Dose-dependent effect of dehydroepiandrosterone, but not of its sulphate ester, on angiogenesis

Dehydroepiandrosterone promotes ovarian angiogenesis and improves ovarian function in a rat model of premature ovarian insufficiency by up-regulating HIF-1α/VEGF signalling

RESEARCH QUESTION

What impact does dehydroepiandrosterone (DHEA) have on ovarian angiogenesis and function in a rat model of with premature ovarian insufficiency (POI), and what are the potential mechanisms of action?

DESIGN

DHEA was added to a culture of human microvascular endothelial cells (HMEC-1) to investigate its effects on cell proliferation, migration and tube formation. A rat model of POI was established by intraperitoneal injection of cyclophosphamide, followed by continuous oral administration of DHEA or vehicle for 28 days. Ovarian angiogenesis, follicular growth and granulosa cell survival in ovarian tissues were assessed through haematoxylin and eosin staining, immunohistochemistry and TdT (terminal deoxynucleotidyl transferase)-mediated dUTP nick-end labelling (TUNEL). The effect of DHEA on the fertility of rats with POI was evaluated in pregnant animals. The expression levels of characteristic genes and proteins in the hypoxia-inducible factor (HIF)-1α/vascular endothelial growth factor (VEGF) pathway was determined using quantitative reverse transcription PCR and western blotting.

RESULTS

In-vitro experiments revealed that DHEA stimulated the proliferation, migration and tube formation of HMEC-1. In in-vivo studies, DHEA treatment improved the disruption of the oestrous cycle and hormone imbalances in POI rats. Key genes in the HIF-1α/VEGF pathway exhibited up-regulated expression, promoting ovarian angiogenesis in POI rats, and enhancing follicular development and granulosa cell survival, thereby restoring fertility in rats.

CONCLUSIONS

DHEA can potentially restore ovarian function in rats with cyclophosphamide-induced POI by up-regulating HIF-1α/VEGF signalling, which promotes the growth of blood vessels in the ovaries.

Effects of dehydroepiandrosterone on proliferation, migration, and death of breast cancer cells

Cancer invasion and metastasis are the leading causes of mortality in patients with breast cancer. Dehydroepiandrosterone (DHEA) has a protective role against cancer, however, the mechanism by which DHEA has this effect remains poorly understood. The present study was aimed at investigating the actions of DHEA on the proliferation, cell cycle, death and migration of breast cancer cell lines. We used MCF-7 cells (estrogen receptors positive) and MDA-MB-231 and Hs578T cells (estrogen receptors negative) for these studies. Cell proliferation was evaluated by crystal violet staining, cell cycle by flow cytometry, and cell death by the carboxyfluorescein FLICA analysis of caspase activation. Migration was evaluated by transwell cell migration and wound assay. We also determined the expression of ECM-1 protein by western blotting and RT-PCR in real time. DHEA inhibited the proliferation of all breast cancer cell lines. This was associated with an arrest in the G1 phase of the cell cycle and death in MCF-7 cells. There was no alteration in any of the cell cycle phases or death in DHEA treated MDA-MB-231 or Hs578T cells. DHEA also suppressed the migration of all breast cancer cell lines, independently of the presence of estrogen receptors and decreased the expression of ECM-1 protein in Hs578T cells. These results suggest that the mechanism of DHEA actions against breast cancer involves the inhibition of cell proliferation and the suppression of migration, indicating that DHEA could be useful in the treatment of breast cancer.

Targeted delivery of antisense inhibitor of miRNA for antiangiogenesis therapy using cRGD-functionalized nanoparticles

MiRNAs are viable therapeutic targets for cancer therapy, but the targeted delivery of miRNA or its anti-miRNA antisense oligonucleotides (AMOs) remains a challenge. We report here a PEGylated LPH (liposome-polycation-hyaluronic acid) nanoparticle formulation modified with cyclic RGD peptide (cRGD) for specific and efficient delivery of AMO into endothelial cells, targeting α(v)β₃ integrin present on the tumor neovasculature. The nanoparticles effectively delivered anti-miR-296 AMO to the cytoplasm and downregulated the target miRNA in human umbilical vein endothelial cells (HUVECs), which further efficiently suppressed blood tube formulation and endothelial cell migration, owing to significant upregulation of hepatocyte growth factor-regulated tyrosine kinase substrate (HGS), whereas nanoparticles without cRGD modification showed only little AMO uptake and miRNA silencing activity. In vivo assessment of angiogenesis using Matrigel plug assay also demonstrated that cRGD modified LPH nanoparticles have potential for antiangiogenesis in miRNA therapeutics. With the delivery of anti-miR-296 AMO by targeted nanoparticles, significant decrease in microvessel formulation within Matrigel was achieved through suppressing the invasion of CD31-positive cells into Matrigel and prompting HGS expression in angiogenic endothelial cells.

