PubMed Health⌕ Search

Biomedical subjects

C Sumida

Publications and source records attributed to C Sumida.

At least 19 recordsLinked to original sources
PubMed1995

Unsaturated fatty acids synergistically enhance glucocorticoid-induced gene expression.

Regulation by unsaturated fatty acids of glucocorticoid-sensitive gene transcription was studied in HeLa cells transiently transfected with a mouse mammary tumour virus-luciferase reporter gene. Arachidonic acid and docosahexaenoic acid by themselves had no effect on basal levels of luciferase expression. However, they were able to enhance dexamethasone-induced transcription by 1.4-2.3 times (25-42 times the control levels) in a dose-dependent manner (ED50: 18 and 8 microM) for arachidonic and docosahexaenoic acid, respectively. The glucocorticoid antagonist RU486 effectively antagonized the dexamethasone response as well as the synergistic effect observed in the presence of arachidonic and docosahexaenoic acids, suggesting that the glucocorticoid receptor was an intermediate in the fatty acid synergism of the dexamethasone response. These studies show that fatty acids may be playing a role in modulating the intracellular steroid hormone signalling pathway to co-regulate a glucocorticoid-sensitive promoter.

Animals↗
PubMed1994

In vivo effect of free fatty acids on the specific binding of glucocorticosteroids to corticosteroid binding globulin and liver receptors in immature rats.

Stimulating lipase activity with heparin (200 IU/kg b.w.) increased the plasma free fatty acid (FFA) concentration of immature rats (15 days). The effect of this elevated FFA concentration on glucocorticoid binding to corticosteroid binding globulin (CBG), and liver cytosol glucocorticoid receptor (GR), was analyzed. The plasma FFA concentration increased 2-fold, 10 minutes (P < 0.001), 20 minutes (P < 0.01), and 60 minutes (P < 0.01) post-heparin. The corticosterone (B) and progesterone concentrations were unchanged 60 minutes post-injection. The binding activity of immature rat CBG for B dropped 50% (P < 0.001) 60 minutes post-heparin injection, decreased B binding and increased plasma FFA were correlated (r = -0.8). The decreased B binding resulted from a 2-fold decrease in the apparent number of CBG binding sites; the affinity constant (Ka) remained unchanged. The liver cytosol endogenous FFA content of immature rats was also increased 2-fold, 60 minutes after heparin-induced lipolysis. The increased cytosol FFA, with no significant change in glucocorticoid, was accompanied by a significant decrease in dexamethasone binding to liver cytosol glucocorticoid receptor. The decrease resulted from a significantly lower apparent Ka for dexamethasone and fewer receptor binding sites (n). There was a good inverse correlation between Ka (r = -0.93) and n (r = -0.90) and the increased liver cytosol FFA content. Thus the higher plasma FFA induced in vivo by lipase activation or a standard FFA mixture probably causes conformational changes in CBG and GR, reducing glucocorticoid binding to immature rat CBG and liver GR.

Animals↗
PubMed1994

Fatty acids and cell signal transduction.

Fatty acids released from membrane phospholipids by cellular phospholipases or available to the cell from the extracellular environment are important cell signalling molecules. Fatty acids can act as second messengers involved in the transduction of external signals because their concentrations are rapidly and transiently altered in response to the binding of specific agonists to plasma membrane receptors, and they substitute for the classical second messengers of the inositide phospholipid and the cyclic AMP signal transduction pathways. Fatty acids are also modulators because they act in a reversible manner at a precise intracellular location for a very short time to amplify, attenuate or deviate a signal. Fatty acids modify the activities of phospholipases, protein kinases, G-proteins, adenylate and guanylate cyclases as well as ion channels and other biochemical events involved in stimulus-response coupling mechanisms. The action of fatty acids on signal transduction pathways can be direct and/or indirect (by catabolic conversion of arachidonic acid to eicosanoids). However, a number of studies clearly show that fatty acids per se are messenger and modulator molecules mediating responses of the cell to extracellular signals.

Animals↗
PubMed1993

Rapid and long-term effects of 17 beta-estradiol on PIP2-phospholipase C-specific activity of MCF-7 cells.

