Changes of learning and memory ability associated with neuronal nitric oxide synthase in brain tissues of rats with acute alcoholism

BACKGROUD： Ethanol can influence neural development and the ability of leaming and memory, but its mechanism of the neural toxicity is not clear till now. Endogenous nitric oxide （NO） as a gaseous messenger is proved to play an important role in the formation of synaptic plasticity, transference of neuronal information and the neural development, but excessive nitro oxide can result in neurotoxicity. OBJECTIVE ： To observe the effects of acute alcoholism on the learning and memory ability and the content of neuronal nitric oxide synthase （nNOS） in brain tissue of rats. DESIGN ： A randomized controlled animal experiment. SETTING ： Department of Physiology, Xinxiang Medical College MATERIALS： Eighteen male clean-degree SD rats of 18-22 weeks were raised adaptively for 2 days, and then randomly divided into control group （n = 8） and experimental group （n = 10）. The nNOS immunohistochemical reagent was provided by Beijing Zhongshan Golden Bridge Biotechnology Co.,Ltd. Y-maze was produced by Suixi Zhenghua Apparatus Plant. METHODS ： The experiment was carded out in the laboratory of the Department of Physiology, Xinxiang Medical College from June to October in 2005. ① Rats in the experimental group were intraperitoneally injected with ethanol （2.5 g/kg） which was dissolved in normal saline （20%）. The loss of righting reflex and ataxia within 5 minutes indicated the successful model. Whereas rats in the control group were given saline of the same volume. ② Examinations of learning and memory ability： The Y-maze tests for learning and memory ability were performed at 6 hours after the models establishment. The rats were put into the Y-maze separately. The test was performed in a quiet and dark room. There was a lamp at the end of each of three pathways in Y-maze and the base of maze had electric net. All the lamps of the three pathways were turned on for 3 minutes and then turned off. One lamp was turned on randomly, and the other two delayed automatically. In 5 seconds after alternation, pulsating electric current presented in the base of unsafe area to stimulate rat＇s feet to run to the safe area. The lighting lasted for 15 seconds as one test. Running from unsafe area to safe area at one time in 10 seconds was justified as successful. Such test was repeated for 10 times for each rat and the successful frequency was recorded. The qualified standard of maze test was that the rat ardved in the safe area g times during 10 experiments. The number of trainings for the qualified standard was used to represent the result of spatial learning. ③ Determination of the content of nNOS in brain tissue： After the Y-maze test, the rats were anaesthetized, and blood was let from the incision on right auricle, transcardially perfused via the left ventricle with about 200 mL saline, then fixed by perfusion of 40 g/L paraformaldehyde. Hippocampal CA1 region, corpus striatum and cerebellum were taken to prepare serial freezing coronal sections. The nNOS contents in the brain regions were determined with the immunohistochemical methods to reflect the changes of nitdc oxide in brain tissue. MAIN OUTCOME MEASURES ： The changes of learning and memory ability and the changes of the nNOS contents in the brain tissue of rats with acute alcoholism were observed. RESULTS ： One rat in the experimental group was excluded due to its slow reaction to electdc stimulation in the Y-maze test, and the other 17 rats were involved in the analysis of results. ① The training times to reach qualifying standards of Y-maze in the expedmental group was more than that in the control group [（34.33 ±13.04）, （27.50±8.79） times, P〈 0.05]. ② Forms and numbers of nNOS positive neurons in brain tissue： It could be observed under light microscope that in the hippocampal CA1 region, there were fewer nNOS positive neurons, which were lightly stained, and the processes were not clear enough; But the numbers of the positive neurons which were deeply stained as huffy were obviously increased in the experimental group, the cell body and cyloplasm of process were evenly stained, but the nucleus was not stained. The nNOS positive neurons in corpus stdatum had similar forms and size in the experimental group and control group. The form of the nNOS positive neurons in cerebellum were similar between the two groups. The numbers of nNOS positive neurons in hippocampal CA1 region and corpus striatum in the expedmental group [（18.22±7.47）, （11.38±5.00） cells/high power field] were obviously higher than those in the control group [（10.15±4.24）, （6.15±3.69） cells/high power field. The number of nNOS positive neurons in cerebellum had no significant difference between the two groups [（49.56±18.84）, （44.43±15.42） cells/high power field, P〉 0.05]. CONCLUSION ： Acute alcoholism may impair learning and memory ability, and nitric oxide may be involved in mediating the neurotoxic role of ethanol.

Mifepristone modulates serotonin transporter function

Regulating serotonin expression can be used to treat psychotic depression. Mifepristone, a glu- cocorticoid receptor antagonist, is an effective candidate for psychotic depression treatment. However, the underlying mechanism related to serotonin transporter expression is poorly un- derstood. In this study, we cloned the human brain serotonin transporter into Xenopus oocytes, to establish an in vitro expression system. Two-electrode voltage clamp recordings were used to detect serotonin transporter activity. Our results show that mifepristone attenuates serotonin transporter activity by directly inhibiting the serotonin transporter, and suggests that the se- rotonin transporter is a pharmacological target of mifepristone for the treatment of psychotic depression.

