Reproductive effects of tris(4-chlorophenyl)methanol in the rat

Tris(4-chlorophenyl)methane and tris(4-chlorophenyl)methanol disrupt pancreatic organogenesis and gene expression in zebrafish embryos

OBJECTIVES

Tris(4-chlorophenyl) methane (TCPM) and tris(4-chlorophenyl)methanol (TCPMOH) are anthropogenic environmental contaminants believed to be manufacturing byproducts of the organochlorine pesticide dichlorodiphenyltrichloroethane (DDT) due to environmental co-occurrence. TCPM and TCPMOH are persistent, bioaccumulate in the environment, and are detected in human breast milk and adipose tissues. DDT exposures have been previously shown to disrupt insulin signaling and glucoregulation, increasing risk for diabetes. We have previously shown that embryonic exposures organochlorines such as polychlorinated biphenyls disrupted pancreatic development and early embryonic glucoregulatory networks. Here, we determined the impacts of the similar compounds TCPM and TCPMOH on zebrafish pancreatic growth and gene expression following developmental exposures.

METHODS

Zebrafish embryos were exposed to 50 nM TCPM or TCPMOH beginning at 24 hr postfertilization (hpf) and exposures were refreshed daily. At 96 hpf, pancreatic growth and islet area were directly visualized in Tg(ptf1a::GFP) and Tg(insulin::GFP) embryos, respectively, using microscopy. Gene expression was assessed at 100 hpf with RNA sequencing.

RESULTS

Islet and total pancreas area were reduced by 20.8% and 13% in embryos exposed to 50 nM TCPMOH compared to controls. TCPM did not induce significant morphological changes to the developing pancreas, indicating TCPMOH, but not TCPM, impairs pancreatic development despite similarity in molecular responses. Transcriptomic responses to TCPM and TCPMOH were correlated (R²  = .903), and pathway analysis found downregulation of processes including retinol metabolism, circadian rhythm, and steroid biosynthesis.

CONCLUSION

Overall, our data suggest that TCPM and TCPMOH may be hazardous to embryonic growth and development.

The ecotoxicological contaminant tris(4-chlorophenyl)methanol (TCPMOH) impacts embryonic development in zebrafish (Danio rerio)

Tris(4-chlorophenyl)methanol (TCPMOH) is a water contaminant with unknown etiology, but is believed to be a byproduct of DDT manufacturing. It is highly persistent in the environment, and bioaccumulates in marine species. TCPMOH has also been measured in human breast milk, which poses a risk for developing infants. However, almost no toxicity data is currently available. In this study, we investigate the hazard posed by developmental TCPMOH exposures using the zebrafish model (Danio rerio). Zebrafish (Danio rerio) embryos were exposed to 0, 0.1, 0.5, 1, or 5 µM TCPMOH beginning at 24 h post fertilization (hpf). Embryonic mortality and incidence of morphological deformities increased in a concentration-dependent manner with TCPMOH exposure. RNA sequencing assessed changes in gene expression associated with acute (4 hour) exposures to 50 nM TCPMOH. Developmental exposure to TCPMOH decreased expression of ahr2, as well as metabolic enzymes cyp1a1, cyp1b1, cyp1c1, cyp1c2, and cyp2y3 (p<0.05). These findings were concordant with decreased Cyp1a1 induction measured by the ethoxyresorufin-O-deethylase (EROD) assay (p<0.05). Pathways associated with xenobiotic metabolism, lipid metabolism, and transcriptional and translational regulation were decreased. Pathways involved in DNA replication and repair, carbohydrate metabolism, and endocrine function were upregulated. Overall, this study demonstrates that TCPMOH is acutely toxic to zebrafish embryos at elevated concentrations.

