The differential effects of azithromycin on the airway epithelium in vitro and in vivo

In vitro modelling of bacterial pneumonia: a comparative analysis of widely applied complex cell culture models

Bacterial pneumonia greatly contributes to the disease burden and mortality of lower respiratory tract infections among all age groups and risk profiles. Therefore, laboratory modelling of bacterial pneumonia remains important for elucidating the complex host-pathogen interactions and to determine drug efficacy and toxicity. In vitro cell culture enables for the creation of high-throughput, specific disease models in a tightly controlled environment. Advanced human cell culture models specifically, can bridge the research gap between the classical two-dimensional cell models and animal models. This review provides an overview of the current status of the development of complex cellular in vitro models to study bacterial pneumonia infections, with a focus on air-liquid interface models, spheroid, organoid, and lung-on-a-chip models. For the wide scale, comparative literature search, we selected six clinically highly relevant bacteria (Pseudomonas aeruginosa, Mycoplasma pneumoniae, Haemophilus influenzae, Mycobacterium tuberculosis, Streptococcus pneumoniae, and Staphylococcus aureus). We reviewed the cell lines that are commonly used, as well as trends and discrepancies in the methodology, ranging from cell infection parameters to assay read-outs. We also highlighted the importance of model validation and data transparency in guiding the research field towards more complex infection models.

Quantity of antibiotic use and its association with clinical outcomes in COVID-19 patients: A snapshot from a provincial referral hospital in Indonesia

Irrational antibiotic use in Indonesia is considered high, yet there are still lacks reliable information regarding the issue. The quantity of antibiotic use studies, in particular during coronavirus disease 2019 (COVID-19) pandemic, was not well reported. The aim of this study was to evaluate antibiotic use in COVID-19 patients at a province referral hospital in Aceh, Indonesia, Dr Zainoel Abidin Hospital, and to assess the association between antibiotic use and COVID-19 clinical outcomes. The defined daily dose (DDD) method was used and expressed in DDDs per 100 patient-days as in hospital setting. The data were obtained from inpatient confirmed COVID-19 patients between March 2020 and December 2021. A logistic regression was used to determine the association between patients' characteristics and antibiotic usage with clinical outcomes. A total of 361 treated COVID-19 patients were included using a random sampling technique and analyzed. Out of 361 patients, 89.2% of them were treated with antibiotic(s). All the antibiotics were given empirically except for cefazoline (5.5%) that was used as prophylaxis to obstetric patients who underwent the c-section. Azithromycin was the most prescribed antibiotic and levofloxacin had the highest DDD. Our data suggested that there was no association between antibiotic use and clinical outcomes of COVID-19 patients (p=0.128). Having sepsis and another pulmonary disease however were associated with mortality of COVID-19 patients with adjusted odds ratio (aOR) 14.14; 95%CI 2.94-67.90, p=0.001 and aOR 8.64; 95%CI 3.30-22.63, p<0.001, respectively. In addition, patients older than 60-year-old had a higher chance to an unfavorable outcome compared to those younger than 30-year-old, aOR: 7.61; 95%CI: 1.07-53.94. In conclusion, the use of antibiotics is prevalent among COVID-19 and it is not directly associated with clinical outcomes.

Elevated PLAUR is observed in the airway epithelium of asthma patients and blocking improves barrier integrity

BACKGROUND

Expression of the urokinase plasminogen activator receptor (uPAR) is elevated in the airway epithelium in asthma; however, the contribution of uPAR to asthma pathogenesis and scope for therapeutic targeting remains unknown.

OBJECTIVES

To determine (i) the expression profile of uPAR in cultured human bronchial epithelial cells (HBEC) from asthma patients, (ii) the relationship between uPAR and the epithelial barrier, including blocking uPAR functions and (iii) the function of different uPAR isoforms.

METHODS

uPAR levels in HBECs isolated from asthma patients and cells at air liquid interface (ALI) during differentiation were quantified. Transepithelial electrical resistance or electrical cell impedance sensing was used to relate uPAR levels to barrier properties, including effects of uPAR blocking antibodies. The functional effects of gain of function was determined using transcriptomics, in cells over-expressing membrane (muPAR), soluble cleaved (scuPAR) or soluble spliced (ssuPAR) isoforms.

