Functional role of phospholipase D (PLD) in di(2-ethylhexyl) phthalate-induced hepatotoxicity in Sprague-Dawley rats.

Phospholipase D (PLD) is an enzyme that catalyzes the hydrolysis of phosphatidyl choline (PC) to generate phosphatidic acid (PA) and choline. PLD is believed to play an important role in cell proliferation, survival signaling, cell transformation, and tumor progression. However, it remains to be determined whether enhanced expression of PLD in liver is sufficient to induce hepatotoxicity. The aim of this study was to investigate the possible role of PLD in di(2-ethylhexyl) phthalate (DEHP)-induced hepatotoxicity in Sprague-Dawley rats. The phthalate, DEHP (500 mg/kg/d), was administered orally, daily to prepubertal rats (4 wk of age, weighing approximately 70-90 g) for 1, 7, or 28 d. In this study, protein expression levels of PLD1/2, peroxisome proliferator-activated receptor (PPAR), and cytochrome P-450 (CYP) were determined by Western blot analysis using specific antibodies. Liver weight was significantly increased in the DEHP treatment groups. Immunohistochemical analysis demonstrated that DEHP produced strong staining of proliferating cell nuclear antigen (PCNA) at 28 d of exposure, suggestive of hepatocyte proliferation. A significant rise in PLD1/2 expression was observed in liver of DEHP-exposed rats after 7 d. Further, PPARα, constitutive androstane receptor (CAR), pregnane X receptor (PXR), and CYP2B1 protein expression levels were markedly elevated in DEHP-treated groups. Our results suggest that DEHP significantly enhanced the expression of PLD, which may be correlated with PPARα-induced hepatotoxicity through a complex interaction with nuclear receptors including CAR and PXR.

Evaluation of liver and thyroid toxicity in Sprague-Dawley rats after exposure to polybrominated diphenyl ether BDE-209.

Our goal in the present study was to evaluate whether decabromodiphenyl ether (BDE-209), which is the most abundant polybrominated diphenyl ether (PBDE) found in human samples, affects against target organs. Sprague-Dawley male rats were exposed to vehicle or BDE-209 (100, 300, or 600 mg/kg body weight, daily) from postnatal day (PND) 10 to PND 42. There was no significant difference in body and male reproductive organ weight changes compared with controls. However, liver, thyroid and adrenal gland weights were significantly increased in the high-dose of BDE-209 group. BDE-209 significantly induced the expression of cytochrome P450 (CYP1A2, CYP3A1, and CYP2B1) enzymes in the liver. Furthermore, constitutive androstane receptor (CAR) and pregnane xenobiotic receptor (PXR) expression levels were also increased in a dose-dependent manner. Total serum triiodothyronine (T3) concentration was significantly reduced in a dose-dependent manner, whereas the level of thyroid-stimulating hormone was significantly increased with BDE-209 treatment. In the histological findings, multiple areas of degenerated follicular epithelium and slight attenuation of the follicular epithelium were observed in the thyroid glands by high doses (300 and 600 mg/kg) of BDE-209 treatment. The presence of hepatocytic fatty degeneration and inflammatory foci were also observed in the 300 and 600 mg/kg of BDE-209 group. These findings demonstrate that BDE-209 induces hyperthyroidism and hepatotoxicity. In the future, further research is needed to determine the relationship between target organ toxicity and blood concentrations of BDE-209.

Effects of gestational exposure to decabromodiphenyl ether on reproductive parameters, thyroid hormone levels, and neuronal development in Sprague-Dawley rats offspring.

