Damaging legacy: maternal cigarette smoking has long-term consequences for male offspring fertility

Transgenerational effects of maternal exposure to nicotine on structures of pituitary-gonadal axis of rats

Smoking can lead to several diseases and cause a reduction in fertility in men and women. Among the various components of cigarettes harmful during pregnancy, nicotine stands out. It can cause a reduction in placental blood flow, compromising the development of the baby with neurological, reproductive and endocrine consequences. Thus, we aimed to evaluate the effects of nicotine on the pituitary-gonadal axis of rats exposed during pregnancy and breastfeeding (1st generation - F1), and whether the possible damage observed would reach the 2nd generation (F2). Pregnant Wistar rats received 2 mg/kg/day of nicotine throughout the entire gestation and lactation. Part of the offspring was evaluated on the first neonatal day (F1) for macroscopic, histopathological and immunohistochemical analyses of brain and gonads. Another part of the offspring was kept until 90 days-old for mating and obtainment of progenies that had the same parameters evaluated at the end of pregnancy (F2). The occurrence of malformations was more frequent and diversified in nicotine-exposed F2. Brain alterations, including reduced size and changes in cell proliferation and death, were seen in both generations of nicotine-exposed rats. Male and female gonads of F1 exposed rats were also affected. The F2 rats showed reduced cellular proliferation and increased cell death on the pituitary and ovaries, besides increased anogenital distance in females. The number of mast cells was not enough altered to indicate an inflammatory process in brain and gonads. We conclude that prenatal exposure to nicotine causes transgenerational alterations in the structures of pituitary-gonadal axis in rats.

Developmental programming: Preconceptional and gestational exposure of sheep to a real-life environmental chemical mixture alters maternal metabolome in a fetal sex-specific manner

BACKGROUND

Everyday, humans are exposed to a mixture of environmental chemicals some of which have endocrine and/or metabolism disrupting actions which may contribute to non-communicable diseases. The adverse health impacts of real-world chemical exposure, characterized by chronic low doses of a mixture of chemicals, are only recently emerging. Biosolids derived from human waste represent the environmental chemical mixtures humans are exposed to in real life. Prior studies in sheep have shown aberrant reproductive and metabolic phenotypes in offspring after maternal biosolids exposure.

OBJECTIVE

To determine if exposure to biosolids perturbs the maternal metabolic milieu of pregnant ewes, in a fetal sex-specific manner.

METHODS

Ewes were grazed on inorganic fertilizer (Control) or biosolids-treated pastures (BTP) from before mating and throughout gestation. Plasma from pregnant ewes (Control n = 15, BTP n = 15) obtained mid-gestation were analyzed by untargeted metabolomics. Metabolites were identified using Agilent MassHunter. Multivariate analyses were done using MetaboAnalyst 5.0 and confirmed using SIMCA.

RESULTS

Univariate and multivariate analysis of 2301 annotated metabolites identified 193 differentially abundant metabolites (DM) between control and BTP sheep. The DM primarily belonged to the super-class of lipids and organic acids. 15-HeTrE, oleamide, methionine, CAR(3:0(OH)) and pyroglutamic acid were the top DM and have been implicated in the regulation of fetal growth and development. Fetal sex further exacerbated differences in metabolite profiles in the BTP group. The organic acids class of metabolites was abundant in animals with male fetuses. Prenol lipid, sphingolipid, glycerolipid, alkaloid, polyketide and benzenoid classes showed fetal sex-specific responses to biosolids.

DISCUSSION

Our study illustrates that exposure to biosolids significantly alters the maternal metabolome in a fetal sex-specific manner. The altered metabolite profile indicates perturbations to fatty acid, arginine, branched chain amino acid and one‑carbon metabolism. These factors are consistent with, and likely contribute to, the adverse phenotypic outcomes reported in the offspring.

Genome-wide evaluation of transcriptomic responses of human tissues to smoke: A systems biology study

The harmful compounds in various sources of smoke threaten human health. So far, many studies have investigated the effects of compounds of smoke on transcriptome changes in different human tissues. However, no study has been conducted on the effects of these compounds on transcriptome changes in different human tissues simultaneously. Hence, the present study was conducted to identify smoke-related genes (SRGs) and their response mechanisms to smoke in various human cells and tissues using systems biology based methods. A total of 6,484 SRGs were identified in the studied tissues, among which 4,095 SRGs were up-regulated and 2,389 SRGs were down-regulated. Totally, 459 SRGs were smoke-related transcription factors (SRTFs). Gene regulatory network analysis showed that the studied cells and tissues have different gene regulation and responses to compounds of smoke. The comparison of different tissues revealed no common SRG among the all studied tissues. However, the CYP1B1 gene was common among seven cells and tissues, and had the same expression trend. Network analysis showed that the CYP1B1 is a hub gene among SRGs in various cells and tissues. To the best of our knowledge, for the first time, our results showed that compounds of smoke induce and increase the expression of CYP1B1 key gene in all target and non-target tissues of human. Moreover, despite the specific characteristics of CYP1B1 gene and its identical expression trend in target and non-target tissues, it can be used as a biomarker for diagnosis and prognosis.

