The flavonoid quercetin regulates growth and gene expression in rat FRTL-5 thyroid cells

Regulation of iodine-glucose flip-flop in SW1736 anaplastic thyroid cancer cell line

AIMS AND BACKGROUND

The alternative manner of iodide and glucose uptake found in different types of thyroid cancer, referred to flip-flop. ATC cells indicate low iodide uptake and high glucose uptake, which lack the morphology and genetic characteristics of well-differentiated tumors and become increasingly invasive. Importance placed on the discovery of innovative multi-targeted medicines to suppress the dysregulated signaling in cancer. In this research, we aimed to clarify molecular mechanism of Rutin as a phytomedicine on anaplastic thyroid cancer cell line based on iodide and glucose uptake.

MATERIAL METHODS

The MTT test was employed to test cell viability. Iodide uptake assay was performed using a spectrophotometric assay to determine iodide uptake in SW1736 cells based on Sandell-Kolthoff reaction. For glucose uptake detection, ''GOD-PAP'' enzymatic colorimetric assay was applied to measure the direct glucose levels inside of the cells. Determination of NIS, GLUT1 and 3 mRNA expression in SW1736 cells was performed by qRT-PCR. Determination of NIS, GLUT1 and 3 protein levels in SW1736 cells was performed by western blotting.

RESULTS

According to our results, Rutin inhibited the viability of SW1736 cells in a time- and dose-dependent manner. Quantitative Real-time RT-PCR analysis exposed that NIS mRNA levels were increased in Rutin treated group compared to the control group. Accordingly, western blot showed high expression of NIS protein and low expression of GLUT 1 and 3 in Rutin treated SW1736 cell line. Rutin increased iodide uptake and decreased glucose uptake in thyroid cancer cell line SW1736 compared to control group.

CONCLUSION

Multiple mechanisms point to Rutin's role as a major stimulator of iodide uptake and inhibitor of glucose uptake, including effects at the mRNA and protein levels for both NIS and GLUTs, respectively. Here in, we described the flip-flop phenomenon as a possible therapeutic target for ATC. Moreover, Rutin is first documented here as a NIS expression inducer capable of restoring cell differentiation in SW1736 cell line. It also be concluded that GLUTs as metabolic targets can be blocked specifically by Rutin for thyroid cancer prevention and treatment.

Radioiodine therapy in advanced differentiated thyroid cancer: Resistance and overcoming strategy

Thyroid cancer is the most prevalent endocrine tumor and its incidence is fast-growing worldwide in recent years. Differentiated thyroid cancer (DTC) is the most common pathological subtype which is typically curable with surgery and Radioactive iodine (RAI) therapy (approximately 85%). Radioactive iodine is the first-line treatment for patients with metastatic Papillary Thyroid Cancer (PTC). However, 60% of patients with aggressive metastasis DTC developed resistance to RAI treatment and had a poor overall prognosis. The molecular mechanisms of RAI resistance include gene mutation and fusion, failure to transport RAI into the DTC cells, and interference with the tumor microenvironment (TME). However, it is unclear whether the above are the main drivers of the inability of patients with DTC to benefit from iodine therapy. With the development of new biological technologies, strategies that bolster RAI function include TKI-targeted therapy, DTC cell redifferentiation, and improved drug delivery via extracellular vesicles (EVs) have emerged. Despite some promising data and early success, overall survival was not prolonged in the majority of patients, and the disease continued to progress. It is still necessary to understand the genetic landscape and signaling pathways leading to iodine resistance and enhance the effectiveness and safety of the RAI sensitization approach. This review will summarize the mechanisms of RAI resistance, predictive biomarkers of RAI resistance, and the current RAI sensitization strategies.

Endocrine disorders and fertility and pregnancy: An update

It is estimated that more and more couples suffer from fertility and pregnancy maintenance disorders. It is associated with impaired androgen secretion, which is influenced by many factors, ranging from genetic to environmental. It is also important to remember that fertility disorders can also result from abnormal anatomy of the reproductive male and female organ (congenital uterine anomalies - septate, unicornuate, bicornuate uterus; acquired defects of the uterus structure - fibroids, polyps, hypertrophy), disturbed hormonal cycle and obstruction of the fallopian tubes resulting from the presence of adhesions due to inflammation, endometriosis, and surgery, abnormal rhythm of menstrual bleeding, the abnormal concentration of hormones. There are many relationships between the endocrine organs, leading to a chain reaction when one of them fails to function properly. Conditions in which the immune system is involved, including infections and autoimmune diseases, also affect fertility. The form of treatment depends on infertility duration and the patient's age. It includes ovulation stimulation with clomiphene citrate or gonadotropins, metformin use, and weight loss interventions. Since so many different factors affect fertility, it is important to correctly diagnose what is causing the problem and to modify the treatment regimen if necessary. This review describes disturbances in the hormone secretion of individual endocrine organs in the context of fertility and the maintenance of pregnancy.

