Platelets provide human tissue to unravel pathogenic mechanisms of Alzheimer disease

Epigenetic rewiring of skeletal muscle enhancers after exercise training supports a role in whole-body function and human health

Objectives

Regular physical exercise improves health by reducing the risk of a plethora of chronic disorders. We hypothesized that endurance exercise training remodels the activity of gene enhancers in skeletal muscle and that this remodeling contributes to the beneficial effects of exercise on human health.

Methods and results

By studying changes in histone modifications, we mapped the genome-wide positions and activities of enhancers in skeletal muscle biopsies collected from young sedentary men before and after 6 weeks of endurance exercise. We identified extensive remodeling of enhancer activities after exercise training, with a large subset of the remodeled enhancers located in the proximity of genes transcriptionally regulated after exercise. By overlapping the position of enhancers with genetic variants, we identified an enrichment of disease-associated genetic variants within the exercise-remodeled enhancers.

Conclusion

Our data provide evidence of a functional link between epigenetic rewiring of enhancers to control their activity after exercise training and the modulation of disease risk in humans.

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Exercise training changes in skeletal muscle gene expression is enriched for secreted factors.

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The activity of skeletal muscle enhancers undergoes substantial remodeling after exercise training.

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Skeletal muscle enhancer activity and gene transcription are strongly associated.

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Exercise training-remodeled enhancer regions are enriched for GWAS SNPs associated with human traits and diseases.

Platelets in Healthy and Disease States: From Biomarkers Discovery to Drug Targets Identification by Proteomics

Platelets are a heterogeneous small anucleate blood cell population with a central role both in physiological haemostasis and in pathological states, spanning from thrombosis to inflammation, and cancer. Recent advances in proteomic studies provided additional important information concerning the platelet biology and the response of platelets to several pathophysiological pathways. Platelets circulate systemically and can be easily isolated from human samples, making proteomic application very interesting for characterizing the complexity of platelet functions in health and disease as well as for identifying and quantifying potential platelet proteins as biomarkers and novel antiplatelet therapeutic targets. To date, the highly dynamic protein content of platelets has been studied in resting and activated platelets, and several subproteomes have been characterized including platelet-derived microparticles, platelet granules, platelet releasates, platelet membrane proteins, and specific platelet post-translational modifications. In this review, a critical overview is provided on principal platelet proteomic studies focused on platelet biology from signaling to granules content, platelet proteome changes in several diseases, and the impact of drugs on platelet functions. Moreover, recent advances in quantitative platelet proteomics are discussed, emphasizing the importance of targeted quantification methods for more precise, robust and accurate quantification of selected proteins, which might be used as biomarkers for disease diagnosis, prognosis and therapy, and their strong clinical impact in the near future.

Heptamer Peptide Disassembles Native Amyloid in Human Plasma Through Heat Shock Protein 70

Proteostasis, which includes the repair and disposal of misfolded proteins, depends, in part, on the activity of heat shock proteins (HSPs), a well-known class of chaperone molecules. When this process fails, abnormally folded proteins may accumulate in cells, tissues, and blood. These species are a hallmark of protein aggregation diseases, but also amass during aging, often in the absence of an identified clinical disorder. We report that a neuroprotective cyclic heptapeptide, CHEC-7, which has been applied systemically as a therapeutic in animal neurodegeneration models, disrupts such aggregates and inhibits amyloidogenesis when added in nanomolar concentrations to human plasma. This effect includes aggregates of amyloid beta (Aβ1-40, 1-42), prominent features of Alzheimer's disease pathology. The activity of endogenous HSP70, a recently discovered target of the peptide, is required as demonstrated by both antibody blocking and application of pifithrin-μ, an HSP70 inhibitor. CHEC-7 is the first high-affinity compound to stimulate HSP70's disaggregase activity and therefore enable this endogenous mechanism in a human systemic environment, increasing the likelihood of a convenient therapy for protein aggregate disease, including age-related failures of protein repair.

