Increased prothrombin, apolipoprotein A-IV, and haptoglobin in the cerebrospinal fluid of patients with Huntington's disease

Diagnostic Potential of Alternations of Bile Acid Profiles in the Plasma of Patients with Huntington's Disease

Huntington's disease (HD) is characterized by progressive involuntary chorea movements and cognitive decline. Recent research indicates that metabolic disturbance may play a role in its pathogenesis. Bile acids, produced during cholesterol metabolism in the liver, have been linked to neurodegenerative conditions. This study investigated variations in plasma bile acid profiles among individuals with HD. Plasma levels of 16 primary and secondary bile acids and their conjugates were analyzed in 20 healthy controls and 33 HD patients, including 24 with symptoms (symHD) and 9 carriers in the presymptomatic stage (preHD). HD patients exhibited significantly higher levels of glycochenodeoxycholic acid (GCDCA) and glycoursodeoxycholic acid (GUDCA) compared to healthy controls. Conversely, isolithocholic acid levels were notably lower in the HD group. Neurotoxic bile acids (glycocholic acid (GCA) + glycodeoxycholic acid (GDCA) + GCDCA) were elevated in symHD patients, while levels of neuroprotective bile acids (ursodeoxycholic acid (UDCA) + GUDCA + tauroursodeoxycholic acid (TUDCA)) were higher in preHD carriers, indicating a compensatory response to early neuronal damage. These results underscore the importance of changes in plasma bile acid profiles in HD and their potential involvement in disease mechanisms. The identified bile acids (GCDCA, GUDCA, and isolithocholic acid) could potentially serve as markers to distinguish between HD stages and healthy individuals. Nonetheless, further research is warranted to fully understand the clinical implications of these findings and their potential as diagnostic or therapeutic tools for HD.

Deregulated Transcriptome as a Platform for Adrenal Huntington's Disease-Related Pathology

Huntington's disease (HD) is a neurodegenerative disorder that affects mainly the central nervous system (CNS) by inducing progressive deterioration in both its structure and function. In recent years, there has been growing interest in the impact of HD on peripheral tissue function. Herein, we used the R6/2 mouse model of HD to investigate the influence of the disease on adrenal gland functioning. A transcriptomic analysis conducted using a well-established quantitative method, an Affymetrix array, revealed changes in gene expression in the R6/2 model compared to genetic background controls. For the first time, we identified disruptions in cholesterol and sterol metabolism, blood coagulation, and xenobiotic metabolism in HD adrenal glands. This study showed that the disrupted expression of these genes may contribute to the underlying mechanisms of Huntington's disease. Our findings may contribute to developing a better understanding of Huntington's disease progression and aid in the development of novel diagnostic or therapeutic approaches.

Quantitative serum proteome analysis using tandem mass tags in dogs with epilepsy

This study included four groups of dogs (group A: healthy controls, group B: idiopathic epilepsy receiving antiepileptic medication (AEM), group C: idiopathic epilepsy without AEM, group D: structural epilepsy). Comparative quantitative proteomic analysis of serum samples among the groups was the main target of the study. Samples were analyzed by a quantitative Tandem-Mass-Tags approach on the Q-Exactive-Plus Hybrid Quadrupole-Orbitrap mass-spectrometer. Identification and relative quantification were performed in Proteome Discoverer. Data were analyzed using R. Gene ontology terms were analyzed based on Canis lupus familiaris database. Data are available via ProteomeXchange with identifier PXD041129. Eighty-one proteins with different relative adundance were identified in the four groups and 25 were master proteins (p < 0.05). Clusterin (CLU), and apolipoprotein A1 (APOA1) had higher abundance in the three groups of dogs (groups B, C, D) compared to controls. Amine oxidase (AOC3) was higher in abundance in group B compared to groups C and D, and lower in group A. Adiponectin (ADIPOQ) had higher abundance in groups C compared to group A. ADIPOQ and fibronectin (FN1) had higher abundance in group B compared to group C and D. Peroxidase activity assay was used to quantify HP abundance change, validating and correlating with proteomic analysis (r = 0.8796). SIGNIFICANCE: The proteomic analysis of serum samples from epileptic dogs indicated potential markers of epilepsy (CLU), proteins that may contribute to nerve tissue regeneration (APOA1), and contributing factors to epileptogenesis (AOC3). AEM could alter extracellular matrix proteins (FN1). Illness (epilepsy) severity could influence ADIPOQ abundance.

Microglia and complement mediate early corticostriatal synapse loss and cognitive dysfunction in Huntington's disease

Huntington's disease (HD) is a devastating monogenic neurodegenerative disease characterized by early, selective pathology in the basal ganglia despite the ubiquitous expression of mutant huntingtin. The molecular mechanisms underlying this region-specific neuronal degeneration and how these relate to the development of early cognitive phenotypes are poorly understood. Here we show that there is selective loss of synaptic connections between the cortex and striatum in postmortem tissue from patients with HD that is associated with the increased activation and localization of complement proteins, innate immune molecules, to these synaptic elements. We also found that levels of these secreted innate immune molecules are elevated in the cerebrospinal fluid of premanifest HD patients and correlate with established measures of disease burden.In preclinical genetic models of HD, we show that complement proteins mediate the selective elimination of corticostriatal synapses at an early stage in disease pathogenesis, marking them for removal by microglia, the brain's resident macrophage population. This process requires mutant huntingtin to be expressed in both cortical and striatal neurons. Inhibition of this complement-dependent elimination mechanism through administration of a therapeutically relevant C1q function-blocking antibody or genetic ablation of a complement receptor on microglia prevented synapse loss, increased excitatory input to the striatum and rescued the early development of visual discrimination learning and cognitive flexibility deficits in these models. Together, our findings implicate microglia and the complement cascade in the selective, early degeneration of corticostriatal synapses and the development of cognitive deficits in presymptomatic HD; they also provide new preclinical data to support complement as a therapeutic target for early intervention.

Ganglioside-focused Glycan Array Reveals Abnormal Anti-GD1b Auto-antibody in Plasma of Preclinical Huntington's Disease

Huntington's disease (HD) is a progressive and devastating neurodegenerative disease marked by inheritable CAG nucleotide expansion. For offspring of HD patients carrying abnormal CAG expansion, biomarkers that predict disease onset are crucially important but still lacking. Alteration of brain ganglioside patterns has been observed in the pathology of patients carrying HD. Here, by using a novel and sensitive ganglioside-focused glycan array, we examined the potential of anti-glycan auto-antibodies for HD. In this study, we collected plasma from 97 participants including 42 control (NC), 16 pre-manifest HD (pre-HD), and 39 HD cases and measured the anti-glycan auto-antibodies by a novel ganglioside-focused glycan array. The association between plasma anti-glycan auto-antibodies and disease progression was analyzed using univariate and multivariate logistic regression. The disease-predictive capacity of anti-glycan auto-antibodies was further investigated by receiver operating characteristic (ROC) analysis. We found that anti-glycan auto-antibodies were generally higher in the pre-HD group when compared to the NC and HD groups. Specifically, anti-GD1b auto-antibody demonstrated the potential for distinguishing between pre-HD and control groups. Moreover, in combination with age and the number of CAG repeat, the level of anti-GD1b antibody showed excellent predictability with an area under the ROC curve (AUC) of 0.95 to discriminate between pre-HD carriers and HD patients. With glycan array technology, this study demonstrated abnormal auto-antibody responses that showed temporal changes from pre-HD to HD.

