5-Bromo-3,4-dihydroxybenzaldehyde from Polysiphonia morrowii attenuate IgE/BSA-stimulated mast cell activation and passive cutaneous anaphylaxis in mice.

Abstract The present study investigates the anti-allergic activity of the marine algal bromophenol, 3-bromo-4,5-dihydroxybenzaldehyde (BDB), isolated from Polysiphonia morrowii Harvey in immunoglobulin (Ig)E/bovine serum albumin (BSA)-stimulated mouse bone marrow-derived cultured mast cells (BMCMCs) and a passive cutaneous anaphylaxis (PCA) mice ear model. BDB effectively inhibited β-hexosaminidase release (IC50 = 80.12 µM), in IgE/BSA-stimulated BMCMCs without a cytotoxic response. Also, BDB down-regulated the expression or secretion of cytokines, interleukin (IL)-1β, IL-4, IL-5, IL-6, IL-10, IL-13, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α and the chemokine (thymus and activation-regulated chemokine (TARC). The above effects could be attributed to the dose-dependent decrease of FceRI expression on the surface of BMCMCs and its stable IgE binding. Moreover, BDB suppressed the NFκB and the signaling axis, spleen tyrosine kinase (SYK)- linker for T-cell activation (LAT)- GRB2 associated binding protein 2 (Gab2) activated by IgE/BSA stimulation. Furthermore, oral administration of BDB to IgE-sensitized mice effectively attenuated IgE-triggered PCA reaction. Collectively, the anti-allergic effects of BDB suggest its potential applicability as a candidate for in-depth test trials.