Melissa officinalis extract palliates redox imbalance and inflammation associated with hyperthyroidism-induced liver damage by regulating Nrf-2/ Keap-1 gene expression in γ-irradiated rats.

BACKGROUND: Melissa officinalis (MO) is a well-known medicinal plant species used in the treatment of several diseases; it is widely used as a vegetable, adding flavour to dishes. This study was designed to evaluate the therapeutic effect of MO Extract against hyperthyroidism induced by Eltroxin and γ-radiation. METHODS: Hyperthyroidism was induced by injecting rats with Eltroxin (100 µg/kg/ day) for 14 days and exposure to γ-radiation (IR) (5 Gy single dose). The hyperthyroid rats were orally treated with MO extract (75 mg/kg/day) at the beginning of the second week of the Eltroxin injection and continued for another week. The levels of thyroid hormones, liver enzymes and proteins besides the impaired hepatic redox status and antioxidant parameters were measured using commercial kits. The hepatic gene expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and its inhibitor Kelch-like ECH-associated protein-1(Keap-1) in addition to hepatic inflammatory mediators including tumor necrosis factor-α (TNF- α), Monocyte chemoattractant protein-1 (MCP-1) and fibrogenic markers such as transforming growth factor-beta1 (TGF-ß1) were determined. RESULTS: MO Extract reversed the effect of Eltroxin + IR on rats and attenuated the thyroid hormones. Moreover, it alleviated hyperthyroidism-induced hepatic damage by inhibiting the hepatic enzymes' activities as well as enhancing the production of proteins concomitant with improving cellular redox homeostasis by attenuating the deranged redox balance and modulating the Nrf2/Keap-1 pathway. Additionally, MO Extract alleviated the inflammatory response by suppressing the TNF- α and MCP-1 and prevented hepatic fibrosis via Nrf2-mediated inhibition of the TGF-ß1/Smad pathway. CONCLUSION: Accordingly, these results might strengthen the hepatoprotective effect of MO Extract in a rat model of hyperthyroidism by regulating the Nrf-2/ Keap-1 pathway.

Preventive Effect of Molecular Iodine in Pancreatic Disorders from Hypothyroid Rabbits.

Pancreatic alterations such as inflammation and insulin resistance accompany hypothyroidism. Molecular iodine (I2) exerts antioxidant and differentiation actions in several tissues, and the pancreas is an iodine-uptake tissue. We analyzed the effect of two oral I2 doses on pancreatic disorders in a model of hypothyroidism for 30 days. Adult female rabbits were divided into the following groups: control, moderate oral dose of I2 (0.2 mg/kg, M-I2), high oral dose of I2 (2.0 mg/kg, H-I2), oral dose of methimazole (MMI; 10 mg/kg), MMI + M-I2,, and MMI + H-I2. Moderate or high I2 supplementation did not modify circulating metabolites or pancreatic morphology. The MMI group showed reductions of circulating thyroxine (T4) and triiodothyronine (T3), moderate glucose increments, and significant increases in cholesterol and low-density lipoproteins. Acinar fibrosis, high insulin content, lipoperoxidation, and overexpression of GLUT4 were observed in the pancreas of this group. M-I2 supplementation normalized the T4 and cholesterol, but T3 remained low. Pancreatic alterations were prevented, and nuclear factor erythroid-2-related factor-2 (Nrf2), antioxidant enzymes, and peroxisome proliferator-activated receptor gamma (PPARG) maintained their basal values. In MMI + H-I2, hypothyroidism was avoided, but pancreatic alterations and low PPARG expression remained. In conclusion, M-I2 supplementation reestablishes thyronine synthesis and diminishes pancreatic alterations, possibly related to Nrf2 and PPARG activation.

Effect of Combined Levothyroxine (L-T4) and 3-Iodothyronamine (T1AM) Supplementation on Memory and Adult Hippocampal Neurogenesis in a Mouse Model of Hypothyroidism.

