(1/7402) The effects of glucocorticoids and progesterone on hormone-responsive human breast cancer in long-term tissue culture.
Glucocorticoids, at physiological concentration, inhibit cell division and thymidine incorporation in three lines of human breast cancer maintained in long-term tissue culture. At steroid concentrations sufficient to inhibit thymidine incorporation 50%, little or no effect is seen on protein synthesis 48 hr after hormone addition. All three of these lines are shown to have glucocorticoid receptors demonstrable by competitive protein binding assays. Receptors are extensively characterized in one line by sucrose density gradient analysis and binding specificity studies. Good correlation between receptor-binding specificity and biological activity is found except for progesterone, which binds to glucocorticoid receptor but is noninhibitory. Cross-competition and quantification studies demonstrate a separate receptor for progesterone. This receptor has limited binding specificities restricted largely to progestational agents, whereas the glucocorticoid receptor bound both glucocorticoids and progesterone. Two other human breast cancer lines neither contain glucocorticoid receptor nor are inhibited by glucocorticoids. It is concluded that in some cases glucocorticoids can directly limit growth in human breast cancer in vitro without requiring alterations in other trophic hormones. (+info)
(2/7402) Expression of nitric oxide synthase in inflammatory bowel disease is not affected by corticosteroid treatment.
AIM: To examine the effect of corticosteroid treatment on the expression of inducible nitric oxide synthase (iNOS) in the colon of patients with inflammatory bowel disease. METHODS: Four groups of patients were studied: (1) ulcerative colitis treated with high dose corticosteroids (six patients, 10 blocks); (2) ulcerative colitis patients who had never received corticosteroids (10 patients, 16 blocks); (3) Crohn's disease treated with high dose corticosteroids (12 patients, 24 blocks); (4) Non-inflammatory, non-neoplastic controls (four patients, six blocks). Full thickness paraffin sections of colons removed at surgery were immunostained with an antibody raised against the C terminal end of iNOS. Sections were assessed semiquantitatively for the presence and degree of inflammation and immunoreactivity for nitric oxide synthase. RESULTS: Cases of ulcerative colitis and Crohn's disease with active inflammation showed strong staining for nitric oxide synthase. The staining was diffuse in ulcerative colitis and patchy in Crohn's disease, in accordance with the distribution of active inflammation. Staining was seen in epithelial cells and was most intense near areas of inflammation such as crypt abscesses. Non-inflamed epithelium showed no immunoreactivity. Treatment with corticosteroids made no difference to the amount of nitric oxide synthase. CONCLUSIONS: Expression of nitric oxide synthase is increased in both ulcerative colitis and Crohn's disease and appears to be unaffected by treatment with corticosteroids. Disease severity necessitated surgery in all the cases included in this study, regardless of whether or not the patients had received long term corticosteroid treatment. It seems therefore that a high level of iNOS expression and, presumably, production of nitric oxide characterise cases which are refractory to clinical treatment; this suggests that specific inhibition of the enzyme may be a useful therapeutic adjunct. (+info)
(3/7402) Production of prostaglandin f2alpha and its metabolite by endometrium and yolk sac placenta in late gestation in the tammar wallaby, Macropus Eugenii.
In this study, we investigated production of prostaglandin (PG) F2alpha and its metabolite, PGFM, by uterine tissues from tammar wallabies in late pregnancy. Endometrial explants were prepared from gravid and nongravid uteri of tammars between Day 18 of gestation (primitive streak) and Day 26.5 (term) and were incubated in Ham's F-10 medium supplemented with glutamine and antibiotics for 20 h. PGF2alpha and PGFM in the medium were assayed by specific, validated RIAs. Control tissues (leg muscle) did not produce detectable amounts of either PG. Both gravid and nongravid endometria secreted PGF2alpha, and production increased significantly in both gravid and nongravid uteri towards term. PGFM was produced in small amounts by both gravid and nongravid uteri, and the rate of production did not increase. Neither oxytocin nor dexamethasone stimulated PG production in vitro in any tissue at any stage. Thus, the surge in peripheral plasma PGFM levels seen at parturition may arise from increased uterine PG production, but further study is needed to define what triggers this release. (+info)
(4/7402) CCAAT/enhancer-binding protein beta is an accessory factor for the glucocorticoid response from the cAMP response element in the rat phosphoenolpyruvate carboxykinase gene promoter.
