Autoantibodies to the adenosine triphosphate synthase play a pathogenetic role in Alzheimer's disease

Inflammation, Autoimmunity and Neurodegenerative Diseases, Therapeutics and Beyond

Neurodegenerative disease (ND) incidence has recently increased due to improved life expectancy. Alzheimer's (AD) or Parkinson's disease (PD) are the most prevalent NDs. Both diseases are poly genetic, multifactorial and heterogenous. Preventive medicine, a healthy diet, exercise, and controlling comorbidities may delay the onset. After the diseases are diagnosed, therapy is needed to slow progression. Recent studies show that local, peripheral and age-related inflammation accelerates NDs' onset and progression. Patients with autoimmune disorders like inflammatory bowel disease (IBD) could be at higher risk of developing AD or PD. However, no increase in ND incidence has been reported if the patients are adequately diagnosed and treated. Autoantibodies against abnormal tau, β amyloid and α- synuclein have been encountered in AD and PD and may be protective. This discovery led to the proposal of immune-based therapies for AD and PD involving monoclonal antibodies, immunization/ vaccines, pro-inflammatory cytokine inhibition and anti-inflammatory cytokine addition. All the different approaches have been analysed here. Future perspectives on new therapeutic strategies for both disorders are concisely examined.

Immune Regulatory Functions of Macrophages and Microglia in Central Nervous System Diseases

Macrophages can be characterized as a very multifunctional cell type with a spectrum of phenotypes and functions being observed spatially and temporally in various disease states. Ample studies have now demonstrated a possible causal link between macrophage activation and the development of autoimmune disorders. How these cells may be contributing to the adaptive immune response and potentially perpetuating the progression of neurodegenerative diseases and neural injuries is not fully understood. Within this review, we hope to illustrate the role that macrophages and microglia play as initiators of adaptive immune response in various CNS diseases by offering evidence of: (1) the types of immune responses and the processes of antigen presentation in each disease, (2) receptors involved in macrophage/microglial phagocytosis of disease-related cell debris or molecules, and, finally, (3) the implications of macrophages/microglia on the pathogenesis of the diseases.

Artificial intelligence-driven meta-analysis of brain gene expression identifies novel gene candidates and a role for mitochondria in Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia. There is no treatment and AD models have focused on a small subset of genes identified in familial AD. Microarray studies have identified thousands of dysregulated genes in the brains of patients with AD yet identifying the best gene candidates to both model and treat AD remains a challenge. We performed a meta-analysis of microarray data from the frontal cortex (n = 697) and cerebellum (n = 230) of AD patients and healthy controls. A two-stage artificial intelligence approach, with both unsupervised and supervised machine learning, combined with a functional network analysis was used to identify functionally connected and biologically relevant novel gene candidates in AD. We found that in the frontal cortex, genes involved in mitochondrial energy, ATP, and oxidative phosphorylation, were the most significant dysregulated genes. In the cerebellum, dysregulated genes were involved in mitochondrial cellular biosynthesis (mitochondrial ribosomes). Although there was little overlap between dysregulated genes between the frontal cortex and cerebellum, machine learning models comprised of this overlap. A further functional network analysis of these genes identified that two downregulated genes, ATP5L and ATP5H, which both encode subunits of ATP synthase (mitochondrial complex V) may play a role in AD. Combined, our results suggest that mitochondrial dysfunction, particularly a deficit in energy homeostasis, may play an important role in AD.

Explore potential disease related metabolites based on latent factor model

Background

In biological systems, metabolomics can not only contribute to the discovery of metabolic signatures for disease diagnosis, but is very helpful to illustrate the underlying molecular disease-causing mechanism. Therefore, identification of disease-related metabolites is of great significance for comprehensively understanding the pathogenesis of diseases and improving clinical medicine.

Results

In the paper, we propose a disease and literature driven metabolism prediction model (DLMPM) to identify the potential associations between metabolites and diseases based on latent factor model. We build the disease glossary with disease terms from different databases and an association matrix based on the mapping between diseases and metabolites. The similarity of diseases and metabolites is used to complete the association matrix. Finally, we predict potential associations between metabolites and diseases based on the matrix decomposition method. In total, 1,406 direct associations between diseases and metabolites are found. There are 119,206 unknown associations between diseases and metabolites predicted with a coverage rate of 80.88%. Subsequently, we extract training sets and testing sets based on data increment from the database of disease-related metabolites and assess the performance of DLMPM on 19 diseases. As a result, DLMPM is proven to be successful in predicting potential metabolic signatures for human diseases with an average AUC value of 82.33%.

Conclusion

In this paper, a computational model is proposed for exploring metabolite-disease pairs and has good performance in predicting potential metabolites related to diseases through adequate validation. The results show that DLMPM has a better performance in prioritizing candidate diseases-related metabolites compared with the previous methods and would be helpful for researchers to reveal more information about human diseases.

