthma Model

Lung microbiota participated in fibrous microplastics (MPs) aggravating OVA-induced asthma disease in mice

Environmental pollution is one of the risk factors for asthma. Currently, whether micro-plastics could aggravate asthma, is still unclear. In the air, fibrous MPs are the predominant shape. Since fibrous micro-plastics are reported to be detected in the lower respiratory tract and other body parts, the relationship of fibrous MP and asthma, as well as the potential mechanism is not well investigated. In this study, we produced fibrous MPs, whose lengths and widths were in accordance with the natural environment, and further, investigated the potential adverse effect of which on the asthma in a OVA (ovalbumin)-induced mice model, aiming at exploring the true life hazard of MP to the respiratory system. Following nasal exposure to fibrous MPs, the airway inflammation, mucus hypersecretion and fibrosis were aggravated in asthmatic mice. Fibrous MPs exposure also significantly increased the levels of total IgE, and, cardinal Th2 and Th1 pro-inflammatory cytokines participated in the etiopathogenesis of allergic airway inflammation. In addition, MP fibers exposure induced lung epithelial cells apoptosis, disruption of epithelial barrier integrity and activation of NLRP3 related signaling pathways. Moreover, fibrous MPs significantly altered the bacterial composition at the genus level. Compared to the control group, the relative abundance of Escherichia-Shigella and Uncultured were decreased to 4.47% and 0.15% in OVA group, while Blautia and Prevotella were elevated to 4.96% and 2.94%. For the OVA + MPs group, the relative abundance of Blautia and Uncultured were decreased to 2.27% and 0.006%, while Prevotella was increased to 3.05%. Our study highlights the detrimental effect of fibrous MPs on asthmatic population and facilitates an indication of the latent mechanisms of fibrous MPs induced airway pathology.

5-Hydroxymethylfurfural Ameliorates Allergic Inflammation in HMC-1 Cells by Inactivating NF-κB and MAPK Signaling Pathways

Allergic inflammation is the foundation of multiple allergic disorders, such as allergic rhinitis and asthma. Mast cells are effector cells that initiate inflammatory response. 5-hydroxymethylfurfural (5-HMF), a furfural compound, is the heat-processed product of various fruit, foods, drinks, as well as some Chinese herbal medicines. 5-HMF was previously reported to inhibit mast cell activation. Our study aimed to explore the functions of 5-HMF in both phorbol 12-mystate 13-acetate (PMA) plus calcium ionophore (A23187)-induced allergic inflammation in human mast cell line HMC-1 and ovalbumin (OVA)-induced asthma mouse models. HMC-1 cells were pretreated with 5-HMF and then stimulated by PMA+A23187. The cytotoxicity of 5-HMF on HMC-1 cells was evaluated by MTT assay. Histamine content in cell supernatants was measured by the o-phthaldialdehyde spectrofluorometric procedure. Intracellular calcium was determined using the fluorescent dye Fura-2AM. The production and expression of pro-inflammatory cytokines were detected by ELISA and RT-qPCR. Caspase-1 colorimetric assay was employed to examine the enzymatic activity of caspase-1. Asthma mouse models were induced by OVA sensitization. The bronchoalveolar lavage fluid (BALF) and blood samples were collected for the detection of total and differential cell count as well as aspartate aminotransferase (AST), alanine aminotransferase (ALT), OVA-immunoglobulin E (OVA-IgE), OVA-immunoglobulin G1 (OVA-IgG1), and pro-inflammatory cytokine levels. The left lung of mouse was dissected for histopathological examination by hematoxylin and eosin (H&E) staining. The protein expression of pro-caspase-1 and the phosphorylation of NF-κB and MAPK pathway-associated molecules were assessed by Western blotting. Our findings revealed that 5-HMF efficiently suppressed the PMA+A23187-induced enhancement in histamine production and intracellular calcium in HMC-1 cells. Pro-inflammatory cytokine production and expression in HMC-1 cells were elevated after PMA plus A23187 stimulation, which, however, were inhibited by pretreatment of 5-HMF. Additionally, 5-HMF suppressed the activity of caspase-1 and the phosphorylation of NF-κB and MAPK-associated molecules including p65 NF-κB, p38 MAPK, ERK, and JNK in HMC-1 cells. In vivo experiments demonstrated that 5-HMF treatment reduced the lung/body weight index and total and differential (macrophages, neutrophils, lymphocytes, and eosinophils) cell counts in BALF of asthmatic mice, but exerted no influence on serum AST and ALT levels. Besides, 5-HMF reduced serum OVA-IgE and OVA-IgG1 levels, mitigated lung inflammation, and inhibited the NF-κB and MAPK signaling pathways in asthma mouse models. 5-HMF mitigates allergic inflammation in asthma by inactivating caspase-1 and NF-κB and MAPK signaling pathways.

Downregulation of otulin induces inflammasome activation in neutrophilic asthma

BACKGROUND

Neutrophilic asthma (NA) is a severe asthma phenotype associated with steroid resistance and IL-1β overproduction; however, the exact mechanism remains unclear. Moreover, the dysfunction of TNF-α signaling pathway, a regulator of IL-1β production, was associated with the deficiency of ovarian tumor protease deubiquitinase with linear linkage specificity (otulin) in autoimmune patients.

OBJECTIVE

We hypothesized that otulin downregulation in macrophages (Mφ) could trigger Mφ activation via the nucleotide-binding domain, leucine-rich repeat, and pyrin domain-containing protein 3 (NLRP3) inflammasome signaling pathway.

METHODS

We assessed the expressions of otulin in blood monocyte subsets from NA patients and in alveolar Mφ from NA mice. Additionally, we evaluated the functional consequences of otulin deficiency in bone marrow-derived Mφ. The effects of inhibiting receptor-interacting protein kinase (RIPK)-1 and RIPK-3 on neutrophils and group 3 innate lymphoid cells (ILC3s) were assessed in vitro and in vivo.

