Browsing Scholarly Projects 2012 by Subjects
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Androgen Receptor Expression in Human Coronary Vascular Smooth Muscle During Cytokine, Angiotensin II or Hypoxic ExposureAn increasing body of evidence suggests that androgens may exert beneficial effects against the development and progression of vascular inflammation during pathological conditions. Our previous data have shown that the potent androgen receptor (AR) agonist, dihydrotestosterone (DHT), attenuates inflammation-induced vascular cell adhesion molecule-1 (VCAM-1) and cyclooxygenase-2 (COX-2) in human primary vascular smooth muscle (VSM) cells. Although this response was not blocked by the AR antagonist bicalutamide, it is not known if AR expression is altered during an inflammatory insult in VSM. The goal of this study was to investigate the effects of a variety of inflammatory stimuli: Angiotensin II (more recently recognized as a mediator of inflammation in the blood vessel wall (Ruiz-Ortega, et al. 2000) (Alvarez, et al. 2004)), hypoxia, and interleukin-1 beta (IL-1β; cytokine) on AR expression in human VSM cells. Since DHT’s effect in the presence of an inflammatory stimulus is AR independent, we hypothesized levels of AR are decreased favoring less of an androgenic contribution during pro-inflammatory conditions. We initially confirmed that human VSM expresses AR and levels of the receptor are increased following androgen treatment in the absence of an 5 inflammatory stimulus. We further demonstrated that in addition to the full-length AR 110 kDa band detected via anti-AR-N20, we also detected a band migrating near 45 kDa in human VSM that is not present in rat testis lysate. Recent studies describe a variant form of the AR called AR45 expressed in human heart but not in rat (Ahrens-Fath, et al. 2005) (Weiss, Faus and Haendler 2007). Although we did not determine whether the bands migrating near 45 kDa were AR45 or possibly an endogenous break down product of the full-length AR (110 kDa) we did however observe expression of the lower migrating band during conditions of inflammation that may be cardioprotective. In the presence of an inflammatory stimulus we demonstrated that there was a consistent trend for IL-1β and angiotensin II (ang II) to decrease AR expression in human coronary artery VSM. Using an in vivo global ischemic model of inflammation, AR was robustly decreased following a 20- and 30-minute occlusion and 21 hr reperfusion in rat pial arteries. However, unlike ang II, cytokine, or ischemia, in vitro hypoxic exposure in human VSM cells increased the lower migrating band density (45 kDa) and had no effect on band density at 110 kDa. In summary, our results confirm that levels of the classic AR (and possibly the novel AR45 variant form) are present in human VSM. 6 Additionally levels of AR may be altered under conditions of inflammation in human VSM cells and following ischemia/reperfusion in rodent cerebral arteries. We conclude that the AR independent attenuation of COX-2 and VCAM-1 by DHT following an inflammatory insult may be due in part to a decrease of AR levels in the blood vessel wall.