The development of enzyme-linked immunosorbent assays (ELISA) for the catecholamines adrenalin and noradrenalin

Epinephrine promotes breast cancer metastasis through a ubiquitin-specific peptidase 22-mediated lipolysis circuit

Chronic stress-induced epinephrine (EPI) accelerates breast cancer progression and metastasis, but the molecular mechanisms remain unclear. Herein, we found a strong positive correlation between circulating EPI levels and the tumoral expression of ubiquitin-specific peptidase 22 (USP22) in patients with breast cancer. USP22 facilitated EPI-induced breast cancer progression and metastasis by enhancing adipose triglyceride lipase (ATGL)-mediated lipolysis. Targeted USP22 deletion decreased ATGL expression and lipolysis, subsequently inhibiting EPI-mediated breast cancer lung metastasis. USP22 acts as a bona fide deubiquitinase for the Atgl gene transcription factor FOXO1, and EPI architects a lipolysis signaling pathway to stabilize USP22 through AKT-mediated phosphorylation. Notably, USP22 phosphorylation levels are positively associated with EPI and with downstream pathways involving both FOXO1 and ATGL in breast cancers. Pharmacological USP22 inhibition synergized with β-blockers in treating preclinical xenograft breast cancer models. This study reveals a molecular pathway behind EPI's tumor-promoting effects and provides a strong rationale for combining USP22 inhibition with β-blockers to treat aggressive breast cancer.

Novel LC-MS/MS Method for Simultaneous Determination of Monoamine Neurotransmitters and Metabolites in Human Samples

For the simultaneous determination of monoamine neurotransmitters (NTs) like dopamine, serotonin, noradrenaline, and epinephrine, and their metabolites (metanephrine, normetanephrine, 3-methoxytyramine, vanillylmandelic acid, 3,4-dihydroxyphenylacetic acid, homovanillic acid, and 5-hydroxyindoleacetic acid), a robust liquid chromatography method coupled with tandem mass spectrometry (LC-MS/MS) was introduced as the analytical method. This analytical method proved to be accurate for the simultaneous measurement of the amounts of 11 NTs and their metabolites in biological samples. The method proved to be more efficient and better than the previously reported method in terms of precision, recovery, sample requirement, and extraction procedure. The reported method requires only 100 μL of blood and 200 μL of urine, and the extraction procedure requires acetonitrile precipitation, filtration, drying, and reconstitution in water. The separation of all analytes was performed on an C18 column (4.6 mm × 150 mm and 1.8 μm). A 10 min gradient elution program with a mobile phase consisting of phase A (0.2% formic acid in water) and phase B (methanol) was used. The positive ionization mode was used for the detection of all analytes in multiple reaction monitoring (MRM). The proposed method was validated with an internal standard and yielded lower limits of detection and quantification ranges of 0.0182-0.0797 ng/mL and 0.0553-0.2415 ng/mL, respectively, with a good linearity (R2) between 0.9959 and 0.9994. The recoveries ranged from 73.37% to 116.63% in blood and from 80.9% to 115.33% in urine. For the NTs and metabolites, the intra- and interday % CV were 0.24-9.36 and 0.85-9.67, respectively. The developed LC-MS/MS method was successfully used for the determination of trace amounts of endogenous compounds in human blood and urine samples.

Sympathetic Innervation and Endogenous Catecholamines in Neuromuscular Preparations of Muscles with Different Functional Profiles

Influence of the sympathetic nervous system on the work of skeletal muscles contractile apparatus is now beyond doubt. However, until recently there was no evidence that the endings of sympathetic nerves can be located in close proximity to the neuromuscular synapses, and there is also no reliable data on how much endogenous adrenaline and noradrenaline can be contained near the synaptic contact in skeletal muscles. In this research, using fluorescent analysis, immunohistochemical and enzyme immunoassays the isolated neuromuscular preparations of three skeletal muscles of different functional profiles and containing different types of muscle fibers were examined. Close contact between the sympathetic and motor cholinergic nerve endings and the presence of tyrosine hydroxylase in this area were demonstrated. Concentrations of endogenous adrenaline and noradrenaline in the solution perfusing the neuromuscular preparation were determined under different modes of its functioning. The effects of α and β adrenoreceptor blockers on the processes of acetylcholine quantal secretion from the motor nerve endings were compared. The data obtained provide evidence for the presence of endogenous catecholamines in the neuromuscular junction region and their role in modulation of the synaptic function.

