Dehydroepiandrosterone and its derivatives: potentially novel anti-proliferative and chemopreventive agents

Metabolomics Profiling Reveals Rehmanniae Radix Preparata Extract Protects against Glucocorticoid-Induced Osteoporosis Mainly via Intervening Steroid Hormone Biosynthesis

Rehmanniae Radix Preparata (RR), the dry rhizome of Rehmannia glutinosa Libosch., is a traditional herbal medicine for improving the liver and kidney function. Ample clinical and pharmacological experiments show that RR can prevent post-menopausal osteoporosis and senile osteoporosis. In the present study, in vivo and in vitro experiments, as well as a UHPLC-Q/TOF-MS-based metabolomics study, were used to explore the preventing effect of RR on glucocorticoid-induced osteoporosis (GIOP) and its underlying mechanisms. As a result, RR significantly enhanced bone mineral density (BMD), improved the micro-architecture of trabecular bone, and intervened in biochemical markers of bone metabolism in dexamethasone (DEX)-treated rats. For the in vitro experiment, RR increased the cell proliferation and alkaline phosphatase (ALP) activity, enhanced the extracellular matrix mineralization level, and improved the expression of runt-related transcription factor 2 (RUNX2) and osteopontin (OPN) in DEX-injured osteoblasts. For the metabolomics study, a total of 27 differential metabolites were detected in the DEX group vs. the control group, of which 10 were significantly reversed after RR treatment. These metabolites were majorly involved in steroid hormone biosynthesis, sex steroids regulation, and amino acid metabolism. By metabolic pathway and Western blotting analysis, it was further ascertained that RR protected against DEX-induced bone loss, mainly via interfering steroid hormone biosynthesis, as evidenced by the up-regulation of cytochrome P450 17A1 (CYP17A1) and aromatase (CYP19A1), and the down-regulation of 11β-hydroxysteroid dehydrogenase (HSD11B1). Collectively, these results indicated that RR had a notable preventing effect on GIOP, and the action mechanism might be related to steroid hormone biosynthesis.

Autophagy and Autophagic Cell Death: Uncovering New Mechanisms Whereby Dehydroepiandrosterone Promotes Beneficial Effects on Human Health

Dehydroepiandrosterone (DHEA) is the most abundant steroid hormone in human serum and a precursor of sexual hormones. Its levels, which are maximum between the age of 20 and 30, dramatically decline with aging thus raising the question that many pathological conditions typical of the elderly might be associated with the decrement of circulating DHEA. Moreover, since its very early discovery, DHEA and its metabolites have been shown to be active in many pathophysiological contexts, including cardiovascular disease, brain disorders, and cancer. Indeed, treatment with DHEA has beneficial effects for the cure of these and many other pathologies in vitro, in vivo, and in patient studies. However, the molecular mechanisms underlying DHEA effects have been only partially elucidated. Autophagy is a self-digestive process, by which cell homeostasis is maintained, damaged organelles removed, and cell survival assured upon stress stimuli. However, high rate of autophagy is detrimental and leads to a form of programmed cell death known as autophagic cell death (ACD). In this chapter, we describe the process of autophagy and the morphological and biochemical features of ACD. Moreover, we analyze the beneficial effects of DHEA in several pathologies and the molecular mechanisms with particular emphasis on its regulation of cell death processes. Finally, we review data indicating DHEA and structurally related steroid hormones as modulators of both autophagy and ACD, a research field that opens new avenues in the therapeutic use of these compounds.

Amphiphilic derivatives of (3β,17β)-3-hydroxyandrost-5-ene-17-carboxylic acid

A series of amphiphilic derivatives of (3β,17β)-3-hydroxyandrost-5-ene-17-carboxylic acid (1) with the polyamine spermine and three other diamines, 1,2-diaminoethane, piperazine and cadaverine, were synthesized and their antimicrobial activity and cytotoxicity were investigated. Among the target compounds, several ones showed antimicrobial activity on Gram positive and Gram negative microorganisms. The most active compounds were 20 (Streptococcus mutans CCM 7409, 3.125 µM), 16 (Streptococcus mutans CCM 7409, 12.5 µM) and 10d (Escherichia coli CCM 3954, 12.5 µM). In addition, compounds 5d, 10d, 13 and 20 displayed cytotoxicity on CEM (12.1 ± 2.1 µM, 7.6 ± 1.0 µM, 19.0 ± 0.4 µM and 5.9 ± 0.7 µM, respectively). Two additional compounds displayed medium cytotoxicity on CEM, 5a (34.6 ± 5.2 µM) and 5c (37.7 ± 5.9 µM). The compound 13 and 20 displayed high toxicity also on normal fibroblasts.

