Comparative study of the effects of experimentally induced hypothyroidism and hyperthyroidism in some brain regions in albino rats

Protective role of the ginsenoside Rg1 against methimazole-induced gestational hypothyroidism on reflexive behaviors, conditioned fear and cortical antioxidant levels in mice offspring

Ginsenoside Rg1(Rg1), a monomer of a tetracyclic triterpenoid derivative, possesses diverse medicinal properties attributed to its unique chemical structure and may have beneficial effects on fetal development. This study aimed to investigate the protective effects of prenatal exposure to Rg1 against Methimazole-induced gestational hypothyroidism on reflexive behaviors, conditioned fear, and cortical antioxidant levels in mouse offspring.40 female virgin mice and 12 male NMRI mice were assigned to four groups: group 1 served as the control, group 2 received Methimazole(MMI) at a concentration of 0.02% in their drinking water, group 3 received Rg1(150 mg/kg), and group 4 received both MMI and Rg1.Groups of 2-4 were administered the substances from days 1-9 of gestation. After delivery, pups were selected, and reflexive motor behaviors and conditioned fear were assessed. Additionally, levels of brain tissue catalase(CAT), malondialdehyde(MDA), superoxide dismutase(SOD), and glutathione peroxidase(GPx) levels were measured. Furthermore, postpartum immobility time in the forced swimming test (FST), tail suspension test (TST), and the number of squares crossed in the open field test (OFT)were determined. The results demonstrated that maternal exposure to Rg1 improved ambulation score, hind-limb suspension score, grip strength, front-limb suspension, hind-limb foot angle, negative geotaxis, surface righting, and conditioned fear in hypothyroidism-induced offspring(P<0.05). Rg1 decreased immobility time in the FST, and TST, and increased the number of squares crossed in the OFT in postpartum hypothyroidism-induced mice(P<0.05). Moreover, Rg1 reduced brain tissue MDA levels and increased brain tissue CAT, SOD, and GPx levels in mice and their offspring(P<0.05). These findings indicate that Rg1 mitigated postpartum depression in mice and improved reflexive motor behaviors in their pups.

Stress-Sensitive Regulators of Fetal Neurodevelopment in HIV and Preeclampsia: An Immunocytochemical Appraisal of Placental OGT and T4 Levels

Preeclampsia and HIV are a significant burden to maternal health globally, especially in low-middle income countries such as South Africa. In the KwaZulu-Natal province, SA antenatal HIV prevalence is 41.1%, while PE is 12%. PE and HIV infections are maternal stress and inflammation that impact placental function and fetal development. Therefore, this study investigated the impact of the comorbidity of PE and HIV on placental stress and neurodevelopment. Placentae were obtained from four cohorts of pregnant women: normotensive HIV negative, normotensive HIV positive, preeclamptic HIV negative, and preeclamptic HIV positive. The placental tissue sections were immunostained for OGT and T4. Our findings showed that the maternal weight, diastolic, and systolic blood pressures (BP) were higher in PE vs. the normotensive groups, irrespective of HIV status. In addition, significant changes were noticed in the placental weight, fetoplacental ratio, and placental efficiency coefficient. Our findings showed that the maternal weight, diastolic, and systolic blood pressures (BP) were statistically higher in the PE compared to the normotensive. No significant differences were observed between HIV positive and HIV negative groups. In addition, significant changes were noticed in the placental weight, fetoplacental ratio, and placental coefficient. Furthermore, considerable upregulation in the placental expression of OGT in both the conducting and exchange villi of PE and concomitant downregulation in HIV-positive patients compared with Normotensive and HIV-negative individuals, respectively. Our results provide inferential evidence on the dysregulation of OGT in the comorbidity of PE and HIV. This may mediate a compromised programmed outcome of an adverse maternal environment during pregnancy and consequently affect fetal development.

Maternal Prenatal Stress, Thyroid Function and Neurodevelopment of the Offspring: A Mini Review of the Literature

