Chie Furuta

Estrogenic Activities of Nitrophenols in Diesel Exhaust Particles

Abstract We recently isolated 3-methyl-4-nitrophenol (4-nitro-m-cresol; PNMC) and 4-nitro-3-phenylphenol (PNMPP) from diesel exhaust particles (DEP) and identified them as vasodilators. Because these compounds are alkylphenolic derivatives that might mimic hormones, we evaluated their estrogenic activity by using recombinant yeast screens, myometrial contractility assays, and in vivo uterotrophic assays. Recombinant yeast screen assays showed that both PNMC and PNMPP possess estrogenic activity. Furthermore, ovariectomized 25-day-old immature female rats injected with PNMC and PNMPP subcutaneously for 2 days showed significant increases in uterine weight among those receiving 100 mg/kg PNMC and 0.1 and 1.0 mg/kg PNMPP. To clarify further the estrogenic activity of PNMC and PNMPP, rat uterine horns were monitored in organ bath chambers for myometrial contractility in response to oxytocin (OT). Significant differences occurred in the initial and maximum contractilities to OT at 0.25 and 25 mIU/ml in uterine horns obtained from animals treated with 100 mg/kg PNMC and in the maximum contractilities to OT at 0.025, 0.25, and 25 mIU/ml in those from rats treated with 0.1 mg/kg PNMPP. These results clearly demonstrated that PNMC and PNMPP in DEP have estrogenic activity both in vitro and in vivo and might therefore be considered as endocrine-disrupting chemicals.

Immunohistological study for estrogenic activities of nitrophenols in diesel exhaust particles

We recently isolated 3-methyl-4-nitrophenol (4-nitro-m-cresol; PNMC) and 4-nitro-3-phenylphenol (PNMPP) from diesel exhaust particles (DEP) and identified them as vasodilators and xenoestrogens. The estrogenic activity of PNMC and PNMPP was further examined by using immunohistochemical staining of proliferating cell nuclear antigen (PCNA) in uterine luminal epithelium of ovariectomized 25-d-old immature female rats injected with PNMC and PNMPP subcutaneously for 2 d. Significant increases were observed in uterine luminal epithelium in PCNA positive cells of animals receiving 10 and 100 mg/kg PNMC and 0.1 mg/kg PNMPP compared with controls. These results clearly show the estrogenic activity of PNMC and PNMPP by cell proliferation on the uterine luminal epithelium.

Nitrophenols isolated from diesel exhaust particles regulate steroidogenic gene expression and steroid synthesis in the human H295R adrenocortical cell line

Studies of nitrophenols isolated from diesel exhaust particles (DEPs), 3-methyl-4-nitrophenol (PNMC) and 4-nitro-3-phenylphenol (PNMPP) have revealed that these chemicals possess estrogenic and anti-androgenic activity in vitro and in vivo and that PNMC accumulate in adrenal glands in vivo. However, the impacts of exposure to these compounds on adrenal endocrine disruption and steroidogenesis have not been investigated. To elucidate the non-receptor mediated effects of PNMC and PNMPP, we investigated the production of the steroid hormones progesterone, cortisol, testosterone, and estradiol-17beta and modulation of nine major enzyme genes involved in the synthesis of steroid hormones (CYP11A, CYP11B1, CYP17, CYP19, 17betaHSD1, 17betaHSD4, CYP21, 3betaHSD2, StAR) in human adrenal H295R cells supplied with cAMP. Exposure to 10(-7) to 10(-5) M PNMC and 1 mM 8-Br-cAMP for 48 h decreased testosterone, cortisol, and estradiol-17beta levels and increased progesterone secretion. At 10(-5) M, PNMC with 1 mM 8-Br-cAMP significantly stimulated expression of the 17betaHSD4 and significantly suppressed expression of 3betaHSD2. In comparison, 10(-7) to 2 x 10(-5) M PNMPP with 1 mM 8-Br-cAMP for 48 h decreased concentrations of estradiol-17beta, increased progesterone levels, but did not affect testosterone and cortisol secretion due to the significant suppression of CYP17 and the non-significant but obvious suppression of CYP19. Our results clarified steroidogenic enzymes as candidates responsible for the inhibition or stimulation for the production of steroid hormones in the steroidogenic pathway, thus providing the first experimental evidence for multiple mechanisms of disruption of endocrine pathways by these nitrophenols.

