Neutrophils induce smooth muscle hyperplasia via neutrophil elastase-induced FGF-2 in a mouse model of asthma with mixed inflammation

Ferroptosis contributes to airway epithelial E-cadherin disruption in a mixed granulocytic asthma mouse model

Aberrant expression of airway epithelial E-cadherin is a key feature of asthma, yet the underlying mechanisms are largely unknown. Ferroptosis is a novel form of regulated cell death involved in asthma pathogenesis. This study was aimed to evaluate the role of ferroptosis and to investigate whether ferroptosis mediates E-cadherin disruption in mixed granulocyte asthma (MGA). Two murine models of MGA were established using toluene diisocyanate (TDI) or ovalbumin with Complete Freund's Adjuvant (OVA/CFA). Specific antagonists of ferroptosis, including Liproxstatin-1 (Lip-1) and Ferrostatin-1 (Fer-1) were given to the mice. The allergen-exposed mice displayed markedly shrunk mitochondria in the airway epithelia, with decreased volume and denser staining accompanied by down-regulated GPX4 as well as up-regulated FTH1 and malondialdehyde, which are markers of ferroptosis. Decreased pulmonary expression of E-cadherin was also observed, with profound loss of membrane E-cadherin in the airway epithelia, as well as increased secretion of sE-cadherin. Treatment with Lip-1 not only showed potent protective effects against the allergen-induced airway hyperresponsiveness and inflammatory responses, but also rescued airway epithelial E-cadherin expression and inhibited the release of sE-cadherin. Taken together, our data demonstrated that ferroptosis mediates airway epithelial E-cadherin dysfunction in MGA.

Machine Learning Prediction of Treatment Response to Inhaled Corticosteroids in Asthma

BACKGROUND

Although inhaled corticosteroids (ICS) are the first-line therapy for patients with persistent asthma, many patients continue to have exacerbations. We developed machine learning models to predict the ICS response in patients with asthma.

METHODS

The subjects included asthma patients of European ancestry (n = 1371; 448 children; 916 adults). A genome-wide association study was performed to identify the SNPs associated with ICS response. Using the SNPs identified, two machine learning models were developed to predict ICS response: (1) least absolute shrinkage and selection operator (LASSO) regression and (2) random forest.

RESULTS

The LASSO regression model achieved an AUC of 0.71 (95% CI 0.67-0.76; sensitivity: 0.57; specificity: 0.75) in an independent test cohort, and the random forest model achieved an AUC of 0.74 (95% CI 0.70-0.78; sensitivity: 0.70; specificity: 0.68). The genes contributing to the prediction of ICS response included those associated with ICS responses in asthma (TPSAB1, FBXL16), asthma symptoms and severity (ABCA7, CNN2, PTRN3, and BSG/CD147), airway remodeling (ELANE, FSTL3), mucin production (GAL3ST), leukotriene synthesis (GPX4), allergic asthma (ZFPM1, SBNO2), and others.

CONCLUSIONS

An accurate risk prediction of ICS response can be obtained using machine learning methods, with the potential to inform personalized treatment decisions. Further studies are needed to examine if the integration of richer phenotype data could improve risk prediction.

IRE1α/XBP-1 promotes β-catenin signaling activation of airway epithelium in lipopolysaccharide-induced acute lung injury

BACKGROUND

Acute lung injury (ALI), along with the more severe condition--acute respiratory distress syndrome (ARDS), is a major cause of respiratory failure in critically ill patients with high morbidity and mortality. Inositol-requiring protein 1α (IRE1α)/X box protein-1 (XBP1) pathway was proved to regulate lipopolysaccharide (LPS)-induced lung injury and inflammation. Yet, its role on epithelial β-catenin in LPS-induced ALI remains to be elucidated.

METHODS

LPS-induced models were generated in mice (5 mg/kg) and Beas-2B cells (200 μg/mL). Two selective antagonists of IRE1α (4μ8c and STF-083010) were respectively given to LPS-exposed mice and cultured cells.

RESULTS

Up-regulated expression of endoplasmic reticulum (ER) stress markers immunoglobulin-binding protein (BIP) and spliced X box protein-1(XBP-1s) was detected after LPS exposure. Besides, LPS also led to a down-regulated total β-catenin level in the lung and Beas-2B cells, with decreased membrane distribution as well as increased cytoplasmic and nuclear accumulation, paralleled by extensively up-regulated downstream targets of the Wnt/β-catenin signaling. Treatment with either 4μ8c or STF-083010 not only significantly attenuated LPS-induced lung injury and inflammation, but also recovered β-catenin expression in airway epithelia, preserving the adhesive function of β-catenin while blunting its signaling activity.

