Erythromycin inhibits tumor necrosis factor alpha and interleukin 6 production induced by heat-killed Streptococcus pneumoniae in whole blood

Epigallocatechin gallate (EGCG) alleviates the inflammatory response and recovers oral microbiota in acetic acid-induced oral inflammation mice

The oral microbiota, the second largest microbiome in the human body, plays an integral role in maintaining both the local oral and systemic health of the host. Oral microecological imbalances have been identified as a potential risk factor for numerous oral and systemic diseases. As a representative component of tea, epigallocatechin gallate (EGCG) has demonstrated inhibitory effects on most pathogens in single-microbial models. In this study, the regulatory effect of EGCG on more complex oral microbial systems was further explored through a mouse model of acetic acid-induced oral inflammation. Acetic acid induces histological damage in the cheek pouch, tongue, and throat, such as broken mucosa, submucosal edema, and muscular disorders. These detrimental effects were ameliorated significantly following EGCG treatment. Additionally, EGCG reduced the levels of the inflammatory cytokines interleukin-6 and tumor necrosis factor-α to alleviate the inflammation of the tongue, cheek pouch, and throat. According to the 16S rDNA gene sequencing data, EGCG treatment contributed to increased diversity of the oral microbiota and the reversal of oral microecological disorder. This study demonstrates the regulatory effect of EGCG on dysregulated oral microbiota, providing a potential option for the prevention and treatment of oral-microbiota-associated diseases.

Immune Memory After Respiratory Infection With Streptococcus pneumoniae Is Revealed by in vitro Stimulation of Murine Splenocytes With Inactivated Pneumococcal Whole Cells: Evidence of Early Recall Responses by Transcriptomic Analysis

The in vitro stimulation of immune system cells with live or killed bacteria is essential for understanding the host response to pathogens. In the present study, we propose a model combining transcriptomic and cytokine assays on murine splenocytes to describe the immune recall in the days following pneumococcal lung infection. Mice were sacrificed at days 1, 2, 4, and 7 after Streptococcus pneumoniae (TIGR4 serotype 4) intranasal infection and splenocytes were cultured in the presence or absence of the same inactivated bacterial strain to access the transcriptomic and cytokine profiles. The stimulation of splenocytes from infected mice led to a higher number of differentially expressed genes than the infection or stimulation alone, resulting in the enrichment of 40 unique blood transcription modules, including many pathways related to adaptive immunity and cytokines. Together with transcriptomic data, cytokines levels suggested the presence of a recall immune response promoting both innate and adaptive immunity, stronger from the fourth day after infection. Dimensionality reduction and feature selection identified key variables of this recall response and the genes associated with the increase in cytokine concentrations. This model could study the immune responses involved in pneumococcal infection and possibly monitor vaccine immune response and experimental therapies efficacy in future studies.

The Anti-Nociceptive Potential of Tulathromycin against Chemically and Thermally Induced Pain in Mice

The present study was conducted to evaluate the analgesic potential of the new triamilide macrolide antibiotic, tulathromycin, at 20 and 40 mg/kg of body weight (BW), subcutaneously against acute pain in mice. Acute pain was induced either chemically (using acetic acid-induced writhing and formalin-induced pain tests) or thermally (using hot-plate, and tail-flick tests). In the acetic acid-induced writhing test, tulathromycin induced a dose-dependent and significant decrease in the number of writhes compared with the control group. In the late phase of the formalin test, a significant decline in hind paw licking time compared with the control group was observed. In the hot-plate and tail-flick tests, tulathromycin caused a dose-dependent and significant prolongation of latency of nociceptive response to heat stimuli, compared with the control group. These findings may indicate that tulathromycin possesses significant peripheral and central analgesic potentials that may be valuable in symptomatic relief of pain, in addition to its well-established antibacterial effect.

The clinical path to deliver encapsulated phages and lysins

The global emergence of multidrug-resistant pathogens is shaping the current dogma regarding the use of antibiotherapy. Many bacteria have evolved to become resistant to conventional antibiotherapy, representing a health and economic burden for those afflicted. The search for alternative and complementary therapeutic approaches has intensified and revived phage therapy. In recent decades, the exogenous use of lysins, encoded in phage genomes, has shown encouraging effectiveness. These two antimicrobial agents reduce bacterial populations; however, many barriers challenge their prompt delivery at the infection site. Encapsulation in delivery vehicles provides targeted therapy with a controlled compound delivery, surpassing chemical, physical and immunological barriers that can inactivate and eliminate them. This review explores phages and lysins' current use to resolve bacterial infections in the respiratory, digestive, and integumentary systems. We also highlight the different challenges they face in each of the three systems and discuss the advances towards a more expansive use of delivery vehicles.

Ex vivo modelling of the formation of inflammatory platelet-leucocyte aggregates and their adhesion on endothelial cells, an early event in sepsis

Septicaemia is an acute inflammatory reaction in the bloodstream to the presence of pathogen-associated molecular patterns. Whole blood stimulation assays capture endotoxin-induced formation of aggregates between platelets and leucocytes using flow cytometry. We wanted to assess extent of spontaneous aggregate formation in whole blood stimulation assays and compare the effects of endotoxin and heat-killed, clinically relevant, bacterial pathogens on aggregate formation and then on adhesion of aggregates to TNFα-stimulated endothelial cells. We found that endotoxin (from Escherichia coli or Salmonella enteritidis) was not a suitable stimulus to provoke platelet-leucocyte aggregates in vitro, as it did not further increase the extent of aggregates formed spontaneously in stasis of hirudin-anticoagulated blood. Specifically, whole blood samples stimulated with or without LPS produced aggregates with a mean surface area of 140.97 and 117.68 μm2, respectively. By contrast, incubation of whole blood with heat-killed Klebsiella pneumoniae or Staphylococcus aureus produced significantly enhanced and complex cellular aggregates (with a mean surface area of 470.61 and 518.39 μm2, respectively) which adhered more frequently to TNFα (and free fatty acid)-stimulated endothelial cells. These were reliably captured by scanning electron microscopy. Adhesion of cellular aggregates could be blocked by incubation of endothelial cells with a commercial P-selectin antibody and an angiopoietin-2 ligand trap. In conclusion, we have developed an in vitro method that models the acute inflammatory reaction in whole blood in the presence of sepsis-relevant bacterial pathogen surfaces.

Macrolide therapy is associated with reduced mortality in acute respiratory distress syndrome (ARDS) patients

Background

Macrolides have been associated with favorable immunological effects in various inflammatory disease states. We investigated the association between macrolide therapy and mortality in patients with the acute respiratory distress syndrome (ARDS).

Methods

This was an unplanned secondary analysis of patients with ARDS within a large prospective observational study of critically ill patients in the intensive care units (ICUs) of two university-affiliated hospitals in the Netherlands. The exposure of interest was low-dose macrolide use prescribed for another reason than infection; we excluded patients who received high-dose macrolides for an infection. The primary endpoint was 30-day mortality. The association between macrolide therapy and mortality was determined in the whole cohort, as well as in a propensity score matched cohort; the association was compared between pulmonary versus non-pulmonary ARDS, and between two biological phenotypes based on plasma levels of 20 biomarkers.

