Perfluoroalkyl Acids: A Review of Monitoring and Toxicological Findings

In recent years, human and wildlife monitoring studies have identified perfluoroalkyl acids (PFAA) worldwide. This has led to efforts to better understand the hazards that may be inherent in these compounds, as well as the global distribution of the PFAAs. Much attention has focused on understanding the toxicology of the two most widely known PFAAs, perfluorooctanoic acid, and perfluorooctane sulfate. More recently, research was extended to other PFAAs. There has been substantial progress in understanding additional aspects of the toxicology of these compounds, particularly related to the developmental toxicity, immunotoxicity, hepatotoxicity, and the potential modes of action. This review provides an overview of the recent advances in the toxicology and mode of action for PFAAs, and of the monitoring data now available for the environment, wildlife, and humans. Several avenues of research are proposed that would further our understanding of this class of compounds.

Maternal nutrient supplementation counteracts bisphenol A-induced DNA hypomethylation in early development

The hypothesis of fetal origins of adult disease posits that early developmental exposures involve epigenetic modifications, such as DNA methylation, that influence adult disease susceptibility. In utero or neonatal exposure to bisphenol A (BPA), a high-production-volume chemical used in the manufacture of polycarbonate plastic, is associated with higher body weight, increased breast and prostate cancer, and altered reproductive function. This study shows that maternal exposure to this endocrine-active compound shifted the coat color distribution of viable yellow agouti (Avy) mouse offspring toward yellow by decreasing CpG (cytosine-guanine dinucleotide) methylation in an intracisternal A particle retrotransposon upstream of the Agouti gene. CpG methylation also was decreased at another metastable locus, the CDK5 activator-binding protein (CabpIAP). DNA methylation at the Avy locus was similar in tissues from the three germ layers, providing evidence that epigenetic patterning during early stem cell development is sensitive to BPA exposure. Moreover, maternal dietary supplementation, with either methyl donors like folic acid or the phytoestrogen genistein, negated the DNA hypomethylating effect of BPA. Thus, we present compelling evidence that early developmental exposure to BPA can change offspring phenotype by stably altering the epigenome, an effect that can be counteracted by maternal dietary supplements.

Perinatal exposure to the phthalates DEHP, BBP, and DINP, but not DEP, DMP, or DOTP, alters sexual differentiation of the male rat

In mammals, exposure to antiandrogenic chemicals during sexual differentiation can produce malformations of the reproductive tract. Perinatal administration of AR antagonists like vinclozolin and procymidone or chemicals like di(2-ethylhexyl) phthalate (DEHP) that inhibit fetal testicular testosterone production demasculinize the males such that they display reduced anogenital distance (AGD), retained nipples, cleft phallus with hypospadias, undescended testes, a vaginal pouch, epididymal agenesis, and small to absent sex accessory glands as adults. In addition to DEHP, di-n-butyl (DBP) also has been shown to display antiandrogenic activity and induce malformations in male rats. In the current investigation, we examined several phthalate esters to determine if they altered sexual differentiation in an antiandrogenic manner. We hypothesized that the phthalate esters that altered testis function in the pubertal male rat would also alter testis function in the fetal male and produce malformations of androgen-dependent tissues. In this regard, we expected that benzyl butyl (BBP) and diethylhexyl (DEHP) phthalate would alter sexual differentiation, while dioctyl tere- (DOTP or DEHT), diethyl (DEP), and dimethyl (DMP) phthalate would not. We expected that the phthalate mixture diisononyl phthalate (DINP) would be weakly active due to the presence of some phthalates with a 6-7 ester group. DEHP, BBP, DINP, DEP, DMP, or DOTP were administered orally to the dam at 0.75 g/kg from gestational day (GD) 14 to postnatal day (PND) 3. None of the treatments induced overt maternal toxicity or reduced litter sizes. While only DEHP treatment reduced maternal weight gain during the entire dosing period by about 15 g, both DEHP and DINP reduced pregnancy weight gain to GD 21 by 24 g and 14 g, respectively. DEHP and BBP treatments reduced pup weight at birth (15%). Male (but not female) pups from the DEHP and BBP groups displayed shortened AGDs (about 30%) and reduced testis weights (about 35%). As infants, males in the DEHP, BBP, and DINP groups displayed femalelike areolas/nipples (87, 70, and 22% (p < 0.01), respectively, versus 0% in other groups). All three of the phthalate treatments that induced areolas also induced a significant incidence of reproductive malformations. The percentages of males with malformations were 82% (p < 0.0001) for DEHP, 84% (p < 0.0001) for BBP, and 7.7% (p < 0.04) in the DINP group. In summary, DEHP, BBP, and DINP all altered sexual differentiation, whereas DOTP, DEP, and DMP were ineffective at this dose. Whereas DEHP and BBP were of equivalent potency, DINP was about an order of magnitude less active.

