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6-Iodolactone, key mediator of antitumoral properties of iodine
Abstract
An iodinated derivative of arachidonic acid, 5-hydroxy-6-iodo-8,11,14-eicosatrienoic acid, δ-lactone (6-IL) has been implicated as a possible intermediate in the autoregulation of the thyroid gland by iodine. In addition to antiproliferative and apoptotic effects observed in thyrocytes, this iodolipid could also exert similar actions in cells derived from extrathyroidal tissues like mammary gland, prostate, colon, or the nervous system. In mammary cancer (solid tumors or tumor cell lines), 6-IL has been detected after molecular iodine (I2) supplement, and is a potent activator of peroxisome proliferator-activated receptor type gamma (PPARγ). These observations led us to propose I2 supplement as a novel coadjutant therapy which, by inducing differentiation mechanisms, decreases tumor progression and prevents chemoresistance. Some kinds of tumoral cells, in contrast to normal cells, contain high concentrations of arachidonic acid, making the I2 supplement a potential “magic bullet” that enables local, specific production of 6-IL, which then exerts antineoplastic actions with minimal deleterious effects on normal tissues.
... Among these, I 2 can react with arachidonic acid generating the iodolipid called 6-iodolactone (6-IL), which has been confirmed to be an agonist of the peroxisome proliferator-activated receptor type gamma (PPARγ). The activation of these receptors decreases the expression of specific markers associated with invasiveness and epithelial-mesenchymal transition [30][31][32][33][34]. Previous studies from our laboratory showed that I 2 impairs chemo-resistance mechanisms, enhances doxorubicin retention and induces downregulation of chemo-resistance markers p21, Bcl-2 and MDR-1 in chemo-resistant MCF-7 cells [35]. ...
... It has been proposed that the antineoplastic effect of the molecular iodine is mediated by activation of PPARγ receptors by 6-iodolactone, in turn causing an increase in these receptors after treatment [33,34]. Monolayer and cervospheres of HeLa cells were incubated with 200 μM of I 2 for 24 h, resulting in a significant increase in PPAR gamma proteins compared to their untreated counterparts (Fig. 6a, b). ...
... Several strategies have been used to inhibit all these properties but they have not been enough, so the chemo-resistance of CSC requires new approaches aimed at eliminating these highly tumorigenic cells. Molecular iodine has been studied in several cancer cell lines showing its ability to inhibit proliferation, chemo-resistance, and apoptotic effects [30][31][32][33][34][35], however there are no reports on its effect on cervical cancer cell lines nor on cultures enriched with cancer stem-like cells. HeLa and SiHa are the most representative cervical cancer cell lines and in this study, we used cultures grown under non adherent conditions (cervospheres) where we obtained a higher proportion of CSCC-like cells compared to traditional monolayer cultures, allowing us to study the effect of I 2 on CSC derived from cervical cancer cell lines. ...
Background:
Cancer stem cells (CSC) are characterized by deregulated self-renewal, tumorigenicity, metastatic potential, aberrant stemness signaling pathways, resistance to conventional therapy, and the ability to give rise to a progeny of proliferating cells that constitute the bulk of tumors. Targeting CSC will provide novel treatments for cancer. Different investigations have focused on developing complementary approaches that involve natural compounds that decrease chemo-resistance and reduce the side effects of conventional therapies. Since, it has been reported that molecular iodine (I2) exhibits antineoplastic effects and decreases tumor progression in some cancer models, we evaluated the potential effect of I2 on cell cultures enriched in cervical cancer stem-like cells.
Methods:
HeLa and SiHa cervical cancer cells were treated with 200uM I2 for 24 h. After time, cells were cultured in CSC-conditioned medium (cervospheres) and viability assays were performed. Following, tumorigenic capabilities in cervospheres treated with I2 were evaluated in NOD/SCID mice. HeLa monolayer cells untreated and their respective cervosphere cells treated or untreated with 200 μM of I2 for 24 h were xenotransplanted subcutaneously at different amounts and mice were monitored for at least 2 months.
Results:
In the present study, monolayer and CSC-enriched cultures (cervospheres) from cervical cancer-derived cell lines, HeLa and SiHa, showed that 200uM I2 supplementation inhibits proliferation of both and decreased their tumorigenic capacity, in vivo. This antineoplastic effect of I2 was accompanied by diminished expression of stemness markers including CD49f, CK17, OCT-4, NANOG, SOX2, and KLF4, as well as increased expression and activation of PPARγ receptors.
Conclusions:
All this data led us to suggest a clinical potential use of I2 for targeting CSC and improve current treatments against cervical cancer.
... In the thyroid gland, intracellular iodine concentration plays an important role in redox balance by modulating hydrogen peroxide generation [8,9] and thyroid iodine deficiency induced intracellular production of reactive oxygen species (ROS) that stabilizes HIF-1α protein and then the expression and secretion of vascular epithelial growth factor (VEGF) for novel blood vessels [10]. It has been proposed that in thyroid and extrathyroid tissues, iodolipids are the mediators of iodine properties, through PPAR-gamma activation [11][12][13][14][15][16]. ...
... In extrathyroid tissues, iodine plays an important role in the redox balance, either by free radical competition or indirectly inducing antioxidant enzymes, mediated by PPAR-gamma transcription factor activated by iodolactones. This ligand has been reported as iodine mediator [12,13,15,16,20,21]. Adequate iodine supplement is important for normal pregnancy, as iodine deficiency has been associated with oxidative stress and pregnant complications such as preeclampsia [22][23][24]. ...
... GCM-1 a master regulator of differentiation is downregulated in the placentas of woman with preeclampsia [28]. Furthermore, previous studies have showed that iodine effects are mediated by PPAR-gamma activation by iodolactones [14][15][16]. All of these suggest that iodine is important on the maintenance of proliferation/differentiation balance in the placenta. ...
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, supplementinglow 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.
... It is known that beside thyroid, also gastric, colon and breast tissues has capacity to uptake Iand tumorigenesis may reduce or eliminate this process. There are in vitro and in vivo studies, according to which molecular iodine (I 2 ), rather than iodide (I -), is responsible for protective effects against cancer [46]. Research in thyroid and breast cancer showed that to induce apoptosis process, it is necessary to enzymatically oxidized Ito I 2 . ...
... Aranda et al. [9] indicated that cancer cells have the ability to reactivate proliferation after discontinuation of iodine treatment, which confirms its protective effect against cancer progression. Iodine may influence apoptosis presumably directly through oxidant/antioxidant activity (mitochondrial pathway) or indirectly through iodolipid formation and activation of PPAR-γ (peroxisome proliferator-activated receptor) [9,46]. ...
Considering the growing number of cancer cases around the world, natural products from
the diet that exhibit potential antitumor properties are of interest. Our previous research demonstrated that fortification with iodine compounds is an effective way to improve the antioxidant potential of lettuce. The purpose of the present study was to evaluate the effect of iodine-biofortified lettuce on antitumor properties in human gastrointestinal cancer cell lines, gastric AGS and colon HT-29. Our results showed that extracts from iodine-biofortified lettuce reduce the viability and proliferation of gastric and colon cancer cells. The extracts mediated cell cycle arrest which was accompanied by inactivation of anti-apoptotic Bcl-2 and activation of caspases, as assessed by flow cytometry.
However, extracts from lettuce fortified with organic forms of iodine acted more effectively than extracts from control and KIO3-enriched plants. Using quantitative PCR, we detected the increase in pro-apoptotic genes BAD, BAX and BID in AGS cells whereas up-regulation of cell cycle progression inhibitor CDKN2A and downregulation of pro-proliferative MDM2 in HT-29 cells. Interestingly, lettuce extracts led to down-regulation of pro-survival AKT1 and protooncogenic MDM2, which was consistent for extracts of lettuce fortified with organic form of iodine, 5-ISA, in both cell lines. MDM2 downregulation in HT-29 colon cancer cells was associated with RB1 upregulation upon
5-ISA-fortified lettuce extracts, which provides a link to the epigenetic regulation of tumor suppressor genes by RB/MDM2 pathway. Indeed, SEMA3A tumor suppressor gene was hypomethylated and upregulated in HT-29 cells treated with 5-ISA-fortified lettuce. Control lettuce exerted similar effects on RB/MDM2 pathway and SEMA3A epigenetic activation in HT-29 cells. Our findings suggest that lettuce as well as lettuce fortified with organic form of iodine, 5-ISA, may exert epigenetic anti-cancer effects that can be cancer type-specific.
... This organic form of iodine may interfere with pathways leading to reduced cells viability. It is indicated, that iodine treatments inhibit cell proliferation by generating iodo-lipids including 6-iodo-5-hydroxy-8,11,14-eicosatrienoic acid (an iodinated arachidonic acid) and iodohexadecanal [33,34]. These compounds have been detected after iodine (I 2 ) supplementation, and it is presumed that they may be potent activators of peroxisome proliferator-activated receptor type gamma (PPARγ) [35]. ...
... XIAP is a direct inhibitor of caspase activity [41], while increased expression of BAG3 in cancers is linked to the maintenance of cell survival, treatment resistance, and increased metastasis [42]. Our results are consistent with the reports of other authors, (i.e. on prostate and breast cancer cells), which show the induction of mitochondrial apoptotic pathway by a direct antioxidant/oxidant mitochondrial action of iodide (I − ) and iodine (I 2 ) [35,43] or indirect formation of iodo-lipids [33,34]. In the MCF-7 breast cancer cell line I 2 was taken up by a facilitated diffusion system and covalently bound to lipids that, in turn, inhibited proliferation. ...
Although iodization of salt is the most common method used to obtain iodine-enriched food, iodine deficiency disorders are still a global health problem and profoundly affect the quality of human life. Iodine is required for the synthesis of thyroid hormones, which are crucial regulators of human metabolism, cell growth, proliferation, apoptosis and have been reported to be involved in carcinogenesis. In this study, for the first time, we evaluated the effect of iodine-biofortified lettuce on transcriptomic profile of Caco-2 cancer cell line by applying the Whole Human Genome Microarray assay. We showed 1326 differentially expressed Caco-2 transcripts after treatment with iodine-biofortified (BFL) and non-fortified (NFL) lettuce extracts. We analysed pathways, molecular functions, biological processes and protein classes based on comparison between BFL and NFL specific genes. Iodine, which was expected to act as a free ion (KI-NFL) or at least in part to be incorporated into lettuce macromolecules (BFL), differently regulated pathways of numerous transcription factors leading to different cellular effects. In this study we showed the inhibition of Caco-2 cells proliferation after treatment with BFL, but not potassium iodide (KI), and BFL-mediated induction of mitochondrial apoptosis and/or cell differentiation. Our results showed that iodine-biofortified plants can be effectively used by cells as an alternative source of this trace element. Moreover, the observed differences in action of both iodine sources may suggest a potential of BFL in cancer treatment.
