DNA slows dissociation of progesterone receptor-steroid ligand complexes

Steroid ligands are known to affect the interactions of their respective receptors with DNA. In the present study, the possibility of DNA interference in progesterone receptor-ligand interactions was investigated. An oligonucleotide containing a hormone response element (HRE) was shown to decrease the dissociation rate of complexes of [3H]progesterone or [3H]16alpha,17alpha-cycloalkanoprogesterones with PRs from rabbit and rat uterine cytosol. The extent to which the oligonucleotide affected the dissociation constant varied from about 4- to 1.5-fold depending on the ligand structure and was ranked in the following order: progesterone>16alpha,17alpha-cyclopropanoprogesterone approximately 16alpha,17alpha-cyclopentanoprogesterone>/=16alpha,17alpha-cyclohex-2'-enoprogesterone approximately 6alpha-methyl-16alpha,17alpha-cyclohexanoprogesterone>/=16alpha,17alpha-cyclohexanoprogesterone. The control oligonucleotide lacking HRE had a weak effect, if any, on the dissociation kinetics. No influence of the HRE-containing oligonucleotide on the equilibrium binding of ligands to PR was observed. The results suggest that the DNA partner affects binding of PR to its ligand.     

Cardiotonic steroids differentially affect intracellular Na+ and [Na+]i/[K+]i-independent signaling in C7-MDCK cells

Recently, we reported that ouabain kills renal epithelial and vascular endothelial cells independently of elevation of the [Na(+)](i)/[K(+)](i) ratio. These observations raised the possibility of finding cardiotonic steroids (CTS) that inhibit the Na(+),K(+) pump without attenuating cell survival and vice versa. To test this hypothesis, we compared CTS action on Na(+),K(+) pump, [Na(+)](i) content, and survival of Madin-Darby canine kidney cells. At a concentration of 1 microM, ouabain and other tested cardenolides, as well as bufadienolides such as bufalin, cinobufagin, cinobufotalin, and telobufotoxin, led to approximately 10-fold inhibition of the Na(+),K(+) pump, a 2-3-fold decrease in staining with dimethylthiazol-diphenyltetrazolium (MTT), and massive death indicated by detachment of approximately 80% of cells and caspase-3 activation. In contrast, Na(+),K(+) pump inhibition and elevation of [Na(+)](i) seen in the presence of 3 microM marinobufagenin (MBG) and marinobufotoxin did not affect MTT staining and cell survival. Inhibition of the Na(+),Rb(+) pump in K(+)-free medium was not accompanied by a decline of MTT staining and cell detachment but increased sensitivity to CTS. In K(+)-free medium, half-maximal inhibition of (86)Rb influx was observed in the presence of 0.04 microM ouabain and 0.1 microM MBG, whereas half-maximal detachment and decline of MTT staining were detected at 0.03 and 0.004 microM of ouabain versus 10 and 3 microM of MBG, respectively. Both ouabain binding and ouabain-induced [Na(+)](i),[K(+)](i)-independent signaling were suppressed in the presence of MBG. Thus, our results show that CTS exhibit distinctly different potency in Na(+),K(+) pump inhibition and triggering of [Na(+)](i)/[K(+)](i)-independent signaling, including cell death.     

Structural Features of Pregna-D′-pentaranes Determining Their Interaction with Three Rat Proteins

Competition of a number of progesterone 16,17-cycloalkane derivatives with ³H-labeled ligands for the binding sites of rat uterine progesterone receptor, uterine pentaranophilin, and blood serum pentaranophilin was studied. We found that the selective ligands for the progesterone receptor are progesterone, 16,17-cyclopropanoprogesterone, and 16,17-cyclopent-3-enoprogesterone and the selective ligands for serum pentaranophilin are 6-methyl-16,17-cyclohexanopregna-1,4-diene-3,20-dione and 3-hydroxy-16,17-cyclohexanopregn-5-en-20-one. No selective ligands for the uterine pentaranophilin were found. The majority of substituents in rings A, B, and D we studied decreased the affinity of ligands for all the three proteins. The substitution of the ⁵-3-hydroxy grouping for the ⁴-3-keto grouping exerted the strongest negative effect in the case of the progesterone receptor and the uterine pentaranophilin, whereas the introduction of the 3,4-dimethyl grouping strongly inhibited the ligand affinity for the uterine pentaranophilin. The extent and even the direction of the effect of a substituent on the affinity of ligands for the proteins substantially depended on the presence of other substituents in the steroid molecules. We hypothesized that a certain similarity exists between three proteins studied in respect to the structures of their ligand-binding pockets.     

