Asthma drugs counter-regulate interleukin-8 release stimulated by sodium sulfite in an A549 cell line

Repression of the expression of proinflammatory genes by mitochondrial transcription factor A is linked to its alternative splicing regulation in human lung epithelial cells

Background

Mitochondrial transcription factor A (TFAM) is associated with a number of neurodegenerative diseases and also with asthma. TFAM deficiency-induced mitochondrial DNA stress primes the antiviral innate immune response in mouse embryonic fibroblasts. However, the role of TFAM in asthma related inflammation remains obscure. The purpose of this study was to investigate the regulatory mechanism of TFAM in asthma.

Results

In this study, we overexpressed TFAM in human lung epithelial cells (A549), then obtained the TFAM-regulated transcriptome by Illumina sequencing technology. Transcriptome analysis revealed that TFAM overexpression down-regulated and up-regulated the expression of 642 and 169 differentially expressed genes (DEGs), respectively. The TFAM-repressed genes were strongly enriched in cytokine-mediated signaling pathway, type I interferon- and INF-γ-mediated signaling pathways, and viral response pathways. We also revealed that 2563 alternative splicing events in 1796 alternative splicing genes (ASGs) were de-regulated upon TFAM overexpression. These TFAM-responding ASGs were enriched in DNA repair, nerve growth factor receptor signaling pathway, and also transcription regulation. Further analysis revealed that the promoters of TFAM-repressed DEGs were enriched by DNA binding motifs of transcription factors whose alternative splicing was regulated by TFAM.

Conclusions

These findings suggest that TFAM regulates not only immune response gene expression in human lung epithelial cells, but also pre-mRNA alternative splicing which may mediate transcriptional regulation; this TFAM-centered gene regulation network could be targeted in developing therapies against various diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-021-00464-2.

In Vitro Effects of 5-Lipoxygenase Pathway Inhibition on Rhinovirus-Associated Bronchial Epithelial Inflammation

Introduction

The leukotriene pathway may be implicated in the induction of virus-induced inflammation. Respiratory epithelial cells may express low levels of 5-lipoxygenase (5-LO) and release leukotrienes (LTs) C4, D4, and E4, upon exposure to viruses or other stimuli. Enhanced expression of 5-LO pathway proteins after rhinovirus (RV) infection has previously been described. We hypothesized that anti-leukotriene treatment of epithelial cells, with or without exposure to RV-infected peripheral blood mononuclear cells (PBMCs)-conditioned media, may inhibit RV-induced up-regulation of inflammatory cytokines.

Methods

PBMCs from a healthy donor were exposed to RV1B and supernatants were harvested at 48 h post infection. BEAS-2B cells were infected with RV, with or without conditioning with the PBMC supernatant. Treatment with anti-LT agents was performed either on both PBMCs and BEAS-2B or at the bronchial epithelial level only, with varying concentrations of montelukast (CysLT receptor antagonist) or MK-886 [FLAP(5-lipoxygenase-activating-protein) inhibitor]. Evaluation of the inflammatory cytokines IL-8, RANTES, IL-11, IL-6, and IP-10 was performed using ELISA.

Results

Our results show that anti-LT treatment of RV-infected bronchial epithelial cells suppresses epithelial RV-mediated cytokine production, independent of conditioning.

Conclusions

This observation may represent an indirect mode of action of the anti-leukotrienes in virus-induced asthma.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41030-021-00152-x.

The Impact of Early-Life Exposure to Air-borne Environmental Insults on the Function of the Airway Epithelium in Asthma

The airway epithelium is both a physical barrier protecting the airways from environmental insults and a significant component of the innate immune response. There is growing evidence that exposure of the airway epithelium to environmental insults in early life may lead to permanent changes in structure and function that underlie the development of asthma. Here we review the current published evidence concerning the link between asthma and epithelial damage within the airways and identify gaps in knowledge for future studies.

Mechanisms of Heightened Airway Sensitivity and Responses to Inhaled SO2 in Asthmatics

Sulfur dioxide (SO2) is a problematic inhalable air pollutant in areas of widespread industrialization, not only in the United States but also in countries undergoing rapid industrialization, such as China, and it can be a potential trigger factor for asthma exacerbations. It is known that asthmatics are sensitive to the effects of SO2; however, the basis of this enhanced sensitivity remains incompletely understood. A PubMed search was performed over the course of 2014, encompassing the following terms: asthma, airway inflammation, sulfur dioxide, IL-10, mouse studies, and human studies. This search indicated that biomarkers of SO2 exposure, SO2 effects on airway epithelial cell function, and animal model data are useful in our understanding of the body's response to SO2, as are SO2-associated amplification of allergic inflammation, and potential promotion of neurogenic inflammation due to chemical irritant properties. While definitive answers are still being sought, these areas comprise important foci of consideration regarding asthmatic responses to inhaled SO2. Furthermore, IL-10 deficiency associated with asthma may be another important factor associated with an inability to resolve inflammation and mitigate oxidative stress resulting from SO2 inhalation, supporting the idea that asthmatics are predisposed to SO2 sensitivity, leading to asthma exacerbations and airway dysfunction.

Inhibitory effects of Montelukast on mediator release by nasal epithelial cells from asthmatic subjects with or without allergic rhinitis

AIMS

This study tested inhibitory effects of in vitro Montelukast treatment on nasal airway epithelial cells (AEC) cultured from asthmatic patients treated with Montelukast with and without concomitant allergic rhinitis. We further examined the effect of Montelukast withdrawal in these patients on cytokine release from cultured nasal AEC.

