PTU-induced hypothyroidism modulates antioxidant defence status in the developing cerebellum

Selenium protects against nesfatin-1 modulation of the hypothalamic-pituitary-testicular axis during hypothyroidism in male rats

Normal gonadal function can be disrupted by hypothyroidism. Hypothyroidism disturbs testicular function directly and centrally by affecting the hypothalamic-pituitary-testicular axis with unclear mechanism. As nesfatin-1 neurons co-localized with TRH and GnRH neurons in the hypothalamus, it could play a role in centrally hypothyroidism induced testicular dysfunction. Selenium (Se), by affecting thyroid iodide supply, could relieve these disturbances. So, we aim to identify the role of nesfatin-1 as a link between testicular dysfunction and hypothyroidism through modulating the MAPK/ERK pathway while discussing the possible role of Se in alleviating hypothyroidism and associated testicular damage. Forty male rats were divided equally into: Control: distilled water, Se: Se orally, Propylthiouracil (PTU): PTU orally, PTU + Se: Se with PTU orally. Serum thyroid function, gonadal hormones, nesfatin-1, testicular redox status, sperm analysis, brain tissue GnRH, nucleobindin 2-derived polypeptide, pMAPK/ERK gene expression, histological changes and immunohistochemical expression of testicular proliferating cell antigen (PCNA) were done. PTU induced hypothyroidism and reduction of gonadal hormones which both were correlated with reduced nesfatin-1. There was testicular stress with reduced GnRH, NUCB2, pMAPK/ERK gene expression, and PCNA immunopositive cells. These parameters were reversed by Se. Nesfatin-1 could be the central link between hypothyroidism and disturbances of the hypothalamic pituitary testicular axis.

Interplay between polycystic ovary syndrome and hypothyroidism on serum testosterone, oxidative stress and StAR gene expression in female rats

INTRODUCTION

Endocrine disorders such as polycystic ovary syndrome (PCOS) and hypothyroidism can cause infertility. There are evidence that they happen jointly in some circumstances. It still remains unknown, how these two illnesses interact and influence the body.

METHODS

Accordingly, a five-group was designed, first is the control group, followed by the PCOS group. Estradiol valerate (EV) induced PCOS, the second group had only PCOS and the third, fourth and fifth groups were given varied dosages of propylthiouracil (PTU) to cause hypothyroidism after induction of PCOS. Steroidogenic acute regulatory protein (StAR) expression was measured in the ovaries, and serum was obtained to determine testosterone levels, as well as superoxide dismutase (SOD) as an antioxidant and malondialdehyde (MDA) as an oxidant.

RESULTS

Based on radioimmunoassay data, testosterone levels were significantly higher in the PCOS group than the control group, and significantly lower (p ˂ .05) in PTU groups comparing with the PCOS group. According to the quantitative real-time polymerase chain reaction (qRT-PCR) data, the same results were obtained for the StAR gene as well. The data also indicated a positive correlation between these two. Although both oxidant and antioxidant level increased in PCOS group compared than control group, after hypothyroidism, oxidant level increased significantly (p ˂ .05), meanwhile antioxidant level decreased significantly (p ˂ .05).

CONCLUSIONS

The results of this study illustrate that the presence of both PCOS and hypothyroidism alters the situation more than just PCOS. They also indicate that this situation is associated with imbalanced oxidative/antioxidative status.

Oxidative Stress Parameters in Goitrogen-Exposed Crested Newt Larvae (Triturus spp.): Arrested Metamorphosis

Thiourea is an established disruptor of thyroid hormone synthesis and is frequently used as an inhibitor of metamorphosis. The changes caused by thiourea can affect processes associated with the oxidative status of individuals (metabolic rate, the HPI axis, antioxidant system). We investigated the parameters of oxidative stress in crested newt (Triturus spp.) larvae during normal development in late larval stage 62 and newly metamorphosed individuals, and during thiourea-stimulated metamorphosis arrest in individuals exposed to low (0.05%) and high (0.1%) concentrations of thiourea. Both groups of crested newts exposed to thiourea retained their larval characteristics until the end of the experiment. The low activities of antioxidant enzymes and the high lipid peroxidation level pointed to increased oxidative stress in larvae at the beginning of stage 62 as compared to fully metamorphosed individuals. The activities of catalase (CAT) and glutathione-S-transferase (GST) and the concentration of sulfhydryl (SH) groups were significantly lower in larvae reared in aqueous solutions containing thiourea than in newly metamorphosed individuals. The high thiourea concentration (0.1%) affected the antioxidative parameters to the extent that oxidative damage could not be avoided, contrary to a lower concentration. Our results provide a first insight into the physiological adaptations of crested newts during normal development and simulated metamorphosis arrest.

Prospective role of thyroid disorders in monitoring COVID-19 pandemic

COVID-19 pandemic has affected more than 200 countries and 1.3 million individuals have deceased within eleven months. Intense research on COVID-19 occurrence and prevalence enable us to understand that comorbidities play a crucial role in spread and severity of SARS-CoV-2 infection. Chronic kidney disease, diabetes, respiratory diseases and hypertension are among the various morbidities that are prevalent in symptomatic COVID-19 patients. However, the effect of altered thyroid-driven disorders cannot be ignored. Since thyroid hormone critically coordinate and regulate the major metabolism and biochemical pathways, this review is on the potential role of prevailing thyroid disorders in SARS-CoV-2 infection. Direct link of thyroid hormone with several disorders such as diabetes, vitamin D deficiency, obesity, kidney and liver disorders etc. suggests that the prevailing thyroid conditions may affect SARS-CoV-2 infection. Further, we discuss the oxidative stress-induced aging is associated with the degree of SARS-CoV-2 infection. Importantly, ACE2 protein which facilitates the host-cell entry of SARS-CoV-2 using the spike protein, are highly expressed in individuals with abnormal level of thyroid hormone. Altogether, we report that the malfunction of thyroid hormone synthesis may aggravate SARS-CoV-2 infection and thus monitoring the thyroid hormone may help in understanding the pathogenesis of COVID-19.

