[The Effect of Maternal Exposure to Dioxins on the Level of Thyroid Hormone in Developing Pups].

Maternal exposure to dioxins causes a number of developmental disorders in the offspring. Previous studies have suggested that lactational exposure to 2,3,7,8-tetrachlorodizenzo-p-dioxin (TCDD) reduces the pup level of thyroid hormone after weaning, leading to the damage to their development including neural maturation. However, the specificity for age and dioxin congeners as well as dose dependency in terms of a reduction in pup thyroid hormone remains to be clarified. To address this issue, we investigated whether TCDD or 2,3,4,7,8-pentachlorodibenzofuran (PenCDF), one of the dioxins which caused 'Yusho' incident, affects the status of thyroid hormone during the fetal and neonatal periods. Treating pregnant rats at gestational day (GD)15 with 1 µg/kg TCDD scarcely affected the serum concentration of thyroxine, although a significant reduction by TCDD was detected at limited endpoints [GD21 and postnatal day (PND)21]. In addition, maternal exposure to TCDD (0.05-30 µg/kg) or PenCDF (1-1,000 µg/kg) did not have any change in the serum level of thyroxine in GD20 fetuses even at the maximum dose. Neither the expression of pituitary thyroid-stimulating hormone ß (TSHß) nor hypothalamic thyrotropin-releasing hormone was sensitive to TCDD treatment. In pregnant dams, TCDD decreased the serum level of thyroxine at GD20 and 21, while the pituitary expression of TSHß was induced. These results suggest that a single administration of dioxins to pregnant rats at GD15 have little effect on the level of thyroxine in the fetuses and infants, while a reduced level of this hormone observed in the offspring at GD21 and PND21 and pregnant dams at GD20 and 21.

[Effect of Cynaropicrin on 2,3,4,7,8-Pentachlorodibenzofuran-induced Wasting Syndrome and Oxidative Stress].

The effect of cynaropicrin that is the major component of an edible plant, artichoke (Cynara scolymus) on 2,3,4,7,8-pentachlorodibenzofuran (PenCDF)-induced toxicity in mice was studied. We evaluated the effect of cynaropicrin on the wasting syndrome and oxidative stress elicited by PenCDF. However, the PenCDF dose-response relationship on the wasting syndrome has been superficial. Therefore, we determined the dose which causes wasting syndrome in C57BL/6J mice, a responsive strain to dioxins. Since 2,3,7,8-tetrachlorodibenzo-p-dioxin (0.1 mg/kg, p.o.) induces hepatic ethoxyresorfin O-deethylase (EROD) activity in mice, we set the doses of PenCDF at 0.3, 1.0, 3.0, 5.0 and 10 mg/kg (once, p.o.) on the basis of its toxic-eqivalency factor (0.3). The wasting syndrome was evaluated by measuring the daily changes of body weight. Thiobarbituric acid-reactive substances were used as an index of oxidative stress. Of PenCDF doses examined, wasting syndrome and oxidative stress took place most markedly in 5 mg/kg. In disagreement with this, EROD activity which is the marker of the aryl hydrocarbon receptor-dependent induction of cytochrome P450 1a1 was elevated most abundantly at 0.3 mg/kg. Then, we examined the effect of cynaropicrin on the wasting syndrome and oxidative stress provoked by PenCDF at 5 mg/kg. However, this compound up to 20 mg/kg (p.o.) did not attenuate PenCDF-induced wasting syndrome. On the contray, PenCDF-induced oxidateive stress was suppressed by cynaropicrin at the highest dose (20 mg/kg), although EROD activity was increased rather than reduced by cynaropicrin at lower doses. Thus, it is suggested that cynaropicrin has an ability to reduce oxidative stress caused by PenCDF.

Effect of adenosine system in the action of oseltamivir on behavior in mice.

