Hyoung Chin Kim

Polysaccharide isolated from the radix of Platycodon grandiflorum selectively activates B cells and macrophages but not T cells

Many polysaccharides isolated from plants are considered to be biological response modifiers and have been shown to enhance various immune responses in vivo and in vitro. Here, we demonstrate that polysaccharide isolated from the radix of Platycodon grandiflorum (PG) has a unique mode of immunostimulation with regard to its cell-type specificity. PG was found to markedly increase polyclonal IgM antibody production and the proliferation of B cells, and to activate iNOS transcription and NO production in macrophages. Moreover, the intraperitoneal administration of PG in mice resulted in increased IgM antibody production in B cells, which were immunized by using T-dependent antigen sheep red blood cells (sRBCs). However, PG did not affect the proliferation of T cells, the IL-2 expression of Th1 cells, or the IL-4 expression of Th2 cells. Although PG and lipopolysaccharide (LPS) had a similar mode of action in B cells and macrophages, they were differentiated by the fact that PG-induced cellular activation was not inhibited by polymyxin B, a specific inhibitor of LPS. Anti-CD19 or anti-CD79b antibody blocked B cell proliferation and anti-CD14 or anti-CD 11b antibody decreased macrophage NO production, indicating the possible cellular binding sites of PG. Our results demonstrate that PG is a specific activator of B cells and macrophages but not of T cells, and suggest that PG is quite distinct from other well-known immunostimulants, such as lentinan and schizophyllan, which mainly act upon macrophages and T cells.

Peroxiredoxin 2 Deficiency Exacerbates Atherosclerosis in Apolipoprotein E–Deficient Mice

Rationale: Peroxiredoxin 2 (Prdx2), a thiol-specific peroxidase, has been reported to regulate proinflammatory responses, vascular remodeling, and global oxidative stress. Objective: Although Prdx2 has been proposed to retard atherosclerosis development, no direct evidence and mechanisms have been reported. Methods and Results: We show that Prdx2 is highly expressed in endothelial and immune cells in atherosclerotic lesions and blocked the increase of endogenous H2O2 by atherogenic stimulation. Deficiency of Prdx2 in apolipoprotein E–deficient (ApoE−/−) mice accelerated plaque formation with enhanced activation of p65, c-Jun, JNKs, and p38 mitogen-activated protein kinase; and these proatherogenic effects of Prdx2 deficiency were rescued by administration of the antioxidant ebselen. In bone marrow transplantation experiments, we found that Prdx2 has a major role in inhibiting atherogenic responses in both vascular and immune cells. Prdx2 deficiency resulted in increased expression of vascular adhesion molecule-1, intercellular adhesion molecule-1, and monocyte chemotactic protein-1, which led to increased immune cell adhesion and infiltration into the aortic intima. Compared with deficiency of glutathione peroxidase 1 or catalase, Prdx2 deficiency showed a severe predisposition to develop atherosclerosis. Conclusions: Prdx2 is a specific peroxidase that inhibits atherogenic responses in vascular and inflammatory cells, and specific activation of Prdx2 may be an effective means of antiatherogenic therapy.

TIS21 Negatively Regulates Hepatocarcinogenesis by Disruption of Cyclin B1-Forkhead Box M1 Regulation Loop

A functional and biochemical interaction of TIS21/BTG2/PC3 with Forkhead box M1 (FoxM1), essential transcription factor for hepatocyte regeneration and a master regulator of mitotic gene expression, was explored. Growth of hepatocellular carcinoma (HCC), developed by a single injection of diethylnitrosamine (DEN), was the same in both the TIS21+/+ and TIS21−/− mice until 6 months, whereas it was significantly higher in the TIS21−/− mice at 9 months. Expression of TIS21 was significantly lower in both human and murine HCCs than in the surrounding tissues. Forced expression of TIS21 impaired growth, proliferation, and tumorigenic potential of Huh7 cells. At the mechanistic level, TIS21 inhibited FoxM1 phosphorylation, a required modification for its activation, by reducing cyclin B1–cdk1 activity, examined by in vitro kinase assay and FoxM1 mutant analyses. These observations were further confirmed in vivo by the reciprocal control of TIS21 expression and FoxM1 phosphorylation in the diethylnitrosamine‐induced HCCs and TIS21−/− mouse embryonic fibroblast (MEF), in addition to increased expression of cyclin B1 and cdk1 activity. Conclusion: TIS21 negatively regulated hepatocarcinogenesis in part by disruption of the FoxM1–cyclin B1 regulatory loop, thereby inhibiting proliferation of transformed cells developed in mouse and human livers. (HEPATOLOGY 2008.)

