Amino acids and biogenic amines in cerebrospinal fluid of patients with Parkinson's disease

Diet and the gut microbiome in patients with Parkinson's disease

It has been suggested that gut microbiota influence Parkinson's disease (PD) via the gut-brain axis. Here, we examine associations between diet and gut microbiome composition and its predicted functional pathways in patients with PD. We assessed gut microbiota in fecal samples from 85 PD patients in central California using 16S rRNA gene sequencing. Diet quality was assessed by calculating the Healthy Eating Index 2015 (HEI-2015) based on the Diet History Questionnaire II. We examined associations of diet quality, fiber, and added sugar intake with microbial diversity, composition, taxon abundance, and predicted metagenomic profiles, adjusting for age, sex, race/ethnicity, and sequencing platform. Higher HEI scores and fiber intake were associated with an increase in putative anti-inflammatory butyrate-producing bacteria, such as the genera Butyricicoccus and Coprococcus 1. Conversely, higher added sugar intake was associated with an increase in putative pro-inflammatory bacteria, such as the genera Klebsiella. Predictive metagenomics suggested that bacterial genes involved in the biosynthesis of lipopolysaccharide decreased with higher HEI scores, whereas a simultaneous decrease in genes involved in taurine degradation indicates less neuroinflammation. We found that a healthy diet, fiber, and added sugar intake affect the gut microbiome composition and its predicted metagenomic function in PD patients. This suggests that a healthy diet may support gut microbiome that has a positive influence on PD risk and progression.

Hyperpolarization-Enhanced NMR Spectroscopy of Unaltered Biofluids Using Photo-CIDNP

The direct and unambiguous detection and identification of individual metabolite molecules present in complex biological mixtures constitute a major challenge in (bio)analytical research. In this context, nuclear magnetic resonance (NMR) spectroscopy has proven to be particularly powerful owing to its ability to provide both qualitative and quantitative atomic-level information on multiple analytes simultaneously in a noninvasive manner. Nevertheless, NMR suffers from a low inherent sensitivity and, moreover, lacks selectivity regarding the number of individual analytes to be studied in a mixture of a myriad of structurally and chemically very different molecules, e.g., metabolites in a biofluid. Here, we describe a method that circumvents these shortcomings via performing selective, photochemically induced dynamic nuclear polarization (photo-CIDNP) enhanced NMR spectroscopy on unmodified complex biological mixtures, i.e., human urine and serum, which yields a single, background-free one-dimensional NMR spectrum. In doing this, we demonstrate that photo-CIDNP experiments on unmodified complex mixtures of biological origin are feasible, can be performed straightforwardly in the native aqueous medium at physiological metabolite concentrations, and act as a spectral filter, facilitating the analysis of NMR spectra of complex biofluids. Due to its noninvasive nature, the method is fully compatible with state-of-the-art metabolomic protocols providing direct spectroscopic information on a small, carefully selected subset of clinically relevant metabolites. We anticipate that this approach, which, in addition, can be combined with existing high-throughput/high-sensitivity NMR methodology, holds great promise for further in-depth studies and development for use in metabolomics and many other areas of analytical research.

Gut microbiota-associated taurine metabolism dysregulation in a mouse model of Parkinson's disease

IMPORTANCE

PD is recognized as a multisystem disease concerning GI dysfunction and microbiota dysbiosis but still lacks ideal therapies. Recently, aberrant microbiota-derived metabolites are emerging as important participants in PD etiology. However, the alterations of gut microbiota community and serum untargeted metabolite profile have not been fully investigated in a PD mice model. Here, we discover sharply reduced levels of Lactobacillus and taurine in MPTP-treated mice. Moreover, Lactobacillus, Adlercreutzia, and taurine-related metabolites showed the most significant correlation with pathological and GI performance of PD mice. The abundances of microbial transporter and enzymes participating in the degeneration of taurine were disturbed in PD mice. Most importantly, taurine supplement ameliorates MPTP-induced motor deficits, DA neuron loss, and microglial activation. Our data highlight the impaired taurine-based microbiome-metabolism axis during the progression of PD and reveal a novel and previously unrecognized role of genera in modulating taurine metabolism.

A metabolomics study in aqueous humor discloses altered arginine metabolism in Parkinson's disease

BACKGROUND

The lack of accessible and informative biomarkers results in a delayed diagnosis of Parkinson's disease (PD), whose symptoms appear when a significant number of dopaminergic neurons have already disappeared. The retina, a historically overlooked part of the central nervous system (CNS), has gained recent attention. It has been discovered that the composition of cerebrospinal fluid influences the aqueous humor composition through microfluidic circulation. In addition, alterations found in the brain of patients with PD have a correlate in the retina. This new paradigm highlights the potential of the aqueous humor as a sample for identifying differentially concentrated metabolites that could, eventually, become biomarkers if also found altered in blood or CSF of patients. In this research we aim at analyzing the composition of the aqueous humor from healthy controls and PD patients.

METHODS

A targeted metabolomics approach with concentration determination by mass spectrometry was used. Statistical methods including principal component analysis and linear discriminants were used to select differentially concentrated metabolites that allow distinguishing patients from controls.

RESULTS

In this first metabolomics study in the aqueous humor of PD patients, elevated levels of 16 compounds were found; molecules differentially concentrated grouped into biogenic amines, amino acids, and acylcarnitines. A biogenic amine, putrescine, alone could be a metabolite capable of differentiating between PD and control samples. The altered levels of the metabolites were correlated, suggesting that the elevations stem from a common mechanism involving arginine metabolism.

CONCLUSIONS

A combination of three metabolites, putrescine, tyrosine, and carnitine was able to correctly classify healthy participants from PD patients. Altered metabolite levels suggest altered arginine metabolism. The pattern of metabolomic disturbances was not due to the levodopa-based dopamine replacement medication because one of the patients was not yet taking levodopa but a dopamine receptor agonist.

Proteomic comparison between non-purified cerebrospinal fluid and cerebrospinal fluid-derived extracellular vesicles from patients with Alzheimer's, Parkinson's and Lewy body dementia

Dementia is a leading cause of death worldwide, with increasing prevalence as global life expectancy increases. The most common neurodegenerative disorders are Alzheimer's disease (AD), dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD). With this study, we took an in-depth look at the proteome of the (non-purified) cerebrospinal fluid (CSF) and the CSF-derived extracellular vesicles (EVs) of AD, PD, PD-MCI (Parkinson's disease with mild cognitive impairment), PDD and DLB patients analysed by label-free mass spectrometry. This has led to the discovery of differentially expressed proteins that may be helpful for differential diagnosis. We observed a greater number of differentially expressed proteins in CSF-derived EV samples (N = 276) compared to non-purified CSF (N = 169), with minimal overlap between both datasets. This finding suggests that CSF-derived EV samples may be more suitable for the discovery phase of a biomarker study, due to the removal of more abundant proteins, resulting in a narrower dynamic range. As disease-specific markers, we selected a total of 39 biomarker candidates identified in non-purified CSF, and 37 biomarker candidates across the different diseases under investigation in the CSF-derived EV data. After further exploration and validation of these proteins, they can be used to further differentiate between the included dementias and may offer new avenues for research into more disease-specific pharmacological therapeutics.

