The Androgen Metabolite, 5α-androstane-3β,17β-diol, Decreases Cytokine-Induced Cyclooxygenase-2, Vascular Cell Adhesion Molecule-1 Expression, and P-Glycoprotein Expression in Male Human Brain Microvascular Endothelial Cells

Abstract

P-glycoprotein (Pgp), a multiple drug resistance transporter expressed by vascular endothelial cells, is a key component of the blood-brain barrier and has been shown to increase after inflammation. The nonaromatizable androgen, dihydrotestosterone (DHT), decreases inflammatory markers in vascular smooth muscle cells, independent of androgen receptor (AR) stimulation. The principal metabolite of DHT, 5α-androstane-3β,17β-diol (3β-diol), activates estrogen receptor (ER)β and similarly decreases inflammatory markers in vascular cells. Therefore, we tested the hypothesis that either DHT or 3β-diol decrease cytokine-induced proinflammatory mediators, vascular cell adhesion molecule-1 (VCAM-1) and cyclooxygenase-2 (COX-2), to regulate Pgp expression in male primary human brain microvascular endothelial cells (HBMECs). Using RT-qPCR, the mRNAs for AR, ERα, and ERβ and steroid metabolizing enzymes necessary for DHT conversion to 3β-diol were detected in male HBMECs demonstrating that the enzymes and receptors for production of and responsiveness to 3β-diol are present. Western analysis showed that 3β-diol reduced COX-2 and Pgp expression; the effect on Pgp was inhibited by the ER antagonist, ICI-182,780. IL-1β-caused an increase in COX-2 and VCAM-1 that was reduced by either DHT or 3β-diol. 3β-diol also decreased cytokine-induced Pgp expression. ICI-182,780 blocked the effect of 3β-diol on COX-2 and VCAM-1, but not Pgp expression. Therefore, in cytokine-stimulated male HBMECs, the effect of 3β-diol on proinflammatory mediator expression is ER dependent, whereas its effect on Pgp expression is ER independent. These studies suggest a novel role of 3β-diol in regulating blood-brain barrier function and support the concept that 3β-diol can be protective against proinflammatory mediator stimulation.

Androgens and the cerebrovasculature: modulation of vascular function during normal and pathophysiological conditions

“…Both A-dione and A-diol have been shown to activate AR target genes [90], and A-diol has recently been shown to bind to ERβ [132]. Furthermore, A-diol exhibits anti-inflammatory properties in brain microglia and microvascular endothelial cells [132,170] although a PubMed search did not reveal any reports regarding vasoactive properties for Adiol in the cerebral circulation. Further metabolism of A-dione and A-diol results in the production of TEST which is then aromatized to E2.…”

“…Unlike 3α-diol, 3β-diol cannot be converted back to DHT and undergoes biotransformation to inactive metabolites by the enzyme CYP7B1 [145,157]. We recently demonstrated that mRNAs for 3β-HSD, 3α-HSD, 17β-HSD, and CYP7B1 are present in human brain microvascular endothelial cells [170]. 3β-Diol is an intriguing endogenous androgen with evidence of having a physiological role in the brain and in the cerebrovasculature.…”

“…2a) and endothelial cells as well as in rodent pial arteries (Fig. 2b) [50, 114,143,170]. Furthermore, AR as well as ERα and ERβ mRNAs were observed in primary adult male human brain microvascular endothelial cells [170].…”

“…2b) [50, 114,143,170]. Furthermore, AR as well as ERα and ERβ mRNAs were observed in primary adult male human brain microvascular endothelial cells [170]. These adult male cells, cultured in hormone-free media, expressed higher mRNA levels of AR compared to both ERα and ERβ suggesting a genetic regulation of steroid receptor expression.…”

“…However, much like other vasculatures, the cerebrovasculature is a target for androgens [50,110]. Several recent studies have shown that androgens elicit responses in cerebral arteries that include modulation of both endothelial and vascular smooth muscle (VSM) function as well as cerebrovascular inflammatory-mediated mechanisms in response to pro-inflammatory stimuli [126,169,170]. Past studies in aorta and peripheral arteries, and to some extent in cerebral arteries, have focused on testosterone (TEST), the primary circulating AR agonist.…”