Increased secretion of leukemia inhibitory factor by immature airway smooth muscle cells enhances intracellular signaling and airway contractility

Exploration and Validation of Potential Biomarkers and Therapeutic Targets in Ferroptosis of Asthma

Purpose

Asthma is a chronic inflammatory airway disease involving multiple mechanisms, of which ferroptosis is a form of programmed cell death. Recent studies have shown that ferroptosis may play a crucial role in the pathogenesis of asthma, but no specific ferroptosis gene has been found in asthma, and the exact mechanism is still unclear. The present study aimed to screen ferroptosis genes associated with asthma and find therapeutic targets, in order to contribute a new clue for the diagnosis and therapy of asthma.

Methods

Ferroptosis-related differentially expressed genes (FR-DEGs) in asthma were selected by the GSE41861, GSE43696 and ferroptosis datasets. Next, the FR-DEGs were subjected by GO and KEGG enrichment, and the mRNA-miRNA network was constructed. Then, GSEA and GSVA enrichment analysis and Immune infiltration analysis were performed, followed by targeted drug prediction. Finally, the expression of FR-DEGs was confirmed using GSE63142 dataset and RT-PCR assay.

Results

We found 13 FR-DEGs by the GSE41861, GSE43696 and ferroptosis database. Functional enrichment analysis revealed that the 13 FR-DEGs were enriched in oxidative stress, immune response, ferroptosis, lysosome, necrosis, apoptosis etc. Moreover, our results revealed the mRNA-miRNA network of the FR-DEGs and identified candidate drugs. Also, immune infiltration revealed that ELAVL1, CREB5, CBR1 and NR1D2 are associated with the immune cells and may be potential targets in asthma. Finally, 10 FR-DEGs were validated by the GSE63142 database. It was verified that 7 FR-DEGs were differentially expressed by collecting asthma patients and healthy controls.

Conclusion

This study ultimately identified 7 FR-DEGs for the diagnosis and therapy of asthma. These 7 FR-DEGs contribute to oxidative stress and immune responses. This study provides potential therapeutic targets and biomarkers for asthma patients, shedding further light on the pathogenesis of asthma as well as providing new insights into the treatment of asthma.

Molecular Mechanisms of RSV and Air Pollution Interaction: A Scoping Review

RSV is one of the major infectious agents in paediatrics, and its relationship with air pollution is frequently observed. However, the molecular basis of this interaction is sparsely reported. We sought to systematically review the existing body of literature and identify the knowledge gaps to answer the question: which molecular mechanisms are implied in the air pollutants-RSV interaction? Online databases were searched for original studies published before August 2022 focusing on molecular mechanisms of the interaction. The studies were charted and a narrative synthesis was based upon three expected directions of influence: a facilitated viral entry, an altered viral replication, and an inappropriate host reaction. We identified 25 studies published between 1993 and 2020 (without a noticeable increase in the number of studies) that were performed in human (n = 12), animal (n = 10) or mixed (n = 3) models, and analysed mainly cigarette smoke (n = 11), particulate matter (n = 4), nanoparticles (n = 3), and carbon black (n = 2). The data on a damage to the epithelial barrier supports the hypothesis of facilitated viral entry; one study also reported accelerated viral entry upon an RSV conjugation to particulate matter. Air pollution may result in the predominance of necrosis over apoptosis, and, as an effect, an increased viral load was reported. Similarly, air pollution mitigates epithelium function with decreased IFN-γ and Clara cell secretory protein levels and decreased immune response. Immune response might also be diminished due to a decreased viral uptake by alveolar macrophages and a suppressed function of dendritic cells. On the other hand, an exuberant inflammatory response might be triggered by air pollution and provoke airway hyperresponsiveness (AHR), prolonged lung infiltration, and tissue remodeling, including a formation of emphysema. AHR is mediated mostly by increased IFN-γ and RANTES concentrations, while the risk of emphysema was related to the activation of the IL-17 → MCP-1 → MMP-9 → MMP-12 axis. There is a significant lack of evidence on the molecular basics of the RSV-air pollution interaction, which may present a serious problem with regards to future actions against air pollution effects. The major knowledge gaps concern air pollutants (mostly the influence of cigarette smoke was investigated), the mechanisms facilitating an acute infection or a worse disease course (since it might help plan short-term, especially non-pharmacological, interventions), and the mechanisms of an inadequate response to the infection (which may lead to a prolonged course of an acute infection and long-term sequelae). Thus far, the evidence is insufficient regarding the broadness and complexity of the interaction, and future studies should focus on common mechanisms stimulated by various air pollutants and a comparison of influence of the different contaminants at various concentrations.

