Effects of acute postnatal exposure to 3,3',4,4'-tetrachlorobiphenyl on sperm function and hormone levels in adult rats

Endocrine-disrupting chemicals and autoimmune diseases

Endocrine-disrupting chemicals (EDCs) widely exist in people's production and life which have great potential to damage human and animal health. Over the past few decades, growing attention has been paid to the impact of EDCs on human health, as well as immune system. So far, researchers have proved that EDCs (such as bisphenol A (BPA), phthalate, tetrachlorodibenzodioxin (TCDD), etc.) affect human immune function and promotes the occurrence and development of autoimmune diseases (ADs). Therefore, in order to better understand how EDCs affect ADs, we summarized the current knowledge about the impact of EDCs on ADs, and elaborated the potential mechanism of the impact of EDCs on ADs in this review.

Association between polychlorinated biphenyl exposure and thyroid hormones: a systematic review and meta-analysis

Purpose: To conduct a comprehensive meta-analysis investigating the association between polychlorinated biphenyl (PCB) exposure and serum thyroid hormone levels among adults. Methods: Eleven studies met inclusion criteria for analysis following systematic search of PubMed, Embase, and Scopus databases. Of these, 7 studies measured exposure by the total sum of PCB congeners (∑PCB), 1 study measured individual PCB congener levels, and 3 studies measured both ∑PCB levels and PCB congener levels. Correlation coefficients (r) were extracted from each study. Summary estimates were calculated for ∑PCB levels and PCB congeners reported by 2 or more studies: PCB 28, 52, 101, 105, 118, 138, 153, and 180, using random effects model. Results: Significant negative correlation was found between ∑PCBs and T3 (r: -0.09; 95% CI: -0.17, -0.02) and FT3 (r: -0.24; 95% CI: -0.36, -0.12). Congener-specific analysis found T3 to be negatively correlated with PCB-153 (r: -0.19; 95% CI: -0.34, -0.03) and PCB-180 (r: -0.14; 95% CI: -0.26, -0.01), whereas TSH was positively correlated with PCB-105 (r: 0.15; 95% CI: 0.02, 0.28). Conclusions: The present study is the first meta-analysis to investigate the association between PCB exposure and thyroid hormone dysfunction among adults. Results suggest a significant association between PCB exposure and thyroid hormone dysregulation.

Systematic review of associations of polychlorinated biphenyl (PCB) exposure with declining semen quality in support of the derivation of reference doses for mixture risk assessments

BACKGROUND

Mixture risk assessments require reference doses for common health endpoints of all the chemicals to be considered together. In support of a mixture risk assessment for male reproductive health, we conducted a systematic review of the literature on associations between exposures to Polychlorinated Biphenyls (PCBs) and declines in semen quality. PCBs can act as Aryl-hydrocarbon Receptor (AhR)-agonists and Androgen Receptor (AR)-antagonists, both mechanisms which can affect sperm parameters. PCBs and other AR-antagonists can produce additive combination effects. Based on these observations our objective was to systematically gather data from animal and human studies to derive a reference dose for declines in semen quality for individual PCB.

METHODS

We systematically reviewed and evaluated the evidence in human epidemiological and experimental animal studies on associations between PCBs and deteriorations in semen quality. Human data and findings from animal studies with PCB mixtures were considered as supporting evidence. Information for individual congeners from animal studies was required for inclusion in mixture risk assessment. Using a robust confidence rating approach, we identified suitable studies to derive reference doses for individual PCB congeners.