Dehydroepiandrosterone triggers autophagic cell death in human hepatoma cell line HepG2 via JNK-mediated p62/SQSTM1 expression

Autophagy is a catabolic process that cancer cells usually exploit during stress conditions to provide energy by recycling organelles and proteins. Beyond its prosurvival role, it is well accepted that occurrence of autophagy is often associated with a particular type of programmed cell death known as autophagic cell death (ACD). Dehydroepiandrosterone (DHEA) is an endogenous hormone showing anticancer properties even if the underlying mechanisms are not fully clear yet. Here, we provide evidence that DHEA induces ACD in human hepatoma cell line, HepG2. Indeed, autophagy inhibitors (i.e. 3-methyladenine or Atg5 siRNA) significantly reduced the percentage of dead cells. DHEA induces p62-dependent autophagy, which turns detrimental and brings about death. DHEA stimulates reactive oxygen species-independent jun N-terminal kinase (JNK) phosphoactivation and the treatment with JNK inhibitor reduces p62 mRNA levels, as well as DHEA-induced ACD. The transcription factor nuclear factor (erythroid-derived-2)-like-2 (Nrf2) constitutes the link between JNK and p62 since its migration to the nucleus is suppressed by JNK inhibitor and its inhibition through a dominant negative Nrf2 plasmid transfection decreases p62 protein levels. Overall, our data indicate that DHEA induces ACD in HepG2 via a JNK-Nrf2-p62 axis. Thus, DHEA could represent a new appealing drug for eliminating tumor cells through autophagy particularly in apoptosis-resistant cases.

Synthesis of sex hormone-derived modified steroids possessing antiproliferative activity

During recent years intensive research has been focused on the synthesis of structurally modified steroid hormones in order to obtain compounds with beneficial biological activity such as cell-growth inhibition. Experimental results have revealed that some steroidal derivatives possess direct cytostatic effect on cancer cells in a hormone receptor-independent manner. After a brief account on the most important biological function and characteristics of the naturally occurring sex hormones in physiological and pathological conditions, structural modifications of estrane and androstane scaffolds are discussed in detail. The review covers literature publications (from 2002 to 2012) relating to the synthesis and antiproliferative activity of semisynthetic sex hormone-derived molecules containing simple or heterocyclic substituents. The compounds reviewed are divided into three main categories according to their sterane framework and the nature of substitution. This article is part of a Special Issue entitled "Synthesis and biological testing of steroid derivatives as inhibitors".

Evidence that adrenal hexose-6-phosphate dehydrogenase can effect microsomal P450 cytochrome steroidogenic enzymes

The role of adrenal hexose-6-phosphate dehydrogenase in providing reducing equivalents to P450 cytochrome steroidogenic enzymes in the endoplasmic reticulum is uncertain. Hexose-6-phosphate dehydrogenase resides in the endoplasmic reticulum lumen and co-localizes with the bidirectional enzyme 11β-hydroxysteroid dehydrogenase 1. Hexose-6-phosphate dehydrogenase likely provides 11β-hydroxysteroid dehydrogenase 1 with NADPH electrons via channeling. Intracellularly, two compartmentalized reactions generate NADPH upon oxidation of glucose-6-phosphate: cytosolic glucose-6-phosphate dehydrogenase and microsomal hexose-6-phosphate dehydrogenase. Because some endoplasmic reticulum enzymes require an electron donor (NADPH), it is conceivable that hexose-6-phosphate dehydrogenase serves in this capacity for these pathways. Besides 11β-hydroxysteroid dehydrogenase 1, we examined whether hexose-6-phosphate dehydrogenase generates reduced pyridine nucleotide for pivotal adrenal microsomal P450 enzymes. 21-hydroxylase activity was increased with glucose-6-phosphate and, also, glucose and glucosamine-6-phosphate. The latter two substrates are only metabolized by hexose-6-phosphate dehydrogenase, indicating that requisite NADPH for 21-hydroxylase activity was not via glucose-6-phosphate dehydrogenase. Moreover, dihydroepiandrostenedione, a non-competitive inhibitor of glucose-6-phosphate dehydrogenase, but not hexose-6-phosphate dehydrogenase, did not curtail activation by glucose-6-phosphate. Finally, the most compelling observation was that the microsomal glucose-6-phosphate transport inhibitor, chlorogenic acid, blunted the activation by glucose-6-phosphate of both 21-hydroxylase and 17-hydroxylase indicating that luminal hexose-6-phosphate dehydrogenase can supply NADPH for these enzymes. Analogous kinetic observations were found with microsomal 17-hydroxylase. These findings indicate that hexose-6-phosphate dehydrogenase can be a source, but not exclusively so, of NADPH for several adrenal P450 enzymes in the steroid pathway. Although the reduced pyridine nucleotides are produced intra-luminally, these compounds may also slowly transverse the endoplasmic reticulum membrane by unknown mechanisms.