CONCLUSION

These results illustrated that IRE1α/XBP1 pathway promoted the activation of airway epithelial β-catenin signaling in LPS-induced ALI.

Macrophage migration inhibitory factor exacerbates asthmatic airway remodeling via dynamin-related protein 1-mediated autophagy activation

BACKGROUND

Macrophage migration inhibitory factor (MIF) and GTPase dynamin-related protein 1 (Drp1)-dependent aberrant mitochondrial fission are closely linked to the pathogenesis of asthma. However, it is unclear whether Drp1-mediated mitochondrial fission and its downstream targets mediate MIF-induced proliferation of airway smooth muscle cells (ASMCs) in vitro and airway remodeling in chronic asthma models. The present study aims to clarify these issues.

METHODS

In this study, primary cultured ASMCs and ovalbumin (OVA)-induced asthmatic rats were applied. Cell proliferation was detected by CCK-8 and EdU assays. Western blotting was used to detect extracellular signal-regulated kinase (ERK) 1/2, Drp1, autophagy-related markers and E-cadherin protein phosphorylation and expression. Inflammatory cytokines production, airway reactivity test, histological staining and immunohistochemical staining were conducted to evaluate the development of asthma. Transmission electron microscopy was used to observe the mitochondrial ultrastructure.

RESULTS

In primary cultured ASMCs, MIF increased the phosphorylation level of Drp1 at the Ser616 site through activation of the ERK1/2 signaling pathway, which further activated autophagy and reduced E-cadherin expression, ultimately leading to ASMCs proliferation. In OVA-induced asthmatic rats, MIF inhibitor 4-iodo-6-phenylpyrimidine (4-IPP) treatment, suppression of mitochondrial fission by Mdivi-1 or inhibiting autophagy with chloroquine phosphate (CQ) all attenuated the development of airway remodeling.

CONCLUSIONS

The present study provides novel insights that MIF promotes airway remodeling in asthma by activating autophagy and degradation of E-cadherin via ERK/Drp1 signaling pathway, suggesting that targeting MIF/ERK/Drp1 might have potential therapeutic value for the prevention and treatment of asthma.

Neutrophil elastase in dexmedetomidine alleviating sepsis-related renal injury in rats

BACKGROUND

This research was to investigate the mechanism of neutrophil elastase (NE) in dexmedetomidine (DEX) alleviates sepsis-related renal injury in rats.

METHODS

Sixty healthy male SD rats aged 6-7 weeks were randomly assigned to the control group (Sham group (S group)), Model group (M group), Model + DEX group (M + DEX group), and Model + DEX + Elaspol group (M + DEX + Elaspol (sivelestat) group), with 15 rats in each group. The renal morphology and pathological changes of different groups of rats after modeling were observed, and renal tubular injury was scored. Serum samples were collected at 6 h, 12 h, and 24 h after modeling, and the rats were sacrificed. Renal function indicators, including neutrophil gelatinase-associated lipoprotein (NGAL), kidney injury molecule-1 (KIM-1), tumor necrosis factor (TNF-α), interleukin-6 (IL-6), NE, serum creatinine (SCr), and blood urea nitrogen (BUN), were analyzed by enzyme-linked immunosorbent assay at different time periods. The level of NF-кB in renal tissue was detected by immunohistochemistry.

RESULTS

It was revealed that the general color of renal tissue in M group was dark red, swollen, and congested, and the renal tubular epithelial cells were significantly enlarged, with obvious vacuolar degeneration and inflammatory cell infiltration. Compared with M group, the color and morphology of renal tissue in M + DEX group and M + DEX + Elaspol group were improved, and the amount of inflammatory cell infiltration was reduced. The renal tubular injury score, SCr level, BUN level, NGAL level, KIM-1 level, TNF-α, IL-6, NE level, and NF-кB level in M group were significant different from S group 12 h after the operation (P < 0.001). The renal tubular injury score, SCr level, BUN level, NGAL level, KIM-1 level, TNF-α, IL-6, NE level, and NF-кB level in M + DEX group were significant different from M group (P < 0.01). The renal tubular injury score, SCr level, BUN level, NGAL level, KIM-1 level, TNF-α, IL-6, NE level, and NF-кB level in M + DEX + Elaspol group were significant different from those in M group at 12 h after the operation (P < 0.001).

CONCLUSION

NE plays an active role in the reduction of sepsis-related renal injury in rats by inhibiting the inflammatory response.

