Testosterone-loaded GM1 micelles targeted to the intracellular androgen receptor for the specific induction of genomic androgen signaling.

Androgens play a central role in homeostatic and pathological processes of the prostate gland. At the cellular level, testosterone activates both the genomic signaling pathway, through the intracellular androgen receptor (AR), and membrane-initiated androgen signaling (MIAS), by plasma membrane receptors. We have previously shown that the activation of MIAS induces uncontrolled proliferation and fails to stimulate the beneficial immunomodulatory effects of testosterone in prostatic cells, becoming necessary to investigate if genomic signaling mediates homeostatic effects of testosterone. However, the lack of specific modulators for genomic androgen signaling has delayed the understanding of this mechanism. In this article, we demonstrate that monosialoganglioside (GM1) micelles are capable of delivering testosterone into the cytoplasm to specifically activate genomic signaling. Stimulation with testosterone-loaded GM1 micelles led to the activation of androgen response element (ARE)-regulated genes in vitro as well as to the recovery of normal prostate size and histology after castration in mice. In addition, these micelles avoided MIAS, as demonstrated by the absence of rapid signaling pathway activation and the inability to induce uncontrolled cell proliferation. In conclusion, our results validate a novel tool for the specific activation of genomic androgen signaling and demonstrate the importance of selective pathway activation in androgen-mediated proliferation.

The Response of Prostate Smooth Muscle Cells to Testosterone Is Determined by the Subcellular Distribution of the Androgen Receptor.

Androgen signaling in prostate smooth muscle cells (pSMCs) is critical for the maintenance of prostate homeostasis, the alterations of which are a central aspect in the development of pathological conditions. Testosterone can act through the classic androgen receptor (AR) in the cytoplasm, eliciting genomic signaling, or through different types of receptors located at the plasma membrane for nongenomic signaling. We aimed to find evidence of nongenomic testosterone-signaling mechanisms in pSMCs and their participation in cell proliferation, differentiation, and the modulation of the response to lipopolysaccharide. We demonstrated that pSMCs can respond to testosterone by a rapid activation of ERK1/2 and Akt. Furthermore, a pool of ARs localized at the cell surface of pSMCs is responsible for a nongenomic testosterone-induced increase in cell proliferation. Through membrane receptor stimulation, testosterone favors a muscle phenotype, indicated by an increase in smooth muscle markers. We also showed that the anti-inflammatory effects of testosterone, capable of attenuating lipopolysaccharide-induced proinflammatory actions, are promoted only by receptors located inside the cell. We postulate that testosterone might perform prohomeostatic effects through intracellular-initiated mechanisms by modulating cell proliferation and inflammation, whereas some pathological, hyperproliferative actions would be induced by membrane-initiated nongenomic signaling in pSMCs.