Sidestream tobacco smoke is a male germ cell mutagen

Severity of effect considerations regarding the use of mutation as a toxicological endpoint for risk assessment: A report from the 8th International Workshop on Genotoxicity Testing (IWGT)

Exposure levels without appreciable human health risk may be determined by dividing a point of departure on a dose-response curve (e.g., benchmark dose) by a composite adjustment factor (AF). An "effect severity" AF (ESAF) is employed in some regulatory contexts. An ESAF of 10 may be incorporated in the derivation of a health-based guidance value (HBGV) when a "severe" toxicological endpoint, such as teratogenicity, irreversible reproductive effects, neurotoxicity, or cancer was observed in the reference study. Although mutation data have been used historically for hazard identification, this endpoint is suitable for quantitative dose-response modeling and risk assessment. As part of the 8th International Workshops on Genotoxicity Testing, a sub-group of the Quantitative Analysis Work Group (WG) explored how the concept of effect severity could be applied to mutation. To approach this question, the WG reviewed the prevailing regulatory guidance on how an ESAF is incorporated into risk assessments, evaluated current knowledge of associations between germline or somatic mutation and severe disease risk, and mined available data on the fraction of human germline mutations expected to cause severe disease. Based on this review and given that mutations are irreversible and some cause severe human disease, in regulatory settings where an ESAF is used, a majority of the WG recommends applying an ESAF value between 2 and 10 when deriving a HBGV from mutation data. This recommendation may need to be revisited in the future if direct measurement of disease-causing mutations by error-corrected next generation sequencing clarifies selection of ESAF values.

Development and application of the Ames test using a direct-exposure module: The assessment of mutagenicity of incense and sidestream cigarette smoke

We had previously developed an improved Ames module to directly determine the mutagenicity of gaseous formaldehyde (HCHO) and toluene without liquid extraction. This study further evaluated the suitability and sensitivity of this module on whole and real polluted air samples. For this, two common brands of stick incense (A and B) and cigarettes (A and B) were harvested, and various types of incense smoke (IS) and sidestream cigarette smoke (SCS) samples were generated by lighting 3, 6, 12, 24, 30, or 36 incense sticks, and by lighting 1, 2, or 3 cigarettes, respectively, in an acrylic box. CO₂ , CO, total volatile organic compound (TVOC), PM_1.0, and HCHO concentrations in the air samples were determined, and all air samples did not partially fit the requirements of the air quality standards. The smoke samples were then directly exposed to TA100 for 10, 20, 30, or 60 min in our exposure module. Exposure to IS (brand A) for 30 to 60 min and exposure to IS (brand B) for 60 min led to statistically (p < 0.05) weak (below the twofold rule) but dose-dependent mutagenic activities either with or without metabolic activation. Furthermore, a short-term exposure (10-60 min) to SCS (brands A and B) displayed statistically significant (p < 0.05) direct-acting, indirect-acting, time- and dose-dependent mutagenic activities. Furthermore, our data also support that the liver S9 enzyme could enhance the mutagenic activities in most IS and SCS samples. This study confirmed that the modified Ames module can be applied to directly detect the mutagenic activities of real polluted air samples.

The mutagenic effect of tobacco smoke on male fertility

Despite the association between tobacco use and the harmful effects on general health as well as male fertility parameters, smoking remains globally prevalent. The main content of tobacco smoke is nicotine and its metabolite cotinine. These compounds can pass the blood-testis barrier, which subsequently causes harm of diverse degree to the germ cells. Although controversial, smoking has been shown to cause not only a decrease in sperm motility, sperm concentration, and an increase in abnormal sperm morphology, but also genetic and epigenetic aberrations in spermatozoa. Both animal and human studies have highlighted the occurrence of sperm DNA-strand breaks (fragmentation), genome instability, genetic mutations, and the presence of aneuploids in the germline of animals and men exposed to tobacco smoke. The question to be asked at this point is, if smoking has the potential to cause all these genetic aberrations, what is the extent of damage? Hence, this review aimed to provide evidence that smoking has a mutagenic effect on sperm and how this subsequently affects male fertility. Additionally, the role of tobacco smoke as an aneugen will be explored. We furthermore aim to incorporate the epidemiological aspects of the aforementioned and provide a holistic approach to the topic.

Exposure to polycyclic aromatic hydrocarbons and nicotine, and associations with sperm DNA fragmentation

Background

Tobacco smoking has been reported to cause DNA fragmentation and has been suggested to cause mutations in spermatozoa. These effects have been ascribed to the action of polycyclic aromatic hydrocarbons (PAH) present in the smoke. Simultaneously, DNA fragmentation has been associated with mutagenesis.

Objective

The aim of this study was to investigate whether levels of urinary biomarkers of PAH and nicotine exposure were associated with sperm DNA fragmentation.

Methods

In the urine of 381 men recruited from two cohorts of young men (17–21 years old) from the general Swedish population, the PAH metabolites 1‐hydroxypyrene and 2‐hydroxyphenanthrene, as well as the nicotine metabolite cotinine, were measured. The sperm DNA fragmentation index (DFI) was analysed using the sperm chromatin structure assay. Associations between the DFI, and PAH metabolite levels as continuous variables as well as in quartiles, were studied by general linear models adjusted for abstinence time. A similar analysis was carried out for cotinine levels, according to which the men were categorised as “non‐smoking” (n = 216) and “smoking” (n = 165).

Results

No association was found between levels of any of the three biomarkers and DFI, either as a continuous variable (p = 0.87–0.99), or when comparing the lowest and the highest quartiles (p = 0.11–0.61). The same was true for comparison of men categorised as non‐smoking or smoking (DFI 11.1% vs. 11.8%, p = 0.31).

Discussion

We found no evidence of PAH or nicotine exposure to be associated with DFI, which does not exclude that these exposures may have other effects on sperm DNA.

Conclusion

In these young men, levels of biomarkers of nicotine and PAH exposure were not associated with DFI.

Secondhand smoke affects reproductive functions by altering the mouse testis transcriptome, and leads to select intron retention in Pde1a

BACKGROUND

Human exposure to secondhand smoke (SHS) is known to result in adverse effects in multiple organ systems. However, the impact of SHS on the male reproductive system, particularly on the regulation of genes and molecular pathways that govern sperm production, maturation, and functions remains largely understudied.

OBJECTIVE

We investigated the effects of SHS on the testis transcriptome in a validated mouse model.

METHODS

Adult male mice were exposed to SHS (5 h/day, 5 days/week for 4 months) as compared to controls (clean air-exposed). RNA-seq analysis was performed on the testis of SHS-exposed mice and controls. Variant discovery and plink association analyses were also conducted to detect exposure-related transcript variants in SHS-treated mice.

RESULTS

Exposure of mice to SHS resulted in the aberrant expression of 131 testicular genes. Whilst approximately two thirds of the differentially expressed genes were protein-coding, the remaining (30.5%) comprised noncoding elements, mostly lncRNAs (19.1%). Variant discovery analysis identified a homozygous frameshift variant that is statistically significantly associated with SHS exposure (P = 7.744e-06) and is generated by retention of a short intron within Pde1a, a key regulator of spermatogenesis. Notably, this SHS-associated intron variant harbors an evolutionarily conserved, premature termination codon (PTC) that disrupts the open reading frame of Pde1a, presumably leading to its degradation via nonsense-mediated decay.

DISCUSSION

SHS alters the expression of genes involved in molecular pathways that are crucial for normal testis development and function. Preferential targeting of lncRNAs in the testis of SHS-exposed mice is especially significant considering their crucial role in the spatial and temporal modulation of spermatogenesis. Equally important is our discovery of a novel homozygous frameshift variant that is exclusively and significantly associated with SHS-exposure and is likely to represent a safeguard mechanism to regulate transcription of Pde1a and preserve normal testis function during harmful exposure to environmental agents.