Cystathionine β-Synthase Suppresses NLRP3 Inflammasome Activation via Redox Regulation in Microglia

Aims: Cystathionine β-synthase (CBS) is essential for homocysteine (Hcy) transsulfuration, yielding cysteine as a common precursor of hydrogen sulfide (H2S), glutathione (GSH), and other sulfur molecules, which produce neuroprotective effects in neurological conditions. We previously reported a disruption of microglial CBS/H2S signaling in a Parkinson's disease (PD) mouse model. Yet, it remains unclear whether CBS affects nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3 (NLRP3) inflammasome activity and other pathologies in PD. Results: Microglial CBS expression decreased after lipopolysaccharide (LPS) stimulation. Elevated GSSG (the oxidized GSH) content and decreased H2S generation were found in the brains of microglial cbs conditional-knockout (cbscKO) mice, whereas serum and brain Hcy levels remained unaltered. Moreover, microglial cbscKO mice were susceptible to NLRP3 inflammasome activation and dopaminergic neuron losses caused by LPS injection into the substantia nigra, whereas cbs overexpression or activation produced opposite effects. In vitro studies showed that cbs overexpression or activation suppressed microglial NLRP3 inflammasome activation and interleukin (IL)-1β secretion by reducing mitochondrial reactive oxygen species (mitoROS) level. Conversely, ablation of cbs enhanced NLRP3 expression and mitoROS generation and augmented microglial NLRP3 inflammasome activity in response to adenosine triphosphate challenge, which was blocked by the mitoROS scavenger. Innovation and Conclusion: The study demonstrated an elevated GSSG level and reduced H2S generation, which correlated with a susceptible status of microglia in the brain of cbscKO mice. Our findings reveal a critical role of CBS in restraining the microglial NLRP3 inflammasome by controlling redox homeostasis and highlight that activation or upregulation of CBS may become a potential strategy for PD treatment.

Metabolomics of blood reveals age-dependent pathways in Parkinson’s Disease

Background

Parkinson’s Disease (PD) is the second most frequent degenerative disorder, the risk of which increases with age. A preclinical PD diagnostic test does not exist. We identify PD blood metabolites and metabolic pathways significantly correlated with age to develop personalized age-dependent PD blood biomarkers.

Results

We found 33 metabolites producing a receiver operating characteristic (ROC) area under the curve (AUC) value of 97%. PCA revealed that they belong to three pathways with distinct age-dependent behavior: glycine, threonine and serine metabolism correlates with age only in PD patients; unsaturated fatty acids biosynthesis correlates with age only in a healthy control group; and, finally, tryptophan metabolism characterizes PD but does not correlate with age.

Conclusions

The targeted analysis of the blood metabolome proposed in this paper allowed to find specific age-related metabolites and metabolic pathways. The model offers a promising set of blood biomarkers for a personalized age-dependent approach to the early PD diagnosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00831-5.

Systematic impacts of fluoride exposure on the metabolomics of rats

Fluoride is widely present in the environment. Excessive fluoride exposure leads to fluorosis, which has become a global public health problem and will cause damage to various organs and tissues. Only a few studies focus on serum metabolomics, and there is still a lack of systematic metabolomics associated with fluorosis within the main organs. Therefore, in the current study, a non-targeted metabolomics method using gas chromatography-mass spectrometry (GC-MS) was used to research the effects of fluoride exposure on metabolites in different organs, to uncover potential biomarkers and study whether the affected metabolic pathways are related to the mechanism of fluorosis. Male Sprague-Dawley rats were randomly divided into two groups: a control group and a fluoride exposure group. GC-MS technology was used to identify metabolites. Multivariate statistical analysis identified 16, 24, 20, 20, 24, 13, 7, and 13 differential metabolites in the serum, liver, kidney, heart, hippocampus, cortex, kidney fat, and brown fat, respectively, in the two groups of rats. Fifteen metabolic pathways were affected, involving toxic mechanisms such as oxidative stress, mitochondrial damage, inflammation, and fatty acid, amino acid and energy metabolism disorders. This study provides a new perspective on the understanding of the mechanism of toxicity associated with sodium fluoride, contributing to the prevention and treatment of fluorosis.

Metabolomic strategies and biochemical analysis of the effect of processed Rehmanniae radix extract on a blood-deficient rat model

Background

Rehmanniae Radix (RR), an herb with numerous pharmacological effects, is widely used in traditional Chinese medicine for the treatment of blood deficiency syndrome, either alone or in combination with other herbs. However, the mechanism by which processed Rehmanniae Radix (PRR) improves blood enrichment efficacy has not been clearly defined.

Methods

Ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass (UPLC-Q-TOF/MS) and biochemical methods were combined to explore the hematopoietic functional mechanisms of PRR on blood deficiency in a rat model, as well as the potential active ingredient for blood enrichment efficacy. The pharmacological effects of PRR were evaluated on a rat blood deficiency model induced by cyclophosphamide in combination with 1-acetyl-2-phenylhydrazine. The blood routine index, including white blood cell (WBC), red blood cell (RBC), and platelet (PLT) counts, as well as hemoglobin (HGB) level, and the changing metabolite profile based on urine and serum were assessed. Nontargeted metabolomic studies, combined with biochemical analyses, were employed to clarify pharmacological mechanisms.

Results

PRR significantly increased the blood routine index levels and reversed the levels of SOD, GSH, and ATP. The PRR group was similar to the control group, as determined from the metabolic profile. All of the 60 biomarkers, representing the typical metabolic characteristics of the blood-deficient rat model, mainly involved energy metabolism dysfunction, the peripheral circulation system, and oxidative damage in the body. This improvement may be attributed to changes in polysaccharide and sixteen non-polysaccharide compounds in PRR, which were caused by processing RR with rice wine.

Conclusions

The strategies of integrated metabolomic and biochemical analyses were combined, revealing the biological function and effective mechanism of PRR.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03560-x.

Taurine attenuates ER stress‑associated apoptosis and catabolism in nucleus pulposus cells

Nucleus pulposus (NP) apoptosis and subsequent excessive degradation of the extracellular matrix (ECM) are key pathological characteristics of intervertebral disc degeneration (IDD). The present study aims to examine the signaling processes underlying the effects of taurine on IDD, with specific focus on endoplasmic reticulum (ER) stress-mediated apoptosis and ECM degradation, in NP cells. To clarify the role of taurine in IDD, NP cells were treated with various concentrations of taurine and IL-1β or thapsigargin (TG). Cell Counting Kit-8, western blotting, TUNEL, immunofluorescence assays and reverse transcription-quantitative PCR were applied to measure cell viability, the expression of ER stress-associated proteins (GRP78, CHOP and caspase-12), apoptosis and the levels of metabolic factors associated with ECM (MMP-1, 3, 9, ADAMTS-4, 5 and collagen II), respectively. Taurine was found to attenuate ER stress and prevent apoptosis in NP cells induced by IL-1β treatment. Additionally, taurine significantly decreased the expression of ER stress-activated glucose regulatory protein 78, C/EBP homologous protein and caspase-12. TUNEL results revealed that taurine decreased the number of apoptotic TG-treated NP cells. TG-treated NP cells also exhibited characteristics of increased ECM degradation, supported by observations of increased MMP-1, MMP-3, MMP-9 and A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4 and ADAMTS-5 expression in addition to decreased collagen-II expression. However, taurine treatment significantly reversed all indicators of excessive ECM catabolism aforementioned. These data suggest that taurine can mediate protection against apoptosis and ECM degradation in NP cells by inhibiting ER stress, implicating therapeutic potential for the treatment of IDD.

Cerebrospinal Fluid Metabolome in Parkinson's Disease and Multiple System Atrophy

Parkinson’s disease (PD) and multiple system atrophy (MSA) belong to the neurodegenerative group of synucleinopathies; differential diagnosis between PD and MSA is difficult, especially at early stages, owing to their clinical and biological similarities. Thus, there is a pressing need to identify metabolic biomarkers for these diseases. The metabolic profile of the cerebrospinal fluid (CSF) is reported to be altered in PD and MSA; however, the altered metabolites remain unclear. We created a single network with altered metabolites in PD and MSA based on the literature and assessed biological functions, including metabolic disorders of the nervous system, inflammation, concentration of ATP, and neurological disorder, through bioinformatics methods. Our in-silico prediction-based metabolic networks are consistent with Parkinsonism events. Although metabolomics approaches provide a more quantitative understanding of biochemical events underlying the symptoms of PD and MSA, limitations persist in covering molecules related to neurodegenerative disease pathways. Thus, omics data, such as proteomics and microRNA, help understand the altered metabolomes mechanism. In particular, integrated omics and machine learning approaches will be helpful to elucidate the pathological mechanisms of PD and MSA. This review discusses the altered metabolites between PD and MSA in the CSF and omics approaches to discover diagnostic biomarkers.

