Clarithromycin inhibits overproduction of muc5ac core protein in murine model of diffuse panbronchiolitis

Solithromycin inhibits IL-13-induced goblet cell hyperplasia and MUC5AC, CLCA1, and ANO1 in human bronchial epithelial cells

Solithromycin is a novel fluoroketolide antibiotic belonging to the class of macrolide antibiotics. Activation of the interleukin (IL)-13 receptor leads to STAT6 activation and subsequent induction of SAM pointed domain containing ETS transcription factor (SPDEF), chloride channel accessory 1 (CLCA1), and anoctamin-1 (ANO1), all of which are associated with the induction of MUC5AC. We examined the effects of solithromycin on mucin production led by IL-13 signaling. Normal human bronchial epithelial cells were grown at the air-liquid interface with IL-13 with/without solithromycin for 14 days. Histochemical analysis was performed using hematoxylin and eosin staining and MUC5AC immunostaining. MUC5AC, SPDEF, CLCA1, and ANO1 mRNA expressions were examined using real-time polymerase chain reaction. Western blot analysis was performed to assess CLCA1 and ANO1 proteins, and phosphorylation of STAT6 and ERK. Solithromycin attenuated IL-13 induction of goblet cell hyperplasia and MUC5AC, CLCA1 and ANO1 mRNA and protein expression induced by IL-13, but had no effect on the phosphorylation of STAT6 and ERK. Our results indicate that solithromycin could attenuate goblet cell hyperplasia and MUC5AC induced by IL-13 through inhibition of CLCA1 and ANO1 mRNA and protein expression. However, much more information is required to clarify the molecular mechanisms underlying the inhibition of CLCA1 and ANO1 by solithromycin.

Invited review: human air-liquid-interface organotypic airway tissue models derived from primary tracheobronchial epithelial cells-overview and perspectives

The lung is an organ that is directly exposed to the external environment. Given the large surface area and extensive ventilation of the lung, it is prone to exposure to airborne substances, such as pathogens, allergens, chemicals, and particulate matter. Highly elaborate and effective mechanisms have evolved to protect and maintain homeostasis in the lung. Despite these sophisticated defense mechanisms, the respiratory system remains highly susceptible to environmental challenges. Because of the impact of respiratory exposure on human health and disease, there has been considerable interest in developing reliable and predictive in vitro model systems for respiratory toxicology and basic research. Human air-liquid-interface (ALI) organotypic airway tissue models derived from primary tracheobronchial epithelial cells have in vivo–like structure and functions when they are fully differentiated. The presence of the air-facing surface allows conducting in vitro exposures that mimic human respiratory exposures. Exposures can be conducted using particulates, aerosols, gases, vapors generated from volatile and semi-volatile substances, and respiratory pathogens. Toxicity data have been generated using nanomaterials, cigarette smoke, e-cigarette vapors, environmental airborne chemicals, drugs given by inhalation, and respiratory viruses and bacteria. Although toxicity evaluations using human airway ALI models require further standardization and validation, this approach shows promise in supplementing or replacing in vivo animal models for conducting research on respiratory toxicants and pathogens.

Macrolides Inhibit Capsule Formation of Highly Virulent Cryptococcus gattii and Promote Innate Immune Susceptibility

Cryptococcus gattii is a fungal pathogen, endemic in tropical and subtropical regions, the west coast of Canada, and the United States, that causes a potentially fatal infection in otherwise healthy individuals. Because the cryptococcal polysaccharide capsule is a leading virulence factor due to its resistance against innate immunity, the inhibition of capsule formation may be a promising new therapeutic strategy for C. gattii Macrolides have numerous nonantibiotic effects, including immunomodulation of mammalian cells and suppression of bacterial (but not fungal) pathogenicity. Thus, we hypothesized that a macrolide would inhibit cryptococcal capsule formation and improve the host immune response. Coincubation with clarithromycin (CAM) and azithromycin significantly reduced the capsule thickness and the amount of capsular polysaccharide of both C. gattii and C. neoformans CAM-treated C. gattii cells were significantly more susceptible to H₂O₂ oxidative stress and opsonophagocytic killing by murine neutrophils. In addition, more C. gattii cells were phagocytosed by murine macrophages, resulting in increased production of tumor necrosis factor alpha (TNF-α) by CAM exposure. After CAM exposure, dephosphorylation of Hog1, one of the mitogen-activated protein kinase (MAPK) signaling pathways of Cryptococcus, was observed in Western blot analysis. In addition, CAM exposure significantly reduced the mRNA expression of LAC1 and LAC2 (such mRNA expression is associated with cell wall integrity and melanin production). These results suggest that CAM may aid in inhibiting capsular formation via the MAPK signaling pathway and by suppressing virulent genes; thus, it may be a useful adjunctive agent for treatment of refractory C. gattii infection.

A Chronic Respiratory Pasteurella multocida Infection Is Well-Controlled by Long-Term Macrolide Therapy

A 57-year-old woman with severe bronchiectasis frequently received antibiotics, including penicillin, for acute exacerbations due to Pasteurella multocida. Although the bacteria showed a decrease in antibiotic susceptibility, her symptoms and X-ray findings became stable, and severe exacerbations were not observed for the last few years after a low-dose erythromycin treatment was started. The development of a respiratory infection with Pasteurella multocida is relatively uncommon, but it can be controlled by immunomodulation which is associated with long-term macrolide therapy.

