Daily data of Global Vertical Insolation in the four cardinal orientations in Burgos, Spain.

Daily data of Global, Diffuse and Beam Horizontal Insolation and Global Vertical (North, South, East and West orientations) insolation recorded in Burgos, Spain, are presented in this paper. Ten-minute irradiance data sets are collected over forty-five months in the experimental campaign to produce estimates of daily insolation levels. This data was derived in association with the article titled: "The PV Potential of Vertical Façades: a classic approach using experimental data from Burgos, Spain" (Díez-Mediavilla et al., in press) [1]. This dataset can be used to develop and test new solar radiation and daylight models and estimate the thermal load and lighting needs in buildings for the improvement of energy efficiency.

Repression of the nuclear receptor small heterodimer partner by steatotic drugs and in advanced nonalcoholic fatty liver disease.

The small heterodimer partner (SHP) (NR0B2) is an atypical nuclear receptor that lacks a DNA-binding domain. It interacts with and inhibits many transcription factors, affecting key metabolic processes, including bile acid, cholesterol, fatty acid, and drug metabolism. Our aim was to determine the influence of steatotic drugs and nonalcoholic fatty liver disease (NAFLD) on SHP expression and investigate the potential mechanisms. SHP was found to be repressed by steatotic drugs (valproate, doxycycline, tetracycline, and cyclosporin A) in cultured hepatic cells and the livers of different animal models of NAFLD: iatrogenic (tetracycline-treated rats), genetic (glycine N-methyltransferase-deficient mice), and nutritional (mice fed a methionine- and choline-deficient diet). Among the different transcription factors investigated, CCAAT-enhancer-binding protein α (C/EBPα) showed the strongest dominant-repressive effect on SHP expression in HepG2 and human hepatocytes. Reporter assays revealed that the inhibitory effect of C/EBPα and steatotic drugs colocalize between -340 and -509 base pair of the SHP promoter, and mutation of a predicted C/EBPα response element at -473 base pair abolished SHP repression by both C/EBPα and drugs. Moreover, inhibition of major stress signaling pathways demonstrated that the mitogen-activated protein kinase kinase 1/2 pathway activates, while the phosphatidylinositol 3 kinase pathway represses SHP in a C/EBP-dependent manner. We conclude that SHP is downregulated by several steatotic drugs and in advanced NAFLD. These conditions can activate signals that target C/EBPα and consequently repress SHP, thus favoring the progression and severity of NAFLD.

Evaluation of the protection exerted by Pisum sativum Ferredoxin-NADP(H) Reductase against injury induced by hypothermia on Cos-7 cells.

Hypothermia is employed as a method to diminish metabolism rates and preserve tissues and cells. However, low temperatures constitute a stress that produces biochemical changes whose extension depends on the duration and degree of cold exposure and is manifested when physiological temperature is restored. For many cellular types, cold induces an oxidative stress that is dependent on the elevation of intracellular iron, damages macromolecules, and is prevented by the addition of iron chelators. Pisum sativum Ferredoxin-NADP(H) Reductase (FNR) has been implicated in protection from injury mediated by intracellular iron increase and successfully used to reduce oxidative damage on bacterial, plant and mammalian systems. In this work, FNR was expressed in Cos-7 cells; then, they were submitted to cold incubation and iron overload to ascertain whether this enzyme was capable of diminishing the harm produced by these challenges. Contrary to expected, FNR was not protective and even exacerbated the damage under certain circumstances. It was also found that the injury induced by hypothermia in Cos-7 cells presented both iron-dependent and iron-independent components of damage when cells were actively dividing but only iron-independent component when cells were in an arrested state. This is in agreement with previous findings which showed that iron-dependent damage is also an energy-dependent process.

The human liver fatty acid binding protein (FABP1) gene is activated by FOXA1 and PPARα; and repressed by C/EBPα: Implications in FABP1 down-regulation in nonalcoholic fatty liver disease.

