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.

The neuroprotective effect of Riparin IV on oxidative stress and neuroinflammation related to chronic stress-induced cognitive impairment.

BACKGROUND: Cognitive impairment is identified as one of the diagnostic criteria for major depressive disorder and can extensively affect the quality of life of patients. Based on these findings, this study aimed to investigate the possible effects of Riparin IV (Rip IV) on cognitive impairment induced by chronic administration of corticosterone in mice. METHODS: Female Swiss mice were divided into four groups: control (Control), corticosterone (Cort), Riparin IV (Cort + Rip IV), and Fluvoxamine (Cort + Flu). Three groups were administered corticosterone (20 mg/kg) subcutaneously during the 22-day study, while the control group received only vehicle. After the 14th day, the groups were administered medications: Riparin IV (Rip IV), fluvoxamine (Flu), or distilled water, by gavage, 1 h after the subcutaneous injections. After treatment, mice underwent behavioral testing, and brain areas were removed for oxidative stress and cytokine content assays. RESULTS: The results revealed that Cort-treated mice developed a cognitive impairment and exhibited a neuroinflammatory profile with an oxidative load and Th1/Th2 cytokine imbalance. Rip IV treatment significantly ameliorated the cognitive deficit induced by Cort and displayed a neuroprotective effect. CONCLUSION: The antidepressant-like ability of Rip IV treatment against chronic Cort-induced stress may be due to its potential to mitigate inflammatory damage and oxidative stress. The antioxidant and anti-inflammatory effect observed indicates Rip IV as a possible drug for antidepressant treatment of non-responsive patients with severe and cognitive symptoms.

Thymol reverses depression-like behaviour and upregulates hippocampal BDNF levels in chronic corticosterone-induced depression model in female mice.

OBJECTIVES: Based on this, the central therapeutic effects of thymol were verified in the neurotrophic pathway. METHODS: Female swiss mice were divided into four groups: control, corticosterone (Cort), thymol (Cort + thymol) and fluvoxamine (Cort + Flu). The administration of corticosterone was used to induce depressive symptoms for 23 days. After the treatment, the animals were exposed the behavioural tests, such as forced swimming test, tail suspension test, sucrose preference test, light/dark test, social interaction test, Y-maze test, plus-maze test and hole-board test. The hippocampus was also removed, and BDNF was measured by ELISA and Western blot. KEY FINDINGS: As a result, thymol and fluvoxamine were able to reverse the depressive symptoms, as well as to improve the anxious frame. The anhedonic and short-term memory was restored with the treatment. In the neurochemical tests, both thymol and fluvoxamine restored BDNF levels, improving the depressive condition. CONCLUSIONS: This work opens up new investigations aiming at the use of this molecule as a therapeutic alternative for treating depression disorders.

Reversal effect of Riparin IV in depression and anxiety caused by corticosterone chronic administration in mice.

Mental disorders have a multifactorial etiology and stress presents as one of the causal factors. In depression, it is suggested that high cortisol concentration contributes directly to the pathology of this disease. Based on that, the study aims to evaluate the potential antidepressant effect of Riparin IV (Rip IV) in mice submitted to chronic stress model by repeated corticosterone administration. Female Swiss mice were selected into four groups: control (Ctrl), corticosterone (Cort), Riparin IV (Cort + Rip IV) and fluvoxamine (Cort + Flu). Three groups were administrated subcutaneously (SC) with corticosterone (20 mg/kg) during twenty-one days, while the control group received only vehicle. After the fourteenth day, groups were administrated tested drugs: Riparin IV, fluvoxamine or distilled water, by gavage, 1 h after subcutaneous injections. After the final treatment, animals were exposed to behavioral models such as forced swimming test (FST), tail suspension test (TST), open field test (OFT), elevated plus maze (EPM) and sucrose preference test (SPT). The hippocampus was also removed for the determination of BDNF levels. Corticosterone treatment altered all parameters in behavioral tests, leading to a depressive- and anxious-like behavior. Riparin IV and fluvoxamine exhibit antidepressant effect in FST, TST and SPT. In EPM and OFT, treatment displayed anxiolytic effect without alteration of locomotor activity. Corticosterone administration decreased BDNF levels and Riparin IV could reestablish them, indicating that its antidepressant effect may be related to ability to ameliorate hippocampal neurogenesis. These findings suggest that Riparin IV improves the depressive and anxious symptoms after chronic stress and could be a new alternative treatment for patients with depression.

