Yifeng Du

Insulin Attenuates Beta-Amyloid-Associated Insulin/Akt/EAAT Signaling Perturbations in Human Astrocytes

The excitatory amino acid transporters 1 and 2 (EAAT1 and EAAT2), mostly located on astrocytes, are the main mediators for glutamate clearance in humans. Malfunctions of these transporters may lead to excessive glutamate accumulation and subsequent excitotoxicity to neurons, which has been implicated in many kinds of neurodegenerative disorders including Alzheimer’s disease (AD). Yet, the specific mechanism of the glutamate system dysregulation remains vague. To explore whether the insulin/protein kinase B (Akt)/EAAT signaling in human astrocytes could be disturbed by beta-amyloid protein (Aβ) and be protected by insulin, we incubated HA-1800 cells with varying concentrations of Aβ1–42 oligomers and insulin. Then the alterations of several key substrates in this signal transduction pathway were determined. Our results showed that expressions of insulin receptor, phospho-insulin receptor, phospho-protein kinase B, phospho-mammalian target of rapamycin, and EAAT1 and EAAT2 were decreased by the Aβ1–42 oligomers in a dose-dependent manner (pxa0<xa00.05) and this trend could be recovered by insulin treatment (pxa0<xa00.05). However, the expressions of total Akt and mTOR were invariant (pxa0>xa00.05), and the mRNA levels of EAAT1 and EAAT2 were also unchanged (pxa0>xa00.05). Taken together, this study indicates that Aβ1–42 oligomers could cause disturbances in insulin/Akt/EAAT signaling in astrocytes, which might be responsible for AD onset and progression. Additionally, insulin can exert protective functions to the brain by modulating protein modifications or expressions.

Relationship between dyslipidemia and carotid plaques in a high‐stroke‐risk population in Shandong Province, China

The precise associations between stroke and carotid plaques and dyslipidemia are unclear. This population‐based study aimed to examine the relationship between carotid plaques and dyslipidemia in a high‐stroke‐risk population.

Effects of Fibrillar Aβ1–40 on the Viability of primary Cultures of Cholinergic Neurons and the Expression of Insulin Signaling–Related Proteins

To investigate the effects of fibrillar Aβ1–40 on the morphology and viability of cholinergic neurons and the involvement of the insulin‐signaling pathway, we established primary cultures of rat basal forebrain cholinergic neurons and observed their responses to treatment with fibrillar Aβ1–40 at different concentrations for different durations. Cell morphology was examined under microscope after immunofluorescence staining for neurofilament protein, cell vitality accessed by the Methyl thiazolyl tetrazolium assay, and expressions of a panel of insulin signaling–related proteins was detected by Western blot analysis. We show here that, at low concentrations of 0.1–1.0 μmol/L, fibrillar Aβ1–40 had little effects on the cells; however, at higher concentrations of 2–10 μmol/L, it caused pathological changes, decreased the cell viability, and reduced the expression of insulin receptor, insulin receptor substrate‐I, Protein Kinase B, and B cell lymphoma/leukemia‐2 in a dose‐ and time‐dependent manner. These results demonstrate that fibrillar Aβ1–40 not only decreases the viability of cholinergic neuron but also down regulates the expression of important proteins in the insulin signal transduction pathway. We speculate that fibrillar Aβ1–40 may contribute to the pathogenesis of Alzheimers through disrupting the insulin signaling pathway, therefore decreasing neuronal activity and eventually leading to the apoptosis and cell loss. Anat Rec, 2011.

