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Suppression of iNOS expression by fucoidan is mediated by regulation of p38 MAPK, JAK/STAT, AP-1 and IRF-1, and depends on up-regulation of scavenger receptor B1 expression in TNF-α- and IFN-γ-stimulated C6 glioma cells

In neurodegenerative disorders, activated glial cells overproduce nitric oxide (NO), which causes neurotoxicity. Inducible NO synthase (iNOS) is a potential therapeutic target in neurodegenerative diseases. Here, we examined the action of fucoidan, a high-molecular-weight sulfated polysaccharide, on tumor necrosis factor-alpha (TNF-alpha)- and interferon-gamma (IFN-gamma)-induced NO production in C6 glioma cells. Fucoidan suppressed TNF-alpha- and IFN-gamma-induced NO production and iNOS expression. In addition, fucoidan inhibited TNF-alpha- and IFN-gamma-induced AP-1, IRF-1, JAK/STAT and p38 mitogen-activated protein kinase (MAPK) activation and induced scavenger receptor B1 (SR-B1) expression. Blocking of SR-B1 did not reverse the inhibitory effect of fucoidan on TNF-alpha- and IFN-gamma- stimulated NO production. However, inhibition of SR-B1 expression by siRNA increased iNOS expression and p38 phosphorylation in TNF-alpha- and IFN-gamma-stimulated C6 cells. Overall, p38 MAPK, AP-1, JAK/STAT and IRF-1 play an important role in the inhibitory effect of fucoidan on TNF-alpha- and IFN-gamma-stimulated NO production, and intracellular SR-B1 expression may be related to the inhibition of iNOS expression by fucoidan via regulation of p38 phosphorylation. The present results also suggest that fucoidan could be a potential therapeutic agent for treating inflammatory-related neuronal injury in neurological disorders.

Differential regulation by fucoidan of IFN-γ-induced NO production in glial cells and macrophages.

Fucoidan has shown numerous biological actions; however, the molecular bases of these actions have being issued. We examined the effect of fucoidan on NO production induced by IFN‐γ and the molecular mechanisms underlying these effects in two types of cells including glia (C6, BV‐2) and macrophages (RAW264.7, peritoneal primary cells). Fucoidan affected IFN‐γ‐induced NO and/or iNOS expression both in macrophages and glial cells but in a contrast way. Our data showed that in C6 glioma cells both JAK/STAT and p38 signaling positively regulated IFN‐γ‐induced iNOS, which were inhibited by fucoidan. In contrast, in RAW264.7 cells JAK/STAT is a positive regulator whereas p38 is a negative regulator of NO/iNOS production. In RAW264.7 cells, fucoidan enhanced p38 activation and induced TNF‐α production. We also confirmed the dual regulation of p38 in BV‐2 microglia and primary peritoneal macrophages. From these results, we suggest that fucoidan affects not only IFN‐γ‐induced NO/iNOS production differently in brain and peritoneal macrophages due to the different roles of p38 but the effects on TNF‐α production in the two cell types. These novel observations including selective and cell‐type specific effects of fucoidan on IFN‐γ‐mediated signaling and iNOS expression raise the possibility that it alters the sensitivity of cells to the p38 activation. J. Cell. Biochem. 111: 1337–1345, 2010.

Ethanol induces cell cycle arrest and triggers apoptosis via Sp1-dependent p75NTR expression in human neuroblastoma cells

Ethanol exposure has deleterious effects on the central nervous system. Although several mechanisms for ethanol-induced damage have been suggested, the precise mechanism underlying ethanol-induced neuronal cell death remains unclear. Recent studies indicate that the p75 neurotrophin receptor (p75NTR) has a critical role in the regulation of neuronal survival. This study was designed to examine the role of p75NTR in ethanol-induced apoptotic signaling in neuroblastoma cells. Ethanol caused highly increased level of p75NTR expression. The use of small interfering RNA to inhibit p75NTR expression markedly attenuated ethanol-induced cell cycle arrest and apoptosis. DNA binding activity of Sp1 was increased by ethanol, whereas inhibition of Sp1 activity by mithramycin, a Sp1 inhibitor, or short hairpin RNA suppressed ethanol-induced p75NTR expression. In addition, inhibitors of casein kinase 2 (CK2) and extracellular signal-regulated kinase (ERK) augmented ethanol-induced p75NTR expression. Our results also demonstrate that inhibition of ERK and CK2 caused a further increase in the activation of the p75NTR proximal promoter induced by ethanol. This increased activation was partially suppressed by the deletion of the Sp1 binding sites. These results suggest that Sp1-mediated p75NTR expression is regulated at least in part by ERK and CK2 pathways. The present study also showed that treatment with ethanol resulted in significant increases in the expression of p21, but not the levels of p53 and p53 target genes such as Bax, Puma, and Bcl-2. Furthermore, the inhibition of p75NTR expression or Sp1 activity suppressed ethanol-induced p21 expression, cell cycle arrest, and apoptosis. These data suggest that ethanol increases p75NTR expression, and CK2 and ERK signaling inversely regulate Sp1-mediated p75NTR expression in ethanol-treated neuroblastoma cells. Thus, our study provides more insight into the mechanisms underlying ethanol actions.

Effects of Non-saponin Red Ginseng Components on the Function of Brain Cells

Non-saponin gingseng fraction components (NSRG) have been known to have a variety of biological activity. However, the effects of these components on the function of brain cell have not been characterized in detail. In this study, we investigated the preventive effect of non-saponin red ginseng components on acrylamide (ACR)-induced suppression of neural cell adhesion molecule (NCAM), which is highly expressed in neuronal cells. The data showed that NSRG blocked the suppression of NCAM expression by ACR in neuroblastoma cells (SK-N-SH). In addition, NSRG significantly increased NCAM expression in ACR-nontreated neuroblastoma cells. NSRG treatment resulted in the increase of cell proliferation in a concentration-dependent manner. We also examined whether NSRG could modulate the NO production of astrocytes. When glioma cells (C6) were treated with various concentrations of NSRG (100-300 ㎍/ml) in the presence or absence of IFN-γ for 24 hours, NO production was suppressed in IFN-γ-stimulated C6 cells. Taken together, these results demonstrate that treatment of brain cells with NSRG results in the enhancement of proliferation, the suppression of NO production and the protective effect on NCAM expression impaired by ACR. Thus, the present data suggest that NSRG has proliferative and neuroprotective effects and these effects could be useful in neuronal diseases.