Heritable consequences of paternal nicotine exposure: from phenomena to mechanisms†

Our understanding of the interactions between genetic and environmental factors in shaping behavioral phenotypes has expanded to include environment-induced epigenetic modifications and the intriguing possibility of their association with heritable behavioral phenotypes. The molecular basis of heritability of phenotypes arising from environment-induced epigenetic modifications is not well defined yet. However, phenomenological evidence in favor of it is accumulating rapidly. The resurgence of interest has led to focus on epigenetic modification of germ cells as a plausible mechanism of heritability. Perhaps partly because of practical reasons such as ease of access to male germ cells compared to female germ cells, attention has turned toward heritable effects of environmental influences on male founders. Public health implications of heritable effects of paternal exposures to addictive substances or to psycho-social factors may be enormous. Considering nicotine alone, over a billion people worldwide use nicotine-containing products, and the majority are men. Historically, the adverse effects of nicotine use by pregnant women received much attention by scientists and public policy experts alike. The implications of nicotine use by men for the physical and mental well-being of their children were not at the forefront of research until recently. Here, we review progress in the emerging field of heritable effects of paternal nicotine exposure and its implications for behavioral health of individuals in multiple generations.

Paternal genetic variants and risk of obstructive heart defects: A parent-of-origin approach

Previous research on risk factors for obstructive heart defects (OHDs) focused on maternal and infant genetic variants, prenatal environmental exposures, and their potential interaction effects. Less is known about the role of paternal genetic variants or environmental exposures and risk of OHDs. We examined parent-of-origin effects in transmission of alleles in the folate, homocysteine, or transsulfuration pathway genes on OHD occurrence in offspring. We used data on 569 families of liveborn infants with OHDs born between October 1997 and August 2008 from the National Birth Defects Prevention Study to conduct a family-based case-only study. Maternal, paternal, and infant DNA were genotyped using an Illumina Golden Gate custom single nucleotide polymorphism (SNP) panel. Relative risks (RR), 95% confidence interval (CI), and likelihood ratio tests from log-linear models were used to estimate the parent-of-origin effect of 877 SNPs in 60 candidate genes in the folate, homocysteine, and transsulfuration pathways on the risk of OHDs. Bonferroni correction was applied for multiple testing. We identified 3 SNPs in the transsulfuration pathway and 1 SNP in the folate pathway that were statistically significant after Bonferroni correction. Among infants who inherited paternally-derived copies of the G allele for rs6812588 in the RFC1 gene, the G allele for rs1762430 in the MGMT gene, and the A allele for rs9296695 and rs4712023 in the GSTA3 gene, RRs for OHD were 0.11 (95% CI: 0.04, 0.29, P = 9.16x10^-7), 0.30 (95% CI: 0.17, 0.53, P = 9.80x10^-6), 0.34 (95% CI: 0.20, 0.57, P = 2.28x10^-5), and 0.34 (95% CI: 0.20, 0.58, P = 3.77x10^-5), respectively, compared to infants who inherited maternally-derived copies of the same alleles. We observed statistically significant decreased risk of OHDs among infants who inherited paternal gene variants involved in folate and transsulfuration pathways.

Obstructive heart defects are birth defects that cause obstruction to the blood flow of the developing heart. Common OHDs include coarctation of the aorta, aortic stenosis and pulmonary stenosis. While there is a fair amount of literature indicating an association between maternal genetic variants and OHDs, less is known about the role of paternal genetic variants in the etiology of OHDs. We used a genotype clustering algorithm, SNPMClust, that was developed in-house at the Arkansas Center for Birth Defects Research and Prevention to study the role of paternal genetic variants in the folate, homocysteine and transsulfuration pathways. Maternal, paternal, and infant DNA specimens were collected from participants of the National Birth Defects Prevention Study, a large population-based case-control study in the United States, and were genotyped using an Illumina Golden Gate custom single nucleotide polymorphism (SNP) panel. We identified 4 SNPs in the folate and transsulfuration pathways, rs6812588, rs1762430, rs9296695, and rs4712023, that were associated with a statistically significant decreased risk of OHDs for infants who inherited a paternally-derived copy of the variant allele compared to infants who inherited a maternal copy of the variant allele. In conclusion, we observed a significantly decreased risk and less epigenetic influence of paternal genetic variants on OHDs compared to maternally-derived variants.

NRF2 loss recapitulates heritable impacts of paternal cigarette smoke exposure

Paternal cigarette smoke (CS) exposure is associated with increased risk of behavioral disorders and cancer in offspring, but the mechanism has not been identified. Here we use mouse models to investigate mechanisms and impacts of paternal CS exposure. We demonstrate that CS exposure induces sperm DNAme changes that are partially corrected within 28 days of removal from CS exposure. Additionally, paternal smoking is associated with changes in prefrontal cortex DNAme and gene expression patterns in offspring. Remarkably, the epigenetic and transcriptional effects of CS exposure that we observed in wild type mice are partially recapitulated in Nrf2-/- mice and their offspring, independent of smoking status. Nrf2 is a central regulator of antioxidant gene transcription, and mice lacking Nrf2 consequently display elevated oxidative stress, suggesting that oxidative stress may underlie CS-induced heritable epigenetic changes. Importantly, paternal sperm DNAme changes do not overlap with DNAme changes measured in offspring prefrontal cortex, indicating that the observed DNAme changes in sperm are not directly inherited. Additionally, the changes in sperm DNAme associated with CS exposure were not observed in sperm of unexposed offspring, suggesting the effects are likely not maintained across multiple generations.

Effects of nicotine on porcine pre-pupertal sertoli cells: An in vitro study

Smoke components, such as nicotine and its major metabolites, cross the blood-testis barrier and are detectable in the seminal plasma of both active smokers and individuals exposed to cigarette smoke. In vivo studies in a rat model have further demonstrated that nicotine exposure reduces the weight of the testis, as well as the number of spermatocytes and spermatids, and affects the ultrastructure of Sertoli cells (SC) - which serve as sentinels of spermatogenesis - causing intense germ cell sloughing in the tubular lumen that compromises offspring fertility. This study sought to determine the effects of nicotine on the viability and function of purified pig pre-pubertal SC. Nicotine exposure reduced the mRNA expression and protein levels of anti-Mullerian hormone (AMH) and inhibin B and impaired FSH-r sensitivity via the downregulation of FSH-r and aromatase gene expression compared to untreated SC. Overall, our study suggests that nicotine can significantly alter extracellular matrix and tight junction protein gene expression (e.g., laminin, integrin, and occludin), thus compromising cross-talk between the interstitial and tubular compartments and enhancing blood-testis barrier (BTB) permeability via downregulation of the mitogen-activated protein kinase (MAPK) pathway. These findings further elucidate a potential mechanism of action underlying nicotine exposure's detrimental effects on SC function in vivo.

A Return to the Origin of the EMGS: Rejuvenating the Quest for Human Germ Cell Mutagens and Determining the Risk to Future Generations

Fifty years ago, the Environmental Mutagen Society (now Environmental Mutagenesis and Genomics Society) was founded with a laser-focus on germ cell mutagenesis and the protection of "our most vital assets"-the sperm and egg genomes. Yet, five decades on, despite the fact that many agents have been demonstrated to induce inherited changes in the offspring of exposed laboratory rodents, there is no consensus on whether human germ cell mutagens exist. We argue that it is time to reevaluate the available data and conclude that we already have evidence for the existence of environmental exposures that impact human germ cells. What is missing are definite data to demonstrate a significant increase in de novo mutations in the offspring of exposed parents. We believe that with over two decades of research advancing knowledge and technologies in genomics, we are at the cusp of generating data to conclusively show that environmental exposures cause heritable de novo changes in the human offspring. We call on the research community to harness our technologies, synergize our efforts, and return to our Founders' original focus. The next 50 years must involve collaborative work between clinicians, epidemiologists, genetic toxicologists, genomics experts and bioinformaticians to precisely define how environmental exposures impact germ cell genomes. It is time for the research and regulatory communities to prepare to interpret the coming outpouring of data and develop a framework for managing, communicating and mitigating the risk of exposure to human germ cell mutagens. Environ. Mol. Mutagen. 61:42-54, 2020. © 2019 Her Majesty the Queen in Right of Canada.