RESULTS

When comparing nonclassical monocytes, a significant downregulation of otulin in the intracellular components was observed in NA patients compared to healthy controls (P = .005). Moreover, isolated alveolar Mφ from the NA mice exhibited lower otulin expression compared to those from control mice. After otulin knockdown in bone marrow-derived Mφ, we observed spontaneous IL-1β production depending on NLRP3 inflammasome. Moreover, the infiltrated neutrophils and ILC3s were significantly decreased by combined treatment of RIPK-1 and RIPK-3 inhibitors through blocking IL-1β release in NA.

CONCLUSIONS

IL-1β overproduction caused by a deficiency of otulin, an upstream triggering factor, could be a promising diagnostic and therapeutic target for NA.

Exploring the role of the inflammasomes on prostate cancer: Interplay with obesity

Obesity is a weight-related disorder characterized by excessive adipose tissue growth and dysfunction which leads to the onset of a systemic chronic low-grade inflammatory state. Likewise, inflammation is considered a classic cancer hallmark affecting several steps of carcinogenesis and tumor progression. In this regard, novel molecular complexes termed inflammasomes have been identified which are able to react to a wide spectrum of insults, impacting several metabolic-related disorders, but their contribution to cancer biology remains unclear. In this context, prostate cancer (PCa) has a markedly inflammatory component, and patients frequently are elderly individuals who exhibit weight-related disorders, being obesity the most prevalent condition. Therefore, inflammation, and specifically, inflammasome complexes, could be crucial players in the interplay between PCa and metabolic disorders. In this review, we will: 1) discuss the potential role of each inflammasome component (sensor, molecular adaptor, and targets) in PCa pathophysiology, placing special emphasis on IL-1β/NF-kB pathway and ROS and hypoxia influence; 2) explore the association between inflammasomes and obesity, and how these molecular complexes could act as the cornerstone between the obesity and PCa; and, 3) compile current clinical trials regarding inflammasome targeting, providing some insights about their potential use in the clinical practice.

Canonical and non-canonical functions of NLRP3

BACKGROUND

Since its discovery, NLRP3 is almost never separated from its major role in the protein complex it forms with ASC, NEK7 and Caspase-1, the inflammasome. This key component of the innate immune response mediates the secretion of proinflammatory cytokines IL-1β and IL-18 involved in immune response to microbial infection and cellular damage. However, NLRP3 has also other functions that do not involve the inflammasome assembly nor the innate immune response. These non-canonical functions have been poorly studied. Nevertheless, NLRP3 is associated with different kind of diseases probably through its inflammasome dependent function as through its inflammasome independent functions.

AIM OF THE REVIEW

The study and understanding of the canonical and non-canonical functions of NLRP3 can help to better understand its involvement in various pathologies. In parallel, the description of the mechanisms of action and regulation of its various functions, can allow the identification of new therapeutic strategies.

KEY SCIENTIFIC CONCEPTS OF THE REVIEW

NLRP3 functions have mainly been studied in the context of the inflammasome, in myeloid cells and in totally deficient transgenic mice. However, for several year, the work of different teams has proven that NLRP3 is also expressed in other cell types where it has functions that are independent of the inflammasome. If these studies suggest that NLRP3 could play different roles in the cytoplasm or the nucleus of the cells, the mechanisms underlying NLRP3 non-canonical functions remain unclear. This is why we propose in this review an inventory of the canonical and non-canonical functions of NLRP3 and their impact in different pathologies.

MUC1 attenuates neutrophilic airway inflammation in asthma by reducing NLRP3 inflammasome-mediated pyroptosis through the inhibition of the TLR4/MyD88/NF-κB pathway

BACKGROUND

Neutrophilic airway inflammation is a challenge in asthma management and is associated with poor patient prognosis. Mucin 1 (MUC1), which contains a cytoplasmic tail (MUC1-CT), has been found to mediate glucocorticoid sensitivity in asthma; however, its role in modulating neutrophilic airway inflammation in asthma remains unknown.

METHODS

Human-induced sputum cells were collected from healthy participants (n = 12), patients with mild-to-moderate asthma (n = 34), and those with severe asthma (n = 18). In vitro human lung bronchial 1 epithelial cell line (BEAS-2B) was transfected with small interfering RNA against MUC1 (MUC1-siRNA) and then stimulated by lipopolysaccharide (LPS), where some cells were pretreated with a TLR4 inhibitor (TAK-242). In vivo mouse model of asthmatic neutrophil airway inflammation was induced by ovalbumin (OVA)/LPS. Some groups were intraperitoneally injected with MUC1-CT inhibitor (GO-203) and/or TAK-242 .

RESULTS

The mRNA expression of MUC1 was downregulated in the induced sputum of patients with asthma and correlated with asthmatic neutrophilic airway inflammation. The mRNA expressions of TLR4, MyD88, nucleotide-binding oligomerization domain-like pyrin domain-containing protein 3 (NLRP3), caspase-1, interleukin (IL)-18, and IL-1β in induced sputum cells of patients with asthma were upregulated and related to the mRNA expression of MUC1. LPS activated the TLR4 pathway and NLRP3-mediated pyroptosis in BEAS-2B cells in vitro, which were significantly aggravated after MUC1-siRNA transfection. Furthermore, MUCl-CT interacted with TLR4, and the interaction between TLR4 and MyD88 was significantly increased after MUCl-siRNA transfection. Moreover, TAK-242 ameliorated TLR4/MyD88/nuclear factor kappa B (NF-κB) pathway activation, NLRP3 inflammasome-mediated pyroptosis, and neutrophilic inflammation exacerbated by MUC1 downregulation. GO-203 exacerbated TLR4/MyD88/NF-κB pathway activation in vivo, and NLRP3 inflammasome-mediated pyroptosis reduced in a mouse model of asthmatic neutrophil airway inflammation induced by OVA/LPS; these pathological changes were partially alleviated after TAK-242 application.

