The combined toxicity of dibutyl phthalate and benzo(a)pyrene on the reproductive system of male Sprague Dawley rats in vivo

A comparative study on antioxidant status combined with integrated biomarker response in Carassius auratus fish exposed to nine phthalates

Laboratory experiments were performed to determine the antioxidant responses to nine phthalates (PAEs) in the liver of the goldfish Carassius auratus. The fish were injected with 10 mg/kg body weight of each PAE for 1 day and 4, 8, and 15 days. The potential biotoxicity of the PAEs were examined using the antioxidase and lipid peroxide indices. We determined that the superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and malondialdehyde (MDA) levels displayed different trends following prolonged treatment, suggesting that metabolism generated either less toxic or more active substances. Based on the intensity of enzymes inhibition, MDA content, and the calculated integrated biomarker response (IBR), the toxicity order was determined as follows: dibutyl phthalate (DBP) > diethyl phthalate (DEP) > diisodecyl phthalate (DIDP) > diphenyl phthalate (DPP) > butyl benzyl phthalate (BBP) > diallyl phthalate (DAP) > dicyclohexyl phthalate (DCHP) > dimethyl phthalate (DMP) > di(2-ethylhexyl) phthalate (DEHP). In particular, DBP, which exhibited significant inhibition of enzyme activity and the greatest decrease in MDA content, may be a highly toxic contaminant. Furthermore, our results suggest that the IBR may be a general marker of pollution.

Short-term exposure to benzo[a]pyrene disrupts reproductive endocrine status in the swimming crab Portunus trituberculatus

The purpose of this study was to investigate the effect of benzo[a]pyrene (B[a]P) on reproductive endocrine disruption and explore the preliminary mechanisms in crustaceans. In this study, sexually mature female Portunus trituberculatus were exposed to 0, 0.1, 0.5 and 2.5 μg/L B[a]P for 10 days. The following were investigated: (1) Gonadosomatic Index (GSI) and oocyte diameter, (2) steroid concentrations in ovary and hemolymph, and (3) mRNA levels of genes involved in sex steroid synthesis (3β-HSD,17β-HSD) or reproduction (estrogen receptor (ER), OUT (Ovarian tumor gene) domain containing ubiquitin aldehyde-binding protein 1 (OTUB1), vitellogenin (VTG),vasa). B[a]P exposure caused significant reductions in the GSI and oocyte diameter in the crabs. Furthermore, 17β-estradiol (E2), testosterone (T) and progesterone (P) levels were inhibited significantly while 3β-HSD and 17β-HSD mRNA expressions were also decreased in a dose-dependent manner at day 10, which suggests that B[a]P can disrupt sex steroid levels through steroid synthesis pathways. In addition, high levels of B[a]P activated transcription of OTUB1 while suppressed ER and VTG expression, which indicates that exposure to waterborne B[a]P could interfere with ubiquitin-proteasome pathway and subsequently affect ER and ER-mediated gene expression. We also observed a reduction in vasa gene expression reflecting the negative effect of B[a]P on oocyte development in the molecular level. This study is the first to demonstrate in vivo B[a]P toxicity in the reproductive endocrine system of female P. trituberculatus and provided a scientific basis of the decline in crustacean populations.

Environmentally relevant concentrations of benzo[a]pyrene affect steroid levels and affect gonad of male scallop Chlamys farreri

Sexually mature male Chlamys farreri were exposed to benzo[a]pyrene for 10 days at four concentrations at 0, 0.025, 0.5 and 10 μg/L. Fluctuations in sex steroids during the exposure period were observed, which indicated that sex steroids have a role in gamete development. Exposure to B[a]P altered levels of 17β-estradiol, testosterone, and progesterone. Furthermore, B[a]P treatments induced oxidative stress in a dose-dependent manner on spermary of scallop and led to delayed development and damaged spermatid in germinal epithelium of spermary. Overall, B[a]P affected the steroid levels and induced gonadal toxicity at environmentally relevant concentrations.

