Novel alpha,beta-unsaturated lactones inhibit mast cell activation induced by intracellular calcium increase

VERA ME; MARIANI ML; FOGAL T; PENISSI AB

Congreso; International Mast Cell and Basophil Meeting (MCBM) 2010; 2010

Background: In previous work we have demonstrated that a sesquiterpene lactone isolated from Artemisia douglasiana Besser (dehydroleucodine, DhL), a xanthanolide isolated from Xanthium cavanillesii Schouw (Xt) and a synthetic butenolide (3-benzyloxymethyl-5H-furan-2-one, But), exhibit a strong antiinflammatory activity and prevent gastrointestinal damage elicited by necrosis-inducing agents. The mechanism of action of these drugs remains unclear. The present work was designed to examine the effect of DhL, Xt and But on calcium ionophore A23187-induced mast cell degranulation, with the goal of testing the hypothesis that such molecules act as mast cell stabilizers. Methods: LAD2 and rat peritoneal mast cells were incubated with: 1) Buffer (basal group) or 2) A23187 (mast cell secretagogue) or 3) DhL+A23187 or 4) Xt+A23187 or 5) But+A23187. Mast cell serotonin and â-hexosaminidase release studies, evaluation of mast cell morphology by light microscopy (toluidine blue stain and differential interference contrast), study of mast cell ultrastructure by transmission and scanning electron microscopy, dose-response (10 mM to 1600 mM) and time-response (5 min to 60 min) curves, cell viability evaluation (tripan blue stain), and comparative studies with the reference compounds ketotifen and sodium chromoglycate, were carried out. Results: A23187 increased serotonin and â-hexosaminidase release from LAD2 and rat peritoneal mast cells, and elicited evident granule ultraestructural changes. These effects were inhibited by DhL, Xt and But in a dose- and time- dependent manner. The inhibitory effects exhibited by DhL and Xt were stronger than those of ketotifen and sodium chromoglycate. Conclusions: DhL, Xt and But inhibit calcium ionophore A23187-induced mast cell activation, acting thus as mast cell stabilizers. These lactones seem to block signaling pathways downstream of cytosolic calcium increase. Our findings may provide an insight into the design of novel pharmacological agents which may be used to regulate the mast cell response.