Azithromycin has an antiproliferative and autophagic effect on airway smooth muscle cells

Airway Remodeling in Asthma: Mechanisms, Diagnosis, Treatment, and Future Directions

Airway remodeling (AR) with chronic inflammation, are key features in asthma pathogenesis. AR characterized by structural changes in the bronchial wall is associated with a specific asthma phenotype with poor clinical outcomes, impaired lung function and reduced treatment response. Most studies focus on the role of inflammation, while understanding the mechanisms driving AR is crucial for developing disease-modifying therapeutic strategies. This review paper summarizes current knowledge on the mechanisms underlying AR, diagnostic tools, and therapeutic approaches. Mechanisms explored include the role of the resident cells and the inflammatory cascade in AR. Diagnostic methods such as bronchial biopsy, lung function testing, imaging, and possible biomarkers are described. The effectiveness on AR of different treatments of asthma including corticosteroids, leukotriene modifiers, bronchodilators, macrolides, biologics, and bronchial thermoplasty is discussed, as well as other possible therapeutic options. AR poses a significant challenge in asthma management, contributing to disease severity and treatment resistance. Current therapeutic approaches target mostly airway inflammation rather than smooth muscle cell dysfunction and showed limited benefits on AR. Future research should focus more on investigating the mechanisms involved in AR to identify novel therapeutic targets and to develop new effective treatments able to prevent irreversible structural changes and improve long-term asthma outcomes.

Beyond bronchial thermoplasty - where to now?

With the impending 'retirement' of bronchial thermoplasty (BT) for the treatment of patients with asthma, there is much to learn from this real-world experiment that will help us develop more effective future therapies with the same primary target i.e., airway smooth muscle (ASM) remodelling. This viewpoint discusses initial controversy surrounding BT (lack of an effect on forced expiratory volume in 1 s), its underutilisation, and importantly how non-standard diagnostics successfully demonstrated therapeutic response which escaped traditional lung function metrics. It is anticipated that the next iteration of BT (likely in a drug form) will have an overall greater effect on the health care system by virtue of evoking ASM remodelling as a treatable trait, and after appropriately drawing on lessons learned from the ∼fifteen-year BT saga.

Azithromycin inhibits the intracellular persistence of Acinetobacter baumannii by inducing host cell autophagy in human bronchial epithelial cells

The invasion of host cells by bacteria, leading to intracellular infections, is a major cause of infection recurrence. Drug-resistant Acinetobacter baumannii (A. baumannii) is one of the most challenging public health issues worldwide, with very limited clinical treatment options available. A. baumannii has been found to be able to invade host cells and proliferate within them in recent studies. In addition to the direct antimicrobial effect of antibiotics, the activation of host autophagic flux also plays an important role in eliminating intracellular pathogens. Herein, this study aimes to evaluate the clearance effect of antibiotics on intracellular A. baumannii both in vivo and in vitro, and explore the relationship between this effect and autophagy. The results showed that intracellular pathogens resulted in a significant increase in the minimum bactericidal concentration, while azithromycin can significantly eliminate intracellular A. baumannii in vitro and in vivo. Notably, 60 μg/mL azithromycin demonstrated intracellular clearance against multidrug-resistant A. baumannii and markedly induced autophagosomes in BEAS-2B cells with a mild stimulation of autophagosomes degradation. These findings indicated that azithromycin can significantly clear intracellular A. baumannii and its ability to clear intracellular A. baumannii may be related to the stimulation of autophagosome formation and the induction of host autophagy, which has important implications for the clinical treatment of A. baumannii infections, especially when intracellular infections are present.

A new cannabigerol derivative, LE-127/2, induces autophagy mediated cell death in human cutaneous melanoma cells

Despite the targeted- and immunotherapies used in the past decade, survival rate among patients with metastatic melanoma remains low, therefore, melanoma is responsible for the majority of skin cancer-related deaths. The ongoing investigation of natural antitumor agents, the nonpsychoactive cannabinoid, cannabigerol (CBG) found in Cannabis sativa is emerging as a promising candidate. CBG offers a potential therapeutic role in the treatment of melanoma demonstrating cell growth inhibition in some tumors. Its low water solubility and bioavailability hinder the potential effectiveness. To address these challenges, a modified CBG, namely LE-127/2 was synthesized by Mannich-type reaction. The aim was to investigate the effect of this novel compound on cell proliferation as well as the mechanism of cell death with a particular focus on autophagy and apoptosis. Human cutan melanoma cell lines, WM35, A2058 and WM3000 were utilized for the present study. Cell proliferation of the cells after the treatment with LE-127/2, parent CBG or vemurafenib was assessed by Cell Titer Blue Assay. Cells were treated with a 1.25-80 µM of the above-mentioned compounds, and it was found that at 20 μM of all drugs showed a comparable effective inhibition of cell proliferation, however, vemurafenib and CBG proved to be more effective than LE-127/2. In addition, clonogenic cell survival assays were performed to examine the inhibitory effect of LE-127/2 on the colony formation ability of melanoma cell lines. Cells treated with 20 µM of LE-127/2 for 14 days showed about a 50% suppression of clonogenic cell survival. LE-127/2 exerted the most intensive inhibition on A2058 cell colonies. Furthermore, notably, LDH cytotoxicity assay performed on HaCaT cell line, proved LE-127/2 to be cytotoxic only at higher concentration, such as 80 μM, while the parent CBG was cytotoxic at concentration as low as 5 μM, suggesting that the new CBG derivative as a drug candidate may be applied in human pharmacotherapy without causing a substantial damage in intact epidermal cells. Analysis of protein expression revealed the impact of LE-127/2 on the expression of basic proteins (LC-3, Beclin-1 and p62) involved in the process of autophagy in the three different melanoma cell lines studied. Elevated expression of these proteins was detected as a result of LE-127/2 (20 µM) treatment. LE-127/2 also induced the expression of some proteins involved in apoptosis, and it is particularly noteworthy the increased level of cleaved PARP. Based on the results obtained, it can be concluded that LE-127/2 induced autophagy could lead to the inhibition of cell proliferation and death in melanoma cells.

The role and mechanism of macrophage autophagy in the experimental model of chronic obstructive pulmonary disease

INTRODUCTION

Macrophages play an important role in chronic obstructive pulmonary disease (COPD). Cigarette smoke (CS) impairs autophagy in alveolar macrophages from COPD patients, and autophagic impairment leads to reduced clearance of protein aggregates, dysfunctional mitochondria, and defective bacterial delivery to lysosomes. However, the exact function of lung macrophage autophagy in the pathogenesis of CS-induced COPD remains largely unknown.