Single-Cell RNA Sequencing of Peripheral Blood Reveals Immune Cell Signatures in Alzheimer's Disease

The peripheral immune system is thought to affect the pathology of the central nervous system in Alzheimer’s disease (AD). However, current knowledge is inadequate for understanding the characteristics of peripheral immune cells in AD. This study aimed to explore the molecular basis of peripheral immune cells and the features of adaptive immune repertoire at a single cell level. We profiled 36,849 peripheral blood mononuclear cells from AD patients with amyloid-positive status and normal controls with amyloid-negative status by 5’ single-cell transcriptome and immune repertoire sequencing using the cell ranger standard analysis procedure. We revealed five immune cell subsets: CD4+ T cells, CD8+ T cells, B cells, natural killer cells, and monocytes–macrophages cells, and disentangled the characteristic alterations of cell subset proportion and gene expression patterns in AD. Thirty-one cell type-specific key genes, comprising abundant human leukocyte antigen genes, and multiple immune-related pathways were identified by protein–protein interaction network and pathway enrichment analysis. We also found high-frequency amplification clonotypes in T and B cells and decreased diversity in T cells in AD. As clone amplification suggested the activation of an adaptive immune response against specific antigens, we speculated that the peripheral adaptive immune response, especially mediated by T cells, may have a role in the pathogenesis of AD. This finding may also contribute to further research regarding disease mechanism and the development of immune-related biomarkers or therapy.

Diet Modifies Pioglitazone's Influence on Hepatic PPARγ-Regulated Mitochondrial Gene Expression

Pioglitazone (Pio) is a thiazolidinedione (TZD) insulin-sensitizing drug whose effects result predominantly from its modulation of the transcriptional activity of peroxisome proliferator-activated-receptor-gamma (PPARγ). Pio is used to treat human insulin-resistant diabetes and also frequently considered for treatment of nonalcoholic steatohepatitis (NASH). In both settings, Pio's beneficial effects are believed to result primarily from its actions on adipose PPARγ activity, which improves insulin sensitivity and reduces the delivery of fatty acids to the liver. Nevertheless, a recent clinical trial showed variable efficacy of Pio in human NASH. Hepatocytes also express PPARγ, and such expression increases with insulin resistance and in nonalcoholic fatty liver disease (NAFLD). Furthermore, mice that overexpress hepatocellular PPARγ and Pio-treated mice with extrahepatic PPARγ gene disruption develop features of NAFLD. Thus, Pio's direct impact on hepatocellular gene expression might also be a determinant of this drug's ultimate influence on insulin resistance and NAFLD. Previous studies have characterized Pio's PPARγ-dependent effects on hepatic expression of specific adipogenic, lipogenic, and other metabolic genes. However, such transcriptional regulation has not been comprehensively assessed. The studies reported here address that consideration by genome-wide comparisons of Pio's hepatic transcriptional effects in wildtype (WT) and liver-specific PPARγ-knockout (KO) mice given either control or high-fat (HFD) diets. The results identify a large set of hepatic genes for which Pio's liver PPARγ-dependent transcriptional effects are concordant with its effects on RXR-DNA binding in WT mice. These data also show that HFD modifies Pio's influence on a subset of such transcriptional regulation. Finally, our findings reveal a broader influence of Pio on PPARγ-dependent hepatic expression of nuclear genes encoding mitochondrial proteins than previously recognized. Taken together, these studies provide new insights about the tissue-specific mechanisms by which Pio affects hepatic gene expression and the broad scope of this drug's influence on such regulation.

ATP synthase and Alzheimer's disease: putting a spin on the mitochondrial hypothesis

It is estimated that over 44 million people across the globe have dementia, and half of these cases are believed to be Alzheimer’s disease (AD). As the proportion of the global population which is over the age 60 increases so will the number of individuals living with AD. This will result in ever-increasing demands on healthcare systems and the economy. AD can be either sporadic or familial, but both present with similar pathobiology and symptoms. Three prominent theories about the cause of AD are the amyloid, tau and mitochondrial hypotheses. The mitochondrial hypothesis focuses on mitochondrial dysfunction in AD, however little attention has been given to the potential dysfunction of the mitochondrial ATP synthase in AD. ATP synthase is a proton pump which harnesses the chemical potential energy of the proton gradient across the inner mitochondrial membrane (IMM), generated by the electron transport chain (ETC), in order to produce the cellular energy currency ATP. This review presents the evidence accumulated so far that demonstrates dysfunction of ATP synthase in AD, before highlighting two potential pharmacological interventions which may modulate ATP synthase.

Peripheral Routes to Neurodegeneration: Passing Through the Blood-Brain Barrier

A bidirectional crosstalk between peripheral players of immunity and the central nervous system (CNS) exists. Hence, blood-brain barrier (BBB) breakdown is emerging as a participant mechanism of dysregulated peripheral-CNS interplay, promoting diseases. Here, we examine the implication of BBB damage in neurodegeneration, linking it to peripheral brain-directed autoantibodies and gut-brain axis mechanisms. As BBB breakdown is a factor contributing to, or even anticipating, neuronal dysfunction(s), we here identify contemporary pharmacological strategies that could be exploited to repair the BBB in disease conditions. Developing neurovascular, add on, therapeutic strategies may lead to a more efficacious pre-clinical to clinical transition with the goal of curbing the progression of neurodegeneration.