The cyclic AMP response element (CRE) of the rat phosphoenolpyruvate carboxykinase (PEPCK) gene promoter is required for a complete glucocorticoid response. Proteins known to bind the PEPCK CRE include the CRE-binding protein (CREB) and members of the CCAAT/enhancer-binding protein (C/EBP) family. We took two different approaches to determine which of these proteins provides the accessory factor activity for the glucocorticoid response from the PEPCK CRE. The first strategy involved replacing the CRE of the PEPCK promoter/chloramphenicol acetyltransferase reporter plasmid (pPL32) with a consensus C/EBP-binding sequence. This construct, termed pDeltaCREC/EBP, binds C/EBPalpha and beta but not CREB, yet it confers a nearly complete glucocorticoid response when transiently transfected into H4IIE rat hepatoma cells. These results suggest that one of the C/EBP family members may be the accessory factor. The second strategy involved co-transfecting H4IIE cells with a pPL32 mutant, in which the CRE was replaced with a GAL4-binding sequence (pDeltaCREGAL4), and various GAL4 DNA-binding domain (DBD) fusion protein expression vectors. Although chimeric proteins consisting of the GAL4 DBD fused to either CREB or C/EBPalpha are able to confer an increase in basal transcription, they do not facilitate the glucocorticoid response. In contrast, a fusion protein consisting of the GAL4 DBD and amino acids 1-118 of C/EBPbeta provides a significant glucocorticoid response. Additional GAL4 fusion studies were done to map the minimal domain of C/EBPbeta needed for accessory factor activity to the glucocorticoid response. Chimeric proteins containing amino acid regions 1-84, 52-118, or 85-118 of C/EBPbeta fused to the GAL4 DBD do not mediate a glucocorticoid response. We conclude that the amino terminus of C/EBPbeta contains a multicomponent domain necessary to confer accessory factor activity to the glucocorticoid response from the CRE of the PEPCK gene promoter. (+info)
(5/7402) Analysis of Chinese herbal creams prescribed for dermatological conditions.
OBJECTIVE: To determine whether Chinese herbal creams used for the treatment of dermatological conditions contain steroids. DESIGN: 11 herbal creams obtained from patients attending general and paediatric dermatology outpatient clinics were analysed with high resolution gas chromatography and mass spectrometry. SETTING: Departments of dermatology and clinical biochemistry. MAIN OUTCOME MEASURE: Presence of steroid. RESULTS: Eight creams contained dexamethasone at a mean concentration of 456 micrograms/g (range 64 to 1500 micrograms/g). All were applied to areas of sensitive skin such as face and flexures. CONCLUSION: Greater regulation needs to be imposed on Chinese herbalists to prevent illegal and inappropriate prescribing of potent steroids. (+info)
(6/7402) Inactivation of the winged helix transcription factor HNF3alpha affects glucose homeostasis and islet glucagon gene expression in vivo.
Mice homozygous for a null mutation in the winged helix transcription factor HNF3alpha showed severe postnatal growth retardation followed by death between P2 and P12. Homozygous mutant mice were hypoglycemic despite unchanged expression of HNF3 target genes involved in hepatic gluconeogenesis. Whereas insulin and corticosteroid levels were altered as expected, plasma glucagon was reduced markedly in the mutant animals despite the hypoglycemia that should be expected to increase glucagon levels. This correlated with a 70% reduction in pancreatic proglucagon gene expression. We also showed that HNF3alpha could bind to and transactivate the proglucagon gene promoter. These observations invoke a central role for HNF3alpha in the regulatory control of islet genes essential for glucose homeostasis in vivo. (+info)
(7/7402) Antisense downregulation of a mouse mammary tumor virus activated protooncogene in mouse mammary tumor cells reverses the malignant phenotype.
