Thyroid hormone-induced oxidative stress in rodents and humans: a comparative view and relation to redox regulation of gene expression

Impact of carbimazole combined with vitamin E on testicular injury induced by experimental hyperthyroidism in adult albino rats: oxidative/inflammatory/apoptotic pathways

Thyroid hormones play essential roles in spermatogenesis, but their effects on infertile males remain poorly understood. This study aimed to evaluate the impact of combining carbimazole (CBZ) with vitamin E (VE) on testicular injury induced by experimental hyperthyroidism in adult albino rats, focusing on oxidative, inflammatory, and apoptotic pathways. In this experimental study, 64 adult male albino Wistar rats were divided into eight groups: Group I (control-untreated), Group II (CBZ-control), Group III (VE-control), Group IV (CBZ + VE-control), Group V (levothyroxine-induced testicular injury), Group VI (levothyroxine + CBZ-treated), Group VII (levothyroxine + VE-treated), and Group VIII (levothyroxine + CBZ + VE-treated). The study was conducted in the Faculty of Medicine, Suez Canal University (Ismailia, Egypt). After cervical decapitation, both testes and epididymis were examined histopathologically and immunohistochemically. Significant differences were observed among groups concerning malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT; all P < 0.001). Polymerase chain reaction analysis showed significant differences in tumor necrosis factor-α (TNF- α ), interleukin-10 (IL-10), Bcl-2-associated X protein (BAX), B-cell lymphoma 2 protein (Bcl2), p53, Caspase-3, Caspase-8, Caspase-9, and nuclear factor-kappa B (NF- κ B) mRNA levels (all P < 0.001). Hyperthyroid group treated with CBZ alone (Group VI) exhibited testicular side effects, affecting seminiferous tubules and spermatogenesis. However, the Group VIII showed improved spermatogenesis and a decrease in testicular side effects. The addition of VE to the treatment of hyperthyroid rats with CBZ reduced testicular side effects and seminiferous tubular affection when potentially improving spermatogenesis. Further research is needed to elucidate the underlying mechanisms fully.

The protective role of nutritional antioxidants against oxidative stress in thyroid disorders

An imbalance between pro-oxidative and antioxidative cellular mechanisms is oxidative stress (OxS) which may be systemic or organ-specific. Although OxS is a consequence of normal body and organ physiology, severely impaired oxidative homeostasis results in DNA hydroxylation, protein denaturation, lipid peroxidation, and apoptosis, ultimately compromising cells' function and viability. The thyroid gland is an organ that exhibits both oxidative and antioxidative processes. In terms of OxS severity, the thyroid gland's response could be physiological (i.e. hormone production and secretion) or pathological (i.e. development of diseases, such as goitre, thyroid cancer, or thyroiditis). Protective nutritional antioxidants may benefit defensive antioxidative systems in resolving pro-oxidative dominance and redox imbalance, preventing or delaying chronic thyroid diseases. This review provides information on nutritional antioxidants and their protective roles against impaired redox homeostasis in various thyroid pathologies. We also review novel findings related to the connection between the thyroid gland and gut microbiome and analyze the effects of probiotics with antioxidant properties on thyroid diseases.

Triiodothyronine or Antioxidants Block the Inhibitory Effects of BDE-47 and BDE-49 on Axonal Growth in Rat Hippocampal Neuron-Glia Co-Cultures

We previously demonstrated that polybrominated diphenyl ethers (PBDEs) inhibit the growth of axons in primary rat hippocampal neurons. Here, we test the hypothesis that PBDE effects on axonal morphogenesis are mediated by thyroid hormone and/or reactive oxygen species (ROS)-dependent mechanisms. Axonal growth and ROS were quantified in primary neuronal-glial co-cultures dissociated from neonatal rat hippocampi exposed to nM concentrations of BDE-47 or BDE-49 in the absence or presence of triiodothyronine (T3; 3-30 nM), N-acetyl-cysteine (NAC; 100 µM), or α-tocopherol (100 µM). Co-exposure to T3 or either antioxidant prevented inhibition of axonal growth in hippocampal cultures exposed to BDE-47 or BDE-49. T3 supplementation in cultures not exposed to PBDEs did not alter axonal growth. T3 did, however, prevent PBDE-induced ROS generation and alterations in mitochondrial metabolism. Collectively, our data indicate that PBDEs inhibit axonal growth via ROS-dependent mechanisms, and that T3 protects axonal growth by inhibiting PBDE-induced ROS. These observations suggest that co-exposure to endocrine disruptors that decrease TH signaling in the brain may increase vulnerability to the adverse effects of developmental PBDE exposure on axonal morphogenesis.

Age-related changes in thyroid hormones, some serum oxidative biomarkers and trace elements and their relationships in healthy Saanen goat kids during the first three month of age

BACKGROUND

Early-life diseases in dairy animals are main causes of economic loss in livestock production. Oxidative stress (OS) and thyroid hormones are important inter-related components in the normal physiology of this critical period of life. However, limited information regarding their physiology in goat kids is available. This study was conducted to investigate the age-related changes of thyroid hormones, some serum oxidative biomarkers and trace elements in healthy Saanen goat kids.

METHODS

Nineteen newborn healthy Saanen goat kids (14 females and five males) were studied longitudinally from birth until three months of age. Blood sampling was performed 24-48 h after birth and was repeated on 10 ± 2, 28 ± 2, 56 ± 2 and 84 ± 2 days of age. The serum levels of thyroid hormones, malondialdehyde (MDA), reduced glutathione (GSH), total antioxidant capacity (TAC), selenium (Se), manganese (Mn) and molybdenum (Mo) were measured.

RESULTS

Age-related changes were observed for all measured variables except for MDA (p < 0.05). A decreasing trend was detected throughout the study in thyroid hormones, T3: T4 ratio and Mn (p < 0.01). Some factors decreased from birth to day 10 (Se) or day 28 (TAC and GSH) and followed by an increasing trend that extended to day 84 (p < 0.01). There were significant correlations between thyroid hormones and TAC, as well as Mn levels (p < 0.05).

CONCLUSIONS

These results imply that specific age-related reference values are essential for proper interpretation of the serum level of thyroid hormones and Mn in Saanen goat kids during the first three months of life. In addition, given the high level of thyroid hormones particularly during the first days of life, and their relationship with oxidative biomarkers and trace elements, improving the antioxidant system in this critical period is essential.

