Impact of Prenatal and Postnatal Exposure to Endocrine Disrupter DDT on Adrenal Medulla Function

Epinephrine is the most abundant catecholamine hormone, produced by the nervous system and adrenal glands. Endocrine disruption of epinephrine synthesis, secretion and signaling is less studied than steroid and thyroid hormones. Dichlorodiphenyltrichloroethane (DDT) is recognized as one of the most prominent environmental contaminants with a long half-life. It is a potent endocrine disrupter affecting sex steroid, mineralocorticoid, glucocorticoid and thyroid hormone production. Exposure to low doses of DDT is universal and begins in utero. Therefore, we studied adrenal medulla growth and function in male Wistar rats exposed to low doses of DDT during prenatal and postnatal development until puberty and adulthood, as well as rats exposed to DDT since the first day of postnatal development. All the exposed rats demonstrated lowered epinephrine blood levels, gradually reducing with age. DDT was found to inhibit the synthesis of tyrosine hydroxylase and affect the mitochondrial apparatus of epinephrine-producing cells during puberty and even after maturation. Low-dose exposure to DDT from birth resulted in more pronounced changes in adrenomedullary cells and a more profound decrease (up to 50%) in epinephrine secretion in adult rats. Prenatal onset of exposure demonstrated a mild effect on epinephrine-producing function (30% reduction), but was associated with lower rate of adrenal medulla growth during maturation and 25% smaller adrenal medullar size in adult rats. All subjects exposed to low doses of DDT failed to develop adaptive changes and restore proper epinephrine production. These results indicate a dysmorphogenetic effect of prenatal exposure and disruption of secretory function of adrenal chromaffin cells by postnatal exposure to DDT.     

Developmental Exposure to Endocrine Disrupter DDT Interferes with Age-Related Involution of Thymus

The impact of endocrine-disrupting chemicals on the development and involution of the immune system is a possible reason for the increased incidence of disorders associated with inappropriate immune function. The thymus is a lymphoid and also an endocrine organ, and, accordingly, its development and functioning may be impaired by endocrine disruptors. The aim was to evaluate age-related thymus involution in mature rats exposed to the endocrine disruptor DDT during prenatal and postnatal ontogeny. Methodology included in vivo experiment on male Wistar rats exposed to low doses of DDT during prenatal and postnatal development and morphological assessment of thymic involution, including the immunohistochemical detection of proliferating thymocytes. The study was carried out at the early stage of involution. Results: DDT-exposed rats exhibited a normal anatomy, and the relative weight of the thymus was within the control ranges. Histological and immunohistochemical examinations revealed increased cellularity of the cortex and the medulla, higher content of lymphoblasts, and more intensive proliferation rate of thymocytes compared to the control. Evaluation of thymic epithelial cells revealed a higher rate of thymic corpuscles formation. Conclusion: The data obtained indicate that endocrine disrupter DDT disturbs postnatal development of the thymus. Low-dose exposure to DDT during ontogeny does not suppress growth rate but violates the developmental program of the thymus by slowing down the onset of age-related involution and maintaining high cell proliferation rate. It may result in excessive formation of thymus-dependent areas in peripheral lymphoid organs and altered immune response.     

Differential Disrupting Effects of Prolonged Low-Dose Exposure to Dichlorodiphenyltrichloroethane on Androgen and Estrogen Production in Males

Dichlorodiphenyltrichloroethane (DDT) is the most widespread, persistent pollutant and endocrine disruptor on the planet. Although DDT has been found to block androgen receptors, the effects of its low-dose exposure in different periods of ontogeny on the male reproductive system remain unclear. We evaluate sex steroid hormone production in the pubertal period and after maturation in male Wistar rats exposed to low doses of o,p’-DDT, either during prenatal and postnatal development or postnatal development alone. Prenatally and postnatally exposed rats exhibit lower testosterone production and increased estradiol and estriol serum levels after maturation, associated with the delayed growth of gonads. Postnatally exposed rats demonstrate accelerated growth of gonads and higher testosterone production in the pubertal period. In contrast to the previous group, they do not present raised estradiol production. All of the exposed animals exhibit a reduced conversion of progesterone to 17OH-progesterone after sexual maturation, which indicates putative attenuation of sex steroid production. Thus, the study reveals age-dependent outcomes of low-dose exposure to DDT. Prenatal onset of exposure results in the later onset of androgen production and the enhanced conversion of androgens to estrogens after puberty, while postnatal exposure induces the earlier onset of androgen secretion.     