Activity of the enzyme phosphatidylinositol 4,5-bisphosphate phospholipase C (PIP2-PLC) was demonstrated in MCF-7 human breast cancer cell homogenate. The addition of 10(-9) M 17 beta-estradiol to the culture medium elicited in the cells two types of responses depending on the period of exposure. Enzyme activity was rapidly activated at 15 s of incubation. After 5 min, PIP2-PLC activity was inhibited, and this effect continued at least until 24 h of exposure to the hormone. When 17 beta-estradiol was added in vitro to the total homogenate of untreated cells, enzyme activity was stimulated in a dose-dependent manner. These findings indicate that 17 beta-estradiol induces early and long-term modifications of the phosphoinositide signal pathway in intact MCF-7 cells as well as in vitro. The rapidity of the early effect suggests a non-genomic action of estradiol.

Cell Division↗
PubMed1993

Role of fatty acids in signal transduction: modulators and messengers.

Many of the steps involved in signal transduction are regulated positively or negatively by fatty acids (FA) per se. FA have been shown to act both as modulators and messengers, particularly of signals triggered at the level of cell membranes. Enzymes and proteins of the cyclic AMP and the protein kinase C signalling pathways and those involving ion fluxes and mobilization are both activated and/or inhibited by FA. FA can also participate in a feedback control mechanism since phospholipases are themselves modulated by FA. FA, particularly arachidonic acid liberated from membrane phospholipids, are also second messengers in signal transduction, and a good example is the activation of protein kinase C by FA. FA play an important role in regulating the transmission of signals from the extracellular environment by acting as modulators and messengers within the complex intracellular network of relays.

Animals↗
PubMed1993

Perturbation of the immunosuppressive action of glucocorticoids in rat thymocytes by liposoluble extracts of serum from AIDS patients.

Liposoluble extracts of serum from healthy men and AIDS patients (stages IVC1 and IVD by CDC criteria) inhibited the incorporation of [3H]thymidine into isolated rat thymocytes, but AIDS extracts were less inhibitory, requiring 1.8 times more cortisol in the AIDS extracts than in the healthy extracts to inhibit [3H]thymidine incorporation by 50%. Although the total serum extracts from AIDS patients contained 1.7 times more cortisol than the extracts from healthy controls, the AIDS extracts decreased the binding affinity (Ka) of [3H]dexamethasone to rat thymus glucocorticoid receptors by 50% less than the healthy control extracts. The present study seems to indicate that a substance(s) can be extracted from the serum of AIDS patients that attenuates the inhibitory effect of cortisol on thymocyte proliferation and interferes with the binding of cortisol to the glucocorticoid receptor.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Interaction of unsaturated fatty acids with rat liver glucocorticoid receptors: studies to localize the site of interaction.

Polyunsaturated fatty acids have been shown to decrease the binding of [3H]dexamethasone to rat liver glucocorticoid receptors by mixed non-competitive inhibition, suggesting that these fatty acids interact at a site on the receptor different from the hormone binding site. The present study was undertaken to localize the site of interaction of polyunsaturated fatty acids on the receptor by comparing the differential effects of docosahexaenoic acid (a 22-carbon polyunsaturated fatty acid of the series n-3) on antagonist (RU486) and agonist binding, by covalent cross-linking of the hsp 90 and other proteins to the receptor to attempt to mask the site of interaction, by limited trypsinization to cleave the site and by using antibodies against specific epitopes to prevent fatty acid access by steric hindrance. Binding [3H]RU486 was not inhibited by docosahexaenoic acid at a concentration (60 mumol/l) that increases the dissociation constant of [3H]dexamethasone eightfold. Covalent stabilization of the hetero-oligomeric glucocorticoid receptor structure did not keep the fatty acid from inhibiting [3H]dexamethasone binding. The binding to the receptor of monoclonal and polyclonal antibodies against different domains of the receptor did not sterically hinder the fatty acid interaction with the receptor. After limited trypsinization of the receptor, the fatty acid still increased the dissociation rate constant of [3H]dexamethasone binding, indicating that the site of interaction of polyunsaturated fatty acids is on a fragment of the receptor containing the hormone-binding domain and some sequences C-terminal of the DNA-binding domain.