Possible activation of NRF2 by Vitamin E/Curcumin against altered thyroid hormone induced oxidative stress via NFĸB/AKT/mTOR/KEAP1 signalling in rat heart

Oxidative stress is implicated in both hypo- and hyper-thyroid conditions. In the present study an attempt has been made to elucidate possible interaction between vitamin E or/and curcumin (two established antioxidants) with active portion (redox signaling intervening region) of nuclear factor erythroid 2-related factor 2 (NRF2) as a mechanism to alleviate oxidative stress in rat heart under altered thyroid states. Fifty Wistar strain rats were divided into two clusters (Cluster A: hypothyroidism; Cluster B: hyperthyroidism). The hypo- (0.05% (w/v) propylthiouracil in drinking water) and hyper- (0.0012% (w/v) T4 in drinking water) thyroid rats in both clusters were supplemented orally with antioxidants (vitamin E or/and curcumin) for 30 days. Interactive least count difference and principal component analyses indicated increase in lipid peroxidation, reduced glutathione level, alteration in the activities and protein expression of antioxidant enzymes like superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase under altered thyroid states. However, the expression of stress survival molecules; nuclear factor κB (NFκB) and the serine-threonine kinase B (Akt), in hyper-thyroidism only points towards different mechanisms responsible for either condition. Co-administration of vitamin E and curcumin showed better result in attenuating expression of mammalian target for rapamycin (mTOR), restoration of total protein content and biological activity of Ca²⁺ ATPase in hyperthyroid rats, whereas, their individual treatment showed partial restoration. Since NRF2 is responsible for activation of antioxidant response element and subsequent expression of antioxidant enzymes, possible interactions of both vitamin E or/and curcumin with the antioxidant enzymes, NRF2 and its regulator Kelch ECH associating protein (KEAP1) were studied in silico. For the first time, a modeled active portion of the zipped protein NRF2 indicated its interaction with both vitamin E and curcumin. Further, curcumin and vitamin E complex showed in silico interaction with KEAP1. Reduction of oxidative stress by curcumin and/or vitamin E may be due to modulation of NRF2 and KEAP1 function in rat heart under altered thyroid states.

Interdependence of oxidative/antioxidant system indicators and thyroid status under conditions of prolonged exposure to small doses of radiation

We have studied the interdependence of the intensity of oxidative processes/antioxidant level and the thyroid status parameters in a group of students aged 18–24 who lived for a long time in the territory of enhanced radioecological control (density of soil contamination by isotopes (137Cs 3.7 ∙ 104 – 18.5 ∙ 104 Bq/m2). We examined 50 people from relatively environmentally friendly areas (control group) and 50 people from IV radiation zone (experimental group). In the experimental group, there were no individuals with clinical manifestations of thyroid pathology. However, subgroups with signs of hyperthyroidism and hypothyroidism were identified. We evaluated the level of cortisol, thyrotrophic hormone (TSH), triiodothyronine (T3), thyroxine (T4), malonic dialdehyde (MDA), ceruloplasmin (CP), transferrin (Tf), sulfhydryl groups (SH); we calculated the oxidative stress index (OSI). The research was conducted one month before the examination time and also during the exams as a factor in increased emotional stress. A lowered CP level was found in the subgroup with signs of hypothyroidism; SH groups – in all subgroups, separated by thyroid status. The oxidative stress index was higher in all students examined of the experimental group, compared with the control. The growth of MDA level is marked in the experimental group – it is the most strongly pronounced in conditions of additional emotional load in people with signs of hyperthyroidism and hypothyroidism. CP level significantly decreased in the subgroup of hyperthyroidism on the background of T3 decrease. OSI increased in all students examined from the experimental group. In the subgroup of hypothyroidism it became significantly higher than in the subgroup of euthyroidism. A positive correlation between the levels of CP and T3 was found. The highest values of the correlation coefficients were noted for subgroups with signs of hyperthyroidism and hypothyroidism, with the coefficient significance increasing under conditions of emotional stress. The index of oxidative stress in the experimental group positively correlated with the level of TSH – in terms of emotional stress, the statistical significance of the coefficients disappeared. In the subgroups divided by thyroid status, variability of interactions between OSI and T3 was observed but it was not statistically significant. It was found that the participation of thyroid status in supporting redox homeostasis in people aged 18–24 who suffered from chronic small-doze radiation exposure was realized mainly by the influence on the antioxidant system. The ability of thyroid hormones to maintain a proper antioxidant state was suppressed in this group. The unbalanced relationship between thyroid hormones and oxidative stress indicators is strongly manifested under conditions of additional emotional stress.

Age-associated increase of thyroid hormone receptor β gene promoter methylation coexists with decreased gene expression

PURPOSE

It is not established if healthy aging of the thyroid axis is associated with alterations other than changes in hormone secretion.

METHODS

The expression of thyroid hormone receptor β gene (THRB) was analyzed in peripheral blood mononuclear cells (PBMC) obtained from young, elderly, and long-lived individuals. The interaction between the 3'UTR of TRβ1 mRNA and selected miRNAs was measured using pmirGLO reporter vector. Methylation of the THRB CpG island was analyzed using methylation-sensitive restriction/RT-PCR and bisulfite sequencing methods.

RESULTS

Old age was associated with a significantly lower amount of total TRβ mRNA (p = 0.033) and of TRβ1 mRNA (p = 0.02). Older age was also associated with significantly higher methylation of the THRB promoter (restriction/RT-PCR: p = 0.0023, bisulfite sequencing: p = 0.0004). Higher methylation corresponded to a lower expression of the THRB mRNA, but this correlation did not reach the level of significance. miR-26a interacted with two sites in the 3'UTR of the TRβ1 mRNA leading to the decrease of the reporter protein activity (p < 0.0001 and p = 0.0005), and miR-496 interacted with one of the two putative binding sites which also decreased the reporter protein activity (p < 0.0001). Analysis of the expression of miR-21, miR-26a, miR-146a, miR-181a, miR-221, and miR-496 showed that the expression of miR-26a was significantly decreased in old subjects (p = 0.017), while the levels of other miRNAs were unaffected.

CONCLUSIONS

Age-related decrease of THRB expression in PBMC of elderly and long-lived humans might be, in part, a result of the increased methylation of its promoter, but is unrelated to the activity of the miRNAs analyzed here.

Variable Linezolid Exposure in Intensive Care Unit Patients-Possible Role of Drug-Drug Interactions

BACKGROUND

Standard doses of linezolid may not be suitable for all patient groups. Intensive care unit (ICU) patients in particular may be at risk of inadequate concentrations. This study investigated variability of drug exposure and its potential sources in this population.

METHODS

Plasma concentrations of linezolid were determined by high-performance liquid chromatography in a convenience sample of 20 ICU patients treated with intravenous linezolid 600 mg twice daily. Ultrafiltration applying physiological conditions (pH 7.4/37°C) was used to determine the unbound fraction. Individual pharmacokinetic (PK) parameters were estimated by population PK modeling. As measures of exposure to linezolid, area under the concentration-time curve (AUC) and trough concentrations (Cmin) were calculated and compared with published therapeutic ranges (AUC 200-400 mg*h/L, Cmin 2-10 mg/L). Coadministered inhibitors or inducers of cytochrome P450 and/or P-glycoprotein were noted.

