Role of spermine in amyloid beta-peptide-associated free radical-induced neurotoxicity

Metabolomics profiling reveals distinct, sex-specific signatures in serum and brain metabolomes in mouse models of Alzheimer's disease

INTRODUCTION

Increasing evidence suggests that metabolic impairments contribute to early Alzheimer's disease (AD) mechanisms and subsequent dementia. Signals in metabolic pathways conserved across species can facilitate translation.

METHODS

We investigated differences in serum and brain metabolites between the early-onset 5XFAD and late-onset LOAD1 (APOE4.Trem2*R47H) mouse models of AD to C57BL/6J controls at 6 months of age.

RESULTS

We identified sex differences for several classes of metabolites, such as glycerophospholipids, sphingolipids, and amino acids. Metabolic signatures were notably different between brain and serum in both mouse models. The 5XFAD mice exhibited stronger differences in brain metabolites, whereas LOAD1 mice showed more pronounced differences in serum.

DISCUSSION

Several of our findings were consistent with results in humans, showing glycerophospholipids reduction in serum of apolipoprotein E (apoE) ε4 carriers and replicating the serum metabolic imprint of the APOE ε4 genotype. Our work thus represents a significant step toward translating metabolic dysregulation from model organisms to human AD.

HIGHLIGHTS

This was a metabolomic assessment of two mouse models relevant to Alzheimer's disease. Mouse models exhibit broad sex-specific metabolic differences, similar to human study cohorts. The early-onset 5XFAD mouse model primarily alters brain metabolites while the late-onset LOAD1 model primarily changes serum metabolites. Apolipoprotein E (apoE) ε4 mice recapitulate glycerophospolipid signatures of human APOE ε4 carriers in both brain and serum.

Polyamine Dysregulation and Nucleolar Disruption in Alzheimer's Disease

A hypothesis of Alzheimer's disease etiology is proposed describing how cellular stress induces excessive polyamine synthesis and recycling which can disrupt nucleoli. Polyamines are essential in nucleolar functions, such as RNA folding and ribonucleoprotein assembly. Changes in the nucleolar pool of anionic RNA and cationic polyamines acting as counterions can cause significant nucleolar dynamics. Polyamine synthesis reduces S-adenosylmethionine which, at low levels, triggers tau phosphorylation. Also, polyamine recycling reduces acetyl-CoA needed for acetylcholine, which is low in Alzheimer's disease. Extraordinary nucleolar expansion and/or contraction can disrupt epigenetic control in peri-nucleolar chromatin, such as chromosome 14 with the presenilin-1 gene; chromosome 21 with the amyloid precursor protein gene; chromosome 17 with the tau gene; chromosome 19 with the APOE4 gene; and the inactive X chromosome (Xi; aka "nucleolar satellite") with normally silent spermine synthase (polyamine synthesis) and spermidine/spermine-N1-acetyltransferase (polyamine recycling) alleles. Chromosomes 17, 19 and the Xi have high concentrations of Alu elements which can be transcribed by RNA polymerase III if positioned nucleosomes are displaced from the Alu elements. A sudden flood of Alu RNA transcripts can competitively bind nucleolin which is usually bound to Alu sequences in structural RNAs that stabilize the nucleolar heterochromatic shell. This Alu competition leads to loss of nucleolar integrity with leaking of nucleolar polyamines that cause aggregation of phosphorylated tau. The hypothesis was developed with key word searches (e.g., PubMed) using relevant terms (e.g., Alzheimer's, lupus, nucleolin) based on a systems biology approach and exploring autoimmune disease tautology, gaining synergistic insights from other diseases.

Metabolomics profiling reveals distinct, sex-specific signatures in the serum and brain metabolomes in the mouse models of Alzheimer's disease

INTRODUCTION

Increasing evidence suggests that metabolic impairments contribute to early Alzheimer's disease (AD) mechanisms and subsequent dementia. Signals in metabolic pathways conserved across species provides a promising entry point for translation. METHODS: We investigated differences of serum and brain metabolites between the early-onset 5XFAD and late-onset LOAD1 (APOE4.Trem2*R47H) mouse models of AD to C57BL/6J controls at six months of age.

RESULTS

We identified sex differences for several classes of metabolites, such as glycerophospholipids, sphingolipids, and amino acids. Metabolic signatures were notably different between brain and serum in both mouse models. The 5XFAD mice exhibited stronger differences in brain metabolites, whereas LOAD1 mice showed more pronounced differences in serum.

DISCUSSION

Several of our findings were consistent with results in humans, showing glycerophospholipids reduction in serum of APOE4 carriers and replicating the serum metabolic imprint of the APOE4 genotype. Our work thus represents a significant step towards translating metabolic dysregulation from model organisms to human AD.

Recent Development in the Understanding of Molecular and Cellular Mechanisms Underlying the Etiopathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that leads to dementia and patient death. AD is characterized by intracellular neurofibrillary tangles, extracellular amyloid beta (Aβ) plaque deposition, and neurodegeneration. Diverse alterations have been associated with AD progression, including genetic mutations, neuroinflammation, blood-brain barrier (BBB) impairment, mitochondrial dysfunction, oxidative stress, and metal ion imbalance.Additionally, recent studies have shown an association between altered heme metabolism and AD. Unfortunately, decades of research and drug development have not produced any effective treatments for AD. Therefore, understanding the cellular and molecular mechanisms underlying AD pathology and identifying potential therapeutic targets are crucial for AD drug development. This review discusses the most common alterations associated with AD and promising therapeutic targets for AD drug discovery. Furthermore, it highlights the role of heme in AD development and summarizes mathematical models of AD, including a stochastic mathematical model of AD and mathematical models of the effect of Aβ on AD. We also summarize the potential treatment strategies that these models can offer in clinical trials.

The Influence of Orthopedic Surgery on Circulating Metabolite Levels, and their Associations with the Incidence of Postoperative Delirium

The mechanisms underlying the occurrence of postoperative delirium development are unclear and measurement of plasma metabolites may improve understanding of its causes. Participants (n = 54) matched for age and gender were sampled from an observational cohort study investigating postoperative delirium. Participants were ≥65 years without a diagnosis of dementia and presented for primary elective hip or knee arthroplasty. Plasma samples collected pre- and postoperatively were grouped as either control (n = 26, aged: 75.8 ± 5.2) or delirium (n = 28, aged: 76.2 ± 5.7). Widespread changes in plasma metabolite levels occurred following surgery. The only metabolites significantly differing between corresponding control and delirium samples were ornithine and spermine. In delirium cases, ornithine was 17.6% higher preoperatively, and spermine was 12.0% higher postoperatively. Changes were not associated with various perioperative factors. In binary logistic regression modeling, these two metabolites did not confer a significantly increased risk of delirium. These findings support the hypothesis that disturbed polyamine metabolism is an underlying factor in delirium that warrants further investigation.