RESULTS

Elevated expression of uPAR was a feature of cultured HBECs from asthma patients, suggesting intrinsic alterations in asthma patient cells. Soluble uPAR levels inversely correlated with barrier properties of the HBEC layer in 2D and ALI. Blocking uPAR-integrin interactions enhanced barrier formation. The gain of function cells showed limited transcriptomic changes.

CONCLUSION

This study provides a significant advance in our understanding of the relationship between asthma, uPAR and the epithelial barrier, where elevated circulating uPAR results in a reduced cell barrier, a phenotype prevalent in asthma.

Asthma and COPD: A Focus on β-Agonists - Past, Present and Future

Asthma has been recognised as a respiratory disorder for millennia and the focus of targeted drug development for the last 120 years. Asthma is one of the most common chronic non-communicable diseases worldwide. Chronic obstructive pulmonary disease (COPD), a leading cause of morbidity and mortality worldwide, is caused by exposure to tobacco smoke and other noxious particles and exerts a substantial economic and social burden. This chapter reviews the development of the treatments of asthma and COPD particularly focussing on the β-agonists, from the isolation of adrenaline, through the development of generations of short- and long-acting β-agonists. It reviews asthma death epidemics, considers the intrinsic efficacy of clinical compounds, and charts the improvement in selectivity and duration of action that has led to our current medications. Important β2-agonist compounds no longer used are considered, including some with additional properties, and how the different pharmacological properties of current β2-agonists underpin their different places in treatment guidelines. Finally, it concludes with a look forward to future developments that could improve the β-agonists still further, including extending their availability to areas of the world with less readily accessible healthcare.

"The effect of 48-weeks azithromycin therapy on levels of soluble biomarkers associated with HIV-associated chronic lung disease"

OBJECTIVES

HIV-associated immune activation contributes to chronic lung disease (CLD) in children and adolescents living with HIV. Azithromycin has immunomodulatory and anti-microbial properties that may be useful for treating HIV-associated CLD (HCLD). This study describes the effect of azithromycin on expression of plasma soluble biomarkers in children and adolescents with HCLD.

METHODS

This study was nested within a multi-site double-blind, placebo controlled, randomised controlled trial (RCT) of azithromycin in individuals aged 6-19 years with HCLD (defined as FEV1 z-score < -1) in Malawi and Zimbabwe (BREATHE (NCT02426112)). Participants were randomized 1:1 to once-weekly oral azithromycin with weight-based dosing, for 48 weeks, or placebo. Twenty-six plasma soluble biomarkers were measured on a MagPix Luminex instrument at enrolment, after 48-weeks of treatment and 24-weeks after treatment cessation. Mixed effects models were constructed to compare biomarker expression across treatment and placebo groups.

RESULTS

Weekly azithromycin was associated with reduced levels of C-Reactive Protein (CRP), E-Selectin, Matrix metalloproteinase 10 (MMP-10). Treatment effects for all soluble biomarkers were not sustained 24-weeks after treatment cessation with biomarker expression returning to pre-treatment levels.

CONCLUSIONS

We observed real-world effects of azithromycin on acute inflammation, neutrophil accumulation, and extracellular matrix degradation, that were not sustained after treatment cessation. These results are pertinent when using azithromycin for its immunomodulatory properties, or targeting pathways represented by the soluble biomarkers in this study.

Human bronchial epithelial cells from patients with asthma have an altered gene expression profile

Asthma is a multifactorial disease presenting with wheeze and shortness of breath, and is known to be exacerbated by triggers such as pollen, house dust mites and viral infection. In the lung, the bronchial epithelium is recognised as a central driver of airway structural changes, including epithelial goblet cell hyperplasia and metaplasia, which are features of asthma. Bronchial epithelial cells (BECs) isolated from patients with asthma and cultured in vitro have altered barrier properties [1], elevated expression of remodelling factors [2] and defective repair [3]. Interestingly, genome-wide association studies (GWAS) of asthma have implicated a number of genes that are known to be expressed and functional in the airway epithelium, including IL33, IL1RL1, TSLP and MUC5AC [4]. To identify the molecular mechanisms underlying altered BECs phenotype in asthma patients, several studies have completed transcriptomic analyses using bronchial brush samples. Two recent meta-analyses [5, 6] suggested that alterations in chemical stimulus, extracellular region, pathways in cancer and arachidonic acid metabolism were features of the bronchial epithelium in the lungs of patients with asthma, and included 78 up- and 75 down-regulated genes [5]. While useful, a key question is how much the airway environment of a patient is driving this differential gene expression profile (GEP) and how much is intrinsic to the BECs themselves? To answer this question, we completed transcriptomic analyses of BECs cultured two-dimensionally through multiple passages in the laboratory that had originally been isolated from control subjects without disease or patients with asthma. An attrition rate (for successful culture) of 54% and 42% was observed in the asthma and control populations respectively.

