Casein kinase II alteration precedes tau accumulation in tangle formation.

Previous studies have shown altered casein kinase II (CK-II) in Alzheimer's disease (AD). For the present study, the authors analyzed CK-II immunoreactivity at various stages of tangle formation using quantitative laser confocal microscopy and immunoelectron microscopy. AD hippocampal pyramidal cells without neurofibrillary tangles (NFTs) displayed 15% more anti-tau immunoreactivity (P less than 0.01) and 43% more anti-CKII immunolabeling than controls (P less than 0.001). In AD, tangle-bearing hippocampal neurons with strong anti-tau immunoreactivity (threefold increase from controls) showed a significant 22% increase in anti-CKII immunolabeling (P less than 0.01), compared with those without NFTs. Neurons with early neurofibrillary changes showed diffuse anti-CKII immunostaining in their cytoplasm and cell processes. In tangle-bearing neurons, in which a higher level of tau immunoreactivity was detected, anti-CKII immunolabeling was distributed along a fibrillar meshwork in cell bodies and processes. Linear regression analysis of anti-CKII and anti-tau immunoreactivity in AD showed a positive correlation (r = 0.53, P less than 0.001). At the ultrastructural level, anti-CKII was immunolocalized to the paired helical filaments (PHF) of the tangle-bearing neurons, as well as to PHF in neuropil threads and some dystrophic neurites in plaques. These results suggest a possible role for CK-II in tangle formation.     

脑内铁积聚与神经退行性疾病

过渡金属(铜、锌、铁等)在脑内异常沉积及其代谢紊乱是多种神经退行性疾病的重要病因。普通老年人和神经退行性疾病患者的脑内均有铁沉积增多的趋势,但调节铁代谢的转铁蛋白在脑组织中并没有相应增多,从而增加产生氧化应激的风险。然而在阿尔茨海默病(Alzheimer′s,AD)和帕金森氏病(Parkinson′s,PD)患者脑内铁含量异常增多的原因尚不明确。因此,研究脑内铁代谢在神经退行性疾病的起病、进展等各阶段中的作用,已成为神经生物学领域的一个重要课题。     

A functional PTPN22 polymorphism associated with several autoimmune diseases is not associated with IgA deficiency in the Spanish population

Background  

The 1858C/T SNP of the PTPN22 gene has been associated with many autoimmune diseases, suggesting the existence of an inflammatory process common to all of them. We studied the association of that polymorphism with immunoglobulin A deficiency (IgAD) following a double approach: a case-control and a TDT study.     

Psychotic Alzheimer's disease is associated with gender-specific tau phosphorylation abnormalities

Converging evidence suggests that psychotic Alzheimer's disease (AD + P) is associated with an acceleration of frontal degeneration, with tau pathology playing a primary role. Previous histopathologic and biomarker studies have specifically implicated tau pathology in this condition. To precisely quantify tau abnormalities in the frontal cortex in AD + P, we used a sensitive biochemical assay of total tau and 4 epitopes of phospho-tau relevant in AD pathology in a postmortem sample of AD + P and AD − P. Samples of superior frontal gyrus from 26 AD subjects without psychosis and 45 AD + P subjects with psychosis were analyzed. Results of enzyme-linked immunosorbent assay demonstrate that AD + P females, but not males, had significantly higher levels of phosphorylated tau in the frontal cortex. In males, but not females, AD + P was associated with the presence of α-synuclein pathology. These results support a gender dissociation of pathology in AD + P. The design of future studies aimed at the elucidation of cognitive and/or functional outcomes; regional brain metabolic deficits; or genetic correlates of AD + P should take gender into consideration.     

