Analysis of human cerebrospinal fluid monoamines and their cofactors by HPLC

Cerebrospinal Fluid Homovanillic and 5-Hydroxyindoleacetic Acids in a Large Pediatric Population; Establishment of Reference Intervals and Impact of Disease and Medication

BACKGROUND

Cerebrospinal fluid (CSF) homovanillic (HVA), and 5-hydroxyindoleacetic acids (5-HIAA) are biomarkers of neurological diseases affecting the dopaminergic and serotoninergic pathways. Establishing reference intervals for these metabolites faces the challenges of a lack of healthy controls and a negative correlation with age, making stratified intervals unrealistic. We propose a pipeline to determine continuous reference intervals for HVA and 5-HIAA using an indirect method. We also studied the confounding effects of different variables and explored the impact of antiepileptic and neuroleptic treatments on HVA and 5-HIAA values.

METHODS

The study used least squares regression to fit age-concentration curves from a cohort of pediatric patients (n = 1533), where the residuals represent metabolite values excluding age effect. Presuming that HVA and 5-HIAA primary deficiencies characterize a distinct subpopulation, we fitted a two-component finite mixture model in age-normalized data and set reference intervals at the central 95% of the nondeficient population.

RESULTS

Patients with primary genetic deficiencies of HVA and/or 5-HIAA consistently fall outside the proposed continuous reference intervals. Using the new continuous reference intervals reduces the number of secondary deficiencies detected compared with using stratified values. No correlations were observed between CSF HVA and 5-HIAA values across the studied drug categories (antiseizure and neuroleptic medications). In addition, biopterin values positively influenced both metabolite concentrations.

CONCLUSION

The proposed continuous reference intervals caused a substantial reduction in the number of secondary deficiencies detected, most of which demonstrated no conclusive correlations between the diseases and altered HVA and 5-HIAA values.

Novel Pseudo-Two-Dimensional 19F NMR Spectroscopy for Rapid Simultaneous Detection of Amines in Complex Mixture

Rapid detection of amines in complex mixtures presents a significant challenge. Here, we introduce a novel nuclear magnetic resonance (NMR) method for amine detection utilizing a probe with two fluorine atoms in distinct chemical environments. Upon interaction with an amine, the probe generates two atomic resonance peaks, which are used to create coordinates, revealing fluorine chemical shifts on the 19F NMR spectroscopy. This innovative approach allows for the clear distinction of amine signals in a two-dimensional plane. This method has been effectively employed in analyzing amines in pharmaceuticals and amino acids in Ophiopogon japonicus and dry white wine, providing a robust and general approach for amine analysis.

Fluorescence sensing probe based on functionalized mesoporous MOFs for non-invasive and detection of dopamine in human fluids

Abnormal amount of dopamine (DA) in human body is closely relate to various diseases, such as Parkinson's disease, pheochromocytoma. Real-time monitoring DA is crucial for disease warning, diagnosis and treatment. Currently, most methods rely on invasive blood testing for detecting DA, which is only completed with the aid of the medical staffs in hospitals. Herein, a non-invasive fluorescence visual strategy is developed for the real-time monitoring DA, based on luminescent nanoparticles and modified mesoporous zeolite imidazole framework (ZIF-8-NH2) dodecahedrons. During the reaction process, DA is enriched through the spatial configuration of ZIF-8-NH2 and hydrogen bonding effect. The luminescence of Cr3+-doped zinc gallate (ZnGa2O4:Cr3+, ZGC) is inhibited by the photo-induced electron transfer (PET) mechanism to realize sensitively detecting DA. The intelligent sensing platform based on the designed fluorescence probe and color recognition system is structured for real-time detection of DA in urine. Furthermore, a skin-fitting hydrogel patch is prepared by combining a fluorescent probe with chitosan, which enables sensitive and accurate detection of DA in sweat without the complex sample pretreatment. The non-invasive fluorescence detection method provides an effective strategy for quantitatively monitoring DA in human fluids.

