Evaluation of developmental toxicity of propylthiouracil and methimazole

Repositioning the existing drugs for neuroinflammation: a fusion of computational approach and biological validation to counter the Parkinson's disease progression

Parkinson's disease is caused by the deficiency of striatal dopamine and the accumulation of aggregated α-synuclein in the substantia nigra pars compacta (SNpc). Neuroinflammation associated with oxidative stress is a key factor contributing to the death of dopaminergic neurons in SNpc and advancement of Parkinson's disease. Two molecular targets, i.e., nuclear factor kappa-light-chain-enhancer (NF-kB) and α-synuclein play a substantial role in neuroinflammation progression. Therefore, the compounds targeting these neuroinflammatory targets hold a great potential to combat Parkinson's disease. Thereby, in this study, molecular docking and Connectivity Map (CMap) based gene expression profiling was utilized to reposition the approved drugs as neuroprotective agents for Parkinson's disease. With in silico screening, two drugs namely theophylline and propylthiouracil were selected for anti-neuroinflammatory activity evaluation in in vivo models of chronic neuroinflammation. The neuroinflammatory effect of the identified compounds was confirmed by quantifying the expression of three important neuroinflammatory mediators, i.e. IL-6, TNF-alpha, and IL-1 beta on brain tissue using ELISA assay. The ELISA experiment demonstrated that both compounds significantly decreased the expression of neuroinflammatory mediators, highlighting the compounds' potential in neuroinflammation management. Furthermore, the drug and disease interaction network of the two identified drugs and diseases (neuroinflammation and Parkinson's disease) suggested that the two drugs might interact with various targets namely adenosine receptors, Poly [ADP-ribose] polymerase-1, myeloperoxidase (MPO) and thyroid peroxidase through multiple pathways associated with neuroinflammation and Parkinson's disease. Computational studies suggest that a particular drug may be effective in managing Parkinson's disease associated with neuroinflammation. However, further research is needed to confirm this in biological experiments.

The first review on prenatal drug exposure and ocular malformation occurrence

Even though a non-negligible portion of congenital eye anomalies has a clear genetic origin, an etiology is not found for most patients. Prenatal medication exposure is recognized to be involved in fetal malformations and several medications are specifically known to alter eye morphogenesis during embryonic development leading to congenital eye defects. We explored and reviewed the role of medications described in the genesis of ocular malformations, a role that has been little evaluated and probably still underestimated especially since several studies have shown the wide exposure of pregnant women to medication. We present our results in two sections; the first describes medications reported to be associated with ocular malformations in humans; the second details medications responsible for ocular malformations in animal models. We have summarized these results in tables, providing a relevant tool for clinicians. As most of the associations between medication exposure and congenital eye defects are either old or single case reports, this study highlights the needs for high epidemiological vigilance, accurate clinical description as well as a combination of studies on human genetics and experimental studies. Since medication exposures are potentially modifiable risk factors for congenital anomalies, this represents an important opportunity to implement preventive measures.

Maternal Hypothyroidism in Rats Reduces Placental Lactogen, Lowers Insulin Levels, and Causes Glucose Intolerance

Hypothyroidism increases the incidence of gestational diabetes mellitus (GDM) but the mechanisms responsible are unknown. This study aimed to assess the pathophysiological mechanisms by which hypothyroidism leads to glucose intolerance in pregnancy. Hypothyroidism was induced in female Sprague-Dawley rats by adding methimazole (MMI) to drinking water at moderate (MOD, MMI at 0.005% w/v) and severe (SEV, MMI at 0.02% w/v) doses from 1 week before pregnancy and throughout gestation. A nonpregnant cohort received the same dose for the same duration but were not mated. On gestational day 16 (GD16), or nonpregnant day 16 (NP16), animals were subjected to an intraperitoneal glucose tolerance test. Tissues and blood samples were collected 4 days later. Hypothyroidism induced a diabetic-like phenotype by GD16 in pregnant females only. Pregnant MOD and SEV females had reduced fasting plasma insulin, less insulin following a glucose load, and altered expression of genes involved in insulin signaling within skeletal muscle and adipose tissue. Hypothyroidism reduced rat placental lactogen concentrations, which was accompanied by reduced percentage β-cell cross-sectional area (CSA) relative to total pancreas CSA, and a reduced number of large β-cell clusters in the SEV hypothyroid group. Plasma triglycerides and free fatty acids were reduced by hypothyroidism in pregnant rats, as was the expression of genes that regulate lipid homeostasis. Hypothyroidism in pregnant rats results in a diabetic-like phenotype that is likely mediated by impaired β-cell expansion in pregnancy. This pregnancy-specific phenomenon is likely due to reduced placental lactogen secretion.

