Recent advances in methods for the analysis of catecholamines and their metabolites

HPLC-Based Metabolomic Analysis of Normal and Inflamed Gut

The idiopathic inflammatory bowel diseases, which include Crohn's disease and ulcerative colitis, are multifactorial chronic conditions that result in numerous perturbations of metabolism in the gastrointestinal mucosa. Thus, methodologies for the qualitative and quantitative analysis of small molecule metabolites in mucosal tissues are important for further elucidation of mechanisms driving inflammation and the metabolic consequences of inflammation. High-performance liquid chromatography (HPLC) is a ubiquitous analytical technique that can be adapted for both targeted and non-targeted metabolomic analysis. Here, protocols for reversed-phase (RP) HPLC-based methods using two different detection modalities are presented. Ultraviolet detection is used for the analysis of adenine nucleotide metabolites, whereas electrochemical detection is used for the analysis of multiple amino acid metabolites. These methodologies provide platforms for further characterization of the metabolic changes that occur during gastrointestinal inflammation.

Effects of low-dose clonidine on cardiovascular and autonomic variables in adolescents with chronic fatigue: a randomized controlled trial

Background

Chronic Fatigue Syndrome (CFS) is a common and disabling condition in adolescence with few treatment options. A central feature of CFS is orthostatic intolerance and abnormal autonomic cardiovascular control characterized by sympathetic predominance. We hypothesized that symptoms as well as the underlying pathophysiology might improve by treatment with the alpha_2A–adrenoceptor agonist clonidine.

Methods

A total of 176 adolescent CFS patients (12–18 years) were assessed for eligibility at a single referral center recruiting nation-wide. Patients were randomized 1:1 by a computer system and started treatment with clonidine capsules (25 μg or 50 μg twice daily, respectively, for body weight below/above 35 kg) or placebo capsules for 9 weeks. Double-blinding was provided. Data were collected from March 2010 until October 2012 as part of The Norwegian Study of Chronic Fatigue Syndrome in Adolescents: Pathophysiology and Intervention Trial (NorCAPITAL). Effect of clonidine intervention was assessed by general linear models in intention-to-treat analyses, including baseline values as covariates in the model.

Results

A total of 120 patients (clonidine group n = 60, placebo group n = 60) were enrolled and started treatment. There were 14 drop-outs (5 in the clonidine group, 9 in the placebo group) during the intervention period. At 8 weeks, the clonidine group had lower plasma norepinephrine (difference = 205 pmol/L, p = 0.05) and urine norepinephrine/creatinine ratio (difference = 3.9 nmol/mmol, p = 0.002). During supine rest, the clonidine group had higher heart rate variability in the low-frequency range (LF-HRV, absolute units) (ratio = 1.4, p = 0.007) as well as higher standard deviation of all RR-intervals (SDNN) (difference = 12.0 ms, p = 0.05); during 20° head-up tilt there were no statistical differences in any cardiovascular variable. Symptoms of orthostatic intolerance did not change during the intervention period.

Conclusions

Low-dose clonidine reduces catecholamine levels in adolescent CFS, but the effects on autonomic cardiovascular control are sparse. Clonidine does not improve symptoms of orthostatic intolerance.

Trial registration

Clinical Trials ID: NCT01040429, date of registration 12/28/2009.

Dual Reaction-Based Multimodal Assay for Dopamine with High Sensitivity and Selectivity Using Functionalized Gold Nanoparticles

A simple and dual chemical reaction-based multimodal assay for dopamine with high sensitivity and selectivity using two types of functionalized gold nanoparticles (FB-AuNPs/NsNHS-AuNPs), i.e. fluorescein modified gold nanoparticles (FB-AuNPs) and Nile blue modified gold nanoparticles (NsNHS-AuNPs), was successfully fabricated. This assay for dopamine presents colorimetric visualization and double channel fluorescence enhancement at 515 and 665 nm. The absorbance and fluorescence changes were linearly proportional to the amounts of dopamine in the range of nanomolar scale (5-100 nM). The detection limits for absorbance and fluorescence were as low as 1.2 nM and 2.9 nM (S/N = 3), respectively. Furthermore, the extent application of this multimodal assay has been successfully demonstrated in human urine samples with high reliability and applicability, showing remarkable promise in diagnostic purposes.