Reaction of antibodies to Campylobacter jejuni and cytolethal distending toxin B with tissues and food antigens

BACKGROUND

The bacteria Campylobacter jejuni (C. jejuni) is commonly associated with Guillane-Barré syndrome (GBS) and irritable bowel syndrome (IBS), but studies have also linked it with Miller Fisher syndrome, reactive arthritis and other disorders, some of which are autoimmune. It is possible that C. jejuni and its toxins may be cross-reactive with some human tissues and food antigens, potentially leading to autoimmune responses.

AIM

To measure the immune reactivity of C. jejuni and C. jejuni cytolethal distending toxin (Cdt) antibodies with tissue and food antigens to examine their role in autoimmunities.

METHODS

Using enzyme-linked immunosorbent assay (ELISA) methodology, specific antibodies made against C. jejuni and C. jejuni Cdt were applied to a variety of microwell plates coated with 45 tissues and 180 food antigens. The resulting immunoreactivities were compared to reactions with control wells coated with human serum albumin (HSA) which were used as negative controls and with wells coated with C. jejuni lysate or C. jejuni Cdt which served as positive controls.

RESULTS

At 3 SD above the mean of control wells coated with HSA or 0.41 OD, the mouse monoclonal antibody made against C. jejuni showed moderate to high reactions with zonulin, somatotropin, acetylcholine receptor, β-amyloid and presenilin. This immune reaction was low with an additional 25 tissue antigens including asialoganglioside, and the same antibody did not react at all with another 15 tissue antigens. Examining the reaction between C. jejuni antibody and 180 food antigens, we found insignificant reactions with 163 foods but low to high immune reactions with 17 food antigens. Similarly, we examined the reaction of C. jejuni Cdt with the same tissues and food antigens. The strongest reactions were observed with zonulin, intrinsic factor and somatotropin. The reaction was moderate with 9 different tissue antigens including thyroid peroxidase, and reaction was low with another 10 different antigens, including neuronal antigens. The reaction of C. jejuni Cdt antibody with an additional 23 tissue antigens was insignificant. Regarding the reaction of C. jejuni Cdt antibody with different food antigens, 160 out of 180 foods showed insignificant reactions, while 20 foods showed reactions ranging from low to high.

CONCLUSION

Our findings indicate that C. jejuni and its Cdt may play a role in inflammation and autoimmunities beyond the gut.

Rusty Microglia: Trainers of Innate Immunity in Alzheimer's Disease

Alzheimer's disease, the most common form of dementia, is marked by progressive cognitive and functional impairment believed to reflect synaptic and neuronal loss. Recent preclinical data suggests that lipopolysaccharide (LPS)-activated microglia may contribute to the elimination of viable neurons and synapses by promoting a neurotoxic astrocytic phenotype, defined as A1. The innate immune cells, including microglia and astrocytes, can either facilitate or inhibit neuroinflammation in response to peripherally applied inflammatory stimuli, such as LPS. Depending on previous antigen encounters, these cells can assume activated (trained) or silenced (tolerized) phenotypes, augmenting or lowering inflammation. Iron, reactive oxygen species (ROS), and LPS, the cell wall component of gram-negative bacteria, are microglial activators, but only the latter can trigger immune tolerization. In Alzheimer's disease, tolerization may be impaired as elevated LPS levels, reported in this condition, fail to lower neuroinflammation. Iron is closely linked to immunity as it plays a key role in immune cells proliferation and maturation, but it is also indispensable to pathogens and malignancies which compete for its capture. Danger signals, including LPS, induce intracellular iron sequestration in innate immune cells to withhold it from pathogens. However, excess cytosolic iron increases the risk of inflammasomes' activation, microglial training and neuroinflammation. Moreover, it was suggested that free iron can awaken the dormant central nervous system (CNS) LPS-shedding microbes, engendering prolonged neuroinflammation that may override immune tolerization, triggering autoimmunity. In this review, we focus on iron-related innate immune pathology in Alzheimer's disease and discuss potential immunotherapeutic agents for microglial de-escalation along with possible delivery vehicles for these compounds.

Acute Sarcomeric M-Line Disease Associated With ATP Synthase Subunit α Autoantibodies in Ankylosing Spondylitis

M-line is the narrow transverse band located in the center of the sarcomeric A-band that is mainly responsible for the stabilization of myosin thick filaments. A 27-year-old male patient with a positive medical history for ankylosing spondylitis presented with one month of proximal upper limb muscle weakness associated with pain on both acromioclavicular joints. A biopsy of deltoid muscle documented the disappearance of M-line, the misalignment of myofilaments, and the loss of the distinction between the A and I bands. Complete resolution of muscle weakness occurred after one year of treatment with antiTNFα agent Etanercept. Because of the acute onset of symptoms and the recovery after immunosuppressive treatment we hypothesized that an immune-mediated mechanism was responsible for the muscle disorder. The serum IgG-mediated autoreactivity to skeletal muscle antigens resolved by bidimensional electrophoresis was assessed in the described patient and compared with that of control subjects. The comparative analysis of the immunoreactive spots revealed that ATP synthase subunit α is specifically recognized by patient's serum, suggesting that the protein might represent a putative antigenic target in the disease. This study reports an acute reversible myopathy pathologically characterized by M-line involvement and associated with serological antibodies to the subunit α of ATP synthase.