Melastatin-related transient receptor potential 2 channel in Aβ_(42)-induced neuroinflammation: implications to Alzheimer's disease mechanism and development of therapeutics

Alzheimer’s disease （AD） is an age-related eurodegenerative disease that represents the most common cause of dementia among the elderly people. With the increasingly aging population, AD has presented an overwhelming healthcare challenge to modern society; the World Alzheimer Report 2015 has estimated that 46.8 million people worldwide lived with dementia in 2015 and this number will rise to 74.7 million in 2030 and that the total cost of dementia was 818 billion in US$ in 2015 and will reach two trillion in 2030. Post-mortem studies have identified two histopathological hallmarks in the brains of AD patients; extracellular senile plaque with elevated deposition of amyloid β （Aβ） peptides, and intracellular neurofibrillary tangle composed of hyper-phosphorylated microtubule-associated protein tau.Etiologically, progressive neuronal loss within the cerebral cortex and hippocampus regions of the brain leads to irreversible decline in, and eventually complete loss of, memory and other cognitive functions that afflict AD patients. The widely-accepted amyloid cascade hypothesis for AD pathogenesis holds that accumulation and aggregation of neurotoxic Aβ peptides, due to imbalance of their generation and clearance as a result of changes in genetic makeup, aging and/or exposure to environmental risk factors, is a major and early trigger of AD. This hypothesis has continuously gained support by preclinical and clinical studies （Selkoe and Hardy, 2016）. However, the intensive and costly drug discovery efforts over the past decades based on such a hypothesis have proved extremely frustrating in developing effective therapeutics to treat or slow down the progress of AD, highlighting the need for more research to improve our understanding towards the cellular and molecular mechanisms by which Aβ peptides bring about neurotoxicity and cognitive dysfunction.

多肽靶向嵌合体通过促进tau蛋白特异性去磷酸化治疗阿尔茨海默病和其他tau蛋白病

Abnormal hyperphosphorylation and accumulation of tau protein play a pivotal role in neurodegeneration in Alzheimer’s disease(AD)and many other tauopathies.Selective elimination of hyperphosphorylated tau is promising for the therapy of these diseases.We have conceptualized a strategy,named dephosphorylation-targeting chimeras(DEPTACs),for specifically hijacking phosphatases to tau to debilitate its hyperphosphorylation.Here,we conducted the step-by-step optimization of each constituent motif to generate DEPTACs with reasonable effectiveness in facilitating the dephosphorylation and subsequent clearance of pathological tau.Specifically,for one of the selected chimeras,D16,we demonstrated its significant efficiency in rescuing the neurodegeneration caused by neurotoxic K18-tau seeds in vitro.Moreover,intravenous administration of D16 also alleviated tau pathologies in the brain and improved memory deficits in AD mice.These results suggested DEPTACs as targeted modulators of tau phosphorylation,which hold therapeutic potential for AD and other tauopathies.

Progesterone treatment before experimental hypoxia-ischemia enhances the expression of glucose transporter proteins GLUT1 and GLUT3 in neonatal rats

Progesterone is an efficient candidate for treating stroke and traumatic brain damage. The current study was designed to investigate the effects of pro gesterone on glucose transporter proteins （GLUT1 and GLUT3） during hypoxicischemic injury in a neo natal rat model. We demonstrated strong staining for GLUT1 in the walls of blood vessels and GLUT3 im munoreactivity in hippocampal neurons after hypoxia ischemia. Hypoxiaischemia elevated GLUT1 and GLUT3 at both the mRNA and protein levels in the hippocampus, and pretreatment with progesterone （8 mg/kg） further enhanced their accumulation until 24 h after hypoxicischemic injury. These results showed that progesterone treatment induced the accumula tion of both GLUT1 and GLUT3 transporters, and an energycompensation mechanism may be involved in the neuroprotective effect of progesterone during hy poxicischemic injury after cerebral ischemic attacks.

A novel dephosphorylation targeting chimera selectively promoting tau removal in tauopathies

Intraneuronal accumulation of hyperphosphorylated tau is a hallmark pathology shown in over twenty neurodegenerative disorders,collectively termed as tauopathies,including the most common Alzheimer's disease(AD).Therefore,selectively removing or reducing hyperphosphorylated tau is promising for therapies of AD and other tauopathies.Here,we designed and synthesized a novel DEPhosphorylation TArgeting Chimera(DEPTAC)to specifically facilitate the binding of tau to Ba-subunit-contalning protein phosphatase 2A(PP2A-Ba),the most active tau phosphatase in the brain.The DEPTAC exhibited high efficiency in dephosphorylating tau at multiple AD-associated sites and preventing tau accumulation both in vitro and in vivo.Further studies revealed that DEPTAC significantly improved microtubule assembly,neurite plasticity,and hippocampus-dependent learning and memory in transgenic mice with inducible overexpression of truncated and neurotoxic human tau N368.Our data provide a strategy for selective removal of the hyperphosphorylated tau,which sheds new light for the targeted therapy of AD and related-tauopathies.