Alternations of Lipoprotein Profiles in the Plasma as Biomarkers of Huntington's Disease

Alterations in lipid composition and disturbed lipoprotein metabolism are involved in the pathomechanism of Huntington's disease (HD). Here, we measured 112 lipoprotein subfractions and components in the plasma of 20 normal controls, 24 symptomatic (sympHD) and 9 presymptomatic (preHD) HD patients. Significant changes were found in 30 lipoprotein subfractions and components in all HD patients. Plasma levels of total cholesterol (CH), apolipoprotein (Apo)B, ApoB-particle number (PN), and components of low-density lipoprotein (LDL) were lower in preHD and sympHD patients. Components of LDL4, LDL5, LDL6 and high-density lipoprotein (HDL)4 demonstrated lower levels in preHD and sympHD patients compared with controls. Components in LDL3 displayed lower levels in sympHD compared with the controls, whereas components in very low-density lipoprotein (VLDL)5 were higher in sympHD patients compared to the controls. The levels of components in HDL4 and VLDL5 demonstrated correlation with the scores of motor assessment, independence scale or functional capacity of Unified Huntington's Disease Rating Scale. These findings indicate the potential of components of VLDL5, LDL3, LDL4, LDL5 and HDL4 to serve as the biomarkers for HD diagnosis and disease progression, and demonstrate substantial evidence of the involvement of lipids and apolipoproteins in HD pathogenesis.

Causal Effects of Plasma Haptoglobin Levels on Alzheimer's Disease: A Two-Sample Mendelian Randomization Study

BACKGROUND

A connection between plasma levels of haptoglobin (Hp) and Alzheimer's disease (AD) has been shown in several observational studies. It is debatable, nonetheless, how the two are related causally.

OBJECTIVE

To establish the causal relationship between Hp and AD using a two-sample Mendelian randomization (MR) study.

METHODS

From the extensive genome-wide association studies and FinnGen dataset, summaries and statistics pertaining to AD were gathered. We investigated the possibility of a causal link between Hp and AD using a two-sample MR study. Inverse variance weighting was used as the primary analytical technique, and it was supported by the joint application of complementary analyses and fixed effects meta-analysis to combine results from various sources.

RESULTS

Genetically determined Hp was causally associated with AD [odds ratio (OR), 1.05; 95% confidence interval (CI), 1.02 to 1.09; p = 8.96×10-4]; Inverse variance-weighted estimates coming from different data sources were combined in a meta-analysis with consistent findings (OR, 1.03; 95% CI, 1.01 to 1.05; p = 2.00×10-3). The outcomes of the inverse MR analysis showed that AD had no appreciable causal impact on Hp.

CONCLUSION

The present MR analysis shows that higher plasma Hp leads to an increased risk of AD. Strategies for plasma Hp testing may open up new doors for the early diagnosis and prevention of AD.

Cerebrospinal fluid biomarkers for assessing Huntington disease onset and severity

The identification of molecular biomarkers in CSF from individuals affected by Huntington disease may help improve predictions of disease onset, better define disease progression and could facilitate the evaluation of potential therapies. The primary objective of our study was to investigate novel CSF protein candidates and replicate previously reported protein biomarker changes in CSF from Huntington disease mutation carriers and healthy controls. Our secondary objective was to compare the discriminatory potential of individual protein analytes and combinations of CSF protein markers for stratifying individuals based on the severity of Huntington disease. We conducted a hypothesis-driven analysis of 26 pre-specified protein analytes in CSF from 16 manifest Huntington disease subjects, eight premanifest Huntington disease mutation carriers and eight healthy control individuals using parallel-reaction monitoring mass spectrometry. In addition to reproducing reported changes in previously investigated CSF biomarkers (NEFL, PDYN, and PENK), we also identified novel exploratory CSF proteins (C1QB, CNR1, GNAL, IDO1, IGF2, and PPP1R1B) whose levels were altered in Huntington disease mutation carriers and/or across stages of disease. Moreover, we report strong associations of select CSF proteins with clinical measures of disease severity in manifest Huntington disease subjects (C1QB, CNR1, NEFL, PDYN, PPP1R1B, and TTR) and with years to predicted disease onset in premanifest Huntington disease mutation carriers (ALB, C4B, CTSD, IGHG1, and TTR). Using receiver operating characteristic curve analysis, we identified PENK as being the most discriminant CSF protein for stratifying Huntington disease mutation carriers from controls. We also identified exploratory multi-marker CSF protein panels that improved discrimination of premanifest Huntington disease mutation carriers from controls (PENK, ALB and NEFL), early/mid-stage Huntington disease from premanifest mutation carriers (PPP1R1B, TTR, CHI3L1, and CTSD), and late-stage from early/mid-stage Huntington disease (CNR1, PPP1R1B, BDNF, APOE, and IGHG1) compared with individual CSF proteins. In this study, we demonstrate that combinations of CSF proteins can outperform individual markers for stratifying individuals based on Huntington disease mutation status and disease severity. Moreover, we define exploratory multi-marker CSF protein panels that, if validated, may be used to improve the accuracy of disease-onset predictions, complement existing clinical and imaging biomarkers for monitoring the severity of Huntington disease, and potentially for assessing therapeutic response in clinical trials. Additional studies with CSF collected from larger cohorts of Huntington disease mutation carriers are needed to replicate these exploratory findings.

Neurodegenerative Disorders of Alzheimer, Parkinsonism, Amyotrophic Lateral Sclerosis and Multiple Sclerosis: An Early Diagnostic Approach for Precision Treatment

Neurodegenerative diseases (NDs) are characterised by progressive dysfunction of synapses, neurons, glial cells and their networks. Neurodegenerative diseases can be classified according to primary clinical features (e.g., dementia, parkinsonism, or motor neuron disease), anatomic distribution of neurodegeneration (e.g., frontotemporal degenerations, extrapyramidal disorders, or spinocerebellar degenerations), or principal molecular abnormalities. The most common neurodegenerative disorders are amyloidosis, tauopathies, a-synucleinopathy, and TAR DNA-binding protein 43 (TDP-43) proteopathy. The protein abnormalities in these disorders have abnormal conformational properties along with altered cellular mechanisms, and they exhibit motor deficit, mitochondrial malfunction, dysfunctions in autophagic-lysosomal pathways, synaptic toxicity, and more emerging mechanisms such as the roles of stress granule pathways and liquid-phase transitions. Finally, for each ND, microglial cells have been reported to be implicated in neurodegeneration, in particular, because the microglial responses can shift from neuroprotective to a deleterious role. Growing experimental evidence suggests that abnormal protein conformers act as seed material for oligomerization, spreading from cell to cell through anatomically connected neuronal pathways, which may in part explain the specific anatomical patterns observed in brain autopsy sample. In this review, we mention the human pathology of select neurodegenerative disorders, focusing on how neurodegenerative disorders (i.e., Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis) represent a great healthcare problem worldwide and are becoming prevalent because of the increasing aged population. Despite many studies have focused on their etiopathology, the exact cause of these diseases is still largely unknown and until now with the only available option of symptomatic treatments. In this review, we aim to report the systematic and clinically correlated potential biomarker candidates. Although future studies are necessary for their use in early detection and progression in humans affected by NDs, the promising results obtained by several groups leads us to this idea that biomarkers could be used to design a potential therapeutic approach and preclinical clinical trials for the treatments of NDs.