杏仁核相关病理性蛋白在神经退行性疾病中作用的研究现状

神经退行性疾病是一种常见病多发病,其发生发展可能与杏仁核结构功能的改变密切相关。杏仁核汇集着影响神经退行性疾病相关的病理性蛋白,包括Aβ蛋白、tau蛋白、α-突触共核蛋白(α-syn)和TDP-43蛋白等,这些蛋白改变影响着疾病的进程。本文综述近年研究这些病理性蛋白表达对神经退行性疾病的作用和影响的进展,以对临床防治这类疾病提供参考。     

Human MSH2 binds to trinucleotide repeat DNA structures associated with neurodegenerative diseases

The expansion of trinucleotide repeat sequences is associated with several neurodegenerative diseases. The mechanism of this expansion is unknown but may involve slipped-strand structures where adjacent rather than perfect complementary sequences of a trinucleotide repeat become paired. Here, we have studied the interaction of the human mismatch repair protein MSH2 with slipped-strand structures formed from a triplet repeat sequence in order to address the possible role of MSH2 in trinucleotide expansion. Genomic clones of the myotonic dystrophy locus containing disease-relevant lengths of (CTG)n x (CAG)n triplet repeats were examined. We have constructed two types of slipped-strand structures by annealing complementary strands of DNA containing: (i) equal numbers of trinucleotide repeats (homoduplex slipped structures or S-DNA) or (ii) different numbers of repeats (heteroduplex slipped intermediates or SI-DNA). SI-DNAs having an excess of either CTG or CAG repeats were structurally distinct and could be separated electrophoretically and studied individually. Using a band-shift assay, the MSH2 was shown to bind to both S-DNA and SI-DNA in a structure- specific manner. The affinity of MSH2 increased with the length of the repeat sequence. Furthermore, MSH2 bound preferentially to looped-out CAG repeat sequences, implicating a strand asymmetry in MSH2 recognition. Our results are consistent with the idea that MSH2 may participate in trinucleotide repeat expansion via its role in repair and/or recombination.      

Casein kinase 1 alpha associates with the tau-bearing lesions of inclusion body myositis

Inclusion body myositis and Alzheimer's disease are age-related disorders characterized in part by the appearance of intracellular lesions composed of filamentous aggregates of the microtubule-associated protein tau. Abnormal tau phosphorylation accompanies tau aggregation and may be an upstream pathological event in both diseases. Enzymes implicated in tau hyperphosphorylation in Alzheimer's disease include members of the casein kinase 1 family of phosphotransferases, a group of structurally related protein kinases that frequently function in tandem with the ubiquitin modification system. To determine whether casein kinase 1 isoforms associate with degenerating muscle fibers of inclusion body myositis, muscle biopsy sections isolated from sporadic disease cases were subjected to double-label fluorescence immunohistochemistry using selective anti-casein kinase 1 and anti-phospho-tau antibodies. Results showed that the alpha isoform of casein kinase 1, but not the delta or epsilon isoforms, stained degenerating muscle fibers in all eight inclusion body myositis cases examined. Staining was almost exclusively localized to phospho-tau-bearing inclusions. These findings, which extend the molecular similarities between inclusion body myositis muscle and Alzheimer's disease brain, implicate casein kinase 1 alpha as one of the phosphotransferases potentially involved in tau hyperphosphorylation.     

Association of micronucleus frequency with neurodegenerative diseases

Micronuclei (MNi) can originate either from chromosome breakage or chromosome malsegregation events and are therefore ideal biomarkers to investigate genomic instability. Studies in peripheral lymphocytes of patients with neurodegenerative diseases, mainly Alzheimer's disease (AD) and Parkinson's disease (PD), revealed an increased micronucleus (MN) frequency in both disorders but originating mainly from chromosome malsegregation events in AD and from chromosome breakage events in PD. Studies in other neurodegenerative diseases are largely missing, and some data in premature ageing disorders characterised by neurodegeneration and/or neurological complications, such as Ataxia telangiectasia, Werner's syndrome, Down's syndrome (DS) and Cockayne's syndrome, indicate that MNi increase with ageing in cultured cells. An increased frequency of aneuploidy characterises several tissues of AD patients, as well as of individuals at increased risk to develop AD, such as mothers of DS individuals and DS subjects themselves. The use of the buccal MN cytome assay in AD and DS subjects allowed finding significant changes in the MN frequency as well as other cellular modifications reflecting reduced regenerative capacity compared to age- and gender-matched controls. These changes in buccal cytome ratios may prove useful as potential future diagnostics to identify individuals of increased risk for these disorders.     