Liver fatty acid binding protein (FABP1) prevents lipotoxicity of free fatty acids and regulates fatty acid trafficking and partition. Our objective is to investigate the transcription factors controlling the human FABP1 gene and their regulation in nonalcoholic fatty liver disease (NAFLD). Adenovirus-mediated expression of multiple transcription factors in HepG2 cells and cultured human hepatocytes demonstrated that FOXA1 and PPARα are among the most effective activators of human FABP1, whereas C/EBPα is a major dominant repressor. Moreover, FOXA1 and PPARα induced re-distribution of FABP1 protein and increased cytoplasmic expression. Reporter assays demonstrated that the major basal activity of the human FABP1 promoter locates between -96 and -229bp, where C/EBPα binds to a composite DR1-C/EBP element. Mutation of this element at -123bp diminished basal reporter activity, abolished repression by C/EBPα and reduced transactivation by HNF4α. Moreover, HNF4α gene silencing by shRNA in HepG2 cells caused a significant down-regulation of FABP1 mRNA expression. FOXA1 activated the FABP1 promoter through binding to a cluster of elements between -229 and -592bp, whereas PPARα operated through a conserved proximal element at -59bp. Finally, FABP1, FOXA1 and PPARα were concomitantly repressed in animal models of NAFLD and in human nonalcoholic fatty livers, whereas C/EBPα was induced or did not change. We conclude that human FABP1 has a complex mechanism of regulation where C/EBPα displaces HNF4α and hampers activation by FOXA1 and PPARα. Alteration of expression of these transcription factors in NAFLD leads to FABP1 gen repression and could exacerbate lipotoxicity and disease progression.

Expression and distribution of aquaporin 8 in rat hepatocytes cold stored 72 hours in modified University of Wisconsin and bes-gluconate-sucrose solutions. Study of their correlation with water content.

Since few data are availble on the genetic responses to low temperatures, we investigated if cold storage of hepatocytes (0 degree C, mUW or BGS solutions, 72 h) can affect gene expression and/or cellular localization of AQP8 and their correlation with water movements. Cold preserved hepatocytes showed a significant decrease in water content (P less than 0.05) but were able to regulate their volume when they returned to physiological conditions. These changes were not related to modulation in the expression and the pattern of distribution of AQP8 suggesting that other mechanisms are involved. The study of the quantitative changes in the expression of genes coding for liver specific proteins in cold preserved hepatic cells is of interest in order to develop new preservation methods or solutions that could contribute to maintain the utility of these cells when destined to be applied in clinical models.

Hepatitis C virus, oxidative stress and steatosis: current status and perspectives.

Reactive oxygen and nitrogen species (ROS/RNS), whether produced endogenously as a consequence of normal cell functions or derived from external sources, pose a constant threat to cells living in an aerobic environment. When the production of ROS/RNS overrides the antioxidant capability of the target cells, oxidative damage may occur as a consequence of the interaction with DNA, protein, and lipids. Hepatitis C virus (HCV) is a major cause of viral hepatitis. Although the molecular mechanisms of HCV pathogenesis remain unclear, oxidative stress is emerging as a key step and a major initiator in the development and the progression of liver damage, and the evaluation of oxidative stress may be useful for a better understanding of the pathogenesis of hepatitis C. Liver steatosis is one of the most important histopathological features in patients with chronic hepatitis C. Both viral and host factors contribute to the development of steatosis, and putative defects caused by ROS/RNS may be involved through abnormalities in lipid metabolism. This review is aimed to offer an updated overview of the relationship between oxidative stress and HCV infection, focusing on the significance of ROS/RNS in the pathogenesis of liver disease. The potential role played by oxidative stress in the pathogenic mechanisms of HCV-related steatosis is also discussed.

Basic mechanisms involved in the anti-cancer effects of melatonin.

