Dehydroepiandrosterone Modulates Endothelial Nitric Oxide Synthesis Via Direct Genomic and Nongenomic Mechanisms
ABSTRACT Dehydroepiandrosterone (DHEA) and its sulfate ester (DHEAS) are the major circulating steroid hormones in humans, and their levels progressively decline with age. Epidemiological studies suggest that DHEA/DHEAS concentrations may be inversely related to cardiovascular risk, but disagreement exists on this issue. Preliminary studies show that DHEA regulates vascular function, but few data have been published on the mechanisms. We show that DHEA administration to human endothelial cells triggers nitric oxide synthesis, due to enhanced expression and stabilization of endothelial nitric oxide synthase (eNOS). Additionally, DHEA rapidly activates eNOS, through a nontranscriptional mechanism that depends on ERK1/2 MAPK, but not on phosphatidylinositol 3-kinase/Akt. DHEA is not converted to estrogens or androgens by endothelial cells, and its genomic and nongenomic effects are not blocked by antagonists of the estrogen, progesterone, glucocorticoid, or androgen receptors, suggesting that DHEA acts through a specific receptor. Oral DHEA administration to ovariectomized Wistar rats dose-dependently restores aortic eNOS levels and eNOS activity, confirming the effects of DHEA in vivo. Our present data suggest that DHEA may have direct genomic and nongenomic effects on the vascular wall that are not mediated by other steroid hormone receptors, leading to eNOS activation and induction.
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ABSTRACT: This review describes the cellular and molecular mechanism heterogeneity of dehydroepiandrosterone (DHEA) and its putative therapeutic role in vascular remodeling diseases such as pulmonary artery hypertension (PAH). PAH is characterized by enhanced pulmonary artery smooth muscle cell (PASMC) proliferation, constriction and resistance to apoptosis, all of which contribute to increase the pulmonary artery wall thickness, resistance and therefore pressure. The etiology of PAH remains elusive. Nonetheless, the implications of endothelial dysfunction (decreased nitric oxide generation and increased endothelin production etc), PASMC K(+) channel/mitochondrial axis disruption (voltage-gated K(+) channel (Kv1.5) downregulation and mitochondrial membrane potential hyperpolarization) and the activation of survival pathways such as PI3K/Akt are now accepted. Therefore, a drug able to target all of these abnormalities would be of a great therapeutic interest for the treatment of PAH. We and others have demonstrated that DHEA, a clinically available drug with a low adverse effect profile, is able to achieve these effects. In several animal models of vascular remodeling diseases such as PAH, DHEA has been demonstrated to be a good anti-proliferative and pro-apoptotic drug, decreasing vascular remodeling, and a potent vasodilator. A better understanding of the DHEA mechanisms of action may allow the development of new and better therapies to treat vascular remodeling diseases such as pulmonary hypertension.Pharmacology [?] Therapeutics 03/2010; 126(2):186-99. DOI:10.1016/j.pharmthera.2010.02.003 · 7.75 Impact Factor
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ABSTRACT: A major achievement from 500 million years of evolution is the establishment of a high secretion rate of dehydroepiandrosterone (DHEA) by the human adrenal glands coupled with the indroduction of menopause which stops secretion of estrogens by the ovary. Cessation of estrogen secretion at menopause eliminates the risks of endometrial hyperplasia and cancer which would result from non-opposed estrogen stimulation during the post-menopausal years. In fact, from the time of menopause, DHEA becomes the exclusive and tissue-specific source of sex steroids for all tissues except the uterus. Intracrinology, a term coined in 1988, describes the local formation, action and inactivation of sex steroids from the inactive sex steroid precursor DHEA. Over the past 25 years most, if not all, the genes encoding the human steroidogenic and steroid-inactivating enzymes have been cloned and sequenced and their enzymatic activity characterized. The problem with DHEA, however, is that its secretion decreases from the age of 30 years and is already decreased, on average, by 60% at time of menopause. In addition, there is a large variability in the circulating levels of DHEA with some post-menopausal women having barely detectable serum concentrations of the steroid while others have normal values. Since there is no feedback mechanism controlling DHEA secretion within 