Targeted Metabolomic Analysis in Alzheimer's Disease Plasma and Brain Tissue in Non-Hispanic Whites

BACKGROUND

Metabolites are biological compounds reflecting the functional activity of organs and tissues. Understanding metabolic changes in Alzheimer's disease (AD) can provide insight into potential risk factors in this multifactorial disease and suggest new intervention strategies or improve non-invasive diagnosis.

OBJECTIVE

In this study, we searched for changes in AD metabolism in plasma and frontal brain cortex tissue samples and evaluated the performance of plasma measurements as biomarkers.

METHODS

This is a case-control study with two tissue cohorts: 158 plasma samples (94 AD, 64 controls; Texas Alzheimer's Research and Care Consortium - TARCC) and 71 postmortem cortex samples (35 AD, 36 controls; Banner Sun Health Research Institute brain bank). We performed targeted mass spectrometry analysis of 630 compounds (106 small molecules: UHPLC-MS/MS, 524 lipids: FIA-MS/MS) and 232 calculated metabolic indicators with a metabolomic kit (Biocrates MxP® Quant 500).

RESULTS

We discovered disturbances (FDR≤0.05) in multiple metabolic pathways in AD in both cohorts including microbiome-related metabolites with pro-toxic changes, methylhistidine metabolism, polyamines, corticosteroids, omega-3 fatty acids, acylcarnitines, ceramides, and diglycerides. In AD, plasma reveals elevated triglycerides, and cortex shows altered amino acid metabolism. A cross-validated diagnostic prediction model from plasma achieves AUC = 82% (CI95 = 75-88%); for females specifically, AUC = 88% (CI95 = 80-95%). A reduced model using 20 features achieves AUC = 79% (CI95 = 71-85%); for females AUC = 84% (CI95 = 74-92%).

CONCLUSION

Our findings support the involvement of gut environment in AD and encourage targeting multiple metabolic areas in the design of intervention strategies, including microbiome composition, hormonal balance, nutrients, and muscle homeostasis.

Spermine protects aluminium chloride and iron-induced neurotoxicity in rat model of Alzheimer's disease via attenuation of tau phosphorylation, Amyloid-β (1-42) and NF-κB pathway

Alzheimer's disease (AD) is the most prevalent type of dementia, characterized by a gradual decline in cognitive and memory functions of the aged peoples. Long-term exposure to heavy metals (aluminium and iron) cause neurotoxicity by amyloid plaques accumulation, tau phosphorylation, increased oxidative stress, neuroinflammation, and cholinergic neurons degeneration, contributes to the development of AD-like symptoms. The present research work is designed to investigate the neuroprotective effect of spermine in aluminium chloride (AlCl₃), and iron (Fe) induced AD-like symptoms in rats. Rats were administered of AlCl₃ (100 mg/kg p.o.) alone and in combination with iron (120 μg/g, p.o.) for 28 days. Spermine (5 and 10 mg/kg) through intraperitoneal (i.p.) route was given for 14 days. The recognition and spatial memory impairment were tasted using Morris water maze (MWM), actophotometer, and Novel Object Recognition test (NORT). All the rats were sacrificed on day 29, brains were isolated, and tissue homogenate was used for neuroinflammatory, biochemical, neurotransmitters, metals concentration, and nuclear factor-kappa B (NF-κB) analysis. In the present study, AlCl₃ and iron administration elevated oxidative stress, cytokines release, dysbalanced neurotransmitters concentration, and biochemical changes. Rats treated with spermine dose-dependently improved the recognition and spatial memory, attenuated proinflammatory cytokine release, and restored neurotransmitters concentration and antioxidant enzymes. Spermine also mitigated the increased beta-amyloid (Aβ42), with downregulation of tau phosphorylation. Furthermore, spermine augmented the hippocampal levels of B cell leukaemia/lymphoma-2 (Bcl-2), diminished nuclear factor-kappa B (NF-κB) and caspase-3 (casp-3) expression. Moreover, spermine exhibited the neuroprotective effect through anti-inflammatory, antioxidant, neurotransmitters restoration, anti-apoptotic Aβ42 concentration.

Chronological Metabolic Response to Intensive Phase TB Therapy in Patients with Cured and Failed Treatment Outcomes

Despite the arguable success of the standardized tuberculosis (TB) treatment regime, a significant number of patients still present with treatment failure. To improve on current TB treatment strategies, we sought to gain a better understanding of the hosts' response to TB therapy. A targeted metabolomics approach was used to compare the urinary acylcarnitine and amino acid profiles of eventually cured TB patients with those of patients presenting with a failed treatment outcome, comparing these patient groups at the time of diagnosis and at weeks 1, 2, and 4 of treatment. Among the significant metabolites identified were histidine, isoleucine, leucine, methionine, valine, proline, tyrosine, alanine, serine, and γ-aminobutyric acid. In general, metabolite fluctuations in time followed a similar pattern for both groups for most compounds but with a delayed onset or shift of the pattern in the successfully treated patient group. These time-trends detected in both groups could potentially be ascribed to a vitamin B6 deficiency and fluctuations in the oxidative stress levels and urea cycle intermediates, linked to the drug-induced inhibition and stimulation of various enzymes. The earlier onset of observed trends in the failed patients is proposed to relate to genotypic and phenotypic variations in drug metabolizing enzymes, subsequently leading to a poor treatment efficiency either due to the rise of adverse drug reactions or to insufficient concentrations of the active drug metabolites. This study emphasizes the need for a more personalized TB treatment approach, by including enzyme phenotyping and the monitoring of oxidative stress and vitamin B6 levels, for example.

Polyamines: Functions, Metabolism, and Role in Human Disease Management

Putrescine, spermine, and spermidine are the important polyamines (PAs), found in all living organisms. PAs are formed by the decarboxylation of amino acids, and they facilitate cell growth and development via different cellular responses. PAs are the integrated part of the cellular and genetic metabolism and help in transcription, translation, signaling, and post-translational modifications. At the cellular level, PA concentration may influence the condition of various diseases in the body. For instance, a high PA level is detrimental to patients suffering from aging, cognitive impairment, and cancer. The levels of PAs decline with age in humans, which is associated with different health disorders. On the other hand, PAs reduce the risk of many cardiovascular diseases and increase longevity, when taken in an optimum quantity. Therefore, a controlled diet is an easy way to maintain the level of PAs in the body. Based on the nutritional intake of PAs, healthy cell functioning can be maintained. Moreover, several diseases can also be controlled to a higher extend via maintaining the metabolism of PAs. The present review discusses the types, important functions, and metabolism of PAs in humans. It also highlights the nutritional role of PAs in the prevention of various diseases.

