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

Role of C3a as a Novel Regulator of 25(OH)D3 to 1α,25-Dihydroxyvitamin D3 Metabolism in Upper Airway Epithelial Cells

In patients with chronic rhinosinusitis with nasal polyps, primary human sinonasal epithelial cell (HSNEC) 1α-hydroxylase levels are reduced, as is their ability to metabolize 25-hydroxycholecalciferol [25(OH)D₃] to its active metabolite, 1α,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃]. In this study, we sought to identify the factor responsible for the regulation of HSNEC metabolism of 25(OH)D₃, focusing on C3 and C3a. Multiple inhaled irritants trigger the release of complement components, C3 and C3a, leading to suppression of 1α-hydroxylase levels in HSNECs. Recombinant C3a was able to decrease 1α-hydroxylase and impair 25(OH)D₃ to 1,25(OH)₂D₃ metabolism, while addition of a C3a receptor antagonist restored conversion. Conversely, 1,25(OH)₂D₃ suppressed Aspergillus fumigatus-induced C3 and C3a levels in HSNEC supernatant. Given the ability of 1,25(OH)₂D₃ to modulate LL37 in other cell types, we examined its regulation in HSNECs and relationship to C3a. 1,25(OH)₂D₃ stimulated the secretion of LL37, whereas A. fumigatus and C3a suppressed it. Conversely, LL37 reduced the release of C3/C3a by HSNECs. Lastly, oral steroid use and in vitro dexamethasone application both failed to increase 1α-hydroxylase or reduce C3a levels. In summary, in this article, we describe for the first time a novel relationship between complement activation and local vitamin D metabolism in airway epithelial cells. The presence of elevated C3/C3a in patients with asthma and/or chronic rhinosinusitis with nasal polyps may account for their impaired HSNEC 25(OH)D₃ to 1,25(OH)₂D₃ metabolism and explain why they receive limited therapeutic benefit from oral vitamin D₃ supplementation.

Inflammatory modulation of the response of bronchial epithelial cells to lipopolysaccharide with pretreatment by montelukast

Montelukast, a leukotriene receptor antagonist, is the most prescribed nonsteroidal anti-inflammatory drug used as an add-on therapy for asthma. Besides its effect on blocking leukotriene action, montelukast has been proposed to have secondary anti-inflammatory properties. This study aimed to investigate the modulatory effect of montelukast on the expression of major genes involved in airway inflammation (TNF, IL6) and remodeling (MMP9, TGFB1) in response to lipopolysaccharide (LPS) in vitro. The expression of selected genes was measured by quantitative real-time polymerase chain reaction 0h and 24h after LPS stimulation in cells pretreated with montelukast. Montelukast was found to significantly attenuate increased TNF and IL6 gene expression, to have a mild effect on MMP9 and have no effect on TGFB1 expression upon stimulation with LPS. The results of our study indicate that patients on montelukast therapy would have an adequate response to acute microorganism-induced inflammation, so additional anti-inflammatory effects of montelukast should be better exploited.

The Leukotriene Receptor Antagonist Montelukast as a Potential COVID-19 Therapeutic

The emergence and global impact of COVID-19 has focused the scientific and medical community on the pivotal influential role of respiratory viruses as causes of severe pneumonia, on the understanding of the underlying pathomechanisms, and on potential treatment for COVID-19. The latter concentrates on four different strategies: (i) antiviral treatments to limit the entry of the virus into the cell and its propagation, (ii) anti-inflammatory treatment to reduce the impact of COVID-19 associated inflammation and cytokine storm, (iii) treatment using cardiovascular medication to reduce COVID-19 associated thrombosis and vascular damage, and (iv) treatment to reduce the COVID-19 associated lung injury. Ideally, effective COVID-19 treatment should target as many of these mechanisms as possible arguing for the search of common denominators as potential drug targets. Leukotrienes and their receptors qualify as such targets: they are lipid mediators of inflammation and tissue damage and well-established targets in respiratory diseases like asthma. Besides their role in inflammation, they are involved in various other aspects of lung pathologies like vascular damage, thrombosis, and fibrotic response, in brain and retinal damages, and in cardiovascular disease. In consequence, leukotriene receptor antagonists might be potential candidates for COVID-19 therapeutics. This review summarizes the current knowledge on the potential involvement of leukotrienes in COVID-19, and the rational for the use of the leukotriene receptor antagonist montelukast as a COVID-19 therapeutic.