Protein kinase C delta is a critical regulator of CD1d-mediated antigen presentation

We have recently demonstrated that the p38 and ERK1/2 MAP kinases play reciprocal roles in the control of CD1d-mediated antigen presentation. Although the use of specific inhibitors for these pathways clearly had an effect, the effects were not complete, leading to speculations that additional pathways were involved. Here, we show that inhibiting protein kinase C delta (PKCdelta) substantially impairs antigen presentation by murine CD1d1 to NKT cells. This effect was accompanied by marked changes in the intracellular localization of CD1d. Expression of a dominant-negative mutant of PKCdelta in CD1d(+) cells resulted in nearly undetectable endogenous antigen presentation, substantially impaired CD1d recycling, a decrease in MAPK activation, and a decrease in the ability to present low (but not high) concentrations of alpha-galactosylceramide at the cell surface. These data strongly suggest that PKCdelta is a critical regulator of CD1d-mediated antigen presentation and is involved in multiple steps of the process.     

Abeta accumulation in choroid plexus is associated with mitochondrial-induced apoptosis

One of the possible mechanisms involved in beta-amyloid (Abeta)-induced neuronal damage is blood-cerebrospinal fluid barrier dysfunction. Recently, we have demonstrated that Alzheimer patients have an elevated expression of Abeta in the choroid plexus (CP), where it could impair the physiological functions of CP epithelium. We investigated whether these alterations were mediated by mitochondrial dysfunction, a common early pathomechanism in Alzheimer's disease. Our main observations were: high Abeta levels; increased nitric oxide levels; impairment of the activity and assembly of mitochondrial respiratory chain complexes I and IV; and a significant increase in reactive oxygen species and caspase expression in CP epithelial cells treated with Abeta. Our results also demonstrate a direct relationship between Abeta toxicity, increased expression of matrix metalloproteinase-9, and blood-cerebrospinal fluid barrier disruption. We propose a sequence of pathological steps that link Abeta accumulation in CP epithelium with an enhanced nitric oxide production, mitochondrial dysfunction, and up-regulation of matrix metalloproteinase-9, which ultimately lead to cell death, and probably to CSF barrier dysfunction.     

Elevated levels of brain-pathologies associated with neurodegenerative diseases in the methionine sulfoxide reductase A knockout mouse

One of the posttranslational modifications to proteins is methionine oxidation, which is readily reversible by the methionine sulfoxide reductase (Msr) system. Thus, accumulation of faulty proteins due to a compromised Msr system may lead to the development of aging-associated diseases like neurodegenerative diseases. In particular, it was interesting to monitor the consequential effects of methionine oxidation in relation to markers that are associated with Alzheimer’s disease as methionine oxidation was implied to play a role in beta-amyloid toxicity. In this study, a knockout mouse strain of the methionine sulfoxide reductase A gene (MsrA ^−/− ) caused an enhanced neurodegeneration in brain hippocampus relative to its wild-type control mouse brain. Additionally, a loss of astrocytes integrity, elevated levels of beta-amyloid deposition, and tau phosphorylation were dominant in various regions of the MsrA ^−/− hippocampus but not in the wild-type. Also, a comparison between cultured brain slices of the hippocampal region of both mouse strains showed more sensitivity of the MsrA ^−/− cultured cells to H₂O₂ treatment. It is suggested that a deficiency in MsrA activity fosters oxidative-stress that is manifested by the accumulation of faulty proteins (via methionine oxidation), deposition of aggregated proteins, and premature brain cell death.     