Glucocorticoid exposure in utero: new model for adult hypertension

Hypertension is strongly predicted by the combination of low birthweight and a large placenta. This association could be due to increased fetal exposure to maternal glucocorticoids. Fetal protection is normally effected by placental 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD), which converts physiological glucocorticoids to inactive products. We found that rat placental 11 beta-OHSD activity correlated positively with term fetal weight and negatively with placental weight. Offspring of rats treated during pregnancy with dexamethasone (which is not metabolised by 11 beta-OHSD) had lower birthweights and higher blood pressure when adult than did offspring of control rats. Increased fetal glucocorticoid exposure secondary to attenuated placental 11 beta-OHSD activity may link low birthweight and high placental weight with hypertension.

Silica and titanium dioxide nanoparticles cause pregnancy complications in mice

The increasing use of nanomaterials has raised concerns about their potential risks to human health. Recent studies have shown that nanoparticles can cross the placenta barrier in pregnant mice and cause neurotoxicity in their offspring, but a more detailed understanding of the effects of nanoparticles on pregnant animals remains elusive. Here, we show that silica and titanium dioxide nanoparticles with diameters of 70 nm and 35 nm, respectively, can cause pregnancy complications when injected intravenously into pregnant mice. The silica and titanium dioxide nanoparticles were found in the placenta, fetal liver and fetal brain. Mice treated with these nanoparticles had smaller uteri and smaller fetuses than untreated controls. Fullerene molecules and larger (300 and 1,000 nm) silica particles did not induce these complications. These detrimental effects are linked to structural and functional abnormalities in the placenta on the maternal side, and are abolished when the surfaces of the silica nanoparticles are modified with carboxyl and amine groups.

Premature delivery of foetal lambs infused with glucocorticoids

SUMMARY

Dexamethasone caused premature delivery when infused into foetal lambs at rates of 0·06–4·0 mg./24 hr. but it had no effect when administered to pregnant ewes at the rate of 4·0 mg./24 hr. Infusions into the foetus of deoxycorticosterone or corticosterone were ineffective; mixtures of dexamethasone and deoxycorticosterone did not cause parturition more rapidly than dexamethasone alone. Thus, the ability of corticosteroids to cause premature parturition appears to depend on glucocorticoid rather than mineralocorticoid activity.

Parturition induced by dexamethasone was not delayed by administration of 100 mg. progesterone/24 hr. to the ewe or to the foetus. This suggests either that withdrawal of inhibitory effects of progesterone on the myometrium can occur independently of the progesterone concentration in peripheral plasma, or that the mechanism of parturition provoked by corticosteroids in the foetus can override any regulatory influence of progesterone on myometrial contractility.

Partial aeration of the lungs was observed in lambs born vaginally at 117–123 days of gestation after receiving dexamethasone. It is suggested that this may be the result of accelerated appearance of surfactant activity.

Selective serotonin-reuptake inhibitors and risk of persistent pulmonary hypertension of the newborn

BACKGROUND

Persistent pulmonary hypertension of the newborn (PPHN) is associated with substantial infant mortality and morbidity. A previous cohort study suggested a possible association between maternal use of the selective serotonin-reuptake inhibitor (SSRI) fluoxetine late in the third trimester of pregnancy and the risk of PPHN in the infant. We performed a case-control study to assess whether PPHN is associated with exposure to SSRIs during late pregnancy.

METHODS

Between 1998 and 2003, we enrolled 377 women whose infants had PPHN and 836 matched control women and their infants. Maternal interviews were conducted by nurses, who were blinded to the study hypothesis, regarding medication use in pregnancy and potential confounders, including demographic variables and health history.

RESULTS

Fourteen infants with PPHN had been exposed to an SSRI after the completion of the 20th week of gestation, as compared with six control infants (adjusted odds ratio, 6.1; 95 percent confidence interval, 2.2 to 16.8). In contrast, neither the use of SSRIs before the 20th week of gestation nor the use of non-SSRI antidepressant drugs at any time during pregnancy was associated with an increased risk of PPHN.

CONCLUSIONS

These data support an association between the maternal use of SSRIs in late pregnancy and PPHN in the offspring; further study of this association is warranted. These findings should be taken into account in decisions as to whether to continue the use of SSRIs during pregnancy.

