Effects of gut microbiota on omega-3-mediated ovary and metabolic benefits in polycystic ovary syndrome mice

BACKGROUND

Polycystic ovary syndrome (PCOS) is a common reproductive endocrine disorder that frequently exhibits low-grade inflammation, pro-oxidant activity, and gut dysbiosis. PCOS has become one of the leading causes of female infertility worldwide. Recently, omega-3 polyunsaturated fatty acids (PUFAs) have been proven to benefit metabolic disorders in PCOS patients. However, its roles in the regulation of metabolic and endocrinal balances in PCOS pathophysiology are not clear. In the present study, we aimed to explore how omega-3 PUFAs alleviate ovarian dysfunction and insulin resistance in mice with dehydroepiandrosterone (DHEA)-induced PCOS by modulating the gut microbiota.

METHODS

We induced PCOS in female mice by injecting them with DHEA and then treated them with omega-3 PUFAs. 16S ribosomal DNA (rDNA) amplicon sequencing, fecal microbiota transplantation (FMT) and antibiotic treatment were used to evaluate the role of microbiota in the regulation of ovarian functions and insulin resistance (IR) by omega-3 PUFAs. To further investigate the mechanism of gut microbiota on omega-3-mediated ovarian and metabolic protective effects, inflammatory and oxidative stress markers in ovaries and thermogenic markers in subcutaneous and brown adipose tissues were investigated.

RESULTS

We found that oral supplementation with omega-3 PUFAs ameliorates the PCOS phenotype. 16S rDNA analysis revealed that omega-3 PUFA treatment increased the abundance of beneficial bacteria in the gut, thereby alleviating DHEA-induced gut dysbiosis. Antibiotic treatment and FMT experiments further demonstrated that the mechanisms underlying omega-3 benefits likely involve direct effects on the ovary to inhibit inflammatory cytokines such as IL-1β, TNF-α and IL-18. In addition, the gut microbiota played a key role in the improvement of adipose tissue morphology and function by decreasing multilocular cells and thermogenic markers such as Ucp1, Pgc1a, Cited and Cox8b within the subcutaneous adipose tissues.

CONCLUSION

These findings indicate that omega-3 PUFAs ameliorate androgen-induced gut microbiota dysbiosis. The gut microbiota plays a key role in the regulation of omega-3-mediated IR protective effects in polycystic ovary syndrome mice. Moreover, omega-3 PUFA-regulated improvements in the ovarian dysfunction associated with PCOS likely involve direct effects on the ovary to inhibit inflammation. Our findings suggest that omega-3 supplementation may be a promising therapeutic approach for the treatment of PCOS by modulating gut microbiota and alleviating ovarian dysfunction and insulin resistance.

Dulaglutide, a long-acting GLP-1 receptor agonist, can improve hyperandrogenemia and ovarian function in DHEA-induced PCOS rats

OBJECTIVE

The purpose of this study was to explore the effect of dulaglutide on DHEA induced PCOS rats and its mechanism, to provide new drugs and research directions for clinical treatment of PCOS.

METHODS

In this study, the PCOS model was established by giving female SD rats subcutaneous injection of DHEA for 21 consecutive days. After modeling, the treatment group was injected subcutaneously with three doses of dulaglutide for 3 weeks. The model group was injected with sterile ultrapure water, and the normal group did not get any intervention. The body weight changes of rats in each group were recorded from the first day when rats received the administration of dulaglutide. Three weeks later, the rats were fasted the night after the last treatment, determined fasting insulin and fasting glucose the next day. After the rats were anesthetized by chloral hydrate, more blood was collected from the heart of the rat. The serum insulin, testosterone and sex hormone binding globulin (SHBG) levels were detected by the enzyme-linked immunoassay method. After removing the adipose tissue, the obtained rat ovary tissue was used for subsequent experimental detection, using HE staining for morphology and follicular development analysis; qRT-PCR for the detection of 3βHSD, CYP17α1, CYP19α1, and StAR gene expression in ovarian tissue; and western blotting analysis of CYP17α1, CYP19α1, StAR protein expression and insulin level to verify whether dulaglutide has a therapeutic effect on PCOS in rats.

RESULTS

After treated with different concentrations of dulaglutide, we found that the body weight of rats in the treatment groups were reduced. Compared with the rats in PCOS group, the serum androgen level of rats in the treatment groups was significantly decreased, and the serum sex hormone binding protein content was significantly increased, and there was statistically significant difference between these groups and PCOS group. In terms of protein expression and gene regulation, the expression of 3βHSD, CYP19α1 and StAR in the ovarian tissue of rats in treatment groups were decreased significantly after received the treatment of dulaglutide, and there was statistically significant difference between these groups and PCOS group. In addition, dulaglutide reduced the insulin content in the ovarian tissue of PCOS rats.

CONCLUSION

Dulaglutide may reduce the hyperandrogenemia of PCOS rats by regulating the content of serum SHBG and the expression of 3βHSD, CYP19α1, and StAR related genes and proteins, thereby inhibiting the excessive development of small follicles and the formation of cystic follicles in the ovaries of PCOS rats, thereby improving polycystic ovary in PCOS rats. In addition, dulaglutide may reduce the weight of PCOS rats, further reducing the level of high androgen in PCOS rats, and improving the morphology of their polycystic ovaries.

