Oxidative stress plays important roles in the pathogenesis of early brain injury (EBI) after subarachnoid hemorrhage (SAH). Tat-NR2B9c has shown efficacy as a neuroprotective agent in several studies. Here, we identified the neuroprotective role of Tat-NR2B9c after SAH and its related mechanisms. The results showed that Tat-NR2B9c treatment attenuated oxidative stress, therefore alleviated neuronal apoptosis and neurological deficits after SAH. Tat-NR2B9c treatment could alleviate mitochondrial vacuolization induced by SAH. Compared to SAH + vehicle group, Tat-NR2B9c resulted in the decrease of Acetylated superoxide dismutase2 (Ac-SOD2), Bcl-2-associated X protein (Bax) and cleaved-caspase3 (CC3) protein expression, and the up-regulation of Sirtunin 3 (Sirt3) and Bcl-2 protein level. Moreover, Tat-NR2B9c attenuated excitotoxicity by inhibiting the interaction of PSD95-NR2B-nNOS. Our results demonstrated that Tat-NR2B9c inhibited oxidative stress via inhibition of PSD95-NR2B-nNOS complex formation after SAH. Tat-NR2B9c may serve as a potential treatment for SAH induced brain injury.

This study aimed to explore the relationship between autophagy and synaptic plasticity in the pathogenesis of vascular dementia (VD). The autophagy inhibitor 3-methyladenine (3-MA) and the autophagy agonist rapamycin (Rap) were injected into the lateral ventricles of rats, and a rat VD model was established using a modified four-vessel occlusion method. The expression of LC3-II, synaptophysin (Syn), and postsynaptic density protein 95 (PSD-95) in the CA1 area of the rat hippocampus were detected using western blotting. Decreased Syn and PSD-95 expression in the VD group was accompanied by an increased LC3-II/LC3-I ratio. The expression of Syn and PSD-95 increased after 3-MA application, but decreased following Rap application. The LC3-II/LC3-I ratio was negatively correlated with Syn and PSD-95 expression. These findings suggest that autophagy may regulate synaptic plasticity in the hippocampus in a VD model of rats. Inhibition of autophagy is beneficial to the remodeling of synapses in the hippocampal CA1 area of the VD rat model, and this may provide a theoretical basis for the treatment and prevention of VD.

Xuefu Zhuyu decoction has been used for treating traumatic brain injury and improving post-traumatic dysfunction, but its mechanism of action needs further investigation. This study established rat models of traumatic brain injury by controlled cortical impact. Rat models were intragastrically administered 9 and 18 g/kg Xuefu Zhuyu decoction once a day for 14 or 21 days. Changes in neurological function were assessed by modified neurological severity scores and the Morris water maze. Immunohistochemistry, western blot assay, and reverse-transcription polymerase chain reaction were used to analyze synapsin protein and mRNA expression at the injury site of rats. Our results showed that Xuefu Zhuyu decoction visibly improved neurological function of rats with traumatic brain injury. These changes were accompanied by increased expression of synaptophysin, synapsin I, and postsynaptic density protein-95 protein and mRNA in a dose-dependent manner. These findings indicate that Xuefu Zhuyu decoction increases synapsin expression and improves neurological deficits after traumatic brain injury.