Bioanalytical validation and clinical application of a liquid chromatography-tandem mass spectrometry method for the quantification of 3-orthomethyldopa, 5-hydroxytryptophan, 5-hydroxyindolacetic acid and homovanillic acid in human cerebrospinal fluid

Inherited disorders of monoamine neurotransmitters are a subset of inborn errors of metabolism affecting biochemical pathways of catecholamines, serotonin or their enzymatic cofactors. Usually, their clinical presentation is similar to those of other common neurological syndromes. For this reason, they are frequently under-recognized and misdiagnosed. Because cerebrospinal fluid concentration of catecholamine metabolites (3-orthomethyldopa and homovanillic acid) and serotonin metabolites (5-hydroxytryptophan and 5-hydroxyindolacetic acid) presents a direct correlation with their brain levels, analysis of this group of compounds is critical to reach an accurate diagnosis. Although there are several published liquid chromatography-based bioanalytical methods for the quantification of these compounds, most of them present disadvantages, making their application difficult to implement in routine clinical practice. In this study, a rapid and simple UHPLC-MS/MS method for simultaneous quantification of 3-orthomethyldopa, 5-hydroxytryptophan, 5-hydroxyindolacetic acid and homovanillic acid in human cerebrospinal fluid was validated. All the evaluated performance parameters, including linearity, carryover, accuracy and precision (within and between-day), lower limit of quantitation, recovery, matrix effect and stability under different conditions met the acceptance criteria from international guidelines. Additionally, 10 human cerebrospinal fluid samples collected via lumbar puncture from 10 pediatric patients were quantified using the validated method to assess its clinical application and diagnostic utility for inherited monoamine neurotransmitter metabolism.

Dispel some mist on circulating biopterins: measurement, physiological interval and pathophysiological implication

BACKGROUND AND AIMS

Biopterins, including tetrahydrobiopterin (BH4), dihydrobiopterin (BH2), and biopterin (B), were crucial enzyme cofactors in vivo. Despite their recognized clinical significance, there remain notable research gaps and controversies surrounding experimental outcomes. This study aims to clarify the biopterins-related issues, including analytical art, physiological intervals, and pathophysiological implications.

MATERIALS AND METHODS

A novel LC-MS/MS method was developed to comprehensively profile biopterins in plasma, utilizing chemical derivatization and cold-induced phase separation. Subsequently, apparently healthy individuals were enrolled to investigate the physiological ranges. And the relationships between biopterins and biochemical indicators were analyzed to explore the pathophysiological implications.

RESULTS

The developed method was validated as reliable for detecting biopterins across the entire physiological range. Timely anti-oxidation was found to be essential for accurate assessment of biopterins. The observed overall mean ± SDs levels were 3.51 ± 0.94, 1.54 ± 0.48, 2.45 ± 0.84 and 5.05 ± 1.14 ng/mL for BH4, BH2, BH4/BH2 and total biopterins. The status of biopterins showed interesting correlations with age, gender, hyperuricemia and overweight.

CONCLUSION

In conjunction with proper anti-oxidation, the newly developed method enables accurate determination of biopterins status in plasma. The observed physiological intervals and pathophysiological implications provide fundamental yet inspiring support for further clinical researches.

Advancements in Cerebrospinal Fluid Biosensors: Bridging the Gap from Early Diagnosis to the Detection of Rare Diseases

Cerebrospinal fluid (CSF) is a body fluid that can be used for the diagnosis of various diseases. However, CSF collection requires an invasive and painful procedure called a lumbar puncture (LP). This procedure is applied to any patient with a known risk of central nervous system (CNS) damage or neurodegenerative disease, regardless of their age range. Hence, this can be a very painful procedure, especially in infants and elderly patients. On the other hand, the detection of disease biomarkers in CSF makes diagnoses as accurate as possible. This review aims to explore novel electrochemical biosensing platforms that have impacted biomedical science. Biosensors have emerged as techniques to accelerate the detection of known biomarkers in body fluids such as CSF. Biosensors can be designed and modified in various ways and shapes according to their ultimate applications to detect and quantify biomarkers of interest. This process can also significantly influence the detection and diagnosis of CSF. Hence, it is important to understand the role of this technology in the rapidly progressing field of biomedical science.

SMN deficiency perturbs monoamine neurotransmitter metabolism in spinal muscular atrophy

Beyond motor neuron degeneration, homozygous mutations in the survival motor neuron 1 (SMN1) gene cause multiorgan and metabolic defects in patients with spinal muscular atrophy (SMA). However, the precise biochemical features of these alterations and the age of onset in the brain and peripheral organs remain unclear. Using untargeted NMR-based metabolomics in SMA mice, we identify cerebral and hepatic abnormalities related to energy homeostasis pathways and amino acid metabolism, emerging already at postnatal day 3 (P3) in the liver. Through HPLC, we find that SMN deficiency induces a drop in cerebral norepinephrine levels in overt symptomatic SMA mice at P11, affecting the mRNA and protein expression of key genes regulating monoamine metabolism, including aromatic L-amino acid decarboxylase (AADC), dopamine beta-hydroxylase (DβH) and monoamine oxidase A (MAO-A). In support of the translational value of our preclinical observations, we also discovered that SMN upregulation increases cerebrospinal fluid norepinephrine concentration in Nusinersen-treated SMA1 patients. Our findings highlight a previously unrecognized harmful influence of low SMN levels on the expression of critical enzymes involved in monoamine metabolism, suggesting that SMN-inducing therapies may modulate catecholamine neurotransmission. These results may also be relevant for setting therapeutic approaches to counteract peripheral metabolic defects in SMA.

