Mechanisms of pulmonary disease in F344 rats after workplace-relevant inhalation exposure to cross-linked water-soluble acrylic acid polymers.

BACKGROUND: Recently in Japan, six workers at a chemical plant that manufactures resins developed interstitial lung diseases after being involved in loading and packing cross-linked water-soluble acrylic acid polymers (CWAAPs). The present study focused on assessing lung damage in rats caused by workplace-relevant inhalation exposure to CWAAP and investigated the molecular and cellular mechanisms involved in lung lesion development. METHODS: Using a whole-body inhalation exposure system, male F344 rats were exposed once to 40 or 100 mg/m3 of CWAAP-A for 4 h or to 15 or 40 mg/m3 of CWAAP-A for 4 h per day once per week for 2 months (9 exposures). In a separate set of experiments, male F344 rats were administered 1 mg/kg CWAAP-A or CWAAP-B by intratracheal instillation once every 2 weeks for 2 months (5 doses). Lung tissues, mediastinal lymph nodes, and bronchoalveolar lavage fluid were collected and subjected to biological and histopathological analyses. RESULTS: A single 4-h exposure to CWAAP-A caused alveolar injury, and repeated exposures resulted in regenerative changes in the alveolar epithelium with activation of TGFß signaling. During the recovery period after the last exposure, some alveolar lesions were partially healed, but other lesions developed into alveolitis with fibrous thickening of the alveolar septum. Rats administered CWAAP-A by intratracheal instillation developed qualitatively similar pulmonary pathology as rats exposed to CWAAP-A by inhalation. At 2 weeks after intratracheal instillation, rats administered CWAAP-B appeared to have a slightly higher degree of lung lesions compared to rats administered CWAAP-A, however, there was no difference in pulmonary lesions in the CWAAP-A and CWAAP-B exposed rats examined 18 weeks after administration of these materials. CONCLUSIONS: The present study reports our findings on the cellular and molecular mechanisms of pulmonary disease in rats after workplace-relevant inhalation exposure to CWAAP-A. This study also demonstrates that the lung pathogenesis of rats exposed to CWAAP-A by systemic inhalation was qualitatively similar to that of rats administered CWAAP-A by intratracheal instillation.

Suspected Immune Thrombocytopenic Purpura Induced by Lenalidomide for the Treatment of Myelodysplastic Syndrome with Deletion of Chromosome 5q: A Case Report.

Lenalidomide (LEN), one of the key drugs in the treatment of myelodysplastic syndromes (MDS) with 5q deletion, as well as multiple myeloma (MM), has various immunomodulatory effects and has been associated with autoimmune diseases, including immune thrombocytopenic purpura (ITP). A 78-year-old man presented with pancytopenia and was diagnosed with MDS with 5q deletion and other chromosomal abnormalities. Two cycles of LEN therapy (one cycle: 10 mg/day for 21 days) resulted in a transient improvement in anemia, followed by MDS progression with severe thrombocytopenia (4 × 109/L) refractory to platelet transfusions. As other non-immune and alloimmune causes of transfusion-refractory thrombocytopenia were excluded, and the level of platelet-associated immunoglobulin G was extremely high compared with the level before treatment with LEN, the diagnosis of ITP was highly suspected. Despite treatment with prednisolone (PSL), eltrombopag, and repeated platelet transfusions, his platelet count did not increase, and he died of a gastrointestinal hemorrhage. Several cases of ITP induced by LEN used to treat MM had been reported, but the platelet count recovered after administration of PSL in these previous cases. However, we should be mindful of using LEN for patients with MDS because its treatment may become extremely difficult if ITP develops.

Clear evidence of the carcinogenic potential of anthracene: A 2-year feeding study in rats and mice.

