Effect of polysaccharides from a Korean ginseng berry on the immunosenescence of aged mice

Abstract

Background: Korean ginseng has been widely evaluated to treat human diseases; however, most studies on Korean ginseng have focused on its root. In this study, polysaccharides [acidic-polysaccharide-linked glycopeptide (APGP) extracted with 90% ethanol and hot water] were prepared from Korean ginseng berries, and their effect on immunosenescence was explored.

Methods: The effect of APGP on thymic involution was evaluated by measuring the size of thymi dissected from aged mice. The effect of APGP on populations of immune cells, including natural killer (NK) cells, dendritic cells, age-correlated CD11c-positive B cells, and several subtypes of T cells [CD4-positive, CD8-positive, and regulatory (Treg) T cells] in the thymi and spleens of aged mice was analyzed by fluorescence-activated cell sorting analysis. Serum levels of interleukin (IL)-2 and IL-6 were evaluated by enzyme-linked immunosorbent assay analysis. Profiles of APGP components were evaluated by high-performance liquid chromatography (HPLC) analysis.

Results: APGP suppressed thymic involution by increasing the weight and areas of thymi in aged mice. APGP increased the population of NK cells, but showed no effect on the population of dendritic cells in the thymi and spleens of aged mice. APGP decreased the population of age-correlated CD11c-positive B cells in the spleens of aged mice. APGP showed no effect on the populations of CD4- and CD8-positive T cells in the thymi of aged mice, whereas it increased the population of Treg cells in the spleens of aged mice. APGP further decreased the reduced serum levels of IL-2 in aged mice, but serum levels of IL-6 were not statistically changed by APGP in aged mice. Finally, HPLC analysis showed that APGP had one major peak at 15 min (a main type of polysaccharide) and a long tail up to 35 min (a mixture of a variety of types of polysaccharides).

Conclusion: These results suggested that APGP exerted an anti-immunosenescent effect by suppressing thymic involution and modulating several types of immune cells.

Keywords: APGP; NK cell; Treg cell; ginseng berry; immunosenescence.

Fig. 1

Effect of APGP on thymic involution in aged mice. (A) Thymi were dissected from old (17 mo) and young (2 mo) mice administered either APGP or PSK, and photographs were taken with a digital camera. (B) The area of each dissected thymus was measured by a ruler. (C) The weight of each dissected thymus was measured by an electronic scale. Data are presented as the means ± SD of one biological experiment performed with six technical replicates (n = 6). *p < 0.05, **p < 0.01 compared to a control group. APGP, acidic-polysaccharide-linked glycopeptide; PSK, polysaccharide-K; SD, standard deviation.

Fig. 2

Effect of APGP on the populations of NK cells and dendritic cells in aged mice. (A) Total thymic and splenic cells (5 × 10⁶ cells/mL) isolated from old and young mice administered the indicated compounds were analyzed by flow cytometry using antibodies specific for NK1.1 (a marker of NK cells) and CD11c (a marker of dendritic cells). The NK cell population in (B, left panel) total splenic cells and (B, right panel) total thymic cells was measured and plotted. The dendritic cell population in (C, left panel) total splenic cells and (C, right panel) total thymic cells was measured and plotted. Data are presented as the means ± SD of one biological experiment performed with six technical replicates (n = 6). *p < 0.05, **p < 0.01 compared to a control group. APGP, acidic-polysaccharide-linked glycopeptide; NK, nakural killer; PSK, polysaccharide-K; SD, standard deviation.

