Dimethylfumarate inhibits microglial and astrocytic inflammation by suppressing the synthesis of nitric oxide, IL-1β, TNF-α and IL-6 in an in-vitro model of brain inflammation

Abstract

BackgroundBrain inflammation plays a central role in multiple sclerosis (MS). Dimethylfumarate (DMF), the main ingredient of an oral formulation of fumaric acid esters with proven therapeutic efficacy in psoriasis, has recently been found to ameliorate the course of relapsing-remitting MS. Glial cells are the effector cells of neuroinflammation; however, little is known of the effect of DMF on microglia and astrocytes. The purpose of this study was to use an established in vitro model of brain inflammation to determine if DMF modulates the release of neurotoxic molecules from microglia and astrocytes, thus inhibiting glial inflammation.MethodsPrimary microglial and astrocytic cell cultures were prepared from cerebral cortices of neonatal rats. The control cells were treated with LPS, an accepted inducer of pro-inflammatory properties in glial cells, and the experimental groups with LPS and DMF in different concentrations. After stimulation/incubation, the generation of nitric oxide (NO) in the cell culture supernatants was determined by measuring nitrite accumulation in the medium using Griess reagent. After 6 hours of treatment RT-PCR was used to determine transcription levels of iNOS, IL-1β, IL-6 and TNF-α mRNA in microglial and astrocytic cell cultures initially treated with DMF, followed after 30 min by LPS treatment. Moreover, we investigated possible involvement of the ERK and Nrf-2 transduction pathway in microglia using western blot analysis.ResultsPretreatment with DMF decreased synthesis of the proinflammatory mediators iNOS, TNF-α, IL-1β and IL-6 at the RNA level in activated microglia and astrocytes in vitro, associated with a decrease in ERK phosphorylation in microglia.ConclusionsCollectively, these results suggest that the neuroprotective effects of DMF may be in part functionally attributable to the compound's ability to inhibit expression of multiple neuroinflammatory mediators in brain of MS patients.

Effects of fumarates on inflammatory human astrocyte responses and oligodendrocyte differentiation

“…Consistent with previously published reports,6, 11, 13, 30 our data demonstrate that fumarates significantly reduce inflammatory cytokine and chemokine secretion in response to proinflammatory stimuli. We further demonstrate that the reduction in cytokine and chemokine production by fumarates within astrocytes is limited to DMF, as MMF had no significant effect on cytokine and chemokine secretion.…”

“…The recruitment of inflammatory cells and modulation of the local inflammatory milieu implicate the astrocyte as an important regulator of neuroinflammation 18. As such, DMTs capable of influencing astrocyte activation may be beneficial in the context of MS. DMF has previously been demonstrated to reduce the activation of astrocytes, highlighting multiple potential mechanisms through which DMF may reduce neuroinflammation 11, 13. Although these studies demonstrated an effect of DMF in vitro, differential effects of MMF and DMF, as well as any potential species effects between humans and mice have not been investigated to date.…”

“…DMF can induce apoptosis in circulating immune cells, including lymphocytes and monocytes,8, 9 and exerts anti‐inflammatory effects on both peripheral and CNS‐resident immune cells 3, 10, 11. Recent reports have demonstrated that the Nrf2‐dependent induction of AREs by DMF may be dispensable for neuroprotection, and the influence of DMF on both the innate and adaptive immune response may be the principle mechanism of action 12.…”

Regulation of APC development, immune response, and autoimmunity by Bach1/HO-1 pathway in mice

“…It has been shown that Nrf2, a relative of Bach 1, inhibits the maturation of DCs in vitro 42 and protects humans from MS development. 25,26 Potentially, Nrf2 and Bach1 might serve as counterparts in the CNC/Maf regulatory network, regulating the homeostatic balance of DC development and MS pathogenesis. Moreover, it is important to highlight that deletion of Bach1 did not completely ablate APC development, suggesting that other CNC and/or small Maf subunits might have compensatory or redundant functions with Bach1.…”

“…For example, the fumaric acid ester dimethylfumarate, which exerts neuroprotection by inducing Nrf2 expression, is currently in a phase 3 clinical trial as an orally active effective treatment of human multiple sclerosis with limited side effects. 25,26 Thus, deciphering the functions of the individual CNC subunits will not only be crucial to unraveling the overlapping and unique functions of these proteins but also provide insights to the potential of targeting CNC proteins for therapy against relevant diseases. In particular, the CNC member Bach1 is up-regulated in fetal Down syndrome (DS) brain.…”