Longitudinal analyses of prenatal and postnatal lead exposure and early cognitive development

In a prospective cohort study of 249 children from birth to two years of age, we assessed the relation between prenatal and postnatal lead exposure and early cognitive development. On the basis of lead levels in umbilical-cord blood, children were assigned to one of three prenatal-exposure groups: low (less than 3 micrograms per deciliter), medium (6 to 7 micrograms per deciliter), or high (greater than or equal to 10 micrograms per deciliter). Development was assessed semiannually, beginning at the age of six months, with use of the Mental Development Index of the Bayley Scales of Infant Development (mean +/- SD, 100 +/- 16). Capillary-blood samples obtained at the same times provided measures of postnatal lead exposure. Regression methods for longitudinal data were used to evaluate the association between infants' lead levels and their development scores after adjustment for potential confounders. At all ages, infants in the high-prenatal-exposure group scored lower than infants in the other two groups. The estimated difference between the overall performance of the low-exposure and high-exposure groups was 4.8 points (95 percent confidence interval, 2.3 to 7.3). Between the medium- and high-exposure groups, the estimated difference was 3.8 points (95 percent confidence interval, 1.3 to 6.3). Scores were not related to infants' postnatal blood lead levels. It appears that the fetus may be adversely affected at blood lead concentrations well below 25 micrograms per deciliter, the level currently defined by the Centers for Disease Control as the highest acceptable level for young children.

Cocaine use in pregnancy

With the increasing use of cocaine in the United States, there has been growing concern regarding its effects on the fetuses and neonates of pregnant cocaine abusers. Twenty-three cocaine-using women enrolled in a comprehensive perinatal-addiction program were divided into two groups: those using cocaine only and those using cocaine plus narcotics. These two groups were compared with a group of women who had used narcotics in the past and were maintained on methadone during pregnancy, and with a group of drug-free women. All four groups were similar in maternal age, socioeconomic status, number of pregnancies, and cigarette, marijuana, and alcohol use. Their medical histories indicated that the cocaine-using women had a significantly higher rate of spontaneous abortion than the women in the other two groups. In the pregnancies under study, four cocaine-using women had onset of labor with abruptio placentae immediately after intravenous self-injection of cocaine. Neonatal gestational age, birth weight, length, and head circumference were not affected by cocaine use. However, the Brazelton Neonatal Behavioral Assessment Scale revealed that infants exposed to cocaine had significant depression of interactive behavior and a poor organizational response to environmental stimuli (state organization). These preliminary observations suggest that cocaine influences the outcome of pregnancy as well as the neurologic behavior of the newborn, but a full assessment will require a larger number of pregnancies and longer follow-up.

Use of chemotherapy during human pregnancy

When cancer is diagnosed in a pregnant woman, life-saving chemotherapy for the mother poses life-threatening concerns for the developing fetus. Depending on the type of cancer and the stage at diagnosis, chemotherapy cannot necessarily be delayed until after delivery. Women diagnosed with acute lymphoblastic leukaemia who decline both termination and chemotherapy often die with the previable fetus in utero. Safe use of chemotherapy, especially during the second and third trimester, have been reported, and pregnant women with cancer can accept therapy without definite neonatal harm. Here, we review the use of chemotherapy in pregnancy by trimester of exposure and summarise neonatal outcomes, including malformations, perinatal complications, and oldest age of neonatal follow-up. We will also discuss the modes of action of the drugs used and look at the multiagent regimens recommended for use during pregnancy.

Role of breast cancer resistance protein in the bioavailability and fetal penetration of topotecan

BACKGROUND AND METHODS

Breast cancer resistance protein (BCRP/MXR/ABCP) is a multidrug-resistance protein that is a member of the adenosine triphosphate-binding cassette family of drug transporters. BCRP can render tumor cells resistant to the anticancer drugs topotecan, mitoxantrone, doxorubicin, and daunorubicin. To investigate the physiologic role of BCRP, we used polarized mammalian cell lines to determine the direction of BCRP drug transport. We also used the BCRP inhibitor GF120918 to assess the role of BCRP in protecting mice against xenobiotic drugs. Bcrp1, the murine homologue of BCRP, was expressed in the polarized mammalian cell lines LLC-PK1 and MDCK-II, and the direction of Bcrp1-mediated transport of topotecan and mitoxantrone was determined. To avoid the confounding drug transport provided by P-glycoprotein (P-gp), the roles of Bcrp1 in the bioavailability of topotecan and the effect of GF120918 were studied in both wild-type and P-gp-deficient mice and their fetuses.