Mood alterations, anxiety, and cognitive impairments associated with adult-onset hypothyroidism often persist despite replacement treatment. In rodent models of hypothyroidism, replacement does not bring 3-iodothyronamine (T1AM) brain levels back to normal. T1AM is a thyroid hormone derivative with cognitive effects. Using a pharmacological hypothyroid mouse model, we investigated whether augmenting levothyroxine (L-T4) with T1AM improves behavioural correlates of depression, anxiety, and memory and has an effect on hippocampal neurogenesis. Hypothyroid mice showed impaired performance in the novel object recognition test as compared to euthyroid mice (discrimination index (DI): 0.02 ± 0.09 vs. 0.29 ± 0.06; t = 2.515, p = 0.02). L-T4 and L-T4+T1AM rescued memory (DI: 0.27 ± 0.08 and 0.34 ± 0.08, respectively), while T1AM had no effect (DI: -0.01 ± 0.10). Hypothyroidism reduced the number of neuroprogenitors in hippocampal neurogenic niches by 20%. L-T4 rescued the number of neuroprogenitors (mean diff = 106.9 ± 21.40, t = 4.99, pcorr = 0.003), while L-T4+T1AM produced a 30.61% rebound relative to euthyroid state (mean diff = 141.6 ± 31.91, t = 4.44, pcorr = 0.004). We performed qPCR analysis of 88 genes involved in neurotrophic signalling pathways and found an effect of treatment on the expression of Ngf, Kdr, Kit, L1cam, Ntf3, Mapk3, and Neurog2. Our data confirm that L-T4 is necessary and sufficient for recovering memory and hippocampal neurogenesis deficits associated with hypothyroidism, while we found no evidence to support the role of non-canonical TH signalling.

Functional Characterization of the Novel and Specific Thyroid Hormone Transporter SLC17A4.

Background: A recent genome-wide association study identified the SLC17A4 locus associated with circulating free thyroxine (T4) concentrations. Human SLC17A4, being widely expressed in the gastrointestinal tract, was characterized as a novel triiodothyronine (T3) and T4 transporter. However, apart from the cellular uptake of T3 and T4, transporter characteristics are currently unknown. In this study, we delineated basic transporter characteristics of this novel thyroid hormone (TH) transporter. Methods: We performed a broad range of well-established TH transport studies in COS-1 cells transiently overexpressing SLC17A4. We studied cellular TH uptake in various incubation buffers, TH efflux, and the inhibitory effects of different TH metabolites and known inhibitors of other TH transporters on SLC17A4-mediated TH transport. Finally, we determined the effect of tunicamycin, a pharmacological inhibitor of N-linked glycosylation, and targeted mutations in Asn residues on SLC17A4 function. Results: SLC17A4 induced the cellular uptake of T3 and T4 by ∼4 times, and of reverse (r)T3 by 1.5 times over control cells. The uptake of T4 by SLC17A4 was Na+ and Cl- independent, stimulated by low extracellular pH, and reduced by various iodothyronines and metabolites thereof, particularly those that contain at least three iodine moieties irrespective of the presence of modification at the alanine side chain. None of the classical TH transporter inhibitors studied attenuated SLC17A4-mediated TH transport. SLC17A4 also facilitates the efflux of T3 and T4, and to a lesser extent of 3,3'-diiodothyronine (T2). Immunoblot studies on lysates of transfected cells cultured in absence or presence of tunicamycin indicated that SLC17A4 is subject to N-linked glycosylation. Complementary mutational studies identified Asn66, Asn75, and Asn90, which are located in extracellular loop 1, as primary targets. Conclusions: Our studies show that SLC17A4 facilitates the transport of T3 and T4, and less efficiently rT3 and 3,3'-T2. Further studies should reveal the physiological role of SLC17A4 in TH regulation.

Amelioration of sperm fertilizability, thyroid activity, oxidative stress, and inflammatory cytokines in rabbit bucks treated with phytogenic extracts.