Fetal exposure to maternal cigarette smoking and male reproductive function in young adulthood

Maternal smoking during pregnancy constitutes a potential, major risk factor for adult male reproductive function. In the hitherto largest longitudinal cohort, we examined biomarkers of reproductive function according to maternal smoking during the first trimester and investigated whether associations were mitigated by smoking cessation prior to the fetal masculinization programming window. Associations between exposure to maternal smoking and semen characteristics, testicular volume and reproductive hormones were assessed among 984 young men from the Fetal Programming of Semen Quality (FEPOS) cohort. Maternal smoking was assessed through interview data and measured plasma cotinine levels during pregnancy. We applied negative binomial, logistic and linear regression models to estimate differences in outcomes according to levels of maternal smoking. Sons of light smokers (≤ 10 cigarettes/day) had a 19% (95% CI - 29%, - 6%) lower sperm concentration and a 24% (95% CI - 35%, - 11%) lower total sperm count than sons of non-smokers. These estimates were 38% (95% CI - 52%, - 22%) and 33% (95% CI - 51%, - 8%), respectively, for sons of heavy smokers (> 10 cigarettes/day). The latter group also had a 25% (95% CI 1%, 54%) higher follitropin level. Similarly, sons exposed to maternal cotinine levels of  > 10 ng/mL had lower sperm concentration and total sperm count. Smoking cessation prior to gestational week seven was not associated with a higher reproductive capacity. We observed substantial and consistent exposure-response associations, providing strong support for the hypothesis that maternal smoking impairs male reproductive function. This association persisted regardless of smoking cessation in early pregnancy.

Resveratrol reverses male reproductive damage in rats exposed to nicotine during the intrauterine phase and breastfeeding

BACKGROUND

Nicotine leads to reproductive changes culminating in male infertility and subfertility. Resveratrol, a polyphenol, is a biological modulator. Sirtuin 1 (SIRT1) protein can positively act on male reproduction, and its expression can be affected by nicotine and modulated by resveratrol.

OBJECTIVES

The capability of resveratrol to reverse the reproductive damage in adult male offspring, which was nicotine-exposed during the intrauterine phase and breastfeeding, was investigated.

MATERIALS AND METHODS

Four groups were established with male offspring born from nicotine-exposed and non-exposed rat dams during pregnancy and lactation. Forty-eight male Wistar rats were distributed into four groups: sham control (SC), resveratrol (R), nicotine (N), and nicotine + resveratrol (NR). Rat dams of the N and NR offspring were exposed to nicotine (2 mg/kg/day) during pregnancy and lactation using a subcutaneously implanted minipump. The offspring of the R and NR groups received resveratrol (300 mg/kg of body weight, gavage) for 63 days from puberty. At 114 days of age, the male rats were euthanized.

RESULTS

Nicotine did not alter the body weight, biometry of reproductive organs, or quantitative sperm parameters of adult offspring but caused an evident worsening of all sperm qualitative parameters studied. Daily treatment with resveratrol from puberty up to adulthood improved all qualitative sperm parameters significantly, leading some of them close to the control values. Resveratrol also improved the morphological integrity and expression of SIRT1 in the seminiferous epithelium of nicotine-exposed offspring.

CONCLUSION AND DISCUSSION

Resveratrol reversed the male reproductive damage caused by nicotine. Nicotine crosses the blood-placental membrane and is present in the breast milk of mothers who smoke. Resveratrol restored the altered reproductive parameters in the male adult offspring that were nicotine-exposed during intrauterine life and breastfeeding. The epigenetic modulating action of resveratrol can be involved in this nicotine damage reversion. Resveratrol may be a promising candidate to be investigated regarding the adjuvant strategies in the treatment of male infertility.

Maternal smoking-induced lung injuries in dams and offspring via inflammatory cytokines

Maternal smoking during pregnancy can induce permanent changes in neonatal inflammation, which will result in lifelong implications. An original study of data from GSE96978, composed of 2 subseries (GSE96976 and GSE96977), investigated genome-wide changes in ELT cells, the lungs of mouse dams and their juvenile offspring and focused on finding an in vitro alternative as a human tissue-based replacement for the use of animals. Therefore, the study only analyzed the similarities of GO terms between ELT cells and dams. However, the relationship between differentially expressed genes (DEGs) in dams and offspring was not investigated. The present study aimed to identify the key molecules involved in maternal smoking-induced dam and offspring lung injuries. Data from GSE96977 were downloaded from Gene Expression Omnibus (GEO) data sets. In our study, differentially expressed genes (DEGs) in dams and offspring were reanalyzed using the limma package. The results of Gene Set Enrichment Analysis (GSEA) showed that the DEGs in the lungs of dams were significantly enriched in immune-related functions and those in the lungs of offspring were enriched in cell growth. Furthermore, a total of 90 DEGs shared in the dam and offspring datasets were screened out. In addition, most of these DEGs were enriched in cytokine and cytokine receptor interaction KEGG pathways. Furthermore, protein-protein interaction (PPI) network analysis screened out 4 core genes in cluster 1. In addition, the miRNAs related to these core genes were predicted, and mmu-miR-1903 was screened out. Taken together, our data indicate that inflammatory responses may play an important role in maternal smoking induced lung injuries in dams and offspring. Furthermore, mmu-miR-1903 is a potential epigenetic biomarker of lung inflammation in the offspring of dams who smoked during pregnancy. In conclusion, by screening shared differential genes, we only need to detect maternal genes to predict maternal smoking-induced lung injuries in offspring.

The effects of thirdhand smoke on reproductive health

Tobacco smoke is an environmental pollutant that can cause follicle destruction and oocyte dysfunction. Thirdhand smoke (THS) is residual tobacco smoke existing in the environment long after cigarettes have been extinguished, which can react with other environmental compounds to produce secondary pollutants. THS contains a variety of toxic and harmful chemicals, such as nicotine and 1-(N-methyl-N-nitrosamino)-1-(3-pyridinyl)-4-butanal (NNA), a logical biomarker of THS exposure. The health hazards of THS exposure and its components have been researched in recent years. In this review, we have summarized research progress on the effects of THS exposure on organs in mice and humans especially on the reproductive system. This review may help evaluate the health risks of THS, in particular reproduction and offspring health. We hope this review will guide public health education on the dangers of THS exposure and promotion of healthy living habits.