Deterioration of semen quality and sperm-DNA integrity as influenced by cigarette smoking in fertile and infertile human male smokers-A prospective study

In modernized lifestyle smoking is one of the trendy, psychological, and socioeconomic scenarios of young adolescents mainly in the age of the reproductive stage. Based on a number of cigarettes smoked, age, and duration of the smoke, the study aims to search for the profound effects of smoking and its impact on semen parameters, sperm-DNA integrity, and fragmentation of sperm DNA with cotinine and apoptotic caspase-3 marker in the seminal plasma of fertile and infertile smokers. To determine oxidative damage by 8-hydroxy deoxyguanosine (8-OHdG) from isolated sperm DNA (steps: reactive oxygen species washing by nitro blue tetrazolium (NBT), sperm lysis, salt digestion, ethanol washing, and finally with high-performance liquid chromatography analysis). Level of DNA fragmentation (percentage) in native and intact DNA, the activity of caspase-3 in infertile smokers will be compared with the control group of nonsmokers. Also, the sperm viability was visualized by eosin-nigrosin and aniline blue staining. Cotinine is one of the best markers of smoking. The cotinine level (2224.24 ± 1.19 *** ng/mL), when abundant it negative correlates with morphology and rapid motility in infertile smokers than nonsmokers. Gel preprogram measured the sperm integrity and was found to be less in smokers than nonsmokers. The spermatic oxidative marker 8-OHdG was high and gave an R ² value of 0.9104 with morphology and 0.9007 for rapid motility of infertile sperm, respectively. Infertile smoking subjects (<10 cigarettes/day) had significant changes increase in sperm fragmentation, caspase-3, and cotinine while negative impact with motility, morphology, and pH of semen compared with fertile, infertile nonsmoking subjects.

Antioxidant and anti-apoptotic effects of royal jelly against nicotine-induced testicular injury in mice

This study describes the effects of royal jelly (RJ) on testicular injury induced by nicotine (NIC) in mice. Thirty-six male BALB/c mice were randomly divided into six groups (n = 6). Group 1 received normal saline, group 2 received 100 mg/kgBW/day RJ, groups 3 and 4 received NIC at doses of 0.50 and 1.00 mg/kgBW/day, respectively, and groups 5 and 6 received NIC at doses of 0.50 and 1.00 mg/kg BW/day, respectively, plus RJ. Following 35 days, the serum level of testosterone, histopathological changes, germ cell apoptosis, proliferating cell nuclear antigen (PCNA), malondialdehyde (MDA) content, and antioxidant indexes including total antioxidant capacity (TAC) and catalase (CAT) activity were determined. In addition, the mitochondria-dependent apoptosis was investigated by assessing the Bcl-2, p53, and Caspase-3 mRNA levels expression by reverse transcription-PCR (RT-PCR). Compared to NIC receiving groups, the concomitant administration of RJ could protect the testosterone reduction and histological damages. After RJ treatment, the level of tissue MDA content decreased, while tissue TAC and CAT levels were remarkably increased compared to NIC-exposed groups. Remarkable higher TUNEL-positive germ cells and low PCNA index were observed in NIC receiving groups. Besides, the expression level of Bcl-2 was significantly higher and the p53 and Caspase-3 levels were significantly lower in the RJ co-administration groups than NIC-only receiving groups. Our results confirmed that RJ effectively protects the testis against NIC evoked damages by antioxidant and anti-apoptotic effects involving the up regulation of the antioxidant status, mitochondria-dependent apoptosis pathway prevention, and the proliferating activity improvement.

Accelerated rates of large-scale mutations in the presence of copper and nickel

Mutation rate variation has been under intense investigation for decades. Despite these efforts, little is known about the extent to which environmental stressors accelerate mutation rates and influence the genetic load of populations. Moreover, most studies on stressors have focused on unicellular organisms and point mutations rather than large-scale deletions and duplications (copy number variations [CNVs]). We estimated mutation rates in Daphnia pulex exposed to low levels of environmental stressors as well as the effect of selection on de novo mutations. We conducted a mutation accumulation (MA) experiment in which selection was minimized, coupled with an experiment in which a population was propagated under competitive conditions in a benign environment. After an average of 103 generations of MA propagation, we sequenced 60 genomes and found significantly accelerated rates of deletions and duplications in MA lines exposed to ecologically relevant concentrations of metals. Whereas control lines had gene deletion and duplication rates comparable to other multicellular eukaryotes (1.8 × 10-6 per gene per generation), the presence of nickel and copper increased these rates fourfold. The realized mutation rate under selection was reduced to 0.4× that of control MA lines, providing evidence that CNVs contribute to mutational load. Our CNV breakpoint analysis revealed that nonhomologous recombination associated with regions of DNA fragility is the primary source of CNVs, plausibly linking metal-induced DNA strand breaks with higher CNV rates. Our findings suggest that environmental stress, in particular multiple stressors, can have profound effects on large-scale mutation rates and mutational load of multicellular organisms.

Dose-response mutation and spectrum analyses reveal similar responses at two microsatellite loci in benzo(a)pyrene-exposed mouse spermatogonia

Identifying chemical exposures that can cause germline mutations is important as these mutations can be inherited, impacting both individual and population health. However, germline mutations are extremely rare and difficult to detect. Chemically induced germline mutations can be detected through analysis of highly unstable tandem repeat DNA. We recently developed a single-molecule PCR (SM-PCR) approach to quantify mutations at a mouse microsatellite locus (Mm2.2.1) in sperm for such purposes. In this study, we refine this approach through the combined analysis of mouse microsatellites Mm2.2.1 and Mm19.2.3. Mice were exposed to 0, 25, 50 or 100 mg/kg/day benzo(a)pyrene (BaP) by oral gavage for 28 days and sperm sampled 42 days after the end of exposure to measure effects on dividing spermatogonia. DNA was diluted to a single genome per PCR well for amplification of microsatellites in singleplex and multiplex reactions, and alleles were sized to identify mutations using capillary electrophoresis. Analysis of ~300-500 molecules per animal at both microsatellite loci, when tested individually, showed a ~2-fold increase in mutations relative to the controls at both the 50 and 100 mg/kg/day BaP doses. Multiplex SM-PCR revealed similar increases in mutation frequencies in both microsatellites. Comparison with results from a previous lacZ mutation assay conducted on the same mice revealed that although microsatellite mutations are a sensitive endpoint for detecting changes in mutation frequencies at lower doses, they appear to be saturable and thus have a reduced dynamic range. These results confirm that BaP is a male germ cell mutagen that broadly impacts tandem repeat DNA. Likewise, addition of a second hypervariable microsatellite increases the sensitivity of this assay.

Father's environment before conception and asthma risk in his children: a multi-generation analysis of the Respiratory Health In Northern Europe study

Background

Whereas it is generally accepted that maternal environment plays a key role in child health, emerging evidence suggests that paternal environment before conception also impacts child health. We aimed to investigate the association between children's asthma risk and parental smoking and welding exposures prior to conception.

Methods

In a longitudinal, multi-country study, parents of 24 168 offspring aged 2-51 years provided information on their life-course smoking habits, occupational exposure to welding and metal fumes, and offspring's asthma before/after age 10 years and hay fever. Logistic regressions investigated the relevant associations controlled for age, study centre, parental characteristics (age, asthma, education) and clustering by family.

Results

Non-allergic early-onset asthma (asthma without hay fever, present in 5.8%) was more common in the offspring with fathers who smoked before conception {odds ratio [OR] = 1.68 [95% confidence interval (CI) = 1.18-2.41]}, whereas mothers' smoking before conception did not predict offspring asthma. The risk was highest if father started smoking before age 15 years [3.24 (1.67-6.27)], even if he stopped more than 5 years before conception [2.68 (1.17-6.13)]. Fathers' pre-conception welding was independently associated with non-allergic asthma in his offspring [1.80 (1.29-2.50)]. There was no effect if the father started welding or smoking after birth. The associations were consistent across countries.

Conclusions

Environmental exposures in young men appear to influence the respiratory health of their offspring born many years later. Influences during susceptible stages of spermatocyte development might be important and needs further investigation in humans. We hypothesize that protecting young men from harmful exposures may lead to improved respiratory health in future generations.

