Goo Taeg Oh

Stimulation of humoral and cell mediated immunity by polysaccharide from mushroom phellinus linteus

Polysaccharide was purified from mycelial culture of Phellinus linteus (PL) and its effect on immunocompetence of normal splenocytes was observed. Overall in vitro immune function was enhanced by addition of PL into culture of mouse spleen lymphocyte and i.p. injection into mouse, while beta-glucans and other polysaccharides only raised the level of T lymphocyte-mediated immunity. PL stimulated immune functions of T lymphocytes, such as proliferation of T lymphocyte induced by mixed lymphocytes reaction and cytotoxicity of cytotoxic T cells responding to alloantigen. Nonspecific immune functions mediated by natural killer cells and macrophages were increased by treatment of PL in vivo and in vitro. PL also stimulated humoral immune function positively, such as T-dependent and T-independent primary antibody response, and acted as a polyclonal activator on B cell. PL exhibited a wider range of immunostimulation and antitumor activity than other polysaccharides isolated from Basidiomycetes.

Active intestinal calcium transport in the absence of transient receptor potential vanilloid type 6 and calbindin-D9k.

To study the role of the epithelial calcium channel transient receptor potential vanilloid type 6 (TRPV6) and the calcium-binding protein calbindin-D9k in intestinal calcium absorption, TRPV6 knockout (KO), calbindin-D9k KO, and TRPV6/calbindin-D(9k) double-KO (DKO) mice were generated. TRPV6 KO, calbindin-D9k KO, and TRPV6/calbindin-D9k DKO mice have serum calcium levels similar to those of wild-type (WT) mice ( approximately 10 mg Ca2+/dl). In the TRPV6 KO and the DKO mice, however, there is a 1.8-fold increase in serum PTH levels (P < 0.05 compared with WT). Active intestinal calcium transport was measured using the everted gut sac method. Under low dietary calcium conditions there was a 4.1-, 2.9-, and 3.9-fold increase in calcium transport in the duodenum of WT, TRPV6 KO, and calbindin-D9k KO mice, respectively (n = 8-22 per group; P > 0.1, WT vs. calbindin-D9k KO, and P < 0.05, WT vs. TRPV6 KO on the low-calcium diet). Duodenal calcium transport was increased 2.1-fold in the TRPV6/calbindin-D9k DKO mice fed the low-calcium diet (P < 0.05, WT vs. DKO). Active calcium transport was not stimulated by low dietary calcium in the ileum of the WT or KO mice. 1,25-Dihydroxyvitamin D3 administration to vitamin D-deficient null mutant and WT mice also resulted in a significant increase in duodenal calcium transport (1.4- to 2.0-fold, P < 0.05 compared with vitamin D-deficient mice). This study provides evidence for the first time using null mutant mice that significant active intestinal calcium transport occurs in the absence of TRPV6 and calbindin-D9k, thus challenging the dogma that TRPV6 and calbindin-D9k are essential for vitamin D-induced active intestinal calcium transport.

Trichostatin A attenuates airway inflammation in mouse asthma model

Background Histone deacetylase (HDAC) inhibition has been demonstrated to change the expression of a restricted set of cellular genes. T cells are essential in the pathogenesis of allergen‐induced airway inflammation. It was recently reported that treatment with HDAC inhibitors induces a T cell‐suppressive effect.

Flt3 signaling-dependent dendritic cells protect against atherosclerosis.

Early events in atherosclerosis occur in the aortic intima and involve monocytes that become macrophages. We looked for these cells in the steady state adult mouse aorta, and surprisingly, we found a dominance of dendritic cells (DCs) in the intima. In contrast to aortic adventitial macrophages, CD11c(+)MHC II(hi) DCs were poorly phagocytic but were immune stimulatory. DCs were of two types primarily: classical Flt3-Flt3L signaling-dependent, CD103(+)CD11b(-) DCs and macrophage-colony stimulating factor (M-CSF)-dependent, CD14(+)CD11b(+)DC-SIGN(+) monocyte-derived DCs. Both types expanded during atherosclerosis. By crossing Flt3(-/-) to Ldlr(-/-) atherosclerosis-prone mice, we developed a selective and marked deficiency of classical CD103(+) aortic DCs, and they were associated with exacerbated atherosclerosis without alterations in blood lipids. Concomitantly, the Flt3(-/-)Ldlr(-/-) mice had fewer Foxp3(+) Treg cells and increased inflammatory cytokine mRNAs in the aorta. Therefore, functional DCs are dominant in normal aortic intima and, in contrast to macrophages, CD103(+) classical DCs are associated with atherosclerosis protection.