Chronic testicular Chlamydia muridarum infection impairs mouse fertility and offspring development†

With approximately 131 million new genital tract infections occurring each year, Chlamydia is the most common sexually transmitted bacterial pathogen worldwide. Male and female infections occur at similar rates and both cause serious pathological sequelae. Despite this, the impact of chlamydial infection on male fertility has long been debated, and the effects of paternal chlamydial infection on offspring development are unknown. Using a male mouse chronic infection model, we show that chlamydial infection persists in the testes, adversely affecting the testicular environment. Infection increased leukocyte infiltration, disrupted the blood:testis barrier and reduced spermiogenic cell numbers and seminiferous tubule volume. Sperm from infected mice had decreased motility, increased abnormal morphology, decreased zona-binding capacity, and increased DNA damage. Serum anti-sperm antibodies were also increased. When both acutely and chronically infected male mice were bred with healthy female mice, 16.7% of pups displayed developmental abnormalities. Female offspring of chronically infected sires had smaller reproductive tracts than offspring of noninfected sires. The male pups of infected sires displayed delayed testicular development, with abnormalities in sperm vitality, motility, and sperm-oocyte binding evident at sexual maturity. These data suggest that chronic testicular Chlamydia infection can contribute to male infertility, which may have an intergenerational impact on sperm quality.

Does maternal exposure to nicotine affect the oocyte quality and reproductive capacity in adult offspring?

Gonadal development begins in the intrauterine phase and females from most species are born with an established oocyte reserve. Exposure to drugs during gestation can compromise the offspring health, also affecting the gametes quality. Nicotine, the main component of cigarettes, is an oxidant agent capable of altering the fertility in men and women. As female gametes are susceptible to oxidative stress, this drug can damage the oolemma and affect oocyte maturation, induce errors during chromosomal segregation and DNA fragmentation. Oocyte mitochondria are particularly susceptible to injuries, contributing to the oocyte quality loss and embryonic development disruption. Thus, considering the high number of women who smoke during pregnancy, while significant events are occurring in the embryo for future fertility of offspring, we seek to verify the quality of the oocytes from adult rats exposed to nicotine during intrauterine phase and breastfeeding. Pregnant Wistar rats received nicotine by osmotic mini-pumps and the female progenies were evaluated in adulthood for oocyte quality (viability, lipid peroxidation, generation of reactive oxygen species and mitochondrial integrity) and reproductive capacity. Embryos (3dpc) and fetuses (20dpc) generated by these rats were also evaluated. The results showed that the dose of 2 mg/kg/day of nicotine through placenta and breast milk does not affect the number of oocytes and the fertility capacity of adult rats. However, it causes some morphological alterations in oocytes, mitochondrial changes, embryonic fragmentation and disruption of fetal development. The malformations in fetuses generated from these gametes can also indicate the occurrence of epigenetic modifications.

Genetic and epigenetic modifications of F1 offspring's sperm cells following in utero and lactational combined exposure to nicotine and ethanol

It is well established that maternal lifestyle during pregnancy and lactation affects the intrauterine programming of F1 offspring. However, despite the co-use of alcohol and nicotine is a common habit, the effects of exposure to both substances on the reproductive system of F1 male offspring and the underlying mechanisms of developmental programming have not been investigated. The present study aimed to examine pre- and postnatal concurrent exposure to these substances on genetic and epigenetic alterations of sperm cells as well as testis properties of F1 offspring compared with exposure to each substance alone. Pregnant dams in the F0 generation randomly received normal saline, nicotine, ethanol, and combinations throughout full gestation and lactation periods. Sperm cells and testes of F1 male offspring were collected at postnatal day 90 for further experiments. High levels of sperm DNA fragmentation were observed in all exposed offspring. Regarding epigenetic alterations, there was a significant increase in the relative transcript abundance of histone deacetylase 1 and 2 in all exposed sperm cells. Moreover, despite a decrease in the expression level of DNA methyltransferase (DNMT) 3A, no marked differences were found in the expression levels of DNMT1 and 3B in any of the exposed sperm cells compared to non-exposed ones. Interestingly, combined exposure had less prominent effects relative to exposure to each substance alone. The changes in the testicular and sperm parameters were compatible with genetic and epigenetic alterations. However, MDA level as an oxidative stress indicator increased in all exposed pups, which may be responsible for such outputs. In conclusion, maternal co-exposure to these substances exhibited epigenotoxicity effects on germline cells of F1 male offspring, although these effects were less marked relative to exposure to each substance alone. These counteracting effects may be explained by cross-tolerance and probably less impairment of the antioxidant defense system.

Fetal and Postnatal Nicotine Exposure Modifies Maturation of Gonocytes to Spermatogonia in Mice

Studies in laboratory animals have shown that male offspring from dams, exposed to nicotine during pregnancy and postnatal periods, show alterations in fertility, although the origin of this is still uncertain. In this study, we examined in a mouse model if the process of gonocyte maturation to spermatogonia was affected in male offspring from dams with nicotine administration during pregnancy and postnatal periods. BALB/C mice, with and without nicotine administrations in pregnancy and postnatal periods, were studied. The animals were euthanized at 3, 7, 10, 16, and 35 days postpartum (dpp). Testicular tissue samples were processed for histological, ultrastructural, and immunohistochemical studies; and testicular lipoperoxidation was determined. It was observed that in the nicotine-exposed animals, there was increased apoptosis and a reduction in the number of gonocytes that matured to spermatogonia. This gonocyte-spermatogonia maturation reduction was associated with a greater immunoreactivity to nicotinic acetylcholine receptors in the germ cells. Lipoperoxidation was similar in both groups until 16 dpp, with significant reduction at 35 dpp. Our findings suggest that nicotine intake during pregnancy and postnatal periods can affect the process of maturation of gonocytes to spermatogonia and the pool of available spermatogonia for spermatogenesis.