Anthracene is an environmental pollutant and its adverse effects on human health have long been a concern due to its persistence and bioaccumulation properties. However, there is insufficient evidence for its chronic toxicity, especially carcinogenicity, in either humans or experimental animals. In this study, its carcinogenicity and chronic toxicity were investigated in compliance with the OECD test guideline 451 (OECD TG 451) and Good Laboratory Practice Standards. Fifty male and 50 female F344 rats and 50 female BDF1 mice were administrated 0, 8000, 20000, or 50000 ppm anthracene in the diet for 104 weeks, and 50 male BDF1 mice were fed diets containing anthracene at 0, 3200, 8000, or 20000 ppm. Anthracene treatment had no adverse effect on either the survival rate or general condition of the rats or mice during the study period. Body weights were lower or tended to be lower in the anthracene-treated groups than in the control groups. Increased incidence of hepatocellular carcinoma and hepatocellular adenoma was observed in male rats and female mice. Renal cell carcinoma and renal cell adenoma, fibroadenoma in the mammary gland, and uterine endometrial stromal sarcoma were increased in female rats. Transitional cell carcinoma and transitional cell papilloma in the urinary bladder were also increased in male and female rats. In addition, several different pre-neoplastic lesions were increased in the anthracene-treated male and female rats and female mice. These results provide clear evidence that oral administration of anthracene for 104 weeks has a carcinogenic effect in male and female rats and female mice.

Pulmonary dust foci as rat pneumoconiosis lesion induced by titanium dioxide nanoparticles in 13-week inhalation study.

BACKGROUND: Most toxicological studies on titanium dioxide (TiO2) particles to date have concentrated on carcinogenicity and acute toxicity, with few studies focusing of pneumoconiosis, which is a variety of airspace and interstitial lung diseases caused by particle-laden macrophages. The present study examined rat pulmonary lesions associated with pneumoconiosis after inhalation exposure to TiO2 nanoparticles (NPs). METHODS: Male and female F344 rats were exposed to 6.3, 12.5, 25, or 50 mg/m3 anatase type TiO2 NPs for 6 h/day, 5 days/week for 13 weeks using a whole-body inhalation exposure system. After the last exposure the rats were euthanized and blood, bronchoalveolar lavage fluid, and all tissues including lungs and mediastinal lymph nodes were collected and subjected to biological and histopathological analyses. RESULTS: Numerous milky white spots were present in the lungs after exposure to 25 and 50 mg/m3 TiO2 NPs. Histopathological analysis revealed that the spots were alveolar lesions, characterized predominantly by the agglomeration of particle-laden macrophages and the presence of reactive alveolar epithelial type 2 cell (AEC2) hyperplasia. We defined this characteristic lesion as pulmonary dust foci (PDF). The PDF is an inflammatory niche, with decreased vascular endothelial cells in the interstitium, and proliferating AEC2 transformed into alveolar epithelial progenitor cells. In the present study, the AEC2 in the PDF had acquired DNA damage. Based on PDF induction, the lowest observed adverse effect concentration for pulmonary disorders in male and female rats was 12.5 mg/m3 and 6.3 mg/m3, respectively. The no observed adverse effect concentration for male rats was 6.3 mg/m3. There was a sex difference in lung lesion development, with females showing more pronounced lesion parameters than males. CONCLUSIONS: Inhalation exposure to TiO2 NPs caused PDF, an air-space lesion which is an alveolar inflammatory niche containing particle-laden macrophages and proliferating AEC2. These PDFs histopathologically resemble some pneumoconiosis lesions (pulmonary siderosis and hard metal pneumoconiosis) in workers and lung disease in smokers, suggesting that PDFs caused by exposure to TiO2 NPs in rats are an early pneumoconiosis lesion and may be a common alveolar reaction in mammals.

Dose-response relationship of pulmonary disorders by inhalation exposure to cross-linked water-soluble acrylic acid polymers in F344 rats.