Berberine improves lipid dysregulation in obesity by controlling central and peripheral AMPK activity

AMP-activated protein kinase (AMPK) plays an important role in regulating whole body energy homeostasis. Recently, it has been demonstrated that berberine (BBR) exerts antiobesity and antidiabetic effects in obese and diabetic rodent models through the activation of AMPK in peripheral tissues. Here we show that BBR improves lipid dysregulation and fatty liver in obese mice through central and peripheral actions. In obese db/db and ob/ob mice, BBR treatment reduced liver weight, hepatic and plasma triglyceride, and cholesterol contents. In the liver and muscle of db/db mice, BBR promoted AMPK activity and fatty acid oxidation and changed expression of genes involved in lipid metabolism. Additionally, intracerebroventricular administration of BBR decreased the level of malonyl-CoA and stimulated the expression of fatty acid oxidation genes in skeletal muscle. Together, these data suggest that BBR would improve fatty liver in obese subjects, which is probably mediated not only by peripheral AMPK activation but also by neural signaling from the central nervous system.

α-Lipoic Acid Prevents Endothelial Dysfunction in Obese Rats via Activation of AMP-Activated Protein Kinase

Objective—Lipid accumulation in vascular endothelial cells may play an important role in the pathogenesis of atherosclerosis in obese subjects. We showed previously that α-lipoic acid (ALA) activates AMP-activated protein kinase (AMPK) and reduces lipid accumulation in skeletal muscle of obese rats. Here, we investigated whether ALA improves endothelial dysfunction in obese rats by activating AMPK in endothelial cells. Methods and Results—Endothelium-dependent vascular relaxation was impaired, and the number of apoptotic endothelial cells was higher in the aorta of obese rats compared with control rats. In addition, triglyceride and lipid peroxide levels were higher, and NO synthesis was lower. Administration of ALA improved all of these abnormalities. AMPK activity was lower in aortic endothelium of obese rats, and ALA normalized it. Incubation of human aortic endothelial cells with ALA activated AMPK and protected cells from linoleic acid–induced apoptosis. Dominant-negative AMPK inhibited the antiapoptotic effects of ALA. Conclusions—Reduced AMPK activation may play an important role in the genesis of endothelial dysfunction in obese rats. ALA improves vascular dysfunction by normalizing lipid metabolism and activating AMPK in endothelial cells.

Trichostatin A Exacerbates Atherosclerosis in Low Density Lipoprotein Receptor–Deficient Mice

Objective—Histone acetylation has been shown to be involved in expression of a restricted set of cellular genes including various proinflammatory molecules. We aimed to investigate the relationship between histone acetylation and atherosclerosis. Methods and Results—In low-density lipoprotein (LDL) receptor-deficient (Ldlr−/−) mice fed an atherogenic diet for 4 or 8 weeks, trichostatin A (TSA), a specific histone deacetylase inhibitor, exacerbated atherosclerosis without alteration on plasma lipid profiles. When we assayed the effects of TSA on expressions of oxidized LDL (oxLDL) receptors on RAW264.7 macrophage, we found that TSA increased CD36 mRNA and protein, as well as cell surface expression of CD36. TSA also increased acetylation at the CD36 promoter region. The uptake of 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine percholate (Dil)-labeled oxLDL was enhanced in RAW264.7 macrophage by TSA. Furthermore, TSA treatment increased CD36 mRNA expression in aorta, and SRA, tumor necrosis factor (TNF)-&agr;, and vascular cell adhesion molecule-1 (VCAM-1) were also elevated, whereas IL-6 and IL-1&bgr; expressions were decreased. Conclusions—Our findings suggest that histone acetylation could play some role in atherogenesis by modulating expressions of oxLDL receptor and some proatherogenic genes. Therefore, our results indicate that increased histone acetylation may affect the progress of atherosclerosis.

Hepatocyte Growth Factor Suppresses Vascular Endothelial Growth Factor-Induced Expression of Endothelial ICAM-1 and VCAM-1 by Inhibiting the Nuclear Factor-κB Pathway

Vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) are potent angiogenic factors that have been used clinically to induce angiogenesis. However, concerns have been raised about VEGF because of its proinflammatory actions, which include enhancing the adhesion of leukocytes to endothelial cells. We have examined the possible antiinflammatory effects of HGF on the vasculature. HGF, unlike VEGF, did not alter leukocyte adhesion to endothelial cells. Instead it inhibited VEGF-induced leukocyte-endothelial cell interactions and the endothelial expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). In a skin inflammation model, VEGF-treated mice showed a significant increase of leukocytes infiltrated or adherent to the luminal surface of blood vessels, as compared with vehicle- or HGF-treated mice. The VEGF effect was markedly suppressed by coadministration of HGF. RT-PCR and promoter analysis revealed that HGF downregulated VEGF-mediated expression of ICAM-1 and VCAM-1 at the transcriptional level. Furthermore, these inhibitory effects coincided with suppression of I&kgr;B kinase activity, and this in turn prevented the activation of the inflammatory transcription factor NF-&kgr;B. Taken together, our results demonstrate that HGF suppresses VEGF-induced inflammation presumably by inhibiting the endothelial NF-&kgr;B pathway. This suggests that combined treatment with HGF and VEGF could be superior to treatment with either factor alone for enhancing therapeutic angiogenesis while avoiding inflammation.

Functional and Clinical Evidence for NDRG2 as a Candidate Suppressor of Liver Cancer Metastasis

We searched for potential suppressors of tumor metastasis by identifying the genes that are frequently down-regulated in hepatocellular carcinomas (HCC) while being negatively correlated with clinical parameters relevant to tumor metastasis, and we report here on the identification of N-myc downstream regulated gene 2 (NDRG2) as a promising candidate. NDRG2 expression was significantly reduced in HCC compared with nontumor or normal liver tissues [87.5% (35 of 40) and 62% (62 of 100) at RNA and protein levels, respectively]. Reduction of NDRG2 expression was intimately associated with promoter hypermethylation because its promoter region was found to carry extensively methylated CpG sites in HCC cell lines and primary tumors. Immunohistochemical analysis of NDRG2 protein in 100 HCC patient tissues indicated that NDRG2 expression loss is significantly correlated with aggressive tumor behaviors such as late tumor-node-metastasis (TNM) stage (P = 0.012), differentiation grade (P = 0.024), portal vein thrombi (P = 0.011), infiltrative growth pattern (P = 0.015), nodal/distant metastasis (P = 0.027), and recurrent tumor (P = 0.021), as well as shorter patient survival rates. Ectopically expressed NDRG2 suppressed invasion and migration of a highly invasive cell line, SK-Hep-1, and experimental tumor metastasis in vivo, whereas small interfering RNA-mediated knockdown resulted in increased invasion and migration of a weakly invasive cell line, PLC/PRF/5. In addition, NDRG2 could antagonize transforming growth factor beta1-mediated tumor cell invasion by specifically down-regulating the expression of matrix metalloproteinase 2 and laminin 332 pathway components, with concomitant suppression of Rho GTPase activity. These results suggest that NDRG2 can inhibit extracellular matrix-based, Rho-driven tumor cell invasion and migration and thereby play important roles in suppressing tumor metastasis in HCC.

Vitamin D: molecular mechanism of action.

Abstract:  Vitamin D maintains calcium homeostasis and is required for bone development and maintenance. Recent evidence has indicated an interrelationship between vitamin D and health beyond bone, including effects on cell proliferation and on the immune system. New developments in our lab related to the function and regulation of target proteins have provided novel insights into the mechanisms of vitamin D action. Studies in our lab have shown that the calcium‐binding protein, calbindin, which has been reported to be a facilitator of calcium diffusion, also has an important role in protecting against apoptotic cell death in different tissues including protection against cytokine destruction of osteoblastic and pancreatic β cells. These findings have important implications for the therapeutic intervention of many disorders including diabetes and osteoporosis. Recent studies in our laboratory of intestinal calcium absorption using calbindin‐D9k null mutant mice as well as mice lacking the 1,25‐dihydroxyvitamin D3 (1,25(OH)2D3) inducible epithelial calcium channel, TRPV6, provide evidence for the first time of calbindin‐D9k and TRPV6 independent regulation of active calcium absorption. Besides calbindin, the other major target of 1,25(OH)2D3 in intestine and kidney is 25(OH)D3 24 hydroxylase (24(OH)ase), which is involved in the catabolism of 1,25(OH)2D3. In our laboratory we have identified various factors that cooperate with the vitamin D receptor in regulating 24(OH)ase expression including C/EBP β, SWI/SNF (complexes that remodel chromatin using the energy of ATP hydrolysis) and the methyltransferases, CARM1 and G9a. Evidence is also presented for C/EBP β as a nuclear coupling factor that coordinates regulation of osteopontin by 1,25(OH)2D3 and PTH. Our findings define novel mechanisms that may be of fundamental importance in understanding how 1,25(OH)2D3 mediates its multiple biological effects.