A Rat Model of Post-Traumatic Stress Syndrome Causes Phenotype-Associated Morphological Changes and Hypofunction of the Adrenal Gland

Background: Rats exposed to chronic predator scent stress mimic the phenotype of complex post-traumatic stress disorder (PTSD) in humans, including altered adrenal morphology and function. High- and low-anxiety phenotypes have been described in rats exposed to predator scent stress (PSS). This study aimed to determine whether these high- and low-anxiety phenotypes correlate with changes in adrenal histomorphology and corticosteroid production. Methods: Rats were exposed to PSS for ten days. Thirty days later, the rats’ anxiety index (AI) was assessed with an elevated plus-maze test. Based on differences in AI, the rats were segregated into low- (AI ≤ 0.8, n = 9) and high- (AI > 0.8, n = 10) anxiety phenotypes. Plasma corticosterone (CORT) concentrations were measured by ELISA. Adrenal CORT, desoxyCORT, and 11-dehydroCORT were measured by high-performance liquid chromatography. After staining with hematoxylin and eosin, adrenal histomorphometric changes were evaluated by measuring the thickness of the functional zones of the adrenal cortex. Results: Decreased plasma CORT concentrations, as well as decreased adrenal CORT, desoxyCORT and 11-dehydroCORT concentrations, were observed in high- but not in low-anxiety phenotypes. These decreases were associated with increases in AI. PSS led to a significant decrease in the thickness of the zona fasciculata and an increase in the thickness of the zona intermedia. The increase in the thickness of the zona intermedia was more pronounced in low-anxiety than in high-anxiety rats. A decrease in the adrenal capsule thickness was observed only in low-anxiety rats. The nucleus diameter of cells in the zona fasciculata of high-anxiety rats was significantly smaller than that of control or low-anxiety rats. Conclusion: Phenotype-associated changes in adrenal function and histomorphology were observed in a rat model of complex post-traumatic stress disorder.     

The Enigma of the Adrenarche: Identifying the Early Life Mechanisms and Possible Role in Postnatal Brain Development

Dehydroepiandrosterone (DHEA) and its sulfated metabolite (DHEAS) are dynamically regulated before birth and the onset of puberty. Yet, the origins and purpose of increasing DHEA[S] in postnatal development remain elusive. Here, we draw attention to this pre-pubertal surge from the adrenal gland—the adrenarche—and discuss whether this is the result of intra-adrenal gene expression specifically affecting the zona reticularis (ZR), if the ZR is influenced by the hypothalamic-pituitary axis, and the possible role of spino-sympathetic innervation in prompting increased ZR activity. We also discuss whether neural DHEA[S] synthesis is coordinately regulated with the developing adrenal gland. We propose that DHEA[S] is crucial in the brain maturation of humans prior to and during puberty, and suggest that the function of the adrenarche is to modulate, adapt and rewire the pre-adolescent brain for new and ever-changing social challenges. The etiology of DHEA[S] synthesis, neurodevelopment and recently described 11-keto and 11-oxygenated androgens are difficult to investigate in humans owing to: (i) ethical restrictions on mechanistic studies, (ii) the inability to predict which individuals will develop specific mental characteristics, and (iii) the difficulty of conducting retrospective studies based on perinatal complications. We discuss new opportunities for animal studies to overcome these important issues.     

The Proteome Profiles of the Cerebellum of Juvenile,Adult and Aged Rats—An Ontogenetic Study

In this study, we searched for proteins that change their expression in the cerebellum (Ce) of rats during ontogenesis. This study focuses on the question of whether specific proteins exist which are differentially expressed with regard to postnatal stages of development. A better characterization of the microenvironment and its development may result from these study findings. A differential two-dimensional polyacrylamide gel electrophoresis (2DE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis of the samples revealed that the number of proteins of the functional classes differed depending on the developmental stages. Especially members of the functional classes of biosynthesis, regulatory proteins, chaperones and structural proteins show the highest differential expression within the analyzed stages of development. Therefore, members of these functional protein groups seem to be involved in the development and differentiation of the Ce within the analyzed development stages. In this study, changes in the expression of proteins in the Ce at different postnatal developmental stages (postnatal days (P) 7, 90, and 637) could be observed. At the same time, an identification of proteins which are involved in cell migration and differentiation was possible. Especially proteins involved in processes of the biosynthesis and regulation, the dynamic organization of the cytoskeleton as well as chaperones showed a high amount of differentially expressed proteins between the analyzed dates.     