BACKGROUND: In Japan, six workers handling cross-linked water-soluble acrylic acid polymer (CWAAP) at a chemical plant suffered from lung diseases, including fibrosis, interstitial pneumonia, emphysema, and pneumothorax. We recently demonstrated that inhalation of CWAAP-A, one type of CWAAP, causes pulmonary disorders in rats. It is important to investigate dose-response relationships and recoverability from exposure to CWAAPs for establishing occupational health guidelines, such as setting threshold limit value for CWAAPs in the workplace. METHODS: Male and female F344 rats were exposed to 0.3, 1, 3, or 10 mg/m3 CWAAP-A for 6 h/day, 5 days/week for 13 weeks using a whole-body inhalation exposure system. At 1 h, 4 weeks, and 13 weeks after the last exposure the rats were euthanized and blood, bronchoalveolar lavage fluid, and all tissues including lungs and mediastinal lymph nodes were collected and subjected to biological and histopathological analyses. In a second experiment, male rats were pre-treated with clodronate liposome or polymorphonuclear leukocyte-neutralizing antibody to deplete macrophages or neutrophils, respectively, and exposed to CWAAP-A for 6 h/day for 2 days. RESULTS: CWAAP-A exposure damaged only the alveoli. The lowest observed adverse effect concentration (LOAEC) was 1 mg/m3 and the no observed adverse effect concentration (NOAEC) was 0.3 mg/m3. Rats of both sexes were able to recover from the tissue damage caused by 13 weeks exposure to 1 mg/m3 CWAAP-A. In contrast, tissue damage caused by exposure to 3 and 10 mg/m3 was irreversible due to the development of interstitial lung lesions. There was a gender difference in the recovery from CWAAP-A induced pulmonary disorders, with females recovering less than males. Finally, acute lung effects caused by CWAAP-A were significantly reduced by depletion of alveolar macrophages. CONCLUSIONS: Pulmonary damage caused by inhalation exposure to CWAAP-A was dose-dependent, specific to the lung and lymph nodes, and acute lung damage was ameliorated by depleting macrophages in the lungs. CWAAP-A had both a LOAEC and a NOAEC, and tissue damage caused by exposure to 1 mg/m3 CWAAP-A was reversible: recovery in female rats was less than for males. These findings indicate that concentration limits for CWAAPs in the workplace can be determined.

Comparison of drug susceptibility between Escherichia coli detected in stool cultures of patients undergoing transrectal prostate needle biopsy and Escherichia coli in hospital-wide urine antibiograms.

A prostate biopsy is essential for prostate cancer diagnosis. However, infections are one of the biopsy-associated complications, and post-biopsy fever is estimated to occur in approximately 1% of all cases. It may thus be beneficial to perform a rectal swab culture before a transrectal prostate biopsy to confirm the presence of resistant bacteria and select preventive antibacterial agents according to the drug susceptibility results. This study aimed to determine whether there is a difference between the drug susceptibility of bacteria detected in the stool of patients who were scheduled to undergo prostate biopsy and the hospital-wide urine antibiogram. Patients suspected of having prostate cancer who underwent transrectal prostate biopsy via transrectal ultrasonography between August 1, 2016, and June 30, 2020, were included in this study. Stool samples were collected and cultured before biopsy. Overall, 99 patients underwent prostate biopsy, and of these, culture results were available for 81 patients (81.8%). Escherichia coli was detected in 74.0% (60 samples) of the stool culture samples, of which 4 samples were extended-spectrum ß-lactamase-producing types. We found greater susceptibility of Escherichia coli to ampicillin, fluoroquinolones, sulfamethoxazole/trimethoprim, and cefixime in the stool culture antibiogram than in the hospital-wide urine antibiogram. We also found a significantly low incidence of ESBL-positive Escherichia coli in the stool culture antibiogram with p-values of 0.009, 0.007, and 0.03 compared to the hospital-wide urine antibiograms for 2017, 2018, and 2019, respectively. Stool culture of prostate cancer patients undergoing biopsy may provide useful information for selecting prophylactic antimicrobial agents.

Decrease of infectious complications in outpatients with autoimmune diseases from 2019 to 2020 under the COVID-19 pandemic: A single-centre, retrospective cohort study in Japan.

