Interaction between genetic polymorphism of cytochrome P450-1B1 and environmental pollutants in breast cancer risk.

Cytochrome P450 1B1 (CYP1B1) is implicated in the activation of potentially carcinogenic xenobiotics and oestrogens. The polymorphism of the CYP1B1 gene at codon 432 (Val-->Leu) is associated with change in catalytic function. In a case-series study of breast cancer patients, we investigated the interaction between this polymorphism and environmental exposure. The women carrying the Val CYP1B1 allele and who had lived near to a waste incinerator for more than 10 years had a higher risk of breast cancer than those never exposed with the Leu/Leu genotype (odds ratio of interactions (ORi)=3.26, 95% confidence interval (CI) 1.20-8.84). Also, the Val CYP1B1 allele increased the susceptibility to breast cancer for women exposed during their life to agricultural products used in farming (ORi = 2.18, 95% CI 1.10-4.32). These xenobiotics, mainly organochlorine hydrocarbons, are known to bind to the aromatic hydrocarbon receptor (AhR), and to induce the expression of CYP1B1 enzyme. The excess risk for exposed women with a Val CYP1B1 homo/heterozygous genotype could result from a higher exposure to activated metabolites of pesticides or dioxin-like substances. Also, a higher induction of CYP1B1 enzyme by xenobiotics could increase the formation of genotoxic catechol-oestrogens among exposed women carrying the Val CYP1B1 allele. Our results suggested that the Val CYP1B1 allele increases the susceptibility to breast cancer in women exposed to waste incinerator or agricultural pollutants.

[Nitrogen dioxide and ozone exposures in a population sample from Ile-de-France]. / Expositions au dioxyde d'azote et à l'ozone d'une population de l'Ile-de-France.

BACKGROUND: Individual exposure to NO(2)and O(3) has been estimated in an urban population sample in southern France and the determinants identified. The present study was conducted to evaluated individual exposure to NO(2) and O(3) and to identify the environmental determinants of exposure in a larger population living in different environmental conditions. METHODS: Two hundred ninety-four volunteers were recruited from the SUVIMAX sample in Ile-de-France. The study covered 2 periods of 5 consecutive days, one in winter and the other in the fall of 1998. Passive monitors were used to estimate individual exposure and indoor concentration at the participant's dwelling. Background atmosphere concentrations were obtained for the AIRPARIF surveillance network. Single and multiple ANOVA were used for statistical analysis. RESULTS: Individual exposures were low, especially for O(3) in the considered periods of time. Mean NO(2) and O(3)concentrations were 41 microg/m(3)/h and 16 microg/m(3)/h, respectively. The NO(2) individual exposure increased with the time spent in traffic and indoor concentration. The correlation coefficient between indoor and individual levels was r=0.73, and indoor concentration explained 50% of the variance in individual exposure. The site of the dwelling with regard to high traffic street, and most strongly, the presence of a gas stove influenced indoor concentration. However, mechanical air extraction decreased the mean indoor NO(2) level of the dwellings. CONCLUSION: This study allowed identification of the environmental determinants of NO(2) exposure in an urban sample. These data, together with those obtained previously, well be used to establish an exposure matrix for NO(2).

Ozone exposure and blood antioxidants: a study in a periurban area in Southern France.

Major carotenoids in plasma--especially beta-carotene--are affected by oxidative stress (e.g., tobacco smoking). Environmental ozone induced oxidative stress in experimental in vitro and in vivo studies, and it also increased the incidence of lung cancer in mice. We proposed to measure, after controlling for other determinants, the impact of personal ozone exposure on carotenoids levels in plasma. During the summer, we recruited 58 volunteer subjects who worked in a periurban zone. We asked each subject to wear a passive sample, which measured ozone exposure for 5 consecutive d. At the end of this period, we assessed plasma antioxidants. We observed a negative significant regression coefficient between alpha- or beta-carotene and ozone exposure (r = -.39, p < .01, and r = -.45, p = .02, respectively). In a subsample of 45 nonsmoker subjects, among whom carotene intake was lower than the median intake value (i.e., 6.6 mg/d) of the overall group, we noted that a relatively low exposure to ozone (> or = 50 microg/m3 x h or > or = 23.8 ppb) induced a significant decrease in plasma beta-carotene levels (i.e., 0.7 micromol/l to 0.4 micromol/l). This significant decrease suggested that a high dietary intake of fruit or vegetables can have a beneficial influence on the levels of plasma antioxidants generated in response to ozone exposure.