Comprehensive Metabolic Fingerprints Characterize Neuromyelitis Optica Spectrum Disorder by Nanoparticle-Enhanced Laser Desorption/Ionization Mass Spectrometry

Timely screening of neuromyelitis optica spectrum disorder (NMOSD) and differential diagnosis from myelin oligodendrocyte glycoprotein associated disorder (MOGAD) are the keys to improving the quality of life of patients. Metabolic disturbance occurs with the development of NMOSD. Still, advanced tools are required to probe the metabolic phenotype of NMOSD. Here, we developed a fast nanoparticle-enhanced laser desorption/ionization mass spectrometry assay for multiplexing metabolic fingerprints (MFs) from trace plasma and cerebrospinal fluid (CSF) samples in 30 s. Machine learning of the plasma MFs achieved the timely screening of NMOSD from healthy donors with an area under receiver operator characteristic curve (AUROC) of 0.998, and it comprehensively revealed the dysregulated neurotransmitter and energy metabolisms. Combining comprehensive MFs from both plasma and CSF, we constructed an integrated panel for differential diagnosis of NMOSD versus MOGAD with an AUROC of 0.923. This approach demonstrated performance superior to that of human experts in classifying two diseases, especially in antibody assay-limited regions. Together, this approach provides an advanced nanomaterial-based tool for identifying vulnerable populations below the antibody threshold of aquaporin-4 positivity.

In-situ immobilization of covalent organic frameworks as stationary phase for capillary electrochromatography

A new kind of covalent organic framework (COF) was first utilized as an stationary phase for open-tubular electrochromatography (OT-CEC) by in situ synthesis immobilized method at room temperature. On the basis of our previous work, 4,4',4″-(1,3,5-Triazine-2,4,6-triyl)trianiline (TZ) and 2,5-bis(2-propyn-1-yloxy)-1,4-benzenedicarboxaldehyde (BPTA) were employed as building blocks for the synthesis of COF TZ-BPTA. The coated capillary and COF TZ-BPTA were characterized by scanning electron microscopy (SEM). Then, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were also applied to characterize COF TZ-BPTA and the modified column. In SEM, it can be seen that COF TZ-BPTA was the spherical shape and the modified capillary was covered with globular particles equably. The COF TZ-BPTA coated column exhibited good separation resolution and efficiency towards two antiepileptic drugs and other kinds of small organic molecules involving alkylbenzene, sulfonamides, polycyclic aromatic hydrocarbon (PAH), parabens, amino acids and herbicides. The maximum column efficiency was over 2.8 × 105 plates·m-1. In addition, the precisions (RSDs) of the retention times for the alkylbenzenes of intra-day runs (n = 3), inter-day runs (n = 3) and column-to-column runs (n = 3) were all less than 1.70% and separation performance was without obvious change within 100 times run. In addition, the real sample was tested on COF TZ-BPTA coated column. Hence, COF TZ-BPTA showed great potential in the separation domain.

A sensitive liquid chromatography-tandem mass spectrometry method for determination biomarkers of monoamine neurotransmitter disorders in cerebrospinal fluid

BACKGROUND

Cerebrospinal fluid (CSF) monoamine neurotransmitters, their precursors and metabolites are essential biomarkers in the diagnosis and follow-up of monoamine neurotransmitter disorders (MNDs). However, their extra low concentrations and potential instability challenge the detection method. Here, we present a method that enables simultaneous quantification of these biomarkers.

METHOD

With propyl chloroformate /n-propanol, 16 biomarkers in 50 μL of CSF were derivatized in situ within seconds under an ambient temperature. The derivatives were extracted by ethyl acetate and separated by a reverse phase column followed by mass spectrometric detection. The method was fully validated. Optimal conditions for standard solution preparation and storage, as well as CSF sample handling, were investigated. CSF samples from 200 controls and 16 patients were analyzed.

