Jian-Zhi Wang

Effect of inhibiting melatonin biosynthesis on spatial memory retention and tau phosphorylation in rat.

Abstract:  We have found recently that melatonin protects SH‐SY5Y neuroblastoma cells from calyculin A‐induced neurofilament impairment and neurotoxicity. In the present study, we further investigated the in vivo effect of inhibiting melatonin biosynthesis on spatial memory retention and tau phosphorylation in rats and the potential underlying mechanisms by using haloperidol, a specific inhibitor of 5‐hydroxyindole‐O‐methyltransferase, and a key enzyme in melatonin biosynthesis. We have found that injection of haloperidol into the lateral ventricle and into peritoneal cavity compromises spatial memory retention of rats and induces hyperphosphorylation of microtubule‐associated protein tau at tau‐1 (Ser199/Ser202) and PHF‐1 (Ser396/Ser404) epitopes. At mean time, the activity of protein phosphatase‐2A (PP‐2A), a deficit phosphatase in the Alzheimers disease brain and superoxide dismutase decreases with an elevated level of malondialdehyde. Supplementation with melatonin by prior injection for 1 wk and reinforcement during the haloperidol administration significantly improves memory retention deficits, arrests tau hyperphosphorylation and oxidative stress, and restores PP‐2A activity. These results strongly support the involvement of decreased melatonin in Alzheimer‐like spatial memory impairment and tau hyperphosphorylation, and PP‐2A may play a role in mediating aberrant melatonin‐induced lesions.

Estradiol Attenuates Tau Hyperphosphorylation Induced by Upregulation of Protein Kinase-A

Protein kinase A (PKA) plays a crucial role in tau hyperphosphorylation, an early event of Alzheimer disease (AD), and 17β-estradiol replacement in aging women forestalls the onset of AD. However, the role of estradiol in PKA-induced tau hyperphosphorylation is not known. Here, we investigated the effect of 17β-estradiol on cAMP/PKA activity and the PKA-induced tau hyperphosphorylation in HEK293 cells stably expressing tau441. We found that 17β-estradiol effectively attenuated forskolin-induced overactivation of PKA and elevation of cAMP, and thus prevented tau from hyperphosphorylation. These data provide the first evidence that 17β-estradiol can inhibit PKA overactivation and the PKA-induced tau hyperphosphorylation, implying a preventive role of 17β-estradiol in AD-like tau pathology.

Melatonin protects SH‐SY5Y neuroblastoma cells from calyculin A‐induced neurofilament impairment and neurotoxicity

Abstract:  Hyperphosphorylation of cytoskeletal proteins seen in Alzheimers disease is most probably the result of an imbalanced regulation in protein kinases and protein phosphatases (PP) in the affected neurons. Previous studies have revealed that PP‐2A and PP‐1 play important roles in the pathogenesis. Employing human neuroblastoma cells, we found that 10 nm calyculin A (CA), a selective inhibitor of PP‐2A and PP‐1, significantly increased phosphorylation and accumulation of neurofilament (NF) in the cells. Levels of NF‐M (middle chain) and NF‐L (light chain) mRNA decreased after CA treatment. Additionally, CA led to a decreased cell viability determined by MTT and crystal violet assay. Melatonin efficiently protects the cell from CA‐induced alterations in NF hyperphosphorylation and accumulation, suppressed NF gene expression as well as decreased cell viability. It is concluded that inhibition of PP‐2A/PP‐1 by CA induces abnormalities in NF metabolism and cell survival, and melatonin efficiently arrests the lesions.

