The Effect of Exogenous Melatonin or Luzindole on OVA-Induced Inflammatory Cells Infiltration, IgE, and Th2 Cytokines Production
Moreover, upon OVA challenge, melatonin treatment dramatically reduced the total number or composition of the BALF cellularity except for monocytes (Figures 5A–E), lowered the concentration of IgE in serum (Figure 5F), and decreased the productions of IL-4 and IL-13 in BALF (Figures 5G,H) in comparison with those in vehicle-treated WT mice. Interestingly, no significant difference was found between luzindole-treated and vehicle-treated TLR2−/− mice in BALF cellularity or production of IgE and Th2-associated cytokines following OVA challenge (Figures 5A–C,E,F). We only found significant increase in monocytes infiltration in luzindole-treated TLR2−/− mice (Figure 5D). These results demonstrated that melatonin remarkably promoted resolution of allergic airway inflammation by down-regulating TLR2 signaling. However, blocking the effect of melatonin in TLR2−/− mice by luzindole only aggravated allergen-induced mucus hyper-secretion, but had null effect on leukocyte infiltration and Th2 cytokines production.
Figure 5  The effect of exogenous melatonin or luzindole on OVA-induced inflammatory cells infiltration, IgE and Th2 cytokines production. (A–E) Analysis of total and differential cells found in BALF of OVA-challenged WT or TLR2−/− mice after melatonin or luzindole treatment, respectively. (F) The level of OVA-specific IgE in serum. (G,H) The levels of IL-4 and IL-13 in BALF. **p < 0.01, ***p < 0.001.