RESULTS

The derivatization reaction stabilized biomarkers and increased sensitivity. Most biomarkers were quantifiable in concentrations between 0.02 and 0.50 nmol/L that were sufficient to measure their endogenous concentrations. The intra- and inter-day imprecision were < 15% for most analytes, and accuracy ranged from 90.3% to 111.6%. The stability study showed that standard stock solutions were stable at -80 °C for six years when prepared in the protection solutions; Analytes in CSF samples were stable for 24 h on wet ice and at least two years at -80 °C; But repeated freeze-thaw should be avoided. With this method, age-dependent reference intervals for each biomarker in the pediatric population were established. Patients with MNDs were successfully identified.

CONCLUSION

The developed method is valuable for MNDs diagnosis and research, benefiting from its advantages of sensitivity, comprehensiveness, and high throughput.

Autoxidation Kinetics of Tetrahydrobiopterin-Giving Quinonoid Dihydrobiopterin the Consideration It Deserves

In humans, tetrahydrobiopterin (H4Bip) is the cofactor of several essential hydroxylation reactions which dysfunction cause very serious diseases at any age. Hence, the determination of pterins in biological media is of outmost importance in the diagnosis and monitoring of H4Bip deficiency. More than half a century after the discovery of the physiological role of H4Bip and the recent advent of gene therapy for dopamine and serotonin disorders linked to H4Bip deficiency, the quantification of quinonoid dihydrobiopterin (qH2Bip), the transient intermediate of H4Bip, has not been considered yet. This is mainly due to its short half-life, which goes from 0.9 to 5 min according to previous studies. Based on our recent disclosure of the specific MS/MS transition of qH2Bip, here, we developed an efficient HPLC-MS/MS method to achieve the separation of qH2Bip from H4Bip and other oxidation products in less than 3.5 min. The application of this method to the investigation of H4Bip autoxidation kinetics clearly shows that qH2Bip's half-life is much longer than previously reported, and mostly longer than that of H4Bip, irrespective of the considered experimental conditions. These findings definitely confirm that an accurate method of H4Bip analysis should include the quantification of qH2Bip.

Laboratory testing for mitochondrial diseases: biomarkers for diagnosis and follow-up

The currently available biomarkers generally lack the specificity and sensitivity needed for the diagnosis and follow-up of patients with mitochondrial diseases (MDs). In this group of rare genetic disorders (mutations in approximately 350 genes associated with MDs), all clinical presentations, ages of disease onset and inheritance types are possible. Blood, urine, and cerebrospinal fluid surrogates are well-established biomarkers that are used in clinical practice to assess MD. One of the main challenges is validating specific and sensitive biomarkers for the diagnosis of disease and prediction of disease progression. Profiling of lactate, amino acids, organic acids, and acylcarnitine species is routinely conducted to assess MD patients. New biomarkers, including some proteins and circulating cell-free mitochondrial DNA, with increased diagnostic specificity have been identified in the last decade and have been proposed as potentially useful in the assessment of clinical outcomes. Despite these advances, even these new biomarkers are not sufficiently specific and sensitive to assess MD progression, and new biomarkers that indicate MD progression are urgently needed to monitor the success of novel therapeutic strategies. In this report, we review the mitochondrial biomarkers that are currently analyzed in clinical laboratories, new biomarkers, an overview of the most common laboratory diagnostic techniques, and future directions regarding targeted versus untargeted metabolomic and genomic approaches in the clinical laboratory setting. Brief descriptions of the current methodologies are also provided.

Quantification of Monoamine Neurotransmitter Metabolites and Cofactors in Cerebrospinal Fluid: State-of-the-Art

Inborn errors of monoamine neurotransmitter metabolism are rare diseases characterized by nonspecific neurological symptoms. These symptoms appear in early childhood and correspond to movement disorders, epilepsy, sleep disorders and/or mental disability. Cerebrospinal fluid biomarkers have been identified and validated to allow specific diagnosis of these diseases. Biomarkers of inborn errors of monoamine neurotransmitter metabolites are divided in two groups: monoamine neurotransmitter metabolites and pterins. Biomarkers quantification in cerebrospinal fluid is based on high-performance liquid chromatography separation coupled to electrochemical detection, fluorescence detection, or mass spectrometry. The following article reviews the advances in the proposed routine methods for the measurement of these analytes in cerebrospinal fluid. The purpose of this review is to compare the various proposed methods in terms of sample preparation, chromatographic conditions and detection modes. Despite the broad range of proposed methods, quantification of inborn errors of monoamine neurotransmitter biomarkers remains a great challenge, given the complexity of biological fluids and the low amounts of analytes that are present in cerebrospinal fluid.