Gene changes observed in asthma bronchial epithelial cells are maintained following repeated culture, presenting with an exaggerated response to viral infection and immune responses as well as having differences in the rate of cell division and replicationhttps://bit.ly/3Cq2xKf

Nonantimicrobial Actions of Macrolides: Overview and Perspectives for Future Development

Macrolides are among the most widely prescribed broad spectrum antibacterials, particularly for respiratory infections. It is now recognized that these drugs, in particular azithromycin, also exert time-dependent immunomodulatory actions that contribute to their therapeutic benefit in both infectious and other chronic inflammatory diseases. Their increased chronic use in airway inflammation and, more recently, of azithromycin in COVID-19, however, has led to a rise in bacterial resistance. An additional crucial aspect of chronic airway inflammation, such as chronic obstructive pulmonary disease, as well as other inflammatory disorders, is the loss of epithelial barrier protection against pathogens and pollutants. In recent years, azithromycin has been shown with time to enhance the barrier properties of airway epithelial cells, an action that makes an important contribution to its therapeutic efficacy. In this article, we review the background and evidence for various immunomodulatory and time-dependent actions of macrolides on inflammatory processes and on the epithelium and highlight novel nonantibacterial macrolides that are being studied for immunomodulatory and barrier-strengthening properties to circumvent the risk of bacterial resistance that occurs with macrolide antibacterials. We also briefly review the clinical effects of macrolides in respiratory and other inflammatory diseases associated with epithelial injury and propose that the beneficial epithelial effects of nonantibacterial azithromycin derivatives in chronic inflammation, even given prophylactically, are likely to gain increasing attention in the future. SIGNIFICANCE STATEMENT: Based on its immunomodulatory properties and ability to enhance the protective role of the lung epithelium against pathogens, azithromycin has proven superior to other macrolides in treating chronic respiratory inflammation. A nonantibiotic azithromycin derivative is likely to offer prophylactic benefits against inflammation and epithelial damage of differing causes while preserving the use of macrolides as antibiotics.

Interleukin-18: A Novel Participant in the Occurrence, Development, and Drug Therapy of Obliterative Bronchiolitis Postlung Transplantation

Background

Obliterative bronchiolitis (OB) was a main cause of deterioration of long-term prognosis in lung transplant recipients after the first posttransplant year. Proinflammatory cytokine interleukin-18 (IL-18) strengthened both the natural immunity and acquired immunity and played an important role in organ transplantation. The roles of IL-18 in the occurrence, development, and drug treatment of OB remained unclear.

Methods

Small interfering RNA (siRNA) against mouse IL-18 (siRNA-IL-18) was used to silence IL-18 expression. Mouse heterotopic tracheal transplantation model was used to simulate OB. Recipient mice were divided into 5 groups (n = 12) according to donor mouse strains and drug treatment: isograft group, allograft group, allograft+tacrolimus group, allograft+azithromycin group, and allograft+tacrolimus+azithromycin group. The luminal obliteration rates were pathological evaluation. Expressions of cytokines and MMPs were detected by real-time PCR, western blot, and enzyme chain immunosorbent assay (ELISA).

Results

The luminal obliteration rates of IL-18 of the siRNA-IL-18 group were significantly lower than those of the negative control group (p < 0.0001) and the blank control group (p = 0.0002). mRNA expressions of IFN-γ, EMMPRIN, MMP-8, and MMP-9 of the siRNA-IL-18 group were significantly lower than those of the negative and blank control groups. No tracheal occlusion occurred in grafts of the isograft group. The rates of tracheal occlusion of the allograft group, allograft+tacrolimus group, allograft+azithromycin group, and allograft+tacrolimus+azithromycin group were 72.17 ± 4.66%, 40.33 ± 3.00%, 38.50 ± 2.08%, and 23.33 ± 3.24%, respectively. There were significant differences between the 4 groups (p < 0.001). Serum protein expressions of IL-17 (p = 0.0017), IL-18 (p = 0.0036), IFN-γ (p = 0.0102), and MMP-9 (p = 0.0194) were significantly decreased in the allograft+tacrolimus+azithromycin group compared to the allograft group.

