Luca Lambertini

First Experimental Demonstration of the Multipotential Carcinogenic Effects of Aspartame Administered in the Feed to Sprague-Dawley Rats

The Cesare Maltoni Cancer Research Center of the European Ramazzini Foundation has conducted a long-term bioassay on aspartame (APM), a widely used artificial sweetener. APM was administered with feed to 8-week-old Sprague-Dawley rats (100–150/sex/group), at concentrations of 100,000, 50,000, 10,000, 2,000, 400, 80, or 0 ppm. The treatment lasted until natural death, at which time all deceased animals underwent complete necropsy. Histopathologic evaluation of all pathologic lesions and of all organs and tissues collected was routinely performed on each animal of all experimental groups. The results of the study show for the first time that APM, in our experimental conditions, causes a) an increased incidence of malignant-tumor–bearing animals with a positive significant trend in males (p ≤ 0.05) and in females (p ≤ 0.01), in particular those females treated at 50,000 ppm (p ≤ 0.01); b) an increase in lymphomas and leukemias with a positive significant trend in both males (p ≤ 0.05) and females (p ≤ 0.01), in particular in females treated at doses of 100,000 (p ≤ 0.01), 50,000 (p ≤ 0.01), 10,000 (p ≤ 0.05), 2,000 (p ≤ 0.05), or 400 ppm (p ≤ 0.01); c) a statistically significant increased incidence, with a positive significant trend (p ≤ 0.01), of transitional cell carcinomas of the renal pelvis and ureter and their precursors (dysplasias) in females treated at 100,000 (p ≤ 0.01), 50,000 (p ≤ 0.01), 10,000 (p ≤ 0.01), 2,000 (p ≤ 0.05), or 400 ppm (p ≤ 0.05); and d) an increased incidence of malignant schwannomas of peripheral nerves with a positive trend (p ≤ 0.05) in males. The results of this mega-experiment indicate that APM is a multipotential carcinogenic agent, even at a daily dose of 20 mg/kg body weight, much less than the current acceptable daily intake. On the basis of these results, a reevaluation of the present guidelines on the use and consumption of APM is urgent and cannot be delayed.

Differential expression of imprinted genes in normal and IUGR human placentas.

Genomic imprinting refers to silencing of one parental allele in the zygotes of gametes depending upon the parent of origin. Loss of imprinting (LOI) is the gain of function from the silent allele that can have a maximum effect of doubling the gene dosage. LOI may play a significant role in the etiology of intrauterine growth restriction (IUGR). Using placental tissue from 10 normal and 7 IUGR pregnancies, we conducted a systematic survey of the expression of a panel of 74 “putatively” imprinted genes using quantitative RT-PCR. We found that 52/74 (~70%) of the genes were expressed in human placentas. Nine of the 52 (17%) expressed genes were significantly differentially expressed between normal and IUGR placentas; 5 were up-regulated (PHLDA2, ILK2, NNAT, CCDC86, PEG10) and 4 down-regulated (PLAGL1, DHCR24, ZNF331, CDKAL1). We also assessed LOI profile of 14 imprinted genes in 14 normal and 24 IUGR placentas using a functional and sensitive assay developed in our laboratory. Little LOI was observed in any placentas for 5 of the genes (PEG10, PHLDA2, MEG3, EPS15, CD44). With the 149 heterozygosities examined, 40 (26.8%) exhibited LOI > 3%. Some genes exhibited frequent LOI in placentas regardless of the disease status (IGF2, TP73, MEST, SLC22A18, PEG3), while others exhibited LOI only in IUGR placentas (PLAGL1, DLK1, H19, SNRPN). Importantly, there was no correlation between gene expression and LOI profile. Our study suggests that genomic imprinting may play a role in IUGR pathogenesis, but mechanisms other than LOI may contribute to dysregulation of imprinted genes.