Novel steroid inhibitors of glucose 6-phosphate dehydrogenase

Novel derivatives of the steroid DHEA 1, a known uncompetitive inhibitor of G6PD, were designed, synthesized, and tested for their ability to inhibit this dehydrogenase enzyme. Several compounds with approximately 10-fold improved potency in an enzyme assay were identified, and this improved activity translated to efficacy in a cellular assay. The SAR for steroid inhibition of G6PD has been substantially developed; the 3β-alcohol can be replaced with 3β-H-bond donors such as sulfamide, sulfonamide, urea, and carbamate. Improved potency was achieved by replacing the androstane nucleus with a pregnane nucleus, provided a ketone at C-20 is present. For pregnan-20-ones incorporation of a 21-hydroxyl group is often beneficial. The novel compounds generally have good physicochemical properties and satisfactory in vitro DMPK parameters. These derivatives may be useful for examining the role of G6PD inhibition in cells and will assist the future design of more potent steroid inhibitors with potential therapeutic utility.

Effects of laparoscopic Roux-en-Y gastric bypass on glucose-6 phosphate dehydrogenase activity in obese type 2 diabetics

BACKGROUND

Glucose-6-phosphate dehydrogenase (G6PD) is the rate-limiting enzyme of the pentose phosphate pathway that provides the majority of NADPH required for lipid biosynthesis. G6PD overexpression has been implicated in insulin resistance, hyperlipidemia, and increased oxidative stress in animals. This study examines G6PD expression in obese diabetic and nondiabetic subjects pre- and post-laparoscopic Roux-en-Y gastric bypass (LRYGB).

METHODS

Patients undergoing LRYGB were recruited for the IRB-approved study and placed in either the diabetic (n = 11) or nondiabetic group (n = 16) (diabetic, HbA1c > 6.5%; nondiabetic, HbA1c < 6.0%). Blood samples were collected at baseline and throughout the first 3 postoperative months. Liver, adipose, and omental samples were taken during surgery. Results are expressed as mean ± SEM and were compared statistically using the Mann-Whitney test.

RESULTS

The two groups were not significantly different at baseline except for fasting glucose and HbA1c. G6PD activity (nm/min/mg protein) was significantly higher in red blood cells (RBCs) (3.12 ± 1.39 vs. 0.67 ± 0.14) and liver (17.23 ± 2.40 vs. 9.74 ± 2.18) in diabetics compared to nondiabetics. There was good correlation between increased liver G6PD activity and the severity of diabetes as measured by HbA1c (r (2) = 0.525) and fasting glucose (r (2) = 0.542). No significant difference was found in the adipose or omental G6PD expression. Both groups experienced a significant increase in G6PD blood activity shortly following surgery (1 week) followed by a reduction 3 months after surgery.

CONCLUSION

These results are the first ever seen in human subjects and demonstrate increased G6PD activity in diabetics compared to nondiabetics. These results suggest a correlation between G6PD activity and the severity of type 2 diabetes. The early increases in G6PD activity after LRYGB were unexpected and longer follow-up is needed to determine the effects of LRYGB on G6PD activity.

