Diospyros kaki (D. kaki) has been cultivated throughout Eastern Asia for hundreds of years. D. kaki contains various biological active compounds, such as amino acids, carotenoids, flavonoids, tannins, catechins and vitamin A. Previous studies have shown that D. kaki has beneficial effects on homeostasis, constipation, hypertension, atherosclerosis and allergic dermatitis and is a good source of antioxidants, polyphenols and dietary fiber. However, the anti-allergic and anti-inflammatory effects of D. kaki have not yet been elucidated. This study aimed to investigate the protective effects of the aqueous extract of Diospyros kaki (AEDK) on mast cell-mediated allergic inflammation and to determine its possible mechanisms of action by using in vitro and in vivo mast cell-based models. The cAMP and intracellular calcium levels were measured to clarify the mechanisms by which AEDK inhibits the release of histamine from mast cells. AEDK inhibited the release of histamine and β-hexosaminidase from mast cells by modulating cAMP and intracellular calcium levels. We also measured the expression of pro-inflammatory cytokines, such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β. AEDK decreased gene expression and the secretion of the pro-inflammatory cytokines, TNF-α and IL-1β by inhibiting nuclear factor-κB. In addition, AEDK inhibited systemic and cutaneous allergic reaction. The inhibitory effects of AEDK on allergic reaction and the release of histamine were found to be similar to those of disodium cromoglycate, a known anti-allergic drug. To isolate the active component of AEDK, activity-guided fractionation was performed, based on the inhibitory effects on systemic anaphylaxis. Catechin was identified as an active compound. The present findings provide evidence that AEDK inhibits allergic inflammation and suggest the therapeutic application of AEDK in allergic inflammatory disorders.
Abstract. The aim of the present study was to elucidate whether extracts of Vigna angularis (EVA) inhibit allergic inflammatory reactions and to elucidate the possible mechanisms of action. For the assessment of allergic inflammatory response, histamine release and the expression of pro-inflammatory cytokines from human mast cells (HMC-1) were examined. To identify the underlying mechanisms of action, intracellular calcium and the activation of nuclear factor (NF)-κB and mitogen-activated protein kinases (MAPKs) were assayed. To confirm the effects of EVA in vivo, systemic and local allergic reaction mouse models were employed. EVA dose-dependently reduced phorbol 12-myristate 13-acetate and calcium ionophore A23187 (PMACI)-induced histamine release from mast cells. The inhibitory effects of EVA on the release of histamine from mast cells were mediated by the reduction of intracellular calcium levels. EVA decreased the PMACI-stimulated gene expression and secretion of pro-inflammatory cytokines, such as tumor necrosis factor (TNF)-α and interleukin (IL)-6. The inhibitory effects of EVA on pro-inflammatory cytokines were NF-κB-and MAPK-dependent. In addition, EVA inhibited compound 48/80-induced systemic anaphylaxis and immunoglobulin E (IgE)-mediated cutaneous anaphylaxis. Our findings provide evidence that EVA inhibits mast cell-derived allergic inflammation, and suggest the possible therapeutic application of EVA in allergic inflammatory disorders.
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