P. P. Golikov,Receptor Mechanisms of Antiglucocorticoid Effect at Emergent States,Moscow: Meditsina, 2002, 311 pp.

Russian Journal of Bioorganic Chemistry -     

Substituted 16α,17α-cyclohexanopregnanes: the anionic oxy-Cope rearrangement of 3β-<Emphasis Type="Italic">tert</Emphasis>-butyldimethylsilyloxy-19-hydroxy-19-vinyl-16α,17α-cyclohexapregn-5-en-20-one

(19R)-and (19S)-tert-Butyldimethylsilyl (TBS) ethers of 19-hydroxy-19-vinyl-16α,17α-cyclohexanopregn-5-en-20-ones were synthesized. These compounds containing the 1,5-oxydienoic motif were subjectedto the anionic oxy-Cope rearrangement to obtain 3β-TBS ether of 6β-(3-oxopropyl)-16α,17α-cyclohexano-19-norpregn-5(10)-en-20-one. The structures of the compounds synthesized were confirmed by the analysis of their ¹H and ¹³C NMR spectra.     

Species and Tissue Distribution of Proteins Binding 16α,17α-Cycloalkanoprogesterone Derivatives

The binding of [³H]progesterone and [³H]16,17-cycloalkanoprogesterones to proteins from rat, rabbit, and human uteri and other organs was studied. We found that 16,17-cycloalkanoprogesterone derivatives display affinities for the uterine progesterone receptors comparable with that of the natural hormone and no substantial species differences in the affinity. Rabbit uterus was found to have no proteins distinct from the progesterone receptor that specifically bind [³H]16,17-cycloalkanoprogesterones. At the same time, in the human uterus, we found another protein that binds some of these progesterone derivatives; it turned out to be similar to the protein from rat uterus. A similar protein with the same selectivity and affinity for steroids was also found in rat and human kidneys. Blood serum, liver, lung, and a number of other tissues were found to contain a protein of the third type that binds the same 16,17-cycloalkanoprogesterones and exhibits submicromolar K _d values for these steroids and a very low affinity for progesterone. We speculated that the introduction of a bulky substituent adjacently to the 17-side chain of progesterone could result in a change in the general biodynamics of the derivative including its transport, uptake, and accumulation in tissues, which may determine the selectivity of its effect.     

The Synthesis of O-Substituted 6-Oximes of 16α,17α-Cyclohexanopregn-4-ene-3,6,20-trione Labeled by Tritium in Position 1,2

6-O-(3-Methoxycarbonylpropyl)- and 6-O-(3-carboxypropyl)oximes of 16,17-cyclohexanopregn-4-ene-3,6,20-trione labeled by tritium in position 1,2 were synthesized. When using homogenous catalysts, the molar radioactivity of the resulting preparations was 1.5–1.7 PBq/mol.     

Acylhydrazones of 20-keto steroids and their transformations: I. Synthesis and properties of 1′-acyl-substituted 3′-methylandrosteno[16,17-<Emphasis Type="Italic">d</Emphasis>]pyrazolines

Acetates of 3β-hydroxy-3′-methyl-1′(N)-acylandrost-5-eno[16,17-d]pyrazolines bearing monothiooxamide acyl groups were synthesized during the study of approaches to the synthesis of 3′-methylandrosteno[16,17-d]azoles, promising biologically active analogues of 20-keto pregnenanes, and their properties were investigated. The cyclization of Δ¹⁶-20-thiooxamidohydrazones to the corresponding heterocycles was shown to proceed under rigorous conditions and to depend partially on the nature of the oxamide grouping.     

Morphological Changes in Rat Uterus Tissues under the Action of Progestins and Antiprogestins of the Pregna-D"-pentaran Series

Changes in the uterus morphology of mature female rats were studied on the model of pseudopregnancyafter treatment with the progestin 16,17-cyclohexanoprogesterone (PR) and the antirpogestins 5(H)-16,17-cyclohexano-4,5-dihydroprogesterone (APR1) and 5(H)-16,17-cyclohexano-4,5-dihydroprogesterone (APR2). The rats were preliminarily estrogenized with 17-estradiol at a dose of 1 g/(animal day) for 4 days and then treated with PR at a dose of 0.2 mg/(animal day) for 14 days. The first group was then left without any treatment, whereas APR1 and APR2 were injected at the dose of 0.2 mg/(animal day) for 4 days to the animals of the second and the third groups, respectively. Light and electron microscopy of the uterus preparations demonstrated that the PR action provoked a complete pseudopregnancy picture characterized by the endometrium functionalization and the myometrium hypertrophy. Subsequent treatment with APR1 and APR2 caused the hypertrophy to cease, which had a more pronounced effect in the case of APR2. At the same time, some indications of the endometrium functionalization remained observable after treatment with APR1 and APR2. The specific binding sites for ³H-labeled APR1 and APR2 were absent from the uterus cytosol for the rats gestagenized with PR.