RESULTS

Evaluation of human epidemiological studies revealed several reports of adverse effects on sperm parameters linked to PCB exposures, although some studies reported improved semen quality. Our review of experimental animal studies found that treatments with PCBs affected semen quality, in most cases adversely. We found robust evidence that PCB-118 and -169 were linked to declines in semen quality. Evidence for adverse effects of PCB-126, -132, -149, and -153 was moderate, whereas for PCB-77 it was slight and for PCB-180 indeterminate. Using widely accepted risk assessment procedures, we estimated reference dose values of 0.0029 µg/kg/day for PCB-118 and 0.00533 µg/kg/day for PCB-169. In addition, we derived values for PCB-126: 0.000073 µg/kg/day, PCB-132: 0.0228 µg/kg/day, PCB-149: 0.656 µg/kg/day, and PCB-153: 0.0058 µg/kg/day.

CONCLUSIONS

We found robust evidence for links between PCB exposure and deteriorations in semen quality, and derived reference doses for a set of congeners. We intend to use these values in combination with congener-specific exposure data in a mixture risk assessment for declines in semen quality, involving several other antiandrogenic chemicals.

Associations of paternal serum dioxin-like polychlorinated biphenyl concentrations with IVF success: A pilot study

Dioxin-like polychlorinated biphenyls (DL-PCBs) are environmental pollutants that have been associated with impaired semen quality. However, research on the potential impact of paternal exposure to DL-PCBs and the risk of adverse pregnancy outcomes are limited. We examine the relationship between serum DL-PCB concentrations and IVF outcomes among 42 males seeking fertility treatment. Concentrations of 12 serum DL-PCBs were analyzed by high-resolution gas chromatography coupled to high-resolution mass spectrometry. Modified Poisson regressions, adjusted for confounders, were used to assess bivariate associations and to estimate risk ratios (RRs) between DL-PCBs and binary IVF outcomes. The median concentration (25th-75th percentiles) of the sum of the 12 DL-PCBs (∑DL-PCBs) obtained for the patients was 5.42 (3.78-7.78) ng/g lipid. No statistically significant association between DL-PCB levels and embryo quality was found. However, men with high serum PCB-77 concentrations present more probability of high-quality embryos (RR: 0.292; 95% CI: 0.090-0.942), whereas the opposite trend is observed for men with lower serum levels of PCB-156 (RR: 7.960; 95% CI: 1.020-62.100), who present increased odds of high-quality embryos. Serum concentrations of PCB-126 and PCB-114 were associated with decreased implantation rates (p < 0.05). Moreover, PCB-77 and ∑non-ortho PCBs were significantly associated with a lower likelihood of clinical pregnancy (p < 0.05). A lower likelihood of live birth was associated with higher levels of PCB-77, PCB-105, PCB-118, and recording significant differences for ∑non-ortho PCBs, ∑mono-ortho PCBs, and ∑DL-PCBs (p < 0.05). These findings suggest that paternal DL-PCB exposure before conception may be related to pregnancy endpoints. However, DL-PCB measurement were limited to male partners. Therefore, we propose that future studies with larger population sizes should include both maternal and paternal factors.

Spatial and temporal trends of polychlorinated biphenyls in water and sediment from Nairobi River, Kenya

Polychlorinated biphenyls (PCBs) are chemicals that have become ubiquitous environmental pollutants due to their past use, persistence, and long-range transport thus requiring continuous monitoring. Therefore, this research was carried out to investigate spatial and temporal trends of seven indicator PCBs and two others (PCB 105 and PCB 156) in the Nairobi River. Levels of PCBs ranged from below detection limit (bdl) to 157.64 ± 1.52 ng g^-1 and bdl to 718.78 ± 1.71 ng L^-1 for sediment and water, respectively. PCBs 28, 138, and 153 were the most dominant contributing 33.4%, 17.9%, and 14.5% to the total PCBs in sediments and 54.6%, 19.3%, and 14.1% to the total PCBs in water. There was a general increase in ΣPCBs from 18.89 to 151.18 ng g^-1 for sediments and 275.52 to 429.84 ng L^-1 for water as the River flowed downstream. The dry season recorded the highest ΣPCB in sediments while the rainy season recorded the highest ΣPCBs in water, with levels exceeding the WHO water quality guidelines. Risk assessment revealed that populations living downstream are exposed to high levels of PCBs through the consumption of water. Levels of ΣPCBs downstream also exceeded the sediment quality guidelines meaning that aquatic organisms are threatened.

