Sulforaphane mitigates mast cell-mediated allergic inflammatory reactions in in silico simulation and in vitro models

Objectives: Sulforaphane, a major ingredient isolated from Brassica oleracea var. italica (broccoli), is known to exhibit anti-inflammatory, anti-cancer, and anti-diabetic effects. In this study, we employed an in vitro model of phorbol 12-myristate 13-acetate and a23187 (PMACI)-stimulated human mast cells (HMC-1 cells) to investigate the anti-allergic inflammatory effects and mechanisms of sulforaphane and Brassica oleracea var. italica extracts. Methods: Cytokine levels were measured by ELISA and quantitative real-time-PCR methods. Caspase-1 activity was determined by caspase-1 assay. Binding mode of sulforaphane within caspase-1 was determined by molecular docking simulation. Protein expression was determined by Western blotting. Results: Water extract of Brassica oleracea var. italica (WE) significantly reduced thymic stromal lymphopoietin (TSLP) secretion and caspase-1 activity on activated HMC-1 cells. In the molecular docking simulation and in vitro caspase-1 assays, sulforaphane regulated caspase-1 activity by docking with the identical binding site of caspase-1. Sulforaphane significantly inhibited the levels of inflammatory mediators including TSLP, tumor necrosis factor (TNF)-alpha, interleukin (IL)-1 beta, IL-6, and IL-8 in a dose-dependent manner. Immunoblotting experiments revealed that sulforaphane and WE reduced translocation of NF-kappa Bp65 into the nucleus and phosphorylation of I kappa B alpha in the cytosol. Furthermore, phosphorylation of mitogen-activated protein kinases (MAPK) was down-regulated by treatment with sulforaphane or WE. Conclusion: Our findings suggest that sulforaphane and WE have anti-allergic inflammatory effects by intercepting caspase-1/NF-kappa B/MAPKs signaling pathways.