Immunomodulatory effect of linezolid on methicillin-resistant Staphylococcus aureus supernatant-induced MUC5AC overexpression in human airway epithelial cells

Linezolid is the first member of the oxazolidinones and is active against drug-resistant Gram-positive pathogens, such as methicillin-resistant Staphylococcus aureus (MRSA). Additionally, linezolid shows an immunomodulatory effect, such as inhibition of inflammatory cytokine production. In this study, we examined the effect of linezolid on MRSA-induced MUC5AC overexpression in airway epithelial cells. In this study, an MRSA supernatant was used to avoid the direct effect of linezolid on MRSA. MUC5AC protein production was significantly increased with a 40-fold dilution of MRSA supernatant. At the mRNA level, MUC5AC gene expression was significantly increased 6 and 9 h after stimulation. In an inhibition study, linezolid significantly reduced MRSA-induced MUC5AC protein and mRNA overexpression at concentrations of 5 and 20 μg/ml, which were the same as the trough and peak concentrations in human epithelial lining fluid. In an analysis of cell signaling, among the mitogen-activated protein kinase inhibitors, only the extracellular signal-regulated protein kinase 1/2 (ERK1/2) inhibitor reduced the MUC5AC protein production to the same level as that of the control; on Western blot analysis, only ERK1/2 was phosphorylated by the MRSA supernatant. In addition, the ERK1/2 phosphorylation was inhibited by linezolid. MUC5AC and MUC5B are the major barrier that traps inhaled microbial organisms, particulates, and foreign irritants. However, in patients with chronic respiratory diseases, pathogen-induced MUC5AC overexpression causes many problems, and control of the overexpression is important. Thus, this study revealed that linezolid showed a direct immunomodulatory effect in airway epithelial cells.

Derangements of lacrimal drainage-associated lymphoid tissue (LDALT) in human chronic dacryocystitis

AIMS

To study the changes in the lacrimal drainage-associated lymphoid tissue of the lacrimal sac in human chronic dacryocystitis and its possible implications in understanding the immune defense mechanisms and etiopathogenesis of primary acquired nasolacrimal duct obstruction.

METHODS

Retrospective interventional study involving 200 lacrimal sacs of 164 consecutive patients seen between July 2009 and July 2012. Data collected include demographics, clinical presentation, laterality, age at presentation, duration of symptoms, diagnostic irrigation, indications for a dacyrocystectomy, pattern and severity of lymphoid infiltrate, types of lymphoid follicles and their locations, plasma cells, and other cellular infiltrates. The associated epithelial, stromal, and luminal changes with an emphasis on acini, mucosal glands, blood vessels, lymphatics, and goblet cells were also noted. Immunohistochemistry using CD3, CD20, CD138, and immunoglobulin A were used to substantiate the lymphoid tissues of the lacrimal sac.

RESULTS

A total of 200 lacrimal sacs were obtained from dacryocystectomy of 164 patients. The patients included 60.5% (99/164) females and 39.6% (65/164) males, with a mean age of 58.4 years at presentation. Laterality showed a predominance of left lacrimal sacs (55%, 110/200) as compared to the right lacrimal sacs (45%, 90/200). Symptoms of epiphora and discharge of more than 6 months duration were considered to be chronic. Lymphoid infiltrate pattern was diffuse in majority of the sacs (81%, 162/200), with subepithelial and intraepithelial together being the commonest location (46.5%, 93/200). Distinct lymphoid follicles were seen in 28% (56/200). Most of the sacs showed mild plasma cell infiltration (66.5%, 133/200). IgA-rich secretions were noted in the lumen and the lining epithelium in 34.5% (69/200). Other common changes noted include increase in the goblet cells (82%, 164/200), dilated lymphatics (94%, 188/200), proliferating blood vessels (99%, 198/200), thickened epithelium (54.5%, 109/200), and stromal fibrosis (88%, 176/200).

CONCLUSION

This study presents the largest series to date (n = 200 lacrimal sacs) exclusively on changes in lacrimal drainage-associated lymphoid tissue in human chronic dacryocystitis. This study could be the starting point for further exploration into the molecular biology, immunological implications, and possible implications of LDALT derangements on etiopathogenesis of primary acquired nasolacrimal duct obstruction.

A novel macrolide solithromycin exerts superior anti-inflammatory effect via NF-κB inhibition

Macrolides are reported to reduce exacerbation of chronic inflammatory respiratory disease, such as chronic obstructive pulmonary disease (COPD), and also show anti-inflammatory effects in vitro and in vivo. However the anti-inflammatory efficacies of current macrolides are relatively weak. Here we found that a novel macrolide/fluoroketolide solithromycin (CEM-101) showed superior anti-inflammatory effects to macrolides in current clinical use. The effects of solithromycin (SOL) on lipopolysaccharide-induced TNFα (tumor necrosis factor α) and/or CXCL8 (C-X-C motif chemokine ligand 8; interleukin-8) release, phorbol 12-myristate 13-acetate-induced MMP9 (matrix metalloproteinase 9) activity and NF-κB (nuclear factor-κB) activity under conditions of oxidative stress have been evaluated and compared with the effects of erythromycin, clarithromycin, azithromycin, and telithromycin in macrophage-like PMA-differentiated U937 cells and peripheral blood mononuclear cells (PBMC) obtained from COPD patients. We also examined effect of SOL on cigarette smoke-induced airway inflammation in mice. SOL exerted superior inhibitory effects on TNFα/CXCL8 production and MMP9 activity in monocytic U937 cells. In addition, SOL suppressed TNFα release and MMP9 activity in PBMC from COPD patients at 10 µM, which is 10 times more potent than the other macrolides tested. Activated NF-κB by oxidative stress was completely reversed by SOL. SOL also inhibited cigarette smoke-induced neutrophilia and pro-MMP9 production in vivo, although erythromycin did not inhibit them. Thus, SOL showed better anti-inflammatory profiles compared with macrolides currently used in the clinic and may be a promising anti-inflammatory and antimicrobial macrolide for the treatment of COPD in future.

Role of long term antibiotics in chronic respiratory diseases

Antibiotics are commonly used in the management of respiratory disorders such as cystic fibrosis (CF), non-CF bronchiectasis, asthma and COPD. In those conditions long-term antibiotics can be delivered as nebulised aerosols or administered orally. In CF, nebulised colomycin or tobramycin improve lung function, reduce number of exacerbations and improve quality of life (QoL). Oral antibiotics, such as macrolides, have acquired wide use not only as anti-microbial agents but also due to their anti-inflammatory and pro-kinetic properties. In CF, macrolides such as azithromycin have been shown to improve the lung function and reduce frequency of infective exacerbations. Similarly macrolides have been shown to have some benefits in COPD including reduction in a number of exacerbations. In asthma, macrolides have been reported to improve some subjective parameters, bronchial hyperresponsiveness and airway inflammation; however have no benefits on lung function or overall asthma control. Macrolides have also been used with beneficial effects in less common disorders such as diffuse panbronchiolitis or post-transplant bronchiolitis obliterans syndrome. In this review we describe our current knowledge the use of long-term antibiotics in conditions such as CF, non-CF bronchiectasis, asthma and COPD together with up-to-date clinical and scientific evidence to support our understanding of the use of antibiotics in those conditions.