Alzheimer's disease as a chronic maladaptive polyamine stress response

Polyamines are nitrogen-rich polycationic ubiquitous bioactive molecules with diverse evolutionary-conserved functions. Their activity interferes with numerous genes' expression resulting in cell proliferation and signaling modulation. The intracellular levels of polyamines are precisely controlled by an evolutionary-conserved machinery. Their transient synthesis is induced by heat stress, radiation, and other traumatic stimuli in a process termed the polyamine stress response (PSR). Notably, polyamine levels decline gradually with age; and external supplementation improves lifespan in model organisms. This corresponds to cytoprotective and reactive oxygen species scavenging properties of polyamines. Paradoxically, age-associated neurodegenerative disorders are characterized by upsurge in polyamines levels, indicating polyamine pleiotropic, adaptive, and pathogenic roles. Specifically, arginase overactivation and arginine brain deprivation have been shown to play an important role in Alzheimer's disease (AD) pathogenesis. Here, we assert that a universal short-term PSR associated with acute stimuli is beneficial for survival. However, it becomes detrimental and maladaptive following chronic noxious stimuli, especially in an aging organism. Furthermore, we regard cellular senescence as an adaptive response to stress and suggest that PSR plays a central role in age-related neurodegenerative diseases' pathogenesis. Our perspective on AD proposes an inclusive reassessment of the causal relationships between the classical hallmarks and clinical manifestation. Consequently, we offer a novel treatment strategy predicated upon this view and suggest fine-tuning of arginase activity with natural inhibitors to preclude or halt the development of AD-related dementia.

Brain lipid peroxidation and alzheimer disease: Synergy between the Butterfield and Mattson laboratories

Brains from persons with Alzheimer disease (AD) and its earlier stage, amnestic mild cognitive impairment (MCI), exhibit high levels of oxidative damage, including that to phospholipids. One type of oxidative damage is lipid peroxidation, the most important index of which is protein-bound 4-hydroxy-2-trans-nonenal (HNE). This highly reactive alkenal changes the conformations and lowers the activities of brain proteins to which HNE is covalently bound. Evidence exists that suggests that lipid peroxidation is the first type of oxidative damage associated with amyloid β-peptide (Aβ), a 38-42 amino acid peptide that is highly neurotoxic and critical to the pathophysiology of AD. The Butterfield laboratory is one of, if not the, first research group to show that Aβ42 oligomers led to lipid peroxidation and to demonstrate this modification in brains of subjects with AD and MCI. The Mattson laboratory, particularly when Dr. Mattson was a faculty member at the University of Kentucky, also showed evidence for lipid peroxidation associated with Aβ peptides, mostly in in vitro systems. Consequently, there is synergy between our two laboratories. Since this special tribute issue of Aging Research Reviews is dedicated to the career of Dr. Mattson, a review of some aspects of this synergy of lipid peroxidation and its relevance to AD, as well as the role of lipid peroxidation in the progression of this dementing disorder seems germane. Accordingly, this review outlines some of the individual and/or complementary research on lipid peroxidation related to AD published from our two laboratories either separately or jointly.

Multimodal Imaging of Amyloid Plaques: Fusion of the Single-Probe Mass Spectrometry Image and Fluorescence Microscopy Image

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases. The formation of amyloid plaques by aggregated amyloid beta (Aβ) peptides is a primary event in AD pathology. Understanding the metabolomic features and related pathways is critical for studying plaque-related pathological events (e.g., cell death and neuron dysfunction). Mass spectrometry imaging (MSI), due to its high sensitivity and ability to obtain the spatial distribution of metabolites, has been applied to AD studies. However, limited studies of metabolites in amyloid plaques have been performed due to the drawbacks of the commonly used techniques such as matrix-assisted laser desorption/ionization MSI. In the current study, we obtained high spatial resolution (∼17 μm) MS images of the AD mouse brain using the Single-probe, a microscale sampling and ionization device, coupled to a mass spectrometer under ambient conditions. The adjacent slices were used to obtain fluorescence microscopy images to locate amyloid plaques. The MS image and the fluorescence microscopy image were fused to spatially correlate histological protein hallmarks with metabolomic features. The fused images produced significantly improved spatial resolution (∼5 μm), allowing for the determination of fine structures in MS images and metabolomic biomarkers representing amyloid plaques.

Polyamines in mammalian pathophysiology

Polyamines (PAs) are essential organic polycations for cell viability along the whole phylogenetic scale. In mammals, they are involved in the most important physiological processes: cell proliferation and viability, nutrition, fertility, as well as nervous and immune systems. Consequently, altered polyamine metabolism is involved in a series of pathologies. Due to their pathophysiological importance, PA metabolism has evolved to be a very robust metabolic module, interconnected with the other essential metabolic modules for gene expression and cell proliferation/differentiation. Two different PA sources exist for animals: PA coming from diet and endogenous synthesis. In the first section of this work, the molecular characteristics of PAs are presented as determinant of their roles in living organisms. In a second section, the metabolic specificities of mammalian PA metabolism are reviewed, as well as some obscure aspects on it. This second section includes information on mammalian cell/tissue-dependent PA-related gene expression and information on crosstalk with the other mammalian metabolic modules. The third section presents a synthesis of the physiological processes described as modulated by PAs in humans and/or experimental animal models, the molecular bases of these regulatory mechanisms known so far, as well as the most important gaps of information, which explain why knowledge around the specific roles of PAs in human physiology is still considered a "mysterious" subject. In spite of its robustness, PA metabolism can be altered under different exogenous and/or endogenous circumstances so leading to the loss of homeostasis and, therefore, to the promotion of a pathology. The available information will be summarized in the fourth section of this review. The different sections of this review also point out the lesser-known aspects of the topic. Finally, future prospects to advance on these still obscure gaps of knowledge on the roles on PAs on human physiopathology are discussed.