'normal' values, women with low DHEA will remain with such a deficit of sex steroids for their remaining lifetime. Since there is no other significant source of sex steroids after menopause, one can reasonably believe that low DHEA is involved, in association with the aging process, in a series of medical problems classically associated with post-menopause, namely osteoporosis, muscle loss, vaginal atrophy, fat accumulation, hot flashes, skin atrophy, type 2 diabetes, memory loss, cognition loss and possibly Alzheimer's disease. A recent randomized, placebo-controlled study has shown that all the signs and symptoms of vaginal atrophy, a classical problem recognized to be due to the hormone deficiency of menopause, can be rapidly improved or corrected by local administration of DHEA without systemic exposure to estrogens. In addition, the four domains of sexual dysfucntion are improved. For the other problems of menopause, although similar large scale, randomized and placebo-controlled studies usually remain to be performed, the available evidence already strongly suggests that they could be improved, corrected or even prevented by exogenous DHEA. In men, the contribution of adrenal DHEA to the total androgen pool has been measured at 40% in 65-75-year-old men. Such data stress the necessity of blocking both the testicular and adrenal sources of androgens in order to achieve optimal benefits in prostate cancer therapy. On the other hand, the comparable decrease in serum DHEA levels observed in both sexes has less consequence in men who continue to receive a practically constant supply of testicular sex steroids during their whole life. In fact, in men, the appearance of hormone-deficiency symptoms common to women is observed at a later age and with a lower degree of severity. Consequently, DHEA replacement has shown much more easily measurable beneficial effects in women. Most importantly, despite the non-scientific and unfortunate availability of DHEA as a food supplement in the United States, a situation that discourages rigorous clinical trials on the crucial physiological and therapeutic role of DHEA, no serious adverse event related to DHEA has ever been reported in the world literature (thousands of subjects exposed) or in the monitoring of adverse events by the FDA (millions of subjects exposed), thus indicating, as expected from its known physiology, the excellent safety profile of DHEA. With today's knowledge, one can reasonably suggest that DHEA offers the promise of a safe and efficient replacement therapy for the multiple problems related to hormone deficiency after menopause without the risks associated with estrogen-based or any other treatments.Progress in brain research 01/2010; 182:97-148. DOI:10.1016/S0079-6123(10)82004-7 · 5.10 Impact Factor
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ABSTRACT: Dehydroepiandrosterone (DHEA) protects neural crest-derived PC12 cells from serum deprivation-induced apoptosis via G protein-associated specific plasma membrane-binding sites (mDBS). Here, we studied the signaling pathways involved in the pro-survival effects of DHEA-mediated activation of the mDBS binding sites. Membrane impermeable DHEA-bovine serum albumin (BSA) conjugate induced an acute phosphorylation of the prosurvival kinases Src, protein kinase A (PKA), MEK1/2/ERK1/2, and PI3K/Akt in serum deprived PC12 cells in parallel to an elevation of intracellular cAMP. The physiological significance of these findings was further assessed in a series of experiments using several selective pro-survival kinase inhibitors. Our combined findings suggest that the following sequence of events may take place following activation of mDBS binding sites: DHEA-BSA induces an acute but transient sequential phosphorylation of the pro-survival kinases Src/PKC(a/b)/MEK1/2/ERK1/2 which, in their turn, activate transcription factors cAMP responsive element binding protein and nuclear factor kappa B which induce the expression of the anti-apoptotic Bcl-2 genes. In parallel, DHEA-BSA increases intracellular cAMP, and the subsequent phosphorylation of PKA kinase and of cAMP responsive element binding protein. Finally, DHEA-BSA induces phosphorylation of PI3K/Akt kinases which, subsequently, lead to phosphorylation/deactivation of the pro-apoptotic Bad. Our findings suggest that the neurosteroid DHEA affects neural crest-derived cell survival by multiple pro-survival signaling pathways comprising an integrated system of non-genomic and genomic mechanisms.Journal of Neurochemistry 01/2009; 107(5):1457-69. DOI:10.1111/j.1471-4159.2008.05732.x · 4.24 Impact Factor