Macrolides: from in vitro anti-inflammatory and immunomodulatory properties to clinical practice in respiratory diseases

BACKGROUND

Macrolides have long been recognised to exert immunomodulary and anti-inflammatory actions. They are able to suppress the "cytokine storm" of inflammation and to confer an additional clinical benefit through their immunomodulatory properties.

METHODS

A search of electronic journal articles was performed using combinations of the following keywords: macrolides, COPD, asthma, bronchitis, bronchiolitis obliterans, cystic fibrosis, immunomodulation, anti-inflammatory effect, diabetes, side effects and systemic diseases.

RESULTS

Macrolide effects are time- and dose-dependent, and the mechanisms underlying these effects remain incompletely understood. Both in vitro and in vivo studies have provided ample evidence of their immunomodulary and anti-inflammatory actions. Importantly, this class of antibiotics is efficacious with respect to controlling exacerbations of underlying respiratory problems, such as cystic fibrosis, asthma, bronchiectasis, panbrochiolitis and cryptogenic organising pneumonia. Macrolides have also been reported to reduce airway hyper-responsiveness and improve pulmonary function.

CONCLUSION

This review provides an overview on the properties of macrolides (erythromycin, clarithromycin, roxithromycin, azithromycin), their efficacy in various respiratory diseases and their adverse effects.

Effect of azithromycin on natural killer cell function

Azithromycin (AZM), a macrolide antibiotic for treating mycoplasma infections, may exhibit anti-inflammatory activity aside from its antimicrobial effect, providing additional therapeutic benefit. Natural killer (NK) cells, a first-line innate immune defense against microbial invasions, paradoxically exert a detrimental effect in protecting mycoplasma infection. Little was known regarding the effect of AZM on NK cells. In the present study, we investigated the ability of azithromycin to influence natural killer (NK) cell function with regard to activation, apoptosis and cytotoxic function. AZM had little effect on NK receptor expression and cytotoxic function of NK-92 cells. However, AZM did show a dose-dependent suppression on IL-15-induced CD69 expression of primary NK cells. AZM inhibited the cytotoxicity against K562 cells of resting and IL-15 activated primary NK cells possibly through down-regulation of perforin expression, especially on CD16(+)CD56(+) NK subsets. AZM exerted a dose-dependent inhibition of IFN-gamma and TNF-alpha production from NK-92 cells, but did not affect the cytokine production of IL-15 activated primary NK cells. Taken together, AZM down-regulates NK cytotoxicity and cytokine production and may provide therapeutic benefits aside from its antimicrobial activity.

A case of refractory chronic respiratory tract infection due to Pseudomonas aeruginosa successfully controlled by combination of clarithromycin and azithromycin

The prognosis of patients with chronic respiratory tract infections, especially diffuse panbronchiolitis, is remarkably improved by long-term administration of low-dose macrolides. However, in some cases, patients are refractory to macrolide treatment and show a low or no response; therefore, new treatment strategies are required. Here we present a patient refractory to either single low-dose clarithromycin or azithromycin but responded remarkably to the combination usage of both macrolides.

Structural changes in the lacrimal sac epithelium and associated lymphoid tissue during experimental dacryocystitis

Purpose

To examine structural changes in the lacrimal sac epithelium and associated lymphoid tissue of rabbits with experimentally induced dacryocystitis.

Methods

Experimental dacryocystitis was induced by an inoculation of Staphylococcus aureus into the lacrimal sac. The histological changes of the inflamed lacrimal sac epithelium and associated lymphoid tissue were studied by light and electron microscopy.

Results

After 1 month, numerous inflammatory cells (CD20-positive B lymphocytes, CD3-positive T lymphocytes, IgA-positive plasma cells, and polymorphonuclear leukocytes) infiltrated the lamina propria and the epithelium overlying the diffuse lymphoid tissue. Three months later, the density of the infiltrated leukocytes was markedly decreased. The epithelial lining overlying the diffuse lymphoid tissue became thicker with numerous secretory granules in the supranuclear regions.

Conclusion

The lacrimal sac epithelium and associated lymphoid tissue play a major role in the defense mechanism during inflammation. Overproduction of secretory granules after bacterial inoculation could enhance the antimicrobial defense.

Clarithromycin inhibits interleukin-13-induced goblet cell hyperplasia in human airway cells

IL-13 is a T-helper class 2 cytokine that induces goblet cell hyperplasia and mucus production in airway epithelial cells. Because macrolide antibiotics are known to have immunomodulatory and mucoregulatory properties, the aim of this study was to examine the effect of clarithromycin on IL-13-induced goblet cell hyperplasia and mucin hypersecretion in normal human bronchial epithelial (NHBE) cells. NHBE cells were cultured to differentiation at an air-liquid interface with IL-13 plus clarithromycin or vehicle. Histochemical analysis was performed using H&E staining, periodic acid-Schiff (PAS) staining, and MUC5AC immunostaining. MUC5AC synthesis was assayed using RT-PCR and ELISA. Western blotting was used to evaluate signaling pathways. IL-13 significantly increased the number of PAS-positive, MUC5AC-positive goblet cells, and this was significantly attenuated by clarithromycin at concentrations greater than 8 μg/ml (P < 0.01). Clarithromycin also dose-dependently decreased MUC5AC mRNA expression induced by IL-13 (P < 0.001), and, at 24 μg/ml, clarithromycin significantly attenuated the amount of MUC5AC protein in cell supernatants (P < 0.01). Western blotting showed that clarithromycin affected IL-13 receptor janus kinase signal transducers, activators of transcription6 (STAT6), and epidermal growth factor receptor mitogen-activated protein kinase signaling and that inhibition of these pathways by clarithromycin decreased goblet cell hyperplasia via nuclear factor-κB inactivation. We conclude that clarithromycin inhibits goblet cell hyperplasia and may directly regulate mucus secretion by IL-13 in NHBE cells.

