Evaluation of parameters of oxidative stress after in vitro exposure to FMCW- and CDMA-modulated radiofrequency radiation fields

The goal of this study was to determine whether radiofrequency (RF) radiation is capable of inducing oxidative stress or affecting the response to oxidative stress in cultured mammalian cells. The two types of RF radiation investigated were frequency-modulated continuous-wave with a carrier frequency of 835.62 MHz (FMCW) and code division multiple access centered on 847.74 MHz (CDMA). To evaluate the effect of RF radiation on oxidative stress, J774.16 mouse macrophage cells were stimulated with gamma-interferon (IFN) and bacterial lipopolysaccharide (LPS) prior to exposure. Cell cultures were exposed for 20-22 h to a specific absorption rate of 0.8 W/kg at a temperature of 37.0 +/- 0.3 degrees C. Oxidative stress was evaluated by measuring oxidant levels, antioxidant levels, oxidative damage and nitric oxide production. Oxidation of thiols was measured by monitoring the accumulation of glutathione disulfide (GSSG). Cellular antioxidant defenses were evaluated by measuring superoxide dismutase activity (CuZnSOD and MnSOD) as well as catalase and glutathione peroxidase activity. The trypan blue dye exclusion assay was used to measure any changes in viability. The results of these studies indicated that FMCW- and CDMA-modulated RF radiation did not alter parameters indicative of oxidative stress in J774.16 cells. FMCW- and CDMA-modulated fields did not alter the level of intracellular oxidants, accumulation of GSSG or induction of antioxidant defenses in IFN/LPS-stimulated cells. Consistent with the lack of an effect on oxidative stress parameters, no change in toxicity was observed in J774.16 cells after either optimal (with or without inhibitors of nitric oxide synthase) or suboptimal stimulation.     

An association between NQO1 genetic polymorphism and risk of bladder cancer

NAD(P)H:quinone oxidoreductase (NQO1) is a detoxification enzyme that plays a critical role in protecting cells against chemically induced oxidative stress, cytotoxicity, mutagenicity, and carcinogenicity. NQO1 protects cells from oxidative damage by preventing the generation of reactive oxygen species and reducing certain environmental carcinogens, such as nitroaromatic compounds, heterocyclic amines, and possible cigarette smoke condensate. A C-->T single nucleotide polymorphism in exon 6 was shown to reduce NQO1 enzyme activity, which may diminish the protection provided by NQO1. Therefore, we hypothesized that people with the variant allele genotypes of NQO1 are at higher risk for bladder cancer. In an ongoing case-control study, the NQO1 genotypes were successfully identified by polymerase chain reaction restriction fragment length polymorphism in 265 bladder cancer patients and 261 control subjects matched for age, sex, and ethnicity. The frequency of the variant NQO1 allele was 18% for controls and 21% for cases. The variant allele genotypes of NQO1 were associated with a higher risk of bladder cancer in Caucasians (odds ratio (OR)=1.51; 95% confidence interval (CI)=1.01-2.25). Further analysis in Caucasians showed an elevated bladder cancer risk in men (OR=1.75; 95% CI=1.08-2.85) but not in women (OR=1.16; 95% CI=0.57-2.37). In addition, the variant allele genotypes were associated with higher bladder cancer risk in ever smokers (OR=1.78; 95% CI=1.06-3.00), but not in never smokers (OR=1.19; 95% CI=0.65-2.20). These results suggest that the NQO1 genetic polymorphism modulates bladder cancer risk, especially in men and ever smokers.     

Rapid assessment of repair of ultraviolet DNA damage with a modified host-cell reactivation assay using a luciferase reporter gene and correlation with polymorphisms of DNA repair genes in normal human lymphocytes

As DNA repair plays an important role in genetic susceptibility to cancer, assessment of the DNA repair phenotype is critical for molecular epidemiological studies of cancer. In this report, we compared use of the luciferase (luc) reporter gene in a host-cell reactivation (HCR) (LUC) assay of repair of ultraviolet (UV) damage to DNA to use of the chloramphenicol (cat) gene-based HCR (CAT) assay we used previously for case-control studies. We performed both the assays on cryopreserved lymphocytes from 102 healthy non-Hispanic white subjects. There was a close correlation between DNA repair capacity (DRC) as measured by the LUC and CAT assays. Although these two assays had similar variation, the LUC assay was faster and more sensitive. We also analyzed the relationship between DRC and the subjects' previously determined genotypes for four polymorphisms of two nucleotide-excision repair (NER) genes (in intron 9 of xeroderma pigmentosum (XP) C and exons 6, 10 and 23 of XPD) and one polymorphism of a base-excision repair gene in exon 10 of X-ray complementing group 1 (XRCC1). The DRC was significantly lower in subjects homozygous for one or more polymorphisms of the two NER genes than in subjects with other genotypes (P=0.010). In contrast, the polymorphic XRCC1 allele had no significant effect on DRC. These results suggest that the post-UV LUC assay measures NER phenotype and that polymorphisms of XPC and XPD genes modulate DRC. For population studies of the DNA repair phenotype, many samples need to be evaluated, and so the LUC assay has several advantages over the CAT assay: the LUC assay was more sensitive, had less variation, was not radioactive, was easier to perform, and required fewer cryopreserved cells. These features make the LUC-based HCR assay suitable for molecular epidemiological studies.     