Association of Platelet Serotonin Levels in Alzheimer's Disease with Clinical and Cerebrospinal Fluid Markers

INTRODUCTION

Serotonin (5-HT) is involved in the pathology of Alzheimer's disease (AD).

OBJECTIVE

We aimed to measure 5-HT level in platelets in AD and explore its association with cerebrospinal fluid (CSF), AD biomarkers (amyloid-β 1-42 (Aβ42), total tau (t-tau), and phosphorylated tau (p-tau)), and clinical symptoms.

METHODS

15 patients with AD and 20 patients with subjective cognitive impairment (SCI) were included. 5-HT metabolites were measured, in a specific fraction, using high performance liquid chromatography with electrochemical detection (HPLC-ECD).

RESULTS

Significantly lower 5-HT concentrations were observed in AD patients compared to SCI patients both after normalization against total protein (p = 0.008) or platelet count (p = 0.019). SCI patients with lower 5-HT level have higher AD CSF biomarkers, total tau (p = 0.026) and tau/Aβ42 ratio (p = 0.001), compared to those with high 5-HT levels.

CONCLUSION

AD patients have reduced platelet 5-HT levels. In SCI, lower 5-HT content was associated with a higher AD-CSF biomarker burden.

Effects of chlorogenic acid on adenine nucleotides hydrolyzing enzyme activities and expression in platelets of rats experimentally demyelinated with ethidium bromide

BACKGROUND

The effects of chlorogenic acid (one of the major phenolic acid found in human diets) were investigated on the adenine nucleotides hydrolyzing enzymes; ecto-nucleotide pyrophosphatase/phophodiesterase (E-NPP), ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase), E-5'- nucleotidase and ecto-adenosine deaminase (E-ADA) activities and expression in platelets of rats experimentally demyelinated with ethidium bromide.

METHODS

Rats were divided into four groups of eight animals each. Group I rats were control rats; injected with saline (CT), group II rats were injected with saline and treated with chlorogenic acid (AC), group III rats were injected with 0.1% ethidium bromide (EB) and group IV rats were injected with 0.1% EB and treated with chlorogenic acid (EB+AC). The activities of the enzymes were analyzed using colorimetric methods, and the gene expression of NTPDase 1, 2 and 3 were analyzed using the polymerase chain reaction (PCR).

RESULTS

The results revealed that there was a significant (P<0.01) reduction in E-NPP activity in EB group (1.63±0.10nmol p-nitrophenol released/min/mg protein) when compared to CT group (2.33±0.14nmol p-nitrophenol released/min/mg protein). However, treatment with chlorogenic acid significantly (P<0.05) increased E-NPP activity in EB group. Furthermore, no significant (P>0.05) change was observed in the E-NPP activity of EB+AC group (2.19±0.08nmol p-nitrophenol released/min/mg protein) when compared to CT group (2.33±0.14nmol p-nitrophenol released/min/mg protein). In addition, there was a significant (P<0.05) increase in AMP hydrolysis in EB rat group when compared to CT group. No significant (P>0.05) difference was observed in AMP hydrolysis between AC, AC+EB and CT groups. Conversely, there were no significant (P>0.05) differences in ATP and ADP hydrolyses between all the groups (AC, EB, AC+EB and CT groups). Likewise, there were no significant (P>0.05) changes in E-ADA activity and percentage platelet aggregation among all groups studied. Similarly, no significant (P>0.05) change was observed in the expression of E-NTPDase 1, 2 and 3 in all the groups tested.

CONCLUSIONS

Our study revealed that chlorogenic acid may modulate the hydrolysis of adenine nucleotides in platelets of rats demyelinated and treated with chlorogenic acid via alteration of E-NPP and ecto-5'-nucleotidase activities.