Effects of Maternal Hypothyroidism on the Pubertal Development in Female Rat Offspring

The present study was performed to investigate the effect of maternal hypothyroidism and puberty onset in female rat pups. To do this, we employed propylthiouracil (PTU) to prepare a hypothyroid rat model. Pregnant rats were treated with PTU (0.025%) in drinking water from gestational day 14 to postnatal day 21 of offspring. Comparison of general indices such as body and tissue weights and puberty indices such as vaginal opening (VO) and tissue histology between control and PTU-treated rats were conducted. There was no significant difference in the date of VO between control and PTU group. The body weights of the PTU group were significantly lower, only 36.8% of the control group (p<0.001). Although the absolute thyroid weight was not changed by PTU treatment, the relative weight increased significantly about 2.8 times (p<0.001), indicating that hypothyroidism was successfully induced. On the other hand, the absolute weights of the ovary and uterus were markedly decreased by PTU administration (p<0.001), and the relative weight was not significantly changed. The ovarian histology of PTU group revealed the advanced state of differentiation (i.e., presence of corpora lutea). Inversely, the uterine histology of PTU group showed underdeveloped structures compared those in control group. Taken together, the present study demonstrates that our maternal hypothyroidism model resulted in minimal effect on pubertal development symbolized by VO despite of huge retardation in somatic growth. More sophisticatedly designed hypothyroidism model will be helpful to achieve a better understanding of pubertal development and related disorders.

The effects of hypothyroidism and hyperthyroidism on placental Hofbauer cells of pregnant rats

We investigated the effects of maternal thyroid disorders on Hofbauer cells of both the placenta and the fetus in pregnant rats. We divided 21 rats into three groups: control group, induced hypothyroidism (hypo) group and induced hyperthyroidism (hyper) group. Hypothyroidism was induced using propylthiouracil and hyperthyroidism was induced using L-thyroxine. We measured maternal weight, maternal free thyroxine, fetal weight, fetal viability and placental morphology. At the end of the experiment, fetuses of the hypo and hyper groups were less developed than those of the control group. In the hypo and hyper groups, the thickness of the labyrinth zone was decreased, but thickness of the basal zone and decidua basalis was increased. The number of Hofbauer cells was increased in both the hypo and hyper groups. Vascular endothelial growth factor expression was increased in both the hypo and hyper groups compared to controls. Our findings indicate that maternal thyroid disorders exert a negative effect on fetal growth and placental development.

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.

Teratogen update: Antithyroid medications

OBJECTIVE

Thyroid disorders including hyperthyroidism are common during pregnancy. Untreated hyperthyroidism can result in adverse outcomes for pregnancy.

METHODS

Iodine, propylthiouracil (PTU), carbimazole (CMZ), and methimazole (MMI) are common medications for hyperthyroidism treatment. The literature regarding antithyroid medication use in pregnancy and breastfeeding is reviewed.

RESULTS

Animal studies for PTU have suggested congenital anomalies while animal studies for MMI have only indicated adverse outcomes at higher doses than used in humans. Epidemiological studies have noted an increased risk of congenital anomalies for PTU less often than CMZ or MMI but the epidemiological evidence remains mixed. A pattern of anomalies has been described for CMZ and MMI, from both case and epidemiological studies, including choanal atresia, aplasia cutis congenita, and other facial, heart, gastrointestinal, and skin anomalies. Closer examination of cases indicates that a few cases of the anomalies have occurred without exposure to CMZ or MMI and outside of the proposed critical period. PTU has a small risk of hepatotoxicity which rarely results in liver transplantation and death. Some authors have suggested that PTU be prescribed in early pregnancy and switched to MMI in late pregnancy. Untreated hyperthyroidism, from either a lack of medications or switching medications during the first trimester, may also increase the chance of congenital anomalies. Multiple case studies and larger epidemiological studies have failed to provide clear, consistent outcomes for the use of PTU, CMZ, and MMI in pregnancy. MMI and PTU both enter the breastmilk in small amounts.

