Epigenetic Impacts

Anway et al., 2005

Anway, Matthew D., Cupp, Andrea S., Uzumcu, Mehmet, and Skinner, Michael K., “Epigenetic Transgenerational Actions of Endocrine Disruptors and Male Fertility,”  Science, 2005, 308:5727,  DOI: 10.1126/SCIENCE.1108190.

ABSTRACT:

Transgenerational effects of environmental toxins require either a chromosomal or epigenetic alteration in the germ line. Transient exposure of a gestating female rat during the period of gonadal sex determination to the endocrine disruptors vinclozolin (an antiandrogenic compound) or methoxychlor (an estrogenic compound) induced an adult phenotype in the F1 generation of decreased spermatogenic capacity (cell number and viability) and increased incidence of male infertility. These effects were transferred through the male germ line to nearly all males of all subsequent generations examined (that is, F1 to F4). The effects on reproduction correlate with altered DNA methylation patterns in the germ line. The ability of an environmental factor (for example, endocrine disruptor) to reprogram the germ line and to promote a transgenerational disease state has significant implications for evolutionary biology and disease etiology.  FULL TEXT

Castillo-Fernandez et al., 2014

Castillo-Fernandez JE, Spector TD, Bell JT, “Epigenetics of discordant monozygotic twins: implications for disease,” Genome Medicine, 2014, 6:7, doi: 10.1186/s13073-014-0060-z.

ABSTRACT: Monozygotic (MZ) twins share nearly all of their genetic variants and many similar environments before and after birth. However, they can also show phenotypic discordance for a wide range of traits. Differences at the epigenetic level may account for such discordances. It is well established that epigenetic states can contribute to phenotypic variation, including disease. Epigenetic states are dynamic and potentially reversible marks involved in gene regulation, which can be influenced by genetics, environment, and stochastic events. Here, we review advances in epigenetic studies of discordant MZ twins, focusing on disease. The study of epigenetics and disease using discordant MZ twins offers the opportunity to control for many potential confounders encountered in general population studies, such as differences in genetic background, early-life environmental exposure, age, gender, and cohort effects. Recently, analysis of disease-discordant MZ twins has been successfully used to study epigenetic mechanisms in aging, cancer, autoimmune disease, psychiatric, neurological, and multiple other traits. Epigenetic aberrations have been found in a range of phenotypes, and challenges have been identified, including sampling time, tissue specificity, validation, and replication. The results have relevance for personalized medicine approaches, including the identification of prognostic, diagnostic, and therapeutic targets. The findings also help to identify epigenetic markers of environmental risk and molecular mechanisms involved in disease and disease progression, which have implications both for understanding disease and for future medical research.  FULL TEXT

Collotta et al., 2013

Collotta, M, Bertazzi, PA, Bollati, V, “Epigenetics and pesticides,” Toxicology, 2013, 307, DOI: 10.1016/j.tox.2013.01.017.

ABSTRACT: Pesticides, a wide class of environmental contaminants, may cause both acute and delayed health effects in exposed subjects. These effects can range from simple irritation of the skin and eyes to more severe effects such as affecting the nervous system, the reproductive system and cancer. The molecular mechanisms underlying such effects are still under investigation. Epigenetics is the study of heritable changes in gene expression that occur without a change in the DNA sequence. Several epigenetic mechanisms, including DNA methylation, histone modifications and microRNA expression, can be triggered by environmental factors.We review current evidences indicating that epigenetic modifications may mediate pesticide effects on human health. In vitro, animal, and human investigations have identified several classes of pesticides that modify epigenetic marks, including endocrine disruptors, persistent organic pollutants, arsenic, several herbicides and insecticides. Several investigations have examined the effects of environmental exposures and epigenetic markers, and identified toxicants that modify epigenetic states. These modifications are similar to the ones found in pathological tissue samples. In spite of the current limitations, available evidence supports the concept that epigenetics holds substantial potential for furthering our understanding of the molecular mechanisms of pesticides health effects, as well as for predicting health-related risks due to conditions of environmental exposure and individual susceptibility.  FULL TEXT

Crews et al., 2007

David Crews, Andrea C. Gore, Timothy S. Hsu, Nygerma L. Dangleben, Michael Spinetta, Timothy Schallert, Matthew D. Anway, and Michael K. Skinner, “Transgenerational epigenetic imprints on mate preference,” PNAS, 2007, 104:14, DOI: 10.1073/PNAS.0610410104.

