BACKGROUND AND PURPOSEHydrogen sulfide (H 2 S) modulates many pathophysiological processes, including inflammation and allergic reactions, in which mast cells act as major effector cells. IgE receptor (FcεRI) cross linking leads to an increase in intracellular calcium ([Ca +2 ] i ), a critical step in mast cell degranulation. The aim of this study was to investigate the role of H 2 S in [Ca +2 ] i -dependent mast cell activation.
EXPERIMENTAL APPROACHWe investigated the effects of H 2 S, either endogenously produced or released by the slow H 2 S donor 4-carboxy-phenyl isothiocyanate (PhNCS-COOH), on antigenic-and non-antigenic degranulation of native murine mast cells, and human and rat (RBL-2H3) mast cell lines. We measured the release of specific mast cell degranulation markers (β-hexosaminidase and renin), as well as changes in [Ca +2 ] i and phosphorylation of proteins downstream of FcεRI activation.
KEY RESULTSEndogenously produced H 2 S inhibited antigen-induced degranulation in RBL-2H3. Similarly, H 2 S released by PhNCS-COOH (10-300 μM) reduced, in a concentration-dependent manner, antigenic and non-antigenic degranulation and renin release in all mast cell types. Notably, PhNCS-COOH also prevented in a concentration-dependent mode the increase in [Ca +2 ] i elicited by Ca +2 ionophore, thapsigargin and FcεRI activation. Moreover, PhNCS-COOH attenuated the phosphorylation of Syk, cPLA-2 and PLCγ1 in antigen-stimulated RBL-2H3 cells.
CONCLUSION AND IMPLICATIONSCollectively, our results demonstrate that, by attenuating the phosphorylation of proteins downstream of FcεRI cross-linking on mast cells, H 2 S diminishes [Ca +2 ] i availability and thus mast cell degranulation and renin release. These findings suggest that PhNCS-COOH could be a strategic therapeutic tool in mast cell-mediated allergic conditions.
AbbreviationsAng I, angiotensin I; BMMC, bone marrow-derived murine mast cells; [Ca 2+ ] i , intracellular Ca 2+ level; CBS, cystathionine β-synthase; cPLA2, cytosolic phospholipase A2; CSE, cystathionine γ-lyase; DNP, dinitrophenylated-human serum albumin; D-Pen, D-penicillamine; FcεRI, high affinity IgE receptor; HMC-1, human mastocytoma cell line; MEF, mouse embryo fibroblast; PhNCS-COOH, 4-carboxy-phenyl-isothiocyanate; PLCγ1, phospholipase Cγ1; RBL-2H3, rat basophilic leukaemia cell line; β-HEX, β-hexosaminidase