Fetal brain is extremely plastic and vulnerable to environmental influences that may have long-term impact on health and development of the offspring. Both the Hypothalamic-Pituitary-Adrenal (HPA) and the Hypothalamic-Pituitary-Thyroid (HPT) axes are involved in stress responses, whereas, their final effectors, the Glucocorticoids (GCs) and the Thyroid Hormones (TH s), mediate several fundamental processes involved in neurodevelopment. The effects of these hormones on brain development are found to be time and dose-dependent. Regarding THs, the developing fetus depends on maternal supply of hormones, especially in the first half of pregnancy. It is acknowledged that inadequate or excess concentrations of both GCs and THs can separately cause abnormalities in the neuronal and glial structures and functions, with subsequent detrimental effects on postnatal neurocognitive function. Studies are focused on the direct impact of maternal stress and GC excess on growth and neurodevelopment of the offspring. Of particular interest, as results from recent literature data, is building understanding on how chronic stress and alterations of the HPA axis interacts and influences HPT axis and TH production. Animal studies have shown that increased GC concentrations related to maternal stress, most likely reduce maternal and thus fetal circulating THs, either directly or through modifications in the expression of placental enzymes responsible for regulating hormone levels in fetal microenvironment. The purpose of this review is to provide an update on data regarding maternal stress and its impact on fetal neurodevelopment, giving particular emphasis in the interaction of two axes and the subsequent thyroid dysfunction resulting from such circumstances.

Effect of thiamazole on kainic acid-induced seizures in mice

Kainic acid (KA) induced epileptic seizures in mice is a commonly used experimental model of epilepsy. Previous studies have suggested the roles of various neurotransmitters and oxidative stress in KA-induced seizures. An important role of hypothyroidism has also been suggested in epilepsy. Thiamazole (TZ) is an anti-hyperthyroid drug with antioxidant property. This study reports the effect of TZ on KA-induced epileptic seizures in mice, produced by intraperitoneal (IP) injection of KA (18 mg/kg). Prior to KA injection, the animals were treated with TZ (12.5, 25 and 50 mg/kg IP). Our results showed that in KA alone group, about half of the animals developed seizures. Pre-treatment of mice with TZ significantly increased the frequency of seizures in dose-dependent manner. Administration of TZ significantly reduced the latency time and aggravated the severity of seizures. TZ also increased the mortality in KA-treated mice. Striatal dopamine and serotonin levels were markedly increased in KA alone treated mice, which were not significantly affected by TZ treatment. Among the indices of oxidative stress, we observed a significant reduction in cerebral vitamin E whereas the levels of cerebral malondialdehyde and conjugated dienes were significantly increased in animals with high severity of seizures. In conclusion, TZ potentiated the frequency and severity of experimental seizure in mice. There is a possibility of altered metabolism of KA in presence of TZ that might have potentiated the toxicity of KA. These findings suggest a caution while administering anti-hyperthyroid drugs in epileptic seizures.

Hyperthyroidism in pregnancy: evidence and hypothesis in fetal programming and development

The management of hyperthyroidism in pregnant patients has been a topic of raised clinical awareness for decades. It is a strong recommendation that overt hyperthyroidism of Graves' disease in pregnant women should be treated to prevent complications. The consequences of hyperthyroidism in pregnancy are less studied than hypothyroidism, and a literature review illustrates that the main burden of evidence to support current clinical guidance emerges from early observations of severe complications in Graves' disease patients suffering from untreated hyperthyroidism in the pregnancy. On the other hand, the more long-term consequences in children born to mothers with hyperthyroidism are less clear. A hypothesis of fetal programming by maternal hyperthyroidism implies that excessive levels of maternal thyroid hormones impair fetal growth and development. Evidence from experimental studies provides clues on such mechanisms and report adverse developmental abnormalities in the fetal brain and other organs. Only few human studies addressed developmental outcomes in children born to mothers with hyperthyroidism and did not consistently support an association. In contrast, large observational human studies performed within the last decade substantiate a risk of teratogenic side effects to the use of antithyroid drugs in early pregnancy. Thus, scientific and clinical practice are challenged by the distinct role of the various exposures associated with Graves' disease including the hyperthyroidism per se, the treatment, and thyroid autoimmunity. More basic and clinical studies are needed to extend knowledge on the effects of each exposure, on the potential interaction between exposures and with other determinants, and on the underlying mechanisms.

Maternal lithium chloride exposure alters the neuroendocrine-cytokine axis in neonatal albino rats