Personal exposure to nitrogen dioxide pollution and effect on plasma antioxidants.

We conducted a cross-sectional epidemiological study to evaluate personal exposure to nitrogen dioxide and its effect on blood antioxidants. Personal exposure of 107 volunteers was assessed for 14 d with passive monitors. We excluded heavy smokers (> 10 cigarettes/d) from the study. Sociodemographic and environmental data, as well as beta-carotene intake, were recorded. We mainly attributed the mean nitrogen dioxide personal exposure (31.9 +/- 12.7 microg/m3 [0.017 ppm or 0.70 microM/m3]) (R2 = 0.75) to residence site in the city, time spent in urban traffic, and use of gas stoves. The correlation between nitrogen dioxide exposure and blood antioxidant concentration was weak; in addition, the correlation coefficients for men and women were inconsistent. Nonetheless, we found some evidence of an interaction between carotene intake and nitrogen dioxide exposure: a significantly lower plasma beta-carotene level was evident among subjects who consumed < or = 4.5 mg/jour of carotene and who were exposed to nitrogen dioxide levels that exceeded 40 microg/m3 (0.021 ppm or 0.87 microM/m3) of nitrogen dioxide.

Measurement of background urban nitrogen dioxide pollution levels with passive samplers in Montpellier, France.

Background nitrogen dioxide (NO2) pollution levels in Montpellier were measured in the context of an assessment operation carried out by the local monitoring network (AMPADI-LR), using Palmes passive samplers. The equipment was validated by continuous measurement with automatic chemiluminescence analyzers. Measurements from representative background pollution sites and the ensuing cartographic representation provide information about local pollution data, a description of seasonal evolution and an assessment of the influence of various sources. The study may be used to define parameters for establishing an exposure index, taking into account roads with heavy traffic, which affects the distribution of NO2 over Montpellier, and meteorological factors. This is a pilot study which will subsequently be used for a more precise assessment measuring the personal exposure of inhabitants, for the purposes of a study on effects on health.

Tumor progression and oxidant-antioxidant status.

We previously reported on a paradoxical oxidant-antioxidant status in breast cancer patients, more so in pre-menopausal than menopausal women. In this study, measurements were performed on 146 patients with various carcinomas. Vitamin E/total cholesterol increased and plasma malondialdehyde decreased with tumor size and progression. To investigate the difference between young pre-menopausal and aged menopausal breast cancer patients, the same measurements were performed in 365 breast cancer patients according to pathology, tumor size and estrogen receptors. The oxidant-antioxidant status varied with these prognosis factors in the same pattern, and was more pronounced in young than aged women.

Tumor progression and oxidant-antioxidant status.

Severity of prognosis factors in breast cancer cases was found to be associated with an increase in plasma vitamin E and a decrease in plasma malondialdehyde (peroxidability index). The first aim of this study was to determine whether this association is also present in other cancers. Measurements were taken before therapy on 129 patients with various carcinomas. Cholesterol was also investigated, as vitamin E is closely related to this analyte. Patients were classified by tumor size (T < or = 5 cm and T > 5 cm) and by invasion status, assessed by the presence of nodes and/or metastasis. The vitamin E/total cholesterol concentration ratio was higher and the cholesterol and malondialdehyde concentrations were significantly lower in the plasma of patients with large tumors or in whom nodes and/or metastasis were present, whatever the site. The multivariate analysis performed to measure the association of these analyte concentrations with tumor progression showed that the presence of nodes and/or metastases was inversely associated with a low vitamin E/total cholesterol ratio (OR, 0.5; CI, 0.3-1.1) and, directly associated with low plasma concentrations of cholesterol and malondialdehyde (OR, 3.0; CI, 1.3-6.8 and OR, 2.8; CI, 1.2-6.7 respectively). The same types of associations were identified with large tumors, but were less strong. Together these findings supported an alteration of lipid parameters related to the oxidant-antioxidant status in cancer patients. This alteration appears to be associated with tumor growth and progression in patients with various cancer sites.