Glucocorticoid Alleviates Mechanical Stress-Induced Airway Inflammation and Remodeling in COPD via Transient Receptor Potential Canonical 1 Channel

Background

Increased airway resistance and hyperinflation in chronic obstructive pulmonary disease (COPD) are associated with increased mechanical stress that modulate many essential pathophysiological functions including airway remodeling and inflammation. Our present study aimed to investigate the role of transient receptor potential canonical 1 (TRPC1), a mechanosensitive cation channel in airway remodeling and inflammation in COPD and the effect of glucocorticoid on this process.

Methods

In patients, we investigated the effect of pathological high mechanical stress on the expression of airway remodeling-related cytokines transforming growth factor β1 (TGF-β1), matrix metalloproteinase-9 (MMP9) and the count of inflammatory cells in endotracheal aspirates (ETAs) by means of different levels of peak inspiratory pressure (PIP) under mechanical ventilation, and analyzed their correlation with TRPC1. Based on whether patients regularly used inhaled corticosteroid (ICS), COPD patients were further divided into ICS group (n = 12) and non-ICS group (n=15). The ICS effect on the expression of TRPC1 was detected by Western blot. In vitro, we imitated the mechanical stress using cyclic stretch and examined the levels of TGF-β1 and MMP-9. The role of TRPC1 was further explored by siRNA transfection and dexamethasone administration.

Results

Our results revealed that the TRPC1 level and the inflammatory cells counts were significantly higher in COPD group. After mechanical ventilation, the expression of TGF-β1 and MMP-9 in all COPD subgroups was significantly increased, while in the control group, only high PIP subgroup increased. Meanwhile, TRPC1 expression was positively correlated with the counts of inflammatory cells and the levels of TGF-β1 and MMP-9. In vitro, mechanical stretch significantly increased TGF-β1 and MMP-9 levels and such increase was greatly attenuated by TRPC1 siRNA transfection and dexamethasone administration.

Conclusion

Our results suggest that the increased TRPC1 may play a role in the airway inflammation and airway remodeling in COPD under high airway pressure. Glucocorticoid could in some degree alleviate airway remodeling via inhibition of TRPC1.

Airway epithelial ITGB4 deficiency induces airway remodeling in a mouse model

BACKGROUND

Airway epithelial cells (AECs) with impaired barrier function contribute to airway remodeling through the activation of epithelial-mesenchymal trophic units (EMTUs). Although the decreased expression of ITGB4 in AECs is implicated in the pathogenesis of asthma, how ITGB4 deficiency impacts airway remodeling remains obscure.

OBJECTIVE

This study aims to determine the effect of epithelial ITGB4 deficiency on the barrier function of AECs, asthma susceptibility, airway remodeling, and EMTU activation.

METHODS

AEC-specific ITGB4 conditional knockout mice (ITGB4^-/-) were generated and an asthma model was employed by the sensitization and challenge of house dust mite (HDM). EMTU activation-related growth factors were examined in ITGB4-silenced primary human bronchial epithelial cells of healthy subjects after HDM stimulation. Dexamethasone, the inhibitors of JNK phosphorylation or FGF2 were administered for the identification of the molecular mechanisms of airway remodeling in HDM-exposed ITGB4^-/- mice.

RESULTS

ITGB4 deficiency in AECs enhanced asthma susceptibility and airway remodeling by disrupting airway epithelial barrier function. Aggravated airway remodeling in HDM-exposed ITGB4^-/- mice was induced through the enhanced activation of EMTU mediated by Src homology domain 2-containing protein tyrosine phosphatase 2/c-Jun N-terminal kinase/Jun N-terminal kinase-dependent transcription factor/FGF2 (SHP2/JNK/c-Jun/FGF2) signaling pathway, which was partially independent of airway inflammation. Both JNK and FGF2 inhibitors significantly inhibited the aggravated airway remodeling and EMTU activation in HDM-exposed ITGB4^-/- mice.

CONCLUSIONS

Airway epithelial ITGB4 deficiency induces airway remodeling in a mouse model of asthma through enhanced EMTU activation that is regulated by the SHP2/JNK/c-Jun/FGF2 pathway.