Disposition of tris(4-chlorophenyl)methanol and tris(4-chlorophenyl)methane in male and female Harlan Sprague Dawley rats and B6C3F1/N mice following oral and intravenous administration

Tris(4-chlorophenyl)methane (TCPME) and tris(4-chlorophenyl)methanol (TCPMOH) have been detected in various biota and human tissues. The current studies were undertaken to investigate the disposition and metabolism of TCPME and TCPMOH in rats and mice. [¹⁴C]TCPME was well absorbed (≥66%) in male rats and mice following a single oral administration of 1, 10, or 100 mg/kg. The excretion of [¹⁴C]TCPME-derived radioactivity in urine (≤2.5%) and feces (≤18%) was low. The administered dose was retained in tissues (≥ 64%) with adipose containing the highest concentrations. The metabolism of TCPME was minimal. The disposition and metabolism of [¹⁴C]TCPME in females was similar to males. The time to reach maximum concentration was ≤7 h, the plasma elimination half-life was ≥31 h, and the bioavailability was ≥82% following a 10 mg/kg oral dose of [¹⁴C]TCPME in male rats and mice. The disposition of [¹⁴C]TCPMOH was similar to that of [¹⁴C]TCPME. Following an intravenous administration of [¹⁴C]TCPME or [¹⁴C]TCPMOH in male rats and mice, the pattern of disposition was similar to that of oral administration. In conclusion, both TCPME and TCPMOH are readily absorbed and highly bioavailable following a single oral administration pointing to importance of assessing the toxicity of these chemicals.

Comprehensive Screening Links Halogenated Organic Compounds with Testosterone Levels in Male Delphinus delphis from the Southern California Bight

While environmental pollutants have been associated with changes in endocrine health in cetaceans, efforts to link contaminant exposure with hormones have largely been limited to a list of known, targeted contaminants, overlooking minimally characterized or unknown compounds of emerging concern. To address this gap, we analyzed a suite of potential endocrine disrupting halogenated organic compounds (HOCs) in blubber from 16 male short-beaked common dolphins ( Delphinus delphis) with known maturity status collected from fishery bycatch in the Southern California Bight. We employed a suspect screening mass spectrometry-based method to investigate a wide range of HOCs that were previously observed in cetaceans from the same region. Potential endocrine effects were assessed through the measurement of blubber testosterone. We detected 167 HOCs, including 81 with known anthropogenic sources, 49 of unknown origin, and 37 with known natural sources. The sum of 11 anthropogenic and 4 unknown HOC classes were negatively correlated with blubber testosterone. Evidence suggests that elevated anthropogenic HOC load contributes to impaired testosterone production in mature male D. delphis. The application of this integrative analytical approach to cetacean contaminant analysis allows for inference of the biological consequences of accumulation of HOCs and prioritization of compounds for future environmental toxicology research.

Optimization of an MCF7-E3 Cell Proliferation Assay and Effects of Environmental Pollutants and Industrial Chemicals

Environmental contaminants might adversely affect human health by acting as endocrine disruptors and thus need to be identified. Our objective was to optimize the MCF7 cell proliferation assay to screen industrial chemicals for potential oestrogenic effects. Growth conditions, performance of the clone E3 and WT-MCF7 cells and five methods to derive proliferation indices were compared. The E3 cells were further characterized by testing the effects of transforming growth factorbeta (TGFbeta), epidermal growth factor (EGF), insulin, testosterone, the anti-oestrogen ICI 164,384 (ICI) and environmental contaminants with known oestrogenic potential. Industrial chemicals with unknown oestrogenic effects were then tested. As expected, induction of proliferation by estradiol-17beta (E2) was greater and less variable using the clone E3. To generate proliferation indices, the alamarBlue assay had a sensitivity comparable to that of [(3)H]thymidine incorporation ((3)H-TI). The E3 cells were not responsive to EGF (0-100 ng/ml) or insulin (0-313 ng/ml) but their proliferation was decreased (P<0.05) by TGFbeta (45 ng/ml) and testosterone (10(-8)m), which might be typical of highly oestrogen-responsive MCF7 cells. ICI (5x10(-7)m) inhibited the proliferative effects of 10(-10)m E2 and that of 10(-6)m 4-tert-octylphenol (Op) but not the proliferative effect of 10(-5)m Op, suggesting displacement of ICI by Op or induction of oestrogen-receptor independent proliferation. N-oxydiethylene-2-benzothiazole sulfenamide (OBTS) altered (3)H-TI in the MCF7 cells, although not in a dose related manner. OBTS did not induce uterotrophic effects in immature female rats, or any response in a human oestrogen chimeric receptor/reporter gene assay, suggesting that its effects were not mediated through the binding of the oestrogen-receptor. Seven other industrial chemicals were tested and had no effects. In conclusion, the MCF7 cell proliferation assay is one screening tool that permits identification of chemicals with oestrogenic potential which thus require further testing.