The Leukotriene Receptor Antagonist Montelukast Reduces Alpha-Synuclein Load and Restores Memory in an Animal Model of Dementia with Lewy Bodies

Dementia with Lewy bodies (DLB) represents a huge medical need as it accounts for up to 30% of all dementia cases, and there is no cure available. The underyling spectrum of pathology is complex and creates a challenge for targeted molecular therapies. We here tested the hypothesis that leukotrienes are involved in the pathology of DLB and that blocking leukotrienes through Montelukast, a leukotriene receptor antagonist and approved anti-asthmatic drug, might alleviate pathology and restore cognitive functions. Expression of 5-lipoxygenase, the rate-limiting enzyme for leukotriene production, was indeed elevated in brains with DLB. Treatment of cognitively deficient human alpha-synuclein overexpressing transgenic mice with Montelukast restored memory. Montelukast treatment resulted in modulation of beclin-1 expression, a marker for autophagy, and in a reduction in the human alpha-synulcein load in the transgenic mice. Reducing the protein aggregation load in neurodegenerative diseases might be a novel model of action of Montelukast. Moreover, this work presents leukotriene signaling as a potential drug target for DLB and shows that Montelukast might be a promising drug candidate for future DLB therapy development.

Epithelial folliculin enhances airway inflammation in aspirin-exacerbated respiratory disease

BACKGROUND

Clinical features of aspirin-exacerbated respiratory disease (AERD) are characterized by overproduction of cysteinyl leukotrienes (LT) and eosinophil activation, in which epithelial cells contribute to eosinophilic airway inflammation. Folliculin (FLCN) helps maintain the integrity of epithelial barrier, but little is known about FLCN in AERD.

OBJECTIVE

We investigated the role of FLCN in the pathogenic mechanisms of AERD.

METHODS

We recruited 178 subjects with AERD, 276 subjects with aspirin-tolerant asthma (ATA) and 71 normal healthy controls (NC) at Ajou Medical Center. Levels of FLCN and interleukin (IL)-8 in sera and supernatants were measured by ELISA. Peripheral blood eosinophils isolated from asthmatic patients were cocultured with human airway epithelial cells (HAECs) pretreated with LTE₄ , dexamethasone and montelukast. The intracellular expressions of FLCN, tight (TJ) (occludins, claudin-1) and adherens (AJ) junctions (E-cadherin) were analysed by Western blotting. shRNA was used to down-regulate FLCN (shFLCN) in HAECs.

RESULTS

Serum FLCN levels were significantly higher in AERD group than in ATA and NC groups (all P < 0.001). The cut-off value of 56.6 pg/mL was used to define the high FLCN phenotype (highFLCN). Asthmatic patients with highFLCN were associated with increased airway hyperresponsiveness to methacholine (P = 0.015). The serum FLCN level could discriminate AERD group from NC group with 82% sensitivity (AUC = 0.793, P < 0.001). When HAECs were exposed to LTE₄ , FLCN release was increased significantly (P < 0.05), which were amplified along with disruption of TJ and AJ expressions when HAECs were cocultured with eosinophils and LTE₄ (all P < 0.05); these effects were suppressed by dexamethasone and montelukast. FLCN knockdown reduced IL-8 release and occludin expression from shFLCN HAECs.

