A macrolide antibiotic, roxithromycin, inhibits the growth of nasal polyp fibroblasts

The Mechanism of Action and Clinical Efficacy of Low-Dose Long-Term Macrolide Therapy in Chronic Rhinosinusitis

Various chronic inflammatory airway diseases can be treated with low-dose, long-term (LDLT) macrolide therapy. LDLT macrolides can be one of the therapeutic options for chronic rhinosinusitis (CRS) due to their immunomodulatory and anti-inflammatory actions. Currently, various immunomodulatory mechanisms of the LDLT macrolide treatment have been reported, as well as their antimicrobial properties. Several mechanisms have already been identified in CRS, including reduced cytokines such as interleukin (IL)-8, IL-6, IL-1β, tumor necrosis factor-α, transforming growth factor-β, inhibition of neutrophil recruitment, decreased mucus secretion, and increased mucociliary transport. Although some evidence of effectiveness for CRS has been published, the efficacy of this therapy has been inconsistent across clinical studies. LDLT macrolides are generally believed to act on the non-type 2 inflammatory endotype of CRS. However, the effectiveness of LDLT macrolide treatment in CRS is still controversial. Here, we reviewed the immunological mechanisms related to CRS in LDLT macrolide therapy and the treatment effects according to the clinical situation of CRS.

Suppression of the TGF-β pathway by a macrolide antibiotic decreases fibrotic responses by ocular fibroblasts in vitro

To elucidate and to inhibit post-surgical fibrotic processes after trabeculectomy in glaucoma therapy, we measured gene expression in a fibrotic cell culture model, based on transforming growth factor TGF-β induction in primary human tenon fibroblasts (hTFs), and used Connectivity Map (CMap) data for drug repositioning. We found that specific molecular mechanisms behind fibrosis are the upregulation of actins, the downregulation of CD34, and the upregulation of inflammatory cytokines such as IL6, IL11 and BMP6. The macrolide antibiotic Josamycin (JM) reverses these molecular mechanisms according to data from the CMap, and we thus tested JM as an inhibitor of fibrosis. JM was first tested for its toxic effects on hTFs, where it showed no influence on cell viability, but inhibited hTF proliferation in a concentration-dependent manner. We then demonstrated that JM suppresses the synthesis of extracellular matrix (ECM) components. In hTFs stimulated with TGF-β1, JM specifically inhibited α-smooth muslce actin expression, suggesting that it inhibits the transformation of fibroblasts into fibrotic myofibroblasts. In addition, a decrease of components of the ECM such as fibronectin, which is involved in in vivo scarring, was observed. We conclude that JM may be a promising candidate for the treatment of fibrosis after glaucoma filtration surgery or drainage device implantation in vivo.

The anti-inflammatory effects of erythromycin, clarithromycin, azithromycin and roxithromycin on histamine-induced otitis media with effusion in guinea pigs

BACKGROUND

Otitis media with effusion is a clinical manifestation characterised by inflammation of middle-ear mucosa. This study investigated the therapeutic effect of erythromycin, clarithromycin, azithromycin and roxithromycin on a histamine-induced animal model of otitis media with effusion.

METHODS

The animals were divided into five groups, receiving erythromycin, clarithromycin, azithromycin, roxithromycin or saline solution. The guinea pigs in the study groups received erythromycin (40 mg/kg/day), clarithromycin (15 mg/kg/day), azithromycin (10 mg/kg/day) or roxithromycin (10 mg/kg/day) for 3 days by gastric tube. Four hours after the end of the administration, histamine solution was injected into the right middle ear.

RESULTS

The lowest neutrophil density value obtained using stereological techniques was in the azithromycin group (0.86 ± 0.25 × 10-5/μm3), while the highest value was observed in the control group (6.68 ± 3.12 × 10-5/μm3). The anti-inflammatory properties of clarithromycin, azithromycin and roxithromycin were similar to one another, but better than that of erythromycin.

CONCLUSION

The use of macrolide antibiotics is recommended, as they show antibacterial and anti-inflammatory efficacy in otitis media with effusion.

PCR Analysis of Nasal Polyps, Chronic Sinusitis, and Hypertrophied Turbinates for DNA Encoding Bacterial 16S rRNA

Background

Nasal polyps are considered to result from chronic inflammation, but the initial or persisting stimulus for the inflammation is not known. A variety of bacteria and fungi have been cultured from nasal polyps, but ∼35% have sterile cultures. Previously, Mycoplasma pneumoniae–specific DNA was detected in human nasal polyps using polymerase chain reaction (PCR) techniques, suggesting M. pneumoniae as a causative agent in the etiology of nasal polyps.