... Background 6-Iodo-5-hydroxy-8,11,14-eicosatrienoic acid, δ-lactone (6-iodolactone or 6IL) is an iodinated arachidonic acid (AA) derivative and has been proposed to mediate the antitumoral effects of iodine [1][2][3]. Molecular iodine (I 2 ), but not iodide (I − ), exerts antineoplastic actions on diverse tissues (mammary, prostate and thyroid glands, and on melanoma, pancreas carcinoma and neuroblastoma cell lines), and various studies suggest that these effects can involve direct or indirect mechanisms [4][5][6][7][8]. In the direct effect, the oxidant/antioxidant property of I 2 can disrupt the mitochondrial membrane potential and trigger mitochondrion-mediated apoptosis [6,9]; on the other hand, the indirect path involves the generation of iodolipid intermediates, and there is evidence that 6IL could be one such intermediate. ...
... It has not yet been determined how I 2 reacts with cell components, but I 2 is known to bind covalently to proteins and lipids [5]. The iodination of fatty acids generates several derivatives, but those from arachidonic acid (AA), like 6IL, are especially relevant since endogenous 6IL has been detected [38,39], and it generates a range of biological effects [3]. ...
Molecular iodine (I 2 ) exhibits antiproliferative and apoptotic effects on in vivo and in vitro cancer models. These effects are thought to be mediated by an iodinated arachidonic acid derivative, 6-iodolactone (6IL), and one of the proposed mechanisms is that 6IL activates Peroxisome Proliferator-Activated Receptors type gamma (PPARG). These receptors have been implicated in the inhibition of carcinogenic processes, in addition to their classical role in maintaining lipid and glucose homeostasis. The aim of this study was to determine whether PPARG participates in the 6IL antiproliferative and apoptotic effects on the mammary cancer cell line MCF-7.
The 6IL/PPARG complex was inhibited by the PPARG antagonist GW9662, in both an endogenous and overexpressed (adenoviral vector infection) context, and stable PPARG-knockdown MCF-7 cells (RNA interference, confirmed with hydrolysis probes and Western blot), were used to corroborate the PPARG participation. 6IL effects on proliferation (measured by Trypan Blue exclusion) and apoptosis (phosphatidylserine identification by flow cytometer) were evaluated in conditions of chemical inhibition (GW9662) and silencing (RNA interference). A wound-healing assay was conducted on wild-type and stable PPARG-knockdown MCF-7 cells to evaluate the antimigrational effect of 6IL. Caspase-8 activity was evaluated to determine if the extrinsic pathway is involved in the effects of 6IL and I 2 treatment.
Antiproliferative and pro-apoptotic 6IL effects require the activation of PPARG. In addition, wound-healing assays show that 6IL is able to inhibit MCF-7 cell migration and that PPARG plays a role in this phenomenon. Finally, the data exclude the participation of the extrinsic apoptotic pathway in 6IL- and I 2 -induced apoptosis.
These results support the previously proposed mechanism, in which the I 2 effects are mediated by 6IL, and they provide further support for the use of I 2 as coadjuvant in breast cancer treatment.
... The antineoplastic effect of iodine is well documented [12,13], with studies showing the antineoplastic activity of povidoneiodine on various mesothelioma cell lines and the involvement of molecular iodine and its derivatives, like 6-iodolactone, in triggering apoptotic effects in cells. 6-iodolactone, a product of molecular iodine transformation, is known to activate apoptosis [14]. Another mechanism for iodine's antitumor activity may involve its effect on activating the immune response via the Th1 pathway [15]. ...
Iodine preparations are widely used in medicine as antiseptic agents. One of the new directions for the use of iodine is the prevention and therapy of certain tumor diseases, particularly breast cancer. The main mechanism of action is the induction of apoptosis. Iodine also has anti-inflammatory activity and affects the polarization of Th1/Th2 lymphocytes and M1/M2 macrophages. The newly developed iodine complex KC-144 includes both dextrin and polypeptides. In this case, lithium enhances the polarization of triiodide. We studied the acute toxicity and prophylactic activity on a model of benz(a)pyrene-induced (BaP) tumor in BALB/c mice. The average lethal dose (LD 50 ) of KC-144 when administered orally was more than 2500 mg/kg, classifying KC-144 as a low-toxicity substance. Intraperitoneal administration of benz(a)pyrene at a dose of 100 mg/kg for two weeks induces tumor development in mice. Oral administration of KC-144 at doses of 2.5 and 25 mg/kg for one week and throughout the entire treatment period increases the lifespan of BaP-induced mice.
... Among natural and synthetic unsaturated lactones, of particular interest is δ-lactone derived from 6-iodo-5-hydroxyicosa-8,11,14-trienoic acid (iodo-δ-lactone) [8,9]. Numerous studies have shown that the natural iodo-δ-lactone, which is an iodinated derivative of arachidonic acid, exhibits antitumor and antiproliferative activities, induces apoptosis in thyroid, mammary, and prostate gland tissues, large intestine cells, and nervous system of humans and animals, and participates in autoregulation of the thyroid gland [10][11][12][13][14][15]. ...
... It was demonstrated that molecular iodine (I 2 ) and IL-δ, but not iodide (I -), exert anti-neoplastic actions in different cancers [3,4]. The antineoplastic effect of iodine could be due to the synthesis of intracellular iodinated lipids [5]. Iodide can generate IL-δ only in cells expressing specific transporters and peroxidases as it must be oxidized to derive into iodinated compounds to induce cytotoxic effects [6][7][8]. ...
Introduction
Several studies have shown the antiproliferative effect of iodine and 5-hydroxy-6 iodo-eicosatrienoic delta lactone (IL-δ) on diverse tissues. It was demonstrated that molecular iodine (I2) and IL-δ, but not iodide (I⁻), exerts anti-neoplastic actions in different cancers. The underlying mechanism through which IL-δ inhibits tumor growth remains unclear. The aim of this study was to analyze the effect of IL-δ on tumor growth and angiogenesis in human HT29 colorectal cancer xenografts.
Methodology and Results
HT29 cells were injected subcutaneously into the flanks of nude mice and IL-δ was i.p. injected at a dose of 15 μg three days a week. IL-δ treatment in HT29 xenografts showed time-dependent inhibition of tumor growth, decrease of mitosis and PCNA expression (p<0.05), increase of P27 expression and Caspase 3 activity after 18 days of treatment (p<0.05). To assess tumor Microvessel Densities (MVD), CD31 staining by immunohistochemistry was analyzed. IL-δ treatment decreased MVD by 17% and 30% after 18 and 30 days respectively (p<0.05), as well as it decreased VEGF and VEGF-R2 expression (p<0.05). Additionally, our findings demonstrated that IL-δ increased VEGF-R1 and Ang-1 mRNA levels (p<0.01).
Conclusion
The antitumor efficacy of IL-δ in vivo involves inhibition of cell proliferation as well as induction of apoptosis. IL-δ has also anti-angiogenic effect associated with VEGF and VEGF-R2 downregulation followed by Ang-1 and VEGF-R1 increased expression. High levels of Ang-1 would contribute to mature vessel stabilization and maintenance while VEGF-R1 increase would produce anti-proliferative effect on endothelial cells.
... Moreover, I 2 exhibited indirect antitumor activity by generating 6-iodolactone (6-IL) through the iodination of arachidonic acid. This iodolipid is an active ligand of peroxisomal-activated receptor type gamma (PPARγ), inducing re-differentiation by inhibiting stem signaling and triggering apoptosis [15]. In addition, I 2 supplementation exerts effects on the immune system, acting as a direct genetic modifier [16] or as an attractor, increasing the amount of CD8+ lymphocytes within the tumor [17]. ...
Molecular iodine (I2) induces apoptotic, antiangiogenic, and antiproliferative effects in breast cancer cells. Little is known about its effects on the tumor immune microenvironment. We studied the effect of oral (5 mg/day) I2 supplementation alone (I2) or together with conventional chemotherapy (Cht+I2) on the immune component of breast cancer tumors from a previously published pilot study conducted in Mexico. RNA-seq, I2 and Cht+I2 samples showed significant increases in the expression of Th1 and Th17 pathways. Tumor immune composition determined by deconvolution analysis revealed significant increases in M0 macrophages and B lymphocytes in both I2 groups. Real-time RT-PCR showed that I2 tumors overexpress T-BET (p = 0.019) and interferon-gamma (IFNγ; p = 0.020) and silence tumor growth factor-beta (TGFβ; p = 0.049), whereas in Cht+I2 tumors, GATA3 is silenced (p = 0.014). Preliminary methylation analysis shows that I2 activates IFNγ gene promoter (by increasing its unmethylated form) and silences TGFβ in Cht+I2. In conclusion, our data showed that I2 supplements induce the activation of the immune response and that when combined with Cht, the Th1 pathways are stimulated. The molecular mechanisms involved in these responses are being analyzed, but preliminary data suggest that methylation/demethylation mechanisms could also participate.
... Moreover, I2 exhibited indirect antitumor activity by generating 6-iodolactone (6-IL) through the iodination of arachidonic acid. This iodolipid is an active ligand of peroxisomal-activated receptor type gamma (PPARγ), inducing re-differentiation by inhibiting stem signaling and triggering apoptosis [ 15 ]. In addition, I2 supplementation exerts effects on the immune system, acting as a direct genetic modifier [ 16 ] or as an attractor, increasing the amount of CD8+ lymphocytes within the tumor [ 17 ]. ...
Molecular iodine (I2) induces apoptotic, antiangiogenic, and antiproliferative effects in breast cancer cells. Little is known about its effects on the tumor immune microenvironment. We studied the effect of oral (5 mg/day) I2 supplementation alone (I2) or together with conventional chemotherapy (Cht+I2) on the im-mune component of breast cancer tumors from a previously published pilot study conducted in Mexico. RNA-seq, I2 and Cht+I2 samples showed significant increases in expression of Th1 and Th17 pathways. Tumor immune composition determined by deconvolution analysis revealed significant increases in M0 macrophages and B lymphocytes in both I2 groups. Real-time RT-PCR showed that I2 tumors overexpress T-BET (p = 0.019) and interferon-gamma (IFNγ; p = 0.020) and silence tumor growth factor-beta (TGFβ; p = 0.049); whereas in Cht+I2 tumors, GATA3 is silenced (p = 0.014). Preliminary methylation analysis shows that I2 activates IFNγ gene promoter (by increasing its unmethylated form) and silences TGFβ in Cht+I2. In conclusion, our data showed that I2 supplements induce the activation of the immune response and that when combined with Cht, the Th1 pathways are stimulated. The molecular mechanisms involved in these responses are being analyzed, but preliminary data suggest that methylation/demethylation mechanisms could also participate.