Fig. 3

Effect of APGP on age-correlated CD11c-positive B cells and on T cell subpopulations in aged mice. (A) Total splenic cells (5 × 10⁶ cells/mL) isolated from old and young mice administered the indicated doses of compounds were analyzed by flow cytometry using antibodies specific for CD11c and B220, a marker of B cells. (B) The population of age-correlated CD11c-positive B cells in total splenic cells was measured and plotted. (C) Total thymic cells (5 × 10⁶ cells/mL) isolated from old and young mice administered the indicated compounds were analyzed by flow cytometry using antibodies specific for CD4, a marker of helper T cells, and CD8, a marker of cytotoxic T cells. The populations of (C, left panel) CD4-positive helper T cells and (C, right panel) CD8-positive cytotoxic T cells in total thymic cells were measured and plotted. (D) Total splenic cells (5 × 10⁶ cells/mL) isolated from old and young mice administered the indicated compounds were analyzed by flow cytometry using antibodies specific for Foxp3 and CD25, markers of activated Treg cells. (E) The populations of Foxp3-positive Treg cells and activated double-positive (Foxp3 and CD25) Treg cells in total splenic cells were measured and plotted. Data are presented as the means ± SD of one biological experiment performed with six technical replicates (n = 6). *p < 0.05, **p < 0.01 compared to a control group. APGP, acidic-polysaccharide-linked glycopeptide; NK, natural killer; PSK, polysaccharide-K; SD, standard deviation; Treg, regulatory T cells.

Fig. 3

Effect of APGP on age-correlated CD11c-positive B cells and on T cell subpopulations in aged mice. (A) Total splenic cells (5 × 10⁶ cells/mL) isolated from old and young mice administered the indicated doses of compounds were analyzed by flow cytometry using antibodies specific for CD11c and B220, a marker of B cells. (B) The population of age-correlated CD11c-positive B cells in total splenic cells was measured and plotted. (C) Total thymic cells (5 × 10⁶ cells/mL) isolated from old and young mice administered the indicated compounds were analyzed by flow cytometry using antibodies specific for CD4, a marker of helper T cells, and CD8, a marker of cytotoxic T cells. The populations of (C, left panel) CD4-positive helper T cells and (C, right panel) CD8-positive cytotoxic T cells in total thymic cells were measured and plotted. (D) Total splenic cells (5 × 10⁶ cells/mL) isolated from old and young mice administered the indicated compounds were analyzed by flow cytometry using antibodies specific for Foxp3 and CD25, markers of activated Treg cells. (E) The populations of Foxp3-positive Treg cells and activated double-positive (Foxp3 and CD25) Treg cells in total splenic cells were measured and plotted. Data are presented as the means ± SD of one biological experiment performed with six technical replicates (n = 6). *p < 0.05, **p < 0.01 compared to a control group. APGP, acidic-polysaccharide-linked glycopeptide; NK, natural killer; PSK, polysaccharide-K; SD, standard deviation; Treg, regulatory T cells.

Fig. 4

Effect of APGP on the serum levels of IL-2 and IL-6 in aged mice. Sera were obtained from the blood of old and young mice administered the indicated compounds, and serum levels of IL-2 and IL-6 in these mice were determined by ELISA. (A) IL-2. (B) IL-6. Data are presented as the means ± SD of one biological experiment performed with six technical replicates (n = 6). *p < 0.05, **p < 0.01 compared to a control group. APGP, acidic-polysaccharide-linked glycopeptide; ELISA, enzyme-linked immunosorbent assay; IL, interleukin PSK, polysaccharide-K; SD, standard deviation.

Fig. 5

HPLC chromatogram of APGP extracted from Korean ginseng berries. HPLC analysis showed that APGP had one major peak at 15 min (a main type of polysaccharide) and a long tail up to 35 min (a mixture of a variety of types of polysaccharides). HPLC, high-performance liquid chromatography.

Fig. 6

Schematic description of the regulatory roles of APGP extracted from Korean ginseng berries on immunosenescence in aged mice. APGP was associated with recovery of thymic involution and also increased the reduced population of thymic and splenic NK cells in aged mice, and reduced the increased population of age-correlated splenic CD11c-positive B cells in aged mice. In addition, APGP restored the population of functionally activated splenic Treg cells in aged mice. APGP, acidic-polysaccharide-linked glycopeptide; NK, natural killer; Treg, regulatory T cells.