Tau蛋白在血管性痴呆发病机制中的作用

目的观察血管性痴呆中Tau蛋白表达和磷酸化程度，研究其在发病机制中的可能作用。采用持久性双侧颈总动脉结扎方法制备血管性痴呆模型，Morns水迷宫检测大鼠空间学习记忆能力的差异，HE染色和免疫组化染色检测海马CA1区Tau蛋白、蛋白磷酸酯酶2A的表达情况。结果发现手术组与对照组大鼠相比，Morris水迷宫隐藏平台逃避潜伏期延长，空间摸索试验时间减少；海马CA1区细胞排列疏松，数目减少，细胞形态异常；手术组大鼠神经元中Tau蛋白含量增多，蛋白磷酸酯酶2A减少，以一个月时最明显。以上结果表明Tau蛋白表达增多及过度磷酸化在血管性痴呆发病机制中可能起到作用。     

Differences in neonatal neurotoxicity of brominated flame retardants, PBDE 99 and TBBPA, in mice

Flame retardants such as polybrominated diphenyl ethers (PBDE) and tetrabromobisphenol A are used as flame retardants and detected in the environmental, wildlife species and human tissues. Exposure to PBDEs during the neonatal development of the brain has been shown to affect behavior and learning and memory in adult mice, while neonatal exposure to TBBPA (another brominated flame retardant) did not affect behavioral variables in the adult. In this study, we hypothesized that the effects of these compounds could be reflected by changes in biochemical substrates and cholinergic receptors and have examined the levels of four proteins involved in maturation of the brain, neuronal growth and synaptogenesis and the densities of both muscarinic and nicotinic cholinergic receptors. We measured the levels of radioactivity in the brain after administration of ¹⁴C-labelled TBBPA at different time points and saw that levels of TBBA peaked earlier and decreased faster than the earlier reported levels of PBDE 99. The protein analysis in the neonatal brain showed changes in the levels of calcium/calmodulin-dependent protein kinase II (CaMKII), growth associated protein-43 (GAP-43) and synaptophysin following neonatal exposure to PBDE 99 (21 μmol/kg body weight), but not following exposure TBBPA. Furthermore, neonatal exposure to PBDE 99 and TBBPA caused a decrease in binding sites of the nicotinic ligand cytisine in frontal cortex. These results confirm earlier reported data that PBDE 99 can act as a developmental neurotoxicant, possibly due to its different uptake and retention in the brain compared to TBBPA. In addition, the changes in protein levels are interesting leads in the search for mechanisms behind the developmental neonatal neurotoxicity of PBDEs in general and PBDE 99 in particular, since also other compounds inducing similar adult behavioral disturbances as PBDE 99, affect these proteins during the period of rapid brain development.     

Peripheral expression of key regulatory kinases in Alzheimer's disease and Parkinson's disease

Alteration of key regulatory kinases may cause aberrant protein phosphorylation and aggregation in Alzheimer's disease (AD) and Parkinson's disease (PD). In this study, we investigated expression and phosphorylation status of glycogen synthase kinase 3 (GSK-3), protein kinase B (Akt) and tau protein in peripheral blood lymphocytes of 20 AD, 25 PD patients and 20 healthy controls.GSK-3 was increased in AD and PD patients. In these latter, GSK-3 levels were positively correlated with daily l-Dopa intake. Phosphorylated Akt expression was augmented in both groups; total Akt levels were increased only in AD patients and were positively correlated with disease duration and severity. Total and phosphorylated tau were increased only in AD, with phospho-tau levels being positively correlated with levels of total tau, Akt, and disease duration. No correlations between protein levels and clinical variables were found in PD patients.Investigation of peripheral changes in the expression of specific kinases may, therefore, lead to the development of innovative biomarkers of neurodegeneration, particularly for AD.     

