NRF2 loss recapitulates heritable impacts of paternal cigarette smoke exposure (RNA-seq)
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ABSTRACT: There is growing evidence that paternal pre-conception cigarette smoke (CS) exposure is associated with increased risk of behavioral disorders and cancer in offspring. To characterize the effects of CS exposure on the sperm epigenome and offspring neurodevelopment, we investigated the impact of pre-conception paternal CS exposure on mouse sperm DNA methylation and gene expression in offspring. We further investigated the role of oxidative stress on sperm epigenetic changes using a mouse model (Nrf-/-) with impaired antioxidant capacity. Lastly, we evaluated the capacity for sperm DNA methylation to recover following removal of CS for 1-5 spermatogenic cycles (28-171 days). We found that smoking significantly impacts sperm DNA methylation as well as DNA methylation and gene expression in offspring. These changes were largely recapitulated in Nrf-/- mice independent of smoke exposure. Recovery experiments indicated that about half of differentially methylated regions returned to normal within 28 days of removal from smoke, however additional recovery following longer periods was not observed. Thus, we present strong evidence that cigarette smoke exposure induces paternally mediated, heritable epigenetic changes. Parallel studies performed in Nrf-/- mice provide evidence for oxidative stress as the predominant underlying mechanism for smoke-induced epigenetic changes to sperm as well as changes in the offspring of smoke-exposed sires. Lastly, recovery experiments indicate that while many epigenetic changes are corrected following removal from smoke exposure, aberrant methylation persists at a significant number of regions even after five spermatogenic cycles
Project description:There is growing evidence that paternal pre-conception cigarette smoke (CS) exposure is associated with increased risk of behavioral disorders and cancer in offspring. To characterize the effects of CS exposure on the sperm epigenome and offspring neurodevelopment, we investigated the impact of pre-conception paternal CS exposure on mouse sperm DNA methylation and gene expression in offspring. We further investigated the role of oxidative stress on sperm epigenetic changes using a mouse model (Nrf-/-) with impaired antioxidant capacity. Lastly, we evaluated the capacity for sperm DNA methylation to recover following removal of CS for 1-5 spermatogenic cycles (28-171 days). We found that smoking significantly impacts sperm DNA methylation as well as DNA methylation and gene expression in offspring. These changes were largely recapitulated in Nrf-/- mice independent of smoke exposure. Recovery experiments indicated that about half of differentially methylated regions returned to normal within 28 days of removal from smoke, however additional recovery following longer periods was not observed. Thus, we present strong evidence that cigarette smoke exposure induces paternally mediated, heritable epigenetic changes. Parallel studies performed in Nrf-/- mice provide evidence for oxidative stress as the predominant underlying mechanism for smoke-induced epigenetic changes to sperm as well as changes in the offspring of smoke-exposed sires. Lastly, recovery experiments indicate that while many epigenetic changes are corrected following removal from smoke exposure, aberrant methylation persists at a significant number of regions even after five spermatogenic cycles
Project description: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.
Project description:Cigarette smoke (CS) imposes a strong oxidative burden on exposed tissues resulting in a severely disturbed oxidant/antioxidant balance, which in the context of chronic exposure is assumed to be a key contributor to CS-related diseases. Because of its emerging central role in orchestrating the general cellular antioxidant response, the pathway leading to the activation of the transcription factor Nrf2 has received mounting attention over the past decade in investigations aimed at elucidating CS-induced patho-physiological mechanisms. To comprehensively characterize the impact of Nrf2 in acute and sub-chronic smoking scenarios, Nrf2 knock-out mice and their wildtype ICR littermates were exposed to either ambient air (sham exposure) or to one of three doses of CS for up to 5 months with two post-exposure endpoints of 1 and 13 days. The lungs of the mice were monitored for transcriptomic changes on a genome-wide level. 110 samples from 28 different groups are analyzed. For each group there are 4 replicates, besides two groups with only 3 replicates. Group parameteres are: genotype (WT, KN), treatment (sham, smoke), dosage of smoke treatment (low, medium, high), time of smoke treatment (1 day, 2 month, 5 month, 5 month + 1 day recovery, 5 month + 13 days recovery)
Project description:Introduction: Prenatal and postnatal cigarette smoke exposure enhances the risk of developing asthma. Despite this as well as other smoking related risks, 11% of women still smoke during pregnancy. We hypothesized that cigarette smoke exposure during prenatal development generates long lasting differential methylation altering transcriptional activity that correlates with disease. Methods: In a house dust mite (HDM) model of allergic airway disease, we measured airway hyperresponsiveness (AHR) and airway inflammation between mice exposed prenatally to cigarette smoke (CS) or filtered air (FA). DNA methylation and gene expression were then measured in lung tissue. Results: We demonstrate that HDM-treated CS mice develop a more severe allergic airway disease compared to HDM-treated FA mice including increased AHR and airway inflammation. While DNA methylation changes between the two HDM-treated groups failed to reach genome-wide significance, 99 DMRs had an uncorrected p-value < 0.001. 