Oxidant-antioxidant status alterations in cancer patients: relationship to tumor progression.

A significant change of vitamin E and malondialdehyde plasma concentrations was reported in breast cancer patients. This change was unexpected because vitamin E was higher and malondialdehyde lower in cases than in controls, and the difference was more significant in young rather than older women. The first aim of this study was to determine whether these changes were associated only with breast cancer, or with hormone-related cancers, and/or cancers associated with nutritional risk factors or with all types of cancers. Measurements were performed before therapy on 269 hospital-based controls and on 146 patients with various carcinomas. Vitamin E:total cholesterol increased and malondialdehyde plasma concentration decreased with tumor size and progression, without relation to the site. The second aim was to understand the difference in the change observed between young and old breast cancer patients. These analytes were measured in 365 breast cancer patients according to three prognosis factors: pathology, tumor size and estrogen receptors. Vitamin E:total cholesterol significantly decreased with estrogen receptor amount. Malondialdehyde plasma concentration decreased with severity of pathology and tumor size. Together, these data support the association of an altered oxidant-antioxidant profile in cancer patients with tumor growth and progression.

Within-subjects seasonal variation and determinants of inter-individual variations of plasma beta-carotene.

We studied determinants of plasma beta-carotene in a sample of 98 normal volunteers. Blood samples were collected and 4-day weighed dietary records kept for each season of the year. Information on tobacco use and demographic and socio-economic data was elicited at the first interview. There was a peak of plasma beta-carotene in the fall, whereas the dietary beta-carotene peak occurred in summer. In a regression analysis involving a variety of independent variables, the only statistically significant determinants of plasma beta-carotene for non-smokers were dietary beta-carotene, sex, serum cholesterol and triglycerides. The number of cigarettes/day was introduced into the model for smokers and a significant negative coefficient was obtained for this variable. Interaction between dietary beta-carotene and tobacco use was shown to be a significant determinant of plasma beta-carotene for the total sample.

Effect of the progesterone antagonist RU486 on human myometrial spontaneous contractility and PGI2 release.

We studied the effect of antiprogesterone RU 486 on spontaneous uterine contractility and PGI2 release with human myometrial strips superfused "in vitro". A decrease of PGI2 release into the superfusion medium was observed after 20 min superfusion. The inhibition was dose-dependent and reversible. After 20 min washing with tyrode medium without RU 486, the uterine strips recovered their initial rate of release. R5020, a progesterone agonist, did not affect PGI2 release nor dexamethasone and testosterone. Parallel to the decrease of PGI2 observed during RU 486 superfusion, the uterine spontaneous contraction frequency decreased, while the amplitude and duration of contractions increased. The alteration of uterine contractility was also rapid, dose-dependent and reversible. Modification of uterine strip spontaneous contractility, similar to those induced by RU 486, were also observed with superfusions of R5020 at concentrations as low as 10(-9)M, dexamethasone (10(-8)M), but not with superfusions of testosterone. These observations are not in favour of a progesterone-receptor mediated effect of RU 486 in our model. The mechanism of action may be related to the antiprogesterone specific structure i.e. the bulky substituent at the C-11 position. The RU 486 effect on uterine strip contractility, mimicked by other steroids, could point to a non-specific lipid/membrane interaction. However, the fact that testosterone did not affect motility, may indicate a possible specificity of steroids having a 3 oxo pregnene structure.

Prostaglandin synthesis from endogenous and exogenous arachidonic acid in the rat uterus. Effect of estradiol and progesterone.