Neurokinin-1 receptor antagonist decreases [Ca2+]i in airway smooth muscle cells by reducing the reverse-mode Na+/Ca2+ exchanger current

Airway smooth muscle (ASM) is involved in asthma airway inflammation. The aim of this study was to evaluate the effect of substance P and neurokinin-1 receptor (NK-1R) antagonist on intracellular calcium concentration ([Ca²⁺]i) in airway smooth muscle cells (ASMCs), ASMC contraction, and the effect on reverse-mode Na⁺-Ca²⁺ exchanger (NCX) currents in ASMCs. In our study, primary rat ASMCs were cultured. ASMCs were identified by immunofluorescence. [Ca²⁺]i variations were measured by fluorescence microscopy. Cell shortening (%) and relaxation (%) were analyzed with phase-contrast microscopy. Patch clamp techniques were used to assess NCX currents in ASMCs. We found that substance P increased, and NK-1R antagonist decreased [Ca²⁺]i in ASMCs. Substance P induced ASMCs contraction, and NK-1R antagonist can make ASMC relax. Patch clamp techniques were implemented to analyze NCX currents in ASMCs. Substance P increased reverse-mode NCX currents in ASMCs but the current density was lower than the one treated with acetylcholine (Ach). NK-1R antagonist reduced reverse-mode NCX current activity in ASMCs, and the current density was similar to the one treated with the reversed NCX inhibitor. So, we concluded that substance P increased [Ca²⁺]i in ASMCs by promoting the reverse-mode NCX current and stimulating ASMCs, whereas NK-1R antagonist decreased [Ca²⁺]i in ASMCs by decreasing the reverse-mode NCX current to make ASMCs relax.

Montelukast reverses airway remodeling in actively sensitized young mice

Asthma is characterized by airway hyperresponsiveness (AHR) and inflammation leading to airway remodeling (AR). In children, AR may occur very early prior to the age of 6 years. Treatments to prevent or reverse AR are unknown.

AIM

We sought to determine (i) whether short allergenic sensitization at a young age in a mouse model may induce enhanced AR and inflammation compared to adults; (ii) the effect of Montelukast on such AR.

METHODS

Immature and adult Balb/c mice were sensitized and challenged with ovalbumin. AHR and AR were measured using cultured precision-cut lung slices and inflammation by bronchoalveolar lavage. Experiments were repeated after administration of Montelukast.

RESULTS

OVA-challenged mice developed AHR to methacholine regardless of age of first exposure to OVA. Young mice developed greater thickened basement membrane, increased smooth muscle mass, and increased area of bronchovascular fibrosis compared with adult mice. Cellular infiltrates in BAL differed depending upon animal age at first exposure with higher eosinophilia measured in younger animals. Montelukast decreased ASM mass, BAL cellularity.

CONCLUSION

We provide thus evidence for a greater degree of AR after allergenic sensitization and challenge in younger mice versus adults. This study provides proof of concept that airway remodeling can be prevented and reversed in this case by anti-asthmatic drug Montelukast in this model.

Nasal airway epithelial cell IL-6 and FKBP51 gene expression and steroid sensitivity in asthmatic children

Background

Many asthmatic patients exhibit uncontrolled asthma despite high-dose inhaled corticosteroids (ICS). Airway epithelial cells (AEC) have distinct activation profiles that can influence ICS response.

Objectives

A pilot study to identify gene expression markers of AEC dysfunction and markers of corticosteroid sensitivity in asthmatic and non-asthmatic control children, for comparison with published reports in adults.