Subtypes evaluation of motor dysfunction in Parkinson’s disease using neuromelanin-sensitive magnetic resonance imaging

Parkinsons disease (PD) is characterized by the loss of neuromelanin (NM)-containing neurons in the substantia nigra pars compacta (SNc), and it is divided into two motor subtypes: the postural instability gait difficulty (PIGD) and the tremor dominant (TD) subtypes. With NM-sensitive Magnetic Resonance Imaging (NM-MRI), investigators have been able to accurately detect signal attenuation in SNc of PD; however, the difference of NM loss between PIGD and TD subtypes is still unclear. Thus, the aim of this study was to evaluate the differences in NM-MRI between PD motor subtypes. PD patients were classified into PIGD (n=14) and TD groups (n=9); 20 age and sex matched controls were recruited. We compared the signal intensity contrast ratios in medial and lateral regions of the SNc using NM-MRI in PIGD, TD, and controls, respectively. Remarkable signal attenuation was observed in the lateral part of SNc in PD when compared with the controls, and we were able to detect more severe signal attenuation in the medial part of SNc in PIGD patients in comparison with that in the TD group. Also, the medial part of SNc, ipsilateral to the most clinically affected side, showed the highest power to discriminate the PD motor subtypes (AUC, 81%; sensitivity, 71.4%; specificity, 77.8%). Our results indicated a potential diagnostic value of NM-MRI to discriminate the PD motor subtypes, providing new evidence for the neuropathology-based differences between the two subtypes.

Loss of nitrergic and cholinergic neurons in the enteric nervous system of APP/PS1 transgenic mouse model

Alzheimers disease (AD) is an age-related neurodegenerative brain disorder characterized by aggregation of amyloid-β (Aβ) peptide, formation of neurofibrillary tangles, synaptic loss, and neuronal cell death; however, the characteristic pathological alterations taking place in the second brain-enteric nervous system is still largely undefined. In this study, we aimed to detect the pathological changes in the APP/PS1 mice ileum by a novel whole mount technique. The deposition of Aβ plaque and the overexpression of phosphorylated Tau (pTau) protein were observed in the myenteric neurons of APP/PS1 mice. Compared to the control mice, the proportions of neuronal nitric oxide synthase (nNOS)+and choline acetyltransferase (ChAT)+neurons in the myenteric plexus of APP/PS1 mice significantly decreased (p<0.05). Moreover, whole mount preparations and paraffin sections both demonstrated that the number of CD68+ macrophages in the APP/PS1 mice ileum significantly increased (p<0.05). But, there was no significant difference (p>0.05) in the number of enteric HuC/D+ neurons and the density of Tuj1 between the APP/PS1 and wild type mice, which may be due to the compensatory function of enteric nervous system. These results suggest that the deposition of Aβ plaque and pTau might activate the enteric resident macrophages, further leading to the loss of myenteric nitrergic and cholinergic neurons in the enteric nervous system.

Unique expression pattern of KIBRA in the enteric nervous system of APP/PS1 mice

KIBRA has been recognized as a memory-related gene, which is abundant in the brain and kidney of mammals. However, the expression pattern of KIBRA in the second brain-enteric nervous system (ENS) is still unknown, especially in neurodegenerative disorders. In this study, we aimed to investigate the detailed expression pattern of KIBRA in the intestinal myenteric nerve plexus of APP/PS1 and wild type mice by whole mount staining technology. The deposition of Aβ and increased levels of phosphorylated Tau (p-Tau) and total Tau (T-Tau) protein were observed in the intestinal myenteric nerve plexus of APP/PS1 mice. Interestingly, the amount of Tuj+ cells remained unchanged between these two groups. Compared to the control mice, the protein levels of KIBRA significantly increased in the jejunal myenteric plexus of APP/PS1 mice, and the proportion of KIBRA+ GABAergic neurons in both the jejunal myenteric nerve plexus and the cortex was much higher in the APP/PS1 mice. But there was no significant difference in the number of KIBRA+ cholinergic neurons and KIBRA+ nitrergic neurons between APP/PS1 and wild type mice. In summary, our study further confirmed that typical pathology features of Alzheimers disease (AD) not only existed in the central nervous system but also in the ENS.