Comparative distribution of somatostatin and somatostatin receptors in PTU-induced hypothyroidism

PURPOSE

Propylthiouracil (PTU)-induced hypothyroidism is a well-established model for assessing hormonal and morphological changes in thyroid as well as other central and peripheral tissues. Somatostatin (SST) is known to regulate hormonal secretion and synthesis in endocrine tissues; however, nothing is currently known about the distribution of SST and its receptor in hypothyroidism.

METHOD

In the present study, the comparative immunohistochemical distribution of SST and somatostatin receptors (SSTRs) were analyzed in PTU-induced hypothyroid rats. Rats were treated with PTU for 15 days followed by a co-administration of levothyroxine (LVT) for 15 days. After PTU and LVT treatments (day 30), rats were further administered LVT alone for 15 more days (day 45). The subcellular distribution of SST and SSTR subtypes was determined by peroxidase immunohistochemistry in the thyroid gland collected from control and treated rats.

RESULTS

SST and SSTR subtypes were found to be moderately expressed in control thyroid tissues. SST and SSTR subtypes like immunoreactivity increased significantly in follicular and parafollicular epithelial cells in the thyroid of PTU-treated rats. The PTU-induced changes in the expression of SST and SSTR subtypes were suppressed by the administration of the LVT. In addition to thyroid tissues, SST and SSTRs expression was also changed in non-follicular tissues including blood vessels, smooth muscle cells, and connective tissue following treatments.

CONCLUSION

The present study revealed a distinct subcellular distribution of SST and SSTR subtypes in the thyroid and provides a new insight for the role of SST and SSTR subtypes in hypothyroidism in addition to its well-established role in negative regulation of hormonal secretion.

Influence of hypothyroidism on testicular mitochondrial oxidative stress by activating the p38 mitogen-activated protein kinase and c-Jun NH2-terminal kinase signaling pathways in rats

Thyroid hormone deficiency can impair testicular function. However, knowledge of the effects of mitogen-activated protein kinase (MAPK) pathways on testicular mitochondrial oxidative damage induced by hypothyroidism is still rudimentary. This study aims to explore the possible mechanisms of testicular mitochondrial oxidative damage in hypothyroidism rats. Wistar male rats were randomly divided into control (C), low- (L), and high-hypothyroidism (H) groups (1 ml/100 g body weights (BWs)/day 0, 0.001% and 0.1% propylthiouracil, respectively) by intragastric gavage for 60 days. Blood samples were collected to measure the levels of serum triiodothyronine (T3), thyroxine (T4), and thyroid stimulating hormone (TSH). Testicular mitochondrial homogenates were used to measure the activities of superoxide dismutase (SOD), catalase (CAT), and Ca2+-ATPase as well as protein and mRNA expression of androgen receptor (AR), p38 MAPK, and c-Jun NH2-terminal kinase (JNK). Results showed that the BWs, testes weights, and levels of T3 and T4 were all significantly decreased and the testes coefficient and level of TSH were significantly increased in the H group. There were significant decreases in SOD activity in the H group as well as decreases in CAT and Ca2+-ATPase activities in the L and H groups. Additionally, protein expression of AR decreased significantly and protein expression of phosphorylated p38MAPK and JNK increased significantly in the H group. Therefore, the study suggests that hypothyroidism could affect male reproductive function by disturbing expression of AR, changing the activity of Ca2+-ATPase, inducing oxidative stress and then leading to activation of p38MAPK and JNK signaling in the testicular mitochondria.

The effects of vitamin E on brain derived neurotrophic factor, tissues oxidative damage and learning and memory of juvenile hypothyroid rats

The effects of vitamin E (Vit E) on brain derived neurotrophic factor (BDNF) and brain tissues oxidative damage as well as on learning and memory impairments in juvenile hypothyroid rats were examined. The rats were grouped as: (1) Control; (2) Propylthiouracil (PTU); (3) PTU-Vit E and (4) Vit E. PTU was added to their drinking water (0.05%) during 6 weeks. Vit E (20 mg/kg) was daily injected (IP). Morris water maze (MWM) and passive avoidance (PA) were carried out. The animals were deeply anesthetized and the brain tissues were removed for biochemical measurements. PTU increased the escape latency and traveled path in MWM (P < 0.001). It also shortened the latency to enter the dark compartment of PA as well as the time spent in the target quadrant in probe trial of MWM (P < 0.01-P < 0.001). All the effects of PTU were reversed by Vit E (P < 0.01-P < 0.001). PTU administration attenuated thiol and BDNF content as well as the activities of superoxide dismutase (SOD) and catalase (CAT) in the brain tissues while increased molondialdehyde (MDA). Moreover, Vit E improved BDNF, thiol, SOD and CAT while diminished MDA. The results of the present study showed that Vit E improved BDNF and prevented from brain tissues oxidative damage as well as learning and memory impairments in juvenile hypothyroid rats.