Results

In total, 873 patients with ARDS were analyzed, of whom 158 patients (18%) received macrolide therapy during stay in ICU for a median duration of 3 (interquartile range, 1-4) days. Erythromycin was the most frequent prescribed macrolide (97%). Macrolide therapy was associated with reduced 30-day mortality in the whole cohort [22.8% vs. 31.6%; crude odds ratio (OR), 0.64 (interquartile range, 0.43-0.96), P=0.03]. The association in the propensity score matched cohort remained significant [22.8% vs. 32.9%; OR, 0.62 (interquartile range, 0.39-0.96), P=0.03]. Propensity matched associations with mortality were different in patients with non-pulmonary ARDS vs. pulmonary ARDS and also varied by biological phenotype.

Conclusions

These data together show that low-dose macrolide therapy prescribed for another reason than infection is associated with decreased mortality in patients with ARDS.

Combination of Erythromycin and Curcumin Alleviates Staphylococcus aureus Induced Osteomyelitis in Rats

Osteomyelitis is commonly caused by Staphylococcus aureus. Both erythromycin and curcumin can suppress S. aureus growth, but their roles in osteomyelitis are barely studied. We aim to explore the activities of erythromycin and curcumin against chronical osteomyelitis induced by methicillin-resistant S. aureus (MRSA). Chronicle implant-induced osteomyelitis was established by MRSA infection in male Wistar rats. Four weeks after bacterial inoculation, rats received no treatment, erythromycin monotherapy, curcumin monotherapy, or erythromycin plus curcumin twice daily for 2 weeks. Bacterial levels, bone infection status, inflammatory signals and side effects were evaluated. Rats tolerated all treatments well, with no death or side effects such as, diarrhea and weight loss. Two days after treatment completion, erythromycin monotherapy did not suppress bacterial growth and had no effect in bone infection, although it reduced serum pro-inflammatory cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-6. Curcumin monotherapy slightly suppressed bacterial growth, alleviated bone infection and reduced TNF-α and IL-6. Erythromycin and curcumin combined treatment markedly suppressed bacterial growth, substantially alleviated bone infection and reduced TNF-α and IL-6. Combination of erythromycin and curcumin lead a much stronger efficiency against MRSA induced osteomyelitis in rats than monotherapy. Our study suggests that erythromycin and curcumin could be a new combination for treating MRSA induced osteomyelitis.

The Nonantibiotic Macrolide EM703 Improves Survival in a Model of Quinolone-Treated Pseudomonas aeruginosa Airway Infection

Macrolide antibiotics are used as anti-inflammatory agents, e.g., for prevention of exacerbations in chronic obstructive pulmonary disease and cystic fibrosis. Several studies have shown improved outcomes after the addition of macrolides to β-lactam antibiotics for treatment of severe community-acquired pneumonia. However, a beneficial effect of macrolides in treating Gram-negative bacterial airway infections, e.g., those caused by Pseudomonas aeruginosa, remains to be shown. Macrolide antibiotics have significant side effects, in particular, motility-stimulating activity in the gastrointestinal tract and promotion of bacterial resistance. In this study, EM703, a modified macrolide lacking antibiotic and motility-stimulating activities but with retained anti-inflammatory properties, was used as an adjunct treatment for experimental P. aeruginosa lung infection, in combination with a conventional antibiotic. Airway infections in BALB/cJRj mice were induced by nasal instillation of P. aeruginosa; this was followed by treatment with the quinolone levofloxacin in the absence or presence of EM703. Survival, inflammatory responses, and cellular influx to the airways were monitored. Both pretreatment and simultaneous administration of EM703 dramatically improved survival in levofloxacin-treated mice with P. aeruginosa airway infections. In addition, EM703 reduced the levels of proinflammatory cytokines, increased the numbers of leukocytes in bronchoalveolar lavage fluid, and reduced the numbers of neutrophils present in lung tissue. In summary, the findings of this study show that the immunomodulatory properties of the modified macrolide EM703 can be important when treating Gram-negative pneumonia, as exemplified by P. aeruginosa infection in this study.

Exploring the Role of CYP3A4 Mediated Drug Metabolism in the Pharmacological Modulation of Nitric Oxide Production

Nitric-oxide synthase, the enzyme responsible for mammalian nitric oxide generation, and cytochrome P450, the major enzymes involved in drug metabolism, share striking similarities. Therefore, it makes sense that cytochrome P450 drug mediated biotransformations might play an important role in the pharmacological modulation of nitric oxide synthase. In this work, we have undertaken an integrated in vitro assessment of the hepatic metabolism and nitric oxide modulation of previously described dual inhibitors (imidazoles and macrolides) of these enzymes in order assess the implication of CYP450 activities over production of nitric oxide. In vitro systems based in human liver microsomes and activated mouse macrophages were developed for these purposes. Additionally in vitro production the hepatic metabolites of dual inhibitor, roxithromycin, was investigated achieving the identification and isolation of main hepatic biotransformation products. Our results suggested that for some macrolide compounds, the cytochrome P450 3A4 derived drug metabolites have an important effect on nitric oxide production and might critically contribute to the pharmacological immunomodulatory activity observed.

On-chip evaluation of neutrophil activation and neutrophil-endothelial cell interaction during neutrophil chemotaxis

Neutrophils are always surrounded by/interacting with other components of the immune system; however, the current mechanistic understanding of neutrophil function is largely based on how neutrophils respond to a single chemical signal in a simplified environment. Such approaches are unable to recapitulate the in vivo microenvironment; thus, cell behavior may not fully represent the physiological behavior. Herein, we exploit a microfluidic model of the complex in vivo milieu to investigate how cell-cell interactions influence human neutrophil migration and surface marker expression. Neutrophil migration against a bacterially derived chemoattractant (formyl-met-leu-phe, fMLP), with and without preactivation by interleukins (interleukin-2 or interleukin-6), was evaluated in the presence and absence of endothelial support cells. Preactivation by interleukins or interaction with endothelial cells resulted in altered migration rates compared to naïve neutrophils, and migration trajectories deviated from the expected movement toward the fMLP signal. Interestingly, interaction with both interleukins and endothelial cells simultaneously resulted in a slight compensation in the deviation-on endothelial cells, 34.4% of untreated neutrophils moved away from the fMLP signal, while only 15.2 or 22.2% (interleukin-2-or interleukin-6-activated) of preactivated cells moved away from fMLP. Neutrophils interacting with interleukins and/or endothelial cells were still capable of prioritizing the fMLP signal over a competing chemoattractant, leukotriene B4 (LTB4). Fluorescence imaging of individual human neutrophils revealed that neutrophils treated with endothelial-cell-conditioned media showed up-regulation of the surface adhesion molecules cluster determinant 11b and 66b (CD11b and CD66b) upon stimulation. On the other hand, CD11b and CD66b down-regulation was observed in untreated neutrophils. These results leverage single cell analysis to reveal that the interaction between neutrophils and endothelial cells is involved in surface marker regulation and thus chemotaxis of neutrophils. This study brings new knowledge about neutrophil chemotaxis in the context of cell-to-cell communications, yielding both fundamental and therapeutically relevant insight.