Taurine Stabilizing Effect on Lysozyme

Taurine is an important organic osmolyte in mammalian cells, and it weakens inflammation and oxidative stress mediated injuries in some diseases. Recently, taurine has been demonstrated to play a therapeutic role against neurodegenerative disorders, although its parallel involvement in several biochemical mechanisms makes not clear taurine specific role in these diseases. Furthermore, the stabilizing effect of this molecule in terms of protein stability is known, but not deeply investigated. In this work we explore by Circular Dichroism the stabilizing impact of taurine in lysozyme thermal denaturation and its influence in lysozyme aggregation into amyloid fibrils. Taurine even at low concentration modifies protein-protein interactions in lysozyme native state, as revealed by Small Angle X-ray Scattering experiments, and alters the amyloid aggregation pattern without completely inhibiting it, as confirmed by UV/Vis spectroscopy with Congo Red and by Atomic Force Microscopy. Evaluation of the cytotoxicities of the amyloid fibrils grown in presence or in absence of taurine is investigated on SH-SY5Y neuroblastoma cells.

Metabolomics profiling of valproic acid-induced symptoms resembling autism spectrum disorders using 1H NMR spectral analysis in rat model

Prenatal exposure to valproic acid (VPA) has been implicated in the manifestation of autism spectrum disorder (ASD)-like behavioral and functional changes both in human and rodents including mice and rats. The objective of this study was to determine metabolomics profiling and biomarkers related to VPA-induced symptoms resembling ASD using proton nuclear magnetic resonance (1H-NMR) spectral data. VPA was administered to pregnant rats at gestation day 12.5 and effects measured subsequently in male 4-week-old offspring pups. The sociability of VPA-treated animals was significantly diminished and exhibited ASD-like behavior as evidenced by reduction of social adaptation disorder and lack of social interactions. To find biomarkers related to ASD, the following were collected prefrontal brain cortices, urine bladder and blood samples directly from heart puncture. In all samples, principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) displayed significant clustering pattern differences between control and treated groups. Valine, taurine, myo-inositol, 3-hydroxybutyrate and 1,3-dihydroxyacetone were significantly decreased in brain cortices in treated rats. Serum metabolites of glucose, creatine phosphate, lactate, glutamine and threonine were significantly increased in VPA-administered animals. Urinary metabolites of pimelate, 3-hydroxyisovalerate and valerate were significantly reduced in VPA-treated rat, whereas galactose and galactonate levels were elevated. Various metabolites were associated with mitochondrial dysfunction metabolism and central nervous system disorders. Data demonstrated that VPA-induced alterations in endogenous metabolites of serum, urine, and brain cortex which might prove useful as biomarkers for symptoms resembling ASD as a model of this disorder.

Plasma Metabolite Markers of Parkinson's Disease and Atypical Parkinsonism

Differentiating between Parkinson’s disease (PD) and the atypical Parkinsonian disorders of multiple system atrophy (MSA) and progressive supranuclear palsy (PSP) is difficult clinically due to overlapping symptomatology, especially at early disease stages. Consequently, there is a need to identify metabolic markers for these diseases and to develop them into viable biomarkers. In the present investigation, solution nuclear magnetic resonance and mass spectrometry metabolomics were used to quantitatively characterize the plasma metabolomes (a total of 167 metabolites) of a cohort of 94 individuals comprising 34 PD, 12 MSA, and 17 PSP patients, as well as 31 control subjects. The distinct and statistically significant differences observed in the metabolite concentrations of the different disease and control groups enabled the identification of potential plasma metabolite markers of each disorder and enabled the differentiation between the disorders. These group-specific differences further implicate disturbances in specific metabolic pathways. The two metabolites, formic acid and succinate, were altered similarly in all three disease groups when compared to the control group, where a reduced level of formic acid suggested an effect on pyruvate metabolism, methane metabolism, and/or the kynurenine pathway, and an increased succinate level suggested an effect on the citric acid cycle and mitochondrial dysfunction.

Severe and Regionally Widespread Increases in Tissue Urea in the Human Brain Represent a Novel Finding of Pathogenic Potential in Parkinson's Disease Dementia

Widespread elevations in brain urea have, in recent years, been reported in certain types of age-related dementia, notably Alzheimer’s disease (AD) and Huntington’s disease (HD). Urea increases in these diseases are substantive, and approximate in magnitude to levels present in uraemic encephalopathy. In AD and HD, elevated urea levels are widespread, and not only in regions heavily affected by neurodegeneration. However, measurements of brain urea have not hitherto been reported in Parkinson’s disease dementia (PDD), a condition which shares neuropathological and symptomatic overlap with both AD and HD. Here we report measurements of tissue urea from nine neuropathologically confirmed regions of the brain in PDD and post-mortem delay (PMD)-matched controls, in regions including the cerebellum, motor cortex (MCX), sensory cortex, hippocampus (HP), substantia nigra (SN), middle temporal gyrus (MTG), medulla oblongata (MED), cingulate gyrus, and pons, by applying ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Urea concentrations were found to be substantively elevated in all nine regions, with average increases of 3–4-fold. Urea concentrations were remarkably consistent across regions in both cases and controls, with no clear distinction between regions heavily affected or less severely affected by neuronal loss in PDD. These urea elevations mirror those found in uraemic encephalopathy, where equivalent levels are generally considered to be pathogenic, and those previously reported in AD and HD. Increased urea is a widespread metabolic perturbation in brain metabolism common to PDD, AD, and HD, at levels equal to those seen in uremic encephalopathy. This presents a novel pathogenic mechanism in PDD, which is shared with two other neurodegenerative diseases.

A six-metabolite panel as potential blood-based biomarkers for Parkinson's disease

Characterisation and diagnosis of idiopathic Parkinson's disease (iPD) is a current challenge that hampers both clinical assessment and clinical trial development with the potential inclusion of non-PD cases. Here, we used a targeted mass spectrometry approach to quantify 38 metabolites extracted from the serum of 231 individuals. This cohort is currently one of the largest metabolomic studies including iPD patients, drug-naïve iPD, healthy controls and patients with Alzheimer's disease as a disease-specific control group. We identified six metabolites (3-hydroxykynurenine, aspartate, beta-alanine, homoserine, ornithine (Orn) and tyrosine) that are significantly altered between iPD patients and control participants. A multivariate model to predict iPD from controls had an area under the curve (AUC) of 0.905, with an accuracy of 86.2%. This panel of metabolites may serve as a potential prognostic or diagnostic assay for clinical trial prescreening, or for aiding in diagnosing pathological disease in the clinic.

Differential abnormalities of cerebrospinal fluid dopaminergic versus noradrenergic indices in synucleinopathies

The synucleinopathies Parkinson's disease (PD), multiple system atrophy (MSA), and pure autonomic failure (PAF) are characterized by intra-cytoplasmic deposition of the protein alpha-synuclein and by catecholamine depletion. PAF, which manifests with neurogenic orthostatic hypotension (nOH) and no motor signs of central neurodegeneration, can evolve into PD+nOH. The cerebrospinal fluid (CSF) levels of catecholamine metabolites may indicate central catecholamine deficiency in these synucleinopathies, but the literature is inconsistent and incomplete. In this retrospective cohort study we reviewed data about CSF catecholamines, the dopamine metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and the norepinephrine metabolites 3,4-dihydroxyphenylglycol (DHPG) and 3-methoxy-4-hydroxyphenylglycol (MHPG). The compounds were measured in 36 patients with PD, 37 patients with MSA, and 19 patients with PAF and in 38 controls. Compared to the control group, the PD, MSA, and PAF groups had decreased CSF MHPG (p < .0001 each by Dunnett's post hoc test), DHPG (p = .004; p < .0001; p < .0001) and norepinephrine (p = .017; p = .0003; p = .044). CSF HVA and DOPAC were decreased in PD (p < .0001 each) and MSA (p < .0001 each) but not in PAF. The three synucleinopathies therefore have in common in vivo evidence of central noradrenergic deficiency but differ in the extents of central dopaminergic deficiency-prominent in PD and MSA, less apparent in PAF. Data from putamen ¹⁸ F-DOPA and cardiac ¹⁸ F-dopamine neuroimaging in the same patients, post-mortem tissue catecholamines in largely separate cohorts, and review of the neuropathology literature fit with these distinctions. The results suggest a 'norepinephrine first' ascending pathogenetic sequence in synucleinopathies, with degeneration of pontine locus ceruleus noradrenergic neurons preceding the loss of midbrain substantia nigra dopaminergic neurons.