Abnormal behaviors and death associated with the use of oseltamivir (Tamiflu(®)) have emerged as a major issue in influenza patients. We have previously reported that the mechanisms underlying the effects of caffeine, a non-selective adenosine A1/A2 receptor antagonist, combined with oseltamivir. Oseltamivir is rapidly hydrolyzed to its active form (oseltamivir carboxylate, OCB). In this study, we investigated the effects of an adenosine system and OCB on the action of oseltamivir on mice behavior. Oseltamivir for 1 day (150 mg/kg, intraperitoneally (i.p.)) alone did not affect ambulation at 2 h post-injection. However, caffeine (10 mg/kg, i.p.) in combination with oseltamivir for 1 day increased ambulation. Moreover, caffeine (30 mg/kg, i.p.) in combination with oseltamivir for 3 days increased ambulation, but caffeine (10 mg/kg, i.p.) in combination with oseltamivir for 3 days did not increase. These enhancements were inhibited by an adenosine A2 receptor agonist, CGS21680 (0.2 mg/kg, subcutaneously (s.c.)). Furthermore, an adenosine A2 receptor antagonist, SCH58261 (1 and 3 mg/kg, i.p.) in combination with oseltamivir for 1 day increased ambulation. Moreover, SCH58261 (3 mg/kg, i.p.) in combination with oseltamivir for 3 days increased ambulation, but SCH58261 (1 mg/kg, i.p.) in combination with oseltamivir for 3 days did not. Conversely, in phenobarbital (PB)-treated mice, caffeine (3 mg/kg, i.p.) in combination with oseltamivir for 1 day increased ambulation. Moreover, OCB for 1 day (0.3 µg/mouse intracerebroventricular (i.c.v.)) alone increased ambulation. These findings suggest that the actions of oseltamivir may involve the adenosine systems and its metabolism. Our findings suggest an interaction between the central blockade of adenosine A2 receptors by caffeine and OCB-induced behavioral changes.

2,3,4,7,8-Pentachlorodibenzofuran is far less potent than 2,3,7,8-tetrachlorodibenzo-p-dioxin in disrupting the pituitary-gonad axis of the rat fetus.

The effect of 2,3,4,7,8-pentachlorodibenzofuran (PnCDF) on the fetal pituitary-gonad axis was compared with that produced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in Wistar rats. Maternal treatment at gestational day (GD) 15 with PnCDF and TCDD reduced the fetal expression at GD20 of pituitary luteinizing hormone (LH) and the testicular proteins necessary for steroidogenesis. The relative potencies of PnCDF ranged from 1/42nd to 1/63rd of the TCDD effect. While PnCDF, at a dose sufficient to cause a reduction in fetal LH, provoked defects in sexual behavior at adulthood, a dose less than the ED50 failed to produce any abnormality. There was a loss of fetal body weight following in utero exposure to PnCDF, and the effect of PnCDF was also much less than that of TCDD. The disturbance in fetal growth was suggested to be due to a reduction in the level of fetal growth hormone (GH) by dioxins. The disorder caused by PnCDF/TCDD in the fetal pituitary-gonad axis occurred at doses less than those needed to cause wasting syndrome in pubertal rats. The harmful effect of PnCDF relative to TCDD was more pronounced in fetal rats than in pubertal rats. These lines of evidence suggest that: 1) PnCDF as well as TCDD imprints defects in sexual behavior by disrupting the fetal pituitary-gonad axis; 2) these dioxins hinder fetal growth by reducing the expression of fetal GH; and 3) the fetal effects of PnCDF/TCDD are more sensitive than sub-acute toxicity during puberty, and the relative effect of PnCDF varies markedly depending on the indices used.

Structure-activity relationships of 44 halogenated compounds for iodotyrosine deiodinase-inhibitory activity.

The aim of this study was to investigate the possible influence of halogenated compounds on thyroid hormone metabolism via inhibition of iodotyrosine deiodinase (IYD) activity. The structure-activity relationships of 44 halogenated compounds for IYD-inhibitory activity were examined in vitro using microsomes of HEK-293 T cells expressing recombinant human IYD. The compounds examined were 17 polychlorinated biphenyls (PCBs), 15 polybrominated diphenyl ethers (PBDEs), two agrichemicals, five antiparasitics, two pharmaceuticals and three food colorants. Among them, 25 halogenated phenolic compounds inhibited IYD activity at the concentration of 1×10(-4)M or 6×10(-4)M. Rose bengal was the most potent inhibitor, followed by erythrosine B, phloxine B, benzbromarone, 4'-hydroxy-2,2',4-tribromodiphenyl ether, 4-hydroxy-2,3',3,4'-tetrabromodiphenyl ether, 4-hydroxy-2',3,4',5,6'-pentachlorobiphenyl, 4'-hydroxy-2,2',4,5'-tetrabromodiphenyl ether, triclosan, and 4-hydroxy-2,2',3,4',5-pentabromodiphenyl ether. However, among PCBs and PBDEs without a hydroxyl group, including their methoxylated metabolites, none inhibited IYD activity. These results suggest that halogenated compounds may disturb thyroid hormone homeostasis via inhibition of IYD, and that the structural requirements for IYD-inhibitory activity include halogen atom and hydroxyl group substitution on a phenyl ring.