ABSTRACT:

Environmental contamination by endocrine-disrupting chemicals (EDC) can have epigenetic effects (by DNA methylation) on the germ line and promote disease across subsequent generations. In natural populations, both sexes may encounter affected as well as unaffected individuals during the breeding season, and any diminution in attractiveness could compromise reproductive success. Here we examine mate preference in male and female rats whose progenitors had been treated with the antiandrogenic fungicide vinclozolin. This effect is sex-specific, and we demonstrate that females three generations removed from the exposure discriminate and prefer males who do not have a history of exposure, whereas similarly epigenetically imprinted males do not exhibit such a preference. The observations suggest that the consequences of EDCs are not just transgenerational but can be ‘‘transpopulational’’, because in many mammalian species, males are the dispersing sex. This result indicates that epigenetic transgenerational inheritance of EDC action represents an unappreciated force in sexual selection. Our observations provide direct experimental evidence for a role of epigenetics as a determinant factor in evolution.  FULL TEXT

Heindel, 2006

Heindel JJ, “Role of exposure to environmental chemicals in the developmental basis of reproductive disease and dysfunction,” Seminars in Reproductive Medicine, 2006, 24:3.

ABSTRACT: There is a paradigm shift in science at present that indicates that the onset of many diseases, including reproductive diseases and dysfunctions, are already programmed in utero or in the early postnatal period. This new field is called the developmental basis of health and disease. Although focus has been on the role of in utero nutrition and its effects on subsequent adult-onset diseases, it is clear that exposure to environmental stressors/toxicants in utero or during early development can also increase susceptibility to disease later in life. The mechanism for this in utero and early developmental effect is thought to be altered epigenetic control of gene expression, which alters developmental programming and results in a tissue that may appear normal but is functionally compromised. Although this concept is still a hypothesis, this review addresses the current state of data relating to proving its importance and role in reproductive diseases. If the developmental basis of disease is shown to be true, then examination of the etiology of disease and prevention and intervention strategies will need to be modified to fit the new paradigm.

Kabasenche and Skinner, 2014

Kabasenche WP, Skinner MK, “DDT, epigenetic harm, and transgenerational environmental justice,” Environmental Health, 2014, 13:62, DOI: 10.1186/1476-069X-13-62.

ABSTRACT: Although the environmentally harmful effects of widespread dichlorodiphenyltrichloroethane (DDT) use became well-known following Rachel Carson’s Silent Spring (1962), its human health effects have more recently become clearer. A ban on the use of DDT has been in place for over 30 years, but recently DDT has been used for malaria control in areas such as Africa. Recent work shows that DDT has transgenerational effects in progeny and generations never directly exposed to DDT. These effects have health implications for individuals who are not able to have any voice in the decision to use the pesticide. The transgenerational effects of DDT are considered in light of some widely accepted ethical principles. We argue that this reframes the decision to use DDT, requiring us to incorporate new considerations, and new kinds of decision making, into the deliberative process that determines its ongoing use. Ethical considerations for intergenerational environmental justice are presented that include concern and respect for autonomy, nonmaleficence, and justice. Here, we offer a characterization of the kinds of ethical considerations that must be taken into account in any satisfactory decisions to use DDT. FULL TEXT

Landrigan and Belpoggi, 2018

Landrigan, P. J., and Belpoggi, F.,”The need for independent research on the health effects of glyphosate-based herbicides,” Environmental Health, 17(1), 51, 2018, doi:10.1186/s12940-018-0392-z.

ABSTRACT:

BACKGROUND: Glyphosate, formulated as Roundup, is the world’s most widely used herbicide. Glyphosate is used extensively on genetically modified (GM) food crops designed to tolerate the herbicide, and global use is increasing rapidly. Two recent reviews of glyphosate’s health hazards report conflicting results. An independent review by the International Agency for Research on Cancer (IARC) found that glyphosate is a “probable human carcinogen”. A review by the European Food Safety Agency (EFSA) found no evidence of carcinogenic hazard. These differing findings have produced regulatory uncertainty.

REGULATORY ACTIONS: Reflecting this regulatory uncertainty, the European Commission on November 27 2017, extended authorization for glyphosate for another 5 years, while the European Parliament opposed this decision and issued a call that pesticide approvals be based on peer-reviewed studies by independent scientists rather than on the current system that relies on proprietary industry studies.

RAMAZZINI INSTITUTE RESPONSE: The Ramazzini Institute has initiated a pilot study of glyphosate’s health hazards that will be followed by an integrated experimental research project. This evaluation will be independent of industry support and entirely sponsored by worldwide crowdfunding. The aim of the Ramazzini Institute project is to explore comprehensively the effects of exposures to glyphosate-based herbicides at current real-world levels on several toxicological endpoints, including carcinogenicity, long-term toxicity, neurotoxicity, endocrine disrupting effects, prenatal developmental toxicity, the microbiome and multi-generational effects. FULL TEXT

Lim et al., 2009

Soo Lim, Sun Young Ahn, In Chan Song, Myung Hee Chung, Hak Chul Jang, Kyong Soo Park, Ki-Up Lee, Youngmi Kim Pak , Hong Kyu Lee, “Chronic Exposure to the Herbicide, Atrazine, Causes Mitochondrial Dysfunction and Insulin Resistance,” PLOS One, 2009, 4:4, DOI: 10.1371/journal.pone.0005186