Determination of catecholamines and their metabolites in rat urine by ultra-performance liquid chromatography-tandem mass spectrometry for the study of identifying potential markers for Alzheimer's disease

In order to investigate the potential links between catecholamines (CAs) and Alzheimer's disease (AD), rapid and sensitive ultra-performance liquid chromatography (UPLC)-tandem mass spectrometry (MS/MS) methods in different ionization modes for the quantification of 14 CAs and their metabolites in rat urine without derivatization or complex sample pre-treatments were developed. After addition of the internal standard, isoproterenol, the urine samples were extracted by protein precipitation and separated on an Inertsil ODS-EP column (Shimadzu, Japan) at a flow of 1.0 ml min(-1). Tandem mass spectrometric detection was performed on a 4000Q UPLC-MS/MS in the multiple reaction monitoring mode with turbo ion spray source. Tyrosine, dopamine, noradrenaline, epinephrine, 3-methoxytyramine, normetanephrine and metanephrine were determined in positive mode, while 3,4-dihyroxy-L-phenylalanine (DOPA), 3,4-dihydroxyphenylacetic acid, DL-3,4-dihydroxymandelic acid, DL-3,4-dihydroxyphenyl glycol, homovanillic acid, DL-4-hydroxy-3-methoxymandelic acid and 4-hydroxy-3-methoxy-phenylglycol were determined in negative mode. The methods were examined and were found to be precise and accurate within the linearity range of the assays. The intra-day and inter-day precision and accuracy of the analytes were well within acceptance criteria (±15%). The mean extraction recoveries of analytes and internal standard were all more than 60%. The validated methods have been successfully applied to compare CAs profiles in normal and AD rats. The results indicated the urine levels of DL-3,4-dihydroxyphenyl glycol and 4-hydroxy-3-methoxy-phenylglycol in AD rats were significantly higher than those in the normal group, and the other CAs have an opposite performance. These may attribute to the difference of some enzyme activity between rats with AD and normal. Furthermore, this may be helpful in clinical diagnostics and monitor the efficacy of AD treatment.

Methodological standardization for the pre-clinical evaluation of renal sympathetic denervation

Transcatheter ablation of renal autonomic nerves is a viable option for the treatment of resistant arterial hypertension; however, structured pre-clinical evaluation with standardization of analytical procedures remains a clear gap in this field. Here we discuss the topics relevant to the pre-clinical model for the evaluation of renal denervation (RDN) devices and report methodologies and criteria toward standardization of the safety and efficacy assessment, including histopathological evaluations of the renal artery, periarterial nerves, and associated periadventitial tissues. The pre-clinical swine renal artery model can be used effectively to assess both the safety and efficacy of RDN technologies. Assessment of the efficacy of RDN modalities primarily focuses on the determination of the depth of penetration of treatment-related injury (e.g., necrosis) of the periarterial tissues and its relationship (i.e., location and distance) and the effect on the associated renal nerves and the correlation thereof with proxy biomarkers including renal norepinephrine concentrations and nerve-specific immunohistochemical stains (e.g., tyrosine hydroxylase). The safety evaluation of RDN technologies involves assessing for adverse effects on tissues local to the site of treatment (i.e., on the arterial wall) as well as tissues at a distance (e.g., soft tissue, veins, arterial branches, skeletal muscle, adrenal gland, ureters). Increasing experience will help to create a standardized means of examining all arterial beds subject to ablative energy and in doing so enable us to proceed to optimize the development and assessment of these emerging technologies.

Evaluation and validation of a method for determining platelet catecholamine in patients with obstructive sleep apnea and arterial hypertension

Background

Measurements of plasma and urinary catecholamine are susceptible to confounding factors that influence the results, complicating the interpretation of sympathetic nervous system (SNS) activity in the Obstructive sleep apnea (OSA) and arterial hypertension (HYP) conditions.

Objective

In this study, we validated a test for platelet catecholamine and compared the catecholamine levels (adrenaline and noradrenaline) in urine, plasma and platelets in patients with OSA and HYP compared with controls.

Methods

In the validation, 30 healthy, nonsmoking volunteers who were not currently undergoing treatment or medication were selected as the control group. One hundred fifty-four individuals (114 OSA, 40 non-OSA) were consecutively selected from the outpatient clinic of the Sleep Institute and underwent clinical, polysomnographic and laboratory evaluation, including the urinary, plasma and platelet levels of adrenaline (AD) and noradrenaline (NA). Patients were then allocated to groups according to the presence of OSA and/or hypertension.

Results

A logistic regression model, controlled for age and BMI, showed that urinary AD and urinary NA were risk factors in the OSA+HYP group and the HYP group; however, the model showed higher levels of platelet NA for OSA without HYP. After 1 year of CPAP (continuous upper airway pressure) treatment, patients (n = 9) presented lower levels of urinary NA (p = 0.04) and platelet NA (p = 0.05).