A Research Strategy to Discover the Environmental Causes of Autism and Neurodevelopmental Disabilities

Autism, attention deficit/hyperactivity disorder (ADHD), mental retardation, dyslexia, and other biologically based disorders of brain development affect between 400,000 and 600,000 of the 4 million children born in the United States each year. The Centers for Disease Control and Prevention (CDC) has reported that autism spectrum disorder (ASD) now affects 1.13% (1 of 88) of American children (CDC 2012) and ADHD affects 14% (CDC 2005; Pastor and Reuben 2008). Treatment of these disorders is difficult; the disabilities they cause can last lifelong, and they are devastating to families. In addition, these disorders place enormous economic burdens on society (Trasande and Liu 2011). Although discovery research to identify the potentially preventable causes of neuro-develop-mental disorders (NDDs) has increased in recent years, more research is urgently needed. This research encompasses both genetic and environ-mental studies. Genetic research has received particular investment and attention (Autism Genome Project Consortium et al. 2007; Buxbaum and Hof 2011; Fernandez et al. 2012; O’Roak et al. 2011; Sakurai et al. 2011) and has demonstrated that ASD and certain other NDDs have a strong hereditary component (Buxbaum and Hof 2011; Sakurai et al. 2011). Linkage studies have identified candidate autism susceptibility genes at multiple loci, most consistently on chromosomes 7q, 15q, and 16p (Autism Genome Project Consortium et al. 2007; Sakurai et al. 2011). Exome sequencing in sporadic cases of autism has detected new mutations (O’Roak et al. 2011), and copy number variant studies have identified several hundred copy number variants putatively linked to autism (Fernandez et al. 2012). The candidate genes most strongly implicated in NDD causation encode for proteins involved in synaptic architecture, neuro-transmitter synthesis (e.g., ©-amino-butyric acid serotonin), oxytocin receptors, and cation trafficking (Sakurai et al. 2011). No single anomaly predominates. Instead, autism appears to be a family of diseases with common pheno-types linked to a series of genetic anomalies, each of which is responsible for no more than 2–3% of cases. The total fraction of ASD attributable to genetic inheri-tance may be about 30–40%. Exploration of the environmental causes of autism and other NDDs has been catalyzed by growing recognition of the exquisite sensitivity of the developing human brain to toxic chemicals (Grandjean and Landrigan 2006). This susceptibility is greatest during unique “windows of vulnerability” that open only in embryonic and fetal life and have no later counter-part (Miodovnik 2011). “Proof of the principle” that early exposures can cause autism comes from studies linking ASD to medications taken in the first trimester of pregnancy—thalidomide, misoprostol, and valproic acid—and to first-trimester rubella infection (Arndt et al. 2005; Daniels 2006). This “proof-of-principle” evidence for environmental causation is supported further by findings from prospective birth cohort epidemio-logical studies, many of them supported by the National Institute of Environmental Health Sciences (NIEHS). These studies enroll women during pregnancy, measure prenatal exposures in real time as they occur, and then follow children longitudinally with periodic direct examinations to assess growth, development, and the presence of disease. Prospective studies are powerful engines for the discovery of etiologic associations between prenatal exposures and NDDs. They have linked autistic behaviors with prenatal exposures to the organophosphate insecticide chlorpyrifos (Eskenazi et al. 2007) and also with prenatal exposures to phthalates (Miodovnik et al. 2011). Additional prospective studies have linked loss of cognition (IQ), dyslexia, and ADHD to lead (Jusko et al. 2008), methyl-mercury (Oken et al. 2008), organophosphate insecticides (London et al. 2012), organo-chlorine insecticides (Eskenazi et al. 2008), polychlorinated biphenyls (Winneke 2011), arsenic (Wasserman et al. 2007), manganese (Khan et al. 2011), polycyclic aromatic hydrocarbons (Perera et al. 2009), bisphenol A (Braun et al. 2011), brominated flame retardants (Herbstman