OBJECTIVES: To examine how the novel coronavirus disease (COVID-19) has changed infectious complications in outpatients with autoimmune diseases. METHODS: We performed a retrospective, record-linked cohort study and questionnaire about lifestyle changes in patients who visited our department in 2019 and 2020. RESULTS: We surveyed 1316 outpatients in 2019 and 1284 in 2020. The most common underlying diseases were rheumatoid arthritis (842 vs. 814) and systemic lupus erythematosus (SLE) (126 vs. 127). No significant difference in median age (66 vs. 67 years), respiratory comorbidities (30.4% vs. 32.0%), or corticosteroid use (42.2% vs. 44.3%) was found between the years. Immunomodulating agents were used more in 2020 (33.1% vs. 39.7%, p < .001). Total number of infections (28.0/100 vs. 19.4/100 person-years), pneumonia (3.6 vs. 1.6), influenza (2.1 vs. 0.1), and nonviral dermatological infections (3.8 vs. 2.1) were significantly lower in 2020. No significant difference was found for herpes zoster (2.2 vs. 1.8), urinary tract infections (3.3 vs. 3.8), or gastrointestinal infections (2.9 vs. 3.0). According to the questionnaire, 75% of the respondents became more conscious about wearing masks and 81% began to use hand sanitizer during the pandemic. CONCLUSION: Under the COVID-19 pandemic, some infectious complications have decreased in outpatients with autoimmune diseases.

Ablation of Selenbp1 Alters Lipid Metabolism via the Pparα Pathway in Mouse Kidney.

Selenium-binding protein 1 (Selenbp1) is a 2,3,7,8-tetrechlorodibenzo-p-dioxin inducible protein whose function is yet to be comprehensively elucidated. As the highly homologous isoform, Selenbp2, is expressed at low levels in the kidney, it is worthwhile comparing wild-type C57BL mice and Selenbp1-deficient mice under dioxin-free conditions. Accordingly, we conducted a mouse metabolomics analysis under non-dioxin-treated conditions. DNA microarray analysis was performed based on observed changes in lipid metabolism-related factors. The results showed fluctuations in the expression of numerous genes. Real-time RT-PCR confirmed the decreased expression levels of the cytochrome P450 4a (Cyp4a) subfamily, known to be involved in fatty acid ω- and ω-1 hydroxylation. Furthermore, peroxisome proliferator-activated receptor-α (Pparα) and retinoid-X-receptor-α (Rxrα), which form a heterodimer with Pparα to promote gene expression, were simultaneously reduced. This indicated that reduced Cyp4a expression was mediated via decreased Pparα and Rxrα. In line with this finding, increased levels of leukotrienes and prostaglandins were detected. Conversely, decreased hydrogen peroxide levels and reduced superoxide dismutase (SOD) activity supported the suppression of the renal expression of Sod1 and Sod2 in Selenbp1-deficient mice. Therefore, we infer that ablation of Selenbp1 elicits oxidative stress caused by increased levels of superoxide anions, which alters lipid metabolism via the Pparα pathway.

Area under the blood concentration-time curve (AUC) of ethylbenzene concentration in rats: relationship to inhalation and oral administration route-dose.

For human risk assessment of toxic chemicals, especially volatile organic compounds (VOCs), the Ministry of the Environment, Government of Japan, has called for the interconversion of inhalation-dose and oral-dose data, two common exposure routes. To address this issue, the present study investigated the time-course changes of ethylbenzene (EB) concentrations in the blood of rats during and after 6-hr inhalation exposure to EB (25, 50, 100, and 200 ppm) and after oral administration of EB by a single oral gavage (25, 50, 100, and 200 mg/kg) of EB. The Area Under the blood concentration-time Curve (AUC) at each blood collection time point (0, 30, 60, 120, 180, 360, 420, 540, and 1440 min, after starting exposure) was determined. The inhalation dose of 25 ppm corresponded closely to the oral administration of 25 mg/kg・bw (r value of 0.859), and the inhalation dose of 200 ppm correlated with the oral administration of 100 mg/kg・bw (r value of 0.948). These results suggest that this comparison using the AUC data at each blood collection time point is valuable for understanding the route- and dose-effects of EB. This study will improve risk assessment of human exposure to EB and other VOCs.

Improvement in early urinary continence recovery after robotic-assisted radical prostatectomy based on postoperative pelvic anatomic features: a retrospective review.