Smoking habit from the paternal line and grand-child's overweight or obesity status in early childhood: prospective findings from the lifeways cross-generation cohort study

BACKGROUND/OBJECTIVES

The role of smoking from the paternal line during the pre-conception period on grand-child's overweight/obesity and associated underlying pathways are uncertain. We examined whether the smoking status from the paternal line was associated with the grand-child's higher weight at birth, and overweight or obesity at 5 and 9 years of age. The grandparental smoking effect from the maternal line was also explored.

SUBJECTS/METHODS

Participants were fathers and grandparents and grand-children from the Lifeways Cross Generational Cohort (N = 1021 for the analysis at birth; N = 562 and N = 284 for the analysis at 5 and 9 years, respectively). Paternal and grandparental smoking was defined as smoking versus non-smoking. Children's weight categories compared were high versus normal weight at birth, and overweight/obesity versus normal weight (based on BMI and waist circumference) at age of five and nine years. Logistic regression models were used to estimate the crude and adjusted associations.

RESULTS

After adjustment for several child and parental factors, at age five there was an association between paternal smoking and offspring's overweight/obesity based on BMI (Adjusted Odds Ratio (AOR), and 95%CI: 1.76, 1.14-2.71, p-value: 0.010), most marked for boys (AOR: 2.05, 1.06-3.96, p-value: 0.032). These associations remained when confined to the children sample with biological fathers only (overall sample, AOR: 1.92, 1.22-3.02, p-value: 0.005; son, AOR: 2.09, 1.06-4.11, p-value: 0.033). At age 9, the paternal grandmothers' smoking was positively associated with their grandchild's overweight/obesity status based on waist circumference (AOR: 3.29, 1.29-8.37), and especially with that of her granddaughter (AOR: 3.44, 1.11-10.69). These associations remained when analysing only the children sample with biological fathers (overall sample, AOR: 3.22,1.25-8.29, p-value: 0.016; granddaughter, AOR: 3.55, 1.13-11.15, p-value: 0.030).

CONCLUSION

The smoking habit from the paternal line is associated with grand-children's adiposity measures during their early childhood, which might be epigenetically transmitted through male-germline cells.

A parent-of-origin analysis of paternal genetic variants and increased risk of conotruncal heart defects

The association between conotruncal heart defects (CTHDs) and maternal genetic and environmental exposures is well studied. However, little is known about paternal genetic or environmental exposures and risk of CTHDs. We assessed the effect of paternal genetic variants in the folate, homocysteine, and transsulfuration pathways on risk of CTHDs in offspring. We utilized National Birth Defects Prevention Study data to conduct a family-based case only study using 616 live-born infants with CTHDs, born October 1997-August 2008. Maternal, paternal and infant DNA was genotyped using an Illumina® Golden Gate custom single nucleotide polymorphism (SNP) panel. Relative risks (RR) and 95% confidence intervals (CI) from log-linear models determined parent of origin effects for 921 SNPs in 60 candidate genes involved in the folate, homocysteine, and transsulfuration pathways on risk of CTHDs. The risk of CTHD among children who inherited a paternally derived copy of the A allele on GLRX (rs17085159) or the T allele of GLRX (rs12109442) was 0.23 (95%CI: 0.12, 0.42; p = 1.09 × 10^-6 ) and 0.27 (95%CI: 0.14, 0.50; p = 2.06 × 10^-5 ) times the risk among children who inherited a maternal copy of the same allele. The paternally inherited copy of the GSR (rs7818511) A allele had a 0.31 (95%CI: 0.18, 0.53; p = 9.94 × 10^-6 ] risk of CTHD compared to children with the maternal copy of the same allele. The risk of CTHD is less influenced by variants in paternal genes involved in the folate, homocysteine, or transsulfuration pathways than variants in maternal genes in those pathways.

Cigarette smoking significantly alters sperm DNA methylation patterns

Numerous health consequences of tobacco smoke exposure have been characterized, and the effects of smoking on traditional measures of male fertility are well described. However, a growing body of data indicates that pre-conception paternal smoking also confers increased risk for a number of morbidities on offspring. The mechanism for this increased risk has not been elucidated, but it is likely mediated, at least in part, through epigenetic modifications transmitted through spermatozoa. In this study, we investigated the impact of cigarette smoke exposure on sperm DNA methylation patterns in 78 men who smoke and 78 never-smokers using the Infinium Human Methylation 450 beadchip. We investigated two models of DNA methylation alterations: (i) consistently altered methylation at specific CpGs or within specific genomic regions and (ii) stochastic DNA methylation alterations manifest as increased variability in genome-wide methylation patterns in men who smoke. We identified 141 significantly differentially methylated CpGs associated with smoking. In addition, we identified a trend toward increased variance in methylation patterns genome-wide in sperm DNA from men who smoke compared with never-smokers. These findings of widespread DNA methylation alterations are consistent with the broad range of offspring heath disparities associated with pre-conception paternal smoke exposure and warrant further investigation to identify the specific mechanism by which sperm DNA methylation perturbation confers risk to offspring health and whether these changes can be transmitted to offspring and transgenerationally.

Paternal programming of offspring cardiometabolic diseases in later life

Early - intrauterine - environmental factors are linked to the development of cardiovascular disease in later life. Traditionally, these factors are considered to be maternal factors such as maternal under and overnutrition, exposure to toxins, lack of micronutrients, and stress during pregnancy. However, in the recent years, it became obvious that also paternal environmental factors before conception and during sperm development determine the health of the offspring in later life. We will first describe clinical observational studies providing evidence for paternal programming of adulthood diseases in progeny. Next, we describe key animal studies proving this relationship, followed by a detailed analysis of our current understanding of the underlying molecular mechanisms of paternal programming. Alterations of noncoding sperm micro-RNAs, histone acetylation, and targeted as well as global DNA methylation seem to be in particular involved in paternal programming of offspring's diseases in later life.

From sperm to offspring: Assessing the heritable genetic consequences of paternal smoking and potential public health impacts

Individuals who smoke generally do so with the knowledge of potential consequences to their own health. What is rarely considered are the effects of smoking on their future children. The objective of this work was to review the scientific literature on the effects of paternal smoking on sperm and assess the consequences to offspring. A literature search identified over 200 studies with relevant data in humans and animal models. The available data were reviewed to assess the weight of evidence that tobacco smoke is a human germ cell mutagen and estimate effect sizes. These results were used to model the potential increase in genetic disease burden in offspring caused by paternal smoking, with specific focus on aneuploid syndromes and intellectual disability, and the socioeconomic impacts of such an effect. The review revealed strong evidence that tobacco smoking is associated with impaired male fertility, and increases in DNA damage, aneuploidies, and mutations in sperm. Studies support that these effects are heritable and adversely impact the offspring. Our model estimates that, with even a modest 25% increase in sperm mutation frequency caused by smoke-exposure, for each generation across the global population there will be millions of smoking-induced de novo mutations transmitted from fathers to offspring. Furthermore, paternal smoking is estimated to contribute to 1.3 million extra cases of aneuploid pregnancies per generation. Thus, the available evidence makes a compelling case that tobacco smoke is a human germ cell mutagen with serious public health and socio-economic implications. Increased public education should be encouraged to promote abstinence from smoking, well in advance of reproduction, to minimize the transmission of harmful mutations to the next-generation.

