Food allergen--induced mast cell degranulation is dependent on PI3K-mediated reactive oxygen species production and upregulation of store-operated calcium channel subunits.

The importance of Ca(2+) influx via store-operated calcium channels (SOCs) leading to mast cell degranulation is well known in allergic disease. However, the underlying mechanisms are not fully understood. With food-allergic rat model, the morphology of degranulated mast cell was analysed by toluidine blue stain and electron microscope. Ca(2+) influx via SOCs was checked by Ca(2+) imaging confocal microscope. Furthermore, the mRNA and protein expression of SOCs subunits were investigated using qPCR and Western blot. We found that ovalbumin (OVA) challenge significantly increased the levels of Th2 cytokines and OVA-specific IgE in allergic animals. Parallel to mast cell activation, the levels of histamine in serum and supernatant of rat peritoneal lavage solution were remarkably increased after OVA treatment. Moreover, the Ca(2+) entry through SOCs evoked by thapsigargin was increased in OVA-challenged group. The mRNA and protein expressions of SOC subunits, stromal interaction molecule 1 (STIM1) and Orail (calcium-release-activated calcium channel protein 1), were dramatically elevated under food-allergic condition. Administration of Ebselen, a scavenger of reactive oxygen species (ROS), significantly attenuated OVA sensitization-induced intracellular Ca(2+) rise and upregulation of SOCs subunit expressions. Intriguingly, pretreatment with PI3K-specific inhibitor (Wortmannin) partially abolished the production of ROS and subsequent elevation of SOCs activity and their subunit expressions. Taken together, these results imply that enhancement of SOC-mediated Ca(2+) influx induces mast cell activation, contributing to the pathogenesis of OVA-stimulated food allergy. PI3K-dependent ROS generation involves in modulating the activity of SOCs by increasing the expressions of their subunit.