Methods

In this study, we tested for the presence of bacterial DNA in nasal polyps resected from 40 patients, in nasal mucosa membrane from 9 patients undergoing turbinectomy for hypertrophy, and in sinus mucosa membrane from 6 patients undergoing endoscopic surgery for chronic sinusitis. Tissue DNA was extracted and analyzed by PCR using M. pneumoniae specific primers for DNA that encode the 16S rRNA gene in 41 specimens (31 polyps, 6 turbinates, and 4 sinus), and by consensus sequence-based PCR using broad range primers for most eubacterial DNA encoding the 16S rRNA gene in 38 specimens (26 polyps, 7 turbinates, and 5 sinuses).

Results

Only two samples were positive for bacterial DNA encoding 16S rRNA: Streptococcus sp. DNA was isolated from one polyp specimen and Pseudomonas aeruginosa DNA was isolated in one maxillary sinusitis specimen. No evidence of M. pneumoniae–specific DNA encoding 16S rRNA was found in any of the tissues.

Conclusions

This study suggests that chronic bacterial infection is not a major component of nasal polyp etiology.

Evaluation on quality of life in patients with nasal polyposis managed with optimal medical therapy

Nasal polyposis (NP) has a great impact on quality of life (QOL) and its management involves a combination of medical therapy and surgery. To the authors' knowledge, no publication has extensively examined NP after optimal medical treatment based on subjective evaluations. The aim of this prospective study was designed to evaluate the QOL in NP patients after (1) a short course of oral steroids, (2) initial 3-month course of macrolide, and (3) long-term treatment with intranasal steroids. A total of 55 patients with grades I and II NP were consecutively treated with oral prednisolone at 25 mg in a single dose for 2 weeks, macrolide at 250 mg daily for the first 3 months, and long-term intranasal steroids. Patients were followed up and evaluated at baseline and 3, 6, and 12 months for QOL measure. At baseline, patients with grade I and grade II NP showed significantly worse QOL scores on all Rhinosinusitis Disability Index domains, particularly for physical function (4.59 ± 1.41) and were significantly higher in social function (3.16 ± 1.17). At 3, 6, and 12 months of treatment, patients showed a significant improvement in all impaired QOL domains compared with baseline after optimal medical therapy (p < 0.05). These results suggest that the optimal medical treatment to improve QOL incorporates medical polypectomy with a short course of oral steroids in addition to macrolide and this can be maintained by long-term intranasal steroid therapy.

Pathogenesis and management of nasal polyposis in cystic fibrosis

Beginning in preschool age, during their lives, up to 50% of cystic fibrosis (CF) patients experience obstructing nasal polyposis (NP), which is rare in non-CF children. Pathogenetic factors of NP in general and especially in CF are still obscure. However, defective epithelial ion transport from mucosal glands plays a central role in CF, and viscous secretions impair mucociliary clearance, promoting chronic pathogen colonization and neutrophil-dominated chronic inflammation. Presently, CF-NP is not curable but can be clinically stabilized, though the large variety of proposed treatment modalities indicates a lack of standardization and of evidence of treatment efficacy. When conservative measures are exhausted, surgical intervention combining individually adapted endoscopic sinus surgery and supportive conservative treatment is performed. Topical steroids, approved as the gold standard for non-CF NP, may be beneficial, but they are discussed to be less effective in neutrophilic inflammation, and CF-specific antimicrobial and mucolytic therapy, as is true of all treatment modalities, urgently requires evaluation by controlled clinical trials within interdisciplinary networks.

Effect of long-term, low-dose clarithromycin on T helper 2 cytokines, eosinophilic cationic protein and the 'regulated on activation, normal T cell expressed and secreted' chemokine in the nasal secretions of patients with nasal polyposis

BACKGROUND

Little is known about the effects of macrolides on the cytokines and chemokines that modulate the function of eosinophils in nasal polyposis.

METHODS

Twenty-two non-allergic and 18 allergic patients with nasal polyps were administered clarithromycin 500 mg/day (single oral dose) for eight weeks. We measured the nasal secretion levels of the T helper 2 (also known as Th2) cytokines interleukin 4, 5 and 6, the 'regulated on activation, normal T cell expressed and secreted' (also known as RANTES) chemokine, and the eosinophilic cationic protein, before and after treatment.