It is commonly accepted that melatonin (N-acetyl-5-methoxytryptamine), the most relevant pineal secretory product, has oncostatic properties in a wide variety of tumors and, especially, in those identified as being hormonedependent. The objective of the present article is to offer a global and integrative view of the mechanisms involved in the oncostatic actions of this indoleamine. Due to the wide spectrum of melatonin's actions, the mechanisms that may be involved in its ability to counteract tumor growth are varied. These include: a) antioxidant effects; b) regulation of the estrogen receptor expression and transactivation; c) modulation of the enzymes involved in the local synthesis of estrogens; d) modulation of cell cycle and induction of apoptosis; e) inhibition of telomerase activity; f) inhibition of metastasis; g) prevention of circadian disruption; h) antiangiogenesis; i) epigenetic effects; j) stimulation of cell differentiation; and k) activation of the immune system. The data supporting each of these oncostatic actions of melatonin are summarized in this review. Moreover, the list of actions described may not be exhaustive in terms of how melatonin modulates tumor growth.

Scientific basis for the potential use of melatonin in bone diseases: osteoporosis and adolescent idiopathic scoliosis.

The objective of this paper was to analyze the data supporting the possible role of melatonin on bone metabolism and its repercussion in the etiology and treatment of bone pathologies such as the osteoporosis and the adolescent idiopathic scoliosis (AIS). Melatonin may prevent bone degradation and promote bone formation through mechanisms involving both melatonin receptor-mediated and receptor-independent actions. The three principal mechanisms of melatonin effects on bone function could be: (a) the promotion of the osteoblast differentiation and activity; (b) an increase in the osteoprotegerin expression by osteoblasts, thereby preventing the differentiation of osteoclasts; (c) scavenging of free radicals generated by osteoclast activity and responsible for bone resorption. A variety of in vitro and in vivo experimental studies, although with some controversial results, point toward a possible role of melatonin deficits in the etiology of osteoporosis and AIS and open a new field related to the possible therapeutic use of melatonin in these bone diseases.

Fruit polyphenols, immunity and inflammation.

Flavonoids are a large class of naturally occurring compounds widely present in fruits, vegetables and beverages derived from plants. These molecules have been reported to possess a wide range of activities in the prevention of common diseases, including CHD, cancer, neurodegenerative diseases, gastrointestinal disorders and others. The effects appear to be related to the various biological/pharmacological activities of flavonoids. A large number of publications suggest immunomodulatory and anti-inflammatory properties of these compounds. However, almost all studies are in vitro studies with limited research on animal models and scarce data from human studies. The majority of in vitro research has been carried out with single flavonoids, generally aglycones, at rather supraphysiological concentrations. Few studies have investigated the anti-inflammatory effects of physiologically attainable flavonoid concentrations in healthy subjects, and more epidemiological studies and prospective randomised trials are still required. This review summarises evidence for the effects of fruit and tea flavonoids and their metabolites in inflammation and immunity. Mechanisms of effect are discussed, including those on enzyme function and regulation of gene and protein expression. Animal work is included, and evidence from epidemiological studies and human intervention trials is reviewed. Biological relevance and functional benefits of the reported effects, such as resistance to infection or exercise performance, are also discussed.

Clinical uses of melatonin: evaluation of human trials.

During the last 20 years, numerous clinical trials have examined the therapeutic usefulness of melatonin in different fields of medicine. The objective of this article is to review, in depth, the science regarding clinical trials performed to date. The efficacy of melatonin has been assessed as a treatment of ocular diseases, blood diseases, gastrointestinal tract diseases, cardiovascular diseases, diabetes, rheumatoid arthritis, fibromyalgia, chronic fatigue syndrome, infectious diseases, neurological diseases, sleep disturbances, aging and depression. Melatonin has been also used as a complementary treatment in anaesthesia, hemodialysis, in vitro fertilization and neonatal care. The conclusion of the current review is that the use of melatonin as an adjuvant therapy seems to be well funded for macular degeneration, glaucoma, protection of the gastric mucosa, irritable bowel syndrome, arterial hypertension, diabetes, side effects of chemotherapy and radiation in cancer patients or hemodialysis in patients with renal insufficiency and, especially, for sleep disorders of circadian etiology (jet lag, delayed sleep phase syndrome, sleep deterioration associated with aging, etc.) as well as in those related with neurological degenerative diseases (Alzheimer, etc.,) or Smith-Magenis syndrome. The utility of melatonin in anesthetic procedures has been also confirmed. More clinical studies are required to clarify whether, as the preliminary data suggest, melatonin is useful for treatment of fibromyalgia, chronic fatigue syndrome, infectious diseases, neoplasias or neonatal care. Preliminary data regarding the utility of melatonin in the treatment of ulcerative colitis, Crohn's disease, rheumatoid arthritis are either ambiguous or negative. Although in a few cases melatonin seems to aggravate some conditions, the vast majority of studies document the very low toxicity of melatonin over a wide range of doses.