Activation of the protooncogene Wnt-1 by insertion of the mouse mammary tumor virus (MMTV) is known to cause mammary tumors in mice. Wnt-1 expression in mammary glands has been postulated to confer direct local growth stimulation of mammary epithelial cells leading to their acquisition of a preneoplastic state. Wnt-1 expression also induces morphological alterations in cultured normal mammary cells. However, it has not been determined whether or not transformed mammary cells require continuous Wnt-1 expression for their ability to form tumors in vivo. To address this question, we constructed antisense and sense Wnt-1 expression vectors containing a synthetic promoter composed of five high-affinity glucocorticoid response elements (GRE5). This promoter is at least 50-fold more inducible by dexamethasone than the promoter contained in the long terminal repeats of MMTV. The vectors were introduced into a mouse mammary tumor cell line (R/Sa-MT) that expresses high levels of endogenous Wnt-1 mRNA and forms rapidly growing tumors when transplanted into syngeneic hosts. Of the 12 stably transfected cell lines established (9 with antisense and 3 with sense constructs), 2 antisense cell lines (R/Sa-MT/antisense) and 1 sense cell line (R/Sa-MT/sense) were examined for inducibility by dexamethasone of antisense and sense Wnt-1 RNAs, changes in endogenous Wnt-1 RNA expression, and changes in cell morphology. The growth patterns of the cells in vitro and in vivo were also examined. Our results show that (1) the levels of the expression of endogenous Wnt-1 mRNA and protein were reduced significantly (>80%) in those cells (R/Sa-MT/antisense) that expressed antisense Wnt-1 RNA at high levels following exposure to dexamethasone, compared to the R/Sa-MT/sense and R/Sa-MT control cells and (2) transplantation of the R/Sa-MT/antisense cells produced smaller tumors ( approximately 0.2 cm in 16 weeks) compared to the tumors ( approximately 2.0 cm in 8 weeks) that were produced by the R/Sa-MT/sense and R/Sa-MT cells. We therefore suggest that Wnt-1 expression is required not only for the transformation of normal mammary cells into tumor cells, but also for the maintenance of their tumorigenicity. (+info)
(8/7402) Role of iNOS in the vasodilator responses induced by L-arginine in the middle cerebral artery from normotensive and hypertensive rats.
1. The substrate of nitric oxide synthase (NOS), L-arginine (L-Arg, 0.01 microM - 1 mM), induced endothelium-independent relaxations in segments of middle cerebral arteries (MCAs) from normotensive Wistar-Kyoto (WKY) and hypertensive rats (SHR) precontracted with prostaglandin F2alpha (PGF2alpha). These relaxations were higher in SHR than WKY arteries. 2. L-N(G)-nitroarginine methyl ester (L-NAME) and 2-amine-5,6-dihydro-6-methyl-4H-1,3-tiazine (AMT), unspecific and inducible NOS (iNOS) inhibitors, respectively, reduced those relaxations, specially in SHR. 3. Four- and seven-hours incubation with dexamethasone reduced the relaxations in MCAs from WKY and SHR, respectively. 4. Polymyxin B and calphostin C, protein kinase C (PKC) inhibitors, reduced the L-Arg-induced relaxation. 5. Lipopolysaccharide (LPS, 7 h incubation) unaltered and inhibited these relaxations in WKY and SHR segments, respectively. LPS antagonized the effect polymyxin B in WKY and potentiated L-Arg-induced relaxations in SHR in the presence of polymyxin B. 6. The contraction induced by PGF2alpha was greater in SHR than WKY arteries. This contraction was potentiated by dexamethasone and polymyxin B although the effect of polymyxin B was higher in SHR segments. LPS reduced that contraction and antagonized dexamethasone- and polymyxin B-induced potentiation, these effects being greater in arteries from SHR. 7. These results suggest that in MCAs: (1) the induction of iNOS participates in the L-Arg relaxation and modulates the contraction to PGF2alpha; (2) that induction is partially mediated by a PKC-dependent mechanism; and (3) the involvement of iNOS in such responses is greater in the hypertensive strain. (+info)