Main Neuro-Endocrine, Endocrine and Paracrine Regulations of Fish Reproduction, and Vulnerability to Xenobiotics

The reproductive function of fish, which is very sensitive to the variations of environmental factors, appears also to be particularly vulnerable to the presence of xenobiotics in the aquatic medium. Many physiological processes can be impaired, from sexual differentiation to female and male gametogenesis, due to disruptions among complex neuro-endrocrine, endocrine or paracrine regulations. This paper describes the main regulation steps that are known or can be suspected to be disrupted by xenobiotics and gives some examples. The large interspecific diversity of reproductive strategies and the complexity of underlying mechanisms are particularly highlighted to draw attention to possible confusions between real endocrine disruptions and natural physiological variations.     

Mechanisms of Endocrine Disruption with Particular Reference to Occurrence in Avian Wildlife: A Review

This review examines the evidence for endocrine disruption in birds. It reviews in vitro and in vivo laboratory based evidence for endocrine disruption by (1) agonism or antagonism of gonadal steroid hormones, (2) altering the activity of cytochrome P450 enzymes, (3) altering thyroid hormone function, (4) affecting intrinsic neuroendocrine control mechanisms and (5) activation of the stress response. It also discusses the evidence for the existence of such effects in free-living birds. In vitro studies demonstrate that mechanisms for potential endocrine disruption exist, but in vivo studies suggest that such mechanisms are insufficient to overwhelm endogenous homeostatic control. There are only two phenomena in wild birds where endocrine disruption has been cited as a possible cause: eggshell thinning and supernormal clutches. Evidence suggests that neither of these is caused by endocrine disruption. Despite three decades of concern, there is no evidence that avian wildlife has suffered endocrine disruption.     

Effects of triclosan on Japanese medaka (Oryzias latipes) during embryo development,early life stage and reproduction

Triclosan has been shown to have endocrine‐disrupting effects in aquatic organisms. In 2016, the US Food and Drug Administration banned the use of triclosan in consumer soaps. Before the ban, triclosan was reported at low concentrations in the aquatic environment, although the effect of triclosan on reproduction in teleost fish species is yet to be clarified. Here we investigated the effects of triclosan on embryo development and reproduction, and during the early life stage, in Japanese medaka (Oryzias latipes) by using Organisation for Economic Co‐operation and Development tests 229, 212 and 210, with minor modifications. In adult medaka, exposure to 345.7 μg l^–1 suppressed fecundity and increased mortality but had no effect on fertility. Exposure to 174.1 or 345.7 μg l^–1 increased liver vitellogenin concentration in females but decreased liver vitellogenin concentration in males. With triclosan exposure, mortality was increased dose dependently during the embryonic and early larval stages, and a particularly steep increase in mortality was observed soon after hatching. The lowest observed effect concentrations of triclosan in Japanese medaka obtained in the present study (mortality [embryonic and larval stages, 276.3 μg l^–1; early life stage, 134.4 μg l^–1; adult stage, 174.1 μg l^–1], growth [134.4 μg l^–1], vitellogenin [174.1 μg l^–1], fecundity [345.7 μg l^–1] and fertility [>345.7 μg l^–1]) were at least 55 times (compared with the USA) and up to 13 400 times (compared with Germany) greater than the detected triclosan levels in the aquatic environment. These results suggest that triclosan may not be affecting fish populations in the aquatic environment.     

Playing in the Mud-Using Gene Expression to Assess Contaminant Effects on Sediment Dwelling Invertebrates

Bioaccumulation and toxicity tests using benthic invertebrates such as the estuarine amphipod Leptocheirus plumulosus are typically used to assess the ecological risk associated with contaminated sediments. Despite their ecological and regulatory importance, little is known about such species at the genetic level. To begin understanding cellular and genetic responses of L. plumulosus to contaminants, we isolated several of their genes and developed quantitative assays to measure the effects of water exposures to 2, 4, 6-trinitrotoluene and phenanthrene on gene expression. Real-time polymerase chain reaction (PCR) assays demonstrated that the expression of the genes for actin and a retrotransposon, hopper, was dependent on the exposure and tissue concentrations of those chemicals. Our data suggests that exposure to the explosive 2, 4, 6-trinitrotoluene and phenanthrene may induce movement of hopper resulting in unexpected genotoxic results.     