Therapeutic effects of acupuncture with MOK, a polyherbal medicine, on PTU-induced hypothyroidism in rats

Acupuncture with MOK, a polyherbal medicine (MOK pharmacopuncture), has been used for the treatment of thyroid syndromes including hypothyroidism and hyperthyroidism in traditional Korean medicine. The present study investigated the effect of MOK pharmacopuncture on hypothyroidism and the mechanism underlying its antioxidation and immune regulation effects. Hypothyroidism was induced in Sprague-Dawley rats by subcutaneous injection of Propylthiouracil (PTU; 10 mg/kg) once daily for 4 weeks. MOK was administered by acupuncture on the acupoints around the thyroid gland of PTU-induced hypothyroidism rats once daily for 2 weeks following hypothyroidism induction. Administration of MOK pharmacopuncture significantly increased the PTU-induced decrease in body temperature of hypothyroidism rats. The weights of the spleen were also significantly decreased in hyperthyroidism rats following MOK pharmacopuncture. MOK pharmacopuncture significantly decreased the thyroid stimulating hormone level and increased the T3 and T4 levels in hypothyroidism rats. Administration of MOK pharmacopuncture significantly increased the glucose levels and decreased the levels of triglycerides, total cholesterol, low-density lipoprotein-cholesterol, and alanine transaminase in the sera of hypothyroidism rats. The expression of transient receptor potential cation channel subfamily V member 1 was increased in dorsal root ganglion and brain tissues by administration of MOK pharmacopuncture, and glutathione levels and the expression of superoxide dismutase 1 and catalase were increased in the liver and brain tissues. Administration of MOK pharmacopuncture significantly inhibited interferon-γ expression and increased the expression of interleukin (IL)-4, IL-10, and Forkhead Box P3 in the spleen tissues of hypothyroidism rats. In histological analysis, the administration of MOK pharmacopuncture improved the pathological features in the thyroid glands of hypothyroidism rats. The results suggested that the administration of pharmacopuncture may ameliorate the pathological progression of hypothyroidism by multiple actions, including normalization of the hypothyroidism-induced thyroid hormone imbalance, stimulation of the antioxidant defense system, and regulation of the T helper (Th)1/Th2 imbalance. Therefore, MOK extract may be used for the treatment of hypothyroidism in Korean clinics as a useful pharmacopuncture medicine.

Contribution of Brain Tissue Oxidative Damage in Hypothyroidism-associated Learning and Memory Impairments

The brain is a critical target organ for thyroid hormones, and modifications in memory and cognition happen with thyroid dysfunction. The exact mechanisms underlying learning and memory impairments due to hypothyroidism have not been understood yet. Therefore, this review was aimed to compress the results of previous studies which have examined the contribution of brain tissues oxidative damage in hypothyroidism-associated learning and memory impairments.

Perinatal hypothyroidism modulates antioxidant defence status in the developing rat liver and heart

In the present study, we investigated oxidative stress parameters and antioxidant defence status in perinatal hypothyroid rat liver and heart. We found that the proteincarbonyl content did not differ significantly between the three groups both in the pup liver and in the heart. The OH˙ level was significantly decreased in the hypothyroid heart but not in the liver compared with controls. A slight but not significant decrease in SOD activity was observed in both perinatal hypothyroid liver and heart. A significantly increased activity of CAT was observed in the liver but not in the heart of hypothyroid pups. The GPx activity was considerably increased compared with controls in the perinatal hypothyroid heart and was unaltered in the liver of hypothyroid pups. We also found that vitamin E levels in the liver decreased significantly in hypothyroidism and were unaltered in the heart of perinatal hypothyroid rats. The GSH content was elevated significantly in both hypothyroid liver and heart. The total antioxidant capacity was higher in the liver of the hypothyroid group but not in the hypothyroid heart. Thyroxine replacement could not repair the above changes to normal. In conclusion, perinatal hypothyroidism modulates the oxidative stress status of the perinatal liver and heart.

Protective Effect of PPARγ Agonists on Cerebellar Tissues Oxidative Damage in Hypothyroid Rats

The aim of the current study was to investigate the effects of peroxisome proliferator-activated receptor gamma (PPARγ) agonists on cerebellar tissues oxidative damage in hypothyroid rats. The animals included seven groups: group I (control), the animals received drinking water; group II, the animals received 0.05% propylthiouracil (PTU) in drinking water; besides PTU, the animals in groups III, IV, V, VI, and VII, were injected with 20 mg/kg vitamin E (Vit E), 10 or 20 mg/kg pioglitazone, and 2 or 4 mg/kg rosiglitazone, respectively. The animals were deeply anesthetized and the cerebellar tissues were removed for biochemical measurements. PTU administration reduced thiol content, superoxide dismutase (SOD), and catalase (CAT) activities in the cerebellar tissues while increasing malondialdehyde (MDA) and nitric oxide (NO) metabolites. Vit E, pioglitazone, and rosiglitazone increased thiol, SOD, and CAT in the cerebellar tissues while reducing MDA and NO metabolites. The results of present study showed that, similar to Vit E, both rosiglitazone and pioglitazone as PPARγ agonists exerted protective effects against cerebellar tissues oxidative damage in hypothyroid rats.