Increased apoptosis in the platelets of patients with Alzheimer's disease and amnestic mild cognitive impairment

OBJECTIVES

Alzheimer's disease (AD), the most common cause of dementia, is a progressive, incurable neurodegenerative disorder. Platelet is a suitable source of human peripheral tissue to study pathological mechanisms occurring in the brain. The present study aims to investigate (1) whether abnormal apoptotic events besides involved in AD within the central neurologic system, could also occur at peripheral platelet level; (2) whether apoptosis at peripheral platelet level starts at the early stage of AD.

PATIENTS AND METHODS

Amnestic mild cognitive impairment (MCI), AD, and age-matched healthy individuals were recruited, and each group had 50 person. In the present study, we investigate whether alterations of caspase family and Bcl2 family could be found in the platelets in Alzheimer's disease (AD) and amnestic mild cognitive impairment (MCI) patients. The platelet levels of caspase protein and Bcl2 family were analyzed by western blot.

RESULTS

The results show that the platelet levels of caspase-3, caspase-9, Bad, and Bax significantly increased in AD and amnestic MCI. The increased apoptosis proteins levels in amnestic MCI were found between AD and normal controls. The anti-apoptosis protein Bcl2 increased in amnestic MCI, while decreased in AD.

CONCLUSION

We suggest that increased apoptosis exist in the platelet and might mirror apoptosis within the brain. Abnormal apoptosis may appear in the early of AD, and the ratio between pro- and anti-apoptotic protein levels partially determines the susceptibility of platelet to a death signal. In conclusion, platelet may be a good model to study apoptotic pathways of AD.

MicroRNA-29c targets β-site amyloid precursor protein-cleaving enzyme 1 and has a neuroprotective role in vitro and in vivo

Alzheimer's disease (AD), characterized by β-amyloid deposition and neurodegeneration, is the most common cause of dementia worldwide. Emerging evidence suggests that ectopic expression of micro (mi)RNAs is involved in the pathogenesis of AD. There is increasing evidence that miRNAs expressed in the brain are involved in neuronal development, survival and apoptosis. The expression of β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) is regulated by dysregulated miRNAs in the brain. The present study determined the expression levels of the miRNA-29 (miR-29) family in peripheral blood samples of patients with AD and demonstrated a marked decrease in the expression of miR-29c compared with age-matched controls. In addition, a significant increase in the expression of BACE1 was observed in the peripheral blood of patients with AD. Correlation analysis revealed that the expression of miR-29c was negatively correlated with the protein expression of BACE1 in the peripheral blood samples from patients with AD. The present study also investigated the role of miR-29 on hippocampal neurons in vitro and in vivo. The results demonstrated that the upregulation of miR-29c promoted learning and memory behaviors in SAMP8 mice, at least partially, by increasing the activity of protein kinase A/cAMP response element-binding protein, involved in neuroprotection. This evidence suggested that miR-29c may be a promising potential therapeutic target against AD.

Decreased platelet APP isoform ratios in autosomal dominant Alzheimer's disease: baseline data from a DIAN cohort subset

INTRODUCTION

This study examines platelet amyloid precursor protein (APP) isoform ratios of 120KDa to 110KDa (APPr) between mutation carriers (MC) carrying a mutation for autosomal dominant Alzheimer's disease (ADAD) and non-carriers (NC). Two previous studies reported no significant difference in APPr between ADAD MC and NC, which may have been due to the small sample size in both studies. The current study examines APPr in MC versus NC in a larger sample. In addition, it investigated whether APPr correlate with neuroimaging data, neuropsychological data and cerebrospinal fluid biomarkers in a cohort subset derived from the Dominantly Inherited Alzheimer Network (DIAN) study.

METHODS

APPr were quantified by western blotting. Fifteen MC (symptomatic and asymptomatic) were compared against twelve NC using univariate general linear model. All participants underwent neuroimaging and neuropsychological testing which were correlated with APPr using Pearson's correlation coefficient (r).

RESULTS

APPr were lower in MC compared to NC (p=0.003) while Mini-Mental State Examination (MMSE) scores were not significantly different (p>0.1). Furthermore, APPr inversely correlated with amyloid imaging in the Caudate Nucleus (r=-0.505; p<0.05) and Precuneus (r=-0.510; p<0.05).

