Dimethyl fumarate decreases short-term but not long-term inflammation in a focal EAE model of neuroinflammation

Abstract

Background Dimethyl fumarate (DMF) is an oral immunomodulatory drug used in the treatment of autoimmune diseases. Here, we sought to study whether the effect of DMF can be detected using positron emission tomography (PET) targeting the 18-kDa translocator protein (TSPO) in the focal delayed-type hypersensitivity rat model of multiple sclerosis (fDTH-EAE). The rats were treated orally twice daily from lesion activation (day 0) with either vehicle (tap water with 0.08% Methocel, 200 µL; control group n = 4 (3 after week four)) or 15 mg/kg DMF (n = 4) in 0.08% aqueous Methocel (200 µL) for 8 weeks. The animals were imaged by PET using the TSPO tracer [18F]GE-180 in weeks 0, 1, 2, 4, 8, and 18 following lesion activation, and the non-displaceable binding potential (BPND) was calculated. Immunohistochemical staining for Iba1, CD4, and CD8 was performed in week 18, and in separate cohorts of animals, following 2 or 4 weeks of treatment. Results Using the fDTH-EAE model, DMF reduced the [18F]GE-180 BPND in the DMF-treated animals compared to control animals after 1 week of treatment (two-tailed unpaired t test, p = 0.031), but not in weeks 2, 4, 8, or 18 when imaged in vivo by PET. Immunostaining for Iba1 showed that DMF had no effect on the perilesional volume or the core lesion volume after 2 or 4 weeks of treatment, or at 18 weeks. However, the optical density (OD) measurements of CD4+ staining showed reduced OD in the lesions of the treated rats. Conclusions DMF reduced the microglial activation in the fDTH-EAE model after 1 week of treatment, as detected by PET imaging of the TSPO ligand [18F]GE-180. However, over an extended time course, reduced microglial activation was not observed using [18F]GE-180 or by immunohistochemistry for Iba1+ microglia/macrophages. Additionally, DMF did affect the infiltration of CD4+ and CD8+ T-lymphocytes at the fDTH-EAE lesion.

Beneficial effect of fingolimod in a Lafora disease mouse model by preventing reactive astrogliosis-derived neuroinflammation and brain infiltration of T-lymphocytes.

“…DMF was selected because of its recognized ability as an antiin ammatory agent, and also as an anti-oxidant compound, enhancing Nrf2-related antioxidant effects [23]. In addition, a recent report indicates that DMF reduced microglial activation and reduced the in ltration of CD4+ and CD8+ T-lymphocytes in the brain [29]. Treatments were administered orally in male and female mice of three months of age (corresponding to an early stage of LD) for fteen weeks.…”

“…In addition, DMF reduces T-cell and macrophage in ltration into the spinal cord in a mouse model of experimental autoimmune encephalitis (EAE) and in multiple sclerosis patients [25], [26]. Recently it has been described that DMF reduced microglial activation (Iba1) in the short term, and reduced the in ltration of CD4+ and CD8+ T-lymphocytes in the brain of a rat model of EAE [29]. DMF also acts as a strong agonist of HCAR2, a G-protein coupled membrane receptor expressed in immune cells, inducing robust anti-in ammatory signaling.…”

“…Three months old mice (corresponding to an early stage of LD) were treated for fteen weeks. Drug doses and administration schedules were based on a bibliographic search for both compounds [27], [28]; [29], [30]. These previous studies concluded that the doses we used in our assays were safe and that all compounds reached the brain to exert their effects.…”

Beneficial Effect of Fingolimod in a Lafora Disease Mouse Model by Preventing Reactive Astrogliosis-Derived Neuroinflammation and Brain Infiltration of T-lymphocytes

“…In addition, DMF reduces T-cell and macrophage infiltration into the spinal cord in a mouse model of experimental autoimmune encephalitis (EAE) and in multiple sclerosis patients [ 25 , 26 ]. Recently, it has been described that DMF reduced microglial activation (Iba1) in the short term and reduced the infiltration of CD4 + and CD8 + T-lymphocytes in the brain of a rat model of EAE [ 29 ]. DMF also acts as a strong agonist of HCAR2, a G protein-coupled membrane receptor expressed in immune cells, inducing robust anti-inflammatory signaling.…”

Established and emerging techniques for the study of microglia: visualization, depletion, and fate mapping

“…PET utilizes the binding of radioactive isotopes to a target molecule to visualize and quantify that molecule ( Berger, 2003 ). PET has already highlighted the activity of microglia in contexts of neurodegeneration, inflammation and neurodevelopmental disorders, as measured using the translocator protein (TSPO) as a target ( Yankam Njiwa et al, 2017 ; Hu et al, 2020 ; Lavisse et al, 2021 ; Seelaar and Van Swieten, 2021 ; Simpson et al, 2022 ; Vainio et al, 2022 ). Furthermore, microglia were shown to be highly active in people with schizophrenia using TSPO, as the upregulation of TSPO correlates with higher mitochondrial activity ( Conen et al, 2021 ).…”