N-Acetylcysteine and Aripiprazole Improve Social Behavior and Cognition and Modulate Brain BDNF Levels in a Rat Model of Schizophrenia

Treatment of negative symptoms and cognitive disorders in patients with schizophrenia is still a serious clinical problem. The aim of our study was to compare the efficacy of chronic administration of the atypical antipsychotic drug aripiprazole (7-{4-[4-(2,3-dichlorophenyl)-1-piperazinyl] butoxy}-3,4-dihydro-2(1H)-quinolinone; ARI) and the well-known antioxidant N-acetylcysteine (NAC) both in alleviating schizophrenia-like social and cognitive deficits and in reducing the decreases in the levels of the brain-derived neurotrophic factor (BDNF) in the prefrontal cortex (PFC) and hippocampus (HIP) of adult Sprague-Dawley rats, that have been induced by chronic administration of the model compound L-buthionine-(S, R)-sulfoximine (BSO) during the early postnatal development (p5–p16). ARI was administered at doses of 0.1 and 0.3 mg/kg while NAC at doses of 10 and 30 mg/kg, alone or in combination. Administration of higher doses of ARI or NAC alone, or co-treatment with lower, ineffective doses of these drugs significantly improved social and cognitive performance as assessed in behavioral tests. Both doses of NAC and 0.3 mg/kg of ARI increased the expression of BDNF mRNA in the PFC, while all doses of these drugs and their combinations enhanced the levels of BDNF protein in this brain structure. In the HIP, only 0,3 mg/kg ARI increased the levels of both BDNF mRNA and its protein. These data show that in the rat BSO-induced neurodevelopmental model of schizophrenia, ARI and NAC differently modulated BDNF levels in the PFC and HIP.     

Intrauterine and Postnatal Exposure to High Levels of Fluoride Is Associated with Motor Impairments,Oxidative Stress,and Morphological Damage in the Cerebellum of Offspring Rats

Fluoride (F) is abundantly present on Earth and plays a beneficial role in human health. However, exposure to high doses of F can be a risk, mainly in endemic fluorosis regions. In light of this, we investigated the effects of F exposure during the intrauterine and postnatal periods of rats, in doses similar to those recommended in drinking water and the levels of F in regions with endemic fluorosis, on the offspring rats’ cerebellum. Pregnant rats were divided into three groups: control (received ultrapure water only), 10 mg F/L, and 50 mg F/L for a period of 42 days (21 days gestation and 21 days lactation). At the end of the lactation period, the male pups were evaluated by behavioral tests, morphological markers, and biochemistry assays. The results pointed out that 50 mg F/L exposure during the intrauterine and lactational period of rats is capable of promoting oxidative stress in the cerebellum with a decrease in Purkinje cell density and myelin basic protein compromise, which could be associated with functional motor impairments. In addition, although 10 mg F/L exposure promoted redox alterations, it did not affect other parameters evaluated, highlighting the safe use of F in low doses.     

Postnatal Changes of Neural Stem Cells in the Mammalian Auditory Cortex

Our previous study reported neural stem cells (NSCs) in the auditory cortex (AC) of postnatal day 3 (P3) mice in vitro. It is unclear whether AC-NSCs exist in vivo. This study aims to determine the presence and changes of AC-NSCs during postnatal development and maturation both in vitro and in vivo. P3, postnatal day 14 (P14), 2-month-old (2M), and 4-month-old (4M) mouse brain tissues were fixed and cryosectioned for NSC marker immunostaining. In vitro, P3, P14, and 2M AC tissues were dissected and cultured in suspension to study NSCs. NSC proliferation was examined by EdU incorporation and cell doubling time assays in vitro. The results show that Nestin and Sox2 double expressing NSCs were observed in the AC area from P3 to 4M in vivo, in which the number of NSCs remarkably reduced with age. In vitro, the neurosphere forming capability, cell proliferation, and percentage of Nestin and Sox2 double expressing NSCs significantly diminished with age. These results suggest that AC-NSCs exist in the mouse AC area both in vitro and in vivo, and the percentage of AC-NSCs decreases during postnatal development and maturation. The results may provide important cues for the future research of the central auditory system.     