Inflammation provoked by Mycoplasma pneumoniae extract: implications for combination treatment with clarithromycin and dexamethasone

Recently, combination treatment with a macrolide and a steroid for Mycoplasma pneumoniae (Mp) pneumonia has been reported to be effective. Thus, the effect of this combination on a mouse model of lung inflammation associated with Mp extract (the LIMEX mouse) was studied. Interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) were induced in Mp extract-treated RAW264.7 cells, and this induction was inhibited by dexamethasone, parthenolide, SB203580 or LY294002. This suggested that Mp extract activates nuclear factor κB-, p38- and PI-3K-linked pro-inflammatory signals. The LIMEX mice were then either treated with or without clarithromycin and/or dexamethasone. Clarithromycin administration enhanced the production of IL-6, TNF-α, macrophage inflammatory protein-1α, monocyte chemotactic protein-1 and RANTES, while their production was perfectly suppressed by the combination of clarithromycin and dexamethasone. IL-17, IL-23, keratinocyte-derived chemokine (KC) and interferon-γ levels were not affected by clarithromycin treatment, but they were significantly suppressed by the combination of dexamethasone and clarithromycin. Collectively, some components of Mp extract provoked an inflammatory reaction in the RAW 264.7 cell line and LIMEX mice. Whereas the lung reaction in LIMEX mice was further exacerbated by clarithromycin treatment, it was resolved by the combinational treatment with clarithromycin and dexamethasone.

High-dose tobramycin inhibits lipopolysaccharide-induced MUC5AC production in human lung epithelial cells

Tobramycin inhalation therapy is an effective therapy for cystic fibrosis as well as severe bronchiectasis that is colonized with Pseudomonas aeruginosa. The mechanism responsible for the efficacy of tobramycin in the treatment of severe chronic infectious diseases has not been elucidated. We demonstrate that high-dose tobramycin decreases MUC5AC gene expression and protein production in NCI-H292 cell stimulated with lipopolysaccharide of P. aeruginosa. MUC5AC protein of NCI-H292 cell stimulated by lipopolysaccharide was analyzed by an enzyme-linked immunosorbent assay and MUC5AC expression at the mRNA level was analyzed by RT-PCR. Western blot was performed to examine a potential role for the signaling molecules upstream of NFκB. High-dose tobramycin (500μg/ml) decreased the level of MUC5AC protein released into the supernatant of the NCI-H292 cell line at 24h after lipopolysaccharide stimulation (P<0.001). The tobramycin treatment also inhibited MUC5AC mRNA expression at 12h after lipopolysaccharide stimulation (P<0.05) and suppressed NFκB activation 60min after lipopolysaccharide stimulation (P<0.001). Tobramycin suppressed the phosphorylation of extracellular signal-regulated protein kinase, p38 MAP kinase. These results suggest that high-dose tobramycin, such as inhalation therapy, can inhibit MUC5AC gene expression and MUC5AC protein production in NCI-H292 cells, in part through the mitogen-activated protein kinase pathway. Thus, the activation of TLR4 and the subsequent immune/inflammatory responses induced by chronic infections such as P. aeruginosa might be modulated by tobramycin. Our data may reveal one of the mechanisms responsible for the clinical effect of tobramycin inhalation therapy against severe chronic respiratory diseases due to P. aeruginosa.

In vivo efficacy of sivelestat in combination with pazufloxacin against Legionella pneumonia

It is important to regulate excessive inflammation when patients with severe infectious disease are treated. Sivelestat sodium hydrate (sivelestat), a neutrophil elastase inhibitor, is used in the treatment of lung injury but its effect on bacterial pneumonia is unknown. The authors examined the efficacy of sivelestat in combination with a fluoroquinolone in a Legionella pneumophila pneumonia mouse model. The combination therapy did not show a significant survival improvement compared to the treatment with fluoroquinolone alone, but reduced bacteria number and inflammatory cells in the early phase. The combination therapy can contribute to treatment of L. pneumophila pneumonia with protecting lungs.

Mechanisms of action and clinical application of macrolides as immunomodulatory medications

Macrolides have diverse biological activities and an ability to modulate inflammation and immunity in eukaryotes without affecting homeostatic immunity. These properties have led to their long-term use in treating neutrophil-dominated inflammation in diffuse panbronchiolitis, bronchiectasis, rhinosinusitis, and cystic fibrosis. These immunomodulatory activities appear to be polymodal, but evidence suggests that many of these effects are due to inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and nuclear factor kappa B (NF-kappaB) activation. Macrolides accumulate within cells, suggesting that they may associate with receptors or carriers responsible for the regulation of cell cycle and immunity. A concern is that long-term use of macrolides increases the emergence of antimicrobial resistance. Nonantimicrobial macrolides are now in development as potential immunomodulatory therapies.

Low expression of T-cell co-stimulatory molecules in bone marrow-derived dendritic cells in a mouse model of chronic respiratory infection with Pseudomonas aeruginosa

Pseudomonas (P.) aeruginosa frequently colonizes the respiratory tract of patients with chronic respiratory tract infections such as diffuse panbronchiolitis (DPB). The number of dendritic cells (DCs) that play a central role in immune functions as antigen-presenting cells is reportedly increased in the bronchiolar tissues of patients with DPB. However, the functions of DCs in chronic P. aeruginosa respiratory tract infection have not been defined. Here, we assessed the functions of DCs and the effect of macrolide antibiotics that are therapeutic agents for DPB, in a murine model of DPB caused by P. aeruginosa. Mice were intubated with either P. aeruginosa- or saline-precoated tubes for 80 days. Thereafter, the expression of T-cell co-stimulatory molecules (CD40, CD80, and CD86) and cytokine secretion (interleukin (IL)-10, IL-6, IL-12p40, and tumor necrosis factor (TNF)-alpha) on bone marrow-derived DCs stimulated by lipopolysaccharide were examined by flow cytometry and enzyme-linked immunosorbent assays. The expression of co-stimulatory molecules was significantly decreased in mice infected with P. aeruginosa compared to the saline-treated control mice, but production of these cytokines did not significantly differ between the two groups. Pretreatment with clarithromycin ex vivo decreased CD40 expression on DCs obtained from P. aeruginosa-infected mice and also decreased the production of IL-6, IL-12p40 and TNF-alpha by DCs. These findings suggest that chronic P. aeruginosa infection alters DC functions and that macrolides function as anti-inflammatory agents by modulating the functions of DCs in chronic P. aeruginosa infection.