Dehydroepiandrosterone stimulates endothelial proliferation and angiogenesis through extracellular signal-regulated kinase 1/2-mediated mechanisms

Dehydroepiandrosterone (DHEA) activates a plasma membrane receptor on vascular endothelial cells and phosphorylates ERK 1/2. We hypothesize that ERK1/2-dependent vascular endothelial proliferation underlies part of the beneficial vascular effect of DHEA. DHEA (0.1-10 nm) activated ERK1/2 in bovine aortic endothelial cells (BAECs) by 15 min, causing nuclear translocation of phosphorylated ERK1/2 and phosphorylation of nuclear p90 ribosomal S6 kinase. ERK1/2 phosphorylation was dependent on plasma membrane-initiated activation of Gi/o proteins and the upstream MAPK kinase because the effect was seen with albumin-conjugated DHEA and was blocked by pertussis toxin or PD098059. A 15-min incubation of BAECs with 1 nm DHEA (or albumin-conjugated DHEA) increased endothelial proliferation by 30% at 24 h. This effect was not altered by inhibition of estrogen or androgen receptors or nitric oxide production. There was a similar effect of DHEA to increase endothelial migration. DHEA also increased the formation of primitive capillary tubes of BAECs in vitro in solubilized basement membrane. These rapid DHEA-induced effects were reversed by the inhibition of either Gi/o-proteins or ERK1/2. Additionally, DHEA enhanced angiogenesis in vivo in a chick embryo chorioallantoic membrane assay. These findings indicate that exposure to DHEA, at concentrations found in human blood, causes vascular endothelial proliferation by a plasma membrane-initiated activity that is Gi/o and ERK1/2 dependent. These data, along with previous findings, define an important vascular endothelial cell signaling pathway that is activated by DHEA and suggest that this steroid may play a role in vascular function.

DHEA decreases HIF-1alpha accumulation under hypoxia in human pulmonary artery cells: potential role in the treatment of pulmonary arterial hypertension

Previous work showed that dehydroepiandrosterone (DHEA) prevents and reverses chronic hypoxic pulmonary artery hypertension in rat via targeting smooth muscle cells. In our study, DHEA was tested on human pulmonary arterial smooth muscle cells (HPASMC) to identify its mechanism of action under hypoxia in vitro. We show that DHEA decreased HIF-1alpha accumulation under both "chemical hypoxia" with treatment by the iron chelator deferroxamin and gas hypoxia (1% O2). The mRNA levels of HIF-1alpha were unchanged whether or not DHEA was applied under chemical and gas hypoxia, as compared to controls in normoxia, suggesting a post-transcriptional effect of the steroid. Protein levels of prolyl hydroxylases responsible for HIF-1alpha degradation were not modified by DHEA treatment. In addition, a synthetic derivative of DHEA, 3beta-methyl-Delta5-androsten-17-one (which cannot be metabolized), was as active as DHEA on HIF-1alpha accumulation, as well as testosterone and 17beta-estradiol (E2). In HPASMC cultures under normoxia and both types of hypoxia, DHEA gave rise to Delta5-androstene-3beta,17beta-diol (ADIOL) and DHEA-sulfate (DHEA-S). Neither testosterone, nor E2 were found. In addition, ADIOL, DHEA-S, 7alpha-hydroxy-DHEA and Delta4-androstene-3,17-dione were ineffective on HIF-1alpha accumulation. The effect of DHEA per se reducing HIF-1alpha accumulation may be relevant to reduced hypoxia effects in pulmonary arterial hypertension.