Grafting of Tetraphenylethylene on Silica Surface, Characterizations, and Their Chromatographic Performance as Reversed-Phase Stationary Phases

Surface modification is an effective way to functionalize the materials so as to get some special properties. Tetraphenylethylene (TPE) has been widely investigated as a well-known reagent which has the nature of aggregation-induced emission (AIE), but has never been reported in the liquid chromatography stationary phase. In this work, TPE-grafted silica (Sil-TPE) was obtained successfully using the derivative of 1-(4-hydroxyphenyl)-1,2,2-triphenylethylene as a ligand, and then characterized by elemental analysis, Fourier transform infrared spectra, thermogravimetric analysis, and so forth. Laser scanning confocal microscopy images reflected the AIE phenomenon of grafted TPE because the internal vibration and rotation of TPE molecules were restrained in the confined silica space. The contact angle test showed superhydrophobic properties of Sil-TPE. In order to understand thoroughly the mechanism of chromatographic performance and retention behavior for Sil-TPE, Tanaka test mixture, alkylbenzenes, polycyclic aromatic hydrocarbons (PAHs), and phenols were separated. This reveals that Sil-TPE has strong aromaticity and certain shape selectivity, especially, has excellent separation performance for PAHs and phenols. The thermodynamic properties and repeatability of Sil-TPE were further studied, which showed the stability of Sil-TPE. This work shows that TPE can be successfully grafted on silica surface and it has the potential to be a new kind of promising stationary phases in the future.

Strong Out-of-Plane Vibrations and Ultrasensitive Detection of Dopamine-like Neurotransmitters

The detection of monoamine neurotransmitters has become a vital research subject due to their high correlations with nervous system diseases, but insufficient detection precisions have obstructed diagnosis of some related diseases. Here, we focus on four monoamine neurotransmitters, dopamine, norepinephrine, epinephrine, and serotonin, to conduct their rapid and ultrasensitive detection. We find that the low-frequency (<200 cm^-1) Raman vibrations of these molecules show some sharp peaks, and their intensities are significantly stronger than those of the high-frequency side. Theoretical calculations identify these peaks to be from strong out-of-plane vibrations of the C-C single bonds at the joint point of the ring-like molecule and its side chain. Using our surface enhanced low-frequency Raman scattering substrates, we show that the detection limit of dopamine as an example can reach 10 nM in artificial cerebrospinal fluid. This work provides a useful way for ultrasensitive and rapid detection of some neurotransmitters.

Analytical Method Validation for Estimation of Neurotransmitters (Biogenic Monoamines) from Cerebrospinal Fluid Using High Performance Liquid Chromatography

Biogenic amine neurotransmitters such as serotonin and dopamine are essential for signaling in both central and peripheral nervous system. Their metabolism is a multistep pathway and any defect in this results in alteration in metabolites of serotonin 5-Hydroxyindole acetic acid (5HIAA) and dopamine homovanillic acid (HVA) and 3-O-Methyl Dopa (3-OMD). Estimation of these metabolites in cerebrospinal fluid (CSF) assists in diagnosis of neurotransmitter defects. Their estimation is technically demanding and is currently available only in referral centers. We aimed to optimize a method for analysis of 5HIAA, HVA and 3-OMD. A high performance liquid chromatography (HPLC) method with electro chemical detector (ECD) was standardized for estimation. Analysis for method validation, reference range verification and clinical correlation was performed. Linearity obtained for 5-HIAA, HVA and 3-OMD was 65.35-2615.0 nmoles/l, 68.62-2745.0 nmoles/l and 236.5-4730.0 nmoles/l respectively. The coefficient of variation for internal quality controls ranged from 5 to 14% and the external proficiency testing samples (n = 16) were within peer group range. CSF metabolite levels of samples for reference range analysis overlapped with age matched ranges reported in literature. Among the 40 suspected patients analyzed for clinical testing four were found to have a neurotransmitter defect. These patients were then confirmed with molecular testing and clinical correlation. The method is validated and can be adapted in a clinical laboratory with analytical competence in HPLC.

Kynurenine pathway in post-mortem prefrontal cortex and cerebellum in schizophrenia: relationship with monoamines and symptomatology

BACKGROUND

The cortico-cerebellar-thalamic-cortical circuit has been implicated in the emergence of psychotic symptoms in schizophrenia (SZ). The kynurenine pathway (KP) has been linked to alterations in glutamatergic and monoaminergic neurotransmission and to SZ symptomatology through the production of the metabolites quinolinic acid (QA) and kynurenic acid (KYNA).

