Interleukin-17A and Toll-Like Receptor 3 Ligand Poly(I:C) Synergistically Induced Neutrophil Chemoattractant Production by Bronchial Epithelial Cells

Vitamin D3 suppresses NLRP3 inflammasome pathway and enhances steroid sensitivity in a neutrophilic steroid hyporesponsive asthma mouse model

OBJECTIVE

Severe steroid hyporesponsive asthma is a heterogeneous group of chronic inflammatory diseases characterized by irreversible airflow limitation, hyperresponsiveness, inflammation, and remodelling of the airways. Severe asthmatics account for more than 60% of asthma-related healthcare cost worldwide given they are hyporesponsive to corticosteroids and due to the absence of targeted treatment specifically for the T helper-17 (Th-17) high endotype. Hence, there is a clear unmet need to investigate other treatment options to control patients' symptoms. The role of the NLRP3 inflammasome pathway has been highlighted in the literature to contribute to disease pathogenesis and severity. Interestingly, vitamin D3 is an important regulator of the NLRP3 inflammasome pathway.

METHODS

Using house dust mite (HDM) and lipopolysaccharide (LPS), we induced a neutrophilic steroid hyporesponsive asthma mouse model to investigate the effect of vitamin D3 on downregulating the NLRP3 inflammasome pathway and enhancing steroid sensitivity.

RESULTS

We showed that calcitriol, the active form of vitamin D3, could downregulate the NLRP3 inflammasome pathway. This was associated with a significant reduction in airway hyperresponsiveness, IL-17 release, neutrophil infiltration, and mucus secretion. Further, calcitriol enhanced steroid sensitivity by inhibiting the expression of GR-β. Mechanistically, calcitriol targeted the NLRP3 inflammasome to ubiquitination.

CONCLUSIONS

Our research highlights the potential use of calcitriol as a low cost and accessible supplement to ameliorate airway inflammation during severe steroid hyporesponsive asthma.

Novel Biological Therapies for Severe Asthma Endotypes

Severe asthma comprises several heterogeneous phenotypes, underpinned by complex pathomechanisms known as endotypes. The latter are driven by intercellular networks mediated by molecular components which can be targeted by specific monoclonal antibodies. With regard to the biological treatments of either allergic or non-allergic eosinophilic type 2 asthma, currently available antibodies are directed against immunoglobulins E (IgE), interleukin-5 (IL-5) and its receptor, the receptors of interleukins-4 (IL-4) and 13 (IL-13), as well as thymic stromal lymphopoietin (TSLP) and other alarmins. Among these therapeutic strategies, the best choice should be made according to the phenotypic/endotypic features of each patient with severe asthma, who can thus respond with significant clinical and functional improvements. Conversely, very poor options so far characterize the experimental pipelines referring to the perspective biological management of non-type 2 severe asthma, which thereby needs to be the focus of future thorough research.

Changes in the phenotype and function of mucosal-associated invariant T cells in neutrophilic asthma

Asthma is a chronic heterogeneous inflammatory disease. Most neutrophilic asthma (NA) cases are severe asthma involving many inflammatory cells and mediators, although the specific pathogenesis is not clear. Mucosal-associated invariant T (MAIT) cells as innate-like T lymphocytes play an important role in the immune response in asthma by producing cytokines. In this study, we evaluated the phenotype and function of circulating MAIT cells in patients with NA and inflammatory-related cytokines in plasma and induced sputum supernatants using flow cytometry. The results showed that the frequency of circulating MAIT cells in asthma patients, particularly NA patients, decreased significantly, and CD8⁺ MAIT and MAIT Temra cells also decreased significantly. Increased expression of CD69 and PD-1 on MAIT cells indicated excessive activation and depletion, leading to the decrease in MAIT cells. Levels of IL-17A and TNF-α secreted by MAIT cells of NA patients increased, whereas IFN-γ levels decreased, indicating that MAIT cells in NA are biased to the Th17 subtype. MAIT cells were also negatively correlated with clinical parameters, indicating that these cells are related to asthma severity. Pro-inflammatory cytokines in plasma and sputum supernatant increased to varying degrees, whereas IL-10 declined, corresponding with asthma severity. We speculate that increased IL-17A and TNF-α synergistically stimulated respiratory epithelial cells to secrete IL-6 and IL-8, thereby recruiting neutrophils to inflammatory sites and aggravating asthma symptoms. Therefore, MAIT cells could serve as a potential therapeutic target in NA immunity, thus providing a new strategy for the treatment of 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.