Chronic Maternal Tobacco Smoke Exposure and/or Alpha-Lipoic Acid Treatment Causes Long-Term Deterioration of Testis and Sexual Behavior in Adult Male Rats

BACKGROUND

Tobacco use during pregnancy is known to have several negative effects on the offspring's reproductive health in the long term. The use of alpha-lipoic acid (ALA) as a dietary supplement during pregnancy has increased greatly in recent years and has been known to have positive effects on various pregnancy outcomes including miscarriage, diabetic embryopathy, preterm delivery, and congenital malformations.

AIM

To evaluate the effects of tobacco smoke exposure (TSE) on sexual behavior, reproductive parameters, and testicles in adult male rats and to reveal the possible role of ALA administration on these parameters.

METHODS

Pregnant rats (n = 7 per group) were treated with tobacco smoke (TS), ALA (20 mg/kg), and TS + ALA for a total of 11 weeks. The following parameters were compared with 8 control rats: puberty parameters, sexual behavior; levels of serum gonadotropins and testosterone, total antioxidant status, and total oxidant status; the expression of the apoptotic protease-activating factor-1 and caspase 9 mRNA levels in the testis; and assessment of immunohistochemistry and terminal deoxynucleotidyl transferase dUTP nick end labeling assay of testis.

MAIN OUTCOME MEASURE

Sexual behavior, changes in puberty parameters, and hormonal and genetic alterations were the outcomes analyzed in this study.

RESULTS

Maternal TSE caused a significant decrease in the number of intromissions compared to the control group. Similarly, ALA decreased erectile function in sexual behavior by decreasing the number of intromissions and intromission ratio in the ALA group compared to the control group. In addition, TSE and ALA treatment caused an impairment of some consummatory sexual behaviors. Also, in parallel with this inhibitory effect, the age of pubertal onset was significantly delayed in the TS + ALA group compared to other groups. Also, histopathological changes in testicular tissue, oxidative stress markers, apoptotic index, and mRNA levels of apoptosis-related genes increased in all treatment groups.

CLINICAL IMPLICATIONS

The use of ALA and/or tobacco products during pregnancy may adversely affect the reproductive health of male newborns in the long term.

STRENGTHS & LIMITATIONS

To the best of our knowledge, this study is the first to show the effects of maternal ALA treatment and/or TSE on the sexual behavior and reproductive parameters in male rats; however, the study is based on an animal model, and the present findings partially reflect the characteristics of human sexual behavior.

CONCLUSION

Maternal TSE and/or ALA treatment may impair sexual behavior in adulthood in male rats because of testicular damage caused by oxidative stress during gonadal development. Yardimci A, Akkoc RF, Tektemur A, et al. Chronic Maternal Tobacco Smoke Exposure and/or Alpha-Lipoic Acid Treatment Causes Long-Term Deterioration of Testis and Sexual Behavior in Adult Male Rats. J Sex Med 2020;17:1835-1847.

Reduced testicular steroidogenesis in rat offspring by prenatal nicotine exposure: Epigenetic programming and heritability via nAChR/HDAC4

Prenatal nicotine exposure (PNE) may lead to offspring's testicular dysplasia. Here, we confirmed the intergenerational effect of PNE on testosterone synthetic function and explored its epigenetic programming mechanism. Pregnant Wistar rats were injected subcutaneously with nicotine (2 mg/kg.d) from gestational day 9-20. Some dams were anesthetized to obtain fetal rats, the rest were allowed to spontaneous labor to generate F1 and F2 generation. In utero, PNE impaired testicular development and testosterone production. Meanwhile, the expression of steroidogenic acute regulatory protein (StAR) and 3β-hydroxysteroid dehydrogenase (3β-HSD) were decreased both in F1 and F2 generations. Furthermore, PNE enhanced the expression of fetal testicular nicotinic acetylcholine receptors (nAChRs) and histone deacetylase 4 (HDAC4), while obviously weakened histone 3 lysine 9 acetylation (H3K9ac) level of StAR/3β-HSD promoter from GD20 to postnatal week 12 and even in F2 generation. In vitro, nicotine increased nAChRs and HDAC4 expression, and decreased the StAR/3β-HSD H3K9ac level and expression, as well as the testosterone production in Leydig cells. Antagonism of nAChRs and inhibition of HDAC4 reversed the aforementioned changes. In conclusion, PNE programmed testicular low steroidogenesis and its heritability in male offspring rats. The underlying mechanism was associated to the low-level programming of StAR/3β-HSD H3K9ac via nAChR/HDAC4.

Associations between major dietary patterns and testicular function in a population-based cohort of young men: results from the Western Australian Pregnancy Cohort (Raine) Study

BACKGROUND

Controversial speculation suggestions that dietary intake may affect semen quality and testicular function, however, there are limited comprehensive studies observing dietary patterns.

OBJECTIVE

To study associations between major dietary patterns and markers of testicular function in adulthood.

MATERIAL AND METHODS

Observational cross-sectional study of two hundred and ninety men with an average age of 20 years, from the Western Australian Pregnancy Cohort (Raine) Study. Usual dietary intake assessed using a semi-quantitative food frequency questionnaire at 20 years of age. Two dietary patterns previously identified using exploratory factor analysis ("Healthy" or "Western") and participants received z-scores for each dietary pattern. Primary endpoints were testicular volume, total sperm per ejaculate, morning serum testosterone concentration. Secondary endpoints were semen sample parameters, inhibin B and sex steroids (DHT: 3α-diol, 3β-diol; LH; FSH; DHEA; estradiol; estrone).