Digital gene expression analysis of reproductive toxicity of benzo[a]pyrene in male scallop chlamys farreri

Benzo[a]pyrene (BaP) is a representative polycyclic aromatic hydrocarbon (PAH) and is studied widely for its strong toxicity and wide distribution. Although BaP pollution in marine environment is increasing, molecular mechanisms underlying reproductive toxicity of BaP in marine mollusks have been seldom systematically studied, especially in males. In this study, genes that regulated reproductive responses of Chlamys farreri under BaP stress were analyzed through digital gene expression (DGE) sequencing with testis tissues. A total of 12,485,055 and 14,454,127 clean reads were generated from control and BaP exposure DGE libraries, respectively. After comparing two libraries, 1051 differentially expressed genes were detected, with 223 up-regulated and 828 down-regulated genes. Gene ontology (GO) annotation and kyoto encyclopedia of genes and genomes (KEGG) pathway analyses were performed on all genes to understand their biological functions and processes. The results showed that numerous enriched, differentially expressed genes related to aromatic compound catabolic processes, spermatid development, microtubule-based movement, energy production and immune response. Quantitative real-time PCR was performed to verify the expressed genes of DGE. The study generated data to show the overall reproductive transcription responses of male C. farreri under BaP stress, and it also can serve as the reference for future study of organic pollutions in aquatic mollusks.

Occurrence and distribution of phthalate esters in riverine sediments from the Pearl River Delta region, South China

Sixty-eight sediment samples collected from Dongjiang River, Xijiang River, Beijiang River and Zhujiang River in the Pearl River Delta (PRD) region, Southern China, were analyzed for 16 phthalate esters (PAEs). PAEs were detected in all riverine sediments analyzed, which indicate that PAEs are ubiquitous environmental contaminants. The Σ16PAEs concentrations in riverine sediments in the PRD region ranged from 0.567 to 47.3 μg g(-1) dry weight (dw), with the mean and median concentrations of 5.34 μg g(-1) dw and 2.15 μg g(-1) dw, respectively. Elevated PAEs concentrations in riverine sediments in the PRD region were found in the highly urbanized and industrialized areas. Of the 16 PAEs, diisobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP) and di(2-ethylhexyl) phthalate (DEHP) dominated the PAEs, with the mean and median concentrations of 1.12 μg g(-1)dw, 0.420 μg g(-1) dw and 3.72 μg g(-1) dw, and 0.429 μg g(-1) dw, 0.152 μg g(-1) dw and 1.55 μg g(-1) dw, respectively, and accounted for 94.2-99.7% of the Σ16PAEs concentrations. Influenced by local sources and the properties of PAEs, a gradient trend of concentrations and a fractionation of composition from more to less industrialized and urbanized areas were discovered. As compared to the results from other studies, the riverine sediments in the PRD region were severely contaminated with PAEs. Information about PAEs contamination status and its effect on the aquatic organisms in the PRD region may deserve further attention.

Influence of lipoic acid on testicular toxicity induced by bi-n-butyl phthalate in rats

Bi-n-butyl phthalate (BNBP) is an environmental pollutant. The aim of this study was to evaluate the protective effect of lipoic acid (LA) against testicular dysfunction associated with the intake of to BNBP- intoxicated rats. Adult male Wistar rats were divided into 4 groups of 6 animals each, and received medication orally for 14 days. Group I rats received 0.5 ml corn oil. Group II rats received LA (20 mg/kg B.W./day). Group III rats received BNBP (250 mg/kg B.W./day). Group IV rats received LA 24h prior to BNBP intake. Testes weight, cauda sperm count and sperm motility were decreased significantly by 18.15%, 13.83% and 13.5%, respectively, after BNBP treatment. Significant increase by 12.1%, 10.20% and 11.51%, respectively, was observed in LA-BNBP rats. Significant increase by 1.53%, 1.5% and 1.8%, for serum follicle stimulating hormone, testosterone and total antioxidant status, respectively, were observed in LA-BNBP rats. Testicular lipid peroxides and lactate dehydrogenase enzyme were significantly decreased by 1.5 and 1.6 folds, respectively, in LA-BNBP rats were decreased after BNBP treatment. Testicular superoxide dismutase, catalase and glutathione reductase enzymes were significantly increased in LA-BNBP rats. LA-BNBP rats, decreased the damage to seminiferous tubules produced by BNBP intake. In conclusion, LA mitigated BNBP-induced testicular toxicity through antioxidant mechanism and by direct free radical scavenging activity.