Vitamin D 3 upregulated protein 1 deficiency promotes N -methyl- N -nitrosourea and Helicobacter pylori -induced gastric carcinogenesis in mice

Objective Vitamin D3 upregulated protein 1 (VDUP1) is a potent tumour suppressor whose expression is dramatically reduced in various types of human cancers, including gastric cancer. However, the precise mechanisms underlying tumour development remain unclear. In the present study, the authors examined the effect of VDUP1 on Helicobacter pylori-induced gastric carcinogenesis in mice. Design Gastric cancer was generated in VDUP1 knockout (KO) and wild-type mice using a combination of N-methyl-N-nitrosourea treatment and H pylori infection. Fifty weeks after treatment, gastric tissues from both types of mice were examined by histopathology, immunohistochemistry and immunoblotting. In vitro tests on the human gastric cancer cell line, AGS, were also performed to identify the underlying mechanisms of cancer development. Results The overall incidence of gastric cancer was significantly higher in VDUP1 KO mice than in wild-type mice. Similarly, VDUP1 KO mice showed more severe chronic gastritis, glandular atrophy, foveolar hyperplasia, metaplasia and dysplasia. Although no differences in the apoptotic index were apparent, lack of VDUP1 increased the rate of gastric epithelial cell proliferation in non-cancerous stomachs, with corresponding increases in tumour necrosis factor alpha (TNFα) level, nuclear transcription factor kappa B (NF-κB) activation and cyclooxygenase-2 (COX-2) expression. An in vitro study showed that H pylori-associated cell proliferation and induction of TNFα, NF-κB and COX-2 were inhibited in cells transfected with VDUP1. In addition, overexpression of VDUP1 in AGS cells suppressed TNFα-induced NF-κB activation and COX-2 expression. Conclusion Our data show that VDUP1 negatively regulates H pylori-associated gastric carcinogenesis, in part by disrupting cell growth and inhibiting the induction of TNFα, NF-κB and COX-2. These findings provide important insights into the role of VDUP1 in H pylori-associated tumourigenesis.

Activation of mitogen-activated protein kinase pathways by angelan in murine macrophages

In our previous studies, we showed that angelan, a polysaccharide purified from Angelica gigas Nakai, specifically activated macrophages to induce cytokines including inducible nitric oxide synthase (iNOS) which has strong anti-tumor activities [Immunopharmacology, 1999; 43: 1.]. In the present study, we investigated the intracellular signal transduction pathways involved in the angelan-induced iNOS synthesis by murine macrophages. Protein tyrosine phosphorylation was induced within 5 min by angelan, and the blocking of protein tyrosine kinases (PTKs) inhibited down-stream pathways leading to iNOS production in response to angelan. Treament of RAW 264.7 cells with angelan resulted in significant activation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) and p38, while stress-activated protein kinase/c-Jun NH2 terminal kinase (SAPK/JNK) was not activated by angelan. The specific p38 inhibitor SB203580 abrogated the angelan-induced iNOS synthesis, whereas the selective mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase 1 (MEK-1) inhibitor PD98059 did not affect the iNOS induction. In conclusion, we demonstrate that PTK and p38 MAPK activation are required to transduce signals leading to iNOS expression in angelan-stimulated murine macrophages.

The adipokine Retnla modulates cholesterol homeostasis in hyperlipidemic mice.

Hyperlipidemia is a well-recognized risk factor for atherosclerosis and can be regulated by adipokines. Expression of the adipokine resistin-like molecule alpha (Retnla) is regulated by food intake; whether Retnla has a role in the pathogenesis of hyperlipidemia and atherosclerosis is unknown. Here we report that Retnla has a cholesterol-lowering effect and protects against atherosclerosis in low-density lipoprotein receptor-deficient mice. On a high-fat diet, Retnla deficiency promotes hypercholesterolaemia and atherosclerosis, whereas Retnla overexpression reverses these effects and improves the serum lipoprotein profile, with decreased cholesterol in the very low-density lipoprotein fraction concomitant with reduced serum apolipoprotein B levels. We show that Retnla upregulates cholesterol-7-α-hydroxylase, a key hepatic enzyme in the cholesterol catabolic pathway, through induction of its transcriptional activator liver receptor homologue-1, leading to increased excretion of cholesterol in the form of bile acids. These findings define Retnla as a novel therapeutic target for treating hypercholesterolaemia and atherosclerosis.

Antibody Responses in Mice Stimulated by Various Doses of the Potato-Derived Major Surface Antigen of Hepatitis B Virus

ABSTRACT The ability of potato-derived major surface antigen of hepatitis B virus (P-HBsAg) to elicit antibody responses to different dosages of P-HBsAg ranging from 0.02 to 30 μg administered orally in mice was examined. All immunized groups produced specific serum IgG and fecal IgA antibodies against P-HBsAg, even at low levels (<5 μg), after administration of a 0.5-μg yeast-derived HBsAg (Y-HBsAg; LG Life Sciences, Republic of Korea) booster.

Anti-atherogenic effect of BHB-TZD having inhibitory activities on cyclooxygenase and 5-lipoxygenase in hyperlipidemic mice.