Evaluation of in vivo mutagenesis for assessing the health risk of air pollutants

Various kind of chemical substances, including man-made chemical products and unintended products, are emitted to ambient air. Some of these substances have been shown to be mutagenic and therefore to act as a carcinogen in humans. National pollutant inventories (e.g., Pollutant Release and Transfer Registration in Japan) have estimated release amounts of man-made chemical products, but a major concern is the release of suspended particulate matter containing potent mutagens, for example, polycyclic aromatic hydrocarbons and related compounds generated by the combustion of fossil fuel, which are not estimated by PRTR system. In situ exposure studies have revealed that DNA adducts in the lung, and possibly mutations in germline cells are induced in rodents by inhalation of ambient air, indicating that evaluating in vivo mutations is important for assessing environmental health risks. Transgenic rodent systems (Muta, Big Blue, and gpt delta) are good tools for analyzing in vivo mutations induced by a mixture of chemical substances present in the environment. Following inhalation of diesel exhaust (used as a model mixture), mutation frequency was increased in the lung of gpt delta mice and base substitutions were induced at specific guanine residues (mutation hotspots) on the target transgenes. Mutation hotspots induced by diesel exhaust were different from those induced by benzo[a]pyrene, a typical mutagen in ambient air, but nearly identical to those induced by 1,6-dinitropyrene contained in diesel exhaust. Comparison between mutation hotspots in the TP53 (p53) gene in human lung cancer (data extracted from the IARC TP53 database) and mutations we identified in gpt delta mice showed that G to A transitions centered in CGT and CGG trinucleotides were mutation hotspots on both TP53 genes in human lung cancers and gpt genes in transgenic mice that inhaled diesel exhaust. The carcinogenic potency (TD50 value) of genotoxic carcinogen was shown to be correlated with the in vivo mutagenicity (total dose per increased mutant frequency). These results suggest that the mutations identified in transgenic rodents can help identify environmental mutagens that cause cancer.

The relationship between husbands' health belief and environment tobacco smoke exposure among their pregnant wife

OBJECTIVE

The aim of the present study was to evaluate the relationship between health belief structures of men and environment tobacco smoke (ETS) exposure among pregnant women.

METHODS

This cross-sectional research was conducted on 120 smoking men who had pregnant wives. Data were gathered through a questionnaire that measured health belief structures related to pregnant women's exposure to cigarette's smoke including perceived susceptibility/severity, benefits, barriers and self-efficacy. Number of exposures to cigarette's smoke was defined by the number of smoked cigarettes in the presence of the pregnant wife.

RESULTS

The number of smoked cigarettes in the presence of pregnant wife had a negative relation with perceived susceptibility/severity and perceived benefits and a positive relation with perceived barriers. The number of smoked cigarettes in men had no relation with health belief constructs. Using multiple regression test showed the perceived barrier for not smoking was the strongest factor in men to anticipate the level of women's ETS exposure.

CONCLUSIONS

Results of this study showed that the level of ETS exposure among pregnant women was dependent on men's health beliefs about the ETS exposure treats among pregnant women.

Evaluating the Influence of Side Stream Cigarette Smoke at an Early Stage of Non-Alcoholic Steatohepatitis Progression in Mice

Side stream cigarette smoke (SSCS) is known to be as harmful and hazardous to human health as is active smoking. In this study, we investigated the relationship between the exposure to SSCS and its stimulatory and subacute effects on the progression of non-alcoholic steatohepatitis (NASH). A methionine and choline-deficient plus high fat (MCDHF) diet was administered to C57BL/6 mice for 6 weeks. During the first three weeks of MCDHF diet feeding, each diet group was exposed to SSCS (0, 20, 40 μg/L) or fresh air for 2 hrs per day and 5 days per week. Additional experiments were performed by increasing the concentration (0, 30, 60 μg/L) and exposure time (6 hours per day) of SSCS. According to histopathologic analysis and serum levels of Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST), there were no differences in hepatic fat deposition, fibrosis, apoptosis or liver damage in MCDHF-fed mice based on SSCS exposure. There were also no differences in the expression of inflammation-, oxidative stress- or fibrosis-related genes between MCDHF-fed mice with or without SSCS exposure. Therefore, it is concluded that SSCS with current exposure amounts does not have additive detrimental effects on the early stage of NASH.

Zygotic chromosomal structural aberrations after paternal drug treatment

In recent years, the field of male-mediated reproductive toxicology has received growing attention. It is now well-established that many drugs, chemicals, and environmental factors can harm male germ cells by inducing DNA damage. Male germ cells have extensive repair mechanisms that allow detection and repair of damaged DNA during the early phases of spermatogenesis. However, during the later phase of spermiogenesis, when the haploid spermatids undergo chromatin condensation and become transcriptionally quiescent, their ability to repair damaged DNA is lost. [1] ,[2] It is also thought that the highly compacted chromatin of the sperm can protect DNA against damage. [3] Therefore, it is expected that late spermatids will be most susceptible to DNA damaging agents. Unrepaired or misrepaired damage in the germ cells leads to the generation of spermatozoa with DNA damage that can be transmitted to the next generation. Fortunately, the maternal DNA repair machinery is capable of recognizing and repairing, at least to some degree, damaged paternal DNA after fertilization in the zygote. Therefore, the efficiency of the maternal repair machinery will greatly influence the risk of transmitting paternal DNA damage to offspring. [4].

Interaction of exposure concentration and duration in determining the apoptosis of testis in rats after cigarette smoke inhalation

The effects of differences in smoke concentration and exposure duration in Sprague Dawley rats to determine variation in type and severity of the testis apoptosis were evaluated. The daily dosages were 10, 20 and 30 non-filter cigarettes for a period of 2, 4, 6, 8 and 12 weeks. Mainstream smoke exposure suppressed body weight gain in all regimens. A dose-related increase in plasma nicotine concentration was observed in smoke-exposed groups for 4, 6, 8 and 12 week regimens. Histopathological examination of the exposed groups showed disturbances in the stages of spermatogenesis, tubules atrophying and these appeared to be dose-related. Cytoplasmic caspase-3 immunostaining was detected both in Sertoli cells and germ cells in smoke-exposure groups. An increase in TUNEL-positive cells of testicular cells was observed after 6 weeks of cigarette exposure. The results indicate that cigarette exposure concentration and duration have interaction effect to induce apoptosis in the rat testes.

Development of the adverse outcome pathway "alkylation of DNA in male premeiotic germ cells leading to heritable mutations" using the OECD's users' handbook supplement

The Organisation for Economic Cooperation and Development's (OECD) Adverse Outcome Pathway (AOP) programme aims to develop a knowledgebase of all known pathways of toxicity that lead to adverse effects in humans and ecosystems. A Users' Handbook was recently released to provide supplementary guidance on AOP development. This article describes one AOP-alkylation of DNA in male premeiotic germ cells leading to heritable mutations. This outcome is an important regulatory endpoint. The AOP describes the biological plausibility and empirical evidence supporting that compounds capable of alkylating DNA cause germ cell mutations and subsequent mutations in the offspring of exposed males. Alkyl adducts are subject to DNA repair; however, at high doses the repair machinery becomes saturated. Lack of repair leads to replication of alkylated DNA and ensuing mutations in male premeiotic germ cells. Mutations that do not impair spermatogenesis persist and eventually are present in mature sperm. Thus, the mutations are transmitted to the offspring. Although there are some gaps in empirical support and evidence for essentiality of the key events for certain aspects of this AOP, the overall AOP is generally accepted as dogma and applies broadly to any species that produces sperm. The AOP was developed and used in an iterative process to test and refine the Users' Handbook, and is one of the first publicly available AOPs. It is our hope that this AOP will be leveraged to develop other AOPs in this field to advance method development, computational models to predict germ cell effects, and integrated testing strategies.

Deteriorating effect on bone metabolism and microstructure by passive cigarette smoking through dual actions on osteoblast and osteoclast

There is no clear evidence to show the direct causal relationship between passive cigarette smoking and osteoporosis. Furthermore, the underlying mechanism is unknown. The objective of this study is to demonstrate the effects of long-term passive cigarette smoking on bone metabolism and microstructure by a mouse model and cell culture systems. BALB/c mice were exposed to 2 or 4 % cigarette smoke for 14 weeks. The bone turnover biochemical markers in urine and serum and also the bone micro-architecture by micro-CT were compared with the control group exposed to normal ambient air. In the cell culture experiments, mouse MC3T3-E1 and RAW264.7 cell lines to be employed as osteoblast and osteoclast, respectively, were treated with the sera obtained from 4 % smoking or control mice. Their actions on cell viability, differentiation, and function on these bone cells were assessed. The urinary mineral and deoxypyridinoline (DPD) levels, and also the serum alkaline phosphatase activity, were significantly higher in the 4 % smoking group when compared with the control group, indicating an elevated bone metabolism after cigarette smoking. In addition, femoral osteopenic condition was observed in the 4 % smoking group, as shown by the decrease of relative bone volume and trabecular thickness. In isolated cell studies, osteoblast differentiation and bone formation were inhibited while osteoclast differentiation was increased. The current mouse smoking model and the isolated cell studies demonstrate that passive cigarette smoke could induce osteopenia by exerting a direct detrimental effect on bone cells differentiation and further on bone remodeling process.