Effects of a Fruit and Vegetable-Based Nutraceutical on Biomarkers of Inflammation and Oxidative Status in the Plasma of a Healthy Population: A Placebo-Controlled, Double-Blind, and Randomized Clinical Trial

There is scientific evidence of the positive effect of polyphenols from plant foods on inflammation and oxidative status. The aim of the present study was to investigate whether treatment with a high-polyphenolic nutraceutical reduces the plasmatic concentration of certain oxidative and inflammatory biomarkers in a healthy population. One hundred and eight subjects were selected and stratified by sex in the intervention group (n = 53) and the placebo group (n = 55). Ninety-two subjects completed the study after two 16-week treatment periods separated by a four-week washout period. The results revealed statistically significant differences in subjects treated with the polyphenolic extract compared to the placebo: A decrease in homocysteine, oxidized low-density lipoprotein (OxLDL), TNF-α, sTNFR1, and C-reactive protein (CRP). The most significant decrease was observed for OxLDL (from 78.98 ± 24.48 to 69.52 ± 15.64; p < 0.05) and CRP (from 1.50 ± 0.33 to 1.39 ± 0.37; p < 0.05), both showing significant differences compared to the placebo (p < 0.001). Moreover, catecholamines increased after the administration of the product under investigation, especially in the case of dopamine (from 15.43 ± 2.66 to 19.61 ± 5.73; p < 0.05). Therefore, the consumption of a nutraceutical based on fruit and vegetables with a high polyphenol content seems to improve the parameters related to health benefits (oxidative and inflammatory biomarkers), including remarkable changes in the expression of catecholamines.

Plant constituents and thyroid: A revision of the main phytochemicals that interfere with thyroid function

In the past few decades, there has been a lot of interest in plant constituents for their antioxidant, anti-inflammatory, anti-microbial and anti-proliferative properties. However, concerns have been raised on their potential toxic effects particularly when consumed at high dose. The anti-thyroid effects of some plant constituents have been known for some time. Indeed, epidemiological observations have shown the causal association between staple food based on brassicaceae or soybeans and the development of goiter and/or hypothyroidism. Herein, we review the main plant constituents that interfere with normal thyroid function such as cyanogenic glucosides, polyphenols, phenolic acids, and alkaloids. In detail, we summarize the in vitro and in vivo studies present in the literature, focusing on the compounds that are more abundant in foods or that are available as dietary supplements. We highlight the mechanism of action of these compounds on thyroid cells by giving a particular emphasis to the experimental studies that can be significant for human health. Furthermore, we reveal that the anti-thyroid effects of these plant constituents are clinically evident only when they are consumed in very large amounts or when their ingestion is associated with other conditions that impair thyroid function.

The flavonoid quercetin reduces cell migration and increases NIS and E-cadherin mRNA in the human thyroid cancer cell line BCPAP

Thyroid cancer is the most frequent cancer of the endocrine system. Most patients are treated with thyroidectomy followed by radioiodine therapy. However, in part of the patients, a reduction of the sodium-iodide symporter (NIS) occurs, rendering radioiodine therapy ineffective. Moreover, epithelial-mesenchymal transition (EMT) may occur, leading to more aggressive and invasive features. Herein, we evaluated the effect of the flavonoid quercetin on EMT and NIS expression in BCPAP, a papillary thyroid carcinoma cell line. BCPAP was treated with 100 μM quercetin for 24 h and cell viability, apoptosis, EMT markers and NIS were evaluated. Quercetin decreased cell viability by enhancing apoptosis. The flavonoid also reduced matrix metalloproteinase 9 and increased E-cadherin mRNA levels, inhibiting BCPAP adhesion and migration. Additionally, quercetin increased NIS expression and function. Thus, our results suggest that quercetin could be useful as adjuvant in thyroid cancer therapy, inducing apoptosis, reducing invasion and increasing the efficacy of radioiodine therapy.