Plier Ligands for Trapping Neurotransmitters into Complexes for Sensitive Analysis by SERS Spectroscopy

Catecholamines-dopamine, noradrenaline and adrenaline are important biomarkers of neurotransmitter metabolism, indicating neuroendocrine tumors and neurodegenerative diseases. Surface-enhanced Raman spectroscopy (SERS) is a promising analytical technique with unprecedented multiplexing capabilities. However, not all important analytes exhibit strong SERS signals on stable and robust nanostructured substrates. In this work, we propose a novel indicator system based on the formation of mixed ligand complexes with bispidine-based bis-azole ligands which can serve as pliers to trap Cu(II) ions and stabilize its complexes with catecholamines. Four synthesized ligands with different functional groups: carboxyl, amino, benzyl, and methoxybenzyl, were applied for forming stable complexes to shift maximum absorbance of catecholamines from the ultraviolet region to 570-600 nm. A new absorbance band in the visible range resonates with the local surface plasmon resonance (LSPR) band of metal nanoparticles and most used laser wavelengths. This match allowed use of Molecular Immobilization and Resonant Raman Amplification by Complex-Loaded Enhancers (MIRRACLE) methodology to measure intense Raman signals on a nanostructured silver-based SERS-active substrate. The synthesized plier-like ligands fixed and stabilized catecholamine complexes with Cu(II) on the SERS sensor surface, which facilitated the determination of dopamine in a 3.2 × 10^-12-1 × 10^-8 M concentration range.

Cryogel Monoliths for Analyte Enrichment by Capture and Release

A platform based on cryogel monoliths in small capillaries, which allows very strong enrichment of an analyte through a capture and release process, is described. For their preparation, a photoreactive copolymer solution containing capture molecules of interest is filled into a capillary, frozen in, and then photochemically transformed into cryogel monoliths through C,H-insertion cross-linking reactions. As a test example, the platform is used for the preconcentration of dopamine from bovine serum albumin and urine samples through capture and release processes. During capture from a large volume and release into a smaller volume, the platform shows recovery rates up to 97% and allows up to a roughly 630-fold enrichment of the concentration of the analyte. The presented platform could be used as a disposable device for the purification and enrichment of a variety of cis-diol-containing samples.

A Convenient Method for Extraction and Analysis with High-Pressure Liquid Chromatography of Catecholamine Neurotransmitters and Their Metabolites

The extraction and analysis of catecholamine neurotransmitters in biological fluids is of great importance in assessing nervous system function and related diseases, but their precise measurement is still a challenge. Many protocols have been described for neurotransmitter measurement by a variety of instruments, including high-pressure liquid chromatography (HPLC). However, there are shortcomings, such as complicated operation or hard-to-detect multiple targets, which cannot be avoided, and presently, the dominant analysis technique is still HPLC coupled with sensitive electrochemical or fluorimetric detection, due to its high sensitivity and good selectivity. Here, a detailed protocol is described for the pretreatment and detection of catecholamines with high pressure liquid chromatography with electrochemical detection (HPLC-ECD) in real urine samples of infants, using electrospun composite nanofibers composed of polymeric crown ether with polystyrene as adsorbent, also known as the packed-fiber solid phase extraction (PFSPE) method. We show how urine samples can be easily precleaned by a nanofiber-packed solid phase column, and how the analytes in the sample can be rapidly enriched, desorbed, and detected on an ECD system. PFSPE greatly simplifies the pretreatment procedures for biological samples, allowing for decreased time, expense, and reduction of the loss of targets. Overall, this work illustrates a simple and convenient protocol for solid-phase extraction coupled to an HPLC-ECD system for simultaneous determination of three monoamine neurotransmitters (norepinephrine (NE), epinephrine (E), dopamine (DA)) and two of their metabolites (3-methoxy-4-hydroxyphenylglycol (MHPG) and 3,4-dihydroxy-phenylacetic acid (DOPAC)) in infants' urine. The established protocol was applied to assess the differences of urinary catecholamines and their metabolites between high-risk infants with perinatal brain damage and healthy controls. Comparative analysis revealed a significant difference in urinary MHPG between the two groups, indicating that the catecholamine metabolites may be an important candidate marker for early diagnosis of cases at risk for brain damage in infants.