Differential antiproliferative effects of calcitriol on tumor-derived and matrigel-derived endothelial cells

The most active metabolite of vitamin D, calcitriol, is growth inhibitory for various tumor types in vitro and in vivo and inhibits the growth of endothelial cells freshly isolated from tumors [tumor-derived endothelial cells (TDEC)]. We compared the effects of calcitriol on Matrigel-derived endothelial cells (MDEC) and TDEC isolated from Matrigel plugs and squamous cell carcinoma tumors, respectively. TDEC and MDEC expressed vitamin D receptor (VDR) and responded to calcitriol by increasing VDR protein expression. Although no mutations were found in VDR from either cell type, Scatchard plot analysis revealed a higher ligand-binding affinity in TDEC (K(d), 0.26 nmol/L) than MDEC (K(d), 0.65 nmol/L). The VDR signaling axis in both cells was intact as shown using nuclear translocation and 24-hydroxylase promoter-luciferase reporter assays. However, unlike TDEC, MDEC were resistant to calcitriol-induced growth inhibition. Calcitriol (10 nmol/L) resulted in a 12.3% growth inhibition of MDEC compared with 47% in TDEC. In TDEC, calcitriol resulted in induction of G(0)/G(1) arrest (10.75%) and reduction of S-phase cells (6.8%) with induction of p27 and down-regulation of p21 protein expression. Apoptotic effects, determined by Annexin V staining were also observed in calcitriol-treated TDEC (38.6%). Calcitriol caused reduced expression of p-Erk and p-Akt and an increase of poly(ADP-ribose) polymerase and caspase-3 cleavage in TDEC. By contrast, none of these effects on cell cycle or apoptosis were seen in calcitriol-treated MDEC. These results show that TDEC were more sensitive than MDEC to the antiproliferative effects of calcitriol despite apparently normal VDR content and structure of signaling axis in both cell types.

Effects of DHEA administration on episodic memory, cortisol and mood in healthy young men: a double-blind, placebo-controlled study

RATIONALE

Dehydroepiandrosterone (DHEA) has been reported to enhance cognition in rodents, although there are inconsistent findings in humans.

OBJECTIVES

The aim of this study was to investigate the effects of DHEA administration in healthy young men on episodic memory and its neural correlates utilising an event-related potential (ERP) technique.

METHODS

Twenty-four healthy young men were treated with a 7-day course of oral DHEA (150 mg b.d.) or placebo in a double blind, random, crossover and balanced order design. Subjective mood and memory were measured using visual analogue scales (VASs). Cortisol concentrations were measured in saliva samples. ERPs were recorded during retrieval in an episodic memory test. Low-resolution brain electromagnetic tomography (LORETA) was used to identify brain regions involved in the cognitive task.

RESULTS

DHEA administration led to a reduction in evening cortisol concentrations and improved VAS mood and memory. Recollection accuracy in the episodic memory test was significantly improved following DHEA administration. LORETA revealed significant hippocampal activation associated with successful episodic memory retrieval following placebo. DHEA modified ERPs associated with retrieval and led to a trend towards an early differential activation of the anterior cingulate cortex (ACC).

CONCLUSIONS

DHEA treatment improved memory recollection and mood and decreased trough cortisol levels. The effect of DHEA appears to be via neuronal recruitment of the steroid sensitive ACC that may be involved in pre-hippocampal memory processing. These findings are distinctive, being the first to show such beneficial effects of DHEA on memory in healthy young men.

C19‐5‐ene Steroids in Nature

Dehydroepiandrosterone (DHEA), produced from cholesterol in the adrenals, is the most abundant steroid in our circulation. It is present almost entirely as the sulfate ester, but the free steroid is the form that serves as a precursor of estrogens and androgens, as well as 7- and 16-oxygenated derivatives. Mammalian tissues reduce the 17-keto Group of DHEA to produce androstenediol-a weak estrogen and full-fledged androgen. Its androgen activity is not inhibited by the anti-androgens commonly used to treat prostate cancer. It is probably responsible for the growth of therapy-resistant prostate cancer. DHEA is hydroxylated at the 7 alpha position, and this derivative is oxidized by 11 beta-hydroxysteroid dehydrogenase to form 7-keto DHEA. The latter is reduced by the same dehydrogenase to form 7 beta-hydroxy DHEA. When fed to rats, each of the latter three steroids induce the formation of two thermogenic enzymes in the liver. The late-term human fetus produces relatively large amounts of 16 alphahydroxy DHEA, which serves the mother as a precursor of estriol.