Current and Emerging MR Methods and Outcome in Rodent Models of Parkinson's Disease: A Review

Parkinson’s disease (PD) is a major neurodegenerative disease characterized by massive degeneration of the dopaminergic neurons in the substantia nigra pars compacta, α-synuclein-containing Lewy bodies, and neuroinflammation. Magnetic resonance (MR) imaging plays a crucial role in the diagnosis and monitoring of disease progression and treatment. A variety of MR methods are available to characterize neurodegeneration and other disease features such as iron accumulation and metabolic changes in animal models of PD. This review aims at giving an overview of how those physiopathological features of PD have been investigated using various MR methods in rodent models. Toxin-based and genetic-based models of PD are first described. MR methods for neurodegeneration evaluation, iron load, and metabolism alterations are then detailed, and the main findings are provided in those models. Ultimately, future directions are suggested for neuroinflammation and neuromelanin evaluations in new animal models.

Metabolomics of sebum reveals lipid dysregulation in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder, which is characterised by degeneration of distinct neuronal populations, including dopaminergic neurons of the substantia nigra. Here, we use a metabolomics profiling approach to identify changes to lipids in PD observed in sebum, a non-invasively available biofluid. We used liquid chromatography-mass spectrometry (LC-MS) to analyse 274 samples from participants (80 drug naïve PD, 138 medicated PD and 56 well matched control subjects) and detected metabolites that could predict PD phenotype. Pathway enrichment analysis shows alterations in lipid metabolism related to the carnitine shuttle, sphingolipid metabolism, arachidonic acid metabolism and fatty acid biosynthesis. This study shows sebum can be used to identify potential biomarkers for PD.

Advances of Mechanisms-Related Metabolomics in Parkinson's Disease

Parkinson's disease (PD) is a multifactorial disorder characterized by progressively debilitating dopaminergic neurodegeneration in the substantia nigra and the striatum, along with various metabolic dysfunctions and molecular abnormalities. Metabolomics is an emerging study and has been demonstrated to play important roles in describing complex human diseases by integrating endogenous and exogenous sources of alterations. Recently, an increasing amount of research has shown that metabolomics profiling holds great promise in providing unique insights into molecular pathogenesis and could be helpful in identifying candidate biomarkers for clinical detection and therapies of PD. In this review, we briefly summarize recent findings and analyze the application of molecular metabolomics in familial and sporadic PD from genetic mutations, mitochondrial dysfunction, and dysbacteriosis. We also review metabolic biomarkers to assess the functional stage and improve therapeutic strategies to postpone or hinder the disease progression.

Fidelity of the PINK1 knockout rat to oxidative stress and other characteristics of Parkinson disease

Parkinson disease (PD) is the second most common age-related neurodegenerative disease in the world, and PD significantly impacts the quality of life, especially as in general people are living longer. Because of the numerous and complex features of sporadic PD that progressively develops, it is difficult to build an ideal animal model for PD research. Genetically modified PD rodent animal models are considered as a major tool with which to study the mechanisms and potential therapeutic targets for PD. Up to now, none of the rodent animal models displays all PD characteristics. The Michael J. Fox Foundation for Parkinson's Research (MJFF) funded SAGE Laboratories to generate a PTEN-induced putative kinase-1 (PINK1) knockout (KO) rat model for familial PD using zinc finger nuclease (ZFN) technology. In the current paper, we review all papers from PubMed that report studies with PINK1 KO rats, presenting the research results, and discussing the fidelity of this rat model to PD according to its phenotypes studied by several laboratories. This review will serve as a critical reference for future studies with this rodent model, providing a better understanding of PD etiology, pathology, and potential treatment strategies.

Cystathionine-γ-lyase drives antioxidant defense in cysteine-restricted IDH1-mutant astrocytomas

BACKGROUND

Mutations in isocitrate dehydrogenase 1 or 2 (IDH1/2) define glioma subtypes and are considered primary events in gliomagenesis, impacting tumor epigenetics and metabolism. IDH enzyme activity is crucial for the generation of reducing potential in normal cells, yet the impact of the mutation on the cellular antioxidant system in glioma is not understood. The aim of this study was to determine how glutathione (GSH), the main antioxidant in the brain, is maintained in IDH1-mutant gliomas, despite an altered NADPH/NADP balance.

METHODS

Proteomics, metabolomics, metabolic tracer studies, genetic silencing, and drug targeting approaches in vitro and in vivo were applied. Analyses were done in clinical specimen of different glioma subtypes, in glioma patient-derived cell lines carrying the endogenous IDH1 mutation and corresponding orthotopic xenografts in mice.

RESULTS

We find that cystathionine-γ-lyase (CSE), the enzyme responsible for cysteine production upstream of GSH biosynthesis, is specifically upregulated in IDH1-mutant astrocytomas. CSE inhibition sensitized these cells to cysteine depletion, an effect not observed in IDH1 wild-type gliomas. This correlated with an increase in reactive oxygen species and reduced GSH synthesis. Propargylglycine (PAG), a brain-penetrant drug specifically targeting CSE, led to delayed tumor growth in mice.

CONCLUSIONS

We show that IDH1-mutant astrocytic gliomas critically rely on NADPH-independent de novo GSH synthesis via CSE to maintain the antioxidant defense, which highlights a novel metabolic vulnerability that may be therapeutically exploited.

Ethanolamine: A Potential Promoiety with Additional Effects in the Brain

Ethanolamine is a bioactive molecule found in several cells, including those in the central nervous system (CNS). In the brain, ethanolamine and ethanolamine-related molecules have emerged as prodrug moieties that can promote drug movement across the blood-brain barrier. This improvement in the ability to target drugs to the brain may also mean that in the process ethanolamine concentrations in the brain are increased enough for ethanolamine to exert its own neurological ac-tions. Ethanolamine and its associated products have various positive functions ranging from cell signaling to molecular storage, and alterations in their levels have been linked to neurodegenerative conditions such as Alzheimer's disease. This mini-review focuses on the effects of ethanolamine in the CNS and highlights the possible implications of these effects for drug design.

Mild traumatic brain injury exacerbates Parkinson's disease induced hemeoxygenase-2 expression and brain pathology: Neuroprotective effects of co-administration of TiO2 nanowired mesenchymal stem cells and cerebrolysin

Mild traumatic brain injury (mTBI) is one of the leading predisposing factors in the development of Parkinson's disease (PD). Mild or moderate TBI induces rapid production of tau protein and alpha synuclein (ASNC) in the cerebrospinal fluid (CSF) and in several brain areas. Enhanced tau-phosphorylation and ASNC alters the molecular machinery of the brain leading to PD pathology. Recent evidences show upregulation of constitutive isoform of hemeoxygenase (HO-2) in PD patients that correlates well with the brain pathology. mTBI alone induces profound upregulation of HO-2 immunoreactivity. Thus, it would be interesting to explore whether mTBI exacerbates PD pathology in relation to tau, ASNC and HO-2 expression. In addition, whether neurotrophic factors and stem cells known to reduce brain pathology in TBI could induce neuroprotection in PD following mTBI. In this review role of mesenchymal stem cells (MSCs) and cerebrolysin (CBL), a well-balanced composition of several neurotrophic factors and active peptide fragments using nanowired delivery in PD following mTBI is discussed based on our own investigation. Our results show that mTBI induces concussion exacerbates PD pathology and nanowired delivery of MSCs and CBL induces superior neuroprotection. This could be due to reduction in tau, ASNC and HO-2 expression in PD following mTBI, not reported earlier. The functional significance of our findings in relation to clinical strategies is discussed.