Proteomics in Zebrafish Exposed to Endocrine Disrupting Chemicals

Embryonic zebrafish were examined for changes in protein expression following exposure to sublethal concentrations of 17beta-estradiol (E2) and the estrogen mimic 4-nonylphenol (4-NP). Protein Expression Signatures were derived from embryo homogenates by two-dimensional electrophoresis and digital imaging. In both experiments approximately 30% of the proteins sampled were specific to either E2 or 4-NP and about 33% were common to the control, 4-NP and E2. However, of the proteins induced by either E2 or 4-NP, 28% were common to both chemicals at 1 ppm but only 7% were common to both at 0.1 ppm. While there are many proteins that respond specifically to each chemical, relatively few are common to the two chemicals suggesting that the response pathways of the two chemicals are distinct.     

The effect of sunscreen 4-methylbenzylidene camphor in different and reproductive models,its bioaccumulation and molecular effects on ligand-receptor interaction,and protein expression

4-Methylbenzylidene camphor (4-MBC) is a photo-absorbing UV filter prevalently used in cosmetics, which can be absorbed into circulation and cause systemic effects. 4-MBC is continued to be released in the environment despite the growing knowledge about its bioaccumulation and endocrine disrupting effects. Previous reviews have mentioned UV-filter together but this review considers 4-MBC alone, due to its prevalence and concerning health effects. This review considers 4-MBC's potential effects on human health regarding systemic and molecular effects, with the main focus on reproduction. Also, the potential bioaccumulation and interactions with receptor systems such as the oestrogen receptors β and α, and progesterone receptor are covered. Additionally, previous studies about 4-MBC's effects on mRNA and protein expression, especially in the prostate and the brain are analysed. Furthermore, 4-MBC is reported to act with inflammatory pathways by activating p38 MAPK and NF-κB, leading to the production of inflammatory TNF-α and IL-6. 4-MBC was also found to induce apoptosis and inhibit cell proliferation and DNA repair. In conclusion, 4-MBC has wide-ranging effects in many different models interacting with multiple pathways causing long-term effects even at low doses and this knowledge can guide governmental risk assessment, regulation divisions and chemical industries.     

内分泌调节对产后抑郁症患者内分泌激素、血清5-HT、NE、5-HIAA及抑郁心理的影响研究

目的:研究内分泌调节的干预方法及在产后抑郁症(PD)患者护理中的应用价值。方法:将某院收治的90例PD患者随机分为C组和C+N组各45例,产后护理中C组实施常规护理,C+N组实施常规护理+内分泌调节护理,于两组患者护理干预前后,分别对比两组患者内分泌激素指标(E 2、P)、血清神经递质指标(5-HT、NE、5-HIAA)和抑郁心理(HAMD量表)。结果:护理后,C+N组患者E 2低于C组,P高于C组(P<0.05);C+N组患者血清5-HT、NE、5-HIAA均高于C组(P<0.05);护理4周、8周后,C+N组患者HAMD量表评分均低于C组(P<0.05)。结论:于PD患者护理中应用内分泌调节护理干预能有效调节患者内分泌激素水平,改善神经递质指标水平,提高抑郁心理的改善效果。     

Effects of endocrine modulators on sex differentiation in birds

This mini-review focuses on sexual differentiation of the reproductive organs and the brain in birds and the effects of endocrine modulators on these processes. Sex determination in birds is genetically controlled, but the genetic events implicated are largely unknown. Female birds have one Z and one W sex chromosome, while males have two Z sex chromosomes. It is not clear whether it is the presence of the W chromosome in females, the double dose of the Z chromosome in males vis-à-vis females, or both of these characteristics that are crucial for the determination of sex in birds. Oestradiol directs sexual differentiation in birds during critical periods of development. Consequently, exogenous compounds that interfere with the endogenous oestrogen balance can disrupt sexual differentiation of the reproductive organs and the brain. Therefore, sexual differentiation in birds provides a good model for studying the effects of endocrine modulators at various biological levels from gene expression to behaviour. Some compounds known to be present in the environment can alter endocrine function and have adverse effects when administered during development, resulting in alterations in gonads, accessory sexual organs, and behaviour. Data reviewed in this paper are mostly from laboratory studies on endocrine modulators with oestrogenic activity, whereas evidence for adverse effects of pollutants on sexual differentiation in avian wildlife is scarce.     