Postsynaptic density protein-95 (PSD95) plays important roles in the formation, differentiation, remodeling, and maturation of neuronal synapses. This study is to estimate the potential role of PSD95 in cognitive dysfunction and synaptic injury following intracerebral hemorrhage (ICH). The interaction between PSD95 and NMDA receptor subunit NR2B-neurotransmitter nitric oxide synthase (nNOS) could form a signal protein complex mediating excitatory signaling. Besides NR2B-nNOS, PSD95 also can bind to neurexin-1-neuroligin-1 to form a complex and participates in maintaining synaptic function. In this study, we found that there were an increase in the formation of PSD95-NR2B-nNOS complex and a decrease in the formation of neurexin-1-neuroligin-1-PSD95 complex after ICH, and this was accompanied by increased neuronal death and degeneration, and behavior dysfunction. PSD95 inhibitor Tat-NR2B9c effectively inhibited the interaction between PSD95 and NR2B-nNOS, and promoted the formation of neurexin-1-nueuroligin-1-PSD95 complex. In addition, Tat-NR2B9c treatment significantly reduced neuronal death and degeneration and matrix metalloproteinase 9 activity, alleviated inflammatory response and neurobehavioral disorders, and improved the cognitive and learning ability of ICH rats. Inhibition of the formation of PSD95-NR2B-nNOS complex can rescue secondary brain injury and behavioral cognitive impairment after ICH. PSD95 is expected to be a target for improving the prognosis of patients with ICH.

4-((3,5-Dichloro-2-hydroxybenzyl)amino)-2-hydroxybenzoic acid (ZL006, 1) is a small-molecular inhibitor of the nNOS/PSD-95 interaction, that is under preclinical evaluation stage for cerebral ischemia. However, the fast metabolism and low permeability across the blood brain barrier (BBB) have restricted its further use. In this manuscript, the mass spectroscopy analysis showed that ZL006 mainly combined with glucuronic acid in mice plasma, which accelerated its metabolism and elimination. Hence, six ZL006 analogs were designed according to the probable metabolism sites of ZL006, and featured the alkylation at phenolic hydroxyl, secondary amine and carboxyl groups. These compounds were synthesized in moderate to good yields, and fully characterized with (1)H NMR and MS. Further metabolism investigation of ZL006 analogs showed that phenolic hydroxyl group of aromatic ring A was the major conjugation site with glucuronic acid, and ZL006 cyclohexyl ester (6) had a better permeability across BBB, which was a potent prodrug for cerebral ischemia.

OBJECTIVE: Ischemic postconditioning, a brief episode of ischemia after a prolonged ischemic insult, has been found to reduce the delayed neuronal loss after stroke. However, the mechanisms underlying such endogenous neuroprotective strategy remain obscure. In this study, we try to explore the excitatory postsynaptic signal events associated with neuroprotective effect of ischemic postconditioning.
METHODS: Global cerebral ischemia was induced for 15 minutes by the 4-vessel occlusion method in male Sprague-Dawley rats. Ischemic postconditioning was conducted 10 minutes later by a single reocclusion for 3 minutes.
RESULTS: A severe global cerebral ischemia after 5 days of reperfusion destroyed almost all hippocampal CA1 pyramidal neurons. A brief ischemic postconditioning robustly reduced the neuronal loss after ischemia. Preadministration of phosphoinositide 3-kinase inhibitor LY294002 blocked the neuroprotection of postconditioning, whereas mitogen-activated protein kinase kinase 1 inhibitor PD98059 had no effect. Ischemic postconditioning significantly increased the Akt phosphorylation (Ser473). In addition, postconditioning not only perturbed the binding of postsynaptic density protein-95 with glutamatergic kainate receptor subunit 2 and mixed lineage kinase 3 but also suppressed the downstream activation of mixed lineage kinase 3, mitogen-activated protein kinase kinase 7, and c-Jun N-terminal kinase 3. LY294002, but not PD98059, abolished the postconditioning-induced decreases in the assembly of glutamatergic kainate receptor subunit 2-postsynaptic density protein-95-mixed lineage kinase 3 complex and in the mixed lineage kinase 3-c-Jun N-terminal kinase 3 signaling. Akt inhibitor IV, a specific Akt inhibitor, showed the same effects as LY294002.
CONCLUSIONS: Ischemic postconditioning protects neurons against stroke by attenuating the postsynaptic glutamatergic kainate receptor subunit 2-postsynaptic density protein-95-mixed lineage kinase 3-c-Jun N-terminal kinase 3 signal cascade via phosphoinositide 3-kinase-Akt pathway.