[Usefulness of macrolides as anti-inflammatories in respiratory diseases]

The macrolides are antibiotics that, besides their anti-bacterial action, have an anti-inflammatory effect, by decreasing the activity of the immune cells and bacteria cell changes. An increase the survival of patients suffering from diffuse panbronchiolitis was already seen in the 1980s, after being treated with erythromycin. Currently, the use of macrolides in various chronic inflammatory diseases has increased significantly. Clinical improvements associated to the administration of macrolides have been observed in diseases such as, cystic fibrosis, asthma, and bronchiectasis. However, despite the apparent clinical benefit they seem to provide, the published results up until now are controversial and conclusive results are unable to be obtained. This means that further clinical trials are necessary to confirm or refute the long-term use of these drugs, which are not free of adverse effects, mainly the appearance of resistant bacteria.

EFFECTS OF SPECIFIC NEUTROPHIL ELASTASE INHIBITOR, SIVELESTAT SODIUM HYDRATE, IN MURINE MODEL OF SEVERE PNEUMOCOCCAL PNEUMONIA

An excessive amount of neutrophil elastase (NE) released from neutrophils accumulated in the lung can cause tissue damage, despite its importance to host defense against microbial pathogens in severe pneumonia. Therefore, NE inhibitors may reduce tissue damage in lungs with severe pneumonia. In this study, the efficacy of a specific NE inhibitor, sivelestat sodium hydrate (sivelestat), was examined using a murine model of severe pneumonia with Streptococcus pneumoniae. Male mice (CBA/JNCrj, aged 5 weeks) were inoculated intranasally with penicillin-susceptible S. pneumonia (1.0 x 10(5) CFU/mouse). Sivelestat (3 mg/kg) or physiological saline was administered every 12 hours beginning at 12 hours after inoculation. Survival was primarily evaluated. Bronchoalveolar lavage fluid (BALF) and blood were collected at 30 hours after inoculation. Thus, cell counts in BALF and numbers of viable bacteria in blood were determined. Histopathological analysis was also performed. Sivelestat significantly prolonged survival when compared with the control group (P < .05), although all animals died within 4 days. Cell count and histopathological analysis indicated that sivelestat prevented the progression of lung inflammation, such as alveolar neutrophil infiltration and hemorrhage. Furthermore, the number of viable bacteria in blood was significantly lower in the sivelestat group than in the control group (5.69 +/- 0.27 and 6.75 +/- 0.32 log CFU/mL, respectively; mean +/- SEM, P < .01). Sivelestat prolonged survival in this model. A possible explanation for the improved survival is that sivelestat prevents tissue damage by inhibiting NE activity in the lung. Therefore, NE inhibitors may be useful for treating with patients with severe pneumonia.

In vivo efficacy of sitafloxacin in a new murine model of non-typeable Haemophilus influenzae pneumonia by sterile intratracheal tube

A novel murine model of non-typeable Haemophilus influenzae (NTHi) pneumonia was established. A plastic tube was inserted into the trachea 7 days before bacterial inoculation. Numbers of NTHi recovered from the lungs and trachea were determined for 7 days. Histologically, bronchioles and adjacent alveoli in the intubation group were filled with numerous inflammatory cells. The efficacy of sitafloxacin was compared with ciprofloxacin using the new murine pneumonia model. The data suggest that sitafloxacin displays equivalent efficacy to ciprofloxacin against H. influenzae pneumonia. This new murine NTHi pneumonia model appears useful not only for in vivo evaluation of antibiotics but also for analysis of the pathogenesis of H. influenzae pneumonia.

Clarithromycin prevents smoke-induced emphysema in mice

RATIONALE

Modulating the low-grade chronic inflammation in chronic obstructive pulmonary disease remains challenging. Clarithromycin (CAM), a macrolide antibiotic, reportedly ameliorates chronic inflammation via mechanisms independent of its antibacterial activity.

OBJECTIVES

The aim of this study was to examine whether CAM can prevent or reduce emphysema induced by chronic cigarette smoke exposure.

METHODS

Mice were exposed to cigarette smoke daily for 6 months and treated with orally administered CAM at doses of 25 to 100 mg/kg twice a day throughout the course of the experiment to test the preventive effects. The administration of CAM at 50 or 100 mg/kg was performed during the second half of a 6-month exposure period to assess the therapeutic effects. Histologic analysis was performed to evaluate the effect of CAM.

MEASUREMENTS AND MAIN RESULTS

CAM treatment for 6 months decreased airspace enlargement and the destruction of the alveolar walls and impaired the accumulation of macrophages in bronchoalveolar lavage fluid in a dose-related fashion. The administration of clarithromycin at 100 mg/kg in the therapeutic protocol reduced emphysema compared with the smoke-exposed group without treatment. An immunohistologic analysis revealed that CAM reduced the number of F4/80-positive macrophages in the lung parenchyma. In an in vitro test, CAM at 5 to 20 microM directly suppressed the activation of macrophages stimulated with tumor necrosis factor-alpha.

CONCLUSIONS

Our data demonstrated that CAM at a clinically achievable dose prevented cigarette smoke-induced emphysema by modulating lung inflammation. This study supports the possibility that low-dose CAM treatment might provide a new therapeutic strategy for chronic obstructive pulmonary diseases.

Different effects of telithromycin on MUC5AC production induced by human neutrophil peptide-1 or lipopolysaccharide in NCI-H292 cells compared with azithromycin and clarithromycin

OBJECTIVES

Mucus hypersecretion is a prominent feature in patients with chronic respiratory tract infections such as cystic fibrosis and diffuse panbronchiolitis, and the clinical effectiveness of macrolide antibiotics has been reported in these patients. Because human neutrophil peptide-1 (HNP-1), an antimicrobial peptide in neutrophils, exists in high concentrations in the airway fluid of these patients, we examined the direct effect of HNP-1 on MUC5AC mucin production using NCI-H292 cells. The effects of macrolide antibiotics on the response were also examined.

