DMF (dimethyl fumarate) exerts anti-inflammatory and pro-metabolic effects in a variety of cell types, and a formulation (BG-12) is being evaluated for monotherapy in multiple sclerosis patients. DMF modifies glutathione (GSH) levels that can induce expression of the anti-inflammatory protein HO-1 (haem oxygenase-1). In primary astrocytes and C6 glioma cells, BG-12 dose-dependently suppressed nitrite production induced by either LI [LPS (lipopolysaccharide) at 1 μg/ml plus IFNγ (interferon γ) at 20 units/ml] or a mixture of pro-inflammatory cytokines, with greater efficacy in C6 cells. BG-12 reduced NOS2 (nitric oxide synthase 2) mRNA levels and activation of a NOS2 promoter, reduced nuclear levels of NF-κB (nuclear factor κB) p65 subunit and attenuated loss of IκBα (inhibitory κBα) in both cell types, although with greater effects in astrocytes. In astrocytes, LI decreased mRNA levels for GSHr (GSH reductase) and GCL (c-glutamylcysteine synthetase), and slightly suppressed GSHs (GSH synthetase) mRNAs. Co-treatment with BG-12 prevented those decreased and increased levels above control values. In contrast, LI reduced GSHp (GSH peroxidase) and GCL in C6 cells, and BG-12 had no effect on those levels. BG-12 increased nuclear levels of Nrf2 (nuclear factor-erythroid 2 p45 subunit-related factor 2), an inducer of GSH-related enzymes, in astrocytes but not C6 cells. In astrocytes, GSH was decreased by BG-12 at 2 h and increased at 24 h. Prior depletion of GSH using buthionine-sulfoximine increased the ability of BG-12 to reduce nitrites. In astrocytes, BG-12 increased HO-1 mRNA levels and effects on nitrite levels were blocked by an HO-1 inhibitor. These results demonstrate that BG-12 suppresses inflammatory activation in astrocytes and C6 glioma cells, but with distinct mechanisms, different dependence on GSH and different effects on transcription factor activation.
The neurotransmitter norepinephrine (NE) can inhibit inflammatory gene expression in glial cells; however, the mechanisms involved are not clear. In primary astrocytes, NE dose-dependently increased the expression of inhibitory IB␣ protein accompanied by an increase in steady state levels of IB␣ mRNA. Maximal increases were observed at 30 -60 min for the mRNA and at 4 h for protein, and these effects were mediated by NE binding to -adrenergic receptors. NE activated a 1.3-kilobase IB␣ promoter transfected into astrocytes or C6 glioma cells, and this activation was prevented by a -antagonist and by protein kinase A inhibitors but not by an NFB inhibitor. NE increased IB␣ protein in both the cytosolic and the nuclear fractions, suggesting an increase in nuclear uptake of IB␣. IB␣ was detected in the frontal cortex of normal adult rats, and its levels were reduced if central NE levels were depleted by lesion of the locus ceruleus. The reduction of brain IB␣ levels was paralleled by increased inflammatory responses to lipopolysaccharide. These results demonstrate that IB␣ expression is regulated by NE at both transcriptional and post-transcriptional levels, which could contribute to the observed anti-inflammatory properties of NE in vitro and in vivo.The activation of inflammatory responses in brain is normally under tight regulation that prevents the accumulation of potentially cytotoxic mediators including cytokines and reactive oxygen species (1-3). It has therefore been suggested that intrinsic mechanisms exist that maintain the brain in a refractory state of inflammatory activation. In primary cultures of rat astrocytes, we showed that neurotransmitter norepinephrine (NE) 1 prevents induction of the inducible form of nitric oxide synthase (NOS2) (4, 5) by bacterial endotoxin lipopolysaccharide (LPS) or by a combination of proinflammatory cytokines (interleukin 1, tumor necrosis factor ␣, and interferon ␥). Similarly, others show that NE reduces glial expression of pro-inflammatory cytokines including interleukin 1 and tumor necrosis factor ␣ (6 -9) and of cell adhesion molecules (13). A similar role for NE in regulating inflammatory events in brain is supported by our recent findings that experimental depletion of brain NE levels by chemical lesion of the locus ceruleus (LC) increases the cortical inflammatory responses to injection of aggregated amyloid  (14). The fact that LC neurons are lost in Alzheimer's disease (15) and that levels of  2 -adrenergic receptor (ARs) are reduced in astrocytes in multiple sclerosis patients (16,17) suggests that diminished NE levels or perturbations of the NE-signaling system contribute to the neuroinflammation that occurs in these diseases.The mechanism(s) by which NE reduces inflammatory gene expression is not yet well defined. In astrocytes, we found that NE induced protein binding to a 27-bp region of the rat NOS2 promoter, which is located immediately upstream of a NFB binding site located at bp position Ϫ107 to Ϫ96 (18). This 27-bp region contains several potenti...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.