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.

Proconvulsant effects of sildenafil citrate on pilocarpine-induced seizures: Involvement of cholinergic, nitrergic and pro-oxidant mechanisms.

Sildenafil is a phosphodiesterase 5 inhibitor used for the treatment of erectile dysfunction and pulmonary hypertension. Proconvulsant effect is a serious adverse event associated with sildenafil use. Here, we investigated the possible proconvulsant effects of sildenafil in pilocarpine (PILO)-induced seizures model, which mimics some aspects of temporal lobe epilepsy. We also evaluated sildenafil's effects on hippocampal markers related to PILO-induced seizure, for instance, acetylcholinesterase (AChE) activity, oxidative stress and nitric oxide (NO) markers, namely nitrite, inducible NO synthase (iNOS) and neuronal NOS (nNOS). The influences of muscarinic receptors blockade on sildenafil proconvulsant effects and brain nitrite levels were also evaluated. Male mice were submitted to single or repeated (7 days) sildenafil administration (2.5, 5, 10 and 20 mg/kg). Thirty minutes later, PILO was injected and mice were further evaluated for 1 h for seizure activity. Sildenafil induced a dose- and time-progressive proconvulsant effect in PILO-induced seizures. Sildenafil also potentiated the inhibitory effect of PILO in AChE activity and induced a further increase in nitrite levels and pro-oxidative markers, mainly in the hippocampus. Repeated sildenafil treatment also increased the hippocampal expression of iNOS and nNOS isoforms, while the blockade of muscarinic receptors attenuated both sildenafil-induced proconvulsant effect and brain nitrite changes. Our data firstly demonstrated the proconvulsant effect of sildenafil in PILO-model of seizures. This effect seems to be related to an increased cholinergic-nitrergic tone and pro-oxidative brain changes. Also, our findings advert to caution in using sildenafil for patients suffering from neurological conditions that reduces seizure threshold, such as epilepsy.

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.

Study of the safety of methylphenidate: Focus on nephrotoxicity aspects.

AIMS: Methylphenidate (MPD) is increasingly prescribed for the treatment of Attention Deficit Hyperactivity Disorder and there are concerns about its appropriate use. Furthermore, little is known about the potential nephrotoxicity in patients using MPD. This study aimed to investigate the safety of MPD, with focus on the possible effects of this drug on renal function. MAIN METHODS: We investigated the effects of MPD on renal perfusion system and renal tubular cells through in vivo and in vitro experimental models. KEY FINDINGS: In the in vivo experiments, 24 h and 48 h after MPD administration, urea, creatinine, creatinine clearance, and the fractional excretion of sodium and potassium were not changed. In the isolated kidney perfusion, MPD significantly reduced urinary flow, glomerular filtration rate and the percentage of tubular sodium transport. However, the perfusion pressure, renal vascular resistance and the percentage of tubular potassium transport were unchanged in this system. In the canine renal epithelial cell line MDCK culture, MPD was not cytotoxic and, in histopathological analysis, MPD did not promote alterations. SIGNIFICANCE: Our findings suggest a possible nephrotoxic effect of MPD, since it altered renal function by reducing the glomerular activity, urinary flow and sodium transport. These effects need to be further investigated in order to minimize potential harms associated with the use of MPD.