Significance of Singlet Oxygen Molecule in Pathologies

Reactive oxygen species, including singlet oxygen, play an important role in the onset and progression of disease, as well as in aging. Singlet oxygen can be formed non-enzymatically by chemical, photochemical, and electron transfer reactions, or as a byproduct of endogenous enzymatic reactions in phagocytosis during inflammation. The imbalance of antioxidant enzymes and antioxidant networks with the generation of singlet oxygen increases oxidative stress, resulting in the undesirable oxidation and modification of biomolecules, such as proteins, DNA, and lipids. This review describes the molecular mechanisms of singlet oxygen production in vivo and methods for the evaluation of damage induced by singlet oxygen. The involvement of singlet oxygen in the pathogenesis of skin and eye diseases is also discussed from the biomolecular perspective. We also present our findings on lipid oxidation products derived from singlet oxygen-mediated oxidation in glaucoma, early diabetes patients, and a mouse model of bronchial asthma. Even in these diseases, oxidation products due to singlet oxygen have not been measured clinically. This review discusses their potential as biomarkers for diagnosis. Recent developments in singlet oxygen scavengers such as carotenoids, which can be utilized to prevent the onset and progression of disease, are also described.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

Neutrophils and Asthma

Although eosinophilic inflammation is characteristic of asthma pathogenesis, neutrophilic inflammation is also marked, and eosinophils and neutrophils can coexist in some cases. Based on the proportion of sputum cell differentiation, asthma is classified into eosinophilic asthma, neutrophilic asthma, neutrophilic and eosinophilic asthma, and paucigranulocytic asthma. Classification by bronchoalveolar lavage is also performed. Eosinophilic asthma accounts for most severe asthma cases, but neutrophilic asthma or a mixture of the two types can also present a severe phenotype. Biomarkers for the diagnosis of neutrophilic asthma include sputum neutrophils, blood neutrophils, chitinase-3-like protein, and hydrogen sulfide in sputum and serum. Thymic stromal lymphoprotein (TSLP)/T-helper 17 pathways, bacterial colonization/microbiome, neutrophil extracellular traps, and activation of nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3 pathways are involved in the pathophysiology of neutrophilic asthma and coexistence of obesity, gastroesophageal reflux disease, and habitual cigarette smoking have been associated with its pathogenesis. Thus, targeting neutrophilic asthma is important. Smoking cessation, neutrophil-targeting treatments, and biologics have been tested as treatments for severe asthma, but most clinical studies have not focused on neutrophilic asthma. Phosphodiesterase inhibitors, anti-TSLP antibodies, azithromycin, and anti-cholinergic agents are promising drugs for neutrophilic asthma. However, clinical research targeting neutrophilic inflammation is required to elucidate the optimal treatment.

Steroid-induced fibroblast growth factors drive an epithelial-mesenchymal inflammatory axis in severe asthma

Asthma and inflammatory airway diseases restrict airflow in the lung, compromising gas exchange and lung function. Inhaled corticosteroids (ICSs) can reduce inflammation, control symptoms, and improve lung function; however, a growing number of patients with severe asthma do not benefit from ICS. Using bronchial airway epithelial brushings from patients with severe asthma or primary human cells, we delineated a corticosteroid-driven fibroblast growth factor (FGF)-dependent inflammatory axis, with FGF-responsive fibroblasts promoting downstream granulocyte colony-stimulating factor (G-CSF) production, hyaluronan secretion, and neutrophilic inflammation. Allergen challenge studies in mice demonstrate that the ICS, fluticasone propionate, inhibited type 2-driven eosinophilia but induced a concomitant increase in FGFs, G-CSF, hyaluronan, and neutrophil infiltration. We developed a model of steroid-induced neutrophilic inflammation mediated, in part, by induction of an FGF-dependent epithelial-mesenchymal axis, which may explain why some individuals do not benefit from ICS. In further proof-of-concept experiments, we found that combination therapy with pan-FGF receptor inhibitors and corticosteroids prevented both eosinophilic and steroid-induced neutrophilic inflammation. Together, these results establish FGFs as therapeutic targets for severe asthma patients who do not benefit from ICS.

Singlet oxygen -derived nerve growth factor exacerbates airway hyperresponsiveness in a mouse model of asthma with mixed inflammation

BACKGROUND

Refractory asthma, which is caused by several factors including neutrophil infiltration is a serious complication of bronchial asthma. We previously reported that nerve growth factor (NGF) is involved in AHR. NGF-derived induction of hyperalgesia is dependent on neutrophils; however, this relationship remains unclear in respiratory disease. In this study, we examined the roles of neutrophils and NGF in refractory asthma.

METHODS

Using intranasal house dust mite sensitization, we established a mouse model of asthma with mixed inflammation (Mix-in). AHR, NGF production and hyperinnervation of the lungs were examined with or without different inhibitory treatments. The levels of the singlet oxygen markers, 10- and 12-(Z,E)-hydroxyoctadecadienoic acids (HODE) in the lungs, were measured by liquid chromatography-tandem mass spectrometry. An in vitro experiment was also performed to evaluate the direct effect of singlet oxygen on NGF production.