CONCLUSION

This study revealed that MUC1 downregulation plays an important role in asthmatic neutrophilic airway inflammation. MUC1-CT reduces NLRP3 inflammasome-mediated pyroptosis by inhibiting the activation of the TLR4/MyD88/NF-κB pathway, thereby attenuating neutrophil airway inflammation in patients with asthma.

Role of NLRP3 in the exacerbation of ozone-induced allergic rhinitis

OBJECTIVE

Allergic rhinitis (AR) is an immunoglobulin E (IgE)-mediated inflammatory disorder of the nasal mucosa, and the impact of ozone on AR is gaining increasing attention. Although NOD-like receptor thermal protein domain associated protein 3 (NLRP3) plays a crucial role in the pathogenesis of AR, its regulatory mechanisms in ozone-induced exacerbation remain unclear. Therefore, we explored the impact of ozone inhalation on inflammation in AR and investigated the regulatory mechanisms involving NLRP3.

METHODS

Fifty female Sprague-Dawley rats were selected and divided into five groups: normal control (NC), normal with ozone exposure (NE), AR model, AR with ozone exposure (ARE), and ARE treated with the NLRP3 inhibitor MCC950 (ARE+MCC950). Behavioral changes were observed in the rats, and the expression of NLRP3, active-caspase 1, and GSDMD-N was detected by western blotting. The expression levels of interleukin (IL)- 4, IL-5, IL-13, IL-1β, and ovalbumin-specific IgE (OVA-sIgE) in nasal lavage fluid as well as IL-6 in the serum were measured by ELISA. The expression and distribution of NLRP3 and IL-1β in nasal mucosal tissue were detected by immunohistochemistry, and pathological changes and eosinophilic infiltration in nasal mucosal tissue were observed by hematoxylin and eosin (HE) staining. The effects of ozone exposure on inflammation in the nasal mucosal tissue of rats with AR and the relationship between NLRP3 and inflammation were analyzed.

RESULTS

Upregulation of NLRP3 was observed in the AR rat model, and ozone further aggravated the expression of NLRP3 in the nasal mucosal tissue. Compared to the AR, NC, and NE groups, NLRP3 inflammasomes were activated in the ARE group, and the expression levels of related indexes active-caspase 1 and GSDMD-N were significantly increased; the expression levels of Th2 inflammatory factors IL-4, IL-5, IL-13, and OVA-sIgE were increased, and inflammatory factors such as IL-1β and IL-6 expression was also significantly increased. HE staining revealed that ozone aggravated damage to the nasal mucosal tissue in AR. Compared with the ARE group, the expression of NLRP3 inflammasomes was downregulated, sneezing and scratching symptoms were reduced, inflammatory indicators in nasal lavage fluid were decreased, and nasal mucosal tissue damage was alleviated in rats in the ARE+MCC950 group.

CONCLUSION

Ozone exposure significantly increased the inflammatory response in an animal model of AR. MCC950 can selectively inhibit the expression of NLRP3, inhibit the activity of inflammasomes, and reduce nasal mucosal inflammation by regulating the NLRP3-caspase-1-IL-1β pathway.

Programmed Cell Death in Asthma: Apoptosis, Autophagy, Pyroptosis, Ferroptosis, and Necroptosis

Bronchial asthma is a complex heterogeneous airway disease, which has emerged as a global health issue. A comprehensive understanding of the different molecular mechanisms of bronchial asthma may be an efficient means to improve its clinical efficacy in the future. Increasing research evidence indicates that some types of programmed cell death (PCD), including apoptosis, autophagy, pyroptosis, ferroptosis, and necroptosis, contributed to asthma pathogenesis, and may become new targets for future asthma treatment. This review briefly discusses the molecular mechanism and signaling pathway of these forms of PCD focuses on summarizing their roles in the pathogenesis and treatment strategies of asthma and offers some efficient means to improve clinical efficacy of therapeutics for asthma in the near future.

The effects of NLRP3 and MAVS gene polymorphisms on the risk of asthma: A case-control study

Genetic factors are important risk factors for asthma. Nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) is closely associated with asthma. Mitochondrial antiviral signaling protein (MAVS) mediates the recruitment of NLRP3 to the mitochondria and activation of the NLRP3 inflammasome. The purpose of this study was to analyze the effects of NLRP3 and MAVS polymorphisms on the risk of asthma and the interactions between them. Children with asthma (n = 127) and healthy children (n = 100) were recruited between August, 2020 and July, 2021. Multiplex polymerase chain reaction and sequencing was used to analyze genotypes of single nucleotide polymorphisms. The multifactor dimensionality reduction statistical method was used to detect and model epistasis of gene-gene interactions. There were significant differences in the distribution of MVAS rs6515831 and NLRP3 rs10925023 genotypes between the asthma and healthy groups. Compared with rs6515831 TT genotype, the results showed that rs6515831CT genotype increased the risk of asthma (odds ratio: 2.243, 95% CI: 1.221-4.122, P = .009). Compared with rs10925023 GG genotype, the results showed that the risk of asthma in the population with rs10925023 TT genotype was lower (odd ratio: 0.643, 95% CI: 0.423-0.979, P = .039). In the genotype of the NLRP3 rs12048215 locus, the IgE level of asthma patients with genotype AG was lower than that of patients with genotype AA. The dendrogram model showed the strongest interaction between rs7272495 and rs10925023, which was expressed in a synergistic manner. Haplotype analysis revealed that rs10925023T/rs7272495G and rs10925023T/rs3272495A were statistically different in distribution between the two groups. The MAVS rs6515831 and NLRP3 rs10925023 polymorphisms were associated with the risk of asthma in children. There may be interactions between NLRP3 and MAVS polymorphisms in the risk of asthma.