Conclusion

Urinary NA and AD levels were significantly associated with the condition of hypertension with and without OSA, whereas platelet NA with OSA without comorbidity. These findings suggest that platelet catecholamine levels might reflect nocturnal sympathetic activation in OSA patients without hypertension.

A cyclodextrin-based approach for selective detection of catecholamine hormone mixtures

This paper presents an electrochemical sensing approach that enables quantitative detection of three major catecholamine hormones from a mixture by specifically employing a chemically-modified microelectrode array with α-, β- and γ-cyclodextrin (CD) ‘catchers’ holding unique physical matching (size and shape) as well as chemical enticing (stereochemistry and surface charge) properties. The developed neurotransmitter sensor has selectively identified L-tyrosine, dihydroxyphenylalanine (L-DOPA) and dopamine in the absence of ascorbic acid. It exhibited the relatively linear sensitivities to each neurotransmitter with logarithmically increasing concentrations range of 5μM-10mM, while demonstrating stability up to 6 hours from the fabrication and the average accuracy of 91.2%.

Neuroblastoma: the impact of biology and cooperation leading to personalized treatments

Neuroblastoma is the most common extra-cranial solid tumor in children. It is a heterogeneous disease, consisting of neural crest-derived tumors with remarkably different clinical behaviors. It can present in a wide variety of ways, including lesions which have the potential to spontaneously regress, or as an extremely aggressive form of metastatic cancer which is resistant to all forms of modern therapy. They can arise anywhere along the sympathetic nervous system. The median age of presentation is approximately 18 months of age. Urinary catecholamines (HVA and VMA) are extremely sensitive and specific tumor markers and are used in diagnosis, treatment response assessment and post-treatment surveillance. The largest national treatment groups from North America, Europe and Japan have formed the International Neuroblastoma Risk Group Task Force (INRG) to identify prognostic factors, to understand the mechanisms of tumorigenesis in this rare disease and to develop multi-modality therapies to improve outcomes and decrease treatment-related toxicities. This international cooperation has resulted in a significant leap in our understanding of the molecular pathogenesis of neuroblastoma. Lower staged disease can be cured if the lesion is resectable. Treatment of unresectable disease (loco-regional and metastatic) is stratified depending on clinical features (age at presentation, staging investigations) and specific tumor biological markers that include histopathological analyses, chromosomal abnormalities and the quantification of expression of an oncogene (MYCN). Modern treatment of high-risk neuroblastoma is the paradigm for the evolution of therapy in pediatric oncology. Outcomes have improved substantially with multi-modality therapy, including chemotherapy, surgery, radiation therapy, myeloablative therapy with stem cell transplant, immunotherapy and differentiation therapy; these comprise the standard of care worldwide. In addition, newer targeted therapies are being tested in phase I/II trials. If successful these agents will be incorporated into mainstream treatment programs.

Identification and structural characterization by LC-ESI-IONTRAP and LC-ESI-TOF of some metabolic conjugation products of homovanillic acid in urine of neuroblastoma patients

The levels of urinary catecholamine metabolites, such as homovanillic acid (HVA) and vanillylmandelic acid, are routinely used as a clinical tool in the diagnosis and follow-up of neuroblastoma (NB) patients. Recently, in the Clinical Pathology Laboratory Unit of G. Gaslini Children Hospital, a commercial method that employs liquid chromatography coupled to electrochemical detection (LC-EC) has been introduced for the measurement of these metabolites in the routine laboratory practice. Using this LC-EC method, an unknown peak could be observed only in samples derived from NB patients. To investigate the nature of this peak, we used a combination of liquid chromatography-time-of-flight mass spectrometry (LC-TOF-MS) and liquid chromatography-ion trap tandem mass spectrometry (LC-IT-MS). The first approach was used to obtain the elemental composition of the ions present in this new signal. To get additional structural information useful for the elucidation of unknown compounds, the ion trap analyzer was exploited. We were able to identify not just one, but three unknown signals in urine samples from NB patients which corresponded to three conjugated products of HVA: HVA sulfate and two glucuronoconjugate isomers. The enzymatic hydrolysis with β-glucuronidase confirmed the proposed structures, while the selective alkaline hydrolysis allowed us to distinguish the difference between phenol- and acyl-glucuronide of HVA. The latter was the unknown peak observed in LC-EC separations of urine samples from NB patients.