Analysis of the effects of cigarette smoke on staphylococcal virulence phenotypes

Cigarette smoking is the leading preventable cause of death, disease, and disability worldwide. It is well established that cigarette smoke provokes inflammatory activation and impairs antimicrobial functions of human immune cells. Here we explore whether cigarette smoke likewise affects the virulence properties of an important human pathogen, Staphylococcus aureus, and in particular methicillin-resistant S. aureus (MRSA), one of the leading causes of invasive bacterial infections. MRSA colonizes the nasopharynx and is thus exposed to inhalants, including cigarette smoke. MRSA exposed to cigarette smoke extract (CSE-MRSA) was more resistant to macrophage killing (4-fold higher survival; P < 0.0001). CSE-MRSA demonstrated reduced susceptibility to cell lysis (1.78-fold; P = 0.032) and antimicrobial peptide (AMP) (LL-37) killing (MIC, 8 μM versus 4 μM). CSE modified the surface charge of MRSA in a dose-dependent fashion, impairing the binding of particles with charge similar to that of AMPs by 90% (P < 0.0001). These changes persisted for 24 h postexposure, suggesting heritable modifications. CSE exposure increased hydrophobicity by 55% (P < 0.0001), which complemented findings of increased MRSA adherence and invasion of epithelial cells. CSE induced upregulation of mprF, consistent with increased MRSA AMP resistance. S. aureus without mprF had no change in surface charge upon exposure to CSE. In vivo, CSE-MRSA pneumonia induced higher mouse mortality (40% versus 10%) and increased bacterial burden at 8 and 20 h postinfection compared to control MRSA-infected mice (P < 0.01). We conclude that cigarette smoke-induced immune resistance phenotypes in MRSA may be an additional factor contributing to susceptibility to infectious disease in cigarette smokers.

Single-molecule PCR analysis of an unstable microsatellite for detecting mutations in sperm of mice exposed to chemical mutagens

Single-molecule PCR (SM-PCR) analysis of long and repetitive DNA sequences, known as expanded simple tandem repeats (ESTRs), has been the most efficient method for studying germline mutation induction in endogenous sequences to date. However, the long length of these sequences makes mutation detection imprecise and laborious, and they have been characterized only in mice. Here, we explore the use of unstable microsatellite sequences that can be typed with high precision by capillary electrophoresis as alternative loci for detecting germline mutations. We screened 24 microsatellite loci across inbred mouse strains and identified Mm2.2.1 as the most polymorphic microsatellite locus. We then optimized SM-PCR of Mm2.2.1 to detect mutations in sperm. SM-PCR analysis of sperm from untreated B6C3F1 and Muta(™)Mouse samples revealed mutation frequencies that are consistent with rates derived from family pedigree analysis (∼ 5 × 10(-3)). To determine whether this locus can be used to detect chemically induced germline mutations, Muta(™)Mouse males were exposed by oral gavage to a single dose of 100mg/kg of N-ethyl-N-nitrosourea (ENU) or to 100mg/kg of benzo(a)pyrene (BaP) for 28 days alongside vehicle treated controls. Sperm were collected 10 weeks post-ENU exposure to sample sperm exposed as spermatogonial stem cells and 6 weeks post-BaP exposure to sample sperm that were dividing spermatogonia when the exposure was terminated. Both treatments resulted in a significant (approximately 2-fold) increase in mutation frequency in sperm compared to the control animals. The work establishes the utility of this microsatellite for studying mutation induction in the germ cells of mice. Because microsatellites are found in virtually every species, this approach holds promise for other organisms, including humans.

Approaches for identifying germ cell mutagens: Report of the 2013 IWGT workshop on germ cell assays(☆)

This workshop reviewed the current science to inform and recommend the best evidence-based approaches on the use of germ cell genotoxicity tests. The workshop questions and key outcomes were as follows. (1) Do genotoxicity and mutagenicity assays in somatic cells predict germ cell effects? Limited data suggest that somatic cell tests detect most germ cell mutagens, but there are strong concerns that dictate caution in drawing conclusions. (2) Should germ cell tests be done, and when? If there is evidence that a chemical or its metabolite(s) will not reach target germ cells or gonadal tissue, it is not necessary to conduct germ cell tests, notwithstanding somatic outcomes. However, it was recommended that negative somatic cell mutagens with clear evidence for gonadal exposure and evidence of toxicity in germ cells could be considered for germ cell mutagenicity testing. For somatic mutagens that are known to reach the gonadal compartments and expose germ cells, the chemical could be assumed to be a germ cell mutagen without further testing. Nevertheless, germ cell mutagenicity testing would be needed for quantitative risk assessment. (3) What new assays should be implemented and how? There is an immediate need for research on the application of whole genome sequencing in heritable mutation analysis in humans and animals, and integration of germ cell assays with somatic cell genotoxicity tests. Focus should be on environmental exposures that can cause de novo mutations, particularly newly recognized types of genomic changes. Mutational events, which may occur by exposure of germ cells during embryonic development, should also be investigated. Finally, where there are indications of germ cell toxicity in repeat dose or reproductive toxicology tests, consideration should be given to leveraging those studies to inform of possible germ cell genotoxicity.

Detection of in vivo DNA damage induced by very low doses of mainstream and sidestream smoke extracts using a novel assay

BACKGROUND

Mainstream (MS) smoke, the main smoke inhaled by active smokers, and sidestream (SS) smoke, the main component of secondhand smoke, induce a wide range of DNA lesions. Owing to technical limitations, the in vivo levels of tobacco-induced DNA damage are unknown. Recently, the authors developed a highly sensitive primer-anchored DNA damage detection assay (PADDA) to quantify endogenous and induced DNA damage.

PURPOSE

To quantify the in vivo levels of DNA damage induced by MS and SS smoke extracts in human cells using PADDA and define the strand-specific patterns of DNA damage and repair following exposure to diverse doses of MS and SS smoke.

METHODS

Human epithelial cells were exposed to escalating doses of hydrogen peroxide (H2O2), MS, or SS smoke. TP53 gene DNA damage was quantified using PADDA at various time points. DNA double-strand breaks were detected by immunofluorescence analysis of phosphorylated histone H2AX (γ-H2AX). Cell viability was determined by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Data were collected and analyzed by t-test in 2012-2014.

RESULTS

A dose-dependent increase in DNA damage was detected in vivo with increasing doses of H2O2, MS, and SS smoke. Even 1 hour of exposure to very low doses of MS or SS smoke resulted in significant DNA damage (p<0.01). MS and SS smoke induced distinctive strand-specific patterns of DNA damage and DNA repair kinetics.

CONCLUSIONS

Very low concentrations of MS and SS smoke induce significant DNA damage in human cells. Application of PADDA to population studies has major potential to establish biomarkers of susceptibility to tobacco-induced diseases.

Simultaneous vitality and DNA-fragmentation measurement in spermatozoa of smokers and non-smokers

BACKGROUND

Because cigarette smoke is a powerful ROS producer, we hypothesized that the spermatozoa of smokers would be more at risk of having increased DNA fragmentation than spermatozoa of non-smoking men.

METHODS

A cross-sectional study was performed on consenting smokers and non-smokers, consulting in an infertility clinic for routine sperm analysis. The application of a novel TUNEL assay coupled to a vitality marker, LIVE/DEAD®, allowed both DNA fragmentation and viability measurement within spermatozoa of participants to be analyzed by flow cytometry.

RESULTS

The coupled vitality-DNA fragmentation analysis revealed that non-smokers and smokers, respectively presented medians of 3.6% [0.6-36.8] and 3.3% [0.9-9.6] DNA fragmented spermatozoa among the living spermatozoa population (P > 0.05).