Cerebrospinal and blood levels of amino acids as potential biomarkers for Parkinson's disease: review and meta-analysis

BACKGROUND AND PURPOSE

The present systematic review and meta-analysis aims to establish the possible value of cerebrospinal fluid (CSF) and serum/plasma levels of amino acids as markers of Parkinson's disease (PD).

METHODS

This is a review of four databases (PubMed, Embase, MEDLINE and Web of Science - Core Collection) from 1966 to 14 March 2020, with identification of references of interest for the topic. The meta-analysis of eligible studies was done using R software package meta, following the PRISMA and MOOSE guidelines.

RESULTS

Compared with age- and sex-matched controls, PD patients showed decreased CSF levels of glutamate and taurine and increased CSF levels of tyrosine; decreased serum/plasma levels of aspartate, serine, tryptophan and lysine, and increased serum/plasma proline and homocysteine levels.

CONCLUSION

Despite the limitations of this study due to the important variability of results between different series, our findings suggest the value of CSF or serum/plasma levels of several amino acids in the discrimination of PD patients from healthy subjects, related to the levels of some amino acids.

Where Is Dopamine and how do Immune Cells See it?: Dopamine-Mediated Immune Cell Function in Health and Disease

Dopamine is well recognized as a neurotransmitter in the brain, and regulates critical functions in a variety of peripheral systems. Growing research has also shown that dopamine acts as an important regulator of immune function. Many immune cells express dopamine receptors and other dopamine related proteins, enabling them to actively respond to dopamine and suggesting that dopaminergic immunoregulation is an important part of proper immune function. A detailed understanding of the physiological concentrations of dopamine in specific regions of the human body, particularly in peripheral systems, is critical to the development of hypotheses and experiments examining the effects of physiologically relevant dopamine concentrations on immune cells. Unfortunately, the dopamine concentrations to which these immune cells would be exposed in different anatomical regions are not clear. To address this issue, this comprehensive review details the current information regarding concentrations of dopamine found in both the central nervous system and in many regions of the periphery. In addition, we discuss the immune cells present in each region, and how these could interact with dopamine in each compartment described. Finally, the review briefly addresses how changes in these dopamine concentrations could influence immune cell dysfunction in several disease states including Parkinson's disease, multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease, as well as the collection of pathologies, cognitive and motor symptoms associated with HIV infection in the central nervous system, known as NeuroHIV. These data will improve our understanding of the interactions between the dopaminergic and immune systems during both homeostatic function and in disease, clarify the effects of existing dopaminergic drugs and promote the creation of new therapeutic strategies based on manipulating immune function through dopaminergic signaling. Graphical Abstract.

Catabolism of biogenic amines in Pseudomonas species

Biogenic amines (BAs; 2-phenylethylamine, tyramine, dopamine, epinephrine, norepinephrine, octopamine, histamine, tryptamine, serotonin, agmatine, cadaverine, putrescine, spermidine, spermine and certain aliphatic amines) are widely distributed organic molecules that play basic physiological functions in animals, plants and microorganisms. Pseudomonas species can grow in media containing different BAs as carbon and energy sources, a reason why these bacteria are excellent models for studying such catabolic pathways. In this review, we analyse most of the routes used by different species of Pseudomonas (P. putida, P. aeruginosa, P. entomophila and P. fluorescens) to degrade BAs. Analysis of these pathways has led to the identification of a huge number of genes, catabolic enzymes, transport systems and regulators, as well as to understanding of their hierarchy and functional evolution. Knowledge of these pathways has allowed the design and collection of genetically manipulated microbes useful for eliminating BAs from different sources, highlighting the biotechnological applications of these studies.

Dopamine activates NF-κB and primes the NLRP3 inflammasome in primary human macrophages

Induction of innate immune genes in the brain is thought to be a major factor in the development of addiction to substances of abuse. As the major component of the innate immune system in the brain, aberrant activation of myeloid cells such as macrophages and microglia due to substance use may mediate neuroinflammation and contribute to the development of addiction. All addictive drugs modulate the dopaminergic system and our previous studies have identified dopamine as a pro-inflammatory modulator of macrophage function. However, the mechanism that mediates this effect is currently unknown. Inflammatory activation of macrophages and induction of cytokine production is often mediated by the transcription factor NF-κB, and prior studies have shown that dopamine can modulate NF-κB activity in T-cells and other non-immune cell lines. Here we demonstrated that dopamine can activate NF-κB in primary human macrophages, resulting in the induction of its downstream targets including the NLRP3 inflammasome and the inflammatory cytokine IL-1β. These data also indicate that dopamine primes but does not activate the NLRP3 inflammasome in human macrophages. Activation of NF-κB was required for dopamine-mediated increases in IL-1β, as an inhibitor of NF-κB was able to abrogate the effects of dopamine on production of these cytokines. Connecting an increase in extracellular dopamine to NF-κB activation and inflammation suggests specific intracellular targets that could be used to ameliorate the inflammatory impact of dopamine in neuroinflammatory conditions associated with myeloid cell activation such as addiction.

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Dopamine exposure primes, but does not activate the NLRP3 inflammasome.

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Inflammasome priming can be mediated, at least partially, by a dopamine-induced increase in the activation and nuclear translocation of NF-κB in primary human macrophages.

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Dopamine additively increases the impact of cytomegalovirus on NF-κB activation in macrophages.

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Dopamine priming increases IL-1β release in response to inflammasome activation.

Profiles of brain oxidative damage, ventricular alterations, and neurochemical metabolites in the striatum of PINK1 knockout rats as functions of age and gender: Relevance to Parkinson disease

Parkinson disease (PD) is the second most common neurodegenerative disease associated with aging. Dopaminergic neuronal degeneration and α-synuclein aggregation are commonly found in PD brain. Oxidative damage and inflammation often are considered as etiological factors of PD, although the detailed mechanisms still remain unknown. Gender and aging are two important risk factors to PD, and gene mutations and certain environmental factors have been implicated in this disease. The current study employed PTEN-induced putative kinase -1 (PINK1) knockout (KO) rats, since mutations in PINK-1 lead to familial PD. We evaluated the oxidative damage in the brain of PINK1 KO rats, and we used MRI and MRS to measure the ventricle sizes and neurochemical metabolite profiles in these rats as a function of age and gender. Distinct gender- and age-related alterations were found. The results are discussed with respect to the suitabililty of this unique rat as a faithful model of known characteristics of PD.

Monoaminergic Markers Across the Cognitive Spectrum of Lewy Body Disease

BACKGROUND

Lewy body disorders, including Parkinson's disease (PD), Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB), are characterized by profound central and peripheral monoaminergic dysfunction.

OBJECTIVE

To investigate whether these alterations depend on dementia status, we measured cerebrospinal fluid (CSF) and serum monoamine and metabolite levels across subgroups of the cognitive spectrum, and evaluated their marker potential afterwards.

METHODS

In total, 153 subjects were included, of which 43 healthy controls (HC), 28 PD patients with normal cognition (PD-NC), 26 patients with PD and mild cognitive impairment (PD-MCI), 18 PDD patients, and 38 DLB patients. The levels of monoamines and metabolites in paired CSF and serum samples were analyzed applying reversed-phase high-performance liquid chromatography with electrochemical detection.