... Similar mechanism for halogen-containing agents was found during alkylation of free thiols and detection of alkylated proteins during evaluating the reactive thiol proteome 49 . The important role of iodine substituent in the mechanism of antitumor action can be also suggested by the induction of apoptosis in different cancer cell lines by 6-iodo-δ-lactone derived from arachidonic acid [50][51][52] . ...
For many years, studies focused on developing new natural or synthetic compounds with antineoplastic activity have attracted the attention of researchers. An interesting group of such compounds seem to be those with both lactone moiety and an aromatic ring which, in addition to antimicrobial or antiviral activity, also exhibit antitumor properties. The study shows antitumor activity of two enantiomeric trans isomers of 5-(1-iodoethyl)-4-(2',5'-dimethylphenyl)dihydrofuran-2-one. Our aim was to determine their antitumor activity manifested as an ability to induce apoptosis in selected canine cancer cell lines as well as to evaluate differences in their strength depending on the configuration of their stereogenic centers. The enantiomers (+)-(4R,5S,6R)-1 and (-)-(4S,5R,6S)-2 were found to induce classical caspase-dependent apoptosis through downregulation of the expression of anti-apoptotic proteins Bcl-xL and Bcl-2. Although the mechanism of apoptosis induction was the same for both enantiomers, they differed in their strength, as stronger antineoplastic activity in vitro was exhibited by isomer (+)-(4R,5S,6R)-1.
... Activation of caspase-3, which is a prominent marker of apoptosis, was also induced by IL-d. These results are consistent with previous reports which demonstrated that iodine and IL-d induce apoptosis in in vitro studies in several human cancer cell lines (Langer et al., 2003;Arroyo-Helguera et al., 2008;Rosner et al., 2010;Nava-Villalba and Aceves, 2014). ...
Introduction:
Iodine is not used only by the thyroid to synthesize thyroid hormones but also directly influences a number of thyroid parameters such as thyroid proliferation and function. Several iodinated lipids, biosynthesized by the thyroid, were postulated as intermediaries in the action of iodide. Among these, iodolactone (IL-δ) and 2-iodohexadecanal (2-IHDA) have shown to inhibit several thyroid parameters. The antiproliferative effect of IL-δ is not restricted to the thyroid gland. IL-δ exhibits anti-tumor properties in breast cancer, neuroblastoma, glioblastoma, melanoma and lung carcinoma cells suggesting that IL-δ could be used as a chemotherapeutic agent. Moreover in a colon cancer cell line (HT-29), IL-δ induced cell death, and this effect was mediated by reactive oxygen species (ROS) generation. The aim of the present study was to analyze the sources of reactive oxygen species induced by IL-δ and to explore the contribution of ROS induced by IL-δ on cell proliferation and apoptosis.
Methodology and results:
Cancer thyroid follicular (WRO) and papilar (TPC-1) cells lines were treated with IL-δ. Proliferation and apoptosis was analyzed. IL-δ caused a significant loss of cell viability on WRO and TPC-1 cells in a concentration dependent manner and induced apoptosis after 3 h of treatment. Furthermore, IL-δ (10 μM) increased ROS production (39% WRO and 20% TPC-1). The concomitant treatment of WRO and TPC-1 cells with Trolox or NAC plus IL-δ abrogated the augment of ROS induced by IL-δ exposure. Additionally Trolox and NAC reversed the effect of IL-δ on cell proliferation and apoptosis. Only in WRO cells IL-δ upregulates NADPH oxidase NOX4 expression, and siRNA targeted knock-down of NOX4 attenuates ROS production, apoptosis (p < 0.05) and the inhibitory effect of IL-δ on cell proliferation and PCNA expression (p < 0.05).
Conclusions:
The antiproliferative and pro-apoptotic effect of IL-δ is mediated by different mechanisms and pathway involving different sources of ROS generation depending on the cellular context.
A three-stage synthesis of 4 Z -unsaturated iodo-δ-lactones based on 5 Z ,9 Z -dienic acids was carried out using the intermolecular cross-cyclomagnesiation reaction of aliphatic and O-containing 1,2-dienes catalyzed by Cp2TiCl2 at the key stage with yields of 92-96% and selectivity 98-99%.
Previously, our research provided evidence that exposure of gastric and colon cancer cells to extracts from iodine-biofortified lettuce leads to a reduction of cell viability and proliferation through cell cycle arrest and upregulation of pro-apoptotic genes. The aim of the present study was to determine the potential cellular mechanisms of induction of cell death in human gastrointestinal cancer cell lines after treatment with iodine-biofortified lettuce. We demonstrated that extracts from lettuce enriched with iodine induce apoptosis in gastric AGS and colon HT-29 cancer cells and the mechanism of programmed cell death may be triggered and executed through different signaling pathways, depending on the type of cells. Western blot analysis revealed that iodine-fortified lettuce leads to cell death through the release of cytochrome c to the cytosolic fraction and activation of the primary drivers of apoptosis: caspase-3, caspase-7, and caspase-9. Furthermore, we have reported that apoptotic effects of lettuce extracts may be mediated by poly (ADP-ribose) polymerase (PARP) and activation of pro-apoptotic Bcl-2 family proteins such as Bad, Bax, and BID. We also observed mitochondrial dysfunction with the dissipation of the mitochondrial membrane potential in cells exposed to lettuce extracts. Taken together, these results indicate that the organic form of iodine such as 5-ISA and 3,5-diISA is an important factor in the activation of intrinsic mitochondrial apoptotic pathway in AGS and HT-29 cancer cells in a p53-independent manner.
Molecular iodine (I2) prevents oxidative stress and prostate hyperplasia induced by hyperandrogenism and reduces cell viability in prostate cancer cell lines. Here, we aimed to evaluate the protective effect of I2 and testosterone (T) on hyperestrogenism-induced prostate inflammation. Additionally, the effects of I2 and/or tumor necrosis factor (TNF) on cell viability and interleukin 6 (IL6) secretion were evaluated in a prostate cancer cell line (DU145). We also investigated whether the effects of I2 on viability are peroxisome proliferator-activated receptor gamma (PPARG)-dependent. Castrated (Cx) rats received pellets of either 17β estradiol (E2) or E2 and T and were treated with I2 (0.05%) in the drinking water for four weeks. The experimental groups were sham, Cx, Cx + E2, Cx + E2+I2, Cx + E2+T, and Cx + E2+T + I2. As expected, inflammation was triggered in the Cx + E2 group (high inflammation score; increase in TNF and transcriptional activity of RELA [nuclear factor-kappa B p65 subunit]), and this effect was diminished in the Cx + E2+T group (medium inflammation score and decrease in TNF). The lowest inflammation score (decrease of TNF and RELA and increase of PPARG) was obtained in the Cx + E2+T + I2 group. In DU145 cells, I2 (400 μM) and TNF (10 ng/ml) additively reduced cell viability, and I2 reduced the production of TNF-stimulated IL6. The PPARG antagonist (GW9662) did not inhibit the effects of I2 on the loss of cell viability. In summary, our data suggest that I2 and T exert a synergistic anti-inflammatory action on the normal prostate, and the interrelationship between I2 and TNF leads to anti-proliferative effects in DU145 cells. PPARG does not seem to participate in the I2-induced cell viability loss in the prostate.
Introducción. Los Sistemas de Retención Infantil (SRI) son
utilizados para proteger y restringir a niños que viajan en
vehículos automotores, y se diseñan de acuerdo con el
tamaño, peso y edad del menor. En caso de siniestro vial, los
niños resultan vulnerables a sufrir lesiones graves e incluso
morir, debido al nivel de desarrollo físico limitado. En México,
la siniestralidad vial representa la sexta causa de mortalidad
en menores de 14 años de edad. Objetivo. Identificar los municipios y describirlas
especificaciones de uso de l os SRI que incluyen los
Reglamentos de Vialidad y Tránsito en Nuevo León, además de
conocer el precio de los SRI.
Metodología. Este estudio es descriptivo y transversal,
además consiste en un análisis legislativo de los Reglamentos
de Vialidad y Tránsito de los municipios de Nuevo León.
También incluye una búsqueda de precios de SRI en
establecimientos comerciales. El análisis estadístico se realizó
por medio de porcentajes.
Resultados. De los 51 municipios en el estado de Nuevo León,
se encontraron disponibles 47 (92.1%), de los cuales sólo 42
(89.4%) contenían información relacionada con SRI. La edad
máxima de uso obligatorio en menores fue de 6 años (13
reglamentos), con un peso máximo para uso de SRI de 25 kg
en 12 reglamentos y una altura máxima de 95 cm (11
reglamentos ). Se revisaron ocho establecimientos
comerciales que ofertaban SRI, en los cuales se encontró que
el precio máximo frecuente osciló entre los 8,000
pesos. Conclusión. En materia de reglamentación acerca de SRI en
Nuevo León, es evidente la necesidad de mejorar y unificar los
reglamentos de vialidad y tránsito. El alto precio de SRI
pudiera ser motivo para no usarlo.
Each year, over 1.7 million women are diagnosed with breast cancer worldwide and about 35% of these diagnosed are expected to die from the disease. A significant barrier to improving treatment of breast cancer lies in our incomplete understanding of breast cancer initiation and metastasis. Regular use of molecular iodine has been shown to reduce the sensitivity of breast cells to the proliferative effects of estrogen, resulting in normalization of breast tissue.The aim of the current study was to evaluate the mechanisms of molecular iodine on two common breast cancer sub-types using well-established breast cancer cell lines. In order to study Luminal A and triple-negative breast cancer in vitro, MCF7 (cells from a luminal A subtype) and MDA-MB231 (cells from a triple-negative subtype), were treated with molecular iodine at various concentrations to measure proliferation and cell death. This was subsequently followed by gene expression analysis of key important molecular markers, which are primarily responsible for cell growth and apoptosis. Primary human mammary epithelial cells derived from healthy female donor were used as an internal control. Data from this study indicated that molecular iodine had potent inhibitory effects on cell growth and showed a dramatic increase in cell death in both breast cancer cell lines. Gene expression analysis using quantitative RT-PCR further confirmed that cell cycle genes controlling G1-S phase transition were largely up-regulated. Changes were not seen in Cyclin B expression levels, which further suggest that cells were arrested before entry into cell division. BCL-2, PPAR-α and PPAR-γ were also up-regulated along with down-regulation of Caspase 3, suggesting molecular iodine induced cell death through activation of a caspase-independent apoptosis pathway. Interestingly, mesenchymal-epithelial transition (MET) occurrence was noticed upon molecular iodine treatment as indicated by sharp increase of GATA3 and E-Cadherin and significant down-regulation of Vimentin in invasive MDA-MB231 cells. Our current study enables us to understand a molecular mechanism controlling tumor cell growth and demonstrates potent cellular effects of molecular iodine on breast cancer cell lines. These results also demonstrate promising effects of molecular iodine for regulation of breast cancer EMT differentiation, which is required for tumor initiation and metastasis. Further studies are underway to determine possible effects of molecular iodine in these breast cancer subtypes using in vitro 3D models.