Long-term treadmill exercise attenuates Aβ burdens and astrocyte activation in APP/PS1 mouse model of Alzheimer’s disease

Alzheimers disease (AD) is a devastating disease characterized with progressive neurodegenerative disorders in the elderly. Epidemiological and clinical studies reported that lifestyle factors could halt the progression of AD, especially physical exercise. In the present work, we investigated the effects of long-term treadmill exercise on the pathological cascades of AD in APP/PS1 mice. After exercise for 5 months, Aβ deposition was significantly ameliorated in terms of Aβ area fraction, plaque number and size. We also found that long-term treadmill exercise increased neuronal density and attenuated activation of astrocytes. However, the activation of microglia was not affected in APP/PS1 mice treated with exercise intervention. In addition, the amyloidogenic pathway of amyloid precursor protein (APP) metabolism was inhibited, with the decrease of β-site amyloid precursor protein cleaving enzyme 1 (BACE1) and presenilin 1 (PS1). Nevertheless, the nonamyloidogenic pathway of APP metabolism was increased after exercise intervention. The expression levels of insulin-degrading enzyme (IDE) and receptor for advanced glycation end products (RAGE) also declined significantly. In conclusion, long-term treadmill exercise is neuroprotective against Aβ burdens and astrocyte activation, which contributes to the therapy for AD.

Estrogen induced the expression of ADAM9 through estrogen receptor α but not estrogen receptor β in cultured human neuronal cells

PURPOSE OF THE STUDYnTo investigate the induction of a disintegrin and metalloprotease 9 (ADAM9) by which estrogen receptor (ER) subtypes and estrogen regulation of expression in cultured human neuronal cells.nnnMETHODSnSH-SY5Y cells were treated with E2 and the expression of ADAM9 were detected by RT-PCR and Western blot analysis. The peGFP-C3-ERα and peGFP-C3-ERβ vectors were constructed and transfected into SH-SY5Y cells. Then, the mRNA and protein expression level of ADAM9 were detected by RT-PCR and Western blot analyses with the treatment of E2. E2, the ERα agonist PPT, the ERβ agonist DPN and the non-specific ER antagonist ICI 182,780 were added, and the expression of ADAM9 protein and transcriptional activities of ADAM9 promoter were detected by Western blot and luciferase assays, respectively.nnnRESULTSnE2 induced ADAM9 expression with a time-dependent manner in SHSY5Y cells, reaching the peak at 24h. peGFP-C3-ERα transfection significantly increased ADAM9 expression in the presence of E2, whereas peGFP-C3-ERβ had no effect. The E2-induced overexpression of ADAM9 protein was downregulated by ICI 182,780. PPT significantly increased ADAM9 protein expression, whereas DPN had no effect. The E2-induced increase in the transcriptional activities of the ADAM9 promoter was downregulated by ICI 182,780. PPT significantly increased the transcriptional activities of the ADAM9 promoter, whereas DPN had no effect.nnnCONCLUSIONSnActivation of ERα but not ERβ increases ADAM9 expression in cultured human neuronal cells, implicating that ERα-activation functions in the direct mechanism underlying the estrogen-mediated preventative effects against Aβ production and further reduction in the risk of Alzheimers disease.

Spectrum construction of differentially expressed circular RNAs in patients with leukoaraiosis and function analysis of differentially expressed genes

Circular RNAs (circRNAs) are class of endogenous RNAs that have a role in the regulation of gene expression. The present study aimed to investigate the diagnostic value and role of circRNA in the pathogenesis of leukoaraiosis (LA). The present study performed Arraystar Human circRNA Array analysis of 6 samples from LA cases and 6 samples from control cases. Differentially expressed (DE) circRNAs between two samples were identified through fold-change (>1.5-fold) screening. Afterwards, based on DE circRNAs, the gene ontology (GO) analysis of upregulated DE genes identified from DE circRNAs demonstrated that DE genes were primarily associated with cellular metabolic processes, membrane-bound organelles and binding. However, none were enriched in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway. Downregulated DE genes were enriched in cellular localization, cytoplasm and kinase binding. For the KEGG pathways, the downregulated DE genes were primarily associated with the insulin signaling pathway. The results of the present study indicated that the DE genes from differently expressed circRNAs may have an important role in the pathogenesis of LA and may be a novel targfet for further research.