Neonatal Persistent Exposure to 6-Propyl-2-thiouracil, a Thyroid-Disrupting Chemical, Differentially Modulates Expression of Hepatic Catalase and C/EBP-β in Adult Rats

Persistent exposure of rats to 6-propyl-2-thiouracil (PTU) from birth resulted in decreases in plasma thyroid hormone (TH) levels and hepatic expression of catalase and CCAAT enhancer binding protein β (C/EBP-β). Catalase promoter region (-185 to +52) that contains binding sites for C/EBP-β showed an augmentation in the methylation level along with a change in methylation pattern of CpG islands in response to PTU treatment. PTU withdrawal on 30 days of birth restored TH levels and C/EBP-β to control rats in adulthood. Although catalase expression was restored to some extent in adult rats in response to PTU withdrawal, a permanent change in its promoter CpG methylation pattern was recorded. The results suggest that downregulation of adult hepatic catalase gene in response to persistent neonatal PTU exposure may not solely be attributed to thyroid-disrupting properties of PTU. It is possible that besides thyroid-disrupting behavior, PTU may impair expression of hepatic catalase by altering methylation pattern of its promoter.

Roles of thyroid hormones in follicular development in the ovary of neonatal and immature rats

Thyroid hormones (TH) play a critical role in ovarian follicular development, maturation and the maintenance of various endocrine functions. However, whether TH can affect ovarian follicular development in neonatal and immature rats remains unclear. Therefore, the aim of the present study was to elucidate the effect of TH on ovarian follicular development in neonatal and immature rats. Thirty female post-lactation mothers of Sprague-Dawley rat pups were randomly divided into three groups: control, hyperthyroid (hyper), and hypothyroid (hypo). On postnatal days (PND) 10 and 21, body weights, serum hormones, ovarian histologic changes, and immunohistochemistry of thyroid hormone receptor alpha 1 (TRα1) and nitric oxide synthase types (NOS), and NOS activities, were determined. The data showed that body weights significantly decreased in both hyper and hypo groups compared with the control group (P < 0.05). In addition, the hyper group had increased serum concentrations of T3, T4, and E2; whereas the hypo group manifested reduced serum concentrations of T3, T4, and E2 on PND 10 and 21. The hyper and hypo groups showed significantly reduced total number of primordial, primary and secondary follicles on PND 10 and 21 compared with the control group (P < 0.05). Similarly, antral follicle numbers in the hyper and hypo groups were significantly decreased on PND 21 compared with the control group (P < 0.05). Immunostaining indicated that TRα1 and NOS were expressed in ovarian surface epithelium and oocytes of growing and antral follicles, with strong staining of the granulosa and theca cells of follicles. NOS activities were significantly augmented in the hyper, but diminished in the hypo groups on PND 10 and 21. In summary, our findings suggest that TH play important roles in ovarian functions and in the regulation of NOS activity. Our results also indicate that a relationship exists between the TH and NO signaling pathways during the process of ovarian follicular development in neonatal and immature rats.

PKC in developmental hypothyroid rat brain

Thyroid hormone (TH) is essential for the proper development of mammalian central nervous system. TH deficiency during the critical period of brain development results in permanent cognitive and neurological impairments. Members of the protein kinase C (PKC) family play a key role in the regulation of cellular functions in the nervous system. Alteration of PKC can be involved in the pathogenesis of neuronal disorders. This review details recent progress made in determining the roles played by PKC isoforms in developing hypothyroid rat brain. Evidence indicates that hippocampus down-regulation of PKCβ and PKCγ may be related to impaired learning and memory observed in perinatal hypothyroid rats. Enhanced PKCα activity in neonatal hypothyroid brain may bring about oxidative stress and cause brain damage. The activated pro-apoptotic PKCs including PKCδ can cause extensive apoptosis in the hypothyroid rat brain.

Hypothyroidism alters antioxidant defence system in rat brainstem during postnatal development and adulthood

The present investigation was carried out to evaluate alterations in oxidative stress parameter [lipid peroxidation (LPx)] and antioxidant enzyme activities [superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)] in rat brainstem in response to neonatal hypothyroidism during development (from birth to 7, 15 and 30 days old) and adulthood (90 days old). Hypothyroidism in rats was induced by feeding the lactating mothers (from the day of parturition till weaning, 25 days old) or directly to the pups with 0.05 % [6-n-propyl 2-thiouracil (PTU)] in drinking water. Increased level of LPx was observed in brainstem of 7 days old hypothyroid rats, accompanied by augmented activities of SOD and GPx. In 15 and 30 days old hypothyroid rat brainstem, a significant decline in LPx was observed. Significantly increased activities of CAT and GPx were observed in 15 and 30 days PTU-treated rats. Decreased level of LPx was observed in brainstem of rats treated with PTU from birth to 30 days followed by withdrawal up to 90 days of age (transient hypothyroidism) as compared to control and persistent treatment of PTU up to 90 days of age. Activities of CAT and GPx were decreased in persistent hypothyroid rats of 90 days old with respect to control and transient hypothyroid rats. On the other hand, SOD activity was decreased in both persistent and transient hypothyroid rats with respect to control rats. These results suggest that the PTU-induced neonatal hypothyroidism modulates the antioxidant defence system during postnatal development and adulthood in brainstem of rats.

Diphenyl diselenide modulates gene expression of antioxidant enzymes in the cerebral cortex, hippocampus and striatum of female hypothyroid rats

INTRODUCTION

Cellular antioxidant signaling can be altered either by thyroid disturbances or by selenium status.

AIMS

To investigate whether or not dietary diphenyl diselenide can modify the expression of genes of antioxidant enzymes and endpoint markers of oxidative stress under hypothyroid conditions.