Amyloid-Beta 1-42 Cross-Reactive Antibody Prevalent in Human Sera May Contribute to Intraneuronal Deposition of A-Beta-P-42

Antibodies against many neural antigens are detected in the sera of both patients with Alzheimer's disease (AD) and some healthy individuals. Blood-brain barrier dysfunction could make it possible for brain-reactive autoantibodies to reach the brain, where they can react with amyloid ß peptide (AßP). The origin of these autoreactive antibodies in the blood is unclear. The goals of this study were as follows: (1) to examine the immune reactivity of anti-AßP-42 with 22 neuronal and other associated antigens, some of which are involved in the pathophysiology of AD; (2) to classify antibodies to these 22 different antigens into those that cross-react with AßP-42 and those that do not; (3) to determine whether these antibodies react with BBB proteins, nerve growth factors, and enteric neuronal antigens. Using monoclonal AßP-42 antibody and ELISA methodology, we found that the antibody was highly reactive with Aß protein, tau protein, presenilin, rabaptin-5, β-NGF, BDNF, mTG, and enteric nerve. The same antibody produced equivocal to moderate reactions with glutamate-R, S100B, AQP4, GFAP, MBP, α-synuclein, tTG-2, and tTG-3, and not with the rest. These antibodies were also measured in blood samples from 47 AD patients and 47 controls. IgG antibodies were found to be elevated against AßP-42 and many other antigens in a significant percentage of controls. Overall, the mean OD values were significantly higher against 9/23 tested antigens (p <0.001) in the samples with AD. We were indeed able to classify the detected neuronal antibodies into those that cross-react with AßP-42 and those that do not. Our main finding is that although these antibodies may be harmless in a subgroup of controls, in individuals with compromised BBBs these antibodies that cross-react with AßP-42 can reach the brain, where their cross-reactivity with AßP-42 may contribute to the onset and progression of AD, and perhaps other neurodegenerative disorders.

Biomarkers for the Early Detection and Progression of Alzheimer's Disease

The recent failures of potential disease-modifying drugs for Alzheimer's disease (AD) may reflect the fact that the enrolled participants in clinical trials are already too advanced to derive a clinical benefit. Thus, well-validated biomarkers for the early detection and accurate diagnosis of the preclinical stages of AD will be crucial for therapeutic advancement. The combinatorial use of biomarkers derived from biological fluids, such as cerebrospinal fluid (CSF), with advanced molecular imaging and neuropsychological testing may eventually achieve the diagnostic sensitivity and specificity necessary to identify people in the earliest stages of the disease when drug modification is most likely possible. In this regard, positive amyloid or tau tracer retention on positron emission tomography imaging, low CSF concentrations of the amyloid-β 1-42 peptide, high CSF concentrations in total tau and phospho-tau, mesial temporal lobe atrophy on magnetic resonance imaging, and temporoparietal/precuneus hypometabolism or hypoperfusion on 18F-fluorodeoxyglucose positron emission tomography have all emerged as biomarkers for the progression to AD. However, the ultimate AD biomarker panel will likely involve the inclusion of novel CSF and blood biomarkers more precisely associated with confirmed pathophysiologic mechanisms to improve its reliability for detecting preclinical AD. This review highlights advancements in biological fluid and imaging biomarkers that are moving the field towards achieving the goal of a preclinical detection of AD.

Function and expression study uncovered hepatocyte plasma membrane ecto-ATP synthase as a novel player in liver regeneration

ATP synthase, canonically mitochondrially located, is reported to be ectopically expressed on the plasma membrane outer face of several cell types. We analysed, for the first time, the expression and catalytic activities of the ecto- and mitochondrial ATP synthase during liver regeneration. Liver regeneration was induced in rats by two-thirds partial hepatectomy. The protein level and the ATP synthase and/or hydrolase activities of the hepatocyte ecto- and mitochondrial ATP synthase were analysed on freshly isolated hepatocytes and mitochondria from control, sham-operated and partial hepatectomized rats. During the priming phase of liver regeneration, 3 h after partial hepatectomy, liver mitochondria showed a marked lowering of the ATP synthase protein level that was reflected in the impairment of both ATP synthesis and hydrolysis. The ecto-ATP synthase level, in 3 h partial hepatectomized hepatocytes, was decreased similarly to the level of the mitochondrial ATP synthase, associated with a lowering of the ecto-ATP hydrolase activity coupled to proton influx. Noteworthily, the ecto-ATP synthase activity coupled to proton efflux was completely inhibited in 3 h partial hepatectomized hepatocytes, even in the presence of a marked intracellular acidification that would sustain it as in control and sham-operated hepatocytes. At the end of the liver regeneration, 7 days after partial hepatectomy, the level and the catalytic activities of the ecto- and mitochondrial ATP synthase reached the control and sham-operated values. The specific modulation of hepatocyte ecto-ATP synthase catalytic activities during liver regeneration priming phase may modulate the extracellular ADP/ATP levels and/or proton influx/efflux trafficking, making hepatocyte ecto-ATP synthase a candidate for a novel player in the liver regeneration process.