CONCLUSION

Additional research is needed to assist in the medical management and exposure counseling of pregnant and breastfeeding women with hyperthyroidism.

Thyroid Disease in Lupus: An Updated Review

In the following review, we seek to provide an overview of the current understanding of various thyroid manifestations affecting patients with systemic lupus erythematosus (SLE), including topics ranging from thyroid‐related complications to SLE in pregnancy. Autoimmune diseases tend to coincide, and an association between thyroid disease and SLE has been reported for more than 50 years. There is no evidence that the coexistence of thyroid disease and lupus alters the disease course or manifestations of either. Both hypothyroidism and thyroid nodules are seen more frequently in patients with SLE than in the general population. The rate of thyroid cancer is twice as prevalent in patients with SLE compared with those without SLE. Several forms of thyroid disease are more common among patients with SLE, with adverse consequences in pregnancy. Future work will require delineating the mechanism behind these associations and understanding the role of antirheumatic agents with concomitant thyroid disease.

Treatment of Graves' hyperthyroidism with thionamides: a position paper on indications and safety in pregnancy

CONTEXT

Graves' disease affects 3% of women and 0.5% of men in the general population. The first line treatment of Graves' hyperthyroidism is based on the administration of antithyroid drugs (ATD), propylthiouracil (PTU), methimazole (MMI) and carbimazole. A recent warning from the Italian Drug Agency (Agenzia Italiana del Farmaco AIFA) reported the risk of MMI-induced acute pancreatitis. In addition, AIFA highlighted the possible association of MMI treatment during the first trimester of pregnancy with congenital malformations, thus recommending the use of effective contraceptive methods in women of childbearing age treated with MMI.

METHODS AND RESULTS

Revision of literature reported less than ten cases of the alleged MMI pancreatitis, allowing the inclusion of MMI in class III drug regarding the relative risk for drug-induced pancreatitis. Data available on the effect of hyperthyroidism per se on the risk of fetal malformations, although scanty, are sufficient to recommend treatment with ATD of the hyperthyroid pregnant woman. Case reports and population studies either suggesting or not suggesting MMI-induced fetal malformations do not allow unquestionable conclusions on this matter.

CONCLUSIONS

This consensus by experts from Italian Endocrine and Gynecologic Scientific Societies has edited recommendations derived form the available data and published guidelines of International Scientific Societies.

Maternal Thyroid Function, Use of Antithyroid Drugs in Early Pregnancy, and Birth Defects

CONTEXT

Antithyroid drug (ATD) therapy in early pregnancy is associated with birth defects, but more data are needed to substantiate the risk associated with different types of ATD. Furthermore, the role of abnormal maternal thyroid function per se remains unclarified.

OBJECTIVE

To evaluate the risk of birth defects associated with the use of ATD in an extended nationwide cohort and the role of abnormal maternal thyroid function in birth cohorts including stored maternal blood samples from early pregnancy.

PARTICIPANTS

Danish pregnant women and their live-born children, including 1,243,353 children from a Nationwide Register-Based Cohort (NRBC), 1997 to 2016; 8830 children from the Danish National Birth Cohort (DNBC), 1997 to 2003; and 14,483 children from the North Denmark Region Pregnancy Cohort (NDRPC), 2011 to 2015.

MAIN OUTCOME MEASURES

Birth defects diagnosed before 2 years of age.

RESULTS

In the NRBC, altogether 2718 (0.2%) children had been exposed to ATD in early pregnancy. The overall frequency of birth defects was 6.7% (95% CI, 6.7% to 6.8%) in nonexposed children and higher after exposure to methimazole/carbimazole (9.6%; 95% CI, 8.2% to 11.2%) and propylthiouracil (8.3%; 95% CI, 6.7% to 10.3%). On the other hand, the frequency of maternal thyroid dysfunction in early pregnancy was similar in the random cohort and in cases of birth defect in the DNBC (12.4 vs 12.6%, P = 0.8) and the NDRPC (15.1 vs 15.4%, P = 0.8).

CONCLUSIONS

Results corroborate an increased risk of birth defects associated with the use of ATD in early pregnancy and suggest that abnormal maternal thyroid function is not a major risk factor for birth defects.