RESULTS

NGF production and hyperinnervation were higher in Mix-in mice than in conventional eosinophilic-asthmatic mice and were positively correlated with AHR. Asthmatic parameters were inhibited by NGF neutralizing Abs and myeloperoxidase (MPO) inhibition. The 10- and 12-(Z,E)-HODEs levels were increased in the lungs and were positively correlated with MPO activity and NGF production. NGF was produced by bronchial epithelial cells in vitro upon stimulation with singlet oxygen.

CONCLUSIONS

Our findings suggest that neutrophil MPO-derived singlet oxygen induces increased NGF production, leading to AHR and 10- and 12-(Z,E)-HODEs production. These findings may help to develop new therapies targeting this mechanism and to establish a new biomarker for non-type 2 and refractory asthma.

Role of Th17 Cytokines in Airway Remodeling in Asthma and Therapy Perspectives

Airway remodeling is a frequent pathological feature of severe asthma leading to permanent airway obstruction in up to 50% of cases and to respiratory disability. Although structural changes related to airway remodeling are well-characterized, immunological processes triggering and maintaining this phenomenon are still poorly understood. As a consequence, no biotherapy targeting cytokines are currently efficient to treat airway remodeling and only bronchial thermoplasty may have an effect on bronchial nerves and smooth muscles with uncertain clinical relevance. Th17 cytokines, including interleukin (IL)-17 and IL-22, play a role in neutrophilic inflammation in severe asthma and may be involved in airway remodeling. Indeed, IL-17 is increased in sputum from severe asthmatic patients, induces the expression of "profibrotic" cytokines by epithelial, endothelial cells and fibroblasts, and provokes human airway smooth muscle cell migration in in vitro studies. IL-22 is also increased in asthmatic samples, promotes myofibroblast differentiation, epithelial-mesenchymal transition and proliferation and migration of smooth muscle cells in vitro. Accordingly, we also found high levels of IL-17 and IL-22 in a mouse model of dog-allergen induced asthma characterized by a strong airway remodeling. Clinical trials found no effect of therapy targeting IL-17 in an unselected population of asthmatic patients but showed a potential benefit in a sub-population of patients exhibiting a high level of airway reversibility, suggesting a potential role on airway remodeling. Anti-IL-22 therapies have not been evaluated in asthma yet but were demonstrated efficient in severe atopic dermatitis including an effect on skin remodeling. In this review, we will address the role of Th17 cytokines in airway remodeling through data from in vitro, in vivo and translational studies, and examine the potential place of Th17-targeting therapies in the treatment of asthma with airway remodeling.

FGF2 is overexpressed in asthma and promotes airway inflammation through the FGFR/MAPK/NF-κB pathway in airway epithelial cells

BACKGROUND

Airway inflammation is the core pathological process of asthma, with the key inflammatory regulators incompletely defined. Recently, fibroblast growth factor 2 (FGF2) has been reported to be an inflammatory regulator; however, its role in asthma remains elusive. This study aimed to investigate the immunomodulatory role of FGF2 in asthma.

METHODS

First, FGF2 expression was characterised in clinical asthma samples and the house dust mite (HDM)-induced mouse chronic asthma model. Second, recombinant mouse FGF2 (rm-FGF2) protein was intranasally delivered to determine the effect of FGF2 on airway inflammatory cell infiltration. Third, human airway epithelium-derived A549 cells were stimulated with either HDM or recombinant human interleukin-1β (IL-1β) protein combined with or without recombinant human FGF2. IL-1β-induced IL-6 or IL-8 release levels were determined using enzyme-linked immunosorbent assay, and the involved signalling transduction was explored via Western blotting.

RESULTS

Compared with the control groups, the FGF2 protein levels were significantly upregulated in the bronchial epithelium and alveolar areas of clinical asthma samples (6.70 ± 1.79 vs. 16.32 ± 2.40, P = 0.0184; 11.20 ± 2.11 vs. 21.00 ± 3.00, P = 0.033, respectively) and HDM-induced asthmatic mouse lung lysates (1.00 ± 0.15 vs. 5.14 ± 0.42, P < 0.001). Moreover, FGF2 protein abundance was positively correlated with serum total and anti-HDM IgE levels in the HDM-induced chronic asthma model (R² = 0.857 and 0.783, P = 0.0008 and 0.0043, respectively). Elevated FGF2 protein was mainly expressed in asthmatic bronchial epithelium and alveolar areas and partly co-localised with infiltrated inflammatory cell populations in HDM-induced asthmatic mice. More importantly, intranasal instillation of rm-FGF2 aggravated airway inflammatory cell infiltration (2.45 ± 0.09 vs. 2.88 ± 0.14, P = 0.0288) and recruited more subepithelial neutrophils after HDM challenge [(110.20 ± 29.43) cells/mm² vs. (238.10 ± 42.77) cells/mm², P = 0.0392] without affecting serum IgE levels and Th2 cytokine transcription. In A549 cells, FGF2 was upregulated through HDM stimulation and promoted IL-1β-induced IL-6 or IL-8 release levels (up to 1.41 ± 0.12- or 1.44 ± 0.14-fold change vs. IL-1β alone groups, P = 0.001 or 0.0344, respectively). The pro-inflammatory effect of FGF2 is likely mediated through the fibroblast growth factor receptor (FGFR)/mitogen-activated protein kinase (MAPK)/nuclear factor kappa B (NF-κB) pathway.