Animals↗
PubMed1992

Modulation of glucocorticoid binding to rat liver cytosol receptor by lipid-soluble extracts from the serum of AIDS patients.

The total liposoluble extract of sera from AIDS patients, IVC1 and IVD stages, containing cortisol and free fatty acids (FFA) inhibited [3H]dexamethasone binding to a lesser extent than did the same quantity of total liposoluble extract of sera from healthy men. FFA isolated from extracts of AIDS sera by Sephadex LH20 chromatography had less effect on [3H]dexamethasone binding to rat liver glucocorticoid receptor than those extracted from sera of healthy men. These results suggest the presence in sera of AIDS patients of a liposoluble substance which could be limiting the inhibitory effect of FFA on [3H]dexamethasone binding to glucocorticoid receptor by inducing a conformational change in glucocorticoid receptor that could alter the biological action of glucocorticoids. The pathological consequence could be the apparent contradiction of high cortisolemia and clinical symptoms of adrenal insufficiency that have been observed in AIDS patients.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Modulatory effects of unsaturated fatty acids on the binding of glucocorticoids to rat liver glucocorticoid receptors.

Binding of the synthetic glucocorticoid dexamethasone to the rat liver cytosol glucocorticoid receptor was inhibited by physiological concentrations of nonesterified fatty acids as a function of increasing dose, degree of unsaturation, and chain length of the fatty acid. Polyunsaturated fatty acids were the most potent inhibitors. Scatchard analysis and Line-weaver-Burk plots of the binding data revealed that both the association constants and number of binding sites decreased and that polyunsaturated fatty acids inhibition was of a mixed non-competitive type. The dissociation rate constant of [3H]dexamethasone from glucocorticoid receptors was increased by up to 10 times in the presence of docosahexaenoic acid, whereas a competitive inhibitor like the glucocorticoid antagonist RU 38486 had no effect. Moreover, sucrose density gradient analysis showed that docosahexaenoic acid inhibited the binding of [3H] dexamethasone to both the 8.8S and 4S forms. The results strongly suggest that unsaturated fatty acids are interacting at a site on the receptor different from the hormone binding site and the heat shock protein and that by binding to a second site unsaturated fatty acids greatly change the conformation of the hormone binding site to reduce its affinity for the hormone, either partially or completely depending on the concentration and the class of the fatty acid.

Animals↗
PubMed1990

Stimulation of progesterone receptors by phorbol ester and cyclic AMP in fetal uterine cells in culture.

The role of growth factor signal transducers in the induction of the progesterone receptor by epidermal growth factor (EGF) and the potential sites of EGF antagonism by an antiestrogen were studied in fetal uterine cells in culture. The effects of EGF and estradiol were not additive, suggesting that EGF and estradiol are acting through common mechanisms where antiestrogens could possibly intervene. Fetal uterine cells in culture were found to contain specific, high affinity binding sites for [125I]EGF. Estradiol treatment of the cells led to a higher number of binding sites, but the site of action of 4-hydroxytamoxifen is not the EGF receptor because this antiestrogen had no effect on EGF binding. Activation of protein kinase C by a phorbol ester (12-O-tetradecanoylphorbol 13-acetate) increased progesterone receptor levels to a similar extent as EGF or estradiol. Increasing the intracellular cAMP concentrations by either adding dibutyryl cyclic AMP or activating adenylate cyclase with forskolin also raised progesterone receptor concentrations. Neither the phorbol ester nor dibutyryl cAMP had any effect on cell proliferation. 4-Hydroxytamoxifen completely abolished the effects of the phorbol ester and cAMP. In conclusion, the levels of an estrogen-induced steroid hormone receptor can be regulated by molecules involved in the signal transduction pathway of peptide factors. Moreover, in fetal uterine cells, a potent antiestrogen appears to act as a multiple antagonist but only on an estrogen-inducible response.

Animals↗
PubMed1989

Antiestrogens antagonize the stimulatory effect of epidermal growth factor on the induction of progesterone receptor in fetal uterine cells in culture.

