Modulation of Th2 type cytokine production from human peripheral blood leukocytes by a macrolide antibiotic, roxithromycin, in vitro

Abstract

The influence of a macrolide antibiotic, roxithromycin (RXM), on Th1 and Th2 cytokine productions from human peripheral blood T cells was examined under stimulation with co-stimulatory molecules. Peripheral blood T cells prepared from both healthy and allergic rhinitis donors were cultured in the presence of RXM on anti-CD3 mAb and anti-CD26 mAb-coated wells, anti-CD3 mAb and anti-CD28 mAb-coated wells, and anti-CD3 and PMA. T-cell proliferation, along with the concentration of interleukin (IL)-2, interferon (IFN)-γ, IL-4 and IL-5 were measured. RXM did not affect T-cell proliferation induced by several ways of co-stimulatory activation as assessed by ³H-thymidine incorporation into DNA. RXM also had no effect on IL-2 and IFN-γ secretion by T cells prepared from both healthy and allergic rhinitis donors. On the other hand, RXM markedly inhibited both IL-4 and IL-5 secretions under each of the co-stimulatory conditions in a dose-dependent manner. These results indicate that RXM inhibits specifically Th2 cytokine secretion from T cells induced by co-stimulatory molecule stimulations. This inhibitory action of RXM may be partially responsible for attenuating effect of the agent on the inflammatory diseases.

Introduction

Systemic administration of macrolide antibiotics (e.g. erythromycin and troleandromycin, etc.) have been shown to be effective in the treatment of lower and upper airway inflammatory diseases such as bronchial asthma, chronic sinusitis and diffuse panbronchiolitis [1], [2], [3]. It is also reported that topical application of erythromycin, the most famous macrolide antibiotic, favorably modify the clinical condition of inflammatory dermatoses including acne and rosacea [4], [5]. Although these inflammatory diseases has been reported to be successfully treated with low-dose administration of antibiotics, which cannot be expected to act as antibacterial agents [6], the precise mechanisms of this therapy are not well understood. In vitro studies clearly showed that macrolide antibiotics strongly inhibit chemotaxis and generation of inflammatory mediators (O₂⁻ and H₂O₂, etc.) by polymorphonuclear leukocytes when the cells were cultured in the presence of macrolides [4], [5], [7], [8]. Our previous works showed the suppressive effects of roxithromycin (RXM) on macrophage functions to produce pro-inflammatory cytokines, interleukin (IL)-1 and tumor necrosis factor (TNF)-α, in response to lipopolysaccharide (LPS) stimulation, when human peripheral blood monocytes were cultured in the presence of RXM [9], [10], [11]. This inhibitory action of RXM on macrophage cytokine production was also observed in vivo: treatment of mice with 2.5 mg/kg RXM for 7 weeks markedly suppressed the appearance of IL-1β and TNF-α in aqueous lung extract induced by intra-tracheal instillation of LPS [9], [10]. Judging from these reports, it is reasonable to speculate that systemic and topical administration of macrolide antibiotics suppresses the inflammatory responses through inhibition of inflammatory mediator productions and results in favorable modification in clinical status of inflammatory diseases.

It is well recognized that local eosinophilia, mast cell replenishment and IgE production are orchestrated in the site of inflammatory diseases [12], [13]. These immune responses are now known to be mediated by T helper (Th) cells and their products, so-called cytokines[12], [13]. When Th cells encounter antigens presented by antigen-presenting cells, they were activated and differentiate into two functionally distinct subsets, Th1 and Th2 [14], [15]. Th1 cells secrete IL-2, interferon (IFN)-γ, and TNF-β and are efficient in eliminating intracellular pathogens via macrophage activation [14], [15]. Th2 cells secrete IL-4, IL-5, IL-10 and IL-13, which effect humoral immunity and are responsible for immune responses to persistent antigens [14], [15]. It is also recognized that these two Th cell subsets cross-regulate each other, so the balance between Th1 and Th2 cytokines can determine whether the immune response is appropriate or will terminate in detrimental immunopathologies [14], [15], [16]. Overproduction of Th1 cytokines has been implicated in delayed type hypersensitivities and autoimmune diseases [14], [15], [16], whereas dysregulation of Th2 cytokines can lead to immediate type hypersensitive reactions such as allergic and inflammatory conditions [14], [15], [16]. These reports may suggest that understanding the faculty of RXM to regulate cytokine production from Th cells is critical for elucidating the mechanisms of the macrolide therapy.

In induction of immediate type hypersensitive reactions, allergens would be engaged by the T cell receptor (TCR), followed by allergic cytokine release [17]. However, this process is not sufficient for induction of full activation of T cells, which is characterized by proliferation and cytokine production [17]. Co-stimulatory signals through the CD28/B7 receptor/ligand system are essential in addition to activation via TCR [17], [18]. In the present study, therefore, we examined the influence of a macrolide antibiotic on cytokine production from human Th cells using RXM and several ways of co-stimulatory activation.