The Effect of Astaxanthin and Metformin on Oxidative Stress in Granulosa Cells of BALB C Mouse Model of Polycystic Ovary Syndrome

Reactive oxygen species (ROS), involved in the pathogenesis of the polycystic ovary syndrome (PCOS), play a key role in the onset of apoptosis in follicles and granulosa cells (GCs). We aimed to investigate the antioxidant effects of AST and metformin separately and in combination on GCs using a PCOS mouse model. Forty-eight prepubertal female BALB C mice aged 25-30 days and weighing 12-14 g were studied. The PCOS model was created by subcutaneous injection of the dehydroepiandrosterone (DHEA) hormone in 8 mice of BALB C for 20 consecutive days. Apoptosis and the amount of ROS were evaluated in GCs of the ovaries via flow cytometry. The activity of AKT protein was measured by western blot, and the viability of GCs was investigated using spectrophotometry. Ovarian tissue sections were prepared, stained with H&E, and the morphology of the sections was examined. Statistical analysis was performed by SPSS v22.0 software using one-way ANOVA. We found that AST administration leads to a significant reduction in oxidative stress (P<0.01) and consequently a significant decrease in the rate of apoptosis (P<0.01). While the expression of AKT in the AST group revealed a significant increase (P<0.05), it decreased in the metformin group. However, it was still significantly higher than the control and PCOS groups. Ovulation was confirmed in both metformin and AST groups. Further studies are warranted to prove the efficacy of AST and to introduce it as a complementary therapeutic agent in PCOS.

Quercetin modulates granulosa cell mRNA androgen receptor gene expression in dehydroepiandrosterone-induced polycystic ovary in Wistar rats via metabolic and hormonal pathways

Background It is estimated that about 5-10% of women suffer from polycystic ovarian syndrome (PCOS) which is a major cause of female reproductive dysfunction. This study examined the role of quercetin on dehydroepiandrosterone (DHEA)-induced PCO in Wistar rats. Methods Twenty-eight pre-pubertal female Wistar rats that are 21 days old weighing 16-21 g were sorted into four groups (n = 7). Group I served as control and was given distilled water only, Group II were injected with 6 mg/100 g BW of DHEA in 0.2 mL of corn oil subcutaneously, Group III received 100 mg/kg BW of quercetin orally and Group IV received 6 mg/100 g BW of DHEA in 0.2 mL of corn oil subcutaneously and 100 mg/kg BW of quercetin orally. Rats were sacrificed after 15 days by cervical dislocation method. Blood samples and ovaries were collected for hormonal, biochemical, and histopathological analysis and expressions of mRNA androgen receptor gene were determined using RT-qPCR. All data were analysed using one-way ANOVA. Results A significant decrease (p < 0.05) in the antioxidant and metabolic enzyme activity in the DHEA treated group was observed when compared with control. DHEA co-administration with quercetin showed a significant decrease in malondialdehyde and cytokines when compared with DHEA treated group. Also a significant increase in progesterone, metabolic and antioxidant enzyme activity was observed. The histopathology demonstrates a reduction in cystic and atretic cells, improved expression of BCl2, E-Cadherin and a decrease in Bax. Conclusions Quercetin alleviated DHEA-induced PCO. These effects could be attributed to its antioxidant property.

Gene Expression Profiles in Rat Liver Slices Exposed to Hepatocarcinogenic Enzyme Inducers, Peroxisome Proliferators, and 17α-Ethinylestradiol

Transcription profiling is used as an in vivo method for predicting the mode-of-action class of nongenotoxic carcinogens. To set up a reliable in vitro short-term test system DNA microarray technology was combined with rat liver slices. Seven compounds known to act as tumor promoters were selected, which included the enzyme inducers phenobarbital, α-hexachlorocyclohexane, and cyproterone acetate; the peroxisome proliferators WY-14,643, dehydroepiandrosterone, and ciprofibrate; and the hormone 17 α-ethinylestradiol. Rat liver slices were exposed to various concentrations of the compounds for 24 h. Toxicology-focused TOXaminer™ DNA microarrays containing approximately 1500 genes were used for generating gene expression profiles for each of the test compound. Hierarchical cluster analysis revealed that (i) gene expression profiles generated in rat liver slices in vitro were specific allowing classification of compounds with similar mode of action and (ii) expression profiles of rat liver slices exposed in vitro correlate with those induced after in vivo treatment (reported previously). Enzyme inducers and peroxisome proliferators formed two separate clusters, confirming that they act through different mechanisms. Expression profiles of the hormone 17 α-ethinylestradiol were not similar to any of the other compounds. In conclusion, gene expression profiles induced by compounds that act via similar mechanisms showed common effects on transcription upon treatment in vivo and in rat liver slices in vitro.

The rainbow trout liver cancer model: response to environmental chemicals and studies on promotion and chemoprevention

Rainbow trout (Oncorhynchus mykiss) are an outstanding model of liver cancer induction by environmental chemicals and development of strategies for chemoprevention. Trout have critical and unique advantages allowing for cancer studies with 40,000 animals to determine dose-response at levels orders of magnitude lower than possible in rodents. Examples of two promoters in this model, the dietary supplement dehydroepiandrosterone (DHEA) and industrial chemical perfluorooctanoic acid (PFOA), are presented. In addition, indole-3-carbinol (I3C) and chlorophyllin (CHL) inhibit initiation following exposure to potent human chemical carcinogens (e.g., aflatoxin B(1) (AFB(1))). Two "ED(001)" cancer studies have been conducted, utilizing approximately 40,000 trout, by dietary exposure to AFB(1) and dibenzo[d,e,f,p]chrysene (DBC). These studies represent the two largest cancer studies ever performed and expand the dose-response dataset generated by the 25,000 mouse "ED(01)" study over an order of magnitude. With DBC, the liver tumor response fell well below the LED(10) line, often used for risk assessment, even though the biomarker (liver DBC-DNA adducts) remained linear. Conversely, the response with AFB(1) remained relatively linear throughout the entire dose range. These contributions to elucidation of mechanisms of liver cancer, induced by environmental chemicals and the remarkable datasets generated with ED(001) studies, make important contributions to carcinogenesis and chemoprevention.