Innovation in Pharmaceutical Experimentation Part 1: Review of Experimental Designs Used in Industrial Pharmaceutics Research and Introduction to Bayesian D-Optimal Experimental Design

The concept of design space, as described in the ICH Harmonized Tripartite Guideline Q8 for Pharmaceutical Development (Q8 Pharmaceutical development, ICH harmonized tripartite guidelines, in International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use, 2005), was introduced to justify regulatory flexibility in pharmaceutical manufacturing operations. The basis for this concept is that advanced understanding of variables affecting product quality, obtained either through historical operation or demonstrated through process modeling, justifies replacement of traditional process targets with acceptable operational ranges. Process adjustments that allow operation within the region defined by the design space do not require regulatory oversight. Whereas there are many advantages to having the flexibility to operate within such ranges, the concept is only valid when the design space has been adequately described by appropriate experimentation. Given the complexity of pharmaceutical processes and the number of variables to consider in developing operational ranges, only a well-executed program of experiments, supported by appropriate statistical analyses, could provide the necessary information to truly capture a design space. Thus, the risk of employing a design space is that the model will be applied to a region outside of the approved design space, either through a false statistical inference or by omitting some important factor effects. This article presents a review of the experimental strategies typically employed to develop pharmaceutical processes with special emphasis on the assumptions and limitations of the approaches. An alternative strategy that provides an opportunity to build on previous information efficiently without requiring extraordinary skill in statistics, Bayesian optimal design, is introduced as an alternative to the classical approaches.     

Endocrine disruption in adolescence: immunologic, hematologic, and bone effects in monkeys.

Environmental contaminants with estrogenic properties have the potential to alter pubertal development. In addition to the reproductive system, other systems that mature under the influence of estrogen could be affected. This study examined the effect on immune, hematologic, and bone mass parameters of treatment with estrogenic agents (methoxychlor, MXC, 25 and 50 mg/kg/day; diethylstilbestrol, DES, 0.5 mg/kg/day) given in the peripubertal period to female rhesus monkeys. DES had striking effects on several parameters assessed measures CBC and clinical chemistry including hematocrit, hemoglobin, serum albumin, liver transaminases, and lipids. Circulating lymphocytes, particularly B cells, were depressed by DES, and a maturational shift in a memory T-cell population was altered. Bone mass and length, as measured after a 9-month recovery period, were significantly lower in the DES group and bone mass tended to be reduced in the femur of the MXC50 group relative to controls. In conclusion, the data indicate that DES had a clear effect on immunohematology and bone growth, while MXC influenced fewer parameters. Disruption in these systems during puberty could alter adolescent risk for anemia and infectious disease and subsequent adult risk for diseases such as osteoporosis, heart disease, and autoimmune disease.     

Effects of neonatal exposure to 4-tert-octylphenol, diethylstilbestrol, and flutamide on steroidogenesis in infantile rat testis.