Conclusions

IL-18 could be a novel molecular involved in the occurrence, development, and drug treatment of OB.

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.

Antimicrobial Peptides SLPI and Beta Defensin-1 in Sputum are Negatively Correlated with FEV1

Background

Chronic obstructive pulmonary disease (COPD) and asthma have heterogeneous inflammation with inhaled corticosteroids (ICS) as a mainstay of treatment. There is increased prevalence of non-typeable Haemophilus influenzae (NTHi) persistence in airways of patients with neutrophilic airway inflammation, potentially due to suppressed host defence after corticosteroid treatment. Antimicrobial peptides (AMPs) have antimicrobial activity against pathogens and immunomodulatory effects. We investigated whether AMPs associate with NTHi presence in COPD and asthma, and whether ICS alter this.

Methods

Secretory leukocyte protease inhibitor (SLPI), osteopontin, elafin and beta defensin-1 were measured in sputum supernatants from healthy donors (n=9), asthmatics (n=21) and patients with COPD (n=14). Elafin and beta defensin-1 were measured in a primary human bronchial epithelial cells (HBECs) from healthy and COPD donors infected with NTHi and pre-treated with fluticasone propionate (FP) and budesonide (BUD). Internalised NTHi was quantified by qPCR.

Results

Sputum SLPI was negatively correlated with FEV1 (p<0.001, r=-0.610), FEV1% predicted (p<0.001, r=-0.583) and FEV1/FVC (p=0.001, r=-0.528). Sputum beta defensin-1 was negatively associated with FEV1 (p<0.001***r=-0.594). SLPI and beta defensin-1 levels in sputum were higher in the healthy controls and COPD group compared to the asthma group (p=0.001 and p=0.014) and (p<0.001 and p=0.007, respectively). ICS use was associated with higher sputum osteopontin compared to those with no ICS use. NTHi infection of COPD HBECs produced higher levels of beta defensin-1 compared to healthy donors (mean (SD) release: 45.1pg/mL (7.3) vs 21.2pg/mL (7.3) respectively, p=0.014). Elafin release from HBECs from COPD donors did not change following NTHi infection; however, elafin from healthy donors was significantly reduced (%mean reduction: 23.7%, 95% confidence intervals (CI) of reduction: 5.3-38.4%, p<0.01).

Conclusion

Sputum SLPI and beta defensin-1 may be markers to identify those patients with declining lung function. ICS use was associated with higher sputum osteopontin compared to those with no ICS use.

Rationale for azithromycin in COVID-19: an overview of existing evidence

Azithromycin has rapidly been adopted as a repurposed drug for the treatment of COVID-19, despite the lack of high-quality evidence. In this review, we critically appraise the current pharmacological, preclinical and clinical data of azithromycin for treating COVID-19. Interest in azithromycin has been fuelled by favourable treatment outcomes in other viral pneumonias, a documented antiviral effect on SARS-CoV-2 in vitro and uncontrolled case series early in the pandemic. Its antiviral effects presumably result from interfering with receptor mediated binding, viral lysosomal escape, intracellular cell-signalling pathways and enhancing type I and III interferon expression. Its immunomodulatory effects may mitigate excessive inflammation and benefit tissue repair. Currently, in vivo reports on azithromycin in COVID-19 are conflicting and do not endorse its widespread use outside of clinical trials. They are, however, mostly retrospective and therefore inherently biased. The effect size of azithromycin may depend on when it is started. Also, extended follow-up is needed to assess benefits in the recovery phase. Safety data warrant monitoring of drug-drug interactions and subsequent cardiac adverse events, especially with hydroxychloroquine. More prospective data of large randomised controlled studies are expected and much-needed. Uniform reporting of results should be strongly encouraged to facilitate data pooling with the many ongoing initiatives.

Azithromycin ameliorates sulfur dioxide-induced airway epithelial damage and inflammatory responses

Background

The airway epithelium (AE) forms the first line of defence against harmful particles and pathogens. Barrier failure of the airway epithelium contributes to exacerbations of a range of lung diseases that are commonly treated with Azithromycin (AZM). In addition to its anti-bacterial function, AZM has immunomodulatory effects which are proposed to contribute to its clinical effectiveness. In vitro studies have shown the AE barrier-enhancing effects of AZM. The aim of this study was to analyze whether AE damage caused by inhalation of sulfur dioxide (SO₂) in a murine model could be reduced by pre-treatment with AZM.