Note: This abstract was not presented at the meeting.
Citation Format: Zack Xu, Xin Chen, Noymi Yam, Kin Chan, Usha Nagavarapu. Elucidating the mechanism of action of molecular iodine on breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2243. doi:10.1158/1538-7445.AM2017-2243
A robust body of information supports the notion that moderately high concentrations of iodine may reduce pathologies in several tissues that concentrate iodine. This paper reviews evidence showing iodine to be an antioxidant and apoptotic agent that may contribute to the differentiation
of normal mammary and prostate glands. In animal and human studies, molecular iodine (I2) supplements suppress the development and size of both benign and malignant neoplasias in these glands and significantly reduce cellular lipoperoxidation. Iodine, in addition to its incorporation into
thyroid hormones, is bound to antiproliferative iodolipids called iodolactones, which, in conjunction with peroxisome proliferatoractivated receptors, may play a role in controlling proliferative pathologies in mammary and prostate glands. These studies are in line with data demonstrating
that the high consumption of iodine by certain Asian populations such as in Japan (25 times more than in the Occident) correlates with a low incidence of benign and cancerous breast and prostate diseases. Based on our data we proposed that an I2 supplement should be considered as an adjuvant
in the treatment of pathologies in breast and prostate.
Many pharmaceuticals on the market suffer from two significant limitations to their activity: lack of specificity toward the pathological site and poor aqueous solubility. Both factors therefore require the application of a large total dose of a drug to achieve high local concentration, causing numerous off-target toxic effects. Consequently, the grand aim of targeted drug delivery - the often-referred "magic bullet"- promises to improve drug concentration at the target site and maximize therapeutic response. Nanomaterial drug delivery systems have been explored extensively in the recent years for just this purpose. In the field of medicine, nanocarriers (NCs) have the potential to improve the biodistribution and pharmacokinetic characteristics of drugs, thereby reducing side effects while improving the therapeutic effect of drugs. Many nanomaterials are exquisitely designed and possess potent properties, yet it is extremely important to note that a general understanding of the interaction of nanomaterials with biological systems is essential for any such model properties to be effective in vivo, since the body presents a host of biological 'barriers' that will be encountered drug NCs. This review offers a general overview of the different biological obstacles that a NC must negotiate before it can carry out its desired role as a medicinal agent. From this standpoint we suggest aspects that should be considered for the rational design of novel nanomaterials possessing physicochemical properties that are appropriate for therapeutic or theragnostic applications.
Background:
Seaweed is an important dietary component and a rich source of iodine in several chemical forms in Asian communities. Their high consumption of this element (25 times higher than in Western countries) has been associated with the low incidence of benign and cancerous breast and prostate disease in Japanese people.
Summary:
We review evidence showing that, in addition to being a component of the thyroid hormone, iodine can be an antioxidant as well as an antiproliferative and differentiation agent that helps to maintain the integrity of several organs with the ability to take up iodine. In animal and human studies, molecular iodine (I2) supplementation exerts a suppressive effect on the development and size of both benign and cancerous neoplasias. Investigations by several groups have demonstrated that these effects can be mediated by a variety of mechanisms and pathways, including direct actions, in which the oxidized iodine dissipates the mitochondrial membrane potential, thereby triggering mitochondrion-mediated apoptosis, and indirect effects through iodolipid formation and the activation of peroxisome proliferator-activated receptors type gamma, which, in turn, trigger apoptotic or differentiation pathways.
Conclusions:
We propose that the International Council for the Control of Iodine Deficient Disorders recommend that iodine intake be increased to at least 3 mg/day of I2 in specific pathologies to obtain the potential extrathyroidal benefits described in the present review.
Induction of differentiation and apoptosis in cancer cells through ligands of nuclear hormone receptors (NHRs) is a novel
and promising approach to cancer therapy. All-trans-retinoic acid (ATRA), an RA receptor-specific NHR ligand, is now used for selective cancers. The NHR, peroxisome proliferator-activated
receptor γ (PPARγ) is expressed in breast cancer cells. Activation of PPARγ through a synthetic ligand, troglitazone (TGZ),
and other PPARγ-activators cause inhibition of proliferation and lipid accumulation in cultured breast cancer cells. TGZ (10−5 M, 4 days) reversibly inhibits clonal growth of MCF7 breast cancer cells and the combination of TGZ (10−5 M) and ATRA (10−6 M, 4 days) synergistically and irreversibly inhibits growth and induces apoptosis of MCF7 cells, associated with a dramatic
decrease of their bcl-2 protein levels. Similar effects are noted with in vitro cultured breast cancer tissues from patients, but not with normal breast epithelial cells. The observed apoptosis mediated
by TGZ and ATRA may be related to the striking down-regulation of bcl-2, because forced over-expression of bcl-2 in MCF7 cells
cultured with TGZ and ATRA blocks their cell death. TGZ significantly inhibits MCF7 tumor growth in triple immunodeficient
mice. Combined administration of TGZ and ATRA causes prominent apoptosis and fibrosis of these tumors without toxic effects
on the mice. Taken together, this combination may provide a novel, nontoxic and selective therapy for human breast cancers.
The arachidonic acid pathway is important in the development and progression of numerous malignant diseases, including prostate cancer. To more fully evaluate the role of individual cyclooxygenases (COXs), lipoxygenases (LOXs) and their metabolites in prostate cancer, we measured mRNA and protein levels of COXs and LOXs and their arachidonate metabolites in androgen-dependent (LNCaP) and androgen-independent (PC-3 and DU145) prostate cancer cell lines, bone metastasis-derived MDA PCa 2a and MDA PCa 2b cell lines and their corresponding xenograft models, as well as core biopsy specimens of primary prostate cancer and nonneoplastic prostate tissue taken ex vivo after prostatectomy. Relatively high levels of COX-2 mRNA and its product PGE2 were observed only in PC-3 cells and their xenografts. By contrast, levels of the exogenous 12-LOX product 12-HETE were consistently higher in MDA PCa 2b and PC-3 cells and their corresponding xenograft tissues than were those in LNCaP cells. More strikingly, the mean endogenous level of 12-HETE was significantly higher in the primary prostate cancers than in the nonneoplastic prostate tissue (0.094 vs. 0.010 ng/mg protein, respectively; p=0.019). Our results suggest that LOX metabolites such as 12-HETE are critical in prostate cancer progression and that the LOX pathway may be a target for treating and preventing prostate cancer.
Background:
Evidence indicates that iodine per se could be implicated in the physiology of several organs that can internalize it. In thyroid and breast cancer, iodine treatments inhibit cell proliferation and induce apoptosis through a direct (mitochondria) and/or indirect effect (iodolipid generation). Here, we determined the uptake of iodide (I(-) ) and iodine (I(2) ), as well as the antiproliferative and apoptotic effects of 6-iodolactone (6-IL) and both forms of iodine in human prostate cells lines.
Methods:
Non-cancerous (RWPE-1) and cancerous (LNCaP, DU-145) cells, as well as nude mice xenotransplanted with DU-145 cells were used as cancer models. Iodine uptake was analyzed with radioactive tracers, transporter expression by qRT-PCR, cell proliferation by blue trypan, apoptosis by enzyme immunoassay or fluorescence, BAX and BCL-2 by western-blot, and caspsase 3 by enzymatic assay.
Results:
All three cell lines take up both forms of iodine. In RWPE-1 cells, I(-) uptake depends on the Na(+) /I(-) symporter (NIS), whereas it was independent of NIS in LNCaP and DU-145 cells. Antiproliferative effects of iodine and 6-IL were dose and time dependent; RWPE-1 was most sensitive to I(-) and 6-IL, whereas LNCaP was more sensitive to I(2) . In the three cell lines both forms of iodine activated the intrinsic apoptotic pathway (increasing the BAX/BCL-2 index and caspases). Iodine supplementation impaired growth of the DU-145 tumor in nude mice.
Conclusion:
Normal and cancerous prostate cells can take up iodine, and depending on the chemical form, it exerts antiproliferative and apoptotic effects both in vitro and in vivo.
Peroxisome proliferator-activated receptors (PPAR) are ligand-activated transcription factors. Three subtypes--PPAR alpha, PPAR beta, and PPAR gamma--have been identified and are differentially expressed in tissues. Originally, they were described as molecular regulators of lipid metabolism; recently, it has been shown that they are also involved in regulating the cell cycle and apoptosis in both normal and tumoral cells. In fact, some synthetic PPAR ligands are used to treat dyslipidemia, metabolic diseases, and type 2 diabetes. Here, we review the role of PPAR gamma (PPARγ) in tumor initiation and progression, emphasizing the relationship between this isoform and the cellular and molecular mechanisms involved in the antineoplastic effect of iodine on mammary cancer.
Epithelial-mesenchymal transition (EMT) was shown to confer tumor cells with abilities essential for metastasis, including migratory phenotype, invasiveness, resistance to apoptosis, evading immune surveillance, and tumor stem cell traits. Therefore, inhibition of EMT can be an important therapeutic strategy to inhibit tumor metastasis. Here, we show that activation of peroxisome proliferator-activated receptor γ (PPAR-γ) inhibits transforming growth factor β (TGF-β)-induced EMT in lung cancer cells and prevents metastasis by antagonizing Smad3 function. Activation of PPAR-γ by synthetic ligands (troglitazone and rosiglitazone) or by a constitutively active form of PPAR-γ prevents TGF-β-induced loss of E-cadherin expression and inhibits the induction of mesenchymal markers (vimentin, N-cadherin, fibronectin) and matrix metalloproteases. Consistently, activation of PPAR-γ also inhibited EMT-induced migration and invasion of lung cancer cells. Furthermore, effects of PPAR-γ ligands were attenuated by siRNA-mediated knockdown of PPAR-γ, indicating that the ligand-induced responses are PPAR-γ dependent. Selective knockdown of Smad2 and Smad3 by siRNA showed that TGF-β-induced EMT is Smad3 dependent in lung cancer cells. Activation of PPAR-γ inhibits TGF-β-induced Smad transcriptional activity but had no effect on the phosphorylation or nuclear translocation of Smads. Consistently, PPAR-γ activation prevented TGF-β-induced transcriptional repression of E-cadherin promoter and inhibited transcriptional activation of N-cadherin promoter. Finally, treatment of mice with troglitazone or knockdown of Smad3 in tumor cells significantly inhibited TGF-β-induced experimental metastasis in SCID-Beige mice. Together, with the low toxicity profile of PPAR-γ ligands, our data show that these ligands may serve as potential therapeutic agents to inhibit metastasis.