Cerebrospinal Fluid Spermidine, Glutamine and Putrescine Predict Postoperative Delirium Following Elective Orthopaedic Surgery

Delirium is a marker of brain vulnerability, associated with increasing age, pre-existing cognitive impairment and, recently, cerebrospinal fluid (CSF) biomarkers of Alzheimer’s disease. This nested case-control study used a targeted quantitative metabolomic methodology to profile the preoperative CSF of patients (n = 54) who developed delirium following arthroplasty (n = 28) and those who did not (n = 26). The aim was to identify novel preoperative markers of delirium, and to assess potential correlations with clinical data. Participants without a diagnosis of dementia (≥65 years) undergoing elective primary hip or knee arthroplasty were postoperatively assessed for delirium once-daily for three days. Groups were compared using multivariate, univariate and receiving operator characteristic (ROC) methods. Multivariate modelling using Orthogonal Partial Least Squares-Discriminant Analysis (OPLS-DA) of metabolomic data readily distinguished between delirium and control groups (R2 ≤ 0.56; Q2 ≤ 0.10). Three metabolites (spermidine, putrescine and glutamine) significantly differed between groups (P < 0.05; FDR < 0.07), and performed well as CSF biomarkers (ROC > 0.75). The biomarker performance of the two polyamines (spermidine/putrescine) was enhanced by ratio with CSF Aβ42 (ROC > 0.8), and spermidine significantly correlated with Aβ42 (pearson r = −0.32; P = 0.018). These findings suggest that spermidine and putrescine levels could be useful markers of postoperative delirium risk, particularly when combined with Aβ42, and this requires further investigation.

Targeting Polyamine Oxidase to Prevent Excitotoxicity-Induced Retinal Neurodegeneration

Dysfunction of retinal neurons is a major cause of vision impairment in blinding diseases that affect children and adults worldwide. Cellular damage resulting from polyamine catabolism has been demonstrated to be a major player in many neurodegenerative conditions. We have previously shown that inhibition of polyamine oxidase (PAO) using MDL 72527 significantly reduced retinal neurodegeneration and cell death signaling pathways in hyperoxia-mediated retinopathy. In the present study, we investigated the impact of PAO inhibition in limiting retinal neurodegeneration in a model of NMDA (N-Methyl-D-aspartate)-induced excitotoxicity. Adult mice (8–10 weeks old) were given intravitreal injections (20 nmoles) of NMDA or NMLA (N-Methyl-L-aspartate, control). Intraperitoneal injection of MDL 72527 (40 mg/kg body weight/day) or vehicle (normal saline) was given 24 h before NMDA or NMLA treatment and continued until the animals were sacrificed (varied from 1 to 7 days). Analyses of retinal ganglion cell (RGC) layer cell survival was performed on retinal flatmounts. Retinal cryostat sections were prepared for immunostaining, TUNEL assay and retinal thickness measurements. Fresh frozen retinal samples were used for Western blotting analysis. A marked decrease in the neuronal survival in the RGC layer was observed in NMDA treated retinas compared to their NMLA treated controls, as studied by NeuN immunostaining of retinal flatmounts. Treatment with MDL 72527 significantly improved survival of NeuN positive cells in the NMDA treated retinas. Excitotoxicity induced neurodegeneration was also demonstrated by reduced levels of synaptophysin and degeneration of inner retinal neurons in NMDA treated retinas compared to controls. TUNEL labeling studies showed increased cell death in the NMDA treated retinas. However, treatment with MDL 72527 markedly reduced these changes. Analysis of signaling pathways during excitotoxic injury revealed the downregulation of pro-survival signaling molecules p-ERK and p-Akt, and the upregulation of a pro-apoptotic molecule BID, which were normalized with PAO inhibition. Our data demonstrate that inhibition of polyamine oxidase blocks NMDA-induced retinal neurodegeneration and promotes cell survival, thus offering a new therapeutic target for retinal neurodegenerative disease conditions.

Temporal Effects of Neuron-specific beta-secretase 1 (BACE1) Knock-in on the Mouse Brain Metabolome: Implications for Alzheimer's Disease

Beta secretase 1 (BACE1) is an enzyme involved in the pathogenesis of Alzheimer's disease (AD). PLB4 mice are a neuron-specific human BACE1 knock-in mouse model characterized by the accumulation of extracellular Aβ and an AD-like phenotype. In this investigation brain hemispheres from 'young' (4-6 months) and 'old' (8 months) female PLB4 mice and age-matched wild-type littermates underwent targeted LC-MS/MS metabolomic profiling. Powdered lyophilized brain tissue was extracted in ethanol:PBS 85%:15% (v/v)) and a total of 187 metabolites were quantified using a targeted metabolomics methodology. Multivariate statistical analysis produced models distinguished PLB4 from wild type (WT) mice regardless of their age group. Univariate analysis (t-test) found that more brain metabolites were perturbed in 'old' PLB4 mice than 'young'. Carnosine and 8 phosphatidylcholine species were significantly decreased (p < 0.05) in 'young' PLB4 mouse brain. In 'old' PLB4 mice a total of 21 metabolites were perturbed including: leucine, creatinine, putrescine and species of acylcarnitines, lysophosphatidylcholines, phosphatidylcholines and sphingomyelin. Within the PLB4 genotype there were a range of age-dependent increases in metabolites. This study indicates that gender-specific responses occur in models of AD-like pathology, but importantly, when changes in PLB4 mice (where Aβ oligomers predominate) are compared with APP/PS1 mice (where Aβ plaques predominate) there are consistent and also divergent effects on the brain metabolome.

Polyamines: Bio-Molecules with Diverse Functions in Plant and Human Health and Disease

Biogenic amines-polyamines (PAs), particularly putrescine, spermidine and spermine are ubiquitous in all living cells. Their indispensable roles in many biochemical and physiological processes are becoming commonly known, including promoters of plant life and differential roles in human health and disease. PAs positively impact cellular functions in plants-exemplified by increasing longevity, reviving physiological memory, enhancing carbon and nitrogen resource allocation/signaling, as well as in plant development and responses to extreme environments. Thus, one or more PAs are commonly found in genomic and metabolomics studies using plants, particulary during different abiotic stresses. In humans, a general decline in PA levels with aging occurs parallel with some human health disorders. Also, high PA dose is detrimental to patients suffering from cancer, aging, innate immunity and cognitive impairment during Alzheimer and Parkinson diseases. A dichotomy exists in that while PAs may increase longevity and reduce some age-associated cardiovascular diseases, in disease conditions involving higher cellular proliferation, their intake has negative consequences. Thus, it is essential that PA levels be rigorously quantified in edible plant sources as well as in dietary meats. Such a database can be a guide for medical experts in order to recommend which foods/meats a patient may consume and which ones to avoid. Accordingly, designing both high and low polyamine diets for human consumption are in vogue, particularly in medical conditions where PA intake may be detrimental, for instance, cancer patients. In this review, literature data has been collated for the levels of the three main PAs, putrescine, spermidine and spermine, in different edible sources-vegetables, fruits, cereals, nuts, meat, sea food, cheese, milk, and eggs. Based on our analysis of vast literature, the effects of PAs in human/animal health fall into two broad, Yang and Yin, categories: beneficial for the physiological processes in healthy cells and detrimental under pathological conditions.