et al. 2010), and perfluorinated compounds (Stein and Savitz 2011). Toxic chemicals likely cause injury to the developing human brain either through direct toxicity or inter-actions with the genome. An expert committee convened by the U.S. National Academy of Sciences (NAS) estimated that 3% of neuro-behavioral disorders are caused directly by toxic environ-mental exposures and that another 25% are caused by inter-actions between environmental factors, defined broadly, and inherited susceptibilities (National Research Council 2000). Epigenetic modification of gene expression by toxic chemicals that results in DNA methyla-tion, histone modification, or changes in activity levels of non-protein-coding RNA (ncRNAs) may be a mechanism of such gene–environment interaction (Grafodatskaya et al. 2010). Epigenetic “marks” have been shown to be able to influence gene expression and alter high-order DNA structure (Anway and Skinner 2006; Waterland and Jirtle 2004). A major unanswered question is whether there are still undiscovered environ-mental causes of autism or other NDDs among the thousands of chemicals currently in wide use in the United States. In the past 50 years, > 80,000 new synthetic chemicals have been developed (Landrigan and Goldman 2011). The U.S. Environmental Protection Agency has identified 3,000 “high production volume” (HPV) chemicals that are in widest use and thus pose greatest potential for human exposure (Goldman 1998). These HPV chemicals are used today in millions of consumer products. Children and pregnant women are exposed extensively to them, and CDC surveys detect quantifiable levels of nearly 200 HPV chemicals in the bodies of virtually all Americans, including pregnant women (Woodruff et al. 2011). The significance of early chemical exposures for children’s health is not yet fully understood. A great concern is that a large number of the chemicals in widest use have not undergone even minimal assessment of potential toxicity, and only about 20% have been screened for potential toxicity during early development (Landrigan and Goldman 2011). Unless studies specifically examine develop-mental consequences of early exposures to untested chemicals, sub-clinical dysfunction caused by these exposures can go unrecognized for years. One example is the “silent epidemic” of childhood lead poisoning: From the 1940s to the 1980s, millions of American children were exposed to excessive levels of lead from paint and gasoline, resulting in reduced average intelligence by 2–5 IQ points (Grosse et al. 2002). The late David Rall, former director of NIEHS, once observed that “If thalidomide had caused a 10-point loss of IQ instead of birth defects of the limbs, it would likely still be on the market” (Weiss 1982). To begin formulation of a systematic strategy for discovery of potentially preventable environmental causes of autism and other NDDs, the Mount Sinai Children’s Environmental Health Center, with the support of the NIEHS and Autism Speaks, convened a workshop on “Exploring the Environmental Causes of Autism and Learning Disabilities.” This workshop produced a series of papers by leading researchers, some of which are published in this issue of Environmental Health Perspectives. It also generated a list of 10 chemi-cals and mixtures widely distributed in the environment that are already suspected of causing develop-mental neuro-toxicity: Lead (Jusko et al. 2008) Methylmercury (Oken et al. 2008) Polychlorinated biphenyls (Winneke 2011) Organophosphate pesticides (Eskenazi et al. 2007; London et al. 2012) Organochlorine pesticides (Eskenazi et al. 2008) Endocrine disruptors (Braun et al. 2011; Miodovnik et al. 2011) Automotive exhaust (Volk et al. 2011) Polycyclic aromatic hydrocarbons (Perera et al. 2009) Brominated flame retardants (Herbstman et al. 2010) Perfluorinated compounds (Stein and Savitz 2011). This list is not exhaustive and will almost certainly expand in the years ahead as new science emerges. It is intended to focus research in environmental causation of NDDs on a short list of chemicals where concentrated study has high potential to generate actionable findings in the near future. Its ultimate purpose is to catalyze new evidence-based programs for prevention of disease in America’s children.