Nuclear receptors (NRs) are a family of highly conserved transcription factors that regulate transcription in response to small lipophilic compounds. They play a role in every aspect of development, physiology and disease in humans. They are also ubiquitous in and unique to the animal kingdom suggesting that they may have played an important role in their evolution. In contrast to the classical endocrine receptors that originally defined the family, recent studies suggest that the first NRs might have been sensors of their environment, binding ligands that were external to the host organism. The purpose of this review is to provide a broad perspective on NR ligands and address the issue of exactly what constitutes a NR ligand from historical, biological and evolutionary perspectives. This discussion will lay the foundation for subsequent reviews in this issue as well as pose new questions for future investigation.
Twelve human cancer cell lines and one non-malignant cell line were investigated with respect to a potential antiproliferative/cytotoxic activity of molecular iodine and iodolactones. Except CCL221 colon carcinoma cells, the growth of all cancer cell lines decreased if the cells were cultured in the presence of 10 microM molecular iodine (I(2)) for at least two days. delta-iodolactone (IL, 5 microM) was found to have a similar effect. SH-SY5Y neuroblastoma cells turned out to be most susceptible to both iodine compounds (total inhibition), followed by MCF-7 mammary carcinoma cells (60% and 77.7% inhibition in the presence of I(2) respect. IL) and HS24 lung carcinoma cells (36.3% respect. 40.3% inhibition). In contrast, MCF-10 normal mammary epithelial cells were much less affected by the iodine treatment. In both, SH-SY5Y and MCF-7 cells, I(2) and IL also abolished EGF-induced promotion of cell growth completely. This effect was, however, not due to an interfering with EGF-signaling, because I(2) and IL did not affect the phosphorylation of EGF-receptors, EGF-induced activation of MAP-kinase (Erk(1/2)), or EGF-induced lamellar actin protrusion. A disruption by molecular iodine of mitochondrial transmembrane electrical potential, which was prevented by a pre-treatment of the cells with N-acetyl-cysteine, supports a mitochondria-mediated apoptotic mechanism.
Studies in mammary cancer demonstrated that moderately high concentrations of molecular iodine (I2) have a antiproliferative and apoptotic effect either in vivo as in vitro, however the cellular intermediated involved in these effects has not been elucidated.
Virgin Sprague-Dawley rats were treated with methyl-nitrosourea (MNU: single dose ip, 50 mg/Kg bw) and the participation of arachidonic acid (AA) and PPAR receptors in the antineoplasic effect of I2 where analyzed.
I2-treated rats for four weeks exhibited a significant reduction in the incidence (62.5 vs. 100%) and size (0.87 +/- 0.98 vs 1.96 +/- 1.5 cm3) of mammary tumors. HPLC analysis showed that tumoral but not normal mammary tissue contained an elevated basal concentration of AA and significantly more AA-iodinated called 6-iodolactone (6-IL) after chronic I2 treatment. Tumors from I2-treated rats showed fewer cells positive to proliferating cell nuclear antigen, lower blood vessel density, as well as decreases in vascular endothelial growth factor, urokinase-type plasminogen activator, and PPAR type alpha (PPARalpha). These same tumors showed increases in the cell death markers, TUNEL-positive cells (p < 0.05) and the enzyme caspase-3 (trend), as well as significant induction of PPAR type gamma (PPARgamma).
Together, these data demonstrate that the antineoplasic effect of iodine involves 6-IL formation and PPARgamma induction.
Previous reports have documented the antiproliferative properties of I(2) and the arachidonic acid (AA) derivative 6-iodolactone (6-IL) in both thyroid and mammary glands. In this study, we characterized the cellular pathways activated by these molecules and their effects on cell cycle arrest and apoptosis in normal (MCF-12F) and cancerous (MCF-7) breast cells. Low-to-moderate concentrations of I(2) (10-20 microM) cause G1 and G2/M phase arrest in MCF-12F and caspase-dependent apoptosis in MCF-7 cells. In normal cells, only high doses of I(2) (40 microM) induced apoptosis, and this effect was mediated by poly (ADP-ribose) polymerase-1 (PARP1) and the apoptosis-induced factor, suggesting an oxidative influence of iodine at high concentrations. Our data indicate that both I(2) and 6-IL trigger the same intracellular pathways and suggest that the antineoplasic effect of I(2) in mammary cancer involves the intracellular formation of 6-IL. Mammary cancer cells are known to contain high concentrations of AA, which might explain why I(2) exerts apoptotic effects at lower concentrations only in tumoral cells.
To gain some understanding of the role of lipids in mammary epithelial growth and in mammary carcinogenesis, the direct effects of free fatty acids on cell growth in primary cultures of mammary epithelial cells and 7,12-dimethyl[α]anthracene-induced 12-dimethylbenz[α]anthracene-induced mammary tumors from rats were studied. The epithelial nature of virgin mammary cultures was confirmed by light and electron microscopy, by association of cells with basement membrane, and by production of α-lactalbumin. In the presence of insulin, hydrocortisone, progesterone, estrogen, prolactin, and delipidized fetal calf serum, both the normal mammary and tumor cells were stimulated in their growth by the addition of unsaturated free fatty acids and inhibited by the addition of saturated free fatty acids to the growth medium. For normal cells, linoleic or linolenic acids at 1.0 and 0.1 μg/ml, respectively, and for 7,12-dimethylbenz[α]anthracene-induced tumor cells, oleic acid or linoleic acid at 0.5 and 1.0 μg/ml, respectively, resulted in greater than a doubling of the growth rate compared to cultures with no added free fatty acid. For both normal and tumor cells, saturated free fatty acids inhibited growth at all concentrations tested. The concentration optima in vitro paralleled the proportions of essential fatty acids (free and esterified) in the normal mammary gland. A state of mammary proliferation in vivo was associated with an increase of 45% in the ratio of linoleic plus oleic:palmitic acids in total mammary lipids. Lipids may play some direct role in normal and neoplastic mammary cell growth.
The incorporation of iodide into proteins (PBI) and lipids (LBI) of horse thyroid slices was measured in various conditions. Their dependency on the concentration of extracellular iodide was strikingly different. For PBI the relationship was biphasic with a decrease above 10 microM, likely to correspond to the Wolff-Chaikoff effect. On the contrary, LBI increased as a function of iodide concentration up to 100 microM. Methimazole (MMI) inhibited the incorporation of iodide into both LBI and PBI, but higher concentrations of MMI were required to depress LBI as compared to PBI. The inhibition of active iodide transport by NaCIO4 reduced both PBI and LBI. Chromatography on silica gel resolved almost equal amounts of low and high polarity iodolipids. The main unpolar iodolipid was identified as 2-iodohexadecanal (2-IHDA), on the basis of proton nuclear magnetic resonance spectroscopy, mass spectrometry, and co-elution with authentic 2-IHDA obtained by chemical synthesis in reversed-phase high performance liquid chromatography and gas chromatography. The presence of 2-IHDA was also detected in dog thyroid slices, following incubation with KI (50 microM) and in the rat thyroid, 4 hours after intraperitoneal injection of KI (650 micrograms). An incubation of bovine brain plasmalogens with lactoperoxidase, iodide, and H2O2 generated 2-IHDA. In conclusion, we have identified a major thyroid iodolipid as 2-iodohexadecanal. The biosynthesis of this compound is likely to involve the addition of iodine to the vinyl ether group of plasmalogens.
Thyroid toxicity of iodide excess has been demonstrated in animals fed with an iodide-rich diet; in vitro iodide is cytotoxic, inhibits cell growth, and induces morphological changes in thyroid cells of some species. In this study, we investigated the effect of iodide excess in an immortalized thyroid cell line (TAD-2) in primary cultures of human thyroid cells and in cells of nonthyroid origin. Iodide displayed a dose-dependent cytotoxicity in both TAD-2 and primary thyroid cells, although at different concentrations, whereas it had no effect on cells of nonthyroid origin. Thyroid cells treated with iodide excess underwent apoptosis, as evidenced by morphological changes, plasma membrane phosphatidylserine exposure, and DNA fragmentation. Apoptosis was unaffected by protein synthesis inhibition, whereas inhibition of peroxidase enzymatic activity by propylthiouracil completely blocked iodide cytotoxicity. During KI treatment, reactive oxygen species were produced, and lipid peroxide levels increased markedly. Inhibition of endogenous p53 activity did not affect the sensitivity of TAD-2 cells to iodide, and Western blot analysis demonstrated that p53, Bcl-2, Bcl-XL, and Bax protein expression did not change when cells were treated with iodide. These data indicate that excess molecular iodide, generated by oxidation of ionic iodine by endogenous peroxidases, induces apoptosis in thyroid cells through a mechanism involving generation of free radicals. This type of apoptosis is p53 independent, does not require protein synthesis, and is not induced by modulation of Bcl-2, Bcl-XL, or Bax protein expression.
Iodine has a direct effect on thyroid function and growth, independent of pituitary TSH regulation in vivo, as well as in vitro. Because the action of iodine is inhibited by compounds inhibiting peroxidase activity such as MMI or PTU, and thyroid hormones have no direct effect on thyroid growth and function, other iodinated compounds must be responsible for the direct iodine effect. It has been shown that iodide is not only the essential substrate for thyroid hormone synthesis, but it is also incorporated into thyroid cell membrane lipids. These iodolipids are able to modulate the action of TSH and growth factors on thyroid cell function and growth. Therefore, the thyroid gland regulates its own function and growth depending on the availability of iodine and the formation of iodolipids. Two iodolipid families have been shown to be mediators of the effects of iodine in thyroid autoregulation: iodinated derivatives of polyunsaturated fatty acids (iodolactones) and iodoaldehydes derived from plasmenylethanolamine. Growth of mammary breast cancer cells, which also express the same NIS as thyroid cells, is inhibited by iodine and also δ-iodolactone. Thus, a sufficient iodine supply has an important role, not only for thyroid function and growth, but also for the mammary gland. 2-IHDA, inhibits nicotinamide adenine dinucleotide hydride (NADH)-dependent H2O2 generation in vitro, as well as in vivo. It also inhibits adenylate-cyclase activity, and therefore is supposed to mediate the well-known Wolff-Chaikoff effect. 2-IHDA also seems to be the iodinated compound, which inhibits the well-known cAMP-dependent thyroid-specific functions of the thyroid. It seems to be the iodinated compound, which decreases thyroid-specific functions during high iodine supply.