Pre-treatment with spermine for acute cerebral ischemia/reperfusion injuries

Acute cerebral ischemia/reperfusion injury (ACIR) rat model was used to investigate the effect of spermine on oxidative stress and apoptosis. Sixty healthy and clean male Sprague-Dawley rats were randomly divided into 3 groups: The sham-operated group (n=12), the model group (n=12) and the experiment group (n=36). The experiment group was further divided into 3 subgroups: The SPE-10 group (n=12), the SPE-25 group (n=12) and the SPE-50 group (n=12). Rats in the experimental sub-groups SPE-10, SPE-25 and SPE-50 were injected with 10, 25 and 50 mg/kg of spermine, respectively, one week before the establishment of rat models. Rats in the sham-operated and model groups were injected with 0.9% NaCl solution. We evaluated the effect of spermine on malondialdehyde (MDA) level and superoxide dismutase (SOD) activity using ELISA kits. Bax and Bcl-2 levels were measured using western blot analysis. Our results showed that after spermine injection, MDA levels markedly decreased, while SOD activity increased significantly. The variations in MDA levels and SOD activity were dose (spermine)-dependent. Bax protein levels increased significantly, while Bcl-2 levels decreased significantly after the onset of ACIR injuries. After spermine injection, there was a significant decrease in Bax levels. Bcl-2 levels in these rats markedly increased. The observed decline in Bax levels and the increase in Bcl-2 levels in the experimental groups were dose-dependent. We concluded that spermine protected nerve tissues in rats with ACIR by decreasing the MDA level, increasing SOD activity and modifying the balance between Bax and Bcl-2 proteins.

Metabolomic-guided discovery of Alzheimer's disease biomarkers from body fluid

The rapid increase in the older population has made age-related diseases like Alzheimer's disease (AD) a global concern. Given that there is still no cure for this neurodegenerative disease, the drastic growth in the number of susceptible individuals represents a major emerging threat to public health. The poor understanding of the mechanisms underlying AD is deemed the greatest stumbling block against progress in definitive diagnosis and management of this disease. There is a dire need for biomarkers that can facilitate early diagnosis, classification, prognosis, and treatment response. Efforts have been directed toward discovery of reliable and distinctive AD biomarkers but with very little success. With the recent emergence of high-throughput technology that is able to collect and catalogue vast datasets of small metabolites, metabolomics offers hope for a better understanding of AD and subsequent identification of biomarkers. This review article highlights the potential of using multiple metabolomics platforms as useful means in uncovering AD biomarkers from body fluids. © 2017 Wiley Periodicals, Inc.

Discovery of DNA dyes Hoechst 34580 and 33342 as good candidates for inhibiting amyloid beta formation: in silico and in vitro study

Combining Lipinski's rule with the docking and steered molecular dynamics simulations and using the PubChem data base of about 1.4 million compounds, we have obtained DNA dyes Hoechst 34580 and Hoechst 33342 as top-leads for the Alzheimer's disease. The binding properties of these ligands to amyloid beta (Aβ) fibril were thoroughly studied by in silico and in vitro experiments. Hoechst 34580 and Hoechst 33342 prefer to locate near hydrophobic regions with binding affinity mainly governed by the van der Waals interaction. By the Thioflavin T assay, it was found that the inhibition constant IC50 ≈ 0.86 and 0.68 μM for Hoechst 34580 and Hoechst 33342, respectively. This result qualitatively agrees with the binding free energy estimated using the molecular mechanic-Poisson Boltzmann surface area method and all-atom simulations with the AMBER-f99SB-ILDN force field and water model TIP3P. In addition, DNA dyes have the high capability to cross the blood brain barrier. Thus, both in silico and in vitro experiments have shown that Hoechst 34580 and 33342 are good candidates for treating the Alzheimer's disease by inhibiting Aβ formation.

Modulation of learning and memory by natural polyamines

Spermine and spermidine are natural polyamines that are produced mainly via decarboxylation of l-ornithine and the sequential transfer of aminopropyl groups from S-adenosylmethionine to putrescine by spermidine synthase and spermine synthase. Spermine and spermidine interact with intracellular and extracellular acidic residues of different nature, including nucleic acids, phospholipids, acidic proteins, carboxyl- and sulfate-containing polysaccharides. Therefore, multiple actions have been suggested for these polycations, including modulation of the activity of ionic channels, protein synthesis, protein kinases, and cell proliferation/death, within others. In this review we summarize these neurochemical/neurophysiological/morphological findings, particularly those that have been implicated in the improving and deleterious effects of spermine and spermidine on learning and memory of naïve animals in shock-motivated and nonshock-motivated tasks, from a historical perspective. The interaction with the opioid system, the facilitation and disruption of morphine-induced reward and the effect of polyamines and putative polyamine antagonists on animal models of cognitive diseases, such as Alzheimer's, Huntington, acute neuroinflammation and brain trauma are also reviewed and discussed. The increased production of polyamines in Alzheimer's disease and the biphasic nature of the effects of polyamines on memory and on the NMDA receptor are also considered. In light of the current literature on polyamines, which include the description of an inborn error of the metabolism characterized by mild-to moderate mental retardation and polyamine metabolism alterations in suicide completers, we can anticipate that polyamine targets may be important for the development of novel strategies and approaches for understanding the etiopathogenesis of important central disorders and their pharmacological treatment.

Alzheimer's disease-like pathology has transient effects on the brain and blood metabolome

The pathogenesis of Alzheimer's disease (AD) is complex involving multiple contributing factors. The extent to which AD pathology affects the metabolome is still not understood nor is it known how disturbances change as the disease progresses. For the first time, we have profiled longitudinally (6, 8, 10, 12, and 18 months) both the brain and plasma metabolome of APPswe/PS1deltaE9 double transgenic and wild-type mice. A total of 187 metabolites were quantified using a targeted metabolomic methodology. Multivariate statistical analysis produced models that distinguished APPswe/PS1deltaE9 from wild-type mice at 8, 10, and 12 months. Metabolic pathway analysis found perturbed polyamine metabolism in both brain and blood plasma. There were other disturbances in essential amino acids, branched-chain amino acids, and also in the neurotransmitter serotonin. Pronounced imbalances in phospholipid and acylcarnitine homeostasis were evident in 2 age groups. AD-like pathology, therefore, affects greatly on both the brain and blood metabolomes, although there appears to be a clear temporal sequence whereby changes to brain metabolites precede those in blood.