Biochemical disorders associated with antiproliferative effect of dehydroepiandrosterone in hepatoma cells as revealed by LC-based metabolomics

DHEA is known to have chemopreventive and antiproliferative activities, and was initially thought to be mediated by inhibition of G6PD. Our previous study has shown that DHEA may act through interference with energy metabolism. To study the effect of pharmacological dose of DHEA on cellular metabolism, and to further delineate the mechanism underlying its antiproliferative effect, we applied a metabolomic approach to globally profile the changes in metabolites in SK-Hep1 cells underexpressing G6PD (Sk-Gi) and control cells (Sk-Sc) after DHEA treatment. RRLC-TOF-MS was used to identify metabolites, and tandem mass spectrometry was used to confirm their identity. DHEA induced changes in glutathione metabolism, lipid metabolism, s-adenosylmethionine (SAM) metabolism, as well as lysine metabolism. Elevation in level of glutathione disulfide, together with a concomitant decrease in level of reduced glutathione, was indicative of increased oxidative stress. Depletion of carnitine and its acyl derivatives reflected decline in fatty acid catabolism. These changes were associated with mitochondrial malfunction and reduction in cellular ATP content. Cardiolipin (CL) and phosphatidylcholine (PC) levels decreased significantly, suggesting that alterations in lipid composition are causally related to decline in mitochondrial function after DHEA treatment. The decline in cellular SAM content was accompanied by decreased expression of methionine adenosyltransferase genes MAT2A and MAT2B. SAM supplementation partially rescued cells from DHEA-induced growth stagnation. Our findings suggest that DHEA causes perturbation of multiple pathways in cellular metabolism. Decreased SAM production, and cardiolipin depletion and the resulting mitochondrial dysfunction underlie the antiproliferative effect of DHEA.

Synthesis of dehydroepiandrosterone analogues modified with phosphatidic acid moiety

Dehydroepiandrosterone (DHEA) and its metabolite 7α-OH DHEA have many diverse physiological, biological and biochemical effects encompassing various cell types, tissues and organs. In in vitro studies, DHEA analogues have myriad biological actions, but in vivo, especially in oral administration, DHEA produces far more limited clinical effects. One of the possible solutions of this problem is conversion of DHEA to active analogues and/or its transformation into prodrug form. In this article, the studies on the conversion of DHEA and 7α-OH DHEA into their phosphatides by the phosphodiester approach are described. In this esterification, N,N-dicyclohexylcarbodiimide (DCC) was the most efficient coupling agent as well as p-toluenesulphonyl chloride (TsCl).

A new antidiabetic compound attenuates inflammation and insulin resistance in Zucker diabetic fatty rats

Tissue macrophage inflammatory pathways contribute to obesity-associated insulin resistance. Here, we have examined the efficacy and mechanisms of action of a novel anti-inflammatory compound (HE3286) in vitro and in vivo. In primary murine macrophages, HE3286 attenuates LPS- and TNFalpha-stimulated inflammation. In Zucker diabetic fatty rats, inflammatory cytokine/chemokine expression was downregulated in liver and adipose tissue by HE3286 treatment, as was macrophage infiltration into adipose tissue. In line with reduced inflammation, HE3286 treatment normalized fasting and fed glucose levels, improved glucose tolerance, and enhanced skeletal muscle and liver insulin sensitivity, as assessed by hyperinsulinemic euglycemic clamp studies. In phase 2 clinical trials, HE3286 treatment led to an enhancement in insulin sensitivity in humans. Gluconeogenic capacity was also reduced by HE3286 treatment, as evidenced by a reduced glycemic response during pyruvate tolerance tests and decreased basal hepatic glucose production (HGP) rates. Since serum levels of gluconeogenic substrates were decreased by HE3286, it indicates that the reduction of both intrinsic gluconeogenic capacity and substrate availability contributes to the decrease in HGP. Lipidomic analysis revealed that HE3286 treatment reduced liver cholesterol and triglyceride content, leading to a feedback elevation of LDL receptor and HMG-CoA reductase expression. Accordingly, HE3286 treatment markedly decreased total serum cholesterol. In conclusion, HE3286 is a novel anti-inflammatory compound, which displays both glucose-lowering and cholesterol-lowering effects.