Expression of the HFE allelic variant H63D in SH-SY5Y cells affects tau phosphorylation at serine residues

A number of genetic association studies have appeared that address HFE gene variants in neurodegenerative disorders. However, the cellular impact of HFE in the nervous system has received little attention. To begin to address the role of the HFE allelic variants on cellular events associated with neurodegeneration, we examined the hypothesis that HFE polymorphisms are associated with alterations in tau phosphorylation in a human neuroblastoma cell line (SH-SY5Y). The results show that in a cell culture model, the H63D allele is associated with increased tau phosphorylation. The mechanisms responsible for these changes appear related to increased glycogen synthase kinase (GSK)-3β activity. GSK-3β activity is up-regulated in the cells expressing H63D HFE and can be modified by the addition of iron or treatment with an iron chelator in SH-SY5Y cells expressing wild-type HFE. Oxidative stress, also associated with elevated cellular iron, is associated with increased tau phosphorylation at the same sites as seen in H63D cells and treatment with Trolox, an anti-oxidant, lowered tau phosphorylation. These results suggest H63D HFE increases tau phosphorylation via GSK-3β activity and iron-mediated oxidative stress.     

Genetic variations in tau-tubulin kinase-1 are linked to Alzheimer's disease in a Spanish case-control cohort

Neurofibrillary tangles, one of the characteristic neuropathological lesions found in Alzheimer's disease (AD) brains, are composed of abnormally hyperphosphorylated tau protein. Tau-tubulin kinase-1 (TTBK1) is a brain-specific protein kinase involved in tau phosphorylation at AD-related sites. We examined genetic variations of TTBK1 by genotyping nine haplotype tagging SNPs (htSNPs) (rs2104142, rs2651206, rs10807287, rs7764257, rs3800294, rs1995300, rs2756173, rs6936397, and rs6458330) in a group of 645 Spanish late-onset AD patients and 738 healthy controls. Using a recessive genetic model, minor allele homozygotes for rs2651206 in intron 1 (OR = 0.50, p = 0.0003), rs10807287 in intron 5 (OR = 0.49, p = 0.0002), and rs7764257 in intron 9 (OR = 0.57, p = 0.023), which are in strong linkage disequilibrium, had a lower risk of developing AD than subjects homozygotes and heterozygotes for the major allele. TTBK1 is a promising new candidate tau phosphorylation-related gene for AD risk.     

Combined expression of tau and the Harlequin mouse mutation leads to increased mitochondrial dysfunction, tau pathology and neurodegeneration

Mitochondrial dysfunction and oxidative stress play an important role in ageing and have been implicated in several age-related neurodegenerative conditions including Alzheimer's disease (AD) and other tauopathies characterized by the presence of intracellular accumulations of the hyperphosphorylated microtubule-associated protein tau. To study the interaction between mitochondrial dysfunction and tau pathology in vivo, we generated a novel mouse model by crossbreeding two existing lines: the Harlequin (Hq) mutant mice which suffer from mitochondrial dysfunction and oxidative stress due to a lack of the mitochondrial apoptosis-inducing factor (AIF), and the P301L tau transgenic mice, a mouse model of human tau pathology.Combined expression of the Hq mouse mutation and the tau transgene in the Tau/Hq double mutant mice led to an increase in tau pathology and apoptotic neurodegeneration when compared to single expression of the two mutations. Neurodegeneration was most prominent in the dentate gyrus and was significantly increased in the cerebellum leading to aggravated motor deficits. Functional activity measurements of the mitochondrial respiratory chain (MRC) in the Tau/Hq mice revealed early decreased activities of multiple MRC complexes and depleted ATP levels which preceded neurodegeneration and elevated oxidative stress markers. These results suggest an age-dependent mutual reinforcement of the tau pathology and mitochondrial dysfunction in vivo, which may contribute to neurodegeneration in patients suffering from AD and other age-related tauopathies.     