RESULT(S)

Participants were on average 20.0 ± 0.4 years old, had a median of 2 days sexual abstinence and a body mass index of 24.1 ± 3.9 kg/m² , 13% were smokers, 52% were 'moderate' alcohol drinkers, 23% frequently used recreational drugs and 68% reported 'high' physical activity levels. Sperm concentration and DHT 3α-diol were negatively associated with a greater z-score for the "Western" dietary pattern (p = 0.007 and; p = 0.044, respectively), and serum estradiol concentration was positively associated with a "Western" dietary pattern (p = 0.007) after adjustment for BMI, varicocele, cryptorchidism and sexual abstinence.

DISCUSSION

Despite associations between greater intake of the "Western" dietary pattern and a decreased male reproductive health markers, our lack of consistent associations of either a "Healthy" or a "Western" dietary pattern, limit clinical or biological significance in isolation.

CONCLUSIONS

A potential negative association of a "Western" dietary pattern with male reproductive health was detected and should be studied further in population-based studies.

The current state of reproductive biology research in Australia and New Zealand: core themes from the Society for Reproductive Biology Annual Meeting, 2016

Because reproduction is essential for all life, it is central to our understanding of all aspects of biology. The Society for Reproductive Biology (SRB) 2016 conference held on the Gold Coast (Qld, Australia) displayed the current breadth of reproductive research in Australia and New Zealand, with additional insights from world leaders in the field. This conference review provides a focused summary of the key questions, emerging ideas and novel technologies that were presented in the symposia. Presented research demonstrated key advances in how stem cell biology may allow us to better understand pluripotency, as well as how environmental and lifestyle factors, such as circadian disruption, smoking, alcohol and diet, affect gametogenesis, embryo implantation, placental function and reproductive capacity. Sessions also highlighted the role of reproductive biology in providing insight into the mechanisms and processes governing a wide range of biological science disciplines, including cancer research and therapies, oncofertility, conservation of native species and chronic non-communicable diseases. Recurring themes included the importance of male and female gamete quality for reproductive potential and the critical and varied roles of the placenta in the maintenance of a healthy pregnancy. Dysregulation of reproductive processes can contribute to a variety of pathological states that affect future health, fertility and fecundity. Research being conducted by the SRB has the potential to shape not only the fertility of the current generation, but also the health and reproductive viability of future generations.

Multigenerational effects of maternal cigarette smoke exposure during pregnancy on sperm counts of F1 and F2 male offspring

Animal models and human studies showed that in utero cigarette smoke exposure decreases sperm counts of offspring. This study used a mouse model to investigate the effects of maternal exposure to cigarette smoke on reproductive systems in F1 and F2 male offspring. Female ICR mice were exposed either to clean air or to cigarette smoke during pregnancy at the post-implantation stage. Epididymal sperm counts were decreased in a cigarette smoke dose-dependent manner in F1 (by 40-60%) and F2 males (by 23-40%) at postnatal day 56. In F1, the seminiferous epithelium heights were lower in the cigarette smoke-exposed groups than in the control group, and these effects were sustained in F2 males. Results suggest that maternal cigarette smoke exposure during pregnancy can have a multigenerational adverse effect on sperm counts in male offspring, which is mediated through in utero exposure of fetal germ cells to cigarette smoke.

Grandmaternal smoke exposure reduces female fertility in a murine model, with great-grandmaternal smoke exposure unlikely to have an effect

STUDY QUESTION

What effect does multigenerational (F2) and transgenerational (F3) cigarette smoke exposure have on female fertility in mice?

SUMMARY ANSWER

Cigarette smoking has a multigenerational effect on female fertility.

WHAT IS KNOWN ALREADY

It has been well established that cigarette smoking decreases female fertility. Furthermore, a growing body of evidence suggests that smoking during pregnancy decreases the fertility of daughters and increases cancer and asthma incidence in grandchildren and great-grandchildren.

STUDY DESIGN, SIZE, DURATION

Six-week-old C57BL/6 female mice were exposed nasally to cigarette smoke or room air (controls) for 5 weeks prior to being housed with males. Females continued to be exposed to smoke throughout pregnancy and lactation until pups were weaned. A subset of F1 female pups born to these smoke and non-smoke exposed females were bred to create the F2 grandmaternal exposed generation (multigenerational). Finally, a subset of F2 females were bred to create the F3 great-grandmaternal exposed generation (transgenerational). The reproductive health of F2 and F3 females was examined at 8 weeks and 9 months.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Ovarian and oocyte quality was examined in smoke exposed and control animals. A small-scale fertility trial was performed before ovarian changes were examined using ovarian histology and immunofluorescence and/or immunoblotting analysis of markers of apoptosis (TUNEL) and proliferation (proliferating cell nuclear antigen (PCNA) and anti-Mullerian hormone (AMH)). Oocyte quality was examined using immunocytochemistry to analyze the metaphase II spindle and ploidy status. Parthenogenetic activation of oocytes was used to investigate meiosis II timing and preimplantation embryo development. Finally, diestrus hormone serum levels (FSH and LH) were quantified.