Pyroptosis and respiratory diseases: A review of current knowledge

Pyroptosis is a relatively newly discovered programmed cell death accompanied by an inflammatory response. In the classical view, pyroptosis is mediated by caspases-1,-4,-5,-11 and executed by GSDMD, however, recently it was demonstrated that caspase-3 and-8 also participate in the process of pyroptosis, by cleaving GSDMD/E and GSDMD respectively. Different from autophagy and apoptosis, many pores are formed on the cell membrane during pyroptosis, which makes the cell membrane lose its integrity, eventually leading to the release of cytokines interleukin(IL)-1β and IL-18. When the body is infected with pathogens or exposed to some stimulations, pyroptosis could play an immune defense role. It is found that pyroptosis exists widely in infectious and inflammatory respiratory diseases such as acute lung injury, bronchial dysplasia, chronic obstructive pulmonary disease, and asthma. Excessive pyroptosis may accompany airway inflammation, tissue injury, and airway damage, and induce an inflammatory reaction, leading to more serious damage and poor prognosis of respiratory diseases. This review summarizes the relationship between pyroptosis and related respiratory diseases.

NOD-like receptors in asthma

Asthma is an extremely prevalent chronic inflammatory disease of the airway where innate and adaptive immune systems participate collectively with epithelial and other structural cells to cause airway hyperresponsiveness, mucus overproduction, airway narrowing, and remodeling. The nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) are a family of intracellular innate immune sensors that detect microbe-associated molecular patterns and damage-associated molecular patterns, well-recognized for their central roles in the maintenance of tissue homeostasis and host defense against bacteria, viruses and fungi. In recent times, NLRs have been increasingly acknowledged as much more than innate sensors and have emerged also as relevant players in diseases classically defined by their adaptive immune responses such as asthma. In this review article, we discuss the current knowledge and recent developments about NLR expression, activation and function in relation to asthma and examine the potential interventions in NLR signaling as asthma immunomodulatory therapies.

Single-cell analysis highlights differences in druggable pathways underlying adaptive or fibrotic kidney regeneration

The kidney has tremendous capacity to repair after acute injury, however, pathways guiding adaptive and fibrotic repair are poorly understood. We developed a model of adaptive and fibrotic kidney regeneration by titrating ischemic injury dose. We performed detailed biochemical and histological analysis and profiled transcriptomic changes at bulk and single-cell level (> 110,000 cells) over time. Our analysis highlights kidney proximal tubule cells as key susceptible cells to injury. Adaptive proximal tubule repair correlated with fatty acid oxidation and oxidative phosphorylation. We identify a specific maladaptive/profibrotic proximal tubule cluster after long ischemia, which expresses proinflammatory and profibrotic cytokines and myeloid cell chemotactic factors. Druggability analysis highlights pyroptosis/ferroptosis as vulnerable pathways in these profibrotic cells. Pharmacological targeting of pyroptosis/ferroptosis in vivo pushed cells towards adaptive repair and ameliorates fibrosis. In summary, our single-cell analysis defines key differences in adaptive and fibrotic repair and identifies druggable pathways for pharmacological intervention to prevent kidney fibrosis.

Blockade of NLRP3/Caspase-1/IL-1β Regulated Th17/Treg Immune Imbalance and Attenuated the Neutrophilic Airway Inflammation in an Ovalbumin-Induced Murine Model of Asthma

Asthma is a heterogeneous inflammatory disorder of the airways, and multiple studies have addressed the vital role of the nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3)/caspase-1/interleukin-1β (IL-1β) pathway in asthma, but its impact on ovalbumin- (OVA-) induced neutrophilic asthma remains unclear. Here, we explored this pathway's effect on airway inflammation in neutrophilic asthma to clarify whether blocking this signaling could alleviate asthmatic airway inflammation. Using an established OVA-induced neutrophilic asthma mouse model, we provided asthmatic mice with a highly selective NLRP3 inhibitor, MCC950, and a specific caspase-1 inhibitor, Ac-YVAD-cmk. Our results indicated that asthmatic mice exhibited increased airway hyperresponsiveness, neutrophil infiltration, and airway mucus hypersecretion, upregulated retinoid-related orphan receptor-γt (RORγt) mRNA expression, and downregulated fork head box p3 (Foxp3) mRNA expression, which was concurrent with NLRP3 inflammasome activation and upregulation of caspase-1, IL-1β, and IL-18 expression in lung. Treatment of NLRP3 inflammasome inhibitors significantly attenuated airway hyperresponsiveness, airway inflammation, and reversed T helper 17 (Th17)/regulatory T (Treg) cell imbalance in asthmatic mice. We propose that the NLRP3/caspase-1/IL-1β pathway plays an important role in the pathological process of neutrophilic asthma and provides evidence that blocking this pathway could potentially be a treatment strategy to ameliorate airway inflammation in asthma after validation with future experimental and clinical studies.

Downregulation of the NLRP3/Caspse-1 Pathway Ameliorates Ketamine-Induced Liver Injury and Inflammation in Developing Rats

Ketamine is an anesthetic drug that is widely used in human and veterinary medicine. In the developmental stage, long-term exposure to ketamine may cause serious side effects. MCC950 and VX765 play protective roles in many disease models by regulating the NLRP3/Caspase-1 pathway. This study aims to explore the potential protective effect of MCC950 and VX765 on ketamine-induced liver injury in neonatal rats and clarify its underlying mechanism. After administration of MCC950 and VX765 in a ketamine-induced liver injury rat model, liver function and inflammatory factors were determined, and immunohistochemistry and western blotting were performed. We found that ketamine caused liver injury in 7-day-old SD rats, decreased liver function indexes, and increased inflammation. MCC950 and VX765 effectively alleviated liver damage and inflammation, and downregulated the expression of proteins such as NLRP3, Caspase-1, and GSDMD-N. In summary, these results indicated that MCC950 and VX765 could have potential protective effects on ketamine-induced liver injury through inhibiting the NLRP3/Caspase-1 pathway.

