Neuroprotective effects of dimethyl fumarate against depression-like behaviors via astrocytes and microglia modulation in mice: possible involvement of the HCAR2/Nrf2 signaling pathway.

We postulated that dimethyl fumarate (DMF) exerts neuroprotective effects against depression-like behaviors through astrocytes and microglia modulation. To ascertain our hypothesis and define the mechanistic pathways involved in effect of DMF on neuroinflammation, we used the depression model induced by chronic unpredictable mild stress (CUMS), in which, the mice were exposed to stressful events for 28 days and from the 14th day they received DMF in the doses of 50 and 100 mg/kg or fluoxetine 10 mg/kg or saline. On the 29th day, the animals were subjected to behavioral tests. Microglia (Iba1) and astrocyte (GFAP) marker expressions were evaluated by immunofluorescence analyzes and the cytokines TNF-α and IL-Iß by immunoenzymatic assay. In addition, computational target prediction, 3D protein structure prediction, and docking calculations were performed with monomethyl fumarate (DMF active metabolite) and the Keap1 and HCAR2 proteins, which suggested that these could be the probable targets related protective effects. CUMS induced anxiety- and depressive-like behaviors, cognitive deficit, decreased GFAP, and increased Iba1, TNF-α, and IL-Iß expression in the hippocampus. These alterations were reversed by DMF. Thus, it is suggested that one of the mechanisms involved in the antidepressant effect of DMF is neuroinflammatory suppression, through the signaling pathway HCAR2/Nrf2. However, more studies must be performed to better understand the molecular mechanisms of this drug.

Ivabradine possesses anticonvulsant and neuroprotective action in mice.

We analyzed whether ivabradine (IVA), a hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker, clinically used for angina and arrhythmia, had anticonvulsant, antioxidant and neuroprotective properties against classical seizure models. Potential molecular targets to IVA anticonvulsant effects were evaluated by molecular docking. Mice were treated with IVA (1, 10 or 20 mg/kg, IP) for 3 days, and 30 min after the last administration were injected with pentylenetetrazole (PTZ - 85 mg/kg, IP), pilocarpine (PILO 400 mg/kg, SC), picrotoxin (PICRO 10 mg/kg, IP). The following measures were performed: presence of seizures, latency for the first seizure, latency for death, percentage of survival. Antioxidant activity was investigated by determination of lipid peroxidation (MDA), reduced glutathione (GSH) and nitrite levels in the prefrontal cortex (PFC), hippocampus and striatum (ST). Immunohistochemistry analysis for cleaved caspase-3, a pro-apoptotic and degenerative marker, in hippocampal subregions namely cornu ammonis (CA)1, CA3 and dentate gyrus (DG), were also performed. IVA attenuated PTZ- and PICRO-induced seizures while presented an antioxidant effect in all brain areas studied. IVA markedly reduced cleaved caspase-3 expression in the CA1 and DG region of PICRO- and PTZ-treated mice, respectively. Molecular docking demonstrated that IVA has high energetic affinity and binding compatibility for GABAA receptor without causing channel obstruction. However, no reproducibility in the binding of IVA to N-methyl-d-aspartate (NMDA) receptor was detected. In conclusion, IVA has anticonvulsant, antioxidant and neuroprotective effects against PTZ- and PICRO-induced seizures. Also, a high affinity of IVA to GABAA receptor was predicted, representing a potential underlying mechanism to these observable effects.