Covalent binding of nitroso-sulfonamides to glutathione S-transferase in guinea pigs with delayed type hypersensitivity.

Drug induced allergies are believed to be induced by conjugates consisting of biological macromolecules and active metabolites. The present study investigated whether guinea pig glutathione S-transferase (gpGST), a protein that binds with sulfanilamide (SA) and sulfamethoxazole (SMX), could be detected in the liver cytosol fraction of guinea pigs that intraperitoneally received SA or SMX, and whether gpGST is a carrier protein. We synthesized three nitroso compounds, i.e., 4-nitroso-sulfanilamide (SA-NO), 4-nitrososulfamethoxazole (SMX-NO) and fluorescent-labeled nitroso compound (DNSBA-NO), and examined binding quantities of nitroso compounds to gpGST purified from untreated female guinea pigs. Furthermore, the concentrations of IgG in serum antibody for nitroso compounds were estimated using ELISA. When guinea pigs were sensitized using the three nitroso compounds, the dose dependent skin reactions were confirmed with each compound. In addition, sensitized guinea pigs using each nitroso compound showed positive skin reactions at an elicitation test performed using gpGST alone. The results confirmed synthesis of antibody against gpGST due to hapten sensitization. Therefore, when a nitroso compound binds with gpGST in the body of guinea pigs, nitroso-gpGST acts as a neoantigen, which induces synthesis of autoantibody. Thus, gpGST appears to be one of the carrier proteins that induce sulfa drug-induced allergies. Immunization of guinea pigs with active metabolite of drugs may give information for predicting the occurrence of delayed type hypersensitivity in human.

Characterization of steroid hormone receptor activities in 100 hydroxylated polychlorinated biphenyls, including congeners identified in humans.

Hydroxylated polychlorinated biphenyls (OH-PCBs), major metabolites of PCBs, have been reported to act as estrogen receptor α (ERα) agonists or antagonists. However, little concern has been paid to the ability of OH-PCBs to interfere with other steroid hormone receptors such as ERß, androgen receptor (AR) or glucocorticoid receptor (GR). In this study, we characterized the agonistic and antagonistic activities of available 100 OH-PCBs (39 ortho-, 24 meta-, and 37 para-OH compounds), including some congeners identified in humans, against human ERα/ß, AR, and GR using in vitro reporter gene assays. In the ERα assay, 45 and 9 of the 100 OH-PCBs tested showed agonistic and antagonistic activities, respectively. In the ERß assay, 45 and 6 compounds showed agonistic and antagonistic activities, respectively. In the AR and GR assays, although none of the compounds tested showed agonistic activity, 83 and 30 of the 100 OH-PCBs showed antagonistic activity, respectively. These AR and/or GR antagonistic compounds had various patterns of substituent in the structure, while relatively potent ERα/ß agonistic and antagonistic compounds possessed para- and ortho-OH structures, respectively. Three OH-PCBs, predominantly identified in human tissues, showed little ERα/ß or AR activities, apart from the weak ERα and/or GR antagonistic activity observed in 4-OH-CB107 and 4-OH-CB187. Taken together, these results suggest that a large number of OH-PCBs might act as agonists and/or antagonists against ERα/ß, AR and GR.

The stimulatory effects of caffeine with oseltamivir (Tamiflu) on light-dark behavior and open-field behavior in mice.

