Simulated Wildfire Smoke Significantly Alters Sperm DNA Methylation Patterns in a Murine Model

Repeated exposure to eucalyptus wood smoke alters pulmonary gene and metabolic profiles in male Long-Evans rats

Exposure to wildfire smoke is associated with both acute and chronic cardiopulmonary illnesses, which are of special concern for wildland firefighters who experience repeated exposure to wood smoke. It is necessary to better understand the underlying pathophysiology by which wood smoke exposure increases pulmonary disease burdens in this population. We hypothesize that wood smoke exposure produces pulmonary dysfunction, lung inflammation, and gene expression profiles associated with future pulmonary complications. Male Long-Evans rats were intermittently exposed to smoldering eucalyptus wood smoke at 2 concentrations, low (11.0 ± 1.89 mg/m3) and high (23.7 ± 0.077 mg/m3), over a 2-week period. Whole-body plethysmography was measured intermittently throughout. Lung tissue and lavage fluid were collected 24 h after the final exposure for transcriptomics and metabolomics. Increasing smoke exposure upregulated neutrophils and select cytokines in the bronchoalveolar lavage fluid. In total, 3446 genes were differentially expressed in the lungs of rats in the high smoke exposure and only 1 gene in the low smoke exposure (Cd151). Genes altered in the high smoke group reflected changes to the Eukaryotic Initiation Factor 2 stress and oxidative stress responses, which mirrored metabolomics analyses. xMWAS-integrated analysis revealed that smoke exposure significantly altered pathways associated with oxidative stress, lung morphogenesis, and tumor proliferation pathways. These results indicate that intermittent, 2-week exposure to eucalyptus wood smoke leads to transcriptomic and metabolic changes in the lung that may predict future lung disease development. Collectively, these findings provide insight into cellular signaling pathways that may contribute to the chronic pulmonary conditions observed in wildland firefighters.

Impact of Wildfires on Cardiovascular Health

Wildfire smoke (WFS) is a mixture of respirable particulate matter, environmental gases, and other hazardous pollutants that originate from the unplanned burning of arid vegetation during wildfires. The increasing size and frequency of recent wildfires has escalated public and occupational health concerns regarding WFS inhalation, by either individuals living nearby and downstream an active fire or wildland firefighters and other workers that face unavoidable exposure because of their profession. In this review, we first synthesize current evidence from environmental, controlled, and interventional human exposure studies, to highlight positive associations between WFS inhalation and cardiovascular morbidity and mortality. Motivated by these findings, we discuss preventative measures and suggest interventions to mitigate the cardiovascular impact of wildfires. We then review animal and cell exposure studies to call attention on the pathophysiological processes that support the deterioration of cardiovascular tissues and organs in response to WFS inhalation. Acknowledging the challenges of integrating evidence across independent sources, we contextualize laboratory-scale exposure approaches according to the biological processes that they model and offer suggestions for ensuring relevance to the human condition. Noting that wildfires are significant contributors to ambient air pollution, we compare the biological responses triggered by WFS to those of other harmful pollutants. We also review evidence for how WFS inhalation may trigger mechanisms that have been proposed as mediators of adverse cardiovascular effects upon exposure to air pollution. We finally conclude by highlighting research areas that demand further consideration. Overall, we aspire for this work to serve as a catalyst for regulatory initiatives to mitigate the adverse cardiovascular effects of WFS inhalation in the community and alleviate the occupational risk in wildland firefighters.

Alterations in sperm DNA methylation may as a mediator of paternal air pollution exposure and offspring birth outcomes: Insight from a birth cohort study

Paternal exposure to environmental risk factors influences the offspring health. This study aimed to evaluate the association between paternal air pollution exposure mediated by sperm DNA methylation and adverse birth outcomes in offspring. We recruited 1607 fertile men and their partners from 2014 to 2016 and collected semen samples to detect sperm DNA methylation. Multivariate linear regression and weighted quantile sum regression models were used to assess the associations between paternal air pollution exposure and offspring birth outcomes. A critical exposure window was identified. Reduced representation bisulfite sequencing was used to detect sperm DNA methylation. The results demonstrated that high paternal exposure to PM2.5 (β = -211.31, 95% CI: (-386.37, -36.24)), PM10 (β = -178.20, 95% CI: (-277.13, -79.27)), and NO2 (β = -84.22, 95% CI: (-165.86, -2.57)) was negatively associated with offspring's birthweight, especially in boys. Additionally, an early exposure window of 15-69 days before fertilization was recognized to be the key exposure window, which increased the risk of low birth weight and small for gestational age. Furthermore, paternal co-exposure to six air pollutants contributed to lower birthweight (β = -51.91, 95% CI: (-92.72, -11.10)) and shorter gestational age (β = -1.72, 95% CI: (-3.26, -0.17)) and PM2.5 was the most weighted pollutant. Paternal air pollution exposure resulted in 10,328 differentially methylated regions and the IGF2R gene was the key gene involved in the epigenetic process. These differentially methylated genes were predominantly associated with protein binding, transcriptional regulation, and DNA templating. These findings indicate that spermatogenesis is a susceptible window during which paternal exposure to air pollution affects sperm DNA methylation and the birth outcomes of offspring.