Melatonin inhibits aromatase promoter expression by regulating cyclooxygenases expression and activity in breast cancer cells.

BACKGROUND: Melatonin reduces the development of breast cancer interfering with oestrogen-signalling pathways, and also inhibits aromatase activity and expression. Our objective was to study the promoters through which melatonin modifies aromatase expression, evaluate the ability of melatonin to regulate cyclooxygenases and assess whether the effects of melatonin are related to its effects on intracellular cAMP, in MCF-7 cells. METHODS: Total aromatase mRNA, aromatase mRNA promoter regions and cyclooxygenases mRNA expression were determined by real-time RT-PCR. PGE(2) and cAMP were measured by kits. RESULTS: Melatonin downregulated the gene expression of the two major specific aromatase promoter regions, pII and pI.3, and also that of the aromatase promoter region pI.4. Melatonin 1 nM was able to counteract the stimulatory effect of tetradecanoyl phorbol acetate on PGE(2) production and inhibit COX-2 and COX-1 mRNA expression. Melatonin 1 nM elicited a parallel time-dependent decrease in both cyclic AMP formation and aromatase mRNA expression. CONCLUSIONS: This study shows that melatonin inhibits aromatase activity and expression by regulating the gene expression of specific aromatase promoter regions. A possible mechanism for these effects would be the regulation by melatonin of intracellular cAMP levels, mediated by an inhibition of cyclooxygenase activity and expression.

Potential of flavonoids as anti-inflammatory agents: modulation of pro-inflammatory gene expression and signal transduction pathways.

Flavonoids are a large class of naturally occurring compounds widely present in fruits, vegetables, and beverages derived from plants. Reports have suggested that these compounds might be useful for the prevention of a number of diseases, partly due to their anti-inflammatory properties. It has been demonstrated that flavonoids are able to inhibit expression of isoforms of inducible nitric oxide synthase, ciclooxygenase and lipooxygenase, which are responsible for the production of a great amount of nitric oxide, prostanoids and leukotrienes, as well as other mediators of the inflammatory process such as cytokines, chemokines or adhesion molecules. Modulation of the cascade of molecular events leading to the over-expression of those mediators include inhibition of transcription factors such as nuclear factor kappa B, activator protein 1, signal transducers and activators of transcription, CCAAT/enhancer binding protein and others. Effects on the binding capacity of transcription factors may be regulated through the inhibition of protein kinases involved in signal transduction, such as mitogen activated protein kinases. Although the numerous studies published with in vitro approaches allow identifying molecular mechanisms of flavonoid effects, the limited bioavailability of these molecules makes necessary validation in humans. Whatever the case, the data available make clear the potential utility of dietary flavonoids or new flavonoid-based agents for the possible treatment of inflammatory diseases. The present review summarizes recent research data focusing on the modulation of the expression of different inflammatory mediators by flavonoids and the effects on cell signaling pathways responsible for their anti-inflammatory activity.

Melatonin as a selective estrogen enzyme modulator.