METHODS

Western blot detected the expression of autophagy-related proteins induced by CSE. The model of COPD mice was established by CS exposure combined with CSE intraperitoneal injection. Double immunofluorescence was used to measure the CD206+LC3B+ cells. The morphological changes and effects on lung function were observed. Masson staining detected the changes in collagen fibers in lung tissue. The expression levels of E-cadherinb and N-cadherinb were detected by immunohistochemistry. Western blot detected the expression of ATP6V1E1 in lung tissue.

RESULTS

At 24 hours of exposure to CSE, the expression levels of LC3B (microtubule-associated protein 1A/1B-light chain 3B) and P62 (nucleoporin 62) were highest at 1% CSE and AGT5 (nucleoporin 62) at 2.5% CSE; at 48 hours, the expression levels of LC3B, P62 and AGT5 were highest at 2.5% CSE, and as the intervention time increased.CD206+LC3B+ cells were significantly higher in the COPD group. Enhanced macrophage autophagy may promote emphysema formation and aggravate lung function damage. The expression of E-cadherinb in lung tissue of the COPD group was decreased, and N-cadherinb expression was increased; the expression of E-cadherinb was increased, and N-cadherinb expression was decreased in ATG5myeΔ COPD mice. The expression of ATP6V1E1 in the lung tissue was increased in the COPD group; ATP6V1E1 expression was decreased in the lung tissues of ATG5myeΔ COPD mice.

CONCLUSIONS

CSE enhanced macrophage autophagy, leads to increased lung function impairment and collagenous fiber in lung tissue, as well as promotes epithelial-mesenchymal transition, and eventually leads to small airway remodeling, which may be achieved through the ATG5/ATP6V1E1 pathway.

A bioinformatic investigation of proteasome and autophagy expression in the central nervous system

The ubiquitin proteasome system (UPS) and autophagy lysosome pathway (ALP) are crucial in the control of protein quality. However, data regarding the relative significance of UPS and ALP in the central nervous system (CNS) are limited. In the present study, using publicly available data, we computed the quantitative expression status of UPS- and ALP-related genes and their products in the CNS as compared with that in other tissues and cells. We obtained human and mouse gene expression datasets from the reference expression dataset (RefEx) and Genevestigator (a tool for handling curated transcriptomic data from public repositories) as well as human proteomics data from the proteomics database (ProteomicsDB). The expression levels of genes and proteins in four categories-ubiquitin, proteasome, autophagy, and lysosome--in the cells and tissues were assessed. Perturbation of the gene expression by drugs was also analyzed for the four categories. Compared with that for ubiquitin, autophagy, and lysosome, gene expression for proteasome was consistently lower in the CNS of mice but was more pronounced in humans. Neural stem cells and neurons showed low proteasome gene expression as compared with embryonic stem cells. Proteomic analyses, however, did not show trends similar to those observed in the gene expression analyses. Perturbation analyses revealed that azithromycin and vitamin D3 upregulated the expression of both UPS and ALP. Gene and proteomic expression data could offer a fresh perspective on CNS pathophysiology. Our results indicate that disproportional expression of UPS and ALP might affect CNS disorders and that this imbalance might be redressed by several therapeutic candidates.

Airway remodeling heterogeneity in asthma and its relationship to disease outcomes

Asthma affects an estimated 262 million people worldwide and caused over 461,000 deaths in 2019. The disease is characterized by chronic airway inflammation, reversible bronchoconstriction, and airway remodeling. Longitudinal studies have shown that current treatments for asthma (inhaled bronchodilators and corticosteroids) can reduce the frequency of exacerbations, but do not modify disease outcomes over time. Further, longitudinal studies in children to adulthood have shown that these treatments do not improve asthma severity or fixed airflow obstruction over time. In asthma, fixed airflow obstruction is caused by remodeling of the airway wall, but such airway remodeling also significantly contributes to airway closure during bronchoconstriction in acute asthmatic episodes. The goal of the current review is to understand what is known about the heterogeneity of airway remodeling in asthma and how this contributes to the disease process. We provide an overview of the existing knowledge on airway remodeling features observed in asthma, including loss of epithelial integrity, mucous cell metaplasia, extracellular matrix remodeling in both the airways and vessels, angiogenesis, and increased smooth muscle mass. While such studies have provided extensive knowledge on different aspects of airway remodeling, they have relied on biopsy sampling or pathological assessment of lungs from fatal asthma patients, which have limitations for understanding airway heterogeneity and the entire asthma syndrome. To further understand the heterogeneity of airway remodeling in asthma, we highlight the potential of in vivo imaging tools such as computed tomography and magnetic resonance imaging. Such volumetric imaging tools provide the opportunity to assess the heterogeneity of airway remodeling within the whole lung and have led to the novel identification of heterogenous gas trapping and mucus plugging as important predictors of patient outcomes. Lastly, we summarize the current knowledge of modification of airway remodeling with available asthma therapeutics to highlight the need for future studies that use in vivo imaging tools to assess airway remodeling outcomes.

New insights into autophagy in inflammatory subtypes of asthma

Asthma is a heterogeneous airway disease characterized by airway inflammation and hyperresponsiveness. Autophagy is a self-degrading process that helps maintain cellular homeostasis. Dysregulation of autophagy is involved in the pathogenesis of many diseases. In the context of asthma, autophagy has been shown to be associated with inflammation, airway remodeling, and responsiveness to drug therapy. In-depth characterization of the role of autophagy in asthma can enhance the understanding of the pathogenesis, and provide a theoretical basis for the development of new biomarkers and targeted therapy for asthma. In this article, we focus on the relationship of autophagy and asthma, and discuss its implications for asthma pathogenesis and treatment.

Azithromycin inhibits mucin secretion, mucous metaplasia, airway inflammation and airways hyperresponsiveness in mice exposed to house dust mite extract