Methods

The leakiness of the AE barrier was evaluated after SO₂ exposure by measuring levels of human serum albumin (HSA) in bronchoalveolar lavage fluid (BALF). Protein composition in BALF was also assessed and lung tissues were evaluated across treatments using histology and gene expression analysis.

Results

AZM pre-treatment (2 mg/kg p.o. 5 times/week for 2 weeks) resulted in reduced glutathione-S-transferases in BALF of SO₂ injured mice compared to control (without AZM treatment). AZM treated mice had increased intracellular vacuolization including lamellar bodies and a reduction in epithelial shedding after injury in addition to a dampened SO₂-induced inflammatory response.

Conclusions

Using a mouse model of AE barrier dysfunction we provide evidence for the protective effects of AZM in vivo, possibly through stabilizing the intracellular microenvironment and reducing inflammatory responses. Our data provide insight into the mechanisms contributing to the efficacy of AZM in the treatment of airway diseases.

Phenotypic and functional translation of IL33 genetics in asthma

BACKGROUND

Asthma is a complex disease with multiple phenotypes that may differ in disease pathobiology and treatment response. IL33 single nucleotide polymorphisms (SNPs) have been reproducibly associated with asthma. IL33 levels are elevated in sputum and bronchial biopsies of patients with asthma. The functional consequences of IL33 asthma SNPs remain unknown.

OBJECTIVE

This study sought to determine whether IL33 SNPs associate with asthma-related phenotypes and with IL33 expression in lung or bronchial epithelium. This study investigated the effect of increased IL33 expression on human bronchial epithelial cell (HBEC) function.

METHODS

Association between IL33 SNPs (Chr9: 5,815,786-6,657,983) and asthma phenotypes (Lifelines/DAG [Dutch Asthma GWAS]/GASP [Genetics of Asthma Severity & Phenotypes] cohorts) and between SNPs and expression (lung tissue, bronchial brushes, HBECs) was done using regression modeling. Lentiviral overexpression was used to study IL33 effects on HBECs.

RESULTS

We found that 161 SNPs spanning the IL33 region associated with 1 or more asthma phenotypes after correction for multiple testing. We report a main independent signal tagged by rs992969 associating with blood eosinophil levels, asthma, and eosinophilic asthma. A second, independent signal tagged by rs4008366 presented modest association with eosinophilic asthma. Neither signal associated with FEV₁, FEV₁/forced vital capacity, atopy, and age of asthma onset. The 2 IL33 signals are expression quantitative loci in bronchial brushes and cultured HBECs, but not in lung tissue. IL33 overexpression in vitro resulted in reduced viability and reactive oxygen species-capturing of HBECs, without influencing epithelial cell count, metabolic activity, or barrier function.

CONCLUSIONS

We identify IL33 as an epithelial susceptibility gene for eosinophilia and asthma, provide mechanistic insight, and implicate targeting of the IL33 pathway specifically in eosinophilic asthma.

Potential Role of Cellular Senescence in Asthma

Cellular senescence is a complicated process featured by irreversible cell cycle arrest and senescence-associated secreted phenotype (SASP), resulting in accumulation of senescent cells, and low-grade inflammation. Cellular senescence not only occurs during the natural aging of normal cells, but also can be accelerated by various pathological factors. Cumulative studies have shown the role of cellular senescence in the pathogenesis of chronic lung diseases including chronic obstructive pulmonary diseases (COPD) and idiopathic pulmonary fibrosis (IPF) by promoting airway inflammation and airway remodeling. Recently, great interest has been raised in the involvement of cellular senescence in asthma. Limited but valuable data has indicated accelerating cellular senescence in asthma. This review will compile current findings regarding the underlying relationship between cellular senescence and asthma, mainly through discussing the potential mechanisms of cellular senescence in asthma, the impact of senescent cells on the pathobiology of asthma, and the efficiency and feasibility of using anti-aging therapies in asthmatic patients.

Azithromycin induces epidermal differentiation and multivesicular bodies in airway epithelia

Background

Azithromycin (Azm) is a macrolide recognized for its disease-modifying effects and reduction in exacerbation of chronic airway diseases. It is not clear whether the beneficial effects of Azm are due to its anti-microbial activity or other pharmacological actions. We have shown that Azm affects the integrity of the bronchial epithelial barrier measured by increased transepithelial electrical resistance. To better understand these effects of Azm on bronchial epithelia we have investigated global changes in gene expression.