Genomic profiling reveals an alternate mechanism for hepatic tumor promotion by perfluorooctanoic acid in rainbow trout

BACKGROUND

Perfluorooctanoic acid (PFOA) is a potent hepatocarcinogen and peroxisome proliferator (PP) in rodents. Humans are not susceptible to peroxisome proliferation and are considered refractory to carcinogenesis by PPs. Previous studies with rainbow trout indicate they are also insensitive to peroxisome proliferation by the PP dehydroepiandrosterone (DHEA), but are still susceptible to enhanced hepatocarcinogenesis after chronic exposure.

OBJECTIVES

In this study, we used trout as a unique in vivo tumor model to study the potential for PFOA carcinogenesis in the absence of peroxisome proliferation compared with the structurally diverse PPs clofibrate (CLOF) and DHEA. Mechanisms of carcinogenesis were identified from hepatic gene expression profiles phenotypically anchored to tumor outcome.

METHODS

We fed aflatoxin B(1) or sham-initiated animals 200-1,800 ppm PFOA in the diet for 30 weeks for tumor analysis. We subsequently examined gene expression by cDNA array in animals fed PFOA, DHEA, CLOF, or 5 ppm 17beta-estradiol (E(2), a known tumor promoter) in the diet for 14 days.

RESULTS

PFOA (1,800 ppm or 50 mg/kg/day) and DHEA treatments resulted in enhanced liver tumor incidence and multiplicity (p < 0.0001), whereas CLOF showed no effect. Carcinogenesis was independent of peroxisome proliferation, measured by lack of peroxisomal beta-oxidation and catalase activity. Alternately, both tumor promoters, PFOA and DHEA, resulted in estrogenic gene signatures with strong correlation to E(2) by Pearson correlation (R = 0.81 and 0.78, respectively), whereas CLOF regulated no genes in common with E(2).

CONCLUSIONS

These data suggest that the tumor-promoting activities of PFOA in trout are due to novel mechanisms involving estrogenic signaling and are independent of peroxisome proliferation.

Synthesis and evaluation of novel 17-indazole androstene derivatives designed as CYP17 inhibitors

A series of novel 1H- and 2H-indazole derivatives of the commercially available dehydroepiandrosterone acetate have been synthesized and tested for inhibition of human cytochrome 17alpha-hydroxylase-C(17,20)-lyase (CYP17), androgen receptor (AR) binding affinity, and cytotoxic potential against three prostate cancer (PC) cell lines.

First synthesis of 7α- and 7β-amino-DHEA, dehydroepiandrosterone (DHEA) analogues and preliminary evaluation of their cytotoxicity on Leydig cells and TM4 Sertoli cells

Efficient syntheses of new DHEA analogues, and their apoptotic and necrotic effects on Leydig cells and TM4 Sertoli cells are described. The key step in the synthetic strategy of 7-amino-DHEA derivatives involves a bromination on C-7 position to give an epimeric mixture of bromides which were substituted by azides and reduced to give 7alpha- and 7beta-amino-3beta-hydroxyandrost-5-en-17-ones. No cytotoxic effect induced by apoptosis mechanism was observed on Leydig and TM4 Sertoli cells by treatment with these amino-DHEA analogues. A necrotic effect was induced only in TM4 Sertoli cells. The best activity was obtained with 7alpha,beta-amino-androst-5-en-3beta-ol and 7beta-amino-3beta-hydroxy-androst-5-en-17-one.

Dehydroepiandrosterone inhibits complex I of the mitochondrial respiratory chain and is neurotoxic in vitro and in vivo at high concentrations

Dehydroepiandrosterone (DHEA) is widely used as a food supplement and considered to be relatively safe. In animal studies, however, additions of high concentrations of DHEA to the diet have led to hepatotoxicity as well as liver mitochondrial dysfunction. This study was therefore designed to find out whether DHEA is able to inhibit the respiratory activity also in neuronal mitochondria and to reveal whether this leads to functional disturbance in the brain. Using different mitochondrial substrates, we show here that DHEA suppresses the mitochondrial respiration in permeabilized neurons (half maximal inhibitory concentration 13 microM) by inhibiting complex I of the mitochondrial electron transport chain. Treatment with DHEA was associated with increased glucose expenditure in intact cultures and led to neuronal death. The latter was most prominent in hypoglycemic conditions. Mice fed with pellet containing 0.6% DHEA for 3 months showed a significant neuronal loss in the cerebral cortex and hippocampus, a slightly decreased dopamine/dihydroxyphenylacetic acid ratio, as well as motor impairment. The main conclusion of the present study is that high concentrations of DHEA inhibit complex I of the mitochondrial respiratory chain and are neurotoxic in vitro and in vivo.

Insulin-Lowering Agents Inhibit Synthesis of Testosterone in Ovaries of DHEA-Induced PCOS Rats

BACKGROUND

Insulin-lowering agents are reported to be useful in treating polycystic ovary syndrome (PCOS) anovulation. It has been suggested that lower insulin levels secondarily affect ovarian tissue, although the direct mechanism of action has not yet been verified. Here we investigated if these agents directly affect the ovary.

METHODS

Thirty female Wister rats were studied. Six control rats were injected subcutaneously with 0.2 ml sesame oil, while 24 rats used as PCOS models were injected subcutaneously with dehydroepiandrosterone (DHEA) and divided into four groups. Six rats were injected with only DHEA, while the remaining 18 rats received metformin, pioglitazone or troglitazone. The ovaries were immunohistochemically stained with anti- testosterone and anti-17beta-HSD antibodies, and then evaluated for morphological changes.

RESULTS

In the DHEA administration group, the number of atretic follicles significantly increased compared to that of control rats. The insulin-lowering agents did not improve the multicystic appearance. Serum testosterone concentrations significantly increased with DHEA administration, but the increase was inhibited by oral administration of insulin-lowering agents. Testosterone deposits in ovarian tissue were also reduced by feeding rats insulin-lowering agents.