Differing effects of azithromycin and doxycycline on cytokines in cells from Chlamydia trachomatis-infected women

Chlamydial infection of the lower genital tract usually spreads to the upper genital tract and is then responsible for more serious consequences, such as infertility, ectopic pregnancy, pelvic pain, and pelvic inflammatory disease. Genital infection with Chlamydia trachomatis and the resulting cytokine response largely determines the outcome of infection and disease. To date, studies showing comparative effects of azithromycin and doxycycline treatment for C. trachomatis infection in women with reproductive sequelae like infertility and their effect on immune molecules like cytokines are lacking. Hence, our objective was to study the effect of azithromycin and doxycycline in vitro on cytokines in cells from C. trachomatis-positive fertile and infertile women as well as their efficacy in C. trachomatis infection. Fertile and infertile women with primary and recurrent C. trachomatis infection attending the gynecology outpatient department of Safdarjung Hospital, New Delhi, India, were enrolled. Enzyme-linked immunosorbent assay and real-time reverse transcription-polymerase chain reaction was performed for evaluating cytokines in cells stimulated with chlamydial elementary bodies (EBs) in the presence and absence of antibiotics (azithromycin and doxycycline). C. trachomatis-infected women were also followed up to assess the efficacy of azithromycin and doxycycline. We observed inhibition of cytokines (interleukin [IL]-1beta (β), IL-6, IL-8, IL-10, and tumor necrosis factor-alpha) in the presence of azithromycin in EB-stimulated cells from both fertile and infertile women with primary and recurrent C. trachomatis infection. However, in presence of doxycycline, inhibition of cytokines (IL-1β and IL-6) was only observed in stimulated cells from fertile women with primary C. trachomatis infection. The clinical efficacy of azithromycin was also better than doxycycline in recurrent C. trachomatis infection in women with complications such as infertility. Overall, this study suggests that azithromycin treatment with broader immunomodulatory effects may be preferable to doxycycline for the treatment of recurrent C. trachomatis infection associated with infertility.

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.

Immuno-modulation and anti-inflammatory benefits of antibiotics: the example of tilmicosin

Exaggerated immune responses, such as those implicated in severe inflammatory reactions, are costly to the metabolism. Inflammation and pro-inflammatory mediators negatively affect production in the food animal industry by reducing growth, feed intake, reproduction, milk production, and metabolic health. An ever-increasing number of findings have established that antibiotics, macrolides in particular, may generate anti-inflammatory effects, including the modulation of pro-inflammatory cytokines and the alteration of neutrophil function. The effects are time- and dose-dependent, and the mechanisms responsible for these phenomena remain incompletely understood. Recent studies, mostly using the veterinary macrolide tilmicosin, may have shed new light on the mode of action of some macrolides and their anti-inflammatory properties. Indeed, research findings demonstrate that this compound, amongst others, induces neutrophil apoptosis, which in turn provides anti-inflammatory benefits. Studies using tilmicosin model systems in vitro and in vivo demonstrate that this antibiotic has potent immunomodulatory effects that may explain why at least parts of its clinical benefits are independent of anti-microbial effects. More research is needed, using this antibiotic and others that may have similar properties, to clarify the biological mechanisms responsible for antibiotic-induced neutrophil apoptosis, and how this, in turn, may provide enhanced clinical benefits. Such studies may help establish a rational basis for the development of novel, efficacious, anti-microbial compounds that generate anti-inflammatory properties in addition to their antibacterial effects.

Valnemulin downregulates nitric oxide, prostaglandin E2, and cytokine production via inhibition of NF-kappaB and MAPK activity

Valnemulin is a pleuromutilin antibiotic used in clinics for the treatment of various infections. We studied the in vitro anti-inflammatory effects of valnemulin and associated signal transduction mechanisms in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. We found that valnemulin inhibited nitric oxide (NO), prostaglandin E2 (PGE2), tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6), and increased interleukin-10 (IL-10) production. Inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein expression were also inhibited by valnemulin. We further observed that valnemulin prevented the LPS-induced NF-kappaB translocation from the cytoplasm into the nucleus. Valnemulin also blocked phosphorylation of three mitogen-activated protein kinases (MAPKs): extracellular signal receptor-activated kinase (ERK) 1/2, p38, and c-Jun N-terminal kinase (JNK). Our data indicate that valnemulin may have therapeutic anti-inflammatory effects independent of its antibacterial activity.

Immunomodulatory effects of macrolide antibiotics in respiratory disease: therapeutic implications for asthma and cystic fibrosis

The macrolide antibiotics are a family of related 14- or 15-membered lactone ring antibiotics. There has been recent interest in the beneficial effects of these drugs as immune modulators in respiratory conditions in children. Cystic fibrosis (CF) and asthma, both of which occur in childhood, have an underlying inflammatory component and are associated with significant morbidity. The pathogenesis of both conditions is poorly understood but several molecular mechanisms have been suggested. In CF, these mechanisms broadly involve altered chloride transport and alteration of the airway surface liquid with disordered neutrophilic inflammation. There is much evidence for a proinflammatory propensity in CF immune effector and epithelial cells and many studies indicate that macrolides modulate these inflammatory processes. Recent studies have confirmed a clinical improvement in CF following treatment with macrolides, but the exact mechanisms by which they work are unknown. Asthma is likely to represent several different phenotypes but in all of these, airway obstruction, bronchial hyperresponsiveness, and inflammation are central processes. Results from trials using macrolides have suggested an improvement in clinical outcome. The putative mechanisms of macrolide immunomodulatory action include improvement of the primary defense mechanisms, inhibition of the bacteria-epithelial cell interaction, modulation of the signaling pathway and chemokine release, and direct neutrophil effects. Putative mechanisms of phenotypic modulation have also been proposed involving interactions with nitric oxide, endothelin-1, and bronchoconstriction, endothelial growth factors and airway remodeling, and bioactive phospholipids in both CF and asthma. Further characterization of these effects and development of targeted designer drugs will further expand our therapeutic repertoire and lead to improved quality and quantity of life for patients with CF and asthma.

Candin family antifungal agent micafungin (FK463) modulates the inflammatory cytokine production stimulated by lipopolysaccharide in THP-1 cells

Systemic inflammatory response syndrome (SIRS) and sepsis have been considered forms of hypercytokinemia in critically ill patients and immunocompromized hosts. It has been reported that some antimicrobial agents, including antifungal agents, not only have an antibiotic effect, but also they affect the host's immunological response. Immunofunctional cells, including monocytes and macrophages, were examined to determine whether they are influenced by the newly synthesized candin family antifungal agent micafungin (MCFG) using the human monocytic cell line THP-1 stimulated with lipopolysaccharide (LPS) as a model of hypercytokinetic conditions. LPS-induced production of TNF-alpha (tumor necrosis factor-alpha) and interleukin-8 (IL-8) in THP-1 cells was significantly suppressed dose-dependently by MCFG, although high concentrations of MCFG may reach toxic levels. It was clarified that MCFG inhibits the LPS-induced expression of TNF-alpha in THP-1 cells at the mRNA (messenger ribonucleic acid) level. In conclusion, administration of MCFG had an immunomodulatory effect on the host by reducing levels of TNF-alpha and IL-8. The effectiveness of MCFG in modulating hypercytokinemia is due not only to its direct antifungal effect, but also to the modulation of cytokine production in macrophages that regulates immunological activity and inflammation.

