Glycogen synthase kinase 3 (GSK3) is a critical regulator of allergen-mediated mast cell activation

Abstract Mast cells are granulated immune sentinels responsible for perpetuating allergic inflammatory events. Allergen-induced FcɛRI signaling leads to the activation of MAPK, PLC and PI3K/Akt signaling cascades, which are responsible for mediating a biphasic mast cell response, characterized by degranulation in the early phase and sustained release of pro-inflammatory mediators in the late phase. Glycogen synthase kinase 3 (GSK3) is a constitutively active serine/threonine kinase and a major convergence point for several highly conserved signaling cascades, including the PI3K/Akt pathway. Due to its central role in regulating downstream pro-inflammatory signals, GSK3 has become a therapeutic target in inflammatory pathologies, however, the role that GSK3 plays in allergen-induced FcɛRI signaling has yet to be characterized. Thus, the objective of this study was to determine the functional role of GSK3 in allergen-activated mast cells. Sensitized murine bone marrow-derived mast cells were incubated with the GSK3 inhibitor CHIR99021 and stimulated with allergen. CHIR99021 treatment significantly inhibited degranulation dose-dependently to 63% (10 μM, p<0.001) and 43% (20 μM, p<0.001) of the control. Release of cytokines TNF (p<0.01), IL-6 (p<0.001), IL-13 (p<0.01) and chemokines CCL1 (p<0.001), CCL2 (p<0.05) and CCL3 (p<0.001) were inhibited following treatment at 20 μM. Finally, inhibition of GSK3 was found to significantly reduce downstream phosphorylation of JNK (10 & 20 μM, p<0.05), while ERK and p38 remained unaffected. These results are the first to characterize GSK3 as a central regulator of allergen-induced FcɛRI signaling, making it an intriguing target to attenuate mast cell functionality in pathological contexts.