RESULTS

After clarithromycin treatment, we found reduced levels of the 'regulated on activation, normal T cell expressed and secreted' chemokine in samples from both non-allergic and allergic patients (p < 0.05). Clarithromycin treatment decreased the levels of eosinophilic cationic protein only in non-allergic patients (p < 0.05), and decreased the level of interleukin 6 only in allergic patients (p < 0.05). Decreased levels of the 'regulated on activation, normal T cell expressed and secreted' chemokine were associated with a reduction in polyp size both in non-allergic and allergic patients.

CONCLUSION

Clarithromycin has a strong anti-inflammatory effect in nasal polyposis, but has different immunomodulatory effects in allergic and non-allergic nasal polyposis patients.

Actual concepts in rhinosinusitis: a review of clinical presentations, inflammatory pathways, cytokine profiles, remodeling, and management

Rhinosinusitis (RS) is a heterogeneous group of diseases. It is a significant and increasing health problem that affects about 15% of the population in Western countries. It has a substantial impact on patients’ health-related quality of life and daily functioning and represents a huge financial burden to society and the health care system as a result of the direct and indirect costs. In addition, RS is not well-understood, and little is known about the etiology and pathophysiology. In the past decade, many papers have been published that have changed our understanding of RS. RS is commonly classified into acute and chronic RS based on symptom duration. In acute RS, an inflammatory reaction initiated by a viral infection characterizes most uncomplicated, mild to moderate cases. Therefore, the first line of treatment for these cases are intranasal steroids and not antibiotics. In severe and complicated cases, antibiotics combined with topical steroids remain the treatment of choice. On the other hand, chronic RS is actually subdivided into two distinct entities (chronic rhinosinusitis with and without polyps), as growing evidence indicates that these entities have specific inflammatory pathways and cytokine profiles. The authors review recent data regarding the clinical presentations, cytokine profiles, tissue remodeling, and modalities of treatment for each form of RS.

The effect of macrolides on myofibroblast differentiation and collagen production in nasal polyp-derived fibroblasts

BACKGROUND

Macrolides are known to have anti-inflammatory, immunomodulatory, and tissue reparative effects. The purpose of this study was to determine the effect of macrolides (erythromycin [EM] and roxithromycin [RXM]) on the differentiation of fibroblasts into myofibroblasts and extracellular matrix accumulation in transforming growth factor (TGF) beta1-induced nasal polyp-derived fibroblasts (NPDFs) and to determine if NADPH oxidase (Nox) 4 and reactive oxygen species (ROS) are involved in the aforementioned processes.

METHODS

Nasal polyps of six patients (three women and three men; 32.3 ± 5.2 years of age) were acquired during surgery and NPDFs were isolated from surgical tissues. NPDFs were pretreated with macrolides for 2 hours before differentiation induction by TGF-beta1. The mRNA expressions of alpha-smooth muscle actin (SMA), collagen types I and III, and Nox4 were determined by reverse-transcription-polymerase chain reaction, and the expression of alpha-SMA protein was determined by immunocytochemical staining. The amount of total collagen production was analyzed by SirCol collagen dye-binding assay. ROS activity was measured by nitroblue tetrazolium reduction assay and was visualized by fluorescent microscopy.

RESULTS

In TGF-beta1-induced NPDFs, EM, and RXM significantly inhibited expressions of alpha-SMA and collagen types I and III mRNA and reduced alpha-SMA and collagen protein levels at concentrations of 5 and 10 μg/mL. EM and RXM also inhibited TGF-β1-induced ROS production and Nox4 mRNA expression at the same concentrations.

CONCLUSION

These results suggest the possibility that EM and RXM may play an important role in inhibiting the development of nasal polyps through their antioxidant effect.

Immunomodulatory and Clinical Effects of Long-Term Low-Dose Macrolide Treatment of Chronic Rhinosinusitis with Nasal Polyposis