CONCLUSION

APPr are lower in ADAD MC compared to NC, and inversely correlated with brain amyloid load prior to significant differences in cognitive health. However, the use of APPr as a biomarker needs to be explored further.

Assessment of platelet indices in patients with neurodegenerative diseases: mean platelet volume was increased in patients with Parkinson's disease

Platelets induce chronic inflammation which is a key step in atherosclerosis and may be involved in the progression of neurodegenerative diseases (NDD). We aimed to measure the mean platelet volume (MPV) and platelet count (PLC) in NDD patients. The present study was designed to investigate the platelet function by measuring MPV and PLC in NDD. A total of 182 outpatients with Alzheimer's (AD) or Parkinson's diseases (PD) were included. The control group consisted of 104 healthy subjects. Platelet count was similar between groups. MPV values of PD patients were higher than those of AD patients and controls (P < 0.001). MPV correlated negatively with Heohn and Yahr scale (HYS) score (P < 0.001). Increased MPV in patients with PD may point to a platelet dysfunction. High-grade inflammation presents with low levels of MPV as seen in PD patients with high HYS scores.

Transfer of the amyloid β and/or of β-amyloid precursor protein of the fetus with trisomy 21 to the maternal blood stream and its possible contribution to the pathogenesis of the maternal Alzheimer's Disease

Down Syndrome (DS) is the most frequent genetic pathology. It affects 1 out of every 800 newborn babies. Approximately between a 90% and a 95% of all the cases of DS are attributed to a trisomy in chromosome 21. One of the genes contained in this chromosome is the gene of β-amyloid precursor protein (βAPP). The metabolism of this protein yields, among others, the amyloid beta peptides made up of 40 amino acids (Aβ40) and 42 amino acids (Aβ42). The evidence that is derived from several sources--genetic, among them--suggests that the Aβ participates in the pathogenesis of Alzheimer's Disease (AD). It is worth pointing at the fact that the transfer of cells, extracellular chromosomal material and some proteins from the fetus to the mother and vice versa has been widely described. The transfer rate from the fetus to the mother is higher when the mother is carrying a baby with trisomy 21. This has led to the hypothesis that sets forth that during the gestation of a baby with DS there is a greater fetomaternal transfer of cells and of products of the genes of chromosome 21--among them, βAPP and its metabolites Aβ40 and Aβ42. It is possible to speculate on the possible contribution of the fetal components--among them, Aβ--to the higher risk of suffering AD, which has been reported in a subpopulation of women who have given birth to children with DS. On the other hand, the detection of the βAPP--mainly intracellular--and of the β amyloid peptides in maternal blood and urine during the early stages of gestation could be taken as a potential non invasive biochemical prenatal marker of DS.

Platelet amyloid precursor protein isoform expression in Alzheimer's disease: evidence for peripheral marker

Alzheimer's disease (AD) is a chronic neurodegenerative disorder characterized by a progressive cognitive and memory decline. Among peripheral markers of AD, great interest has been focused on the amyloid precursor protein (APP). In this regard, platelets represent an important peripheral source of APP since it has been demonstrated that the three major isoforms, that are constituted of 770, 751 and 695 aa residues, are inserted in the membrane of resting platelets. APP 751 and APP 770 contain a Kunitz-type serine protease inhibitor domain (APP KPI) and APP 695 lacks this domain. To address this issue, we first examined the platelet APP isoform mRNAs prospectively as biomarker for the diagnosis of AD by means of real-time quantitative PCR, and then evaluated the correlation between APP mRNA expression levels and cognitive impairment of enrolled subjects. Differential gene expression measurements in the AD patient group (n=18) revealed a significant up-regulation of APP TOT (1.52-fold), APP KPI (1.32-fold), APP 770 (1.33-fold) and APP 751 (1.26-fold) compared to controls (n=22). Moreover, a statistically significant positive correlation was found between APP mRNA levels (TOT, KPI, 770 and 751) and cognitive impairment. Since AD definitive diagnosis still relies on pathological evaluation at autopsy, the present results are consistent with the hypothesis that platelet APP could be considered a potential reliable peripheral marker for studying AD and could contribute to define a signature for the presence of AD pathology.

