In vitro study of the effect of medical-grade Manuka honey on the viability and integrity of the urinary bladder urothelium: A potential intravesical treatment for interstitial cystitis/bladder pain syndrome

Abstract

Introduction: Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic inflammatory debilitating bladder disease characterized by urgency, frequency, nocturia and pain. Its aetiology is not fully understood, but it may involve a “vicious circle” of urothelial dysfunction, inflammation, peripheral and central sensitization. A defective urothelium allows harmful urine to penetrate the bladder wall inducing nerve depolarisation, mast cell degranulation and tissue inflammation. Such is associated with increased levels of pro-inflammatory cytokines and chemokines, such as TNF-α, both in the bladder tissue and urine. These cytokines reduce urothelial viability and integrity, inducing further inflammatory cytokines from the urothelial cells.
Honey has been shown to promote healing in chronic wounds, where it has been used topically as a poultice for wounds. Manuka honey (Leptospermum scoparium) is among the most potent and is the type incorporated into medical honey preparations and devices (e.g. Activon, Medihoney). Recent reports have supported the therapeutic effects of honey on wound healing, i.e. it reduces inflammation, promotes angiogenesis and combats infection “the triple effect”.
Methodology: In the current studies, the effects of Medihoney on the viability of primary human urothelial cells at various dilutions and time points were investigated using a viability MTT assay. In addition, an experimental model of IC/BPS was established using primary human urothelial cells, human fibroblasts and LAD2 human mast cells in a co-culture model. In such model, cystitis was induced by TNF-α, as indicated by enhanced urothelial cytotoxicity, pro-inflammatory cytokine release (assessed by ELISA) and disruption of the urothelial integrity (assessed by TEER). Finally, human phospho-kinase array kits (R&D systems) were used to study the associated intracellular signalling events.
Results: 2 and 4% MH were well tolerated by the primary human urothelial cells (HUCs). In the co-culture model system, both TNF-α and the C48/80- activated LAD2 mast cells induced significant decrease in the urothelial viability, TEER values indicating severe disruption of the urothelial integrity, which was accompanied by increased supernatant levels of zona-occludens-1 (ZO-1) and the pro-inflammatory cytokines IL-8 and IL-6. Interestingly, all of these events were completely blocked upon pre-incubation with 4% Medihoney. Nevertheless, Medihoney altered (inhibited)
TNF-α induced phosphorylation of key regulatory mitogen activated protein kinases, such as Akt 1/2/3 and Chk-2 but down-regulated the phosphorylation of the protein kinase Hsp27, suggesting that TNF-α induces pro-inflammatory responses from the urothelial cells, besides its cytotoxic effects. Results from a whole rat bladder model indicated that up to 10% MH is well tolerated by the whole rat bladder tissue with very minimal cytotoxicity on bladder urothelial cells.
Conclusion: These results have established a novel in vitro model to assess the efficacy of various therapeutic agent for treatment of inflammatory bladder conditions including IC/BPS. Our results suggest that Medihoney might be useful as an additional intravesical agent for the management of IC/BPS.

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Identifiers

ORCID for Muhammadbakhoree Yusuh: orcid.org/0000-0002-6608-4919

ORCID for Bashir Lwaleed: orcid.org/0000-0001-5748-4892

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