HPLC analysis of metabolically produced formaldehyde

Urine Formaldehyde Predicts Cognitive Impairment in Post-Stroke Dementia and Alzheimer's Disease

Although Alzheimer's disease (AD) was first described over 100 years ago, there is still no suitable biomarker for diagnosing AD in easily collectable samples (e.g., blood plasma, saliva, and urine). Here, we investigated the relationship between morning urine formaldehyde concentration and cognitive impairment in patients with post-stroke dementia (PSD) or AD in this cross-sectional survey for 7 years. Cognitive abilities of the study participants (n = 577, four groups: 231 controls, 61 stroke, 65 PSD, and 220 AD) were assessed by Mini-Mental State Examination (MMSE). Morning urine formaldehyde concentrations were measured by high performance liquid chromatography (HPLC). Gender- and age-matched participants were selected from the four groups (n = 42 in each group). Both semicarbazide-sensitive amine oxidase (SSAO, a formaldehyde-generating enzyme) and formaldehyde levels in the blood and urine were analyzed by using an enzyme-linked immunosorbent assay (ELISA) and HPLC, respectively. We found that morning urine formaldehyde levels were inversely correlated with MMSE scores. The threshold value (the best Cut-Off value) of formaldehyde concentration for predicting cognitive impairment was 0.0418 mM in patients with PSD (Sensitivity: 92.3%; Specificity: 77.1%), and 0.0449 mM in patients with AD (Sensitivity: 94.1%; Specificity: 81.8%), respectively. The results of biochemical analysis revealed that the observed increase in urine formaldehyde resulted from an overexpression of SSAO in the blood. The findings suggest that measuring the concentration of formaldehyde in overnight fasting urine could be used as a potentially noninvasive method for evaluating the likelihood of ensuing cognitive impairment or dementia.

Chronic experimental diabetes accelerates urinary elimination of deprenyl and its metabolites

Many diabetic patients take several medications to treat diabetes-associated complications and other ailments. The mode of elimination of these drugs and their metabolites are poorly understood. The elimination of deprenyl, a MAO-B inhibitor, used for the treatment of the early stage of Parkinson's disease and senile dementia was investigated using thin layer chromatography.Male Wistar rats (180-200 g) were rendered diabetic by streptozotocin (STZ) treatment (60 mg/kg, i.v.). Rats having at least three times higher plasma glucose level than the normal were considered diabetic. Rats were treated with a single oral dose of 5 mg/kg (14)C-(methyl)-labeled (-)-deprenyl, 98 microCi/mg. Diabetic rats excreted the majority of urinary radioactivity in 8 hours, while control rats did it in 16 hours. The approximate ratio of major metabolites as determined using thin-layer chromatography did not change. In conclusion, diabetic rats excreted radiolabelled-deprenyl more rapidly compared to control animals. Increased elimination of deprenyl should be taken into account in the management of patients suffering from diabetes.

Evaluation of toxicological monitoring markers using proteomic analysis

In our study, we chose three different concentrations of FA (0, 5, and 10 ppm), and cytotoxic (lipid peroxidation and protein oxidation) and genotoxic assays (DNA damage) were carried out on plasma, blood, and liver cells of rats subjected to FA-inhalation treatment. The profiles of plasma protein changes determined using 2-DE analysis were also evaluated to identify potential toxicological monitoring markers in FA-exposed rats. Concern was raised that our genotoxic analyses did not follow previously published research data and that the results of our rat plasma proteomic studies were difficult to interpret because we did not directly determine the plasma concentration of FA. However, we had already determined the concentration of FA using HPLC in an exposure chamber to monitor FA inhalation concentrations. We suggest that our experimental design was suitable to determine the FA effects on rat using an inhalation chamber system. For the similarity of genotoxic effects in lymphocytes and liver cells, we chose to present our data on the general cytological toxic effects on lipid peroxidation and protein oxidation which revealed a similarity between plasma and liver cells of FA-exposed rats. We have shown strong correlations between genotoxicity and lipid peroxidation, and lipid peroxidation is known to mediate DNA damage in many in vitro, and in vivo studies. We are well aware of the 'implausibility' of leukemia induction by FA, but for precisely this reason, we feel the need for further study to prove the systemic genotoxic effects of FA.