6 of these 99 DMRs were selected for validation, based on the immune function of adjacent genes, and only 2 of the 6 DMRs confirmed the bisulfite sequencing data. Additionally, genes near these 6 DMRs (Lif, Il27ra, Tle4, Ptk7, Nfatc2, and Runx3) are differentially expressed between HDM-treated CS mice and HDM-treated FA mice. Conclusions: Our findings confirm that prenatal exposure to cigarette smoke is sufficient to modify allergic airway disease, however, it is unlikely that specific methylation changes account for the exposure-response relationship. These findings highlight the important role in utero cigarette smoke exposure plays in the development of allergic airway disease. Lung DNA methylation profiles of mice exposed in utero to cigarette smoke (CS) then treated with house dust mite (HDM, n = 8) or saline (n = 6), or exposed in utero to filtered air (FA) then treated with HDM (n = 9) or saline (n = 6)
Project description:Introduction: Prenatal and postnatal cigarette smoke exposure enhances the risk of developing asthma. Despite this as well as other smoking related risks, 11% of women still smoke during pregnancy. We hypothesized that cigarette smoke exposure during prenatal development generates long lasting differential methylation altering transcriptional activity that correlates with disease. Methods: In a house dust mite (HDM) model of allergic airway disease, we measured airway hyperresponsiveness (AHR) and airway inflammation between mice exposed prenatally to cigarette smoke (CS) or filtered air (FA). DNA methylation and gene expression were then measured in lung tissue. Results: We demonstrate that HDM-treated CS mice develop a more severe allergic airway disease compared to HDM-treated FA mice including increased AHR and airway inflammation. While DNA methylation changes between the two HDM-treated groups failed to reach genome-wide significance, 99 DMRs had an uncorrected p-value < 0.001. 6 of these 99 DMRs were selected for validation, based on the immune function of adjacent genes, and only 2 of the 6 DMRs confirmed the bisulfite sequencing data. Additionally, genes near these 6 DMRs (Lif, Il27ra, Tle4, Ptk7, Nfatc2, and Runx3) are differentially expressed between HDM-treated CS mice and HDM-treated FA mice. Conclusions: Our findings confirm that prenatal exposure to cigarette smoke is sufficient to modify allergic airway disease, however, it is unlikely that specific methylation changes account for the exposure-response relationship. These findings highlight the important role in utero cigarette smoke exposure plays in the development of allergic airway disease.
Project description:In the context of male reproductive health, epidemiological studies have observed reduced testis size and abnormal sperm counts and morphology in adult men exposed in utero, although these findings are not always repeated. The ambiguity of these reports is confounded by a lack of controlled animal studies investigating the effects of maternal cigarette smoke exposure on male offspring reproductive health. In this study we examined the effects of cigarette induced reproductive toxicity on male offspring exposed during the gestational and weaning period using our novel direct nasal exposure mouse model of cigarette smoke-induced chronic obstructive pulmonary disease and female subfertility. This was done too gain a better understanding of the adverse effects of gestational maternal smoking on male offspring fertility.
Project description:Purpose: The purpose of this study was to identify cigarette smoke (CS) induced changes in circulatory microRNA (miRNA) in the plasma and ocular fluids of the Rhesus macaque and compare them to normal age-related changes, with the ultimate goal to develop an animal model of early dry age-related macular degeneration (AMD). AMD is a blinding disease having both genetic and environmental components, with cigarette smoke exposure (CS) as the leading environmental risk factor. Methods: All Rhesus macaques were housed at the California National Primate Research Center (CNPRC) at UC Davis. We used 6 animals of the same gender per group: Group 1 (young, 2-4 years old), Group 2 (old, 20-25 years old), Group 3 (middle aged, 9-12 years old) and Group 4 (9-12 years old, exposed to smoke for 1 month). Group 4 macaques were clinically assessed prior to and following CS exposure. Ocular fluids and plasma samples were collected, miRNA isolated, and expression data obtained from Affymetrix miRNA GeneTitan Array Plates 4.0, followed by bioinformatics analysis on Affymetrix Expression Console (EC) and Transcriptome Analysis Software (TAS), and using ANOVA. Results: Statistically significant changes were seen in miRNA populations in ocular fluids and plasma. In the plasma samples, 45 miRNAs were strongly upregulated (Fold Change >+/-1.5, p<0.05) upon CS exposure, while in aging monkeys different miRNAs in plasma were affected, and downregulated. In the vitreous, 3 miRNAs were downregulated in animals exposed to CS, intriguing enough two of them (miR-6794 and miR-6790) were the same ones downregulated with age. Retinal imaging using OCT did not show any significant changes in retinal thickness. Cotinine assays showed that animals received on average dose of 50-60 ng/ml cotinine, a marker for significant CS exposure. Conclusions: One month of CS exposure of Rhesus macaques resulted in significant changes of expression of circulatory miRNAs. We identified several CS related miRNA changes that are plasma or ocular fluid-specific. Healthy aging changes of miRNAs populations were different from the CS exposure induced changes in plasma, while the ones in vitreous were similar. This data will be utilized to develop an animal model of early dry AMD, using a monkey model exposed to CS.