This study investigated the beneficial effect of phytogenic extracts on semen quality, reproductive hormones, thyroid activity, immunity, hepatic antioxidant activity, and fertility in rabbit bucks. We divided 70 bucks into seven groups (10 in each). Group 1 was fed a basal diet (control); groups 2, 3, and 4 were fed the control diet with 30, 60, and 90 mg/kg of turmeric, respectively; and groups 5, 6, and 7 were fed the control diet with 50, 75, and 100 mg/kg of garlic extract, respectively, for 8 weeks. Rectal and skin temperatures decreased, while follicle-stimulating hormone, luteinizing hormone, triiodothyronine, thyroxine, testosterone, immunoglobulin M, tumor necrosis factor-alpha, and interleukin-6 in blood serum and glutathione peroxidase in the liver increased in all groups (p < .05). Garlic extract (100 mg/kg diet) increased adenosine triphosphate and glutathione in the liver tissues. All treatments significantly increased net semen volume, percentages of progressive motility, livability, curled tail, and intact acrosomes of spermatozoa, sperm cell concentration, and outputs of total and motile spermatozoa, while significantly decreased percentage of sperm abnormality. In conclusion, dietary supplementation of turmeric or garlic extract can be used as a suitable tool for enhancing the hepatic antioxidant activity, immunity, and semen quality in rabbit bucks.

Thyroxine binding to type III iodothyronine deiodinase.

Iodothyronine deiodinases (Dios) are important selenoproteins that control the concentration of the active thyroid hormone (TH) triiodothyronine through regioselective deiodination. The X-ray structure of a truncated monomer of Type III Dio (Dio3), which deiodinates TH inner rings through a selenocysteine (Sec) residue, revealed a thioredoxin-fold catalytic domain supplemented with an unstructured Ω-loop. Loop dynamics are driven by interactions of the conserved Trp207 with solvent in multi-microsecond molecular dynamics simulations of the Dio3 thioredoxin(Trx)-fold domain. Hydrogen bonding interactions of Glu200 with residues conserved across the Dio family anchor the loop's N-terminus to the active site Ser-Cys-Thr-Sec sequence. A key long-lived loop conformation coincides with the opening of a cryptic pocket that accommodates thyroxine (T4) through an I⋯Se halogen bond to Sec170 and the amino acid group with a polar cleft. The Dio3-T4 complex is stabilized by an I⋯O halogen bond between an outer ring iodine and Asp211, consistent with Dio3 selectivity for inner ring deiodination. Non-conservation of residues, such as Asp211, in other Dio types in the flexible portion of the loop sequence suggests a mechanism for regioselectivity through Dio type-specific loop conformations. Cys168 is proposed to attack the selenenyl iodide intermediate to regenerate Dio3 based upon structural comparison with related Trx-fold proteins.

Thyroxine modulation of immune toxicity induced by mixture pesticides mancozeb and fipronil in mice.

AIM: The cross regulation between neuroendocrine system, particularly Hypothalamus-Pituitary-Thyroid (HPT) axis and immune system during embryonic/early neonatal developmental stages shapes the functional attribute of immune response throughout the life. Thus, disruption of immune system was anticipated on exposure to thyroid disrupting pesticides (TDPs) mancozeb (MCZ) and fipronil (FPN) during critical windows of early postnatal days (PND) development. MAIN METHODS: Mice were exposed to MCZ and FPN as individual (0.5% LD 50 each) and as mixtures (0.25% and 0.5% LD 50 each) from PND 31 (initiation phase of immune response) till PND 60 (Maturation phase). Thyroxine (T4) supplementation was given from PND 51 to PND 60. Assessment was done at PND 61 as well as at PND 91 (adults). KEY FINDINGS: Plasma level of thyroid hormones (T3 and T4) was reduced but pituitary hormone (TSH) increased till adulthood on exposure to mixture pesticides but not on individual exposure. Mixture pesticides also increased body weight gain and reduced survival rate in adults. Exposure of individual pesticides exert immunotoxicity but more pronounced immune suppression was observed in mixture pesticides exposed group as reflected in reduced relative weight and cellularity in spleen and thymus, reduced in vitro mitogenic (Con A/LPS) response of splenocytes and thymocytes (reduced proliferative index and increased apoptotic/necrotic death). T4 supplementation ameliorated thyroid disruptive and immunotoxic effect of pesticides. SIGNIFICANCE: The additive/synergistic toxicity as well as hypothyroidism induced by mixture pesticides has produced pronounced immune suppression that reflected till adulthood. Supplementation of T4 prevented thyroid axis disruption mediated immunosuppression.