CONCLUSION

No deleterious effect of smoking on spermatozoa was found in our study. More studies concerning potential mutagenic capacities of cigarette smoke on spermatozoa are necessary. In addition, the coupled vitality-DNA fragmentation analysis may orient Assisted Reproductive Technology teams when confronted with patients having a high percentage of DNA-fragmented living spermatozoa.

Transgenic rodent assay for quantifying male germ cell mutant frequency

De novo mutations arise mostly in the male germline and may contribute to adverse health outcomes in subsequent generations. Traditional methods for assessing the induction of germ cell mutations require the use of large numbers of animals, making them impractical. As such, germ cell mutagenicity is rarely assessed during chemical testing and risk assessment. Herein, we describe an in vivo male germ cell mutation assay using a transgenic rodent model that is based on a recently approved Organisation for Economic Co-operation and Development (OECD) test guideline. This method uses an in vitro positive selection assay to measure in vivo mutations induced in a transgenic λgt10 vector bearing a reporter gene directly in the germ cells of exposed males. We further describe how the detection of mutations in the transgene recovered from germ cells can be used to characterize the stage-specific sensitivity of the various spermatogenic cell types to mutagen exposure by controlling three experimental parameters: the duration of exposure (administration time), the time between exposure and sample collection (sampling time), and the cell population collected for analysis. Because a large number of germ cells can be assayed from a single male, this method has superior sensitivity compared with traditional methods, requires fewer animals and therefore much less time and resources.

Early-life exposure to benzo[a]pyrene increases mutant frequency in spermatogenic cells in adulthood

Children are vulnerable to environmental mutagens, and the developing germline could also be affected. However, little is known about whether exposure to environmental mutagens in childhood will result in increased germline mutations in subsequent adult life. In the present study, male transgenic lacI mice at different ages (7, 25 and 60 days old) were treated with a known environmental mutagen (benzo[a]pyrene, B[a]P) at different doses (0, 50, 200 or 300 mg/kg body weight). Mutant frequency was then determined in a meiotic cell type (pachytene spermatocyte), a post-meiotic cell type (round spermatid) and epididymal spermatozoa after at least one cycle of spermatogenesis. Our results show that 1) mice treated with B[a]P at 7 or 25 days old, both being pre-adult ages, had significantly increased mutant frequencies in all spermatogenic cell types tested when they were 60 days old; 2) spermatogenic cells from mice treated before puberty were more susceptible to B[a]P-associated mutagenesis compared to adult mice; and 3) unexpectedly, epididymal spermatozoa had the highest mutant frequency among the spermatogenic cell types tested. These data show that pre-adult exposure to B[a]P increases the male germline mutant frequency in young adulthood. The data demonstrate that exposure to environmental genotoxins at different life phases (e.g., pre-adult and adult) can have differential effects on reproductive health.

Time-resolved analysis of the emission of sidestream smoke (SSS) from cigarettes during smoking by photo ionisation/time-of-flight mass spectrometry (PI-TOFMS): towards a better description of environmental tobacco smoke

In this study, the chemical composition of sidestream smoke (SSS) emissions of cigarettes are characterised using a laser-based single-photon ionisation time-of-flight mass spectrometer. SSS is generated from various cigarette types (2R4F research cigarette; Burley, Oriental and Virginia single-tobacco-type cigarettes) smoked on a single-port smoking machine and collected using a so-called fishtail chimney device. Using this setup, a puff-resolved quantification of several SSS components was performed. Investigations of the dynamics of SSS emissions show that concentration profiles of various substances can be categorised into several groups, either depending on the occurrence of a puff or uninfluenced by the changes in the burning zone during puffing. The SSS emissions occurring directly after a puff strongly resemble the composition of mainstream smoke (MSS). In the smouldering phase, clear differences between MSS and SSS are observed. The changed chemical profiles of SSS and MSS might be also of importance on environmental tobacco smoke which is largely determined by SSS. Additionally, the chemical composition of the SSS is strongly affected by the tobacco type. Hence, the higher nitrogen content of Burley tobacco leads to the detection of increased amounts of nitrogen-containing substances in SSS.

Parental tobacco and alcohol use and risk of hepatoblastoma in offspring: a report from the children's oncology group

BACKGROUND

Hepatoblastoma is a rare pediatric liver tumor that has significantly increased in incidence over the last several decades. The International Agency for Research on Cancer (IARC) recently classified hepatoblastoma as a tobacco-related cancer. Parental alcohol use has shown no association. We examined associations between parental tobacco and alcohol use around the time of pregnancy and hepatoblastoma in a large case-control study.

METHODS

Maternal interviews were completed for 383 cases diagnosed in the United States during 2000-2008. Controls (n = 387) were identified through U.S. birth registries and frequency-matched to cases on birth weight, birth year, and region of residence. We used unconditional logistic regression to calculate ORs and 95% confidence intervals (CI) for associations between parental smoking and maternal drinking and offspring hepatoblastoma.

RESULTS

We found no association between hepatoblastoma and maternal smoking at any time (OR, 1.0; 95% CI, 0.7-1.4), within the year before pregnancy (OR, 1.1; 95% CI, 0.8-1.6), early in pregnancy (OR, 1.0; 95% CI, 0.7-1.6), or throughout pregnancy (OR, 0.9; 95% CI, 0.5-1.6). We observed marginally positive associations between hepatoblastoma and paternal smoking in the year before pregnancy (OR, 1.4; 95% CI, 1.0-2.0) and during pregnancy (OR, 1.4; 95% CI, 0.9-2.0). Maternal alcohol use was not associated with hepatoblastoma.

CONCLUSION

Our results do not provide evidence for an etiologic relationship between maternal smoking or drinking and hepatoblastoma, and only weak evidence for an association for paternal smoking in the year before pregnancy.

IMPACT

Our study provides limited support for hepatoblastoma as a tobacco-related cancer; however, it remains wise to counsel prospective parents on the merits of smoking cessation.

In utero exposure to nanosized carbon black (Printex90) does not induce tandem repeat mutations in female murine germ cells

Inhalation of particles has been shown to induce mutations in the male germline in mice following both prenatal and adult exposures in several experiments. In contrast, the effects of particles on female germ cell mutagenesis are not well established. Germline mutations are induced during active cell division, which occurs during fetal development in females. We investigated the effects of prenatal exposure to carbon black nanoparticles (CB) on induction of mutations in the female mouse germline during fetal development, spanning the critical developmental stages of oogenesis. Pregnant C57BL/6J mice were exposed four times during gestation by intratracheal instillation of 67μg/animal of nanosized carbon black Printex90 or vehicle (gestation days 7, 10, 15 and 18). Female offspring were raised to maturity and mated with unexposed CBA males. Expanded simple tandem repeat (ESTR) germline mutation rates in the resulting F2 generation were determined from full pedigrees (mother, father, offspring) of F1 female mice (178 CB-exposed and 258 control F2 offspring). ESTR mutation rates in CB-exposed F2 female offspring were not statistically different from those of F2 female control offspring.

Paternal lifestyle as a potential source of germline mutations transmitted to offspring

Paternal exposure to high levels of radioactivity causes heritable germline minisatellite mutations. However, the effect of more general paternal exposures, such as cigarette smoking, on germline mutations remains unexplored. We analyzed two of the most commonly used minisatellite loci (CEB1 and B6.7) to identify germline mutations in blood samples of complete mother-father-child triads from the Norwegian Mother and Child Cohort Study (MoBa). The presence of mutations was subsequently related to general lifestyle factors, including paternal smoking before the partner became pregnant. Paternally derived mutations at the B6.7 locus (mutation frequency 0.07) were not affected by lifestyle. In contrast, high gross yearly income as a general measure of a healthy lifestyle coincided with low-mutation frequencies at the CEB1 locus (P=0.047). Income was inversely related to smoking behavior, and paternally derived CEB1 mutations were dose dependently increased when the father smoked in the 6 mo before pregnancy, 0.21 vs. 0.05 in smoking and nonsmoking fathers, respectively (P=0.061). These results suggest that paternal lifestyle can affect the chance of heritable mutations in unstable repetitive DNA sequences. To our knowledge, this is the first study reporting an effect of lifestyle on germline minisatellite mutation frequencies in a human population with moderate paternal exposures.

