Establishing the UK DNA Bank for motor neuron disease (MND).

In 2003 the Motor Neurone Disease (MND) Association, together with The Wellcome Trust, funded the creation of a national DNA Bank specific for MND. It was anticipated that the DNA Bank would constitute an important resource to researchers worldwide and significantly increase activity in MND genetic research. The DNA Bank houses over 3000 high quality DNA samples, all of which were donated by people living with MND, family members and non-related controls, accompanied by clinical phenotype data about the patients. Today the primary focus of the UK MND DNA Bank still remains to identify causative and disease modifying factors for this devastating disease.

The formation of AFB(1)-macromolecular adducts in rats and humans at dietary levels of exposure.

The levels of aflatoxin B(1)-DNA and aflatoxin B(1)-albumin adducts were investigated by accelerator mass spectrometry (AMS) in humans and rats following exposure to a known, dietary relevant amount of carbon-14 labeled aflatoxin B(1) ([(14)C]AFB(1)). The aims of the study were to: (a) investigate the dose-dependent formation of DNA and protein adducts at very low doses of AFB(1) (0.16 ng/kg-12.3 microg/kg) in the rat; (b) measure the levels of AFB(1)-albumin and AFB(1)-DNA adducts at known, relevant exposures in humans (c) study rat to human extrapolations of AFB(1)-albumin and DNA adduct levels. The results in the rat showed that both AFB(1)-albumin adduct and AFB(1)-DNA adduct formation were linear over this wide dose range. The order of adduct formation within the tissues studied was liver>kidney>colon>lung=spleen. Consenting volunteers received 1 microg ( approximately 15 ng/kg) of [(14)C]AFB(1) in a capsule approximately approximately 3.5-7 h prior to undergoing colon surgery. The mean level of human AFB(1)-albumin adducts was 38.8+/-19.55 pg [(14)C]AFB(1)/mg albumin/microg AFB(1)/kg body weight (b.w.), which was not statistically different to the equivalent dose in the rat (15 ng/kg) 42.29+/-7.13 pg [(14)C]AFB(1)/mg albumin/microg AFB(1)/kg b.w. There was evidence to suggest the formation of AFB(1)-DNA adducts in the human colon at very low doses. Comparison of the linear regressions of hepatic AFB(1)-DNA adduct and AFB(1)-albumin adduct levels in rat found them to be statistically similar suggesting that the level of AFB(1)-albumin adducts are useful biomarkers for AFB(1) dosimetry and may reflect the DNA adduct levels in the target tissue. [(14)C]AFB(1)-DNA and [(14)C]AFB(1)-albumin adducts were hydrolysed and analysed by HPLC to confirm that the [(14)C] measured by AMS was derived from the expected [(14)C]AFB(1) adducts.

Analysis of DNA adducts by accelerator mass spectrometry in human breast tissue after administration of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine and benzo[a]pyrene.

Epidemiological evidence has suggested an association between meat consumption and the risk of breast cancer. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a heterocyclic amine found in cooked meat, has been implicated in the aetiology of breast cancer and has been shown to induce tumour formation in rodent mammary glands. In addition, polycyclic aromatic hydrocarbons, such as benzo[a]pyrene (B[a]P) which has also been shown to induce tumour formation at a number of sites in rodents including the breast, are produced during the cooking of meat through the pyrolysis of fats. The aim of this study was to examine the bioavailability of these compounds to human breast tissue and their ability to bind to DNA to form DNA adducts. Patients undergoing breast surgery at York District Hospital were orally administered prior to surgery a capsule containing 20microg of 14C PhIP (182kBq, specific activity 2.05GBq/mmol) or 5microg of 14C B[a]P (36kBq, specific activity 1.81GBq/mmol). At surgery, normal and tumour breast tissue was resected and tissue concentrations of carcinogen measured by liquid scintillation counting and DNA adduct levels by accelerator mass spectrometry (AMS) were subsequently determined. It was found that both 14C PhIP and 14C B[a]P were able to reach the target organ where they had the ability to form DNA adducts. The level of adducts ranged from 26.22-477.35 and 6.61-208. 38 adducts/10(12) nucleotides following administration of 14C PhIP and 14C B[a]P, respectively, with no significant difference observed between levels in normal or tumour tissue. In addition, the data obtained in this study were comparable to adduct levels previously found in colon samples following administration of the same compounds to individuals undergoing colorectal surgery. This is the first report that these two carcinogens bind to human breast DNA after administration of a defined low dose.