Seizure duration may increase thyroid-stimulating hormone levels in children experiencing a seizure.

OBJECTIVE: Variations in hormone levels are a direct effect of epileptic discharges in both animals and humans, and seizure can affect the hypothalamus-pituitary-thyroid axis. The purpose of this study was to determine which parameters could affect the alternation of thyroid hormones in children experiencing seizure. METHODS: We retrospectively reviewed the medical records of 181 pediatric patients with seizure and compared three thyroid hormones (serum thyroid-stimulating hormone [TSH], free thyroxine [fT4], and triiodothyronine [T3]) between initial (admission to hospital) and follow-up (2 weeks later) testing. RESULTS: Multivariable logistic regression models were used to determine which six parameters (gender, age, seizure accompanying with fever, seizure type, seizure duration, and anti-epileptic drug medication) could help to explain the higher initial TSH levels in pediatric seizure. Only seizure duration in patients with an increase in TSH levels was significantly longer compared with patients with normal TSH at the time of initial testing. CONCLUSION: Neuronal excitability by seizure can cause thyroid hormonal changes, which likely reflects changes in hypothalamic function.

A model of the cost of delaying treatment of Hashimotos thyroiditis: thyroid cancer initiation and growth.

Hashimoto's thyroiditis (HT) is an autoimmune disorder that drives the function of thyroid gland to the sequential clinical states:euthyroidism (normal condition), subclinical hypothyroidism (asymptomatic period) and overt hypothyroidism (symptomatic period). In this disease, serum thyroidstimulating hormone (TSH) levels increase monotonically, stimulating the thyroid follicular cells chronically and initiating benign (non-cancerous) thyroid nodules at various sites of the thyroid gland. This process can also encourage growth of papillary thyroid microcarcinoma. Due to prolonged TSH stimulation, thyroid nodules may grow and become clinically relevant without the administration of treatment by thyroid hormone replacement. Papillary thyroid cancer (80% of thyroid cancer) whose incidence is increasing worldwide, is associated with Hashimoto's thyroiditis. A stochastic model is developed here to produce the statistical distribution of thyroid nodule sizes and growth by taking serum TSH value as the continuous input to the model using TSH values from the output of the patientspecific deterministic model developed for the clinical progression of Hashimoto's thyroiditis.

The possible ameliorative effect of Olea europaea L. oil against deltamethrin-induced oxidative stress and alterations of serum concentrations of thyroid and reproductive hormones in adult female rats.

This study aimed to verify whether Olea europaea L. (olive) oil (OEO) exerted a protective effect against oxidative stress induced by deltamethrin (DM) and alterations of pituitary, thyroid and gonadal hormones in adult female rats. DM (0,00256 g/kg body weight),OEO (0,6 g/kg body weight) and DM with OEO were administered to rats orally for 28 days. Volatile compounds present in olive oil were analysed by GC-MS. Estradiol (E2), Thyroxine (T4),Thyroid Stimulating Hormone (TSH), Triiodothyronine (T3), Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH), Progesterone (Pg) were measured in serum using Chemiluminescent Microparticle Immunoassay (CMIA). Lipid peroxidation (LPO), protein carbonyls (PCs), reduced glutathione (GSH) levels along with superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST) and glutathione peroxidase (GPx) activities were determined in thyroid and ovarian tissues. Sesquiterpenes, (E,E)-α-farnesene (16.45%) and α-copaene (9,86%), were analysed as the main volatile compounds of OEO. The relative weight of ovaries and thyroid and body weight significantly decreased in rats treated with DM. DM caused significant alterations in TSH, T4, FSH, Pg and E2 levels while T3 and LH concentrations remained unchanged when compared to control. DM also increased significantly LPO and PCs levels. In addition, GSH reserves as well as CAT, GPx, SOD and GST activities were suppressed in DM-received rats. The presence of OEO with DM returned the levels of oxidative stress markers, thyroid and reproductive hormones at the control values. Our results indicate that OEO is a powerful agent able to protect against DM oxidative stress and endocrine changes.