The aim of this work was to clarify whether maternal lithium chloride (LiCl) exposure disrupts the neonatal neuroendocrine-cytokine axis. Pregnant Wistar rats were orally administrated 50 mg LiCl/kg b.wt. from gestational day (GD) 1 to postpartum day 28. Maternal administration of LiCl induced a hypothyroid state in both dams and their neonates compared to the control dams and neonates at lactation days (LDs) 14, 21 and 28, where the levels of serum free triiodothyronine (FT3) and free thyroxin (FT4) were decreased and the level of serum thyrotropin (TSH) level was increased. A noticeable depression in maternal body weight gain, neonatal body weight and neonatal serum growth hormone (GH) was observed on all examined postnatal days (PNDs; 14, 21 and 28). A single abortion case was recorded at GD 17, and three dead neonates were noted at birth in the LiCl-treated group. Maternal administration of LiCl disturbed the levels of neonatal serum tumor necrosis factor-alpha (TNF-α), transforming growth factor-beta (TGF-β), interleukin-1 beta (IL-1β), interferon-gamma (INF-γ), leptin, adiponectin and resistin at all tested PNDs compared to the control group. This administration produced a stimulatory action on the level of neonatal cerebral serotonin (5-HT) at PND 14 and on the level of neonatal cerebral norepinephrine (NE) at PNDs 21 and 28. However, this administration produced an inhibitory action on the level of neonatal cerebral dopamine (DA) at all examined PNDs and on the level of neonatal cerebral NE at PND 14 and the level of neonatal cerebral 5-HT at PNDs 21 and 28 compared to the corresponding control group. Thus, maternal LiCl exposure-induced hypothyroidism disrupts the neonatal neuroendocrine-cytokine system, which delay cerebral development.

Overdoses of Acetaminophen Disrupt the Thyroid-Liver Axis in Neonatal Rats

OBJECTIVE

The aim of the study was to examine the impact of neonatal acetaminophen (APAP; paracetamol) administrations on the thyroid-liver axis in male Wistar rats.

METHODS

APAP (100 or 350mg/kg) was orally administered to neonates from Postnatal Day (PND) 20 to 40.

RESULTS

Both APAP doses elicited a substantial increase in serum TSH, albumin, AST, ALT, and ALP values, and a profound decrease in serum FT4 and FT3 values at PND 40 relative to those in the control group. Additionally, the hypothyroid state in both APAP-treated groups may increase the histopathological variations in the neonatal liver, such as destructive degeneration, fibrosis, fatty degeneration, fibroblast proliferation, haemorrhage, oedema, and vacuolar degeneration, at PND 40. Moreover, in the APAP groups, a marked depression was recorded in the t-SH and GSH levels and GPx and CAT activities at PND 40 in the neonatal liver compared to those in the control group. However, the levels of hepatic LPO, H2O2, and NO were increased in both APAP-treated groups at PND 40. All previous alterations were dose- dependent.

CONCLUSION

Neonatal APAP caused a hypothyroidism and disturbed hepatic cellular components by increasing prooxidant markers and decreasing antioxidant markers, causing hepatotoxicity. Thus, neonatal administrations of APAP may act as a neonatal thyroid-liver disruptor.

Gestational Arsenic Trioxide Exposure Acts as a Developing Neuroendocrine-Disruptor by Downregulating Nrf2/PPARγ and Upregulating Caspase-3/NF-ĸB/Cox2/BAX/iNOS/ROS

The goal of this investigation was to evaluate the effects of gestational administrations of arsenic trioxide (ATO; As₂O₃) on fetal neuroendocrine development (the thyroid-cerebrum axis). Pregnant Wistar rats were orally administered ATO (5 or 10 mg/kg) from gestation day (GD) 1 to 20. Both doses of ATO diminished free thyroxine and free triiodothyronine levels and augmented thyrotropin level in both dams and fetuses at GD 20. Also, the maternofetal hypothyroidism in both groups caused a dose-dependent reduction in the fetal serum growth hormone, insulin growth factor-I (IGF-I), and IGF-II levels at embryonic day (ED) 20. These disorders perturbed the maternofetal body weight, fetal brain weight, and survival of pregnant and their fetuses. In addition, destructive degeneration, vacuolation, hyperplasia, and edema were observed in the fetal thyroid and cerebrum of both ATO groups at ED 20. These disruptions appear to depend on intensification in the values of lipid peroxidation, nitric oxide, and H₂O₂, suppression of messenger RNA (mRNA) expression of nuclear factor erythroid 2-related factor 2 and peroxisome proliferator-activated receptor gamma, and activation of mRNA expression of caspase-3, nuclear factor kappa-light-chain-enhancer of activated B cells, cyclooxygenase-2, Bcl-2–associated X protein, and inducible nitric oxide synthase in the fetal cerebrum. These data suggest that gestational ATO may disturb thyroid-cerebrum axis generating fetal neurodevelopmental toxicity.