PCB 77 action in ovary cells--toxic effects, apoptosis induction and cell cycle analysis

CONTEXT

PCB 77 (3,3',4,4'-tetrachlorobiphenyl), a non-ortho congener with planar configuration, has been identified as potential endocrine disrupter capable to increase the risk of reproductive and developmental failure.

OBJECTIVE

In the present study, in vitro PCB 77 toxic potential, apoptosis induction and cell cycle alterations were investigated to reveal direct toxic effects on ovarian cells.

METHODS

Chinese Hamster Ovary (CHO-K1) cell line was selected as a model system and decreased cell viability was confirmed by application of four bioassays. Cellular morphology and quantitative analysis of apoptotic, necrotic and viable cells were determined with fluorescent microscopy and cell cycle phase distributions by measuring DNA content using flow cytometry.

RESULTS

We have indicated Trypan blue exclusion assay as the most sensitive for quantifying cytotoxicity of PCB 77 in terms of IC50 values, while the results obtained by other methods pointed to a possible localized effect on the lysosomes/endosomes (Neutral red), compromised intracellular metabolic processes (MTT) and possible interferation with the rate of protein synthesis (Kenacid blue). The loss of cell viability, as a consequence of treatment with 10-100 μM PCB 77, fundamentally was due to induction of apoptosis with observed common series of specific morphological changes characteristic to apoptotic phenomenon. The level of alterations of normal cell cycle progression was low without significant changes at analyzed time intervals.

CONCLUSION

These results indicate toxic outcomes of PCB 77 at ovarian cellular level with regard to potential direct adverse effects to female reproductive system.

Acute and subacute oral toxicity of polychlorinated diphenyl sulfides in mice: determining LD50 and assessing the status of hepatic oxidative stress

Polychlorinated diphenyl sulfides (PCDPSs), a series of dioxin-like compounds, have been detected in various environmental samples. However, information on the toxicity of these compounds is limited. In the present study, the toxic effects of PCDPSs were assessed after acute and subacute exposure in mice. Relationships between acute toxicity, number, and position of substituted Cl atoms were assessed. In the acute study, 11 types of PCDPSs were administered to female Kunming mice by gavage, and median lethal doses (LD50s) were determined by the Karber method. Results indicated that the LD50s of lower substituted PCDPSs were smaller than higher substituted PCDPSs. Substituted positions also influenced the LD50 of PCDPSs. Terminal necropsy showed increased relative liver weights and decreased relative kidney weights. Histological examination of livers demonstrated swollen cells, inflammation, vacuolization, and necrosis. In the 28-d subacute exposure tests, 11 types of PCDPSs were dissolved in corn oil and administered to mice at doses of 1, 10, and 100 mg/kg. Superoxide dismutase (SOD) activity and malondialdehyde (MDA) levels in mouse liver were determined after the exposure period. Results suggested that lower substituted PCDPSs decreased SOD activity in the high-dose groups compared with controls, and MDA level in the 100-mg/kg dose group was significantly increased. In addition, acute toxicity of PCDPSs partly corresponded to the hepatic oxidative damage observed.

Adverse effects of neonatal exposure to 3,3',4,4',5,5'-hexachlorobiphenyl on hormone levels and testicular function in male Sprague-Dawley rats

