Copper Induces Apoptosis of Neuroblastoma Cells Via Post-translational Regulation of the Expression of Bcl-2-family Proteins and the tx Mouse is a Better Model of Hepatic than Brain Cu Toxicity

The basic mechanism(s) by which altered Cu homeostasis is toxic to hepatocytes and neurons, the two major cell types affected in copper storage diseases such as Wilson's disease (WD), remain unclear. Using human M17 neuroblastoma cells as a model to examine Cu toxicity, we found that there was a time- and concentration-dependent induction of neuronal death, such that at 24 h there was a approximately 50 % reduction in viability with 25 muM Cu-glycine(2). Cu-glycine(2) (25:50 muM) treatment for 24 h significantly altered the expression of 296 genes, including 8 genes involved with apoptosis (BCL2-associated athanogene 3, BCL2/adenovirus E1B 19kDa interacting protein caspase 5, regulator of Fas-induced apoptosis, V-jun sarcoma virus 17 oncogene homolog, claudin 5, prostaglandin E receptor 3 and protein tyrosine phosphatase, non-receptor type 6). Surprisingly, changes in the expression of more 'traditional' apoptotic genes (Bcl-2, Bax, Bak and Bad) did not vary more than 20 %. To test whether the induction of apoptosis in neuroblastoma cells was via post-translational mechanisms, we measured the protein expression of these apoptotic markers in M17 neuroblastoma cells treated with Cu-glycine(2) (0-100 muM) for 24-48 h. Compared with glycine treated cells, Cu-glycine(2) reduced Bcl-2 expression by 50 %, but increased Bax and Bak expression by 130% and 400 %, respectively. To assess whether Cu also induced apoptotic cell death in a mouse model of WD, we measured the expression of these apoptotic markers in the liver and brain of mice expressing an ATP7b gene mutation (tx(J) mice) at 10 months of age (near the end of their lives when overt liver pathology is displayed). Changes in the liver expression of these apoptotic markers in tx(J) mice compared to background mice mirrored those of Cu treated neuroblastoma cells. In contrast, few changes in apoptotic protein expression were detected in the brain between tx(J) and background mice, indicating the tx(J) mouse is a good model of hepatic, but not brain, Cu toxicity. Our results indicate that Cu-induction of neuronal apoptosis does not require de novo synthesis or degradation of apoptotic genes, and that Cu accumulation in the aged tx(J) mouse brain is insufficient to induce apoptosis.

Redox proteomics identification of oxidatively modified brain proteins in inherited Alzheimer's disease: an initial assessment

OBJECTIVE

To identify oxidatively modified proteins in brains of persons with inherited Alzheimer's disease.

METHODS

Redox proteomics was used to identify oxidatively modified brain proteins in persons with mutations in the genes for presenilin-1 (PS-1).

RESULTS

An initial redox proteomics assessment of oxidatively modified proteins from brains of individuals with PS-1 mutations was performed. These PS1 mutations, Q222H and M233T, are completely penetrant causing early-onset familial AD as previously reported in these Australian families. We show that oxidative modifications of ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1), gamma-enolase, actin, and dimethylarginine dimethylaminohydrolase 1 (DMDMAH-1) are present in the brain of familial AD subjects.

CONCLUSIONS

These initial results suggest that oxidatively modified proteins are important common features in both familial and sporadic AD.

Predicting outcomes and complications of percutaneous endoscopic gastrostomy

BACKGROUND AND STUDY AIMS

Percutaneous endoscopic gastrostomy (PEG) is the preferred route for long-term enteral feeding. Our aims were to prospectively evaluate the outcome ("PEG status") and complications of PEG and to determine whether these can be predicted by patients' baseline characteristics.

PATIENTS AND METHODS

We conducted a prospective study in two tertiary hospitals between August 2003 and January 2005, enrolling all patients who were undergoing PEG placement. We completed a questionnaire with details of demographic data, diagnosis, indication for PEG, Charlson's co-morbidity index, Barthel's index, laboratory tests, complications, and date and cause of death. Patients were followed at scheduled appointments. Univariate and multivariate analyses were performed.