CONCLUSION

Our findings suggest that FGF2 is a potential inflammatory modulator in asthma, which can be induced by HDM and acts through the FGFR/MAPK/NF-κB pathway in the airway epithelial cells.

Neutrophil elastase promotes neointimal hyperplasia by targeting toll-like receptor 4 (TLR4)-NF-κB signalling

BACKGROUND AND PURPOSE

Neointimal hyperplasia (NIH) is the fundamental cause for vascular diseases and vascular smooth muscle cell (VSMC) dysregulation has been widely implicated in NIH. Neutrophil elastase is a potential therapeutic target for multiple diseases. We investigated the role of neutrophil elastase in VSMC functions and injury-induced NIH and explored the therapeutic potential of targeting neutrophil elastase in NIH.

EXPERIMENTAL APPROACH

VSMCs were used to analyse the effects of neutrophil elastase. Proteomic analysis was used to identify potential neutrophil elastase targets. Artery injury model and neutrophil elastase inhibitor GW311616A were used to investigate the role of neutrophil elastase in NIH.

KEY RESULTS

TNF-α up-regulated neutrophil elastase in VSMCs through modulating GAPBα/Runx1/CEBPα/c-Myb signalling. Up-regulated neutrophil elastase promoted VSMC migration, proliferation and inflammation. Toll-like receptor 4 (TLR4) was identified as a target protein for neutrophil elastase in VSMCs and the TLR4/MyD88/IRAK1/TRAF6/NF-κB regulatory axis was shown to be the signalling pathway for neutrophil elastase in VSMC pathology. Importantly, TLR4 inhibition abolished neutrophil elastase-mediated VSMC dysregulation. Injury-induced NIH was significantly reduced in both neutrophil elastase-deficient mice and mice treated with GW311616A. The formation of neutrophil extracellular traps was impaired in injured arteries from neutrophil elastase-deficient mice. Finally, a similar role for neutrophil elastase in human VSMC pathology was confirmed and we observed higher expression levels of neutrophil elastase but lower expression levels of TLR4 in human atherosclerotic lesions.

CONCLUSION AND IMPLICATIONS

We provide new insight into the molecular mechanisms underlying NIH and identify neutrophil elastase as a potential therapeutic target for vascular disease.

Exosomal transfer of activated neutrophil-derived lncRNA CRNDE promotes proliferation and migration of airway smooth muscle cells in asthma

BACKGROUND

Activated neutrophil-derived exosomes reportedly contribute to the proliferation of airway smooth muscle cells (ASMCs), thereby aggravating the airway wall remodeling during asthma; however, the specific mechanism remains unclear.

METHODS

Lipopolysaccharide (LPS)-EXO and si-CRNDE-EXO were extracted from the media of human neutrophils treated with LPS and LPS + si-CRNDE (a siRNA targets long non-coding RNA CRNDE), respectively. Human ASMCs were co-cultured with LPS-EXO or si-CRNDE-EXO, and cell viability, proliferation, and migration were measured. The interplay of CRNDE, inhibitor of nuclear factor kappa B kinase subunit beta (IKKβ), and nuclear receptor subfamily 2 group C member 2 (TAK1) was explored using RNA immunoprecipitation (RIP) and Co-IP assays. A mouse model of asthma was induced using ovalbumin.

RESULTS

CRNDE was upregulated in LPS-EXO and successfully transferred from LPS-treated neutrophils to ASMCs through exosome. Mechanically, CRNDE loaded in LPS-EXO reinforced TAK1-mediated IKKβ phosphorylation, thereby activating the nuclear factor kappa B (NF-κB) pathway. Functionally, silencing CRNDE in LPS-EXO, an IKKβ inhibitor, and an NF-κB inhibitor all removed the upregulation of cell viability, proliferation, and migration induced by LPS-EXO in ASMCs. In the end, the in vivo experiment demonstrated that CRNDE knockdown in neutrophils effectively reduced the thickness of bronchial smooth muscle in a mouse model for asthma.