Flavonoids-Macromolecules Interactions in Human Diseases with Focus on Alzheimer, Atherosclerosis and Cancer

Flavonoids, a class of polyphenols, consumed daily in our diet, are associated with a reduced risk for oxidative stress (OS)-related chronic diseases, such as cardiovascular disease, neurodegenerative diseases, cancer, and inflammation. The involvement of flavonoids with OS-related chronic diseases have been traditionally attributed to their antioxidant activity. However, evidence from recent studies indicate that flavonoids' beneficial impact may be assigned to their interaction with cellular macromolecules, rather than exerting a direct antioxidant effect. This review provides an overview of the recent evolving research on interactions between the flavonoids and lipoproteins, proteins, chromatin, DNA, and cell-signaling molecules that are involved in the OS-related chronic diseases; it focuses on the mechanisms by which flavonoids attenuate the development of the aforementioned chronic diseases via direct and indirect effects on gene expression and cellular functions. The current review summarizes data from the literature and from our recent research and then compares specific flavonoids' interactions with their targets, focusing on flavonoid structure-activity relationships. In addition, the various methods of evaluating flavonoid-protein and flavonoid-DNA interactions are presented. Our aim is to shed light on flavonoids action in the body, beyond their well-established, direct antioxidant activity, and to provide insights into the mechanisms by which these small molecules, consumed daily, influence cellular functions.

Nutraceuticals in Thyroidology: A Review of in Vitro, and in Vivo Animal Studies

Nutraceuticals are defined as a food, or parts of a food, that provide medical or health benefits, including the prevention of different pathological conditions, and thyroid diseases, or the treatment of them. Nutraceuticals have a place in complementary medicines, being positioned in an area among food, food supplements, and pharmaceuticals. The market of certain nutraceuticals such as thyroid supplements has been growing in the last years. In addition, iodine is a fundamental micronutrient for thyroid function, but also other dietary components can have a key role in clinical thyroidology. Here, we have summarized the in vitro, and in vivo animal studies present in literature, focusing on the commonest nutraceuticals generally encountered in the clinical practice (such as carnitine, flavonoids, melatonin, omega-3, resveratrol, selenium, vitamins, zinc, and inositol), highlighting conflicting results. These experimental studies are expected to improve clinicians’ knowledge about the main supplements being used, in order to clarify the potential risks or side effects and support patients in their use.

Impact of Antioxidant Natural Compounds on the Thyroid Gland and Implication of the Keap1/Nrf2 Signaling Pathway

BACKGROUND

Natural compounds with potential antioxidant properties have been used in the form of food supplements or extracts with the intent to prevent or treat various diseases. Many of these compounds can activate the cytoprotective Nrf2 pathway. Besides, some of them are known to impact the thyroid gland, often with potential side-effects, but in other instances, with potential utility in the treatment of thyroid disorders.

OBJECTIVE

In view of recent data regarding the multiple roles of Nrf2 in the thyroid, this review summarizes the current bibliography on natural compounds that can have an effect on thyroid gland physiology and pathophysiology, and it discusses the potential implication of the Nrf2 system in the respective mechanisms.

METHODS & RESULTS

Literature searches for articles from 1950 to 2018 were performed in PubMed and Google Scholar using relevant keywords about phytochemicals, Nrf2 and thyroid. Natural substances were categorized into phenolic compounds, sulfur-containing compounds, quinones, terpenoids, or under the general category of plant extracts. For individual compounds in each category, respective data were summarized, as derived from in vitro (cell lines), preclinical (animal models) and clinical studies. The main emerging themes were as follows: phenolic compounds often showed potential to affect the production of thyroid hormones; sulfur-containing compounds impacted the pathogenesis of goiter and the proliferation of thyroid cancer cells; while quinones and terpenoids modified Nrf2 signaling in thyroid cell lines.

CONCLUSION

Natural compounds that modify the activity of the Nrf2 pathway should be evaluated carefully, not only for their potential to be used as therapeutic agents for thyroid disorders, but also for their thyroidal safety when used for the prevention and treatment of non-thyroidal diseases.

Herbal Active Ingredients: An Emerging Potential for the Prevention and Treatment of Papillary Thyroid Carcinoma

Papillary thyroid carcinoma (PTC) is the most common subtype of differentiated thyroid cancers in Asian coastal cities, where the patients have increased risk of potentially high or excessive iodine intake. Given the high metastasis and recurrence of patients with BRAF^V600E mutation, the mortality rate of thyroid cancer has recently shown an upward trend. A variety of therapies, including surgery, radiotherapy, and chemotherapy, have been used to treat thyroid cancer, but these therapies still have limitations, including postoperative complications, drug resistance, poor efficacy, or serious side effects. Recent studies have shown the potential of active ingredients derived from herbal medicine in inhibiting PTC via various cell signaling pathways. Some plant-derived compounds, such as apigenin, genistein, and curcumin, are also known to prevent and treat PTC. This article summarizes the recent advances in the structure-functional impact of anti-PTC active ingredients and their effects on PTC cells and tumor microenvironments with an emphasis on their challenges from basic research to clinical practice.