Is Parenteral Levothyroxine Therapy Safe in Intractable Hypothyroidism?

CASE: A 32-year old woman was admitted to the hospital due to intractable hypothyroidism refractory to high dose of oral l-thyroxine therapy. She underwent total thyroidectomy and radioactive iodine therapy due to papillary thyroid cancer. After excluding poor adherence to therapy and malabsorption, levothyroxine absorption test was performed. No response was detected. Transient neurologic symptoms developed during the test. She developed 3 attacks consisting of neurologic symptoms during high dose administration. The patient was considered a case of isolated l-thyroxine malabsorption. She became euthyroid after intramuscular twice weekly l-thyroxine therapy. DISCUSSION: There are a few case reports regarding isolated l-thyroxine. We report successful long term results of twice weekly administered intramuscular l-thyroxine therapy. We also draw attention to neurologic side effects of high dose l-thyroxine therapy.

MOK, a pharmacopuncture medicine, regulates thyroid dysfunction in L-thyroxin-induced hyperthyroidism in rats through the regulation of oxidation and the TRPV1 ion channel.

BACKGROUND: In this study, we evaluated the therapeutic effect of MOK, a pharmacopuncture medicine, on thyroid dysfunction in L-thyroxin (LT4)-induced hyperthyroidism rats. METHODS: The experimental hyperthyroidism model was prepared by the intraperitoneal injection of LT4 (0.5 mg/kg) once daily for 2 weeks in SD rats. MOK extract was injected at doses of 0.3 or 3 mg/kg on acupuncture points in the thyroid glands of LT4-induced hypothyroidism rats once a day for 2 weeks. The body temperature, body weight, and food/water intake were measured once a week for 2 weeks. The levels of thyroid hormones, total cholesterol, LDL-cholesterol, GOT, and GPT were measured in the sera of rats using ELISA and an automatic blood analyzer. The histological changes of thyroid tissues were observed by H&E staining. The expression of thermo-regulating protein, TRPV1 was determined by western blot in dorsal root ganglion (DRG) and brain tissues. We also measured the contents of GSH in the liver and antioxidant enzymes, SOD, and catalase in the liver, heart, and brain tissues by enzyme-based assay and Western blot, respectively. RESULTS: The acupuncture of MOK extract on the thyroid gland of LT4-induced hyperthyroidism rats significantly decreased the body temperature, and did not change body weight and food and water intakes. MOK acupuncture significantly increased the level of TSH, and decreased the levels of T3 and T4 in hyperthyroidism rats. The expression of TRPV1 was inhibited in both DRG and brain tissues after MOK acupuncture, and the levels of GOT, GPT, total cholesterol, and LDL-cholesterol were also decreased. MOK acupuncture also inhibited the pathological feature with follicular lining epithelial thicknesses and increased follicular colloid depositions in the thyroid glands of hypothyroidism. MOK acupuncture significantly increased hepatic GSH levels and decreased the expression of SOD and catalase in the liver, heart, and brain tissues of hyperthyroidism rats. CONCLUSIONS: These results suggest that the pharmacopuncture with MOK extract in hyperthyroidism can improve the pathophysiological changes through regulating the body temperature, thyroid hormones imbalance, lipid accumulation, and oxidation. This anti-hyperthyroidism effect of MOK pharmacopuncture is thought to be related to the control of thermo-regulating protein TRPV1 in DRG and brain.