Expression of Nerve Growth Factor (NGF), and Its Receptors TrkA and p75 in the Reproductive Organs of the Adult Male Rats

Abstract Immunolocalization of nerve growth factor (NGF) and its receptors, TrkA and p75 in the reproductive organs of adult male rats was investigated. Sections of the testis, efferent duct, epididymis, deferent duct, seminal vesicle, coagulating gland and prostate of adult male rats were immunostained by the avidin-biotin-peroxidase complex methods (ABC). NGF was expressed in Leydig cells, primary spermatocytes and pachytene spermatocytes in the testis. TrkA only immunoreacted to elongate spermatids and p75 showed positive immunostaining in the Sertoli cells, Leydig cells, the pachytene spermatocytes and elongate spermatids. Immunoreactions for NGF and its two receptors were detected in epithelial cells of efferent duct, deferent duct and epididymis. In addition, immunoreactions for NGF and its two receptors were also observed in columnar secretory epithelium lines of the seminal vesicles, prostate and coagulating gland. These results suggest that NGF is an important growth factor in gonadal function of adult male rats.

Nitrophenols isolated from diesel exhaust particles promote the growth of MCF-7 breast adenocarcinoma cells

Diesel exhaust particles (DEPs) cause many adverse health problems, and reports indicate increased risk of breast cancer in men and women through exposure to gasoline and vehicle exhaust. However, DEPs include vast numbers of compounds, and the specific compound(s) responsible for these actions are not clear. We recently isolated two nitrophenols from DEPs-3-methyl-4-nitrophenol (4-nitro-m-cresol; PNMC) and 4-nitro-3-phenylphenol (PNMPP)-and showed that they had estrogenic and anti-androgenic activities. Here, we tried to clarify the involvement of these two nitrophenols in promoting the growth of the MCF-7 breast cancer cell line. First, comet assay was used to detect the genotoxicity of PNMC and PNMPP in a CHO cell line. At all doses tested, PNMC and PNMPP showed negative genotoxicity, indicating that they had no tumor initiating activity. Next, the estrogen-responsive breast cancer cell line MCF-7 was used to assess cell proliferation. Proliferation of MCF-7 cells was stimulated by PNMC, PNMPP, and estradiol-17beta and the anti-estrogens 4-hydroxytamoxifen and ICI 182,780 inhibited the proliferation. To further investigate transcriptional activity through the estrogen receptor, MCF-7 cells were transfected with a receptor gene that allowed expression of luciferase enzyme under the control of the estrogen regulatory element. PNMC and PNMPP induced luciferase activity in a dose-dependent manner at submicromolar concentrations. ICI 182,780 inhibited the luciferase activity induced by PNMC and PNMPP. These results clearly indicate that PNMC and PNMPP do not show genotoxicity but act as tumor promoters in an estrogen receptor alpha-predominant breast cancer cell line.

Placental activin A is required for follicular development during the second half of pregnancy in the golden hamster (Mesocricetus auratus).

Numerous antral follicles develop during the second half of pregnancy in the golden hamster even though LH and FSH are maintained at basal levels. To investigate the possible hormone actions of activin A associated with follicular development, pregnant golden hamsters were placentectomized on day 6 of pregnancy and animals were sacrificed at day 8, 10, 12, or 14 of pregnancy. There was a drastic decrease in the plasma concentrations of activin A from day 10 of pregnancy in the operated group compared to the controls. Positive immunohistochemical staining of inhibin/activin subunits βA and βB in the syncytiotrophoblast of the placenta revealed the source of activin A, AB, or B. The number of healthy follicles did not change until day 12 between the operated and the control groups, but decreased in numbers in the operated groups thereafter. The decreased concentrations of inhibin A, B, and estradiol-17β in the operated groups at day 10 and 12 correlated well with the number of mature follicles in response to hCG treatment. In conclusion, we revealed that activin A secreted from the placenta induces folliculogenesis to maintain the high levels of estradiol-17β needed to induce uterine dilatation for fetus growth and impending parturition.