Abnormal behaviors and death associated with the use of oseltamivir (Tamiflu) have emerged as a major issue in influenza patients taking the drug. Here, we investigated the mechanisms underlying the effects of oseltamivir on the behavior of mice using light-dark and open-field preference tests. Oseltamivir (75 and 150 mg/kg, intraperitoneally (i.p.)) alone affected neither time spent in the open area in the light-dark preference test nor ambulation in the open-field test at 2h post-injection. However, a non-selective adenosine A(1)/A(2) receptor antagonist, caffeine (10mg/kg, i.p.) in combination with oseltamivir (150 mg/kg, i.p.) increased time spent in the open area in the light-dark preference test. This enhancement was not inhibited by a benzodiazepine receptor antagonist, flumazenil (10-20mg/kg, subcutaneously (s.c.)). Enhancement of ambulation in the open-field test was also observed when caffeine (10mg/kg, i.p.) was combined with oseltamivir (150 mg/kg, i.p.). This enhancement was inhibited by a dopamine D(2) receptor antagonist, haloperidol (0.1mg/kg, s.c.). Furthermore, an adenosine A(2) receptor antagonist, SCH58261 (3mg/kg, i.p.) in combination with oseltamivir (150 mg/kg, i.p.) increased ambulation in the open-field test, while an adenosine A(1) receptor antagonist, DPCPX (1-3mg/kg, i.p.) did not. These findings suggest that the actions of oseltamivir may involve the dopamine and adenosine systems. Our findings suggest that due to the interaction between central blockade of adenosine A(2) receptors by caffeine, and oseltamivir-induced behavioral changes, patients being treated with oseltamivir should be closely monitored.

Thyroid hormone-like and estrogenic activity of hydroxylated PCBs in cell culture.

The thyroid hormone-disrupting activity of hydroxylated PCBs was examined. 4-Hydroxy-2,2',3,4',5,5'-hexachlorobiphenyl (4-OH-2,2',3,4',5,5'-HxCB), 4-hydroxy-3,3',4',5-tetrachlorobiphenyl (4-OH-3,3',4',5-TCB) and 4,4'-dihydroxy-3,3',5,5'-tetrachlorobiphenyl (4,4'-diOH-3,3',5,5'-TCB), which have been detected as metabolites of PCBs in animals and humans, and six other 4-hydroxylated PCBs markedly inhibited the binding of triiodothyronine (1x10(-10)M) to thyroid hormone receptor (TR) in the concentration range of 1 x 10(-6) to 1 x 10(-4) M. However, 4-hydroxy-2',4',6'-trichlorobiphenyl (4-OH-2',4',6'-TCB), 3-hydroxy-2,2',5,5'-tetrachlorobiphenyl, 4-hydroxy-2,2',5,5'-tetrachlorobiphenyl, 4-hydroxy-2,3,3',4'-tetrachlorobiphenyl, 2,3',5,5'-tetrachlorobiphenyl and 2,3',4',5,5'-pentachlorodiphenyl did not show affinity for TR. The thyroid hormonal activity of PCBs was also examined using rat pituitary cell line GH3 cells, which grow and release growth hormone in a thyroid hormone-dependent manner. 4-OH-2,2',3,4',5,5'-HxCB, 4,4'-diOH-3,3',5,5'-TCB and 4-OH-3,3',4',5-TCB enhanced the proliferation of GH3 cells and stimulated their production of growth hormone in the concentration range of 1 x 10(-7) to 1 x 10(-4) M, while PCBs which had no affinity for thyroid hormone receptor were inactive. In contrast, only 4-OH-2',4',6'-TCB exhibited a significant estrogenic activity using estrogen-responsive reporter assay in MCF-7 cells. However, the 3,5-dichloro substitution of 4-hydroxylated PCBs markedly decreased the estrogenic activity. These results suggest that, at least for the 17 PCB congeners and hydroxylated metabolites tested, a 4-hydroxyl group in PCBs is essential for thyroid hormonal and estrogenic activities, and that 3,5-dichloro substitution favors thyroid hormonal activity, but not estrogenic activity.

Determination of tetrabromobisphenol A in human serum by liquid chromatography-electrospray ionization tandem mass spectrometry.