Decreased sperm motility in rats orally exposed to single or mixed pesticides

The Brazilian Agency of Sanitary Vigilance (ANVISA) conducted a study that demonstrated the presence of residues of several pesticides in fresh fruits and vegetables that were available for purchase by the general populace. In order to evaluate potential adverse health effects of low-level exposure to agrochemicals, the reproductive toxicity of the pesticides dicofol, dichlorvos, permethrin, endosulfan, and dieldrin was evaluated in rats dosed with these chemicals individually or as mixtures. Sixty male Lewis rats (6 wk old, 200 x g) were randomly allocated to 8 groups: (1) control group, received basal diet; (2) 5 groups designated a to e received the diet containing each pesticide individually, at the respective effective doses: lowest-observed-adverse-effect level (LOAEL) for dieldrin and endosulfan, lowest-observed-effect level (LOEL) for dicofol, and lowest effect level (LEL) for dichlorvos and permethrin, respectively, depending on the published data; (3) effective dose group, which received a mixture of pesticides added to basal diet at the respective doses reported to produce adverse effects; and (4) low dose group, which received a pesticide mixture added to the basal diet, where each pesticide was at its no-observed-effect level (NOEL). After 8 wk of treatment, reproductive parameters were evaluated. Sperm morphology, daily sperm production (DSP), sperm transit time through the epididymis, hormonal levels, and histopathological evaluation of testis and epididymis did not differ significantly among the groups. However, sperm motility was significantly decreased in animals that received a mixture of dieldrin, endosulfan, dicofol, dichlorvos, and permethrin, as well as in the group receiving dicofol alone. Exposure to the individual pesticides endosulfan, dichlorvos, and permethrin did not markedly affect sperm motility. The impairment of sperm motility in the mixture of pesticides at the NOEL level indicates that reproductive effects not seen with individual pesticides may occur in presence of several pesticides due to an additive effect. However, the pesticide mixtures did not appear to affect DSP or spermatogenesis despite reduced 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.

p,p'-DDE fails to reduce the competitive reproductive fitness in Nigerian male guppies

The ecologically highly important effect of intermale competition is assessed here in a new approach to evaluating endocrine disruption at the population level. A guppy (Poecilia reticulata) male exposed to the antiandrogenic DDT metabolite p,p'-DDE competed against an unexposed male for the opportunity to fertilize a female. Offspring were then assigned to sires using microsatellites in genetic paternity analysis. In addition, a suite of male sexual characteristics including sperm count, coloration, and sexual behavior were also measured. p,p'-DDE produced no significant harmful effect on either the male sexual characteristics or the success in siring young, although the highest sublethal dose tested was only a factor 10 below the dose producing 100% mortality. At present, data on the antiandrogenic potency of p,p'-DDE are highly ambiguous. This study supports the increasing amount of evidence that the demasculinizing action of this chemical is often weak and highly variable across populations, even within the same species.

Polybrominated diphenyl ethers and organochlorines in archived northern fur seal samples from the Pacific coast of Japan, 1972-1998

The present study clearly indicated possible prolonged and chronic marine pollution by polybrominated diphenyl ethers (PBDEs) unless the international regulatory measures are reinforced substantially. Fat tissues of female northern fur seals (Callorhinus ursinus), collected at 10 time periods between 1972 and 1998 from the Pacific coast of northern Japan, were analyzed for PBDEs and organochlorine compounds (OCs). PCBs and DDTs were the predominant contaminants in the fur seal samples. PBDEs were detected in all the samples analyzed, the values ranging from 0.33 to 100 ng/g lipid wt. with predominance of BDE-47. The lowest PBDE levels were in the fur seals collected in 1972, with the peak concentration around 1991-1994 and then decreased to about 50% in 1997-1998. Compositions of higher brominated congeners increased since 1972, while some lower brominated congeners decreased, implying a change in the pattern of use, particularly the increased use of highly brominated diphenyl ethers during 1972-1998. In the meantime, PCB compositions in fur seals showed no temporal variation, suggesting a continuous input of PCBs into the marine environment in significant quantities. As peak concentrations of PBDEs occurred later than OCs, it is essential to follow up the patterns of PBDEs pollution that may be of great concern in the future. To our knowledge, this is the first report on the contamination by PBDEs in marine mammals from the Asia-Pacific waters.