BACKGROUND: We investigated the impact of postoperative membranous urethral length and other anatomic characteristics of the pelvic floor shape as measured by magnetic resonance imaging on the improvement in continence following robotic-assisted radical prostatectomy. METHODS: We retrospectively reviewed data from 73 patients who underwent postoperative prostate magnetic resonance imaging following robotic-assisted radical prostatectomy between 2013 and 2018. Patient demographics; pre-, peri-, and post-operative parameters; and pelvic anatomic features on magnetic resonance imaging were reviewed. Patients who used no urinary incontinence pads or pads for protection were considered to have achieved complete continence. RESULTS: Urinary continence was restored in 27.4, 53.4, 68.5, and 84.9% of patients at 1, 3, 6, and 12 months after robotic-assisted radical prostatectomy, respectively. When patients were divided into early and late continence groups based on urinary continence at 3 months after robotic-assisted radical prostatectomy, no significantly different clinical characteristics or surgical outcomes were found. However, the mean membranous urethral length (18.5 mm for the early continence group vs. 16.9 mm for the late continence group), levator muscle width (7.1 vs. 6.5 mm, respectively), and bladder neck width on the trigone side (7.2 mm vs. 5.4 mm, respectively) were significantly different between groups (all p < 0.05). Multivariate logistic regression analysis showed that membranous urethral length (odds ratio, 1.227; 95% confidence interval, 1.011-1.489; p = 0.038) and bladder neck width (odds ratio, 1.585; 95% confidence interval, 1.050-2.393; p = 0.028) were associated with the period of early urinary continence. CONCLUSIONS: Postoperative membranous urethral length and bladder neck width were significantly associated with early urinary continence recovery after robotic-assisted radical prostatectomy. It is highly recommended that surgeons focus on preserving the membranous urethral length and increasing the bladder neck width on the trigone side during surgery to achieve optimal continence outcomes after robotic-assisted radical prostatectomy.

Dioxin-induced increase in leukotriene B4 biosynthesis through the aryl hydrocarbon receptor and its relevance to hepatotoxicity owing to neutrophil infiltration.

Dioxin and related chemicals alter the expression of a number of genes by activating the aryl hydrocarbon receptors (AHR) to produce a variety of disorders including hepatotoxicity. However, it remains largely unknown how these changes in gene expression are linked to toxicity. To address this issue, we initially examined the effect of 2,3,7,8-tetrachrolodibenzo-p-dioxin (TCDD), a most toxic dioxin, on the hepatic and serum metabolome in male pubertal rats and found that TCDD causes many changes in the level of fatty acids, bile acids, amino acids, and their metabolites. Among these findings was the discovery that TCDD increases the content of leukotriene B4 (LTB4), an inducer of inflammation due to the activation of leukocytes, in the liver of rats and mice. Further analyses suggested that an increase in LTB4 comes from a dual mechanism consisting of an induction of arachidonate lipoxygenase-5, a rate-limiting enzyme in LTB4 synthesis, and the down-regulation of LTC4 synthase, an enzyme that converts LTA4 to LTC4. The above changes required AHR activation, because the same was not observed in AHR knock-out rats. In agreement with LTB4 accumulation, TCDD caused the marked infiltration of neutrophils into the liver. However, deleting LTB4 receptors (BLT1) blocked this effect. A TCDD-produced increase in the mRNA expression of inflammatory markers, including tumor-necrosis factor and hepatic damage, was also suppressed in BLT1-null mice. The above observations focusing on metabolomic changes provide novel evidence that TCDD accumulates LTB4 in the liver by an AHR-dependent induction of LTB4 biosynthesis to cause hepatotoxicity through neutrophil activation.

[A Case of Primary Hyperparathyroidism Complicated with Hypercalcemic Crisis during Treatment with Cinacalcet and Improved by Active Treatment].

