The glucocorticoid receptor's oligomerization state is revealed to not correlate with its activity; this challenges the current prevailing view that this state defines its transcriptional activity.

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B-Lapachone, an o-naphthoquinone, induces a novel caspase-and p53-independent apoptotic pathway dependent on NAD(P)H:quinone oxidoreductase1 (NQO1). NQO1reduces B-lapachone to an unstable hydroquinone that rapidly undergoes a two-step oxidation back to the parent compound, perpetuating a futile redox cycle. A deficiency or inhibition of NQO1rendered cells resistant to B-lapachone. Thus, B-lapachone has great potential for the treatment of specific cancers with elevated NQO1levels (e.g., breast, non^small cell lung, pancreatic, colon, and prostate cancers). We report the development of mono(arylimino) derivatives of B-lapachone as potential prodrugs. These derivatives are relatively nontoxic and not substrates for NQO1when initially diluted in water. In solution, however, they undergo hydrolytic conversion to B-lapachone at rates dependent on the electron-withdrawing strength of their substituent groups and pH of the diluent. NQO1enzyme assays, UV-visible spectrophotometry, high-performance liquid chromatographyelectrospray ionization-mass spectrometry, and nuclear magnetic resonance analyses confirmed and monitored conversionof each derivative to B-lapachone. Once converted, B-lapachone derivatives caused NQO1-dependent, A-calpain-mediated cell death in human cancer cells identical to that caused by B-lapachone. Interestingly, coadministration of N-acetyl-L-cysteine prevented derivative-induced cytotoxicity but did not affect B-lapachone lethality. Nuclear magnetic resonance analyses indicated that prevention of B-lapachone derivative cytotoxicity was the result of direct modification of these derivatives by N-acetyl-L-cysteine, preventing their conversion to B-lapachone. The use of B-lapachone mono(arylimino) prodrug derivatives, or more specifically a derivative converted in a tumor-specific manner (i.e., in the acidic local environment of the tumor tissue), should reduce normal tissue toxicity while eliciting tumor-selective cell killing by NQO1 bioactivation.

Thirty-seven naturally occurring withanolides (1-37), previously isolated in our laboratories, were evaluated for their potential to induce quinone reductase with cultured murine hepatoma cells (Hepa 1c1c7). Spiranoid (29, 32) and 18-functionalized withanolides (2-5, 7-9, 24) were found to be potent inducers of the enzyme, while 5alpha-substituted derivatives exhibited weak activity. Preliminary studies were performed with compound 29 to evaluate enzyme-inducing capacity in multiple organ sites of BALB/c mice. Significant induction was observed in liver and colon, but not in lung, stomach, or mammary gland.

Twelve new withanolides were isolated from the aerial part of Jaborosa rotacea: five had a spiranoid delta-lactone (1-5); one contained a 26,12-delta-lactone and a C-12-C-23 bond (6); five corresponded to trechonolide-type withanolides with configuration at C-23 opposite of those previously isolated (7, 8, 10-12); two of these have an additional oxido-bridge between C-21 and C-24; finally a withanolide with a hemiketal ring formed between a 21-hydroxyl and a 12-ketone (13) and the closely related jaborosalactone R were also isolated. New compounds were fully characterized by a combination of spectroscopic methods (1D and 2D NMR and MS). The structures of the spiranoid withanolide and of the epimer of trechonolide A were confirmed by X-ray diffraction studies. Compounds 4, 5, 6, and 8 showed selective phytotoxicity toward monocotyledoneous and dicotyledoneous species.

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BackgroundThe 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.Methodology/Principal FindingsHere, the behavior of four GR-ligand complexes with different glucocorticoid and antiglucocorticoid properties were evaluated. The ability of GR-ligand complexes to oligomerize in vivo was analyzed by performing the novel Number and Brightness assay. Results showed that most of GR molecules form homodimers inside the nucleus upon ligand binding. Additionally, in vitro GR-DNA binding analyses suggest that ligand structure modulates GR-DNA interaction dynamics rather than the receptor's ability to bind DNA. On the other hand, by coimmunoprecipitation studies we evaluated the in vivo interaction between the transcriptional intermediary factor 2 (TIF2) coactivator and different GR-ligand complexes. No correlation was found between GR intranuclear distribution, cofactor recruitment and the homodimerization process. Finally, Molecular determinants that support the observed experimental GR LBD-ligand/TIF2 interaction were found by Molecular Dynamics simulation.Conclusions/SignificanceThe data presented here sustain the idea that in vivo GR homodimerization inside the nucleus can be achieved in a DNA-independent fashion, without ruling out a dependent pathway as well. Moreover, since at least one GR-ligand complex is able to induce homodimer formation while preventing TIF2 coactivator interaction, results suggest that these two events might be independent from each other. Finally, 21-hydroxy-6,19-epoxyprogesterone arises as a selective glucocorticoid with potential pharmacological interest. Taking into account that GR homodimerization and cofactor recruitment are considered essential steps in the receptor activation pathway, results presented here contribute to understand how specific ligands influence GR behavior.

[reaction: see text] Olefinic sulfamates derived from primary and secondary alcohols undergo intramolecular copper-catalyzed aziridination in the presence of iodosylbenzene to afford novel bicyclic fused aziridines. The latter were opened by various nucleophiles to give the corresponding substituted cyclic sulfamates, which in turn reacted, after nitrogen activation, with a second nucleophile at the carbon atom bearing the oxygen atom. Concomitant removal of the sulfonyloxy moiety thus gave access to polysubstituted amines.