Comparative biotransformation studies of MeIQx and PhIP in animal models and humans.

MeIQx and PhIP are putative carcinogenic heterocyclic amines formed during the cooking of meat and fish. Using accelerator mass spectrometry, we have investigated the metabolism and macromolecule binding of 14C-labelled MeIQx and PhIP in human cancer patients compared to the rat. Following oral administration of MeIQx and PhIP, more DNA adducts were formed in human colon tissue compared with rats. Differences were also observed between rats and humans in the metabolite profile and urine excretion for these compounds. These results suggest humans metabolise heterocyclic amines differently to laboratory rodents and question their use as models of human risk.

Quantitative structure-metabolism relationships (QSMR) using computational chemistry: pattern recognition analysis and statistical prediction of phase II conjugation reactions of substituted benzoic acids in the rat.

1. Quantitative relationships between molecular physico-chemical properties of 22 substituted benzoic acids and the extent of excretion of their metabolites in rat urine have been investigated using computational chemistry and multivariate statistics. 2. A data set of 34 theoretically derived physico-chemical descriptors calculated was used to classify the benzoic acids according to their predominant urinary metabolic fate. 3. Quantitative structure-metabolism relationships were obtained by linear regression using combinations of physico-chemical descriptors allowing the prediction of % urinary excretion of glycine (r = 0.73) and glucuronide conjugates (r = 0.82) and % urinary excretion of the parent compound (r = 0.91).

Investigation of the feasibility of directly-coupled HPLC-NMR with 2H detection with application to the metabolism of N-dimethylformamide-d7.

The use of 2H NMR spectroscopy as a detector for HPLC has been investigated using the continuous flow method in which rat urine containing metabolites of N-dimethylformamide-d7 was employed as a test case. Three xenobiotic-related species, including DMF-d7 itself, were detected. It is shown that for small molecules which give relatively sharp 2H NMR resonances, 2H HPLC-NMR spectroscopy is a feasible technique. For larger molecules, the resulting broad lines are likely to preclude the determination of detailed structural information. However, extension of the approach is possible by the use of selectively 2H-labelled xenobiotics to determine HPLC retention times of metabolites with continuous-flow 2H NMR spectroscopy detection, followed by stop-flow 1H HPLC-NMR spectroscopy for structural characterisation.

Quantitative structure-metabolism relationships for substituted benzoic acids in the rabbit: prediction of urinary excretion of glycine and glucuronide conjugates.

1. Quantitative relationships between molecular physicochemical properties of 24 substituted benzoic acids and their metabolic fate in the rabbit have been investigated using computational chemistry and multivariate statistical methods. 2. A total of 34 molecular properties were calculated for each compound using computational chemistry and were related statistically to the % molar recovery of glycine and glucuronide conjugates excreted in the urine of rabbits for the 24 compounds. 3. Compounds were successfully classified according to their dominant metabolic fate based on urinary excretion data, where stepwise linear regression analysis of the theoretical property data achieved good predictive fits for observed versus predicted % molar urinary recovery as glucuronide conjugates (r2 = 0.79) and % molar urinary recovery as glycine conjugates (r2 = 0.66). 4. Quantitative prediction of the urinary excretion of glucuronide and glycine conjugates of the parent compounds was achieved based on a statistical model using calculated molecular physicochemical parameters. Interpretation of the molecular properties, which are important for predicting the metabolic class, should give new insights into basic mechanisms of drug metabolism and underlying molecular recognition events that determine disposition and metabolism.

Deuterium NMR spectroscopy of biofluids for the identification of drug metabolites: application to N,N-dimethylformamide.

The metabolism of N,N-dimethylformamide in the Sprague-Dawley rat has been reinvestigated using NMR spectroscopy of urine. In particular, through the use of N,N-dimethylformamide-d7 (DMF-d7) and 2H-NMR spectroscopy, the principal metabolites of this compound have been confirmed in a direct manner. The use of inverse-detected two-dimensional 2H-13C correlation with 13C decoupling aided metabolite identification through the provision of 13C chemical shifts.