Abstract
BackgroundDimethyl fumarate (DMF), working via its metabolite monomethylfumarate (MMF), acts as a potent antioxidant and immunomodulator in animal models of neurologic disease and in patients with multiple sclerosis. These properties and their translational potential led us to investigate whether DMF/MMF could also protect at-risk and/or dying neurons in models of ischemic stroke in vitro and in vivo. Although the antioxidant effects have been partially addressed, the benefits of DMF immunomodulation after ischemic stroke still need to be explored.MethodsIn vitro neuronal culture with oxygen-glucose deprivation and rats with middle cerebral artery occlusion were subjected to DMF/MMF treatment. Live/dead cell counting and LDH assay, as well as behavioral deficits, plasma cytokine assay, western blots, real-time PCR (Q-PCR) and immunofluorescence staining, were used to evaluate the mechanisms and neurological outcomes.ResultsWe found that MMF significantly rescued cortical neurons from oxygen-glucose deprivation (OGD) in culture and suppressed pro-inflammatory cytokines produced by primary mixed neuron/glia cultures subjected to OGD. In rats, DMF treatment significantly decreased infarction volume by nearly 40 % and significantly improved neurobehavioral deficits after middle cerebral artery occlusion (MCAO). In the acute early phase (72 h after MCAO), DMF induced the expression of transcription factor Nrf2 and its downstream mediator HO-1, important for the protection of infarcted cells against oxidative stress. In addition to its antioxidant role, DMF also acted as a potent immunomodulator, reducing the infiltration of neutrophils and T cells and the number of activated microglia/macrophages in the infarct region by more than 50 % by 7–14 days after MCAO. Concomitantly, the levels of potentially harmful pro-inflammatory cytokines were greatly reduced in the plasma and brain and in OGD neuron/glia cultures.ConclusionsWe conclude that DMF is neuroprotective in experimental stroke because of its potent immunomodulatory and antioxidant effects and thus may be useful as a novel therapeutic agent to treat stroke in patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0733-1) contains supplementary material, which is available to authorized users.
Highlights
Dimethyl fumarate (DMF), working via its metabolite monomethylfumarate (MMF), acts as a potent antioxidant and immunomodulator in animal models of neurologic disease and in patients with multiple sclerosis
The greatest behavioral improvement was seen in the first 72 h after DMF, modified neurological severity score (mNSS) scores continued to gradually decline with longer treatment times. These results demonstrate that 25 mg/kg DMF is less effective than 50 mg/kg in the middle cerebral artery occlusion (MCAO) model when neurological behavior test and infarct size (i.e., triphenyltetrazolium chloride (TTC) staining) are assessed
DMF reduces immune cell infiltration and microglial activation in the infarct region Supporting the notion of DMF-mediated immunomodulation in the brain, we found that the number of MPO+ neutrophils (Fig. 5a–f, m) and CD3+ T cells (Fig. 5g–l, n), which had infiltrated the penumbra region surrounding the infarct, was significantly lower in DMF-treated compared to vehicle-treated MCAO rats
Summary
Dimethyl fumarate (DMF), working via its metabolite monomethylfumarate (MMF), acts as a potent antioxidant and immunomodulator in animal models of neurologic disease and in patients with multiple sclerosis. Several recent reports showed that DMF can reduce brain edema and improve blood-brain barrier (BBB) integrity and improve neurological outcomes in a short-term rat model of hemorrhagic stroke [40, 44] and ischemic stroke [45, 46] In all of these cases, DMF/MMF is thought to act via activation of the antioxidant transcription factor (erythroid-derived 2)-like 2 (Nrf2) which up-regulates proteins like heme oxygenase-1 (HO-1) [33, 36,37,38, 40, 41, 44, 47], thereby protecting cells against damage triggered by oxidant insult. DMF is a potent modulator of inflammatory cytokines which are known as important in stroke [11, 15, 20,21,22, 26, 27, 48, 49], in particular Th1-type pro-inflammatory cytokines that can lead to tissue damage [37, 38, 40, 50, 51]
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