Role of diets and exercise in ameliorating obesity-related hepatic steatosis: Insights at the microRNA-dependent thyroid hormone synthesis and action

AIMS

The present study was designed to compare the effects of a low-fat diet (LF), calorie restriction (CR), quercetin (Que) and exercise (Ex) on hepatic steatosis in a high-fat (HF) diet-induced obesity prone (OP) model in the perspective of microRNA (miR)-dependent thyroid hormone (TH) synthesis and action.

MAIN METHODS

Male C57BL/6J mice were administered a HF diet for 10 weeks to induce OP phenotype and then divided into 5 groups, HF diet (OP-HF), LF diet (OP-LF), 70% CR (OP-CR), 0.05% Que (OP-Que) and a treadmill exercise regimen (OP-Ex); one additional group fed LF diet served as control (LF). 7 weeks later, serum indexes, metabolic alterations, redox status and histological appearance in the thyroid and liver, and TH related miRs with their targets expressions were determined.

KEY FINDINGS

No significance on T3 levels was observed among the six groups. LF, CR, Que and Ex significantly ameliorated HF-induced hepatic steatosis to varying degrees, inhibited T4 production via differentially elevating miR-339, miR-383 and miR-146b to decrease NIS expression and regulating miR-200a/Nrf2 to maintain redox status in the thyroid. Furthermore, these four interventions differentially and significantly decreased miR-383 and miR-146b to elevate TRb and DIO1 expression, and subsequent TH responsive lipid metabolism genes regulation. Among them, the effects of CR on hepatic steatosis were the most prominent.

SIGNIFICANCE

Our data indicated that amelioration of hepatic steatosis by LF, CR, Que and Ex resulted in many shared, but also many differential changes in the miR-dependent TH production and action.

Genome-wide localization of the polyphenol quercetin in human monocytes

BACKGROUND

Quercetin is a polyphenol of great interest given its antioxidant activity and involvement in the immune response. Although quercetin has been well studied at the molecular level as a gene regulator and an activator of specific cellular pathways, not much attention has been given to its mechanism of action at the genome-wide level. The present study aims to characterize quercetin's interaction with cellular DNA and to show its subsequent effect on downstream transcription.

RESULTS

Two massive parallel DNA-sequencing technologies were used: Chem-seq and RNA-seq. We demonstrate that upon binding to DNA or genome-associated proteins, quercetin acts as a cis-regulatory transcription factor for the expression of genes that are involved in the cell cycle, differentiation and development.

CONCLUSIONS

Such findings could provide new and important insights into the mechanisms by which the dietary polyphenol quercetin influences cellular functions.

The Flavonoid Quercetin Induces AP-1 Activation in FRTL-5 Thyroid Cells

Previous studies have shown that quercetin inhibits thyroid function both in vitro and in vivo. An attempt to evaluate the effect of quercetin at the promoter level of the thyroid-specific genes led to the observation that this compound induces the basal activity of the reporter vector. Therefore, the action of quercetin has been evaluated on the basal activity of several reporter vectors: The PGL3 basic, promoter and control vectors from Promega, and a pSV-based chloramphenicol acetyltransferase (CAT) reporter vector. In the Fisher Rat Thyroid cell Line FRTL-5 thyroid cells transiently transfected, quercetin 10 μM increased the basal activity of all the reporter vectors evaluated, although the degree of the effect was significantly different among them. The analysis of the difference among the regulatory regions of these vectors identified the activator protein 1 (AP-1) binding site as one of the potential sites involved in the quercetin effect. Electromobility shift assay experiments showed that the treatment with quercetin induced the binding of a protein complex to an oligonucleotide containing the AP-1 consensus binding site. This is the first study showing an effect of quercetin on AP-1 activity in thyroid cells. Further studies are in progress to understand the role of AP-1 activation in the effects of quercetin on thyroid function.