RESULTS

Bcrp1 mediated apically directed transport of drugs in polarized cell lines. When both topotecan and GF120918 were administered orally, the bioavailability (i.e., the extent to which a drug becomes available to a target tissue after administration) of topotecan in plasma was dramatically increased in P-gp-deficient mice (greater than sixfold) and wild-type mice (greater than ninefold), compared with the control (i.e., vehicle-treated) mice. Furthermore, treatment with GF120918 decreased plasma clearance and hepatobiliary excretion of topotecan and increased (re-)uptake by the small intestine. In pregnant GF120918-treated, P-gp-deficient mice, relative fetal penetration of topotecan was twofold higher than that in pregnant vehicle-treated mice, suggesting a function for BCRP in the maternal-fetal barrier of the placenta.

CONCLUSIONS

Bcrp1 mediates apically directed drug transport, appears to reduce drug bioavailability, and protects fetuses against drugs. We propose that strategic application of BCRP inhibitors may thus lead to more effective oral chemotherapy with topotecan or other BCRP substrate drugs.

Brain malformations related to prenatal exposure to ethanol

Microcephaly and mental retardation have been principal features of the fetal alcohol syndrome. This article describes the neuropathologic findings in four human neonates who were exposed to large quantities of ethanol at frequent intervals during gestation. The findings suggest that intrauterine exposure to ethanol can result in structural abnormalities of the brain. All four brains displayed similar malformations stemming from errors in migration of neuronal and glial elements. Hydrocephalus was one consequence of the malformations in two of the infants. Futhermore, the brain alterations may be the only distinct abnormality produced by in utero ethanol exposure. Only two of the four subjects were diagnosed as having the fetal alcohol syndrome from external criteria.

Glucocorticoids and fetal programming part 1: Outcomes

Fetal development is a critical period for shaping the lifelong health of an individual. However, the fetus is susceptible to internal and external stimuli that can lead to adverse long-term health consequences. Glucocorticoids are an important developmental switch, driving changes in gene regulation that are necessary for normal growth and maturation. The fetal hypothalamic-pituitary-adrenal (HPA) axis is particularly susceptible to long-term programming by glucocorticoids; these effects can persist throughout the life of an organism. Dysfunction of the HPA axis as a result of fetal programming has been associated with impaired brain growth, altered behaviour and increased susceptibility to chronic disease (such as metabolic and cardiovascular disease). Moreover, the effects of glucocorticoid-mediated programming are evident in subsequent generations, and transmission of these changes can occur through both maternal and paternal lineages.

Barrier capacity of human placenta for nanosized materials

BACKGROUND

Humans have been exposed to fine and ultrafine particles throughout their history. Since the Industrial Revolution, sources, doses, and types of nanoparticles have changed dramatically. In the last decade, the rapidly developing field of nanotechnology has led to an increase of engineered nanoparticles with novel physical and chemical properties. Regardless of whether this exposure is unintended or not, a careful assessment of possible adverse effects is needed. A large number of projects have been carried out to assess the consequences of combustion-derived or engineered nanoparticle exposure on human health. In recent years there has been a growing concern about the possible health influence of exposure to air pollutants during pregnancy, hence an implicit concern about potential risk for nanoparticle exposure in utero. Previous work has not addressed the question of whether nanoparticles may cross the placenta.

OBJECTIVE

In this study we investigated whether particles can cross the placental barrier and affect the fetus.

METHODS

We used the ex vivo human placental perfusion model to investigate whether nanoparticles can cross this barrier and whether this process is size dependent. Fluorescently labeled polystyrene beads with diameters of 50, 80, 240, and 500 nm were chosen as model particles.

RESULTS

We showed that fluorescent polystyrene particles with diameter up to 240 nm were taken up by the placenta and were able to cross the placental barrier without affecting the viability of the placental explant.

CONCLUSIONS

The findings suggest that nanomaterials have the potential for transplacental transfer and underscore the need for further nanotoxicologic studies on this important organ system.

Cytokine induction in fetal rat brains and brain injury in neonatal rats after maternal lipopolysaccharide administration