Sidestream cigarette smoke and cardiac autonomic regulation

BACKGROUND

The literature has already demonstrated that cigarette influences the cardiovascular system. In this study, we performed a literature review in order to investigate the relationship between sidestream cigarette smoke (SSCS) and cardiac autonomic regulation.

METHODS

Searches were performed on Medline, SciELO, Lilacs and Cochrane databases using the crossing between the key-words: "cigarette smoking", "autonomic nervous system", "air pollution" and "heart rate variability".

RESULTS

The selected studies indicated that SSCS exposure affects the sympathetic and parasympathetic responses to changes in arterial blood pressure. Moreover, heart rate responses to environmental tobacco smoke are increased in smokers compared to non-smokers. The mechanism involved on this process suggest increased oxidative stress in brainstem areas that regulate the cardiovascular system.

CONCLUSION

Further studies are necessary to add new elements in the literature to improve new therapies to treat cardiovascular disorders in subjects exposed to sidestream cigarette smoke.

Can Male Fertility Be Improved Prior to Assisted Reproduction through The Control of Uncommonly Considered Factors?

Male factor infertility or subfertility is responsible for up to 50% of infertility cases. A considerable body of recent studies indicates that lifestyle as well as environmental and psychological factors can negatively affect male fertility, more than previously thought. These negative effects have been shown in many cases to be reversible. This review aims to provide a rationale for early clinical attention to these factors and presents a non-exhaustive evidence-based collection of primary relevant conditions and recommendations, specifically with a view to making first line diagnostics and recommendations. The presently available evidence suggests that considering the high cost, success rates, and possible side effects of assisted reproduction techniques (ART), such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), early efforts to improve male fertility appear to be an attainable and worthwhile primary goal. A series of searches was conducted of Medline, Cochrane and related databases from November 14(th), 2010 to January 26(th), 2012 with the following keywords: male, fertility, infertility, sperm defects, IVF, ICSI, healthy habits, and lifestyle. Subsequent follow-up searches were performed for upcoming links. The total number of studies contemplated were 1265; of these, 296 studies were reviewed with criteria of relevance; the date of study or review; study sample size and study type; and publishing journal impact status. Data were abstracted based upon probable general clinical relevancy and use. Only a selection of the references has been reflected here because of space limitations. The main results obtained were evidence-supported indications as to the other causes of male infertility, their early detection, and treatment.

Tumor-specific microsatellite instability: do distinct mechanisms underlie the MSI-L and EMAST phenotypes?

Microsatellite DNA sequences display allele length alterations or microsatellite instability (MSI) in tumor tissues, and MSI is used diagnostically for tumor detection and classification. We discuss the known types of tumor-specific MSI patterns and the relevant mechanisms underlying each pattern. Mutation rates of individual microsatellites vary greatly, and the intrinsic DNA features of motif size, sequence, and length contribute to this variation. MSI is used for detecting mismatch repair (MMR)-deficient tumors, which display an MSI-high phenotype due to genome-wide microsatellite destabilization. Because several pathways maintain microsatellite stability, tumors that have undergone other events associated with moderate genome instability may display diagnostic MSI only at specific di- or tetranucleotide markers. We summarize evidence for such alternative MSI forms (A-MSI) in sporadic cancers, also referred to as MSI-low and EMAST. While the existence of A-MSI is not disputed, there is disagreement about the origin and pathologic significance of this phenomenon. Although ambiguities due to PCR methods may be a source, evidence exists for other mechanisms to explain tumor-specific A-MSI. Some portion of A-MSI tumors may result from random mutational events arising during neoplastic cell evolution. However, this mechanism fails to explain the specificity of A-MSI for di- and tetranucleotide instability. We present evidence supporting the alternative argument that some A-MSI tumors arise by a distinct genetic pathway, and give examples of DNA metabolic pathways that, when altered, may be responsible for instability at specific microsatellite motifs. Finally, we suggest that A-MSI in tumors could be molecular signatures of environmental influences and DNA damage. Importantly, A-MSI occurs in several pre-neoplastic inflammatory states, including inflammatory bowel diseases, consistent with a role of oxidative stress in A-MSI. Understanding the biochemical basis of A-MSI tumor phenotypes will advance the development of new diagnostic tools and positively impact the clinical management of individual cancers.

Research opportunities for cancer associated with indoor air pollution from solid-fuel combustion

BACKGROUND

Indoor air pollution (IAP) derived largely from the use of solid fuels for cooking and heating affects about 3 billion people worldwide, resulting in substantial adverse health outcomes, including cancer. Women and children from developing countries are the most exposed populations. A workshop was held in Arlington, Virginia, 9-11 May 2011, to better understand women's and children's potential health effects from IAP in developing countries. Workshop participants included international scientists, manufacturers, policy and regulatory officials, community leaders, and advocates who held extensive discussions to help identify future research needs.

OBJECTIVES

Our objective was to identify research opportunities regarding IAP and cancer, including research questions that could be incorporated into studies of interventions to reduce IAP exposure. In this commentary, we describe the state of the science in understanding IAP and its associations with cancer and suggest research opportunities for improving our understanding of the issues.

DISCUSSION

Opportunities for research on IAP and cancer include studies of the effect of IAP on cancers other than lung cancer; studies of genetic factors that modify susceptibility; studies to determine whether the effects of IAP are mediated via germline, somatic, and/or epigenetic changes; and studies of the effects of IAP exposure via dermal and/or oral routes.

CONCLUSIONS

IAP from indoor coal use increases the risk of lung cancer. Installing chimneys can reduce risk, and some genotypes, including GSTM1-null, can increase risk. Additional research is needed regarding the effects of IAP on other cancers and the effects of different types of solid fuels, oral and dermal routes of IAP exposure, genetic and epigenetic mechanisms, and genetic susceptibility.

Harnessing genomics to identify environmental determinants of heritable disease

Next-generation sequencing technologies can now be used to directly measure heritable de novo DNA sequence mutations in humans. However, these techniques have not been used to examine environmental factors that induce such mutations and their associated diseases. To address this issue, a working group on environmentally induced germline mutation analysis (ENIGMA) met in October 2011 to propose the necessary foundational studies, which include sequencing of parent-offspring trios from highly exposed human populations, and controlled dose-response experiments in animals. These studies will establish background levels of variability in germline mutation rates and identify environmental agents that influence these rates and heritable disease. Guidance for the types of exposures to examine come from rodent studies that have identified agents such as cancer chemotherapeutic drugs, ionizing radiation, cigarette smoke, and air pollution as germ-cell mutagens. Research is urgently needed to establish the health consequences of parental exposures on subsequent generations.

Investigating the effects of dietary folic acid on sperm count, DNA damage and mutation in Balb/c mice

To date, fewer than 50 mutagens have been studied for their ability to cause heritable mutations. The majority of those studied are classical mutagens like radiation and anti-cancer drugs. Very little is known about the dietary variables influencing germline mutation rates. Folate is essential for DNA synthesis and methylation and can impact chromatin structure. We therefore determined the effects of folic acid-deficient (0mg/kg), control (2mg/kg) and supplemented (6mg/kg) diets in early development and during lactation or post-weaning on mutation rates and chromatin quality in sperm of adult male Balb/c mice. The sperm chromatin structure assay and mutation frequencies at expanded simple tandem repeats (ESTRs) were used to evaluate germline DNA integrity. Treatment of a subset of mice fed the control diet with the mutagen ethylnitrosourea (ENU) at 8 weeks of age was included as a positive control. ENU treated mice exhibited decreased cauda sperm counts, increased DNA fragmentation and increased ESTR mutation frequencies relative to non-ENU treated mice fed the control diet. Male mice weaned to the folic acid deficient diet had decreased cauda sperm numbers, increased DNA fragmentation index, and increased ESTR mutation frequency. Folic acid deficiency in early development did not lead to changes in sperm counts or chromatin integrity in adult mice. Folic acid supplementation in early development or post-weaning did not affect germ cell measures. Therefore, adequate folic acid intake in adulthood is important for preventing chromatin damage and mutation in the male germline. Folic acid supplementation at the level achieved in this study does not improve nor is it detrimental to male germline chromatin integrity.