Cyclooxygenase (COX) and 5-lipoxygenase (5-LOX), which play pivotal roles in atherogenesis, have been reported to be involved in plaque stability. Licofelone, a dual COX and 5-LOX inhibitor, has been reported to possess anti-atherogenic effect in rabbit atherosclerosis model. We therefore investigated the anti-atherogenic effect of BHB-TZD [5-(3,5-di-tert-butyl-4-hydroxybenzylidene)thiazolidin-2,4-dione], a dual COX and 5-LOX inhibitor, in low density lipoprotein receptor null (LDLR-/-) mice. Fifteen LDLR-/- mice were fed a western diet (control group), whereas 15 were fed a western diet plus 0.1% (w/w) BHB-TZD (BHB-TZD group). After 8 weeks, the BHB-TZD group had markedly lower serum levels of leukotriene B(4) and prostaglandin E(2) than the control group. Interestingly, BHB-TZD treatment also reduced plasma triglyceride level without significant changes in total cholesterol and HDL levels. Compared with control mice, BHB-TZD fed mice had 52% fewer fatty streak lesions in the aortic sinus, as well as fewer initial lesions in the aortic arch. Macrophage infiltration into the lesions was 40% lower, and collagen and smooth muscle cells were increased by 102% and 96%, respectively, in the BHB-TZD group compared with the control group. In addition, aortic expression of proatherogenic molecules including TNF-alpha, IL-1beta, IL-6, MCP-1 and VCAM-1, was lower in the BHB-TZD group than the control group. BHB-TZD treatment also reduced MMP-2 and MMP-9 expressions in aorta. In conclusion, BHB-TZD effectively attenuated atherosclerosis in mouse model, suggesting its therapeutic potential for atherosclerosis.

Diallyl Disulfide Prevents Cyclophosphamide-Induced Hemorrhagic Cystitis in Rats through the Inhibition of Oxidative Damage, MAPKs, and NF-κB Pathways.

This study investigated the possible effects and molecular mechanisms of diallyl disulfide (DADS) against cyclophosphamide (CP)-induced hemorrhagic cystitis (HC) in rats. Inflammation response was assessed by histopathology and serum cytokines levels. We determined the protein expressions of nuclear transcription factor kappa-B (NF-κB), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and tumor necrosis factor-α (TNF-α), oxidative stress, urinary nitrite-nitrate, malondialdehyde (MDA), and 8-hydroxy-2’-deoxyguanosine (8-OHdG). Finally, we studied the involvement of mitogen-activated protein kinases (MAPKs) signaling in the protective effects of DADS against CP-induced HC. CP treatment caused a HC which was evidenced by an increase in histopathological changes, proinflammatory cytokines levels, urinary nitrite-nitrate level, and the protein expression of NF-κB, COX-2, iNOS, TNF-α, p-c-Jun N-terminal kinase (JNK), and p-extracellular signal regulated kinase (ERK). The significant decreases in glutathione content and glutathione-S-transferase and glutathione reductase activities, and the significant increase in MDA content and urinary MDA and 8-OHdG levels indicated that CP-induced bladder injury was mediated through oxidative DNA damage. In contrast, DADS pretreatment attenuated CP-induced HC, including histopathological lesion, serum cytokines levels, oxidative damage, and urinary oxidative DNA damage. DADS also caused significantly decreased the protein expressions of NF-κB, COX-2, iNOS, TNF-α, p-JNK, and p-ERK. These results indicate that DADS prevents CP-induced HC and that the protective effects of DADS may be due to its ability to regulate proinflammatory cytokines production by inhibition of NF-κB and MAPKs expressions, and its potent anti-oxidative capability through reduction of oxidative DNA damage in the bladder.

Effects of dietary supplementation with red-pigmented leafy lettuce (Lactuca sativa) on lipid profiles and antioxidant status in C57BL/6J mice fed a high-fat high-cholesterol diet

The present study was undertaken to assess the beneficial effects of a daily consumption of 8 % freeze-dried red-pigmented leafy lettuce (Lactuca sativa) on CVD. C57BL/6J mice were fed a high-fat high-cholesterol diet supplemented with or without red-pigmented leafy lettuce for 4 weeks. The present results showed that the red-pigmented leafy lettuce-supplemented diet significantly decreased the level of total and LDL-cholesterol and TAG in the plasma of the mice. The atherosclerotic index was calculated to be 46 % lower in the mice fed with the lettuce diet compared with the control diet. Lipid peroxidation measured by 2-thiobarbituric acid-reactive substances was markedly reduced in the plasma, liver, heart and kidney of the mice fed the lettuce diet. The content of antioxidants (total glutathione and beta-carotene) was significantly increased by lettuce supplementation. The antioxidant defence system by antioxidant enzymes including glutathione S-transferase, glutathione peroxidase, glutathione reductase, superoxide dismutase and paraoxanase in blood or liver tissues was also increased, and showed the improved oxidative stress in the mice fed the lettuce diet. The measurement of tail DNA (%), tail extent moment and olive tail moment indicated that the lettuce diet increased the resistance of hepatocyte and lymphocyte DNA to oxidative damage. The present study showed that the supplementation of a high-cholesterol high-fat diet with 8 % red-pigmented leafy lettuce resulted in an improvement of plasma cholesterol and lipid levels, prevention of lipid peroxidation and an increase of the antioxidant defence system and, therefore, could contribute to reduce the risk factors of CVD.