The MT2 receptor stimulates axonogenesis and enhances synaptic transmission by activating Akt signaling

The MT2 receptor is a principal type of G protein-coupled receptor that mainly mediates the effects of melatonin. Deficits of melatonin/MT2 signaling have been found in many neurological disorders, including Alzheimer’s disease, the most common cause of dementia in the elderly, suggesting that preservation of the MT2 receptor may be beneficial to these neurological disorders. However, direct evidence linking the MT2 receptor to cognition-related synaptic plasticity remains to be established. Here, we report that the MT2 receptor, but not the MT1 receptor, is essential for axonogenesis both in vitro and in vivo. We find that axon formation is retarded in MT2 receptor knockout mice, MT2-shRNA electroporated brain slices or primary neurons treated with an MT2 receptor selective antagonist. Activation of the MT2 receptor promotes axonogenesis that is associated with an enhancement in excitatory synaptic transmission in central neurons. The signaling components downstream of the MT2 receptor consist of the Akt/GSK-3β/CRMP-2 cascade. The MT2 receptor C-terminal motif binds to Akt directly. Either inhibition of the MT2 receptor or disruption of MT2 receptor-Akt binding reduces axonogenesis and synaptic transmission. Our data suggest that the MT2 receptor activates Akt/GSK-3β/CRMP-2 signaling and is necessary and sufficient to mediate functional axonogenesis and synaptic formation in central neurons.

Temporal correlation of the memory deficit with Alzheimer-like lesions induced by activation of glycogen synthase kinase-3.

We have reported that activation of glycogen synthase kinase‐3 (GSK‐3) by ventricle injection of wortmannin (WT) and GF‐109203X (GFX) induces Alzheimer‐like memory deficit in rats [ Liu et al., J. Neurochem. 87 (2003), 1333 ]. To further explore the factors responsible for the memory loss, we studied here the temporal alterations of GSK‐3, tau phosphorylation, β‐amyloid (Aβ), and acetylcholine (ACh) after injection of WT/GFX, and analyzed their correlation with the memory loss. We observed that the severe memory deficit occurred at 24 and 48 h, and simultaneously, GSK‐3 activation, tau hyperphosphorylation at Thr231, Ser396, and Ser404 and decline of ACh in hippocampus were detected, and these changes were mostly recovered at 72 and 96 h after the injection of WT/GFX. Remarkable increase of Aβ and intracellular accumulation of argentophilic substances were detected at 72 h. Pearson analysis showed that the memory deficit was correlated with GSK‐3 activation, tau hyperphosphorylation, and decline of ACh but not with Aβ overproduction. Our data provide direct evidence demonstrating that activation of GSK‐3 by WT/GFX may cause memory deficit through tau hyperphosphorylation and suppression of ACh in hippocampus.

Reduction and the intracellular translocation of EphB2 in Tg2576 mice and the effects of β-amyloid.

EphB2 is a member of receptor tyrosine kinases (RTKs) family that is essential for the cell adhesion, neural crest migration, axon guidance and synaptogenesis in the nervous system. Recent studies show that preservation of EphB2 in a transgenic mouse model of Alzheimers disease (AD) rescues the cognitive deficit, suggesting a crucial role of EphB2 in AD. However, the expression and distribution profiles of EphB2 in the early stage of AD have not been reported.

Fluorocitrate induced the alterations of memory-related proteins and tau hyperphosphorylation in SD rats

Astrocytes provide structural, metabolic and trophic supports for neurons. However, there are no direct evidences whether astrocytes involve in the regulation of synaptic proteins expression and tau phosphorylation until now. Here, we injected 1 nmol fluorocitrate (FC), which preferentially taken up by astrocytes and results in reversible inhibition of the astrocytic tricarboxylic acid cycle, into the left lateral ventricle of the brain in the SD rats for 1h, and found that FC treatment decreased several memory-related proteins levels, such as AMPA receptor GluR1/2, postsynaptic density protein 93/95, Arc and phosphorylated cAMP response element binding proteins, while increased synaptophysin and synapsin I levels in the hippocampus. FC treatment also increased the levels of phosphorylated tau at multiple Alzheimer-related phosphorylation sites, as well as activation of glycogen synthase kinase-3β and inactivation of protein phosphatase-2A. Similar effects were also observed in the primary hippocampal neurons, which were cultured with the conditioned media from FC-treatment primary astrocytes. Our data suggest that astrocytes regulate neuronal tau phosphorylation and several synaptic proteins expression.

