Involvement of estrogen receptor ß in maintenance of serotonergic neurons of the dorsal raphe.

The serotonergic neurons of the dorsal raphe (DR) nucleus in the CNS are involved in fear, anxiety and depression. Depression and anxiety occur quite frequently in postmenopausal women, but estrogen replacement to correct these CNS disorders is at present not favored because estrogen carries with it an increased risk for breast cancer. Serotonin synthesis, release and reuptake in the DR are targets of pharmaceuticals in the treatment of depression. In the present study we have examined by immunohistochemistry, the expression of two nuclear receptors, that is, the estrogen receptors ERα and ERß. We found that ERß but not ERα is strongly expressed in the DR and there is no sex difference and no change with ageing in the number of tryptophan hydroxylase (TPH)-positive neurons in the DR of wild-type (WT) mice. However, in ovariectomized (OVX) WT and in ERß(-/-) mice, there was a marked reduction in the number of TPH-positive normal-looking neurons and a marked increase in TPH-positive spindle-shaped cells. These neuronal changes were prevented in mice 1-3 weeks (but not 10 weeks) after OVX by the selective ERß agonist, LY3201, given as continuous release pellets for 3 days. The ERß agonist had no effects on glucose homeostasis. Thus, the onset of action of the ERß agonist is rapid but there is a limited window in time after estrogen loss when the drug is useful. We conclude that, rather than estradiol, ERß agonists could be useful pharmaceuticals in maintaining functional DR neurons to treat postmenopausal depression.

Development of a selective androgen receptor modulator for transdermal use in hypogonadal patients.

We have identified a non-steroidal selective androgen receptor modulator (SARM), termed LY305, that is bioavailable through a transdermal route of administration while highly cleared via hepatic metabolism to limit parent compound exposure in the liver. Selection of this compound and its transdermal formulation was based on the optimization of skin absorption properties using both in vitro and in vivo skin models that supported PBPK modeling for human PK predictions. This molecule is an agonist in perineal muscle while being a weak partial agonist in the androgenic tissues such as prostate. When LY305 was tested in animal models of skeletal atrophy it restored the skeletal muscle mass through accelerated repair. In a bone fracture model, LY305 remained osteoprotective in the regenerating tissue and void of deleterious effects. Finally, in a small cohort of healthy volunteers, we assessed the safety and tolerability of LY305 when administered transdermally. LY305 showed a dose-dependent increase in serum exposure and was well tolerated with minimal adverse effects. Notably, there were no statistically significant changes to hematocrit or HDL after 4-week treatment period. Collectively, LY305 represents a first of its kind de novo development of a non-steroidal transdermal SARM with unique properties which could find clinical utility in hypogonadal men.

The nongenotropic synthetic ligand 4-estren-3alpha17beta-diol is a high-affinity genotropic androgen receptor agonist.

The nongenotropic ligand estren (Science 298:843-846, 2002) was evaluated for its transcriptional activity mediated by the human androgen receptor (AR). Our results show that estren can bind, translocate, transactivate, and regulate two known target genes of AR in androgen-responsive cell lines. Estren binds recombinant AR with 10-fold higher affinity than either estrogen receptor (ER)-alpha or ERbeta. Estren-bound AR can translocate AR to the nucleus and stimulate the androgen response element-luciferase reporter activity with an efficacy similar to that of androgen. Estren also increased the expression of prostate-specific antigen (PSA) in a dose-dependent manner in human LnCaP cells. Using chromatin immunoprecipitation analysis, we show that the estren-bound AR coimmunoprecipitates with a region of the PSA gene promoter. Therefore, cotreatment with an AR antagonist, bicalutamide, blocked the estren-induced increase in PSA expression. In contrast, phosphoinositol 3-kinase inhibitor wortmannin, or extracellular signal-regulated kinase inhibitor 1,4-diamino-2,3-dicyano-1,4-bis(2-aminophynyltio)butadiene (U0126), and ER antagonist ICI-182780 failed to block the effects of estren. In vivo analysis of estren's action on male-orchidectomized ICR mice revealed estren's AR agonist actions on the levator ani and seminal vesicle target tissues. Taken together, our results reveal the hitherto unidentified genotropic action of estren mediated by AR in androgen-responsive cells and tissues.