RESULTS

Firstly, when comparing subgroups, CSF 3-methoxy-4-hydroxyphenylglycol (MHPG) levels were found lowest in HC and PD-NC groups and significantly higher in PDD/DLB patients. In addition, CSF 5-hydroxyindoleacetic acid (5-HIAA) levels differed significantly between HC and PD-MCI/PDD, and DLB patients (P≤0.001), but not between HC and PD-NC patients. Secondly, when performing logistic regression, it was shown that particularly CSF/serum MHPG levels and the serum MHPG to noradrenaline (NA) ratio effectively differentiated between HC and (non-)pooled PD subgroups (AUC = 0.914-0.956), and PDD and DLB patients (AUC = 0.822), respectively. Furthermore, CSF 5-HIAA was the most discriminative parameter to differentiate between PD-NC and PD-MCI (AUC = 0.808), and, PD-NC and PDD subgroups (AUC = 0.916).

CONCLUSIONS

Our data revealed that especially alterations of the noradrenergic neurotransmitter system could distinguish between Lewy body disorder subtypes, pinpointing CSF/serum MHPG and NA as potential stage markers across the cognitive spectrum.

Metabonomics study on the effect of Siwu Decoction for blood deficiency syndrome in rats using UPLC-Q/TOF-MS analysis

Siwu decoction (SWD), a traditional Chinese medicinal formula with over 1000 years of clinical history, is widely used for gynecological disease, especially blood deficiency syndrome, which is similar to anemia in modern medicine. In view of metabonomics being useful approach to investigate the potential mechanisms of action from the point of view of systems biology, in this study an ultra-performance liquid chromatography-quadrupole-time of flight mass spectrometry method was employed for a holistic evaluation of SWD on a blood-deficiency rat model induced by N-acetylphenylhydrazine and cyclophosphamide via plasma metabonomics study. Routine blood examination results showed that SWD could significantly improve the declining hemogram indices. Meanwhile, the plasma metabonomics profiles in different groups were analyzed and differentiating metabolites were primarily visualized through chemometric analysis. Seven biomarkers were identified in plasma samples of blood-deficiency rat model compared with the normal group. Five main metabolism pathways were suggested using the Kyoto Encyclopedia of Genes and Genomes Pathway Analysis and Pathway Activity Profiling algorithm analysis. This indicated that SWD played a therapeu role in blood deficiency by regulating the aberrant endogenous metabolites. To sum up, this study provides clear evidence that a metabonomics study could serve as a useful tool to elucidate the systematic therapeutic profiles and mechanisms for blood deficiency syndrome of Chinese herbal medicines.

Age- and disease-specific changes of the kynurenine pathway in Parkinson's and Alzheimer's disease

The kynurenine (Kyn) pathway, which regulates neuroinflammation and N‐methyl‐d‐aspartate receptor activation, is implicated in Parkinson’s disease (PD) and Alzheimer’s disease (AD). Age‐related changes in Kyn metabolism and altered cerebral Kyn uptake along large neutral amino acid transporters, could contribute to these diseases. To gain further insight into the role and prognostic potential of the Kyn pathway in PD and AD, we investigated systemic and cerebral Kyn metabolite production and estimations of their transporter‐mediated uptake in the brain. Kyn metabolites and large neutral amino acids were retrospectively measured in serum and cerebrospinal fluid (CSF) of clinically well‐characterized PD patients (n = 33), AD patients (n = 33), and age‐matched controls (n = 39) using solid‐phase extraction‐liquid chromatographic‐tandem mass spectrometry. Aging was disease independently associated with increased Kyn, kynurenic acid and quinolinic acid in serum and CSF. Concentrations of kynurenic acid were reduced in CSF of PD and AD patients (p = 0.001; p = 0.002) but estimations of Kyn brain uptake did not differ between diseased and controls. Furthermore, serum Kyn and quinolinic acid levels strongly correlated with their respective content in CSF and Kyn in serum negatively correlated with AD disease severity (p = 0.002). Kyn metabolites accumulated with aging in serum and CSF similarly in PD patients, AD patients, and control subjects. In contrast, kynurenic acid was strongly reduced in CSF of PD and AD patients. Differential transporter‐mediated Kyn uptake is unlikely to majorly contribute to these cerebral Kyn pathway disturbances. We hypothesize that the combination of age‐ and disease‐specific changes in cerebral Kyn pathway activity could contribute to reduced neurogenesis and increased excitotoxicity in neurodegenerative disease.

Taurine and its analogs in neurological disorders: Focus on therapeutic potential and molecular mechanisms

Taurine is a sulfur-containing amino acid and known as semi-essential in mammals and is produced chiefly by the liver and kidney. It presents in different organs, including retina, brain, heart and placenta and demonstrates extensive physiological activities within the body. In the several disease models, it attenuates inflammation- and oxidative stress-mediated injuries. Taurine also modulates ER stress, Ca2+ homeostasis and neuronal activity at the molecular level as part of its broader roles. Different cellular processes such as energy metabolism, gene expression, osmosis and quality control of protein are regulated by taurine. In addition, taurine displays potential ameliorating effects against different neurological disorders such as neurodegenerative diseases, stroke, epilepsy and diabetic neuropathy and protects against injuries and toxicities of the nervous system. Several findings demonstrate its therapeutic role against neurodevelopmental disorders, including Angelman syndrome, Fragile X syndrome, sleep-wake disorders, neural tube defects and attention-deficit hyperactivity disorder. Considering current biopharmaceutical limitations, developing novel delivery approaches and new derivatives and precursors of taurine may be an attractive option for treating neurological disorders. Herein, we present an overview on the therapeutic potential of taurine against neurological disorders and highlight clinical studies and its molecular mechanistic roles. This article also addresses the neuropharmacological potential of taurine analogs.

Visible Light Detection of Dopamine Enhanced by Cloud Point Extraction

Background:

Monitoring of DA, in the presence of other chemical analogues such as epinephrine, norepinephrine, serotonin, ascorbic acid, uric acid, catechol, phenethylamine, tyramine, and tyrosine, is crucial in the diagnosis and mechanistic understanding of human neuropathology. Therefore, the determination of DA at trace levels has become a very important analytical task, as part of health safety and forensic analysis.

Introduction:

A cloud point extraction (CPE) process was developed for the isolation and detection of dopamine in food, urine, and pharmaceutical samples.

Methods:

In this procedure, dopamine was derivatized with o-phthalaldehyde (OPA) and sodium sulphite in aqueous solution. The isoindole derivative was synthesized by the reaction of OPA and sodium sulphite with the amino group of dopamine and the resulted isoindole derivatives were extracted by cloud point extraction. After extraction process, the concentration of enriched analyte was measured by UV-VIS spectrophotometry. The parameters affecting the CPE such as concentration of surfactant and electrolyte, equilibration temperature and time and pH of sample solution were investigated.

Results:

After optimization of the CPE conditions, the linear range of 8-80 µM (without extraction 100- 1000 µM) was established for dopamine with detection limit at 2.6 µM.

Conclusion:

The developed extraction procedure was applied to the quantification of dopamine in chocolate, urine, and pharmaceutical samples. The study ensures a promising strategy for the detection of dopamine in the presence of biological constituents, e.g. ascorbic acid, uric acid, and serotonin.