Quantitative determination of free and total dopamine in human plasma by LC–MS/MS: the importance of sample preparation

Background: Two methods have been developed and validated for the determination of free and total dopamine in human plasma. They are based on solid-phase extraction of the analyte from the matrix by covalent complexation with phenylboronic acid, followed by derivatization with ethylchloroformate. The derivative is quantified by reversed-phase liquid chromatography on a C18 column and positive electrospray ionization MS/MS. Results: The high selectivity obtained, in combination with the stable and relatively non-polar nature of the derivatized analyte, enables the reliable quantification of dopamine in the range 0.05 to 20 ng/ml in a 5 min run time, using only 100 µl of sample. Total dopamine concentrations are determined (range 1 to 400 ng/ml) by including an acidic hydrolysis step, which converts the sulphate and glucuronide conjugates to free dopamine prior to extraction. The method was applied to quantify free and total dopamine levels in human plasma after dosing with the anti-Parkinson’s drug combination L-dopa/carbidopa with and without entacapone. Conclusion: A sensitive and selective LC–MS/MS method has been developed and validated for the determination of free and total dopamine in human plasma. This article demonstrates how essential careful optimization of the sample preparation procedures was for developing a successful method.

Adrenaline, Noradrenaline and Dopamine Level Estimation in Depression : Does it Help?

BACKGROUND

Abnormalities of catecholaminergic function have been hypothesised in causation of depressive illness. Electroconvulsive therapy (ECT) is postulated to have noradrenergic mechanism of action. We studied the clinical utility of estimating catecholamines level changes after ECT.

METHODS

Plasma adrenaline, noradrenaline and dopamine in healthy controls and depressed patients were estimated by high performance liquid chromatography with electrochemical detection method before and after ECT.

RESULT

Mean ± standard deviation of plasma adrenaline, noradrenaline and dopamine in controls was 36.7 ± 13.2, 209.3 ± 76, 21.8 ± 9.5 ng/L respectively, while in depressed patients before and after ECT it was found to be 32.5 ± 12.0, 419.3 ± 167.7, 22.1 ± 16.0ng/ L and 37.2 ± 19.6, 386.1 ± 168.4, 22.3 ± 15.5ng/L respectively. Correlation of adrenaline, noradrenaline and dopamine concentration with scores of Beck Depression Inventory, Suicidal Ideation Scale and Melancholia Inventory was positive but statistically not significant and poor. Based on the cut off values of noradrenaline, only 62% cases could be categorized as abnormal, which after ECT reduced to 50%, whereas post ECT psychiatric ratings was normal in about 78% cases.

CONCLUSION

There is no clinical significance of estimating adrenaline, noradrenaline and dopamine in depressed patients.

Improved plasma free metadrenaline analysis requires mixed mode cation exchange solid-phase extraction prior to liquid chromatography tandem mass spectrometry detection

Background

The investigation and effective management of phaeochromocytoma involves biochemical measurement of either conjugated total urine or plasma free metadrenalines. Current analytical methods include enzyme-linked immunosorbent assays, high-performance liquid chromatography (HPLC) with electrochemical detection (ECD) or liquid chromatography tandem mass spectrometry (LCMS/MS). Since the first two methods are either extremely laborious, necessitate low sample run numbers, result in slow turnaround times or are subject to analytical interference, a robust, routine clinical method is not achievable. We established a novel sample preparation method to measure plasma free metadrenalines using LCMS/MS.

Methods

Three different solid-phase extraction (SPE) methods were compared: hydrophilic–lipophilic balance sorbent (HLB), weak cation exchange (WCX) and mixed mode cation exchange (MCX) and their ability to remove interfering compounds prior to LCMS/MS analysis. Maximum recovery of plasma free metadrenaline and plasma free normetadrenaline were achieved by positively charging compounds prior to SPE application.

Results

Compared with HLB and WCX cartridges, MCX extraction resulted in chromatography without co-eluting interference with superior assay precision and accuracy. Additionally, samples that could not be quantified because of interference using HPLC/ECD could be readily assayed using this new method.

Conclusions

The use of the MCX SPE method with LCMS/MS detection provides an improved assay to measure plasma free metadrenalines in comparison to many available alternative methods.

Development and validation of an ultra-high performance liquid chromatography-tandem mass-spectrometry (UHPLC-MS/MS) method for the simultaneous determination of neurotransmitters in rat brain samples

A simple method for the simultaneous determination of glutamate, γ-aminobutyric acid (GABA), choline, acetylcholine, dopamine, 5-hydroxyindole-3-acetic (5-HIAA), serotonin, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) was developed by using ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS). These compounds are analysed in a single chromatographic run in less than 8 min, adding heptafluorobutyric acid (HFBA) in the mobile phase to improve the separation of the selected neurotransmitters. The analytes were detected using electrospray ionization (ESI)-MS/MS in positive mode with multiple reaction monitoring (MRM). Good linearity was obtained (R² > 0.98) and the intra and inter-day precision of the method (expressed as relative standard deviation) were lower than 26%. Limits of quantification were lower than 2.440 μg/g of brain in all the cases, allowing the sensitive determination of these compounds in rat brain extracts. Therefore, the method was successfully applied for the quantitative determination of neurotransmitters in several rat brain regions (prefrontal cortex, striatum, nucleus accumbens and amygdala), detecting glutamate, GABA and choline at concentrations higher than 1000 μg/g, 30 μg/g and 100 μg/g respectively, whereas the other compounds were found at lower concentrations.