Exposure to air pollution is associated with DNA methylation changes in sperm

Exposure to air pollutants has been associated with adverse health outcomes in adults and children who were prenatally exposed. In addition to reducing exposure to air pollutants, it is important to identify their biologic targets in order to mitigate the health consequences of exposure. One molecular change associated with prenatal exposure to air pollutants is DNA methylation (DNAm), which has been associated with changes in placenta and cord blood tissues at birth. However, little is known about how air pollution exposure impacts the sperm epigenome, which could provide important insights into the mechanism of transmission to offspring. In the present study, we explored whether exposure to particulate matter less than 2.5 microns in diameter, particulate matter less than 10 microns in diameter, nitrogen dioxide (NO2), or ozone (O3) was associated with DNAm in sperm contributed by participants in the Early Autism Risk Longitudinal Investigation prospective pregnancy cohort. Air pollution exposure measurements were calculated as the average exposure for each pollutant measured within 4 weeks prior to the date of sample collection. Using array-based genome-scale methylation analyses, we identified 80, 96, 35, and 67 differentially methylated regions (DMRs) significantly associated with particulate matter less than 2.5 microns in diameter, particulate matter less than 10 microns in diameter, NO2, and O3, respectively. While no DMRs were associated with exposure to all four pollutants, we found that genes overlapping exposure-related DMRs had a shared enrichment for gene ontology biological processes related to neurodevelopment. Together, these data provide compelling support for the hypothesis that paternal exposure to air pollution impacts DNAm in sperm, particularly in regions implicated in neurodevelopment.

Sperm epigenetics landscape: correlation with embryo quality, reproductive outcomes and offspring's health

Epigenetics refers to how gene expression and function are modulated without modifying the DNA sequence but through subtle molecular changes or interactions with it. As spermatogenesis progresses, male germ cells suffer plenty of epigenetic modifications, resulting in the definitive epigenome of spermatozoa conditioning its functionality, and this process can be altered by several internal and external factors. The paternal epigenome is crucial for sperm function, fertilization, embryo development, and offspring's health, and altered epigenetic states are associated with male infertility with or without altered semen parameters, embryo quality impairment, and worse ART outcomes together with the future offspring's health risks mainly through intergenerational transmission of epigenetic marks. Identifying epigenetic biomarkers may improve male factor diagnosis and the development of targeted therapies, not only to improve fertility but also to allow an early detection of risk and disease prevention in the progeny. While still there is much research to be done, hopefully in the near future, improvements in high-throughput technologies applied to epigenomes will permit our understanding of the underlying epigenetic mechanisms and the development of diagnostics and therapies leading to improved reproductive outcomes. In this review, we discuss the mechanisms of epigenetics in sperm and how epigenetics behave during spermatogenesis. Additionally, we elaborate on the relationship of sperm epigenetics with sperm parameters and male infertility, and highlight the impact of sperm epigenetic alterations on sperm parameters, embryo quality, ART outcomes, miscarriage rates and offspring's health. Furthermore, we provide insights into the future research of epigenetic alterations in male infertility.

Preconception origins of asthma, allergies and lung function: The influence of previous generations on the respiratory health of our children

Emerging research suggests that exposures occurring years before conception are important determinants of the health of future offspring and subsequent generations. Environmental exposures of both the father and mother, or exposure to disease processes such as obesity or infections, may influence germline cells and thereby cause a cascade of health outcomes in multiple subsequent generations. There is now increasing evidence that respiratory health is influenced by parental exposures that occur long before conception. The strongest evidence relates adolescent tobacco smoking and overweight in future fathers to increased asthma and lower lung function in their offspring, supported by evidence on parental preconception occupational exposures and air pollution. Although this literature is still sparse, the epidemiological analyses reveal strong effects that are consistent across studies with different designs and methodologies. The results are strengthened by mechanistic research from animal models and (scarce) human studies that have identified molecular mechanisms that can explain the epidemiological findings, suggesting transfer of epigenetic signals through germline cells, with susceptibility windows in utero (both male and female line) and prepuberty (male line). The concept that our lifestyles and behaviours may influence the health of our future children represents a new paradigm. This raises concerns for future health in decades to come with respect to harmful exposures but may also open for radical rethinking of preventive strategies that may improve health in multiple generations, reverse the imprint of our parents and forefathers, and underpin strategies that can break the vicious circle of propagation of health inequalities across generations.