Excessive production, secretion and retention of abnormal mucus is a pathologic feature of many obstructive airways diseases including asthma, chronic obstructive pulmonary disease, cystic fibrosis and bronchiectasis. Azithromycin is an antibiotic that also possesses immunomodulatory and mucoregulatory activities, which may contribute to the clinical effectiveness of azithromycin in these obstructive airway diseases. The current study investigated these non-antibiotic activities of azithromycin (or saline) in mice exposed daily to intranasal house dust mite (HDM) extract (or SHAM inoculation) for 10 days. HDM-exposed mice exhibited airways hyperresponsiveness to aerosolised methacholine, a pronounced mixed eosinophilic and neutrophilic inflammatory response, increased airway smooth muscle (ASM) thickness and elevated levels of epithelial mucin staining (compared to SHAM mice). Azithromycin (50 mg/kg s.c., 2 h prior to each HDM exposure) significantly attenuated HDM-induced airways hyperresponsiveness to methacholine, airways inflammation (bronchoalveolar lavage eosinophil and neutrophils numbers, and cytokine/chemokine levels), and epithelial mucin staining (mucous metaplasia) (P<0.05, 2-way ANOVA). Isolated tracheal segments of HDM-exposed mice secreted Muc5ac and Muc5b (above baseline levels) in response to exogenous ATP. Moreover, ATP-induced secretion of mucins was significantly attenuated in segments obtained from azithromycin-treated, HDM-exposed mice (P<0.05, 2-way ANOVA). In additional ex vivo studies, ATP-induced secretion of Muc5ac from HDM-exposed tracheal segments was inhibited by in vitro exposure to azithromycin. In vitro azithromycin also inhibited ATP-induced secretion of Muc5ac and Muc5b in tracheal segments from IL-13-exposed mice. In summary, azithromycin inhibited ATP-induced mucin secretion and airways inflammation in HDM-exposed mice, both of which are likely to contribute to suppression of airways hyperresponsiveness.

A short focus, azithromycin in the treatment of respiratory viral infection COVID-19: efficacy or inefficacy?

Azithromycin is a macrolide antibiotic. Recent evidence has demonstrated in vitro activity against a wide variety of respiratory tract viruses, including SARS-CoV-2 responsible for the current global pandemic COVID-19. A mechanism of action acting on different phases of the viral cycle is assumed. In addition to its in vitro antiviral properties, some evidence also suggests immunomodulatory and antifibrotic activity. These properties of azithromycin could be useful in the treatment of viral respiratory tract infections such as COVID-19. However, clinical data on the antiviral efficacy of azithromycin in the treatment of respiratory tract infections are inconsistent, both when used as monotherapy and in polypharmacological combination. In addition, cases of azithromycin-induced QT long and malignant arrhythmias are reported. In this short review, we attempt to determine the role of azithromycin in the treatment of viral respiratory tract infections such as COVID-19, therapeutic efficacy, or inefficacy?

Effects of azithromycin on bronchial remodeling in the natural model of severe neutrophilic asthma in horses

Steroid resistance in asthma has been associated with neutrophilic inflammation and severe manifestations of the disease. Macrolide add-on therapy can improve the quality of life and the exacerbation rate in refractory cases, possibly with greater effectiveness in neutrophilic phenotypes. The mechanisms leading to these beneficial effects are incompletely understood and whether macrolides potentiate the modulation of bronchial remodeling induced by inhaled corticosteroids (ICS) is unknown. The objective of this study was to determine if adding azithromycin to ICS leads to further improvement of lung function, airway inflammation and bronchial remodeling in severe asthma. The combination of azithromycin (10 mg/kg q48h PO) and inhaled fluticasone (2500 µg q12h) was compared to the sole administration of fluticasone for five months in a randomized blind trial where the lung function, airway inflammation and bronchial remodeling (histomorphometry of central and peripheral airways and endobronchial ultrasound) of horses with severe neutrophilic asthma were assessed. Although the proportional reduction of airway neutrophilia was significantly larger in the group receiving azithromycin, the lung function and the peripheral and central airway smooth muscle mass decreased similarly in both groups. Despite a better control of airway neutrophilia, azithromycin did not potentiate the other clinical effects of fluticasone.

Azithromycin induces apoptosis in airway smooth muscle cells through mitochondrial pathway in a rat asthma model

Background

The proliferation of airway smooth muscle cells (ASMCs) is a key feature of airway remodeling in asthma. Azithromycin (AZM) has been shown to decrease bronchial hyperresponsiveness and airway inflammation in asthmatics; however, the role of AZM in ASMC proliferation remains unclear. Thus, we investigated the effect of AZM on ASMC proliferation in a rat model of experimental asthma.

Methods

We isolated ASMCs from rats sensitized and challenged by ovabulmin (OVA), and then treated with different concentrations of AZM. Cytotoxicity of ASMC was evaluated by Cell Counting Kit-8 (CCK-8) assay, morphological change was examined with laser confocal microscope after Annexin V/propidium iodide (PI) double staining, mitochondrial membrane potential was determined with JC-1 staining, and the expression of cytochrome C was examined by western blot.

Results

The relative surface areas of airway wall and smooth muscle layers in OVA-sensitized rats were significantly increased compared to those in the control group. Furthermore, in OVA-sensitized rats, the mitochondrial membrane potential of ASMC was higher, while the expression of mitochondria cytochrome C was lower compared to that in control rats. After AZM treatment, ASMC apoptosis was increased, mitochondrial membrane potential reduced, and the protein level of cytosolic cytochrome C was increased.

Conclusions

This study demonstrated that AZM increased the apoptosis of ASMCs through a mitochondrial pathway, which might play an important role in ASMs proliferation during asthmatic remodeling.

Pharmacological ablation of the airway smooth muscle layer-Mathematical predictions of functional improvement in asthma

Airway smooth muscle (ASM) plays a major role in acute airway narrowing and reducing ASM thickness is expected to attenuate airway hyper‐responsiveness and disease burden. There are two therapeutic approaches to reduce ASM thickness: (a) a direct approach, targeting specific airways, best exemplified by bronchial thermoplasty (BT), which delivers radiofrequency energy to the airway via bronchoscope; and (b) a pharmacological approach, targeting airways more broadly. An example of the less well‐established pharmacological approach is the calcium‐channel blocker gallopamil which in a clinical trial effectively reduced ASM thickness; other agents may act similarly. In view of established anti‐proliferative properties of the macrolide antibiotic azithromycin, we examined its effects in naive mice and report a reduction in ASM thickness of 29% (p < .01). We further considered the potential functional implications of this finding, if it were to extend to humans, by way of a mathematical model of lung function in asthmatic patients which has previously been used to understand the mechanistic action of BT. Predictions show that pharmacological reduction of ASM in all airways of this magnitude would reduce ventilation heterogeneity in asthma, and produce a therapeutic benefit similar to BT. Moreover there are differences in the expected response depending on disease severity, with the pharmacological approach exceeding the benefits provided by BT in more severe disease. Findings provide further proof of concept that pharmacological targeting of ASM thickness will be beneficial and may be facilitated by azithromycin, revealing a new mode of action of an existing agent in respiratory medicine.