This chapter presents the direct physiological and pharmacological controls of the thyroid by iodide. In vivo studies in humans and animals have demonstrated that at low or physiological levels, iodide uptake limits the synthesis of thyroid hormones and therefore their secretion. These serum thyroid hormones depress the secretion of the main physiological activator of the gland, pituitary thyroid stimulating hormone (TSH). Thus, iodine deficiency leads to decreased thyroid hormone levels and compensatory TSH secretion. At these levels, there is an inverse relationship between iodide supply and TSH secretion. Iodide also directly inhibits the activity and growth of the thyroid due to the generation of an organified inhibitor XI in the thyroid. The direct effects of iodide and XI account for an inhibition of iodide oxidation itself, of iodide uptake, and of thyroid hormone secretion and thyroid growth. Besides the XI effects, iodide at very high pharmacological or toxicological concentrations appears to directly inhibit thyroid blood flow and secretion. The latter effects are used in the preoperative treatment of patients suffering from Graves' disease with Lugol. The indirect effects of iodide through thyroid hormones are observed at low or physiological levels of iodide intake and serum concentrations. The direct effects are mostly observed at supraphysiological, therapeutic, or toxic levels. The chapter also describes the clinical consequences of the diverse iodide actions the various experimental models used to elucidate the direct effects of iodide on the thyroid are discussed and analyzed. © 2009 Elsevier Inc. All rights reserved..
In 1948, Wolff and Chaikoff reported that organic binding of iodide in the thyroid was decreased when plasma iodide levels were elevated (acute Wolff-Chaikoff effect), and that adaptation or escape from the acute effect occurred in approximately 2 days, in the presence of continued high plasma iodide concentrations. We later demonstrated that the escape is attributable to a decrease in iodide transport into the thyroid, lowering the intrathyroidal iodine content below a critical inhibitory threshold and allowing organification of iodide to resume. We have now measured the rat thyroid sodium/iodide symporter (NIS) messenger RNA (mRNA) and protein levels, in response to both chronic and acute iodide excess, in an attempt to determine the mechanism responsible for the decreased iodide transport. Rats were given 0.05% NaI in their drinking water for 1 and 6 days in the chronic experiments, and a single 2000-μg dose of NaI ip in the acute experiments. Serum was collected for iodine and hormone measurements, and thyroids were frozen for subsequent measurement of NIS, TSH receptor, thyroid peroxidase (TPO), thyroglobulin, and cyclophilin mRNAs (by Northern blotting) as well as NIS protein (by Western blotting). Serum T4 and T3 concentrations were significantly decreased at 1 day in the chronic experiments and returned to normal at 6 days, and were unchanged in the acute experiments. Serum TSH levels were unchanged in both paradigms. Both NIS mRNA and protein were decreased at 1 and 6 days after chronic iodide ingestion. NIS mRNA was decreased at 6 and 24 h after acute iodide administration, whereas NIS protein was decreased only at 24 h. TPO mRNA was decreased at 6 days of chronic iodide ingestion and 24 h after acute iodide administration. There were no iodide-induced changes in TSH receptor and thyroglobulin mRNAs. These data suggest that iodide administration decreases both NIS mRNA and protein expression, by a mechanism that is likely to be, at least in part, transcriptional. Our findings support the hypothesis that the escape from the acute Wolff-Chaikoff effect is caused by a decrease in NIS, with a resultant decreased iodide transport into the thyroid. The observed decrease in TPO mRNA may contribute to the iodine-induced hypothyroidism that is common in patients with Hashimoto’s thyroiditis.
Introduction:
The thiazolidinedione (TZD) class of PPAR-γ ligands is predominantly known for its insulin sensitization activity. Unfortunately, these drugs have discernible side effects at diabetic dose. However, rosiglitazone and pioglitazone are still in the market with controversies. Past few years have noted the use of these drugs for the treatment of various other ailments.
Areas covered:
In this review, the authors present the anticancer mechanisms of established TZDs and highlight some of the new-fangled agents discovered. Remarkable preclinical and clinical activity of the known and newly developed agents, alone or in combination with the known cytotoxic agents, offer a new perspective for clinical studies carving a niche in cancer chemotherapy.
Expert opinion:
Various preclinical and clinical studies strongly suggest a role for TZDs both alone and in combination with existing chemotherapeutic agents, for the treatment of cancer. The exploration of newer TZDs at different doses, as well as developing partial agonists, can potentially help in unveiling the underlying mechanisms of these therapeutics, and consequently, treat this dreadful group of diseases.
The newly described iron/hydrogen peroxide (H2O2)/iodide antimicrobial system iodinates arachidonic acid to form the same products which are generated by peroxidase/H2O2/iodide systems. Arachidonic acid is multiply iodinated with the formation ofbis-iodohydrins and monoiodinated products which were identified as iodolactones by their high performance liquid chromatography
elution patterns and by gas chromatography-mass spectrometric analysis. Iodination of arachidonic acid by the iron/H2O2/iodide system appears to proceed via the formation of hydroxyl radicals as an intermediate species. Iodination of unsaturated
lipids may contribute to the cytotoxicity of the iron/H2O2/iodide system.
A total of 42 human thyroid glands (nodular goitre 9, adenoma with cystic degeneration 6; toxic goitre 10; carcinoma 14; and normal thyroid gland 3) were examined in vitro for iodination of an unidentified polar non-phosphatide lipid fraction (fraction II). The radioiodine incorporation in fraction II was 49.3 %, 43.6 %, 32.8 %, 20.7 %, and 22.0 % respectively in normal, nodular goitre, adenoma with cystic degeneration, toxic goitre and thyroid carcinoma.
In vitro studies with surviving sheep thyroid slices did not show any relation between the iodination of fraction II and thyroxine formation over a period of 120 min.
However, a highly significant correlation (r-value= 0.96375) was observed between the iodination of fraction II and thyroxine formation in vivo in the rat thyroid gland over a period of 24 h.
We have previously postulated that iodination of fraction II may be interrelated to thyroxine formation. In the light of this hypothesis and the above results we suggest that the iodination of fraction II and thyroxine formation in the thyroid gland may be interrelated, the degree of iodination of fraction II being modulated by the amount of thyroxine formed within the thyroid gland.
Background:
IL-δ (5-hydroxy-6 iodo-8,11,14-eicosatrienoic delta lactone) an iodinated arachidonic acid (AA) derivative, is one of the iodolipids biosynthesized by the thyroid. Although IL-δ regulates several thyroid parameters such as cell proliferation and goiter growth it was found that this iodolipid inhibits the growth of other non thyroid cell lines.
Objectives:
To study the effect of IL-δ on cell proliferation and apoptosis in the colon cancer cell line HT-29.
Results:
Treatment with IL-δ reduced cell viability in a concentration-dependent manner: 1μM 20%, 5μM 25%, 10μM 31%, 50μM 47% and caused a significant decrease of PCNA expression (25%). IL-δ had pro-apoptotic effects, evidenced by morphological features of programmed cell death such as pyknosis, karyorrhexis, cell shrinkage and cell blebbing observed by fluorescence microscopy, and an increase in caspase-3 activity and in Bax/Bcl-2 ratio (2.5 after 3h of treatment). Furthermore, IL-δ increased ROS production (30%) and lipid peroxidation levels (19%), suggesting that apoptosis could be a result of increased oxidative stress. A maximum increase in c-fos and c-jun protein expression in response to IL-δ was observed 1h after initiation of the treatment. IL-δ also induced a tumour growth delay of 70% compared to the control group in NIH nude mice implanted with HT-29 cells.
Conclusion:
Our study shows that IL-δ inhibits cell growth and induces apoptosis in the colon cancer cell line, HT-29 and opens the possibility that IL-δ could be a potential useful chemotherapy agent.
The total syntheses of the racemates of the bis-α-methylenelactonic sesquiterpenes, vernolepin and vernomenin, have been achieved. These tumor inhibitors were synthesized in 17 steps starting with dienone ester 29, itself the result of two Diels-Alder reactions. The key elements of the total syntheses were (i) the use of an angular carboxyl group to establish three centers of asymmetry in the B ring (29 → 37), (ii) the conversion of a cis-fused cyclohexenone to a cis δ-lactone (37 → 41), (iii) the protection of a δ-lactone as an ethylene glycol mixed orthoester (41 → 42), (iv) the opening of a very hindered epoxide to control the stereochemistry of the C ring (52 → 54), and (v) the bis-α-methylenation of the bisnor precursor (55 → 1 and 56 → 2) using dimethyl(methylene)ammonium iodide.
A randomized, double-blind, placebo-controlled, multicenter clinical trial was conducted with 111 otherwise healthy euthyroid women with a history of breast pain. Patients had to document moderate or severe breast pain by recording a score ≥5 on a visual analog scale (VAS) of pain for ≥6 days per cycle and had to present with fibrosis involving at least 25% of both breast surfaces. Subjects could not be effectively treated with more conservative measures such as local heat or nonprescription analgesics. There was not a statistically significant difference in the dropout rate for patients on placebo (11.8%), 1.5 mg/day (31.3%), 3.0 mg/day (18.4%), or 6.0 mg/day (25%) of molecular iodine for 6 months. Physicians assessed breast pain, tenderness, and nodularity each cycle; patients assessed breast pain and tenderness with the Lewin breast pain scale at 3-month intervals and with a VAS at each cycle. A statistically significant improvement (p < 0.01) associated with dose was observed in the Lewin overall pain scale for all treated groups compared to placebo. Reductions in all three physician assessments were observed in patients after 5 months of therapy in the 3.0 mg/day (7/28; 25%) and 6.0 mg/day (15/27; 18.5%) treatment groups, but not the 1.5 mg/day or placebo group. Patients recorded statistically significant decreases in pain by month 3 in the 3.0 and 6.0 mg/day treatment groups, but not the 1.5 mg/day or placebo group; more than 50% of the 6.0 mg/day treatment group recorded a clinically significant reduction in overall pain. All doses were associated with an acceptable safety profile. No dose-related increase in any adverse event was observed.