Global Methylation in the Placenta and Umbilical Cord Blood From Pregnancies With Maternal Gestational Diabetes, Preeclampsia, and Obesity

Emerging evidence indicates that maternal medical risk during pregnancy, such as gestational diabetes mellitus (GDM), preeclampsia, and obesity, predisposes the offspring to suboptimal development. However, the underlying biological/epigenetic mechanism in utero is still unknown. The current pilot study (N = 50) compared the levels of global methylation in the placenta and umbilical cord blood among women with and without each risk condition (GDM, preeclampsia, and obesity) and explored whether the levels of global methylation were associated with fetal/infant growth. Results show that global methylation levels in the placenta were lower in patients with gestational diabetes (P = .003) and preeclampsia (P = .05) but higher with obesity (P = .01). Suggestive negative associations were found between global methylation level in the placenta and infant body length and head circumference. While preliminary, it is possible that the placenta tissue, but not umbilical cord blood, may be epigenetically programmed by maternal GDM, preeclampsia, and obesity to carry out its own specific functions that influence fetal growth.

Results of Long‐Term Experimental Studies on the Carcinogenicity of Ethylene‐bis‐Dithiocarbamate (Mancozeb) in Rats

Abstract: Mancozeb, an ethylene‐bis‐dithiocarbamate (EBDC), has been one of the most commonly used fungicides in commercial use for several decades. Nevertheless, up to now, no adequate published experimental studies on the carcinogenicity of Mancozeb have been published. Because of the importance of the compound and of the number of people potentially exposed (workers engaged in the production and use of the fungicide, people living in agricultural areas where the compound is sprayed, and people consuming polluted products), a long‐term experimental study of Mancozeb was begun at the Cancer Research Center of the Ramazzini Foundation. Groups of 150 male and female Sprague‐Dawley rats, 8 weeks old at the start of the treatment, were administered Mancozeb at the concentration of 1000, 500, 100, 10, and 0 ppm in feed supplied ad libitum for 104 weeks. At the end of the treatment, animals were kept under controlled conditions until spontaneous death. Mancozeb caused an increase in (1) total malignant tumors, (2) malignant mammary tumors, (3) Zymbal gland and ear duct carcinomas, (4) hepatocarcinomas, (5) malignant tumors of the pancreas, (6) malignant tumors of the thyroid gland, (7) osteosarcomas of the bones of the head, and (8) hemolymphoreticular neoplasias. On the basis of these data, Mancozeb must be considered a multipotent carcinogenic agent.

A sensitive functional assay reveals frequent loss of genomic imprinting in human placenta

Loss of imprinting (LOI) is the gain of expression from the silent allele of an imprinted gene normally expressed from only one parental copy. LOI has been associated with neurodevelopmental disorders and reproductive abnormalities. The mechanisms of imprinting are varied, with DNA methylation representing only one. We have developed a functional transcriptional assay for LOI that is not limited to a single mechanism of imprinting. The method employs allele-specific PCR analysis of RT-PCR products containing common readout polymorphisms. With this method, we are able to measure LOI at the sensitivity of 1%. The method has been applied to measurement of LOI in human placentas. We found that RNA was stable in placentas stored for more than 1 hour at 4°C following delivery. We analyzed a test panel of 26 genes known to be imprinted in the human genome. We found that 18 genes were expressed in placenta. Fourteen of the 18 expressed genes contained common readout polymorphisms in the transcripts with a minor allele frequency >20%. We found that 5 of the 14 genes were not imprinted in placenta. Using the remaining 9 genes, we examined 93 heterozygosities in 27 samples. The range of LOI was 0% - 96%. Among the 93 heterozygosities, we found 23 examples (25%) had LOI >3% and 8 examples (9%) had LOI 1 - 3%. Our results indicate that LOI is common in human placentas. Because LOI in placenta is common, it may be an important new biomarker for influences on prenatal epigenetics.

Genomic loss of imprinting in first-trimester human placenta.

OBJECTIVE The purpose of this study was to investigate imprinting patterns in first-trimester human placentas. STUDY DESIGN Using samples of 17 first-trimester and 14 term placentas from uncomplicated pregnancies, we assessed loss of imprinting (LOI) at the RNA level in a panel of 14 genes that are known to be imprinted in the placenta with the use of a quantitative allele-specific reverse transcriptase polymerase chain reaction analysis of those genes that contained readout single nucleotide polymorphisms in their transcripts. RESULTS There is significant LOI (ie, biallelic expression) in all 14 genes in first-trimester placentas. LOI was more variable and generally at lower levels at term. Although there is little difference in gene expression, the level of LOI is higher in the first-trimester placentas, compared with term placentas. CONCLUSION Genomic imprinting appears to be a dynamic maturational process across gestation in human placenta. In contrast with prevailing theories, epigenetic imprints may continue to evolve past 12 weeks of gestation.

