Estrogen deprivation has a profound effect on the female brain. One of the most obvious examples of this condition is hot flushes. Although estrogens relieve these typical climacteric symptoms, many women do not want to take them owing to unwanted side-effects impacting, for example, the uterus, breast and blood. Therefore, there is a need for developing safer estrogen therapies. We show here that treatment with 10β,17β-dihydroxyestra-1,4-dien-3-one (DHED), a novel brain-targeting bioprecursor prodrug of the main human estrogen, 17β-estradiol, alleviates hot flushes in rat models of thermoregulatory dysfunction of the brain. Oral administration of DHED elicits a significant reduction of tail skin temperature (TST) rise representing hot flushes in the morphine-dependent ovariectomized rat model and results in the restoration of estrogen deprivation-induced loss of diurnal rhythm in TST. These beneficial effects occur without detrimental peripheral hormonal exposure; thus, the treatment avoids potentially harmful stimulation of estrogen-sensitive peripheral organs, including the uterus and the anterior pituitary, or the proliferation of MCF-7a breast cancer cell xenografts. Our promising preclinical assessments warrant further considerations of DHED for the development of a brain-selective 17β-estradiol therapy to relieve hot flushes without undesirable peripheral side-effects.

Catecholamines have been shown to modulate gonadal functions via interactions with hypothalamic LH-releasing hormone (LHRH)-synthesizing neurons. To reveal the morphological background of this phenomenon, the distribution of LHRH neurons and tyrosine hydroxylase (TH)-immunoreactive (IR), catecholaminergic structures were mapped in the human diencephalon. First, the location of LHRH and TH-IR neuronal elements was analyzed, and then the relationship between the two different systems was examined. The LHRH-IR cell bodies were mainly present in the medial preoptic and infundibular areas. The TH-IR perikarya were located in the periventricular, paraventricular, and supraoptic hypothalamic nuclei and also in the median eminence. The TH-IR fibers were numerous in septal, infundibular, periventricular, and lateral hypothalamic regions. The brown, diaminobenzidine-labeled LHRH-containing perikarya were found to receive black, silver-intensified, TH-positive axon terminals in the infundibular and medial preoptic areas. However, in the preoptic and caudal parts of the diencephalon, only a few juxtapositions were noted. The present results indicate that hormone released from diencephalic LHRH-IR neurons in humans may be influenced by the central catecholaminergic system via direct synaptic mechanisms.

Objective An increase in the use of selective serotonin reuptake inhibitors (SSRIs) and/or serotonin-norepinephrine reuptake inhibitors (SNRIs) to relieve menopausal hot flashes (HFs) has been observed recently. However, response to them has been heterogeneous. We hypothesized that this heterogeneity might be partially attributed to genetic variations in genes encoding the serotonin and/or norepinephrine transporters (SLC6A4 and SLC6A2). As a first step in testing the role of genetics in response to SSRIs/SNRIs, we examined the association between HFs and genetic variants within these two genes. Methods We tested 29 haplotype-tagging single nucleotide polymorphisms within SLC6A4 and SLC6A2 for their association with HFs separately for European-American (396 cases and 392 controls) and African-American (125 cases and 81 controls) premenopausal and perimenopausal women. Results We found that the minor allele of SLC6A4_rs11080121 was associated with protection against HFs (odds ratio, 0.75; 95% CI, 0.60-0.94) only in European-American women. Bioinformatics analyses indicated that rs11080121 is fully correlated with rs1042173 in the 3′ untranslated region of SLC6A4. The minor allele of rs1042173 seems to disrupt a conserved binding site for hsa-miR-590-3p microRNA. Conclusions Disruption of a microRNA binding site leads to higher expression of SLC6A4, higher expression of SLC6A4 leads to depletion of serotonin in synaptic clefts, and depletion of serotonin triggers the presynaptic autoreceptor feedback mechanism to produce more serotonin, which is protective against HFs. This is the first study to test the association between HFs in both European-American and African-American premenopausal and perimenopausal women and genetic variants in two neurotransmitter transporter genes, SLC6A2 and SLC6A4. This information can be used in tailoring the pharmaceutical use of SSRIs/SNRIs for HF relief.

Hot flushes are best-known for affecting menopausal women, but men who undergo life-saving castration due to androgen-sensitive prostate cancer also suffer from these vasomotor symptoms. Estrogen deficiency in these patients is a direct consequence of androgen deprivation, because estrogens (notably 17β-estradiol, E₂) are produced from testosterone. Although estrogens alleviate hot flushes in these patients, they also cause adverse systemic side effects. Because only estrogens can provide mitigation of hot flushes on the basis of current clinical practices, there is an unmet need for an effective and safe pharmacotherapeutic intervention that would also greatly enhance patient adherence. To this end, we evaluated treatment of orchidectomized (ORDX) rats with 10β, 17β-dihydroxyestra-1,4-dien-3-one (DHED), a brain-selective bioprecursor prodrug of E₂. A pilot pharmacokinetic study using oral administration of DHED to these animals revealed the formation of E₂ in the brain without the appearance of the hormone in the circulation. Therefore, DHED treatment alleviated androgen deprivation-associated hot flushes without peripheral impact in the ORDX rat model. Concomitantly, we showed that DHED-derived E₂ induced progesterone receptor gene expression in the hypothalamus without stimulating galanin expression in the anterior pituitary, further indicating the lack of systemic estrogen exposure upon oral treatment with DHED.