RESULTS

Data from 18 patients were included into the PK evaluation. Drug exposure was highly variable (median, range: AUC 185, 48-618 mg*h/L, calculated Cmin 2.92, 0.0062-18.9 mg/L), and only a minority of patients had values within the target ranges (6 and 7, respectively). AUC and Cmin were linearly correlated (R = 0.98), and classification of patients (underexposed/within therapeutic range/overexposed) according to AUC or Cmin was concordant in 15 cases. Coadministration of inhibitors was associated with a trend to higher drug exposure, whereas 3 patients treated with levothyroxine showed exceedingly low drug exposure (AUC ∼60 mg*h/L, Cmin <0.4 mg/L). The median unbound fraction in all 20 patients was 90.9%.

CONCLUSIONS

Drug exposure after standard doses of linezolid is highly variable and difficult to predict in ICU patients, and therapeutic drug monitoring seems advisable. PK drug-drug interactions might partly be responsible and should be further investigated; protein binding appears to be stable and irrelevant.

An extremely high dietary iodide supply forestalls severe hypothyroidism in Na+/I- symporter (NIS) knockout mice

The sodium/iodide symporter (NIS) mediates active iodide (I⁻) accumulation in the thyroid, the first step in thyroid hormone (TH) biosynthesis. Mutations in the SLC5A5 gene encoding NIS that result in a non-functional protein lead to congenital hypothyroidism due to I⁻ transport defect (ITD). ITD is a rare autosomal disorder that, if not treated promptly in infancy, can cause mental retardation, as the TH decrease results in improper development of the nervous system. However, in some patients, hypothyroidism has been ameliorated by unusually large amounts of dietary I⁻. Here we report the first NIS knockout (KO) mouse model, obtained by targeting exons 6 and 7 of the Slc5a5 gene. In NIS KO mice, in the thyroid, stomach, and salivary gland, NIS is absent, and hence there is no active accumulation of the NIS substrate pertechnetate (^99mTcO₄⁻). NIS KO mice showed undetectable serum T₄ and very low serum T₃ levels when fed a diet supplying the minimum I⁻ requirement for rodents. These hypothyroid mice displayed oxidative stress in the thyroid, but not in the brown adipose tissue or liver. Feeding the mice a high-I⁻ diet partially rescued TH biosynthesis, demonstrating that, at high I⁻ concentrations, I⁻ enters the thyroid through routes other than NIS.

The Effect of Experimental Thyroid Dysfunction on Markers of Oxidative Stress in Rat Pancreas

Preclinical Research The aim of the present study was to evaluate the effects of thyroid dysfunction on markers of oxidative stress in rat pancreas. Hypothyroidism and hyperthyroidism were, respectively, induced in rats via administration of propylthiouracil (PTU) and L-thyroxine sodium salt in drinking water for 45 days. The activities of superoxide dismutase (SOD), catalase (CAT), glutathioen peroxidase (GPx), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PD), xanthine oxidase (XO), and nonenzymatic markers of oxidative stress including malondialdehyde (MDA), protein carbonyl (PC), reduced glutathione (GSH), and total thiols (T-SH) were determined in the rat pancreas. In hyperthyroid rats, pancreatic CAT, SOD, GPx, GR, XO, G6PD activities were increased compared with those in hypothyroid and control groups. There were no differences in activities of antioxidant enzymes between hypothyroid and control rats. Pancreatic MDA and PC in hyperthyroid rats increased compared with hypothyroid and the control animals. Whereas, hyperthyroid rats had decreased levels of tissue GSH and T-SH compared with hypothyroid and the control groups. The findings showed that only GSH level has decreased significantly in the hypothyroid group compared with control groups. In conclusion, our results showed that experimental hyperthyroidism induces oxidative stress in pancreas of rats, but hypothyroidism has no major impact on oxidative stress markers. Drug Dev Res 77 : 199-205, 2016.   © 2016 Wiley Periodicals, Inc.

Iodine Affects Differentiation and Migration Process in Trophoblastic Cells

Iodine deficiency is associated with oxidative stress increase and preeclampsia during gestation, suggesting that iodine concentration plays an important role in the normal placenta physiology. The question raised is to analyze the effect of iodine deficiency on oxidative stress, viability, differentiation, and migration process and changes in the expression of differentiation and migration markers. Iodine deprivation was done using potassium perchlorate (KCLO4) to block sodium iodide symporter (NIS) transporter and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid DIDS to inhibit pendrine (PEN) transport for 3-48 h. Then trophoblast cells were treated with low iodine doses of 5-500 μM and high iodine doses of 100-5000 μM. Oxidative stress, viability, and human chorionic gonadotropin (hGC) were measured by colorimetric methods. Migration throphoblast cells were evaluated by both wound healing and Boyden chamber assays. Changes in mRNA expression were analyzed by real-time RT-PCR. Iodine deprivation induces a significant increase of reactive oxygen species (ROS), viability, and migration process vs control cells. We found a significant overregulation in the mRNA's peroxisome proliferator-activated receptor (PPAR-gamma), Snail, and matrix metalloproteinase-9 (MMP-9) mRNA's in cells deprived of iodine, as well as a down glial cell missing-1 (GCM-1) regulation, hGC, pregnancy-associated plasma protein-A (PAPP-A), and E-cadherin mRNA expression. The expression of hypoxic induction factor alpha (HIFα) mRNA does not change with iodine deprivation. In cells deprived of iodine, supplementing low iodine doses (5-500 μM) does not induce any significant changes in viability. However, ROS and migration process were decreased, although we found an increased human chorionic gonadotropin (hCG) secretion as a differentiation marker. In addition, we found that PPAR-gamma, Snail, and MPP-9 mRNAs expression are downregulated with low iodine doses, in contrast with GCM-1, PAPP-A, hGC, and E-cadherin that increase their expression vs cells deprived of iodine. High iodine doses (1000-5000 μM) have shown cytotoxic effects. Based on our results, iodine is important for keeping the proliferation/differentiation balance in the placenta.

Lipid peroxidation, proteins modifications, anti-oxidant enzymes activities and selenium deficiency in the plasma of hashitoxicosis patients

OBJECTIVES

The aim of this study was to explore the oxidative stress profile in hashitoxicosis (HTX) and to compare it with that of healthy subjects.

PATIENTS AND METHODS

Spectrophotometric methods were used to evaluate the oxidative stress markers. The selenium level was investigated by atomic absorption.