CONCLUSION

Insulin-lowering agents affected ovarian tissue by inhibiting testosterone biosynthesis in vivo.

Impact of dehydroepiandrosterone on hepatocarcinogenesis in the rat (Review)

The role of dehydroepiandrosterone (DHEA) in liver carcinogenesis remains a topic of widespread research. Studies in rats suggest a hepatocarcinogenetic effect of DHEA. The incidence of DHEA-induced hepatocellular neoplasms depends on the rat strain, the gender, and the dose and duration of the treatment. Gender specific differences observed regarding the incidence of DHEA-induced hepatocellular neoplasms suggest a hormonal impact of the treatment. Studies in rats, which initially had been treated with chemical carcinogens and subsequently underwent a DHEA administration with various doses, disclose both, DHEA associated hepatic tumour promotion and hepatic tumour inhibition. These findings depend on the type, dose and duration of the initial intoxication and of the DHEA treatment. DHEA administration to rats also induces multiple profound alterations of the liver metabolism. Metabolism during DHEA treatment is characterized by an overall increase in energy expenditure. Lipid and glucose metabolism of the liver is changed profoundly switching from an anabolic to a catabolic state. This energy waste may be related to the inhibitory action of DHEA on tumour growth. Tumour enhancement is due to promotion of a specific type of preneoplastic liver lesions with a basophilic phenotype. This review summarizes the current knowledge on DHEA effects on the liver and discusses molecular and functional aspects that may explain the paradoxical effects of DHEA regarding hepatocarcinogenesis.

Induction and modulation of hepatic preneoplasia and neoplasia in the rat by dehydroepiandrosterone

Dehydroepiandrosterone (DHEA), the main adrenal steroid in humans and a precursor in androgen and estrogen biosynthesis, acts as a peroxisome proliferator and as a hepatocarcinogen in rats. Neoplasms emerge from a glycogenotic/amphophilic/basophilic preneoplastic cell lineage. A higher female tumor incidence suggests a relevant influence of sex hormones. DHEA enhances hepatocarcinogenesis induced by N-nitrosomorpholine (NNM), which is characterized by the glycogenotic/basophilic cell lineage. The tumor promoting effect is related to an additional amphophilic/basophilic preneoplastic lesion sequence and to faster proliferation of the basophilic preneoplastic lesions. Nevertheless, hepatocellular carcinomas provided under DHEA treatment seem to have a less malignant phenotype compared to tumors induced by NNM only. Further, DHEA treatment reduces growth and generation of glycogen storage foci (GSF) in initial NNM-treated rats. Thus, DHEA treatment results in both, a growth stimulation of the late basophilic lesion type with an additional amphophilic lesion sequence, and in a growth inhibition of early preneoplastic lesions, addressing especially GSF. DHEA also inhibits the growth of physiologically proliferating liver tissue. This might be explained by a DHEA related cellular metabolism, which results in significant energy consumption. Additionally, a DHEA-induced alteration of cytokine levels might contribute to this growth inhibition as well.

Effect of castration on dehydroepiandrosterone-induced hepatocarcinogenesis in male rats

Dehydroepiandrosterone (DHEA), a peroxisome proliferator, is a hepatocarcinogen in male and female rats. The incidence of DHEA-induced hepatic tumors was much higher in males compared to females, although the peroxisome proliferative effect is similar in both sexes. In this study, we have evaluated the effect of castration in male rats on DHEA-induced hepatocarcinogenesis. Orchiectomy resulted in a significant reduction in hepatocellular carcinomas (15% in castrated rats versus 81% in control rats). However, the incidence of neoplastic nodules was comparable in both orchiectomized and control groups (84% versus 94% in orchiectomized and control groups, respectively). Sixty-two percent of livers in the control group contained tumors larger than 10 mm compared to 8% in the orchiectomized group. These findings indicate that testosterone promotes the growth of neoplastic lesions induced by DHEA.

2-difluoromethylornithine and dehydroepiandrosterone inhibit mammary tumor progression but not mammary or prostate tumor initiation in C3(1)/SV40 T/t-antigen transgenic mice

Female transgenic mice that express SV40 T/t antigens under the regulatory control of the rat C3(1) gene spontaneously develop multifocal mammary lesions that predictably evolve into invasive, hormone-independent carcinomas, whereas male mice are prone to develop prostate cancer. Chemopreventive agents were administered to female C3(1)/SV40 large T-antigen mice from 7 to 19 weeks of age, during which time the mammary lesions developed and progressed to invasive carcinomas. No significant differences in the numbers of preinvasive mammary intraepithelial neoplasia lesions (histologically similar to human ductal carcinoma in situ) were observed after 2 or 8 weeks of treatment between mice receiving either vehicle alone, dehydroepiandrosterone (DHEA), or 2-difluoromethylornithine (DFMO). However, a dose-response reduction in invasive carcinoma growth was observed for both DFMO, an inhibitor of ornithine decarboxylase, and DHEA, the primary steroid precursor to both androgens and estrogens in primates. Despite unaltered expression of the transgene, tumor incidence was reduced approximately 20% by DFMO (8000 mg/kg) and 30% by DHEA (4000 mg/kg; P < 0.05). Tumor multiplicity was reduced by approximately 50% by both DFMO and DHEA (P < 0.05). DFMO had a dose-dependent effect on total tumor burden, which was reduced by 25% at low doses (4000 mg/kg) and 70% at high doses (8000 mg/kg). DHEA reduced tumor burden by 50% and 66% at low (2000 mg/kg) and high (4000 mg/kg) doses, respectively. Interestingly, despite its inhibitory effects on tumor development, DHEA caused a dose-dependent increase of serum estradiol levels that we have previously shown to increase mammary tumor formation in this model. No effect on the development of the prostate cancer precursor lesions (prostate intraepithelial neoplasia) was observed when mice were treated with DHEA, DFMO, tocopherol acetate, selenomethionine, or 9-cis-retinoic acid, although the effects on late-stage prostate cancer development were not determined. These results demonstrate that despite the expression of the highly transforming C3(1)/SV40 large T-antigen transgene, this transgenic model can be used to study the effects of chemopreventive agents on mammary cancer progression. The tumor-inhibitory effects of DHEA and DFMO on mammary cancer growth appear to occur after the development of preinvasive lesions, suggesting that these agents inhibit tumor progression but not initiation.