Dissociated amyloid-beta antibody levels as a serum biomarker for the progression of Alzheimer's disease: a population-based study

With an ever growing population of aged individuals who are at risk of developing Alzheimer disease (AD), there is an urgent need for a sensitive, specific, and preferably non-invasive diagnostic standard of disease progression. Mainstream thinking suggests that early intervention is key to maximizing the opportunity for a successful treatment regimen in AD and, as such, an early and accurate means of diagnosis is essential. In this study, we applied a recently described antibody-antigen dissociation technique to samples obtained as part of a population-based analysis of the prevalence of AD. Stratified sampling and random selection strategies were combined to obtain a representative population for screening of individuals older than 55 years. Serum antibodies to amyloid-beta (Abeta)(1-42) were measured before and after antigen dissociation. The difference between the two measurements was indicated as the dissociation delta (Delta). Our analyses showed that the levels of dissociated antibody in AD patients were always significantly different from controls and that levels of Abeta antibody after dissociation, but not those of non-dissociated antibody, correlated negatively (p<0.05) with both duration of the disease and age in the AD patients. Moreover, the change in concentration of Abeta antibody from pre- to post-dissociation (i.e., the dissociation Delta) directly reflected the progression of AD in terms of both time since diagnosis and age of the patients, with a lower dissociation Delta indicating a more advanced stage of AD. Ultimately, these data suggest that dissociated Abeta antibody levels are of significant diagnostic value at the onset of the neurodegenerative process and, thereafter, may be a useful biomarker for disease progression.

Platelet serotonin concentration and monoamine oxidase type B activity in female patients in early, middle and late phase of Alzheimer's disease

Alzheimer's disease (AD) is a progressive, neurodegenerative disorder with unclear aetiology. Cognitive impairment in AD might be associated with altered serotonergic system. The aim of the study was to determine platelet serotonin (5-HT) concentrations and platelet monoamine oxidase type B (MAO-B) activity in patients with different severity of AD. Platelet 5-HT concentrations and MAO-B activity were determined spectrofluorimetrically in 74 female patients with AD (NINCDS-ADRDA, DSM-IV-TR criteria), subdivided according to the Mini Mental State Examination (MMSE) scores in three groups with a) 23 patients in early (MMSE scores 19-24), b) 23 patients in middle (MMSE 10-18), and c) 28 patients in late (MMSE 0-9) phase of AD, and in 49 age-matched healthy women. Platelet 5-HT concentrations and MAO-B activity were similar between all patients with AD and healthy subjects, but were significantly lower in patients in the late phase of AD than in other phases of AD, and in healthy controls. The significant correlations were found between MMSE scores and platelet 5-HT concentrations, MAO-B activity and age. Lower platelet 5-HT concentration and MAO-B activity in the late phase of AD suggested that these markers might indicate severity and/or clinical progress of AD.

[Biomarkers for early diagnosis of Alzheimer's disease: current update and future directions]

INTRODUCTION

The increased prevalence of the sporadic form of Alzheimer's disease (AD) has become a significant health issue in the elderly population. The need for early diagnosis is imperative because this, along with the development of novel therapeutic treatments, would permit the rapid and perhaps more efficient treatment of these debilitating disorders early on.