Elovanoids Counteract Inflammatory Signaling, Autophagy, Endoplasmic Reticulum Stress, and Senescence Gene Programming in Human Nasal Epithelial Cells Exposed to Allergens

To contribute to further understanding the cellular and molecular complexities of inflammatory-immune responses in allergic disorders, we have tested the pro-homeostatic elovanoids (ELV) in human nasal epithelial cells (HNEpC) in culture challenged by several allergens. ELV are novel bioactive lipid mediators synthesized from the omega-3 very-long-chain polyunsaturated fatty acids (VLC-PUFA,n-3). We ask if: (a) several critical signaling events that sustain the integrity of the human nasal epithelium and other organ barriers are perturbed by house dust mites (HDM) and other allergens, and (b) if ELV would participate in beneficially modulating these events. HDM is a prevalent indoor allergen that frequently causes allergic respiratory diseases, including allergic rhinitis and allergic asthma, in HDM-sensitized individuals. Our study used HNEpC as an in vitro model to study the effects of ELV in counteracting HDM sensitization resulting in inflammation, endoplasmic reticulum (ER) stress, autophagy, and senescence. HNEpC were challenged with the following allergy inducers: LPS, poly(I:C), or Dermatophagoides farinae plus Dermatophagoides pteronyssinus extract (HDM) (30 µg/mL), with either phosphate-buffered saline (PBS) (vehicle) or ELVN-34 (500 nM). Results show that ELVN-34 promotes cell viability and reduces cytotoxicity upon HDM sensitization of HNEpC. This lipid mediator remarkably reduces the abundance of pro-inflammatory cytokines and chemokines IL-1β, IL-8, VEGF, IL-6, CXCL1, CCL2, and cell adhesion molecule ICAM1 and restores the levels of the pleiotropic anti-inflammatory IL-10. ELVN-34 also lessens the expression of senescence gene programming as well as of gene transcription engaged in pro-inflammatory responses. Our data also uncovered that HDM triggered the expression of key genes that drive autophagy, unfolded protein response (UPR), and matrix metalloproteinases (MMP). ELVN-34 has been shown to counteract these effects effectively. Together, our data reveal a novel, pro-homeostatic, cell-protective lipid-signaling mechanism in HNEpC as potential therapeutic targets for allergies.

Viral mimetic triggers cerebral arteriopathy in juvenile brain via neutrophil elastase and NETosis

Stroke is among the top ten causes of death in children but has received disproportionally little attention. Cerebral arteriopathies account for up to 80% of childhood arterial ischemic stroke (CAIS) cases and are strongly predictive of CAIS recurrence and poorer outcomes. The underlying mechanisms of sensitization of neurovasculature by viral infection are undefined. In the first age-appropriate model for childhood arteriopathy-by administration of viral mimetic TLR3-agonist Polyinosinic:polycytidylic acid (Poly-IC) in juvenile mice-we identified a key role of the TLR3-neutrophil axis in disrupting the structural-functional integrity of the blood-brain barrier (BBB) and distorting the developing neurovascular architecture and vascular networks. First, using an array of in-vivo/post-vivo vascular imaging, genetic, enzymatic and pharmacological approaches, we report marked Poly-IC-mediated extravascular leakage of albumin (66kDa) and of a small molecule DiI (∼934Da) and disrupted tight junctions. Poly-IC also enhanced the neuroinflammatory milieu, promoted neutrophil recruitment, profoundly upregulated neutrophil elastase (NE), and induced neutrophil extracellular trap formation (NETosis). Finally, we show that functional BBB disturbances, NETosis and neuroinflammation are markedly attenuated by pharmacological inhibition of NE (Sivelestat). Altogether, these data reveal NE/NETosis as a novel therapeutic target for viral-induced cerebral arteriopathies in children.

