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Objective:To investigate the protective effect of interfering peptide TAT-GluA2CT on hippocampal neurons in the Lithium chlorine-Pilocarpine status epilepticus model and the optimal time of administration.Methods:Male SD rats (72 cases) were induced to status epilepticus by using Lithium chlorine-Pilocarpine, while a control group ( n=12) was established.The 72 rats were divided into epilepsy group ( n=12), TAT-sham peptide group ( n=12), TAT-GluA2CT peptide group ( n=48) according to the random number table method, and the TAT-GluA2CT peptide group were further divided into the pre-1 h group ( n=12), the post-2 h group ( n=12), the post-4 h group( n=12), and the post-6 h group ( n=12) according to the administration time of the TAT-GluA2CT peptide.Nissl staining and terminal dUTP nick end labeling (TUNEL) assay were performed on 6 rats each from control group, epilepsy group, TAT-shampeptide group, pre-1 h group, post-2 h group, post-4 h group, and post-6 h group to observe the morphological changes and apoptosis of neurons in the CA1 region of the rat hippocampus.Western blot and co-immunopercipitation test were used to detect the expression of GluA2[second subunit of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) recepter] and the coupling of GluA2/transmembrane AMPA receptor regulatory protein (TARP γ-8) complex in control group, epilepsy group, pre-1 h group, post-2 h group, post-4 h group and post-6 h group.The t-test was used to compare the data differences between 2 groups, and one-way ANOVA was adopted to compare the differences between the groups. Results:Compared with the epilepsy group, the number of neurons in each TAT-GluA2CT peptide group increased significantly, and the difference was statistically significant( epilepsy group 20.07±3.51, pre-1 h group 39.40±2.39, post-2 h group 38.43±2.42, post-4 h group 30.30±2.55, and post-6 h group 27.93±3.20, F=235.28, P<0.05). Compared with the epilepsy group, the number of apoptotic cells in each TAT-GluA2CT peptide group was significantly reduced, and the difference was statistically significant(epilepsy group 31.47±3.19, pre-1 h group 7.30±3.45, post-2 h group 9.27±3.81, post-4 h group 12.86±3.08, and post-6 h group 14.43±3.13, F=248.60, P<0.05). Compared with the control group, the expression of hippocampal GluA2 decreased after epilepsy induction, and the difference was statistically significant(control group 21 626.53±2 700.58, epilepsy group 14 578.16±2 917.02, pre-1 h group 13 375.47±3 180.54, post-2 h group 15 244.10±1 390.41, post-4 h group 15 799.16±4 559.49, post-6 h group 15 722.95±1 756.01, F=3.83, P<0.05). No statistical difference was observed in the expression of GluA2 between the TAT-GluA2CT peptide group and the epilepsy group( F=0.45, P=0.77). Compared with the epilepsy group, GluA2/TARPγ-8 complex coupling was decreased in each TAT-GluA2CT peptide group, and the difference was statistically significant(epilepsy group 24 509.80±3 718.54, pre-1 h group 12 055.18±5 847.11, post-2 h group 9 630.51±5 805.17, post-4 h group 12 749.35±7 108.45, post-6 h group 11 092.98±7 330.08, F=10.68, P<0.05). Compared with the epilepsy group, the incubation period of seizures in the pre-1 h group was prolonged and the seizure rating was decreased, with statistically significant differences[epilepsy group (18.58±3.99) min, pre-1 h group (103.25±9.21) min, t=29.23, P<0.05]. Conclusions:TAT-GluA2CT peptide can attenuate the neuronal damage in hippocampus of epileptic rats.The neuroprotective effect of TAT-GluA2CT peptide was most obvious at 1 h before or 2 h after administration of Pilocarpine.
RESUMEN
Objective:To investigate the effect of GluA2-3Y which is an inhibitor of AMPA(α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid) receptor internalization on cognitive function and hippocampal postsynaptic protein expression in rats with chronic cerebral hypoperfusion.Methods:Forty-eight adult male SD rats were randomly divided into Sham group, 2VO group, high-dose GluA2-3Y group and low-dose GluA2-3Y group according to random number table, with 12 rats in each group.The chronic cerebral hypoperfusion model of rat was established by two vessel occlusion (2VO) while the Sham operation was performed in rats of Sham group.The rats in high dose GluA2-3Y group and low dose GluA2-3Y group were intraperitoneal injected with 3 μmol/kg and 0.03 μmol/kg GluA2-3Y respectively once a day for 2 weeks. Rats in 2VO group and Sham group were intraperitoneally injected with control peptide. Morris water maze test and new object recognition test were performed to evaluate the learning and memory ability of rats, and Western blot was used to evaluate the expression of Akt1、GSK3β、p-GSK3β、GluA2 and PSD-95 in rat hippocampus. The expressions of GluA2 and PSD-95 in rat hippocampus were evaluated by immunofluorescence. SPSS 23.0 software was used for data analysis. The comparison between multiple groups was analyzed by one-way ANOVA and repeated measurement ANOVA was used to analyze Morris water maze results. And independent-samples t-test was used for pairwise comparisons. Results:(1)In Morris water maze trials, the results of repeated measurement ANOVA showed that the interaction between group and time of escape latency of rats in each group was not significant ( F=0.79, P>0.05), and the group main effect and time main effect were significant ( F=24.44, 40.42, both P<0.05). On the 5th day of navigation