BACKGROUND

Over the last decade, the potential use of certain biomarkers in the cerebrospinal fluid (CSF), and more recently, in the plasma has been investigated. Among the candidates studied includes the neurotoxic amyloid beta peptide and the Tau protein. However, although these two proteins have been clearly shown to be directly related to the pathophysiology of this disorder, it has proven difficult to establish a clear relationship between plasma or CSF levels of Abeta and Tau and the incidence and severity of AD in patients. This is due in part to differences in methodologies related to the detection sensitivity, as well as the variations in the biological data and consequent interpretation of the biochemical and biological data. Peripheral cells, in particular platelets and skin fibroblasts, could be an alternative solution as peripheral biological markers for the early diagnosis of AD. These cells are easily accessible from patients. Furthermore, they would provide a means not only to validate potential therapeutic strategies, but also to study the mechanisms involved in the development of AD, including APP processing.

PERSPECTIVES

A combined strategy using both a fundamental mechanistic and an analytical approach of patient peripheral cells will allow the identification of new biological markers for AD, and hence permit immediate therapeutic strategies to be implemented.

Association of platelet-derived soluble glycoprotein VI in plasma with Alzheimer's disease

Accumulating evidence from epidemiological, clinical and experimental studies suggests that vascular risk factors and angiopathic mechanisms are involved in the pathogenesis of Alzheimer's disease (AD). Platelets could be the missing link between AD and the vasculature. Soluble glycoprotein VI (sGPVI) and beta-thromboglobulin (beta-TG) plasma and cerebrospinal fluid (CSF) levels as markers of platelet activity were measured in 30 AD patients and 20 age-matched healthy elderly controls by ELISA. The severity of dementia was assessed by mini-mental state examination (MMSE). We found in AD patients significantly decreased sGPVI plasma levels (0.55+/-0.18ng/ml) as compared to healthy controls (0.75+/-0.43ng/ml; p=0.033). In AD patients, sGPVI levels were positively correlated with beta-TG plasma levels (r=0.244, p=0.05) and with cognitive status as measured by MMSE score (r=0.271; p=0.048). In unconcentrated CSF samples, levels of beta-TG and sGPVI were below the detection limit of the assays in AD patients and healthy controls. Our results suggest an association of sGPVI with the pathogenesis of AD. These findings encourage future research into whether sGPVI plasma levels may reflect or even mediate neuroprotective mechanisms in AD.

Effects in vitro of guanidinoacetate on adenine nucleotide hydrolysis and acetylcholinesterase activity in tissues from adult rats

Guanidinoacetate methyltransferase (GAMT) deficiency is a disorder of creatine metabolism characterized by low plasma creatine concentrations in combination with elevated guanidinoacetate (GAA) concentrations. The aim of this work was to investigate the in vitro effect of guanidinoacetate in NTPDase, 5'-nucleotidase and acetylcholinesterase activities in the synaptosomes, platelets and blood of rats. The results showed that in synaptosomes the NTPDase and 5'-nucleotidase activities were inhibited significantly in the presence of GAA at concentrations of 50, 100, 150 and 200 microM (P < 0.05). However, in platelets GAA at the same concentrations caused a significant increase in the activities of these two enzymes (P < 0.05). In relation to the acetylcholinesterase activity, GAA caused a significant inhibition in the activity of this enzyme in blood at concentrations of 150 and 200 microM (P < 0.05), but did not alter the acetylcholinesterase activity in synaptosomes from the cerebral cortex. Our results suggest that alterations caused by GAA in the activities of these enzymes may contribute to the understanding of the neurological dysfunction of GAMT-deficient patients.

Aqueous humor sCD44 concentration and visual field loss in primary open-angle glaucoma

PURPOSE

To correlate aqueous humor soluble CD44 (sCD44) concentration, visual field loss, and glaucoma risk factors in primary open-angle glaucoma (POAG) patients.

METHODS

Aqueous samples were obtained by paracentesis from normal and glaucoma patients who were undergoing elective surgery and analyzed for sCD44 concentration by enzyme-linked immunosorbent assay.