Evolutionary Implications of Environmental Toxicant Exposure

Homo sapiens have been exposed to various toxins and harmful compounds that change according to various phases of human evolution. Population genetics studies showed that such exposures lead to adaptive genetic changes; while observing present exposures to different toxicants, the first molecular mechanism that confers plasticity is epigenetic remodeling and, in particular, DNA methylation variation, a molecular mechanism proposed for medium-term adaptation. A large amount of scientific literature from clinical and medical studies revealed the high impact of such exposure on human biology; thus, in this review, we examine and infer the impact that different environmental toxicants may have in shaping human evolution. We first describe how environmental toxicants shape natural human variation in terms of genetic and epigenetic diversity, and then we describe how DNA methylation may influence mutation rate and, thus, genetic variability. We describe the impact of these substances on biological fitness in terms of reproduction and survival, and in conclusion, we focus on their effect on brain evolution and physiology.

Effects of Daily Peat Smoke Exposure on Present and Next Generations

This study aimed to follow the neurotoxic effect of peat smoke on adult outbred rats and its influence on central nervous system (CNS) parameters in first-generation offspring. Under experimental conditions, exposure to peat smoke was carried out on adult male Wistar rats for 24 h. After the end of the exposure, an open field test (OFT), electroencephalography (EEG), and histological analysis of the testes and brains of smoke-exposed males were performed, after which they were mated with intact females to obtain F1 offspring. Stillbirth, neonatal mortality, and body weight at 4, 7, 14, and 21 postnatal days, as well as behavior in the OFT and EEG parameters during puberty (3 months), were assessed. The results of the examination of F0 males showed a significant increase in motor activity and anxiety in the open field test and a violation of EEG parameters. Histopathologically, peat smoke caused a sharp increase in shadow cells (homogeneous cells with pale-stained cytoplasm, in which the cell and nuclear membranes are not visualized) and degeneratively altered neurons in the brain; we found no changes in the testicles. Peat smoke exposure during preconception did not affect neonatal mortality and weight gain in F1 offspring. Adult females born to peat-smoke-exposed males showed an increase in locomotor activity, and the behavior of adult F1 males did not differ from the control. In F1 males, a statistically significant increase in slow-wave activity indices in the delta band was observed.

Systematic review of climate change effects on reproductive health

Climate change is a major risk factor for overall health, including reproductive health, and well-being. Increasing temperatures, due mostly to increased greenhouse gases trapping excess heat in the atmosphere, result in erratic weather patterns, wildfires, displacement of large communities, and stagnant water resulting in vector-borne diseases that, together, have set the stage for new and devastating health threats across the globe. These conditions disproportionately affect disadvantaged and vulnerable populations, including women, pregnant persons, young children, the elderly, and the disabled. This review reports on the evidence for the adverse impacts of air pollution, wildfires, heat stress, floods, toxic chemicals, and vector-borne diseases on male and female fertility, the developing fetus, and obstetric outcomes. Reproductive health care providers are uniquely positioned and have an unprecedented opportunity to educate patients and policy makers about mitigating the impact of climate change to assure reproductive health in this and future generations.

Indoor Air Quality Considerations for Laboratory Animals in Wildfire-Impacted Regions-A Pilot Study

Wildfire events are increasing across the globe. The smoke generated as a result of this changing fire landscape is potentially more toxic than air pollution from other ambient sources, according to recent studies. This is especially concerning for populations of humans or animals that live downwind of areas that burn frequently, given that ambient exposure to wildfire smoke cannot be easily eliminated. We hypothesized that a significant indoor air pollution risk existed for laboratory animal facilities located proximal to fire-prone areas. Here, we measured real time continuous outdoor and indoor air quality for 28 days at a laboratory animal facility located in the Rocky Mountain region. We demonstrated that during a wildfire event, the indoor air quality of this animal facility is influenced by ambient smoke events. The daily average indoor fine particulate matter value in an animal room exceeded the Environmental Protection Agency's ambient annual standard 14% of the time and exceeded the World Health Organization's ambient annual guideline 71% of the time. We further show that specialized cage filtration systems are capable of mitigating air pollution penetrance and could improve an animal's microenvironment. The potential effects for laboratory animal physiology that occur in response to the exposure levels and durations measured in this study remain to be determined; yet, even acute wildfire exposure events have been previously correlated with significant differences in gene regulatory and metabolic processes in vivo. We believe these findings warrant consideration for indoor laboratory animal facility air quality monitoring and development of smoke exposure prevention and response protocols, especially among facilities located downwind of fire-prone landscapes.

Climate change and global health: A call to more research and more action

There is increasing understanding, globally, that climate change and increased pollution will have a profound and mostly harmful effect on human health. This review brings together international experts to describe both the direct (such as heat waves) and indirect (such as vector-borne disease incidence) health impacts of climate change. These impacts vary depending on vulnerability (i.e., existing diseases) and the international, economic, political, and environmental context. This unique review also expands on these issues to address a third category of potential longer-term impacts on global health: famine, population dislocation, and environmental justice and education. This scholarly resource explores these issues fully, linking them to global health in urban and rural settings in developed and developing countries. The review finishes with a practical discussion of action that health professionals around the world in our field can yet take.