Identification of Key Signaling Pathways and Genes in Eosinophilic Asthma and Neutrophilic Asthma by Weighted Gene Co-Expression Network Analysis

Background: Asthma is a heterogeneous disease with different subtypes including eosinophilic asthma (EA) and neutrophilic asthma (NA). However, the mechanisms underlying the difference between the two subtypes are not fully understood.

Methods: Microarray datasets (GSE45111 and GSE137268) were acquired from Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) in induced sputum between EA (n = 24) and NA (n = 15) were identified by “Limma” package. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses and Gene set enrichment analysis (GSEA) were used to explore potential signaling pathways. Weighted gene co-expression network analysis (WGCNA) were performed to identify the key genes that were strongly associated with EA and NA.

Results: A total of 282 DEGs were identified in induced sputum of NA patients compared with EA patients. In GO and KEGG pathway analyses, DEGs were enriched in positive regulation of cytokine production, and cytokine-cytokine receptor interaction. The results of GSEA showed that ribosome, Parkinson’s disease, and oxidative phosphorylation were positively correlated with EA while toll-like receptor signaling pathway, primary immunodeficiency, and NOD-like receptor signaling pathway were positively correlated with NA. Using WGCNA analysis, we identified a set of genes significantly associated NA including IRFG, IRF1, STAT1, IFIH1, IFIT3, GBP1, GBP5, IFIT2, CXCL9, and CXCL11.

Conclusion: We identified potential signaling pathways and key genes involved in the pathogenesis of the asthma subsets, especially in neutrophilic asthma.

The onset, development and pathogenesis of severe neutrophilic asthma

Bronchial asthma is divided into Th2 high, Th2 low and mixed types. The Th2 high type is dominated by eosinophils while the Th2 low type is divided into neutrophilic and paucigranulocytic types. Eosinophilic asthma has gained increased attention recently, and its pathogenesis and treatment are well understood. However, severe neutrophilic asthma requires more in-depth research because its pathogenesis is not well understood, and no effective treatment exists. This review looks at the advances made in asthma research, the pathogenesis of neutrophilic asthma, the mechanisms of progression to severe asthma, risk factors for asthma exacerbations, and biomarkers and treatment of neutrophilic asthma. The pathogenesis of neutrophilic asthma is further discussed from four aspects: Th17-type inflammatory response, inflammasomes, exosomes and microRNAs. This review provides direction for the mechanistic study, diagnosis and treatment of neutrophilic asthma. The treatment of neutrophilic asthma remains a significant challenge for clinical therapists and is an important area of future clinical research.

Prevention of IL-6 signaling ameliorates toluene diisocyanate-induced steroid-resistant asthma

BACKGROUND

Accumulating evidence indicated the crucial role for interleukin 6 (IL-6) signaling in the development of allergic asthma. Yet, the role of IL-6 signaling in toluene diisocyanate (TDI)-induced mixed granulocytic airway inflammation still remains unclear. Thus, the aims of this study were to dissect the role of IL-6 signaling and to evaluate the effect of tocilizumab on TDI-induced steroid-resistant asthma.

METHODS

TDI-induced asthma model was prepared and asthmatic mice were respectively given IL-6 monoclonal antibody, IL-6R monoclonal antibody (tocilizumab, 5 mg/kg, i.p. after each challenge) for therapeutic purposes or isotype IgG as control.

RESULTS

TDI exposure just elevated IL-6R expression in the infiltrated inflammatory cells around the airway, but increased glycoprotein 130 expression in the whole lung, especially in bronchial epithelium. Moreover, TDI inhalation increased airway hyperresponsiveness (AHR) to methacholine, coupled with mixed granulocytic inflammation, exaggerated epithelial denudation, airway smooth muscle thickening, goblet cell metaplasia, extensive submucosal collagen deposition, dysregulated Th2/Th17 responses, as well as innate immune responses and raised serum IgE. And almost all these responses except for raised serum IgE were markedly ameliorated by the administration of IL-6 neutralizing antibody or tocilizumab, but exhibited poor response to systemic steroid treatment. Also, TDI challenge induced nucleocytoplasm translocation of HMGB1 and promoted its release in the BALF, as well as elevated lung level of STAT3 phosphorylation, which were inhibited by anti-IL-6 and anti-IL-6R treatment.

CONCLUSIONS

Our data suggested that IL-6 monoclonal antibody and tocilizumab might effectively abrogate TDI-induced airway inflammation and remodeling, which could be used as a clinical potential therapy for patients with severe asthma.

Lung Inflammatory Response to Environmental Dust Exposure in Mice Suggests a Link to Regional Respiratory Disease Risk

PURPOSE

The Salton Sea, California's largest lake, is designated as an agricultural drainage reservoir. In recent years, the lake has experienced shrinkage due to reduced water sources, increasing levels of aerosolized dusts in surrounding regions. Communities surrounding the Salton Sea have increased asthma prevalence versus the rest of California; however, a connection between dust inhalation and lung health impacts has not been defined.

METHODS

We used an established intranasal dust exposure murine model to study the lung inflammatory response following single or repetitive (7-day) exposure to extracts of dusts collected in regions surrounding the Salton Sea (SSDE), complemented with in vitro investigations assessing SSDE impacts on the airway epithelium.

RESULTS

In these investigations, single or repetitive SSDE exposure induced significant lung inflammatory cytokine release concomitant with neutrophil influx. Repetitive SSDE exposure led to significant lung eosinophil recruitment and altered expression of genes associated with allergen-mediated immune response, including Clec4e. SSDE treatment of human bronchial epithelial cells (BEAS-2B) induced inflammatory cytokine production at 5- and 24-hours post-treatment. When BEAS-2B were exposed to protease activity-depleted SSDE (PDSSDE) or treated with SSDE in the context of protease-activated receptor-1 and -2 antagonism, inflammatory cytokine release was decreased. Furthermore, repetitive exposure to PDSSDE led to decreased neutrophil and eosinophilic influx and IL-6 release in mice compared to SSDE-challenged mice.