METHODS

Nasal AEC were collected by brushings from subjects with a history of stable (no exacerbations or change in medication for ≥ 1 month) physician confirmed mild/moderate asthma whose asthma symptoms were documented to benefit from Montelukast treatment (NCT01230437). Release of the following mediators by nasal AEC were measured: IL-8, IL-6, IL-10, GM-CSF, RANTES, eotaxin and IFN-γ. Nasal AEC were cultured before and one week after withdrawal of their Montelukast treatment.

RESULTS

Forty two asthmatics were recruited. Nasal AEC were successfully cultured in 17 at the first assessment, 14 at the second assessment and in 10 individuals at both assessments. Nasal AEC release was no different between asthmatics with or without allergic rhinitis. Montelukast significantly suppressed the release of IL-8 (p = 0.016), IL-6 (p = 0.006), RANTES (p = 0.002) and IFN-γ (p = 0.046), in a dose dependent manner in unstimulated cultures but not in those stimulated with IL-1/TNF. Withdrawal of Montelukast treatment, was associated with increased IL-8 and RANTES secretion in unstimulated nasal AEC cultured from subjects with asthma and allergic rhinitis but not with asthma alone.

CONCLUSIONS

Montelukast treatment for asthma symptoms reversibly suppresses nasal AEC release of pro-inflammatory mediators (i.e. IL-8 and RANTES) but only in those cells cultured from subjects with concomitant allergic rhinitis.

Antimicrobial peptide LL-37 attenuates LTA induced inflammatory effect in macrophages

LL-37/hCAP-18, as the only human cathelicidin, plays an important role in inflammation. Lipoteichoic acid (LTA) is an important bacterial component of Staphylococcus aureus, which is one of the common human pathogens for severe respiratory infection with increasing morbidity in recent years. The present study is to investigate the role of LL-37 in LTA induced inflammatory reaction in macrophages. We examined TNF-α and IL-6 production after LL-37 treatment and discussed its signal transduction pathways such as p38MAPK and Akt activation in macrophages. The expression of pro-inflammatory cytokines was analyzed by quantitative real-time RT-PCR and enzyme-linked immunosorbent assay (ELISA). The LL-37 expression was determined by Western blot and immunofluorescence staining. The results showed that LL-37 was upregulated after LTA treatment. It could inhibit LTA induced p38MAPK and Akt phosphorylation and attenuate TNF-α and IL-6 production in macrophages in some specific concentration. These results suggest that LL-37 exerts an anti-inflammatory property and attenuates the pro-inflammatory cytokine release in macrophages.

Sodium sulfite enhances rhinovirus-induced chemokine production in airway epithelial cells

We investigated the effects of sodium sulfite (Na(2)SO(3)) on rhinovirus (RV)-induced chemokine production in A549 airway epithelial cells. Our results demonstrated that the treatment of A549 cells with 2,500 μM Na(2)SO(3) enhanced the mRNA expression of RV-induced interleukin (IL)-8 1.8 fold (p = 0.025); and regulated on activation, normal T cell expressed and secreted (RANTES), 2.9 fold (p = 0.025). Moreover, the secretion of IL-8, RANTES, and interferon-γ-inducible protein (IP)-10 was increased in a statistically significant manner without affecting cell viability and RV replication. Our results suggest that Na(2)SO(3) may potentiate RV infection by enhancing chemokine production.

Hippocampal neuron number loss in rats exposed to ingested sulfite

Sulfite, which is continuously formed in the body during metabolism of sulfur-containing amino acids, is commonly used in preservatives. It has been shown that there are toxic effects of sulfite on many cellular components. The aim of this study was to investigate the possible toxic effects of sulfite on pyramidal neurons by counting cell numbers in CA1 and CA2-CA3 subdivisions of the rat hippocampus. For this purpose, male albino rats were divided into a control group and a sulfite group (25 mg/kg). Sulfite was administered to the animals via drinking water for 8 weeks. At the end of the experimental period, brains were removed and neurons were estimated in total and in a known fraction of CA1 and CA2-CA3 subdivisions of the left hippocampus by using the optical fractionator method—a stereological method. Results showed that sulfite treatment caused a significant decrease in the total number of pyramidal neurons in three subdivisions of the hippocampus (CA1 and CA2-CA3) in the sulfite group compared with the control group (p < 0.05, Mann Whitney U test). It was concluded that exogenous administration of sulfite causes loss of pyramidal neurons in CA1 and CA2-CA3 subdivisions of the rat hippocampus.

A novel approach for a toxicity prediction model of environmental pollutants by using a quantitative structure-activity relationship method based on toxicogenomics

The development of automobile emission reduction technologies has decreased dramatically the particle concentration in emissions; however, there is a possibility that unexpected harmful chemicals are formed in emissions due to new technologies and fuels. Therefore, we attempted to develop new and efficient toxicity prediction models for the myriad environmental pollutants including those in automobile emissions. We chose 54 compounds related to engine exhaust and, by use of the DNA microarray, examined their effect on gene expression in human lung cells. We focused on IL-8 as a proinflammatory cytokine and developed a prediction model with quantitative structure-activity relationship (QSAR) for the IL-8 gene expression by using an in silico system. Our results demonstrate that this model showed high accuracy in predicting upregulation of the IL-8 gene. These results suggest that the prediction model with QSAR based on the gene expression from toxicogenomics may have great potential in predictive toxicology of environmental pollutants.