Pharmacokinetic/pharmacodynamic modelling of roxithromycin for the inhibitory effect of tumour necrosis factor-alpha and interleukin-6 production in dogs

The objective of the present study was to determine and characterize the relationship between the plasma concentration of roxithromycin, and its inhibitory effect on cytokine production, in order to predict its possible clinical relevance. Six healthy beagle dogs received a single intravenous dose of 20-mg roxithromycin per kg body weight. Blood samples were obtained at different time points. The plasma was analysed with respect to roxithromycin, tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6). The concentration-effect relationship was explored by modelling the data using two compartmental model and an indirect response model with an E(max) concentration-effect relationship. The estimated pharmacokinetic parameters (geometric mean) were as follows: V(c) = 2.59 l; k(10) = 0.08/h; k(12) = 0.26/h; k(21) = 0.40/h. The pharmacodynamic parameters (geometric mean) for the inhibitory effect on cytokine production induced by heat-killed Staphylococcus aureus (HKSA) were for TNF-alpha (k(in) = 1.42 microg/h; k(out) = 1.10 microg/h; EC(50) > 5.69 mg/l) and for IL-6 (k(in) = 2.31 microg/h; k(out) = 2.04 microg/h; EC(50) = 21.07 mg/l) production, respectively. The inhibitory effect of roxithromycin on production can be adequately described by the indirect response model with an E(max) concentration-effect relationship.

Effects of claritromycin on inflammatory parameters and clinical conditions in children with bronchiectasis1

BACKGROUND

The effects of the macrolides cannot be ascribed to their antibacterial action alone. Their immunoregulatory and anti-inflammatory functions are significant too. They are frequently used in the treatment of diffuse panbronchiolitis and cystic fibrosis (CF).

AIM

To evaluate the effects of a macrolide antibiotic [clarithromycin (CAM)] on the process of inflammation [by measuring IL-8, TNF-alpha, IL-10 levels and cell profiles in bronchoalveolar lavage (BAL) fluid], pulmonary function and sputum production in children with steady-state bronchiectasis, secondary to causes other than CF or primary immunodeficiencies.

METHODS

Seventeen patients randomized to the treatment group received CAM and supportive therapies for 3 months and 17 patients in the control group were given supportive therapies only.

RESULTS

Compared with the control group, the treatment group showed a significant decrease in IL-8 levels, total cell count, neutrophil ratios in BAL fluid and daily sputum production at the end of the third month. There was also a significant increase in the treatment group's BAL fluid macrophage ratios. The differences in pulmonary function test parameters were not significant.

CONCLUSION

Use of CAM in children with steady-state bronchiectasis results in laboratory improvement by reducing the inflammatory processes in the lungs. No corresponding clinical improvement could be shown but although this is possible with long-term use, trial validation is necessary.

Airway biofilms: implications for pathogenesis and therapy of respiratory tract infections

The differentiation of bacterial biofilms in the airway environment, the pathogenesis of airway biofilm, and possible therapeutic methods are discussed. Biofilm diseases that characteristically involve the respiratory system include cystic fibrosis (CF), diffuse panbronchiolitis (DPB), and bronchiectasia with Pseudomonas aeruginosa (P. aeruginosa) infection. There is evidence to suggest that almost all strains of P. aeruginosa have the genetic capacity to synthesize alginate, a main matrix of biofilms, when ecological conditions are unfavorable for their survival. The bacteria inside the mature biofilm show increased resistance to both antibacterials and phagocytic cells, express fewer virulence factors because of their stationary state of growth, and are less stimulatory to the mucosa because of the 'sandwich binding'. These factors facilitate both the colonization of bacteria and their extended survival even under unfavorable conditions. Since the biofilm limits colonization to a latent form, the clinical symptoms in this situation are unremarkable. However, the clinical progression of both CF and DPB proceeds in two characteristic directions. The first is an acute exacerbation caused by planktonic bacteria that have germinated from the biofilm. The second is a slow progression of disease that is induced by harmful immune reactions. The harmful reactions are mediated by alginate, which induces antigen antibody reactions around the airways, as well as formation of circulating immune complexes that are deposited on lung tissue. Furthermore, the highest titer of bacterial permeability increasing anti-neutrophil cytoplasmic autoantibodies (BPI-ANCA) is observed in association with highly impaired pulmonary function in patients with CF and DPB, as well as in patients with a lengthy period of colonization with P. aeruginosa. BPI-ANCA subsequently makes chronic airway infection even more intractable. The long-term use of 14- or 15-ring membered macrolides results in a favorable clinical outcome for patients with DPB and in some patients with CF. In the last 10 years, an increasing number of studies have reported secondary actions of macrolides that include effects on both airway and phagocytic cells, as well as an anti-biofilm activity. The 14- or 15-ring membered macrolides inhibit: (i) the alginate production from P. aeruginosa; (ii) the antibody reaction to alginate, which leads to a decrease in the immune complex formation; and (iii) the activation of the autoinducer 3-O-C12-homoserine lactone and subsequent expression of lasI and rhlI in quorum sensing systems in P. aeruginosa. These anti-biofilm actions of macrolides may represent their basic mechanisms of action on airway biofilm disease.

Macrolides in the treatment of asthma and cystic fibrosis

Asthma and cystic fibrosis are two respiratory diseases characterized by chronic inflammation, leading to remodelling of the airways. Macrolides are widely used antibiotics, with a peculiar anti-inflammatory effect. On the basis of the methodologies used by the Cochrane collaboration, this review discusses the evidence for their long-term use as anti-inflammatory agents in these two diseases. Three randomized-controlled trials (RCTs) were identified for both asthma and cystic fibrosis. A positive effect of macrolides on reducing eosinophil numbers and markers of eosinophilic inflammation was demonstrated in patients with asthma. Data on cystic fibrosis demonstrated an effect on lung function with an increase of 5.4% in forced vital capacity (FVC) in patients treated with macrolide vs. placebo, but without a significant effect on FEV1. Side-effects were rare, mild and reversible on withdrawal of treatment. Although preliminary data from small studies are promising, the role of macrolides in the treatment of these chronic disorders needs to be more firmly established with larger, well-designed trials, targeted to investigate major clinical outcomes.

Monotherapy versus combination antimicrobial therapy for pneumococcal pneumonia

PURPOSE OF REVIEW

In the past 5 years a number of studies have suggested that combination antibiotic therapy may be superior to monotherapy for pneumococcal pneumonia. This review outlines the major findings for and against combination therapy.

RECENT FINDINGS

The evidence for a benefit of multiple antibiotics is strongest in patients with severe, bacteremic pneumococcal disease. All of these studies have limitations due to their retrospective or uncontrolled design. Unfortunately prospective, randomized, double-blind, controlled studies have not been performed in an appropriately severe disease cohort and are therefore urgently needed. Several viable mechanisms for a benefit of combination therapy have been proposed, especially related to non-antibiotic effects of macrolides. There is also some evidence that third-generation cephalosporins may be superior to penicillins as the non-macrolide component of combination therapy.

SUMMARY

Although based on retrospective and observational data, there is substantial evidence to support combination antibiotic therapy, at least in patients with severe bacteremic pneumococcal pneumonia. What evidence is available supports a cephalosporin/macrolide combination as being associated with the highest survival, but proper prospective studies in patients with severe pneumonia are urgently required to clarify this issue.

