RESUMEN
Agmatine is an endogenous neuromodulator that has been shown to have antidepressant-like properties. We have previously demonstrated that it can induce a rapid increase in BDNF levels after acute administration, suggesting that agmatine may be a fast-acting antidepressant. To investigate this hypothesis, the present study evaluated the effects of a single administration of agmatine in mice subjected to chronic unpredictable stress (CUS), a model of depression responsive only to chronic treatment with conventional antidepressants. The ability of agmatine to reverse CUS-induced behavioral and biochemical alterations was evaluated and compared with those elicited by the fast-acting antidepressant (ketamine) and the conventional antidepressant (fluoxetine). After exposed to CUS for 14days, mice received a single oral dose of agmatine (0.1mg/kg), ketamine (1mg/kg) or fluoxetine (10mg/kg), and were submitted to behavioral evaluation after 24h. The exposure to CUS caused an increased immobility time in the tail suspension test (TST) but did not change anhedonic-related parameters in the splash test. Our findings provided evidence that, similarly to ketamine, agmatine is able to reverse CUS-induced depressive-like behavior in the TST. Western blot analyses of prefrontal cortex (PFC) demonstrated that mice exposed to CUS and/or treated with agmatine, fluoxetine or ketamine did not present alterations in the immunocontent of synaptic proteins [i.e. GluA1, postsynaptic density protein 95 (PSD-95) and synapsin]. Altogether, our findings indicate that a single administration of agmatine is able to reverse behavioral alterations induced by CUS in the TST, suggesting that this compound may have fast-acting antidepressant-like properties. However, there was no alteration in the levels of synaptic proteins in the PFC, a result that need to be further investigated in other time points.
Asunto(s)
Agmatina/farmacología , Antidepresivos/farmacología , Trastorno Depresivo/tratamiento farmacológico , Ketamina/farmacología , Estrés Psicológico/complicaciones , Animales , Femenino , Suspensión Trasera , Ratones , Actividad Motora/efectos de los fármacos , Corteza Prefrontal/químicaRESUMEN
Considering that intracellular signaling pathways that modulate brain BDNF are implicated in antidepressant responses, this study investigated whether signaling pathway inhibitors upstream to BDNF might influence the antidepressant-like effect of zinc, a metal that has been shown to display antidepressant properties. To this end, the influence of i.c.v. administration of H-89 (1µg/site, PKA inhibitor), KN-62 (1µg/site, CAMKII inhibitor), chelerythrine (1µg/site, PKC inhibitor), PD98059 (5µg/site, MEK1/2 inhibitor), U0126 (5µg/site, MEK1/2 inhibitor), LY294002 (10nmol/site, PI3K inhibitor) on the reduction of immobility time in the tail suspension test (TST) elicited by ZnCl2 (10mg/kg, p.o.) was investigated. Moreover, the effect of the combination of sub-effective doses of ZnCl2 (1mg/kg, p.o.) and AR-A014418 (0.001µg/site, GSK-3ß inhibitor) was evaluated. The occurrence of changes in CREB phosphorylation and BDNF immunocontent in the hippocampus and prefrontal cortex of mice following ZnCl2 treatment was also investigated. The anti-immobility effect of ZnCl2 in the TST was prevented by treatment with PKA, PKC, CAMKII, MEK1/2 or PI3K inhibitors. Furthermore, ZnCl2 in combination with AR-A014418 caused a synergistic anti-immobility effect in the TST. None of the treatments altered locomotor activity of mice. ZnCl2 treatment caused no alteration in CREB phosphorylation and BDNF immunocontent. The results extend literature data regarding the mechanisms underlying the antidepressant-like action of zinc by indicating that its antidepressant-like effect may be dependent on the activation of PKA, CAMKII, PKC, ERK, and PI3K/GSK-3ß pathways. However, zinc is not able to acutely increase BDNF in the hippocampus and prefrontal cortex.
