The effect of benzo(a)pyrene on murine ovarian and corpora lutea volumes

Associations of urinary polycyclic aromatic hydrocarbons with age at natural menopause in U.S. women aged 35-65, NHANES 2003-2012

Polycyclic aromatic hydrocarbons (PAHs) mediated ovarian toxicity has been demonstrated in animal experiments. However, this issue has not been assessed in humans. Based on the National Health and Nutrition Examination Survey (NHANES) 2003-2012, data analysis was restricted to 1221 general U.S. women aged 35-65 years with complete data of interest. Levels of nine PAH metabolites in spot urine specimens were measured by isotope dilution gas chromatography/tandem mass spectrometry (GC-MS/MS). Self-reported information on the menopause status and age at menopause were obtained during interview. Cox proportional hazards regression was employed to assess the associations between PAH levels and natural menopause. Compared with women in the first quartile, subjects in the highest quartile of 1-Hydroxynapthalene [hazard ratio (HR) = 1.46, 95% confidence interval (CI) = 1.06 to 2.01], 2-Hydroxynapthalene (HR = 1.51, 95% CI = 1.12 to 2.05) and 3-Hydroxyfluorene (HR = 1.51, 95% CI = 1.06 to 2.16), or in the second quartile of 9-Hydroxyfluorene (HR = 1.53, 95% CI = 1.05 to 2.22), had elevated risks of earlier onset of natural menopause. Our findings suggested positive associations between urinary PAH levels and earlier age at natural menopause in the general U.S. women. Prospective studies are warranted to confirm the causality in the future.

Cigarette smoking and hormones

PURPOSE OF REVIEW

The purpose is to provide a summary of the effects of cigarette smoking on steroid hormone metabolism and how it affects female fertility.

RECENT FINDINGS

Components of tobacco smoke such as polycyclic aromatic hydrocarbons lead to transcriptional upregulation of a number of genes, including members of the cytochrome P450 (CYP) family, in particular CYP1B1 and CYP1A1. In humans, CYP1A1 and CYP1A2 are the primary enzymes catalyzing the 2-hydroxylation of estradiol. This pathway shunts available estrogen away from the more estrogenically potent 16α-hydroxylation to the production of catechol estrogens, mainly 2 and 4 hydroxyestradiol.

SUMMARY

Smoking has multiple effects on hormone secretion and metabolism. These effects are mainly mediated by the pharmacological action of tobacco alkaloids (nicotine and its metabolite cotinine). A strong body of evidence indicates that the negative effects of cigarette smoking on fertility compromises nearly every system involved in the reproductive process.

Cigarette smoke impaired maturation of ovarian follicles and normal growth of uterus inner wall of female wild-type and hypertensive rats

Cigarette smoke (CS) is well known to be very harmful to human body functions such as fertility, reproduction, and development. CS is considered to more affect patients with hypertension (HT). To estimate the effect of CS associated with female rat's fertility, we examined the histopathological characteristics of the uterus and ovary which were obtained from the female rats exposed to smoke of the standard cigarette (3R4F) for 4 weeks (10h a week) according to the OECD guidelines. The female wild-type Wistar Kyoto (WK) rats (WTR) and spontaneously hypertensive WK rats (SHR) were used to compare the effect of CS on healthy and hypertensive rats. After CS exposure, we manufactured tissue slides from uterine and ovarian samples and evaluated the maturation of follicles of ovary and cell proliferation in the uterus by H&E staining and immunohistochemistry (IHC). In IHC analysis on ovarian tissues, the expression of proliferating cell nuclear antigen (PCNA) and the number of follicles were decreased by CS exposure. On the contrary, PCNA expression and cell proliferation in the uterine inner layers were increased by CS exposure. The protein expression of C/EBP homologous protein (CHOP), an endoplasmic reticulum (ER)-stress marker, and BAX, a pro-apoptotic protein, was decreased by CS exposure. This phenomenon was more exacerbated in SHR rats than in WTR rats. Taken together, acute exposure to CS induced the decreased maturation of ovarian follicles and abnormal over-growth of uterine inner wall, leading to a harmful effect on female rat's normal function. In addition, this harmful effect of CS may be displayed more seriously in rats with HT.

Exposure to benzo[a]pyrene impairs decidualization and decidual angiogenesis in mice during early pregnancy

Benzo[a]pyrene (BaP) is a ubiquitous environmental persistent organic pollutant and a well-known endocrine disruptor. BaP exposure could alter the steroid balance in females. Endometrium decidualization and decidual angiogenesis are critical events for embryo implantation and pregnancy maintenance during early pregnancy and are modulated by steroids. However, the effect of BaP on decidualization is not clear. This study aimed to explore the effects of BaP on decidualization and decidual angiogenesis in pregnant mice. The result showed that the uteri in the BaP-treated groups were smaller and exhibited an uneven size compared with those in the control group. Artificial decidualization was detected in the uteri of the controls, but weakened decidualization response was observed in the BaP-treated groups. BaP significantly reduced the levels of estradiol, progesterone, and their cognate receptors ER and PR, respectively. The expression of several decidualization-related factors, including FOXO1, HoxA10, and BMP2, were altered after BaP treatment. BaP reduced the expression of cluster designation 34 (CD34), which indicated that the decidual angiogenesis was inhibited by BaP treatment. In addition, BaP induced the downregulation of vascular endothelial growth factor A. These data suggest that oral BaP ingestion compromised decidualization and decidual angiogenesis. Our results provide experimental data for the maternal reproductive toxicity of BaP during early pregnancy, which is very important for a comprehensive risk assessment of BaP on human reproductive health.