ORMDL3 regulates poly I:C induced inflammatory responses in airway epithelial cells

BACKGROUND

Oroscomucoid 3 (ORMDL3) has been linked to susceptibility of childhood asthma and respiratory viral infection. Polyinosinic-polycytidylic acid (poly I:C) is a synthetic analog of viral double-stranded RNA, a toll-like receptor 3 (TLR3) ligand and mimic of viral infection.

METHODS

To investigate the functional role of ORMDL3 in the poly I:C-induced inflammatory response in airway epithelial cells, ORMDL3 knockdown and over-expression models were established in human A549 epithelial cells and primary normal human bronchial epithelial (NHBE) cells. The cells were stimulated with poly I:C or the Th17 cytokine IL-17A. IL-6 and IL-8 levels in supernatants,  mRNA levels of genes in the TLR3 pathway and inflammatory response from cell pellets were measured. ORMDL3 knockdown models in A549 and BEAS-2B epithelial cells were then infected with live human rhinovirus (HRV16) followed by IL-6 and IL-8 measurement.

RESULTS

ORMDL3 knockdown and over-expression had little influence on the transcript levels of TLR3 in airway epithelial cells. Time course studies showed that ORMDL3-deficient A549 and NHBE cells had an attenuated IL-6 and IL-8 response to poly I:C stimulation. A549 and NHBE cells over-expressing ORMDL3 released relatively more IL-6 and IL-8 following poly I:C stimulation. IL-17A exhibited a similar inflammatory response in ORMDL3 knockdown and over-expressing cells, but co-stimulation of poly I:C and IL-17A did not significantly enhance the IL-6 and IL-8 response. Transcript abundance of IFNB following poly I:C stimulation was not significantly altered by ORMDL3 knockdown or over-expression. Dampening of the IL-6 response by ORMDL3 knockdown was confirmed in HRV16 infected BEAS-2B and A549 cells.

CONCLUSIONS

ORMDL3 regulates the viral inflammatory response in airway epithelial cells via mechanisms independent of the TLR3 pathway.

Targeting neutrophils in asthma: A therapeutic opportunity?

Suppression of airway inflammation with inhaled corticosteroids has been the key therapeutic approach for asthma for many years. Identification of inflammatory phenotypes in asthma has moreover led to important breakthroughs, e.g. with specific targeting of the IL-5 pathway as add-on treatment in difficult-to-treat eosinophilic asthma. However, the impact of interfering with the neutrophilic component in asthma is less documented and understood. This review provides an overview of established and recent insights with regard to the role of neutrophils in asthma, focusing on research in humans. We will describe the main drivers of neutrophilic responses in asthma, the heterogeneity in neutrophils and how they could contribute to asthma pathogenesis. Moreover we will describe findings from clinical trials, in which neutrophilic inflammation was targeted. It is clear that neutrophils are important actors in asthma development and play a role in exacerbations. However, more research is required to fully understand how modulation of neutrophil activity could lead to a significant benefit in asthma patients with airway neutrophilia.

ASCL1 promotes tumor progression through cell-autonomous signaling and immune modulation in a subset of lung adenocarcinoma

The master regulator of neuroendocrine differentiation, achaete-scute complex homolog 1 (ASCL1) defines a subgroup of lung adenocarcinoma. However, the mechanistic role of ASCL1 in lung tumorigenesis and its relation to the immune microenvironment is principally unknown. Here, the immune landscape of ASCL1-positive lung adenocarcinomas was characterized by immunohistochemistry. Furthermore, ASCL1 was transduced in mouse lung adenocarcinoma cell lines and comparative RNA-sequencing and secretome analyses were performed. The effects of ASCL1 on tumorigenesis were explored in an orthotopic syngeneic transplantation model. ASCL1-positive lung adenocarcinomas revealed lower infiltration of CD8⁺, CD4⁺, CD20⁺, and FOXP3⁺ lymphocytes and CD163⁺ macrophages indicating an immune desert phenotype. Ectopic ASCL1 upregulated cyclin transcript levels, stimulated cell proliferation, and enhanced tumor growth in mice. ASCL1 suppressed secretion of chemokines, including CCL20, CXCL2, CXCL10, and CXCL16, indicating effects on immune cell trafficking. In accordance with lower lymphocytes infiltration, ASCL1-positive lung adenocarcinomas demonstrated lower abundance of CXCR3-and CCR6-expressing cells. In conclusion, ASCL1 mediates its tumor-promoting effect not only through cell-autonomous signaling but also by modulating chemokine production and immune responses. These findings suggest that ASCL1-positive tumors represent a clinically relevant lung cancer entity.