Nadifloxacin, an antiacne quinolone antimicrobial, inhibits the production of proinflammatory cytokines by human peripheral blood mononuclear cells and normal human keratinocytes

BACKGROUND

Acne vulgaris is a chronic inflammatory disease involving colonization of Propionibacterium acnes (P. acnes), activation of neutrophils and lymphocytes. Circumstantial evidence suggests that antigen-independent and -dependent immune responses against P. acnes are involved in the pathogenesis of inflammatory acne. Epidermal keratinocytes are also suggested to be involved in initiation and progression of cutaneous inflammation. Nadifloxacin, a fluorinated quinolone, has potent antimicrobial activities against Gram-negative and -positive microbes and is used to treat multiple inflamed acne lesions. However, its effect on immune conferring cells such as mononuclear cells and keratinocytes has not been examined.

OBJECTIVE

To evaluate the possible involvement of potential anti-inflammatory activity of nadifloxacin in its therapeutic effect on inflammatory acne, we examined the effects of nadifloxacin, in comparison with other antibiotics used to treat acne vulgaris, on cytokine production by human peripheral blood mononuclear cells (PBMC) and keratinocytes.

METHODS

Cytokine production by PBMC was determined after treatment with heat-killed P. acnes in the presence or absence of antimicrobials using a real-time PCR and ELISA. Cultured human epidermal keratinocytes were stimulated by IFN-gamma plus IL-1beta and the effects of antimicrobials were examined by using ELISA.

RESULTS

Nadifloxacin as well as macrolide antibiotics and clindamycin inhibited IL-12 and IFN-gamma production by PBMC stimulated by heat-killed P. acnes. The drug also inhibited the IL-1alpha, Il-6, IL-8 and GM-CMS production by keratinocytes treated with IFN-gamma plus IL-1beta.

CONCLUSIONS

Inhibitory effects of nadifloxacin to activate T cells and keratinocytes may be involved at least in part in the mechanism of its therapeutic effect against inflammatory acne.

Anti-inflammatory and immunomodulating effects of clarithromycin in patients with cystic fibrosis lung disease

BACKGROUND AND AIM: Macrolide antibiotics are widely used in the treatment of suppurative lung diseases including cystic fibrosis (CF), the most common inherited fatal disease in the Caucasian population. This condition is characterized by secondary Pseudomonas infection resulting in neutrophil infiltration within the airways. The aim of the study was to investigate the evolution of inflammatory process in CF patients receiving long-term clarithromycin therapy. METHODS: Twenty-seven CF patients (mean age, 12 years) were enrolled into the study. Beside the basic therapy the patients were treated with clarithromycin at a dose of 250 mg every other day orally. All patients were routinely examined every 3 months. Blood and sputum were collected before clarithromycin treatment and then again 3, 6 and 12 months after the drug prescription. Cytokine concentrations (tumor necrosis factor-alpha, interleukin-8, interleukin-4, interferon-gamma) in the sputum and plasma were assayed. Peripheral blood lymphocyte response to phytohemagglutinin was also evaluated. RESULTS: Clarithromycin treatment resulted in a marked reduction of the cytokine levels both in the sputum and plasma specimens. At the same time, the interferon-gamma/interleukin-4 ratio has been significantly elevated. In addition, a sustained increase of peripheral blood lymphocyte response to phytohemagglutinin was demonstrated. These changes were associated with a significant improvement of the lung function. CONCLUSIONS: The beneficial effect of the prolonged treatment of CF patients with a 14-membered ring macrolide antibiotic clarithromycin seems to be associated not only with down-regulation of the inflammatory response, but also with immunological changes including the switch from Th2 to Th1 type response.

TNFα Measurement in Rat and Human Whole Blood as an in vitro Method to Assay Pyrogens and its Inhibition by Dexamethasone and Erythromycin

To ensure the safety of potential drugs, pyrogen tests are traditionally performed in rabbits. New methods have been developed as alternatives to the test to reduce the use of experimental animals. Among these methods there are the Limulus amoebocyte lysate test and the determination of cytokine production by human leukocytes and whole blood. When exposed to a range of concentrations of endotoxins, human and rat whole blood release TNFalpha at amounts that are detectable by a commercially available enzyme-linked immunosorbent assay (ELISA). Our results show that the sensitivity of human and rat blood to endotoxins from Salmonella abortus equi and Escherichia coli is similar. In rat blood, TNFalpha was detected after contact with the pyrogens only in fresh blood, collected on the same day of incubation with the pyrogenic substances. The measurement of TNFalpha production would be a reliable alternative to the rabbit pyrogen test. However, given that the addition of erythromycin and dexamethasone inhibited the production of this cytokine, this method is limited when parenteral formulations contain these two drugs. Similar inhibition has been observed in the rabbit test. Additional experiments will be necessary to demonstrate that the rat whole blood test system is useful and reliable for the pyrogens evaluation.

Effect of multiple doses of clarithromycin and amoxicillin on IL-6, IFNgamma and IL-10 plasma levels in patients with community acquired pneumonia

Inflammation is crucial for the pathogenesis of both infectious and chronic obstructive pulmonary diseases. It is therefore important to modulate pulmonary inflammation in patients with these lung disorders. Macrolide antibiotics modulate inflammation in vitro and in in vivo by inhibiting the production of proinflammatory cytokines and prostaglandin E2, neutrophil chemotactic activity and elastase activity. This study evaluates the effect of clarithromycin (500 mg b.i.d. x 7 days) in comparison to amoxicillin (1 g t.i.d. x 7 days) in patients with community acquired pneumonia by testing plasma levels of IL-6, IFNgamma and IL-10 before starting therapy and at the 3rd and 7th days of therapy. Clarithromycin significantly decreased plasma levels of IL-6 and significantly increased those of IFNgamma and IL-10 at the 3rd and 7th day in comparison to basal levels. In patients treated with amoxicillin a significant decrease in IL-6 plasma levels was observed at the 7th day of therapy, probably in relation to the resolution of inflammatory symptoms. In the same patients IFNgamma plasma levels decreased during treatment while IL-10 plasma levels were unaffected.

Modulation of polymorphonuclear cell interleukin-8 secretion by human monoclonal antibodies to type 8 pneumococcal capsular polysaccharide

Pneumococcal capsular polysaccharide (PS) vaccines induce type-specific immunoglobulin M (IgM), IgG, and IgA. Type-specific IgG to the PS is sufficient to confer protection against the homologous serotype of the pneumococcus, but the efficacies of type-specific IgM and IgA are less well understood. We examined the in vitro activities and efficacies in mice of two human monoclonal antibodies (MAbs) to type 8 PS, NAD (IgA) and D11 (IgM). MAb-mediated opsonophagocytic killing was evaluated after coculture of type 8 pneumococci with human polymorphonuclear cells (PMNs), type-specific or control MAbs, and human complement sources. The effects of the MAbs on PMN interleukin-8 (IL-8) and IL-6 secretion were determined in supernatants from cocultures containing pneumococci and PMNs by enzyme-linked immunosorbent assay. MAb efficacy was determined in an intratracheal model of type 8 infection in mice with classical complement pathway deficiency. Both MAbs were protective in 100% of infected mice. Neither MAb promoted a significant amount of killing of type 8 pneumococci compared to its isotype control MAb. Both type-specific MAbs mediated complement-dependent modulation of PMN IL-8 secretion, with increased secretion at effector/target (E:T) ratios of 500:1 and 50:1 and reduced secretion at 1:5. Trypan blue staining revealed that PMNs cocultured with D11 were less viable at an E:T ratio of 1:5 than PMNs cocultured with the control MAb. PMN IL-6 secretion was increased by both type-specific and control MAbs. These results suggest that certain type-specific IgM and IgAs might contribute to host defense by modulation of the inflammatory response to pneumococci.