CONCLUSION

Activated neutrophils-derived CRNDE was transferred to ASMCs through exosomes and activated the NF-κB pathway by enhancing IKKβ phosphorylation. The latter promoted the proliferation and migration of ASMCs and then contributed to airway remodeling in asthma.

FGF/FGFR signaling: From lung development to respiratory diseases

The fibroblast growth factor/fibroblast growth factor receptor (FGF/FGFR) signaling system regulates a variety of biological processes, including embryogenesis, angiogenesis, wound repair, tissue homeostasis, and cancer. It exerts these regulatory functions by controlling proliferation, differentiation, migration, survival, and metabolism of target cells. The morphological structure of the lung is a complex tree-like network for effective oxygen exchange, and the airway terminates in the middle and distal ends of many alveoli. FGF/FGFR signaling plays an important role in the pathophysiology of lung development and pathogenesis of various human respiratory diseases. Here, we mainly review recent advances in FGF/FGFR signaling during human lung development and respiratory diseases, including lung cancer, acute lung injury (ALI), pulmonary arterial hypertension (PAH), chronic obstructive pulmonary disease (COPD), asthma, and pulmonary fibrosis.

Modern View of Neutrophilic Asthma Molecular Mechanisms and Therapy

For a long time asthma was commonly considered as a homogeneous disease. However, recent studies provide increasing evidence of its heterogeneity and existence of different phenotypes of the disease. Currently, classification of asthma into several phenotypes is based on clinical and physiological features, anamnesis, and response to therapy. This review describes five most frequently identified asthma phenotypes. Neutrophilic asthma (NA) deserves special attention, since neutrophilic inflammation of the lungs is closely associated with severity of the disease and with the resistance to conventional corticosteroid therapy. This review focuses on molecular mechanisms of neutrophilic asthma pathogenesis and on the role of Th1- and Th17-cells in the development of this type of asthma. In addition, this review presents current knowledge of neutrophil biology. It has been established that human neutrophils are represented by at least three subpopulations with different biological functions. Therefore, total elimination of neutrophils from the lungs can result in negative consequences. Based on the new knowledge of NA pathogenesis and biology of neutrophils, the review summarizes current approaches for treatment of neutrophilic asthma and suggests new promising ways to treat this type of asthma that could be developed in future.

A Critical Role for the CXCL3/CXCL5/CXCR2 Neutrophilic Chemotactic Axis in the Regulation of Type 2 Responses in a Model of Rhinoviral-Induced Asthma Exacerbation

Rhinovirus (RV) infections in asthmatic patients are often associated with asthma exacerbation, characterized by worsened airways hyperreactivity and increased immune cell infiltration to the airways. The C-X-C chemokines, CXCL3 and CXCL5, regulate neutrophil trafficking to the lung via CXCR2, and their expression in the asthmatic lung is associated with steroid-insensitive type 2 inflammatory signatures. Currently, the role of CXCL3 and CXCL5 in regulating neutrophilic and type 2 responses in viral-induced asthma exacerbation is unknown. Inhibition of CXCL3 or CXCL5 with silencing RNAs in a mouse model of RV-induced exacerbation of asthma attenuated the accumulation of CXCR2⁺ neutrophils, eosinophils, and innate lymphoid cells in the lung and decreased production of type 2 regulatory factors IL-25, IL-33, IL-5, IL-13, CCL11, and CCL24. Suppression of inflammation was associated with decreased airways hyperreactivity, mucus hypersecretion, and collagen deposition. Similar results were obtained by employing RC-3095, which has been shown to bind to CXCR2, or by depletion of neutrophils. Our data demonstrate that CXCL3 and CXCL5 may be critical in the perpetuation of RV-induced exacerbation of asthma through the recruitment of CXCR2-positive neutrophils and by promoting type 2 inflammation. Targeting the CXCL3/CXCL5/CXCR2 axis may provide a new therapeutic approach to attenuating RV-induced exacerbations of asthma.

FGF2, an Immunomodulatory Factor in Asthma and Chronic Obstructive Pulmonary Disease (COPD)

The fibroblast growth factor 2 (FGF2) is a potent mitogenic factor belonging to the FGF family. It plays a role in airway remodeling associated with chronic inflammatory airway diseases, including asthma and chronic obstructive pulmonary disease (COPD). Recently, research interest has been raised in the immunomodulatory function of FGF2 in asthma and COPD, through its involvement in not only the regulation of inflammatory cells but also its participation as a mediator between immune cells and airway structural cells. Herein, this review provides the current knowledge on the biology of FGF2, its expression pattern in asthma and COPD patients, and its role as an immunomodulatory factor. The potential that FGF2 is involved in regulating inflammation indicates that FGF2 could be a therapeutic target for chronic inflammatory diseases.