Thiosemicarbazone modification of 3-acetyl coumarin inhibits Aβ peptide aggregation and protect against Aβ-induced cytotoxicity

Aggregation of amyloid β peptide (Aβ) is an important event in the progression of Alzheimer's disease. Therefore, among the available therapeutic approaches to fight with disease, inhibition of Aβ aggregation is widely studied and one of the promising approach for the development of treatments for Alzheimer's disease. Thiosemicarbazone compounds are known for their variety of biological activities. However, the potential of thiosemicarbazone compounds towards inhibition of Aβ peptide aggregation and the subsequent toxicity is little explored. Herein, we report synthesis and x-ray crystal structure of novel compound 3-acetyl coumarin thiosemicarbazone and its efficacy toward inhibition of Aβ(1-42) peptide aggregation. Our results indicate that 3-acetyl coumarin thiosemicarbazone inhibits Aβ(1-42) peptide aggregation up to 80% compared to the parent 3-acetyl coumarin which inhibits 52%. Further, 3-acetyl coumarin thiosemicarbazone provides neuroprotection against Aβ-induced cytotoxicity in SH-SY5Y cell line. These findings indicate that thiosemicarbazone modification renders 3-acetyl coumarin neuroprotective properties.

The Chemistry of Neurodegeneration: Kinetic Data and Their Implications

We collected experimental kinetic rate constants for chemical processes responsible for the development and progress of neurodegeneration, focused on the enzymatic and non-enzymatic degradation of amine neurotransmitters and their reactive and neurotoxic metabolites. A gross scheme of neurodegeneration on the molecular level is based on two pathways. Firstly, reactive species oxidise heavy atom ions, which enhances the interaction with alpha-synuclein, thus promoting its folding to the beta form and giving rise to insoluble amyloid plaques. The latter prevents the function of vesicular transport leading to gradual neuronal death. In the second pathway, radical species, OH(·) in particular, react with the methylene groups of the apolar part of the lipid bilayer of either the cell or mitochondrial wall, resulting in membrane leakage followed by dyshomeostasis, loss of resting potential and neuron death. Unlike all other central neural system (CNS)-relevant biogenic amines, dopamine and noradrenaline are capable of a non-enzymatic auto-oxidative reaction, which produces hydrogen peroxide. This reaction is not limited to the mitochondrial membrane where scavenging enzymes, such as catalase, are located. On the other hand, dopamine and its metabolites, such as dopamine-o-quinone, dopaminechrome, 5,6-dihydroxyindole and indo-5,6-quinone, also interact directly with alpha-synuclein and reversibly inhibit plaque formation. We consider the role of the heavy metal ions, selected scavengers and scavenging enzymes, and discuss the relevance of certain foods and food supplements, including curcumin, garlic, N-acetyl cysteine, caffeine and red wine, as well as the long-term administration of non-steroid anti-inflammatory drugs and occasional tobacco smoking, that could all act toward preventing neurodegeneration. The current analysis can be employed in developing strategies for the prevention and treatment of neurodegeneration, and, hopefully, aid in the building of an overall kinetic molecular model of neurodegeneration itself.

Untargeted metabolomic analysis of human plasma indicates differentially affected polyamine and L-arginine metabolism in mild cognitive impairment subjects converting to Alzheimer's disease

This study combined high resolution mass spectrometry (HRMS), advanced chemometrics and pathway enrichment analysis to analyse the blood metabolome of patients attending the memory clinic: cases of mild cognitive impairment (MCI; n = 16), cases of MCI who upon subsequent follow-up developed Alzheimer's disease (MCI_AD; n = 19), and healthy age-matched controls (Ctrl; n = 37). Plasma was extracted in acetonitrile and applied to an Acquity UPLC HILIC (1.7μm x 2.1 x 100 mm) column coupled to a Xevo G2 QTof mass spectrometer using a previously optimised method. Data comprising 6751 spectral features were used to build an OPLS-DA statistical model capable of accurately distinguishing Ctrl, MCI and MCI_AD. The model accurately distinguished (R2 = 99.1%; Q2 = 97%) those MCI patients who later went on to develop AD. S-plots were used to shortlist ions of interest which were responsible for explaining the maximum amount of variation between patient groups. Metabolite database searching and pathway enrichment analysis indicated disturbances in 22 biochemical pathways, and excitingly it discovered two interlinked areas of metabolism (polyamine metabolism and L-Arginine metabolism) were differentially disrupted in this well-defined clinical cohort. The optimised untargeted HRMS methods described herein not only demonstrate that it is possible to distinguish these pathologies in human blood but also that MCI patients 'at risk' from AD could be predicted up to 2 years earlier than conventional clinical diagnosis. Blood-based metabolite profiling of plasma from memory clinic patients is a novel and feasible approach in improving MCI and AD diagnosis and, refining clinical trials through better patient stratification.

Ion mobility-mass spectrometry-based screening for inhibition of α- synuclein aggregation

Aberrant protein folding and formation of amyloid fibrils are associated with numerous debilitating human diseases, for which there are currently no suitable therapeutic treatments. For instance, Parkinson's disease is characterised pathologically by the intraneural accumulation of the amyloid protein α- synuclein. In order to search for new therapeutic agents that are effective in preventing the early conformational changes that precede protein aggregation, it is necessary to devise new analytical screening approaches. Here we demonstrate the use of ion mobility-mass spectrometry for screening of molecules capable of inhibiting the misfolding and aggregation of α-synuclein (specifically, the A53T human mutant). Importantly, this assay allows for the analysis of conformational changes that precede aggregation, and therefore is unique in its ability to identify inhibitors working at the earliest stages of amyloid formation. In addition, we use complementary mass spectrometry methods to probe selected protein-ligand interactions responsible for fibril inhibition.

