RESUMEN
alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are responsible for excitotoxicity induced by ischemic injury in hippocampal CA1 neurons, whereas the molecular mechanisms responsible for their neurotrophic activities are much less studied. Here, we examined the neuroprotective effect of positive modeulation of AMPARs by coapplication of AMPA with PEPA, an allosteric potentiator of AMPARs. We showed that coapplication of AMPA with PEPA protected hippocampal CA1 neurons from brain ischemia-induced death. Coapplication of AMPA with PEPA could prevent downregulated expression of GluR2 subunit caused by ischemia and increase BDNF expression via Lyn-ERK1/2-CREB signaling. Furthermore, TrkB receptor-mediated PI3K/Akt signal pathway was activated after coapplication of AMPA with PEPA, which was related to MAPK pathway and protected CA1 neurons against ischemic insults through depression of JNK3 activity, release of cytochrome c to cytosol and depression of capase-3 activity. Our results revealed that positive modulation of AMPARs could exert neuroprotective effects and the possible signaling pathways underlied.
Asunto(s)
Isquemia Encefálica/metabolismo , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/metabolismo , Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Receptores AMPA/metabolismo , Familia-src Quinasas/metabolismo , Animales , Región CA1 Hipocampal/metabolismo , Regulación de la Expresión Génica , Sistema de Señalización de MAP Quinasas , Masculino , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteína Quinasa 3 Activada por Mitógenos/metabolismo , Neuronas/metabolismo , ARN Mensajero/metabolismo , Ratas , Ratas Endogámicas , Receptores AMPA/genética , Transducción de SeñalRESUMEN
Previous studies have shown that KA receptor subunit GluR6 mediated c-Jun N-terminal protein kinase (JNK) signaling is involved in global ischemia injury. Our present study indicates that focal ischemic brain insult on rat middle cerebral artery occlusion (MACo) model enhances the assembly of the GluR6-PSD95-MLK3 module and facilitates the phosphorylation of JNK. Most importantly, a peptide containing the TAT protein transduction sequence, Tat-GluR6-9c, can perturb the assembly of the GluR6-PSD95-MLK3 signaling module and suppress the activation of MLK3, MKK7/4 and JNK. As result, the inhibition of JNK activation caused by Tat-GluR6-9c diminishes the phosphorylation of the transcription factor c-Jun, down-regulates FasL expression and attenuates bax translocation, release of cytochrome c and the activation of caspase-3. Furthermore, MCAo induced infract volume is reduced by intracerebroventricular injection of Tat-Glur6-9c. Oxygen-glucose-deprivation (OGD) cultured cortical neuronal cell also shows an improved cell viability by application of Tat-GluR6-9c. Taken together, our findings strongly suggest that GluR6-PSD95-MLK3 signaling module mediated activation of nuclear and non-nuclear pathways of JNK activation are involved in focal ischemia injury and OGD. Tat-GluR6-9c, the peptide we constructed, gives a new insight into the therapy for ischemic stroke.
Asunto(s)
Glucosa/deficiencia , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Ataque Isquémico Transitorio/prevención & control , Proteínas de la Membrana/metabolismo , Fármacos Neuroprotectores/farmacología , Oxígeno/farmacología , Receptores de Ácido Kaínico/metabolismo , Proteínas Recombinantes de Fusión/farmacología , Productos del Gen tat del Virus de la Inmunodeficiencia Humana/genética , Animales , Corteza Cerebral/citología , Corteza Cerebral/metabolismo , Homólogo 4 de la Proteína Discs Large , Técnicas In Vitro , Ataque Isquémico Transitorio/metabolismo , Masculino , Mutación , Neuronas/citología , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Fármacos Neuroprotectores/uso terapéutico , Ratas , Ratas Sprague-Dawley , Receptores de Ácido Kaínico/genética , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/uso terapéutico , Receptor de Ácido Kaínico GluK2RESUMEN
In this study, we investigated whether the increase of inhibitory gamma-amino butyric acid (GABA) signal suppresses the excitatory glutamate signal induced by cerebral ischemia and the underlying mechanisms. In global cerebral ischemia, focal cerebral ischemia and oxygen-glucose deprivation, application of muscimol and baclofen, agonists of GABA(A) receptor and GABA(B) receptor, exerted neuroprotection. The agonists inhibited the increased assembly of the GluR6-PSD-95-MLK3 module induced by cerebral ischemia and the activation of the MLK3-MKK4/7-JNK3 cascade. Our results suggest that stimulation of the inhibitory GABA receptors can attenuate the excitatory JNK3 apoptotic signaling pathway via inhibiting the increased assembly of the GluR6-PSD-95-MLK3 signaling module in cerebral ischemia.