METHODS

Female rats were rendered hypothyroid by continuous exposure to methimazole (MTZ; 20 mg/100 ml in the drinking water) for 3 months. Concomitantly, MTZ-treated rats were either fed or not with a diet containing diphenyl diselenide (5 ppm). mRNA levels of antioxidant enzymes and antioxidant/oxidant status were determined in the cerebral cortex, hippocampus and striatum.

RESULTS

Hypothyroidism caused a marked upregulation in mRNA expression of catalase, superoxide dismutase (SOD-1, SOD-3), glutathione peroxidase (GPx-1, GPx-4) and thioredoxin reductase (TrxR-1) in brain structures. SOD-2 was increased in the cortex and striatum, while TrxR-2 increased in the cerebral cortex. The increase in mRNA expression of antioxidant enzymes was positively correlated with the Nrf-2 transcription in the cortex and hippocampus. Hypothyroidism caused oxidative stress, namely an increase in lipid peroxidation and reactive oxygen species levels in the hippocampus and striatum, and a decrease in nonprotein thiols in the cerebral cortex. Diphenyl diselenide was effective in reducing brain oxidative stress and normalizing most of the changes observed in gene expression of antioxidant enzymes.

CONCLUSION

The present work corroborates and extends that hypothyroidism disrupts antioxidant enzyme gene expression and causes oxidative stress in the brain. Furthermore, diphenyl diselenide may be considered a promising molecule to counteract these effects in a hypothyroidism state.

The role of thyroid hormones as inductors of oxidative stress and neurodegeneration

Reactive oxygen species (ROS) are oxidizing agents amply implicated in tissue damage. ROS production is inevitably linked to ATP synthesis in most cells, and the rate of production is related to the rate of cell respiration. Multiple antioxidant mechanisms limit ROS dispersion and interaction with cell components, but, when the balance between ROS production and scavenging is lost, oxidative damage develops. Many traits of aging are related to oxidative damage by ROS, including neurodegenerative diseases. Thyroid hormones (THs) are a major factor controlling metabolic and respiratory rates in virtually all cell types in mammals. The general metabolic effect of THs is a relative acceleration of the basal metabolism that includes an increase of the rate of both catabolic and anabolic reactions. THs are related to oxidative stress not only by their stimulation of metabolism but also by their effects on antioxidant mechanisms. Thyroid dysfunction increases with age, so changes in THs levels in the elderly could be a factor affecting the development of neurodegenerative diseases. However, the relationship is not always clear. In this review, we analyze the participation of thyroid hormones on ROS production and oxidative stress, and the way the changes in thyroid status in aging are involved in neurodegenerative diseases.

The protective effect of propylthiouracil against hepatotoxicity induced by chromium in adult mice

Environmental and occupational exposure to chromium compounds, especially hexavalent chromium (Cr(VI)), is widely recognized as potentially hepatotoxic in humans and animals. Its toxicity is associated with overproduction of free radicals, which induces oxidative damage. This study focused on the possible protective effect of propylthiouracil (PTU) against potassium dichromate (K2Cr2O7). Female mice were divided into four groups (groups I–IV) with seven animals in each group. Group I served as a control, which received tap water; group II received K2Cr2O7 alone (75 mg kg−1 body weight (b.w.)) via drinking water; group III received both K2Cr2O7 via drinking water and PTU by intramuscular injection at a dose 2.5 mg/100 g−1 b.w. twice a week, and group IV received PTU alone twice a week for 30 days. Exposure of mice to Cr promoted oxidative stress with an increase in malondialdehyde, protein carbonyl, and advanced oxidation protein product levels. Nonenzymatic antioxidants such as glutathione, nonprotein thiol, vitamin C levels and enzymatic antioxidant activities such as glutathione peroxidase and superoxide dismutase were decreased, while catalase activity was increased. Biomarkers of liver injury such as aspartate and alanine transaminases, lactate dehydrogenase activities, bilirubin, albumin, and glucose levels were increased, while triglyceride and cholesterol levels decreased. Coadministration of PTU restored the above-mentioned parameters to near-normal values. The histological findings confirmed the biochemical results.

Propylthiouracil-induced hypothyroidism during lactation alters leucine and mannose metabolism in rat cerebellar slices

Thyroid hormone deficiency during perinatal development results in significant alterations in neurological functions. The relationship between such events and brain metabolism is not completely understood. The aim of this study was to investigate the effects of hypothyroidism on leucine, mannose, glucose and lactate metabolism in rat cerebellar slices. Experimental hypothyroidism was induced by exposing mothers and pups to propylthiouracil (PTU) until weaning - postnatal day 21. Metabolic analyses were performed in postnatal day 10 (PND10) and 21 (PND21) animals. A matching group of animals received the same oral treatment also after weaning until adulthood PND60 with T3 supplement during lactation (P1-P21). In PND21 animals, PTU treatment significantly increased the rate of leucine oxidation to CO2, although glucose and lactate oxidations were not affected. PTU treatment also increased the oxidation of leucine to CO2 at PND60 (adult animals). PND10 hypothyroidism animals showed a decrease in conversion of mannose to glycolipids and glycoprotein compared with the control group. However, PTU treatment increased the conversion of mannose to glycolipids and glycoprotein in PND21 animals. The replacement of T3 normalized mannose and leucine metabolism in adult rats. These results indicate that deficits in thyroid hormones during lactation could delay or alter brain development and metabolism.