Methods

AEC were obtained by nasal brushings and primary submerged cultures, and incubated in control conditions or in the presence of 10 ng/ml TNFalpha, 10^-8M dexamethasone, or both. RT-PCR-based expression of FKBP51 (a steroid hormone receptor signalling regulator), NF-kB, IL-6, LIF (an IL-6 family neurotrophic cytokine), serpinB2 (which inhibits plasminogen activation and promotes fibrin deposition) and porin (a marker of mitochondrial mass) were determined.

Results

6 patients without asthma (median age 11yr; min-max: 7–13), 8 with controlled asthma (11yr, 7–13; median daily fluticasone dose = 100 μg), and 4 with uncontrolled asthma (12yr, 7–14; 1000 μg fluticasone daily) were included. Baseline expression of LIF mRNA was significantly increased in uncontrolled vs controlled asthmatic children. TNFalpha significantly increased LIF expression in uncontrolled asthma. A similar trend was observed regarding IL-6. Dexamethasone significantly upregulated FKBP51 expression in all groups but the response was blunted in asthmatic children. No significant upregulation was identified regarding NF-kB, serpinB2 and porin.

Conclusion

LIF and FKBP51 expression in epithelial cells were the most interesting markers of AEC dysfunction/response to corticosteroid treatment.

Effects of transient receptor potential canonical 1 (TRPC1) on the mechanical stretch-induced expression of airway remodeling-associated factors in human bronchial epithelioid cells

Research has shown that mechanical stress stimulation can cause airway remodeling. We investigate the effects of mechanical stretch on the expression of the airway remodeling-associated factors interleukin-13 (IL-13) and matrix metalloprotein-9 (MMP-9) and signaling pathways in human bronchial epithelioid (16HBE) cells under mechanical stretch. A Flexcell FX-4000 Tension System with a flexible substrate was applied to stretch 16HBE cells at a 15% elongation amplitude and 1Hz frequency, with stretching for 0.5h, 1h, 1.5h and 2h. The experimental group with higher IL-13, MMP-9, and TRPC1 expression and higher Ca²⁺ levels was selected for performing intervention experiment. These cells were pretreated with the transient receptor potential canonical 1 (TRPC1) channel antagonist SKF96365 and TRPC1-specific siRNA, and then mechanical stretch was applied. Our results provided evidences that mechanical pressure significantly increased IL-13, MMP-9, and TRPC1 protein and mRNA expression levels and intracellular Ca²⁺ fluorescence intensity at 4 time points compared with the control group. The peak IL-13, MMP-9, and TRPC1 expression levels were observed at 0.5h after exposure to mechanical pressure. IL-13 and MMP-9 expression levels and Ca²⁺ fluorescence intensity in the stretch+SKF96365 group and in the stretch+TRPC1 siRNA group were significantly lower than those were in the mechanical stretch group. By incubating the cells with the intracellular calcium chelator BAPTA-AM, the expression of IL-13 and MMP9 was significantly decreased, and the expression level of TRPC1 remained unchanged. These observations suggest that mechanical stretch may induce an influx of Ca²⁺ and up-regulation of IL-13 and MMP-9 expression in 16HBE cells via activation of TRPC1.

An age-wise comparison of human airway smooth muscle proliferative capacity

We compared the proliferation of neonatal and adult airway smooth muscle cells (ASMC) with no/moderate lung disease, in glucose- (energy production by glycolysis) or glucose-free medium (ATP production from mitochondrial oxidative phosphorylations only), in response to 10% fetal calf serum (FCS) and PDGF-AA. In the presence of glucose, cell counts were significantly greater in neonatal vs. adult ASMC. Similarly, neonatal ASMC DNA synthesis in 10% FCS and PDGF-AA, and [Ca²⁺]i responses in the presence of histamine were significantly enhanced vs. adults. In glucose-free medium, cell proliferation was preserved in neonatal cells, unlike in adult cells, with concomitant increased porin (an indicator of mitochondrial activity) protein expression. Compared to adults, stimulated neonatal human ASMC are in a rapid and robust proliferative phase and have the capacity to respond disproportionately under abnormal environmental conditions, through increased mitochondrial biogenesis and altered calcium homeostasis.