Exposure of neonatal testis, populated by fetal-type Leydig cells, to endocrine-active compounds may have far-reaching consequences. Our aim was to resolve the sensitivity of testosterone synthesis of infant rat (Sprague-Dawley) testis to diethylstilbestrol (DES; 0.1-1.0 mg/kg), 4-tert-octylphenol (OP; 10-100 mg/kg), and Flutamide (FLU; 2.0-25 mg/kg) given by daily sc injections from birth to postnatal day 4. Testes and serum were collected on day 14 when body and testis weight, testicular histology, circulating testosterone, LH and FSH levels, and steroidogenic acute regulatory protein (StAR) and 3beta-hydroxy-steroid-dehydrogenase (3beta-HSD) protein levels were determined. DES at each dose and FLU at 25 mg/kg dose reduced testis weight and the diameter of seminiferous cords. FLU caused some Leydig cell hyperplasia. Plasma testosterone was reduced in all DES animals, LH elevated in DES 0.5 mg/kg and FLU 25 mg/kg animals, and FSH reduced in the DES 1.0 mg/kg group. Basal testicular ex vivo progesterone and human chorionic gonadotropin (hCG)-stimulated testosterone production were decreased in DES animals. Despite a decrease in hCG-induced cyclic adenosine-3',5'-monophosphate (cAMP) production, intratesticular testosterone was increased in the FLU 10 and 25 mg/kg groups. OP 100 mg/kg elevated hCG-induced progesterone production only. No changes were seen in 3beta-HSD protein levels in any treatment group. StAR levels were reduced in DES animals. The results indicate the sensitivity of postnatal fetal-type Leydig cells to endocrine-active compounds. Suppression of StAR expression level was an early sign of the DES-induced steroidogenic lesion. FLU-induced changes suggest the importance of androgen receptor-mediated regulation of testosterone synthesis in the postnatal rat testis. Octylphenol appeared less effective in bringing about acute steroidogenic changes.     

Developmental Exposure to Tetrabromobisphenol A Has Minimal Impact on Male Rat Reproductive Health

The flame retardant and plasticizer, tetrabromobisphenol-A (TBBPA) has rapidly become a common component in the manufacture of circuit boards and plastics worldwide. It is also an analog of bisphenol A (BPA), an endocrine disrupting chemical identified by the Endocrine Society. As such, TBBPA needs to be investigated for similar potential human health risks. Using rats as a model, we exposed pregnant dams and their progeny to 0, 0.1, 25, or 250 mg TBBPA/kg of body weight until the offspring reached adulthood and assessed the first generation of males for any reproductive tract abnormalities. We found no differences in the morphology of testes, sperm, prostates, or secondary sex organs from post-natal day 21 through one-year of age. A delay in the time to preputial separation was found with the 250 mg/kg treatment. Also, minor differences of sperm count at one-year old with the 25 mg/kg treatment and expression levels of two steroidogenic pathway enzymes at either post-natal day 90 or one-year old in the 250 mg/kg treatment group were detected, but spermatogenesis was not disrupted. While these results may lead to the supposition that TBBPA is less harmful than its parent compound BPA, more studies need to be conducted to assess long-term exposure effects.     

A computational insight into the molecular interactions of chlorpyrifos and its degradation products with the human progesterone receptor leading to endocrine disruption

Chlorpyrifos (CPF) is a widely used pesticide effective against a large number of target pests, which is used by farmers to protect food crops. Based on earlier epidemiologic reports, which indicate that CPF might interfere with the progesterone signaling pathway and can affect conception, the present study was undertaken to evaluate the binding interaction of CPF with the human progesterone receptor (hPR). Progesterone is one of the important hormones of the reproductive system and through its receptor, PR, the progesterone signaling pathway regulates important reproductive functions including reproductive cyclicity and initiation and continuation of pregnancy. The binding interactions of four major degradation products of CPF, viz. chlorpyrifos-oxon (CPYO), des-ethyl chlorpyrifos (DEC), 3,5,6-trichloro-2-methoxypyridine (TMP), 3,5,6-trichloro-2-pyridinol (TCP), were also studied to evaluate the possibility of endocrine disruption caused by these metabolites. Docking studies revealed that CPF, CPYO, and DEC were able to involve important interacting amino acid residues of the hPR during molecular interactions and are capable of competing with progesterone. Thus, CPF and its degradation products can act as potential xenoligands for the hPR and can disrupt normal progesterone signaling pathway.     