Asunto(s)
Antidepresivos/uso terapéutico , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Cloruros/uso terapéutico , Depresión/tratamiento farmacológico , Transducción de Señal/fisiología , Compuestos de Zinc/uso terapéutico , Animales , Antidepresivos/farmacología , Proteína de Unión a CREB/metabolismo , Corteza Cerebral/efectos de los fármacos , Corteza Cerebral/metabolismo , Cloruros/farmacología , Depresión/patología , Depresión/fisiopatología , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Inhibidores Enzimáticos/farmacología , Conducta Exploratoria/efectos de los fármacos , Femenino , Suspensión Trasera , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Ratones , Fosforilación/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Estadísticas no Paramétricas , Compuestos de Zinc/farmacologíaRESUMEN
The excitotoxicity induced by excessive activation of the glutamatergic neurotransmission pathway is involved in several neuropathologies. In this sense, molecules that prevent the release of glutamate or the excessive activation of its receptors can be useful in preventing the neuronal cell death observed in these diseases. Lectins are proteins capable of reversible binding to the carbohydrates in glycoconjugates, and some have been used in the study and purification of glutamate receptors. ConBr is a mannose/glucose-binding lectin purified from Canavalia brasiliensis seeds. In the present study, we aimed to evaluate the neuroprotective activity of ConBr against glutamate-induced excitotoxicity. Hippocampal slices were isolated from adult male mice and incubated for 6h in Krebs saline/DMEM buffer alone (control), in the presence of glutamate or glutamate plus ConBr. The phosphorylation of Akt and mitogen activated protein kinases (MAPKs) such as ERK1/2, p38(MAPK) and JNK1/2/3 was evaluated with western blotting. The results indicate that glutamate provoked a reduction in the hippocampal slice viability (-25%), diminished the phosphorylation of Akt and augmented p38(MAPK) and ERK1 phosphorylation. No changes were observed in the phosphorylation of JNK1/2/3 or ERK2. Notably, ConBr, through a mechanism dependent on carbohydrate interaction, prevented the reduction of cell viability and Akt phosphorylation induced by glutamate. Furthermore, in the presence of the PI3K inhibitor LY294002, ConBr was unable to reverse glutamate neurotoxicity. Taken together, our data suggest that the neuroprotective effect of ConBr against glutamate neurotoxicity requires oligosaccharide interaction and is dependent on the PI3K/Akt pathway.
Asunto(s)
Canavalia/química , Antagonistas de Aminoácidos Excitadores , Ácido Glutámico/toxicidad , Hipocampo/efectos de los fármacos , Fármacos Neuroprotectores , Proteína Oncogénica v-akt/fisiología , Fosfatidilinositol 3-Quinasas/fisiología , Lectinas de Plantas/farmacología , Transducción de Señal/efectos de los fármacos , Animales , Western Blotting , Metabolismo de los Hidratos de Carbono/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Cromonas/farmacología , Inhibidores Enzimáticos/farmacología , Hipocampo/patología , Técnicas In Vitro , Masculino , Ratones , Proteínas Quinasas Activadas por Mitógenos/fisiología , Morfolinas/farmacología , Fosforilación , Lectinas de Plantas/química , Lectinas de Plantas/aislamiento & purificación , Sales de Tetrazolio , TiazolesRESUMEN
While manganese (Mn) is essential for proper central nervous system (CNS) development, excessive Mn exposure may lead to neurotoxicity. Mn preferentially accumulates in the basal ganglia, and in adults it may cause Parkinson's disease-like disorder. Compared to adults, younger individuals accumulate greater Mn levels in the CNS and are more vulnerable to its toxicity. Moreover, the mechanisms mediating developmental Mn-induced neurotoxicity are not completely understood. The present study investigated the developmental neurotoxicity elicited by Mn exposure (5, 10 and 20 mg/kg; i.p.) from postnatal day 8 to PN27 in rats. Neurochemical analyses were carried out on PN29, with a particular focus on striatal alterations in intracellular signaling pathways (MAPKs, Akt and DARPP-32), oxidative stress generation and cell death. Motor alterations were evaluated later in life at 3, 4 or 5 weeks of age. Mn exposure (20 mg/kg) increased p38(MAPK) and Akt phosphorylation, but decreased DARPP-32-Thr-34 phosphorylation. Mn (10 and 20 mg/kg) increased caspase activity and F2-isoprostane production (a biological marker of lipid peroxidation). Paralleling the changes in striatal biochemical parameters, Mn (20 mg/kg) also caused motor impairment, evidenced by increased falling latency in the rotarod test, decreased distance traveled and motor speed in the open-field test. Notably, the antioxidant Trolox™ reversed the Mn (20 mg/kg)-dependent augmentation in p38(MAPK) phosphorylation and reduced the Mn (20 mg/kg)-induced caspase activity and F2-isoprostane production. Trolox™ also reversed the Mn-induced motor coordination deficits. These findings are the first to show that long-term exposure to Mn during a critical period of neurodevelopment causes motor coordination dysfunction with parallel increment in oxidative stress markers, p38(MAPK) phosphorylation and caspase activity in the striatum. Moreover, we establish Trolox™ as a potential neuroprotective agent given its efficacy in reversing the Mn-induced neurodevelopmental effects.