Placental expression profile of imprinted genes impacts birth weight

The importance of imprinted genes in regulating feto-placental development has been long established. However, a comprehensive assessment of the role of placental imprinted gene expression on fetal growth has yet to be conducted. In this study, we examined the association between the placental expression of 108 established and putative imprinted genes and birth weight in 677 term pregnancies, oversampled for small for gestational age (SGA) and large for gestational age (LGA) infants. Using adjusted multinomial regression analyses, a 2-fold increase in the expression of 9 imprinted genes was positively associated with LGA status: BLCAP [odds ratio (OR) = 3.78, 95% confidence interval (CI): 1.83, 7.82], DLK1 [OR = 1.63, 95% CI: 1.27, 2.09], H19 [OR = 2.79, 95% CI: 1.77, 4.42], IGF2 [OR = 1.43, 95% CI:1.31, 2.40], MEG3 [OR = 1.42, 95% CI: 1.19, 1.71], MEST [OR = 4.78, 95% CI: 2.64, 8.65], NNAT [OR = 1.40, 95% CI: 1.05, 1.86], NDN [OR = 2.52, 95% CI: 1.72, 3.68], and PLAGL1 [OR = 1.85, 95% CI: 1.40, 2.44]. For SGA status, a 2-fold increase in MEST expression was associated with decreased risk [OR = 0.31, 95% CI: 0.17, 0.58], while a 2-fold increase in NNAT expression was associated with increased risk [OR = 1.52, 95% CI: 1.1, 2.1]. Following a factor analysis, all genes significantly associated with SGA or LGA status loaded onto 2 of the 8 gene-sets underlying the variability in the dataset. Our comprehensive placental profiling of imprinted genes in a large birth cohort supports the importance of these genes for fetal growth. Given that abnormal birth weight is implicated in numerous diseases and developmental abnormalities, the expression pattern of placental imprinted genes has the potential to be developed as a novel biomarker for postnatal health outcomes.

Effect of postnatal low-dose exposure to environmental chemicals on the gut microbiome in a rodent model

BackgroundThis proof-of-principle study examines whether postnatal, low-dose exposure to environmental chemicals modifies the composition of gut microbiome. Three chemicals that are widely used in personal care products—diethyl phthalate (DEP), methylparaben (MPB), triclosan (TCS)—and their mixture (MIX) were administered at doses comparable to human exposure to Sprague-Dawley rats from birth through adulthood. Fecal samples were collected at two time points: postnatal day (PND) 62 (adolescence) and PND 181 (adulthood). The gut microbiome was profiled by 16S ribosomal RNA gene sequencing, taxonomically assigned and assessed for diversity.ResultsMetagenomic profiling revealed that the low-dose chemical exposure resulted in significant changes in the overall bacterial composition, but in adolescent rats only. Specifically, the individual taxon relative abundance for Bacteroidetes (Prevotella) was increased while the relative abundance of Firmicutes (Bacilli) was reduced in all treated rats compared to controls. Increased abundance was observed for Elusimicrobia in DEP and MPB groups, Betaproteobacteria in MPB and MIX groups, and Deltaproteobacteria in TCS group. Surprisingly, these differences diminished by adulthood (PND 181) despite continuous exposure, suggesting that exposure to the environmental chemicals produced a more profound effect on the gut microbiome in adolescents. We also observed a small but consistent reduction in the bodyweight of exposed rats in adolescence, especially with DEP and MPB treatment (p < 0.05), which is consistent with our findings of a reduced Firmicutes/Bacteroidetes ratio at PND 62 in exposed rats.ConclusionsThis study provides initial evidence that postnatal exposure to commonly used environmental chemicals at doses comparable to human exposure is capable of modifying the gut microbiota in adolescent rats; whether these changes lead to downstream health effects requires further investigation.

Differential methylation of imprinted genes in growth-restricted placentas.

A complex network of epigenetic factors participates in regulating the monoallelic expression of a small subset of genes (˜1%) in the human genome. This phenomenon goes under the definition of genomic imprinting, a parent-of-origin effect that, when altered during early embryogenesis, may influence fetal development into adulthood. Pertubations in genomic imprinting have been associated with placental and fetal growth restrictions. We analyzed the differential DNA methylation of all known imprinted genes on 10 appropriate-for-gestational-age, clinically normal, placentas and 7 severe intrauterine growth-restricted placentas. Samples were pooled according to the diagnosis and analyzed by methylated DNA immunoprecipitation (MeDIP) on a tiling microarray platform. The distribution of the differentially methylated regions (DMRs) identified in growth-restricted placentas showed a slight tendency toward hypermethylation. Imprinted genes not expressed in placenta showed a unique DMR profile with the fewest hyper- and hypomethylated DMRs. Promoter and CpG island DMRs were sporadic and randomly distributed. The vast majority of DMR identified (˜99%) were mapped in introns, showing no common sequence features. Also, by using the more advanced array data mining softwares, no significant patterns emerged. In contrast, differential methylation showed a highly significant correlation with gene length. Overall these data suggest that differential methylation changes in growth-restricted placentas occur throughout the genomic regions, encompassing genes actively expressed in the placenta. These findings warrant caution in interpreting the significance of genes carrying clustered DMRs because the distribution of DMRs in a gene may be attributed as a function of its length rather than as a specific biological role.