CONCLUSIONS

Our findings suggest that high LT and airway eosinophilia increased FLCN release from HAECs, which enhance epithelial activation and disruption. Modulation of FLCN may be a potential target for AERD.

Current and future biomarkers in allergic asthma

Diagnosis early in life, sensitization, asthma endotypes, monitoring of disease and treatment progression are key motivations for the exploration of biomarkers for allergic rhinitis and allergic asthma. The number of genes related to allergic rhinitis and allergic asthma increases steadily; however, prognostic genes have not yet entered clinical application. We hypothesize that the combination of multiple genes may generate biomarkers with prognostic potential. The current review attempts to group more than 161 different potential biomarkers involved in respiratory inflammation to pave the way for future classifiers. The potential biomarkers are categorized into either epithelial or infiltrate-derived or mixed origin, epithelial biomarkers. Furthermore, surface markers were grouped into cell-type-specific categories. The current literature provides multiple biomarkers for potential asthma endotypes that are related to T-cell phenotypes such as Th1, Th2, Th9, Th17, Th22 and Tregs and their lead cytokines. Eosinophilic and neutrophilic asthma endotypes are also classified by epithelium-derived CCL-26 and osteopontin, respectively. There are currently about 20 epithelium-derived biomarkers exclusively derived from epithelium, which are likely to innovate biomarker panels as they are easy to sample. This article systematically reviews and categorizes genes and collects current evidence that may promote these biomarkers to become part of allergic rhinitis or allergic asthma classifiers with high prognostic value.

Primary airway epithelial cell culture and asthma in children-lessons learnt and yet to come

Until recently the airway epithelial cell (AEC) was considered a simple barrier that prevented entry of inhaled matter into the lung parenchyma. The AEC is now recognized as having an important role in the inflammatory response of the respiratory system to inhaled exposures, and abnormalities of these responses are thought to be important to asthma pathogenesis. This review first explores how the challenges of studying nasal and bronchial AECs in children have been addressed and then summarizes the results of studies of primary AEC function in children with and without asthma. There is good evidence that nasal AECs may be a suitable surrogate for the study of certain aspects of bronchial AEC function, although bronchial AECs remain the gold standard for asthma research. There are consistent differences between children with and without asthma for nasal and bronchial AEC mediator release following exposure to a range of pro-inflammatory stimulants including interleukins (IL)-1β, IL-4, and IL-13. However, there are inconsistencies between studies, e.g., release of IL-6, an important pro-inflammatory cytokine, is not increased in children with asthma relative to controls in all studies. Future work should expand current understanding of the "upstream" signalling pathways in AEC, study AEC from children before the onset of asthma symptoms and in vitro models should be developed that replicate the in vivo status more completely, e.g., co-culture with dendritic cells. AECs are difficult to obtain from children and collaboration between centers is expected to yield meaningful advances in asthma understanding and ultimately help deliver novel therapies.

Association of PCBs and allergies in children

Recently, the incidence rates of childhood allergies have been rising around the world. The presence of persistent chemical pollutants in the environment and exposure to air pollutants are often cited as potential causes of childhood allergies. Accordingly, epidemiological studies of the associations between exposure to low levels of pollutants and adverse health effects are essential. However, at present no useful biomarkers for evaluating such associations have been developed. Thus, using a molecular epidemiological approach we planned to identify candidate biomarkers of pollutant-induced adverse health effects that can be used in children. In asthmatic children, we found that the serum levels of several polychlorinated biphenyl (PCB) congener sub-types were significantly positively correlated with interleukin (IL)-8 mRNA expression, whereas in a sub-group of children who displayed positive immunoglobulin E (IgE) responses to milk or egg proteins IL-22 mRNA expression was demonstrated to be useful for detecting the adverse health effects of environmental pollutants, particularly PCB congeners. In conclusion, the mRNA expression levels of IL-8 and IL-22 can be used to detect children who are at particular risk of adverse health events caused by environmental pollutants, especially PCBs.