METHODS

This work describes alterations in KP in the post-mortem prefrontal cortex (PFC) and cerebellum (CB) of 15 chronic SZ patients and 14 control subjects in PFC and 13 control subjects in CB using immunoblot for protein levels and ELISA for interleukins and QA and KYNA determinations. Monoamine metabolites were analysed by high-performance liquid chromatography and SZ symptomatology was assessed by Positive and Negative Syndrome Scale (PANSS). The association of KP with inflammatory mediators, monoamine metabolism and SZ symptomatology was explored.

RESULTS

In the PFC, the presence of the anti-inflammatory cytokine IL-10 together with IDO2 and KATII enzymes decreased in SZ, while TDO and KMO enzyme expression increased. A network interaction analysis showed that in the PFC IL-10 was coupled to the QA branch of the kynurenine pathway (TDO-KMO-QA), whereas IL-10 associated with KMO in CB. KYNA in the CB inversely correlated with negative and general PANSS psychopathology. Although there were no changes in monoamine metabolite content in the PFC in SZ, a network interaction analysis showed associations between dopamine and methoxyhydroxyphenylglycol degradation metabolite. Direct correlations were found between general PANSS psychopathology and the serotonin degradation metabolite, 5-hydroxyindoleacetic acid. Interestingly, KYNA in the CB inversely correlated with 5-hydroxyindoleacetic acid in the PFC.

CONCLUSIONS

Thus, this work found alterations in KP in two brain areas belonging to the cortico-cerebellar-thalamic-cortical circuit associated with SZ symptomatology, with a possible impact across areas in 5-HT degradation.

Inborn errors in the vitamin B6 salvage enzymes associated with neonatal epileptic encephalopathy and other pathologies

Pyridoxal 5'-phosphate (PLP), the active cofactor form of vitamin B6 is required by over 160 PLP-dependent (vitamin B6) enzymes serving diverse biological roles, such as carbohydrates, amino acids, hemes, and neurotransmitters metabolism. Three key enzymes, pyridoxal kinase (PL kinase), pyridoxine 5'-phosphate oxidase (PNPO), and phosphatases metabolize and supply PLP to PLP-dependent enzymes through the salvage pathway. In born errors in the salvage enzymes are known to cause inadequate levels of PLP in the cell, particularly in neuronal cells. The resulting PLP deficiency is known to cause or implicated in several pathologies, most notably seizures. One such disorder, PNPO-dependent neonatal epileptic encephalopathy (NEE) results from natural mutations in PNPO and leads to null or reduced enzymatic activity. NEE does not respond to conventional antiepileptic drugs but may respond to treatment with the B6 vitamers PLP and/or pyridoxine (PN). In born errors that lead to PLP deficiency in cells have also been reported in PL kinase, however, to date none has been associated with epilepsy or seizure. One such pathology is polyneuropathy that responds to PLP therapy. Phosphatase deficiency or hypophosphatasia disorder due to pathogenic mutations in alkaline phosphatase is known to cause seizures that respond to PN therapy. In this article, we review the biochemical features of in born errors pertaining to the salvage enzyme's deficiency that leads to NEE and other pathologies. We also present perspective on vitamin B6 treatment for these disorders, along with attempts to develop zebrafish model to study the NEE syndrome in vivo.

Natural α,β-unsaturated lactones inhibit neuropeptide-induced mast cell activation in an in vitro model of neurogenic inflammation

INTRODUCTION

Mast cells are involved in not only inducing, but also maintaining neurogenic inflammation and neuropathic pain. In previous work, we have demonstrated that dehydroleucodine, xanthatin and 3-benzyloxymethyl-5H-furan-2-one inhibit rat peritoneal and human LAD2 mast cell degranulation induced by compound 48/80 and calcium ionophore A23187. However, the effect of these molecules on neuropeptide-induced mast cell activation has not been studied so far.

OBJECTIVE

The aim of this study was to determine whether dehydroleucodine, xanthatin, and 3-benzyloxymethyl-5H-furan-2-one inhibit neuropeptide-induced mast cell activation.

METHODS

This work is based on in vitro simulation of a neurogenic inflammation scenario involving neuropeptides and mast cells, to subsequently analyze potential therapeutic strategies for neuropathic pain.

RESULTS

Neuromedin-N did not stimulate mast cell serotonin release but substance P and neurotensin did induce serotonin release from peritoneal mast cells in a dose-dependent manner. Mast cell serotonin release induced by substance P and neurotensin was inhibited by dehydroleucodine and xanthatin, but not by 3-benzyloxymethyl-5H-furan-2-one. The inhibitory potency of dehydroleucodine and xanthatin was higher than that obtained with the reference compounds, ketotifen and sodium chromoglycate, when mast cells were preincubated with dehydroleucodine before substance P incubation, and with dehydroleucodine or xanthatin before neurotensin incubation.

