| BackgroundSchizophrenia is a syndrome with serious symptoms in cognition,mind,emotion,and behavior.The disease often relapses and persists,causing heavy burden to individuals and families.The pathogenic mechanism of schizophrenia is extremely complicated and unclear.There is no effective treatment until now.In previous studies,many researchers supposed that schizophrenia is a functional disease.Due to the imbalance of excitability and inhibitory properties of neurons in the brain,the abnormal release of related neurotransmitters causes mental and emotional disorders.However,recent studies have found that morphological abnormalities in neurons and tissue structures exist in the brain of patients with schizophrenia.The volume of the ventricles of patients with schizophrenia is enlarged and the volume of brain parenchyma is reduced.Additionally,neuropathological studies indicate that the density and length of dendrites and dendritic spine of schizophrenia patients decrease.These studies show that neuronal damage and synaptic plasticity in the brain play an important role in the pathogenesis of schizophrenia.Paliperidone is a new generation of atypical antipsychotic drug developed in recent years,which can significantly improve positive,negative symptoms and social communication defects.Previous studies of our group also proved paliperidone play a role in neuroprotective.However,whether pal iperidone affects neurosynaptic plasticity and protects neuron ultrastructure structural changes is unclear,and the molecular mechanisms underlying these effects still need further research.Objective(1)To clarify the improvement effect of paliperidone on the mental behavior of schizophrenia model mice.(2)To clarify the protective effect of paliperidone on prefrontal cortical neurons of schizophrenia model mice and synaptic plasticity damage through ultrastructural observation and Golgi staining.(3)To study the possible molecular mechanism of paliperidone exerting its neuroprotective effects.Methods and ResultsThe experiment has two parts.First,a mouse model of schizophrenia was established.After treatment with paliperidone,the behavior and neuronal morphology and related molecular changes in the brain were observed.Details as follows:(1)C57BL/6J mice were injected intraperitoneally with MK-801(0.5mg/kg)to establish an animal model of schizophrenia,and paliperidone was injected intraperitoneally for treatment.Then the behavior of the mice was detected by stereotyped behavior,open field exercise,and light-dark box.The results showed that the stereotyped behavior of MK-801 model mice was significantly increased,and the total distance of open field movement and the number of light-dark box shuttles were also significantly increased compared with normal mice.In the paliperidone treatment group,the stereotyped behavior of mice was significantly reduced compared with model mice.Both the movement distance and the number of shuttles were significantly reduced.(2)The ultrastructure of the frontal cortex neurons and the changes in dendritic spines were observed by transmission electron microscope and Golgi staining.It can be seen that the mitochondria of the frontal cortex neurons in the MK-801 model mouse are swollen.The cristae of mitochondria were interrupted and the Golgi apparatus was atrophied.The number of synapses was significantly reduced,the presynaptic membrane was empty,and dendritic branches and dendritic intersections were also significantly reduced.In the paliperidone treatment group,the mitochondrial structure was relatively complete,the Golgi was slightly swollen,the presynaptic membrane vesicles were abundant,and dendritic intersections increased significantly compared with model group.(3)Through intracerebral injection of a virus containing calcium indicator,the changes in the concentration of calcium ions in the cerebral cortex were detected.And the changes in the expression of PP2A and PTEN proteins in the cerebral cortex were detected by Western blots.The results showed that the calcium level of neurons in the cerebral cortex of the schizophrenia model rats was higher than that of the normal control group,while the calcium level of the paliperidone treatment group was lower than that of the model group.At the same time,the protein levels of PP2A and PTEN in the MK-801 model group were lower than control group,while the expression levels of PP2A and PTEN protein were up-regulated after paliperidone treatment.In the second part of the experiment,by culturing primary cerebral cortex neurons and HT-22 cells,the neuroprotective effect of paliperidone and possible molecular mechanisms were addressed.Details as follows:(1)Detect the effect of MK-801 and paliperidone on neuronal activity by CCK-8 experiment.The results showed that MK-801 can significantly reduce the activity of HT-22 cells.As the concentration of MK-801 increases,the cell activity gradually decreases in a concentration-dependent manner.After adding paliperidone,cell activity increased,and 20μM paliperidone had a significant effect.(2)Detect the level of reactive oxygen species(ROS)by the DCFH-DA fluorescent probe.And stain the cultured primary cerebral cortical neurons and HT-22 nerve cells with ROS.The results showed that MK-801 significantly increases the level of ROS.And the ROS level after paliperidone treatment was significantly lower than the MK-801 treatment group.Then,TUNEL staining and flow cytometry were performed on primary cerebral cortex neurons and HT-22 neurons,respectively.It was shown that the effect of MK-801 induced neuronal apoptosis which was significantly reduced by paliperidone.(3)In order to further analyze the molecular mechanism of paliperidone,experiment was performed to detect the protein levels of PP2A and PTEN.The results showed that MK-801 can reduce the level of PP2A protein after exposure to MK-801,while paliperidone could up-regulate the change of PP2A protein,which was consistent with the change trend of animal.However,at the cellular level,the PTEN protein level did not change significantly.After LB-100 specifically inhibited PP2A,ROS staining and flow cytometry showed that the number of apoptosis,the apoptotic rate and the level of ROS in the LB-100 co-treatment group was higher than paliperidone treatment group.LB-100 inhibited the protective effect of paliperidone on neurons.Therefore,we speculate that paliperidone can play a neuroprotective effect by regulating PP2A.ConclusionThis study reveals that paliperidone can reduce stereotyped behaviors and locomotor activity,and improve the behavioral performance of schizophrenia model mice.And,paliperidone can significantly reduce the neuronal and synaptic plastic damage caused by MK-801.Further mechanism studies have shown that PP2A/PTEN plays an important role in the neuroprotective effect of paliperidone. |
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