Chronic toxicity of chlordane to Daphnia magna and Ceriodaphnia dubia: A comparative study

Chronic toxicity of chlordane, an organochlorine insecticide, was assessed on Ceriodaphnia dubia under standardized conditions of testing. Results were compared to Daphnia magna to determine the sensitivity of the two freshwater cladoceran species to this persistent organic pollutant (POP) and to explore the possibility of using the 7‐day C. dubia test as an alternative to the 21‐day D. magna test in chronic toxicity assessment of POPs. The NOEC‐7d value of chlordane on reproduction of C. dubia (2.9 μg/L) was much higher than the NOEC‐21d value of D. magna (0.18 μg/L), attesting that the 7‐day test on C. dubia was less sensitive than the 21‐day reproduction test on D. magna to chlordane. However, extending the period of exposure of C. dubia to chlordane from 7 to 14 days led to a NOEC‐14d value similar to the NOEC‐21d value in D. magna (0.18 μg/L). This study highlights the usefulness of prolonging the exposure time of the reproduction test in C. dubia from 7 to 14 days to increase the performances of the reproduction test on C. dubia for assessing chronic toxicity of POPs. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2012.     

Fluctuating Asymmetry and Growth as Biomarkers for Exposure to Androgen Disrupting Chemicals in Japanese Quail

The effects of embryonic exposure to androgen disrupting chemicals (ADCs) on growth and fluctuating asymmetry (FA) were determined in Japanese quail chicks. Embryos were exposed to an anti-androgenic chemical, 1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane (p,p′-DDE) at 20 or 40 μg , or to an androgenic chemical, trenbolone acetate, at 5 or 50 μg on day one of incubation. Growth was measured by body weight and tarsus and culmen lengths from day of hatch until day 29. FA was measured as differences in right versus left lengths of the tarsus, radius, zygomatic process, and premaxilla in day old carcasses. No differences in FA were observed for either treatment. Embryonic exposure to DDE resulted in no significant differences in all measures of growth, although the same quail exhibited significant differences in immunological, reproductive, and behavioral measurements (reported elsewhere). Chicks exposed to trenbolone exhibited no differences in body weight or measures of FA at day of hatch, however, subsequent growth was inhibited. This study shows that although growth and FA are often used as measures of chemical stress experienced during embryonic development, they are not sensitive measures for exposure to these ADCs at these levels in Japanese quail.     

氯米芬联合HCG对不孕症患者内分泌指标及子宫内膜容受性的影响

目的:探讨氯米芬联合人绒毛膜促性腺激素(HCG)对不孕症患者内分泌指标及子宫内膜容受性(ER)的影响。方法:回顾性分析某院妇产科2018年11月~2019年11月接收的96例不孕症患者临床资料,将采用氯米芬联合HCG治疗的患者归为观察组(49例),将单独采用氯米芬治疗的患者归为对照组(47例),对比两组患者治疗前、治疗3个月内分泌指标、ER及卵巢体积变化情况以及治疗期间不良反应发生情况。结果:治疗3个月后,两组促卵泡刺激素(FSH)、黄体生成素(LH)、雌二醇(E_2)及孕酮(P)水平均较治疗前高,且观察组FSH、LH、E_2及P水平高于对照组,差异有统计学意义(P<0.05);治疗3个月后,两组子宫内膜厚度(Em)指标较治疗前上升,卵巢体积较治疗前缩小,且观察组Em指标较大,卵巢体积较小,差异有统计学意义(P<0.05);两组不良反应发生率比较,差异无统计学意义(P>0.05)。结论:不孕症患者采用氯米芬联合HCG治疗效果良好,可有效改善内分泌指标,提升ER指标,且安全性较高,值得临床推广。     

Effects of tebuconazole on cytochrome P450 enzymes,oxidative stress,and endocrine disruption in male rats