Erythromycin inhibits wear debris-induced osteoclastogenesis by modulation of murine macrophage NF-kappaB activity

Activation of nuclear factor kappa B (NF-kappaB) signaling in response to cell stimulation by wear debris may be critical in the pathogenesis of aseptic loosening. Erythromycin (EM), a macrolide antibiotic, has been shown to effectively suppress some types of inflammatory reactions. In this study, we examined the effect of EM on wear debris-induced osteoclastic bone resorption in vitro. EM inhibited Ca+ release from neonatal calvaria co-cultured with conditioned medium from mouse RAW264.7 macrophages activated by wear debris. Inhibition of Ca+ release was associated with a decreased number of tartrate-resistant acid phosphatase (TRAP)-positive cells in cultured bones. To investigate the mechanism whereby EM inhibits bone-resorption, RAW cells were incubated with wear debris in the presence EM. Real time RT-CR analysis revealed that EM (5 microg/ml) significantly inhibited mRNA expression of NF-kappaB, cathepsin K (CPK), IL-1beta and TNFalpha, but not RANK in RAW cells stimulated with wear debris. Furthermore, electrophoretic mobility-shift assay showed that EM (0.2 microg-5 microg/ml) could reduce DNA-binding activity of NF-kappaB in RAW cells stimulated with wear debris. The inhibition of inflammatory osteoclastogenesis by EM treatment was further confirmed by an osteoclast (OC) formation assay using primary cultures of mouse bone marrow progenitor cells stimulated with macrophage colony-stimulating factor and RANK ligand (RANKL). EM treatment (5 microg/ml) resulted in more than 70% reduction in multinucleated OC formation and 50% reduction of TRAP+ cells by bone marrow progenitor cells. Our findings support that EM suppresses wear debris-induced osteoclastic bone resorption by, at least, down-regulation of NF-kappaB signaling pathway. It appears that EM represents a potential therapeutic candidate for the treatment and prevention of aseptic loosening.

Does acetaminophen interfere in the antibiotic treatment of acute otitis media caused by a penicillin-resistant pneumococcus strain? A gerbil model

The possible interference of acetaminophen, combined with antibiotics, in the treatment of acute otitis media (AOM) caused by a penicillin-resistant (minimal inhibitory concentration [MIC], 2 microg/mL), amoxicillin/clavulanic acid- and erythromycin-sensitive pneumococcus was evaluated in a gerbil model. Animals were challenged with approximately 5 x 106 bacteria in each ear through transbullar instillation. Acetaminophen was administered s.c. at 50 mg/kg 30 min before each antibiotic dose. Amoxicillin/clavulanic acid and erythromycin (2.5 and 10 mg/kg) were administered s.c. at 2, 10, and 18 h after inoculation. Samples were obtained from the middle ear (ME) on day 2 after inoculation for bacterial count. The overall results showed no difference between animals that received acetaminophen, with or without antibiotics, and those that did not receive acetaminophen. The antibiotic concentrations in the ME were practically identical in both groups of animals, so acetaminophen did not interfere with the pharmacokinetics of antibiotics in the ME. However, both antibiotics significantly reduced the number of culture-positive and the bacterial concentration in ME samples when compared with antibiotic-untreated animals. Both antibiotics, whether combined with acetaminophen or not, lowered the number of AOM to <25%, but >75% of animals presented otitis media with effusion, and no differences were shown between groups. A high rate of bacterial eradication from the ME correlated with antibiotic serum concentrations being over the MIC of the infecting organism for only >15% of the dose interval and with an ME concentration exceeding the MIC by a factor of 1.7. In this experimental model, acetaminophen had neither a synergistic nor an antagonistic effect on the antibiotics tested.

Macrolides inhibit epithelial cell-mediated neutrophil survival by modulating granulocyte macrophage colony-stimulating factor release

Macrolides have been shown to be effective in treating diffuse panbronchiolitis (DPB), although the precise modes of action remain unclear. At sites of airway inflammation, respiratory epithelium is considered an active participant in regulating neutrophil survival. We therefore examined the effect of erythromycin, clarithromycin, azithromycin, and josamycin on both neutrophil survival and on epithelial-derived factors, which influence neutrophil longevity. Media conditioned with transiently tumor necrosis factor (TNF)-alpha-stimulated A549 human airway epithelial cells prolonged neutrophil survival compared with control media. The presence of dexamethasone during neutrophil culture led to further prolongation of neutrophil survival. In contrast, none of the tested macrolides modulated neutrophil survival, suggesting a lack of direct effect of these drugs. On the other hand, pretreatment of TNF-alpha-stimulated A549 cells by erythromycin, clarithromycin, azithromycin, or dexamethasone, but not josamycin, decreased the neutrophil survival-enhancing effects in a dose-dependent manner. Neutralizing antibodies to granulocyte macrophage colony-stimulating factor (GM-CSF) dampened the prolonged neutrophil survival observed in TNF-alpha-stimulated A549 conditioned media. Erythromycin, clarithromycin, azithromycin, and dexamethasone inhibited TNF-alpha-induced GM-CSF expression in A549 cells at both the protein and messenger RNA levels. These results suggest that macrolides inhibit epithelial cell-mediated neutrophil survival by modulating GM-CSF release, which may, at least in part, explain the effectiveness of this family of drugs on DPB.

In vitro effects of ciprofloxacin and roxithromycin on apoptosis of jurkat T lymphocytes

Ciprofloxacin (CPFX) and roxithromycin (RXM) induced apoptosis of activated Jurkat T cells in vitro. CPFX showed concentration-dependent acceleration of apoptosis of activated Jurkat T cells by enhancing the expression of FasL and activities of caspase-3 and -8. RXM accelerated cell death, enhanced expression of FasL and caspase-3 but not caspase-8, and did not show the concentration dependency.

Inflammatory cytokine (interleukin 6 and tumour necrosis factor alpha) release in a human whole blood system in response to Streptococcus pneumoniae serotype 14 and its capsular polysaccharide

Gram-positive bacteria, which lack lipopolysaccharide (LPS), produce a septic-shock-like condition, accompanied by release of pro-inflammatory cytokines. Various components of the bacteria may be responsible for this. We stimulated a whole blood system with heat-inactivated Streptococcus pneumoniae serotype 14 (S14) bacteria, with pneumococcal S14 capsular polysaccharide (PPS S14) and with PPS S14 coated on to latex beads, to compare interleukin 6 (IL-6) and tumour necrosis factor alpha (TNFalpha) production over a six hour period, to ascertain the contribution of PPS to the inflammatory response. This was compared with the response to LPS. After sonication of the bacteria, their PPS content was estimated by an enzyme-linked immunoabsorbent assay, to compare this with the concentration of free PPS needed to generate cytokine release. The whole bacteria elicited a much larger cytokine response than the equivalent amount of PPS alone, whereas the PPS-coated beads gave minimal response. The different cytokine responses to PPS and LPS suggest that there are differences in the receptors and/or signalling pathways for Gram-negative and Gram-positive bacteria. We conclude that the estimated amount of PPS in the bacteria is not enough to account for the large cytokine response we observed. Since PPS could not be shown to contribute significantly to cytokine induction, specific antibodies to PPS would not play any significant role in combating cytokine release associated with pneumococcal infection and possible septic shock. This needs to be considered in production of future vaccines.

