Abstract
<jats:p>ABSTRACT Rationale: Mast degranulation is a driver of several pathologies. Several endogenous peptides have been established as stimulators of mast cell degranulation. Compounds that stabilise mast cells have in part demonstrated inhibitory effect on the inflammatory cascade. Manuka honey has been widely used for the treatments of various inflammatory diseases. However, its effect on A23187 (Calcium ionophore) stimulated mast cell degranulation, cytokine release and cellular signalling pathways has not yet been investigated. Aim of the study: We aim to investigate the effect of Medical Grade Manuka Honey (MGMH) on A23187 induced mast cell degranulation, cytokine release and downstream signalling pathways in a human mast cell lines LAD2 model. Materials and methods: The cytotoxic effect of MGMH on LAD2 cells was assessed using LDH assay. LAD2 cells were pre-incubated with MGMH and challenged with A23187.Mast cell degranulation was measured by β-hexosaminidase release whilst histamine and cytokines released were measured by ELISA. The effect of MGMH on downstream signalling of Mitogen Activated Protein Kinase (MAPK) pathways was determined and quantified by SDS-PAGE western blotting. Results: MGMH at 2% and 4% was well tolerated by LAD2 cells. MGMH at all concentrations tested significantly inhibited the A23187 triggered release of β-hexosaminidase but failed to inhibit the release of histamine. MGMH 4% significantly inhibited the release of GM-CSF and IL-8. MGMH (2% and 4%) significantly down regulated the expression of both ERK I and ERK II. However, MGMH at all the doses tested had no effect on the expressions of JNK and p38. On the contrary, an increase expression of these p38 and JNK were noted with MGMH pre-incubation. Conclusion: Our present study provides evidence that MGMH inhibition of A23187 stimulated degranulation of mast cells and cytokine release through down regulation of ERK I and II signalling. The results suggest potential use as a mast cell stabiliser and effective treatments of mast cell mediated inflammatory diseases. Impact: This study provides the first evidence that Medical Grade Manuka Honey (MGMH) can attenuate A23187-induced mast cell activation and pro-inflammatory cytokine release in human LAD2 mast cells through modulation of ERK1/2 signalling pathways. The findings advance our understanding of the cellular and molecular mechanisms underlying the anti-inflammatory properties of Manuka honey. The demonstration that MGMH inhibits β-hexosaminidase release suggests a mast cell-stabilising effect, highlighting its potential as a novel natural therapeutic agent for mast cell-mediated disorders, including allergic diseases, interstitial cystitis, asthma, chronic inflammatory skin conditions, and mast cell activation syndromes. The observed reduction in GM-CSF and IL-8 production further indicates that MGMH may help limit the amplification and persistence of inflammatory responses. Mechanistically, the selective downregulation of ERK1/2 signalling provides new insight into how MGMH exerts its biological effects and identifies a potential molecular target through which its anti-inflammatory activity is mediated. These findings contribute to the growing evidence base supporting the therapeutic value of Manuka honey beyond its established antimicrobial and wound-healing properties. Overall, this work lays the foundation for future preclinical and clinical studies investigating MGMH as a safe, naturally derived mast cell stabiliser and anti-inflammatory intervention, with potential applications across a broad spectrum of allergic and inflammatory diseases.</jats:p>