Induction of proinflammatory cytokines has been proposed to be a link between prenatal maternal intrauterine infection and neonatal brain damage. It is known that the endotoxin, lipopolysaccharide (LPS), released during bacterial infection crosses the placenta. Cytokine induction in the fetal rat brain after maternal administration of LPS was determined by reverse transcriptase-polymerase chain reaction method. LPS suspension in pyrogen-free saline was administered (i.p.) to pregnant rats at 18 d of gestation. The control group was treated with pyrogen-free saline. Expression of the proinflammatory cytokines, tumor necrosis factor-alpha and IL-1beta mRNA, in the fetal rat brain was increased in a dose-dependent manner at 1 h after LPS administration. The great increase in expression of IL-1beta mRNA was only observed at 1 h after injection of LPS (4 mg/kg), whereas the increased expression of tumor necrosis factor-alpha was still detectable from 4 to 24 h after LPS administration. Brain injuries were examined by immunohistochemistry in 8-d-old rat pups born to the dams that were consecutively treated with LPS (500 microg/kg) or pyrogen-free saline on gestation d 18 and 19. No apparent necrotic tissue damage was found in either the LPS group or the control group. Myelin basic protein staining, as a marker of myelin, was clearly observed in the internal capsule and the fimbria hippocampus in the rat brain from the control group. Myelin basic protein staining was much less and weaker in the brains of the LPS-treated group. Glial fibrillary acidic protein-positive astrocytes were observed in both the control and the LPS-treated groups. The LPS-treated group appeared to have more glial fibrillary acidic protein-positive astrocytes in the hippocampal and the cortex areas of the brain than the control group. Immunoblotting data showed that glial fibrillary acidic protein content in the cortex or the hippocampus of the LPS-treated rat brain was higher than in the control group. OX-42-positive staining (a marker of the type 3 complement receptors) of microglial cells was greatly reduced in the 8-d-old rat brain after maternal LPS administration. However, histochemistry with tomato lectin showed that staining of both amoeboid and ramified microglial cells in the LPS-treated rat brain was similar to that in the control group. The overall results indicate that maternal LPS administration induces an increased expression of IL-1beta and tumor necrosis factor-alpha mRNA in the fetal brain. Maternal LPS administration also increases glial fibrillary acidic protein-positive astrocytes, decreases myelin basic protein and alters immunoreactivity of microglia in the brain of offspring. Although results from the current study do not provide direct evidence linking LPS-induced cytokines with the abnormalities in the neonatal rat brain, our animal model may be appropriate for exploring the mechanisms involved in the effects of maternal infection on glial cells in the brains of offspring.

Rapamycin attenuates load-induced cardiac hypertrophy in mice

BACKGROUND

Cardiac hypertrophy, or an increase in heart size, is an important risk factor for cardiac morbidity and mortality. The mammalian target of rapamycin (mTOR) is a component of the insulin-phosphoinositide 3-kinase pathway, which is known to play a critical role in the determination of cell, organ, and body size.

METHODS AND RESULTS

To examine the role of mTOR in load-induced cardiac hypertrophy, we administered rapamycin, a specific inhibitor of mTOR, to mice with ascending aortic constriction. Activity of p70 ribosomal S6 kinase 1 (S6K1), an effector of mTOR, was increased by 3.8-fold in the aortic-constricted heart. Pretreatment of mice with 2 mg. kg-1. d-1 of rapamycin completely suppressed S6K1 activation and S6 phosphorylation in response to pressure overload. The heart weight/tibial length ratio of vehicle-treated aortic-banded mice was increased by 34.4+/-3.6% compared with vehicle-treated sham-operated mice. Rapamycin suppressed the load-induced increase in heart weight by 67%. Attenuation of cardiac hypertrophy by rapamycin was associated with attenuation of the increase in myocyte cell size induced by aortic constriction. Rapamycin did not cause loss of body weight, lethality, or left ventricular dysfunction.

CONCLUSIONS

mTOR or its target(s) seems to play an important role in load-induced cardiac hypertrophy. Because systemic administration of rapamycin has been used successfully for the treatment of transplant rejection in clinical practice, it may be a useful therapeutic modality to suppress cardiac hypertrophy in patients.

Biosynthesis and toxicological effects of patulin

Patulin is a toxic chemical contaminant produced by several species of mold, especially within Aspergillus, Penicillium and Byssochlamys. It is the most common mycotoxin found in apples and apple-derived products such as juice, cider, compotes and other food intended for young children. Exposure to this mycotoxin is associated with immunological, neurological and gastrointestinal outcomes. Assessment of the health risks due to patulin consumption by humans has led many countries to regulate the quantity in food. A full understanding of the molecular genetics of patulin biosynthesis is incomplete, unlike other regulated mycotoxins (aflatoxins, trichothecenes and fumonisins), although the chemical structures of patulin precursors are now known. The biosynthetic pathway consists of approximately 10 steps, as suggested by biochemical studies. Recently, a cluster of 15 genes involved in patulin biosynthesis was reported, containing characterized enzymes, a regulation factor and transporter genes. This review includes information on the current understanding of the mechanisms of patulin toxinogenesis and summarizes its toxicological effects.