Extraction of catecholamines from urine using a monolithic disk-packed spin column and high-performance liquid chromatography-electrochemical detection

A simple method for the determination of catecholamines (norepinephrine, epinephrine, and dopamine) in urine is described. The analytes were extracted from urine by extraction using a monolithic silica disk-packed spin column. The spin column has a phenylboronate moiety, which forms a stable negatively charged complex with cis-hydroxyl groups of catecholamines. The extraction recoveries of catecholamines were above 92.2%. The extracted catecholamines were separated on a reversed-phase column followed by electrochemical detection using a boron-doped diamond electrode. The limits of detection for the catecholamine were 0.2 ng mL-1. The developed method was successfully applied for the determination of catecholamines in urine samples.

Monitoring of dopamine and its metabolites in brain microdialysates: method combining freeze-drying with liquid chromatography-tandem mass spectrometry

A sensitive assay method was developed for a parallel, rapid and precise determination of dopamine and its metabolites, homovanillic acid, 3-methoxytyramine and 3,4-dihydroxyphenylacetic acid, from brain microdialysates. The method consisted of a pre-treatment step, freeze-drying (lyophilization), to concentrate dopamine and its metabolites from the microdialysates, and a detection step using liquid chromatography combined with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). In particular, the reaction monitoring mode was selected for its extremely high degree of selectivity and the stable-isotope-dilution assay for its high precision of quantification. The developed method was characterized by the following parameters: the precision of the developed method was determined as ≥88.6% for dopamine, ≥89.9% for homovanillic acid, ≥86.1% for 3-methoxytyramine and ≥88.1% for 3,4-dihydroxyphenylacetic acid; the mean accuracy was determined as ≥88.2% for dopamine, ≥88.3% for homovanillic acid, ≥85.9% for 3-methoxytyramine and ≥88.6% for 3,4-dihydroxyphenylacetic acid. The developed method was compared to (1) other combinations of pre-treatment methods (solid phase extraction and nitrogen stripping) with LC-MS and (2) another detection method, liquid chromatography, with electrochemical detection. The novel developed method using combination of lyophilization with LC-ESI-MS/MS was tested on real samples obtained from the nucleus accumbens of rat pups after an acute methamphetamine administration. It was proven that the developed assay could be applied to both a simultaneous analysis of all four substrates (dopamine, homovanillic acid, 3-methoxytyramine and 3,4-dihydroxyphenylacetic acid) in microdialysis samples acquired from the rat brain and the monitoring of their slight concentration changes on a picogram level over time following methamphetamine stimulus.

Application of multiway-variate calibration to simultaneous voltammetric determination of three catecholamines

Three structurally similar catecholamines, adrenaline (AA), dopamine (DA) and noradrenaline (NA), which are neurotransmitters well known for their treatment of neural disorders and many other diseases, were investigated at a glassy carbon electrode (GCE) with the use of differential pulse stripping voltammetry (DPSV). The aim was to develop a simple, rapid and cost effective method of simultaneous analysis of these three substances in typical samples such as human urine. Each analyte showed typical reversible redox behaviour with the use of cyclic voltammetry in aqueous medium in the pH range of 4.0-7.9, and composite voltammograms of the three analytes were found to consist of three significantly overlapping peaks corresponding to the three individual substances. Thus, two- and three-way multi-variate data analysis methods were investigated. These included unfolding methods such as-partial least squares (UPLS), principal component regression (UPCR) and radial basis function-artificial neural networks (URBF-ANN), as well as trilinear models, such as parallel factor analysis (PARAFAC) and N-way PLS (NPLS). The results were compared with those obtained from two-way voltammetric data matrix with the use of conventional models, PLS, PCR and RBF-ANN. It was found that most of the three-way models, such as PARAFAC and UPLS, performed somewhat better than others on the basis of the %RPET (5.6∼5.9) and mean %Recovery (94∼102). The proposed methods were then applied for the determination of human urine samples spiked with the three catecholamines, and the results were satisfactory.