Ginger extract inhibits LPS induced macrophage activation and function

Abstract

Background: Macrophages play a dual role in host defence. They act as the first line of defence by mounting an inflammatory response to antigen exposure and also act as antigen presenting cells and initiate the adaptive immune response. They are also the primary infiltrating cells at the site of inflammation. Inhibition of macrophage activation is one of the possible approaches towards modulating inflammation. Both conventional and alternative approaches are being studied in this regard. Ginger, an herbal product with broad anti inflammatory actions, is used as an alternative medicine in a number of inflammatory conditions like rheumatic disorders. In the present study we examined the effect of ginger extract on macrophage activation in the presence of LPS stimulation.

Methods: Murine peritoneal macrophages were stimulated by LPS in presence or absence of ginger extract and production of proinflammatory cytokines and chemokines were observed. We also studied the effect of ginger extract on the LPS induced expression of MHC II, B7.1, B7.2 and CD40 molecules. We also studied the antigen presenting function of ginger extract treated macrophages by primary mixed lymphocyte reaction.

Results: We observed that ginger extract inhibited IL-12, TNF-alpha, IL-1beta (pro inflammatory cytokines) and RANTES, MCP-1 (pro inflammatory chemokines) production in LPS stimulated macrophages. Ginger extract also down regulated the expression of B7.1, B7.2 and MHC class II molecules. In addition ginger extract negatively affected the antigen presenting function of macrophages and we observed a significant reduction in T cell proliferation in response to allostimulation, when ginger extract treated macrophages were used as APCs. A significant decrease in IFN-gamma and IL-2 production by T cells in response to allostimulation was also observed.

Conclusion: In conclusion ginger extract inhibits macrophage activation and APC function and indirectly inhibits T cell activation.

Figures

Figure 1

Effect of alcoholic ginger extract on cytokine and chemokine release by LPS stimulated macrophages. Peritoneal macrophages from C57Bl/6 mouse were isolated and stimulated with 100 ng/ml LPS in the absence or presence of ginger extract for 24 h. The cell supernatants were collected and cytokine and chemokine production was determined by ELISA. C- Control, LPS- LPS stimulated, LPS + G- LPS stimulation in the presence of ginger extract. Data represent mean ± S.D (n = 9). * p ≤ 0.05 in comparison to LPS stimulated macrophages. # p ≤ 0.05 in comparison to LPS.

Figure 2

Effect of alcoholic ginger extract on costimulatory molecule expression on murine peritoneal macrophage. Peritoneal macrophages from C57Bl/6 mouse were isolated and stimulated with 100 ng/ml LPS in presence or absence of ginger extract for 24 h. The cells were harvested and stained with fluorophore conjugated mAb against B7.1 (A), B7.2 (B) and CD40 (C) and analyzed in LSR II flow cytometer. Data are representative result of six replicates.

Figure 3

Effect of alcoholic ginger extract on MHC class II molecule expression on murine peritoneal macrophages. Peritoneal macrophages from C57Bl/6 mouse were isolated and stimulated with 100 ng/ml LPS in presence or absence of ginger extract for 24 h. The cells were harvested and stained with fluorophore conjugated mAb against MHC II and analyzed in LSR II flow cytometer. Data are representative result of six replicates.

Figure 4

Effect of alcoholic ginger extract on the antigen presenting function of murine peritoneal macrophages. Peritoneal macrophages were incubated with LPS in the presence or absence of ginger extract for 24 h. These pre-treated macrophages were used as the sole source of APCs along with syngeneic T cells as the responder cells in the presence of allostimulation. T cell proliferation was measured by MTS assay after 72 h. incubation time. Results are presented as proliferation index equating the absorbance value (at 490 nm) of responder cells as 1. Responder cells only – no macrophages, Control- macrophages were not pre-treated, LPS- macrophages pre-treated with LPS only, LPS + G - macrophages pre-treated with LPS and ginger extract. Data represent mean ± S.D (n = 9). * p ≤ 0.05 in comparison to Control. # p ≤ 0.05 in comparison to LPS.

Figure 5

Effect of alcoholic ginger extract on IL-2 (A) and IFN-γ (B) production by T cells in presence of alloantigen stimulation. Peritoneal macrophages were incubated with LPS in the presence or absence of ginger extract for 24 h. These pre-treated macrophages were used as the sole source of APCs along with syngeneic T cells as the responder cells in the presence of allostimulation. IL-2 and IFN-γ production was measured in the culture supernates after 72 h. incubation period. * p ≤ 0.05 in comparison to Control. # p ≤ 0.05 in comparison to LPS.