Azithromycin in viral infections

Azithromycin (AZM) is a synthetic macrolide antibiotic effective against a broad range of bacterial and mycobacterial infections. Due to an additional range of anti-viral and anti-inflammatory properties, it has been given to patients with the coronaviruses SARS-CoV or MERS-CoV. It is now being investigated as a potential candidate treatment for SARS-CoV-2 having been identified as a candidate therapeutic for this virus by both in vitro and in silico drug screens. To date there are no randomised trial data on its use in any novel coronavirus infection, although a large number of trials are currently in progress. In this review, we summarise data from in vitro, murine and human clinical studies on the anti-viral and anti-inflammatory properties of macrolides, particularly AZM. AZM reduces in vitro replication of several classes of viruses including rhinovirus, influenza A, Zika virus, Ebola, enteroviruses and coronaviruses, via several mechanisms. AZM enhances expression of anti-viral pattern recognition receptors and induction of anti-viral type I and III interferon responses. Of relevance to severe coronavirus-19 disease (COVID-19), which is characterised by an over-exuberant innate inflammatory response, AZM also has anti-inflammatory properties including suppression of IL-1beta, IL-2, TNF and GM-CSF. AZM inhibits T cells by inhibiting calcineurin signalling, mammalian target of rapamycin activity and NFκB activation. AZM particularly targets granulocytes where it concentrates markedly in lysosomes, particularly affecting accumulation, adhesion, degranulation and apoptosis of neutrophils. Given its proven safety, affordability and global availability, tempered by significant concerns about antimicrobial stewardship, there is an urgent mandate to perform well-designed and conducted randomised clinical trials.

Addressing Non-linear System Dynamics of Single-Strand RNA Virus-Host Interaction

Positive single-strand ribonucleic acid [(+)ssRNA] viruses can cause multiple outbreaks, for which comprehensive tailored therapeutic strategies are still missing. Virus and host cell dynamics are tightly connected, generating a complex dynamics that conveys in virion assembly to ensure virus spread in the body. Starting from the knowledge of relevant processes in (+ss)RNA virus replication, transcription, translation, virions budding and shedding, and their respective energy costs, we built up a systems thinking (ST)-based diagram of the virus-host interaction, comprehensive of stocks, flows, and processes as well-described in literature. In ST approach, stocks and flows are expressed by a proxy of the energy embedded and transmitted, respectively, whereas processes are referred to the energy required for the system functioning. In this perspective, healthiness is just a particular configuration, in which stocks relevant for the system (equivalent but not limited to proteins, RNA, DNA, and all metabolites required for the survival) are constant, and the system behavior is stationary. At time of infection, the presence of additional stocks (e.g., viral protein and RNA and all metabolites required for virion assembly and spread) confers a complex network of feedbacks leading to new configurations, which can evolve to maximize the virions stock, thus changing the system structure, output, and purpose. The dynamic trajectories will evolve to achieve a new stationary status, a phenomenon described in microbiology as integration and symbiosis when the system is resilient enough to the changes, or the system may stop functioning and die. Application of external driving forces, acting on processes, can affect the dynamic trajectories adding a further degree of complexity, which can be captured by ST approach, used to address these new configurations. Investigation of system configurations in response to external driving forces acting is developed by computational analysis based on ST diagrams, with the aim at designing novel therapeutic approaches.

Oral cysteamine as an adjunct treatment in cystic fibrosis pulmonary exacerbations: An exploratory randomized clinical trial

BACKGROUND

Emerging data suggests a possible role for cysteamine as an adjunct treatment for pulmonary exacerbations of cystic fibrosis (CF) that continue to be a major clinical challenge. There are no studies investigating the use of cysteamine in pulmonary exacerbations of CF. This exploratory randomized clinical trial was conducted to answer the question: In future pivotal trials of cysteamine as an adjunct treatment in pulmonary exacerbations of CF, which candidate cysteamine dosing regimens should be tested and which are the most appropriate, clinically meaningful outcome measures to employ as endpoints?

METHODS AND FINDINGS

Multicentre double-blind randomized clinical trial. Adults experiencing a pulmonary exacerbation of CF being treated with standard care that included aminoglycoside therapy were randomized equally to a concomitant 14-day course of placebo, or one of 5 dosing regimens of cysteamine. Outcomes were recorded on days 0, 7, 14 and 21 and included sputum bacterial load and the patient reported outcome measures (PROMs): Chronic Respiratory Infection Symptom Score (CRISS), the Cystic Fibrosis Questionnaire-Revised (CFQ-R); FEV1, blood leukocyte count, and inflammatory markers. Eighty nine participants in fifteen US and EU centres were randomized, 78 completed the 14-day treatment period. Cysteamine had no significant effect on sputum bacterial load, however technical difficulties limited interpretation. The most consistent findings were for cysteamine 450mg twice daily that had effects additional to that observed with placebo, with improved symptoms, CRISS additional 9.85 points (95% CI 0.02, 19.7) p = 0.05, reduced blood leukocyte count by 2.46x109 /l (95% CI 0.11, 4.80), p = 0.041 and reduced CRP by geometric mean 2.57 nmol/l (95% CI 0.15, 0.99), p = 0.049.

CONCLUSION

In this exploratory study cysteamine appeared to be safe and well-tolerated. Future pivotal trials investigating the utility of cysteamine in pulmonary exacerbations of CF need to include the cysteamine 450mg doses and CRISS and blood leukocyte count as outcome measures.

CLINICAL TRIAL REGISTRATION

NCT03000348; www.clinicaltrials.gov.

Azithromycin and ambroxol as potential pharmacotherapy for SARS-CoV-2

Knowing the ability of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to bind to the angiotensin-converting enzyme 2 (ACE2) receptor and to enter cells via endocytosis paved the way for repositioning of old drugs as potential treatment of COVID-19, the disease caused by SARS-CoV-2 infection. This paper highlights the potential of azithromycin and ambroxol to treat COVID-19. Azithromycin and ambroxol share lysosomotropic characteristics, i.e. they penetrate and accumulate inside the late endosomes and lysosomes and may possibly interfere with multiplication of the virus inside cells. In addition, both of these drugs have anti-inflammatory effects. Ambroxol has a proven antiviral effect and a unique stimulatory action on the secretion of surfactant by alveolar type II cells, the main target of SARS-CoV-2. Surfactant may form a fundamental defence mechanism against the virus. Involvement of nasal epithelial cells in SARS-CoV-2 entry suggested advantageous use of inhaled drug delivery of these two drugs over the use of systemic administration. Inhaled drug delivery could aid in targeting the drug to the exact site of action with little or no side effects. To conclude, administration of these two drugs using a special drug delivery system provides two kinds of drug targeting: (i) tissue targeting through using an inhaled drug delivery system to achieve high drug concentrations at the respiratory epithelial tissue that overexpress the ACE2 receptor for virus binding; and (ii) cellular targeting of the virus in the acidic vesicles (late endosomes and lysosomes), which represent the fate of endocytic viruses.