Analysis of the neuroprotective effect of GLP-1 receptor agonist peptide on cerebral ischemia-reperfusion injury by Quantitative Proteomics Mass Spectrometry

OBJECTIVE

The pathological characteristics of cerebral ischemia-reperfusion injury (CIRI) are complex, and the mechanism involved remains unknown. The treatment for CIRI has become an increasingly important challenge in the clinic, prompting us to explore the mechanism of CIRI. It was reported that GLP-1 receptor agonist, Liraglutide, exhibited alleviating effects on CIRI. The previous findings suggested that the administration of Liraglutide in rodents results in the attenuation of the infarct volume following ischemia-reperfusion injury by mediating the reactive oxygen species, apoptotic and necroptotic pathways.

METHODS

Here, a proteomic study was performed aiming to clarify the physiological protection role of GLP-1 receptor agonist during the development of CIRI in MCAO mice. This proteomic investigations is contributed to reveal the mechanism associated with the treatment of GLP-1 receptor agonist in MCAO mice.

RESULTS

The results indicated that the occurrence of ischemia-reperfusion led to complex pathological processes, including inflammation, necroptosis and apoptosis. The treatment of Liraglutide significantly reduced the infract volume resulted from ischemia reperfusion injury. The proteomic data revealed that the administration of Liraglutide in MCAO mice induced the various effects on proteins expression level and phosphorylation.

CONCLUSIONS

The findings in this study was beneficial for identifying the novel therapeutic target for the treatment of ischemia reperfusion.

Nusinersen Modulates Proteomics Profiles of Cerebrospinal Fluid in Spinal Muscular Atrophy Type 1 Patients

Spinal muscular atrophy (SMA) type 1 is a severe infantile autosomal-recessive neuromuscular disorder caused by a survival motor neuron 1 gene (SMN1) mutation and characterized by progressive muscle weakness. Without supportive care, SMA type 1 is rapidly fatal. The antisense oligonucleotide nusinersen has recently improved the natural course of this disease. Here, we investigated, with a functional proteomic approach, cerebrospinal fluid (CSF) protein profiles from SMA type 1 patients who underwent nusinersen administration to clarify the biochemical response to the treatment and to monitor disease progression based on therapy. Six months after starting treatment (12 mg/5 mL × four doses of loading regimen administered at days 0, 14, 28, and 63), we observed a generalized reversion trend of the CSF protein pattern from our patient cohort to that of control donors. Notably, a marked up-regulation of apolipoprotein A1 and apolipoprotein E and a consistent variation in transthyretin proteoform occurrence were detected. Since these multifunctional proteins are critically active in biomolecular processes aberrant in SMA, i.e., synaptogenesis and neurite growth, neuronal survival and plasticity, inflammation, and oxidative stress control, their nusinersen induced modulation may support SMN improved-expression effects. Hence, these lipoproteins and transthyretin could represent valuable biomarkers to assess patient responsiveness and disease progression.

Taming the Huntington's Disease Proteome: What Have We Learned?

Mass spectrometry (MS) is a physical technique used to identify specific chemicals and molecules by precise analysis of their mass and charge; this technology has been adapted for biological sciences applications. Investigators have used MS to identify differential expressions of proteins in Huntington's disease (HD), to discover Huntingtin (HTT) interacting proteins and to analyze HTT proteoforms. Using systems biology and computational approaches, data from MS screens have been leveraged to find differentially expressed pathways. This review summarizes the data from most of the MS studies done in the HD field in the last 20 years and compares it to the protein data reported before the use of MS technology. The MS results validate early findings in the field such as differential expression of PDE10a and DARPP-32 and identify new changes. We offer a perspective on the MS approach in HD, particularly for identification of disease pathways, the challenges in interpreting data across different studies, and its application to protein studies moving forward.

Paraoxonase Role in Human Neurodegenerative Diseases

The human body has biological redox systems capable of preventing or mitigating the damage caused by increased oxidative stress throughout life. One of them are the paraoxonase (PON) enzymes. The PONs genetic cluster is made up of three members (PON1, PON2, PON3) that share a structural homology, located adjacent to chromosome seven. The most studied enzyme is PON1, which is associated with high density lipoprotein (HDL), having paraoxonase, arylesterase and lactonase activities. Due to these characteristics, the enzyme PON1 has been associated with the development of neurodegenerative diseases. Here we update the knowledge about the association of PON enzymes and their polymorphisms and the development of multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD) and Parkinson's disease (PD).

Quantitative proteomics of cerebrospinal fluid using tandem mass tags in dogs with recurrent epileptic seizures

This prospective study included four dog groups (group A: healthy dogs, groups B: dogs with idiopathic epilepsy under antiepileptic medication (AEM), C: idiopathic epilepsy dogs without AEM administration, D: dogs with structural epilepsy). The purpose of the study was to compare the proteomic profile among the four groups. Samples were analyzed by a quantitative Tandem Mass Tags approach using a Q-Exactive-Plus mass-spectrometer. Identification and relative quantification were performed using Proteome Discoverer, and data were analyzed using R. Gene ontology terms were analyzed based on Canis lupus familiaris database. Data are available via ProteomeXchange with identifier PXD018893. Eighteen proteins were statistically significant among the four groups (P < 0.05). MMP2 and EFEMP2 appeared down-regulated whereas HP and APO-A1 were up-regulated (groups B, D). CLEC3B and PEBP4 were up-regulated whereas APO-A1 was down-regulated (group C). IGLL1 was down-regulated (groups B, C) and up-regulated (group D). EFEMP2 was the only protein detected among the four groups and PEBP4 was significantly different among the epileptic dogs. Western blot and SPARCL immunoassay were used to quantify HP abundance change, validating proteomic analysis. Both, showed good correlation with HP levels identified through proteomic analysis (r = 0.712 and r = 0.703, respectively). SIGNIFICANCE: The proteomic analysis from CSF of dogs with epileptic seizures could reflect that MMP2, HP and APO-A1 may contribute to a blood-brain barrier disruption through the seizure-induced inflammatory process in the brain. MMP2 change may indicate the activation of protective mechanisms within the brain tissue. Antiepileptic medication could influence several cellular responses and alter the CSF proteome composition.