The placenta as a window to the brain: A review on the role of placental markers in prenatal programming of neurodevelopment

BACKGROUND

During development, the placenta can be said to be the most important organ, however, the most poorly researched. There is currently a broader understanding of how specific insults during development affect the fetal brain, and also the importance of placental signaling in neurodevelopmental programming. Epigenetic responses to maternal and fetal signals are an obvious candidate for transforming early life inputs into long-term programmatic outcomes. As a mediator of maternal and environmental signals to the developing fetus, epigenetic processes within the placenta are particularly powerful such that alterations of placental gene expression, downstream function, and signalling during foetal development have the potential for dramatic changes in developmental programming.

SUMMARY

In this article, we reviewed emerging evidence for a placental role in prenatal neurodevelopmental programming with a specific focus on nutrient and prenatal stress signals integration into chromatin changes; this new understanding, we hope will provide the means for lowering developmentally based disorder risk, and new therapeutic targets for treatment in adulthood.

KEY MESSAGES

Based on this review, the placenta is a potent micro-environmental player in neurodevelopment as it orchestrates a series of complex maternal-foetal interactions. Maternal insults to this microenvironment will impair these processes and disrupt foetal brain development resulting in the prenatal programming of neurodevelopmental disorders. These findings should inspire advance animal model and human research drive to appraise gene-environment impacts during pregnancy that will target the developmental cause of adult-onset mental disorders.

WITHDRAWN: Toxic effects of gestational arsenic trioxide on the neuroendocrine axis of developing rats

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Suppressive effects of neonatal bisphenol A on the neuroendocrine system

The aim of this study was to assess the effects of neonatal bisphenol A (BPA) administration on neuroendocrine features (the thyroid–brain axis). BPA (20 or 40 µg/kg) was orally administered to juvenile male albino rats ( Rattus norvegicus) from postnatal days (PNDs) 15 to 30. Both doses resulted in lower serum thyroxine (T4), triiodothyronine (T3), and growth hormone levels and higher thyrotropin level than the control levels at PND 30. In the neonatal cerebellum and cerebrum, vacuolation, pyknosis, edema, degenerative changes, and reductions in the size and number of the cells were observed in both treated groups. Alternatively, elevations in oxidative markers (lipid peroxidation, nitric oxide, and hydrogen peroxide [H2O2]) at both dose levels were recorded at PND 30, along with decreased activities of antioxidant markers (ascorbic acid, total thiol [t-SH], glutathione, glutathione peroxidase, glutathione reductase, glutathione-S-transferase, and catalase) with respect to control levels. Thus, the BPA-induced hypothyroid state may disturb the neonatal thyroid–brain axis via production of free radicals, and this could damage the plasma membrane and cellular components, delaying cerebrum and cerebellum development.

Thyroid Hormone-Dependent Epigenetic Regulation of Melanocortin 4 Receptor Levels in Female Offspring of Obese Rats

Maternal obesity is a risk factor for offspring obesity. The melanocortin 4 receptor (Mc4r) is one of the mediators of food intake and energy balance. The present study examined the epigenetic mechanisms underlying altered Mc4r levels in the hypothalamic paraventricular nucleus in the offspring of high-fat diet (HFD)-induced obese dams and sought to elucidate the role of thyroid hormones in epigenetic regulation and tagging of their nucleosome at the Mc4r promoter. Female Wistar rats were fed an HFD or standard chow from weaning through gestation and lactation. Epigenetic alterations were analyzed in the offspring on postnatal day 21 at the Mc4r promoter using chromatin immunoprecipitation and bisulfite sequencing. To study the role of triiodothyronine (T3) in Mc4r downregulation, dams received methimazole (MMI), an inhibitor of thyroid hormone production. Offspring of HFD-fed dams had a greater body weight, elevated plasma T3 concentrations, and lower Mc4r messenger RNA levels than controls. At the Mc4r promoter, offspring of HFD-fed mothers demonstrated increased histone 3 lysine 27 acetylation (H3K27ac) with a greater association to thyroid hormone receptor-β (TRβ), an inhibitor of Mc4r transcription. Moreover, TRβ coimmunoprecipitated with H3K27ac, supporting their presence in the same complex. Maternal MMI administration prevented the HFD reduction in Mc4r levels, the increase in TRβ, and the increase in the TRβ-H3K27ac association, providing further support for the role of T3 in downregulating Mc4r levels. These findings demonstrate that a perinatal HFD environment affects Mc4r regulation through a T3 metabolic pathway involving histone acetylation of its promoter.

