Malaysian Tualang honey and its immunomodulatory properties

• Main Author: Chua, Chong Kuan
• Published: University of Nottingham 2017
• Subjects: QR180 Immunology
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.728485

Discoveries of antibiotic resistant pathogens and failure in some conventional modern cancer treatments have led to the re-evaluation of ancient therapeutic remedies such as honey. In recent years, Malaysian Tualang honey (MTH) had been proven scientifically to possess many beneficial properties such as antimicrobial, antioxidant, anticancer, anti-inflammatory and wound healing potential. However, little scientific evidence about its immunomodulatory property has been published, therefore this study aimed to investigate the immunomodulatory effect of MTH. Initially, human monocytic cell lines (THP-1 and U-937) were first cultured and tested against MTH as part of methodology optimization before proceeding to peripheral blood mononuclear cells (PBMCs) isolated from healthy donors. PBMCs were used in this study because these cells can mimic the in vivo system of immune responses more closely. The cytotoxic effect of MTH on THP-1, U-937 and PBMCs was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5,diphenyltetrazolim bromide (MTT) assay. It was found that the combination of 0.125 % to 2 % MTH and incubation durations 16, 24 and 48 hours yielded at least 90 % cell viability in PBMCs (except 2 % MTH for 48 hours of incubation). Hence, 0.125 % MTH was selected to treat the PBMCs in subsequent experiments. Using microarray approach, the gene expression profile in MTH-treated PBMCs were studied and it was found that 361 genes were significantly regulated by at least two fold changes (p < 0.05). Among these genes, the expression of immunorelated genes such as IFNG, IL10, IL20, IL24, CXCL1, CXCL3, CXCL9, IL2 and IL4 were validated using reverse transcription quantitative real time polymerase chain reaction (RT-qPCR). Functionally, these genes play crucial role in wound healing by facilitating the recruitment of leukocytes to sites of infection, supporting the wound healing activity in honey. Using flow cytometry, the immunomodulatory effect of MTH in activating PBMCs subpopulations was also determined using cell surface marker cluster of differentiation (CD) 69. It was found that MTH did not possessed any immunosuppressive effect in regulating cell activation in helper T cells (CD3+ CD4+), cytotoxic T cells (CD3+ CD4-) and B cells (CD3- CD19+). The production of interferon gamma (IFN-γ) and interleukin (IL)-10 from mitogen-stimulated and non-stimulated PBMCs after MTH treatment were also quantified using enzyme-linked immunosorbent assay (ELISA). IL-10 (immunoregulatory cytokine) and IFN-γ (pro-inflammatory cytokine) production were found elevated significantly (p < 0.05). These results suggested that MTH involved in early immunoregulation and late pro-inflammatory responses, supporting the antimicrobial activity of honey. This is the first study ever conducted to investigate the gene expression profile in PBMCs treated with MTH. Overall, present findings showed that MTH possessed immunomodulatory effect by regulating the expression of immune related genes, leading to significant increase in the production of type 1 cytokine (IFN-γ) and type 2 cytokine (IL-10) in PBMCs. This suggested that MTH possessed immunomodulatory effect that can potentially contribute to the antimicrobial and wound healing activities in honey. These findings can further justify the application of MTH as topical dressing especially in wound management potentially by eliminating wound infection as well as promoting wound healing process.