RESULTS

168 patients (48% male, 52% female; mean age +/- standard deviation 74 +/- 16 years) underwent PEG using the pull technique. The main indication was neurogenic dysphagia (156 patients, 92.9%). Although most indications were appropriate, in half the cases these were established too late. There were no procedure-related deaths. Major complications occurred in four patients (2.4%); minor complications occurred in 52 patients (31%). No single variable could predict complications. Fifteen patients (9%) had the PEG removed. No single variable was independently associated with PEG removal. The mortality was 6.5% at 30 days, 17.3% at 90 days and 33.9% at 1 year. The C-reactive protein was the only predictive factor of early mortality (< or = 30 days), and Charlson's co-morbidity index was the only predictive factor of late mortality (> 30 days).

CONCLUSIONS

PEG placement is an easy and safe procedure, although it is often requested too late. No single variable could predict complications or PEG removal. C-reactive protein was found to be predictive of early mortality and Charlson's index was predictive of late mortality.

The role of presenilin and its interacting proteins in the biogenesis of Alzheimer's beta amyloid

The biogenesis and accumulation of the beta amyloid protein (Abeta) is a key event in the cascade of oxidative and inflammatory processes that characterises Alzheimer's disease. The presenilins and its interacting proteins play a pivotal role in the generation of Abeta from the amyloid precursor protein (APP). In particular, three proteins (nicastrin, aph-1 and pen-2) interact with presenilins to form a large multi-subunit enzymatic complex (gamma-secretase) that cleaves APP to generate Abeta. Reconstitution studies in yeast and insect cells have provided strong evidence that these four proteins are the major components of the gamma-secretase enzyme. Current research is directed at elucidating the roles that each of these protein play in the function of this enzyme. In addition, a number of presenilin interacting proteins that are not components of gamma-secretase play important roles in modulating Abeta production. This review will discuss the components of the gamma-secretase complex and the role of presenilin interacting proteins on gamma-secretase activity.

Cerebrospinal fluid antimicroglial antibodies in Alzheimer disease: A putative marker of an ongoing inflammatory process

Immunocompetent microglia play an important role in the pathogenesis of Alzheimer's disease (AD). Antimicroglial antibodies in the cerebrospinal fluid (CSF) in clinically diagnosed AD patients have been previously recorded. Here, we report the results of the analysis of the CSF from 38 autopsy cases: 7 with definite AD; 14 with mild and 10 with moderate Alzheimer's type pathology; and 7 controls. Antimicroglial antibodies were identified in 70% of patients with definite AD, in 80% of patients with moderate and in 28% of patients with mild Alzheimer's type pathology. CSF antimicroglial antibodies were not observed in any of the control cases. The results show that CSF antimicroglial antibodies are present in the majority of patients with definite AD and also in cases with moderate Alzheimer's type changes. They may also indicate dysregulation of microglial function. Together with previous observations, these findings indicate that compromised immune defense mechanisms play an important role in the pathogenesis of AD.

Mutations in progranulin explain atypical phenotypes with variants in MAPT

Mutations in presenilin-1 (PSEN1) cause autosomal dominant Alzheimer's disease and mutations in MAPT cause the familial tauopathy Frontotemporal dementia linked to chromosome 17 (FTDP-17). However, there have been reports of mutations in PSEN1 and MAPT associated with cases of FTD with ubiquitin-positive tau-negative inclusion pathology. Here, we demonstrate that the MAPT variants are almost certainly rare benign polymorphisms as all of these cases harbour mutations in Progranulin (PGRN). Mutations in PGRN were recently shown to cause ubiquitin-positive FTDP-17.

B-vitamins reduce plasma levels of beta amyloid

Elevated plasma homocysteine (tHcy) is a risk factor for Alzheimer's disease (AD), and thus B vitamins may have a role in the prevention of AD. The objective of this study was to determine if tHcy lowering vitamins decrease the circulating levels of A-beta protein 1-40 (A beta 40). We randomized 299 older men to treatment with 2mg of folate, plus 25mg of B6 and 400 microg of B12, or placebo. After 2 years of treatment the mean (S.E.) increase of A beta 40 was 7.0 pg/ml (8.4) in the vitamin group (4.9%), and 26.8 pg/ml (7.7) (18.5%) in the placebo group. We conclude that B vitamins may decrease the plasma level of A beta 40 and have a role in the prevention of AD.