RESULTS

In normal aqueous (n=124) the sCD44 concentration was 5.88+/-0.27 ng/mL, whereas in POAG aqueous (n=90) the sCD44 concentration was 12.76+/-0.66 ng/mL, a 2.2-fold increase (P<0.000001). In POAG patients with prior successful filtration surgery (n=13), the sCD44 concentration was decreased by 43% to 7.32+/-1.44 (P=0.001) in comparison with POAG patients without filtration surgery; however, the sCD44 concentration in the prior successful filtration subgroup with no medications and normal intraocular pressure was 12.62+/-3.81 (P=0.05) compared with normal. The sCD44 concentration of normal pressure glaucoma patients was 9.19+/-1.75 ng/mL, a 1.6-fold increase compared with normal (P=0.02). Race and intraocular pressure pulse amplitude were significant POAG risk factors in this cohort of patients. In both normal and POAG patients with mild and moderate visual field loss, sCD44 concentration was greater in African Americans than in whites (P=0.04).

CONCLUSIONS

sCD44 concentration in the aqueous of POAG patients correlated with the severity of visual field loss in all stages in white patients and in mild to moderate stages in African American patients. sCD44 concentration in aqueous is a possible protein biomarker of visual field loss in POAG.

Proteomic analysis of platelet alpha-granules using mass spectrometry

BACKGROUND

Platelets have three major types of secretory organelles: lysosomes, dense granules, and alpha-granules. alpha-Granules contain several adhesive proteins involved in hemostasis, as well as glycoproteins involved in inflammation, wound healing, and cell-matrix interactions. This article represents the first effort to define the platelet alpha-granule proteome using mass spectrometry (MS).

METHODS

We prepared a subcellular fraction enriched in intact alpha-granules from human platelets using sucrose gradient ultracentrifugation. alpha-Granule proteins were separated and identified using sodium dodecylsulfate polyacrylamide gel electrophoresis and liquid chromatography-tandem MS.

RESULTS

In the sucrose fraction enriched in alpha-granules, we identified 284 non-redundant proteins, 44 of which appear to be new alpha-granule proteins, on the basis of a literature review. Immunoelectron microscopy confirmed the presence of Scamp2, APLP2, ESAM and LAMA5 in platelet alpha-granules for the first time. We identified 65% of the same proteins that were detected in the platelet releasate (J. A. Coppinger et al. [Blood 2004;103: 2096-104]) as well as additional soluble and membrane proteins. Our method provides a suitable tool for analyzing the granule proteome of patients with storage pool deficiencies.

Previous treatment with ebselen and vitamin E alters adenine nucleotide hydrolysis in platelets from adult rats experimentally demyelinated with ethidium bromide

Many aspects of the relationship between the demyelinating pathology and platelet function need to be elucidated. Thus, the activity of NTPDase and 5'-nucleotidase enzymes was analyzed in platelets from rats demyelinated with ethidium bromide (EB) and previously treated with ebselen (Ebs) and vitamin E (Vit. E). The animals were divided into four groups: for ebselen, the groups were: I-control (saline), II-(saline and Ebs), III-(EB) and IV-(EB and Ebs); and for vitamin E, the groups were: I - control (saline), II-(saline and Vit. E), III-(EB) and IV-(EB and Vit. E). After 3 and 21 days, the blood was collected and the platelets were separated for enzymatic assays. For the treatment with Ebs, the NTPDase activity for ATP substrate was significantly lower in groups II, III and IV (p < 0.05) after 3 days, while after 21 days, a reduction was observed in group III (p < 0.05). ADP hydrolysis was reduced in group II (p < 0.05) and increased in group IV (p < 0.05) after 3 days, while after 21 days there was an increase in group IV (p < 0.05). In the treatment with Vit. E, ATP hydrolysis was lower in groups II, III and IV (p < 0.05) after 3 and 21 days. ADP hydrolysis was increased in group II (p < 0.05) after 3 days, and in group IV (p < 0.05) after 21 days. However, 5'-nucleotidase activity was not altered by the treatments. These findings demonstrate that NTPDase activity in platelets is diminished in demyelinating events and the treatments with Ebs and Vit. E modulated adenine nucleotide hydrolysis.