Lipids extracted from fresh beef thyroid glands were purified by alumina chromatography. Fractions designated the “head” and “tail” fractions of the lecithin peak were used in studies of anion binding. Such binding was measured as the distribution coefficient between an aqueous phase (1 mM sodium acetate buffer (pH 4.2) and 1 mM methylmercaptoimidazole) and an organic phase containing the lipid (10 % chloroform in n-heptane). The relative binding of I−, ReO4−, and Br− was a function of the lipid concentration. The “head” fraction had greater overall activity and was enriched in ReO4−-binding capacity, whereas the “tail” fraction was relatively enriched in I−-binding capacity. The binding of both anions is reversible. The ability of other univalent anions (ClO4−, ReO4−, SCN−, Br−, NO3−) to displace I− from the lipid phase was in the same sequence as their displacing ability in thyroid slices, but with a smaller spread in potencies.Destruction of activity by phosphatidase A or hydrogenation and characterization by thin-layer chromatography indicate the active lipids to be unsaturated lecithins or choline plasmalogens. The inactivity of l-α-dipalmitoyl, l-α-dioleyl, as well as soy bean and calf brain, lecithins shows that anion binding is more than a trivial property of these choline phosphatides and suggests they may be involved in thyroidal anion transport or may serve as models for systems that exhibit such anion specificity.
Multidrug resistance is resistance to structurally unrelated anticancer agents. Large-scale expression analysis by using high-density oligonucleotide microarrays may provide information about new candidate genes contributing to MDR. This study demonstrates alterations in expression levels of several genes related to epithelial-mesenchymal transition (EMT) in paclitaxel, docetaxel, and doxorubicin resistant MCF-7 cells.
Resistant sublines were developed from sensitive cells by selective paclitaxel, docetaxel, and doxorubicin applications in dose increments. cDNA microarray analysis was performed for sensitive and resistant cells. Genes having statistically significantly altered expression levels more than two-folds compared to the sensitive MCF-7 cells were considered. Genes encoding the determinants of the EMT were evaluated. Immunostaining was performed for relevant protein expressions.
Key elements of EMT were transcriptionally activated in paclitaxel, docetaxel and doxorubicin resistant sublines. One of the upregulated genes was Slug, a transcription factor of E-cadherin, occludin repression, and N-cadherin, vimentin activation. Decreased estrogen receptor-α (ER) levels in cells might have stimulated Slug expression. Increased expression levels of TGF-beta receptor2 (TGFBR2) together with SMAD3 might have stimulated EMT in resistant cells. Immunocytochemistry results confirmed loss of ER and E-cadherin, together with high vimentin levels.
EMT was induced in multidrug resistant MCF-7 cells indicating a relationship of this process and drug resistance. However, the relationship of each specific component of EMT with drug resistance requires further analysis.
As we previously demonstrated, the inhibitory effect of iodine on thyroid cell growth is mediated by iodolactones, especially 6-iodo-5-hydroxy-eicosatrienoic acid (delta-iodolactone). In this communication we compare the effect of iodide, molecular iodine and delta-iodolactone on growth inhibition and apoptosis on three human thyroid carcinoma cell lines (B-CPAP cells, FTC-133 cells and 8505C cells) as well as on human breast cancer cells (MCF 7).
Thyroid carcinoma cells were cultured in Dulbecco's modified Eagle's medium (DMEM) and MCF 7 cells in Rowswell Park Memorial Institute (RPMI) culture medium, both containing 10% (v/v) Fetal Calf Serum (FCS), until they were confluent. Around 2000 cells were then distributed in 12-well plates and grown for 48 h in either DMEM (thyroid cancer cells) or in RPMI medium (MCF 7 cells) both containing 5% FCS. Thereafter, different concentrations of iodide, iodine or delta-iodolactone were added for 24 h. Growth rate was estimated by cell counting in a Coulter Counter adapted for epithelial cells. Apoptosis was determined by a mitochondrial potential assay.
The growth rate of B-CPAP cells was unaffected by iodide, but was reduced by high concentreations of molecular iodine (100 and 500 microM). However, delta-iodolactone significantly reduced cell proliferation already with low concentrations (5 microM and 10 microM) and further in a dose-dependent manner up to 82%. FTC-133 and 8505C cells were unaffected by iodide, iodine or delta-iodolactone. In contrast, in MCF 7 cells, molecular iodine (100 microM) inhibited growth from 100% to 83% but delta-iodolactone (1, 5 and 10 microM) dose-dependently decreased growth rate from 100% to 82% and 62%, respectively. The inhibition of growth was through apoptosis, and not necrosis, as the amount of apoptotic cells corresponded to the growth inhibition.
delta-Iotaodolactone seems to be the main iodocompound which can inhibit growth and induce apoptosis in B-CPAP cells as well as in MCF 7 breast cancer cells.
Iodide has direct effects on thyroid function. Several iodinated lipids are biosynthesized by the thyroid and they were postulated as intermediaries in the action of iodide. Among them 6 iodo-delta-lactone (IL-delta) has been identified and proposed to play a role in thyroid autoregulation. The aim of this study was to compare the effect of iodide and IL-delta on several thyroid parameters.
Thyroid bovine follicles were incubated with the different compounds during three days.
KI and IL-delta inhibited iodide uptake, total protein and Tg synthesis but only KI had an effect on NIS and Tg mRNAs levels. Both compounds inhibited Na+/K+ ATPase and deoxy-glucose uptake. As PAX 8, FOXE 1 and TITF1 are involved in the regulation of thyroid specific genes their mRNA levels were measured. While iodide inhibited the expression of the first two, the expression of TITF1 was stimulated by iodide and IL-delta had no effect on these parameters.
These findings indicate that IL-delta reproduces some but not all the effects of excess iodide. These observations apply for higher micromolar concentrations of iodide while no such effects could be demonstrated at nanomolar iodide concentrations.
The aim of this article is to pay tribute to Paul Ehrlich and his contributions to science, in particular those related to antimicrobial therapy, at the end of a prodigious decade of celebrations to fête his person and work. The year 2009 marks the centenary of the discovery of the experimental anti-syphilitic activity of Salvarsan and the first clinical studies showing its efficacy against syphilis. This homage is conveyed through the presentation of bibliographic data, mention of his most important scientific achievements based on his original publications, and by analyzing the film Dr. Ehrlich's Magic Bullet (1940) by William Dieterle.
Thyroid autoregulation has been related to intraglandular content of an unknown putative iodocompound. The thyroid is capable of producing different iodolipids such as 6-iodo-deltalactone (ILdelta) and 2-iodohexadecanal (2-IHDA). Data from different laboratories have shown that these iodolipids inhibit several thyroid parameters. ILdelta has an antigoitrogenic action but no data about the action of 2-IHDA on this parameter has been published.
to study the action of 2-IHDA on methimazole (MMI)-induced goiter and analyze if this compound can cause the involution of preformed goiter.
Administration of MMI to rats during 10 days increased thyroid weight by 112%. This effect was significantly inhibited by the simultaneous injection of 20mug/day of 2-IHDA (51% vs. MMI) while iodine or non iodinated hexadecanal were without action. Thyroidal proliferating cell nuclear antigen (PCNA) content was increased by MMI while 2-IHDA decreased this value (control: 100%; MMI: 190+/-11; MMI+2-IHDA: 134+/-10). Serum TSH was increased after MMI administration and 2-IHDA did not modify this parameter (control: 1.89+/-0.10; MMI: 8.19+/-0.93ng/ml; MMI+2-IHDA: 7.38+/-0.72). Treatment with MMI increased thyroidal cAMP content (control: 16.1+/-0.82, MMI: 42.4+/-4.6 fmol/mg protein) while injection of 2-IHDA significantly decreased this value (22.3+/-2.0). Goiter prevention by 2-IHDA was also observed at 30 days of treatment reducing total number of cells (51% inhibition) and epithelial height (81% inhibition). Goiter involution was induced after withdrawal of MMI and injection with 2-IHDA, KI or saline. 2-IHDA led to a reduction of 74.5% in thyroid weight after 3 days while spontaneous involution (saline) was only of 32%. KI failed to alter this value. This significant involution was accompanied by a reduction in the number of cells (66%). Administration of the iodolipids did not produce significant changes in several serum parameters such as total T(3) and T(4), cholesterol, transaminases, urea and creatinine.
2-Iodohexadecanal, as 6-iodo-deltalactone, prevents goiter growth in rats and opens a potential therapeutic application of iodolipids.
Recently we and other groups have shown that molecular iodine (I(2)) exhibits potent antiproliferative and apoptotic effects in mammary cancer models. In the human breast cancer cell line MCF-7, I(2) treatment generates iodine-containing lipids similar to 6-iodo-5-hydroxy-eicosatrienoic acid and the 6-iodolactone (6-IL) derivative of arachidonic acid (AA), and it significantly decreases cellular proliferation and induces caspase-dependent apoptosis. Several studies have shown that AA is a natural ligand of the peroxisome proliferator-activated receptors (PPARs), which are nuclear transcription factors thought to participate in regulating cancer cell proliferation. Our results show that in MCF-7 cells: (1) 6-IL binds specifically and with high affinity to PPAR proteins (EMSA assays), (2) 6-IL activates both transfected (by transactivation assays) and endogenous (by lipid accumulation) peroxisome proliferator response elements, and (3) 6-IL supplementation increases PPAR gamma and decreases PPAR alpha expression. These results implicate PPARs in a molecular mechanism by which I(2), through formation of 6-IL, inhibits the growth of human breast cancer cells.
In the phospholipid fractions, arachidonic acid represented a several fold higher percentage of fatty acids from DMBA-induced tumors and in mammary glands from midpregnant rats when compared to mammary glands from virgin rats. Arachidonic acid was not present in measurable quantities in the neutral lipid fractions of mammary glands from virgin rats. The arachidonic acid in the neutral lipid fraction of mammary glands from midpregnant rats was only detectable in the triglyceride-sterol ester fraction, but in that fraction less than 1% of the fatty acids were arachidonic acid. In the neutral lipids of the DMBA-induced tumors, it was of particular interest that a high proportion (19%) of the fatty acids in the diglyceride fraction consisted of arachidonic acid; no arachidonic acid was detected in the diglycerides of the normal tissues.