Role of reactive oxygen species and NADPH-oxidase in the development of rat cerebellum

Experimental evidence suggests that reactive oxygen species (ROS) could participate in the regulation of some physiological conditions. In the nervous system, ROS have been suggested to act as signaling molecules involved in several developmental processes including cell differentiation, proliferation and programmed of cell death. Although ROS can be generated by several sources, it has been suggested that NADPH oxidase (NOX) could be critical in the production of ROS acting as a signal in some of these events. It has been reported that ROS production by NOX enzymes participate in neuronal maturation and differentiation during brain development. In the present study, we found that during rat cerebellar development there was a differential ROS generation at different ages and areas of the cerebellum. We also found a differential expression of NOX homologues during rat cerebellar development. When we treated developing rats with an antioxidant or with apocynin, an inhibitor of NOX, we found a marked decrease of the ROS levels in all the cerebellar layers at all the ages tested. Both treatments also induced a significant change in the cerebellar foliation as well as an alteration in motor behavior. These results suggest that both ROS and NOX have a critical role during cerebellar development.

Impact of experimental hypothyroidism on monoamines level in discrete brain regions and other peripheral tissues of young and adult male rats

The levels of dopamine (DA), norepinephrine (NE) and serotonin (5-HT) in different brain regions as well as in blood plasma, cardiac muscle and adrenal gland of young and adult male albino rats were measured following experimentally induced hypothyroidism. Hypothyroidism induced by daily oral administration of propylthiouracil (PTU, 5mg/kg body wt) caused a significant reduction in DA levels in most of the tissues examined of both young and adult rats after 21 and 28 days, in NE levels after all the time intervals studied in young rats, and after 21 and 28 days in adult rats. 5-HT exhibited a significant reduction in the selected brain regions and blood plasma after 21 and 28 days and in cardiac muscle after all the time intervals in the two age groups of animals. It may be suggested that the changes in monoamine levels induced by hypothyroidism may be due to disturbance in the synthesis and release of these amines through the neurons impairment or may be due to an alteration pattern of their synthesizing and/or degradative enzymes.

Iodine plus n-3 fatty acid supplementation augments rescue of postnatal neuronal abnormalities in iodine-deficient rat cerebellum

High prevalence of hypothyroxinaemia in iodine-deficient (ID) mothers has serious implications for mental health of the progeny. Independent supplementation of iodine and n-3 fatty acids (FA) markedly improves growth and cognitive performance of school children. Discerning effects of n-3 FA and iodine on the developing cerebellum have not been ascertained. The present study investigates effects of these two micronutrients separately as well as together in an ID rat model. We studied the effects of these micronutrients on progeny of ID dams by instituting the following supplementation diets: (1) low-iodine diet (LID), (2) LID+potassium iodide (KI), (3) LID+n-3 FA and (4) LID+KI+n-3 FA. Pups were investigated for morphological and biochemical parameters at the peak of cerebellar histogenesis on postnatal day (P) 16 and for neurobehavioural as well as motor coordination parameters at P40. Results indicate that n-3 FA alone, without improvement in circulating thyroid hormone (TH), significantly improves functional, morphological and biochemical indices of the developing cerebellum. Further, results show that co-supplementation with iodine and n-3 FA rescues not only the loss of neurotrophic support, but also salvages motor coordination, memory and learning. This additive effect results in significantly improving neurotrophic support and seems to be mediated by parallel significant increase in TH receptor (TR)α and normalisation of TRβ, retinoic orphan receptor α and p75 neurotrophin receptor, as well as noteworthy prevention of apoptotic cell death and strengthening of anti-oxidative defence. The overall results indicate important mitigating role that n-3 FA may play in enhancing TH nuclear receptor-mediated signalling in the developing cerebellum.

Protein kinase Cα is involved in impaired perinatal hypothyroid rat brain development

Protein kinase Cα (PKCα) has been implicated in the regulation of a variety of cellular functions, such as proliferation, differentiation, and apoptosis, in response to a diverse range of stimuli. Activated PKCα mediates oxidative stress, apoptosis, and inflammatory reaction. Thyroid hormone (TH) is essential for the proper development of the mammalian central nervous system. TH deficiency during critical periods of brain development results in permanent cognitive and neurological impairments. In the present study, we attempted to explore whether PKCα is involved in impaired brain function in developing hypothyroid rat brain. Severe perinatal hypothyroidism was obtained by administration of 30 mg/day propylthiouracil to dams. Brain PKC activity in hypothyroid pups was increased significantly in cytosol and membrane fractions. The change of membrane PKC activity was more marked than that of cytosol, and hypothyroidism led to a higher ratio of membrane PKC activity to that in cytosol, which means abnormal activation of PKC in developing hypothyroid rat brain. Thyroxine replacement partially corrected these changes. After being treated with bisindolmaleimide XI, a mainly selective inhibitor for PKCα, the hypothyroid pups showed improved place navigation test results, and further Western blot analysis showed that PKCα expression in cytosol fractions was increased in hypothyroid rat brain with or without bisindolmaleimide XI treatment, but, after treatment with bisindolmaleimide XI, PKCα content in membrane fractions decreased almost to normal. Therefore, we conclude that PKCα appears to be involved in the impaired brain development observed in perinatal hypothyroid rat brain.

