Postnatal Exposure to the Endocrine Disruptor Dichlorodiphenyltrichloroethane Affects Adrenomedullary Chromaffin Cell Physiology and Alters the Balance of Mechanisms Underlying Cell Renewal

Dichlorodiphenyltrichloroethane (DDT) is a wide-spread systemic pollutant with endocrine disrupting properties. Prenatal exposure to low doses of DDT has been shown to affect adrenal medulla growth and function. The role of postnatal exposure to DDT in developmental disorders remains unclear. The aim of the present investigation is to assess growth parameters and the expression of factors mediating the function and renewal of chromaffin cells in the adult adrenal medulla of male Wistar rats exposed to the endocrine disruptor o,p'-DDT since birth until sexual maturation. The DDT-exposed rats exhibited normal growth of the adrenal medulla but significantly decreased tyrosine hydroxylase production by chromaffin cells during postnatal period. Unlike the control, the exposed rats showed enhanced proliferation and reduced expression of nuclear β-catenin, transcription factor Oct4, and ligand of Sonic hedgehog after termination of the adrenal growth period. No expression of pluripotency marker Sox2 and absence of Ascl 1-positive progenitors were found in the adrenal medulla during postnatal ontogeny of the exposed and the control rats. The present findings indicate that an increase in proliferative activity and inhibition of the formation of reserve for chromaffin cell renewal, two main mechanisms for cell maintenance in adrenal medulla, in the adult DDT-exposed rats may reflect a compensatory reaction aimed at the restoration of catecholamine production levels. The increased proliferation of chromaffin cells in adults suggests excessive growth of the adrenal medulla. Thus, postnatal exposure to DDT alters cell physiology and increases the risk of functional insufficiency and hyperplasia of the adrenal medulla.

Features of Spleen Development in Newborn Rats Exposed to Endocrine Disrupter Dichlorodiphenyltrichloroethane during the Prenatal Period

The development of the spleen in newborn male Wistar rats exposed to low-dose endocrine disruptor dichlorodiphenyltrichloroethane during the prenatal period was studied. Histological examination of the spleen revealed a more active development of periarterial lymphoid sheaths and lower granulocyte content in the organ. Cytofluorimetry showed a significantly lower content of B cells. Thus, low-dose exposure of the endocrine disruptor dichlorodiphenyltrichloroethane on the developing organism during the prenatal period induced changes in spleen morphogenesis resulting in extensive development of lymphoid formations and a lower intensity of lymphocyte and granulocyte differentiation.

Regulation of Morphogenetic Processes during Postnatal Development and Physiological Regeneration of the Adrenal Medulla

Regulation of morphogenetic processes during postnatal development of the rat adrenal medulla was studied. Termination of the adrenal medulla growth was found to be associated with decreased chromaffin cell proliferation, activation of canonical Wnt-signaling pathway, and enhanced expression of Sonic Hedgehog ligand. Analysis of transcription factors associated with pluripotency revealed increased percentage of Oct4-expressing cells by the end of medulla growth and no signs of Sox2 expression. All the cells demonstrating activation of Wnt-signaling and expression of Oct4 and Sonic Hedgehog were found to be highly differentiated chromaffin cells actively producing tyrosine hydroxylase. These findings allow considering the formation of the cell pools for dedifferentiation as a putative mechanism for physiological regeneration of the adrenal medulla.

Changes in Secretion of the Thyroid and Pituitary Glands with a Gradual Decrease in Deuterium Body Content

We studied changes in the secretion of thyroid hormones and pituitary thyroid-stimulating hormone (TSH) in young mature male Wistar rats during gradual decrease in deuterium body content. The rats received deuterium-depleted water ([D]=10 ppm) instead of tap water for 21 days. As soon as after 1 day, an increase in the secretion of thyroid hormones was recorded. On day 14, secondary hypothyroidism due to a sharp decrease in TSH secretion by the pituitary gland was found. By day 21, secretion of the thyroid hormones increased, and the reciprocal dependence between the concentrations of thyroid hormones and TSH was restored. Thus, the thyroid gland showed a higher sensitivity to a decrease in the deuterium content in the body than the hypothalamic-pituitary complex. The second difference was in type of response: activation of the secretory processes in the thyroid gland and a transient decrease in the secretory activity of pituitary gland thyrotropes to a decrease in deuterium content.