Haptoglobin: From hemoglobin scavenging to human health

Haptoglobin (Hp) belongs to the family of acute-phase plasma proteins and represents the most important plasma detoxifier of hemoglobin (Hb). The basic Hp molecule is a tetrameric protein built by two α/β dimers. Each Hp α/β dimer is encoded by a single gene and is synthesized as a single polypeptide. Following post-translational protease-dependent cleavage of the Hp polypeptide, the α and β chains are linked by disulfide bridge(s) to generate the mature Hp protein. As human Hp gene is characterized by two common Hp1 and Hp2 alleles, three major genotypes can result (i.e., Hp1-1, Hp2-1, and Hp2-2). Hp regulates Hb clearance from circulation by the macrophage-specific receptor CD163, thus preventing Hb-mediated severe consequences for health. Indeed, the antioxidant and Hb binding properties of Hp as well as its ability to stimulate cells of the monocyte/macrophage lineage and to modulate the helper T-cell type 1 and type 2 balance significantly associate with a variety of pathogenic disorders (e.g., infectious diseases, diabetes, cardiovascular diseases, and cancer). Alternative functions of the variants Hp1 and Hp2 have been reported, particularly in the susceptibility and protection against infectious (e.g., pulmonary tuberculosis, HIV, and malaria) and non-infectious (e.g., diabetes, cardiovascular diseases and obesity) diseases. Both high and low levels of Hp are indicative of clinical conditions: Hp plasma levels increase during infections, inflammation, and various malignant diseases, and decrease during malnutrition, hemolysis, hepatic disease, allergic reactions, and seizure disorders. Of note, the Hp:Hb complexes display heme-based reactivity; in fact, they bind several ferrous and ferric ligands, including O₂, CO, and NO, and display (pseudo-)enzymatic properties (e.g., NO and peroxynitrite detoxification). Here, genetic, biochemical, biomedical, and biotechnological aspects of Hp are reviewed.

Increased CSF Levels of Apolipoproteins and Complement Factors in Trigeminal Neuralgia Patients-In Depth Proteomic Analysis Using Mass Spectrometry

The main cause of trigeminal neuralgia (TN) is compression of a blood vessel at the root entry zone of the trigeminal nerve. However, a neurovascular conflict does not seem to be the only etiology and other mechanisms are implicated in the development of the disease. We hypothesized that TN patients may have distinct protein expression in the CSF. In this study, lumbar CSF from TN patients (n = 17), scheduled to undergo microvascular decompression, and from controls (n = 20) was analyzed and compared with in depth mass spectrometry TMTbased quantitative proteomics. We identified 2552 unique proteins, of which 46 were significantly altered (26 increased, and 20 decreased, q-value < .05) in TN patients compared with controls. An over-representation analysis showed proteins involved in high-density lipoprotein, such as Apolipoprotein A4, Apolipoprotein M, and Apolipoprotein A1, and the extracellular region, including proteins involved in the complement cascade to be over-represented. We conclude that TN patients have distinct protein expression in the CSF compared to controls. The pathophysiological background of the protein alterations found in this study warrants further investigation in future studies. PERSPECTIVE: In this article, cerebrospinal fluid from patients with trigeminal neuralgia was analyzed using in depth shotgun proteomics, revealing 46 differentially expressed proteins compared to controls. Among these, apolipoproteins and proteins involved in the complement system were elevated and significantly over-represented, implying an inflammatory component in the pathophysiology of the disease.

A Critical Evaluation of Wet Biomarkers for Huntington's Disease: Current Status and Ways Forward

There is an unmet clinical need for objective biomarkers to monitor disease progression and treatment response in Huntington's disease (HD). The aim of this review is, therefore, to provide practical advice for biomarker discovery and to summarise studies on biofluid markers for HD. A PubMed search was performed to review literature with regard to candidate saliva, urine, blood and cerebrospinal fluid biomarkers for HD. Information has been organised into tables to allow a pragmatic approach to the discussion of the evidence and generation of practical recommendations for future studies. Many of the markers published converge on metabolic and inflammatory pathways, although changes in other analytes representing antioxidant and growth factor pathways have also been found. The most promising markers reflect neuronal and glial degeneration, particularly neurofilament light chain. International collaboration to standardise assays and study protocols, as well as to recruit sufficiently large cohorts, will facilitate future biomarker discovery and development.

Biomarkers mapping of neuropathic pain in a nerve chronic constriction injury mice model

Neuropathic pain is caused by a lesion or disease of the somatosensory nervous system and has a considerable impact on the quality of life. Neuropathic pain has a dynamic and complex aetiology and gives heterogeneous symptoms across patients; therefore, it represents an important clinical challenge. Current pharmacological treatment includes tricyclic antidepressant serotonin-noradrenaline uptake inhibitors such as duloxetine, pregabalin, and gabapentin. However, these drugs do not show efficacy in all patients suffering from neuropathic pain. In this work we used a nerve chronic constriction injury mice model based on the ligation of sciatic nerve to analyse, by two-dimensional electrophoresis and mass spectrometry, blood proteins significantly altered by neuropathic pain one-week after surgery. A sham-ligated group of mice acting as control and a group of ligated mice treated with gabapentin were also analysed. The results indicated that four haptoglobin isoforms were significantly more expressed, while transthyretin and alpha-2-macroglobulin expression decreased in the serum of the murine neuropathic pain model with respect to the control mice. Interestingly, the treatment with the gabapentin reversed these conditions. The outcomes of this study can provide a further understanding of the pathophysiological meaning of the biomarkers involved in neuropathic pain.

Proteomic analysis of protein homeostasis and aggregation

Protein homeostasis (proteostasis) refers to the ability of cells to preserve the correct balance between protein synthesis, folding and degradation. Proteostasis is essential for optimal cell growth and survival under stressful conditions. Various extracellular and intracellular stresses including heat shock, oxidative stress, proteasome malfunction, mutations and aging-related modifications can result in disturbed proteostasis manifested by enhanced misfolding and aggregation of proteins. To limit protein misfolding and aggregation cells have evolved various strategies including molecular chaperones, proteasome system and autophagy. Molecular chaperones assist folding of proteins, protect them from denaturation and facilitate renaturation of the misfolded polypeptides, whereas proteasomes and autophagosomes remove the irreversibly damaged proteins. The impairment of proteostasis results in protein aggregation that is a major pathological hallmark of numerous age-related disorders, such as cataract, Alzheimer's, Parkinson's, Huntington's, and prion diseases. To discover protein markers and speed up diagnosis of neurodegenerative diseases accompanied by protein aggregation, proteomic tools have increasingly been used in recent years. Systematic and exhaustive analysis of the changes that occur in the proteomes of affected tissues and biofluids in humans or in model organisms is one of the most promising approaches to reveal mechanisms underlying protein aggregation diseases, improve their diagnosis and develop therapeutic strategies. Significance: In this review we outline the elements responsible for maintaining cellular proteostasis and present the overview of proteomic studies focused on protein-aggregation diseases. These studies provide insights into the mechanisms responsible for age-related disorders and reveal new potential biomarkers for Alzheimer's, Parkinson's, Huntigton's and prion diseases.