Asthma: Pharmacological degradation of the airway smooth muscle layer

Asthma: A disease characterised by excessive and variable airway narrowing, and pathologies of inflammation and remodelling, particularly thickening of the airway smooth muscle (ASM). Treatment approaches dilate narrowed airways and reduce inflammation; however, remodelling seems largely neglected. This review considers the evolution of remodelling in asthma and whether conventional hypotheses that inflammation causes ASM thickening has mislead the medical community into thinking that anti-inflammatories will remedy this ASM defect. There is instead reasonable evidence that ASM thickening occurs independently of inflammation, such that therapies should employ strategies to directly modify ASM growth. Lessons have been learned from the use of untargeted bronchial thermoplasty and there should also be consideration of pharmacological therapies to ablate ASM. We discuss several new approaches to target ASM remodelling in asthma. A major current obstacle is our inability to image the ASM layer and assess treatment response. In this regard, polarisation-sensitive optical coherence tomography offers future promise.

COPD-Related Modification to the Airway Epithelium Permits Intracellular Residence of Nontypeable Haemophilus influenzae and May Be Potentiated by Macrolide Arrest of Autophagy

Introduction

COPD is an inflammatory airway pathology associated with recurrent infection by nontypeable Haemophilus influenzae (NTHi) that is not effectively managed by macrolide antibiotic therapy. We hypothesised that NTHi is able to reside intracellularly within COPD-derived airway epithelial cells (AEC), and that the factors contained in cigarette smoke when coupled with exposure to erythromycin or azithromycin arrest autophagy, the principle mechanism responsible for clearing intracellular bacteria (called "xenophagy").

Methods

Cultures of bronchial airway epithelial cells derived from control and COPD participants were differentiated at an air-liquid interface and exposed to macrolide antibiotics, 10% cigarette smoke-extract (CSE) and NTHi. Markers of autophagic flux and intracellular NTHi were assessed using Western blot analysis and transmission electron microscopy.

Results

AEC treated with macrolide antibiotics or 10% CSE exhibited a block in autophagic flux as evidenced by a concomitant increase in LC3-II and Sequestosome abundance (vs control; both P < 0.01). While control AEC showed no clear evidence of intracellular NTHi, COPD-derived cultures exhibited abundant NTHi within the cytoplasm. Further, intracellular NTHi that were encapsulated within vesicles propagated from the apical epithelial layer to the basal cell layer.

Discussion

Taken together, our findings indicate that COPD, cigarette smoke and macrolide antibiotics potentiate the susceptibility to persistent intracellular NTHi. A major mechanism for this is arresting normal autophagic flux in airway epithelial cells. Hence, structural modifications that mitigate this off-target effect of macrolides have significant potential to clear intracellular NTHi and thereby reduce the influence of this pathogen in the airways afflicted by COPD.

Azithromycin has enhanced effects on lung fibroblasts from idiopathic pulmonary fibrosis (IPF) patients compared to controls [corrected]

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a chronic fatal lung disease without a cure and new drug strategies are urgently needed. Differences in behavior between diseased and healthy cells are well known and drug response can be different between cells isolated from IPF patients and controls. The macrolide Azithromycin (AZT) has anti-inflammatory and immunomodulatory properties. Recently anti-fibrotic effects have been described. However, the anti-fibrotic effects on primary IPF-fibroblasts (FB) directly compared to control-FB are unknown. We hypothesized that IPF-FB react differently to AZT in terms of anti-fibrotic effects.

METHODS

Primary normal human lung and IPF-FB were exposed to TGF-β (5 ng/ml), Azithromycin (50 μM) alone or in combination prior to gene expression analysis. Pro-collagen Iα1 secretion was assessed by ELISA and protein expression by western blot (αSMA, Fibronectin, ATP6V1B2, LC3 AB (II/I), p62, Bcl-xL). Microarray analysis was performed to screen involved genes and pathways after Azithromycin treatment in control-FB. Apoptosis and intraluminal lysosomal pH were analyzed by flow cytometry.

RESULTS

AZT significantly reduced collagen secretion in TGF-β treated IPF-FB compared to TGF-β treatment alone, but not in control-FB. Pro-fibrotic gene expression was similarly reduced after AZT treatment in IPF and control-FB. P62 and LC3II/I western blot revealed impaired autophagic flux after AZT in both control and IPF-FB with significant increase of LC3II/I after AZT in control and IPF-FB, indicating enhanced autophagy inhibition. Early apoptosis was significantly higher in TGF-β treated IPF-FB compared to controls after AZT. Microarray analysis of control-FB treated with AZT revealed impaired lysosomal pathways. The ATPase and lysosomal pH regulator ATP6V0D2 was significantly less increased after additional AZT in IPF-FB compared to controls. Lysosomal function was impaired in both IPF and control FB, but pH was significantly more increased in TGF-β treated IPF-FB.

CONCLUSION

We report different treatment responses after AZT with enhanced anti-fibrotic and pro-apoptotic effects in IPF compared to control-FB. Possibly impaired lysosomal function contributes towards these effects. In summary, different baseline cell phenotype and behavior of IPF and control cells contribute to enhanced anti-fibrotic and pro-apoptotic effects in IPF-FB after AZT treatment and strengthen its role as a new potential anti-fibrotic compound, that should further be evaluated in clinical studies.

The muscarinic antagonist gallamine induces proliferation of airway smooth muscle cells regardless of the cell phenotype

BACKGROUND

Muscarinic receptor antagonists are a usual treatment for chronic airway diseases, with increased bronchoconstriction, like asthma and chronic obstructive pulmonary disease. These diseases are usually accompanied by airway remodeling, involving airway smooth muscle cell (ASMC) proliferation. The purpose of this study was to examine the effect of the muscarinic receptor modulator gallamine on rabbit tracheal ASMC proliferation.

METHODS

ASMCs were incubated with gallamine (1 nM-10 mM), atropine (1 fM-10 mM), and/or acetylcholine (1 nM-1 mM), in the presence or absence of FBS (1% or 10%). Cell proliferation was estimated by incorporation of radioactive thymidine, the Cell Titer AQueous One Solution method and cell number counting after Trypan blue exclusion. The mechanisms mediating cell proliferation were studied using the PI3K and MAPK inhibitors LY294002 (20 μM) and PD98059 (100 μM), respectively. Cell phenotype was studied by indirect immunofluorescence for α-actin, Myosin Heavy Chain and desmin.

RESULTS

ASMC incubation with the muscarinic receptor allosteric modulator gallamine or the muscarinic receptor antagonist atropine increased methyl-[³H]thymidine incorporation and cell number in a dose-dependent manner. ASMC proliferation was mediated via PI3K and MAPK activation and was transient. Gallamine antagonized the mitogenic effect of 1% FBS. Furthermore, gallamine had a similar effect on contractile ASMCs, without synergizing with or affecting acetylcholine induced proliferation, or altering the percentage of ASMCs expressing contractile phenotype marker proteins.