A potential benefit of albinism in Astyanax cavefish: downregulation of the oca2 gene increases tyrosine and catecholamine levels as an alternative to melanin synthesis

Albinism, the loss of melanin pigmentation, has evolved in a diverse variety of cave animals but the responsible evolutionary mechanisms are unknown. In Astyanax mexicanus, which has a pigmented surface dwelling form (surface fish) and several albino cave-dwelling forms (cavefish), albinism is caused by loss of function mutations in the oca2 gene, which operates during the first step of the melanin synthesis pathway. In addition to albinism, cavefish have evolved differences in behavior, including feeding and sleep, which are under the control of the catecholamine system. The catecholamine and melanin synthesis pathways diverge after beginning with the same substrate, L-tyrosine. Here we describe a novel relationship between the catecholamine and melanin synthesis pathways in Astyanax. Our results show significant increases in L-tyrosine, dopamine, and norepinephrine in pre-feeding larvae and adult brains of Pachón cavefish relative to surface fish. In addition, norepinephrine is elevated in cavefish adult kidneys, which contain the teleost homologs of catecholamine synthesizing adrenal cells. We further show that the oca2 gene is expressed during surface fish development but is downregulated in cavefish embryos. A key finding is that knockdown of oca2 expression in surface fish embryos delays the development of pigmented melanophores and simultaneously increases L-tyrosine and dopamine. We conclude that a potential evolutionary benefit of albinism in Astyanax cavefish may be to provide surplus L-tyrosine as a precursor for the elevated catecholamine synthesis pathway, which could be important for adaptation to the challenging cave environment.

Errors during the preparation of drug infusions: a randomized controlled trial

BACKGROUND

We investigated the extent and frequency of dose errors and treatment delays made as a consequence of preparing drug infusions at the bedside, rather than using pre-filled syringes.

METHODS

Forty-eight nurses with critical care experience volunteered to take part in this randomized, blinded, controlled study conducted in the simulation centre of an urban hospital. They assisted in the management of a simulated patient with septic shock. Vasopressor infusions were prepared either by diluting concentrated drugs from ampoules or were provided in syringes pre-filled beforehand by an intensive care unit resident.

RESULTS

The time taken for the infusion to be started and the final concentration of the drugs were measured. We also measured the concentration of infusions prepared by a pharmacist and a pharmaceutical company. Nurses took 156 s to start infusions when using pre-filled syringes compared with 276 s when preparing them de novo, a mean delay of 106 s [95% confidence interval (CI) 73-140 s, P<0.0001]. One infusion prepared from ampoules contained one-fifth of the expected concentration of epinephrine; another contained none at all. Medication errors were 17.0 times less likely when pre-filled syringes were used (95% CI 5.2-55.5), and infusions prepared by pharmacy and industry were significantly more likely to contain the expected concentration (P<0.001 for norepinephrine and P=0.001 for epinephrine).

CONCLUSIONS

Providing drug infusions in syringes pre-filled by pharmacists or pharmaceutical companies would reduce medication errors and treatment delays, and improve patient safety. However, this approach would have substantial financial implications for healthcare providers, especially in less developed countries.

Protective effect of Melothria maderaspatana leaf fraction on electrolytes, catecholamines, endothelial nitric oxide synthase and endothelin-1 peptide in uninephrectomized deoxycorticosterone acetate-salt hypertensive rats

This study was designed to investigate the protective effect of ethyl acetate fraction of Melothria maderaspatana (EAFM) leaf on electrolytes, catecholamines, endothelial nitric oxide synthase (eNOS) and endothelin-1 (ET-1) peptide in uninephrectomized deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Administration of DOCA-salt significantly increased the systolic and diastolic blood pressure and treatment with EAFM significantly lowered the blood pressure. In DOCA-salt rats, the levels of sodium and chloride increased significantly while potassium level decreased and administration of EAFM brought these parameters to normality. The levels of epinephrine and norepinephrine increased significantly in DOCA-salt rats and administration of EAFM significantly decreased these parameters to normality. DOCA-salt hypertensive rats exhibited significantly decreased L: -arginine and nitrite + nitrate levels and administration of EAFM brought these parameters to normality. DOA-salt hypertensive rats showed down-regulation of eNOS and up-regulation of ET-1 protein expressions in heart and kidney, and treatment with EAFM prevented down-regulation of eNOS and significantly down-regulated the ET-1 protein expressions. In conclusion, EAFM provides good blood pressure control by enhancing potassium and decreasing sodium levels, decreasing levels of epinephrine and norepinephrine, and preventing down-regulation of eNOS and significantly down-regulating ET-1 protein expression.