GL-701 Genelabs

Genelabs is developing GL-701 (prasterone), oral dehydroepiandrosterone (DHEA), for the potential treatment of systemic lupus erythematosus (SLE) [154020]. In September 2000, the company completed submission of its rolling NDA, begun in May 2000 [340361], [355642], [361381], [380239], [383545]. In October 2000, the FDA granted the company's NDA Priority Review designation [387020]. Genelabs began its NDA submission for GL-701 in May 2000, by submitting the complete clinical, statistical and human pharmacokinetic sections to the FDA. This includes all the human efficacy and safety data for the NDA [368932]. In March 1999, Genelabs received Fast Track designation for GL-701 from the US FDA, allowing the development and review of an NDA to be expedited [319963]. Genelabs met with the US FDA in November 1999 to present the data from the two phase III trials in women and was advised by the FDA that its NDA proposal appeared adequatefor submission [348192], [361381]. Because of the public domain nature of DHEA, Genelabs was not certain that it would obtain patent protection. In the US it received Orphan Drug designation, providing seven years of exclusive marketing rights, and in October 1996, Genelabs received US-05567696, covering the use of GL-701 in lupus patients to reduce their dosage of concomitant corticosteroids [222741], [329646]. The US FDA has also granted Subpart E designation to GL-701, which permits expedited development [169754], [222741]. Genelabs licensed the product exclusively worldwide from Stanford University, which performed the early-stage clinical studies. The Asian marketing rights have been licensed to Genelabs Biotechnology Ltd (GBL), a joint investment with the government of Taiwan [229812]. In January 2001, analysts at UBS Warburg predicted that GL-701 would be launched in 2001, and reach sales of US $ 90 million by 2004 [398731].

Oxythiamine and dehydroepiandrosterone induce a G1 phase cycle arrest in Ehrlich's tumor cells through inhibition of the pentose cycle

Transketolase (TK) reactions play a crucial role in tumor cell nucleic acid ribose synthesis utilizing glucose carbons, yet, current cancer treatments do not target this central pathway. Experimentally, a dramatic decrease in tumor cell proliferation after the administration of the TK inhibitor oxythiamine (OT) was observed in several in vitro and in vivo tumor models. Here, we demonstrate that pentose cycle (PC) inhibitors, OT and dehydroepiandrosterone (DHEA), efficiently regulate the cell cycle and tumor proliferation processes. Increasing doses of OT or DHEA were administered by daily intraperitoneal injections to Ehrlich's ascites tumor hosting mice for 4 days. The tumor cell number and their cycle phase distribution profile were determined by DNA flow histograms. Tumors showed a dose dependent increase in their G0-G1 cell populations after both OT and DHEA treatment and a simultaneous decrease in cells advancing to the S and G2-M cell cycle phases. This effect of PC inhibitors was significant, OT was more effective than DHEA, both drugs acted synergistically in combination and no signs of direct cell or host toxicity were observed. Direct inhibition of PC reactions causes a G1 cell cycle arrest similar to that of 2-deoxyglucose treatment. However, no interference with cell energy production and cell toxicity is observed. PC inhibitors, specifically ones targeting TK, introduce a new target site for the development of future cancer therapies to inhibit glucose utilizing pathways selectively for nucleic acid production.

Toxicological and antioxidant effects of short-term dehydroepiandrosterone injection in young rats fed diets deficient or adequate in vitamin E

This study examined the in vivo antioxidant and/or prooxidant effect of short-term dehydroepiandrosterone (DHEA) injection and the effect of dietary vitamin E. Male Sprague-Dawley rats (4 wk old) were fed vitamin E-deficient or vitamin E-adequate (30 mg DL-alpha-tocopheryl acetate/kg) diet for 4 weeks followed by intraperitoneal injection of DHEA for 1 week. The results showed that DHEA injection caused a dose-dependent decrease in body weight, and this effect was more pronounced in vitamin E-deficient rats. In contrast, DHEA injection significantly increased liver, kidney and adrenal weights. Hepatic vitamin E content was significantly lowered by vitamin E deficiency, which led to significantly increased ex vivo and iron-induced lipid peroxidation. DHEA injection did not affect hepatic vitamin E content but significantly decreased ex vivo and iron-induced lipid peroxidation in vitamin E-deficient rats. Hepatic total sulfhydryl (SH) groups and non-protein SH contents were not affected by vitamin E but were significantly increased by DHEA injection, which at 100 mg/kg was not more effective than at 50 mg/kg. Hepatic glutathione S-transferase (GST) activity was significantly decreased by DHEA, but vitamin E alleviated such a decrease. DHEA injection significantly increased hepatic glucose 6-phosphate dehydrogenase (G6PD) activity, and the effect was dose dependent in vitamin E-deficient rats. Thus, DHEA may compensate for vitamin E deficiency in vivo, and this effect is masked when dietary vitamin E is adequate. The antioxidant effect of DHEA is accompanied by decreased body weights, enlarged (fat-laden) tissues and altered activities of hepatic GST and G6PD.