Metabolomic screening of regional brain alterations in the APP/PS1 transgenic model of Alzheimer's disease by direct infusion mass spectrometry

The identification of pathological mechanisms underlying to Alzheimer's disease is of great importance for the discovery of potential markers for diagnosis and disease monitoring. In this study, we investigated regional metabolic alterations in brain from the APP/PS1 mice, a transgenic model that reproduces well some of the neuropathological and cognitive deficits observed in human Alzheimer's disease. For this purpose, hippocampus, cortex, cerebellum and olfactory bulbs were analyzed using a high-throughput metabolomic approach based on direct infusion mass spectrometry. Metabolic fingerprints showed significant differences between transgenic and wild-type mice in all brain tissues, being hippocampus and cortex the most affected regions. Alterations in numerous metabolites were detected including phospholipids, fatty acids, purine and pyrimidine metabolites, acylcarnitines, sterols and amino acids, among others. Furthermore, metabolic pathway analysis revealed important alterations in homeostasis of lipids, energy management, and metabolism of amino acids and nucleotides. Therefore, these findings demonstrate the potential of metabolomic screening and the use of transgenic models for understanding pathogenesis of Alzheimer's disease.

Inhibition of the polyamine system counteracts β-amyloid peptide-induced memory impairment in mice: involvement of extrasynaptic NMDA receptors

In Alzheimer's disease (AD), the β-amyloid peptide (Aβ) has been causally linked to synaptic dysfunction and cognitive impairment. Several studies have shown that N-Methyl-D-Aspartate receptors (NMDAR) activation is involved in the detrimental actions of Aβ. Polyamines, like spermidine and spermine, are positive modulators of NMDAR function and it has been shown that their levels are regulated by Aβ. In this study we show here that interruption of NMDAR modulation by polyamines through blockade of its binding site at NMDAR by arcaine (0.02 nmol/site), or inhibition of polyamine synthesis by DFMO (2.7 nmol/site), reverses Aβ25-35-induced memory impairment in mice in a novel object recognition task. Incubation of hippocampal cell cultures with Aβ25-35 (10 µM) significantly increased the nuclear accumulation of Jacob, which is a hallmark of NMDAR activation. The Aβ-induced nuclear translocation of Jacob was blocked upon application of traxoprodil (4 nM), arcaine (4 µM) or DFMO (5 µM), suggesting that activation of the polyamine binding site at NMDAR located probably at extrasynaptic sites might underlie the cognitive deficits of Aβ25-35-treated mice. Extrasynaptic NMDAR activation in primary neurons results in a stripping of synaptic contacts and simplification of neuronal cytoarchitecture. Aβ25-35 application in hippocampal primary cell cultures reduced dendritic spine density and induced alterations on spine morphology. Application of traxoprodil (4 nM), arcaine (4 µM) or DFMO (5 µM) reversed these effects of Aβ25-35. Taken together these data provide evidence that polyamine modulation of extrasynaptic NMDAR signaling might be involved in Aβ pathology.

Anti-cancer palladium complexes: a focus on PdX2L2, palladacycles and related complexes

Much success has been achieved with platinum-based chemotherapeutic agents, i.e. through interactions with DNA. The long-term application of Pt complexes is thwarted by issues, leading scientists to examine other metals such as palladium which could exhibit complementary modes of action (given emphasis wherever known). Over the last 10 years several research groups have focused on the application of an eclectic array of palladium complexes (of the type PdX2L2, palladacycles and related structures) as potential anti-cancer agents. This review therefore provides readers with an up to date account of the advances that have taken place over the past several decades.

Metabolic profiling of Alzheimer's disease brains

Alzheimer's disease (AD) is an irreversible, progressive brain disease and can be definitively diagnosed after death through an examination of senile plaques and neurofibrillary tangles in several brain regions. It is to be expected that changes in the concentration and/or localization of low-molecular-weight molecules are linked to the pathological changes that occur in AD, and determining their identity would provide valuable information regarding AD processes. Here, we propose definitive brain metabolic profiling using ultra-performance liquid chromatography coupled with electrospray time-of-flight mass spectrometry analysis. The acquired data were subjected to principal components analysis to differentiate the frontal and parietal lobes of the AD/Control groups. Significant differences in the levels of spermine and spermidine were identified using S-plot, mass spectra, databases and standards. Based on the investigation of the polyamine metabolite pathway, these data establish that the downstream metabolites of ornithine are increased, potentially implicating ornithine decarboxylase activity in AD pathology.

Cellular polyamines promote amyloid-beta (Aβ) peptide fibrillation and modulate the aggregation pathways

The cellular polyamines spermine, spermidine, and their metabolic precursor putrescine, have long been associated with cell-growth, tumor-related gene regulations, and Alzheimer's disease. Here, we show by in vitro spectroscopy and AFM imaging, that these molecules promote aggregation of amyloid-beta (Aβ) peptides into fibrils and modulate the aggregation pathways. NMR measurements showed that the three polyamines share a similar binding mode to monomeric Aβ(1-40) peptide. Kinetic ThT studies showed that already very low polyamine concentrations promote amyloid formation: addition of 10 μM spermine (normal intracellular concentration is ~1 mM) significantly decreased the lag and transition times of the aggregation process. Spermidine and putrescine additions yielded similar but weaker effects. CD measurements demonstrated that the three polyamines induce different aggregation pathways, involving different forms of induced secondary structure. This is supported by AFM images showing that the three polyamines induce Aβ(1-40) aggregates with different morphologies. The results reinforce the notion that designing suitable ligands which modulate the aggregation of Aβ peptides toward minimally toxic pathways may be a possible therapeutic strategy for Alzheimer's disease.

Curcumin binds to Aβ1-40 peptides and fibrils stronger than ibuprofen and naproxen

Binding of curcumin, naproxen, and ibuprofen to Aβ1-40 peptide and its fibrils is studied by docking method and all-atom molecular dynamics simulations. The Gromos96 43a1 force field and simple point charge model of water have been used for molecular dynamics simulations. It is shown that if the receptor is a monomer then naproxen and ibuprofen are bound to the same place that is different from the binding position of curcumin. However all of three ligands have the same binding pocket in fibrillar structures. The binding mechanism is studied in detail showing that the van der Waals interaction between ligand and receptor dominates over the electrostatic interaction. The binding free energies obtained by the molecular mechanic-Poisson-Boltzmann surface area method indicate that curcumin displays higher binding affinity than nonsteroidal anti-inflammatory drugs. Our results are in good agreement with the experiments.

α-Synuclein aggregation and modulating factors

Aggregated a-synuclein is the major component of inclusions in Parkinson's disease and other synucleinopathy brains indicating that a-syn aggregation is associated with the pathogenesis of neurodegenerative disorders. Although the mechanisms underlying a-syn aggregation and toxicity are not fully elucidated, it is clear that a-syn undergoes post-translational modifications and interacts with numerous proteins and other macromolecules, metals, hormones, neurotransmitters, drugs and poisons that can all modulate its aggregation propensity. The current and most recent findings regarding the factors modulating a-syn aggregation process are discussed in detail.