Potential protective effect of Pistacia lentiscus oil against chlorpyrifos-induced hormonal changes and oxidative damage in ovaries and thyroid of female rats.

The purpose of this study was to evaluate the protective effect of Pistacia lentiscus oil (PLO), known for its antioxidant properties, on chlorpyrifos (CPF)-induced alterations in the thyroid, reproductive hormone levels, and oxidative damage in the ovaries and thyroid of adult Wistar rats. The animals were treated with orally administered PLO (2 mL/kg), CPF (6.75 mg/kg), and a combination of CPF and PLO for 30 days. Serum levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), progesterone (Pg), estradiol (E2), triiodothyronine (T3), thyroxine (T4), and thyroid-stimulating hormone (TSH) were assessed using chemiluminescence assay. Malondialdehyde (MDA), protein carbonyl (PC), and reduced glutathione (GSH) levels were examined in the ovaries and thyroid glands. The oil principal volatile compounds detected by gas chromatography analysis were: myrcene, α-pinene and limonene (26.21, 22.66 and 10.33%, respectively). No significant differences were observed between serum concentrations of TSH and FSH in the examined experimental groups. However, serum concentrations of LH, E2, Pg, T3, and T4 decreased significantly in CPF-treated rats in comparison with the controls. The body weight and relative weight of ovaries and thyroids in this group were also significantly reduced. The MDA and PC content increased significantly, while the GSH content was markedly depressed in the thyroid and ovaries of rats treated with CPF. Co-administration of PLO and CPF effectively ameliorated the adverse effects; the oxidative damage was reduced and the levels of thyroid and reproductive hormones restored to a normal range. In conclusion, it appears that PLO substantially alleviates the CPF-induced oxidative damage and hormonal alterations.

Sorafenib-Induced Changes in Thyroid Hormone Levels in Patients Treated for Hepatocellular Carcinoma.

Context: The pathogenesis of tyrosine kinase inhibitor-induced thyroid hormone (TH) alterations are still a matter of debate. Objective: The objective of this study was to determine the effects of sorafenib on TH levels in patients with hepatocellular carcinoma (HCC) and to evaluate possible mechanisms. Design: We performed a prospective cohort study between 2009 and 2016. Setting: This study was conducted at a tertiary referral center. Patients: This study included 57 consecutive patients with HCC who were treated with sorafenib. Main Outcome Measure: Thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels were measured every 6 weeks, and extensive thyroid function tests (TFTs) were measured before treatment (t0), after 6 weeks (t6), and at the end of therapy. The effect of sorafenib on TH transport by monocarboxylate transporter (MCT)8 or MCT10 was tested in transfected COS1 cells. Results: Four patients (7%) developed thyroiditis. Among the other patients, 30% had elevation of TSH or FT4 above the normal range. Overall, between t0 and t6, mean TSH increased from 1.28 to 1.57 mU/L (P < 0.001) and mean FT4 from 18.4 to 21.2 pmol/L (P < 0.001). Simultaneously, the serum triiodothyronine (T3)/reverse triiodothyronine ratio and the (T3/thyroxine) ×100 ratio decreased. Sorafenib decreased cellular T3 uptake by MCT8 and to a lesser extent by MCT10. Conclusions: These in vivo data suggest that sorafenib affects TFTs on multiple levels. Our in vitro experiments suggest a possible role of sorafenib-induced inhibition of T3 transport into the cell by MCT8 and MCT10.

Central hypothyroidism - a neglected thyroid disorder.