CONCLUSIONS

Gallamine, in the absence of any agonist, has a transient mitogenic effect on ASMCs, regardless of the cell phenotype, mediated by the PI3K and the MAPK signaling pathways.

The Anti-atherosclerotic Effect of Paeonol against Vascular Smooth Muscle Cell Proliferation by Up-regulation of Autophagy via the AMPK/mTOR Signaling Pathway

Introduction: Paeonol (2′-hydroxy-4′-methoxyacetophenone), isolated from moutan cortex, is an active component and has been shown to have anti-atherosclerotic and anti-proliferation effects on vascular smooth muscle cells (VSMCs). However, the possible role of Paeonol in protecting against VSMC proliferation as related to autophagy has yet to be elucidated.

Materials and Methods: The athero-protective effects of Paeonol were evaluated in apoE^-/- mice. The effects of Paeonol on VSMC proliferation and autophagy were examined by staining α-SMA and LC3II spots in the media layer of apoE^-/- mice, respectively. CCK8 and BrdU assays were used to investigate the effects of Paeonol on cell proliferation in vitro. The autophagic levels in VSMCs were evaluated by detecting LC3II accumulation and p62 degradation by immunoblot analysis. To investigate if Paeonol could prevent VSMCs proliferation through autophagy induction, we tested the change in autophagy and cell proliferation by inhibition of autophagy. The levels of the AMPK/mTOR pathway in autophagy regulation were detected by immunoblot analysis. An AMPK inhibitor and si-AMPK transfection in VSMCs was used to confirm whether AMPK activity plays a key role in autophagy regulation of Paeonol.

Results:In vivo experiments confirmed that Paeonol restricted atherosclerosis development and decreased the amount of VSMCs in the media layer of apoE^-/- mice. Paeonol increased protein levels of LC3II and the presence of autophagosomes in the media layer of arteries, which implies that Paeonol may induce VSMCs autophagy in vivo. Paeonol showed potential in inhibiting ox-LDL-induced proliferation in vitro experiments. Paeonol dose-dependently enhanced the formation of acidic vesicular organelles and autophagosmomes, up-regulated the expression of LC3II and increased p62 degradation. The autophagy inhibitor CQ obviously attenuated Paeonol-induced autophagy and the anti-proliferation effect in VSMCs. In addition, Paeonol induced phosphorylation of AMPK and reduced phosphorylation of mTOR. An AMPK inhibitor reversed the Paeonol-induced p-mTOR/mTOR decrease. Paeonol induced LC3II conversion, increased p62 degradation and inhibited cell proliferation in VSMCs, the effects of which were abolished by si-AMPK.

Conclusion: These results imply that Paeonol inhibits proliferation of VSMCs by up-regulating autophagy, and activating the AMPK/mTOR signaling pathway, providing new insights into the anti-atherosclerosis activity of Paeonol.

Long-term macrolides in diffuse interstitial lung diseases

In the present review we provide currently available evidence for the use of macrolides in the treatment of diffuse interstitial lung diseases (ILDs). Up to now, research on macrolides has mainly focused on three areas. First, macrolides have shown some promising results in cellular models and case reports as antifibrotic agents, by promoting autophagy and clearance of intracellular protein aggregates and acting as regulators of surfactant homeostasis. Secondly, macrolides have an immunomodulatory effect, which has been applied in some organising pneumonia cases. In particular, macrolides have been tested in association with systemic corticosteroids as steroid-sparing agents and alone as either first-line agents in mild cases or second-line agents where steroids were poorly tolerated or had failed. Thirdly, a recent area of research concerns the possible role of macrolides as modulators of lung microbiota and the host–microbiota interaction. This function has been particularly studied in idiopathic pulmonary fibrosis patients, in whom changes in microbiota have been proved to be associated with disease progression. However, the lack of high-quality studies makes the application of macrolide therapy in ILDs a field in which research should be conducted on a large scale.

Neurodegenerative effects of azithromycin in differentiated PC12 cells

Azithromycin is a widely used macrolide antibiotic with sustained and high tissue penetration and intracellular accumulation. While short-term exposure to low-dose azithromycin is usually well tolerated, prolonged treatment can lead to unwanted neurological effects like paresthesia and hearing loss. However, the mechanism causing neurodegeneration is still unknown. Here, we show that even low therapeutically relevant azithromycin concentrations like 1µg/ml decreased cell viability by 15% and induced neurite loss of 47% after 96h in differentiated PC12 cells, which are a well-established model system for neuronal cells. When higher concentrations were used, the drug-induced effects occurred earlier and were more pronounced. Thereby, azithromycin altered tropomyosin-related kinase A (TrkA) signaling and attenuated protein kinase B (Akt) activity, which subsequently induced autophagy. Simultaneously, the antibiotic impaired lysosomal functions by blocking the autophagic flux, and this concurrence reduced cell viability. In good agreement with reversible effects observed in patients, PC12 cells could completely recover if azithromycin was removed after 24h. In addition, the detrimental effects of azithromycin were limited to differentiated cells, as confirmed in the human neuronal model cell line SH-SY5Y. Thus, azithromycin alters cell surface receptor signaling and autophagy in neuronal cells, but does not automatically induce irreversible damage when used in low concentrations and for a short time.

A Phosphorylatable Sphingosine Analog Induces Airway Smooth Muscle Cytostasis and Reverses Airway Hyperresponsiveness in Experimental Asthma

In asthma, excessive bronchial narrowing associated with thickening of the airway smooth muscle (ASM) causes respiratory distress. Numerous pharmacological agents prevent experimental airway hyperresponsiveness (AHR) when delivered prophylactically. However, most fail to resolve this feature after disease is instated. Although sphingosine analogs are primarily perceived as immune modulators with the ability to prevent experimental asthma, they also influence processes associated with tissue atrophy, supporting the hypothesis that they could interfere with mechanisms sustaining pre-established AHR. We thus assessed the ability of a sphingosine analog (AAL-R) to reverse AHR in a chronic model of asthma. We dissected the pharmacological mechanism of this class of agents using the non-phosphorylatable chiral isomer AAL-S and the pre-phosphorylated form of AAL-R (AFD-R) in vivo and in human ASM cells. We found that a therapeutic course of AAL-R reversed experimental AHR in the methacholine challenge test, which was not replicated by dexamethasone or the non-phosphorylatable isomer AAL-S. AAL-R efficiently interfered with ASM cell proliferation in vitro, supporting the concept that immunomodulation is not necessary to interfere with cellular mechanisms sustaining AHR. Moreover, the sphingosine-1-phosphate lyase inhibitor SM4 and the sphingosine-1-phosphate receptor antagonist VPC23019 failed to inhibit proliferation, indicating that intracellular accumulation of sphingosine-1-phosphate or interference with cell surface S1P₁/S1P₃ activation, are not sufficient to induce cytostasis. Potent AAL-R-induced cytostasis specifically related to its ability to induce intracellular AFD-R accumulation. Thus, a sphingosine analog that possesses the ability to be phosphorylated in situ interferes with cellular mechanisms that beget AHR.