Determination of monoamines in urine by capillary electrophoresis with field-amplified sample stacking and amperometric detection

A simple, rapid and low-cost method using capillary electrophoresis coupled with field-amplified sample stacking and electrochemical detection was developed for the separation and determination of monoamines. In this present work, a systematic study of the parameters (pH value and concentration of electrophoretic buffer, composition of sample solvent, injection voltage and time) affecting separation and on-line concentration of monoamines has been performed enabling the detection sensitivity of these monoamines to be improved by 5,000 times compared with the conventional electrokinetic injection. This developed method was applied to the direct analysis of these monoamines in human urine without off-line sample preconcentration. Due to the requirement for urine dilution to minimize the detrimental effects of high salt on analyte stacking, the real sensitivity improvement is about 50-fold when applying the optimized method to urine samples. In order to quantitate these monoamines accurately, internal standard calibration curves were constructed with standard monoamines in presence of salt with similar concentration as in human urine. In the method validation, the calibration curves were linear over a range of 1.0 x 10(-9) to 2.5 x 10(-8) mol/L for each monoamine and the limits of detection (signal to noise ratio of 3) for these monoamines were in the sub-nmol/L concentration range (6.0 x 10(-10) mol/L).

Systematic study of long-term stability of 3,4-dihydroxyphenylglycol in plasma for subsequent determination with liquid chromatography

The effect of three storage temperature levels (i.e. +4, -20 and -80 degrees C) and time intervals from sampling (3, 6 and 9 months) on the degradation of 3,4-dihydroxyphenylglycol (DHPG) and norepinephrine (NE) was investigated in a systematic study. Extracted human plasma samples and acidified standard solutions were stored for long periods (up to 9 months) without the addition of any stabilizing agent. DHPG and NE values, determined using a ion-pair reversed-phase high-performance liquid chromatography method with electrochemical detection of coulometric type (IP-RP-HPLC-CD), remained constant over time in those plasma samples and standard solutions that had been stored at the lowest storing temperature (i.e. -80 degrees C). The expected degradation was observed at higher temperature levels. Plasma and standard DHPG degradation can, therefore, be prevented by storing samples at a lower temperature than previously suggested with no need to add any stabilizing agent.

Preparation and characterization of immunogens for antibody production against metanephrine and normetanephrine

A two-step zero-length cross-linking procedure using active esters was successfully adopted for conjugating metanephrine (MN) and normetanephrine (NM) to bovine serum albumin (BSA). The protein was activated with water-soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) in the presence of N-hydroxysulfosuccimide (sulfo-NHS), leading to the formation of active N-succinimidyl esters of some glutamic and aspartic acid carboxyls. The pertinence of this reaction for the coupling of these haptens to carboxylate groups was confirmed via reaction with a model compound, 2-hydroxybenzoic acid, and subsequent characterization using atmospheric pressure chemical ionization mass spectrometry (APCI-MS). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was used for the quantitative assessment of the hapten/protein ratios of these conjugates. This technique of conjugate characterization demonstrated greater resolution in molecular weight determination compared to nondenaturing polyacrylamide gel electrophoresis (native PAGE). Preliminary results from enzyme-linked immunosorbent assay (ELISA) and inhibition ELISA procedures using test antisera confirmed that the synthesized immunogens were highly antigenic and elicited specific antibody responses in BALB/c mice against the haptens.

