Impact of Cadmium Exposure during Pregnancy on Hepatic Glucocorticoid Receptor Methylation and Expression in Rat Fetus

Abstract

Adverse fetal environment due to maternal undernutrition or exposure to environmental chemicals alters glucocorticoid (GC) metabolism increasing the risk of metabolic disorders in adulthood. In this study, we investigated the effects of maternal exposure to cadmium (Cd, 50 ppm) during pregnancy in the methylation of fetal hepatic glucocorticoid receptor promoter (GR) and the correlation with its expression and that of the DNA methyltransferases (DNMT1a and 3a). We also studied the expression of liver phosphoenolpyruvate carboxykinase (PEPCK) and acyl-CoA oxidase (AOX), two enzymes involved in the metabolism of carbohydrates and lipids respectively. The methylation of the rat GR gene exon 110 (GR110) in nucleotides -2536 to -2361 was analyzed by pyrosequencing. Quantitative real time PCR was used to assess hepatic GR, PEPCK and AOX mRNA, and their protein levels using Western blotting analysis. Differential methylation was noted across groups at all CpG sites in the GR exon 110 in a sex-dependent manner. In males, CpG were more methylated than the controls (185±21%, p<0.001) but only CpG sites 1,6,7 and 9 showed a significantly different extent of methylation. In addition, a lower expression of GR (mRNA and protein) was found. On the contrary, in females, CpG were less methylated than the controls (62±11%, p<0.05) and overexpressed, affecting PEPCK and AOX expression, which did not change in males. The GR methylation profile correlates with DNMT3a expression which may explain epigenetic sex-dependent changes on GR110 promoter induced by Cd treatment. In conclusion, Cd exposure during pregnancy affects fetal liver DNMT3a resulting in sex-dependent changes in methylation and expression of GR110. Although these effects do not seem to be directly involved in the low birth weight and height, they may have relevant implications for long-term health.

Epigenetic marks responsible for cadmium-induced melanoma cell overgrowth

“…The silencing of p16 INK4A and caspase8 by Cd in melanoma cells that we have shown is of particular importance in the light of several considerations. As constitutional epimutations of CDKN2A (p16 INK4A and p14 ARF ) genes in melanoma families play a negligible role (Castillo et al, 2012) and no association has been found between the risk of cutaneous malignant melanoma and peripheral blood mononuclear cell methylation levels of p16 INK4A (Zhang et al, 2009), it is apparent the crucial role of the environment in inducing epigenetic changes in a key gene in melanoma development we have evidenced. This is even more relevant in light of the contribution of p16 INK4A in uveal melanoma (Hearle et al, 2003;Buecher et al, 2010) and the correlation of p16 INK4A promoter methylation with increased melanoma thickness (Kostaki et al, 2014), and more, of the association between loss of CDKN2A expression and adverse prognostic markers of melanoma (Young et al, 2014;Lade-Keller et al, 2014;Chang and Cassarino, 2014).…”

Gestational N-hexane inhalation alters the expression of genes related to ovarian hormone production and DNA methylation states in adult female F1 rat offspring

“…Therefore, gestational exposure to environmental endocrine disruptors, especially non-genotoxic chemicals, can induce functional disorders in offspring through the alteration of genome methylation. Several reports have supported this hypothesis (Castillo et al, 2012;Manikkam et al, 2012a;Sanders et al, 2014).…”

Select Prenatal Environmental Exposures and Subsequent Alterations of Gene-Specific and Repetitive Element DNA Methylation in Fetal Tissues

“…Cadmium is a partial transplacental toxic metal, accumulating in the placenta, and has been implicated as a potential cause of adverse birth outcomes [65]. Specifically, in a rat model, prenatal exposure to cadmium altered methylation of the hepatic glucocorticoid receptor [17], which may correlate with human data demonstrating an altered glucocorticoid response in human placental trophoblasts following cadmium exposure [66]. A lack of epigenetic data on the role of cadmium in glucocorticoid-related stress responses in utero represents a major gap in current understanding of the molecular mechanisms of intrauterine cadmium exposure.…”

“…Animal toxicological models have focused researchers’ attention on specific environmental factors that will be discussed more extensively throughout this review, including fetal exposure to cigarette smoke [12, 13], endocrine disruptors, such as bisphenol A [14–16], heavy metals [17, 18], and maternal nutrition including obesity and diabetes [19]. We aim to address the role of these different environmental exposures (Figure 2) on the human fetus or neonate and the subsequent alteration of DNA methylation patterns in varying tissue samples (Summarized in Table 1).…”