In fetal uterine cells in culture, epidermal growth factor (EGF) increased progesterone receptor concentrations more than 2-fold. Two other growth factors, transforming growth factor-alpha and fibroblast growth factor, were not able to cause the same increase. This response to EGF was dose dependent; a half-maximal effect was obtained at 10(-10) M. The antiestrogens tamoxifen and 4-hydroxytamoxifen were able to antagonize the stimulatory effect of EGF on progesterone receptor concentrations, but they did not affect its mitogenic effect. The inhibitory effect of 4-hydroxytamoxifen depended on concentration; half-maximal inhibition was observed between 0.5-1 X 10(-9) M. 4-Hydroxytamoxifen could completely inhibit the progesterone receptor increase due to EGF even when added to cells already exposed to the growth factor for 6 days. EGF seems to be acting as an estrogen in increasing progesterone receptors in fetal uterine cells, and antiestrogens are potent antagonists of this response, indicating that growth factors may also be involved in some protein-inducing effects of estrogens. Since estrogen receptor levels were at the limits of detectability under all of the experimental conditions studied, nonestrogen receptor-mediated pathways may be involved. These observations show the potential importance of other factors acting in combination with estrogens in the modulation of progesterone receptor levels.

Animals↗
PubMed1989

[Epidermal growth factor induces the progesterone receptor in fetal uterine cells in culture: antagonistic effect of antiestrogens].

Cells isolated from the uterus of the guinea pig foetus can be maintained in culture even through several sub-cultures. In these cells, estradiol increases progesterone receptor concentrations 2 o 3 times, although estradiol has no effect on cell proliferation. Epidermal growth factor (EGF) stimulates both cell proliferation and the progesterone receptor 4-Hydroxytamoxifen, a tamoxifen metabolite and potent anti-oestrogen, completely inhibits the stimulatory effect of EGF on the progesterone receptor but has no effect on the EGF-induced cell growth. These cells have specific binding sites with high affinity for 125I-EGF. Estradiol increases the number of binding sites but does not affect the affinity for EGF. 4-Hydroxytamoxifen has no significant effect on either the number of binding sites or the binding affinity. In conclusion, EGF could be an autocrine or paracrine factor in estrogen-sensitive cells not only as a potent mitogen but also as a factor capable of increasing an estrogen-induced protein like the progesterone receptor. The observation that an anti-estrogen can also act as an "anti-growth factor" suggests a close relationship between estrogens and growth factors.

Animals↗
PubMed1988

Pharmacodynamic and biological effects of anti-estrogens in different models.

The biological response to anti-estrogens is very variable and depends on the animal species considered, the target organ, the parameter studied, and the experimental conditions. Anti-estrogens can bind specifically, (1) to the estrogen receptor, (2) to the typical anti-estrogen specific binding site, and (3) to low density lipoproteins in the plasma. Using a monoclonal antibody against the estrogen receptor, different immunological characteristics of the anti-estrogen-receptor complex can be observed. This difference could explain some of the different biological effects. Studies using different human mammary cancer cell lines (hormone-dependent) show that anti-estrogens are active in decreasing cell proliferation. Also, anti-estrogens can block proteins specifically produced by these cells. Some of these proteins could act as growth or inhibitory factors. Estrogen sulfates are the main precursors of estradiol in breast tissues and this conversion is significantly decreased by anti-estrogens. It is accepted that the main pathway of action of anti-estrogens is through the estrogen receptor, but recent information suggests the possibility that this is not the only step in the mechanism of action of anti-estrogens.

Animals↗
PubMed1988

Control of progesterone receptors in fetal uterine cells in culture: effects of estradiol, progestins, antiestrogens, and growth factors.