Methods

VA10 bronchial epithelial cells were treated with Azm and cultivated in air-liquid interface conditions for up to 22 days. RNA was isolated at days 4, 10 and 22 and analyzed using high-throughput RNA sequencing. qPCR and immunostaining were used to confirm key findings from bioinformatic analyses. Detailed assessment of cellular changes was done using microscopy, followed by characterization of the lipidomic profiles of the multivesicular bodies present.

Results

Bioinformatic analysis revealed that after 10 days of treatment genes encoding effectors of sterol and cholesterol metabolism were prominent. Interestingly, expression of genes associated with epidermal barrier differentiation, KRT1, CRNN, SPINK5 and DSG1, increased significantly at day 22. Together with immunostaining, these results suggest an epidermal differentiation pattern. We also found that Azm induced the formation of multivesicular and lamellar bodies in two different airway epithelial cell lines. Lipidomic analysis revealed that Azm was entrapped in multivesicular bodies linked to different types of lipids, most notably palmitate and stearate. Furthermore, targeted analysis of lipid species showed accumulation of phosphatidylcholines, as well as ceramide derivatives.

Conclusions

Taken together, we demonstrate how Azm might confer its barrier enhancing effects, via activation of epidermal characteristics and changes to intracellular lipid dynamics. These effects of Azm could explain the unexpected clinical benefit observed during Azm-treatment of patients with various lung diseases affecting barrier function.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-1101-3) contains supplementary material, which is available to authorized users.

Repair Process Impairment by Pseudomonas aeruginosa in Epithelial Tissues: Major Features and Potential Therapeutic Avenues

Epithelial tissues protecting organs from the environment are the first-line of defense against pathogens. Therefore, efficient repair mechanisms after injury are crucial to maintain epithelial integrity. However, these healing processes can be insufficient to restore epithelial integrity, notably in infectious conditions. Pseudomonas aeruginosa infections in cutaneous, corneal, and respiratory tract epithelia are of particular concern because they are the leading causes of hospitalizations, disabilities, and deaths worldwide. Pseudomonas aeruginosa has been shown to alter repair processes, leading to chronic wounds and infections. Because of the current increase in the incidence of multi-drug resistant isolates of P. aeruginosa, complementary approaches to decrease the negative impact of these bacteria on epithelia are urgently needed. Here, we review the recent advances in the understanding of the impact of P. aeruginosa infections on the integrity and repair mechanisms of alveolar, airway, cutaneous and corneal epithelia. Potential therapeutic avenues aimed at counteracting this deleterious impact of infection are also discussed.

Idiopathic chronic productive cough and response to open-label macrolide therapy: An observational study

BACKGROUND AND OBJECTIVE

Adult patients with chronic productive cough of unknown cause are commonly seen in respiratory clinics. We have previously described a subgroup of these patients who have a short-lived response to standard antibiotic treatment but a prolonged response to 3 months of low-dose azithromycin therapy.

METHODS

This observational study describes the physiological, radiological and pathological features of this patient cohort along with their response to a 12-week open-label trial of 250 mg azithromycin thrice weekly.

RESULTS

A total of 30 subjects with a mean age of 57 were recruited. The majority demonstrated airway dilatation on high-resolution computed tomography (HRCT) scan without evidence of established bronchiectasis (n = 21) and non-specific chronic inflammatory changes on bronchial biopsy (n = 15/17). Twenty-nine subjects completed 3 months of azithromycin with a significant improvement in median Leicester Cough Questionnaire (LCQ) score (-6.3 points, P < 0.00001), reduction in median 24-h sputum volume (-5.8 mL, P = 0.0003) and improvement in sputum colour (P = 0.003). Patients responsive to azithromycin (n = 22) demonstrated neutrophilic or paucigranulocytic airway inflammation, whereas five subjects with eosinophilic airways inflammation did not respond symptomatically to azithromycin.

CONCLUSION

We describe a cohort of patients with chronic productive cough not adequately described by existing disease labels whose symptoms responded well to low-dose azithromycin. Many of the features are similar to the paediatric condition protracted bacterial bronchitis.