Prevention of pentylenetetrazole-induced kindling and behavioral comorbidities in mice by levetiracetam combined with the GLP-1 agonist liraglutide: Involvement of brain antioxidant and BDNF upregulating properties.

Kindling is a model for studying epileptogenesis and associated neuropsychiatric conditions. The antiepileptic drug levetiracetam (LEV) presents anti-kindling properties, but some severe neuropsychiatric events, especially depression, have been associated with its use in epileptic patients. The positive modulation of glucagon-like peptide-1 (GLP-1) receptors emerged as a potential target for the treatment of epilepsy and other neurological disorders. Here, we investigated behavioral and neurochemical effects of liraglutide (LIRA), a GLP-1 receptor agonist, alone or combined with LEV in mice subjected to PTZ-induced kindling. Male mice received PTZ on alternate days for 21 days. Before PTZ, the animals received LIRA, LEV (alone or in combination with LIRA) or saline. After seizures staging according to Racine's scale, behavioral evaluations were performed to verify anxiety-, depressive-like and cognitive performance. Brain oxidative alterations and BDNF levels were also measured. LEV showed anti-kindling properties, but aggravated depressive-like behavior in PTZ-kindling. In control conditions, LEV induced a pro-depressant effect and impaired avoidance memory retention. LIRA delayed but did not prevent the full kindling development. LIRA prevented the depressive-like behavior induced by PTZ kindling and PTZ + LEV. LEV + LIRA protected against PTZ-induced anxiety-like alterations and impairments in locomotion and cognition. Furthermore, LEV + LIRA reduced nitrite levels and lipid peroxidation in the hippocampus and prefrontal cortex, while it increased reduced glutathione levels in all evaluated brain areas. LIRA or LEV + LIRA increased hippocampal BDNF levels. In conclusion, our results showed that LIRA can be a promising adjunctive therapy for epilepsy-related neuropsychiatric comorbidities and to improve the management of antiepileptic drug associated behavioral adverse effects.

Riparin II ameliorates corticosterone-induced depressive-like behavior in mice: Role of antioxidant and neurotrophic mechanisms.

Riparin II (RIP II) is an alkamide isolated from Aniba riparia that has presented antidepressant and anxiolytic effects in acute stress behavioral models. This study aimed to investigate the activity of RIP II in a corticosterone-induced depression mice model. Corticosterone (20 mg/kg, s.c.) was administered once a day for 21 days. RIP II (50 mg/kg, p.o.) or fluvoxamine (FLU, 50 mg/kg, standard antidepressant, p.o.) was administered after corticosterone (CORT) injection, for the last 7 days of CORT treatment. Mice were exposed to the following behavioral tests: forced swimming, tail suspension, open field, sucrose preference, elevated plus maze and ymaze. After behavioral evaluation, brain areas (prefrontal cortex, hippocampus and striatum) were dissected for neurochemical evaluation: oxidative stress parameters (MDA, nitrite and GSH) and BDNF dosage. Repeated CORT administration caused depressive-like behavior in mice as indicated by increased despair effects in forced swimming and tail suspension tests and anhedonia in sucrose preference test. In addition, CORT decreased BDNF levels in the mice hippocampus and induced oxidative load in the brain with significative increase in pro-oxidant markers (lipid peroxidation and nitrite levels) and a decline in anti-oxidant defense system (reduced glutathione levels), indicating a direct effect of stress hormones in the induction of the brain oxidative stress. On the other hand, RIP II treatment reversed CORT-induced depressive-like behavior. Furthermore, this treatment reversed the impairment in BDNF levels and oxidative brain insults caused by CORT. This may demonstrate the mechanisms involved in antidepressant-like effect of RIP II. These findings further support that RIP II may be implicated as pharmacological intervention targeting depression associated with HPA-axis dysregulation.