Jacint Corbella

Microsomal epoxide hydrolase and glutathione S-transferase polymorphisms in relation to laryngeal carcinoma risk

Two polymorphic sites of the microsomal epoxide hydrolase gene (EPHX1, 113Tyr-->113His, 139His-->139Arg) and four glutathione S-transferase genes (GSTM1, GSTM3, GSTP1, GSTT1) were genotyped in a group of patients with larynx cancer (N=204) and in a group of healthy controls (N=203), all Spanish caucasians. After adjusting for gender, age, and tobacco smoking, none of the polymorphisms alone were found to be associated with larynx cancer risk. The analysis of EPHX1/GST combinations, however, showed a significant over-representation of patients with a combination of 113Tyr/113Tyr EPHX1 and 105Ile/105Ile GSTP1 (adjusted odds ratio (OR): 1.95; 95% confidence interval (CI): 1.02-3.78). The calculation of the predicted epoxide hydrolase (EH) activity also showed an increased risk for the individuals with both predicted high activity EH and 105Ile/105Ile GSTP1 (OR: 2.90; 95% CI: 1.10-7.67). These results on larynx cancer tend to confirm a former study on lung cancer (Cancer Lett. 173 (2001) 155) suggesting the existence of an interaction between variants of EH and GSTpi, both enzymes being involved in the metabolism of aromatic hydrocarbons, that may increase susceptibility to tobacco-related cancers.

Genetic polymorphism of glutathione S-transferase P1 gene and lung cancer risk.

Objectives: The human GSTTP1 gene is polymorphic with an A → G transition in exon 5 causing a replacement 105 Ile→Val in the GSTP1 protein. The two isoforms, encoded by the alleles GSTP1*A and GSTP1*B, respectively, show different catalytic efficiencies towards some carcinogenic epoxides. In this study we have addressed the possible role of the Ile105Val GSTP1 polymorphism in lung cancer susceptibility.Methods: The polymorphic site was genotyped by RFLP in a group of lung cancer patients (n=164) and in two control groups (healthy smokers, n=132; general population, n=200). All patients and controls were Northwestern Mediterranean Caucasians of the same ethnic origin.Results and Conclusions: The cancer patients showed frequencies of GSTP1*A/A; GSTP1*A/B and GSTP1*B/B (50%, 38%, 11%, respectively) very similar to those of both control groups (healthy smokers: 48%, 41%, 11%). After adjusting for age, sex and smoking status, no association was found between the GSTP1*B allele and lung cancer risk (OR: 1.18; 95% CI: 0.67–2.07). The Ile105val GSTP1 polymorphism was also analysed in combination with the GSTM1 and GSTT1 genes. The results showed that allelism at GSTP1 did not increase the risk associated with the GSTM1 or GSTT1 deletions.

Lung cancer susceptibility in relation to combined polymorphisms of microsomal epoxide hydrolase and glutathione S-transferase P1

Human microsomal epoxide hydrolase (mEH) catalyzes a key step in the biotransformation of benzo[a]pyrene that yields the highly mutagenic (+)-anti-7,8-diol-9,10 epoxide (BPDE). Two polymorphisms have been described in the coding region of the mEH gene (EPHX1) that produce two protein variants: 113Tyr-->113His (exon 3) and 139His-->139Arg (exon 4). We performed a case-control study among Northwestern Mediterranean Caucasians to investigate a possible association between these EPHX1 variants and lung cancer risk. Both EPHX1 polymorphisms were analyzed in a group of lung cancer patients (n=176) and in a control group of healthy smokers (n=187). The results showed a significantly decreased risk for the rare homozygous 113His/113His (adjusted odds ratio (OR): 0.44, 95% confidence interval (CI): 0.27-0.71) and 139Arg/139Arg (adjusted OR: 0.55, 95% CI: 0.33-0.91) compared with the major wild-types 113Tyr/113Tyr and 139His/139His, respectively, as the references. Thereafter, we analyzed the EPHX1 variants in combination with three glutathione S-transferase polymorphic genes (GSTM1, GSTT1, and GSTP1) and we found a significant overepresentation of cancer patients with a combination of exon 3 113Tyr/113Tyr EPHX1 and exon 5 105Ile/105Ile GSTP1 (adjusted OR: 2.34, 95% CI: 1.21-4.52). The polymorphic site within the exon 5 of GSTP1 results in a Ile-->Val substitution, and the isoleucine GSTpi isoform has been found in vitro to be less active than the valine isoform towards the conjugation of BPDE. The 113 Tyr/Tyr EPHX1 encodes for a high-activity mEH. Our results agree with these observations in vitro and suggest that a genetically determined combination of a high-activity mEH and a low-activity GSTpi may increase lung cancer risk among smokers.