Central hypothyroidism is a rare and heterogeneous disorder that is characterized by a defect in thyroid hormone secretion in an otherwise normal thyroid gland due to insufficient stimulation by TSH. The disease results from the abnormal function of the pituitary gland, the hypothalamus, or both. Moreover, central hypothyroidism can be isolated or combined with other pituitary hormone deficiencies, which are mostly acquired and are rarely congenital. The clinical manifestations of central hypothyroidism are usually milder than those observed in primary hypothyroidism. Obtaining a positive diagnosis for central hypothyroidism can be difficult from both a clinical and a biochemical perspective. The diagnosis of central hypothyroidism is based on low circulating levels of free T4 in the presence of low to normal TSH concentrations. The correct diagnosis of both acquired (also termed sporadic) and congenital (also termed genetic) central hypothyroidism can be hindered by methodological interference in free T4 or TSH measurements; routine utilization of total T4 or T3 measurements; concurrent systemic illness that is characterized by low levels of free T4 and normal TSH concentrations; the use of the sole TSH-reflex strategy, which is the measurement of the sole level of TSH, without free T4, if levels of TSH are in the normal range; and the diagnosis of congenital hypothyroidism based on TSH analysis without the concomitant measurement of serum levels of T4. In this Review, we discuss current knowledge of the causes of central hypothyroidism, emphasizing possible pitfalls in the diagnosis and treatment of this disorder.

A lamprey view on the origins of neuroendocrine regulation of the thyroid axis.

This mini review summarizes the current knowledge of the hypothalamic-pituitary-thyroid (HPT) endocrine system in lampreys, jawless vertebrates. Lampreys and hagfish are the only two extant members of the class of agnathans, the oldest lineage of vertebrates. The high conservation of the hypothalamic-pituitary-gonadal (HPG) axis in lampreys makes the lamprey model highly appropriate for comparative and evolutionary analyses. However, there are still many unknown questions concerning the hypothalamic-pituitary (HP) axis in its regulation of thyroid activities in lampreys. As an example, the hypothalamic and pituitary hormone(s) that regulate the HPT axis have not been confirmed and/or characterized. Similar to gnathostomes (jawed vertebrates), lampreys produce thyroxine (T4) and triiodothyronine (T3) from thyroid follicles that are suggested to be involved in larval development, metamorphosis, and reproduction. The existing data provide evidence of a primitive, overlapping yet functional HPG and HPT endocrine system in lamprey. We hypothesize that lampreys are in an evolutionary intermediate stage of hypothalamic-pituitary development, leading to the emergence of the highly specialized HPG and HPT endocrine axes in jawed vertebrates. Study of the ancient lineage of jawless vertebrates, the agnathans, is key to understanding the origins of the neuroendocrine system in vertebrates.

Maternal marginal iodine deficiency limits dendritic growth of cerebellar purkinje cells in rat offspring by NF-κB signaling and MAP1B.

Iodine deficiency (ID) during early pregnancy had an adverse effect on children's psychomotor and motor function. It is worth noting that maternal marginal ID tends to be a common public health problem. Whether marginal ID potentially had adverse effects on the development of cerebellum and the underlying mechanisms remain unclear. Therefore, our aim was to study the effects of marginal ID on the dendritic growth in filial cerebellar Purkinje cells (PCs) and the underlying mechanism. In the present study, we established Wistar rat models by feeding dam rats with a diet deficient in iodine and deionized water supplemented with potassium iodide. We examined the total dendritic length using immunofluorescence, and Western blot analysis was conducted to investigate the activity of nuclear factor-κB (NF-κB) signaling and microtubule-associated protein 1B (MAP1B). Our results showed that marginal ID reduced the total dendritic length of cerebellar PCs, slightly down-regulated the activity of NF-κB signaling and decreased MAP1B in cerebellar PCs on postnatal day (PN) 7, PN14, and PN21. Our study may support the hypothesis that decreased T4 induced by marginal ID limits PCs dendritic growth, which may involve in the disturbance of NF-κB signaling and MAP1B on the cerebellum. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1241-1251, 2017.

Neuro-Modulation of Immuno-Endocrine Response Induced by Kaliotoxin of Androctonus Scorpion Venom.