A method for the determination of tetrabromobisphenol A (TBBPA) in human serum utilizing solid-phase extractions (SPEs) and liquid chromatography (LC) with electrospray ionization tandem MS (MS/MS) has been developed. After purification and concentration of TBBPA using consecutive SPEs on reversed-phase and normal-phase cartridges, the serum sample was subjected to LC. TBBPA was separated on a C18 reversed-phase column by gradient elution with a mixture of water, methanol, and acetonitrile as the mobile phase, and then detected with electrospray ionization MS/MS in negative ion mode. 13C12-TBBPA was suitable as an internal standard for the reproducible determination of TBBPA in human serum samples (5 g). The method has been validated in TBBPA concentration range of 5-100 pg per g serum, and the recoveries in the concentration range were higher than 83.3%. The repeatabilities of the proposed method of non-spiked control serum (6.3 pg per g serum) and spiked serum (added 5-100 pg per g serum) were within 10.0% as relative standard deviations. The limit of quantification (LOQ) for TBBPA was 4.1 pg per g serum, which was corresponded to 0.63 fmol on column.

[Metabolism of 2,3,3',4,4'-pentachlorobiphenyl in hamsters].

The in vivo metabolism of 2,3,3',4,4'-pentachlorobiphenyl (CB105) was studied in hamsters and the effect of cytochrome P450 inducers, phenobarbital (PB) and 3-methylcholanthrene (MC) on its metabolism was compared to rats. After administration of CB105 intraperitoneally at a dose of 3 mg/body, four metabolites, named M-1, M-2, M-3 and M-4, were detected in 5 days-feces of all groups and the formation ratio of the metabolites M-1-M-4 was 1:39:84:0.2 in untreated hamsters and 1:19:6.7:0.7 in untreated rats. On the basis of the mass spectra of four synthetic authentic compounds and the retention times on DB-1 and MPS50 columns, M-1, M-2, M-3 and M-4 were identified as 4'-hydroxy-2,3,3',4,5'-PenCB, 5'-hydroxy-CB105, 5-hydroxy-CB105 and 4-hydroxy-2,3,3',4',5-PenCB, respectively. The pretreatment of PB and MC resulted in about 2-fold fecal excretion of four metabolites in hamsters and in about 3-fold in rats. Of four metabolites, only M-4 were detected in the serum at 5 days after CB105 administration and the concentration was 0.39 microgram/ml of hamster serum and 0.28 microgram/ml of rat serum. In hamsters, the concentration of M-4 was increased to 1.8-fold of untreated animals by PB treatment and 2.6-fold by MC treatment. On the other hand, the treatment of rats with PB and MC did not show such an increase of serum M-4. These results suggested that the hamster oxidized 2,3,4-trichloro-substituted benzene ring predominantly rather than 3',4'-dichloro-substituted benzene ring differently from the rat and that M-4 formed in hamster liver distributed to the blood and retained there to a considerable extent in comparison with that formed in rat liver.

Thyroid hormonal activity of the flame retardants tetrabromobisphenol A and tetrachlorobisphenol A.

The thyroid hormonal-disrupting activity of the flame retardants tetrabromobisphenol A (TBBPA) and tetrachlorobisphenol A (TCBPA) was examined and compared with that of bisphenol A, a typical estrogenic xenobiotic. TBBPA and TCBPA, halogenated derivatives of bisphenol A, markedly inhibited the binding of triiodothyronine (T(3); 1 x 10(-10) M) to thyroid hormone receptor in the concentration range of 1 x 10(-6) to 1 x 10(-4) M, but bisphenol A did not. The thyroid hormonal activity of TBBPA and TCBPA was also examined using rat pituitary cell line GH3 cells, which grow and release growth hormone (GH) depending on thyroid hormone. TBBPA and TCBPA enhanced the proliferation of GH3 cells and stimulated their production of GH in the concentration range of 1 x 10(-6) to 1 x 10(-4) M, while bisphenol A was inactive. TBBPA, TCBPA, and bisphenol A did not show antagonistic action, i.e., these compounds did not inhibit the hormonal activity of T(3) to induce growth and GH production of GH3 cells. TBBPA and TCBPA, as well as bisphenol A, enhanced the proliferation of MtT/E-2 cells, whose growth is estrogen-dependent. These results suggest that TBBPA and TCBPA act as thyroid hormone agonists, as well as estrogens.