Immunomodulatory treatment of chronic rhinosinusitis with nasal polyposis (CRSwNP) by macrolide antibiotics represents a challenging alternative to conventional therapy and surgery, still being at the very beginning. Immune and inflammatory processes in nasal and paranasal sinus mucosa, crucial in the etiopathogenesis of nasal polyps (NPs) are reflected in levels of various local mediators, found both in mucosa and nasal fluid. In this prospective study, we assessed the immunomodulatory and clinical effects of longterm low-dose oral macrolide treatment in the management of CRSwNP. Twenty-two (n = 22) nonasthmatic, nonallergic patients with CRSwNP were administered clarithromycin (CAM) 500 mg/day single oral dose for eight weeks. We measured the levels of proinflammatory cytokines TNF-α, TNF-β, and IL-1β, Th1 cytokines IL-2, IL-12, and IFN-γ, Th2 cytokines IL-4, IL-5, IL-6, and IL-10, and chemokine IL-8 in the nasal fluid samples, before and after treatment, using a flow cytometric method. We also scored each of the 22 patients before and after therapy according to Tsicopoulos' global nasal symptom score and Malm's endoscopic score. Following treatment, we found significantly reduced levels of IL-8 (p<0.01) and TNF-α (p<0.01) in nasal secretions. Macrolide therapy decreased the size of polyps in 45.45% of the patients. We concluded that long-term low-dose treatment with CAM was effective in the management of CRSwNP. We suggest that macrolides can be an alternative to topical and systemic corticosteroids in the management of CRSwNP.

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.

The role of local steroid injection for nasal polyposis

Sinonasal polyps affect a small but significant percentage of patients with chronic sinusitis. Treatments vary and range from oral and topical medical treatments to surgical removal. Corticosteroids typically have been regarded as the gold standard medical treatment for sinonasal polyps. Delivery of steroids is traditionally via oral or topical means. Over the years, otolaryngologists have also found that intrapolyp injection of corticosteroids is an effective means to treat some patients with sinonasal polyps. This article reviews the prevalence, pathophysiology, and medical treatment options for sinonasal polyps. Focused attention is paid to treatment with steroid injections, including a review of its associated risks and benefits.

Effect of erythromycin A and its new derivative EM201 on type I collagen production by cultured dermal fibroblasts

Thinning of the dermis is the principal histological change in atrophic skin disorders and aged skin. It is caused due to a decreased amount of collagen in the dermis. Macrolides have been reported to exert various pharmacological activities, including anti-inflammatory activity, tumor angiogenesis inhibition and growth inhibition of fibroblasts, in addition to antimicrobial activity. In this study, we investigated the effects of erythromycin A (EMA) and its new derivative EM201 on type I collagen production by cultured dermal fibroblasts. Dermal fibroblasts were cultured with 10(-9) M-10(-5) M EMA or EM201, and collagen production was measured by incubation with radioactive proline, SDS-polyacrylamide gel electrophoresis and fluorography. mRNA levels were measured by Northern blots analysis, and to investigate transcriptional levels luciferase assays were also performed. The results showed that both EMA and EM201 increased collagen production and type I collagen mRNA level (to a maximum of 200% with EMA and 250% with EM201) in a dose-dependent manner in cultured dermal fibroblasts. Transcription of the type I collagen gene was also increased by both macrolides. These results suggest that EMA and EM201 have the potential to improve the thinning of the dermis in atrophic skin disorders and aged skin.

EM703, the new derivative of erythromycin, inhibits transcription of type I collagen in normal and scleroderma fibroblasts

BACKGROUND

Excessive accumulation of collagen in the skin and internal organs in systemic sclerosis (SSc) is considered to result from enhanced transcription of collagen in fibroblasts. Macrolides have been reported to show various pharmacological activities. Recently, it was reported that EM703, a new derivative of erythromycin, improved bleomycin-induced pulmonary fibrosis in mice.

OBJECTIVE

Therefore, we attempted to examine the effects of EM703 on the type I collagen synthetic activity in normal and SSc dermal fibroblasts.

METHODS

Normal and SSc dermal fibroblasts were cultured with various concentrations of Erythromycin A or EM703 for 48h. Amount of type I collagen in the culture medium was measured with ELISA with anti-type I collagen antibody. Type I collagen mRNA levels were measured by northern blots analysis and type I collagen transcription and regulation of the human COL1A1 promoter activity were examined by transient transfection and luciferase assay. Electrophoretic gel mobility shift assay was also performed for measurement of binding activities of DNA binding factors to the COL1A1 promoter.

RESULTS

We found that EM703 reduced collagen production and the mRNA levels of alpha1(I) collagen in a dose-dependent manner in the normal fibroblasts. The transcription of COL1A1 was downregulated as detected by the luciferase assay. The downregulation was also detected using DNA containing various short lengths of the COL1A1 promoter region. EM703 did not inhibit COL1A1 transcription when the luciferase assay was performed using DNA containing the COL1A1 promoter with a short substitution mutation of the CCAAT box. Decreased production of type I collagen at the transcriptional level was also found in SSc fibroblasts treated with EM703.

CONCLUSION

These results suggest that EM703 inhibits the transcription of type I collagen in both normal and SSc fibroblasts, and that the transcription is inhibited through the CCAAT box of the COL1A1 promoter.

