monomethyl-fumarate and citraconic-acid

α,β-Unsaturated carbonyls are a common motif in environmental toxins (e.g. acrolein) as well as therapeutic drugs, including dimethylfumarate (DMFU) and monomethylfumarate (MMFU), which are used to treat multiple sclerosis and psoriasis. These compounds form adducts with protein Cys residues as well as other nucleophiles. The specific targets ('adductome') that give rise to their therapeutic or toxic activities are poorly understood. This is due, at least in part, to the absence of antigens or chromophores/fluorophores in these compounds. We have recently reported click-chemistry probes of DMFU and MMFU (Redox Biol., 2022, 52, 102299) that allow adducted proteins to be visualized and enriched for further characterization. In the current study, we hypothesized that adducted proteins could be 'clicked' to agarose beads and thereby isolated for LC-MS analysis of DMFU/MMFU targets in primary human coronary artery smooth muscle cells. We show that the probes react with thiols with similar rate constants to the parent drugs, and give rise to comparable patterns of gene induction, confirming similar biological actions. LC-MS proteomic analysis identified ∼2970 cellular targets of DMFU, ∼1440 for MMFU, and ∼140 for the control (succinate-probe) treated samples. The most extensively modified proteins were galectin-1, annexin-A2, voltage dependent anion channel-2 and vimentin. Other previously postulated DMFU targets, including glyceraldehyde-3-phosphate dehydrogenase (GAPDH), cofilin, p65 (RELA) and Keap1 were also identified as adducted species, though at lower levels with the exception of GAPDH. These data demonstrate the utility of the click-chemistry approach to the identification of cellular protein targets of both exogenous and endogenous compounds.

Topics: Dimethyl Fumarate; Galectin 1; Humans; Kelch-Like ECH-Associated Protein 1; NF-E2-Related Factor 2; Proteomics

Hyperexcitability-induced neuronal damage plays a role both in epilepsy as well as in inflammatory brain diseases such as multiple sclerosis (MS) and as such represents an important disease pathway which potentially can be targeted to mitigate neuronal damage. Dimethyl fumarate (DMF) and its pharmacologically active metabolite monomethyl fumarate (MMF) are FDA-approved therapeutics for MS, which can induce immunosuppressive and antioxidant pathways, and their neuroprotective capacity has been demonstrated in other preclinical neurological disease models before. In this study, we used an unbiased proteomic approach to identify potential new targets upon the treatment of MMF in glio-neuronal hippocampal cultures. MMF treatment results in induction of antioxidative (HMOX1, NQO1) and anaplerotic metabolic (GAPDH, PC) pathways, which correlated with reduction in ROS production, increased mitochondrial NADH-redox index and decreased NADH pool, independent of glutathione levels. Additionally, MMF reduced glycolytic capacity indicating individual intra-cellular metabolic programs within different cell types. Furthermore, we demonstrate a neuroprotective effect of MMF upon hyperexcitability in vitro (low magnesium model), where MMF prevents glio-neuronal death via reduced ROS production. These results highlight MMF as a potential new therapeutic opportunity in hyperexcitability-induced neurodegeneration.

Topics: Antioxidants; NAD; Neuroprotective Agents; NF-E2-Related Factor 2; Proteomics; Reactive Oxygen Species

Multiple sclerosis (MS) is the most common chronic inflammatory, demyelinating disease of the central nervous system. Dimethyl fumarate (DMF) and monomethyl fumarate (MMF) belong to the disease-modifying drugs in treatment of MS. There is evidence that astrocytes and microglia are involved in MS pathology, but few studies are available about MMF and DMF effects on astrocytes and microglia. The aim of this study was to investigate the effects of MMF and DMF on microglial activation and morphology as well as potential effects on glial viability, Cx43, and AQP4 expressions in different set-ups of an in vitro astrocyte-microglia co-culture model of inflammation.. Primary rat glial co-cultures of astrocytes containing 5% (M5, mimicking "physiological" conditions) or 30% (M30, mimicking "pathological, inflammatory" conditions) of microglia were treated with different concentrations of MMF (0.1, 0.5, and 2 μg/mL) or DMF (1.5, 5, and 15 μM) for 24 h. Viability, proliferation, and cytotoxicity of glial cells were examined using MTT assay. Immunocytochemistry was performed to analyze the microglial phenotypes. Connexin 43 (Cx43) and aquaporin 4 (AQP4) expressions were quantified by immunoblot analysis.. Treatment with different concentrations of MMF or DMF for 24 h did not change the glial cell viability in M5 and M30 co-cultures. Microglial phenotypes were not altered by DMF under physiological M5 conditions, but treatment with higher concentration of DMF (15 μM) induced microglial activation under inflammatory M30 conditions. Incubation with different concentrations of MMF had no effects on microglial phenotypes. The Cx43 expression in M5 and M30 co-cultures was not changed significantly by immunoblot analysis after incubation with different concentrations of DMF or MMF for 24 h. The AQP4 expression was significantly increased in M5 co-cultures after incubation with 5 μm DMF. Under the other conditions, AQP4 expression was not affected by DMF or MMF.. In different set-ups of the astrocyte-microglia co-culture model of inflammation, MMF has not shown significant effects. DMF had only limited effects on microglia phenotypes and AQP4 expression. In summary, mechanisms of action of fumarates probably do not involve direct effects on microglia phenotypes as well as Cx43 and AQP4 expression.