Phthalate ester leachates in aquatic mesocosms: implications for ecotoxicity studies of endocrine disrupting compounds

Aquatic mesocosm experiments have become common throughout the fields of ecology and ecotoxicology. Mesocosm containers are often composed of plastic materials as these are lighter and cheaper than steel cattle tanks. Plastics may contain phthalate esters which may leach from containers, potentially confounding experiments via toxicity or endocrine disruption. The objective of this experiment was to determine the extent to which plastic containers (="tanks") used for mesocosms leach phthalates, and if there are significant differences between tank types and phthalate profiles. We investigated four tank types: fiberglass, polyethylene, poly-vinyl chloride, and polyethylene tanks containing an established aquatic community. We measured six common phthalate esters in water samples collected from each tank every 2 weeks for 8 weeks. There was a significant effect of tank type, time, and time x type interactions on phthalate ester concentrations. Di-(2-ethylhexyl) phthalate was the predominant congener measured in all samples. Fiberglass tanks had greater concentrations of dimethyl phthalate compared to other tank types (more than 600x larger concentration), but no other differences in phthalate profiles among tank types were evident. In addition, tanks with established communities had much higher concentrations of most phthalates at the 6 and 8 week timepoints. Our study confirms that mesocosm tanks of different materials leach phthalates starting immediately after they are filled and continuing for at least 8 weeks, but do so at different rates. Future ecotoxicity experiments should consider the potentially confounding effects of phthalates that may leach from tanks used in experimental mesocosms.

An investigation of endocrine disrupting effects and toxic mechanisms modulated by benzo[a]pyrene in female scallop Chlamys farreri

The purpose of this study was to investigate the endocrine disrupting effects induced by benzo[a]pyrene (B[a]P) and explore the underlying mechanisms in mollusks. In this study, sexually mature female Chlamys farreri were exposed to benzo[a]pyrene for 10 days at four different concentrations as 0, 0.025, 0.5 and 10 μg/L. Sex steroids were identified and quantified by electrochemiluminescence immunoassay (ECLIA) method and results showed that exposure to B[a]P exerts great suppression on 17β-estradiol, testosterone production and disrupts progesterone levels in ovary. Transcription of genes were detected and measured by real-time RT-PCR. It showed that at day 10 B[a]P inhibited 3 β-HSD, CYP17 and 17β-HSD mRNA expression in a dose-dependent manner, which suggests that they could be potential targets of B[a]P that disrupt steroidogenic machinery. Moreover, 0.025 μg/L B[a]P activated transcription of aryl hydrocarbon receptor (AHR), AHR nuclear translocator (ARNT), CYP1A1 and estrogen receptor (ER), while 10 μg/L B[a]P suppressed all of them. The consistency of their responses to B[a]P exposure implies that AHR action may be involved in invertebrate CYP regulation and ER transcription despite of unknown mechanisms. Additionally, B[a]P exposure could induce ovarian impairment and developmental delay in C. farreri. Overall, sensitivity of C. farreri to endocrine disruption and toxicity suggests that C. farreri is a suitable species for study of endocrine-disrupting effects in marine invertebrates. This study will form a solid basis for a realistic extrapolation of endocrine disrupting effects across taxonomic groups and phyla.