Autoantibody signatures defined by serological proteome analysis in sera from patients with cholangiocarcinoma

BACKGROUND

The challenging diagnosis and poor prognosis of cholangiocarcinoma require the determination of biomarkers. Autoantibodies could be used in the clinic as diagnostic markers for the early detection of tumours. By proteomic approaches, several autoantibodies were proposed as potential markers. We tried in this study, to perform a serological proteome analysis, using various antigenic substrates, including tumours and human liver.

METHODS

Sera from patients (n = 13) and healthy donors (n = 10) were probed on immunoblots performed using 2-dimensionally separated proteins from cholangiocarcinoma cell lines (CCLP1 and CCSW1), from the liver of healthy subject and interestingly, from tumour and adjacent non-tumour liver tissues from five patients with cholangiocarcinoma and tested with their corresponding serum. Spots of interest were identified using mass spectrometry and classified according gene ontology analysis.

RESULTS

A comparison of the whole immunoblotting patterns given by cholangiocarcinoma sera against those obtained with normal control sera enabled the definition of 862 spots. Forty-five different proteins were further analysed, corresponding to (1) spots stained with more than four of 13 (30 %) sera tested with the CCLP1 or the CCSW1 cell line and with the normal liver, and (2) to spots immunoreactive with at least two of the five sera probed with their tumour and non-tumour counter-part of cholangiocarcinoma. Immunoreactive proteins with catalytic activity as molecular function were detected at rates of 93 and 64 % in liver from healthy subjects or cholangiocarcinoma non-tumour tissues respectively, compared to 43, 33, 33 % in tumour tissues, or CCSW1 and CCLP1 cell lines. A second pattern was represented by structural proteins with rates of 7 and 7 % in normal liver or non-tumour tissues compared to 14, 33 and 67 % in tumour tissue, CCSW1 or CCLP1 cell lines. Proteins with a binding function were detected at rates of 7 % in non-tumour tissue and 14 % in tumour tissue. Using the extracted tumour tissue, serotransferrin was targeted by all cholangiocarcinoma-related sera.

CONCLUSIONS

Immunological patterns depended on the type of antigen substrate used; i.e. tumour versus non tumour specimens. Nevertheless, a combination of multiple autoantibodies tested with the most appropriate substrate might be more sensitive and specific for the diagnosis of cholangiocarcinoma.

Autoantibodies in Alzheimer's disease: potential biomarkers, pathogenic roles, and therapeutic implications

Alzheimer’s disease (AD) is a prevalent and debilitating neurodegenerative disorder in the elderly. The etiology of AD has not been fully defined and currently there is no cure for this devastating disease. Compelling evidence suggests that the immune system plays a critical role in the pathophysiology of AD. Autoantibodies against a variety of molecules have been associated with AD. The roles of these autoantibodies in AD, however, are not well understood. This review attempts to summarize recent findings on these autoantibodies and explore their potential as diagnostic/ prognostic biomarkers for AD, their roles in the pathogenesis of AD, and their implications in the development of effective immunotherapies for AD.

Brain Atrophy, Anti-Smooth Muscle Antibody and Cognitive Impairment: An Association Study

Cortical atrophy, neuronal loss, beta-amyloid deposition, neuritic plaques, and neurofibrillary tangles are neuropathological key features in the Alzheimer's disease (AD). Antibodies against beta-amyloid, neurotransmitters, microvascular endothelium components and microglial cells have been detected in AD serum suggesting that AD could be another autoimmune disease and provides a link between vascular pathology, endothelium dysfunction and neuronal cells death. Aim of the present study was to evaluate the association between autoantibody profile and cognitive impairment in geriatric patients, accounting for ApoE genotype as a potential confounding factor. Three hundred and forty-four geriatric patients, attending the clinic for the cognitive decline, underwent a biochemical and immunological profile, chest X-ray, cerebral computed tomography scan and complete cognitive evaluation. All patients were also screened for the ApoE genotype. A significantly higher prevalence of Anti-Smooth Muscle Antibody (ASMA) positivity was found in 89/204 (43.63%) patients with diagnosed neuroradiological signs of cerebral atrophy compared with 15/140 (10.71%) patients without the condition (p<0.001). Multivariable logistic model evidenced that such association was independent of patient's age, gender and Mini-Mental State Examination (OR=8.25, 95%CI: 4.26-15.99) and achieved a good discriminatory power (c-statistic=0.783). Results were also independent of ApoE genotype, which resulted not associated both with the presence of brain atrophy and with the presence of ASMA positivity. Our results shows a strong association between brain atrophy and ASMA positivity and are consistent with several studies that focused attention on the mechanisms of endothelial immune response in the development of dementia.

An introduction to the roles of purinergic signalling in neurodegeneration, neuroprotection and neuroregeneration

Purinergic signalling appears to play important roles in neurodegeneration, neuroprotection and neuroregeneration. Initially there is a brief summary of the background of purinergic signalling, including release of purines and pyrimidines from neural and non-neural cells and their ectoenzymatic degradation, and the current characterisation of P1 (adenosine), and P2X (ion channel) and P2Y (G protein-coupled) nucleotide receptor subtypes. There is also coverage of the localization and roles of purinoceptors in the healthy central nervous system. The focus is then on the roles of purinergic signalling in trauma, ischaemia, stroke and in neurodegenerative diseases, including Alzheimer's, Parkinson's and Huntington's diseases, as well as multiple sclerosis and amyotrophic lateral sclerosis. Neuroprotective mechanisms involving purinergic signalling are considered and its involvement in neuroregeneration, including the role of adult neural stem/progenitor cells. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.