Differences in Age-Related Changes in the Thymus in Rats Developmentally Exposed to Endocrine Disrupter Dichlorodiphenyltrichloroethane

We studied features of age-related changes in the thymus of mature male Wistar rats developmentally exposed to the endocrine disruptor dichlorodiphenyltrichloroethane (DDT). The study was carried out at the stage of early thymus involution. Differences in the thymus morphology associated with imbalance of morphogenetic processes in the cortex and medulla were observed after puberty in rats developmentally exposed to DDT. Increased proliferation of thymocytes, higher content of lymphoblasts, and concomitant decrease in T-cell migration in comparison with the control were found. Our findings indicate lower functional maturity of the thymus and prolonged disorders in the program of postnatal thymus development induced by the endocrine disruptor DDT.

Bilateral Shifts in Deuterium Supply Similarly Change Physiology of the Pituitary–Thyroid Axis, but Differentially Influence Na+/I− Symporter Production

Deuterium, a stable isotope of hydrogen, is abundant in organisms. It is known to produce various biological effects. However, its impact in thyroid hormone synthesis and secretion is poorly studied. The aim of this investigation was to evaluate the dynamics of thyroid hormones and pituitary thyroid-stimulating hormone secretion during bilateral shifts in deuterium supply and assess a possible role of the Na+/I− symporter (NIS), the main iodide transporter, in altered thyroid function. The experiment was performed on adult male Wistar rats, which consumed deuterium-depleted ([D] = 10 ppm) and deuterium-enriched ([D] = 500,000 ppm) water for 21 days. The assessment of total thyroxine and triiodothyronine and their free fractions, as well as thyroid-stimulating hormone in blood serum, revealed the rapid response of the thyroid gland to shifts in the deuterium/protium balance. The present investigation shows that the bilateral changes in the deuterium body content similarly modulate thyroid hormone production and functional activity of the pituitary gland, but the responses of the thyroid and pituitary glands differ. The response of the thyroid cells was to increase the synthesis of the hormones and the pituitary thyrotropes, in order to reduce the production of the thyroid-stimulating hormone. The evaluation of NIS serum levels found a gradual increase in the rats that consumed deuterium-enriched water and no differences in the group exposed to deuterium depletion. NIS levels in both groups did not correlate with thyroid hormones and pituitary thyroid-stimulating hormone production. The data obtained show that thyroid gland has a higher sensitivity to shifts in the deuterium body content than the hypothalamic–pituitary complex, which responded later but similarly in the case of deuteration or deuterium depletion. It indicates a different sensitivity of the endocrine glands to alterations in deuterium content. It suggests that thyroid hormone production rate may depend on deuterium blood/tissue and cytosol/organelle gradients, which possibly disturb the secretory process independently of the NIS.

Emerging Role of Deuterium/Protium Disbalance in Cell Cycle and Apoptosis

Deuterium, a stable isotope of hydrogen, is a component of water and organic compounds. It is the second most abundant element in the human body after sodium. Although the concentration of deuterium in an organism is much lower than that of protium, a wide variety of morphological, biochemical, and physiological changes are known to occur in deuterium-treated cells, including changes in fundamental processes such as cell division or energy metabolism. The mode and degree of changes in cells and tissues, both with an increase and a decrease in the concentration of deuterium, depends primarily on the time of exposure, as well as on the concentration. The reviewed data show that plant and animal cells are sensitive to deuterium content. Any shifts in the D/H balance outside or inside cells promote immediate responses. The review summarizes reported data on the proliferation and apoptosis of normal and neoplastic cells in different modes of deuteration and deuterium depletion in vivo and in vitro. The authors propose their own concept of the effects of changes in deuterium content in the body on cell proliferation and death. The altered rate of proliferation and apoptosis indicate a pivotal role of the hydrogen isotope content in living organisms and suggest the presence of a D/H sensor, which is yet to be detected.

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.

Impact of Reduced Deuterium Intake on Thermoregulation

The role of stable hydrogen isotopes in the thermoregulation and its regulation is poorly studied. We analyzed fluctuations in body temperature and changes in thermoregulation parameters in mice under conditions of reduced deuterium intake. The study was performed on male C57BL/6 mice that consumed water with a low (10 ppm) and normal (146 ppm) deuterium content. In 7 days, fluctuations of body temperature, locomotor activity, and oxygen uptake were assessed. Deuterium depletion in the body reduced the mean value of minute fluctuations of body temperature and the mean spectral density of minute fluctuations in body temperature in the 2-20-min periods. This attested to a stabilizing effect of deuterium depletion on the rhythms of body temperature fluctuations, without significant shifts in the thermogenesis parameters. Thus, drinking water with reduced deuterium content makes them less sensitive to external influences.