Widespread nitration of pathological inclusions in neurodegenerative synucleinopathies

Reactive nitrogen species may play a mechanistic role in neurodegenerative diseases by posttranslationally altering normal brain proteins. In support of this hypothesis, we demonstrate that an anti-3-nitrotyrosine polyclonal antibody stains all of the major hallmark lesions of synucleinopathies including Lewy bodies, Lewy neurites and neuraxonal spheroids in dementia with Lewy bodies, the Lewy body variant of Alzheimer's disease, and neurodegeneration with brain iron accumulation type 1, as well as glial and neuronal cytoplasmic inclusions in multiple system atrophy. This antibody predominantly recognized nitrated alpha-synuclein when compared to other in vitro nitrated constituents of these pathological lesions, such as neurofilament subunits and microtubules. Collectively, these findings imply that alpha-synuclein is nitrated in pathological lesions. The widespread presence of nitrated alpha-synuclein in diverse intracellular inclusions suggests that oxidation/nitration is involved in the onset and/or progression of neurodegenerative diseases.     

The extended haplotype of the microtubule associated protein tau gene is not associated with Pick's disease

Pick's disease (PiD) is a rare neurodegenerative condition and is a member of a heterogeneous group of disorders known as tauopathies, so-called because of the predominantly neuronal aberrant tau accumulations found in these diseases. The tauopathy, familial frontotemporal dementia (FTD), is caused by mutations in the tau gene. Moreover, progressive supranuclear palsy (PSP) is associated with the tau H1 haplotype. In certain familial forms of FTD and in PSP the microtubule-binding four repeat tau isoform principally accumulates in neuropathological lesions. However, in PiD three repeat tau accumulations are found. We therefore investigated whether either the tau H1 or H2 haplotype was associated with PiD. Our results indicate a slight increase in H2H2 frequency in Pick's cases which is not statistically significant.     

Ferritin is associated with the aberrant tau filaments present in progressive supranuclear palsy.

Tau-containing filaments purified from the brain of progressive supranuclear palsy (PSP) patients were isolated and characterized. These filaments co-purify with regular particles that biophysical and biochemical methods identified as ferritin shells. In vivo, brain tau accumulation in PSP co-localized with ferritin. These results suggest that ferritin/iron could modulate the formation of tau aggregates in PSP.     

Ubiquitin is a component of neurofibrillary tangles in a variety of neurodegenerative diseases

Ubiquitin has been shown to be a component of neurofibrillary tangles in Alzheimer's disease. We now show immunocytochemically that it is also a component of neurofibrillary tangles in several other neurodegenerative diseases of diverse aetiology, including Down's syndrome, dementia pugilistica and postencephalitic parkinsonism, and in normal ageing. Ubiquitin immunoreactivity is not, however, generally found in the neurofibrillary tangles of progressive supranuclear palsy. These findings show that while associated ubiquitin is not a feature unique to the tangles of Alzheimer's disease, it is not simply a non-specific response to the presence of an inclusion body within the cell. The observations suggest that ubiquitin may have an important role in the formation of neurofibrillary tangles in a variety of neurodegenerative diseases.     

Oxidized low-density-lipoprotein accumulation is associated with liver fibrosis in experimental cholestasis