METHODS

MUC5AC synthesis was assayed using RT-PCR and ELISA. Phosphorylation of ERK1/2 was determined by western blotting.

RESULTS

Stimulation with HNP-1 or lipopolysaccharide (LPS) derived from Pseudomonas aeruginosa increases the production of MUC5AC mRNA and protein, and an additive effect was found upon co-stimulation with both HNP-1 and LPS. Azithromycin and clarithromycin had inhibitory effects on overproduction of MUC5AC induced by HNP-1 or LPS stimulation. Telithromycin also had an inhibitory effect on MUC5AC production induced by LPS, but not on production by HNP-1. Phosphorylation of ERK1/2 was induced by HNP-1 or LPS stimulation, and azithromycin, clarithromycin and telithromycin had inhibitory effects on ERK1/2 phosphorylation induced by LPS, but not by HNP-1.

CONCLUSIONS

These findings suggest that neutrophil-derived defensins as bacterial components contribute to excessive mucus production in patients with respiratory tract infections, and that macrolide and ketolide antibiotics directly inhibit these actions by interfering with intracellular signal transduction. However, the mechanism of telithromycin inhibition of MUC5AC synthesis may differ from the response induced by azithromycin and clarithromycin.

Erythromycin attenuates MUC5AC synthesis and secretion in cultured human tracheal cells infected with RV14

BACKGROUND AND OBJECTIVE

The common cold is a major cause of asthma exacerbation and chronic obstructive lung disease. Rhinovirus is reported to be responsible for more than 50% of cases of the common cold. In a previous study, we reported that rhinovirus infection of cultured airway cells induced MUC5AC mucin overproduction and hypersecretion by activating the p44/42 mitogen-activated protein kinase (p44/42 MAPK) pathway. The aim of this study was to examine the effect of erythromycin on RV14-induced airway mucin overproduction and hypersecretion.

METHODS

RV14-infected human tracheal epithelial cells were treated with erythromycin.

RESULTS

Erythromycin blocked RV14-induced MUC5AC protein overproduction and hypersecretion, and also blocked RV14-induced p44/42 MAPK activation in the cells.

CONCLUSIONS

Erythromycin may attenuate RV14-induced MUC5AC overproduction and hypersecretion by blocking the p44/42 MAPK pathway or its upstream regulators.

Macrolide antibiotics as immunomodulatory medications: proposed mechanisms of action

Macrolide antibiotics administered in sub-antimicrobial doses improve pulmonary function and decrease exacerbation frequency for persons with diffuse panbronchiolitis or cystic fibrosis. Data also suggest a beneficial effect of macrolide antibiotics in the treatment of steroid dependent asthma. Many potential immunomodulatory effects of macrolide antibiotics have been reported including the ability to down-regulate prolonged inflammation, decreasing airway mucus secretion, inhibiting bacterial biofilm, decreasing the production of reactive oxygen species, inhibiting neutrophil activation and mobilization, accelerating neutrophil apoptosis, and blocking the activation of nuclear transcription factors. Macrolides initially decrease, then increase, and have finally a sustained suppression of cytokine secretions from normal human bronchial epithelial cells through inhibition and activation of extracellular signal-regulated kinases (ERK) and then reversibly retard cell proliferation probably through ERK. Consistent with this, macrolide antibiotics possibly reduce mucin production as well as neutrophil migration by interfering with ERK signal transduction.

Macrolides beyond the conventional antimicrobials: a class of potent immunomodulators

The historical change in the natural course of diffuse panbronchiolitis (DPB), a fatal disorder of the airways, following the introduction of erythromycin in its treatment has focused attention of researchers on the anti-inflammatory properties of macrolides. Chronic inflammation of the airways accompanied by infiltration by neutrophils and overproduction of mucus and pro-inflammatory cytokines is observed in bronchial asthma, cystic fibrosis (CF), DPB, chronic obstructive pulmonary disease (COPD) and bronchiectasis. The airways of these patients are often colonised by mucoid Pseudomonas aeruginosa attached to epithelium by a biofilm. Bacteria intercommunicate for biofilm formation by a system of lactones known as quorum sensing. Macrolides inhibit mobility and quorum sensing of P. aeruginosa; they also decrease production of mucus by epithelial cells and biosynthesis of pro-inflammatory cytokines from monocytes and epithelial cells by inhibiting nuclear factor-kappaB. Large, randomised clinical trials for the management of these disorders with macrolides are not available, with the sole exception of four trials denoting benefit following long-term administration of azithromycin in patients with CF. That benefit is consistent with an increase in forced expiratory volume in 1s (FEV(1)) and a decrease in the rate of bacterial exacerbations. Studies with small numbers of patients with COPD revealed attenuation of the inflammatory reaction by macrolides. Experimental studies of Gram-negative sepsis have shown considerable attenuation of the systemic inflammatory response following intravenous administration of clarithromycin. Results of the effects of clarithromycin in patients with ventilator-associated pneumonia and sepsis in a large, randomised study of 200 patients are awaited.

The transition metal gallium disrupts Pseudomonas aeruginosa iron metabolism and has antimicrobial and antibiofilm activity

A novel antiinfective approach is to exploit stresses already imposed on invading organisms by the in vivo environment. Fe metabolism is a key vulnerability of infecting bacteria because organisms require Fe for growth, and it is critical in the pathogenesis of infections. Furthermore, humans have evolved potent Fe-withholding mechanisms that can block acute infection, prevent biofilm formation leading to chronic infection, and starve bacteria that succeed in infecting the host. Here we investigate a "Trojan horse" strategy that uses the transition metal gallium to disrupt bacterial Fe metabolism and exploit the Fe stress of in vivo environments. Due to its chemical similarity to Fe, Ga can substitute for Fe in many biologic systems and inhibit Fe-dependent processes. We found that Ga inhibits Pseudomonas aeruginosa growth and biofilm formation and kills planktonic and biofilm bacteria in vitro. Ga works in part by decreasing bacterial Fe uptake and by interfering with Fe signaling by the transcriptional regulator pvdS. We also show that Ga is effective in 2 murine lung infection models. These data, along with the fact that Ga is FDA approved (for i.v. administration) and there is the dearth of new antibiotics in development, make Ga a potentially promising new therapeutic for P. aeruginosa infections.

