LAUSR

Mast cell activation through the high‐affinity IgE receptor (FcεRI) plays a central role in allergic reactions. FcεRI‐mediated activation triggers multiple signaling pathways leading to degranulation and synthesis of different inflammatory mediators. IgE‐mediated mast cell activation can be modulated by different molecules, including several drugs. Herein, we investigated the immunomodulatory activity of the histone deacetylase inhibitor valproic acid (VPA) on IgE‐mediated mast cell activation. To this end, bone marrow‐derived mast cells (BMMC) were sensitized with IgE and treated with VPA followed by FcεRI cross‐linking. The results indicated that VPA reduced mast cell IgE‐dependent degranulation and cytokine release. VPA also induced a significant reduction in the cell surface expression of FcεRI and CD117, but not other mast cell surface molecules. Interestingly, VPA treatment inhibited the phosphorylation of PLCγ2, a key signaling molecule involved in IgE‐mediated degranulation and cytokine secretion. However, VPA did not affect the phosphorylation of other key components of the FcεRI signaling pathway, such as Syk, Akt, ERK1/2, or p38. Altogether, our data demonstrate that VPA affects PLCγ2 phosphorylation, which in turn decreases IgE‐mediated mast cell activation. These results suggest that VPA might be a key modulator of allergic reactions and might be a promising therapeutic candidate.