RESULTS

High levels of thiobarbituric acid reactive species (TBARS) and conjugated dienes were found in HTX patients (p = 0.034 and p = 0.043, respectively) compared with healthy controls. For antioxidant enzymes, superoxide dismutase (SOD) and catalase activities increased, whereas that of glutathione peroxidase (GPx) decreased (p = 0.000, p = 0.014, p = 0.000, respectively) compared with controls. A reduction in the level of selenium (p = 0.029) and thiol groups (p = 0.008) were shown in patients; however, levels of carbonyl group and malondialdehyde (MDA) protein adducts decreased (p = 0.000) compared with controls. Positive correlation was shown between levels of free thyroxine (FT4) and TBARS (r = 0.711, p = 0.048) and between FT4 level and SOD activity (r = 0.713, p = 0.047). Conversely, GPx activity presented a negative correlation with FT4 and free triiodothyronine (FT3) levels (r = -0.934, p = 0.001; r = -0.993, p = 0.000, respectively). In addition, GPx activity showed positive correlation with selenium level (r = 0.981, p = 0.019) and the FT3 level correlated negatively with the level of thiol groups (r = -0.892, p = 0.017).

CONCLUSIONS

This study shows the presence of an oxidative stress and selenium deficiency in HTX patients and suggests that the hyperthyroid state is strongly implicated in the establishment of this disturbed oxidative profile.

Association Between Thyroid Hormones, Lipids and Oxidative Stress Markers in Subclinical Hypothyroidism

BACKGROUND

Oxidative stress plays a role in the pathogenesis of many chronic diseases. It is recognized in overt hypothyroidism while its existence in subclinical hypothyroidism (SCH) is not well established. The aim of this study was to determine whether there was increased oxidation of lipids and proteins in SCH, and examine their association with lipids and thyroid hormones.

METHODS

Male adults (35-59 years) with SCH (n=467) and euthyroid controls (n=190) were studied. Anthropometric measurements, plasma lipids, thyroid stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), total antioxidant capacity (T-AOC), lipid peroxidation products, malondialdehyde (MDA), advanced oxidation protein products (AOPP) and dityrosine concentrations were measured.

RESULTS

Plasma concentrations of MDA were significantly higher (p<0.05) in SCH (8.11±1.39 nmol/mL) compared with euthyroid controls (7.34±1.31 nmol/mL) while AOPP, dityrosine and T-AOC levels were not different. MDA was not associated with TSH (β=-0.019, P=0.759), FT4 (β=-0.062, P=0.323) and FT3 (β=-0.018, P=0.780) in SCH while levels increased with elevated total cholesterol (β=0.229, P=0.001), LDL (β=0.203, P=0.009) and triglycerides (β=0.159, P=0.036) after adjustment for age and body mass index. T-AOC reduced (β=-0.327, P=0.030) with increased MDA in euthyroid controls and not in SCH (β=-0.068, P=0.349), while levels increased with elevated triglycerides in both groups.

CONCLUSIONS

Oxidative stress was increased in subclinical hypothyroidism as evidenced by the elevated lipid peroxidation product, malondialdehyde, while protein oxidation was absent. Thus, reduction of oxidative stress may be beneficial in patients with subclinical hypothyroidism.

Dry olive leaf extract counteracts L-thyroxine-induced genotoxicity in human peripheral blood leukocytes in vitro

The thyroid hormones change the rate of basal metabolism, modulating the consumption of oxygen and causing production of reactive oxygen species, which leads to the development of oxidative stress and DNA strand breaks. Olive (Olea europaea L.) leaf contains many potentially bioactive compounds, making it one of the most potent natural antioxidants. The objective of this study was to evaluate the genotoxicity of L-thyroxine and to investigate antioxidative and antigenotoxic potential of the standardized oleuropein-rich dry olive leaf extract (DOLE) against hydrogen peroxide and L-thyroxine-induced DNA damage in human peripheral blood leukocytes by using the comet assay. Various concentrations of the extract were tested with both DNA damage inducers, under two different experimental conditions, pretreatment and posttreatment. Results indicate that L-thyroxine exhibited genotoxic effect and that DOLE displayed protective effect against thyroxine-induced genotoxicity. The number of cells with DNA damage, was significantly reduced, in both pretreated and posttreated samples (P < 0.05). Comparing the beneficial effect of all tested concentrations of DOLE, in both experimental protocols, it appears that extract was more effective in reducing DNA damage in the pretreatment, exhibiting protective role against L-thyroxine effect. This feature of DOLE can be explained by its capacity to act as potent free radical scavenger.

Thyroid hormone induction of mitochondrial activity is coupled to mitophagy via ROS-AMPK-ULK1 signaling

Currently, there is limited understanding about hormonal regulation of mitochondrial turnover. Thyroid hormone (T3) increases oxidative phosphorylation (OXPHOS), which generates reactive oxygen species (ROS) that damage mitochondria. However, the mechanism for maintenance of mitochondrial activity and quality control by this hormone is not known. Here, we used both in vitro and in vivo hepatic cell models to demonstrate that induction of mitophagy by T3 is coupled to oxidative phosphorylation and ROS production. We show that T3 induction of ROS activates CAMKK2 (calcium/calmodulin-dependent protein kinase kinase 2, β) mediated phosphorylation of PRKAA1/AMPK (5' AMP-activated protein kinase), which in turn phosphorylates ULK1 (unc-51 like autophagy activating kinase 1) leading to its mitochondrial recruitment and initiation of mitophagy. Furthermore, loss of ULK1 in T3-treated cells impairs both mitophagy as well as OXPHOS without affecting T3 induced general autophagy/lipophagy. These findings demonstrate a novel ROS-AMPK-ULK1 mechanism that couples T3-induced mitochondrial turnover with activity, wherein mitophagy is necessary not only for removing damaged mitochondria but also for sustaining efficient OXPHOS.

Experimentally induced hyperthyroidism influences oxidant and antioxidant status and impairs male gonadal functions in adult rats

The objective of the present experiment was to study the effect of hyperthyroidism on male gonadal functions and oxidant/antioxidant biomarkers in testis of adult rats. Induction of hyperthyroidism by L-thyroxine (L-T4, 300 μg kg(-1) body weight) treatment once daily for 3 or 8 weeks caused a decrease in body weight gain as well as in absolute genital sex organs weight. The epididymal sperm counts and their motility were significantly decreased in a time-dependent manner following L-T4 treatment. Significant decline in serum levels of luteinising hormone, follicle stimulating hormone and testosterone along with significant increase in serum estradiol level was observed in hyperthyroid rats compared with euthyroid ones. Significant increase in malondialdehyde and nitric oxide concentration associated with significant decrease in superoxide dismutase and catalase activity was also noticed following hyperthyroidism induction. Both reduced glutathione content and glutathione peroxidase activity were increased in hyperthyroid rats compared with control rats. Marked histopathological alterations were observed in testicular section of hyperthyroid rats. These results provide evidence that hypermetabolic state induced by excess level of thyroid hormones may be a causative factor for the impairment of testicular physiology as a consequence of oxidative stress.

