Ai Okamura

Bisphenol A may cause testosterone reduction by adversely affecting both testis and pituitary systems similar to estradiol.

Bisphenol A (BPA) causes reproductive toxicities, but the mechanisms are still unclear. In the present study, we sought to clarify these mechanisms in comparison with those of 17beta-estradiol (E2). Prepubertal Wistar/ST male rats (4 weeks old) were subcutaneously administered BPA (0, 20, 100 and 200 mg/kg/day) or E2 (10 and 100 microg/kg/day) for 6 weeks. Both BPA and E2 treatments decreased plasma and testicular testosterone levels, and plasma luteinizing hormone (LH), but not E2 and follicle-stimulating hormone levels, though E2 treatment increased its plasma level. In relation to the decreased testosterone levels, BPA and E2 decreased expressions of steroidogenic enzymes and cholesterol carrier protein in Leydig cells. Thus, decreased testosterone levels in plasma might have resulted from decreased expressions of these enzymes and protein as well as from decreased plasma LH levels. Interestingly, the changes in steroidogenic enzymes and carrier protein were observed at lower levels of exposure to BPA or E2 than those inhibiting plasma LH levels. Microscopically, 200 mg/kg BPA and 100 microg/kg E2 significantly decreased Leydig cell numbers in the testis. In addition, BPA and E2 also decreased expression of estrogen receptor alpha-mRNA, which might be related to the decreased numbers of Leydig cells. Thus, BPA directly affects not only the Leydig cells but also the pituitary gland, but the former may be impaired at lower exposure concentrations than the latter.

Permethrin may induce adult male mouse reproductive toxicity due to cis isomer not trans isomer.

Permethrin, the most popular insecticide among the synthetic pyrethroids, has been used worldwide to control a wide range of insects in agriculture, forestry, public health, and homes. Humans may have suffered potential exposure to this compound. The commercial formulation of permethrin contains trans and cis isomers. Here, at the same dosage, we made a comparison of the reproductive effects between these two isomers. Male adult ICR mice were orally administered trans- or cis-permethrin daily for 6 weeks at a dose of 0 or 70 mg/(kg day). In the cis-permethrin exposure group, the caudal epididymal sperm count and sperm motility were significantly reduced, and testosterone levels in testes and plasma also fell. Moreover, cis-permethrin induced abnormal seminiferous tubules in testes and suppressed testicular mRNA expression levels of peripheral benzodiazepine receptor, steroidogenic acute regulatory protein, and the cytochrome P450 side-chain cleavage enzyme. Although such adverse effects were not observed in the trans-permethrin exposure group, testicular and urinary metabolite 3-phenoxybenzoic acid levels in trans-permethrin-exposed mice were about three- and sevenfold higher than those in cis-permethrin-exposed mice, respectively. Furthermore, in vitro, hepatic microsomal hydrolase activity for trans-permethrin was nearly 62-fold higher than that for cis-permethrin. Taken together, the difference in metabolic activity between cis- and trans-permethrin might contribute to the difference in the reproductive toxicity between both isomers.

Molecular mechanism of trichloroethylene-induced hepatotoxicity mediated by CYP2E1

Cytochrome P450 (CYP) 2E1 was suggested to be the major enzyme involved in trichloroethylene (TRI) metabolism and TRI-induced hepatotoxicity, although the latter molecular mechanism is not fully understood. The involvement of CYP2E1 in TRI-induced hepatotoxicity and its underlying molecular mechanism were studied by comparing hepatotoxicity in cyp2e1+/+ and cyp2e1-/- mice. The mice were exposed by inhalation to 0 (control), 1000, or 2000 ppm of TRI for 8 h a day, for 7 days, and TRI-hepatotoxicity was assessed by measuring plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities and histopathology. Urinary metabolites of trichloroethanol and trichloroacetic acid (TCA) were considerably greater in cyp2e1+/+ compared to cyp2e1-/- mice, suggesting that CYP2E1 is the major P450 involved in the formation of these metabolites. Consistent with elevated plasma ALT and AST activities, cyp2e1+/+ mice in the 2000 ppm group showed histopathological inflammation. TRI significantly upregulated PPARalpha, which might function to inhibit NFkappaB p50 and p65 signalling. In addition, TRI-induced NFkappaB p52 mRNA, and significantly positive correlation between NFkappaB p52 mRNA expression and plasma ALT activity levels were observed, suggesting the involvement of p52 in liver inflammation. Taken together, the current study directly demonstrates that CYP2E1 was the major P450 involved in the first step of the TRI metabolism, and the metabolites produced may have two opposing roles: one inducing hepatotoxicity and the other protecting against the toxicity. Intermediate metabolite(s) from TRI to chloral hydrate produced by CYP2E1-mediated oxidation may be involved in the former, and TCA in the latter.