Intestinal epithelial vitamin D receptor deletion leads to defective autophagy in colitis

OBJECTIVE

Vitamin D and the vitamin D receptor (VDR) appear to be important immunological regulators of inflammatory bowel diseases (IBD). Defective autophagy has also been implicated in IBD, where interestingly, polymorphisms of genes such as ATG16L1 have been associated with increased risk. Although vitamin D, the microbiome and autophagy are all involved in pathogenesis of IBD, it remains unclear whether these processes are related or function independently.

DESIGN

We investigated the effects and mechanisms of intestinal epithelial VDR in healthy and inflamed states using cell culture models, a conditional VDR knockout mouse model (VDR(ΔIEC)), colitis models and human samples.

RESULTS

Absence of intestinal epithelial VDR affects microbial assemblage and increases susceptibility to dextran sulfate sodium-induced colitis. Intestinal epithelial VDR downregulates expressions of ATG16L1 and lysozyme, and impairs antimicrobial function of Paneth cells. Gain and loss-of-function assays showed that VDR levels regulate ATG16L1 and lysozyme at the transcriptional and translational levels. Moreover, low levels of intestinal epithelial VDR correlated with reduced ATG16L1 and representation by intestinal Bacteroides in patients with IBD. Administration of the butyrate (a fermentation product of gut microbes) increases intestinal VDR expression and suppresses inflammation in a colitis model.

CONCLUSIONS

Our study demonstrates fundamental relationship between VDR, autophagy and gut microbial assemblage that is essential for maintaining intestinal homeostasis, but also in contributing to the pathophysiology of IBD. These insights can be leveraged to define therapeutic targets for restoring VDR expression and function.

Azithromycin suppresses CD4(+) T-cell activation by direct modulation of mTOR activity

Advanced macrolides, such as azithromycin (AZM) or clarithromycin (CLM), are antibiotics with immunomodulatory properties. Here we have sought to evaluate their in vitro influence on the activation of CD4(+) T-cells. Isolated CD4(+) T-cells were stimulated with agonistic anti-CD3/anti-CD28 monoclonal antibodies in the presence of 0.6 mg/L, 2.5 mg/L, 10 mg/L or 40 mg/L AZM or CLM. Cell proliferation, cytokine level in supernatants and cell viability was assessed. Intracellular signaling pathways were evaluated using reporter cell lines, FACS analysis, immunoblotting and in vitro kinase assays. AZM inhibited cell proliferation rate and cytokine secretion of CD4(+) T-cells in a dose-dependent manner. Similarly, high concentrations of CLM (40 mg/L) also suppressed these T-cell functions. Analysis of molecular signaling pathways revealed that exposure to AZM reduced the phosphorylation of the S6 ribosomal protein, a downstream target of mTOR. This effect was also observed at 40 mg/L CLM. In vitro kinase studies using recombinant mTOR showed that AZM inhibited mTOR activity. In contrast to rapamycin, this inhibition was independent of FKBP12. We show for the first time that AZM and to a lesser extent CLM act as immunosuppressive agents on CD4(+) T-cells by inhibiting mTOR activity. Our results might have implications for the clinical use of macrolides.

Azithromycin: mechanisms of action and their relevance for clinical applications

Azithromycin is a macrolide antibiotic which inhibits bacterial protein synthesis, quorum-sensing and reduces the formation of biofilm. Accumulating effectively in cells, particularly phagocytes, it is delivered in high concentrations to sites of infection, as reflected in rapid plasma clearance and extensive tissue distribution. Azithromycin is indicated for respiratory, urogenital, dermal and other bacterial infections, and exerts immunomodulatory effects in chronic inflammatory disorders, including diffuse panbronchiolitis, post-transplant bronchiolitis and rosacea. Modulation of host responses facilitates its long-term therapeutic benefit in cystic fibrosis, non-cystic fibrosis bronchiectasis, exacerbations of chronic obstructive pulmonary disease (COPD) and non-eosinophilic asthma. Initial, stimulatory effects of azithromycin on immune and epithelial cells, involving interactions with phospholipids and Erk1/2, are followed by later modulation of transcription factors AP-1, NFκB, inflammatory cytokine and mucin release. Delayed inhibitory effects on cell function and high lysosomal accumulation accompany disruption of protein and intracellular lipid transport, regulation of surface receptor expression, of macrophage phenotype and autophagy. These later changes underlie many immunomodulatory effects of azithromycin, contributing to resolution of acute infections and reduction of exacerbations in chronic airway diseases. A sub-group of post-transplant bronchiolitis patients appears to be sensitive to azithromycin, as may be patients with severe sepsis. Other promising indications include chronic prostatitis and periodontitis, but weak activity in malaria is unlikely to prove crucial. Long-term administration of azithromycin must be balanced against the potential for increased bacterial resistance. Azithromycin has a very good record of safety, but recent reports indicate rare cases of cardiac torsades des pointes in patients at risk.

Long-term exposure to muscarinic agonists decreases expression of contractile proteins and responsiveness of rabbit tracheal smooth muscle cells

Background

Chronic airway diseases, like asthma or COPD, are characterized by excessive acetylcholine release and airway remodeling. The aim of this study was to investigate the long-term effect of muscarinic agonists on the phenotype and proliferation of rabbit tracheal airway smooth muscle cells (ASMCs).

Methods

ASMCs were serum starved before treatment with muscarinic agonists. Cell phenotype was studied by optical microscopy and indirect immunofluorescence, using smooth muscle α-actin, desmin and SM-Myosin Heavy Chain (SM-MHC) antibodies. [N-methyl-³H]scopolamine binding studies were performed in order to assess M₃ muscarinic receptor expression on isolated cell membranes. Contractility studies were performed on isolated ASMCs treated with muscarinic agonists. Proliferation was estimated using methyl-[³H]thymidine incorporation, MTT or cell counting methods. Involvement of PI3K and MAPK signalling pathways was studied by cell incubation with the pathway inhibitors LY294002 and PD98059 respectively.