Rutin Scavenges Reactive Oxygen Species, Inactivates 5'-Adenosine Monophosphate-Activated Protein Kinase, and Increases Sodium-Iodide Symporter Expression in Thyroid PCCL3 Cells

BACKGROUND

Thyroid iodide uptake, mediated by the sodium-iodide symporter (NIS), is essential for thyroid hormone synthesis and also for treatment of thyroid diseases, such as thyroid cancer, through radioiodine therapy. Therefore, compounds able to increase thyroid iodide uptake could be clinically useful, and it is of great importance to unravel the mechanisms underlying such an effect. It has been shown previously that the flavonoid rutin increases thyroid radioiodide uptake in vivo in rats. This study aimed to investigate the mechanisms involved in the stimulatory effect of rutin on iodide uptake.

METHODS

This study evaluated iodide uptake, NIS expression and its subcellular distribution, iodide efflux, reactive oxygen species levels, and the intracellular pathways involved in NIS regulation in a rat thyroid PCCL3 cell line treated with rutin.

RESULTS

Similar to previous results found in vivo, rutin increased radioiodide uptake in PCCL3 cells, which was accompanied by increased NIS expression (at both the mRNA and protein levels) and a reduction of radioiodide efflux. Moreover, the results suggest that rutin could regulate NIS subcellular distribution, leading to higher levels of NIS at the cell membrane. In addition, rutin decreased the levels of intracellular reactive oxygen species and phospho-5'-adenosine monophosphate-activated protein kinase.

CONCLUSIONS

The flavonoid rutin seems to be an important stimulator of radioiodide uptake, acting at multiple levels, an effect that can be due to decreased oxidative stress, reduced 5'-adenosine monophosphate-activated protein kinase activation, or both. Since thyroid iodide uptake is crucial for effective radioiodine therapy, the results suggest that rutin could be useful as an adjuvant in radioiodine therapy.

Safety Aspects of the Use of Quercetin as a Dietary Supplement

The flavonoid quercetin is frequently found in low amounts as a secondary plant metabolite in fruits and vegetables. Isolated quercetin is also marketed as a dietary supplement, mostly as the free quercetin aglycone, and frequently in daily doses of up to 1000 mg d^-1 exceeding usual dietary intake levels. The present review is dedicated to safety aspects of isolated quercetin used as single compound in dietary supplements. Among the numerous published human intervention studies, adverse effects following supplemental quercetin intake have been rarely reported and any such effects were mild in nature. Published adequate scientific data for safety assessment in regard to the long-term use (>12 weeks) of high supplemental quercetin doses (≥1000 mg) are currently not available. Based on animal studies involving oral quercetin application some possible critical safety aspects could be identified such as the potential of quercetin to enhance nephrotoxic effects in the predamaged kidney or to promote tumor development especially in estrogen-dependent cancer. Furthermore, animal and human studies with single time or short-term supplemental quercetin application revealed interactions between quercetin and certain drugs leading to altered drug bioavailability. Based on these results, some potential risk groups are discussed in the present review.

Epigenetic modifications of gene expression by lifestyle and environment

Epigenetics oftenly described as the heritable changes in gene expression independent of changes in DNA sequence. Various environmental factors such as nutrition-dietary components, lifestyle, exercise, physical activity, toxins, and other contributing factors remodel the genome either in a constructive or detrimental way. Since epigenetic changes are reversible and nutrition is one of the many epigenetic regulators that modify gene expression without changing the DNA sequence, dietary nutrients and bioactive food components contribute to epigenetic phenomena either by directly suppressing DNA methylation or histone catalyzing enzymes or by changing the availability of substrates required for enzymatic reactions. Diets that contain catechol-dominant polyphenols are reported to suppress enzyme activity and activate epigenetically silenced genes. Furthermore, several dietary nutrients play a crucial role in one-carbon metabolism including folate, cobalamin, riboflavin, pyridoxine, and methionine by directly affecting S-adenosyl-L-methionine. Soy polyphenols block DNA methyltransferases and histone deacetylases to reverse aberrant CpG island methylation. Organosulfur rich compounds such as the sulforaphane found in broccoli appear to normalize DNA methylation and activate miR-140 expression, which represses SOX9 and ALDH1 and decreases tumor growth. The purpose of this short communication is to overview the epigenetic regulatory mechanisms of diet and other environmental factors. We discuss the epigenetic contributions of dietary components with a particular focus on nutritional polyphenols and flavonoids as epigenetic mediators that modify epigenetic tags and control gene expression. These mechanisms provide new insights to better understand the influence of dietary nutrients on epigenetic modifications and gene expression.

