Development of biological assays for identification of steroid receptor ligands and determination of activity of steroidogenic enyzme aromatase

Abstract

<p>U ovoj doktorskoj disertaciji&nbsp; razvijen&nbsp; je fluorescentni test u kvascu za identifikaciju potencijalnih prirodnih ili sintetičkih liganada&nbsp; ER&alpha;, ER&beta; ili AR i kvantifikaciju&nbsp; njihovog&nbsp; afiniteta&nbsp; vezivanja sa mogućno&scaron;ću testiranja čitavih biblioteka modifikovanih steroida i ksenoestrogena. Takođe, opisana&nbsp; je primena optimizovanog biosenzora&nbsp; za&nbsp; procenu&nbsp; estrogenog&nbsp; potencijala sintetskih steroida i odabranih biljnih ekstrakata bogatih jedinjenjima fitoestrogenih osobina. U cilju potpunijeg sagledavanja mehanizma&nbsp; delovanja&nbsp; odabranih&nbsp; modifikovanih&nbsp; steroida&nbsp; ispitana&nbsp; je&nbsp; njihova antiproliferativna aktivnost prema ćelijskim&nbsp; linijama estrogen receptor pozitivnog kancera dojke&nbsp; (MCF-7) i kancera prostate (PC-3), dok su&nbsp; in silico metodom molekularnog&nbsp; dokinga&nbsp; predviđene&nbsp; energije&nbsp; i&nbsp; geometrije&nbsp; vezivanja&nbsp; ovih&nbsp; jedinjenja za ligand-vezujuće&nbsp; domene&nbsp; ER&alpha; i ER&beta;. Drugi deo ovog rada obuhvata razvoj testa za&nbsp; ispitivanje aktivnosti humanog enzima aromataze,&nbsp; heterologno eksprimiranog u ćelijama&nbsp; kvasca&nbsp; Saccharomyces cerevisiae&nbsp; i/ili&nbsp; bakterija Escherichia coli, u prisustvu&nbsp; ili&nbsp; odsustvu&nbsp; inhibitora.&nbsp; Interakcije modifikovanih&nbsp; steroida, odabranih na osnovu strukture,&nbsp; sa&nbsp; aromatazom&nbsp; ispitane&nbsp; su&nbsp; osetljivim spektroskopskim metodama, praćenjem promene spinskog stanja Fe iz hem grupe ili promene fluorescencije ostatka&nbsp; triptofana&nbsp; iz&nbsp; aktivnog&nbsp; centra usled konformacione&nbsp; promene&nbsp; proteina, izazvane interakcijom sa ligandom. Razvijeni in vitro testovi bez upotrebe radioaktivnih izotopa su, osim&nbsp; visoke efikasnosti&nbsp; i&nbsp; bezbednosti&nbsp; po&nbsp; korisnika&nbsp; i&nbsp; okolinu, pokazali&nbsp; specifičnost&nbsp; i&nbsp; ekonomičnost&nbsp; u preliminarnom&nbsp; skriningu&nbsp; liganada&nbsp; steroidnih receptora&nbsp; i inhibitora aromataze. Jedinjenja&nbsp; kod kojih je detektovana&nbsp; značajna biolo&scaron;ka aktivnost mogu potencijalno poslužiti kao osnova za razvoj terapeutika u lečenju hormon-zavisnih bolesti i stanja, koja danas predstavljaju globalni zdravstveni problem.</p>