Kaliotoxin (KTX), a specific blocker of potassium channels, exerts various toxic effects due to its action on the central nervous system. Its use in experimental model could help the understanding of the cellular and molecular mechanisms involved in the neuropathological processes related to potassium channel dysfunctions. In this study, the ability of KTX to stimulate neuro-immuno-endocrine axis was investigated. As results, the intracerebroventricular injection of KTX leads to severe structural-functional alterations of both hypothalamus and thyroid. These alterations were characterized by a massive release of hormones' markers of thyroid function associated with damaged tissue which was infiltrated by inflammatory cell and an imbalanced redox status. Taken together, these data highlight that KTX is able to modulate the neuro-endocrine response after binding to its targets leading to the hypothalamus and the thyroid stimulation, probably by inflammatory response activation and the installation of oxidative stress in these organs.

Development of a Novel Thyroid Function Fluctuated Animal Model for Thyroid-Associated Ophthalmopathy.

BACKGROUND: The establishment of a suitable and stable animal model is critical for research on thyroid-associated ophthalmopathy (TAO). In clinical practice, we found that patients treated with I-131 often exhibit TAO; therefore, we aimed to establish a novel thyroid function fluctuated animal model of TAO by simulating the clinical treatment process. METHODS: We treated SD rats with I-131 to damage the thyroid and then used sodium levothyroxine (L-T4) to supplement the thyroid hormone (TH) levels every seven days, leading to a fluctuating level of thyroid hormones that simulated the status of clinical TAO patients. Rats administered normal saline were considered as a control. The weight, intraocular pressure, and serum T3, T4, TSH and TRAb levels of the rats were measured, and the pathological changes were analyzed by H&E staining and transmission electron microscopy (TEM). RESULTS: The experimental rats (TAO group) exhibited significantly reduced weight and elevated intraocular pressure compared with the control rats. Meanwhile, the serum levels of T3 and T4 were up-regulated in the TAO group, but the TSH level decreased during the 10-week study. Moreover, increased numbers of blood vessels and inflammatory cell infiltrations were observed in the orbital tissues of the TAO rats, while no abnormal changes occurred in the control rats. The orbital myofibrils in the TAO rats appeared fractured and dissolved, with twisted structures. Mitochondrial swelling and vacuoles within the endoplasmic reticulum, swelling nerve fibers, shedding nerve myelin, and macrophages were found in the TAO group. CONCLUSION: Rats treated with I-131 and sodium levothyroxine exhibited characteristics similar to those of TAO patients in the clinic, providing an effective and simple method for the establishment of a stable animal model for research on the pathogenesis and treatment of TAO.

Increased Thyroid Hormone Activation Accompanies the Formation of Thyroid Hormone-Dependent Negative Feedback in Developing Chicken Hypothalamus.

The hypothalamic-pituitary-thyroid axis is governed by hypophysiotropic TRH-synthesizing neurons located in the hypothalamic paraventricular nucleus under control of the negative feedback of thyroid hormones. The mechanisms underlying the ontogeny of this phenomenon are poorly understood. We aimed to determine the onset of thyroid hormone-mediated hypothalamic-negative feedback and studied how local hypothalamic metabolism of thyroid hormones could contribute to this process in developing chicken. In situ hybridization revealed that whereas exogenous T4 did not induce a statistically significant inhibition of TRH expression in the paraventricular nucleus at embryonic day (E)19, T4 treatment was effective at 2 days after hatching (P2). In contrast, TRH expression responded to T3 treatment in both age groups. TSHß mRNA expression in the pituitary responded to T4 in a similar age-dependent manner. Type 2 deiodinase (D2) was expressed from E13 in tanycytes of the mediobasal hypothalamus, and its activity increased between E15 and P2 both in the mediobasal hypothalamus and in tanycyte-lacking hypothalamic regions. Nkx2.1 was coexpressed with D2 in E13 and P2 tanycytes and transcription of the cdio2 gene responded to Nkx2.1 in U87 glioma cells, indicating its potential role in the developmental regulation of D2 activity. The T3-degrading D3 enzyme was also detected in tanycytes, but its level was not markedly changed before and after the period of negative feedback acquisition. These findings suggest that increasing the D2-mediated T3 generation during E18-P2 could provide the sufficient local T3 concentration required for the onset of T3-dependent negative feedback in the developing chicken hypothalamus.