Melatonin exerts oncostatic effects on different kinds of tumors, especially on hormone-dependent breast cancer. The general conclusion is that melatonin, in vivo, reduces the incidence and growth of chemically-induced mammary tumors in rodents, and, in vitro, inhibits the proliferation and invasiveness of human breast cancer cells. Both studies support the hypothesis that melatonin inhibits the growth of breast cancer by interacting with estrogen-signaling pathways through three different mechanisms: (a) the indirect neuroendocrine mechanism which includes the melatonin down-regulation of the hypothalamic-pituitary-reproductive axis and the consequent reduction of circulating levels of gonadal estrogens, (b) direct melatonin actions at tumor cell level by interacting with the activation of the estrogen receptor, thus behaving as a selective estrogen receptor modulator (SERM), and (c) the regulation of the enzymes involved in the biosynthesis of estrogens in peripheral tissues, thus behaving as a selective estrogen enzyme modulator (SEEM). As melatonin reduces the activity and expression of aromatase, sulfatase and 17beta-hydroxysteroid dehydrogenase and increases the activity and expression of estrogen sulfotransferase, it may protect mammary tissue from excessive estrogenic effects. Thus, a single molecule has both SERM and SEEM properties, one of the main objectives desired for the breast antitumoral drugs. Since the inhibition of enzymes involved in the biosynthesis of estrogens is currently one of the first therapeutic strategies used against the growth of breast cancer, melatonin modulation of different enzymes involved in the synthesis of steroid hormones makes, collectively, this indolamine an interesting anticancer drug in the prevention and treatment of estrogen-dependent mammary tumors.

Selective estrogen enzyme modulator actions of melatonin in human breast cancer cells.

Melatonin exerts oncostatic effects on different kinds of neoplasias, especially on estrogen-dependent mammary tumors. Current knowledge about the mechanisms by which melatonin inhibits the growth of breast cancer cells point to an interaction of melatonin with estrogen-responsive pathways. The intratumoral production of estrogens in breast carcinoma tissue plays a pivotal role in the proliferation of mammary tumoral cells and its blockade is one of the main objectives of the treatment of breast cancer. The aim of the present work is centered on the study of the role of melatonin in the control of some enzymes involved in the formation and transformation of estrogens in human breast cancer cells. The present study demonstrates that melatonin, at physiologic concentrations, modulates the synthesis and transformation of biologically active estrogens in MCF-7 cells, through the inhibition of sulfatase (STS) and 17beta-hydroxysteroid dehydrogenase type 1 (17beta-HSD1) activity and expression, enzymes involved in the estradiol formation in breast cancer cells. Physiologic concentrations of melatonin also stimulate the activity and expression of estrogen sulfotransferase (EST), the enzyme responsible for the formation of the biologically inactive estrogen sulfates. The level of EST mRNA steady-state of cells treated with melatonin was three times higher than that in control cells. These findings which document that melatonin has an inhibitory effect on STS and 17beta-HSD1 and a stimulatory effect on EST, in combination with its previously described antiaromatase effect, can open up new and interesting possibilities in clinical applications of melatonin in breast cancer.

[Perceived pain and weather changes in rheumatic patients]. / A percepçao da dor e alteracoes climatéricas em doentes reumáticos.

INTRODUCTION: Rheumatic patients with chronic pain describe in a vivid way the influence of climate on pain and disease activity. Several studies seem to confirm this association. OBJECTIVES: To evaluate and compare in a population of rheumatic patients the perceived influence of weather changes on pain and disease activity METHODS: This is a retrospective cross-sectional study. For three weeks an assisted self-reported questionnaire with nine dimensions and a VAS pain scale was performed on consecutive out-patients in our clinic. RESULTS: 955 patients 787 female 168 male mean age 57.9 years with several rheumatologic diagnosis were evaluated. Overall 70 of the patients believed that the weather influenced their disease and 40 believed that the influence was high. Morning stiffness was influenced in 54 high influenced in 34 . Autumn and Winter were the most influential periods as well as humidity 67 and low temperatures 59 . CONCLUSION: In our study as well as in literature we found that a high percentage of patients 70 perceived that weather conditions influenced their pain and disease. Fibromyalgia patients seemed to be strongly influenced by weather changes. Our study confirms that patients perception on the influence of climate on pain and therefore their disease is an important clinical factor and it should be considered when evaluating rheumatic patients.

Melatonin and estradiol effects on food intake, body weight, and leptin in ovariectomized rats.