The major objective of the present study was to determine the ability of a triazole fungicide tebuconazole to induce cytochrome P450‐dependent monooxygenases, oxidative stress, and endocrine‐disrupting activity using male rats treated with tebuconazole at 10, 25, and 50 mg/kg p.o. once daily for 28 days. In liver, tebuconazole dose‐dependently increased microsomal contents of cytochrome P450 and cytochrome b₅ and the activities of NADPH‐cytochrome P450 reductase, 7‐ethoxyresorufin O‐deethylase, methoxyresorufin O‐demethylase, pentoxyresorufin O‐dealkylase, 7‐ethoxycoumarin O‐deethylase, aniline hydroxylase, and erythromycin N‐demethylase. In kidney, tebuconazole increased 7‐ethoxycoumarin O‐deethylase activity without affecting other monooxygenase activities. In marked contrast to liver and kidney, tebuconazole decreased testicular 7‐ethoxyresorufin O‐deethylase, methoxyresorufin O‐demethylase, 7‐ethoxycoumarin O‐deethylase, aniline hydroxylase, and erythromycin N‐demethylase activities. The results of immunoblot analysis of liver microsomes of controls and tebuconazole‐treated rats revealed that tebuconazole induced CYP1A1/2, CYP2B1/2, CYP2E1, and CYP3A proteins in liver. Additions of tebuconazole to liver microsomes inhibited microsomal 7‐ethoxycoumarin O‐deethylase activity in vitro (IC₅₀ = 1.50–1.69 µM). Treatment of rats with tebuconazole decreased glutathione content and increased glutathione S‐transferase, superoxide dismutase, catalase, and glutathione peroxidase activities in liver; increased superoxide dismutase activities in kidney and testis; but decreased glutathione S‐transferase activity in testis. Treatments with tebuconazole decreased serum testosterone concentration and cauda epididymal sperm count. The present study demonstrates that tebuconazole induces a multiplicity of CYPs and oxidative stress in liver; inhibits testicular P450 and glutathione S‐transferase activities; and produces anti‐androgenic effects in male rats.     

Non-Monotonic Dose Responses in Studies of Endocrine Disrupting Chemicals: Bisphenol A as a Case Study

Non-monotonic dose response curves (NMDRCs) have been demonstrated for natural hormones and endocrine disrupting chemicals (EDCs) in a variety of biological systems including cultured cells, whole organ cultures, laboratory animals and human populations. The mechanisms responsible for these NMDRCs are well known, typically related to the interactions between the ligand (hormone or EDC) and a hormone receptor. Although there are hundreds of examples of NMDRCs in the EDC literature, there are claims that they are not ‘common enough’ to influence the use of high-to-low dose extrapolations in risk assessments. Here, we chose bisphenol A (BPA), a well-studied EDC, to assess the frequency of non-monotonic responses. Our results indicate that NMDRCs are common in the BPA literature, occurring in greater than 20% of all experiments and in at least one endpoint in more than 30% of all studies we examined. We also analyzed the types of endpoints that produce NMDRCs in vitro and factors related to study design that influence the ability to detect these kinds of responses. Taken together, these results provide strong evidence for NMDRCs in the EDC literature, specifically for BPA, and question the current risk assessment practice where ‘safe’ low doses are predicted from high dose exposures.     

Pubertal and early adult exposure to fenvalerate disrupts steroidogenesis and spermatogenesis in mice at adulthood

Fenvalerate, a pyrethroid insecticide used worldwide, has been shown to have a potentially adverse effect on male reproduction. Our earlier study showed that maternal fenvalerate exposure during lactation impaired testicular development in male offspring. In this study, we investigated the effects of pubertal and early adult exposure to fenvalerate on steroidogenesis and spermatogenesis in mice. Male mice were administered fenvalerate (60 mg/kg) by gavage daily from postnatal day 35 (PND35) to PND63. Results showed that sperm count was significantly decreased in fenvalerate‐treated mice. In addition, fenvalerate markedly decreased the layers of spermatogenic cells, disturbed the array of spermatogenic cells and increased the number of apoptotic cells in testes. The adverse effects of fenvalerate on male reproduction seemed to be associated with a decrease in serum and testicular testosterone (T). Although pubertal and early adult exposure to fenvalerate had little effect on the number of Leydig cells in testes, mRNA and protein levels of testicular T biosynthetic enzymes including P450_17α and P450scc were significantly downregulated in fenvalerate‐treated mice. In conclusion, pubertal and early adult fenvalerate exposure induces a deleterious effect on steroidogenesis and spermatogenesis in adulthood. The decreased testicular T synthesis partially contributes to fenvalerate‐induced impairment on spermatogenesis. Copyright © 2010 John Wiley & Sons, Ltd.