MAIN RESULTS AND THE ROLE OF CHANCE

F2 smoke exposed females had no detectable change in ovarian follicle quality at 8 weeks, although by 9 months ovarian somatic cell proliferation was reduced (P = 0.0197) compared with non-smoke exposed control. Further investigation revealed changes between control and smoke exposed F2 oocyte quality, including altered meiosis II timing at 8 weeks (P = 0.0337) and decreased spindle pole to pole length at 9 months (P = 0.0109). However, no change in preimplantation embryo development was observed following parthenogenetic activation. The most noticeable effect of cigarette smoke exposure was related to the subfertility of F2 females; F2 smoke exposed females displayed significantly increased time to conception (P = 0.0042) and significantly increased lag time between pregnancies (P = 0.0274) compared with non-smoke exposed F2 females. Conversely, F3 smoke exposed females displayed negligible oocyte and follicle changes up to 9 months of age, and normal preimplantation embryo development.

LARGE SCALE DATA

None.

LIMITATIONS, REASONS FOR CAUTION

This study focused solely on a mouse model of cigarette smoke exposure to simulate human exposure.

WIDER IMPLICATIONS OF THE FINDINGS

Our results demonstrate that grandmaternal cigarette smoke exposure reduces female fertility in mice, highlighting the clinical need to promote cessation of cigarette smoking in pregnant women.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the Australian Research Council, National Health and Medical Research Council, Hunter Medical Research Institute, Newcastle Permanent Building Society Charitable Trust, and the University of Newcastle Priory Research Centers in Chemical Biology, Healthy Lungs and Grow Up Well. The authors declare no conflict of interest.

Lifestyle causes of male infertility

Objective

To examine the potential effects of lifestyle factors on male reproductive health. Evidence of a global decline in human sperm quality over recent decades has been accumulating. Environmental, occupational, and modifiable lifestyle factors may contribute to this decline. This review focuses on key lifestyle factors that are associated with male infertility such as smoking cigarettes, alcohol intake, use of illicit drugs, obesity, psychological stress, advanced paternal age, dietary practices, and coffee consumption. Other factors such as testicular heat stress, intense cycling training, lack of sleep and exposure to electromagnetic radiation from mobile phone use are briefly discussed.

Materials and method

A comprehensive literature search was performed to identify and synthesise all relevant information, mainly from within the last decade, on the major lifestyle factors associated with male infertility and semen quality. Database searches were limited to reports published in English only. A manual search of bibliographies of the reports retrieved was conducted to identify additional relevant articles.

Results

In all, 1012 articles were identified from the database search and after reviewing the titles and abstract of the reports, 104 articles met the inclusion criteria. Of these, 30 reports were excluded as the full-text could not be retrieved and the abstract did not have relevant data. The remaining 74 reports were reviewed for data on association between a particular lifestyle factor and male infertility and were included in the present review.

Conclusion

The major lifestyle factors discussed in the present review are amongst the multiple potential risk factors that could impair male fertility. However, their negative impact may well be mostly overcome by behaviour modification and better lifestyle choices. Greater awareness and recognition of the possible impact of these lifestyle factors are important amongst couples seeking conception.

Tobacco smoking and breastfeeding: Effect on the lactation process, breast milk composition and infant development. A critical review

Approximately 10% of women report smoking during pregnancy. The number of breastfeeding women who relapse back to smoking is even greater. Smoking may cause adverse changes to the milk's composition by not only reducing its protective properties, but also by affecting the infant's health. The pathophysiological mechanisms underlying these adverse effects are not entirely known. This article is a review of previous reports about the effects of smoking on the lactation process, breast milk composition and infant development. A systematic search for English language articles published until 2015 was made, using a MEDLINE data. The key search terms were "smoking and breastfeeding", "smoking and lactation", "smoking and milk composition", "nicotine and breast milk". Studies have shown that nicotine levels in breast milk of women who smoke are three times higher than those in the plasma levels. Breast milk volume is reduced and the duration of lactation period is shorter. Smoking causes adverse changes to the milk's composition by not only reducing its protective properties, but also affecting infants' response to breastfeeding and to breast milk.

Developmental origins of male subfertility: role of infection, inflammation, and environmental factors

Male gamete development begins with the specification of primordial cells in the epiblast of the early embryo and is not complete until spermatozoa mature in the epididymis of adult males. This protracted developmental process involves extensive alteration of the paternal germline epigenome. Initially, epigenetic reprogramming in fetal germ cells results in removal of most DNA methylation, including parent-specific epigenetic information. The germ cells then establish sex-specific epigenetic information through de novo methylation and undergo spermatogenesis. Chromatin in haploid germ cells is repackaged into protamines during spermiogenesis, providing further widespread epigenetic reorganization. Finally, after fertilization, epigenetic reprogramming in the preimplantation embryo is necessary for regaining totipotency. These events provide substantial windows during which epigenetic errors either may be corrected or may occur in the germline. There is now increasing evidence that environmental factors such as exposure to toxicants, the parents' and individual's diet, and even infectious and inflammatory events in the male reproductive tract may influence epigenetic reprogramming. This, together with other damage inflicted on the germline chromatin, may result in negative consequences for fertility and health. Large epidemiological birth cohort studies have yielded insight into possible causative environmental factors. Together with experimental animal studies, a clearer view of environmental impacts on fetal development and their intergenerational and even transgenerational effects on reproductive health has emerged and is reviewed in this article.