The effect of age on aluminum retention in rats

The present study was designed to assess potential changes in aluminum (Al) retention during advanced age. Young (21 day old), adult (8 months), and old (16 months) rats were exposed to 0, 50, and 100 mg Al/kg/day administered as aluminum nitrate in drinking water for a period of 6.5 months. Urinary Al levels were measured after 3 and 6.5 months of Al exposure. Organ weights and tissue Al concentrations were examined at 6.5 months of Al administration. Differences in the tissue accumulation of Al with age included higher liver, kidneys, spleen, bone and testes levels in old rats than in tissues of both young or adult animals. In contrast, brain concentrations were higher in young rats. Urinary Al levels of young, adult or old Al-exposed rats showed different trends at 6.5 months of Al exposure: compared with young values adult values declined, while those of old rats tended to increase further. The current results show that tissue Al retention patterns may be significantly altered depending on the age at Al exposure. This finding may be of concern for future investigations on the potential role of Al in certain neurological disorders.

Optimized procedure for lamotrigine analysis in serum by high-performance liquid chromatography without interferences from other frequently coadministered anticonvulsants

The authors have developed a simple isocratic high-pressure liquid chromatographic (HPLC) assay for the simultaneous determination of lamotrigine and other frequently coadministered antiepileptic drugs in serum samples. Lamotrigine extraction was performed on a reversed-phase Oasis HBL preparation column. The eluates containing butalbital as internal standard were separated with a 7-&mgr;m Chromsystems C18 250 × 4.0 mm I.D. reversed-phase column at a temperature of 40°C using a mobile phase consisting of pH 3.8 phosphate-acetonitrile buffer (55:45, v/v), at a flow rate of 0.8 mL/min. Ultraviolet detection was carried out at 210 nm. Measurement of the peak:height ratio allowed quantitative determination of the samples. The method was linear over a concentration range of 0.2 to 20 &mgr;g/mL for lamotrigine. Recovery was >90%. Within-day and between-day coefficients of variation ranged from 1.8% to 6.7%. The mean lamotrigine concentration was 8.01 ± 5.63 &mgr;g/mL. After studying sera from 130 patients treated with lamotrigine the authors confirmed that associated antiepileptic therapy affected the serum lamotrigine levels, which were significantly higher in patients under valproic acid treatment.

Excretion of hexachlorobenzene and metabolites in feces in a highly exposed human population.

A set of 53 individuals from a population highly exposed to airborne hexachlorobenzene (HCB) were selected to study the elimination kinetics of this chemical in humans. The volunteers provided blood, 24-hr urine, and feces samples for analysis of HCB and metabolites. The serum HCB concentrations ranged from 2.4 to 1,485 ng/mL (mean +/- SD, 124 +/- 278), confirming that this human population has the highest HCB blood levels ever reported. All analyzed feces samples contained unchanged HCB (range, 11-3,025 ng/g dry weight; mean +/- SD, 395 +/- 629). The HCB concentration in feces strongly correlated with HCB in serum (r = 0.85; p < 0.001), suggesting an equilibrium in feces/serum that is compatible with a main pulmonary entrance of the chemical and low intestinal excretion of nonabsorbed foodborne HCB. The equilibrium is also compatible with a nonbiliary passive transfer of the chemical to the intestinal lumen. Two HCB main metabolites, pentachlorophenol (PCP) and pentachlorobenzenethiol (PCBT), were detected in 51% and 54% of feces samples, respectively. All urine samples contained PCP and PCBT, confirming the conclusions of a previous study [Environ Health Perspect 105:78-83 (1997)]. The comparison between feces and urine showed that whereas daily urinary elimination of metabolites may account for 3% of total HCB in blood, intestinal excretion of unchanged HCB may account for about 6%, thus showing the importance of metabolism in the overall elimination of HCB. The elimination of HCB and metabolites by both routes, however, appears to be very small (< 0.05%/day) as compared to the estimated HCB adipose depots. Features of HCB kinetics that we present in this study, i.e., nonsaturated intestinal elimination of HCB and excretion in feces and urine of inert glutathione derivatives, may explain, in part, the absence of porphyria cutanea in this human population heavily exposed to HCB. ImagesFigure 1Figure 2