Broken Sperm, Cytoplasmic Droplets and Reduced Sperm Motility Are Principal Markers of Decreased Sperm Quality Due to Organophosphorus Pesticides in Rats

Broken Sperm, Cytoplasmic Droplets and Reduced Sperm Motility Are Principal Markers of Decreased Sperm Quality Due to Organophosphorus Pesticides in Rats: Ai Okamura, et al. Department of Occupational and Environmental Health, Nagoya University Graduate School of Medicine

Biological Monitoring of Pyrethroid Exposure of Pest Control Workers in Japan

Biological Monitoring of Pyrethroid Exposure of Pest Control Workers in Japan: Dong Wang, et al. Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine—Synthetic pyrethroids such as cypermethrin, deltamethrin and permethrin, which are usually used in pest control operations, are metabolized to 3‐phenoxybenzoic acid (3‐PBA) and excreted in urine. Though 3‐PBA can be used to assess exposure to pyrethroids, there are few reports describing urinary 3‐PBA levels in Japan. This study aimed to investigate the seasonal variation of the exposure levels of pyrethroids and the concentration of urinary 3‐PBA among pest control operators (PCOs) in Japan. The study subjects were 78 and 66 PCOs who underwent a health examination in December 2004 and in August 2005, respectively. 3‐PBA was determined using gas chromatography‐mass spectrometry. The geometric mean concentration of urinary 3‐PBA in winter (3.9 µg/ g creatinine) was significantly lower than in summer (12.2 µg/g creatinine) (p<0.05). Geometric mean concentrations of urinary 3‐PBA in the spraying workers and the not‐spraying workers within 2 d before the survey were 5.4 µg/g creatinine and 0.9 µg/g creatinine for winter with a significant difference between the groups (p<0.05), and 12.3 µg/g creatinine and 8.7 µg/ g creatinine for summer (p>0.05), respectively. A significant association of 3‐PBA levels and pyrethroid spraying was thus observed only in winter. In conclusion, the results of the present study show that the exposure level of pyrethroids among PCOs in Japan assessed by monitoring urinary 3‐PBA was higher than that reported in the UK but comparable to that in Germany. Further research should be accumulated to establish an occupational reference value in Japan.

Occupational trichloroethylene hypersensitivity syndrome: Human herpesvirus 6 reactivation and rash phenotypes

BACKGROUND Trichloroethylene (TCE) is an industrial solvent which can cause severe generalized dermatitis, i.e., occupational TCE hypersensitivity syndrome. Reactivation of latent human herpesvirus 6 (HHV6) can occur in such patients, which has made TCE known as a causative chemical of drug-induced hypersensitivity syndrome (DIHS). OBJECTIVE This study aimed to clarify HHV6 status, cytokine profiles and their association with rash phenotypes in patients with TCE hypersensitivity syndrome. METHODS HHV6 DNA copy numbers, anti-HHV6 antibody titers, and cytokines were measured in blood prospectively sampled 5-7 times from 28 hospitalized patients with the disease. RESULTS The patients (19 had exfoliative dermatitis (ED) and 9 had non-ED type rash) generally met the diagnostic criteria for DIHS. Viral reactivation defined as increases in either HHV6 DNA (≥100 genomic copies/10(6) peripheral blood mononuclear cells) or antibody titers was identified in 24 (89%) patients. HHV6 DNA, tumor necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-5, IL-6 and IL-10 concentrations were remarkably higher in the patients than in the healthy workers (p<0.01). Positive correlations between HHV6 DNA, TNF-α, IFN-γ, IL-6 and IL-10 were significant (p<0.05) except for that between HHV6 DNA and IFN-γ. An increase in HHV6 DNA was positively associated with an increase in TNF-α on admission (p<0.01). HHV6 DNA, the antibody titers, TNF-α and IL-10 concentrations were significantly higher in ED than in the non-ED type (p<0.05). CONCLUSION Reactivated HHV6 and the increased cytokines could be biomarkers of TCE hypersensitivity syndrome. The higher-level reactivation and stronger humoral responses were associated with ED-type rash.

Ammonium perfluorooctanoate may cause testosterone reduction by adversely affecting testis in relation to PPARα.