Histamine catabolism in Pseudomonas putida U: identification of the genes, catabolic enzymes and regulators

In this study, the catabolic pathway required for the degradation of the biogenic amine histamine (Hin) was genetically and biochemically characterized in Pseudomonas putida U. The 11 proteins (HinABCDGHFLIJK) that participate in this pathway are encoded by genes belonging to three loci hin1, hin2 and hin3 and by the gene hinK. The enzymes HinABCD catalyze the transport and oxidative deamination of histamine to 4-imidazoleacetic acid (ImAA). This reaction is coupled to those of other well-known enzymatic systems (DadXAR and CoxBA-C) that ensure both the recovery of the pyruvate required for Hin deamination and the genesis of the energy needed for Hin uptake. The proteins HinGHFLKIJ catalyze the sequential transformation of ImAA to fumaric acid via N₂ -formylisoasparagine, formylaspartic acid and aspartic acid. The identified Hin pathway encompasses all the genes and proteins (transporters, energizing systems, catabolic enzymes and regulators) needed for the biological degradation of Hin. Our work was facilitated by the design and isolation of genetically engineered strains that degrade Hin or ImAA and of mutants that accumulate Ala, Asp and Hin catabolites. The implications of this research with respect to potential biotechnological applications are discussed.

Homovanillic acid and 5-hydroxyindole acetic acid as biomarkers for dementia with Lewy bodies and coincident Alzheimer's disease: An autopsy-confirmed study

Dementia with Lewy bodies (DLB) and Alzheimer’s disease (AD) are the two most common causes of dementia. Both pathologies often coexist, and AD patients with concomitant neocortical LB pathology (referred to as the Lewy body variant of AD) generally show faster cognitive decline and accelerated mortality relative to patients with pure AD. Thus, discriminating among patients with DLB, AD, and coincident DLB and AD is important in clinical practice. We examined levels of homovanillic acid (HVA), 5-hydroxyindole acetic acid (5-HIAA), tau, phosphorylated tau (p-tau), and beta-amyloid (Aβ) 1–42 in cerebrospinal fluid (CSF) to evaluate their viability as biomarkers to discriminate among different forms of dementia. We obtained a total of 3498 CSF samples from patients admitted to our hospital during the period from 1996 to 2015. Of these patients, we were able to carry out a brain autopsy in 94 cases. Finally, 78 neuropathologically diagnosed cases (10 AD, six DLB, five DLB with AD, five controls without neurological diseases, and 52 cases with other neurological diseases) were studied. CSF levels of HVA and 5-HIAA were consistently decreased in pathologically advanced Lewy body disorder (LBD; Braak LB stages >3) compared with pathologically incipient LBD (Braak LB stages <2). These results suggest that if an individual has LB pathology in the central nervous system, CSF levels of HVA and 5-HIAA may decrease after the onset of clinical symptoms. In addition, CSF levels of HVA and 5-HIAA decreased with LB pathology, and were especially low in cases of DLB and DLB with AD. Furthermore, the combination of HVA, 5-HIAA, and brain specific proteins t-tau, p-tau, and Aβ 1–42 in CSF were useful for discriminating among DLB, DLB with AD, and AD with high diagnostic accuracy.

Hypochlorite converts cysteinyl-dopamine into a cytotoxic product: A possible factor in Parkinson's Disease

The dopamine oxidation product cysteinyl-dopamine has attracted attention as a contributor to the death of dopaminergic neurons in Parkinson's disease. Treatment of cysteinyl-dopamine with hypochlorite yields an even more cytotoxic product. This product has potent redox-cycling activity and initiates production of superoxide in PC12 cells. Taurine, which scavenges hypochlorite, protects PC12 cells from cysteinyl-dopamine but not from the hypochlorite product, suggesting that the product, not cysteinyl-dopamine itself, is toxic. Furthermore, rotenone, which enhances expression of the hypochlorite-producing enzyme myeloperoxidase, increases the cytotoxicity of cysteinyl-dopamine but not of the hypochlorite product. This suggests that dopamine oxidation to cysteinyl-dopamine followed by hypochlorite-dependent conversion to a cytotoxic redox-cycling product leads to the generation of reactive oxygen species and oxidative stress and may contribute to the death of dopaminergic neurons.

L-DOPA Reverses the Increased Free Amino Acids Tissue Levels Induced by Dopamine Depletion and Rises GABA and Tyrosine in the Striatum

Perturbations in the cerebral levels of various amino acids are associated with neurological disorders, and previous studies have suggested that such alterations have a role in the motor and non-motor symptoms of Parkinson's disease. However, the direct effects of chronic L-DOPA treatment, that produces dyskinesia, on neural tissue amino acid concentrations have not been explored in detail. To evaluate whether striatal amino acid concentrations are altered in peak dose dyskinesia, 6-hydroxydopamine (6-OHDA)-lesioned hemiparkinsonian mice were treated chronically with L-DOPA and tissue amino acid concentrations were assessed by HPLC analysis. These experiments revealed that neither 6-OHDA nor L-DOPA treatment are able to alter glutamate in the striatum. However, glutamine increases after 6-OHDA and returns back to normal levels with L-DOPA treatment, suggesting increased striatal glutamatergic transmission with lack of dopamine. In addition, glycine and taurine levels are increased following dopamine denervation and restored to normal levels by L-DOPA. Interestingly, dyskinetic animals showed increased levels of GABA and tyrosine, while aspartate striatal tissue levels are not altered. Overall, our results indicate that chronic L-DOPA treatment, besides normalizing the altered levels of some amino acids after 6-OHDA, robustly increases striatal GABA and tyrosine levels which may in turn contribute to the development of L-DOPA-induced dyskinesia.

Comprehensive urinary metabolomic profiling and identification of potential noninvasive marker for idiopathic Parkinson's disease

Urine metabolic phenotyping has been associated with the development of Parkinson’s disease (PD). However, few studies using a comprehensive metabolomics approach have investigated the correlation between changes in the urinary markers and the progression of clinical symptoms in PD. A comprehensive metabolomic study with robust quality control procedures was performed using gas chromatography - mass spectrometry (GC - MS) and liquid chromatography - mass spectrometry (LC - MS) to characterize the urinary metabolic phenotypes of idiopathic PD patients at three stages (early, middle and advanced) and normal control subjects, with the aim of discovering potential urinary metabolite markers for the diagnosis of idiopathic PD. Both GC-MS and LC-MS metabolic profiles of idiopathic PD patients differed significantly from those of normal control subjects. 18 differentially expressed metabolites were identified as constituting a unique metabolic marker associated with the progression of idiopathic PD. Related metabolic pathway variations were observed in branched chain amino acid metabolism, glycine derivation, steroid hormone biosynthesis, tryptophan metabolism, and phenylalanine metabolism. Comprehensive, successive metabolomic profiling revealed changes in the urinary markers associated with progression of idiopathic PD. This profiling relies on noninvasive sampling, and is complementary to existing clinical modalities.

Reduced plasma taurine level in Parkinson's disease: association with motor severity and levodopa treatment

PURPOSE

This study aimed to evaluate the level of taurine in plasma, and its association with the severity of motor and non-motor symptoms (NMS) and chronic levodopa treatment in Parkinson's disease (PD).

PATIENTS AND METHODS

Plasma taurine level was measured in treated PD (tPD), untreated PD (ntPD) and control groups. Motor symptoms and NMS were assessed using the Unified Parkinson's Disease Rating Scale, the short form of the McGill Pain Questionnaire, the Hamilton Depression Scale, the Scale for Outcomes in Parkinson's disease for Autonomic Symptoms and the Pittsburgh Sleep Quality Index. Longtime exposure to levodopa was indicated by its approximate cumulative dosage.

RESULTS

The plasma taurine levels of PD patients were decreased when compared with controls and negatively associated with motor severity but not NMS. Moreover, tPD patients exhibited lower levels of plasma taurine than ntPD patients. Interestingly, plasma taurine levels negatively correlated with cumulative levodopa dosage in tPD. After controlling for potential confounders, the association between taurine and levodopa remained significant.

CONCLUSION

Our study supports that taurine may play important roles in the pathophysiology of PD and the disturbances caused by chronic levodopa administration.