OBJECTIVE: The aim of the present study was to examine the probable relationship between the accumulation of oxLDL and hepatic fibrogenesis in cholestatic rats. INTRODUCTION: There is growing evidence to support the current theories on how oxidative stress that results in lipid peroxidation is involved in the pathogenesis of cholestatic liver injury and fibrogenesis. One of the major and early lipid peroxidation products, OxLDL, is thought to play complex roles in various immuno-inflammatory mechanisms. METHODS: A prolonged (21-day) experimental bile duct ligation was performed on Wistar-albino rats. Biochemical analysis of blood, histopathologic evaluation of liver, measurement of the concentration of malondialdehyde (MDA) and superoxide-dismutase (SOD) in liver tissue homogenates, and immunofluorescent staining for oxLDL in liver tissue was conducted in bile-duct ligated (n=8) and sham-operated rats (n=8). RESULTS: Significantly higher levels of MDA and lower concentrations of SOD were detected in jaundiced rats than in the sham-operated rats. Positive oxLDL staining was also observed in liver tissue sections of jaundiced rats. Histopathological examination demonstrated that neither fibrosis nor other indications of hepatocellular injury were found in the sham-operated group, while features of severe hepatocellular injury, particularly fibrosis, were found in jaundiced rats. CONCLUSION: Our results support the finding that either oxLDLs are produced as an intermediate agent during exacerbated oxidative stress or they otherwise contribute to the various pathomechanisms underlying the process of liver fibrosis. Whatever the mechanism, it is clear that an association exists between elevated oxLDL levels and hepatocellular injury, particularly with fibrosis. Further studies are needed to evaluate the potential effects of oxLDLs on the progression of secondary biliary cirrhosis.     

The unfolded protein response is associated with early tau pathology in the hippocampus of tauopathies

The unfolded protein response (UPR) is a stress response activated upon disturbed homeostasis in the endoplasmic reticulum (ER). Previously, we reported that the activation of the UPR closely correlates with the presence of phosphorylated tau (p-tau) in Alzheimer's disease (AD). As well as increased presence of intracellular p-tau, AD brains are characterized by extracellular deposits of β amyloid (Aβ). Recent in vitro studies have shown that Aβ can induce ER stress and activation of the UPR. The aim of the present study is to investigate UPR activation in sporadic tauopathies like progressive supranuclear palsy (PSP) and Pick's disease (PiD), and familial cases with frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) which carry mutations in the gene encoding for tau (MAPT). The presence of phosphorylated pancreatic ER kinase (pPERK) and phosphorylated inositol requiring enzyme 1α (pIRE1), which are indicative of an activated UPR, was assessed by immunohistochemistry in cases neuropathologically defined as frontotemporal lobar degeneration with tau pathology (FTLD-tau). Increased presence of UPR activation markers pPERK and pIRE1 was observed in neurons and glia in FTLD-tau cases, in contrast to FTLD subtypes negative for tau pathology or in non-neurological controls. pPERK and pIRE1 were also prominently present in relatively young carriers of MAPT mutation. A strong association between the presence of UPR activation markers and p-tau was observed in the hippocampus of FTLD-tau cases. Double immunohistochemical staining on FTLD-tau cases revealed that UPR activation is predominantly observed in neurons that show diffuse staining of p-tau. These data demonstrate that UPR activation is intimately connected with the accumulation and aggregation of p-tau, and occurs independently from Aβ deposits. Our findings provide new pathological insight into the close association between p-tau and UPR activation in tauopathies.     

The tau locus is not significantly associated with pathologically confirmed sporadic Parkinson's disease

Tetrahydrobiopterin (BH(4)) has a trophic effect on pheochromocytoma-12 (PC12) cells such as insulin-like growth factor-1 (IGF-1). We investigated involvement of BH(4) in the trophic effect of IGF-1 on PC12 cells. IGF-1 (10-300 ng/ml) increased cellular BH(4) content in a dose-related manner. Cellular BH(4) content increased after 6-36 h incubation with IGF-1. IGF-1-induced increase in the cellular BH(4) content was blunted by 0.3 mM 2,4-diamino-6-hydroxypyrimidine (DAHP), an inhibitor for BH(4) synthesis. IGF-1 protected PC12 cells from the cell death induced by depletion of serum and nerve growth factor, which was attenuated by DAHP. The effects of IGF-1 on the cellular BH(4) content and cell viability were eliminated by 0.2 microM wortmannin. These results suggest that BH(4) is involved in the trophic effect of IGF-1 on PC12 cells and that the effect of IGF-1 on BH(4) synthesis is mediated by phosphatidylinositol 3-kinase.