Project description:In the context of male reproductive health, epidemiological studies have observed reduced testis size and abnormal sperm counts and morphology in adult men exposed in utero, although these findings are not always repeated. The ambiguity of these reports is confounded by a lack of controlled animal studies investigating the effects of maternal cigarette smoke exposure on male offspring reproductive health. In this study we examined the effects of cigarette induced reproductive toxicity on male offspring exposed during the gestational and weaning period using our novel direct nasal exposure mouse model of cigarette smoke-induced chronic obstructive pulmonary disease and female subfertility. This was done too gain a better understanding of the adverse effects of gestational maternal smoking on male offspring fertility. C57BL/6 5 week-old female mice were exposed via the nose-only to cigarette smoke [twelve 3R4F reference cigarettes (University of Kentucky, USA) twice/day, five times per week, for 12-18 weeks]. Each exposure lasted 60 minutes. Control mice received room air. In total, 27 mice underwent cigarette smoke exposure. Eleven week-old female mice exposed to cigarette smoke for 6 weeks were separated into groups of three and housed with a single control stud male aged 7-8 weeks with proven fertility for a maximum of 12 weeks. Females were monitored every second day for post-coital plugs and pregnancy. Pregnant females were separated into single cages and litter sizes/pup weights recorded. Smoke exposure via dams continued throughout mating/pregnancy/lactation until weaning of pups at 21days post birth. The testis of exposed offspring were then collected for RNA extraction and hybridization on an Illumina Sentrix Mouse ref-8 v2 Beadchip
Project description:Cigarette smoking causes serious diseases, including lung cancer, heart disease, and emphysema. While cessation remains the most effective approach to minimize smoking-related disease, alternative non-combustible tobacco-derived nicotine containing products may reduce disease risks among those unable or unwilling to quit. E-vapor aerosols typically contain significantly lower levels of smoke-related harmful and potentially harmful constituents; however, health risks of long-term inhalation exposures are unknown. We designed a 7-month inhalation study in C57BL/6 mice to evaluate long-term respiratory toxicity of e-vapor aerosols compared to cigarette smoke and to assess the impact of smoking cessation or switching to an e-vapor product after 3 months of exposure to 3R4F cigarette smoke (CS). There were no significant changes in in-life observations (body weights, clinical signs) in e-vapor groups compared to the Sham Control. The 3R4F CS group showed reduced respiratory function during exposure and had lower body weight and showed transient signs of distress post-exposure. Following 7 months of exposure, e-vapor aerosols resulted in no or minimal increase in pulmonary inflammation, while exposure to 3R4F CS led to impairment of lung function and caused marked lung inflammation and emphysematous changes. Biological changes observed in the Switching group were similar to the Cessation group. 3R4F CS exposure dysregulated lung and nasal tissue transcriptome, while these molecular effects were substantially lower in the e-vapor group. Results from this study demonstrate that in comparison with 3R4F CS, e-vapor aerosols induce substantially lower biological responses including pulmonary inflammation and emphysema, and that complete switching from CS to e-vapor products significantly reduces biological changes associated with cigarette smoke in C57BL/6 mice.
Project description:Our previous studies have shown that tobacco smoke exposure exacerbated the lung response to crystalline silica exposure in rats. The objective of the present study, a follow-up to our previous study, was to determine the effect of tobacco smoke exposure cessation on the lung response to crystalline silica exposure in the rats. Rats were exposed to air, crystalline silica (1 week followed by a 1 year progression/recovery period with no exposure), tobacco smoke (6 months of exposure followed by 6 months of recovery with no exposure), or crystalline silica (1 week) plus tobacco smoke (6 months of exposure followed by 6 months of recovery with no exposure). Lung toxicity was determined at the end of the 1-year progression/recovery period in all 4 groups of the rats. Silica exposure resulted in significant lung toxicity which was further exacerbated by tobacco smoke exposure in the rats. Cessation of cigarette smoke exposure did not result in reversal of the silica-induced lung toxicity despite exacerbation of the toxicity by tobacco smoke.