Extracellular spermine exacerbates ischemic neuronal injury through sensitization of ASIC1a channels to extracellular acidosis

Ischemic brain injury is a major problem associated with stroke. It has been increasingly recognized that acid-sensing ion channels (ASICs) contribute significantly to ischemic neuronal damage, but the underlying mechanism has remained elusive. Here, we show that extracellular spermine, one of the endogenous polyamines, exacerbates ischemic neuronal injury through sensitization of ASIC1a channels to extracellular acidosis. Pharmacological blockade of ASIC1a or deletion of the ASIC1 gene greatly reduces the enhancing effect of spermine in ischemic neuronal damage both in cultures of dissociated neurons and in a mouse model of focal ischemia. Mechanistically, spermine profoundly reduces desensitization of ASIC1a by slowing down desensitization in the open state, shifting steady-state desensitization to more acidic pH, and accelerating recovery between repeated periods of acid stimulation. Spermine-mediated potentiation of ASIC1a activity is occluded by PcTX1 (psalmotoxin 1), a specific ASIC1a inhibitor binding to its extracellular domain. Functionally, the enhanced channel activity is accompanied by increased acid-induced neuronal membrane depolarization and cytoplasmic Ca(2+) overload, which may partially explain the exacerbated neuronal damage caused by spermine. More importantly, blocking endogenous spermine synthesis significantly attenuates ischemic brain injury mediated by ASIC1a but not that by NMDA receptors. Thus, extracellular spermine contributes significantly to ischemic neuronal injury through enhancing ASIC1a activity. Our data suggest new neuroprotective strategies for stroke patients via inhibition of polyamine synthesis and subsequent spermine-ASIC interaction.

Brain neurons express ornithine decarboxylase-activating antizyme inhibitor 2 with accumulation in Alzheimer's disease

Polyamines are small cationic molecules that in adult brain are connected to neuronal signaling by regulating inward-rectifier K(+)-channels and different glutamate receptors. Antizyme inhibitors (AZINs) regulate the cellular uptake of polyamines and activate ornithine decarboxylase (ODC), the rate-limiting enzyme of polyamine synthesis. Elevated levels of ODC activity and polyamines are detected in various brain disorders including stroke and Alzheimer's disease (AD). We originally reported a novel brain- and testis-specific AZIN, called AZIN2, the distribution of which we have now studied in normal and diseased human brain by in situ hybridization and immunohistochemistry. We found the highest accumulation of AZIN2 in a pearl-on-the-string-like distribution along the axons in both the white and gray matter. AZIN2 was also detected in a vesicle-like distribution in the somas of selected cortical pyramidal neurons. Double-immunofluorescence staining revealed co-localization of AZIN2 and N-methyl D-aspartate-type glutamate receptors (NMDARs) in pyramidal neurons of the cortex. Moreover, we found accumulation of AZIN2 in brains affected by AD, but not by other neurodegenerative disorders (CADASIL or Lewy body disease). ODC activity is mostly linked to cell proliferation, whereas its regulation by AZIN2 in post-mitotically differentiated neurons of the brain apparently serves different purposes. The subcellular distribution of AZIN2 suggests a role in vesicular trafficking.

The impact of spermine synthase (SMS) mutations on brain morphology

Snyder-Robinson syndrome (SRS) is a form of X-linked mental retardation resulting from mutations in spermine synthase (SMS), which impact neurodevelopment and cognitive outcome. We obtained cerebral, cerebellum, hippocampus, and red nucleus volumes from two males with SRS and 24 age- and gender-matched typically developing controls using volumetric neuroimaging analyses. Total brain volume was enlarged in males with SRS while cerebellum, hippocampus, and red nucleus volumes tended to be reduced compared to controls. Mutations of the X chromosome may modulate the risk for mental retardation through altered early neurodevelopment, disruption in receptor function, and ongoing neural organization and plasticity. Disruption of SMS function may negatively affect regional brain volumes that subserve cognitive and motor abilities. This research provides valuable insight into the effects of polyamine function on brain development.

Amyloid beta-protein assembly as a therapeutic target of Alzheimer's disease

Alzheimer's disease (AD), the most common neurodegenerative disorder in the aged, is characterized by the cerebral deposition of fibrils formed by the amyloid beta-protein (Abeta), a 40-42 amino acid peptide. The folding of Abeta into neurotoxic oligomeric, protofibrillar, and fibrillar assemblies is hypothesized to be the key pathologic event in AD. Abeta is formed through cleavage of the Abeta precursor protein by two endoproteinases, beta-secretase and gamma-secretase, that cleave the Abeta N-terminus and C-terminus, respectively. These facts support the relevance of therapeutic strategies targeting Abeta production, assembly, clearance, and neurotoxicity. Currently, no disease-modifying therapeutic agents are available for AD patients. Instead, existing therapeutics provide only modest symptomatic benefits for a limited time. We summarize here recent efforts to produce therapeutic drugs targeting Abeta assembly. A number of approaches are being used in these efforts, including immunological, nutraceutical, and more classical medicinal chemical (peptidic inhibitors, carbohydrate-containing compounds, polyamines, "drug-like" compounds, chaperones, metal chelators, and osmolytes), and many of these have progressed to phase III clinical trails. We also discuss briefly a number of less mature, but intriguing, strategies that have therapeutic potential. Although initial trials of some disease-modifying agents have failed, we argue that substantial cause for optimism exists.

Mitochondrial dysfunction, oxidative stress, and apoptosis revealed by proteomic and transcriptomic analyses of the striata in two mouse models of Parkinson's disease

The molecular mechanisms underlying the changes in the nigrostriatal pathway in Parkinson's disease (PD) are not completely understood. Here, we use mass spectrometry and microarrays to study the proteomic and transcriptomic changes in the striatum of two mouse models of PD, induced by the distinct neurotoxins 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and methamphetamine (METH). Proteomic analyses resulted in the identification and relative quantification of 912 proteins with two or more unique peptides and 86 proteins with significant abundance changes following neurotoxin treatment. Similarly, microarray analyses revealed 181 genes with significant changes in mRNA, following neurotoxin treatment. The combined protein and gene list provides a clearer picture of the potential mechanisms underlying neurodegeneration observed in PD. Functional analysis of this combined list revealed a number of significant categories, including mitochondrial dysfunction, oxidative stress response, and apoptosis. These results constitute one of the largest descriptive data sets integrating protein and transcript changes for these neurotoxin models with many similar end point phenotypes but distinct mechanisms.