In this study, we investigated the time-course changes of hormone levels and sperm numbers in male Sprague-Dawley (SD) rats after neonatal exposure to 3,3',4,4',5,5'-hexachlorobiphenyl (PCB169). Neonatal rats were given (through oral gavages) doses of 0, 0.025, 0.25, or 0.5 mg/kg-day of PCB169 in corn oil from postnatal day 1 (PND1) to PND7. The rats were sacrificed at PND8, PND21, and PND90. PCB169 exposure was confirmed by the marked induction of liver CYP1A1 mRNA expression at these three time points. The testicular daily sperm production and the sperm counts of the epididymis cauda significantly decreased at PND90 compared to that of control. Although reductions in serum thyroxine and triiodothyronine levels occurred at all these three time points and at both PND21 and PND90, respectively, the mRNA expression of testicular thyroid hormone receptor α1 was suppressed significantly only at PND8. The serum and testicular testosterone (T) levels declined markedly at PND90 compared to the controls, but there was no effect at PND21. The mRNA expression of testicular steroidogenic factor 1 was inhibited markedly at the three time points, whereas those of StAR, P450c17, P450scc, and 3β-HSD were suppressed significantly only at PND90 relative to the controls. PCB169 treatment had no effects on pituitary follicle-stimulating hormone and luteinizing hormone levels and on their receptors' expression in the testes. These results indicate that neonatal exposure to PCB169 damages hormone levels and testicular function in the long-term, resulting in persistent hypothyroidism and decreases in adult T levels and sperm counts.

Effect of human pharmaceutical Carbamazepine on the quality parameters and oxidative stress in common carp (Cyprinus carpio L.) spermatozoa

The effects of CBZ (a human pharmaceutical commonly present in aquatic environment) on the quality parameters and oxidative stress of common carp spermatozoa were investigated in vitro. Fish spermatozoa were incubated with different concentration of CBZ (0.2, 2.0 and 20 mgL(-1)) for 2h. Results revealed that the percentage of spermatozoa motile and velocity were decreased significantly at higher concentration of CBZ (2.0 and 20 mgL(-1)) and a dose-dependent reduction was observed. But the viability of fish spermatozoa was not affected significantly in all CBZ treatment groups. After 2h exposure of CBZ at higher test concentration (2.0 or 20 mgL(-1)), oxidative stress was apparent as reflected by the significant higher LPO and CP levels in fish spermatozoa, as well as the significant inhibition of antioxidant enzymes activities including SOD, GR and GPx. In short, CBZ can induce ROS stress in fish spermatozoa, which could impair the sperm quality and antioxidant defense system. Our results suggested that the use of fish spermatozoa in vitro assays may provide a novel and efficiently means for monitoring residual pharmaceutical in aquatic environment.

Polychlorinated biphenyls have inhibitory effect on testicular steroidogenesis by downregulation of P45017α and P450scc

Polychlorinated biphenyls (PCBs) are environmental pollutants that are quite toxic to biological systems. This study examined the inhibitory effect of PCB126 and PCB114 on testicular steroidogenesis in male rats. Male Sprague Dawley rats received weekly intraperitoneal injections of PCB126 (0.2 mg/kg) or PCB114 (20 mg/kg) or vehicle (corn oil). Animals from each group were sacrificed at 2, 5 and 8 weeks after the injections. Blood and testis tissue samples were collected for the hormone assay, Western blotting and reverse transcriptase polymerase chain reaction (RT-PCR). The testosterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels were assayed, and the expression levels of the mRNA and proteins associated with the testosterone biosynthesis pathway were measured to determine the effect of PCB126 and PCB114 on testicular steroidogenesis. The results showed that the testis weight was significantly higher in the PCB126-treated rats given eight shots. Moreover, the serum testosterone levels were significantly lower in the PCB126 and PCB114-treated groups than the control. The transcription and translation levels of P45017α and P450scc were significantly lower in the PCB126-treated groups than the control. These results suggest that PCB126 may affect testicular steroidogenesis by downregulating P45017α, P450 scc and have inhibitory effect on the testicular functions.

Fertility and markers of male reproductive function in Inuit and European populations spanning large contrasts in blood levels of persistent organochlorines

OBJECTIVE

We synthesized the main findings from an international epidemiologic study on the impact of biopersistent organic pollutants (POPs) on human reproductive function.