Design, synthesis and α-amylase inhibitory activity of novel chromone derivatives

Quercetin is one of the naturally occurring polyphenol flavonoid predominantly known for antidiabetic activity. In the present study, by considering the structural requirements, twenty two novel chromone derivatives (5-26) as α-amylase inhibitor were designed and subsequently in silico evaluated for drug likeness behavior. Designed compounds were synthesized, characterized by spectral analysis and finally evaluated for the inhibition of α-amylase activity by in vitro assay. Tested compounds exhibited significant to weak activity with IC₅₀ range of 12-125µM. Among the tested compounds, analogues 5, 8, 12, 13, 15, 17 and 22 exhibited significant human α-amylase inhibitory activity with IC₅₀ values <25µM, which can be further explored as anti-hyperglycemic agents. Putative binding mode of the significant and least active α-amylase inhibitors with the target enzyme was also explored by the docking studies.

Resveratrol has anti-thyroid effects both in vitro and in vivo

Resveratrol is a natural polyphenol with antioxidant, anti-inflammatory, and antiproliferative properties. We have shown previously that resveratrol decreases sodium/iodide symporter expression and iodide uptake in thyrocytes, both in vitro and in vivo. In the present study, we further investigated the effects of resveratrol, with evaluation of the expression of additional thyroid-specific genes in the FRTL-5 rat thyroid cell line: thyroglobulin, thyroid peroxidase, TSH receptor, Nkx2-1, Foxe1 and Pax8. We observed decreased expression of these genes in FRTL-5 cells treated with 10 μM resveratrol. The effects of resveratrol was further evaluated in vivo using Sprague-Dawley rats treated with resveratrol 25 mg/kg body weight intraperitoneally, for 60 days. No clinical signs of hypothyroidism were seen, although the treated rats showed significant increase in thyroid size. Serum TSH and thyroid hormone levels were in the normal range, with significantly higher TSH seen in resveratrol-treated rats, compared with control rats. Histological and immunohistochemical analyses confirmed increased proliferative activity in the thyroid from resveratrol-treated rats. These data suggest that resveratrol acts as a thyroid disruptor and a goitrogen, which indicates the need for caution as a supplement and for therapeutic uses.

Flavonoids, Thyroid Iodide Uptake and Thyroid Cancer-A Review

Thyroid cancer is the most common malignant tumor of the endocrine system and the incidence has been increasing in recent years. In a great part of the differentiated carcinomas, thyrocytes are capable of uptaking iodide. In these cases, the main therapeutic approach includes thyroidectomy followed by ablative therapy with radioiodine. However, in part of the patients, the capacity to concentrate iodide is lost due to down-regulation of the sodium-iodide symporter (NIS), the protein responsible for transporting iodide into the thyrocytes. Thus, therapy with radioiodide becomes ineffective, limiting therapeutic options and reducing the life expectancy of the patient. Excessive ingestion of some flavonoids has been associated with thyroid dysfunction and goiter. Nevertheless, studies have shown that some flavonoids can be beneficial for thyroid cancer, by reducing cell proliferation and increasing cell death, besides increasing NIS mRNA levels and iodide uptake. Recent data show that the flavonoids apingenin and rutin are capable of increasing NIS function and expression in vivo. Herein we review literature data regarding the effect of flavonoids on thyroid cancer, besides the effect of these compounds on the expression and function of the sodium-iodide symporter. We will also discuss the possibility of using flavonoids as adjuvants for therapy of thyroid cancer.

Resveratrol inhibits sodium/iodide symporter gene expression and function in rat thyroid cells

Resveratrol is a polyphenol found in grapes and berries that has antioxidant, antiproliferative and anti-inflammatory properties. For these reasons, it is available as a dietary supplement, and it is under investigation in several clinical trials. Few data are available regarding the effects of resveratrol on thyroid function. A previous study showed that resveratrol transiently increases iodide influx in FRTL-5 rat thyroid cells. Indeed, this increase arises after short treatment times (6–12 h), and no further effects are seen after 24 h. The aim of the present study was to investigate the effects of resveratrol on iodide uptake and sodium/iodide symporter expression in thyroid cells after longer times of treatment. For this purpose, the effects of resveratrol were evaluated both in vitro and in vivo using the rat thyroid FRTL-5 cell line and Sprague-Dawley rats, respectively. In FRTL-5 cells, resveratrol decreased the sodium/iodide symporter RNA and protein expression as a function of time. Furthermore, resveratrol decreased cellular iodide uptake after 48 h of treatment. The inhibitory effect of resveratrol on iodide uptake was confirmed in vivo in Sprague-Dawley rats. This study demonstrates that with longer-term treatment, resveratrol is an inhibitor of sodium/iodide symporter gene expression and function in the thyroid. These data suggest that resveratrol can act as a thyroid disruptor, which indicates the need for caution as a supplement and in therapeutic use.