A 77-year-old man was referred to our department for surgical treatment of a right ureteral stone identified on computed tomography (CT) during intensive examination for spondylolisthesis of L4-L5. At the initial visit, performance status was 4, and renal dysfunction was identified (Cr 1.3 mg/dl). Corrected calcium level was 11.8 mg/dl, and intact parathyroid hormone level was 555 pg/ml. A CT scan showed a well-defined mass measuring 22×16×20 mm on the right side of the esophagus, along with 99mTc-MIBI uptake in the lesion. Based on these findings, we diagnosed the patient with primary hyperparathyroidism. Considering his general condition, we determined that parathyroidectomy was difficult, and we started treatment using cinacalcet. A temporary therapeutic effect was observed, but the turning point was occurrence of hypercalcemic crisis with aspiration pneumonia. After recovery of his general condition and improvement of blood data by multidisciplinary therapy, we performed parathyroidectomy. Histopathological examination showed that the tumor was a parathyroid adenoma. He is free of reccurence at one year postoperatively. In addition, surgery for spondylolisthesis was performed, and he started to walk independently.

[A Case of Spindle Cell Lipoma in the Inguinal Region].

A 68-year-old man presented to our hospital for the first time because of a left inguinal mass that had been gradually enlarging over the past 20 years. At the initial visit, a 10×5 cm, soft, movable mass was detected in the left inguinal region. Magnetic resonance imaging revealed a smoothly shaped, internally heterogeneous tumor, with suppressed areas on a fat-suppressed image. In addition, the tumor showed partial enhancement with gadolinium and it did not continue into the spermatic cord. We performed excision of mass. During surgery, we observed that the tumor was well circumscribed and located on an aponeurosis of the external abdominal oblique muscle; therefore, we inferred it occurred from the subcutaneous tissue. The excised tumor was smoothly shaped and contained yellow and white nodes. On histopathological examination, the tumor was identified as a spindle cell lipoma.

Dioxin-Produced Alteration in the Profiles of Fecal and Urinary Metabolomes: A Change in Bile Acids and Its Relevance to Toxicity.

This study investigated dioxin-induced changes in metabolomes in pubertal rat excrement. The administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or restricting dietary intake (pair-fed group) markedly altered the metabolomic profile including lipids, hormones, and vitamins in the urine and feces. TCDD caused an increase in the fecal chenodeoxycholic acid and taurocholic acid content and in urinary adrenaline and 17ß-estradiol, while the urinary melatonin level was reduced by TCDD. These changes were not observed in the pair-fed group. In accordance with the elevated level of fecal bile acids, TCDD reduced the intestinal expression of the apical sodium-dependent bile salt transporter, which plays a role in resorbing bile acids from the bile duct. In addition, CYP7A1, a rate-limiting enzyme for bile acid biosynthesis, was attenuated by TCDD treatment, although TCDD induced hepatic CYP8B1, an enzyme essential for cholic acid synthesis. Supplying cholic acid or chenodeoxycholic acid to TCDD-exposed rats tended to restore the TCDD-produced reduction in serum triglycerides, whereas no similar trend was observed in wasting syndrome and lipid accumulation in the liver. These results suggest that: 1) TCDD alters the circulating levels of bile acids and hormones via a mechanism distinct from an attenuation in dietary intake, although the majority of TCDD-induced changes in nutrient contents in the excrement is due to a reduction in food intake; and 2) TCDD facilitates the excretion of bile acids and disrupts their biosynthesis, resulting in the disturbance of lipid homeostasis.

[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.

Maternal exposure to dioxin imprints sexual immaturity of the pups through fixing the status of the reduced expression of hypothalamic gonadotropin-releasing hormone.

Our previous studies have shown that treatment of pregnant rats with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 1 µg/kg) at gestational day (GD) 15 reduces the pituitary synthesis of luteinizing hormone (LH) during the late fetal and early postnatal period, leading to the imprinting of defects in sexual behaviors at adulthood. However, it remains unclear how the attenuation of pituitary LH is linked to sexual immaturity. To address this issue, we performed a DNA microarray analysis to identify the gene(s) responsible for dioxin-induced sexual immaturity on the pituitary and hypothalamus of male pups, born of TCDD-treated dams, at the age of postnatal day (PND) 70. Among the reduced genes, we focused on gonadotropin-releasing hormone (GnRH) in the hypothalamus because of published evidence that it has a role in sexual behaviors. An attenuation by TCDD of GnRH expression emerged at PND4, and no subsequent return to the control level was seen. A change in neither DNA methylation nor histone acetylation accounted for the reduced expression of GnRH. Intracerebroventricular infusion of GnRH to the TCDD-exposed pups after reaching maturity restored the impairment of sexual behaviors. Supplying equine chorionic gonadotropin, an LH-mimicking hormone, to the TCDD-exposed fetuses at GD15 resulted in a recovery from the reduced expression of GnRH, as well as from the defects in sexual behavior. These results strongly suggest that maternal exposure to TCDD fixes the status of the lowered expression of GnRH in the offspring by reducing the LH-assisted steroidogenesis at the perinatal stage, and this mechanism imprints defects in sexual behaviors at adulthood.