Leukemia inhibitory factor in the neuroimmune communication pathways in allergic asthma

In the pathogenesis of asthma, central sensitization is suggested to be an important neural mechanism, and neurotrophins and cytokines are likely to be the major mediators in the neuroimmune communication pathways of asthma. However, their impact on the central nervous system in allergic asthma remains unclear. We hypothesize that central neurogenic inflammation develops in the pathogenesis of allergic asthma, and nerve growth factor (NGF) and leukemia inhibitory factor (LIF) are important mediators in its development. An asthma model of rats was established by sensitization and challenged with ovalbumin (OVA). For further confirmation of the role of LIF in neurogenic inflammation, a subgroup was pretreated with intraperitoneally (i.p.) LIF antibody before OVA challenge. The levels of LIF and NGF were measured with reverse transcription and polymerase chain reaction (RT-PCR), in situ hybridization (ISH) and immunohistochemistry stain in lung tissue, airway-specific dorsal root ganglia (DRG, C7-T5) and brain stem of asthmatic rats, anti-LIF pretreated rats and controls. A significantly increased number of LIF- and NGF-immunoreactive cells were detected in lung tissue, DRG and the brain stem of asthmatic rats. In the asthma group a significantly increase level of mRNA encoding LIF and NGF in lung tissue was detected, but not in DRG and the brain stem. Pretreatment with LIF antibody decreased the level of LIF and NGF in all tissues. LIF is an important mediator in the crosstalk between nerve and immune systems. Our study demonstrate that the increased level of LIF and NGF in DRG and brain stem may be not based on result from de novo synthesis, but rather on result from retrograde nerve transport or passage across the blood-brain-barrier.

Interleukin (IL)-4, IL-13, and IL-17A differentially affect the profibrotic and proinflammatory functions of fibrocytes from asthmatic patients

Fibrocytes contribute to the fibrotic changes most frequently observed in forms of asthma where inflammation is driven by T helper type 2 (Th2) cells. The mechanisms that regulate the profibrotic function of asthmatic fibrocytes are largely unknown. We isolated circulating fibrocytes from patients with allergen-exacerbated asthma, who showed the presence of fibrocytes, together with elevated concentrations of interleukin (IL)-4 and IL-13 and slightly increased concentrations of the Th17 cell-derived IL-17A, in induced sputum. Fibrocytes stimulated with IL-4 and IL-13 produced high levels of collagenous and non-collagenous matrix components and low levels of proinflammatory cytokines. Conversely, fibrocytes stimulated with IL-17A proliferated and released proinflammatory factors that may promote neutrophil recruitment and airway hyperresponsiveness. IL-17A also indirectly increased α-smooth muscle actin but not collagen expression in fibrocytes. Thus, fibrocytes may proliferate and express a predominant profibrotic or proinflammatory phenotype in asthmatic airways depending on the local concentrations of Th2- and Th17-derived cytokines.

Pathogenic mechanisms of allergic inflammation: atopic asthma as a paradigm

Prospective studies tracking birth cohorts over periods of years indicate that the seeds for atopic asthma in adulthood are sewn during early life. The key events involve programming of functional phenotypes within the immune and respiratory systems which determine long-term responsiveness to ubiquitous environmental stimuli, particularly respiratory viruses and aeroallergens. A crucial component of asthma pathogenesis is early sensitization to aeroallergens stemming from a failure of mucosal tolerance mechanisms during the preschool years, which is associated with delayed postnatal maturation of a range of adaptive and innate immune functions. These maturational defects also increase risk for severe respiratory infections, and the combination of sensitization and infections maximizes risk for early development of the persistent asthma phenotype. Interactions between immunoinflammatory pathways stimulated by these agents also sustain the disease in later life as major triggers of asthma exacerbations. Recent studies on the nature of these interactions suggest the operation of an infection-associated lung:bone marrow axis involving upregulation of FcERlalpha on myeloid precursor populations prior to their migration to the airways, thus amplifying local inflammation via IgE-mediated recruitment of bystander atopic effector mechanisms. The key participants in the disease process are airway mucosal dendritic cells and adjacent epithelial cells, and transiting CD4(+) effector and regulatory T-cell populations, and increasingly detailed characterization of their roles at different stages of pathogenesis is opening up novel possibilities for therapeutic control of asthma. Of particular interest is the application of genomics-based approaches to drug target identification in cell populations of interest, exemplified by recent findings discussed below relating to the gene network(s) triggered by activation of Th2-memory cells from atopics.

