Mechanism of action of anabolic-androgenic steroids.

摘要

Anabolic-androgenic steroids (AAS), which activate the human androgen receptor (hAR), are used clinically to treat hypogonadism, impotence, and muscle wasting disorders. In addition, there is significant nonprescribed abuse of AAS by athletes. This illicit use leads to serious health problems. Understanding the mechanisms of action (MOA) of AAS can lead to improved abuse prevention, reversing of adverse effects, and improved detection methods. These compounds are known to have varying anabolic and androgenic properties; however, a relationship between AAS and subsequent activity has not been made. Typically, AAS are taken at supraphysiological levels by abusers. These high levels of AAS may exert actions through interactions at hAR, but also via repression of the human glucocorticoid receptor (hGR). Repression of hGR action may be due to competitive antagonism via AAS binding, the result of nuclear receptor (NR) coactivator squelching, or a result of NR heterodimer formation. The contribution of AAS-mediated hGR repression and its relationship to hAR and resulting activity have not been demonstrated, interactions between hAR and hGR and coactivators have not been assessed, and little information regarding hAR/hGR heterodimer formation exists. In order to understand the poorly defined MOA of AAS, anti-glucocorticoid activity must be addressed. We hypothesize AAS have multiple mechanisms of action including activation of the hAR, repression of hGR activity via competitive antagonism, and repression of hGR activity via coactivator squelching or heterodimer formation. This dissertation utilized fluorescence microscopy to address the kinetics of AAS and glucocorticoid induced shuttling of fluorescent-labeled hAR and hGR. Transactivation via hAR and hGR specific steroid promoters is evaluated with a luciferase reporter gene assay. The contribution of the NR coactivators SRC-1 and GRIP1 to the transactivation of hAR and hGR were evaluated. Finally, coactivator recruitment and hAR/hGR heterodimer formation were evaluated using mutant hARs. The data obtained from these studies indicate that hAR and hGR nuclear translocation and transactivation are ligand- and dose-dependent, and hGR is repressed in the presence of hAR. The results of these experiments increase our understanding of the actions of AAS, hAR and hGR, and improve our ability to detect and prevent the abuse of these drugs.