In vitro performances of novel co-spray-dried azithromycin/rifampicin microparticles for Rhodococcus equi disease treatment

This work was aimed at providing clues on the in vitro performances of novel azithromycin/rifampicin combinations, in the form of co-spray-dried microparticles (AZM/RIF MP), against Rhodococcus equi, an animal and emerging human pathogen found responsible for worrying zoonosis. Various AZM/RIF combinations were spray-dried and characterized for their morphology and size. Susceptibility studies included determination of MIC, MBC, Fractional Inhibitory/Bactericidal Concentration Indexes and intracellular activity in R. equi-infected THP-1 cells. Cytotoxicity was tested on BEAS-2B cells through MTT assay and combination index assessment for drug interaction. Spray-dried MP were collapsed and 3-10 times smaller than commercial powders. Drug combinations showed an enhancement of in vitro antibacterial activity with a remarkable synergistic bactericidal effect. Azithromycin MP and AZM/RIF MP 2:1 led to a CFU reduction of >90% up to 4 days after treatment at all tested concentrations (p = 0.001) but AZM/RIF MP 2:1 were at least four-fold more potent than AZM MP alone. IC50 values of >100 mg/L supported low cytotoxicity of drug combinations and the combination index suggested an antagonistic toxic effect. Co-spray-drying enhanced powder dispersibility and solubility, which may improve bioavailability as well as provide administration alternatives. The novel AZM/RIF MP combinations could result a valid platform to develop new treatment strategies against R. equi infections in animals and humans.

Post-ischemic treatment with azithromycin protects ganglion cells against retinal ischemia/reperfusion injury in the rat

Purpose

Retinal ischemic phenomena occur in several ocular diseases that share the degeneration and death of retinal ganglion cells (RGCs) as the final event. We tested the neuroprotective effect of azithromycin, a widely used semisynthetic macrolide antibiotic endowed with anti-inflammatory and immunomodulatory properties, in a model of retinal ischemic injury induced by transient elevation of intraocular pressure in the rat.

Methods

Retinal ischemia was induced in adult rats with transient elevation of intraocular pressure. RGCs were retrogradely labeled with Fluoro-Gold, and survival was assessed following a single dose of azithromycin given systemically at the end of the ischemia. The expression of death-associated proteins and extracellular signal-regulated kinase (ERK) activation was studied with western blotting. Expression and activity of matrix metalloproteinase-2 (MMP-2) and -9 were analyzed with gelatin zymography.

Results

Acute post-injury administration of azithromycin significantly prevented RGC death. This effect was accompanied by reduced calpain activity and prevention of Bcl-2-associated death promoter (Bad) upregulation. The observed neuroprotection was associated with a significant inhibition of MMP-2/-9 gelatinolytic activity and ERK1/2 phosphorylation.

Conclusions

Azithromycin provides neuroprotection by modifying the inflammatory state of the retina following ischemia/reperfusion injury suggesting potential for repurposing as a drug capable of limiting or preventing retinal neuronal damage.

The differential effects of azithromycin on the airway epithelium in vitro and in vivo

Macrolides including azithromycin (AZM) can improve clinical symptoms in asthma regardless of infection status. The mechanisms underlying these beneficial effects are yet to be elucidated. The aim of this study was to determine the effect of AZM on the airway epithelial barrier both in an in vitro model and in patients with asthma. Primary human bronchial epithelial cells (HBEC) were grown at air liquid interface (ALI) and challenged using lipopolysaccharides from Pseudomonas aeruginosa AZM was added at various stages and barrier integrity assessed using transepithelial electrical resistance (TEER) and permeability to FITC-dextran. MMP-9 levels were measured using ELISA AZM enhanced barrier integrity (TEER/FITC-dextran), increased thickness, suppressed mucin production, and MMP-9 release during the formation of a normal epithelial barrier in vitro. MMP-9 levels inversely correlated with TEER AZM also enhanced maintenance of the barrier and facilitated repair post-LPS challenge. To provide translation of our findings, 10 patients with moderate-severe asthma were recruited and received 250 mg AZM o.d for 6 weeks. Bronchial biopsies taken pre- and post-AZM treatment did not show evidence of increased epithelial barrier thickness or decreased mucin production. Similarly, bronchial wash samples did not show reduced MMP-9 levels. Overall, our data show that AZM can significantly improve the development of a normal bronchial epithelial barrier in vitro, mimicking reepithelization postinjury. AZM also suppressed MMP-9 release which correlated with barrier integrity, suggesting a putative mechanism. However, these effects were not observed in biopsy samples from asthma patients treated with AZM, possibly due to small sample size.