The hidden phenomenon of oxidative stress during treatment of subclinical-mild hypothyroidism: a protective nutraceutical intervention

Recent studies suggest that subjects with hypothyroidism under therapy with levothyroxine (L-T4) might develop oxidative stress. The aim of this study was to test a redox-balance modulator, fermented papaya-based nutraceutical (FPP), together with subclinical (SH) or mild hypothyroidism (MH) treatment in view of biochemical changes. A total of 60 females treated for SH-MH were divided into two matched groups and received either FPP 3 grams 1 sachet three times a day (t.i.d.) or placebo for 3 months. A significant baseline increase of all oxidative markers was observed in SH-MH (p<0.05 vs. control) and even more under T4 treatment (p<0.05). FPP caused a normalization of redox markers (p<0.01 vs. placebo). Thyroid supplementation accelerates mitochondrial oxygen consumption and oxidative stress, whereas a redox-modulator therapy is advisable, given the long-lasting treatment in such cases.

Triiodothyronine regulates angiogenic growth factor and cytokine secretion by isolated human decidual cells in a cell-type specific and gestational age-dependent manner

STUDY QUESTION

Does triiodothyronine (T3) regulate the secretion of angiogenic growth factors and cytokines by human decidual cells isolated from early pregnancy?

SUMMARY ANSWER

T3 modulates the secretion of specific angiogenic growth factors and cytokines, with different regulatory patterns observed amongst various isolated subpopulations of human decidual cells and with a distinct change between the first and second trimesters of pregnancy.

WHAT IS KNOWN ALREADY

Maternal thyroid dysfunction during early pregnancy is associated with complications of malplacentation including miscarriage and pre-eclampsia. T3 regulates the proliferation and apoptosis of fetal-derived trophoblasts, as well as promotes the invasive capability of extravillous trophoblasts (EVT). We hypothesize that T3 may also have a direct impact on human maternal-derived decidual cells, which are known to exert paracrine regulation upon trophoblast behaviour and vascular development at the uteroplacental interface.

STUDY DESIGN, SIZE, DURATION

This laboratory-based study used human decidua from first (8–11 weeks; n = 18) and second (12–16 weeks; n = 12) trimester surgical terminations of apparently uncomplicated pregnancies.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Primary cultures of total decidual cells, and immunomagnetic bead-isolated populations of stromal-enriched (CD10+) and stromal-depleted (CD10−) cells, uterine natural killer cells (uNK cells; CD56+) and macrophages (CD14+) were assessed for thyroid hormone receptors and transporters by immunocytochemistry. Each cell population was treated with T3 (0, 1, 10, 100 nM) and assessments were made of cell viability (MTT assay) and angiogenic growth factor and cytokine secretion (immunomediated assay). The effect of decidual cell-conditioned media on EVT invasion through Matrigel^® was evaluated.

MAIN RESULTS AND THE ROLE OF CHANCE

Immunocytochemistry showed the expression of thyroid hormone transporters (MCT8, MCT10) and receptors (TRα1, TRβ1) required for thyroid hormone-responsiveness in uNK cells and macrophages from the first trimester. The viability of total decidual cells and the different cell isolates were unaffected by T3 so changes in cell numbers could not account for any observed effects. In the first trimester, T3 decreased VEGF-A secretion by total decidual cells (P < 0.05) and increased angiopoietin-2 secretion by stromal-depleted cells (P < 0.05) but in the second trimester total decidual cells showed only increased angiogenin secretion (P < 0.05). In the first trimester, T3 reduced IL-10 secretion by total decidual cells (P < 0.05), and reduced granulocyte macrophage colony stimulating factor (P < 0.01), IL-8 (P < 0.05), IL-10 (P < 0.01), IL-1β (P < 0.05) and monocyte chemotactic protein -1 (P < 0.001) secretion by macrophages, but increased tumour necrosis factor-α secretion by stromal-depleted cells (P < 0.05) and increased IL-6 by uNK cells (P < 0.05). In contrast, in the second trimester T3 increased IL-10 secretion by total decidual cells (P < 0.01) but did not affect cytokine secretion by uNK cells and macrophages. Conditioned media from first trimester T3-treated total decidual cells and macrophages did not alter EVT invasion compared with untreated controls. Thus, treatment of decidual cells with T3 resulted in changes in both angiogenic growth factor and cytokine secretion in a cell type-specific and gestational age-dependent manner, with first trimester decidual macrophages being the most responsive to T3 treatment, but these changes in decidual cell secretome did not affect EVT invasion in vitro.

LIMITATIONS, REASONS FOR CAUTION

Our results are based on in vitro findings and we cannot be certain if a similar response occurs in human pregnancy in vivo.

WIDER IMPLICATIONS OF THE FINDINGS

Optimal maternal thyroid hormone concentrations could play a critical role in maintaining a balanced inflammatory response in early pregnancy to prevent fetal immune rejection and promote normal placental development through the regulation of the secretion of critical cytokines and angiogenic growth factors by human decidual cells. Our data suggest that there is an ontogenically determined regulatory ‘switch’ in T3 responsiveness between the first and second trimesters, and support the notion that the timely and early correction of maternal thyroid dysfunction is critical in influencing pregnancy outcomes.

STUDY FUNDING/COMPETING INTEREST(S)

This study is funded by Wellbeing of Women (RG/1082/09 to S.Y.C., M.D.K., J.A.F., L.S.L., G.E.L.) and Action Medical Research – Henry Smith Charity (SP4335 to M.D.K., S.Y.C., L.S.L., J.A.F.). The authors have no conflicts of interest to disclose.

Levothyroxine and lung cancer in females: the importance of oxidative stress

BACKGROUND

Levothyroxine (LT4) treatment can lead to iatrogenic hyperthyroidism and oxidative stress that can cause patient discomfort. Oxidative stress is also recognized as one of the causes of chronic diseases and cancer.

METHODS

The prevalence of breast, colorectal, gastric and lung cancer in 18 Italian Regions during 2010 was correlated with the sales of LT4 in 2009. The cancer prevalence was analyzed in women aged 30-84. This age range corresponds to more than 80% of the consumers of the drug and to about 99% of all malignant cancers. The correlation between sales of LT4 and cancers was determined with the technique of Density Ellipses. The age and smoking contribution for lung cancer was determined with the Sequential test.

RESULTS

No significant correlation was seen between LT4 sales and breast, colorectal and gastric cancers. A significant correlation was instead found for lung cancer (p<0.05) corrected for smoking and age.