Response of Pituitary-Thyroid Axis to a Short-Term Shift in Deuterium Content in the Body

We studied functional changes in rat pituitary-thyroid axis after a short-term shift in deuterium body content. Male Wistar rats consumed deuterium-enriched (500,000 ppm) or deuterium-depleted water (10 ppm) for 24 h. Rats of both experimental groups demonstrated elevated concentration of bound with transport proteins thyroxine and reduced level of thyroid-stimulating hormone in serum. No changes in the rate of thyroxine conversion to triiodothyronine were found. Thus, both the increase and reduction of deuterium body content produced similar changes in the function of the pituitary-thyroid axis with primary affection of the thyroid gland, indicative of its higher sensitivity to shift in deuterium levels.

Impaired Morphogenesis and Function of Rat Adrenal Zona Glomerulosa by Developmental Low-Dose Exposure to DDT Is Associated with Altered Oct4 Expression

Dichlorodiphenyltrichloroethane (DDT) is a persistent organic pollutant and one of the most widespread endocrine disrupting chemicals. The impact of low-dose exposure to DDT on the morphogenesis of the adrenal gland is still poorly understood. The development and function of zona glomerulosa in rats has been found to be associated with changes in the expression of the transcription factor Oct4 (Octamer 4), which is the most important player in cell pluripotency. The aim of the study was to investigate the morphogenesis and function of rat adrenal zona glomerulosa in rats exposed to low doses of DDT during prenatal and postnatal development and to determine the possible role of Oct4 in DDT-mediated structural and functional changes. The DDT-exposed rats demonstrated slower development and lower functional activity of the zona glomerulosa during the pubertal period associated with higher expression of Oct4. Further, accelerated growth and restoration of hormone production was associated with, firstly, a decrease in Oct4 expressing cells and secondly, the loss of the inverse relationship between basal aldosterone levels and the number of Oct4 expressing cells. Thus, the transcriptional factor Oct4 exhibited an altered pattern of expression in the DDT-exposed rats during postnatal development. The results of the study uncover a novel putative mechanism by which low doses of DDT disrupt the development of adrenal zona glomerulosa.

Low-Dose Exposure to Endocrine Disruptor Dichlorodiphenyltrichloroethane (DDT) Affects Transcriptional Regulation of Adrenal Zona Reticularis in Male Rats

The study examined transcriptional regulation of adrenal zona reticularis development in male Wistar rats exposed to low doses of endocrine disruptor dichlorodiphenyltrichloroethane (DDT) prenatally and postnatally. At pubertal age, zona reticularis demonstrated a retarded growth with a low proliferative activity of its cells. At this age, zona reticularis was characterized with overexpression of β-catenin by steroid-producing cells; a high percentage of cells with membrane and cytoplasmic localization of β-catenin, and reduced number of cells with nuclear β-catenin attesting to insufficient activation of Wnt signaling. Expression of transcriptional factor Oct4 by reticularis cells was down-regulated indicating their diminished proliferative potency. No significant alterations in Sonic Hedgehog expression were observed. Thus, DDT-provoked disorders of transcriptional regulation result in abnormal development of zona reticularis thereby disturbing sexual maturation in males.

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.

Changes in Histophysiology of the Adrenal Medulla in Rats after Prenatal and Postnatal Exposure to Endocrine Disruptor DDT

We studied histophysiology of the adrenal medulla in adult (70-day-old) male Wistar rats developmentally exposed to low doses of endocrine disruptor DDT. It was found that exposure to DDT during the prenatal and postnatal ontogeny decelerated the development of the adrenal medulla and reduced the synthesis of tyrosine hydroxylase, the rate-liming enzyme of catecholamine synthesis, in chromaffin cells, which led to a decrease in epinephrine secretion into the blood.

Developmental exposure to low doses of dichlorodiphenyltrichloroethane impairs proliferative response of thymic lymphocytes to Concanavalin A in rats

The aim of the research was to study formation of thymic lymphocytes proliferative response to T cell mitogen Concanavalin A in 7, 42, and 70 days-old male Wistar rats developmentally exposed to low doses of endocrine disruptor dichlorodiphenyltrichloroethane (2.90 ± 0.13 μg/kg body weight). The thymus of the exposed rats did not show morphological abnormalities. Exposure to the endocrine disrupter was found to alter age-dependent changes of thymic lymphocyte proliferative activity and attenuate proliferative response to Concanavalin A in puberty and adulthood. Insufficient response to mitogen was mediated by higher content of actively proliferating Ki-67-positive lymphoblasts compared to the control values. Insufficient proliferative response to mitogen in developmentally exposed to the endocrine disruptor rats may provide higher risk of impaired cellular immune reactions.