Modulation of antioxidant enzyme expression by PTU-induced hypothyroidism in cerebral cortex of postnatal rat brain

This study aimed to elucidate the effect of 6-n-propylthiouracil (PTU)-induced hypothyroidism on oxidative stress parameters and expression of antioxidant enzymes in cerebral cortex of rat brain during postnatal development. A significant decrease in levels of lipid peroxidation and H(2)O(2) were seen in 7 and 30 days old PTU-treated rats with respect to their controls. Significantly decreased activities of superoxide dismutase (SOD) and catalase (CAT) along with the translated products of SOD1 and SOD2 were observed in 7, 15 and 30 days old PTU-treated rats as compared to their respective controls. However, increase in translated product of CAT was seen in all age groups of PTU-treated rats. Glutathione peroxidase activity was decreased in 7 days and increased in 15 days old PTU-treated rats with respect to their control groups. Histological sections clearly show a decline in neuronal migration with neurons packed together in the hypothyroid group as compared to the control.

Ischemia-modified albumin in patients with hyperthyroidism and hypothyroidism

BACKGROUND

The relationship between ischemia-modified albumin (IMA) and thyroid dysfunction remains uncertain. This study aimed to investigate the influence of overt hypothyroidism (Oho), overt hyperthyroidism (Ohe), and their treatments on serum IMA levels.

METHODS

A total of 35 untreated patients with Ohe, 35 untreated patients with Oho, and 35 control subjects were enrolled in the study. C-reactive protein (CRP), homocysteine (Hcy), IMA, and lipid profiles were measured and evaluated before and after treatment.

RESULTS

CRP, Hcy, and IMA levels and lipid profiles were higher in patients with Oho than in euthyroid or Ohe subjects (p<0.05). Basal IMA levels were reduced after treatments in all patients (p<0.05). In Ohe patients, serum IMA levels were positively correlated with free triiodothyronine (r=0.424, p=0.011) and free thyroxine (r=0.567, p<0.001) levels. In Oho patients, serum IMA levels were inversely correlated with free triiodothyronine (r=-0.555, p=0.001) and free thyroxine (r=-0.457, p=0.006) but positively correlated with anti-thyroid peroxidase antibody, C-reactive protein, and homocysteine levels (p<0.05). Linear regression analyses showed that free triiodothyronine was the most important factor affecting serum IMA levels in Ohe (β=0.694, p=0.019) and in Oho (β=-0.512, p=0.025).

CONCLUSIONS

IMA levels are increased in patients with thyroid dysfunction, particularly in overt hypothyroidism. Thyroid dysfunction has a significant impact on the oxidative stress status.

Hypothyroidism modulates renal antioxidant gene expression during postnatal development and maturation in rat

In the present study effects of 6-n-propyl thiouracil (PTU)-induced hypothyroidism on renal antioxidant defence system during postnatal development (from birth to 7, 15 and 30days old) and on adult rats were reported. Hypothyroidism in rats was induced by feeding the lactating mothers (from the day of parturition till weaning, 25days old) or directly to the pups with 0.05% PTU in drinking water. The activities of Cu/Zn-superoxide dismutase (SOD1) and glutathione peroxidase (GPx) were increased in 30days old hypothyroid rats with respect to their respective controls, on the other hand, levels of translated products and activities of Mn-superoxide dismutase (SOD2) and catalase (CAT) were decreased in hypothyroid rats of all age groups as compared to their respective control rats. SOD1 activity remained unchanged in persistent (PTU-treatment from birth to 90days old) hypothyroid rats as compared to euthyroid. However, a decreased activity of SOD1 was recorded in transient (PTU-treatment from birth to 30days then withdrawal till 90days old) hypothyroid rats with respect to control rats. The mRNA level, protein expression and activity of SOD2 and CAT were significantly decreased in persistent hypothyroid rats as compared to euthyroid rats. The activity of GPx was significantly increased in both persistent and transient hypothyroid rats with respect to euthyroid rats. The present study indicates modulation of antioxidant defence status of rat kidney during postnatal development and maturation by hypothyroidism.

Perinatal iodine deficiency and hypothyroidism increase cell apoptosis and alter doublecortin and reelin protein expressions in rat cerebellum

BACKGROUND AND AIMS

Adequate thyroid hormone is critical for cerebellar development. Developmental hypothyroidism induced by iodine deficiency during the perinatal period results in permanent impairments of cerebellar development with an unclear mechanism. In the present study we investigated effects of perinatal iodine deficiency and hypothyroidism on cerebellar cell apoptosis, doublecortin (Dcx) and reelin. Apoptosis is an essential part of neural development. Dcx and reelin are two important molecules involved in neuronal migration, structure, and development in cerebellum.

METHODS

Two developmental rat models were created by administering dam rats with either iodine-deficient diet or propylthiouracil (PTU, 5 ppm or 15 ppm)-added drinking water from gestational day (GD) 6 until postnatal day (PND) 28. TUNEL assay and protein levels of Dcx and reelin in cerebella were assessed on PND14, 21 and 28.

RESULTS

Apoptotic cells were increased in the iodine-deficient and PTU-treated rats. Dcx protein levels in the cerebella of iodine-deficient and PTU-treated rats were significantly downregulated on PND14. Interestingly, iodine deficiency and PTU treatment upregulated the levels of Dcx protein on PND21 and 28. Reelin expressions in iodine-deficient and PTU-treated rats were significantly decreased on PND14 and 21. On PND28, reelin expressions of three treated groups were still lower than control group, although without significant difference.

CONCLUSIONS

These findings may implicate alterations in cell apoptosis and levels of Dcx and reelin in the impairments of cerebellar development induced by developmental iodine deficiency and hypothyroidism.