Anti-cancer potential of flavonoids: recent trends and future perspectives

Cancer is a major public health concern in both developed and developing countries. Several plant-derived anti-cancer agents including taxol, vinblastine, vincristine, the campothecin derivatives, topotecan, irinotecan and etoposide are in clinical use all over the world. Other promising anti-cancer agents include flavopiridol, roscovitine, combretastatin A-4, betulinic acid and silvestrol. From this list one can well imagine the predominance of polyphenols, flavonoids and their synthetic analogs in the treatment of ovarian, breast, cervical, pancreatic and prostate cancer. Flavonoids present in human diet comprise many polyphenolic secondary metabolites with broad-spectrum pharmacological activities including their potential role as anti-cancer agents. A positive correlation between flavonoids-rich diet (from vegetables and fruits) and lower risk of colon, prostate and breast cancers lead to a question that whether flavonoids mediate the protective effects as chemopreventive agents or can interact with different genes and proteins to play role in chemotherapy. The current review emphasizes onto the therapeutic potential of flavonoids and their synthetic analogs as anti-cancer agents by providing new insights into the factors, regulation and molecular mechanisms along with their significant protein interactions.

Anticarcinogenic effect of quercetin by inhibition of insulin-like growth factor (IGF)-1 signaling in mouse skin cancer

It has been shown that dysregulation of IGF-1 signaling is associated with tumor incidence and progression, whereas blockade of the signaling can effectively inhibit carcinogenesis. Although several mechanisms of anticancer activity of quercetin were proposed, molecular targets of quercetin have not been identified yet. Hence, we assessed the effect of quercetin on IGF-1 signaling inhibition in BK5.IGF-1 transgenic (Tg) mice, which over-expresses IGF-1 in the skin epidermis. A quercetin diet (0.02% wt/wt) for 20 weeks remarkably delayed the incidence of skin tumor by 2 weeks and reduced tumor multiplicity by 35% in a 7,12-dimethylbenz(a)anthracene (DMBA)-tetradecanoyl phorbol-13-acetate (TPA) two stage mouse skin carcinogenesis protocol. Moreover, skin hyperplasia in Tg mice was significantly inhibited by a quercetin supplementation. Further analysis of the MT1/2 skin papilloma cell line showed that a quercetin treatment dose dependently suppressed IGF-1 induced phosphorylation of the IGF-1 receptor (IGF-1R), insulin receptor substrate (IRS)-1, Akt and S6K; however, had no effect on the phosphorylation of PTEN. Additionally, the quercetin treatment inhibited IGF-1 stimulated cell proliferation in a dose dependent manner. Taken together, these data suggest that quercetin has a potent anticancer activity through the inhibition of IGF-1 signaling.

Sterol regulatory element-binding proteins are regulators of the NIS gene in thyroid cells

The uptake of iodide into the thyroid, an essential step in thyroid hormone synthesis, is an active process mediated by the sodium-iodide symporter (NIS). Despite its strong dependence on TSH, the master regulator of the thyroid, the NIS gene was also reported to be regulated by non-TSH signaling pathways. In the present study we provide evidence that the rat NIS gene is subject to regulation by sterol regulatory element-binding proteins (SREBPs), which were initially identified as master transcriptional regulators of lipid biosynthesis and uptake. Studies in FRTL-5 thyrocytes revealed that TSH stimulates expression and maturation of SREBPs and expression of classical SREBP target genes involved in lipid biosynthesis and uptake. Almost identical effects were observed when the cAMP agonist forskolin was used instead of TSH. In TSH receptor-deficient mice, in which TSH/cAMP-dependent gene regulation is blocked, the expression of SREBP isoforms in the thyroid was markedly reduced when compared with wild-type mice. Sterol-mediated inhibition of SREBP maturation and/or RNA interference-mediated knockdown of SREBPs reduced expression of NIS and NIS-specific iodide uptake in FRTL-5 cells. Conversely, overexpression of active SREBPs caused a strong activation of the 5'-flanking region of the rat NIS gene mediated by binding to a functional SREBP binding site located in the 5'-untranslated region of the rat NIS gene. These findings show that TSH acts as a regulator of SREBP expression and maturation in thyroid epithelial cells and that SREBPs are novel transcriptional regulators of NIS.

