Cholestenoic acid analogues as inverse agonists of the liver X receptors.

Liver X Receptors (LXRs) are ligand dependent transcription factors activated by oxidized cholesterol metabolites (oxysterols) that play fundamental roles in the transcriptional control of lipid metabolism, cholesterol transport and modulation of inflammatory responses. In the last decade, LXRs have become attractive pharmacological targets for intervention in human metabolic diseases and thus, several efforts have concentrated on the development of synthetic analogues able to modulate LXR transcriptional response. In this sense, we have previously found that cholestenoic acid analogues with a modified side chain behave as LXR inverse agonists.

Synthesis and biological activity of fluorinated analogues of the DAF-12 receptor antagonist 24-hydroxy-4-cholen-3-one.

The DAF-12 receptor is a ligand-activated transcription factor that in its ligand-bound form allows the expression of target genes needed to support the reproductive life cycle of the free-living nematode Caenorhabditis elegans, whereas unbound DAF-12 receptor leads to the developmentally arrested "dauer larvae", specialized for survival and dispersal. The endogenous ligands of the DAF-12 receptor are 3-keto-cholestenoic acids dubbed dafachronic acids. In a previous publication we reported that oxysterols with a shorter side chain (C) modulate the DAF-12 receptor activity either as partial agonists or, in the case of the C alcohol 24-hydroxy-4-cholen-3-one, as an antagonist both in vitro and in vivo.

Synthesis and activity evaluation of a series of cholanamides as modulators of the liver X receptors.

The Liver X receptors (LXRs) are members of the nuclear receptor family, that play fundamental roles in cholesterol transport, lipid metabolism and modulation of inflammatory responses. In recent years, the synthetic steroid N,N-dimethyl-3β-hydroxycholenamide (DMHCA) arised as a promising LXR ligand. This compound was able to dissociate certain beneficial LXRs effects from those undesirable ones involved in triglyceride metabolism.

Synthesis of new C-25 and C-26 steroidal acids as potential ligands of the nuclear receptors DAF-12, LXR and GR.

A new methodology to obtain C-25 and C-26 steroidal acids starting from pregnenolone is described. Construction of the side chain was achieved by applying the Mukaiyama aldol reaction with a non-hydrolytic work-up to isolate the trapped silyl enol ether with higher yields. Using this methodology we synthesized three new steroidal acids as potential ligands of DAF-12, Liver X and Glucocorticoid nuclear receptors and studied their activity in reporter gene assays.

Fluorinated oxysterol analogues: Synthesis, molecular modelling and LXRβ activity.

Liver X receptors (LXRs) are nuclear receptors that play central roles in the transcriptional control of lipid metabolism. The ability of LXRs to integrate metabolic and inflammation signalling makes them attractive targets for intervention in human metabolic diseases. Several oxidized metabolites of cholesterol (oxysterols) are endogenous LXR ligands, that modulate their transcriptional responses.

C(16)-C(22) oxygen-bridged analogues of ceDAF-12 and LXR ligands.

The DAF-12 receptor in nematodes and the Liver X Receptor (LXR) in mammals are structurally related transcription factors that play key roles in determining the life span of the organism. Both types of receptors are activated by oxysterols, cholesterol metabolites with oxidized side chains. Restricting the movement of the oxysterol side chain to certain orientations may have profound effects in the activity profile, however this has not been explored so far.

Destabilization of the torsioned conformation of a ligand side chain inverts the LXRβ activity.

Background: Liver X receptors (LXRs) are transcription factors activated by cholesterol metabolites containing an oxidized side chain. Due to their ability to regulate lipid metabolism and cholesterol transport, they have become attractive pharmacological targets. LXRs are closely related to DAF-12, a nuclear receptor involved in nematode lifespan and regulated by the binding of C-27 steroidal acids.

Exploring the molecular basis of action of ring D aromatic steroidal antiestrogens.

Salpichrolides are natural plant steroids that contain an unusual six-membered aromatic ring D. We recently reported that some of these compounds, and certain analogs with a simplified side chain, exhibited antagonist effects toward the human estrogen receptor (ER), a nuclear receptor whose endogenous ligand has an aromatic A ring (estradiol). Drugs acting through the inhibition or modulation of ERs are frequently used as a hormonal therapy for ER(+) breast cancer.