Reproductive hormones modulate oxidative stress in Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by gradual cognitive decline, impairments in speech and language, and dysfunction in the sensorimotor systems, culminating in complete reliance on nursing care. Oxidative stress, caused by an imbalance in the pro-oxidant/antioxidant mechanisms in the body, has been implicated in AD pathogenesis, as in many other age-associated diseases such as atherosclerosis, Parkinson disease, and amyotrophic lateral sclerosis. Although the hormones estrogen, progesterone, testosterone, and luteinizing hormone are best known for their roles in reproduction, many studies show these hormones have other roles, including neuroprotection. Changes in the levels of these hormones that occur in reproductive senescence are hypothesized to increase risk of AD, as a result of reduced protection against oxidative insults. The Abeta peptide, overproduction of which is thought to be a key pathogenic event in the development of AD, is neurotoxic, most likely due to its ability to promote oxidative stress. The reproductive hormones are known to influence Abeta metabolism, and this review discusses the beneficial and detrimental effects these hormones have on Abeta production and oxidative stress, and their relevance in potential AD therapies.

TNF polymorphisms in Alzheimer disease and functional implications on CSF beta-amyloid levels

Alzheimer disease (AD), vascular dementia, and stroke are all associated with inflammation though their respective initiating factors differ. Recently a polymorphism in the proinflammatory cytokine tumor necrosis factor (TNF), in association with apolipoprotein E (APOE), was reported to increase AD risk. Two SNPs, rs1799724 (-850C>T; NT_007592.14:g.22400733C>T) and rs1800629 (-308G>A; [NT_007592.14:g.22401282G>A]), and the APOE polymorphism were genotyped in 506 patients with sporadic AD and in 277 cognitively healthy controls. In a subset of 90 individuals we also investigated whether these SNPs exerted any functional effects on cerebrospinal fluid (CSF) beta-amyloid (Abeta) levels. The frequency of the rs1799724 genotypes and the rs1799724-T allele were significantly different in AD individuals (P=0.009; odds ratio [OR], 1.63; 95% confidence interval [CI], 1.13-2.34), while the rs1800629 SNP was not associated with AD. Significant interaction was observed between the rs1799724-T and APOE epsilon4 alleles in that the rs1799724-T allele significantly modified risk associated with possession of the epsilon4 allele only (epsilon4 in absence of rs1799724-T: OR, 2.92; 95% CI, 2.00-4.27; epsilon4 in presence of rs1799724-T: OR, 6.65; 95% CI, 3.26-13.55; P=0.03). Haplotyping analysis revealed a significant overrepresentation of an rs1799724-T/rs1800629-G haplotype in AD (P=0.012; OR, 1.60; 95% CI, 1.11-2.29), although to a lesser degree than rs1799724-T alone. Further, the rs1799724-T allele was found to be associated with lower levels of CSF Abeta42 (P=0.023), thus corroborating the genetic findings. Inheritance of the rs1799724-T allele appears to synergistically increase the risk of AD in APOEepsilon4 carriers and is associated with altered CSF Abeta42 levels. Further investigations are warranted to assess the significance of these novel findings.

Apolipoprotein E, cholesterol metabolism, diabetes, and the convergence of risk factors for Alzheimer's disease and cardiovascular disease

High fat diets and sedentary lifestyles are becoming major concerns for Western countries. They have led to a growing incidence of obesity, dyslipidemia, high blood pressure, and a condition known as the insulin-resistance syndrome or metabolic syndrome. These health conditions are well known to develop along with, or be precursors to atherosclerosis, cardiovascular disease, and diabetes. Recent studies have found that most of these disorders can also be linked to an increased risk of Alzheimer's disease (AD). To complicate matters, possession of one or more apolipoprotein E epsilon4 (APOE epsilon4) alleles further increases the risk or severity of many of these conditions, including AD. ApoE has roles in cholesterol metabolism and Abeta clearance, both of which are thought to be significant in AD pathogenesis. The apparent inadequacies of ApoE epsilon4 in these roles may explain the increased risk of AD in subjects carrying one or more APOE epsilon4 alleles. This review describes some of the physiological and biochemical changes that the above conditions cause, and how they are related to the risk of AD. A diversity of topics is covered, including cholesterol metabolism, glucose regulation, diabetes, insulin, ApoE function, amyloid precursor protein metabolism, and in particular their relevance to AD. It can be seen that abnormal lipid, cholesterol and glucose metabolism are consistently indicated as central in the pathophysiology, and possibly the pathogenesis of AD. As diagnosis of mild cognitive impairment and early AD are becoming more reliable, and as evidence is accumulating that health conditions such as diabetes, obesity, and coronary artery disease are risk factors for AD, appropriate changes to diets and lifestyles will likely reduce AD risk, and also improve the prognosis for people already suffering from such conditions.