Mitochondrial Targeting in Neurodegeneration: A Heme Perspective

Mitochondrial dysfunction has achieved an increasing interest in the field of neurodegeneration as a pathological hallmark for different disorders. The impact of mitochondria is related to a variety of mechanisms and several of them can co-exist in the same disease. The central role of mitochondria in neurodegenerative disorders has stimulated studies intended to implement therapeutic protocols based on the targeting of the distinct mitochondrial processes. The review summarizes the most relevant mechanisms by which mitochondria contribute to neurodegeneration, encompassing therapeutic approaches. Moreover, a new perspective is proposed based on the heme impact on neurodegeneration. The heme metabolism plays a central role in mitochondrial functions, and several evidences indicate that alterations of the heme metabolism are associated with neurodegenerative disorders. By reporting the body of knowledge on this topic, the review intends to stimulate future studies on the role of heme metabolism in neurodegeneration, envisioning innovative strategies in the struggle against neurodegenerative diseases.

Biofluid Biomarkers in Huntington's Disease

Huntington's disease (HD) is a chronic progressive neurodegenerative condition where new markers of disease progression are needed. So far no disease-modifying interventions have been found, and few interventions have been proven to alleviate symptoms. This may be partially explained by the lack of reliable indicators of disease severity, progression, and phenotype.Biofluid biomarkers may bring advantages in addition to clinical measures, such as reliability, reproducibility, price, accuracy, and direct quantification of pathobiological processes at the molecular level; and in addition to empowering clinical trials, they have the potential to generate useful hypotheses for new drug development.In this chapter we review biofluid biomarker reports in HD, emphasizing those we feel are likely to be closest to clinical applicability.

Aging Systemic Milieu Impairs Outcome after Ischemic Stroke in Rats

Compelling evidence indicates that factors in the blood can profoundly reverse aging-related impairments, as exposure of aged mice to young blood rejuvenates adult stem cell function, improves cognition, and ameliorates cardiac hypertrophy. Systemic factors from mice can also extend the life span of a partner exposed to a lethal treatment or disease. These findings suggest that the systemic milieu of a healthy young partner may be beneficial for an aged organism. However, it is unknown whether a healthy young systemic milieu can improve functional recovery after ischemic stroke. Intraperitoneal administration of young plasma into aged rats after ischemic stroke induced by distal middle cerebral artery occlusion (dMCAO) reduced infarct volume and motor impairment, compared with vehicle group. On the contrary, intraperitoneal administration of plasma from aged rats into young ischemic rats worsened brain injury and motor deficits. Using a proteomic approach, we found that haptoglobin levels were significantly increased in serum of aged rats and that intraperitoneal administration of haptoglobin impaired outcome after ischemic stroke in young rats. Our data suggest that the aging systemic milieu plays a critical role in functional outcome after ischemic stroke.

Variations in the cerebrospinal fluid proteome following traumatic brain injury and subarachnoid hemorrhage

BACKGROUND

Proteomic analysis of cerebrospinal fluid (CSF) has shown great promise in identifying potential markers of injury in neurodegenerative diseases [1-13]. Here we compared CSF proteomes in healthy individuals, with patients diagnosed with traumatic brain injury (TBI) and subarachnoid hemorrhage (SAH) in order to characterize molecular biomarkers which might identify these different clinical states and describe different molecular mechanisms active in each disease state.

METHODS

Patients presenting to the Neurosurgery service at the Louisiana State University Hospital-Shreveport with an admitting diagnosis of TBI or SAH were prospectively enrolled. Patients undergoing CSF sampling for diagnostic procedures were also enrolled as controls. CSF aliquots were subjected to 2-dimensional gel electrophoresis (2D GE) and spot percentage densities analyzed. Increased or decreased spot expression (compared to controls) was defined in terms of in spot percentages, with spots showing consistent expression change across TBI or SAH specimens being followed up by Matrix-Assisted Laser Desorption/Ionization mass spectrometry (MALDI-MS). Polypeptide masses generated were matched to known standards using a search of the NCBI and/or GenPept databases for protein matches. Eight hundred fifteen separately identifiable polypeptide migration spots were identified on 2D GE gels. MALDI-MS successfully identified 13 of 22 selected 2D GE spots as recognizable polypeptides.

RESULTS

Statistically significant changes were noted in the expression of fibrinogen, carbonic anhydrase-I (CA-I), peroxiredoxin-2 (Prx-2), both α and β chains of hemoglobin, serotransferrin (Tf) and N-terminal haptoglobin (Hp) in TBI and SAH specimens, as compared to controls. The greatest mean fold change among all specimens was seen in CA-I and Hp at 30.7 and -25.7, respectively. TBI specimens trended toward greater mean increases in CA-I and Prx-2 and greater mean decreases in Hp and Tf.

CONCLUSIONS

Consistent CSF elevation of CA-I and Prx-2 with concurrent depletion of Hp and Tf may represent a useful combination of biomarkers for the prediction of severity and prognosis following brain injury.

Insights into the human brain proteome: Disclosing the biological meaning of protein networks in cerebrospinal fluid

Cerebrospinal fluid (CSF) is an excellent source of biological information regarding the nervous system, once it is in close contact and accurately reflects alterations in this system. Several studies have analyzed differential protein profiles of CSF samples between healthy and diseased human subjects. However, the pathophysiological mechanisms and how CSF proteins relate to diseases are still poorly known. By applying bioinformatics tools, we attempted to provide new insights on the biological and functional meaning of proteomics data envisioning the identification of putative disease biomarkers. Bioinformatics analysis of data retrieved from 99 mass spectrometry (MS)-based studies on CSF profiling highlighted 1985 differentially expressed proteins across 49 diseases. A large percentage of the modulated proteins originate from exosome vesicles, and the majority are involved in either neuronal cell growth, development, maturation, migration, or neurotransmitter-mediated cellular communication. Nevertheless, some diseases present a unique CSF proteome profile, which were critically analyzed in the present study. For instance, 48 proteins were found exclusively upregulated in the CSF of patients with Alzheimer's disease and are mainly involved in steroid esterification and protein activation cascade processes. A higher number of exclusively upregulated proteins were found in the CSF of patients with multiple sclerosis (76 proteins) and with bacterial meningitis (70 proteins). Whereas in multiple sclerosis, these proteins are mostly involved in the regulation of RNA metabolism and apoptosis, in bacterial meningitis the exclusively upregulated proteins participate in inflammation and antibacterial humoral response, reflecting disease pathogenesis. The exploration of the contribution of exclusively upregulated proteins to disease pathogenesis will certainly help to envision potential biomarkers in the CSF for the clinical management of nervous system diseases.