EM703 improves bleomycin-induced pulmonary fibrosis in mice by the inhibition of TGF-beta signaling in lung fibroblasts

BACKGROUND

Fourteen-membered ring macrolides have been effective in reducing chronic airway inflammation and also preventing lung injury and fibrosis in bleomycin-challenged mice via anti-inflammatory effects. EM703 is a new derivative of erythromycin (EM) without the bactericidal effects. We investigated the anti-inflammatory and antifibrotic effects of EM703 in an experimental model of bleomycin-induced lung injury and subsequent fibrosis in mice.

METHODS

Seven-week-old male ICR mice were used. All experiments used eight mice/group, unless otherwise noted in the figure legends. Bleomycin was administered intravenously to the mice on day 0. EM703 was orally administered daily to mice. All groups were examined for cell populations in the bronchoalveolar lavage (BAL) fluid and for induction of messenger RNA (mRNA) of Smad3 and Smad4 in the lung tissues by reverse transcriptase (RT)-polymerase chainreaction (PCR) on day 7. Fibroblastic foci were assessed histologically, and the hydroxyproline content was chemically determined in the lung tissues on day 28. We performed assay of proliferation and soluble collagen production, and examined the induction of mRNA of Smad3 and Smad4 by RT-PCR in murine lung fibroblast cell line MLg2908. We also examined Smad3, Smad4 and phosphorylated Smad2/3 (p-Smad2/3) protein assay by western blotting in MLg2908.

RESULTS

Bleomycin-induced lung fibrosis, and the infiltration of macrophages and neutrophils into the airspace were inhibited by EM703. The expression of Smad3 and Smad4 mRNA was clearly attenuated by bleomycin, but was recovered by EM703. EM703 also inhibited fibroblast proliferation and the collagen production in lung fibroblasts induced by Transforming growth factor-beta (TGF-beta). The expression of Smad3 and Smad4 mRNA in murine lung fibroblasts disappeared due to TGF-beta, but was recovered by EM703. EM703 inhibited the expression of p-Smad2/3 and Smad4 protein in murine lung fibroblasts induced by TGF-beta.

CONCLUSION

These findings suggest that EM703 improves bleomycin-induced pulmonary fibrosis in mice by actions of anti-inflammation and regulation of TGF-beta signaling in lung fibroblasts.

The influence of anti-inflammatory drugs on the proliferation of fibroblast derived from nasal polyps

OBJECTIVE

Fibroblasts are the main cells of the polyp architecture and play an important role in nasal polyposis through the release of biologically active factors. It has been recently shown that a number of differentiation factors and inflammatory mediators may be involved in nasal polyps growth, but there are not many studies on nasal polyps fibroblast proliferation. In this study, we investigated the influence of Ibuprofen, Nimesulid and Rofecoxib, cyclooxygenase 1 (COX-1) and cyclooxygenase 2 (COX-2) inhibitors and Budesonide on the nasal polyps fibroblasts proliferation.

METHODS

Nasal fibroblasts were grown from nasal polyp tissue obtained during usual surgical procedure. Fibroblast proliferation was measured by 3H-thymidine incorporation.

RESULTS

Ibuprofen and Nimesulid showed no influence on fibroblast proliferation. Inhibition of fibroblast proliferation was shown by Rofecoxib at a concentration of 10,000 nM and Budesonide at a concentration of 100 nM.

CONCLUSION

Proliferation of nasal polyps fibroblasts may be inhibited by Budesonide and a specific COX-2 inhibitor -Rofecoxib.

Clinical implications of the immunomodulatory effects of macrolides on sinusitis

This article reviews the treatment of chronic sinusitis with macrolides. Chronic sinusitis is often the result of bacterial infections that lead to chronic inflammation with thickening of the sinus mucosa and hypersecretion of mucus. In addition to their anti-infective properties, some macrolides possess immunomodulatory effects. These macrolides have been used successfully to treat diffuse panbronchiolitis, a progressive inflammatory lung disease, and may be useful for treatment of asthma, chronic bronchitis, chronic sinusitis, cystic fibrosis, and bronchiectasis. The clinical benefits of macrolides in patients with chronic sinusitis include decreased nasal secretions and postnasal drip, with improvement in nasal obstruction. In vivo and in vitro studies show that some macrolides affect neutrophil chemotaxis and infiltration, inflammatory cytokine production, mucus production, and the transportability of airway secretions. These findings indicate that macrolides are promising agents for treating chronic inflammation of the airways.