Sex differences in dehydroepiandrosterone-induced hepatocarcinogenesis in the rat

Dehydroepiandrosterone (DHEA), a steroid secreted by the adrenal gland, is a peroxisome proliferator and a hepatocarcinogen. Previously, we have shown that 15-week-old male rats given DHEA in AIN-76 diet without vitamin E developed liver tumors. In the present study, we have examined the carcinogenic effect of DHEA in 5-6-week-old male rats and in intact and ovariectomized female rats. Rats were fed Purina chow containing DHEA at a concentration of 0.45% for 100 weeks and livers were evaluated for tumor incidence and multiplicity. In male rats the incidence of total tumors and hepatocellular carcinomas (HCC) was 94 and 81%, respectively, with 1.9 +/- 0.3 (mean +/- SD) tumors per liver. In intact and ovariectomized females the total tumor incidence was 46 and 60%, respectively. However, the incidence of HCC and the mean number of tumors were similar in both intact and ovariectomized groups. Phenotypically the neoplastic nodules and HCC in female rats were negative for gamma-glutamyltranspeptidase. The results of these studies further confirm that DHEA is a hepatocarcinogen in male and female rats. The possible reasons for the decreased incidence of liver tumors in females in relation to the peroxisome proliferative effect of DHEA is discussed.

Modulation of aflatoxin-B1 hepatocarcinogenesis in trout by dehydroepiandrosterone: initiation/post-initiation and latency effects

Previously, we demonstrated that dehydroepiandrosterone (DHEA) enhances aflatoxin B1 (AFB1) hepatocarcinogenesis in trout when administered following AFB1 exposure. This paper examines the effect of DHEA on tumor latency and the comparative potency for DHEA to modulate AFB1 carcinogenesis when administered prior to and concurrent with AFB1 compared with a post-initiation exposure. Trout were initiated by a 30 min water bath exposure to 10 p.p.b. AFB1. At 3 months post-initiation, animals were started on either control diet or a diet containing 444 p.p.m. dehydroepiandrosterone (DHEA). Fifty trout per treatment were sampled prior to the start of experimental diets, and then at monthly intervals for the next 7 months and examined for the presence of tumors. Tumors were not detected in initiated controls until 7 months after initiation. In initiated trout fed DHEA, the first tumor was detected 5 months after initiation (after just 2 months of dietary DHEA). At 6 months post-initiation, 20% of the AFB1-initiated trout fed DHEA had tumors, while no tumors were visible in either AFB1-initiated controls or noninitiated trout fed DHEA. A second experiment was designed to determine if the enhancing effect of DHEA on AFB1 carcinogenesis is dependent on the time of DHEA administration relative to the time of AFB1 exposure, and if DHEA could be chemopreventive if administered prior to and concurrent with AFB1. Trout were fed one of two levels of DHEA (888 or 1776 p.p.m.) either prior to and during a 4-week initiation period of dietary AFB1 administration, or for 8 weeks following initiation with AFB1. At 9 months after initiation the livers were examined for tumors. Neither exposure protocol provided protection towards AFB1 hepatocarcinogenesis. The strongest enhancement occurred when DHEA was fed during the post-initiation period. Levels of p53 and p34cdc2 were decreased by DHEA treatment, indicating that DHEA may act through alterations in cell-cycle control.

Enhancement and phenotypic modulation of N-nitrosomorpholine-induced hepatocarcinogenesis by dehydroepiandrosterone

Hepatocarcinogenesis was induced in male and female rats by continuous administration of the adrenal steroid dehydroepiandrosterone (DHEA; 0.6% in the diet) with and without previous treatment with N-nitrosomorpholine (NNM; 120 mg/l drinking water for 7 weeks). DHEA treatment alone resulted in hepatocellular adenomas (HCA) and carcinomas (HCC) after 72-84 weeks, the incidence of both benign and malignant neoplasms being higher in females than in males. After DHEA administration for up to 32 weeks subsequent to NNM, the incidence of HCA and HCC was significantly higher (HCA, 42%; HCC, 42%) than after NNM alone (HCA, 33%; HCC, 28%). While total tumor incidence was similar in male (63%) and female (60%) rats after NNM treatment alone, it was higher in females (87%) than in males (80%) after NNM/DHEA treatment. The difference between the genders was mainly due to the higher incidence of HCC in females. Morphometric analysis of preneoplastic foci of altered hepatocytes (FAH) yielded that DHEA treatment did not increase the average total number of FAH induced by NNM, but caused a modulation of the phenotype of FAH from the glycogenotic/basophilic to the amphophilic cell lineage. The results confirm that DHEA acts as a hepatocarcinogen and show for the first time that it enhances NNM-induced hepatocarcinogenesis in rats.

Dietary alpha-tocopherol prevents dehydroepiandrosterone-induced lipid peroxidation in rat liver microsomes and mitochondria

Dehydroepiandrosterone (DHEA), an adrenal steroid, causes lipid peroxidation in rat liver microsomes and mitochondria and induces hepatocarcinogenesis. It was investigated whether alpha-tocopherol, a naturally occurring free radical chain terminator, could decrease lipid peroxidation. When DHEA-free diet supplemented with increasing concentrations of alpha-tocopherol (25, 50, 100, 200, 400 and 1000 mg/kg diet) was fed to rats for 7 days, a marked lipid peroxidation (measured as thiobarbituric acid reactive substances formation) was observed at concentrations 25 and 50 mg/kg in liver microsomes and mitochondria isolated from these animals. Lipid peroxidation was significantly reduced at concentrations > or = 100 mg/kg. When DHEA (500 mg/kg diet) was fed to rats simultaneously with increasing concentrations of alpha-tocopherol, strong lipid peroxidation was observed at alpha-tocopherol concentrations < or = 200 mg/kg diet. However, microsomes and mitochondria isolated from livers of rats fed alpha-tocopherol at doses of 400 and 1000 mg/kg diet produced only negligible amounts of thiobarbituric acid reactive substances. The data show that high concentrations of alpha-tocopherol in the diet decrease DHEA-induced microsomal and mitochondrial lipid peroxidation. Our results support the concept that alpha-tocopherol can protect against DHEA-induced lipid peroxidation and consequently against steroid-induced liver cell damage and, perhaps, also tumour development.