Morphological and Cytophysiological Changes in the Adult Rat Adrenal Medulla after Prenatal and Postnatal Exposure to Endocrine-Disrupting DDT

The aim of the investigation was to study morphological and cytophysiological changes in the adult rat adrenal medulla after prenatal and postnatal exposure to endocrine-disrupting chemical dichlorodiphenyltrichloroethane (DDT).

Morphological Changes in the Thymus of Newborn Rats Exposed to Endocrine Disruptor Dichlorodiphenyltrichloroethane (DDT) during the Prenatal Period

The structure of the thymus in newborn rats exposed in utero to endocrine disruptor DDT was studied. We found that exposure to low doses of DDT during pregnancy does not disturb thymus formation in the offspring, but leads to changes in its structure than manifested as slower lobulation, wider epithelium-free areas in the cortex, and lower number of thymic corpuscles in the medulla. The results attest to sensitivity of the reticuloepithelial stroma of the thymus to the effects of endocrine disruptor.

Changes in Canonical β-Catenin/Wnt Signaling Activation in the Adrenal Cortex of Rats Exposed to Endocrine Disruptor Dichlorodiphenyltrichloroethane (DDT) during Prenatal and Postnatal Ontogeny

Prenatal and postnatal exposure to low doses of the endocrine disruptor dichlorodiphenyltrichloroethane (DDT) leads to delayed activation of the canonical β-catenin/Wnt signaling in zona glomerulosa and zona reticularis of the adrenal cortex in rats, which changed the rate of their postnatal development. Suppression of the Wnt pathway in zona fasciculata promotes its regeneration after DDT-induced blood circulation disorders and cell death.

Sex Differences in the Production of SLC5A5, Thyroid Peroxidase, and Thyroid Hormones in Pubertal Rats Exposed to Endocrine Disruptor Dichlorodiphenyltrichloroethane (DDT) during Postnatal Ontogeny

Sex differences in the expression of iodide transporter SLC5A5 and thyroid peroxidase in thyroid follicular epithelium and thyroid serum profile were assessed in pubertal rats exposed to endocrine disruptor DDT starting from the first postnatal day. It was found that exposure to DDT reduced expression of SLC5A5 in peripheral regions of thyroid lobes in males and in central regions in females. The most pronounced sex differences were observed in thyroid peroxidase expression that remained sensitive to thyroid stimulating hormone regulation in males and lost sensitivity to pituitary stimulation in females after exposure to disruptor, which determines more pronounced hypothyroidism in females.

[Differences in adrenal steroid hormones production in pubertal rats exposed to low doses of endocrine disruptor DDT during prenatal and postnatal development]

Production of adrenal steroid hormones in pubertal male Wistar rats exposed to low doses of DDT during both prenatal and postnatal and only postnatal development was evaluated. Altered production of all types of steroid hormones and serum steroid profile with opposite changes in rats exposed prenatally and postnatally, and only postnatally was found. The study showed that daily exposure to low doses of DDT enhanced conversion of progesterone to 17OH-progesterone and did not exert selective antiandrogenic or proestrogenic action unlike effect of toxic and subtoxic doses. Impaired morphogenesis of the adrenal cortex and circulatory disorders in zona glomerulosa contributed to reduced aldosterone and sex steroid hormones production.

Effect of Prenatal and Postnatal Exposure to Low Doses of DDT on Catecholamine Secretion in Rats in Different Period of Ontogeny

We studied the effects of prenatal and postnatal exposure to low doses of DDT on secretion of basic catecholamines epinephrine and norepinephrine in pubertal and adult rats. It was found that the endocrine-disrupting chemical under study led to a progressive decrease in the content of epinephrine and especially norepinephrine in systemic circulation, which indicated their disturbed secretion by the adrenal medulla and sympathetic nervous system cells. In animals exposed to low doses of DDT in both pre- and postnatal periods, the decrease in catecholamine secretion after puberty was less pronounced than in animals exposed only during the postnatal period, which can indicate the development of compensatory processes.