The action of iodide on the cyclic AMP system of dog thyroid slices has been studied. Iodide inhibits the enhancement of cyclic AMP accumulation in the presence of TSH. Such an effect is also observed in horse, beef and sheep thyroid slices, but not in dog kidney slices stimulated by parathyroid hormone or in rat parotid slices stimulated by isoproterenol. The effect in dog thyroid slices is suppressed by 1mM NaClO4, 1mM methimazole and 1mM propylthiouracil. Similar data have been obtained for prostaglandin E1 stimulation. Effects of thyrotropin mediated by cyclic AMP, i.e., activation of iodothyronine secretion, 1-14C-glucose oxidation, and lactate formation, were also inhibited by iodide but not by iodide and methimazole. Similar activations when caused by dbcAMP were not inhibited by iodide. The data suggest a model in which an intracellular agent resulting from the oxidation of iodide acts on the thyroid cyclic AMP system.
1. Introduction Iodine has a generally inhibitory effect on the thyroid gland. Excess iodide has been shown to inhibit hormone synthesis and release in man and animals [I] Increased iodide intake leads to depression of iodide concentration activity [2] . Since the effect of iodide was blocked by drugs which inhibited intrathyroidal iodination processes, it was postulated that the administrated iodide was incorporated into a sub- stance which acted as an inhibitor of the iodide trans- port mechanism [3]. We have recently demonstrated [4,5] that iodide inhibited the stimulatory effect of TSH on cyclic AMP accumulation in dog thyroid slices in vitro. Sherwin and Tong [6] have also reported such an effect in bovine isolated thyroid cells. This report presents evidence that horse thyroid adenylate cyclase activity from slices preincubated with iodide is inhibited. This inhibition can be presented by methimazole. 2. Materials and methods Horse thyroid was collected at a local slaughter house just after killing, trimmed of fat tissue and sliced with a Stadie-Riggs microtome. The slices (* 2 g) were incubated for 90 min at 37°C in 100 ml of Krebs- Ringer bicarbonate buffer enriched with 8 mM glucose 0.5 g/l bovine serum albumin and KI (0.1 mM). When TSH was used, the hormone (0.5 mu/ml) was added
Previous studies have shown that iodoarachidonates (IAs) prevent goiter production in rats. In the present studies we show that both IL-d and IL-w (IAs bearing the iodine atom at the positions 6 and 14, respectively), cause a significant involution of preformed goiter. This effect was evident when IAs were administered either orally or via i.p., although the first one required larger doses to obtain the same degree of inhibition. No changes were observed in serum protein, urea, cholesterol, cholinesterase, T3 or T4. In vitro studies with FRTL-5 cells showed that both IAs inhibit iodide and alpha-AIB uptake, as well as ATPase activity.
It has been reported previously that radioactivity derived from iodine distributes differently in the Sprague-Dawley rat depending on the chemical form administered (Thrall and Bull, 1990). In the present communication we report the differential distribution of radioactivity derived from iodine (I2) and iodide (I-) into blood components. Twice as much radioiodine is in the form of I- in the plasma of animals treated with 125I- compared to 125I2-treated rats. No I2 could be detected in the plasma. With an increase in dose, increasing amounts of radioactivity derived from 125I2-treated animals distribute to whole blood compared to equivalent doses of 125I-, reaching a maxima at a dose of 15.8 mumol I/kg body weight. Most of the radioactivity derived from I2 associates with serum proteins and lipids, in particular with albumin and cholesteryl iodide. These data indicate a differential distribution of radioactivity depending on whether it is administered as iodide or iodine. This is inconsistent with the commonly held view that iodine (I2) is reduced to iodide (I-) before it is absorbed systemically from the gastrointestinal tract.
Excess iodide inhibits several thyroid parameters, by a putative organic iodocompound. Different iodolipids, including iodinated derivatives of arachidonic acid (IAs), are produced by rat, calf and pig thyroid. The action of two iodolactones, one bearing the iodine atom at the position 6 (IL-d) and the other at position 14 (IL-w) on growth of FRTL-5 cells was studied. KI, IL-w and IL-d exert a dose-related inhibition on FRTL-5 cell proliferation. The first two compounds caused inhibition at 1 microM while IL-d was effective at 10 microM. This inhibitory action of iodolactones (ILs) was not altered by 1 mM methyl-mercaptoimidazol (MMI), indicating that they exert their effect per se. The action of ILw on cell growth was reversible. The growth-stimulating effect of 10 microM forskolin was inhibited by IAs, showing that one possible site of action lies at the cAMP pathway. The present results give further support to our hypothesis about the role of IAs in thyroid growth autoregulation.
Iodolipids are the possible mediators of excess iodide in thyroid autoregulation. Previous work from our laboratory has shown that 14-iodo-15-hydroxy-5,8,11 eicosatrienoic acid (I-HO-A) and its omega lactone (IL-w) mimic the inhibitory action of excess iodide upon several parameters of thyroid metabolism. The present experiments were performed in order to study the mechanism of the inhibitory effect of I-HO-A and IL-w on 2-deoxy-D-glucose (DOG) and aminoisobutyric acid (AIB) uptake by calf slices. I-HO-A, IL-w and KI 0.1 mM caused a 33, 31 and 25% inhibition, respectively, of AIB uptake. The presence of 0.1 mM methimazole (MMI) only reversed the effect of KI. The transport of DOG was inhibited by both compounds: I-HO-A caused a 62% decrease, while IL-w produced a 64% inhibition; and MMI failed to relieve their action. On the contrary, the 33% inhibition caused by KI disappeared when MMI was present. Taking into account that AIB and DOG transport across the membrane requires energy, supplied by Na-K-ATPase, changes in its activity were studied. TSH (10 mU/ml) produced a 74% increase in the enzyme activity which was significantly blocked by KI (82%), I-HO-A (100%) and IL-w (100%). Basal enzyme activity was impaired by IL-w (33%), but not by KI. These results were correlated with the decrease of DOG uptake produced by 1 mM ouabain. Tissue specificity effect of iodoarachidonates was demonstrated by the absence of action on DOG transport in kidney and liver.(ABSTRACT TRUNCATED AT 250 WORDS)
High intake of iodine inhibits iodide trapping, iodide organification, and hormone release from the human thyroid. We investigated whether iodine intake also affects thyroid blood flow, as was suggested by a recent study in euthyroid rats. With a Color Doppler device we made 14 consecutive Duplex-Doppler registrations of both superior thyroid arteries in 10 euthyroid volunteers during baseline iodine intake (1 week), iodine restriction (2 weeks), return to baseline (1 week), and iodine excess (1 week; 80 mumol sodium iodide/day). Vessel diameters and mean flow velocity were measured on videotape recordings by a "blinded" observer. Baseline iodide excretion was 0.88 +/- 0.38 (+/- SD) mumol/day. Mean flow velocity was 13.9 +/- 4.1 cm/s, and vessel diameter was 1.07 +/- 0.22 mm. Blood flow was 7.7 +/- 3.8 mL/min.superior thyroid artery. During the low iodine diet, excretion dropped to 0.49 +/- 0.16 mumol/day, and blood flow increased to 11.0 +/- 5.0 mL/min (P less than 0.001), remaining elevated (10.3 +/- 4.4 mL/min) during the second baseline diet. During high iodide intake, blood flow averaged 5.8 +/- 3.4 mL/min (P less than 0.001), and the expected decrease in thyroid hormone levels and increase in TSH were seen. We conclude that thyroid blood flow responds inversely, and independently from TSH, to changes in iodine intake in euthyroid humans.
Iodolactone (6-iodo-8,11,14-eicosatrienoic-delta-lactone), an iodinated derivative of arachidonic acid, was found to be synthesized in rat thyroid slices; however, the physiological role of this compound is still unknown. We tried to detect iodolactone in isolated porcine thyroid follicles and investigated the effects of in vitro synthesized iodolactone on epidermal growth factor-induced thyroid cell proliferation and TSH-induced cAMP formation. In vitro synthesis of iodolactone was performed with lactoperoxidase-catalyzed iodination of arachidonic acid in the presence of trace amounts of [125I]- and [3H]arachidonic acid. After purification by silica gel chromatography, HPLC of the reaction products revealed one main peak containing trace amounts of both [125I]- and [3H]arachidonic acid. With gas chromatography-mass spectrometry (GC-MS) a molecular mass of 391 m/z, corresponding to the derivatization product of iodolactone, was found. An ethanol-chloroform extract of isolated thyroid follicles preincubated with KI (10 microM) and arachidonic acid (1 microM) revealed peaks in HPLC and GC comparable with those of in vitro synthesized iodolactone. This indicates the ability of thyroid follicles to form iodolactone. Iodolactone (0.1-1.0 microM) dose-dependently inhibited epidermal growth factor-induced thyroid cell growth. This growth-inhibiting effect of iodolactone was 50-fold more pronounced than the inhibitory effect of KI (4 X 10(-5) microM) on thyroid cell proliferation. In contrast to the effect of iodide, the inhibitory effect of iodolactone on thyroid cell growth could not be abolished by methimazole (1 mM). Basal as well as TSH (0.5 U/liter)-induced cAMP formation were not changed by iodolactone. These experiments suggest a physiological role of iodolactone as a mediator of the known inhibitory effect of iodide on thyroid growth.
Differences in the Distribution of Iodine and Iodide in the Sprague-Dawley Rat. THRALL, K. D., AND BULL, R. J. (1990). Fundam Appl. Toxicol. 15, 75–81. Use of iodine as a drinking water disinfectant for extended space flight raises concerns about potential chronic
effects on health. A key question is whether the chemical form of iodine might play a role. To address this question the influence
chemical form has on the uptake and distribution of radioiodine was studied in fed and fasted rats. Following oral administration
of 125I2 or 125I−, blood 125I levels were maximal at 2 hr and reached similar concentrations in fed animals receiving 125I− and fasted animals receiving either 125I2 or 125I− However, when 125I2 was administered to fed animals the initial levels of 125I into blood were significantly lower than after the other treatments. The half-life of elimination of 125I from the blood appeared independent of the form of iodine administered. The initial distribution of 125I to the thyroid depended sharply on chemical form, being greater when iodide rather than iodine was administered, whether
animals were fed or fasted. In fed animals administered I2, this may largely be explained by the increased retention of 125I in the stomach contents. In fasted animals, both stomach content and blood levels of I− were similar whether I2 or I− was administered. Since thyroid uptake of iodine is specific for I−, this suggests that the form of iodine in the blood was different in animals administered I2. This notion was further supported by the finding that pretreatment of animals with varying concentrations of I− in drinking water was four times as effective in suppressing the uptake of a test dose of 125I− than pretreatment with equivalent concentrations of I2.