Potential effect of smoking on semen quality through DNA damage and the downregulation of Chk1 in sperm

Previous studies have found that smoking is associated with decreased male fertility via altering the quality of semen. However, the mechanism by which cigarette smoking affects semen quality remains to be fully elucidated. Heavy smoking-induced DNA damage has been reported to correlate with abnormal spermatozoa and male infertility. It has been reported that, in response to DNA damage, activation of the checkpoint kinase 1 (Chk1) facilitates S and G2 checkpoint arrest. The aim of the present study was to investigate the expression levels of Chk1 in sperm cells of smoking and non-smoking men, and to further examine the correlation between DNA fragmentation rates and the expression levels of Chk1 with smoking. The present study was performed on a cohort of 841 smoking men and 287 non-smoking men. In the investigation, sperm concentration, motility, viability, seminal plasma zinc concentration, acrosin activity and sperm DNA fragmentation were examined. The gene and protein expression levels of Chk1 were detected using reverse transcription quantitative-polymerase chain reaction and western blot analyses, respectively. It was observed that the progressive motility of the sperm was significantly decreased in the moderate and heavy smoking groups, whereas no significant changes were observed in the mild smoking group. The sperm in the medium-term smoking group had significantly decreased progressive motility, and the semen concentration, sperm count and progressive motility vitality were markedly decreased in the long-term smoking group. Compared with the non-smoking group, the abnormal head rates in the heavy smoking group and long-term smoking group were significantly increased. The sperm viability and seminal plasma zinc concentration were markedly increased in the smoking group. Increased DNA fragmentation rates were found in the smoking group. The expression of Chk1 was significantly decreased in the smoking group, compared with the non-smoking group. Progressive motility and sperm concentration showed a nonlinear association with the relative mRNA expression of Chk1. However, an inverse association was found between DNA fragmentation rates and the progressive motility and sperm concentration. These data suggested that the decrease of semen quality caused by cigarette smoking was not only correlated with sperm DNA fragmentation rates, but was also correlated with a decline in the expressive level of Chk1. The expression of Chk1 was associated with DNA damage and apoptosis, the reduction of which may lead to decreased sperm repair and increased sperm apoptosis, with a subsequent effect on semen quality.

The relationship between mitochondrial DNA haplotype and the reproductive capacity of domestic pigs (Sus scrofa domesticus)

Background

The maternally inherited mitochondrial genome encodes key proteins of the electron transfer chain, which produces the vast majority of cellular ATP. Mitochondrial DNA (mtDNA) present in the mature oocyte acts as a template for all mtDNA that is replicated during development to meet the specific energy requirements of each tissue. Individuals that share a maternal lineage cluster into groupings known as mtDNA haplotypes. MtDNA haplotypes confer advantages and disadvantages to an organism and this affects its phenotype. In livestock, certain mtDNA haplotypes are associated with improved milk and meat quality, whilst, other species, mtDNA haplotypes have shown increased longevity, growth and susceptibility to diseases. In this work, we have set out to determine whether mtDNA haplotypes influence reproductive capacity. This has been undertaken using a pig model.

Results

To determine the genetic diversity of domestic pigs in Australia, we have sequenced the D-loop region of 368 pigs, and identified five mtDNA haplotypes (A to E). To assess reproductive capacity, we compared oocyte maturation, fertilization and development to blastocyst, and found that there were significant differences for maturation and fertilization amongst the haplotypes. We then determined that haplotypes C, D and E produced significantly larger litters. When we assessed the conversion of developmentally competent oocytes and their subsequent developmental stages to offspring, we found that haplotypes A and B had the lowest reproductive efficiencies. Amongst the mtDNA haplotypes, the number of mtDNA variants harbored at >25 % correlated with oocyte quality. MtDNA copy number for developmentally competent oocytes positively correlated with the level of the 16383delC variant. This variant is located in the conserved sequence box II, which is a regulatory region for mtDNA transcription and replication.

Conclusions

We have identified five mtDNA haplotypes in Australian domestic pigs indicating that genetic diversity is restricted. We have also shown that there are differences in reproductive capacity amongst the mtDNA haplotypes. We conclude that mtDNA haplotypes affect pig reproductive capacity and can be used as a marker to complement current selection methods to identify productive pigs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-016-0375-4) contains supplementary material, which is available to authorized users.

The paternal genome and the health of the assisted reproductive technology child

As a number of children born by assisted reproductive technology (ART) are increasing each year across the developed world, the health of such offspring is a matter of public concern. Does the integrity of the paternal genome impact on offspring health? In societal terms, as birth rates fall, and the Western population become unsustainable, do the benefits outweigh the costs of creating and providing for this ART conceived subpopulation? There are little data to date to answer these questions. The long-term health of such children has largely been ignored, and success measured only by early (prebirth) outcomes such as embryo quality or pregnancy. However, there are powerful paradigms such as ageing and smoking that give vital clues as to the potential impact of unhealthy spermatozoa on disease risk, mental and physical health, fertility and mortality of these offspring.

Prenatal and lactation nicotine exposure affects Sertoli cell and gonadotropin levels in rats

Nicotine is largely consumed in the world as a component of cigarettes. It can cross the placenta and reach the milk of smoking mothers. This drug induces apoptosis, affects sex hormone secretion, and leads to male infertility. To investigate the exposure to nicotine during the whole intrauterine and lactation phases in Sertoli cells, pregnant rats received nicotine (2 mg/kg per day) through osmotic minipumps. Male offsprings (30, 60, and 90 days old) had blood collected for hormonal analysis (FSH and LH) and their testes submitted for histophatological study, analysis of the frequency of the stages of seminiferous epithelium cycle, immunolabeling of apoptotic epithelial cells (TUNEL and Fas/FasL), analysis of the function and structure of Sertoli cells (respectively using transferrin and vimentin immunolabeling), and analysis of Sertoli-germ cell junctional molecule (β-catenin immunolabeling). The exposure to nicotine increased the FSH and LH plasmatic levels in adult rats. Although nicotine had not changed the number of apoptotic cells, neither in Fas nor FasL expression, it provoked an intense sloughing of epithelial cells and also altered the frequency of some stages of the seminiferous epithelium cycle. Transferrin and β-catenin expressions were not changed, but vimentin was significantly reduced in the early stages of the seminiferous cycle of the nicotine-exposed adult rats. Thus, we concluded that nicotine exposure during all gestational and lactation periods affects the structure of Sertoli cells by events causing intense germ cell sloughing observed in the tubular lumen and can compromise the fertility of the offspring.