[Alteration of rat adrenal cortex after low-dose exposure to endocrine disrupting chemical dichlorodiphenyltrichloroethane since the first day of postnatal development]

The purpose of the present study was to examine morphological and functional alterations in adrenal cortex of rats exposed to low doses of DDT since the first day of postnatal development till puberty. Daily consumption of DDT was 3.71±0.15 μg/kg bw. This level of exposure corresponds with human daily intake of DDT with food products according to maximum permissive levels of food contamination. Production of steroid hormones of the adrenal cortex was evaluated by quantification of aldosterone, corticosterone, estradiol, and estronе serum levels by enzyme-linked immunosorbent assay. Organometry and light microscopy of the adrenal glands were performed. After six weeks of exposure serum concentration of aldosterone was elevated by 50% in average, estradiol - by 25%, estrone - by 29%, but serum level of corticosterone was decreased by 53% compared to the control values. The adrenal glands had decreased weight and reduced cortex width from 897.75±23.31 to 776.25±19.91 μm mainly due to narrowing of reticularis zona by 11.35%. Histological examination also found proportional increase of cell number in mm2 of reticularis zona and therefore found no differences in total endocrine cell count in reticularis zona between the control (14 085.94±704.30) and DDT exposed rats (13 678.20±410.34). Light microscopy revealed hemorrhages between glomerulosa zona and fasciculata zona as well as fasciculate zona and reticularis zona, foci of discomplexity in fasciculate zona, dystrophy and decreased size of fasculata cells. The data obtained demonstrated that low-dose exposure to DDT during postnatal development led to obvious changes in morphology and function of rat adrenal gland. Low doses of DDT disrupt steroid hormone production by all layers of adrenal cortex in puberty. The results show that very low-dose exposure to DDT needs further investigations, and safety of maximum permissible levels of DDT and other endocrine disrupting chemicals in food products should be reassessed.

Changes in Differentiation of Thymic T Cells in the Progeny of Female Mice Subjected to Immune System Stimulation during Early Pregnancy

Differentiation of T cells was studied in the progeny of female C57Bl/6 mice subjected to immunostimulation by administration of concanavalin A or adoptive transfer of concanavalin A-activated splenocytes. Acceleration of T cell maturation during the prepubertal period and decelerated differentiation during the pubertal and post-pubertal periods were revealed.

[The effect of long-term exposure to low doses of endocrine disruptor ddt on serum levels of thyroid protein autoantigenes and antithyroid autoantibodies]

Changes in secretion of thyroid autoantigenes and production of antithyroid autoantibodies after long-term exposure to low doses of DDT were studied. Changes in serum levels of antithyroid peroxidase antibodies and thyroid peroxidase, attributed to disruption of thyroxine production by DDT were found. Long-term exposure of rats to low doses of DDT revealed no specific impact on serum autoantibodies to all thyroid autoantigenes studied. The increase of the ratio of autoantibody/autoantigen for thyroid peroxidase and thyroglobulin was rather small and thus could not be considered as a significant symptom of thyroid autoimmunity.

Inherited Alopecia Areata in Mice as a Result of Adoptive Transfer of In Vivo Mitogen-Activated Splenic Cells to Females During Early Period of Gestation

Postnatal morphogenesis of the skin and its appendages were studied in the progeny of mice subjected during early gestation period to adoptive transfer of in vivo activated splenic cells. Reversible focal hair loss was observed on postnatal day 17 in the progeny. The number of hair follicles and sebaceous glands, the level of extracellular matrix, and the content of cells in the skin, including mast cells in the derma, decreased, while neutrophils prevailed. Alopecia areata was found in the subsequent generations after mating of male and female progeny. Hence, stimulation of the maternal immune system during early pregnancy led to disorders of the pre- and postnatal morphogenesis of the skin in the progeny and to development of alopecia areata that became an inherited sign.

Morphological and functional changes in the thymus and spleen of mouse offspring in the development of systemic inflammatory response after a single immunity stimulation in early pregnancy

We studied morphological and functional changes in the thymus and spleen of mouse offspring subjected to single immune stimulation with concanavalin A at early pregnancy terms against the background of systemic inflammatory response. The offspring was characterized less pronounced accidental involution of the thymus, reduced counts of neutrophils in the marginal zone and red pulp of the spleen, mast cell degranulation, and their reduced content in the red pulp.

Ultrastructural characteristics of molecular release of secretory products from thyroid mast cells induced by lipopolysaccharide

Ultrastructural characteristics of molecular release of secretory products from thyroid mast cells during different periods after LPS injection were studied in rats. The main morphological manifestation of this mechanism was progressing hydration of the hyaloplasm around secretory granules and dissolution and release of osmiophilic contents from the granules to the cytoplasm with the formation of a hydropic vacuole at the site of the granule.