Artemisia Pollen Extracts Exposed to Diesel Exhaust Enhance Airway Inflammation and Immunological Imbalance in Asthmatic Mice Model

BACKGROUND

Vehicle-induced air pollution may increase the prevalence and severity of asthma. Pollens are important sources of outdoor allergens associated with asthma. Outdoor pollution may influence the structure of pollen grains, resulting in enhanced immune reactions.

OBJECTIVE

This study aims to investigate the impact that artemisia pollen extracts exposed to diesel emissions (APEDE) may induce - allergic airway inflammation, pulmonary pathology and immune imbalance - in mice.

METHODS

Sixty male Balb/c mice were equally randomized into 5 groups, sensitized with 30 μL artemisia pollen extracts (APE) or APEDE adsorbed on 2 mg aluminum hydroxide gel by intraperitoneal injection on day 0, 7, 14, and 22, and challenged intranasally once per day with 30 μL APE or APEDE from day 29 to 36. The controlling group used phosphate-buffered saline as control.

RESULTS

In mice immunized and challenged by APEDE, the clinical phenotype of eosinophils, neutrophils in bronchoalveolar lavage fluid (BALF), tracheal wall thickness, airway smooth muscle thickness and airway resistance increased significantly. Pathophysiological parameters such as interleukin (IL)-17A and tumour necrosis factor-α production in BALF and serum, and the ratio of Th17/Treg cells in CD4+ cells increased significantly, while IL-10 in BALF and serum and the ratio of Treg cells decreased significantly. It was further found that the expression of oxidative stress marker 3-nitrotyrosine (3-NT) and the activation of nuclear factor kappa B (NF-κB) were significantly increased. The correlation analysis showed that the expression of 3-NT was positively correlated with the activation of NF-κB.

CONCLUSION

Our findings suggested that pollens exposed to diesel exhaust enhance allergic responses, which may contribute to an increased prevalence of allergic diseases in urban environments with serious exhaust emissions.

Reduced expression of miR-146a in human bronchial epithelial cells alters neutrophil migration

Background

The role of miRNAs in the pathogenesis and determining the phenotypes of asthma is not fully elucidated. miR-146a has been previously shown to suppress inflammatory responses in different cells. In this study, we investigated the functions of miR-146a in human bronchial epithelial cells (HBECs) in association with neutrophilic, eosinophilic, and paucigranulocytic phenotypes of asthma.

Methods

Bronchial brushing specimens and brochial mucosal biopsy samples were collected from adult patients with asthma and from age- and gender-matched non-asthmatic individuals. The expression of miR-146a in bronchial brushing specimens, bronchial biopsy tissue sections or cultured primary bronchial epithelial cells was analyzed by RT-qPCR or by in situ hybridization. The expression of direct and indirect miR-146a target genes was determined by RT-qPCR or ELISA. The migration of neutrophils was studied by neutrophil chemotaxis assay and flow cytometry. For statistical analysis, unpaired two-way Student’s t test, one-way ANOVA or linear regression analysis were used.

Results

Reduced expression of miR-146a was found in bronchial brushing specimens from asthma patients as compared to non-asthmatics and irrespective of the phenotype of asthma. In the same samples, the neutrophil attracting chemokines IL-8 and CXCL1 showed increased expression in patients with neutrophilic asthma and increased IL-33 expression was found in patients with eosinophilic asthma. Linear regression analysis revealed a significant negative association between the expression of miR-146a in bronchial brushings and neutrophil cell counts in bronchoalveolar lavage fluid of patients with asthma. In bronchial biopsy specimens, the level of miR-146a was highest in the epithelium as determined with in situ hybridization. In primary conventional HBEC culture, the expression of miR-146a was induced in response to the stimulation with IL-17A, TNF-α, and IL-4. The mRNA expression and secretion of IL-8 and CXCL1 was inhibited in both stimulated and unstimulated HBECs transfected with miR-146a mimics. Supernatants from HBECs transfected with miR-146a had reduced capability of supporting neutrophil migration in neutrophil chemotaxis assay.