Targeting the Pentose Phosphate Pathway in Syndrome X-related Cardiovascular Complications

Syndrome X is a combination or co-occurrence of several known cardiovascular risk factors (including central obesity, dyslipidemias, fatty liver disease, hyperinsulinemia, insulin resistance, and hypertension) that affects at least one in five people in developed countries. Syndrome X shortens life and increases morbidity by contributing to the development of both diabetes and cardiovascular disease. Type 1 or 2 diabetes affects approximately 170 million people globally and these numbers are rapidly rising. In patients with diabetes, vascular diseases develop early and progress at an accelerated rate. It has recently become evident that glucose-6-phosphate dehydrogenase (G6PD), the rate limiting enzyme in the pentose-phosphate pathway and its reaction products play key roles in regulating vascular function. Epidemiological studies have also shown that G6PD deficiency markedly reduces retinopathy and mortality due to cardiovascular diseases in males from certain Mediterranean regions. Conversely, G6PD expression and activity are upregulated in rat and mouse models of obesity, hyperglycemia and hyperinsulinemia, and a role for G6PD in the development of insulin resistance in type 2 diabetes has been proposed. Unfortunately, there are no selective drugs available to validate the hypothesis that G6PD and its products are involved in the development of Syndrome X in humans. This review discusses the potential mechanisms by which G6PD could be implicated in vascular diseases in Syndrome X and the need to develop new approaches, including new drugs and molecular tools, to ameliorate diabetes-induced vascular dysfunction and vasculopathies.

The effects of DHEA, 3beta-hydroxy-5alpha-androstane-6,17-dione, and 7-amino-DHEA analogues on short term and long term memory in the mouse

Neurosteroids have been reported to modulate memory processes in rodents. Three analogues of dehydroepiandrosterone (DHEA), two of them previously described (7beta-aminoDHEA and 7beta-amino-17-ethylenedioxy-DHEA), and a new one (3beta-hydroxy-5alpha-androstane-6,17-dione) were synthesized, and their effects were evaluated on memory. This study examined their effects on long term and short term memory in male (6 weeks old) NMRI mice in comparison with the reference drug. Long term memory was assessed using the passive avoidance task and short term memory (spatial working memory) using the spontaneous alternation task in a Y maze. Moreover, the effects of DHEA and its analogues on spontaneous locomotion were measured. In all tests, DHEA and analogues were injected at three equimolar doses (0.300-1.350-6.075 microM/kg). DHEA and its three analogues administered immediately post-training at the highest doses (6.075 microM/kg, s.c.) improved retention in passive avoidance test. Without effect per se in the spatial working memory task, the four compounds failed to reverse scopolamine (1mg/kg, i.p.)-induced deficit in spontaneous alternation. These data suggested an action of DHEA and analogues in consolidation of long term memory particularly when emotional components are implied. Moreover, data indicated that pharmacological modulation of DHEA as performed in this study provides derivatives giving the same mnemonic profile than reference molecule.

Involvement of the PI3K/Akt pathway in estrogen-mediated regulation of human CYP7B1: identification of CYP7B1 as a novel target for PI3K/Akt and MAPK signalling

The steroid hydroxylase CYP7B1 metabolizes neurosteroids, cholesterol derivatives, and estrogen receptor (ER) ligands. Previous studies identified CYP7B1 as a target for regulation by estrogen. The present study examines the mechanism for estrogen-mediated regulation of the human CYP7B1 gene promoter. Treatment with LY294002, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K), abolished ER-mediated up-regulation of a CYP7B1 promoter-luciferase reporter in HepG2 cells, whereas overexpression of PI3K or Akt significantly increased estrogenic up-regulation of CYP7B1. Overexpression of dominant-negative mutant Akt abolished ER-mediated stimulation of CYP7B1 in HepG2 cells. Data indicated no binding of ER to CYP7B1 promoter sequences, suggesting that ER interacts with the PI3K/Akt pathway without binding to the gene. At low ER levels, overexpression of Akt suppressed CYP7B1 promoter activity, suggesting that its effect on CYP7B1 is different when estrogens are absent. In HEK293 cells, CYP7B1 transcription was much less affected by Akt, indicating that the mechanism for up-regulation of CYP7B1 is different in different cell types. Other experiments indicated that MAPK signalling may affect basal CYP7B1 levels. The current results, indicating that regulation of CYP7B1 by ER can be mediated via the PI3K/Akt signal pathway, a regulatory pathway important for cellular survival and growth, suggest an important role for CYP7B1 in cellular growth, particularly in connection with estrogenic signalling.