Effects of exposure to extremely low frequency magnetic fields on spermatogenesis in adult rats

The constant exposure of modern society to extremely low frequency magnetic fields (ELF-MF) has raised considerable concerns about the potential risks to male reproduction. However, the epidemiological and experimental data remain contradictory and inconclusive. In the present study, we investigated the effects of 50 Hz ELF-MF of 500 µT applied 4 h/day, 7 days/week for 4 and 8 weeks on male reproduction, focusing on changes in spermatogenesis. Several biological endpoints related to testicular function and spermatogenesis were measured, including the following: body mass, masses of testes and epididymis, sperm count and abnormal sperm ratio in the caudal epididymis, serum testosterone level, testicular histology, frequency of 14 stages of the cycle of the seminiferous epithelium and of four stages of meiosis I, germ cell apoptosis and testicular oxidative status. No significant differences were found in the biological endpoints between the sham control and the exposed rats in either the 4- or 8-week exposure period. These negative results may result from the lack of change in serum testosterone. In conclusion, our study indicates that exposure to low intensity ELF-MF may have no adverse effects on spermatogenesis.

Occurrence of phthalate esters in sediments in Qiantang River, China and inference with urbanization and river flow regime

Phthalate esters (PAEs), a group of emerging organic contaminants, have become a serious issue arousing much attention for their ubiquitous presence and hazardous impact on the environment. This study provides the first data on distribution of PAEs in the sediments in the Qiantang River, Zhejiang Province, China, and the inference with urbanization and river flow regime. PAEs were detected in all 23 sediment samples analyzed, and the total concentrations of their 16 congeners in sediments ranged from 0.59 to 6.74μg/g dry weight (dw), with the geometric mean value of 2.03μg/g dw. Of the 16 PAE congeners, di-n-butyl phthalate (DnBP), diisobutyl phthalate (DiBP), and di(2-ethylhexyl) phthalate (DEHP) were present in all sediment samples. The PAEs concentrations in urban regions were higher than those in rural regions because of higher discharge of PAEs from plastic materials in urbanized areas. Concentrations of PAEs were positively correlated with sediment organic matter (fOM) and negatively correlated with logistic value of annual average flow volume at sample sites. River flow regime modified by man-made dams significantly affected the distribution of PAEs. Analysis of congener composition of PAEs indicated that the DEHP was predominant congener in the Qiantang River. The normalized concentration of DEHP exceeded recommended environmental risk limit (ERL).

Linking empirical estimates of body burden of environmental chemicals and wellness using NHANES data

Biomonitoring of industrial chemicals in human tissues and fluids has shown that all people carry a "body burden" of synthetic chemicals. Although measurement of an environmental chemical in a person's tissues/fluids is an indication of exposure, it does not necessarily mean the exposure concentration is sufficient to cause an adverse effect. Since humans are exposed to multiple chemicals, there may be a combination effect (e.g., additive, synergistic) associated with low-level exposures to multiple classes of contaminants, which may impact a variety of organ systems. The objective of this research is to link measures of body burden of environmental chemicals and a "holistic" measure of wellness. The approach is demonstrated using biomonitoring data from the National Health and Nutrition Examination Surveys (NHANES). Forty-two chemicals were selected for analysis based on their detection levels. Six biological pathway-specific indices were evaluated using groups of chemicals associated with each pathway. Five of the six pathways were negatively associated with wellness. Three non-zero interaction terms were detected which may provide empirical evidence of crosstalk across pathways. The approach identified five of the 42 chemicals from a variety of classes (metals, pesticides, furans, polycyclic aromatic hydrocarbons) as accounting for 71% of the weight linking body burden to wellness. Significant interactions were detected indicating the effect of smoking is exacerbated by body burden of environmental chemicals. Use of a holistic index on both sides of the exposure-health equation is a novel and promising empirical "systems biology" approach to risk evaluation of complex environmental exposures.