Topics: Animals; Astrocytes; Coculture Techniques; Connexin 43; Dimethyl Fumarate; Inflammation; Microglia; Rats

Dimethyl fumarate (DMF) is approved as a treatment for multiple sclerosis (MS), however, its mode of action remains unclear. One hypothesis proposes that Michael addition to thiols by DMF, notably glutathione is immunomodulatory. The alternative proposes that monomethyl fumarate (MMF), the hydrolysis product of DMF, is a ligand to the fatty acid receptor GPR109A found in the lysosomes of immune cells. We prepared esters of MMF and macrolides derived from azithromycin, which were tropic to immune cells by virtue of lysosomal trapping. We tested the effects of these substances in an assay of response to Lipopolysaccharide (LPS) in freshly isolated human peripheral blood mononuclear cells (PBMCs). In this system, we observed that the 4'' ester of MMF (compound 2 and 3) reduced levels of Interleukins (IL)-1β, IL-12 and tumor necrosis factor alpha (TNFα) significantly at a concentration of 1 µM, while DMF required about 25 µM for the same effect. The 2' esters of MMF (compound 1 and 2) were, like MMF itself, inactive in vitro. The 4'' ester formed glutathione conjugates rapidly while the 2' conjugates did not react with thiols but did hydrolyze slowly to release MMF in these cells. We then tested the substances in vivo using the imiquimod/isostearate model of psoriasis where the 2' ester was the most active at 0.06-0.12 mg/kg (approximately 0.1 µmol/kg), improving skin score, body weight and cytokine levels (TNFα, IL-17A, IL-17F, IL-6, IL-1β, NLRP3 and IL-23A). In contrast, the thiol reactive 4'' ester was less active than the 2' ester while DMF was ca. 300-fold less active. The thiol reactive 4'' ester was not easily recovered from either plasma or organs while the 2' ester exhibited conventional uptake and elimination. The 2' ester also reduced levels of IL-6 in acute monosodium urate (MSU) induced inflammation. These data suggest that mechanisms that are relevant in vivo center on the release of MMF. Given that GPR109A is localized to the lysosome, and that lysosomal trapping increases 2' ester activity by > 300 fold, these data suggest that GPR109A may be the main target in vivo. In contrast, the effects associated with glutathione (GSH) conjugation in vitro are unlikely to be as effective in vivo due to the much lower dose in use which cannot titrate the more concentrated thiols. These data support the case for GPR109A modulation in autoimmune diseases.

Topics: Dimethyl Fumarate; Esters; Glutathione; Humans; Interleukin-6; Leukocytes, Mononuclear; Tumor Necrosis Factor-alpha

Nicotinic acid has been used for several decades to treat dyslipidemia. In mice, the lipid-lowing effect of nicotinic acid is mediated by the Gi coupled receptor PUMA-G. In humans, high (GPR109A) and low (GPR109B) affinity nicotinic acid receptors have been characterized. Here we identify monomethylfumarate as a GPR109A agonist. Monomethylfumarate is the active metabolite of the psoriasis drug Fumaderm. We show that monomethylfumarate activates GPR109A in a calcium based aequorin assay, cAMP assay and demonstrate competitive binding with nicotinic acid. We show that GPR109A is highly expressed in neutrophils and epidermal keratinocytes, and that its expression is increased in human psoriatic lesions. Our findings provide evidence that GPR109A is a target for the drug Fumaderm and suggest that niacin should be investigated to treat psoriasis in addition to its role in treating lipid disorders.

Topics: Cell Line; Dermatologic Agents; Dimethyl Fumarate; Fumarates; Humans; Hypolipidemic Agents; Maleates; Niacin; Psoriasis; Receptors, G-Protein-Coupled; Receptors, Nicotinic