Structural Architecture of Prothrombin in Solution Revealed by Single Molecule Spectroscopy

The coagulation factor prothrombin has a complex spatial organization of its modular assembly that comprises the N-terminal Gla domain, kringle-1, kringle-2, and the C-terminal protease domain connected by three intervening linkers. Here we use single molecule Förster resonance energy transfer to access the conformational landscape of prothrombin in solution and uncover structural features of functional significance that extend recent x-ray crystallographic analysis. Prothrombin exists in equilibrium between two alternative conformations, open and closed. The closed conformation predominates (70%) and features an unanticipated intramolecular collapse of Tyr(93) in kringle-1 onto Trp(547) in the protease domain that obliterates access to the active site and protects the zymogen from autoproteolytic conversion to thrombin. The open conformation (30%) is more susceptible to chymotrypsin digestion and autoactivation, and features a shape consistent with recent x-ray crystal structures. Small angle x-ray scattering measurements of prothrombin wild type stabilized 70% in the closed conformation and of the mutant Y93A stabilized 80% in the open conformation directly document two envelopes that differ 50 Å in length. These findings reveal important new details on the conformational plasticity of prothrombin in solution and the drastic structural difference between its alternative conformations. Prothrombin uses the intramolecular collapse of kringle-1 onto the active site in the closed form to prevent autoactivation. The open-closed equilibrium also defines a new structural framework for the mechanism of activation of prothrombin by prothrombinase.

Metabolic disturbances in plasma as biomarkers for Huntington's disease

Huntington's disease (HD), caused by expanded CAG repeats encoding a polyglutamine tract in the huntingtin protein, presents with a predominant degeneration of neurons in the striatum and cortex. Although a few studies have identified substantial metabolite alterations in plasma, the picture of plasma metabolomics of HD has not been clearly depicted yet. Using a global metabolomics screening for plasma from 15 HD patients and 17 controls, HD patient group was separated from the control group by a panel of metabolites belonging to carnitine, amino acid and phosphatidylcholine species. The quantification of 184 related metabolites (including carnitine, amino acid and phosphatidylcholine species) in 29 HD patients, 9 presymptomatic HD carriers and 44 controls further showed one up-regulated (glycine) and 9 down-regulated metabolites (taurine, serotonin, valine, isoleucine, phosphatidylcholine acyl-alkyl C36:0 and C34:0 and lysophosphatidylcholine acyl C20:3). To understand the biosynthetic alterations of phosphatidylcholine in HD, we examined the expression levels and activities of a panel of key enzymes responsible for phosphatidylcholine metabolism. The results showed down-regulation of PCYT1A and increased activity of phospholipase A2 in HD leukocytes. These metabolic profiles strongly indicate that disturbed metabolism is involved in pathogenesis of HD and provide clue for the development of novel treatment strategies for HD.

Differential proteomic and genomic profiling of mouse striatal cell model of Huntington's disease and control; probable implications to the disease biology

Huntington's disease (HD) is an autosomal dominant disorder of central nervous system caused by expansion of CAG repeats in exon1 of the huntingtin gene (Htt). Among various dysfunctions originated from the mutation in Htt gene, transcriptional deregulation has been considered to be one of the most important abnormalities. Large numbers of investigations identified altered expressions of genes in brains of HD patients and many models of HD. In this study we employed 2D SDS-PAGE/MALDI-MS coupled with 2D-DIGE and real-time PCR experiments of an array of genes focused to HD pathway to determine altered protein and gene expressions in STHdh(Q111)/Hdh(Q111) cells, a cell model of HD and compared with STHdh(Q7)/Hdh(Q7) cells, its wild type counterpart. We annotated 76 proteins from these cells and observed differential expressions of 31 proteins (by 2D-DIGE) involved in processes like unfolded protein binding, negative regulation of neuron apoptosis, response to superoxides etc. Our PCR array experiments identified altered expressions of 47 genes. Altogether significant alteration of 77 genes/proteins could be identified in this HD cell line with potential relevance to HD biology.

BIOLOGICAL SIGNIFICANCE

In this study we intended to find out differential proteomic and genomic profiles in HD condition. We used the STHdh cells, a cellular model for HD and control. These are mouse striatal neuronal cell lines harboring 7 and 111 knock-in CAG repeats in their two alleles. The 111Q containing cell line (STHdh(Q111)/Hdh(Q111)) mimics diseased condition, whereas the 7Q containing ones (STHdh(Q7)/Hdh(Q7)), serves as the proper control cell line. Proteomic experiments were performed earlier to obtain differential expressions of proteins in R6/2 mice models, Hdh(Q) knock-in mice and in plasma and CSF from HD patients. However, no earlier report on proteomic alterations in these two HD cell lines and control was available in literature. It was, therefore, an important objective to find out differential expressions of proteins in these two cell lines. In this study, we annotated 76 proteins from STHdh(Q7)/Hdh(Q7) and STHdh(Q111)/Hdh(Q111) cells using 2D-gel/mass spectrometry. Next, by performing 2D-DIGE, we observed differential expressions of 31 proteins (16 upregulated and 15 downregulated) between these two cell lines. We also performed customized qRT-PCR array focused to HD pathway and found differential expressions of 47 genes (8 gene expressions increased and 39 genes were decreased significantly). A total of 77 genes/proteins (Htt downregulated in both the studies) were found to be significantly altered from both the experimental paradigms. We validated the differential expressions of Vim, Hypk, Ran, Dstn, Hspa5 and Sod2 either by qRT-PCR or Western blot analysis or both. Out of these 77, similar trends in alteration of 19 out of 31 and 38 out of 47 proteins/genes were reported in earlier studies. Thus our study confirmed earlier observations on differential gene/protein expressions in HD and are really useful. Additionally, we observed differential expression of some novel genes/proteins. One of this was Hypk, a Htt-interacting chaperone protein with the ability to solubilize mHtt aggregated structures in cell lines. We propose that downregulation of Hypk in STHdh(Q111)/Hdh(Q111) has a causal effect towards HD pathogenesis. Thus the novel findings from our study need further research and might be helpful to understand the molecular mechanism behind HD pathogenesis.

Ubiquitin: a potential cerebrospinal fluid progression marker in Huntington's disease

BACKGROUND

Finding early and dynamic biomarkers in Huntington's disease is a key to understanding the early pathology of Huntington's disease and potentially to tracking disease progression. This would benefit the future evaluation of potential neuroprotective and disease-modifying therapies, as well as aid in identifying an optimal time point for initiating a potential therapeutic intervention.

METHODS

This explorative proteomics study evaluated cerebrospinal fluid from 94 Huntington's disease gene-expansion carriers (39 premanifest and 55 manifest) and 27 Huntington's disease gene-expansion negative individuals using surface-enhanced laser desorption/ionization time-of-flight (SELDI-TOF) mass spectrometry. Differences in peak intensity from SELDI-TOF spectra were evaluated.

RESULTS

Levels of 10 peaks were statistically significantly different between manifest gene-expansion carriers and controls. One of them identified as ubiquitin was shown to be dependent on the Unified Huntington Disease Rating Scale Total Functional Capacity, a pseudo-measure of disease severity (P = 0.001), and the Symbol Digit Modalities Test (0.04) in manifest and CAG-age product score (P = 0.019) in all gene-expansion carriers.