CONCLUSION

These investigations demonstrate potent lung inflammatory responses and tissue remodeling in response to SSDE, in part due to environmental proteases found within the dusts. These studies provide the first evidence supporting a link between environmental dust exposure, protease-mediated immune activation, and respiratory disease in the Salton Sea region.

Pharmacological Inhibition of the Nod-Like Receptor Family Pyrin Domain Containing 3 Inflammasome with MCC950

Activation of the Nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome drives release of the proinflammatory cytokines interleukin (IL)-1β and IL-18 and induces pyroptosis (lytic cell death). These events drive chronic inflammation, and as such, NLRP3 has been implicated in a large number of human diseases. These range from autoimmune conditions, the simplest of which is NLRP3 gain-of-function mutations leading to an orphan disease, cryopyrin-associated period syndrome, to large disease burden indications, such as atherosclerosis, heart failure, stroke, neurodegeneration, asthma, ulcerative colitis, and arthritis. The potential clinical utility of NLRP3 inhibitors is substantiated by an expanding list of indications in which NLRP3 activation has been shown to play a detrimental role. Studies of pharmacological inhibition of NLRP3 in nonclinical models of disease using MCC950 in combination with human genetics, epigenetics, and analyses of the efficacy of biologic inhibitors of IL-1β, such as anakinra and canakinumab, can help to prioritize clinical trials of NLRP3-directed therapeutics. Although MCC950 shows excellent (nanomolar) potency and high target selectivity, its pharmacokinetic and toxicokinetic properties limited its therapeutic development in the clinic. Several improved, next-generation inhibitors are now in clinical trials. Hence the body of research in a plethora of conditions reviewed herein may inform analysis of the potential translational value of NLRP3 inhibition in diseases with significant unmet medical need. SIGNIFICANCE STATEMENT: The nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is one of the most widely studied and best validated biological targets in innate immunity. Activation of NLRP3 can be inhibited with MCC950, resulting in efficacy in more than 100 nonclinical models of inflammatory diseases. As several next-generation NLRP3 inhibitors are entering proof-of-concept clinical trials in 2020, a review of the pharmacology of MCC950 is timely and significant.

microRNA-22-3p plays a protective role in a murine asthma model through the inhibition of the NLRP3-caspase-1-IL-1β axis

NEW FINDINGS

What is the central question of this study? How does miR-22-3p exert a protective role in asthma? What is the main finding and its importance? Upregulation of miR-22-3p hampered airway inflammation and release of inflammatory cytokines through blocking the activation of the NLRP3-caspase-1-IL-1β signalling pathway in asthma.

ABSTRACT

Asthma, a great public health burden, is triggered by inflammatory responses in the airways and these are not addressed appropriately by current therapies. This study aims to investigate the regulatory mechanism of microRNA-22-3p (miR-22-3p) on the proliferation of bronchial epithelial cells exposed to lipopolysaccharide (LPS) and expression of pro-inflammatory cytokines in a murine asthma model challenged by ovalbumin. We first confirmed the downregulation of miR-22-3p in the murine asthma model and bronchial epithelial cells. miR-22-3p remarkably reversed the decline in bronchial epithelial cell viability, enhancement in apoptosis rate and release of inflammatory factors induced by LPS. miR-22-3p targeted and conversely regulated NACHT, LRR and PYD domains-containing protein 3 (NLRP3). Overexpression of NLRP3 counteracted the inhibitory effect of miR-22-3p on inflammatory damage in bronchial epithelial cells through activation of caspase-1/interleukin (IL)-1β. In an in vivo model, overexpression of miR-22-3p significantly attenuated airway obstruction and tissue damage in mice. In summary, our study underscores that miR-22-3p serves both as a negative regulator of the NLRP3-caspase-1-IL-1β axis and as a protective factor against the inflammatory response, suggesting a future therapeutic role in asthma.

Anti-DLL4 ameliorates toluene diisocyanate-induced experimental asthma by inhibiting Th17 response

Toluene diisocyanate (TDI) exhibits an ability to induce steroid insensitive asthma with the involvement of Th17 cells. And emerging evidence has indicated that DLL4 signaling promotes Th17 differentiation through directly upregulating Rorc and IL-17 transcription. Thus, we sought to evaluate the effects of DLL4 blocking antibody on TDI-induced asthma model. Female BALB/c mice were sensitized and challenged with TDI to generate an asthma model. TDI-exposed mice were intraperitoneally injected with anti-DLL4 antibody and then analyzed for various parameters of the airway inflammatory responses. Increased expression of DLL4 in spleen and lung was detected in TDI-exposed mice. Furthermore, anti-DLL4 treatment alleviated TDI-induced airway hyperreactivity (AHR), airway inflammation, airway epithelial injury and airway smooth muscle (ASM) thickening. In the meantime, neutralizing DLL4 also blunted Th17 response via downregulation of ROR-γt expression, while had no effect on Th2 cells and regulatory T (Treg) cells. Overall, anti-DLL4 ameliorated TDI-induced experimental asthma by inhibiting Th17 response, implying the feasibility of targeting DLL4 for therapy of Th17-predominant severe asthma.

The Role of Group 3 Innate Lymphoid Cells in Lung Infection and Immunity

The lung is constantly exposed to environmental particulates such as aeroallergens, pollutants, or microorganisms and is protected by a poised immune response. Innate lymphoid cells (ILCs) are a population of immune cells found in a variety of tissue sites, particularly barrier surfaces such as the lung and the intestine. ILCs play a crucial role in the innate immune system, and they are involved in the maintenance of mucosal homeostasis, inflammation regulation, tissue remodeling, and pathogen clearance. In recent years, group 3 innate lymphoid cells (ILC3s) have emerged as key mediators of mucosal protection and repair during infection, mainly through IL-17 and IL-22 production. Although research on ILC3s has become focused on the intestinal immunity, the biology and function of pulmonary ILC3s in the pathogenesis of respiratory infections and in the development of chronic pulmonary inflammatory diseases remain elusive. In this review, we will mainly discuss how pulmonary ILC3s act on protection against pathogen challenge and pulmonary inflammation, as well as the underlying mechanisms.