Cells from the fetal uterus of the guinea pig have been grown as monolayer cell cultures both as primary cultures and through several passages. The cells have a fibroblast-like morphology and ultrastructure, and the subcultures are estrogen responsive. Estradiol induced a 2- to 3-fold increase in specific binding of [3H]R5020 by 9 days in culture, with no effect on proliferation. This binding has the characteristics of the progesterone receptor from the fetal guinea pig uterus (saturable, high affinity, specific for progestins). The increase in progesterone receptor depended on the dose of estradiol, with a half-maximal response at about 5 X 10(-11) M. Progesterone receptor concentrations were inhibited to below basal levels by progesterone and R5020 and the nonsteroidal antiestrogens, tamoxifen, and 4-hydroxytamoxifen. Both progestins and antiestrogens antagonized the stimulatory effect of estradiol. None of these compounds had any effect on cell growth. On the other hand, insulin and epidermal growth factor caused a great increase in cell proliferation. Insulin alone had no effect on progesterone receptor concentrations, but epidermal growth factor stimulated the progesterone receptor about as much as estradiol. Furthermore, coincubation of insulin with estradiol produced a synergistic effect. Estrogen receptor levels were low or undetectable at any time in either the primary culture or the subcultures. It is concluded that fetal uterine cells in culture can serve as a good in vitro model for study of the control of the progesterone receptor in a fetal target tissue.

Animals↗
PubMed1987

Modulation of the progesterone receptor in the fetal uterus of the progesterone-primed guinea pig in vivo and in organ culture.

Guinea pig fetuses were treated with progesterone for 7 days before placing fetal uteri in organ culture to see if progesterone pre-treatment of fetuses in utero would permanently inhibit the spontaneous rise in progesterone receptor which occurs in organ culture. The data show that: the basal level of progesterone receptor in fetal uteri was not affected by the progesterone treatment and progesterone receptor concentrations in vitro were also not inhibited. When guinea pig fetuses were treated sequentially with progesterone and estradiol, estradiol failed to provoke an uterotrophic effect but it retained its ability to stimulate progesterone receptor concentrations.

Animals↗
PubMed1987

4-Hydroxyandrostenedione is not an aromatase inhibitor in the neonatal guinea pig.

One-day-old newborn guinea pigs were treated with 4-hydroxyandrostenedione (50 mg/kg body weight/day) for 5 or 12 consecutive days. This compound did not decrease unconjugated or sulfoconjugated estradiol and estrone levels in the plasma or in the uterine tissue itself. It also did not have any effect on uterine wet weight or the estrogen and progesterone receptor concentrations in the uterus. Moreover, progesterone receptor synthesis which is maintained when neonatal uteri are placed in organ culture conditions for 2 days was not affected by the 4-hydroxyandrostenedione treatment.

Androstenedione↗
PubMed1987

The complexity of anti-estrogen responses.

The actions and biological responses of anti-estrogens are a function of: the experimental conditions, the parameters, the organ and the animal species considered. Target tissues for estrogens in the guinea-pig during the perinatal period are interesting models to explore the action of anti-estrogens. The summary of the data indicates: (1) In the fetal uterus of guinea-pig in in vivo experiments (after injection to the maternal compartment) tamoxifen acts as a real agonist concerning growth, as a partial agonist concerning the stimulation of the progesterone receptor. (2) In in vitro experiments (in organ culture of fetal uterus or in isolated cells) anti-estrogens (tamoxifen or 4-hydroxy-tamoxifen) act as antagonists and also inhibit the effects provoked by estrogens. (3) In the uterus and vagina of newborn guinea-pigs, tamoxifen and its derivatives: 4-hydroxytamoxifen and N-desmethyltamoxifen act as real agonists concerning the uterotrophic and vaginotrophic effects, and also stimulate the amount of DNA per organ, but concerning the progesterone receptor in the uterus, in the short treatment anti-estrogens act as partial agonists but they have no effect in the long treatment. In the vagina in the short treatment anti-estrogens provoke no significant effects, but in the long treatment they are full agonists. In neither of the two biological responses studied (growth and progesterone receptor) does tamoxifen and its derivatives block the action of estradiol. (4) The use of a monoclonal antibody to the estrogen receptor revealed quantitative differences in the activation of the estrogen receptor when bound to estradiol or tamoxifen. This observation was in agreement with the lesser extent of binding to DNA-cellulose of the tamoxifen-estrogen receptor complex as compared with the estradiol-estrogen receptor complex. This fact suggests an impaired activation of the estrogen receptor induced by tamoxifen which might be related to the different biological responses provoked by estrogens and anti-estrogens.

Animals↗