Immunohistochemical Expression Pattern of FGFR1, FGFR2, RIP5, and HIP2 in Developing and Postnatal Kidneys of Dab1−/− (yotari) Mice

This study aimed to explore how Dab1 gene functional silencing influences the spatial and temporal expression patterns of fibroblast growth factor receptor 1 (FGFR1), fibroblast growth factor receptor 2 (FGFR2), receptor-interacting protein kinase 5 (RIP5), and huntingtin-interacting protein 2 (HIP2) in the developing and postnatal kidneys of the yotari mice as potential determinants of normal kidney formation and function. Dab1^−/− animal kidneys exhibit diminished FGFR1/FGFR2 expression in all examined developmental stages, whereas RIP5 cell immunoreactivity demonstrated negligible variation. The HIP2 expression revealed a discernible difference during the postnatal period, where we noted a significant decrease in almost all the observed kidney structures of yotari animals. An extracellular signal-regulated kinase (Erk1/2) and mammalian target of rapamycin (mTOR) expression in yotari kidneys decreased in embryonic and postnatal developmental phases for which we can hypothesize that the Erk1/2 signaling pathway in the yotari mice kidneys is dependent on Reelin with Dab1 only partially implicated in Reelin-mediated MEK/Erk1/2 activation. The impairment of FGFR1 and FGFR2 expression suggests the involvement of the observed markers in generating the CAKUT phenotype resulting in renal hypoplasia. Our study demonstrates the critical role of HIP2 in reducing cell death throughout nephrogenesis and maturation in wild-type mice and indicates a possible connection between decreased HIP2 expression in postnatal kidney structures and observed podocyte injury in yotari. Our results emphasize the crucial function of the examined markers throughout normal kidney development and their potential participation in kidney pathology and diagnostics, where they might serve as biomarkers and therapeutic targets.     

Glutathione Deficiency during Early Postnatal Development Causes Schizophrenia-Like Symptoms and a Reduction in BDNF Levels in the Cortex and Hippocampus of Adult Sprague–Dawley Rats

Growing body of evidence points to dysregulation of redox status in the brain as an important factor in the pathogenesis of schizophrenia. The aim of our study was to evaluate the effects of l-buthionine-(S,R)-sulfoximine (BSO), a glutathione (GSH) synthesis inhibitor, and 1-[2-Bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine dihydrochloride (GBR 12909), a dopamine reuptake inhibitor, given alone or in combination, to Sprague–Dawley pups during early postnatal development (p5–p16), on the time course of the onset of schizophrenia-like behaviors, and on the expression of brain-derived neurotrophic factor (BDNF) mRNA and its protein in the prefrontal cortex (PFC) and hippocampus (HIP) during adulthood. BSO administered alone decreased the levels of BDNF mRNA and its protein both in the PFC and HIP. Treatment with the combination of BSO + GBR 12909 also decreased BDNF mRNA and its protein in the PFC, but in the HIP, only the level of BDNF protein was decreased. Schizophrenia-like behaviors in rats were assessed at three time points of adolescence (p30, p42–p44, p60–p62) and in early adulthood (p90–p92) using the social interaction test, novel object recognition test, and open field test. Social and cognitive deficits first appeared in the middle adolescence stage and continued to occur into adulthood, both in rats treated with BSO alone or with the BSO + GBR 12909 combination. Behavior corresponding to positive symptoms in humans occurred in the middle adolescence period, only in rats treated with BSO + GBR 12909. Only in the latter group, amphetamine exacerbated the existing positive symptoms in adulthood. Our data show that rats receiving the BSO + GBR 12909 combination in the early postnatal life reproduced virtually all symptoms observed in patients with schizophrenia and, therefore, can be considered a valuable neurodevelopmental model of this disease.     

An interaction of DDT in the metabolism of essential fatty acids

The growth of female rats was depressed further by the incorporation of DDT into a ration deficient in essential fatty acids (EFA). With female rats fed a ration supplemented with EFA, DDT produced a slight stimulation in growth. DDT also produced an increase in the 20∶3ω9/20∶4ω6 ratio in liver lipids of male rats fed a ration deficient in EFA. These data indicate an effect in EFA nutrition. Substantial changes in the fatty acid composition of liver lipids resulted from the feeding of DDT. The proportion of 16∶0 was decreased, while that of 18∶0 was increased. With rats on the supplemented rations an increase in the proportion of 20∶4ω6 was observed, while in the deficient rats a comparable increase was observed in the proportion of 20∶3ω9. These changes in fatty acid composition have been related to the proliferation of hepatic smooth endoplasmic reticulum induced by the DDT, and it is suggested that this effect could increase the demand for EFA by the liver, thus influencing EFA nutrition. Technical Paper No. 3156, Oregon Agricultural Experiment Station.     