OBJECTIVE: The study in ovariectomized (Ovx) rats, as a model of menopausal status, of the effects of melatonin (M) and/or estradiol (E), associated or not with food restriction, on body weight (BW) and serum leptin levels. METHODS: Female SD rats (200-250 g) were Ovx and treated with E, M, E+M or its diluents. Control sham-Ovx rats were treated with E-M diluents. After 7 weeks being fed ad libitum, the animals were exposed for 7 more weeks to a 30% food restriction. We measured: food intake, BW, nocturnal and diurnal urinary excretion of sulphatoxymelatonin (aMT6s), leptin in midday and midnight blood samples, glucose, total cholesterol, LDL, HDL and triglycerides. RESULTS: Day/night rhythm of aMT6s excretion was preserved in all cases. The increase of aMT6s excretion in M-treated animals basically affected the nocturnal period. In animals fed ad libitum, E fully prevented Ovx-induced increase of BW, leptin and cholesterol. Melatonin reduced food intake and partially prevented the increase of BW and cholesterol, without changing leptin levels. Under food restriction, M was the most effective treatment in reducing BW and cholesterol. Leptin levels were similar in M, E or E+M treated rats, and lower than in untreated Ovx rats. CONCLUSIONS: Our result gives a preliminary experimental basis for a post-menopausal co-treatment with estradiol and melatonin. It could combine the effectiveness of estradiol (not modified by melatonin) with the positive effects of melatonin (improvement of sleep quality, prevention of breast cancer, etc.). The possible beneficial effects of melatonin which could justify its use, need to be demonstrated in clinical trials.

Inhibitory effects of pharmacological doses of melatonin on aromatase activity and expression in rat glioma cells.

Melatonin exerts oncostatic effects on different kinds of neoplasias, especially on oestrogen-dependent tumours. Recently, it has been described that melatonin, on the basis of its antioxidant properties, inhibits the growth of glioma cells. Glioma cells express oestrogen receptors and have the ability to synthesise oestrogens from androgens. In the present study, we demonstrate that pharmacological concentrations of melatonin decreases the growth of C6 glioma cells and reduces the local biosynthesis of oestrogens, through the inhibition of aromatase, the enzyme that catalyses the conversion of androgens into oestrogens. These results are supported by three types of evidence. Firstly, melatonin counteracts the growth stimulatory effects of testosterone on glioma cells, which is dependent on the local synthesis of oestrogens from testosterone. Secondly, we found that melatonin reduces the aromatase activity of C6 cells, measured by the tritiated water release assay. Finally, by (RT)-PCR, we found that melatonin downregulates aromatase mRNA steady-state levels in these glioma cells. We conclude that melatonin inhibits the local production of oestrogens decreasing aromatase activity and expression. By analogy to the implications of aromatase in other forms of oestrogen-sensitive tumours, it is conceivable that the modulation of the aromatase by pharmacological melatonin may play a role in the growth of glioblastomas.

Melatonin prevents the estrogenic effects of sub-chronic administration of cadmium on mice mammary glands and uterus.

Cadmium (Cd) is a heavy metal classified as a human carcinogen. Occupational exposure, dietary consumption and cigarette smoking are sources of Cd contamination. Cd-induced carcinogenicity depends on its oxidative and estrogenic actions. A possible role of Cd in breast cancer etiology has been recently suggested. Melatonin, because of its antioxidant and antiestrogenic properties could counteract the toxic effects of this metalloestrogen. Our aim was both to determine the effects of relevant doses of Cd on mice mammary glands and uterus and to test whether melatonin would counteract its effects. Female mice of different ages and estrogenic status (prepuberal, adult intact, adult ovariectomized) were treated with CdCl(2) (2-3 mg/kg, i.p.), melatonin (10 microg/mL in drinking water), CdCl(2) + melatonin, or diluents. Whereas in prepuberal animals Cd disturbs mammary ductal growth and reduces the number of terminal end buds, in adults, regardless of the steroidal milieu, Cd exerts estrogenic effects on mammary glands, increasing lobuloalveolar development and ductal branching. Uterine weight also increased as a result of Cd treatment. The effects of Cd are partially inhibited by melatonin. In adult ovariectomized mice, Cd concentration in blood of animals treated with CdCl(2) + melatonin was lower than in mice receiving only Cd; the opposite effects were found in non-castrated animals. As Cd mimics the effect of estrogens, the high incidence of breast cancer in tobacco smokers and women working in industries related with Cd could be explained because of the properties of this metal. The effects of melatonin point to a possible role of this indoleamine as a preventive agent for environmental or occupational Cd contamination.