Macrolide antibiotics: current and future uses

After a long history of anti-infective therapeutic use, macrolide antibiotics have not yet given up all their secrets. Interest in their therapeutic potential in inflammatory diseases (possibly including non-infectious diseases) has generated abundant fundamental research and therapeutic trials worldwide. The main question regarding the future prospects of this class of drugs is whether some macrolides are beneficial in such settings because they modulate host inflammatory responses (and cellular targets) or rather because they eliminate a latent, unidentified pathogen which triggers chronic inflammation. However, no clearcut results have yet been obtained.

Roxithromycin decreases ultraviolet B irradiation-induced reactive oxygen intermediates production and apoptosis of keratinocytes

BACKGROUND

In addition to their antimicrobial action, roxithromycin (RXM), a new 14-membrane macrolide antibiotics, have immunomodulatory, anti-inflammatory and anti-oxidative activity. Ultraviolet B (UVB) irradiation induces reactive oxygen intermediates and apoptosis of keratinocytes.

OBJECTIVE

To examine the anti-apoptotic and anti-oxidative effect of RXM on UVB-irradiated keratinocytes.

METHODS

UVB-induced apoptosis was determined by cell death assay using crystal violet staining, and DNA fragmentation assay. Superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), and calatase activities were measured in UVB-irradiated SV40-trasnformed human keratinocytes (SVHK cells). Detection of superoxide was performed histologically using hydroethidine and colorimetric quantitative assay using ferrous irons. H(2)O(2) was measured by colorimetrical assay.

RESULTS

RXM suppressed UVB-induced apoptosis of SVHK cells. UVB-irradiated SVHK cells showed decreased SOD, GPx, GR, and catalase activities. RXM pretreatment suppressed the decrease in these enzyme activities with the maximal effect detected at 10microM of RXM. The effect was associated with suppression of UVB-induced superoxide and H(2)O(2) production.

CONCLUSION

The present study demonstrated that RXM has anti-apoptotic and anti-oxidative effects against UVB-irradiated keratinocytes.

Anti-inflammatory effects of macrolide antibiotics

Macrolides are widely used as antibacterial drugs. Clinical and experimental data, however, indicate that they also modulate inflammatory responses, both contributing to the treatment of infective diseases and opening new opportunities for the therapy of other inflammatory conditions. Considerable evidence, mainly from in vitro studies, suggests that leukocytes and neutrophils in particular, are important targets for modulatory effects of macrolides on host defense responses. This underlies the use of the 14-membered macrolide erythromycin for the therapy of diffuse panbronchiolitis. A variety of other inflammatory mediators and processes are also modulated by macrolides, suggesting that the therapeutic indications for these drugs may be extended significantly in future.

The anti-inflammatory effect of erythromycin and its derivatives, with special reference to nasal polyposis and chronic sinusitis

Macrolides have been used for decades as an important chemotherapeutic agent in the treatment of infectious diseases. In the last 10 years there has also been increasing interest in the interaction between macrolide antibiotics and the immune system. The aim of this review is to focus on the anti-inflammatory action of erythromycin and its derivatives in the treatment of chronic sinusitis and nasal polyps. Systematic clinical investigations have been few and to the author's knowledge there have been no placebo-controlled studies. However there have been, especially from Japan, a number of clinical reports stating that long-term, low-dose macrolide antibiotics are effective in treating chronic sinusitis incurable by surgery or glucocorticosteroid treatment, with an improvement in symptoms varying between 60% and 80% in different studies. In animal studies macrolides have increased mucociliary transport, reduced goblet cell secretion and accelerated apoptosis of neutrophils, all factors that may reduce the symptoms of chronic inflammation. There is also increasing evidence in vitro of the anti-inflammatory effects of macrolides. Several studies have shown macrolides to inhibit interleukin gene expression for IL-6 and IL-8 and also to inhibit the expression of intercellular adhesion molecule essential for the recruitment of inflammatory cells. There is also evidence in vitro, as well as clinical experience, showing that macrolides reduce the virulence and tissue damage caused by chronic bacterial colonization without eradicating the bacteria. The benefit of long-term, low-dose macrolide treatment seems to be that it is, in selected cases, effective when steroids fail. The exact mechanism of action is not known, but it probably involves downregulation of the local host immune response as well as a downgrading of the virulence of the colonizing bacteria. In the future, placebo-controlled studies should be performed to establish the efficacy of macrolides if this treatment is to be accepted as evidence-based medicine.