Muc5b and Muc5ac are the major oligomeric mucins in equine airway mucus

Horses frequently suffer from respiratory diseases, which, irrespective of etiology, are often associated with airway mucus accumulation. Studies on human airways have shown that the key structural components of the mucus layer are oligomeric mucins, which can undergo changes of expression and properties in disease. However, there is little information on these gel-forming glycoproteins in horse airways mucus. Therefore, the aims of this study were to isolate equine airways oligomeric mucins, characterize their macromolecular properties, and identify their gene products. To this end, pooled tracheal washes, collected from healthy horses and horses suffering from respiratory diseases, were solubilized with 6 M guanidinium chloride (GdmCl). The oligomeric mucins were purified by density gradient centrifugation followed by size exclusion chromatography. Biochemical and biophysical analyses showed the mucins were stiffened random coils in solution that were polydisperse in size (M(r) = 6-20 MDa, average M(r) = 14 MDa) and comprised of disulfide-linked subunits (average M(r) = 7 MDa). Agarose gel electrophoresis showed that the pooled mucus sample contained at least two populations of oligomeric mucins. Electrospray ionization tandem mass spectrometry of tryptic digests of the unfractionated mucin preparation showed that the oligomeric mucins Muc5b and Muc5ac were present. In summary, we have shown that equine airways mucus is a mixture of Muc5b and Muc5ac mucins that have a similar macromolecular organization to their human counterparts. This study will form the basis for future studies to analyze the contribution of these two mucins to equine airways pathology associated with mucus accumulation.

Clarithromycin delays progression of bronchial epithelial cells from G1 phase to S phase and delays cell growth via extracellular signal-regulated protein kinase suppression

The nonsteroidal anti-inflammatory drugs have been shown to support cytoprotection of cells by shifting cells toward a quiescent state (G(0)/G(1)). Extracellular signal-regulated kinase (ERK) is required for cells to pass from G(1) phase into S phase, and macrolide antibiotics can inhibit ERK1/2 phosphorylation. However, previous reports suggest that macrolide antibiotics do not affect cell growth in bronchial epithelial cells. Therefore, we studied normal human bronchial epithelial (NHBE) cells to determine whether clarithromycin (CAM) suppresses ERK, delays bronchial epithelial cells from progressing to S phase, and delays cell growth. Exposure to CAM at 10 microg/ml daily over 4 days irreversibly decreased the cell proliferation with and without growth supplements (P < 0.0001). CAM also inhibited ERK1/2 phosphorylation over the first 90 min of exposure (P < 0.05 for 30 min, P < 0.0001 for 60 min, and P < 0.01 for 90 min) and decreased the ratio of phosphorylated ERK1/2 (pERK1/2) to total ERK1/2 (tERK1/2) (P < 0.0001). Incubation with CAM for 48 h increased the proportion of cells in G(1) phase (means +/- standard deviations) from 63.5% +/- 0.9% to 79.1% +/- 1.4% (P < 0.0001), decreased that in S phase from 19.8% +/- 1.2% to 10.0% +/- 2.1% (P < 0.01), and decreased that in G(2)/M phase from 16.7% +/- 0.4% to 11.0% +/- 0.8% (P < 0.001). In contrast, the ratio of pMEK1/2 to tMEK1/2 was not altered after exposure to CAM. These results suggest that macrolide antibiotics can delay the progression of NHBE cells from G(1) phase to S phase and can slow cell growth, probably through the suppression of ERK1/2.

Macrolide antibiotics modulate ERK phosphorylation and IL-8 and GM-CSF production by human bronchial epithelial cells

Macrolide antibiotics decrease proinflammatory cytokine production in airway cells from subjects with chronic airway inflammation. However, in subjects with chronic obstructive pulmonary disease, short-term azithromycin (AZM) therapy causes a transient early increase in the blood neutrophil oxidative burst followed by a decrease in inflammatory markers with longer administration. We studied the effects of clarithromycin (CAM) and AZM on proinflammatory cytokine production from normal human bronchial epithelial (NHBE) cells. CAM decreased IL-8 over the first 6 h and then significantly increased interleukin (IL)-8 at 12–72 h after exposure ( P < 0.0001). AZM also increased IL-8 at 24 and 48 h, and CAM increased granulocyte-macrophage colony-stimulating factor at 48 h. In the presence of LPS, both CAM and AZM dose-dependently increased IL-8 secretion over 24 h, but after 5 days of exposure to 10 μg/ml CAM there is suppression of IL-8 ( P < 0.001). PD-98059, an inhibitor of MAP kinase/ERK kinase, inhibited CAM-induced IL-8 ( P < 0.0001) and GM-CSF ( P < 0.01) release. The p38 MAP kinase inhibitor SB-203580 increased CAM-induced IL-8 release ( P < 0.001), and the c-jun NH2-terminal kinase inhibitor SP-600125 had no effect on IL-8. At 120 min and 6 h, CAM increased phospho-ERK1/2 (pERK) but not phospho-p38 or phospho-JNK. Over the first 90 min, CAM at 10 μg/ml inhibited pERK and then increased pERK in parallel with measured IL-8 secretion. After daily CAM exposure for 5 days, both IL-8 and pERK returned to baseline. The p38 MAP kinase inhibitor, SB-203580 increased ERK phosphorylation and IL-8 secretion. These results suggest that macrolide antibiotics can differentially modulate proinflammatory cytokine secretion in NHBE cells, in part through ERK.