Interaction between tris(4-chlorophenyl)methanol and the human androgen receptor in vitro

The interaction between tris(4-chlorophenyl)methanol (TCPM), an environmental contaminant of uncertain origin, and the human androgen receptor was examined in vitro using a previously characterized human androgen receptor reporter gene assay in which PC-3 LUC(AR+) cells respond to 5alpha-dihydrotestosterone (DHT) with enhanced luciferase activity. In two preliminary studies, TCPM (1 microM) had no effect on androgen receptor activation in the absence of DHT (50 pM), but DHT-mediated activation of the androgen receptor was decreased more than 90% by TCPM at 1 microM. This was not due to an effect of TCPM on cell viability since, with TCPM concentrations of 0.1 and 1.0 microM, cell viability was 111 and 102%, respectively, but at 10 microM TCPM, cell viability was reduced to 60% compared with controls. For kinetic studies of the effects of TCPM on androgen receptor activation, DHT was added at 0, 5, 25, 50, 75, 100, 250 and 500 pM and the TCPM concentrations used were 0, 1, 10, 100, 300 and 1000 nM. This range incorporated the levels of TCPM in human adipose tissue, where concentrations up to 55 nM (20 ng/g lipid) have been measured. TCPM increased the value of the K(m(app)) of the androgen receptor for DHT 4-6-fold with little or no effect on the V(max(app)). Slope and intercept replots revealed that TCPM inhibited the DHT-mediated activation of the androgen receptor in a competitive manner with K(i(app)) values of 0.26, 0.26 and 0.20 microM compared with respective K(m(app)) values of 9.8, 3.1 and 3.9 pM. Thus, TCPM is a competitive antagonist of human androgen receptor activation and the value of the K(i(app)) indicates that TCPM would be approximately 10-50 times more potent as an inhibitor than the previously identified androgen receptor antagonists p,p'-DDE and vinclozilin and also, the K(i(app)) values (200-260 nM) are very close to the concentration of TCPM found in the adipose tissue of some humans (55 nM).

Tris (4-chlorophenyl) methane and tris (4-chlorophenyl) methanol in marine mammals from the Estuary and Gulf of St. Lawrence

Levels of tris (4-chlorophenyl) methanol (TCPM) and its presumed precursor tris (4-chlorophenyl) methane (TCPMe) are reported in marine mammals from the Estuary and Gulf of St. Lawrence, Canada. These compounds were measured in blubber samples of seals and whales using ion trap mass spectrometry (MS/MS) detection. Detectable concentrations of both TCPM and TCPMe were observed in all of the samples analysed. Concentrations of these compounds varied with species ranging from 1.7 to 153 and from 1.3 to 50.6 ng/g lipid wt. for TCPM and TCPMe, respectively. TCPM was from 1.3 to 10 times more concentrated than TCPMe. The highest levels of both TCPM and TCPMe were observed in adult male beluga whales (Delphinapterus leucas) from the St. Lawrence Estuary, while adult female beluga whales from the same area showed levels similar to those in the seals examined. Among the four seal species investigated, TCPM and TCPMe levels were the highest in grey (Halichoerus grypus) and hooded (Cystophora cristata) seals, and lowest in harp seals (Phoca groenlandica). Intermediate levels were found in harbour seals (Phoca vitulina); however, their concentrations might be underestimated considering the younger mean age of these animals. Ratios of both 4,4'-DDE/sigma DDT and TCPM/sigma TCP were very similar between animals from the same species. Strong correlations between sigma TCP and sigma DDT were also observed for each species of mammals, most likely indicating that both sigma TCP and sigma DDT are bioaccumulated in marine mammals. The relationships between sigma DDT and sigma TCP also demonstrate that sigma TCP are less bioaccumulated than sigma DDT by the marine mammal species examined.