Polybrominated diphenyl ethers (PBDE) are a class of brominated flame retardants that are recognized as global environmental contaminants with potential adverse effects on human health. This study examined the effects of prenatal exposure to PBDE on reproductive organs, neuronal development, and levels of thyroid hormones. Pregnant rats were exposed to the vehicle or deca-bromodiphenyl ether (BDE) (BDE-209; 5, 40, or 320 mg/kg body weight/d) during gestation days (GD) 6-18. There was a significant decrease in body weight gain in F1 male offspring exposed to high-dose (320 mg/kg) BDE-209. Significant increases in thyroid weight and a decrease in adrenal weight were observed in high-dose BDE-209. Thyroxine (T4) concentrations were significantly lower in F1 female offspring exposed to BDE-209 at postnatal day (PND) 42. This reduction was more pronounced in the group exposed to higher doses. A low dose (5 mg/kg) of BDE-209 significantly reduced serum estradiol concentration in female offspring but did not affect testosterone levels in males. There was no significant effect on hippocampal neurogenesis in BDE-209 treatment groups. In conclusion, there was no apparent association between thyroid hormone concentrations and low birth weight in F1 rats after gestational exposure to BDE-209.

Exposure assessment of polybrominated diphenyl ethers (PBDE) in umbilical cord blood of Korean infants.

This study examined the levels of polybrominated diphenyl ethers (PBDE) in the umbilical cord blood of infants, and investigated the relationship between PBDE concentration and thyroid hormone levels. The concentration of PBDE were measured in the cord blood samples of 108 infants collected in Cheil Woman's Hospital, Seoul, Korea, in 2007. Of 108 pregnant woman reported, the average age was 31.9 +/- 3.54 yr (range 20-42 yr). The mean body weight of the infants was 3.15 +/- 0.57 kg (1.89-4.43 kg), and no birth defects were documented. The concentrations of the total PBDEs (7 congeners) found in the umbilical cord blood averaged 8.377 +/- 6.381 ng/g lipid, ranging from not determined (ND) to 29.407 ng/g lipid. Of the seven congeners detected, BDE-47 (4.571 +/- 2.903 ng/g lipid) accounted for the majority (38% of total PBDE) of total PBDE, followed in descending order by BDE-153 (3.080 +/- 2.231 ng/g lipid) and BDE-183 (2.933 +/- 2.386). There was no apparent correlation between the serum PBDE levels and thyroid hormone concentrations. Similarly, there was no apparent relationship between the infant thyroxine (T4) levels and four prevalent PBDE congener concentrations. Data suggest that the concentration of PBDE in umbilical cord blood of Korean infants is similar to or lower than concentrations reported from North America. In addition, PBDE readily crossed the blood placenta barrier. Therefore, further study on the relationship between the maternal and fetal blood concentrations of PBDE is recommended for a more comprehensive exposure assessment of PBDE in Koreans.

Time-response effects of testicular gene expression profiles in Sprague-Dawley male rats treated with di(n-butyl) phthalate.

Phthalate esters were reported to damage fetal and postnatal testes of experimental animals, but the molecular mechanisms underlying these effects remain unknown. The time-response effects of di(n-butyl) phthalate (DBP) on the expression patterns of the testicular genes in male Sprague-Dawley rats were examined for different periods of exposure (1, 7, 14, or 28 d). The steroidogenic- or spermatogenic-related gene expression patterns were measured using reverse-transcription polymerase chain reaction (RT-PCR). After 28 d of exposure, the serum concentrations of DBP and monobutyl phthalate (MBP) increased in a dose-dependent manner, and were significantly higher in the DBP-treated rats than in the control rats. Liver weight was increased markedly at 28 d after DBP exposure at 750 mg/kg/d. Testicular weight was reduced significantly after 14 and 28 d of exposure. DBP (750 mg/kg/d) produced a significant increase in scavenger receptor class B1 (SR-B1) and steroidogenic acute regulatory (StAR) mRNA after 14 and 28 d of exposure. The level of cytochrome P-450 (P450) side-chain cleavage (P450scc) mRNA decreased in the group treated with DBP at 750 mg/kg/d at 7 d. After 14 and 28 d of exposure, there was an apparent increase in P450scc mRNA. High doses of DBP significantly increased the Cyp17 mRNA level after 28 d of exposure. At 7 d, a significant decrease in Cyp19 mRNA was observed only in the group exposed to 750 mg/kg/d DBP. In addition, DBP significantly decreased the levels of a spermatid-specific gene (Spag4) and lactate dehydrogenase A (LDHA) mRNA after 7 d of exposure. The levels of androgen receptor (AR), estrogen receptor-alpha (ER-alpha), and retinoid X receptor-gamma (RXR-r) expression decreased significantly in a time- or dose-dependent manner. DBP significantly increased the peroxisome proliferator-activated receptor-gamma (PPAR-r) and phosphorylated extracellular-signal-regulated kinase (p-ERK1/2) levels in the testis. These results suggest that the acute and chronic effects of DBP on the steroidogenic pathways in the testes show mechanistically distinct patterns. Data thus provide some insights into the molecular mechanisms underlying DBP-induced testicular dysgenesis.