Cosmetics use and age at menopause: is there a connection?

Cosmetics contain a vast number of chemicals, most of which are not under the regulatory purview of the Food and Drug Administration. Only a few of these chemicals have been evaluated for potential deleterious health impact: parabens, phthalates, polycyclic aromatic hydrocarbons, and siloxanes. A review of the ingredients in the best-selling and top-rated products of the top beauty brands in the world, as well as a review of highlighted chemicals by nonprofit environmental organizations, reveals 11 chemicals and chemical families of concern: butylated hydroxyanisole/butylated hydroxytoluene, coal tar dyes, diethanolamine, formaldehyde-releasing preservatives, parabens, phthalates, 1,4-dioxane, polycyclic aromatic hydrocarbons, siloxanes, talc/asbestos, and triclosan. Age at menopause can be affected by a variety of mechanisms, including endocrine disruption, failure of DNA repair, oxidative stress, shortened telomere length, and ovarian toxicity. There is a lack of available studies to make a conclusion regarding cosmetics use and age at menopause. What little data there are suggest that future studies are warranted. Women with chronic and consistent use of cosmetics across their lifespan may be a population of concern. More research is required to better elucidate the relationship and time windows of vulnerability and the effects of mixtures and combinations of products on ovarian health.

[Effects of cigarette smoking on female reproduction: from oocyte to embryo (Part I)]

Cigarette smoking is associated with lower fecundity rate, adverse reproductive outcomes and higher risk of IVF failure. Over the last decades, prevalence of smoking among women of reproductive age has increased. The aim of this work was to focus on the knowledge of the effects of cigarette smoking on all reproductive stages, from oocyte to embryo. For each reproductive functions human clinical and experimental studies were analysed in order to find hypothesis and explanations for effects observed. All reproductive functions are targets of smoke compounds and cigarette smoking impairs ovarian reserve, sexual steroids synthesis, Fallopian tubes functions and embryo development, leading to reduced fecundity. Some of smoke compounds were identified in ovarian tissue, in uterine fluid and in the embryo, suggesting direct toxicity.

Effects of cigarette smoking on reproduction

BACKGROUND Cigarette smoking is associated with lower fecundity rates, adverse reproductive outcomes and a higher risk of IVF failures. Over the last few decades, prevalence of smoking among women of reproductive age has increased. This review focuses on current knowledge of the potential effects of smoke toxicants on all reproductive stages and the consequences of smoke exposure on reproductive functions. METHODS We conducted a systematic review of the scientific literature on the impact of cigarette smoking and smoke constituents on the different stages of reproductive function, including epidemiological, clinical and experimental studies. We attempted to create hypotheses and find explanations for the deleterious effects of cigarette smoke observed in experimental studies. RESULTS Cigarette smoke contains several thousand components (e.g. nicotine, polycyclic aromatic hydrocarbons and cadmium) with diverse effects. Each stage of reproductive function, folliculogenesis, steroidogenesis, embryo transport, endometrial receptivity, endometrial angiogenesis, uterine blood flow and uterine myometrium is a target for cigarette smoke components. The effects of cigarette smoke are dose-dependent and are influenced by the presence of other toxic substances and hormonal status. Individual sensitivity, dose, time and type of exposure also play a role in the impact of smoke constituents on human fertility. CONCLUSIONS All stages of reproductive functions are targets of cigarette smoke toxicants. Further studies are necessary to better understand the deleterious effects of cigarette smoke compounds on the reproductive system in order to improve health care, help to reduce cigarette smoking and provide a better knowledge of the molecular mechanisms involved in reproductive toxicology.

Alteration of pregnancy related hormones and fetal survival in F-344 rats exposed by inhalation to benzo(a)pyrene

The objective of this study was to evaluate the effect of subacute exposure to inhaled benzo(a)pyrene (BaP) on fetal survival and luteal maintenance using timed-pregnant Fisher 344 rats. Prior to assignment of pregnant rats to treatment and control groups, numbers of implantation sites were determined on gestation day (GD) 8 via midventral laparotomy. Subsequently, animals were assigned randomly to three treatment groups and two control groups. Treatment consisted of subacute exposure of rats via inhalation to BaP 25, 75, and 100 micro g/m(3), 4h daily for 10 days (GD-11-20). Control animals were either sham exposed to carbon black (CB) to control for inert BaP carrier or remained unexposed (UNC). Blood samples were collected on days 15 and 17 of gestation via sinus orbital veini-puncture for plasma. Number of pups per litter was determined postpartum and fetal survival rate was expressed as a percentage of the corresponding implantation sites. Radioimmunoassays were used to determine plasma progesterone, estrogen, and prolactin (indirect measurement of decidual luteotropin) concentrations. Fetal survival among BaP-treated rats declined in a dose-dependent manner (25 micro g/m(3), 78.3% per litter; 75 micro g/m(3), 38.0% per litter; 100 micro g/m(3), 33.8% per litter; P<0.05) compared with CB (96.7% per litter) and UNC (98.9% per litter). Plasma progesterone, estrogen, and prolactin concentrations also declined as a result of subacute exposure of rats to BaP compared to controls. These data suggest that inhaled BaP compromised fetal survival and consequently luteotropic activity in the exposed animals.

