Marine brevetoxin induces IgE-independent mast cell activation. - GreenMedInfo Summary

Brevetoxins (PbTx) are sodium channel neurotoxins produced by the marine dinoflagellate Karenia brevis during red tide blooms. Inhalation of PbTx in normal individuals and individuals with pre-existing airways disease results in adverse airway symptoms including bronchoconstriction. In animal models of allergic inflammation, inhalation of PbTx results in a histamine H₁-mediated bronchoconstriction suggestive of mast cell activation. How mast cells would respond directly to PbTx is unknown. We thus explored the activation of mouse bone marrow-derived mast cells (BMMCs) following exposure to purified PbTx-2. Following in vitro exposure to PbTx-2, we examined cellular viability, mast cell degranulation (β-hexosaminidase release), intracellular Ca²+ and Na+ flux, and the production of inflammatory mediators (IL-6). PbTx-2 induced significant cellular toxicity within 24 h as measured by LDH release and Annexin-V staining. However, within 1 h of exposure, PbTx-2 induced BMMC degranulation and an increase in IL-6 mRNA expression independent of the high-affinity IgE receptor (FcεRI) stimulation. Activation of BMMCs by PbTx-2 was associated with altered intracellular Ca²+ and Na+ levels. Brevenal, a naturally produced compound that antagonizes the activity of PbTx, prevented changes in intracellular Na+ levels but did not alter activation of BMMCs by PbTx-2. These findings demonstrate that PbTx-2 activates mast cells independent of FcεRI providing insight into critical events in the pathogenesis and a potential therapeutic target in brevetoxin-induced airway symptoms.