Hong-Gu Joo

Expression and immunohistochemical localization of galectin-3 in various mouse tissues

The expression and immunohistochemical localization of galectin‐3, a β‐galactoside‐binding protein, was studied in several mouse tissues. Galectin‐3 expression was low in the cerebrum, heart, and pancreas, and moderate in the liver, ileum, kidney, and adrenal gland. High expression of galectin‐3 was found in the lung, spleen, stomach, colon, uterus, and ovary. The results of Western blot analysis largely matched the immunohistochemical findings for galectin‐3. These findings suggest that galectin‐3 is differentially expressed in a variety of organs in the mouse. This study provides valuable information for research on galectin‐3.

Radioprotective effects of an acidic polysaccharide of Panax ginseng on bone marrow cells

An acidic polysaccharide of Panax ginseng (APG), so called ginsan is known to have important immunomodulatory activities. It was recently reported that APG has radioprotective effects in mice but the detailed mechanism was not fully elucidated. This study examined the effects of APG on bone marrow cells (BMs). The phenotypical and functional changes in APG-treated BMs after gamma radiation were studied. The benefit of APG on BMs damaged by gamma radiation was determined by measuring the cell viability. Using 2 different assays, a pretreatment with APG significantly increased the viability of BMs against gamma radiation. APG-treated BMs had a significantly higher amount of IL-12, which is a major cytokine for immune responses, compared with the medium-treated BMs. The expression of MHC class II molecules of APG-treated BMs was also increased, and APG-treated BMs showed significantly higher levels of allogeneic CD4+ T lymphocyte proliferation. Furthermore, APG-treated mice had a larger number of BMs after gamma radiation than the control mice, and the BMs of APG-treated mice were successfully cultured into dendritic cells, which are the representative antigen-presenting cells. Overall, this study shows that APG alters the phenotype of BMs, increases the viability and alloreactivity of BMs after gamma radiation both in vitro and in vivo. Therefore, APG may be a good candidate radioprotective agent for BMs.

Immunomodulatory Activity of Ginsan, a Polysaccharide of Panax Ginseng, on Dendritic Cells

Ginsan, a Panax ginseng polysaccharide that contains glucopyranoside and fructofuranoside, has immunomodulatory effects. Although several biologic studies of ginsan have been performed, its effects on dendritic cells (DCs), which are antigen-presenting cells of the immune system, have not been studied. We investigated the immunomodulatory effects of ginsan on DCs. Ginsan had little effect on DC viability, even when used at high concentrations. Ginsan markedly increased the levels of production by DCs of IL-12 and TNF-alpha, as measured by ELISA. To examine the maturation-inducing activity of ginsan, we measured the surface expression levels of the maturation markers MHC class II and CD86 (B7.2) on DCs. It is interesting that ginsan profoundly enhanced the expression of CD86 on DC surfaces, whereas it increased that of MHC class II only marginally. In (3)H-thymidine incorporation assays, ginsan-treated DCs stimulated significantly higher proliferation of allogeneic CD4(+) T lymphocytes than did medium-treated DCs. Taken together, our data demonstrate that ginsan stimulates DCs by inducing maturation. Because DCs are critical antigen-presenting cells in immune responses, this study provides valuable information on the activities of ginsan.

Cytoprotective effects of fucoidan, an algae-derived polysaccharide on 5-fluorouracil-treated dendritic cells

Although chemotherapeutic anticancer agents are effective, they also attack normal immune cells due to a lack of selectivity. 5-Fluorouracil (5-FU) is a representative anticancer agent that induces immunosuppression in cancer patients as a side effect. Fucoidan is an algae-derived sulfated polysaccharide that has recently been recognized as a hematopoietic mobilizer and immunomodulator. In this study, we investigated the cytoprotective effect of fucoidan on dendritic cells (DCs) against 5-FU-induced cellular damage. Several kinds of assays including flow cytometric analysis demonstrated the cytoprotective efficacy of fucoidan. In addition, fucoidan increased the expression of immune-related surface markers on and the alloproliferative capacity of DCs exposed to 5-FU. For investigating action mechanism, the expression levels of apoptosis-related molecules were measured. Taken together, the results of this study suggest that fucoidan, a marine-derived polysaccharide, has cytoprotective effects on DCs, the most potent antigen-presenting cell type, against 5-FU-induced cellular damage. These results provide valuable information to use fucoidan as an immunostimulatory agent for the chemotherapy of cancer patients.

Radioprotective effects of fucoidan on bone marrow cells: improvement of the cell survival and immunoreactivity.

Fucoidan is a sulfated polysaccharide purified from brown algae including Fucus vesiculosus and has a variety of biological effects including mobilization of hematopoietic progenitor cells. Recently, we demonstrated that fucoidan stimulates the antigen-presenting functions of dendritic cells. In this study, we investigated the radioprotective effects of fucoidan on bone marrow cells (BMCs), which are the main cellular reservoir for the hematopoietic and immune system. To evaluate the effects of fucoidan, we assayed cell viability and immune responses. In a viability assay, fucoidan significantly increased the viability of BMCs. Based on the results of flow cytometric analysis, the increased viability of fucoidan-treated BMCs was attributed to the inhibition of radiation-induced apoptosis. Furthermore, fucoidan altered the production of immune-related cytokines from BMCs and increased the capability of BMCs to induce proliferation of allogeneic splenocytes. Taken together, our study demonstrated that fucoidan has radioprotective effects on BMCs with respect to cell viability and immunoreactivity. These results may provide valuable information, useful in the field of radiotherapy.