CONCLUSIONS

LT4 consumption in Italy is about 0.7 boxes/women/year. There is a correlation between lung cancer and LT4 treatment and oxidative stress caused by LT4 supplementation can be one of the causes. Although we cannot exclude that dysthyroidism needing LT4 supplementation might be the ground for lung cancer itself and measuring oxidative stress could be helpful in avoiding excessive use of the drug.

Anti-oxidant activity and attenuation of bladder hyperactivity by the flavonoid compound kaempferol

OBJECTIVES

To evaluate the anti-oxidant activity of the flavonoid compound, kaempferol, and to examine its role in the suppression of oxidative stress and attenuation of bladder hyperactivity in a rat model of bladder injury.

METHODS

The anti-oxidative activity of kaempferol was examined in lipopolysaccharide-treated RAW264.7 macrophages by using flow cytometry. For in vivo studies, rats were pretreated with kaempferol or vehicle for 24 h. The rat urothelium was injured by the administration of protamine sulfate for 1.5 h and irritated by the subsequent infusion of potassium chloride for 4 h. Oxidative stress in the bladder tissue was assessed using chemiluminescence assay, and the bladder pressure was determination by cystomertrogram.

RESULTS

Kaempferol significantly suppressed lipopolysaccharide-induced reactive oxygen species production in RAW264.7 rat macrophages. Exposure of the rat bladder to sequential infusion of protamine sulfate and potassium chloride induced bladder hyperactivity. Pretreatment with kaempferol, prevented the formation of reactive oxygen species and prolonged the intercontraction interval.

CONCLUSION

Kaempferol suppresses oxidative stress and attenuates bladder hyperactivity caused by potassium chloride after protamine sulfate-induced bladder injury.

Ferrous ferric chloride downregulates the inflammatory response to Rhodococcus aurantiacus infection in mice

The healthy drink Pairogen is mainly composed of ferrous ferric chloride water that reportedly changes the status of intracellular water from oxidative to antioxidative. Here, we investigated whether Pairogen affects host immune function in a murine model of granulomatous inflammation in response to Rhodococcus aurantiacus (R. aurantiacus) infection. Longitudinal ingestion of Pairogen markedly improved the survival of infected mice in a concentration-dependent manner. Compared to mice received water, mice that ingested 10-fold-diluted Pairogen displayed rapid bacterial elimination, decreased production of tumor necrosis factor (TNF)-α and interleukin (IL)-6, and high levels of IL-10 in organs during the initial phase of infection. Moreover, histological studies showed significant reduction in the number and size of granulomas as well as amelioration of oxidative stress in the livers of mice ingested 10-fold-diluted Pairogen at 14 d post-infection. These characteristics were further pronounced in first-generation (F1) mice that also ingested 10-fold-diluted Pairogen. Following stimulation with heat-killed R. aurantiacus, the production of TNF-α, IL-6, and IL-10 by macrophages from F1 mice was similar to that detected in vivo, while their gene expression levels in these cells were significantly lower than the levels in macrophages from mice received water. Heat-killed R. aurantiacus also induced the expression of heme oxygenase-1 mRNA in the cells from F1 mice. Taken together, these results indicate that Pairogen contributes to the negative regulation of the immuno-inflammatory response to R. aurantiacus infection in mice by modulating the cellular redox state. Longitudinal ingestion of Pairogen further enhances the defense function in mouse progeny.

NADPH oxidase as an important source of reactive oxygen species at the mouse maternal-fetal interface: putative biological roles

Oxygen derivatives that comprise the large family of reactive oxygen species (ROS) are actively involved in placental biology. They are generated at the maternal-fetal interface at the level of decidual, trophoblast and mesenchymal components. In normal conditions, ROS produced in low concentrations participate in different functions as signalling molecules, regulating activation of redox-sensitive transcription factors and protein kinases involved in cell survival, proliferation and apoptosis, hence much of cell functioning. Physiological ROS generation is also associated with such defence mechanisms as phagocytosis and microbiocidal activities. In mice, particularly but not exclusively, trophoblast cells phagocytose intensively during implantation and post-implantation periods and express enzymic machinery to address a ROS-producing response to changes in the environment. The cells directly associated with ROS production are trophoblast giant cells, which mediate each and every relationship with the maternal organism. In this review, the production of ROS by the implanting mouse trophoblast is discussed, focusing on NADPH oxidase expression, regulatory mechanisms and similarities with NOX2 from phagocytes. Some of the current controversies are assessed by attempting to integrate data from studies in human trophoblast and mouse models.

Heme oxygenase-1 is induced by thyroid hormone and involved in thyroid hormone preconditioning-induced protection against renal warm ischemia in rat

Thyroid hormone pretreatment was indicated to increase tissue tolerance to ischemia-reperfusion injury (IRI) in various organs, but the underlying molecular mechanisms remains largely unknown. Induction of heme oxygenase-1 (HO-1) protects organs against IRI. The present study investigated the effect of thyroid hormone on HO-1 expression and the possible relation between HO-1 and the thyroid hormone induced renal protection. T(3) administration in rat kidneys induced HO-1 expression in a time-dependent and dose-dependent way, and its expression was accompanied with significant depletion of reduced glutathione and increase in malondialdehyde content, showing a moderate oxidative stress that turns to normal level 48 h after drug injection. Thyroid hormone pretreatment (10 μg/100g body weight) 48 h before IR procedure significantly decreased serum creatinine and urea nitrogen and preserved renal histology, with significant reduction of parameters about oxidative stress and over-expression of HO-1 compared with that of IR group. In conclusion, T(3) administration involving oxidative stress in kidney exerts significant enhancement of HO-1 expression which may, at least in part, account for the renal preconditioning induced by T(3).

Thyroid hormone administration induces rat liver Nrf2 activation: suppression by N-acetylcysteine pretreatment

BACKGROUND

Oxidative stress associated with 3,3',5-triiodo-l-thyronine (T(3))-induced calorigenesis upregulates the hepatic expression of mediators of cytoprotective mechanisms. The aim of this study was to evaluate the hypothesis that in vivo T(3) administration triggers a redox-mediated translocation of the cytoprotective nuclear transcription factor erythroid 2-related factor 2 (Nrf2) from the cytosol to the nucleus in rat liver. Such translocation of transcription factors is considered to be an activating step.

MATERIALS AND METHODS

The effect of T(3) administration in the presence and absence of N-acetylcysteine (NAC) on cytosol-to-nuclear translocation of Nrf2 was evaluated, with inhibition of this process by NAC taken as evidence that the process was redox mediated. Male Sprague-Dawley rats weighing 180-200 g were given a single intraperitoneal dose of 0.1 mg T(3)/kg. Another group of rats were given the same dose of T(3) and were also pretreated with NAC (0.5 g/kg) at 0.5 hour before T(3) administration. Two other groups of rats received vehicle treatment and NAC, respectively. Following these treatments, rectal temperature of the animals, liver O(2) consumption, serum and hepatic levels of 8-isoprostanes, and liver protein levels of Nrf2, Akt, p38, and thioredoxin (Western blot) were determined at different times up to 48 hours.