CONCLUSIONS AND RELEVANCE

Multiple studies have shown that the ubiquitin-proteasome system is involved in Huntington's disease pathogenesis and understanding of this involvement may have therapeutic potential in humans. This is the first study on cerebrospinal fluid to confirm the involvement of the ubiquitin-proteasome system in Huntington's disease. Furthermore it is shown that ubiquitin increases with disease progression and CAG-age product score and therefore may have the potential as a Huntington's disease progression marker, also prior to motor onset.

Challenges of Huntington's disease and quest for therapeutic biomarkers

Huntington's disease (HD) is the most common inherited neurodegenerative disorder among polyglutamine (polyQ) diseases caused by cytosine-adenine-guanine repeat expansion in exon 1 of the huntingtin gene whose translation results in polyQ stretch in the N-terminus of the huntingtin protein (HD protein). This mutation significantly affects huntingtin conformation, proteolysis, PTMs, as well as its ability to bind interacting proteins. As a consequence, a variety of cellular mechanisms such as transcription, mitochondrial energy metabolism, axonal transport, neuronal vulnerability to oxidative stress, neurotransmission, and immune response are altered and involved in the pathogenesis of HD. Promising candidate molecular biomarkers of HD have emerged from proteomic studies. Recent analyses focused on HD protein itself, its PTM, and interacting proteins, which are of great importance for disease course. Furthermore, brain, body fluids, and immune system are intensively studied in order to search for additional proteins with a view to their use as a biomarker(s) or set of biomarkers in clinical trials in HD translational research.

Prothrombin structure: unanticipated features and opportunities

The structure of prothrombin has eluded investigators for decades but recent efforts have succeeded in revealing the architecture of this important clotting factor. Unanticipated features have emerged outlining the significant flexibility of the zymogen due to linker regions connecting the γ carboxyglutamic domain, kringles and protease domain. A new, structure-based framework helps in defining a molecular mechanism of prothrombin activation, rationalizes the severe bleeding phenotypes of several naturally occurring mutations and identifies targets for drug design.

Haptoglobin interacts with apolipoprotein E and beta-amyloid and influences their crosstalk

Beta-amyloid accumulation in brain is a driving force for Alzheimer's disease pathogenesis. Apolipoprotein E (ApoE) represents a critical player in beta-amyloid homeostasis, but its role in disease progression is controversial. We previously reported that the acute-phase protein haptoglobin binds ApoE and impairs its function in cholesterol homeostasis. The major aims of this study were to characterize the binding of haptoglobin to beta-amyloid, and to evaluate whether haptoglobin affects ApoE binding to beta-amyloid. Haptoglobin is here reported to form a complex with beta-amyloid as shown by immunoblotting experiments with purified proteins, or by its immunoprecipitation in brain tissues from patients with Alzheimer's disease. The interaction between ApoE and beta-amyloid was previously shown to be crucial for limiting beta-amyloid neurotoxicity and for promoting its clearance. We demonstrate that haptoglobin, rather than impairing ApoE binding to beta-amyloid, promotes to a different extent the formation of the complex between beta-amyloid and ApoE2 or ApoE3 or ApoE4. Our data suggest that haptoglobin and ApoE functions in brain should be evaluated taking into account their mutual interaction with beta-amyloid. Hence, the risk of developing Alzheimer's disease might not only be linked to the different ApoE isoforms, but also rely on the level of critical ligands, such as haptoglobin.

Haptoglobin increases with age in rat hippocampus and modulates Apolipoprotein E mediated cholesterol trafficking in neuroblastoma cell lines

Alteration in cholesterol metabolism has been implicated in the pathogenesis of several neurodegenerative disorders. Apolipoprotein E (ApoE) is the major component of brain lipoproteins supporting cholesterol transport. We previously reported that the acute-phase protein Haptoglobin (Hpt) binds ApoE, and influences its function in blood cholesterol homeostasis. Major aim of this study was to investigate whether Hpt influences the mechanisms by which cholesterol is shuttled from astrocytes to neurons. In detail it was studied Hpt effect on ApoE-dependent cholesterol efflux from astrocytes and ApoE-mediated cholesterol incorporation in neurons. We report here that Hpt impairs ApoE-mediated cholesterol uptake in human neuroblastoma cell line SH-SY5Y, and limits the toxicity of a massive concentration of cholesterol for these cells, while it does not affect cholesterol efflux from the human glioblastoma-astrocytoma cell line U-87 MG. As aging is the most important non-genetic risk factor for various neurodegenerative disorders, and our results suggest that Hpt modulates ApoE functions, we evaluated the Hpt and ApoE expression profiles in cerebral cortex and hippocampus of adolescent (2 months), adult (5 and 8 months), and middle-aged (16 months) rats. Hpt mRNA level was higher in hippocampus of 8 and 16 month-old than in 2-month old rats (p < 0.05), and Hpt concentration increased with the age from adolescence to middle-age (p < 0.001). ApoE concentration, in hippocampus, was higher (p < 0.001) in 5 month-old rats compared to 2 month but did not further change with aging. No age-related changes of Hpt (protein and mRNA) were found in the cortex. Our results suggest that aging is associated with changes, particularly in the hippocampus, in the Hpt/ApoE ratio. Age-related changes in the concentration of Hpt were also found in human cerebrospinal fluids. The age-related changes might affect neuronal function and survival in brain, and have important implications in brain pathophysiology.

Protein-protein interactions: switch from classical methods to proteomics and bioinformatics-based approaches

Following the sequencing of the human genome and many other organisms, research on protein-coding genes and their functions (functional genomics) has intensified. Subsequently, with the observation that proteins are indeed the molecular effectors of most cellular processes, the discipline of proteomics was born. Clearly, proteins do not function as single entities but rather as a dynamic network of team players that have to communicate. Though genetic (yeast two-hybrid Y2H) and biochemical methods (co-immunoprecipitation Co-IP, affinity purification AP) were the methods of choice at the beginning of the study of protein-protein interactions (PPI), in more recent years there has been a shift towards proteomics-based methods and bioinformatics-based approaches. In this review, we first describe in depth PPIs and we make a strong case as to why unraveling the interactome is the next challenge in the field of proteomics. Furthermore, classical methods of investigation of PPIs and structure-based bioinformatics approaches are presented. The greatest emphasis is placed on proteomic methods, especially native techniques that were recently developed and that have been shown to be reliable. Finally, we point out the limitations of these methods and the need to set up a standard for the validation of PPI experiments.