DATA SOURCES AND EXTRACTION

We used a database with interview and biological data from 2,269 women and their spouses, and 18 published core papers.

DATA SYNTHESIS

The study did not provide direct evidence of hormone-like activity of the polychlorinated biphenyl (PCB) congener CB-153 and the main dichlorodiphenyltrichloroethane (DDT) metabolite, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE), as serum concentrations of these compounds were not consistently related to either endogenous or exogenous hormone activity in serum. Nevertheless several links bewteen POP exposure and biomarkers of male reproductive function were identified. First, an association between high CB-153 serum levels and low sperm counts was detected within a subgroup of men with short androgen receptor CAG repeat length. Second, a relationship between increased CB-153 serum concentrations and decreased sperm motility was seen in all four studied regions, and indications of reduced neutral alpha-glucosidase activity in seminal plasma point to a post-testicular effect. Third, damage of sperm chromatin integrity was considerably less frequent in Greenlandic Inuits compared with that in European groups, and only in the latter was impairment of sperm chromatin integrity related to POPs. Despite these effects, fertility in terms of time taken to conceive was not related to POPs except in Inuits. A likely explanation of the latter was not identified.

CONCLUSIONS

POPs may interfere with male reproductive function without major impact on fertility. The data do not provide direct evidence for endocrine disruption, hence other mechanisms should also be considered.

Semen Quality and Exposure to Persistent Organochlorine Pollutants

BACKGROUND

Inconsistent results have been found in previous human studies on male reproductive toxicity of persistent organochlorine pollutants. The majority of studies have been conducted among selected populations of infertility clients or among occupational cohorts including a limited number of participants.

METHODS

We conducted a cross-sectional study of semen quality and serum concentration of 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) and 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (p,p'-DDE) among 763 men. We included men from all regions in Greenland (n = 194), fishermen from Sweden (n = 185), inhabitants of the city of Kharkiv, Ukraine (n = 195), and inhabitants of the city of Warsaw, Poland (n = 189). Blood samples were analyzed for CB-153 and p,p'-DDE using gas chromatography-mass spectrometry and adjusted for serum lipids.

RESULTS

Sperm concentration was not impaired with increasing serum CB-153 or p,p'-DDE levels in any of the separate groups or overall. Similarly, the proportion of morphologically normal sperm was not associated with either CB-153 or p,p'-DDE blood concentration. However, sperm motility was inversely related to CB-153 concentration in Greenland and the Swedish fishermen population. Across all 4 regions, the sperm motility decreased on average by 3.6% (95% confidence interval = 1.7% to 5.6%) per one-unit increase in the log of blood CB-153 (ng/g lipid). The concentration of p,p'-DDE was negatively associated with sperm motility in the Greenlandic population and in the compiled dataset.

CONCLUSION

Adult exposure to persistent organochlorine pollutants within the ranges observed in the present study is not likely to cause reduction in sperm concentration or morphology. However, higher exposure may be associated with impaired sperm motility.

Influence of tris(4-chlorophenyl)methanol, non-ortho PCB 77 and gamma-hexachlorocyclohexane on human sperm function in vitro