Attempt to separate the fluorescence spectra of adrenaline and noradrenaline using chemometrics

An investigation was conducted on whether the fluorescence spectra of the very similar catecholamines adrenaline and noradrenaline could be separated using chemometric methods. The fluorescence landscapes (several excitation and emission spectra were measured) of two data sets with respectively 16 and 6 samples were measured, the smaller data set with higher resolution and i.e. precision. The samples were artificial urine (pH approximately equal to 3) spiked with the catecholamines in the concentration ranges 40--1200 nmol/L and 5.5--18 micromol/L, respectively. Unfold partial least squares regression (Unfold-PLSR) on the larger data set and parallel factor analysis (PARAFAC) of the six samples of the smaller set showed that there was no difference between the fluorescence landscapes of adrenaline and noradrenaline. It can be concluded that chemometric separation of adrenaline and noradrenaline is not obtainable using this type of fluorescence measurement. Raman scatter, which overlaps the catecholamine spectra, was shown not to have any influence on the models calculated.

Determination of urine catecholamines by capillary electrophoresis with dual-electrode amperometric detection

Demonstrated in this study is that without pretreatment and preconcentration nanomolar-level catecholamines in human urine samples can be quantitatively determined with ease by utilizing capillary electrophoresis coupled with amperometric detection. The detector employs a parallel-opposed dual-electrode scheme assembled with an on-capillary electrode and a disk electrode and takes advantage of the redox cycling of analytes between the two working electrodes to improve the limit of detection. The matrix effect of urine samples significantly decreases the detection sensitivity from that obtained in standard solutions. Therefore, calibration curves derived from standard solutions cannot be used in quantitative determination of catecholamines. Methods of standard addition and internal standard have been studied. The results suggest that isoproterenol is a good internal standard to facilitate the measurements of dopamine, epinephrine, and norepinephrine in human urine samples.

Freedom from Drug Interference in New Immunoassays for Urinary Catecholamines and Metanephrines

Background: Determination of urinary free catecholamine and total (i.e., free plus conjugated) metanephrine excretion is considered the most clinically sensitive biochemical test for pheochromocytoma. In this study, we evaluated new immunoassay methods for the measurement of these analytes for potential drug-based interference.

Methods: Urine samples collected from patients on a variety of medications were grouped by specific drug type. The significance of any difference in the free catecholamine or total metanephrine concentrations in the different groups was assessed by one-way ANOVA. A group of patients receiving no medication was included as a control (no analytical interference). Additionally, analytical accuracy, detection limit, and precision were determined.

Results: No significant differences were found in the concentrations of free catecholamines or total metanephrines in urine from patients taking the medications investigated and the control group: P = 0.649 (fE), 0.221 (fNE), 0.149 (tM), and 0.170 (tNM). For free catecholamines, intraassay CVs were 4.6–18%; interassay CVs were 10–25%. For total metanephrines, intraassay CVs were 9.6–27%; interassay CVs were 5.8–22%. Detection limits were 0.009 and 0.027 μmol/L for fE and fNE and 0.119 and 0.346 μmol/L for tM and tNM, respectively.

Conclusions: None of the drugs examined in this study interfered in the measurement of free catecholamines or total metanephrines by these immunoassays. The technique is easier to use, requires less equipment, and is more accessible than HPLC. In combination, these assays are suitable as initial screening tests for pheochromocytoma.

The development of a sensitive and specific enzyme immunoassay for FK480, a novel cholecystokinin type-A receptor antagonist, in human plasma

A sensitive and specific enzyme immunoassay for FK480, a novel cholecystokinin type-A (CCK-A) receptor antagonist, was developed to study the pharmacokinetics of the drug at low-dose administration using a specific monoclonal antibody. The high performance liquid chromatography (HPLC) method had been used for studying toxicokinetics, but its determination limit (2.5 ng ml-1) was too high for use in clinical studies. Subsequently we developed an enzyme immunoassay (EIA) using rabbit anti-FK480 serum (polyclonal antibody). It had higher sensitivity (0.1 ng ml-1) when 0.5 ml of plasma was used but its specificity was low because of the cross-reactivity of the metabolites of FK480. Therefore we produced several monoclonal antibodies for FK480 by cell fusion, and selected the antibody which was least cross-reactive for the isolated metabolites of FK480. Finally we developed a sensitive and specific EIA using this monoclonal antibody. The lower limit of quantification of this method was 0.2 ng ml-1 when 0.2 ml of human plasma was used. The coefficient of variation over the calibration range (0.2-10 ng ml-1) was less than 15%. We used this method for clinical studies, and it showed a good correlation to the HPLC method when plasma concentration was 2.5 ng ml-1 or more.