Effects of dehydroepiandrosterone and other sex steroid hormones on mammary carcinogenesis by direct injection of 7,12-dimethylbenz(a) anthracene (DMBA) in hyperprolactinemic female rats

The present study was performed to investigate the effects of dehydroepiandrosterone (DHEA) compared with those of sex steroid hormones on the mammary tumor induced by local injection of 7,12-dimethylbenz(a) anthracene (DMBA) in hyperprolactinemic female rats. Under sustained hyperprolactinemia induced by pimozide (PMZ) from day 21, DMBA was injected locally into the mammary glandular tissues on day 73. Rats were divided into 5 groups as follows; steroid free (DP group), 17 beta-estradiol (DP + E2 group), testosterone (DP + T group), progesterone (DP + Prog group), or dehydroepiandrosterone (DP + DHA group). The growth pattern and histological classification of the tumor in these 5 groups and rats treated only with DMBA (D group) were examined. All of the tumors grew to a size of 10 mm in diameter and after retaining the size for a certain duration, increased the size rapidly again (onset of rapid tumor growth). The period from the day of DMBA administration to that of onset of the rapid tumor growth in DP group was shorter than in D group, and the period in DP + DHA was longer than DP group and longest in steroid-treated groups. The incidence of adenocarcinoma was 2 tumors/16 animals in D group, 9/11 in DP group, 5/11 in DP + Prog group, 2/7 in DP + E2 group, 2/8 in DP + T group, and 0/10 in DP + DHA group. The incidence of adenocarcinoma in each steroid group except in DP + Prog group was lower than in DP group. These results suggest that prolactin (PRL) increases the incidence of adenocarcinoma in the DMBA-induced mammary tumor model, and DHEA especially decreases the incidence of adenocarcinoma.

Effects of ubiquinone and mevalonic acid on hepatic peroxisomal enzymes induced by dehydroepiandrosterone

The adrenal steroid, dehydroepiandrosterone (DHEA) has been identified as a peroxisome proliferator. We examined the effects of the cellular antioxidant ubiquinone and its precursor mevalonic acid on the induction of enzymes associated with DHEA-mediated peroxisome proliferation in male F-344 rats. Upon treatment with DHEA (300 mg/kg orally for 14 days), there was a significant increase in hepatic activities of peroxisomal beta-oxidation (3 fold), 3-ketoacyl-CoA thiolase (4 fold) and catalase (1.8 fold). Co-administration of either mevalonic acid (100 mg/kg intraperitoneally) or ubiquinone (50 mg/kg orally) with DHEA significantly attenuated the DHEA-mediated induction of these enzymes. However, neither ubiquinone nor mevalonic acid alone significantly altered peroxisomal enzyme activities in rat liver. These data suggest that exogenous administration of ubiquinone or mevalonic acid can modulate the induction of the enzymes involved in peroxisome proliferation.

Comparison of the enhancing effects of dehydroepiandrosterone with the structural analog 16 alpha-fluoro-5-androsten-17-one on aflatoxin B1 hepatocarcinogenesis in rainbow trout

Dehydroepiandrosterone (DHEA) is an adrenal steroid with chemoprotective effects against a wide variety of conditions including cancer, obesity, diabetes, and cardiovascular disease. However, DHEA is also a carcinogen in laboratory animals, possibly through its function as a precursor of sex steroids or peroxisome proliferation. The structural analog 16 alpha-fluoro-5-androsten-17-one (8354) has been reported to have enhanced chemopreventive activity without the steroid precursor and peroxisome proliferating effects of DHEA. This study compares DHEA and 8354 in rainbow trout, a species that is resistant to peroxisome proliferation but is highly susceptible to the carcinogenic and tumor enhancing effects of DHEA. Trout were exposed as fry to aflatoxin B1 (AFB1) or given a sham exposure, then were fed diets containing 444 ppm DHEA or 8354 for 6 months. Postinitiation treatment with DHEA significantly increased liver tumor incidence, multiplicity, and size compared to initiated controls. The analog 8354 slightly increased tumor incidence (p = 0.06) but had no effect on multiplicity or size. Six percent of trout treated with DHEA alone developed tumors, whereas no tumors occurred in noninitiated trout fed control or 8354-containing diets. Serum levels of androstenedione were elevated by DHEA (48-fold) or 8354 (6-fold) treatment. Serum beta-estradiol titers were increased in DHEA- but not 8354-treated trout. Vitellogenin was induced significantly by either DHEA (434-fold) or 8354 (21-fold). Peroxisomal beta-oxidation was not increased by either compound and catalase activity was decreased in DHEA-treated animals. Both steroids were potent inhibitors in vitro of trout liver glucose-6-phosphate dehydrogenase with IC50s of 24 and 0.5 microM for DHEA and 8354, respectively. This research suggests that in trout the tumor enhancing effects of DHEA may be due to its function as a sex steroid precursor and are unrelated to peroxisome proliferation. These carcinogenic properties are reduced in the analog 8354 which has been advocated as an alternative to DHEA for chemoprevention.

Dehydroepiandrosterone is a complete hepatocarcinogen and potent tumor promoter in the absence of peroxisome proliferation in rainbow trout

Dehydroepiandrosterone (DHEA), fed for 30 weeks to rainbow trout after initiation with the hepatocarcinogen aflatoxin B1 (AFB1), produced a dose-dependent enhancement of carcinogenesis as measured by increased tumor incidence, multiplicity and size. Significant enhancement was observed at 222 p.p.m., which corresponds to a daily dosage one-half that previously administered to humans in clinical trials. DHEA was also capable of acting as a complete carcinogen in this model, producing liver tumors at doses as low as 222-444 p.p.m. Tumors isolated from trout treated with DHEA alone contained mutations in Ki-ras, primarily codon 12[1] G-->A transitions, providing the first suggestive evidence that DHEA could be a genotoxic carcinogen. The carcinogenicity of DHEA in trout is independent of peroxisome proliferation, as measurements of peroxisomal beta-oxidation and catalase activity support previous observations that trout, like humans, are weak responders to peroxisome proliferators.