IL-11 and IL-11Rα immunolocalisation at primate implantation sites supports a role for IL-11 in placentation and fetal development

Embryo implantation, endometrial stromal cell decidualization and formation of a functional placenta are critical processes in the establishment and maintenance of pregnancy. Interleukin (IL)-11 signalling is essential for adequate decidualization in the mouse uterus and IL-11 promotes decidualization in the human. IL-11 action is mediated via binding to the specific IL-11 receptor α (IL-11Rα). The present study examined immunoreactive IL-11 and IL-11Rα in cycling rhesus monkey endometrium, at implantation sites in cynomolgus and rhesus monkeys and in human first trimester decidua and defined distinct spatial and temporal patterns. In cycling rhesus monkey endometrium, IL-11 and IL-11Rα increased in both basalis and functionalis regions during the secretory compared with the proliferative phase, with changing cellular locations in luminal and glandular epithelium and stroma. The patterns were similar overall to those previously described in human endometrium. Differences were seen in immunostaining during implantation in cynomologus and rhesus monkey. In the cynomolgus, very little staining for IL-11 or IL-11Rα was seen in syncytio- and cyto-trophoblast cells in the villi between days 12 and 150 of pregnancy although there was moderate staining in cytotrophoblast in the shell between days 12 and 17 and in subpopulations of cytotrophoblast cells invading the arteries at day 17. By contrast in the rhesus monkey between days 24 and 35 of pregnancy and in human first trimester placenta, cyto- and syncytio-trophoblast in the villi but not cytotrophoblast in the shell were positively stained. The most intense staining for both IL-11 and IL-11Rα was present within the decidua in the maternal component of implantation sites in all three primates but moderate staining was also present in maternal vascular smooth muscle and glands perivascular cells and epithelial plaques. These results are consistent with a role for IL-11 both during decidualization and placentation in primates.     

Effects of progesterone on uterine leiomyoma growth and apoptosis

Uterine leiomyomas appear during the reproductive years and regress after menopause, indicating the ovarian steroid-dependent growth potential. Recently we have found that the use of levonorgestrel-releasing intrauterine system (IUS) is effective in the long-term contraception and management of menorrhagic women with uterine myomas because of a striking reduction in menorrhagia. These clinical experiences prompted us to characterize the effects of progestin on the proliferation and apoptosis of leiomyoma cells cultured in vitro. As epidermal growth factor (EGF) has been shown to mediate estrogen action and play a crucial role in regulating leiomyoma growth, we also investigated the effects of sex steroids on EGF and EGF receptor (EGF-R) expression in leiomyoma cells. In cultures of leiomyoma cells, the addition of either E(2) (10 ng/ml) or P(4) (100 ng/ml) resulted in an increase in proliferating cell nuclear antigen (PCNA) expression in the cells; whereas in cultures of normal myometrial cells, the addition of E(2) augmented PCNA expression in the cells, but P(4) did not. Immunoblot analysis revealed that leiomyoma cells contained immunoreactive EGF and that P(4) treatment resulted in an increase in EGF expression in the cells. In contrast, E(2) treatment augmented EGF-R expression in cultured leiomyoma cells, but P(4) did not. These results indicate that P(4) up-regulates the expression of PCNA and EGF in leiomyoma cells, whereas E(2) up-regulates the expression of PCNA and EGF-R in those cells. It is, therefore, conceivable that P(4) and E(2) act in combination to stimulate the proliferative potential of leiomyoma cells through the induction of EGF and EGF-R expression. We also found that Bcl-2 protein, an apoptosis-inhibiting gene product, was abundantly expressed in leiomyoma relative to that in normal myometrium, suggesting that the abundant expression of Bcl-2 protein in leiomyoma cells may be one of the molecular bases for the enhanced growth of leiomyoma relative to that of normal myometrium in the uterus. Furthermore, Bcl-2 protein expression in leiomyoma cells was up-regulated by P(4), but down-regulated by E(2). Therefore, it seems likely that P(4) may also participate in leiomyoma growth through the induction of Bcl-2 protein in leiomyoma cells.