Honey as an immunomodulator during sepsis in animal model

Introduction

Malaysian honey (Gelam) has antibacterial activity and it also has a high antioxidant capacity and free radical scavenger activities. Honey extracts showed potent activity against TNFα in L929 cell and NO in RAW 264.7 macrophage as well as inhibitory effects on the prostaglandin E₂ and nitric oxide (NO) in inflammatory tissues of rat. Sepsis is mediated in part by bacterial endotoxin, which stimulates macrophages/monocytes to sequentially release early (for example, TNF, IL-1) cytokines and inducible enzymes such as inducible nitric oxide (iNOS) synthase and heme oxygenase 1 (HO-1) and late such as high-mobility group box 1 (HMGB1).

Objective

To investigate the role of honey as an immunomodulator in sepsis induced by LPS in rats.

Methods

Four groups (n = 6) of rats were used. The treatment group received honey with LPS, the positive control group were given LPS (5 mg/kg), the negative control group were given saline only, while the fourth group were only given honey; all doses were 1 ml by intravenous route. Blood samples were collected 4 hours later and all rats were sacrificed after 24 hours. TNFα, IL-1β, IL-6, IL-10, NO, HO-1 and HMGB1 were quantified using ELISA. The effect of honey on coagulation (PT and APPT) in whole blood ex vivo from healthy volunteers (n = 10) was measured.

Results

After 4 hours of treatment, the cytokines, NO and HO-1 were measured in all groups. Honey showed evidence of immuno-modulatory effects with reduced cytokines (TNFα (P < 0.001), IL-1β (P < 0.001), IL-10 (P < 0.001)) and NO (P < 0.037) in the treatment group, while the change in IL-6 was not significant between all groups, HO-1 (P < 0.001) was increased in the treatment group, but only slightly increased in the honey group. After 24 hours of treatment, HMGB1 (P < 0.025) and IL-1β (P < 0.001) were reduced in the treatment group as well. HO-1 (P < 0.013) continuously increased in all groups. Curiously, honey alone induced TNFα (P < 0.001) and IL-1β (P < 0.03) at 4 hours, and HO-1 (P < 0.028) at 24 hours compared with saline. Honey prolonged the time of PT and APPT in a dose-dependent manner.

Conclusion

Honey behaves as immunomodulator by acting in two ways, by inducing HO-1, TNFα, and IL-1β and at the same time inhibiting cytokines, NO and HMGB1 that is induced by LPS. However, the exact mechanism remain unclear, but our suggestion is that since honey induces HO-1, TNFα and IL-1β this may cause changes or inhibition in the signaling of cytokines and NF-κB. Honey could therefore be used as a pharmacological tool in sepsis in the future.