trials, the escape latency of rats in 2VO group was longer than that in sham group ( t=5.87, P<0.05). The escape latency of rats in low dose GluA2-3Y group and high dose GluA2-3Y group were significantly shorter than that in 2VO group ( t=2.20, 3.41, both P<0.05), but there was no significant difference between low dose GluA2-3Y group and high dose GluA2-3Y group ( t=1.37, P>0.05). The target quadrant residence time and resolution coefficient ((14.57±1.40)s, (0.15±0.10)) in 2VO group were significantly lower than those in Sham group ((23.71±2.57)s, (0.40±0.06)) ( t=3.23, 2.24, both P<0.05), while the target quadrant residence time in high dose GluA2-3Y group ((20.19±1.53)s) and low dose GluA2-3Y group ((20.31±2.06)s) were longer than that in 2VO group( t=2.71, 2.35, both P<0.05). The discrimination coefficients in high dose GluA2-3Y group (0.47±0.10) and low dose GluA2-3Y group (0.59±0.06) were higher than that of 2VO group ( t=2.21, 3.94, both P<0.05). (2)The Western blot results showed that the expression of PSD-95 and GluA2 in hippocampus of rats in 2VO group were significantly lower than those in Sham group ( t=2.31, 2.20, both P<0.05), and the expression of PSD-95 in high dose GluA2-3Y group (1.026±0.056) was significantly higher than that in 2VO group ((0.760±0.061), t=2.49, P<0.05), while there was no significant difference between low-dose GluA2-3Y group and 2VO group( t=0.96, P>0.05). The expression of GluA2 in low-dose GluA2-3Y group was higher than that in 2VO Group ((1.130±0.087), (0.766±0.080), t=2.37, P<0.05), but there was no significant difference between high-dose GluA2-3Y group and 2VO group( t=1.06, P>0.05). (3) Immunofluorescence showed that compared with Sham group, the expression of PSD-95 and GluA2 in 2VO group decreased ( t=4.23, 2.57, P<0.05). Compared with 2VO group, the expression of PSD-95 and GluA2 in high dose GluA2-3Y group and low dose GluA2-3Y group increased significantly, and the differences were statistically significant (PSD-95: (7.757±0.578), (12.057±0.578), t=3.14, 6.96, both P<0.05; (9.721±0.950), (16.610±0.950), t=4.56, 9.34, both P<0.05). (4) The results of Western blot showed that the expression GSK3β in hippocampus of rats in each group were not statistically different( F=2.03, P>0.05). There were significant differences in the expression of Akt1, p-GSK3β and the percentage of p-GSK3β/GSK3β in hippocampus of rats in each group ( F=8.30, 4.76, 3.57, all P<0.05). Compared with Sham group, the levels of Akt1, p-GSK3β and the percentage of p-GSK3β/GSK3β in 2VO group were significantly lower ( t=3.00, 2.81, 3.17, all P<0.05). Compared with 2VO group, the levels of Akt1, p-GSK3β and p-GSK3β/GSK3β percentage in low dose GluA2-3Y group and high-dose GluA2-3Y group were significantly higher (Akt1: t=2.05, 5.20, both P<0.05; p-GSK3β: t=2.49, 4.15, both P<0.05; p-GSK3β/GSK3β percentage: t=2.30, 2.97, both P<0.05). Conclusion:GluA2-3Y, an AMPA receptor internalization inhibitor, can alleviate the cognitive impairment in rats with chronic cerebral hypoperfusion, which may be related to the increased expression of Akt1, p-GSK3β and postsynaptic proteins.
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Epilepsy occurs as a result of episodic abnormal synchronous discharges in cerebral neuronal networks.It is characterized by an imbalance between excitatory and inhibitory neurotransmission.Although various non-conventional mechanisms are implicated in epileptic synchronization, glutamate excitatory neurons play an essential role.AMPA receptors mediate fast synaptic excitation within and between brain regions relevant to epilepsy, and play a role in epileptogenesis and in seizure-induced brain damage.However, direct modulation of AMPA receptors may have undesirable consequences, given its wide expression within the central nervous system and critical roles on brain circuitry development.Hippocampal CA1 region, as the main site of epilepsy, selectively regulates the high expression of AMPA receptor GluA2 subunit and transmembrane AMPA receptor regulatory protein family(TARPs)γ-8 subtype and its complex GluA2/TARPγ-8, whether it can produce anti-epileptic and avoid adverse reactions.
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Aim To investigate the distribution of postsynaptic density protein 95 (PSD95) and AMPA receptor GluA2 subunit during the maturation of rat hippocampal neurons in vitro. Methods Cultured rat hippocampal neurons at 4(days in vitro, DIV), 7DIV, 14DIV and 20DIV were used in an immunofluorescence assay to test co-localization of PSD95 and GluA2 by laser confocal microscope at a magnification of 60 ×. Results PSD95 puncta were gradually distributed densely in dendrites and dendritic spines during neuron maturation progresses. GluA2 subunits were uniformly distributed in the cell body, axons, dendrites and dendritic spines. The Pearson' s correlation of PSD95 and GluA2 was 0. 830 ±0. 033 and 0. 734 ±0. 019 respectively at the dendrites of 4DIV and 7DIV neurons, which showed strong co-localization. While at the dendrites of 14DIV and 20DIV neurons, a moderate correlation was demonstrated by the Pearson correlation 0. 547 ± 0. 021 and 0. 574 ± 0. 024. Conclusions GluA2 has no specific intracellular distribution during neuron maturation, while the functional localization of PSD95 depends on the appearance of dendritic spines. The co-localization of GluA2 with PSD95 in dendritic spines suggests that there are stable synapses containing AMPA receptors.