Synthetic DAF-12 modulators with potential use in controlling the nematode life cycle.

Dafachronic acids (DAs) are 3-keto cholestenoic acids bearing a carboxylic acid moiety at the end of the steroid side chain. These compounds interact with the DAF-12 receptor, a ligand-dependent transcription factor that acts as a molecular switch mediating the choice between arrest at diapause or progression to reproductive development and adult lifespan in different nematodes. Recently, we reported that the 27-nor-Δ4-DA was able to directly activate DAF-12 in a transactivation cell-based luciferase assay and rescued the Mig phenotype of daf-9(rh50) Caenorhabditis elegans mutants.

Synthesis and biological evaluation of salpichrolide analogs as antiestrogenic agents.

The antiestrogenic activity of three natural salpichrolides A, G and B (1, 3 and 4) and of five synthetic analogs containing an aromatic D ring and a simplified side chain (5-9), was evaluated on MCF-7 cells. The 2,3-ene-1-keto steroids 8 and 9 were obtained from 3β-acetoxy-17(13→18)-abeo-5αH-pregna-13,15,17-trien-20-one, the key step for these syntheses being a Wharton carbonyl rearrangement of a 1,2-epoxy-3-keto steroid to the allylic alcohol using hydrazine hydrate. The antiestrogenic activity was evaluated by performing dose-response experiments in ER(+) MCF-7 breast cancer cells.

The rigid steroid 21-hydroxy-6,19-epoxyprogesterone (21OH-6,19OP) is a dissociated glucocorticoid receptor modulator potentially useful as a novel coadjuvant in breast cancer chemotherapy.

Glucocorticoids (GCs) are steroid hormones widely used as coadjuvants in the treatment of solid tumors due to their anti-inflammatory effects. However, evidence show that they also may induce chemotherapy resistance, probably through their capacity to inhibit apoptosis triggered by antineoplastic drugs. GCs exert their action by regulating gene expression throughout two main mechanisms: transactivation, where the activated glucocorticoid receptor (GR) directly binds to certain genes; and transrepression, an indirect mechanism by which GR regulates other transcription factors activities.

Neuroprotective action of synthetic steroids with oxygen bridge. Activity on GABAA receptor.

Allopregnanolone (A) and pregnanolone (P) are able to modify neural activities acting through the GABAA receptor complex. This capacity makes them useful as anticonvulsant, anxiolytic, or anti-stress compounds. In this study, the performance of seven synthetic steroids (SS) analogous of A or P containing an intramolecular oxygen bridge was evaluated using different assays.

27-Nor-Δ(4)-dafachronic acid is a synthetic ligand of Caenorhabditis elegans DAF-12 receptor.

27-Nor-Δ(4)-dafachronic acid was prepared in nine steps and 14% overall yield by two sequential 2-carbon homologations from 20β-carboxyaldehyde-4-pregnen-3-one. Its activity was evaluated in vivo, where it rescued the Mig phenotype of daf-9(rh50) Caenorhabditis elegans mutants and restored their normal resistance to oxidative stress. 27-Nor-Δ(4)-dafachronic acid was also able to directly bind and activate DAF-12 in a transactivation cell-based luciferase reporter assay, although it was less active than the corresponding 25R-and 25S dafachronic acids.

Synthesis and antifungal activity of C-21 steroids with an aromatic D ring.

Six analogues of salpichrolides with a simplified side chain (6-11) were synthesized using a new methodology to obtain steroids with an aromatic D-ring. The key step was the elimination of HBr in a vicinal dibromo D-homosteroid by treatment with 1,4-diazabicyclo[2.2.

Microwave assisted preparation of C1-C11 oxygen-bridged pregnanes.

1,11-Epoxysteroids may be obtained by an intramolecular remote functionalization using Suarez reagent (diacetoxyiodobenzene/I(2)) and irradiation with visible light. We have found that photolysis with visible light may be advantageously replaced by microwave irradiation to prepare 1,11-oxygen bridges resulting in higher yields and shorter reaction times especially in the case of sensitive substrates. Both methodologies were compared on a set of representative 11-α-hydroxypregnanes (3, 8, 10 and 11).

Insights on glucocorticoid receptor activity modulation through the binding of rigid steroids.