<p>In&nbsp; this&nbsp; doctoral&nbsp; dissertation,&nbsp; a&nbsp; fluorescent&nbsp; assay&nbsp; in&nbsp; yeast&nbsp; was&nbsp; developed&nbsp; for&nbsp; identification&nbsp; of&nbsp; potential&nbsp; natural or synthetic ligands of ER&alpha;, ER&beta; or AR and<br />quantification&nbsp; of&nbsp; their&nbsp; binding&nbsp; affinity,&nbsp; as&nbsp; well&nbsp; asevaluation&nbsp; of&nbsp; the&nbsp; estrogenic&nbsp; potential&nbsp; of&nbsp; synthetic steroids&nbsp; and&nbsp; selected&nbsp; plant&nbsp; extracts&nbsp; rich&nbsp; in phytoestrogen&nbsp; content.&nbsp; The&nbsp; assay&nbsp; could&nbsp; be&nbsp; used&nbsp; to&nbsp; screen&nbsp; libraries&nbsp; of&nbsp; modified&nbsp; steroids&nbsp; and xenoestrogens.&nbsp; In&nbsp; order&nbsp; to&nbsp; better&nbsp; understand&nbsp; the biomedical&nbsp; potential&nbsp; of&nbsp; selected&nbsp; modified&nbsp; steroids, results&nbsp; were&nbsp; compared&nbsp; to&nbsp; antiproliferative&nbsp; activity against&nbsp; estrogen&nbsp; receptor&nbsp; positive&nbsp; breast&nbsp; cancer (MCF-7)&nbsp; and&nbsp; prostate&nbsp; cancer&nbsp; (PC-3)&nbsp; cell&nbsp; lines. Binding&nbsp; energies&nbsp; and&nbsp; the&nbsp; geometry&nbsp; of&nbsp; binding&nbsp; of these&nbsp; compounds&nbsp; for&nbsp; ER&alpha;&nbsp; and&nbsp; ER&beta;&nbsp; ligand&nbsp; binding domains&nbsp; were&nbsp; predicted&nbsp; in&nbsp; silico&nbsp; by&nbsp; molecular&nbsp; docking&nbsp; methods.&nbsp; The&nbsp; second&nbsp; part&nbsp; of&nbsp; this&nbsp; study includes development&nbsp; of&nbsp; an&nbsp; assay&nbsp; for&nbsp; study&nbsp; of&nbsp; aromatase&nbsp; activity&nbsp; in&nbsp; the&nbsp; presence&nbsp; or&nbsp; absence&nbsp; of inhibitors&nbsp; by&nbsp; heterologous&nbsp; expression&nbsp; of&nbsp; human aromatase&nbsp; in&nbsp; Saccharomyces&nbsp; cerevisiae&nbsp; and/or Escherichia&nbsp; coli&nbsp; cells,&nbsp; as&nbsp; model-organisms. Furthermore, interactions between modified steroids, selected&nbsp; according&nbsp; to&nbsp; their&nbsp; structure,&nbsp; and&nbsp; aromatase were&nbsp; tested&nbsp; using&nbsp; sensitive&nbsp; spectroscopic&nbsp; methods based on ligand-induced changes&nbsp; in&nbsp; the&nbsp; spin state of Fe&nbsp; from&nbsp; the&nbsp; heme&nbsp; group&nbsp; or&nbsp; changes&nbsp; in&nbsp; the fluorescence&nbsp; of&nbsp; a&nbsp; tryptophan&nbsp; residue&nbsp; in&nbsp; the&nbsp; active site.&nbsp; The&nbsp; non-radioactive&nbsp; in&nbsp; vitro&nbsp; assays&nbsp; developed&nbsp; here, besides high efficiency, user and environmental safety,&nbsp; also&nbsp; have&nbsp; greater&nbsp; specificity&nbsp; and&nbsp; are&nbsp; more cost-effective&nbsp; for&nbsp; preliminary&nbsp; screening&nbsp; of&nbsp; steroid receptor&nbsp; ligands&nbsp; and&nbsp; aromatase&nbsp; inhibitors. Additionally,&nbsp; compounds&nbsp; identified&nbsp; to&nbsp; express significant biological activity can serve as a basis for the&nbsp; development&nbsp; of&nbsp; potential&nbsp; therapeutics&nbsp; in&nbsp; the treatment&nbsp; of&nbsp; hormone-dependent&nbsp; diseases&nbsp; and conditions, a global health issue today.</p>