Hypothyroidism protects di(n-butyl) phthalate-induced reproductive organs damage in Sprague-Dawley male rats.

This study examined the deleterious effects of di(n-butyl) phthalate (DBP) on the male reproductive organs in hypothyroid rats. Hypothyroidism was induced in prepubertal male rats (28 days of age) by an intraperitonial (i.p.) injection of 10 mg/kg/day propylthiouracil (PTU) for 30 days. DBP (100 and 500 mg/kg/day) was administered by oral gavages to the intact or hypothyroid rats for 30 days. The body weight of the PTU-treated rats was significantly lower than the control group. The total triiodothyronine (T3) and thyroxine (T4) serum level was lower, and the thyroid-stimulating hormone (TSH) level was higher in the hypothyroid rats than in the control rats. The DBP treatment rats showed significantly lower testes, epididymides, seminal vesicles, and ventral prostate weights than the untreated rats. The hypothyroid rats had significantly higher thyroid weights and lower adrenal glands weights than the control rats. The histomorphological examination showed diffused Leydig cells hyperplasias and germ cells loss in the DBP (500 mg/kg)-treated rats, whereas these effects were mild in the DBP-treated hypothyroid rats. The serum levels of monobutyl phthalate (MBP) were significantly lower in PTU-induced hypothyroid rats than in the DBP-treated rats. This data suggests that the hypothyroid status might offer some protection from male reproductive organ toxicity caused by a disturbance in the metabolic activation of the parent compound, DBP.

Effect of di(n-butyl) phthalate on testicular oxidative damage and antioxidant enzymes in hyperthyroid rats.

This study compared the effects of di(n-butyl) phthalate (DBP) on the oxidative damage and antioxidant enzymes activity in testes of hyperthyroid rats. Hyperthyroidism was induced in pubertal male rats by intraperitoneal injection of triiodothyronine (T3, 10 microg/kg body weight) for 30 days. An oral dose of DBP (750 mg/kg) was administered simultaneously to normal or hyperthyroid (T3) rats over a 30-day period. No changes in body weight were observed in the hyperthyroid groups (T3, T3 + DBP) compared with controls. There were significantly higher serum T3 levels observed in the hyperthyroid rats than in the control, but the serum thyroid stimulating hormone levels were markedly lower in the hyperthyroid rats. DBP significantly decreased the weight of the testes in the normal (DBP) and hyperthyroid (T3 + DBP) groups. The serum testosterone concentrations were significantly lower in only DBP group. DBP significantly increased the 8-hydroxy-2-deoxyguanosine (8-OHdG) level in the testes, whereas the DBP-induced 8-OHdG levels were slightly higher in T3 + DBP group. Superoxide dismutase and glutathione peroxidase activities were significantly higher in the testes of the DBP or T3 + DBP groups. Catalase (CAT) activity was significantly higher in the DBP treatment group, but the T3 + DBP group showed slightly lower DBP-induced CAT activity. The testicular expression of thyroid hormone receptor alpha-1 (TRalpha-1) was significantly higher in the DBP groups, and androgen receptor (AR) expression was not detected in the DBP treatment group. In addition, DBP significantly increased the peroxisome proliferator-activated receptor-r (PPAR-r) levels in the testis. These results suggest that hyperthyroidism can cause a change in the expression level of PPAR-r in testes, and may increase the levels of oxidative damage induced by the metabolic activation of DBP.