RESULTS

T(3) administration induced a significant increase in the hepatic nuclear levels of Nrf2 at 1 and 2 hours after treatment and a concomitant decrease in cytosolic Nrf2. It also increased hepatic thioredoxin, a protein whose gene transcription is induced by nuclear Nrf2. Levels of nuclear Nrf2 were at a plateau from 4 to 6 hours after T(3). Rectal temperature of the animals rose from 36.6°C to 37.5°C as did liver O(2) consumption. Serum and liver 8-isoprostanes levels increased (p < 0.05) from 38.4 ± 4.0 pg/mL (n = 4) to 69.2 ± 2.0 pg/mL (n = 3) and from 0.75 ± 0.09 ng/g liver (n = 3) to 1.53 ± 0.10 ng/g liver (n = 5), respectively. In the group of rats pretreated with NAC, the increase in cytosol-to-nuclear translocation of Nrf2 was only 28% that induced by T(3). In addition, T(3) induced liver Akt and p38 activation during the period of 1-4 hours after T(3) administration. p38 activation at 2 hours after T(3) administration was abolished in NAC-pretreated animals.

CONCLUSIONS

In vivo T(3) administration leads to a rapid and transient cytosol-to-nuclear translocation of liver Nrf2. This appears to be promoted by a redox-dependent mechanism as it is blocked by NAC. It may also be contributed by concomitant p38 activation, which in turn promoted Nrf2 phosphorylation. Nrf2 cytosol-to-nuclear translocation may represent a novel cytoprotective mechanism of T(3) to limit free radical or electrophile toxicity, as this would likely entail promoting thioredoxin production.

Effect of leucovorin (folinic acid) on the developmental quotient of children with Down's syndrome (trisomy 21) and influence of thyroid status

Background

Seven genes involved in folate metabolism are located on chromosome 21. Previous studies have shown that folate deficiency may contribute to mental retardation in Down's syndrome (DS).

Methodology

We investigated the effect of oral folate supplementation (daily dose of 1.0±0.3 mg/kg) on cognitive functions in DS children, aged from 3 to 30 months. They received 1 mg/kg leucovorin or placebo daily, for 12 months, in a single-centre, randomised, double-blind study. Folinic acid (leucovorin, LV) was preferred to folic acid as its bioavailability is higher. The developmental age (DA) of the patients was assessed on the Brunet-Lezine scale, from baseline to the end of treatment.

Results

The intent-to-treat analysis (113 patients) did not show a positive effect of leucovorin treatment. However, it identified important factors influencing treatment effect, such as age, sex, and concomitant treatments, including thyroid treatment in particular. A per protocol analysis was carried out on patients evaluated by the same examiner at the beginning and end of the treatment period. This analysis of 87 patients (43 LV-treated vs. 44 patients on placebo) revealed a positive effect of leucovorin on developmental age (DA). DA was 53.1% the normal value with leucovorin and only 44.1% with placebo (p<0.05). This positive effect of leucovorin was particularly strong in patients receiving concomitant thyroxin treatment (59.5% vs. 41.8%, p<0.05). No adverse event related to leucovorin was observed.

Conclusion

These results suggest that leucovorin improves the psychomotor development of children with Down's syndrome, at least in some subgroups of the DS population, particularly those on thyroxin treatment.

Trial Registration

ClinicalTrials.gov, NCT00294593

T3 and the thyroid hormone beta-receptor agonist GC-1 differentially affect metabolic capacity and oxidative damage in rat tissues

We compared the changes in tissue aerobic metabolism and oxidative damage elicited by hypothyroid rat treatment with T3 and its analog GC-1. Aerobic capacities, evaluated by cytochrome oxidase activities, were increased more by T3 than by GC-1. Furthermore, the response of the tissues to T3 was similar, whereas the response to GC-1 was high in liver, low in muscle and scarce in heart. Both treatments induced increases in ADP-stimulated O2 consumption, which were consistent with those in aerobic capacities. However, unlike T3, GC-1 differentially affected pyruvate/malate- and succinate-supported respiration, suggesting that respiratory chain components do not respond as a unit to GC-1 stimulation. According to the positive relationship between electron carrier levels and rates of mitochondrial generation of oxidative species, the most extensive damage to lipids and proteins was found in T3-treated rats. Examination of antioxidant enzyme activities and scavenger levels did not clarify whether oxidative damage extent also depended on different antioxidant system effectiveness. Conversely, the analysis of parameters determining tissue susceptibility to oxidants showed that pro-oxidant capacity was lower in GC-1- than in T3-treated rats, while antioxidant capacity was similar in treatment groups. Interestingly, both agonists decreased serum cholesterol levels, but only GC-1 restored euthyroid values of heart rate and indices of tissue oxidative damage, indicating that GC-1 is able to lower cholesterolemia, bypassing detrimental effects of T3.

Is euthyroid sick syndrome a defensive mechanism against oxidative stress?

The body has a hierarchy of defence strategies to deal with oxidative stress. Among these arrays of defence mechanisms, the over expression and increased activity of glutathione peroxidases has been suggested as the first line of defence. The two main cofactors required for glutathione peroxidase activity are selenium and reduced glutathione. These two factors have been shown to be required for the deiodinase activity also. In vitro and in vivo studies have shown that oxidative stress decreases the activity of deiodinase. Thus, a decrease in deiodinase activity would facilitate the use of these cofactors by glutathione peroxidase in combating oxidative stress. Lowering of serum T3 is generally regarded as a valuable calorie-sparing economy. A decreased metabolic state of the cells as found in euthyroid sick syndrome indicates a decreased free radical generation from the mitochondria. For this reason, euthyroid sick syndrome could be considered as a physiological mechanism activated in response to oxidative stress.

Distinct genomic signatures of adaptation in pre- and postnatal environments during human evolution

The human genome evolution project seeks to reveal the genetic underpinnings of key phenotypic features that are distinctive of humans, such as a greatly enlarged cerebral cortex, slow development, and long life spans. This project has focused predominantly on genotypic changes during the 6-million-year descent from the last common ancestor (LCA) of humans and chimpanzees. Here, we argue that adaptive genotypic changes during earlier periods of evolutionary history also helped shape the distinctive human phenotype. Using comparative genome sequence data from 10 vertebrate species, we find a signature of human ancestry-specific adaptive evolution in 1,240 genes during their descent from the LCA with rodents. We also find that the signature of adaptive evolution is significantly different for highly expressed genes in human fetal and adult-stage tissues. Functional annotation clustering shows that on the ape stem lineage, an especially evident adaptively evolved biological pathway contains genes that function in mitochondria, are crucially involved in aerobic energy production, and are highly expressed in two energy-demanding tissues, heart and brain. Also, on this ape stem lineage, there was adaptive evolution among genes associated with human autoimmune and aging-related diseases. During more recent human descent, the adaptively evolving, highly expressed genes in fetal brain are involved in mediating neuronal connectivity. Comparing adaptively evolving genes from pre- and postnatal-stage tissues suggests that different selective pressures act on the development vs. the maintenance of the human phenotype.