The detection of formaldehyde in textiles using interdigitated microelectrode array diffusion layer titration with electrogenerated hypobromite

An interdigitated microelectrode array (IDA) was applied to the determination of formaldehyde released from textiles produced in industry. The proposed method is based on formaldehyde reaction with hypobromite which is formed in weakly basic media by control current electrooxidation of bromide on the generator segment of the IDA array. The unreacted hypobromite diffuses through the gap between individually polarisable IDA segments and it is amperometrically detected on the collector segment of the IDA. The efficiency of this nonconvective transfer process in the absence of formaldehyde was substantially higher (78%) in comparison with that when using the rotating ring disc electrode. The influence of the added formaldehyde on the transfer process can be utilised to develop a simple and sensitive analytical procedure for formaldehyde detection with a detection limit of 4 x 10(-6) mol dm(-3).

Detection of Nepsilon-monomethyllysine using high-performance liquid chromatography and high-performance liquid chromatography-mass spectrometry

Nepsilon-Monomethyllysine was identified in the serum, urine, brain, and liver samples of rats treated per os with L-deprenyl. The identification procedure included reaction with Fmoc chloride, clean-up, and analysis using HPLC-UV-MS. Oral administration of (-)-N-14C-methyl-N-propynyl(2-phenyl-1-methyl)ethylammonium hydrochloride L-deprenyl) to rats resulted in transfer of the radiolabelled methyl group to the Nepsilon-amino group of the endogenous lysine. The radiolabelled Nepsilon-monomethyllysine was urinary eliminated together with the other radiolabelled deprenyl metabolites, such as deprenyl-N-oxide and methamphetamine. The presence of Nepsilon-monomethyllysine has also been traced, and its concentrations were compared in the serum, liver and brain of rats subjected to L-deprenyl treatment. Methyl group transfer from the L-deprenyl to endogenous compounds; and the urinary elimination of their products may offer a vital way to eliminate or to decrease the degree of drug transmethylation to the lysine constituents of blood vessels' proteins.

Evaluation of (R)-[11C]verapamil as PET tracer of P-glycoprotein function in the blood-brain barrier: kinetics and metabolism in the rat

There is evidence that P-glycoprotein (P-gp) in the blood-brain barrier (BBB) may be involved in the aetiology of neurological disorders. For quantification of P-gp function in vivo, (R)-[11C]verapamil can be used as a positron emission tomography (PET) tracer, provided that a mathematical model describing kinetics of uptake and clearance of verapamil is available. To develop and validate such a model, the kinetic profile and metabolism of (R)-[11C]verapamil have to be known. The aim of this study was to investigate the presence of labeled metabolites of [11C]verapamil in the plasma and (brain) tissue of Wistar rats. For this purpose, extraction and high-performance liquid chromatography (HPLC) methods were developed. The radioactive metabolites of (R)-[11C]verapamil in the liver were N-dealkylated compounds, O-demethylated compounds and a polar fraction formed from N-demethylation products of (R)-[11C]verapamil. Apart from this [11C] polar fraction, other radioactive metabolites of [11C]verapamil were not detected in the brain tissue. Thirty minutes after injection, unmetabolized (R)-[11C]verapamil accounted for 47% of radioactivity in the plasma and 69% in the brain. Sixty minutes after injection, unmetabolized (R)-[11C] verapamil was 27% and 48% in the plasma and the brain, respectively.

Detection of N-monomethyl-lysine generated by metabolic transmethylation

Administration of radiolabelled deprenyl to rats resulted in the urinary elimination of a (14)C-labelled N(epsilon)-monomethyl-lysine. An increased level of N(epsilon)-monomethyl-lysine was found following an oral dose of another drug, also containing an N-methyl group. The urine sample was treated with 9-fluorenylmethoxycarbonyl chloride and then subjected to high-performance liquid chromatography (HPLC); the radioactive fraction was identified as N(epsilon)-monomethyl-lysine by using HPLC-MS in electrospray mode. Identification of N(epsilon)-monomethyl-lysine in the radioactive fraction gives experimental proof of transmethylation from a well-known drug to an endogenous compound.