Mechanism of Thymus- and Activation-Regulated Chemokine (TARC)/CCL17 Production and its Modulation by Roxithromycin

Stimulation with tumor necrosis factor (TNF)alpha and interferon (IFN)gamma synergistically induced thymus- and activation-regulated chemokine (TARC)/CCL17 production from HaCaT keratinocytes (KC). Inhibitors for nuclear factor kappa B (NFkappaB), parthenolide, and Bay 11-7085, and an inhibitor of p38, SB202190, inhibited TNFalpha- and IFNgamma-induced production of CCL17 by HaCaT KC. Surprisingly, an inhibitor of epidermal growth factor receptor tyrosine kinase, PD153035, enhanced the production of CCL17 in HaCaT KC. Roxithromycin (RXM), a 14-membered ring macrolide, suppressed CCL17 production by HaCaT KC induced by IFNgamma and TNFalpha. RXM partially suppressed p38 phosphorylation and NFkappaB-driven luciferase activity induced by TNFalpha and IFNgamma. Degradation of inhibitor of nuclear factor kappa B (IkappaB) alpha upon stimulation with IFNgamma and TNFalpha was not affected by the addition of RXM. Through elucidating the mechanism of CCL17 production, our study indicates that RXM suppresses the production through the inhibition of p38 and NFkappaB, independent of the inhibition of IkappaB degradation.

Role of Pseudomonas aeruginosa quorum-sensing systems in a mouse model of chronic respiratory infection

The role of quorum-sensing systems in a mouse model of chronic Pseudomonas aeruginosa infection was studied. A chronic P. aeruginosa respiratory infection model was established by placement of a tube pre-coated with strain PAO1 (wild-type) or a quorum-sensing mutant, namely PAO-JP1 (Delta lasI), PDO100 (Delta rhlI) or PAO-JP2 (Delta lasI/Delta rhlI), in the bronchus. At day 14 after infection, the numbers of viable bacteria in the quorum-sensing-mutant groups were lower than in the wild-type group. Histopathological examination showed milder inflammatory changes in the lungs infected with the mutant groups compared with the wild-type group. In the bronchoalveolar lavage fluid from the quorum-sensing-system-mutant groups the proportion of neutrophils was lower than in wild-type group. These findings indicate that the quorum-sensing system plays an important role in chronic P. aeruginosa respiratory infection.

Immunomodulatory effects of antimicrobials in the therapy of respiratory tract infections

PURPOSE OF REVIEW

Several classes of antibiotics, particularly macrolides and to some extent quinolones, exert modulatory effects on inflammatory cells. With a growing number of experimental and clinical studies being performed, the relevance of the immunomodulatory actions of antibiotics to the therapy of respiratory infections is discussed in the light of recent reports.

RECENT FINDINGS

Antibiotics, particularly macrolides, exert both stimulatory and inhibitory effects on leukocytes. These effects seem to be related to the activation state of the leukocytes, facilitating bacterial killing as well as the resolution of local inflammation. In community-acquired pneumonia, this may account for the therapeutic benefit of macrolides, even when bacterial eradication is not complete. A variety of effects of macrolides on Pseudomonas aeruginosa, including the inhibition of biofilm matrix, contribute with immunomodulation to the improvement of respiratory function seen with macrolides in cystic fibrosis.

SUMMARY

Macrolides can facilitate the killing of microorganisms in acute respiratory infections through the stimulation of neutrophil activation. On long-term administration, anti-inflammatory, T helper type 1 lymphocyte-enhancing and biofilm-thinning actions, among others, make macrolides valid therapeutic options in chronic infectious/inflammatory disorders, even for infections with microorganisms that are not completely eradicated.

Azithromycin Blocks Neutrophil Recruitment inPseudomonasEndobronchial Infection

Macrolides exert their effects on the host by modulation of immune responses. In this study, we assessed the therapeutic efficacy of azithromycin in a murine model of mucoid Pseudomonas aeruginosa endobronchial infection. The clearance of Pseudomonas from the airway of mice treated with the macrolide azithromycin was not different than untreated mice challenged with Pseudomonas beads. However, the azithromycin-treated mice showed a remarkable reduction in lung cellular infiltrate in response to Pseudomonas beads, as compared with untreated mice. This effect was associated with significant decreases in lung levels of tumor necrosis factor-alpha and keratinocyte-derived chemokine in azithromycin-treated mice compared with untreated mice. Furthermore, there was a significant reduction in the response of both mouse and human neutrophils to chemokine-dependent and -independent chemoattractants when studied in vitro. Inhibition of chemotaxis correlated with azithromycin-mediated inhibition of extracellular signal-regulated kinase-1 and -2 activation. This study indicates that the azithromycin treatment in vivo results in significant reduction in airway-specific inflammation, which occurs in part by inhibition of neutrophil recruitment to the lung through reduction in proinflammatory cytokine expression and inhibition of neutrophil migration via the extracellular signal-regulated kinase-1 and -2 signal transduction pathway.

Azithromycin inhibits MUC5AC production induced by the Pseudomonas aeruginosa autoinducer N-(3-Oxododecanoyl) homoserine lactone in NCI-H292 Cells

The features of chronic airway diseases, including chronic bronchitis, cystic fibrosis, bronchiectasis, and diffuse panbronchiolitis, include chronic bacterial infection and airway obstruction by mucus. Pseudomonas aeruginosa is one of the most common pathogens in chronic lung infection, and quorum-sensing systems contribute to the pathogenesis of this disease. The quorum-sensing signal molecule [N-(3-oxododecanoyl) homoserine lactone (3O-C(12)-HSL)] not only regulates bacterial virulence but also is associated with the immune response. In this study, we investigated whether 3O-C(12)-HSL could stimulate the production of a major mucin core protein, MUC5AC. The effect of a macrolide on MUC5AC production was also studied. 3O-C(12)-HSL induced NCI-H292 cells to express MUC5AC at both the mRNA and the protein levels in time- and dose-dependent manners. A 15-membered macrolide, azithromycin, inhibited MUC5AC production that was activated by 3O-C(12)-HSL. 3O-C(12)-HSL induced extracellular signal-regulated kinase (ERK) 1/2 and I-kappa B phosphorylation in cells, and this induction was suppressed by azithromycin. 3O-C(12)-HSL-induced MUC5AC production was blocked by the ERK pathway inhibitor PD98059. Our findings suggest that the P. aeruginosa autoinducer 3O-C(12)-HSL contributes to excessive mucin production in chronic bacterial infection. Azithromycin seems to reduce this mucin production by interfering with intracellular signal transduction.