In recent years, there has been growing concern that environmental pollutants in general, and organochlorines in particular, adversely affect male fertility. Therefore, we investigated the effects of tris(4-chlorophenyl)methanol (TCPM), non-ortho PCB 77 and gamma-hexachlorocyclohexane (gamma-HCH, lindane) on human sperm functions in vitro. Human spermatozoa from healthy donors were washed in human tubular fluid medium containing 1% human serum albumin, filtered through glass wool and exposed to different concentrations of TCPM, PCB 77 or gamma-HCH. After incubation for 5 h at 37 degrees C and 5% CO(2), sperm vitality and the percentage of living acrosome-reacted spermatozoa were examined using triple stain technique. Total sperm motility was evaluated by computer-assisted sperm analysis (Stroemberg-Mika) after 5 h. For TCPM, total motility was additionally measured after 18 and 40 h. Different concentrations of PCB 77 and gamma-HCH did not alter the percentage of spontaneous living acrosome-reacted spermatozoa, vitality and total motility. TCPM dose-dependently altered sperm motility, vitality and acrosome reaction. The percentage of living acrosome-reacted spermatozoa was increased at overtly toxic concentrations. Therefore, it is suggested that unspecific acrosomal loss has been induced by degenerative processes. In conclusion, even high concentrations of PCB 77 and gamma-HCH did not affect human sperm functions in vitro. Only very high cytotoxic TCPM concentrations modulated spontaneous acrosome reaction and total motility. Therefore, in vivo effects on human sperm function seem to be unlikely. However, individual susceptibility has to be considered and little is known about additive and possible synergistic effects as other environmental pollutants with similar potencies have been found in the human male and female reproductive tract.

Effects of single non-ortho, mono-ortho, and di-ortho chlorinated biphenyls on human sperm functions in vitro

Polychlorinated biphenyls (PCBs) are ubiquitous pollutants in the environment. They are present in body fluids associated with reproduction such as follicular fluid, seminal fluid and cervical mucus. Most PCB effects are mediated through the aryl hydrocarbon receptor, which is present in human spermatozoa. Additionally, PCBs may alter various biochemical reactions, such as calcium homeostasis. Therefore we investigated the effects of single non-ortho PCB 126, mono-ortho PCB 118, and di-ortho PCB 153 on human sperm motility, vitality, and calcium-dependent acrosome reaction (AR) in vitro. Human spermatozoa were either treated with different single PCB congeners or their combinations for 5 h at 37 degrees C (spontaneous AR), or for 16 h at room temperature and 4 degrees C (induced AR). Motility was measured after 5 h of incubation. Compared with the controls, PCB exposure had no effects on the percentage of living acrosome reacted spermatozoa, vitality, and motility. There was no difference in the inducibility of the AR between treatment groups and the respective controls after long term incubation. The PCB concentrations used were far higher than those found in cervical mucus or seminal fluid. In vivo effects of PCB congeners on human ejaculated spermatozoa seem to be unlikely. However these results cannot be easily transferred to the in vivo situation, because individual susceptibility has to be considered, and there is no information about synergistic or additive effects with other chemicals present in the male and female reproductive tract.

Endocrine Disruptive Effects of Polychlorinated Biphenyls on the Thyroid Gland in Female Rats

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants. Aroclor 1221 (A1221) and Aroclor 1254 (A1254) are commercial PCB mixtures with low and high number of chlorination, respectively. We have comparatively investigated effects of A1221 and A1254 on serum levels of thyroid hormones and thyroid gland histology in adult female Wistar rats. Animals were subcutaneously injected with A1221 (10 mg/kg) or A1254 (10 mg/kg) for six weeks. One group of animals served as control. At the end, all animals were decapitated and trunk blood collected. Serum levels of triiodothyronine (T3) and thyroxine (T4) were measured by the electrochemiluminescence immunoassay method. Thyroid glands were removed for histopathological examination under light microscopy. Serum total T4 levels were significantly increased in A1221- and A1254-treated rats (p < 0.05). Serum free T4 levels were significantly increased in the A1254-treated rats (p < 0.01), but not in the A1221-treated rats. In contrast, the treatment with A1221 caused a significant increase in serum free T3 concentrations (p < 0.05) but not with A1254. Notably, either A1221 or A1254 caused distinct histopathological changes, such as formation of many microfollicles in the thyroid gland, which mimic the changes seen in thyrotoxicosis. In conclusion, both PCB mixtures induce toxic effects in the thyroid gland regardless of their degree of chlorination. We suggest that these environmental contaminants may disrupt thyroid hormone homeostasis in exposed individuals and thus pose a threat to human health.