Corrigendum to “Fluorocitrate induced the alterations of memory-related proteins and tau hyperphosphorylation in SD rats’’ [Neurosci. Lett. 584 (2014) 230–235]

a Department of Pathophysiology, The School of Basic Medicine, Tongji Medical College, Wuhan, PR China b Key Laboratory of Ministry of Education for Neurological Disorders, The School of Basic Medicine, Tongji Medical College, Wuhan, PR China c Department of Neurology, The People’s Hospital of Linyi City, Shangdong Province 276000, PR China d Yichang Central People’s Hospital, The First College of Clinical Medical Science, China Three Gorges University, Yichang, China

Olfactory deprivation hastens Alzheimer-like pathologies in a human tau overexpressed mouse model via activation of cdk5

Olfactory dysfunction is a recognized risk factor for the pathogenesis of Alzheimer’s disease (AD), while the mechanisms are still not clear. Here, we applied bilateral olfactory bulbectomy (OBX), an olfactory deprivation surgery to cause permanent anosmia, in human tau-overexpressed mice (htau mice) to investigate changes of AD-like pathologies including aggregation of abnormally phosphorylated tau and cholinergic neuron loss. We found that tau phosphorylation in hippocampus was increased at Thr-205, Ser-214, Thr-231, and Ser-396 after OBX. OBX also increased the level of sarkosyl-insoluble Tau at those epitopes and accelerated accumulation of somatodendritic tau. Moreover, OBX resulted in the elevation of calpain activity accompanied by an increased expression of the cyclin-dependent kinase 5 (cdk5) neuronal activators, p35 and p25, in hippocampus. Furthermore, OBX induces the loss of the cholinergic neurons in medial septal. Administration of cdk5 pharmacological inhibitor roscovitine into lateral ventricles suppressed tau hyperphosphorylation and mislocalization and restored the cholinergic neuron loss. These findings suggest that olfactory deprivation by OBX hastens tau pathology and cholinergic system impairment in htau mice possibly via activation of cdk5.

P4-415: The effect of moxibustion on spatial memory of aging rats and the underlying mechanisms

through activation of both ER and ER . Objective: The goal of this research is to investigate the impact of ER or ER -selective phytoestrogens and select combinations on neuronal survival and morphogenesis, and ultimately, develop a formulation with efficacy to promote cognition and prevent age-related neurodegeneration associated with AD. Methods & Results: Using in silico molecular docking and physicochemical properties analyses followed by a competitive binding assay, we have identified a series of ER or ER -selective plant-derived estrogenic molecules (so we called PhytoSERMs) from a natural source chemical database. Five candidate PhytoSERMs that have the greatest binding selectivity for ER were assessed for their neuroprotective efficacy in primary cortical neurons. Dose-response analyses indicated that individually each of the 5 candidate PhytoSERMs was moderately protective against supraphysiological glutamate-induced neurotoxicity determined by LDH measurements, with the greatest neuronal response occurring at 100 nM 1 M. Western blot analyses demonstrated that 4 out of 5 candidate PhytoSERMs significantly increased the expression of the anti-apoptotic protein, Bcl-2, in neurons. Further analyses demonstrated that combined use of these candidate PhytoSERMs induced significantly increased neuroprotective efficacy compared to single components. Co-administration of all 4 candidate PhytoSERMs induced the maximal protection against glutamate-induced loss in neuron metabolic viability determined by Calcein AM assay, with an efficacy significantly greater than that induced by 17 -estradiol. We are currently investigating the impact of these PhytoSERMs and combined formulations on neuronal morphogenesis, a marker of neuroplasticity associated with memory function. Conclusions: These results contribute to generating conclusive proof of principle that an ER -selective PhytoSERM formulation could serve as an effective alternative to estrogen therapy for sustaining neurological health, function and prevention of AD.