Immunological Roles of NLR in Allergic Diseases and Its Underlying Mechanisms

Our understanding on the immunological roles of pathogen recognition in innate immunity has vastly increased over the past 20 years. Nucleotide-binding oligomerization domain (NOD)-like receptors (NLR) are cytosolic pattern recognition receptors (PRR) that are responsible for sensing microbial motifs and endogenous damage signals in mammalian cytosol for immune surveillance and host defense. The accumulating discoveries on these NLR sensors in allergic diseases suggest that the pathogenesis of allergic diseases may not be confined to the adaptive immune response. Therapy targeting NLR in murine models also shields light on its potential in the treatment of allergies in man. In this review, we herein summarize the recent understanding of the role of NLR sensors and their molecular mechanisms involved in allergic inflammation, including atopic dermatitis and allergic asthma.

VX-765 reduces neuroinflammation after spinal cord injury in mice

Inflammation is a major cause of neuronal injury after spinal cord injury. We hypothesized that inhibiting caspase-1 activation may reduce neuroinflammation after spinal cord injury, thus producing a protective effect in the injured spinal cord. A mouse model of T9 contusive spinal cord injury was established using an Infinite Horizon Impactor, and VX-765, a selective inhibitor of caspase-1, was administered for 7 successive days after spinal cord injury. The results showed that: (1) VX-765 inhibited spinal cord injury-induced caspase-1 activation and interleukin-1β and interleukin-18 secretion. (2) After spinal cord injury, an increase in M1 cells mainly came from local microglia rather than infiltrating macrophages. (3) Pro-inflammatory Th1Th17 cells were predominant in the Th subsets. VX-765 suppressed total macrophage infiltration, M1 macrophages/microglia, Th1 and Th1Th17 subset differentiation, and cytotoxic T cells activation; increased M2 microglia; and promoted Th2 and Treg differentiation. (4) VX-765 reduced the fibrotic area, promoted white matter myelination, alleviated motor neuron injury, and improved functional recovery. These findings suggest that VX-765 can reduce neuroinflammation and improve nerve function recovery after spinal cord injury by inhibiting caspase-1/interleukin-1β/interleukin-18. This may be a potential strategy for treating spinal cord injury. This study was approved by the Animal Care Ethics Committee of Bengbu Medical College (approval No. 2017-037) on February 23, 2017.

MiR-223 plays a protecting role in neutrophilic asthmatic mice through the inhibition of NLRP3 inflammasome

Background

Neutrophilic subtype asthma occurs in approximately 15–25% of the asthma cases and is associated with severe airflow obstruction, corticosteroid resistance. MicroRNA plays a vital role in regulating many immune processes, but how miRNA circuits coordinate airway inflammation during neutrophilic asthma is unclear.

Methods

To investigate the molecular mechanism of miR-223 in regulation of neutrophilic airway inflammation, miR-223 knockout mice were used to the OVA/CFA-induced neutrophilic asthma or treated with NLRP3 inhibitor and IL-1β receptor antagonist. Based on the results obtained, wide-type mice were subsequently treated with miR-223 agomirs or negative control agomirs, and the effects on airway inflammation were assessed using morphometric techniques, quantitative RT-PCR, western blot, ELISA and other molecular approaches.

Results

The expression of miR-223 was upregulated in lung tissues of experimental mice model. Furthermore, miR-223^−/− mice led to aggravated neutrophilic airway inflammation with heightened histopathological, inflammatory cells and cytokines readouts. Moreover, miR-223^−/− mice also presented with enhanced NLRP3 inflammasome level with elevated IL-1β. Blocking NLRP3 or IL-1β diminished this phenotype. Finally, overexpression of miR-223 via treatment with miR-223 agomirs attenuated airway inflammation, NLRP3 levels and IL-1β release.

Conclusions

The findings of this study revealed a crucial role for miR-223 in regulating the immunoinflammatory responses by depressing the NLRP3/ IL-1β axis in neutrophilic asthma.

NLRP3 Inflammasome is Activated in Rat Pancreatic Islets by Transplantation and Hypoxia

Hypoxia, IL-1β production and oxidative stress are involved in islet graft dysfunction and destruction. However, the link between these events has not yet been determined in transplanted islets. The goal of this study was to determine whether NLRP3 inflammasome is responsible for IL-1β production and if it is activated by hypoxia-induced oxidative stress in transplanted islets. Rat islets were transplanted under the kidney capsule of immunodeficient mice. At different times post-transplantation, blood samples were collected and islet grafts harvested. Rat islets were also incubated in vitro either under normoxia or hypoxia for 24 h, in the absence or presence of inhibitors of NLRP3 inflammasome (CASP1 inhibitor) or oxidative stress (NAC). NLRP3, CASP1, IL1B, BBC3 pro-apoptotic and BCL2 anti-apoptotic genes in transplanted and in vitro incubated islets were then studied using real time PCR. IL-1β released in the blood and in the supernatant was quantified by ELISA. Cell death was analysed by propidium iodide and Annexin-V staining. NLRP3, CASP1 and BBC3 in transplanted rat islets and IL-1β in blood transiently increased during the first days after transplantation. In islets incubated under hypoxia, NRLP3, IL1B and CASP1 and IL-1β released in supernatant increased compared to islets incubated under normoxia. These effects were prevented by the inhibition of NLRP3 inflammasome by CASP1 or oxidative stress by NAC. However, these inhibitors did not prevent hypoxia-induced rat islet death. These data show that NLRP3 inflammasome in rat islets is transiently activated after their transplantation and induced through oxidative stress in vitro. However, NRLP3 inflammasome inhibition does not protect islet cells against hypoxia.