Selenium-binding protein 1: its physiological function, dependence on aryl hydrocarbon receptors, and role in wasting syndrome by 2,3,7,8-tetrachlorodibenzo-p-dioxin.

BACKGROUND: Selenium-binding protein 1 (Selenbp1) is suggested to play a role in tumor suppression, and may be involved in the toxicity produced by dioxin, an activator of aryl hydrocarbon receptors (AhR). However, the mechanism or likelihood is largely unknown because of the limited information available about the physiological role of Selenbp1. METHODS: To address this issue, we generated Selenbp1-null [Selenbp1 (-/-)] mice, and examined the toxic effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in this mouse model. RESULTS: Selenbp1 (-/-) mice exhibited only a few differences from wild-type mice in their apparent phenotypes. However, a DNA microarray experiment showed that many genes including Notch1 and Cdk1, which are known to be enhanced in ovarian carcinoma, are also increased in the ovaries of Selenbp1 (-/-) mice. Based on the different responses to TCDD between C57BL/6J and DBA/2J strains of mice, the expression of Selenbp1 is suggested to be under the control of AhR. However, wasting syndrome by TCDD occurred equally in Selenbp1 (-/-) and (+/+) mice. CONCLUSIONS: The above pieces of evidence suggest that 1) Selenbp1 suppresses the expression of tumor-promoting genes although a reduction in Selenbp1 alone is not very serious as far as the animals are concerned; and 2) Selenbp1 induction by TCDD is neither a pre-requisite for toxicity nor a protective response for combating TCDD toxicity. GENERAL SIGNIFICANCE: Selenbp1 (-/-) mice exhibit little difference in their apparent phenotype and responsiveness to dioxin compared with the wild-type. This may be due to the compensation of Selenbp1 function by a closely-related protein, Selenbp2.

Dioxin-induced retardation of development through a reduction in the expression of pituitary hormones and possible involvement of an aryl hydrocarbon receptor in this defect: a comparative study using two strains of mice with different sensitivities to dioxin.

We have previously revealed that treating pregnant rats with 2,3,7,8-tetracholorodibenzo-p-dioxin (TCDD) reduces the expression of gonadotropins and growth hormone (GH) in the fetal and neonatal pituitary. A change in gonadotropin expression impairs the testicular expression of steroidogenic proteins in perinatal pups, and imprint defects in sexual behavior after reaching maturity. In this study, we examined whether TCDD also affects the expression of gonadotropin and GH in mice using C57BL/6J and DBA/2J strains which express the aryl hydrocarbon receptor (Ahr) exhibiting a different affinity for TCDD. When pregnant C57BL/6J mice at gestational day (GD) 12 were given oral TCDD (0.2-20 µg/kg), all doses significantly attenuated the pituitary expression of gonadotropin mRNAs in fetuses at GD18. On the other hand, in DBA/2J mice, a much higher dose of TCDD (20 µg/kg) was needed to produce a significant attenuation. Such reduction in the C57BL/6J strain continued until at least postnatal day (PND) 4. In agreement with this, TCDD reduced the testicular expression of steroidogenic proteins in C57BL/6J neonates at PND2 and 4, although the same did not occur in the fetal testis and ovary. Furthermore, TCDD reduced the perinatal expression of GH, litter size and the body weight of newborn pups only in the C57BL/6J strain. These results suggest that 1) also in mice, maternal exposure to TCDD attenuates gonadotropin-regulated steroidogenesis and GH expression leading to the impairment of pup development and sexual immaturity; and 2) Ahr activation during the late fetal and early postnatal stages is required for these defects.