Combined effects of in vitro penicillin and sickle cell disease sera on normal lymphocyte functions

Previously published work has shown that sera from healthy sickle cell disease (SCD) patients inhibits normal lymphocyte response to phytohemagglutinin (PHA) in vitro. The objective of the current study is to ascertain what the combined effects of SCD sera plus penicillin have on normal lymphocyte cytokine production and mitogenic response to PHA. Steady state sera from 20 SCD patients not on penicillin prophylaxis and 20 comparable healthy controls were used in all experiments. Four normal healthy individuals were used as donors for obtaining peripheral blood mononuclear cells (PBMC), by density gradient. PBMC with or without penicillin were PHA stimulated by standard in vitro culture for mitogenic response and cytokine production. Supernatant cytokine levels for interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha and interleukin (IL)2 were quantified by ELISA technique. Results revealed suppression of mitogenic response in the SCD group with or without penicillin, compared to control sera (P < .001). Cytokine production in the SCD sera group showed increased production of IFN-gamma and TNF-alpha in the absence of penicillin, but suppression at all doses of penicillin. The control group results were as follows: no significant difference in IFN-gamma production with or without penicillin, mean TNF-alpha levels were the opposite of SCD sera with lower levels in the absence of penicillin. IL-2 production demonstrated a similar pattern for both groups of sera. IL-2 production was low without penicillin, but there was increased production with penicillin, which appeared dose related. The data suggests that sera from healthy SCD patients and in vitro added penicillin may have a combined suppressive effect on normal lymphocyte in vitro production of IFN-gamma and TNF-alpha. The current study results suggest that penicillin has the beneficial effect of decreasing TNF-alpha production and increasing IL-2 production when combined with SCD steady state sera. However, this in vitro benefit must be weighed against suppression of IFN-gamma production and ultimately, perhaps the long-term utility of penicillin prophylaxis in patients with SCD.

Local levels of interleukin-1beta, -4, -6 and tumor necrosis factor alpha in an experimental model of murine osteomyelitis due to staphylococcus aureus

The purpose of this study is to evaluate local levels of interleukin-1 beta (IL-1 beta), -4 (IL-4), -6 (IL-6), and tumour necrosis factor-alpha (TNF-alpha), in a model of murine osteomyelitis due to Staphylococcus aureus. Cytokine levels in supernatants derived from bone homogenates were determined by enzyme-linked immunosorbent assay, for 28 days following the direct implantation of murine tibiae with S.aureus. Levels of IL-1 beta and IL-6 in infected bone were elevated in the early post-infection period and then decreased. In contrast, TNF-alpha levels remained elevated 3 to 28 days post-infection, while IL-4 levels were elevated late in the course of infection. The histopathology of infected bone showed predominant infiltration of inflammatory cells and bone resorption 3 to 7 days after infection, and bone resorption and adjacent areas of formation 14 to 28 days after infection. These results suggest that the elevated IL-1 beta and IL-6 levels induced by infection may be related to bone damage mainly in the early phase of infection, and that TNF-alpha and IL-4 may at least in part be associated with histopathological changes, including both bone resorption and formation in the later phase of this osteomyelitis model.

Pharmacokinetic-pharmacodynamic modeling of the inhibitory effect of erythromycin on tumour necrosis factor-alpha and interleukin-6 production

Erythromycin inhibits the production of tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL6) induced by heat-killed Streptococcus pneumoniae in human whole blood ex-vivo. The objective of the present study was to determine and characterize the concentration-effect relationship of this phenomenon in order to predict its possible clinical relevance. Six healthy volunteers received a single intravenous dose of 1000 mg erythromycin. Blood samples were obtained up to 4 h after drug administration. Samples were assayed for erythromycin concentrations and (after heat-killed Streptococcus pneumoniae stimulation) for TNF-alpha and IL6 concentrations. Effect vs. time data from individual subjects were fitted to the indirect response model with an Emax concentration-effect relationship. Simulations of these effects were performed for therapeutic intravenous and oral erythromycin dosage regimens. The geometric means of the values of Kin, Kout and EC50 were 15.4 microg/h, 0.82/h, 9.4 mg/L for TNF-alpha and 321 microg/h, 2.02/h, 18.3 mg/L for IL6. Simulations revealed a maximal inhibition of TNF-alpha concentrations of 35%, 50%, 16% and 27% at erythromycin dosages of 500 mg i.v., 1000 mg i.v., 500 mg p.o and 1000 mg p.o. q 6 h, respectively, whereas a maximal inhibition of IL6 of 29%, 44%, 13% and 22% are predicted for the respective regimens. The inhibitory effect of erythromycin on TNF-alpha and IL6 production can be adequately described by the indirect response model with an Emax concentration-effect relationship. Simulations predicted a substantial decrease of production of these cytokines at intravenous and to a much lesser extent at oral erythromycin dosage regimens.

Clarithromycin inhibits NF-kappaB activation in human peripheral blood mononuclear cells and pulmonary epithelial cells

Macrolide antibiotics modulate the production of proinflammatory cytokines in vivo and in vitro. Transcription of the genes for these proinflammatory cytokines is regulated by nuclear factor kappaB (NF-kappaB). We examined whether or not clarithromycin inhibits the activation of NF-kappaB induced by tumor necrosis factor alpha (TNF-alpha) or staphylococcal enterotoxin A (SEA) in human monocytic U-937 cells, a T-cell line (Jurkat), a pulmonary epithelial cell line (A549), and peripheral blood mononuclear cells (PBMC). Flow cytometry revealed that clarithromycin suppresses NF-kappaB activation induced by TNF-alpha in U-937 and Jurkat cells in a concentration-related manner. Western blot analysis also demonstrated that clarithromycin inhibits NF-kappaB activation induced by TNF-alpha in U-937, Jurkat, and A549 cells and PBMC and by SEA in PBMC. Western blot analysis of cytoplasmic extracts of A549 cells revealed that this inhibition is not linked to preservation of expression of the IkappaBalpha protein. The chloramphenicol acetyltransferase assay indicated that NF-kappaB-dependent reporter gene expression is suppressed in U-937 cells pretreated with clarithromycin. These findings are consistent with the idea that clarithromycin suppresses the production of proinflammatory cytokines via inhibition of NF-kappaB activation.

Interference of antibacterial agents with phagocyte functions: immunomodulation or "immuno-fairy tales"?