CONCLUSIONS

These results are the first strong evidence supporting the hypothesis that dehydroleucodine and xanthatin inhibit substance P- and neurotensin-induced serotonin release from rat peritoneal mast cells. Our findings suggest, additionally, that these α,β-unsaturated lactones could be of value in future pharmacological research related to inappropriate mast cell activation conditions such as neurogenic inflammation and neuropathic pain.

Effect of blood contamination of cerebrospinal fluid on amino acids, biogenic amines, pterins and vitamins

BACKGROUND

Cerebrospinal fluid (CSF) metabolomic investigations are a powerful tool for studying neurometabolic diseases. We aimed to assess the effect of CSF contamination with blood on the concentrations of selected biomarkers.

METHODS

CSF samples were spiked in duplicate with increasing volumes of whole blood under two conditions: (A) pooled CSF spiked with fresh whole blood and frozen to cause red blood cell (RBC) lysis; (B) pooled CSF spiked with fresh blood and centrifuged (the supernatant with no RBCs was frozen until the moment of analysis). CSF concentrations of amino acids, biogenic amines, pterins, and vitamins were analysed by HPLC coupled with tandem mass spectrometry, electrochemical and fluorescence detection.

RESULTS

Aspartate, glutamate, taurine, ornithine, glycine, citrulline, pyridoxal 5´-phosphate, 5-methyltetrahydrofolate, and thiamine showed higher values when RBCs were lysed when compared with those of CSF with no RBC, while arginine, 5-hydroxyindoleacetic and homovanillic acids showed lower values. When RBCs were removed from CSF, only some amino acids, thiamine and pyridoxal 5´-phosphate showed moderately higher values when compared with the non-spiked CSF sample.

CONCLUSIONS

CSF-targeted metabolomic analysis is feasible even when substantial RBC contamination of CSF has occurred since CSF centrifugation to remove RBC prior to freezing eliminated most of the interferences observed.

Infectious stress triggers a POLG-related mitochondrial disease

A 3-year-old girl presented with severe epilepsy in the context of Borrelia infection. After ceftriaxone/lidocaine administration, she showed secondarily generalized focal crises that led to neurological and motor sequelae. Genetic studies identified in the patient two heterozygous POLG mutations (c.2591A>G; p.Asn864Ser and c.3649G>C; p.Ala1217Pro). Through analysis of POLG activity in cultured fibroblasts, we confirmed that the mutations altered the mtDNA turnover. Moreover, patient fibroblasts were more sensitive than controls in the presence of a mitochondrial replication-affecting drug, the antiretroviral azidothymidine. To test if ceftriaxone treatment could worsen the deleterious effect of the patient mutations, toxicity assays were performed. Cell toxicity, without direct effect on mitochondrial respiratory function, was detected at different antibiotic concentrations. The clinical outcome, together with the different in vitro sensitivity to ceftriaxone among patient and control cells, suggested that the mitochondrial disease symptoms were hastened by the infection and were possibly worsened by the pharmacological treatment. This study underscores the benefit of early genetic diagnosis of the patients with mitochondrial diseases, since they may be a target group of patients especially vulnerable to environmental factors.

Analysis of Catecholamines and Pterins in Inborn Errors of Monoamine Neurotransmitter Metabolism-From Past to Future

Inborn errors of monoamine neurotransmitter biosynthesis and degradation belong to the rare inborn errors of metabolism. They are caused by monogenic variants in the genes encoding the proteins involved in (1) neurotransmitter biosynthesis (like tyrosine hydroxylase (TH) and aromatic amino acid decarboxylase (AADC)), (2) in tetrahydrobiopterin (BH₄) cofactor biosynthesis (GTP cyclohydrolase 1 (GTPCH), 6-pyruvoyl-tetrahydropterin synthase (PTPS), sepiapterin reductase (SPR)) and recycling (pterin-4a-carbinolamine dehydratase (PCD), dihydropteridine reductase (DHPR)), or (3) in co-chaperones (DNAJC12). Clinically, they present early during childhood with a lack of monoamine neurotransmitters, especially dopamine and its products norepinephrine and epinephrine. Classical symptoms include autonomous dysregulations, hypotonia, movement disorders, and developmental delay. Therapy is predominantly based on supplementation of missing cofactors or neurotransmitter precursors. However, diagnosis is difficult and is predominantly based on quantitative detection of neurotransmitters, cofactors, and precursors in cerebrospinal fluid (CSF), urine, and blood. This review aims at summarizing the diverse analytical tools routinely used for diagnosis to determine quantitatively the amounts of neurotransmitters and cofactors in the different types of samples used to identify patients suffering from these rare diseases.