Conclusion

Our results suggest that decreased level of miR-146a in HBECs from patients with asthma may contribute to the development of neutrophilic phenotype of asthma.

IL-17A Attenuates IFN-λ Expression by Inducing Suppressor of Cytokine Signaling Expression in Airway Epithelium

IFN-λ is a cytokine expressed in epithelial tissues and plays a central role in antiviral mucosal immune response. The expression of IFN-λ in the airway is impaired in chronic airway diseases (e.g., asthma, chronic obstructive pulmonary disease), which renders patients susceptible to viral infection. IL-17A is associated with asthma and chronic obstructive pulmonary disease pathogenesis; however, IL-17A regulation of IFN-λ expression remains unclear. The aim of the current study is to clarify IL-17A-mediated regulatory mechanisms of IFN-λ expression in human airway epithelial cells. In this study, we have shown that polyinosinic:polycytidylic acid (polyI:C) and influenza A virus (IAV) infection increased IFN-λ expression at mRNA and protein levels in primary cultures of normal human bronchial epithelial cells, whereas IL-17A attenuated polyI:C- or IAV-induced IFN-λ expression. IFN-λ receptor 1 knockdown and a JAK inhibitor, ruxolitinib, attenuated polyI:C-induced IFN-λ expression, confirming that a positive autocrine feedback loop, the IFN-λ receptor-JAK-STAT pathway, was involved in IFN-λ expression. In Western blotting analysis, we demonstrated that polyI:C and IAV infection induced STAT1 phosphorylation in normal human bronchial epithelial cells, whereas IL-17A suppressed polyI:C- or IAV-mediated STAT1 phosphorylation. Furthermore, we found that cotreatment with IL-17A and polyI:C or IAV infection synergistically increased suppressor of cytokine signaling (SOCS)1 and SOCS3 expression. SOCS1 small interfering RNA and SOCS3 small interfering RNA negated the inhibitory effect of IL-17A in polyI:C-induced IFN-λ expression by restoring attenuated STAT1 phosphorylation. Taken together, these findings indicate that IL-17A attenuates virus-induced IFN-λ expression by enhancing SOCS1 and SOCS3 expression to inhibit autocrine signaling loops in human airway epithelial cells.

Chemorepellent Semaphorin 3E Negatively Regulates Neutrophil Migration In Vitro and In Vivo

Neutrophil migration is an essential step in leukocyte trafficking during inflammatory responses. Semaphorins, originally discovered as axon guidance cues in neural development, have been shown to regulate cell migration beyond the nervous system. However, the potential contribution of semaphorins in the regulation of neutrophil migration is not well understood. This study examines the possible role of a secreted chemorepellent, Semaphorin 3E (Sema3E), in neutrophil migration. In this study, we demonstrated that human neutrophils constitutively express Sema3E high-affinity receptor, PlexinD1. Sema3E displayed a potent ability to inhibit CXCL8/IL-8-induced neutrophil migration as determined using a microfluidic device coupled to real-time microscopy and a transwell system in vitro. The antimigratory effect of Sema3E on human neutrophil migration was associated with suppression of CXCL8/IL-8-mediated Ras-related C3 botulinum toxin substrate 1 GTPase activity and actin polymerization. We further addressed the regulatory role of Sema3E in the regulation of neutrophil migration in vivo. Allergen airway exposure induced higher neutrophil recruitment into the lungs of Sema3e^-/- mice compared with wild-type controls. Administration of exogenous recombinant Sema3E markedly reduced allergen-induced neutrophil recruitment into the lungs, which was associated with alleviation of allergic airway inflammation and improvement of lung function. Our data suggest that Sema3E could be considered an essential regulatory mediator involved in modulation of neutrophil migration throughout the course of neutrophilic inflammation.