[Smoking and ovarian fertility]

Smoking reduce the natural fertility and the delay to conceive increase with the number of cigarettes. In In Vitro Fertilization, the pregnancy rates per cycle are reduced with smokers compared with no smokers (OR: 0.66). The menopause arrive on average 2 years before with the smokers and the damages of ovarian reserve increase with smoking. The deleterious effects on ovary arrive, early in utero with regard to maternal smoking, and after the puberty, on the pre-ovulatory period where toxic, vascular and mutagen effects induce inhibition of ovocyte apoptosis, promoting ovocyte aneuploidy and subsequently miscarriage. The protection of ovarian fertility is one argument more to stop early smoking.

ATSDR evaluation of health effects of chemicals. IV. Polycyclic aromatic hydrocarbons (PAHs): understanding a complex problem

Polycyclic Aromatic Hydrocarbons (PAHs) are a group of chemicals that are formed during the incomplete burning of coal, oil, gas, wood, garbage, or other organic substances, such as tobacco and charbroiled meat. There are more than 100 PAHs. PAHs generally occur as complex mixtures (for example, as part of products such as soot), not as single compounds. PAHs are found throughout the environment in the air, water, and soil. As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals, including PAHs (ATSDR, 1995), found at facilities on the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) and which pose the most significant potential threat to human health, as determined by ATSDR and the Environmental Protection Agency (EPA). These profiles include information on health effects of chemicals from different routes and durations of exposure, their potential for exposure, regulations and advisories, and the adequacy of the existing database. Assessing the health effects of PAHs is a major challenge because environmental exposures to these chemicals are usually to complex mixtures of PAHs with other chemicals. The biological consequences of human exposure to mixtures of PAHs depend on the toxicity, carcinogenic and noncarcinogenic, of the individual components of the mixture, the types of interactions among them, and confounding factors that are not thoroughly understood. Also identified are components of exposure and health effects research needed on PAHs that will allow estimation of realistic human health risks posed by exposures to PAHs. The exposure assessment component of research should focus on (1) development of reliable analytical methods for the determination of bioavailable PAHs following ingestion, (2) estimation of bioavailable PAHs from environmental media, particularly the determination of particle-bound PAHs, (3) data on ambient levels of PAHs metabolites in tissues/fluids of control populations, and (4) the need for a critical evaluation of current levels of PAHs found in environmental media including data from hazardous waste sites. The health effects component should focus on obtaining information on (1) the health effects of mixtures of PAHs particularly their noncarcinogenic effects in humans, and (2) their toxicokinetics. This report provides excerpts from the toxicological profile of PAHs (ATSDR, 1995) that contains more detailed information.

Sites of female reproductive vulnerability: implications for testing and risk assessment

All reproductive toxicity testing, whether in vivo or in vitro, should be conducted with consideration of the ultimate use of the data for reproductive risk assessment and the protection of human reproductive health. In this review selected sites of vulnerability in the female reproductive system are identified. These sites of female reproductive vulnerability may be utilized for in vitro toxicity testing assays, and the data from assays may be employed in the hazard identification and hazard characterization steps necessary for reproductive risk assessment. Using biomarkers of female reproductive function derived from in vitro toxicity testing it is possible to define functions that characterize female fecundity. These characterizations of female fecundity may be used to quantitate reproductive risk in human populations.

Morphometric assessment of the murine ovarian toxicity of 7,12-dimethylbenz(a)anthracene

7,12-Dimethylbenz(a)anthracene (DMBA) is a polycyclic aromatic hydrocarbon and a component of cigarette smoke that has been identified as a murine reproductive toxicant. The morphometric parameters of total ovarian volume, individual corpus luteum volumes, and total corpora lutea volume were measured in C57BL/6N mice treated with DMBA. Each group received single intraperitoneal injections of 0, 0.1, 1.0, or 10 mg/kg and were sacrificed at 1, 2, 3, or 4 weeks after treatment. DMBA produced a dose-dependent decrease in ovarian volume and number of corpora lutea in each ovary. The observed reduction in total corpora lutea volume did not fully account for the loss in total ovarian volume. This is consistent with previous descriptions of a toxic effect on all ovarian components including growing and resting follicles. Growing follicles that escaped the toxic effects of DMBA and achieved ovulation resulted in a corpus luteum that appeared histologically normal. Morphometric analysis of this animal model further defines the dynamic changes in the mouse ovary in response to DMBA.