Exposure to the UV Filter Octyl Methoxy Cinnamate in the Postnatal Period Induces Thyroid Dysregulation and Perturbs the Immune System of Mice

Evidence demonstrates the bidirectional communication and regulation between the neuroendocrine and immune systems. Thyroid hormones play key roles in nervous system development and can exert influence on various immune cells contributing to pathophysiological conditions. Octyl methoxycinnamate (OMC) is one of the most commonly used UV filters, and in vitro and in vivo studies have found thyroid disrupting effects. The present study assessed whether OMC administration in mice dams during the lactational period can cause thyroid disruption and generate immunologic alterations in the offspring. Indirect exposure to the OMC (1,000 mg/kg) in the lactational period affected neurodevelopment parameters, such as delayed eye-opening and weight gain in mice of both sexes, and these alterations are corroborated by the decrease in the T4 levels present in the pups' blood. No significant changes were observed in the thymus of these pups, but the number of lymphocytes increased in the spleen of the animals exposed to OMC, similar to the animals treated with propyl-thiouracil (PTU), a well-known thyroid disruptor. OMC modulated the percentage of leukocyte populations in peripheral blood, and the number of circulating polymorphonuclear cells increased two-fold. In vitro, OMC exhibited an inhibitory effect on splenocyte proliferation and IL-2 production induced by anti-CD3 antibody; however, this effect was reversed with the addition of T4 in the cell culture. In summary, the results of the present study demonstrate the influence of OMC on thyroid dysregulation and its impact on the modulation of the immune system in mice pups.

Low-expressional IGF1 mediated methimazole-induced liver developmental toxicity in fetal mice

Anti-thyroid drugs (ATDs) therapy is necessary for pregnant women with hyperthyroidism. However, there is a lack of studies on developmental toxicity of ATDs. In this study, we observed the developmental toxicity of fetal liver induced by prenatal methimazole exposure (PME) in mice, and explored the potential mechanism. Pregnant Kunming mice were administered intragastrically with 4.5 or 18 mg/kg·d methimazole from gestational day (GD) 9∼18. After PME, the birth weights of the offspring mice were decreased, and the liver morphology, development indexes and metabolic function were all altered in different degree in the PME fetuses. Meanwhile, PME decreased the levels of serum and hepatic insulin-like growth factor 1 (IGF1), and reduced the gene expression of IGF1 downstream signaling pathway. Furthermore, the protein levels of phosphorylated-extracellular regulated protein kinases (p-ERK) and serine-threonine protein kinase (p-Akt) were also reduced. Furthermore, methimazole disturb hepatocyte differentiation, maturation and metabolic function through suppressing IGF1 signaling pathway in HepG2 cells. These results demonstrated that PME could induce fetal liver developmental toxicity, and the underlying mechanism was related to low-expression of hepatic IGF1 caused by methimazole, which mediated abnormal liver morphology and metabolic function.

Antenatal/early postnatal hypothyroidism alters arterial tone regulation in 2-week-old rats

The mechanisms of vascular alterations resulting from early thyroid hormones deficiency are poorly understood. We tested the hypothesis that antenatal/early postnatal hypothyroidism would alter the activity of endothelial NO pathway and Rho-kinase pathway, which are specific for developing vasculature. Dams were treated with propylthiouracil (PTU, 7 ppm) in drinking water during gestation and 2 weeks after delivery, and their progeny had normal body weight but markedly reduced blood levels of thyroid hormones (ELISA). Small arteries from 2-week-old male pups were studied using wire myography, qPCR and Western blotting. Mesenteric arteries of PTU pups, compared to controls, demonstrated smaller maximum response to α1-adrenergic agonist methoxamine and reduced mRNA contents of smooth muscle differentiation markers α-actin and SERCA2A. Inhibition of basal NO synthesis by l-NNA led to tonic contraction of mesenteric arteries and augmented their contractile responses to methoxamine; both l-NNA effects were impaired in PTU pups. PTU pups demonstrated lower blood level of NO metabolites compared to control group (Griess reaction). Rho-kinase inhibitor Y27632 strongly reduced mesenteric arteries responses to methoxamine in PTU pups, that was accompanied by elevated Rho-kinase content in their arteries in comparison to control ones. Unlike mesenteric, saphenous arteries of PTU pups, compared to controls, had no changes in α-actin and SERCA2A contents and in responses to l-NNA and Y27632. In conclusion, thyroid hormones deficiency suppresses the anticontractile effect of NO and potentiates the procontractile Rho-kinase effects in mesenteric arteries of 2-week-old pups. Such alterations disturb perinatal cardiovascular homeostasis and might lead to cardiovascular pathologies in adulthood.