Lipid peroxidation triggers neurodegeneration: a redox proteomics view into the Alzheimer disease brain

Lipid peroxidation involves a cascade of reactions in which production of free radicals occurs selectively in the lipid components of cellular membranes. Polyunsaturated fatty acids easily undergo lipid peroxidation chain reactions, which, in turn, lead to the formation of highly reactive electrophilic aldehydes. Among these, the most abundant aldehydes are 4-hydroxy-2-nonenal (HNE) and malondialdehyde, while acrolein is the most reactive. Proteins are susceptible to posttranslational modifications caused by aldehydes binding covalently to specific amino acid residues, in a process called Michael adduction, and these types of protein adducts, if not efficiently removed, may be, and generally are, dangerous for cellular homeostasis. In the present review, we focused the discussion on the selective proteins that are identified, by redox proteomics, as selective targets of HNE modification during the progression and pathogenesis of Alzheimer disease (AD). By comparing results obtained at different stages of the AD, it may be possible to identify key biochemical pathways involved and ideally identify therapeutic targets to prevent, delay, or treat AD.

Ectopic F0F 1 ATP synthase contains both nuclear and mitochondrially-encoded subunits

Over the past few years, several reports have described the presence of F0F1 ATP synthase subunits at the surface of hepatocytes, where the hydrolytic activity of F1 sector faces outside and triggers HDL endocytosis. An intriguing question is whether the ectopic enzyme has same subunit composition and molecular mass as that of the mitochondrial ATP synthase. Also due to the polar nature of hepatocytes, the enzyme may be localized to a particular cell boundary. Using different methods to prepare rat liver plasma membranes, which have been subjected to digitonin extraction, hr CN PAGE, immunoblotting, and mass spectrometry analysis, we demonstrate the presence of ecto-F0F1 complexes which have a similar molecular weight to the monomeric form of the mitochondrial complexes, containing both nuclear and mitochondrially-encoded subunits. This finding makes it unlikely that the enzyme assembles on the plasma membranes, but suggest it to be transported whole after being assembled in mitochondria by still unknown pathways. Moreover, the plasma membrane preparation enriched in basolateral proteins contains much higher amounts of complete and active F0F1 complexes, consistent with their specific function to modulate the HDL uptake on hepatocyte surface.

Sevoflurane induces short-term changes in proteins in the cerebral cortices of developing rats

BACKGROUND

Exposure to intravenous or inhaled anesthetic agents has potential deleterious effects on the developing brain. However, the mechanisms are not clear. Herein, we investigated protein expression changes in neonatal rat brains after exposure to sevoflurane, an inhalational anesthetic commonly used for pediatric patients.

METHODS

Seven-day-old rats were treated with 1.8% sevoflurane or 30% oxygen for 4 h. Cerebral cortices were obtained at 3 h and 3 days after sevoflurane exposure for cell apoptosis detection, proteomic analysis and Western blotting.

RESULTS

There was a significant increase of cleaved caspase 3 at 3 h after sevoflurane exposure. Six proteins had 1.5-fold or higher changes in expression at 3 h after sevoflurane anesthesia as compared with sham-treated pups. No proteins had this degree of change at 3 days after sevoflurane anesthesia. Proteins whose expression was downregulated included collapsin response mediator protein-1 (CRMP-1), truncated CRMP-4, beta-tubulin IIc and neuron-specific class III beta-tubulin. These four proteins are important for neuronal migration and differentiation. Adenosine triphosphate synthase beta subunit, a protein associated with energy metabolism, was also downregulated. Guanine nucleotide-binding protein beta 1, a signaling protein, was upregulated. Sevoflurane also increased phosphorylation of glycogen synthase kinase 3β (GSK-3β) at 3 h after anesthesia and inhibited the normal increase of GSK-3β at 72 h after anesthesia.

CONCLUSION

These findings suggest that sevoflurane may cause short-term neuronal apoptosis and disturbances of neuronal migration, differentiation and energy metabolism in neonatal rat brains, and that these disturbances may contribute to its neurodegenerative effects.

Cell surface estrogen receptor alpha is upregulated during subchronic metabolic stress and inhibits neuronal cell degeneration