Background: The glucocorticoid receptor (GR) is a transcription factor that regulates gene expression in a ligand-dependent fashion. This modular protein is one of the major pharmacological targets due to its involvement in both cause and treatment of many human diseases. Intense efforts have been made to get information about the molecular basis of GR activity.

Antiproliferative activity of withanolides against human breast cancer cell lines.

The in vitro antiproliferative activity of a series of 22 naturally occurring withanolides was examined against the T-47D, MCF7, MCF7/BUS, MDA-MB-231, and SK-Br-3 human solid tumor breast cancer cell lines. The most active compound showed GI(50) values in the range 0.16-0.

Allopregnanolone (3alpha-hydroxy-5alpha-pregnan-20-one) derivatives with a polar chain in position 16alpha: synthesis and activity.

The lipophilic nature of allopregnanolone prevents its user-friendly application in human medicine. On inspiration by previously prepared allopregnanolone with a 16alpha-bound tetraethylammonium salt, an attempt was made to produce allopregnanolone analogues with polar groups introduced into position 16alpha with the goal of increasing water solubility, brain accessibility, and potency of neuroactive steroids. The Michael addition to derivatives of pregn-16-en-20-one was the key reaction step.

Structure-activity relationships of neuroactive steroids acting on the GABAA receptor.

The term "neuroactive steroid" (NAS) refers to steroids which, independent of their origin, are capable of modifying neural activities. These steroids positively or negatively modulate the function of members of the ligand-gated ion channel superfamily. Those with positive allosteric actions on the gamma-amino butyric acid type A receptor (GABAA receptor) have been shown to be potent anticonvulsants, anxiolytics, and antistress agents and to possess sedative, hypnotic, and anesthetic activities.

New lead compounds in the search for pure antiglucocorticoids and the dissociation of antiglucocorticoid effects.

Antiglucocorticoids that act as antagonists at the glucocorticoid receptor (GR) level may be used to block or modulate the undesirable effects of glucocorticoid excess (from endogenous or exogenous origin). RU486 developed in the early 80s, is an antiglucocorticoid but also a potent antiprogestin and abortifacient, nevertheless it still remains as the only GR antagonist drug in the market. Further on, in view of the variety of physiological processes in which glucocorticoids are involved, selective antiglucocorticoids that can block only some of these processes (eventually with tissue specificity) would be highly desirable.

Hemisuccinate of 21-hydroxy-6,19-epoxyprogesterone: a tissue-specific modulator of the glucocorticoid receptor.

The introduction of a hemisuccinate group at the 21-position of the passive antiglucocorticoid 21OH-6,19OP leads to a compound (21HS-6,19OP) with a notable activity profile toward the glucocorticoid receptor (GR). In contrast to the parent steroid, 21HS-6,19OP behaves as a pure agonist of GR activity in direct transactivation assays. However, the apoptotic effects of 21HS-6,19OP show that the effect depends on cell type: while 21HS-6,19OP is a pure agonist in L929 mouse fibroblasts, in thymocytes 21HS-6,19OP had significant antiglucocorticoid activity.

Exploring the molecular basis of action of the passive antiglucocorticoid 21-hydroxy-6,19-epoxyprogesterone.

21-Hydroxy-6,19-epoxyprogesterone (21OH-6,19OP) is a selective antiglucocorticoid that lacks the bulky substituent at C-11 found in active antagonists of the glucocorticoid receptor (GR). Ligand-free GR ligand-binding domain (LBD) and GR LBD complexed with 21OH-6,19OP or the agonist dexamethasone were simulated during 6 ns using molecular dynamics. Results suggest that the time fluctuation and average position adopted by the H1-H3 loop affect the ability of GR LBD-21OH-6,19OP complex to homodimerize, a necessary step in transcriptome assembly.

Synthesis and GABA(A) receptor activity of oxygen-bridged neurosteroid analogs.

Three analogs of neuroactive steroids were prepared (4-6) in which 1,11- or 11,19-oxygen bridges give a constrained conformation. Their 3D structures were obtained by ab initio calculations and in the case of 3alpha-hydroxy-11,19-epoxypregn-4-ene-20-one (4), confirmed by X-ray analysis. Biological activity of the synthetic steroids was assayed in vitro using t-[(3)H]butylbicycloorthobenzoate as radiolabeled ligand for the GABA(A) receptor.