Oxidative stress: A bridge between Down's syndrome and Alzheimer's disease

Besides the genetic, biochemical and neuropathological analogies between Down's syndrome (DS) and Alzheimer's disease (AD), there is ample evidence of the involvement of oxidative stress (OS) in the pathogenesis of both disorders. The present paper reviews the publications on DS and AD in the past 10 years in light of the "gene dosage" and "two-hit" hypotheses, with regard to the alterations caused by OS in both the central nervous system and the periphery, and the main pipeline of antioxidant therapeutic strategies. OS occurs decades prior to the signature pathology and manifests as lipid, protein and DNA oxidation, and mitochondrial abnormalities. In clinical settings, the assessment of OS has traditionally been hampered by the use of assays that suffer from inherent problems related to specificity and/or sensitivity, which explains some of the conflicting results presented in this work. For DS, no scientifically proven diet or drug is yet available, and AD trials have not provided a satisfactory approach for the prevention of and therapy against OS, although most of them still need evidence-based confirmation. In the future, a balanced up-regulation of endogenous antioxidants, together with multiple exogenous antioxidant supplementation, may be expected to be one of the most promising treatment methods.

Porcine APP cDNAs: Molecular cloning and characterization, expression analysis, chromosomal localization and SNP analysis

The human amyloid precursor protein (APP) is the precursor of Abeta, a peptide with the potential to create amyloid plaques in neurons. Mutations in the human APP gene are associated with the familial form of Alzheimer's disease. In addition, differential expression of three alternative pre-mRNA APP splicing variants of 695, 751, and 770 amino acids is linked to the pathogenesis. In this study, two novel transcript variants of porcine APP have been identified, producing isoforms of 695 and 751 amino acids, respectively. These are highly homologous to APP orthologues from other vertebrate species. Expression analyses revealed that the gene is expressed in all 30 examined porcine tissues and in a selected subset of these, differential representation of the three major APP transcript variants was observed. The APP isoform of 770 amino acids clearly predominates in non-neuronal tissues while in porcine cerebellum, the APP isoforms of 695 and 770 amino acids are expressed at equivalent levels. Employing a somatic cell hybrid panel, the APP gene was mapped to porcine chromosome 13 in either the 13q41 or 13q46-q49 region. A large pig population was screened for single nucleotide polymorphisms (SNPs) in APP exon 17 and flanking intron sequences. No missense mutations were detected; however, the allele frequencies of two silent mutations and two intron polymorphisms varied significantly among breeds.

Functional Pharmacology in Human Brain

Most neurological and psychiatric disorders involve selective or preferential impairments of neurotransmitter systems. Therefore, studies of functional transmitter pathophysiology in human brain are of unique importance in view of the development of effective, mechanism-based, therapeutic modalities. It is well known that central nervous system functional proteins, including receptors, transporters, ion channels, and enzymes, can exhibit high heterogeneity in terms of structure, function, and pharmacological profile. If the existence of types and subtypes of functional proteins amplifies the possibility of developing selective drugs, such heterogeneity certainly increases the likelihood of interspecies differences. It is therefore essential, before choosing animal models to be used in preclinical pharmacology experimentation, to establish whether functionally corresponding proteins in men and animals also display identical pharmacological profiles. Because of evidence that scaffolding proteins, trafficking between plasma membrane and intracellular pools, phosphorylation and allosteric modulators can affect the function of receptors and transporters, experiments with human clones expressed in host cells where the environment of native receptors is rarely reproduced should be interpreted with caution. Thus, the use of neurosurgically removed fresh human brain tissue samples in which receptors, transporters, ion channels, and enzymes essentially retain their natural environment represents a unique experimental approach to enlarge our understanding of human brain processes and to help in the choice of appropriate animal models. Using this experimental approach, many human brain functional proteins, in particular transmitter receptors, have been characterized in terms of localization, function, and pharmacological properties.