Immunohistochemical localization of galectin-3 in the reproductive organs of the cow.

The protein levels and immunohistochemical localization of galectin-3, which is a beta-galactoside-binding protein, were studied in the cow reproductive organs. Using Western blot analysis, galectin-3 was detected at low levels in the ovary and oviduct, at moderate levels in the uterus, and at high levels in the cervix. Using immunohistochemistry, galectin-3 was immunolocalized in macrophages in the interstitium, in cells in the atretic follicles, and in luteal cells in the regressing corpus luteum, but not in the growing follicles in the ovary. In the oviduct, galectin-3 was detected in some macrophages in the lamina propria, submucosa and muscle layers, as well as in some cells in the covering epithelium. In the uterus, galectin-3 was immunolocalized in some epithelial cells and in some macrophages in the submucosa, but not in the endometrial glands at the non-pregnant stage. In the cervix, galectin-3 was immunolocalized in many mucus-secreting cells in the mucosa and in a few macrophages in the submucosa and muscle layers. Based on its localization, we postulate that galectin-3 in the covering epithelium is involved in the mucosal defense system, and that galectin-3-positive macrophages in all tissues are involved in either cell survival or death. In addition, galectin-3 plays an important role in the regression of follicles and the corpus luteum.

Differential effects of fucoidans with low and high molecular weight on the viability and function of spleen cells

Fucoidan is an edible sulfated polysaccharide purified from brown algae that has multiple biological activities. However, the effects of fucoidans of different molecular weights on immune cells have not been determined. Thus, we treated spleen cells with low- and high-molecular-weight fucoidans (LMF and HMF, respectively). Viability assays demonstrated that HMF enhanced the viability and prevented the death of spleen cells. Furthermore, functional analysis revealed that HMF significantly increased the production of interferon-γ and nitric oxide. In contrast, LMF had low activity and was relatively toxic to spleen cells. Taken together, these results indicate that HMF makes the greatest contribution to the immunostimulatory activity of fucoidan mixtures. Additionally, fucoidans with different molecular weights may have different effects on the viability and function of immune cells. This study increases our understanding of fucoidans, and may broaden their use in the basic research and clinical fields.

Galectin-3 expression is correlated with abnormal prion protein accumulation in murine scrapie.

To investigate the involvement of galectin-3 in the process of neurodegeneration in prion diseases, the expression and cellular localization of galectin-3 in the brain were studied in scrapie, a mouse model of prion disease. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analyses showed that the expression of galectin-3 protein and mRNA was induced in scrapie-affected brains, particularly at the time when the abnormal prion protein PrP(Sc) began to accumulate in the brains. Immunohistochemically, immunostaining for galectin-3 was found mainly in B4-isolectin-positive cells (presumably activated microglia/macrophages), but not in astrocytes. Galectin-3 immunoreactivity was localized mainly in areas of PrP(Sc) accumulation and neuronal death in scrapie-infected brains. These findings suggest that the expression of galectin-3 by activated microglia/macrophages in prion disease correlates with abnormal prion protein accumulation.

Possible involvement of galectin-3 in microglial activation in the hippocampus with trimethyltin treatment.

Trimethyltin (TMT) is an organotin neurotoxicant with effects that are selectively localized to the limbic system (especially the hippocampus), which produces memory deficits and temporal lobe seizures. Galectin-3 (Gal-3) is a beta-galactoside-binding lectin that is important in cell proliferation and regulation of apoptosis. The present study evaluated the temporal expression of Gal-3 in the hippocampus of adult BALB/c mice after TMT treatment (i.p., 2.5mg/kg). Western blotting analyses showed that Gal-3 immunoreactivity began to increase days after treatment; the immunoreactivity peaked significantly within days after treatment but significantly declined between days 4 and 8. Immunohistochemical analysis indicated that Gal-3 expression was very rare in the hippocampi of vehicle-treated controls. However, Gal-3 immunoreactivity appeared between 2 and 8 days after TMT treatment and was primarily localized to the hippocampal dentate gyrus (DG), in which neuronal degeneration occurred. The immunoreactivity was detected predominantly in most of the Iba1-positive microglia and in some GFAP-positive astrocytes of the hippocampal DG. Furthermore, Gal-3 expression co-localized with the pro-inflammatory enzymes cyclooxygenase-2 and inducible nitric oxide synthase in the hippocampal DG. Therefore, we suggest that Gal-3 is involved in the inflammatory process of neurodegenerative disorder induced by organotin intoxication.

Stimulatory Effects of Ginsan on the Proliferation and Viability of Mouse Spleen Cells

Ginsan is an acidic polysaccharide purified from Panax ginseng, a famous oriental herb. Although a variety of biological activities of ginsan have been studied, the effects of ginsan on spleen cells are not fully elucidated. We investigated the effect of ginsan on the viability and proliferation of spleen cells. Using Cell Counting Kit-8(R) solution and trypan blue solution, we found that ginsan significantly enhanced viability and proliferation. Multiple clusters, indicating proliferation, were observed in ginsan-treated spleen cells and, carboxyfluorescein succinimidyl ester and surface marker staining assay revealed that ginsan promoted proliferation from CD19(+) B cells rather than CD4(+) or CD8(+) T cells. In addition, ginsan decreased the percentage of late apoptotic cells. Ginsan increased the surface expression of CD25 and CD69 as well as production of interleukin-2 from spleen cells, suggesting increased activation. Taken together, these results demonstrate that ginsan increases the viability and proliferation of spleen cells via multiple mechanisms, valuable information for broadening the use of ginsan in clinical and research settings.