Effects of MT1 melatonin receptor overexpression on the aromatase-suppressive effect of melatonin in MCF-7 human breast cancer cells.

A major mechanism through which melatonin reduces the development of breast cancer is based on its anti-estrogenic actions by interfering at different levels with the estrogen-signalling pathways. Melatonin inhibits both aromatase activity and expression in vitro (MCF-7 cells) as well as in vivo, thus behaving as a selective estrogen enzyme modulator. The objective of this study was to study the effect of MT1 melatonin receptor overexpression in MCF-7 breast cancer cells on the aromatase-suppressive effects of melatonin. Transfection of the MT1 melatonin receptor in MCF-7 cells significantly decreased aromatase activity of the cells and MT1-transfected cells showed a level of aromatase activity that was 50% of vector-transfected MCF-7 cells. The proliferation of estrogen-sensitive MCF-7 cells in an estradiol-free media but in the presence of testosterone (an indirect measure of aromatase activity) was strongly inhibited by melatonin in those cells overexpressing the MT1 receptor. This inhibitory effect of melatonin on cell growth was higher on MT1 transfected cells than in vector transfected ones. In MT1-transfected cells, aromatase activity (measured by the tritiated water release assay) was inhibited by melatonin (20% at 1 nM; 40% at 10 microM concentrations). The same concentrations of melatonin did not significantly influence the aromatase activity of vector-transfected cells. MT1 melatonin receptor transfection also induced a significant 55% inhibition of aromatase steady-state mRNA expression in comparison to vector-transfected MCF-7 cells (p<0.001). In addition, in MT1-transfected cells melatonin treatment inhibited aromatase mRNA expression and 1 nM melatonin induced a higher and significant down-regulation of aromatase mRNA expression (p<0.05) than in vector-transfected cells. The findings presented herein point to the importance of MT1 melatonin receptor in mediating the oncostatic action of melatonin in MCF-7 human breast cancer cells and confirm MT1 melatonin receptor as a major mediator in the melatonin signalling pathway in breast cancer.

Melatonin inhibits both ER alpha activation and breast cancer cell proliferation induced by a metalloestrogen, cadmium.

Cadmium (Cd) is a heavy metal affecting human health both through environmental and occupational exposure. There is evidence that Cd accumulates in several organs and is carcinogenic to humans. In vivo, Cd mimics the effect of estrogens in the uterus and mammary gland. In estrogen-responsive breast cancer cell lines, Cd stimulates proliferation and can also activate the estrogen receptor independent of estradiol. The ability of this metalloestrogen to increase gene expression in MCF7 cells is blocked by anti-estrogens suggesting that the activity of these compounds is mediated by ER alpha. The aims of this work were to test whether melatonin inhibits Cd-induced proliferation in MCF7 cells, and also to study whether melatonin specifically inhibits Cd-induced ER alpha transactivation. We show that melatonin prevents the Cd-induced growth of synchronized MCF7 breast cancer cells. In transient transfection experiments, we prove that both ER alpha- and ER beta-mediated transcription are stimulated by Cd. Melatonin is a specific inhibitor of Cd-induced ER alpha-mediated transcription in both estrogen response elements (ERE)- and AP1-containing promoters, whereas ER beta-mediated transcription is not inhibited by the pineal indole. Moreover, the mutant ER alpha-(K302G, K303G), unable to bind calmodulin, is activated by Cd but becomes insensitive to melatonin treatment. These results proved that melatonin inhibits MCF7 cell growth induced by Cd and abolishes the stimulatory effect of the heavy metal in cells expressing ER alpha at both ERE-luc and AP1-luc sites. We can infer from these experiments that melatonin regulates Cd-induced transcription in both ERE- and AP1 pathways. These results also reinforce the hypothesis of the anti-estrogenic properties of melatonin as a valuable tool in breast cancer therapies.