Protective Effect of Dimethyl Fumarate on an Oxidative Stress Model Induced by Sodium Nitroprusside in Mice.

Recent reports have shown that dimethyl fumarate (DMF) prevents brain damage induced by intracerebral hemorrhage and this beneficial effect is mediated by the nuclear erythroid 2 p45-related factor-2-antioxidant response element (Nrf2-ARE) pathway. However, the downstream mechanism underlying the activation of the Nrf2-ARE pathway is unclear. Here, we investigated the protective effect of DMF using an in vivo model of oxidative stress induced by sodium nitroprusside (SNP) and rat primary striatal cultures. Oral administration of DMF prevented SNP-induced motor dysfunction. Pre-administration of DMF (60-200 mg/kg) for 24 h dose-dependently protected against brain damage induced by the striatal injection of SNP. Next, we investigated the protective effect and mechanism of DMF against oxidative stress using rat primary striatal cell cultures. Treatment of striatal cells with DMF (10 µM) markedly prevented hydrogen peroxide-induced cytotoxicity. The protective effect of DMF against oxidative stress in vitro was inhibited by zinc protoporphyrin IX, an inhibitor of heme oxygenase-1, but not by buthionine sulfoximine, an inhibitor of glutathione synthesis. These results suggest that the activation of heme oxygenase-1 plays an important role in the protective effect of DMF.

Effects of human antithymocyte globulin on acetylcholine synthesis, its release and choline acetyltransferase transcription in a human leukemic T-cell line.

Lymphocytes possess an independent, nonneuronal cholinergic system. In the present study, we investigated the short- and long-term effects of antithymocyte globulin (ATG)-Fresenius (ATG-F), a human antithymocyte globulin that binds to CD2, CD7 and CD11a, on acetylcholine (ACh) synthesis and transcription of choline acetyltransferase (ChAT) in CCRF-CEM cells, a human leukemic T-cell line. In the short-term (6 h), ATG-F enhanced ACh release, likely through transient increases in intracellular Ca(2+) ([Ca(2+)](i)) mediated by CD7, which led to declines in intracellular ACh content. By 48 h, however, the ACh content had increased as compared to control due to up-regulation of ChAT expression mediated by CD11a.

Up-regulation of lymphocytic cholinergic activity by ONO-4819, a selective prostaglandin EP4 receptor agonist, in MOLT-3 human leukemic T cells.

We used a selective EP4 receptor agonist, ONO-4819, and a human leukemic T cell line MOLT-3 cells, which express all four prostaglandin E2 (PGE2) receptors (EP1-EP4), to investigate whether the EP4 PGE2 receptor subtype is involved in regulating lymphocytic cholinergic activity. Phytohemagglutinin (PHA), a T cell activator, significantly enhanced the expression of EP4 receptor mRNA during the first 3-6 h of exposure, after which, expression gradually declined. Furthermore, PHA stimulation slightly but significantly up-regulated the expression of EP2 mRNA after 12 h and of EP3 mRNA after 6 h. By contrast, expression level of EP1 receptor mRNA was not affected by PHA. ONO-4819 (1 microM), which was added to cultures after 3 h of PHA stimulation, significantly increased cellular ACh content and release, and up-regulated ChAT mRNA expression and activity but inhibited MOLT-3 cell proliferation. These findings suggest that the activation of T lymphocytes up-regulates EP4 receptor mRNA expression and, to a lesser extent, EP2 and EP3 receptors and that PGE2 enhances nonneuronal lymphocytic cholinergic transmission in activated T cells, at least in part, via EP4 receptor-mediated pathways.

Effect of orthovanadate on platelet aggregation induced by platelet-activating factor.

Orthovanadate (vanadate) inhibited the platelet aggregation induced by platelet-activating factor (PAF) in a dose-dependent manner. Propranolol, a nonspecific beta-adrenergic receptor antagonist, and H-8, a selective inhibitor of cAMP-dependent protein kinase (PKA), suppressed the inhibition of the PAF-induced platelet aggregation by vanadate. Vanadate increased the cAMP content in platelets accompanied by the activation of PKA. The beta-adrenergic receptors of platelets have been reported to be abundant in the beta(2) isoform, coupled to adenylyl cyclases (R. Kerry and M. C. Scrutton, Br. J. Pharmacol., 79, 681-691 (1983)). When the washed platelets were preincubated with vanadate, salbutamol, a selective beta(2)-adrenergic receptor agonist, or 8-Br-cAMP, the latter two mimicked the vanadate-induced anti-platelet aggregation and prolongation of clotting time of plasma, suggesting involvement of the increased intracellular cAMP content in both actions of vanadate. Butoxamine, a selective beta(2)-adrenergic receptor antagonist, suppressed both actions of vanadate. The vanadate-induced increase in cAMP content was inhibited in part by butoxamine or genistein. These results suggest that vanadate inhibits the PAF-induced platelet aggregation by the stimulation of a cAMP/PKA-dependent process via the beta(2)-adrenergic receptor and receptor tyrosine kinases, and that the anti-platelet aggregation is involved in part in mechanisms of the anticoagulant action of vanadate.