ABSTRACT:

There is an apparent overlap between areas in the USA where the herbicide, atrazine (ATZ), is heavily used and obesity-prevalence maps of people with a BMI over 30. Given that herbicides act on photosystem II of the thylakoid membrane of chloroplasts, which have a functional structure similar to mitochondria, we investigated whether chronic exposure to low concentrations of ATZ might cause obesity or insulin resistance by damaging mitochondrial function. Sprague-Dawley rats (n = 48) were treated for 5 months with low concentrations (30 or 300 µg kg−1 day−1) of ATZ provided in drinking water. One group of animals was fed a regular diet for the entire period, and another group of animals was fed a high-fat diet (40% fat) for 2 months after 3 months of regular diet. Various parameters of insulin resistance were measured. Morphology and functional activities of mitochondria were evaluated in tissues of ATZ-exposed animals and in isolated mitochondria. Chronic administration of ATZ decreased basal metabolic rate, and increased body weight, intra-abdominal fat and insulin resistance without changing food intake or physical activity level. A high-fat diet further exacerbated insulin resistance and obesity. Mitochondria in skeletal muscle and liver of ATZ-treated rats were swollen with disrupted cristae. ATZ blocked the activities of oxidative phosphorylation complexes I and III, resulting in decreased oxygen consumption. It also suppressed the insulin-mediated phosphorylation of Akt. These results suggest that long-term exposure to the herbicide ATZ might contribute to the development of insulin resistance and obesity, particularly where a high-fat diet is prevalent. FULL TEXT

Manikkam et al., 2012

Manikkam M, Tracey R, Guerrero-Bosagna C, Skinner MK, “Pesticide and insect repellent mixture (permethrin and DEET) induces epigenetic transgenerational inheritance of disease and sperm epimutations,” Reproductive Toxicology, 2012,  34:4,  DOI: 10.1016/j.reprotox.2012.08.010.

ABSTRACT: Environmental compounds are known to promote epigenetic transgenerational inheritance of disease. The current study was designed to determine if a “pesticide mixture” (pesticide permethrin and insect repellent N,N-diethyl-meta-toluamide, DEET) promotes epigenetic transgenerational inheritance of disease and associated DNA methylation epimutations in sperm. Gestating F0 generation female rats were exposed during fetal gonadal sex determination and the incidence of disease evaluated in F1 and F3 generations. There were significant increases in the incidence of total diseases in animals from pesticide lineage F1 and F3 generation animals. Pubertal abnormalities, testis disease, and ovarian disease (primordial follicle loss and polycystic ovarian disease) were increased in F3 generation animals. Analysis of the pesticide lineage F3 generation sperm epigenome identified 363 differential DNA methylation regions (DMR) termed epimutations. Observations demonstrate that a pesticide mixture (permethrin and DEET) can promote epigenetic transgenerational inheritance of adult onset disease and potential sperm epigenetic biomarkers for ancestral environmental exposures.  FULL TEXT

Manikkam et al., 2012b

Manikkam M, Guerrero-Bosagna C, Tracey R, Haque MM, Skinner MK, “Transgenerational actions of environmental compounds on reproductive disease and identification of epigenetic biomarkers of ancestral exposures,” PLoS One, 2012, 7:2.
ABSTRACT:
Environmental factors during fetal development can induce a permanent epigenetic change in the germ line (sperm) that then transmits epigenetic transgenerational inheritance of adult-onset disease in the absence of any subsequent exposure. The epigenetic transgenerational actions of various environmental compounds and relevant mixtures were investigated with the use of a pesticide mixture (permethrin and insect repellant DEET), a plastic mixture (bisphenol A and phthalates), dioxin (TCDD) and a hydrocarbon mixture (jet fuel, JP8). After transient exposure of F0 gestating female rats during the period of embryonic gonadal sex determination, the subsequent F1-F3 generations were obtained in the absence of any environmental exposure. The effects on the F1, F2 and F3 generations pubertal onset and gonadal function were assessed. The plastics, dioxin and jet fuel were found to promote early-onset female puberty transgenerationally (F3 generation). Spermatogenic cell apoptosis was affected transgenerationally. Ovarian primordial follicle pool size was significantly decreased with all treatments transgenerationally. Differential DNA methylation of the F3 generation sperm promoter epigenome was examined. Differential DNA methylation regions (DMR) were identified in the sperm of all exposure lineage males and found to be consistent within a specific exposure lineage, but different between the exposures. Several genomic features of the DMR, such as low density CpG content, were identified. Exposure-specific epigenetic biomarkers were identified that may allow for the assessment of ancestral environmental exposures associated with adult onset disease.  FULL TEXT