Enhanced pulmonary expression of the TrkB neurotrophin receptor in hypoxic rats is associated with increased acetylcholine-induced airway contractility

AIM

We have recently reported that hypoxia stimulates transcription of the TrkB neurotrophin receptor in cultured cells via stabilization of hypoxia-inducible factor-1alpha. Here we investigated whether the expression of TrkB and other neurotrophin receptors is oxygen-sensitive also in vivo, and explored the functional consequences of an oxygen-regulated TrkB expression.

METHODS

Rats were exposed either to 21% O(2) or 8% O(2) for 6 h and TrkB was analysed by reverse transcription real-time PCR, in situ mRNA hybridization, and immunological techniques. The importance of the brain-derived neurotrophic factor (BDNF)-TrkB pathway in the control of mechanical airway function was assessed on isolated tracheal segments from normoxic and hypoxic rats.

RESULTS

TrkB transcripts were increased approx. 15-fold in the lungs of hypoxic rats, and the respiratory epithelium was identified as the site of enhanced TrkB expression in hypoxia. The TrkB ligand, BDNF, significantly increased the contractile response to acetylcholine (ACh) of isolated tracheal segments from hypoxic but not from normoxic rats. This effect of BDNF was prevented by pre-incubation of the tissue specimens with the tyrosine kinase inhibitor K252a and by mechanical removal of the TrkB containing airway epithelium. Likewise, the nitric oxide (NO) synthase inhibitor l-NAME abrogated the influence of BDNF on ACh-induced contractions of isolated tracheal segments from hypoxic rats.

CONCLUSION

These results demonstrate that systemic hypoxia stimulates expression of the TrkB neurotrophin receptor in the airway epithelium. Furthermore, activation of TrkB signalling by BDNF in hypoxia enhances mechanical airway contractility to ACh through a mechanism that requires NO.

Dorsal root ganglion: the target of acupuncture in the treatment of asthma

Recently, high levels of neurotrophic factors have been found in bronchial asthma; these factors include nerve growth factor, brain-derived neurotrophic factor, and leukemia inhibitory factor, among others. Neurotrophic factors are first synthesized in bronchial epithelial cells, immune cells, and other cells in the airway; they are then taken up by the synapse and are finally transported to dorsal root ganglia (C7-T5). Increased neurotrophic factors in dorsal root ganglia promote the synthesis and release of substance P. As a result, substance P causes a series of reactions such as contraction of airway smooth muscles, secretion of mucous fluids, seepage of capillary vessels, release of mediators of inflammation, and aggravation of airway hyperreactivity. It is interesting to note that the anatomic locations of dorsal root ganglia (C7-T5) are similar to a series of acupuncture points in traditional Chinese medicine. These points are all situated on 2 sides of the midspinal line, and most of them belong to Back-shu acupuncture points. In traditional Chinese medicine, Back-shu points can be used to treat patients with bronchial asthma through acupuncture and moxibustion. Is it a coincidence, or is there a real connection? These points possess similar neurotonia, physical function, and therapeutic effects; the functional area of Back-shu is composed of these points. When these points are pricked with a needle along the lower border of the spinous process, dorsal root ganglia and spinal nerves are stimulated; this can help to regulate the synthesis and release of neurotransmitters. It is hypothesized that dorsal root ganglia may be the targets of acupuncture in the treatment of asthma; in this process, acupuncture has an inhibitory effect on the uptake of neurotrophic factors, or it inhibits the synthesis and release of substance P in dorsal root ganglia. As a result, airway neurogenic inflammation in asthma is relieved.