Immunologic and Non-Immunologic Mechanisms Leading to Airway Remodeling in Asthma

Asthma increases worldwide without any definite reason and patient numbers double every 10 years. Drugs used for asthma therapy relax the muscles and reduce inflammation, but none of them inhibited airway wall remodeling in clinical studies. Airway wall remodeling can either be induced through pro-inflammatory cytokines released by immune cells, or direct binding of IgE to smooth muscle cells, or non-immunological stimuli. Increasing evidence suggests that airway wall remodeling is initiated early in life by epigenetic events that lead to cell type specific pathologies, and modulate the interaction between epithelial and sub-epithelial cells. Animal models are only available for remodeling in allergic asthma, but none for non-allergic asthma. In human asthma, the mechanisms leading to airway wall remodeling are not well understood. In order to improve the understanding of this asthma pathology, the definition of “remodeling” needs to be better specified as it summarizes a wide range of tissue structural changes. Second, it needs to be assessed if specific remodeling patterns occur in specific asthma pheno- or endo-types. Third, the interaction of the immune cells with tissue forming cells needs to be assessed in both directions; e.g., do immune cells always stimulate tissue cells or are inflamed tissue cells calling immune cells to the rescue? This review aims to provide an overview on immunologic and non-immunologic mechanisms controlling airway wall remodeling in asthma.

Divergent Roles of miR-3162-3p in Pulmonary Inflammation in Normal and Asthmatic Mice as well as Antagonism of miR-3162-3p in Asthma Treatment

MicroRNA (miRNA) mimics or antagomirs hold great promise for asthma treatment compared with glucocorticoids as mainstay therapy for asthma. But the role of miRNA in regulating asthmatic inflammation is largely unclear. We previously reported that miR-3162-3p in the peripheral blood of children with asthma was obviously upregulated compared to that in healthy children. This study aimed to elucidate the role of miR-3162-3p in pulmonary inflammation in normal and asthmatic mice as well as preliminarily explore the potential of miR-3162-3p antagomir in asthma treatment. A noninvasive whole-body plethysmograph measured airway responsiveness. Both qRT-PCR and Western blot were used to detect the expression of miRNA, mRNA, or protein. Cells in bronchoalveolar lavage fluid were counted by platelet counting and Wright's staining. Inflammatory infiltration and mucus secretion were identified by hematoxylin and eosin and periodic acid-Schiff  staining, respectively. Cytokines in the lungs were detected by ELISA. The miR-3162-3p mimic intraperitoneally administered to normal mice decreased β-catenin levels in the lungs without obviously altering the lung histology and cytokine levels. Antagonizing miR-3162-3p in ovalbumin-induced asthmatic mice effectively alleviated the typical features of asthma, such as airway hyper-responsiveness, airway inflammation, and Th1/Th2 cytokine imbalance, and concomitantly rescued the total and active β-catenin expression. Collectively, we discovered divergent roles of miR-3162-3p in lung inflammation between normal and asthmatic mice. The anti-inflammatory effects of the miR-3162-3p antagomir were comparable to those of glucocorticoid treatment. Our study helped in understanding the contribution of miRNAs to the pathogenesis of asthma.

RNA Sequencing of H3N2 Influenza Virus-Infected Human Nasal Epithelial Cells from Multiple Subjects Reveals Molecular Pathways Associated with Tissue Injury and Complications

The human nasal epithelium is the primary site of exposure to influenza virus, the initiator of host responses to influenza and the resultant pathologies. Influenza virus may cause serious respiratory infection resulting in major complications, as well as severe impairment of the airways. Here, we elucidated the global transcriptomic changes during H3N2 infection of human nasal epithelial cells from multiple individuals. Using RNA sequencing, we characterized the differentially-expressed genes and pathways associated with changes occurring at the nasal epithelium following infection. We used in vitro differentiated human nasal epithelial cell culture model derived from seven different donors who had no concurrent history of viral infections. Statistical analysis highlighted strong transcriptomic signatures significantly associated with 24 and 48 h after infection, but not at the earlier 8-h time point. In particular, we found that the influenza infection induced in the nasal epithelium early and altered responses in interferon gamma signaling, B-cell signaling, apoptosis, necrosis, smooth muscle proliferation, and metabolic alterations. These molecular events initiated at the infected nasal epithelium may potentially adversely impact the airway, and thus the genes we identified could serve as potential diagnostic biomarkers or therapeutic targets for influenza infection and associated disease management.