New insight into neurodegeneration: the role of proteomics

Recent advances within the field of proteomics, including both upstream and downstream protocols, have fuelled a transition from simple protein identification to functional analysis. A battery of proteomics approaches is now being employed for the analysis of protein expression levels, the monitoring of cellular activities and for gaining an increased understanding into biochemical pathways. Combined, these approaches are changing the way we study disease by allowing accurate and targeted, large scale protein analysis, which will provide invaluable insight into disease pathogenesis. Neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), prion disease, and other diseases that affect the neuromuscular system, are a leading cause of disability in the aging population. There are no effective intervention strategies for these disorders and diagnosis is challenging as it relies primarily on clinical symptomatic features, which often overlap at early stages of disease. There is, therefore, an urgent need to develop reliable biomarkers to improve early and specific diagnosis, to track disease progression, to measure molecular responses towards treatment regimes and ultimately devise new therapeutic strategies. To accomplish this, a better understanding of disease mechanisms is needed. In this review we summarize recent advances in the field of proteomics applicable to neurodegenerative disorders, and how these advances are fueling our understanding, diagnosis, and treatment of these complex disorders.

Proteomic profiling of serum samples from chikungunya-infected patients provides insights into host response

BACKGROUND

Chikungunya is a highly debilitating febrile illness caused by Chikungunya virus, a single-stranded RNA virus, which is transmitted by Aedes aegypti or Aedes albopictus mosquito species. The pathogenesis and host responses in individuals infected with the chikungunya virus are not well understood at the molecular level. We carried out proteomic profiling of serum samples from chikungunya patients in order to identify molecules associated with the host response to infection by this virus.

RESULTS

Proteomic profiling of serum obtained from the infected individuals resulted in identification of 569 proteins. Of these, 63 proteins were found to be differentially expressed (≥ 2-fold) in patient as compared to control sera. These differentially expressed proteins were involved in various processes such as lipid metabolism, immune response, transport, signal transduction and apoptosis.

CONCLUSIONS

This is the first report providing a global proteomic profile of serum samples from individuals infected with the chikungunya virus. Our data provide an insight into the proteins that are involved as host response factors during an infection. These proteins include clusterin, apolipoproteins and S100A family of proteins.

Neurovascular abnormalities in humans and mice with Huntington's disease

Cerebral microvascular aberrations have recently become recognized as a source of pathologies in neurodegenerative disorders, but this concept has not been fully examined with respect to Huntington's disease (HD). A novel in vivo technique, three-dimensional microscopic magnetic resonance angiography (μMRA), allows visualization of the neurovascular system in exquisite detail and provides quantitative structural and functional information. This technique was applied in the present study, in parallel with immunohistological analysis and behavioral assessment, to a well-characterized mouse model of HD (R6/2). Dynamic contrast-enhanced magnetic resonance imaging was used to examine the integrity of the blood-brain barrier (BBB). The μMRA findings revealed an increase in vessel volume fraction and cerebral blood volume in the brains of R6/2 mice at the age of 7weeks when no apparent motor dysfunction was detected. Collagen IV immunostaining disclosed an enhancement in vessel density, but not in vessel size of the microvasculature in the mouse HD brain. This change in neurovasculature worsened with disease progression, with no apparent disruption in the BBB. Most importantly, immunohistological assays of human tissues revealed that the vessel densities in the cortex, caudate/putamen, and substantia nigra were higher in HD patients than in non-HD human subjects. The early onset of such vessel aberrations could be used as a biomarker for the early diagnosis of HD.

Neurovascular abnormalities in brain disorders: highlights with angiogenesis and magnetic resonance imaging studies

The coupling between neuronal activity and vascular responses is controlled by the neurovascular unit (NVU), which comprises multiple cell types. Many different types of dysfunction in these cells may impair the proper control of vascular responses by the NVU. Magnetic resonance imaging, which is the most powerful tool available to investigate neurovascular structures or functions, will be discussed in the present article in relation to its applications and discoveries. Because aberrant angiogenesis and vascular remodeling have been increasingly reported as being implicated in brain pathogenesis, this review article will refer to this hallmark event when suitable.

Recent advances in quantitative neuroproteomics

The field of proteomics is undergoing rapid development in a number of different areas including improvements in mass spectrometric platforms, peptide identification algorithms and bioinformatics. In particular, new and/or improved approaches have established robust methods that not only allow for in-depth and accurate peptide and protein identification and modification, but also allow for sensitive measurement of relative or absolute quantitation. These methods are beginning to be applied to the area of neuroproteomics, but the central nervous system poses many specific challenges in terms of quantitative proteomics, given the large number of different neuronal cell types that are intermixed and that exhibit distinct patterns of gene and protein expression. This review highlights the recent advances that have been made in quantitative neuroproteomics, with a focus on work published over the last five years that applies emerging methods to normal brain function as well as to various neuropsychiatric disorders including schizophrenia and drug addiction as well as of neurodegenerative diseases including Parkinson's disease and Alzheimer's disease. While older methods such as two-dimensional polyacrylamide electrophoresis continued to be used, a variety of more in-depth MS-based approaches including both label (ICAT, iTRAQ, TMT, SILAC, SILAM), label-free (label-free, MRM, SWATH) and absolute quantification methods, are rapidly being applied to neurobiological investigations of normal and diseased brain tissue as well as of cerebrospinal fluid (CSF). While the biological implications of many of these studies remain to be clearly established, that there is a clear need for standardization of experimental design and data analysis, and that the analysis of protein changes in specific neuronal cell types in the central nervous system remains a serious challenge, it appears that the quality and depth of the more recent quantitative proteomics studies is beginning to shed light on a number of aspects of neuroscience that relates to normal brain function as well as of the changes in protein expression and regulation that occurs in neuropsychiatric and neurodegenerative disorders.

Disulfide proteomics for identification of extracellular or secreted proteins

The combination of SDS-PAGE and MS is one of the most powerful and perhaps most frequently used gel-based proteomics approaches in protein identification. However, one drawback of this method is that separation takes place under denaturing and reducing (R) conditions and as a consequence, all proteins with identical apparent molecular mass (Mr) will run together. Therefore, low-abundant proteins may not be easily identified. Another way of investigating proteins by proteomics is by analyzing subproteomes from a total proteome such as phosphoproteomics, glycoproteomics, or disulfide proteomics. Here, we took advantage of the property of secreted proteins to form disulfide bridges and investigated disulfide-linked proteins, using SDS-PAGE under nonreducing (NR) conditions. We separated sera from normal subjects and from patients with various diseases by SDS-PAGE (NR) and (R) conditions, followed by LC-MS/MS analysis. Although we did not see any detectable difference between the sera separated by SDS-PAGE(R), we could easily identify the disulfide-linked proteins separated by SDS-PAGE (NR). LC-MS/MS analysis of the disulfide-linked proteins correctly identified haptoglobin (Hp), a disulfide-linked protein usually found as a heterotetramer or as a disulfide-linked heteropolymer. Western blotting under NR and R conditions using anti-Hp antibodies confirmed the LC-MS/MS experiments and further confirmed that upon reduction, the disulfide-linked Hp heterotetramers and polymers were no longer disulfide-linked polymers. These data suggest that simply by separating samples on SDS-PAGEunder NR conditions, a different, new proteomics subset can be revealed and then identified.