Effect of roxithromycin on eotaxin-primed reactive oxygen species from eosinophils

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.

Infections and asthma

A new paradigm is developing in regard to the interaction between infection and asthma. This paradigm comprises the acute exacerbations seen in asthma and also asthma chronicity. Viral infections have been commonly evaluated in acute exacerbations, but findings suggest viral-allergen and viral-bacterial interactions are important for chronicity. Most recently, studies are also invoking atypical bacterial infections, Mycoplasma pneumoniae and Chlamydia pneumoniae, as factors in both acute exacerbation and chronic asthma.

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

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

Antibiotics in asthma

Asthma pathogenesis appears to be a result of a complex mixture of genetic and environmental influences. There is evidence that Mycoplasma pneumoniae and Chlamydia pneumoniae play a role in promoting airway inflammation that could contribute to the onset and clinical course of asthma. If antimicrobial therapy can eradicate these organisms, it might be possible to alter the course of the disease. Although antibiotics have no role in the routine management of acute exacerbations of asthma, certain macrolide antibiotics have been shown to have anti-inflammatory activity. Part of this effect is due to their known inhibition of steroid and theophylline metabolism, but through a myriad of mechanisms that are incompletely understood, macrolide antibiotics have additional broad anti-inflammatory properties that might prove useful in the management of asthma and other inflammatory diseases.

Inhibitory effects of ketotifen on eotaxin-dependent activation of eosinophils: consequences for allergic eye diseases

BACKGROUND

The aim of this study was to investigate the effects of ketotifen on different parameters of human eosinophil functions, namely chemotaxis, oxidative metabolism and mediator release, induced after activation.

METHODS

Eosinophils from hypereosinophilic patients or normal donors were purified by Percoll gradient and the magnetic cell separation system. Chemotaxis was studied using the Boyden chamber technique using three potent chemoattractants: formyl-methionine-leucine-phenylalanine (fMLP), interleukin (IL)-5 and eotaxin. Oxidative metabolism was determined by a luminol-dependent chemiluminescence assay after activation with eotaxin or secretory immunoglobulin A (sIgA). The release of eosinophil cationic protein (ECP) and eosinophil derived neurotoxin (EDN) was measured by radioimmunoassay after activation with sIgA.

RESULTS

At pharmacologically active concentrations and in a dose-dependent manner, ketotifen significantly inhibited the chemotaxis of eosinophils to fMLP, IL-5 and eotaxin. The production of reactive oxygen species induced by eotaxin and sIgA was decreased by ketotifen, showing a more pronounced effect when cells were activated by eotaxin. Activation by sIgA resulted in ECP and EDN release, which was partially inhibited by ketotifen.

CONCLUSIONS

Through inhibition of chemotaxis, ketotifen might limit the number of eosinophils at the inflammation site during allergic reaction. Furthermore, inhibition by ketotifen of main inflammatory mediators release suggests a potential role of the drug in limiting the pathological potential of eosinophils.