In addition to the classical nuclear estrogen receptor, the expression of non-nuclear estrogen receptors localized to the cell surface membrane (mER) has recently been demonstrated. Estrogen and its receptors have been implicated in the development or progression of numerous neurodegenerative disorders. Furthermore, the pathogenesis of these diseases has been associated with disturbances of two key cellular programs: apoptosis and autophagy. An excess of apoptosis or a defect in autophagy has been implicated in neurodegeneration. The aim of this study was to clarify the role of ER in determining neuronal cell fate and the possible implication of these receptors in regulating either apoptosis or autophagy. The human neuronal cell line SH-SY5Y and mouse neuronal cells in primary culture were thus exposed to chronic minimal peroxide treatment (CMP), a form of subcytotoxic minimal chronic stress previously that mimics multiple aspects of long-term cell stress and represents a limited molecular proxy for neurodegenerative processes. We actually found that either E2 or E2-bovine serum albumin construct (E2BSA, i.e. a non-permeant form of E2) was capable of modulating intracellular cell signals and regulating cell survival and death. In particular, under CMP, the up-regulation of mERα, but not mERβ, was associated with functional signals (ERK phosphorylation and p38 dephosphorylation) compatible with autophagic cytoprotection triggering and leading to cell survival. The mERα trafficking appeared to be independent of the microfilament system cytoskeletal network but was seemingly associated with microtubular apparatus network, i.e., to MAP2 molecular chaperone. Importantly, antioxidant treatments, administration of siRNA to ERα, or the presence of antagonist of ERα hindered these events. These results support that the surface expression of mERα plays a pivotal role in determining cell fate, and that ligand-induced activation of mER signalling exerts a powerful cell-survival signal. These results shed new light on the pathogenetic mechanisms leading to neuronal cell degeneration.

Beyond amyloid: the future of therapeutics for Alzheimer's disease

Currently, the field is awaiting the results of several pivotal Phase III clinical Alzheimer's disease (AD) trials that target amyloid-β (Aβ). In light of the recent biomarker studies that indicate Aβ levels are at their most dynamic 5-10 years before the onset of clinical symptoms, it is becoming uncertain whether direct approaches to target Aβ will achieve desired clinical efficacy. AD is a complex neurodegenerative disease caused by dysregulation of numerous neurobiological networks and cellular functions, resulting in synaptic loss, neuronal loss, and ultimately impaired memory. While it is clear that Aβ plays a key role in the pathogenesis of AD, it may be a challenging and inefficient target for mid-to-late stage AD intervention. Throughout the course of AD, multiple pathways become perturbed, presenting a multitude of possible therapeutic avenues for design of AD intervention and prophylactic therapies. In this chapter, we sought to first provide an overview of Aβ-directed strategies that are currently in development, and the pivotal Aβ-targeted trials that are currently underway. Next, we delve into the biology and therapeutic designs associated with other key areas of research in the field including tau, protein trafficking and degradation pathways, ApoE, synaptic function, neurotrophic/neuroprotective strategies, and inflammation and energy utilization. For each area we have provided a comprehensive and balanced overview of the therapeutic strategies currently in preclinical and clinical development, which will shape the future therapeutic landscape of AD.

Alzheimer's Disease: APP, Gamma Secretase, APOE, CLU, CR1, PICALM, ABCA7, BIN1, CD2AP, CD33, EPHA1, and MS4A2, and Their Relationships with Herpes Simplex, C. Pneumoniae, Other Suspect Pathogens, and the Immune System

Alzheimer's disease susceptibility genes, APP and gamma-secretase, are involved in the herpes simplex life cycle, and that of other suspect pathogens (C. pneumoniae, H. pylori, C. neoformans, B. burgdorferri, P. gingivalis) or immune defence. Such pathogens promote beta-amyloid deposition and tau phosphorylation and may thus be causative agents, whose effects are conditioned by genes. The antimicrobial effects of beta-amyloid, the localisation of APP/gamma-secretase in immunocompetent dendritic cells, and gamma secretase cleavage of numerous pathogen receptors suggest that this network is concerned with pathogen disposal, effects which may be abrogated by the presence of beta-amyloid autoantibodies in the elderly. These autoantibodies, as well as those to nerve growth factor and tau, also observed in Alzheimer's disease, may well be antibodies to pathogens, due to homology between human autoantigens and pathogen proteins. NGF or tau antibodies promote beta-amyloid deposition, neurofibrillary tangles, or cholinergic neuronal loss, and, with other autoantibodies, such as anti-ATPase, are potential agents of destruction, whose formation is dictated by sequence homology between pathogen and human proteins, and thus by pathogen strain and human genes. Pathogen elimination in the ageing population and removal of culpable autoantibodies might reduce the incidence and offer hope for a cure in this affliction.

Auto-antibodies to β-F1-ATPase and vimentin in malignant mesothelioma

Patients with Malignant Mesothelioma (MM) develop unidentified auto-antibodies to MM tumour antigens. This study was conducted to identify the targets of MM patient auto-antibodies in order to try to understand more of the anti-tumour response and to determine if these antibodies might be helpful for diagnosis or prognostication. Using MM patient sera in a Western immunoblott screening strategy, no common immunoreactive proteins were identified. The sera from one long-term survivor recognised a protein band of 50-60 kDa present in cell lysates from four of five MM cell lines tested. The immunoreactive proteins in this band were identified by 2D electrophoretic separation of a MM cell line protein lysate, followed by analysis of excised immunoreactive proteins on a MALDI TOF mass spectrometer and peptide mass fingerprinting. The immunoreactive proteins identified were vimentin (accession gi55977767) and the ATP synthase (F1-ATPase) beta chain (accession gi114549 and gi47606749). ELISA assays were developed for antibodies to these proteins. Neither vimentin (median and 95% CI 0.346; 0.32-0.468 for MM patients, 0.327; 0.308-0.428 for controls) nor ß-F1-ATPase (0.257; 0.221-0.453 for MM patients, 0.263; 0.22-0.35 for controls) showed significant differences in autoantibody levels between a group of MM patients and controls. Using a dichotomized antibody level (high, low) for these targets we demonstrated that vimentin antibody levels were not associated with survival. In contrast, high ß-F1-ATPase antibody levels were significantly associated with increased median survival (18 months) compared to low ß F1 ATPase antibody levels (9 months; p = 0.049). Immunohistochemical analysis on a MM tissue microarray showed cytoplasmic staining in 28 of 33 samples for vimentin and strong cytoplasmic staining in14 and weak in 16 samples for ß-F1-ATPase. Therefore antibodies to neither vimentin nor ß-F1-ATPase are useful for differential diagnosis of MM, however high antibody levels to ß-F1-ATPase may be associated with increased survival and this warrants further investigation.