Increased serum chitotriosidase activity following restoration of euthyroidism in patients with subclinical hypothyroidism

OBJECTIVE

Whether to treat subclinical hypothyroidism (SH) remains controversial. Serum chitotriosidase activity, a marker of activated macrophages, predicts new cardiovascular events. Chitotriosidase activity (ChT) is a new cardiovascular risk marker and is independent of C-reactive protein. The purpose of this study was to determine ChT levels in SH and to examine the effect of levothyroxine replacement on ChT.

SUBJECTS AND METHODS

A cohort of 60 patients with subclinical hypothyroidism and 62 healthy controls were enrolled in this study. Serum total and LDL cholesterol, total homocysteine (t-Hyc), highly sensitive C-reactive protein (hsCRP) levels and serum ChT in patients with subclinical hypothyroidism at baseline and after achieving euthyroid state by levothyroxine were assessed.

RESULTS

Pretreatment levels of TSH (10.06+/-5.09 vs. 2.08+/-0.95 mIU/L, p<0.05), and free T4 (0.94+/-0.21 vs. 1.35+/-0.26 ng/dl, p<0.05) were significantly higher than controls while total cholesterol, LDL cholesterol, t-Hyc, ChT and hsCRP levels were not different. ChT levels significantly increased after replacement therapy (137.2+/-14.18 vs. 156.88+/-13.10 nmol/mL/h, p<0.05). T-Hyc and hsCRP levels were not significantly different after treatment with levothyroxine therapy even in this subgroup of patients. None of the other biochemical risk factors improved after euthyroidism in patients with SH with average dose of 85+/-30 mug/day when compared to pretreatment levels.

CONCLUSION

We conclude that clinical management of subclinical hypothyroidism does not decrease the serum hsCRP or t-Hyc levels but does increase the serum ChT levels. The clinical significance of this increment should be studied in further studies.

Activation of NF-kappaB in lymphocytes and increase in serum immunoglobulin in hyperthyroidism: possible role of oxidative stress

This study evaluated oxidative stress, serum IgM and IgG, and nuclear factor (NF)-kappaB signaling in lymphocytes of hyperthyroidism patients. GSH content in lymphocytes was significantly lower and serum malondialdehyde, IgM and IgG levels were significantly higher in hyperthyroidism as compared to controls. In lymphocytes, the NF-kappaB signaling pathway was studied by western blot analysis of p65 and p-IkappaBalpha. Density of p-IkappaBalpha and p65 (in nuclear fraction) was significantly higher in hyperthyroidism as compared to controls. The density of p-IkappaBalpha and p65 had significant positive correlation with serum malondialdehyde level and negative correlation with lymphocyte GSH level in hyperthyroid cases. The serum IgG and IgM levels were correlated significantly with density of p-IkappaBalpha and p65. As immunoglobulin production is regulated by the NF-kappaB pathway, we conclude that the oxidative stress-induced activation of the NF-kappaB pathway might play a role in the rise of serum immunoglobulin level in hyperthyroidism.

Involvement of Kupffer cell-dependent signaling in T3-induced hepatocyte proliferation in vivo

Thyroid hormone-induced calorigenesis triggers liver oxidative stress with concomitant TNF-alpha production by Kupffer cells and up-regulation of gene expression. Considering that cyclin-dependent kinase-2 (CDK-2) performs essential functions for cellular proliferation, our aim was to test the hypothesis that l-3,3',5-triiodothyronine (T(3)) stimulates liver cell proliferation by upstream mechanisms involving CDK-2 expression dependent on Kupffer cell signaling. T(3) administration induced a calorigenic response at 60-70 h after treatment, with increased TNF-alpha generation and hepatic oxidative stress status, as shown by enhanced protein carbonyls and decreased glutathione content compared to controls. In this time interval, liver c-jun N-terminal kinase (JNK) phosphorylation, activator protein-1 (AP-1) DNA binding, and CDK-2 expression were enhanced, with concomitantly higher levels of the proliferation markers Ki-67 and proliferating cell nuclear antigen. These changes are abolished by administration of the Kupffer cell inactivator gadolinium chloride prior to T(3) treatment. We conclude that T(3) administration triggers liver CDK-2 expression and cellular proliferation through a cascade associated with Kupffer cell-dependent TNF-alpha generation, JNK phosphorylation, and AP-1 activation. Since CDK-2 promotes phase S progression within the cell cycle, this response may constitute a major mechanism involved in T(3)-induced liver preconditioning to ischemia/reperfusion injury.

Down-regulation of iNOS and TNF-alpha expression by kaempferol via NF-kappaB inactivation in aged rat gingival tissues

The primary objective of this study was to evaluate the ability and mechanism of action of kaempferol, which is contained in extracts from Nelumbo nucifera, a well-known Oriental herb used in traditional medicine, with regard to the inhibition of iNOS and TNF-alpha expression in aged rat gingival tissues. We conducted an investigation into the age-related effects of kaempferol on reactive oxygen species (ROS) and GSH oxidative status in samples of aged gingival tissues. Western blotting was conducted in order to determine the expression of iNOS, TNF-alpha, p38 MAPK, NIK/IKK, p65 and IkappaBalpha in the sample tissues. Electrophoretic mobility shift assays (EMSA) were conducted in an effort to characterize the binding activities of NF-kappaB transcription factors in the aged rat gingival nuclear extracts. Our results indicate that kaempferol reduced ROS levels and augmented GSH levels in a dose-dependent manner in the aged gingival tissues. Kaempferol was shown to effect a significant reduction in iNOS and TNF-alpha protein levels, as compared to control gingival tissue samples. The results of Western blot analysis revealed that kaempferol treatment effected the reduction of iNOS and TNF-alpha expression, decreased nuclear p65 and increased cytosolic p65, down-regulation of Erk, p38, JNK and NIK/IKK expression. The EMSA results also indicated that kaempferol, when administered to the rat tissues, attenuated the NF-kappaB nuclear binding activity. Kaempferol may inhibit ROS generation via the inhibition of iNOS and TNF-alpha expression in aged gingival tissues, via the modulation of the NF-kappaB and mitogen-activated protein kinase (MAPK) pathways.