Risk of embryopathies with use of antithyroidal medications

PURPOSE OF REVIEW

Hyperthyroidism in pregnant women should be adequately treated to prevent maternal and fetal complications. The treatment of choice in pregnancy is antithyroidal medications (ATDs). The risk of embryopathies associated with the use of Methimazole (MMI) and Propylthiouracil (PTU) in early pregnancy is a matter of clinical attention and concern. This review describes current evidence and how scientific findings are reflected in current clinical guidelines.

RECENT FINDINGS

Embryopathies after the use of ATDs were previously mainly described in case reports and considered rare. Recent large observational studies, including nonexposed control groups, have quantified an increased risk of embryopathies associated with use of ATDs during pregnancy. Findings suggest a risk of embryopathies with the use of both MMI and PTU, but the pattern of embryopathies differs, and embryopathies with the use of PTU appear less severe.

SUMMARY

Current guidelines highlight the need for clinical attention on the use of ATDs in early pregnancy. Patients managed on ATDs for the treatment of hyperthyroidism should be counseled to report a pregnancy as early as possible. PTU is the recommended treatment in early pregnancy, but if the risk of relapse or worsening of hyperthyroidism is considered low, it is suggested that ATD treatment can be withdrawn followed by frequent monitoring of thyroid function.

Opposing Effects of Maternal Hypo- and Hyperthyroidism on the Stability of Thalamocortical Synapses in the Visual Cortex of Adult Offspring

Insufficient or excessive thyroid hormone (TH) levels during fetal development can cause long-term neurological and cognitive problems. Studies in animal models of perinatal hypo- and hyperthyroidism suggest that these problems may be a consequence of the formation of maladaptive circuitry in the cerebral cortex, which can persist into adulthood. Here we used mouse models of maternal hypo- and hyperthyroidism to investigate the long-term effects of altering thyroxine (T4) levels during pregnancy (corresponding to embryonic days 6.5-18.5) on thalamocortical (TC) axon dynamics in adult offspring. Because perinatal hypothyroidism has been linked to visual processing deficits in humans, we performed chronic two-photon imaging of TC axons and boutons in primary visual cortex (V1). We found that a decrease or increase in maternal serum T4 levels was associated with atypical steady-state dynamics of TC axons and boutons in V1 of adult offspring. Hypothyroid offspring exhibited axonal branch and bouton dynamics indicative of an abnormal increase in TC connectivity, whereas changes in hyperthyroid offspring were indicative of an abnormal decrease in TC connectivity. Collectively, our data suggest that alterations to prenatal T4 levels can cause long-term synaptic instability in TC circuits, which could impair early stages of visual processing.

Effects of maternal hypothyroidism during pregnancy on learning, memory and hippocampal BDNF in rat pups: Beneficial effects of exercise

Hypothyroidism during early development leads to numerous morphological, biochemical and functional changes in developing brain. In this study, we investigated the effects of voluntary and treadmill exercise on learning, memory and hippocampal BDNF levels in both hypothyroid male and female rat pups. To induce hypothyroidism in the mothers, 6-propyl-2-thiouracil (PTU) was added to their drinking water (100mg/L) from their embryonic day 6 to their postnatal day (PND) 21. For 14days, from PNDs 31 to 44, the rat pups were trained with one of the two different exercise protocols, namely the mild treadmill exercise and the voluntary wheel exercise. On PNDs 45-52, a water maze was used for testing their learning and memory ability. The rats were sacrificed one day later and their BDNF levels were then measured in the hippocampus. The findings of the present study indicate that hypothyroidism during the fetal period and the early postnatal period is associated with the impairment of spatial learning and memory and reduced hippocampal BDNF levels in both male and female rat offspring. Both the short-term treadmill exercise and the voluntary wheel exercise performed during the postnatal period reverse the behavioral and neurochemical deficits induced by developmental thyroid hormone insufficiency in both male and female rat offspring. The findings of this study thus demonstrate a marked reversibility of both behavioral and neurochemical disorders induced by developmental thyroid hormone insufficiency through the performance of exercise.