Purinergic signalling: from normal behaviour to pathological brain function

Purinergic neurotransmission, involving release of ATP as an efferent neurotransmitter was first proposed in 1972. Later, ATP was recognised as a cotransmitter in peripheral nerves and more recently as a cotransmitter with glutamate, noradrenaline, GABA, acetylcholine and dopamine in the CNS. Both ATP, together with some of its enzymatic breakdown products (ADP and adenosine) and uracil nucleotides are now recognised to act via P2X ion channels and P1 and P2Y G protein-coupled receptors, which are widely expressed in the brain. They mediate both fast signalling in neurotransmission and neuromodulation and long-term (trophic) signalling in cell proliferation, differentiation and death. Purinergic signalling is prominent in neurone-glial cell interactions. In this review we discuss first the evidence implicating purinergic signalling in normal behaviour, including learning and memory, sleep and arousal, locomotor activity and exploration, feeding behaviour and mood and motivation. Then we turn to the involvement of P1 and P2 receptors in pathological brain function; firstly in trauma, ischemia and stroke, then in neurodegenerative diseases, including Alzheimer's, Parkinson's and Huntington's, as well as multiple sclerosis and amyotrophic lateral sclerosis. Finally, the role of purinergic signalling in neuropsychiatric diseases (including schizophrenia), epilepsy, migraine, cognitive impairment and neuropathic pain will be considered.

The Fox and the Rabbits-Environmental Variables and Population Genetics (1) Replication Problems in Association Studies and the Untapped Power of GWAS (2) Vitamin A Deficiency, Herpes Simplex Reactivation and Other Causes of Alzheimer's Disease

Classical population genetics shows that varying permutations of genes and risk factors permit or disallow the effects of causative agents, depending on circumstance. For example, genes and environment determine whether a fox kills black or white rabbits on snow or black ash covered islands. Risk promoting effects are different on each island, but obscured by meta-analysis or GWAS data from both islands, unless partitioned by different contributory factors. In Alzheimer's disease, the foxes appear to be herpes, borrelia or chlamydial infection, hypercholesterolemia, hyperhomocysteinaemia, diabetes, cerebral hypoperfusion, oestrogen depletion, or vitamin A deficiency, all of which promote beta-amyloid deposition in animal models—without the aid of gene variants. All relate to risk factors and subsets of susceptibility genes, which condition their effects. All are less prevalent in convents, where nuns appear less susceptible to the ravages of ageing. Antagonism of the antimicrobial properties of beta-amyloid by Abeta autoantibodies in the ageing population, likely generated by antibodies raised to beta-amyloid/pathogen protein homologues, may play a role in this scenario. These agents are treatable by diet and drugs, vitamin supplementation, pathogen detection and elimination, and autoantibody removal, although again, the beneficial effects of individual treatments may be tempered by genes and environment.

Favourable prognostic value of antibodies anti-HSP20 in patients with cystic echinococcosis: a differential immunoproteomic approach

Seeking biomarkers reflecting disease development in cystic echinococcosis (CE), we used a proteomic approach linked to immunological characterisation for the identification of respective antigens. Two-dimensional gel electrophoresis (2-DE) of sheep hydatid fluid, followed by immunoblot analysis (IB) with sera from patients with distinct phases of disease, enabled us to identify by mass spectrometry heat shock protein 20 (HSP20) as a potential marker of active CE. Using IB, antibodies specific to the 34 kDa band of HSP20 were detected in sera from 61/95 (64%) patients with CE, but not in sera from healthy subjects. IB revealed anti-HSP20 antibodies in a higher percentage of sera from patients with active disease than in sera from patients with inactive disease (81 vs. 24%; P = 10(-4)). These primary results were confirmed in a long-term follow-up study after pharmacological and surgical treatment. Herewith anti-HSP20 antibody levels significantly decreased over the course of treatment in sera from patients with cured disease, relative to sera from patients with progressive disease (P = 0·017). Thus, during CE, a comprehensive strategy of proteomic identification combined with immunological validation represents a promising approach for the identification of biomarkers useful for the prognostic assessment of treatment of CE patients.

Fishing for biomarkers with antigen mimics

Current efforts to identify antibodies that are biomarkers of disease rely on knowing the antigens they target. In many diseases, however, the relevant antigens are unknown. Reddy et al. (2010) now present an approach for discovering antibody biomarkers that avoids the need for antigen identification.