Ameliorative effect of selective NLRP3 inflammasome inhibitor MCC950 in an ovalbumin-induced allergic rhinitis murine model

Allergic rhinitis (AR) is a complex IgE-mediated nasal allergic and inflammatory disease. Nucleotide-binding domain (NOD)-like receptor protein 3 (NLRP3) is essential in the process of allergic and inflammatory responses. MCC950 is a selective NLRP3 inhibitor. However, its role and mechanism in AR remains undetermined. The present study aimed to explore the effect and mechanism of MCC950 on an ovalbumin (OVA) induced mouse model of AR. The AR BALB/c mice were constructed using OVA and administrated intranasally with MCC950. Concentrations of OVA-specific IgE, histamines and leukotrienes C4 (LTC4) in serum, and OVA-specific IgE, ECP, IFN-γ, IL-4, IL-5, IL-13, IL-1β and IL-18 in nasal lavage fluid (NLF) were assayed by enzyme-linked immunosorbent assay (ELISA). Inflammatory cells were counted in NLF. HE and PAS staing were used for evaluating eosinophils and goblet cells. Immunohistochemistry (IHC) staining were employed to evaluate immunolabeling of NLRP3, Caspase-1, ASC, IL-1β and IL-18 in nasal mucosas of mice. Real-time PCR was conducted to assay NLRP3, Caspase-1, ASC, IL-1β and IL-18 mRNA levels. In vitro studies, western blotting, real-time PCR and ELISA were performed to evaluate the effects and mechanisms of OVA and NLRP3 inhibitor MCC950 on spleen mononuclear cells. We found significant downregulation of sneezing, nasal rubbing, inflammatory cytokines, inflammatory cells and NLRP3, Caspase-1, ASC, IL-1β and IL-18 expression in MCC950 treated mice compared with untreated AR mice. In spleen mononuclear cells culture and stimulation experiment, NLRP3, Caspase-1, ASC, IL-1β and IL-18 levels were upregulated by OVA but inhibited by MCC950. In conclusion, MCC950 could effectively exert its ameliorative effect in murine AR by inhibiting NLRP3 and leads to reduction of Caspase-1, ASC, IL-1β and IL-18, resulting in the attenuation of the allergic and inflammatory responses.

Bronchial epithelial pyroptosis promotes airway inflammation in a murine model of toluene diisocyanate-induced asthma

Airway epithelial injury in response to allergens such as toluene diisocyanate (TDI) leads to persistent airway inflammation. Pyroptosis is recognized as a strong proinflammatory cell death process. However, the role of pyroptosis in bronchial epithelial injury and airway inflammation in TDI-induced asthma remains unknown. In this study, cytotoxic effect of TDI on 16HBE cells (a human bronchial epithelial cell line) was detected. Then a TDI-induced experimental asthma mouse model was established for in vivo study. Here we found that TDI induced pyroptosis in 16HBE cells, as evidenced by enhanced expressions of caspase-1 and elevated levels of LDH, IL-1β and HMGB1. As expected, TDI-induced inflammatory cell death was significantly blocked by a specific NLRP3 inflammasome inhibitor. Intriguingly, in asthmatic mice, the increased cleavages of caspase-1 and pyroptotic executioner gasdermin D (GSDMD) in bronchial epithelial cells were decreased by NLRP3 inflammasome inhibitor. Furthermore, inhibition of NLRP3 inflammasome attenuated airway hyper-responsiveness and airway inflammation, accompanied by lower levels of IL-1β, IgE and Th2-related cytokines. Our data suggest that bronchial epithelial pyroptosis exacerbates airway inflammation and hyper-responsiveness in TDI-induced asthma via NLRP3 inflammasome activation and GSDND cleavage. Therefore, NLRP3 inflammasome-mediated pyroptosis may be a potential treatment target for TDI-induced asthma.

Toll-like Receptor 4 Deficiency Aggravates Airway Hyperresponsiveness and Inflammation by Impairing Neutrophil Apoptosis in a Toluene Diisocyanate-Induced Murine Asthma Model

PURPOSE

Accumulating evidence has suggested that toll-like receptor 4 (TLR4) is critically involved in the pathogenesis of asthma. The aim of this study was to investigate the role of TLR4 in toluene diisocyanate (TDI)-induced allergic airway inflammation.

METHODS

TLR4^-/- and wild-type (WT) C57BL/10J mice were sensitized and challenged with TDI to generate a TDI-induced asthma model. B-cell lymphoma 2 (Bcl-2) inhibitors, ABT-199 (4 mg/kg) and ABT-737 (4 mg/kg), were intranasally given to TDI-exposed TLR4^-/- mice after each challenge.

RESULTS

TDI exposure led to increased airway hyperresponsiveness (AHR), granulocyte flux, bronchial epithelial shedding and extensive submucosal collagen deposition, which were unexpectedly aggravated by TLR4 deficiency. Following TDI challenge, TLR4^-/- mice exhibited down-regulated interleukin-17A and increased colony-stimulating factor 3 in bronchoalveolar lavage fluid (BALF), while WT mice did not. In addition, TLR4 deficiency robustly suppressed the expression of NOD-like receptor family pyrin domain containing 3 and NLR family CARD domain containing 4, decreased caspase-1 activity in TDI-exposed mice, but had no effect on the level of high mobility group box 1 in BALF. Flow cytometry revealed that TDI hampered both neutrophil and eosinophil apoptosis, of which neutrophil apoptosis was further inhibited in TDI-exposed TLR4^-/- mice, with marked up-regulation of Bcl-2. Moreover, inhibition of Bcl-2 with either ABT-199 or ABT-737 significantly alleviated neutrophil recruitment by promoting apoptosis.

CONCLUSIONS

These data indicated that TLR4 deficiency promoted neutrophil infiltration by impairing its apoptosis via up-regulation of Bcl-2, thereby resulting in deteriorated AHR and airway inflammation, which suggests that TLR4 could be a negative regulator of TDI-induced neutrophilic inflammation.