Honey supplementation in spontaneously hypertensive rats elicits antihypertensive effect via amelioration of renal oxidative stress

Oxidative stress is implicated in the pathogenesis and/or maintenance of elevated blood pressure in hypertension. This study investigated the effect of honey on elevated systolic blood pressure (SBP) in spontaneously hypertensive rats (SHR). It also evaluated the effect of honey on the amelioration of oxidative stress in the kidney of SHR as a possible mechanism of its antihypertensive effect. SHR and Wistar Kyoto (WKY) rats were randomly divided into 2 groups and administered distilled water or honey by oral gavage once daily for 12 weeks. The control SHR had significantly higher SBP and renal malondialdehyde (MDA) levels than did control WKY. The mRNA expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and glutathione S-transferase (GST) were significantly downregulated while total antioxidant status (TAS) and activities of GST and catalase (CAT) were higher in the kidney of control SHR. Honey supplementation significantly reduced SBP and MDA levels in SHR. Honey significantly reduced the activities of GST and CAT while it moderately but insignificantly upregulated the Nrf2 mRNA expression level in the kidney of SHR. These results indicate that Nrf2 expression is impaired in the kidney of SHR. Honey supplementation considerably reduces elevated SBP via amelioration of oxidative stress in the kidney of SHR.

Identification of classifiers for increase or decrease of thyroid peroxidase activity in the FTC-238/hTPO recombinant cell line

Thyroid peroxidase (TPO) plays an important role in thyroid hormone biosynthesis, as it catalyzes all of the essential steps in iodide organification. TPO activity can be detected using the guaiacol assay; however, this assay is complex and very time-consuming. Therefore, we focused on devising a simplified method using microarrays to detect changes in TPO activity, which is a target for disruption of the thyroid hormone axis. These experiments have systematically assessed the potential utility of transcriptomic end points as enhancements to the guaiacol assay. Previously, we demonstrated that benzophenone-2, benzophenone, perfluorooctane sulfonate, bisphenol A bis ether, and vinclozolin decreased TPO activity, and that dibutyl phthalate, carbaryl, dibenzo(a,h)anthracene, benzo(a)pyrene, and methylmercury increased TPO activity. In this work, we used human oligonucleotide chips to examine changes in the gene expression profile of FTC-238 human follicular thyroid carcinoma cells expressing human recombinant TPO, after exposure of the cells to TPO activity-disrupting agents. We identified 362 classifiers that could predict the effect of the toxicants on TPO activity with about 70% accuracy. These classifiers are potential markers for predicting the effects of chemicals on thyroid hormone production.

Spatial and temporal patterns of oxidative stress in the brain of gerbils submitted to different duration of global cerebral ischemia

The present study was undertaken to examine spatial and temporal patterns of oxidative stress rate in the brain of Mongolian gerbils submitted to different duration of global ischemia/reperfusion. The common carotid arteries of gerbils were occluded for 5, 10, or 15 min. We followed the temporal ischemia-induced oxidative stress rate, the most important factor that exacerbates brain damage by reperfusion, starting from 24 h up to 28 days after reperfusion. The spatial ischemia-induced oxidative stress distribution was measured parallely in different brain regions: forebrain cortex, striatum, hippocampus and cerebellum. Post-ischemic effects were followed in vivo by monitoring the neurological status of whole animals and at the intracellular level by standard biochemical assays in different brain regions. We measured superoxide production, superoxide dismutase activity, nitric oxide production, index of lipid peroxidation, and reduced glutathione. Our results revealed a pattern of dynamic changes in each oxidative stress parameter that corresponded with ischemia duration in all tested brain structures. The highest levels were obtained in the first 24h after the insult. After that, they slowly returned to nearly control values 28 days after reperfusion (with the exception of SOD activity that returned to control values at fourth day after reperfusion). The most sensitive oxidative stress parameter was index of lipid peroxidation. Our study confirmed spatial distribution of ischemia-induced oxidative stress. Tested brain structures showed different sensitivity to each oxidative stress parameter, although their basal levels were similar. These new findings could be valuable for creation and strategy of post-ischemic therapy.

MK-801 effect on regional cerebral oxidative stress rate induced by different duration of global ischemia in gerbils

We investigated MK-801 effect on ischemia-induced oxidative stress-the most important factor that exacerbates brain damage by reperfusion. The common carotid arteries of gerbils were occluded for 5, 10, or 15 min. Immediately after the occlusion, MK-801 (3 mg/kg i.p.) or saline were given in normothermic conditions. The MK-801 effects were followed in vivo by monitoring the neurological status of animals and at the intracellular level by standard biochemical assays. We investigated nitric oxide levels, superoxide production, superoxide dismutase activity, index of lipid peroxidation (ILP), and reduced glutathione content in hippocampus, striatum, forebrain cortex, and cerebellum. The measurements took place at different times (1, 2, 4, 7, 14, and 28 days) after reperfusion. Increased duration of cerebral ischemia resulted in a progressive induction of oxidative stress. Our results revealed pattern of dynamic changes in each oxidative stress parameter level which corresponded with ischemia duration in all tested brain structures. Most sensitive oxidative stress parameters were ILP and superoxide production. Our study confirmed spatial distribution of ischemia-induced oxidative stress. Tested brain structures showed different sensitivity to each oxidative stress parameter. As judged by biochemical and neurological data, applied MK-801 showed neuroprotective efficiency by reduction of ischemia-induced oxidative stress in brain.