Results

Prolonged culture of ASMCs with acetylcholine, carbachol or FBS, reduced the expression of α-actin, desmin and SM-MHC compared to cells cultured in serum free medium. Treatment of ASMCs with muscarinic agonists for 3-15 days decreased muscarinic receptor expression and their responsiveness to muscarinic stimulation. Acetylcholine and carbachol induced DNA synthesis and increased cell number, of ASMCs that had acquired a contractile phenotype by 7 day serum starvation. This effect was mediated via a PI3K and MAPK dependent mechanism.

Conclusions

Prolonged exposure of rabbit ASMCs to muscarinic agonists decreases the expression of smooth muscle specific marker proteins, down-regulates muscarinic receptors and decreases ASMC contractile responsiveness. Muscarinic agonists are mitogenic, via the PI3K and MAPK signalling pathways.

Impairment of lysosomal functions by azithromycin and chloroquine contributes to anti-inflammatory phenotype

Azithromycin and chloroquine have been shown to exhibit anti-inflammatory activities in a number of cellular systems, but the mechanisms of these activities have still not been clarified unequivocally. Since both drugs are cationic, accumulate in acidic cellular compartments and bind to phospholipids with a consequent increase in lysosomal pH and induce phospholipidosis, we examined the relevance of these common properties to their anti-inflammatory activities. We compared also these effects with effects of concanamycin A, compound which inhibits acidification of lysosomes. All three compounds increased lysosomal pH, accumulation of autophagic vacuoles and ubiquitinated proteins and impaired recycling of TLR4 receptor with consequences in downstream signaling in LPS-stimulated J774A.1 cells. Azithromycin and chloroquine additionally inhibited arachidonic acid release and prostaglandin E2 synthesis. Therefore, impairment of lysosomal functions by azithromycin and chloroquine deregulate TLR4 recycling and signaling and phospholipases activation and lead to anti-inflammatory phenotype in LPS-stimulated J774A.1 cells.

Anti-inflammatory and immunomodulatory properties of azithromycin involved in treatment and prevention of chronic lung allograft rejection

Chronic lung allograft rejection is the single most important cause of death in lung transplant recipients after the first postoperative year, resulting in a 5-year survival rate of approximately 50%, which is far behind that of other solid organ transplantations. Spirometry is routinely used as a clinical marker for assessing pulmonary allograft function and diagnosing chronic lung allograft rejection after lung transplantation (LTx). As such, a progressive obstructive decline in pulmonary allograft function (forced expiratory volume in 1 sec [FEV1]) in absence of all other causes (currently defined as bronchiolitis obliterans syndrome [BOS]) is considered to reflect the evolution of chronic lung allograft rejection. BOS has a 5-year prevalence of approximately 45% and is thought to be the final common endpoint of various alloimmunologic and nonalloimmunologic injuries to the pulmonary allograft, triggering different innate and adaptive immune responses. Most preventive and therapeutic strategies for this complex process have thus far been largely unsuccessful. However, the introduction of the neomacrolide antibiotic azithromycin (AZI) in the field of LTx as of 2003 made it clear that some patients with established BOS might in fact benefit from such therapy due to its various antiinflammatory and immunomodulatory properties, as summarized in this review. Particularly in patients with an increased bronchoalveolar lavage neutrophilia (i.e., 15%-20% or more), AZI treatment could result in an increase in FEV1 of at least 10%. More recently, it has become clear that prophylactic therapy with AZI actually may prevent BOS and improve FEV1 after LTx, most likely through its interactions with the innate immune system. However, one should always be aware of possible adverse effects related to AZI when implementing this drug as prophylactic or long-term treatment. Even so, AZI therapy after LTx can generally be considered as safe.

Cytokines and growth factors promote airway smooth muscle cell proliferation

Chronic airway diseases, such as asthma or chronic obstructive pulmonary disease, are characterized by the presence in the airways of inflammation factors, growth factors and cytokines, which promote airway wall remodelling. The aim of this study was to investigate the effect of cytokines and growth factors on airway smooth muscle cell (ASMC) proliferation, phenotype and responsiveness. Incubation of serum starved human bronchial ASMCs with TNF- α , TGF, bFGF, and PDGF, but not IL-1 β , increased methyl-[(3)H]thymidine incorporation and cell number, mediated by the PI3K and MAPK signalling pathways. Regarding rabbit tracheal ASMC proliferation, TNF- α , IL-1 β , TGF, and PDGF increased methyl-[(3)H]thymidine incorporation in a PI3K- and MAPK-dependent manner. bFGF increased both methyl-[(3)H]thymidine incorporation and cell number. Moreover, incubation with TGF, bFGF and PDGF appears to drive human ASMCs towards a synthetic phenotype, as shown by the reduction of the percentage of cells expressing SM- α actin. In addition, the responsiveness of epithelium-denuded rabbit tracheal strips to carbachol was not significantly altered after 3-day treatment with bFGF. In conclusion, all the tested cytokines and growth factors increased ASMC proliferation to a different degree, depending on the specific cell type, with bronchial ASMCs being more prone to proliferation than tracheal ASMCs.

The mitogenic effect of testosterone and 17β-estradiol on airway smooth muscle cells

Airway disease distribution and/or severity exhibit sex differences suggesting that sex hormones are involved in the respiratory system physiology and pathophysiology. The implication of airway smooth muscle cells (ASMCs) in the physiology of the airways and the pathogenetic mechanism of airway remodeling is of great interest. Therefore, we studied the effect of testosterone and 17β-estradiol on ASMC proliferation and the mechanisms involved. Cell proliferation was estimated using the methyl-[³H]thymidine incorporation and Cell Titer 96® AQueous One Solution Assay methods. ASMC isolated from adult male or female rabbit trachea were incubated with testosterone (1 pM-1 μM) or 17β-estradiol (1 pM-1 μM), in the presence or absence of the androgen receptor antagonist flutamide (10 nM) or estrogen receptor antagonist ICI182780 (10 nM), as well as of the PI3K inhibitors LY294002 (20 μM) or wortmannin (1 μM), or the MAPK inhibitors PD98059 (100 μM) or U0126 (1 μM). After 24 h of incubation, testosterone and 17β-estradiol increased methyl-[³H]thymidine incorporation and cell number, in ASMC isolated from male or female animals. The induction of ASMC proliferation by testosterone or 17β-estradiol was inhibited by flutamide or ICI182780 respectively, as well as by LY294002, wortmannin, PD98059 or U0126. In conclusion, testosterone and 17β-estradiol have a mitogenic effect on ASMC, which is receptor-mediated and involves the MAPK and PI3K signaling pathways. Moreover, their effect is the same for ASMC from male and female animals. It is possible that gender-related differences in ASMC remodeling, may be influenced by the different patterns of sex steroid hormone secretion in males and females.