Impact of flavonoids on thyroid function

Flavonoids are polyphenolic compounds of natural occurrence produced by plants that are largely consumed both for therapeutic purposes and as food. Experimental data have shown that many flavonoids could inhibit thyroperoxidase activity, decreasing thyroid hormones levels thus increasing TSH and causing goiter. In humans, infants fed with soy formula have been shown to develop goiter. However, in post-menopausal women soy intake did not affect thyroid function. In thyroid tumor cell line, flavonoids were shown to inhibit cell growth, but they can also decrease radioiodine uptake, that could reduce the efficacy of radioiodine therapy. Flavonoids could also affect the availability of thyroid hormones to target tissues, by inhibiting deiodinase activity or displacing T4 from transthyretin. Thus, flavonoids have been shown to interfere with many aspects of the thyroid hormones synthesis and availability in in vivo and in vitro models. In the present article, we review and synthesize the literature on the effects of flavonoids on thyroid and discuss the possible relevance of these effects for humans.

Regulation of major histocompatibility complex gene expression in thyroid epithelial cells by methimazole and phenylmethimazole

Increased expression of major histocompatibility complex (MHC) class-I genes and aberrant expression of MHC class-II genes in thyroid epithelial cells (TECs) are associated with autoimmune thyroid diseases. Previous studies have shown that methimazole (MMI) reduces MHC class-I expression and inhibits interferon-gamma (IFN-gamma or IFNG as listed in the MGI Database)-induced expression of the MHC class-II genes in TECs. The action of MMI on the MHC class-I genes is transcriptional, but its mechanism has not been investigated previously. In the present study, we show that in Fisher rat thyroid cell line 5 cells, the ability of MMI and its novel derivative phenylmethimazole (C10) to decrease MHC class-I promoter activity is similar to TSH/cAMP suppression of MHC class-I and TSH receptor genes, and involves a 39 bp silencer containing a cAMP response element (CRE)-like site. Furthermore, we show that C10 decreases MHC class-I gene expression to a greater extent than MMI and at 10- to 50-fold lower concentrations. C10 also reduces the IFN-gamma-induced increase in the expression of MHC class-I and MHC class-II genes more effectively than MMI. Finally, we show that in comparison to MMI, C10 is a better inhibitor of specific protein-DNA complexes that are formed with a CRE-like element on the MHC class-II promoter. These data support the conclusion that the immunosuppressive mechanism by which MMI and C10 inhibit MHC gene expression mimics 'normal' hormonal suppression by TSH/cAMP.

Stimulus-specific regulation of CD63 and CD203c membrane expression in human basophils by the flavonoid quercetin

BACKGROUND

Flavonoids, such as quercetin, were reported to inhibit histamine release and cytokine production by basophils, but there is no evidence describing their action on membrane markers and intracellular biochemical pathways.

OBJECTIVE

The aim of the study was to examine the effect of several quercetin doses on an in vitro human basophil activation system that evaluates up-regulation of membrane markers in response to agonists.

METHODS

Leukocyte buffy coats from K(2)-EDTA anti-coagulated blood were treated with different concentrations of quercetin and triggered with anti-IgE ("allergy model") and with N-formyl-Met-Leu-Phe (fMLP) ("inflammation model"). Basophils were captured as CD123(bright)/HLA-DR(non-expressing) cells in a flow cytometry analysis and fluorescence values of CD63-FITC, CD203c-PE and CD123-PECy5 were used to produce dose response curves.

RESULTS

Quercetin at a dose of 10 microg/ml strongly inhibited CD63 and CD203c membrane up-regulation triggered by both agonists, but it neither affected cell viability nor changed the expression of the phenotypic marker CD123. The anti-IgE model appeared highly sensitive to the effect of quercetin: a dose as low as 0.01 microg/ml was able to significantly decrease CD63 and CD203c membrane expression. In the fMLP model the dose response was different: quercetin doses from 0.01 to 0.1 microg/ml significantly increased up-regulation of membrane markers, achieving the highest effect with CD63.

CONCLUSION

Very low doses of quercetin, within the pharmacological range, inhibit IgE-mediated membrane marker's up-regulation but prime the response to the chemotactic peptide fMLP; this stimulus specificity may have implications on the possible therapeutic action of the flavonoid in different pathologies.