A functional polymorphism within plasminogen activator urokinase (PLAU) is associated with Alzheimer's disease

A number of susceptibility loci for Alzheimer's disease (AD) have been identified including a region on Chromosome 10q21-q22. Within this region the plasminogen activator urokinase gene (PLAU) was considered as a reasonable candidate from its functional implication in plasmin generation, a serine protease capable of degrading beta-Amyloid (Abeta) protein. We screened 56 single nucleotide polymorphisms (SNPs) around PLAU using 1751 individuals from four independent case-control samples (Munich, N=679; Bonn N=282; Brescia (Italy) N=219; Perth (Australia) N=557 and one discordant sib-pair sample (Munich N=622). In brain tissue samples of neuropathologically confirmed cases with AD (N=33) we analyzed plaque counts according to the risk allele. We identified that one functional exonic SNP (rs2227564) is associated with development of AD using the four independent case-control samples (Munich, P=0.02; Bonn, P=0.005; Brescia (Italy), P=0.001; Perth (Australia), P=0.03) and the discordant sib-pair sample (P=0.001). In brain tissue, from neuropathologically confirmed cases with AD, we identified significantly higher plaque counts in carriers of the risk allele (N=6; 60.3+/-16.9) compared with non-carriers (N=9; 26.3+/-8.8; P=0.007). This study provides compelling evidence of a genetic and functional involvement of a common PLAU variant into the pathogenesis of AD. Further functional investigations are warranted to elucidate the specific role of PLAU, respectively, PLAU variants in the metabolism of Abeta proteins.

The role of gonadotropins in Alzheimer's disease: potential neurodegenerative mechanisms

In addition to the classical role of gonadotropins as a modulator of sex hormone production, it is now becoming apparent that the gonadotropins may have actions within the central nervous system. Evidence is also mounting that age-related increases in levels of the gonadotropin, luteinizing hormone (LH), may exert neurodegenerative effects such as those seen in Alzheimer's disease (AD). LH has been implicated in key cellular and biochemical processes that contribute to the pathogenesis of AD. These processes include the altered metabolism of key proteins in AD pathology, beta amyloid (Abeta), and its parent molecule, the amyloid precursor protein (APP). Evidence in the literature suggests that gonadotropins may be involved in processes that contribute to the etiology/pathogenesis of AD such as inflammation, cholesterol homeostasis, and insulin status. Here we examine the potential mechanisms by which gonadotropins could influence neurodegenerative processes. The role of gonadotropins in the brain and potential direct neuropathological effects of elevated gonadotropin levels is an exciting new topic in neuroendocrinology that in turn will lead to the development of novel therapeutic approaches for AD.

Gonadotropins: potential targets for preventive and therapeutic interventions in Alzheimer’s disease

Increased prevalence of Alzheimer’s disease (AD) in women has led to an interest in the role of hormonal changes in the neurodegenerative process. In particular, research has been directed towards investigating the effect of changes in sex hormone levels following reproductive senescence. Clinical trials of hormone-replacement therapy for the prevention of AD are proving contentious, and considerably more research is necessary before the benefit of the hormone replacement strategy can be ascertained. However, evidence is now emerging to support the notion that increased gonadotropin levels may confer an increased risk of AD. Gonadotropins have been implicated in the metabolism of β-amyloid, a key protein that is central to the pathogenesis of AD. Gonadotropin reduction represents a promising new target for therapeutic intervention in AD and, potentially, dementia in general. In this review, the authors discuss the therapeutic and preventive potential of gonadotropin-reducing agents in the management of AD.