Cerebral folate deficiency: Analytical tests and differential diagnosis

Cerebral folate deficiency is typically defined as a deficiency of the major folate species 5-methyltetrahydrofolate in the cerebrospinal fluid (CSF) in the presence of normal peripheral total folate levels. However, it should be noted that cerebral folate deficiency is also often used to describe conditions where CSF 5-MTHF is low, in the presence of low or undefined peripheral folate levels. Known defects of folate transport are deficiency of the proton coupled folate transporter, associated with systemic as well as cerebral folate deficiency, and deficiency of the folate receptor alpha, leading to an isolated cerebral folate deficiency associated with intractable seizures, developmental delay and/or regression, progressive ataxia and choreoathetoid movement disorders. Inborn errors of folate metabolism include deficiencies of the enzymes methylenetetrahydrofolate reductase, dihydrofolate reductase and 5,10-methenyltetrahydrofolate synthetase. Cerebral folate deficiency is potentially a treatable condition and so prompt recognition of these inborn errors and initiation of appropriate therapy is of paramount importance. Secondary cerebral folate deficiency may be observed in other inherited metabolic diseases, including disorders of the mitochondrial oxidative phosphorylation system, serine deficiency, and pyridoxine dependent epilepsy. Other secondary causes of cerebral folate deficiency include the effects of drugs, immune response activation, toxic insults and oxidative stress. This review describes the absorption, transport and metabolism of folate within the body; analytical methods to measure folate species in blood, plasma and CSF; inherited and acquired causes of cerebral folate deficiency; and possible treatment options in those patients found to have cerebral folate deficiency.

Cerebrospinal Fluid Neopterin in Children With Enterovirus-Related Brainstem Encephalitis

BACKGROUND

Enterovirus-A71 causes outbreaks of brainstem encephalitis, ranging from self-limited disease to acute flaccid paralysis. The aim of this study was to assess the role of cerebrospinal fluid (CSF) neopterin as a biomarker of disease severity in children with enterovirus-related brainstem encephalitis.

METHODS

A descriptive, prospective cohort study was conducted from April 2016 to March 2017 in a tertiary hospital. Pediatric patients with a diagnosis of brainstem encephalitis with or without myelitis due to enterovirus infection were enrolled. The final study group comprised a convenience sample including all patients with sufficient CSF volume for neopterin determination. The major variables considered in estimating the severity were the diagnosis of encephalomyelitis, the presence of lesions and extensive lesions on brain and spinal magnetic resonance imaging (MRI), hospital stay length greater than seven days, and sequelae at day 30.

RESULTS

Of 60 patients, CSF neopterin could be measured in 36. Median age was 26 months (interquartile range: 19 to 32). Thirty-three were diagnosed with brainstem encephalitis and three with encephalomyelitis. Enterovirus-A71 was the only identified genotype (25 of 25). CSF neopterin levels were elevated (>61 nmol/L) in 33 of 36 (92%), with a median of 347 nmol/L (interquartile range: 204 to 525). CSF neopterin was useful to distinguish patients with lesions on MRI (area under the receiver operating characteristic curve = 0.76; P = 0.02) and extensive lesions (area under the receiver operating characteristic curve = 0.76; P = 0.04).

CONCLUSIONS

This study suggests an association between CSF neopterin levels and the presence of inflammatory lesions on MRI.

Integrating a Microwave Resonator and a Microchannel with an Immunochromatographic Strip for Stable and Quantitative Biodetection

An immunochromatographic strip is an effective diagnostic tool in various fields because of its simplicity, rapidity, and cost-effectiveness. However, typical strips for preliminary screening provide only qualitative or semiquantitative results, and common solutions for quantitative detection by incorporating different kinds of nanoparticles as biomarkers still do not solve this problem thoroughly. Here, we try to tackle this challenge by integrating low-cost membrane-compatible square split-ring resonators and structure-design-flexible microchannels with flexible strips. We experimentally demonstrate that the limit of detection (LOD) and sensitivity of the strip for quantitative detection of Staphylococcus aureus reach 0.784 ng/mL and 10.214 MHz/(ng/mL), respectively. The LOD level is about 63 times higher than that of the color-based strip determined by the naked eye, and the stability is about 18 times higher than that of the fluorescent strip. This work could not only provide a powerful diagnosis tool for the quantitative detection of S. aureus or other molecules but also deliver new avenues for achieving electric field detection of biomolecules, system-level integration of biosensors, and the development of portable diagnostic devices.