Regulation of uterine prostaglandin (PG) synthesis by steroid sex hormones was studied in female rats. Animals were ovariectomized (OVX) and received silastic implants of estradiol (E2) or progesterone (Pg); the implants were maintained for 7 days. The animals were sacrificed and their uteri homogenized at 4 degrees C. Basal levels of PGs and PGs synthesized during 20 min incubations at 37 degrees C, either without exogenous arachidonic acid (AA), or in the presence of 2.10(-5)M added AA were measured by RIA. Comparison between the various treatments shows that the regulation of uterine PG synthesis in the rat is a multistep process and depends on the type of PG. PGI2 (6 keto PGF1 alpha) is synthesised in very large amounts but is not very significantly influenced by hormonal treatment. PGF2 alpha and PGE2 are synthesized in much smaller quantities but are very dependent on hormonal treatment. E2 stimulates PGF2 alpha and inhibits PGE2, shifting the ratio from 0.5 in untreated OVX rats to 3.3 in OVX E2-treated rats. TXA2 (TXB2) is stimulated by E2. Pg significantly stimulates endogenous PGF2 alpha levels but does not change the profile of PGs synthesized from the endogenous substrate. It inhibits PGE2 synthesis from exogenously added AA. These results show that E2 favors PGF2 alpha synthesis at the expense of PGE2 and that the synthesis of PGI2, which is the main AA metabolite in the rat uterus is not hormone dependent, (at least not under the conditions of our experiments).

Effect of oestradiol 17 beta on prostaglandin biosynthesis by the uterus of ovariectomized rat and guinea pig.

In vitro prostaglandin biosynthesis by uteri of ovariectomized rats and guinea pigs treated or untreated with oestradiol 17 beta, administered subcutaneously, was measured by R.I.A. of PGF2 alpha and PGE2. Incubations with [1-14C] arachidonic acid were also performed and labelled metabolites were analyzed by TLC. The main metabolite in rats was 6 keto PGF1 alpha and in decreasing order of magnitude, PGF2 alpha and PGE2. In guinea pig PGF2 alpha was the main product. Ovariectomy in rats completely changed the pattern of synthetized prostanoids : PGI2 production was doubled when compared to cycling rats and PGE2 increased 10 fold. PGF2 alpha values were similar to the mean value measured during the cycle. OE2 treatment almost completely inhibited PGI2 synthesis and reduced PGE2 by half. Total PG synthesis in OE2 treated animals was decreased by 5 fold when compared to spayed rats. Endogenous PGF2 alpha synthesis was slightly stimulated. In the guinea pig OE2 treatment of ovariectomized animals increased the total synthesis from 50 per cent. PGF2 alpha was always the main metabolite. In conclusion OE2 regulation of uterine PG synthesis is depending on the animal species and cannot be explained by a unique effect on the cyclooxygenase, but rather by an interplay on the various enzymes of the arachidonic acid cascade.

Prostaglandin biosynthesis by the rat uterus during the oestrus cycle, temporal correlation with plasma oestradiol and progesterone concentrations, identification of 6 keto PGF1 alpha as the major metabolite.

Prostaglandin biosynthesis was studied in the rat uterus during the oestrous cycle. Uterine homogenates were incubated for 20 minutes inthe presence of exogenous substrate (2.10(-5)M). PGF2 alpha and PGE2 were measured by R.I.A.. A sharp peak of PGF2 alpha and a smaller peak of PGE2 were observed at prooestrus, 20 h. Another small PGE2 peak occurred at dioestrus II, 15 h. The lowest values of both PGs were found on dioestrus, 15 h. Plasma oestradiol concentrations were highest at proestrus, 15 h and 20 h. A sharp progesterone peak occurred at prooestrus, 20 h. The PGF2 alpha peak is next to the oestradiol peak and is superimposable or lags slightly beyond the progesterone peak. Incubation with 14C arachidonic acid and subsequent analysis of extracts by TLC and scanning showed that the major metabolite is PGI2, identified as 6 keto PGF1 alpha. The conversion rate of arachidonic acid into 6 keto PGF1 alpha is 5 times higher than into PGF2 alpha. 6 Keto PGF1 alpha was further identified by GC/MS. No significant difference was observed between 6 keto PGF1 alpha production during oestrus and dioestrus.