Perfluorooctanoate, a peroxisome proliferator-activated receptor alpha (PPARα) agonist, has the potential to lower testosterone levels as a result of testicular toxicity. To elucidate the mechanism and impact of PPARα on this reproductive toxicity, ammonium perfluorooctanoate (APFO) at doses of 0, 1.0 (low) mg/kg/day, or 5.0 (high) mg/kg/day was orally given daily to 129/sv wild-type (mPPARα), Pparα-null and PPARα-humanized (hPPARα) mice for 6 weeks. Both low- and high-dose APFO significantly reduced plasma testosterone concentrations in mPPARα and hPPARα mice, respectively. These decreases may, in part, be associated with decreased expression of mitochondrial cytochrome P450 side-chain cleavage enzyme, steroidogenic acute regulatory protein or peripheral benzodiazepine receptor as well as microsomal cytochrome P450(17α) involved in the steroidogenesis. Additionally, both doses increased abnormalities in sperm morphology and vacuolated cells in the seminiferous tubules of both mouse lines. In contrast, APFO caused only a marginal effect either on the testosterone synthesis system or sperm and testis morphology in Pparα-null mice. These results suggest that APFO may disrupt testosterone biosynthesis by lowering the delivery of cholesterol into the mitochondria and decreasing the conversion of cholesterol to pregnenolone and androstandione in the testis of mPPARα and hPPARα mice, which may, in part, be related to APFO-induced mitochondrial damage.

Evidence for diazinon-mediated inhibition of cis-permethrin metabolism and its effects on reproductive toxicity in adult male mice.

The potential toxicity resulting from combinatorial effects of organophosphorus and pyrethroid insecticides are not completely known. We evaluated male reproductive toxicity in mice co-exposed to diazinon and cis-permethrin. Nine-week-old male Sv/129 mice were exposed to diazinon (10 μmol/kg/day) or cis-permethrin (90 μmol/kg/day) alone or in combination (100 μmol/kg/day), or vehicle (corn oil), for 6 weeks. Diazinon and the diazinon-permethrin mixture inhibited plasma and liver carboxylesterase activities. In the mixture group, urinary excretion of cis-permethrin metabolite 3-phenoxybenzoic acid decreased along with increased plasma and testicular concentrations of cis-permethrin, while excretion of diazinon metabolites, diethylphosphate and diethylthiophosphate, did not change, versus mice exposed to each chemical alone, which suggested that inhibition of carboxylesterase decreased the metabolic capacity to cis-permethrin. Though the co-exposure decreased testosterone biosynthesis, increased degenerate germ cells in seminiferous tubule and sperm morphological abnormalities versus controls more clearly than exposure to cis-permethrin alone, the expected potentiation of toxicity was not evident.

Relationship between Urinary Pesticide Metabolites and Pest Control Operation among Occupational Pesticide Sprayers

Received Jun 23, 2007; Accepted Oct 16, 2008 Published online in J-ST AGE Dec 5, 2008 Correspondence to: T. Kondo, Program in Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, 1–1–20, Daikominami, Higashi-ku, Nagoya 461-8673, Japan (e-mail: taka@met.nagoya-u.ac.jp) Relationship between Urinary Pesticide Metabolites and Pest Control Operation among Occupational Pesticide Sprayers

Effect of oral exposure to fenitrothion and 3-methyl-4-nitrophenol on splenic cell populations and histopathological alterations in spleen in Wistar rats

Fenitrothion (FNT) is used throughout the world as an insecticide in agriculture. To investigate the effect of FNT on the splenocytes and the underlying mechanism, FNT and its main metabolite, 3-methyl-4-nitrophenol (MNP), were administered orally to Wistar rats in daily doses of 0, 5 and 10 mg/kg, 4-5 days/week for 9 weeks. Splenocytes were harvested from control and exposed rats, and the following cell phenotypes were quantified by flow cytometry: (1) B cells (PE-CD45RA), (2) T cells (FITC-CD3), (3) T cell subsets (PE-CD4 and PerCPCD8), (4) natural killer (NK) cells (FITC-CD161a), (5) macrophages (FITC-CD11b), and (6) granulocyte (PE-granulocyte). Body weight, weight of the spleen, and histopathological alterations of spleens were also examined. The percentage of splenic CD8+ T cells and the ratio of CD8/CD4 in the group receiving 10 mg/kg FNT, and the percentages of splenic CD3+ and CD8+ T cells in the group receiving 10 mg/kg MNP were significantly decreased compared with those in the controls. FNT exposure also significantly decreased the weight of the spleen and body weight. In addition, apoptotic lymphocytes in spleen were observed in FNT-exposed rats under transmission electron microscope. However, FNT and MNP exposures did not affect splenic NK cells, B cells, macrophages, and granulocytes. The above findings indicate that FNT and MNP may selectively affect splenic T cells in rats.