Professional phagocytes (polymorphonuclear neutrophils and monocytes/macrophages) are a main component of the immune system. These cells are involved in both host defenses and various pathological settings characterized by excessive inflammation. Accordingly, they are key targets for immunomodulatory drugs, among which antibacterial agents are promising candidates. The basic and historical concepts of immunomodulation will first be briefly reviewed. Phagocyte complexity will then be unravelled (at least in terms of what we know about the origin, subsets, ambivalent roles, functional capacities, and transductional pathways of this cell and how to explore them). The core subject of this review will be the many possible interactions between antibacterial agents and phagocytes, classified according to demonstrated or potential clinical relevance (e.g., neutropenia, intracellular accumulation, and modulation of bacterial virulence). A detailed review of direct in vitro effects will be provided for the various antibacterial drug families, followed by a discussion of the clinical relevance of these effects in two particular settings: immune deficiency and inflammatory diseases. The prophylactic and therapeutic use of immunomodulatory antibiotics will be considered before conclusions are drawn about the emerging (optimistic) vision of future therapeutic prospects to deal with largely unknown new diseases and new pathogens by using new agents, new techniques, and a better understanding of the phagocyte in particular and the immune system in general.

Interference of antibacterial agents with phagocyte functions: immunomodulation or "immuno-fairy tales"?

Professional phagocytes (polymorphonuclear neutrophils and monocytes/macrophages) are a main component of the immune system. These cells are involved in both host defenses and various pathological settings characterized by excessive inflammation. Accordingly, they are key targets for immunomodulatory drugs, among which antibacterial agents are promising candidates. The basic and historical concepts of immunomodulation will first be briefly reviewed. Phagocyte complexity will then be unravelled (at least in terms of what we know about the origin, subsets, ambivalent roles, functional capacities, and transductional pathways of this cell and how to explore them). The core subject of this review will be the many possible interactions between antibacterial agents and phagocytes, classified according to demonstrated or potential clinical relevance (e.g., neutropenia, intracellular accumulation, and modulation of bacterial virulence). A detailed review of direct in vitro effects will be provided for the various antibacterial drug families, followed by a discussion of the clinical relevance of these effects in two particular settings: immune deficiency and inflammatory diseases. The prophylactic and therapeutic use of immunomodulatory antibiotics will be considered before conclusions are drawn about the emerging (optimistic) vision of future therapeutic prospects to deal with largely unknown new diseases and new pathogens by using new agents, new techniques, and a better understanding of the phagocyte in particular and the immune system in general.

Proinflammatory effects of IL-10 during human endotoxemia

IL-10 is considered a potent antiinflammatory cytokine that strongly inhibits the production of proinflammatory cytokines. Recent studies have suggested that IL-10 also has immunostimulatory properties on CD4+, CD8+ T cells, and/or NK cells, resulting in increased IFN-gamma production. To determine the effect of IL-10 on IFN-gamma production and related inflammatory responses in humans, 16 healthy subjects received a bolus i.v. injection of LPS (4 ng/kg) in combination with either placebo or recombinant human IL-10 (25 microg/kg), administered just before or 1 h after LPS. IL-10 treatment, particularly when administered after LPS, enhanced LPS-induced IFN-gamma release, as well as the release of the IFN-gamma-dependent chemokines IFN-gamma-inducible protein-10 and monokine induced by IFN-gamma, while inhibiting or not influencing the production of IFN-gamma-inducing cytokines. In addition, IL-10 treatment enhanced activation of CTLs and NK cells after LPS injection, as reflected by increased levels of soluble granzymes. These data indicate that high-dose IL-10 treatment in patients with inflammatory disorders can be associated with undesired proinflammatory effects.

Erythromycin inhibits beta2-integrins (CD11b/CD18) expression, interleukin-8 release and intracellular oxidative metabolism in neutrophils

Macrolides have therapeutic benefits on chronic inflammatory airway diseases. Thus, macrolides are supposed to have variable biological effects apart from antimicrobial activity. Neutrophil adherence and influx with oxidants and cytokines production implicates involvement in airway inflammation. To investigate whether erythromycin (EM) affects neutrophil activity in vitro, lipopolysaccharide (LPS)-treated neutrophils were continuously incubated for 4 h in the absence or presence of increasing doses of EM from 1 microg ml(-1) to 100 microg ml(-1) in the last 2 h. Leukocyte adhesion molecules Mac-1 and intracellular H2O2(DCFH) were determined by flowcytometric assay. IL-8 and TNFalpha in supernatant was measured by ELISA method. The expression of Mac-1 and mean intracellular DCF fluorescence intensity (DCFH) of neutrophils significantly increased after stimulation with LPS. Pretreatment with EM significantly decreased LPS induced Mac-1 expression on neutrophils compared with LPS stimulation only. EM alone (100 microg ml(-1)) also decreased Mac-1 expression on neutrophils. EM significantly reduced the LPS-increased DCFH. EM alone (100 microg ml(-1)) also caused a decrease in DCFH. Increasing doses of EM also significantly decreased the IL-8 released by LPS-stimulated neutrophils. In conclusion, EM exerts a direct effect on the neutrophils by downregulating the expression of beta2-integrin on neutrophils, thus leading to a decrease in the intracellular H2O2, as well as the production of IL-8. Our conclusion provides an explanation for the clinical efficacy of erythromycin in neutrophil-mediated airway inflammation.

Erythromycin inhibits transcriptional activation of NF-kappaB, but not NFAT, through calcineurin-independent signaling in T cells

The molecular mechanism of the anti-inflammatory effect of erythromycin (EM) was investigated at the level of transcriptional regulation of cytokine gene expression in T cells. EM (>10(-6) M) significantly inhibited interleukin-8 (IL-8) expression but not IL-2 expression from T cells induced with 20 ng of phorbol 12-myristate 13-acetate (PMA) per ml plus 2 microM calcium ionophore (P-I). In electrophoretic mobility shift assays EM at 10(-7) to 10(-5) M concentrations inhibited nuclear factor kappa B (NF-kappaB) DNA-binding activities induced by P-I. Reporter gene assays also showed that EM (10(-5) M) inhibited IL-8 NF-kappaB transcription by 37%. The inhibitory effects of EM on transcriptional activation of IL-2 and DNA-binding activity of nuclear factor of activated T cells (NFAT) were not seen in T cells. On the other hand, FK506, which is also a macrolide derivative, inhibited transcriptional activation of both NF-kappaB and NFAT more strongly than EM did. The mechanism of EM inhibition of transactivation of NF-kappaB was further investigated in transiently transfected T cells that express calcineurin A and B subunits. Expression of calcineurin did not render transactivation of NF-kappaB in T cells more resistant to EM, while the inhibitory effect of FK506 on transactivation of NF-kappaB was attenuated. These findings indicate that EM is capable of inhibiting expression of the IL-8 gene in T cells through transcriptional inhibition and that this inhibition is mediated through a non-calcineurin-dependent signaling event in T lymphocytes.

Recent developments in macrolides and ketolides

Emergence of bacterial resistance to macrolide antibiotics, particularly in Gram-positive bacteria, has been observed. Novel macrolides having C-4" carbamate functional groups and ketolides, the 3-keto derivatives of macrolides, have been found to have activities against macrolide-resistant strains. Several potential non-antibacterial activities of macrolides have been reported, such as inhibition of cytokine production, neutrophil attachment to human bronchial epithelial cells and vesicular transport.