Segregation of Naturally Occurring Mitochondrial DNA Variants in a Mini-Pig Model

The maternally inherited mitochondrial genome (mtDNA) is present in multimeric form within cells and harbors sequence variants (heteroplasmy). While a single mtDNA variant at high load can cause disease, naturally occurring variants likely persist at low levels across generations of healthy populations. To determine how naturally occurring variants are segregated and transmitted, we generated a mini-pig model, which originates from the same maternal ancestor. Following next-generation sequencing, we identified a series of low-level mtDNA variants in blood samples from the female founder and her daughters. Four variants, ranging from 3% to 20%, were selected for validation by high-resolution melting analysis in 12 tissues from 31 animals across three generations. All four variants were maintained in the offspring, but variant load fluctuated significantly across the generations in several tissues, with sex-specific differences in heart and liver. Moreover, variant load was persistently reduced in high-respiratory organs (heart, brain, diaphragm, and muscle), which correlated significantly with higher mtDNA copy number. However, oocytes showed increased heterogeneity in variant load, which correlated with increased mtDNA copy number during in vitro maturation. Altogether, these outcomes show that naturally occurring mtDNA variants segregate and are maintained in a tissue-specific manner across generations. This segregation likely involves the maintenance of selective mtDNA variants during organogenesis, which can be differentially regulated in oocytes and preimplantation embryos during maturation.

Maternal Smoke Exposure Impairs the Long-Term Fertility of Female Offspring in a Murine Model

The theory of fetal origins of adult disease was first proposed in 1989, and in the decades since, a wide range of other diseases from obesity to asthma have been found to originate in early development. Because mammalian oocyte development begins in fetal life it has been suggested that environmental and lifestyle factors of the mother could directly impact the fertility of subsequent generations. Cigarette smoke is a known ovotoxicant in active smokers, yet disturbingly 13% of Australian and 12% of US women continue to smoke throughout pregnancy. The focus of our investigation was to characterize the adverse effects of smoking on ovary and oocyte quality in female offspring exposed in utero. Pregnant mice were nasally exposed to cigarette smoke for 12 wk throughout pregnancy/lactation, and ovary and oocyte quality of the F1 (maternal smoke exposed) generation was examined. Neonatal ovaries displayed abnormal somatic cell proliferation and increased apoptosis, leading to a reduction in follicle numbers. Further investigation found that altered somatic cell proliferation and reduced follicle number continued into adulthood; however, apoptosis did not. This reduction in follicles resulted in decreased oocyte numbers, with these oocytes found to have elevated levels of oxidative stress, altered metaphase II spindle, and reduced sperm-egg interaction. These ovarian and oocyte changes ultimately lead to subfertility, with maternal smoke-exposed animals having smaller litters and also taking longer to conceive. In conclusion, our results demonstrate that in utero and lactational exposure to cigarette smoke can have long-lasting effects on the fertility of the next generation of females.

The hazardous effects of tobacco smoking on male fertility

The substantial harmful effects of tobacco smoking on fertility and reproduction have become apparent but are not generally appreciated. Tobacco smoke contains more than 4000 kinds of constituents, including nicotine, tar, carbonic monoxide, polycyclic aromatic hydrocarbons, and heavy metals. Because of the complexity of tobacco smoke components, the toxicological mechanism is notably complicated. Most studies have reported reduced semen quality, reproductive hormone system dysfunction and impaired spermatogenesis, sperm maturation, and spermatozoa function in smokers compared with nonsmokers. Underlying these effects, elevated oxidative stress, DNA damage, and cell apoptosis may play important roles collaboratively in the overall effect of tobacco smoking on male fertility. In this review, we strive to focus on both the phenotype of and the molecular mechanism underlying these harmful effects, although current studies regarding the mechanism remain insufficient.

Maternal passive smoking during pregnancy and age of menarche in daughters: a study of elementary and middle school students in Shanghai

The objective of this study was to estimate the prevalence and determinants of passive smoking in pregnancy and to examine its association with an earlier age of menarche in offspring. This retrospective study enrolled 751 students 8 to 20 years old in Shanghai selected by stratified cluster sampling. Data were obtained through structured self-administered questionnaires and physical examinations. It was found that daughters with maternal tobacco exposure experienced relatively earlier menarche and had shorter cycle lengths, although both findings were not statistically significant. The unadjusted odds ratio for prenatal tobacco smoke exposure on the relatively earlier onset of menarche was 1.84 (95% confidence interval = 1.05-3.22) compared with no exposure, and the associations remained statistically significant after adjusting for birth weight, birth length, maternal age of menarche, and present height and weight. In conclusion, our study provides limited evidence supporting the hypothesis that maternal passive smoking during pregnancy leads to an earlier age of menarche of daughters.

Factors in Early-Life Programming of Reproductive Fitness

Fertility rates have been declining worldwide, with a growing number of young women suffering from infertility. Infectious and inflammatory diseases are important causes of infertility, and recent evidence points to the critical role of the early-life microbial environment in developmental programming of adult reproductive fitness. Our laboratory and others have demonstrated that acute exposure to an immunological challenge early in life has a profound and prolonged impact on male and female reproductive development. This review presents evidence that perinatal exposure to immunological challenge by a bacterial endotoxin, lipopolysaccharide, acts at all levels of the hypothalamic-pituitary-gonadal axis, resulting in long-lasting changes in reproductive function, suggesting that disposition to infertility may begin early in life.