Early weaning PCB 95 exposure alters the neonatal endocrine system: thyroid adipokine dysfunction

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants that can severely disrupt the endocrine system. In the present study, early-weaned male rats were administered a single dose of 2,3,6-2',5'-pentachlorinated biphenyl (PCB 95; 32 mg/kg per day, by i.p. injection) for two consecutive days (postnatal days (PNDs) 15 and 16) and killed 24 and 48 h after the administration of the last dose. Compared with the control group, administration of PCB 95 induced a reduction (P<0.01) in serum concentrations of thyroxine, triiodothyronine, and GH and an increase (P<0.01) in the serum concentration of TSH at PNDs 17 and 18. These conspicuous perturbations led to some histopathological deterioration in the thyroid gland characterized by follicular degeneration, edema, fibrosis, hemorrhage, luminal obliteration, and hypertrophy with reduced colloidal contents at PND 18. The dyshormonogenesis and thyroid dysgenesis may be attributed to the elevation of DNA fragmentation at PNDs 17 and 18. Furthermore, this hypothyroid state revealed higher (P<0.01) serum concentrations of leptin, adiponectin, and tumor necrosis factor and lower (P<0.01) serum concentrations of IGF1 and insulin at both PNDs compared with the control group. Interestingly, the body weight of the neonates in the PCB 95 group exhibited severe decreases throughout the experimental period in relation to that of the control group. These results imply that PCB 95 may act as a disruptor of the developmental hypothalamic-pituitary-thyroid axis. Hypothyroidism caused by PCB 95 may impair the adipokine axis, fat metabolism, and in general postnatal development. Thus, further studies need to be carried out to understand this concept.

Experimental hypothyroidism during pregnancy affects nociception and locomotor performance of offspring in rats

BACKGROUND

Thyroid hormones (THs) play a crucial role in the development of several organic systems. An adequate support of maternal THs may be required to ensure a normal nociceptive function of offspring into adulthood. We investigated the impact of experimental gestational hypothyroidism (EGH) on nociceptive threshold and motor performance in the offspring at different post-natal days (PND) in both male and female rats.

METHODS

EGH was induced by the administration of 0.02% methimazole (MMI) in the drinking water from the ninth day of gestation until birth. The offspring from MMI-treated dams (OMTDs) or from water-treated dams (OWTDs) were assessed for thermal and mechanical nociception using the tail-flick test and von Frey filaments, respectively. Both rota-rod and grip strength were used to assess motor function.

RESULTS

OMTD had reduced thermal (p<0.05) but not mechanical threshold at all studied ages (60 and 120 PND). Sixty-day-old OMTD presented reduced latency to the tail-flick test (p=0.01). Grip strength in 120-day-old OMTD was reduced (p<0.01). However, only male OMTD presented a lower locomotor performance on the rota-rod test when analysed on the 60th PND (p<0.01).

CONCLUSIONS

EGH promotes hypersensitivity to noxious thermal but not mechanical stimulus. Moreover, motor force is similarly reduced in male and female OMTDs, whereas motor performance is reduced only in mature male OMTD, suggesting the presence of a protective factor in females.

Gestational doxorubicin alters fetal thyroid-brain axis

Administration of chemotherapy during pregnancy may represent a big risk factor for the developing brain, therefore we studied whether the transplacental transport of doxorubicin (DOX) may affect the development of neuroendocrine system. DOX (25 mg/kg; 3 times interaperitoneally/week) was given to pregnant rats during whole gestation period. The disturbances in neuroendocrine functions were investigated at gestation day (GD) 15 and 20 by following the maternal and fetal thyroid hormone levels, fetal nucleotides (ATP, ADP, AMP) levels and adenosine triphosphatase (Na(+), K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase) activities in two brain regions, cerebrum and cerebellum. In control group, the levels of maternal and fetal serum thyroxine (T4), triiodothyronine (T3), thyrotropin (TSH), and fetal serum growth hormone (GH) increased from days 15 to 20, whereas in the DOX group, a decrease in maternal and fetal T4, T3 and increase in TSH levels (hypothyroid status) were observed. Also, the levels of fetal GH decreased continuously from GD 15 to 20 with respect to control group. In cerebrum and cerebellum, the levels of fetal nucleotides and the activities of fetal ATPases in control group followed a synchronized course of development. The fetal hypothyroidism due to maternal administration of DOX decreased the levels of nucleotides, ATPases activities, and total adenylate, instead, the adenylate energy charge showed a trend to an increase in both brain regions at all ages tested. These alterations were dose- and age-dependent and this, in turn, may impair the nerve transmission. Finally, DOX may act as neuroendocrine disruptor causing hypothyroidism and fetal brain energetic dysfunction.