Reduced plasma serotonin and 5-hydroxyindoleacetic acid levels in Parkinson's disease are associated with nonmotor symptoms

BACKGROUND

Accumulating evidence suggests that serotonergic system may be implicated in the pathophysiology of Parkinson's disease (PD), and particularly in nonmotor symptoms such as depression, fatigue, sleep disorders, sensory and autonomic dysfunction. This study aimed to evaluate plasma levels of serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in PD patients, and investigate their associations with nonmotor symptoms.

METHODS

Eighty-two PD patients and sixty-four controls underwent a series of clinical assessments, including Hamilton Depression Scale, Fatigue Severity Scale, Pittsburgh Sleep Quality Index, Visual Analog Scale for Pain, and Scale for Outcomes in PD for Autonomic Symptoms. Plasma 5-HT and 5-HIAA levels were measured by HPLC-ECD.

RESULTS

PD patients exhibited worse performance on nonmotor symptom scales (all P-values <0.001) and presented lower plasma levels of 5-HT (P < 0.001) and 5-HIAA (P < 0.001) than control individuals. Within the PD group, decreased concentrations of plasma 5-HT and 5-HIAA were correlated with more severe depression (r = -0.447, P < 0.001; r = -0.407, P < 0.001, respectively) and pain (r = -0.485, P < 0.001; r = -0.416, P < 0.001, respectively). After performing multiple linear regression, plasma 5-HT (P = 0.01) and 5-HIAA (P = 0.006) remained significantly associated with depression.

CONCLUSIONS

Our results suggest that serotonergic dysfunction might exist in PD, and specifically correlated with depression and pain in PD. Plasma levels of 5-HT and 5-HIAA may be considered as peripheral markers for depression in PD.

Early Expression of Parkinson's Disease-Related Mitochondrial Abnormalities in PINK1 Knockout Rats

PTEN-induced kinase 1 (PINK1) mutations are responsible for an autosomal recessive, familial form of Parkinson's disease. PINK1 protein is a Ser/Thr kinase localized to the mitochondrial membrane and is involved in many processes including mitochondrial trafficking, mitophagy, and proteasomal function. Using a new PINK1 knockout (PINK1 KO) rat model, we found altered brain metabolomic markers using magnetic resonance spectroscopy, identified changes in mitochondrial pathways with quantitative proteomics using sequential window acquisition of all theoretical spectra (SWATH) mass spectrometry, and demonstrated mitochondrial functional alterations through measurement of oxygen consumption and acidification rates. The observed alterations included reduced creatine, decreased levels of complex I of the electron transport chain, and increased proton leak in the electron transport chain in PINK1 KO rat brains. In conjunction, these results demonstrate metabolomic and mitochondrial alterations occur during the asymptomatic phase of Parkinson's disease in this model. These results indicate both potential early diagnostic markers and therapeutic pathways that can be used in PD.

Cerebrospinal fluid biochemical studies in patients with Parkinson's disease: toward a potential search for biomarkers for this disease

The blood-brain barrier supplies brain tissues with nutrients and filters certain compounds from the brain back to the bloodstream. In several neurodegenerative diseases, including Parkinson's disease (PD), there are disruptions of the blood-brain barrier. Cerebrospinal fluid (CSF) has been widely investigated in PD and in other parkinsonian syndromes with the aim of establishing useful biomarkers for an accurate differential diagnosis among these syndromes. This review article summarizes the studies reported on CSF levels of many potential biomarkers of PD. The most consistent findings are: (a) the possible role of CSF urate on the progression of the disease; (b) the possible relations of CSF total tau and phosphotau protein with the progression of PD and with the preservation of cognitive function in PD patients; (c) the possible value of CSF beta-amyloid 1-42 as a useful marker of further cognitive decline in PD patients, and (d) the potential usefulness of CSF neurofilament (NFL) protein levels in the differential diagnosis between PD and other parkinsonian syndromes. Future multicentric, longitudinal, prospective studies with long-term follow-up and neuropathological confirmation would be useful in establishing appropriate biomarkers for PD.

Characterization of metabolites determined by means of 1H HR MAS NMR in intervertebral disc degeneration

Object

The objective of this study is the identification of metabolites by means of ¹H high resolution magic angle spinning nuclear magnetic resonance (¹H HR MAS NMR) spectroscopy and the evaluation of their applicability in distinguishing between healthy and degenerated disc tissues.

Materials and methods

Differences between the metabolic profiles of healthy and degenerated disc tissues were studied by means of ¹H HR MAS NMR. Analysis was performed for 81 disc tissue samples (control samples n = 21, degenerated disc tissue samples n = 60). Twenty six metabolites (amino acids, carbohydrates, and alcohols) were identified and quantified.

Results

The results indicate that the metabolic profile of degenerated discs is characterized by the presence of 2-propanol and the absence of scyllo-inositol and taurine. The concentrations of 2-propanol and lactate increase with age.

Conclusion

PCA analysis of ex vivo ¹H HR MAS NMR data revealed the occurrence of two groups: healthy and degenerative disc tissues. The effects of insufficient nutrient supply of discs, leading to their degeneration and back pain, are discussed.

Electronic supplementary material

The online version of this article (doi:10.1007/s10334-014-0457-0) contains supplementary material, which is available to authorized users.

Presumed hydrogen sulfide-mediated neurotoxicity after streptococcus anginosus group meningitis

Hydrogen sulfide is an environmental toxicant and gaseous neurotransmitter. It is produced enterically by sulfur-reducing bacteria and invasive pathogens including Streptococcus anginosus group, Salmonella and Citrobacter. We describe putative focal hydrogen sulfide neurotoxicity after Streptococcus constellatus meningitis, treated with adjunctive sodium nitrite and hyperbaric oxygen therapy.

Analysis of neurotransmitter amino acids by CE-LIF detection in biological fluids

Neurotransmitter amino acids like Alanine (Ala), Glutamic acid (Glu), Aspartic acid (Asp), Serine (Ser), Taurine (Tau), and Glycine (Gly) are widely distributed in biological fluids and tissues and they have important physiological functions, so that the evaluation of their levels in organisms plays an essential role in physiology. We here report a new capillary electrophoresis (CE) method with laser-induced fluorescence detection by which analytes are resolved and detected in less than 12 min both in human plasma and in other samples types, such as red blood cells, urine, cultured cells, cerebrospinal fluid, saliva, and vitreous humor, thus avoiding the typical limitations of the other methods normally suitable only in one or two matrix types.

Biomarkers, mechanisms, and potential prevention of catecholamine neuron loss in Parkinson disease

This chapter is on biomarkers, mechanisms, and potential treatment of catecholamine neuron loss in Parkinson disease (PD). PD is characterized by a movement disorder from loss of nigrostriatal dopamine neurons. An intense search is going on for biomarkers of the disease process. Theoretically, cerebrospinal fluid (CSF) levels of the deaminated DA metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), should be superior to other neurochemical indices of loss of central dopamine. CSF DOPAC is low in PD-even in patients with recent onset of Parkinsonism. Cardiac norepinephrine depletion is as severe as the loss of putamen dopamine. PD importantly involves nonmotor manifestations, including anosmia, dementia, REM behavior disorder, and orthostatic hypotension, and all of these nonmotor features are associated with neuroimaging evidence for cardiac sympathetic denervation, which seems to occur independently of the movement disorder and striatal dopaminergic lesion. Analogy to a bank robber's getaway car conveys the catecholaldehyde hypothesis, according to which buildup of the dopamine metabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL), the immediate product of the action of monoamine oxidase on cytosolic dopamine, causes or contributes to the death of dopamine neurons. Decreased vesicular uptake of dopamine and decreased DOPAL detoxification by aldehyde dehydrogenase (ALDH) determine this buildup. Vesicular uptake is also markedly decreased in the heart in PD. Multiple factors influence vesicular uptake and ALDH activity. Evidence is accruing for aging-related induction of positive feedback loops and an autotoxic final common pathway in the death of catecholamine neurons, mediated by metabolites produced continuously in neuronal life. The catecholaldehyde hypothesis also leads to testable experimental therapeutic ideas.