Signal Transduction of Mineralocorticoid and Angiotensin II Receptors in the Central Control of Sodium Appetite: A Narrative Review

Sodium appetite is an innate behavior occurring in response to sodium depletion that induces homeostatic responses such as the secretion of the mineralocorticoid hormone aldosterone from the zona glomerulosa of the adrenal cortex and the stimulation of the peptide hormone angiotensin II (ANG II). The synergistic action of these hormones signals to the brain the sodium appetite that represents the increased palatability for salt intake. This narrative review summarizes the main data dealing with the role of mineralocorticoid and ANG II receptors in the central control of sodium appetite. Appropriate keywords and MeSH terms were identified and searched in PubMed. References to original articles and reviews were examined, selected, and discussed. Several brain areas control sodium appetite, including the nucleus of the solitary tract, which contains aldosterone-sensitive HSD2 neurons, and the organum vasculosum lamina terminalis (OVLT) that contains ANG II-sensitive neurons. Furthermore, sodium appetite is under the control of signaling proteins such as mitogen-activated protein kinase (MAPK) and inositol 1,4,5-thriphosphate (IP3). ANG II stimulates salt intake via MAPK, while combined ANG II and aldosterone action induce sodium intake via the IP3 signaling pathway. Finally, aldosterone and ANG II stimulate OVLT neurons and suppress oxytocin secretion inhibiting the neuronal activity of the paraventricular nucleus, thus disinhibiting the OVLT activity to aldosterone and ANG II stimulation.     

Intrauterine L-NAME Exposure Weakens the Development of Sympathetic Innervation and Induces the Remodeling of Arterial Vessels in Two-Week-Old Rats

Nitric oxide (NO) has been shown to stimulate differentiation and increase the survival of ganglionic sympathetic neurons. The proportion of neuronal NOS-immunoreactive sympathetic preganglionic neurons is particularly high in newborn rats and decreases with maturation. However, the role of NO in the development of vascular sympathetic innervation has never been studied before. We tested the hypothesis that intrauterine NO deficiency weakened the development of vascular sympathetic innervation and thereby changed the contractility of peripheral arteries and blood pressure level in two-week-old offspring. Pregnant rats consumed NOS inhibitor L-NAME (250 mg/L in drinking water) from gestational day 10 until delivery. Pups in the L-NAME group had a reduced body weight and blood level of NO metabolites at 1–2 postnatal days. Saphenous arteries from two-week-old L-NAME offspring demonstrated a lower density of sympathetic innervation, a smaller inner diameter, reduced maximal active force and decreased α-actin/β-actin mRNA expression ratio compared to the controls. Importantly, pups in the L-NAME group exhibited decreased blood pressure levels before, but not after, ganglionic blockade with chlorisondamine. In conclusion, intrauterine L-NAME exposure is followed by the impaired development of the sympathetic nervous system in early postnatal life, which is accompanied by the structural and functional remodeling of arterial blood vessels.     

Docosapentaenoic acid does not completely replace DHA in n−3 FA-deficient rats during early development

The reciprocal replacement of DHA by docosapentaenoic acid (DPAn−6) was studied in rats that consumed an n−3 FA-deficient or n−3 FA-adequate diet. Dams were fed the two experimental diets from weaning and throughout pregnancy and lactation. Their pups were then fed the respective diets after weaning. Cortex FA analysis was performed at various times (0, 5, 10, 20, 50, and 91 d) after birth to determine whether DPAn−6 completely replaced DHA in the n−3-deficient group. Cortical DHA levels were significantly lower (average 86%) in the n−3-deficient rats. DPAn−6 increased significantly in the n−3-deficient rats starting with a 6.5-fold increase at day 0 up to a 54-fold increase at day 91 compared with the n−3-adequate group. However, this significant increase did not completely replace the loss of DHA at postnatal days 5, 10, and 20 in which there was still an 11.5, 10.3, and 8.0% deficit in the sum of DHA and DPAn−6, respectively, in the n−3-deficient group. Once docosatetraenoic (DTA) and arachidonic acids (AA) were included in the sum (DHA+DPAn−6+DTA+AA), the levels between the two groups were similar, These results suggest that not only DPAn−6 but also other n−6 FA, including DTA and AA, replace DHA in n−3-deficient rats. The lack of total 22-carbon (22C) FA in the brain during the rapid membrane biogenesis that occurs during early development could be a factor in the nervous ystem functional deficits associated with n−3 FA deficiency.