轴索损伤在大鼠实验性变态反应性脑脊髓炎不同时期的动态变化及意义

目的: 研究不同发病时期实验性变态反应性脑脊髓炎(EAE)大鼠轴索损伤的动态变化及意义。方法: 对不同发病时期EAE大鼠进行HE染色判断炎症损害,以免疫组化方法标记β-淀粉样前体蛋白(β-APP)和磷酸化tau蛋白,了解轴索急性损伤及反复发病后的神经变性情况。结果: 急性组大鼠脊髓组织内可见大量炎症细胞弥散分布,在炎症细胞区内有大量β-APP阳性表达,神经纤维变性标志物tau蛋白只有少量沉积;瘫痪组大鼠血管周围有淋巴细胞浸润,呈袖套样分布,β-APP在无炎症的区域也有部分表达,并有tau蛋白大量沉积,提示反复发病的瘫痪大鼠存在持续的轴索损伤,并发生明显的轴索变性。急性组、瘫痪组轴索中β-APP和tau蛋白阳性数均多于正常组,差异显著,急性组和瘫痪组比较,轴索中β-APP和tau蛋白阳性表达数亦有显著差异。结论: (1)发病早期轴索损伤与炎症破坏有关,并呈可逆性。(2)神经变性主要存在于EAE的慢性病程中。(3)在EAE发病过程中轴索损伤呈动态变化,疾病后期轴索发生神经变性并导致神经功能不可逆损伤,在EAE研究中有重要意义。     

Metabolic profiling studies on the toxicological effects of realgar in rats by H NMR spectroscopy

The toxicological effects of realgar after intragastrical administration (1 g/kg body weight) were investigated over a 21 day period in male Wistar rats using metabonomic analysis of ¹H NMR spectra of urine, serum and liver tissue aqueous extracts. Liver and kidney histopathology examination and serum clinical chemistry analyses were also performed. ¹H NMR spectra and pattern recognition analyses from realgar treated animals showed increased excretion of urinary Kreb's cycle intermediates, increased levels of ketone bodies in urine and serum, and decreased levels of hepatic glucose and glycogen, as well as hypoglycemia and hyperlipoidemia, suggesting the perturbation of energy metabolism. Elevated levels of choline containing metabolites and betaine in serum and liver tissue aqueous extracts and increased serum creatine indicated altered transmethylation. Decreased urinary levels of trimethylamine-N-oxide, phenylacetylglycine and hippurate suggested the effects on the gut microflora environment by realgar. Signs of impairment of amino acid metabolism were supported by increased hepatic glutamate levels, increased methionine and decreased alanine levels in serum, and hypertaurinuria. The observed increase in glutathione in liver tissue aqueous extracts could be a biomarker of realgar induced oxidative injury. Serum clinical chemistry analyses showed increased levels of lactate dehydrogenase, aspartate aminotransferase, and alkaline phosphatase as well as increased levels of blood urea nitrogen and creatinine, indicating slight liver and kidney injury. The time-dependent biochemical variations induced by realgar were achieved using pattern recognition methods. This work illustrated the high reliability of NMR-based metabonomic approach on the study of the biochemical effects induced by traditional Chinese medicine.     

Long-term treatment of l-3-n-butylphthalide attenuated neurodegenerative changes in aged rats

It is shown that l-3-n-butylphthalide (l-NBP), the isomer of dl-NBP (racemic 3-n-butylphthalide, a new anti-cerebral ischemic agent) significantly attenuated cerebral hypoperfusion-induced learning dysfunction and brain damage in rats. In the present study, l-NBP (10 and 30 mg/kg) long-term (3-month) treatment of aged rat (21-month-old) significantly improved the learning and memory capability measured by the Morris water maze test. Hematoxylin–eosin-stained slices showed that both l-NBP at 30 mg/kg, and memantine as control at 20 mg/kg, attenuated the neurodegenerative changes in aged rats. l-NBP treatment significantly increased the choline acetyltransferase activity and dose-dependently decreased the acetylcholinesterases activity in the hippocampus of aged rats. The immunohistological study demonstrated that expressions of β-secretase and hyperphosphorylated tau protein were significantly increased in the hippocampus CA1 subfield and parietal cortex in aged rats. However, they were decreased significantly by treatment of l-NBP and memantine for 3 months. Our results indicated that long-term treatment with l-NBP might prevent age-related neurodegenerative changes by modulation of cholinergic system, reduction of phosphorylated tau and maintain structure and morphology of neurons. Therefore, l-NBP might be a potential drug for treatment of senile dementia.