Asunto(s)
Antioxidantes/farmacología , Ganglios Basales/efectos de los fármacos , Conducta Animal/efectos de los fármacos , Cromanos/farmacología , Intoxicación por Manganeso/tratamiento farmacológico , Actividad Motora/efectos de los fármacos , Fármacos Neuroprotectores/farmacología , Estrés Oxidativo/efectos de los fármacos , Factores de Edad , Animales , Animales Recién Nacidos , Ganglios Basales/metabolismo , Ganglios Basales/fisiopatología , Caspasas/metabolismo , Modelos Animales de Enfermedad , Activación Enzimática , Femenino , Masculino , Intoxicación por Manganeso/etiología , Intoxicación por Manganeso/metabolismo , Intoxicación por Manganeso/fisiopatología , Intoxicación por Manganeso/psicología , Fosforilación , Ratas , Ratas Wistar , Prueba de Desempeño de Rotación con Aceleración Constante , Transducción de Señal/efectos de los fármacos , Proteínas Quinasas p38 Activadas por Mitógenos/metabolismoRESUMEN
Manganese (Mn) is an essential metal for development and metabolism. However, exposures to high Mn levels may be toxic, especially to the central nervous system (CNS). Neurotoxicity is commonly due to occupational or environmental exposures leading to Mn accumulation in the basal ganglia and a Parkinsonian-like disorder. Younger individuals are more susceptible to Mn toxicity. Moreover, early exposure may represent a risk factor for the development of neurodegenerative diseases later in life. The present study was undertaken to investigate the developmental neurotoxicity in an in vivo model of immature rats exposed to Mn (5, 10 and 20 mg/kg; i.p.) from postnatal day 8 (PN8) to PN12. Neurochemical analysis was carried out on PN14. We focused on striatal alterations in intracellular signaling pathways, oxidative stress and cell death. Moreover, motor alterations as a result of early Mn exposure (PN8-12) were evaluated later in life at 3-, 4- and 5-weeks-of-age. Mn altered in a dose-dependent manner the activity of key cell signaling elements. Specifically, Mn increased the phosphorylation of DARPP-32-Thr-34, ERK1/2 and AKT. Additionally, Mn increased reactive oxygen species (ROS) production and caspase activity, and altered mitochondrial respiratory chain complexes I and II activities. Mn (10 and 20 mg/kg) also impaired motor coordination in the 3(rd), 4(th) and 5(th) week of life. Trolox™, an antioxidant, reversed several of the Mn altered parameters, including the increased ROS production and ERK1/2 phosphorylation. However, Trolox™ failed to reverse the Mn (20 mg/kg)-induced increase in AKT phosphorylation and motor deficits. Additionally, Mn (20 mg/kg) decreased the distance, speed and grooming frequency in an open field test; Trolox™ blocked only the decrease of grooming frequency. Taken together, these results establish that short-term exposure to Mn during a specific developmental window (PN8-12) induces metabolic and neurochemical alterations in the striatum that may modulate later-life behavioral changes. Furthermore, some of the molecular and behavioral events, which are perturbed by early Mn exposure are not directly related to the production of oxidative stress.