Characterisation of three Amerindian populations from Hidalgo State (Mexico) by 15 STR-PCR polymorphisms

The purpose of this study is to report allele frequency data of three ethnic Amerindian population samples: the Otomi (Hña-hñu) from eastern Sierra Madre and Ixmiquilpan valley and the Huasteco from La Huasteca. These groups were characterised by 15 STR-PCR polymorphisms (HumTH01, HumvWA, D18S51, HumTPOX, D19S433, D16S539, D13S317, D8S1179, D7S820, D5S818, HumFGA, CSF1PO, D2S1338, D3S1358 and D21S11). No significant deviations in observed allelic frequencies from Hardy-Weinberg equilibrium were found for all the studied systems. From the forensic point of view, the heterozygosity value, power of discrimination and the a priori chance of exclusion were calculated.

TRANSPORT OF ORGANOCHLORINE RESIDUES IN THE RAT AND HUMAN BLOOD

Organochlorine residues (OCR)2 are poorly soluble in water and are transported in the organism bound by the blood components. The distribution among blood fractions (cells/plasma, lipoproteins/rest of plasma proteins) were variable depending on the residue (HCB,p p′-DDE, HCH, Aroclor® 1260, PCP) and on the species (rat, man). Differences were not found betweenin vivo (after oral single dosing) andin vitro (blood incubation) experiments. Results indicated a high affinity of organochlorine residues for lipo-proteins; however, binding to blood carriers was very weak as demonstrated by the rapid release of residues by elution through a reverse phase column. The effects of residue binding to blood components on the distribution kinetics to tissues are discussed.

Inhibition of intratesticular testosterone synthesis by inorganic lead

The alterations in testicular testosterone synthesis produced by exposure to inorganic lead were investigated in BALB/c+ mice. Lead concentration in blood and testes and the levels of testosterone and delta 4-androgen biosynthesis pathway precursors (4-androstenedione, 17-hydroxyprogesterone, and progesterone) were measured in animals which were exposed to lead acetate in the drinking water (366 mg/l, 0.97 +/- 0.12 mg lead/animal/day) during 6 months. The results showed a significant reduction of the intratesticular testosterone levels after 30 days of exposure and of the androstenedione levels after 150 days. Intratesticular progesterone and hydroxyprogesterone levels showed no changes during the assay.

Influence of posttransplant time on dose and concentration of tacrolimus in liver transplant patients

Abstract The dosage of tacrolimus (D), the trough blood concentrations (C) and the evolution of the D/C ratio were followed for 1 year after transplantation in so adult patients (38 males and 12 females) undergoing liver allograft. A total of 1489 samples were analysed by the IMx tacrolimus method. The overall median concentration was 11.27 ng/ml. During the 1st month the median of the tacrolimus levels was 8.4 ng/ml, and 73.1 % of the analysed samples were within the established therapeutic range. The median oral tacrolimus dose was progressively reduced from 0.12 mg/kg per day during the 1st month to 0.06 mg/kg per day at the end of studied period. A significant negative association was observed between the D/C ratio and the posttransplantation period (r= ‐0.3892; P < 0.0001). The median D/C ratio ranged from 0.0144 at 1st month to 0.0053 at 1 year. Significant D/C declines were observed after the 1st and 3rd months posttransplant. The decrease in corticosteroid doses and the increase in serum albumin may explain the reduction in clearance with time.