Sequential appearance and ultrastructure of amphophilic cell foci, adenomas, and carcinomas in the liver of male and female rats treated with dehydroepiandrosterone

Dehydroepiandrosterone (DHEA), a hormone of the adrenal cortex, acts as a peroxisome proliferator and hepatocarcinogen in rats upon long-term treatment with high doses in the diet. The aim of the present study was to identify the site of origin of hepatocellular neoplasms and the sequence of preneoplastic lesions. Twenty-five female and 25 male rats were given 0.6% DHEA in the diet; 25 animals of each sex were controls. Groups of 5 treated and untreated animals were sacrificed after 4, 20, 32, 70, and 84 wk. Amphophilic cell foci were detected after 32 wk of treatment; they developed from the liver parenchyma almost exclusively in the vicinity of portal tracts. Adenomas of the amphophilic or amphophilic/tigroid cell phenotype were observed at 70 wk of treatment. Highly differentiated hepatocellular carcinomas presenting a similar cellular phenotype occurred after 70-84 wk. The incidence of hepatocellular carcinomas was 44% in female and 11% in male rats. Ultrastructural studies of the amphophilic cell foci and tumors revealed a marked proliferation of mitochondria and a moderate proliferation of peroxisomes in all lesions. In addition, a very strong peroxisome proliferation was observed in perivenular hepatocytes in the liver of female rats. Peroxisomes usually lacked core and showed flocculent matrices. In male rats, weak peroxisomal proliferation was observed. Typical morphological abnormalities of these peroxisomes were paracrystalline inclusions of striated appearance. Although the most prominent peroxisome proliferation was observed in perivenular hepatocytes, these cells did not seem to be involved in tumor development. In contrast, the morphological similarity of the amphophilic cell foci and the amphophilic/tigroid cell adenomas and carcinomas, their coincident localization near portal tracts, and the sequential appearance of these lesions suggest that the amphophilic cell foci represent an early stage in DHEA-induced hepatocellular neoplasia. Mitochondrial proliferation as the most prominent feature in all stages of this model of hepatocarcinogenesis may offer a new approach for analysis of hepatocarcinogenesis induced by DHEA and possibly other peroxisomal proliferators.

Expression of peroxisomal enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase enzyme and its mRNA in peroxisome proliferator-induced liver tumors

We have examined ciprofibrate and dehydroepiandrosterone (DHEA)-induced hepatic lesions for the peroxisomal beta-oxidation system enzyme peroxisomal enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase (PBE) and its mRNA using SDS-polyacrylamide gel electrophoresis, antibodies and cDNA probe. All 12 neoplastic nodules and nine hepatocellular carcinomas (HCCs) that were analyzed for PBE mRNA by in situ hybridization showed an intense signal comparable to the adjacent non-neoplastic liver. SDS-polyacrylamide gel electrophoresis of postnuclear fractions of six HCC and adjacent liver tissue showed a marked increase in an 80 kDa polypeptide. Immunoblot and Northern blot analysis showed a marked increase in PBE enzyme and PBE mRNA respectively in HCC and adjacent non-neoplastic liver tissue. In control livers (animals not treated with peroxisome proliferators), the levels of PBE enzyme and mRNA were very low or undetectable. The results of this study clearly indicate that peroxisome proliferator (PP)-induced liver lesions express peroxisomal enzymes to the same extent as adjacent liver and that these enzymes are not useful markers for identification of PP-induced lesions.

Characteristics of the hepatocarcinogenesis caused by dehydroepiandrosterone, a peroxisome proliferator, in male F-344 rats

The characteristics of the hepatocarcinogenesis induced by dehydroepiandrosterone (DHEA) were compared with that induced by other peroxisome proliferators such as [4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio]acetic acid (Wy-14,643) and di(2-ethylhexyl)phthalate (DEHP). Male F-344 rats were given a diet containing DHEA at 0.5 or 1%, Wy-14,643 at 0.1% and DEHP at 2% for up to 78 weeks. In rats fed 0.5 or 1% DHEA the incidence of neoplasias was 20% after 52 weeks. At 78 weeks all rats treated with 1% DHEA had numerous grossly visible nodules and the incidence of hepatic neoplasia was dose-dependent. The magnitude of hepatocellular tumorigenicity after DHEA treatment was less potent than that after Wy-14,643, but more than that after DEHP treatment. Peroxisomal beta-oxidation activity increased three- or six-fold after a 10 week course of 0.5 or 1% DHEA respectively and this was significantly lower than that induced in Wy-14,643- or DEHP-fed rats. From 52 to 78 weeks these activities increased 3-9 times over that in controls. In both the group of rats treated with Wy-14,643 and those treated with DEHP, peroxisomal beta-oxidation constantly increased 11- to 15-fold during the experiment. Catalase activity increased 1.3- to 1.5-fold for the first 10 weeks of DHEA treatment and then recovered to the control level. The activities of glutathione peroxidase and glutathione S-transferase decreased markedly after 30 weeks in DHEA-treated rats and the decreases were sustained for up to 78 weeks. The profile of changes in enzyme activities in the rats fed DHEA was not significantly different from that of those fed Wy-14,643 or DEHP. There were no increases in 8-hydroxydeoxyguanosine, oxidative DNA damage or lipid peroxide level in the liver in any of the treated rats at 10 or 30 weeks. Since these results showed that the characteristics of hepatocarcinogenesis caused by DHEA were basically similar to those caused by Wy-14,643 and DEHP, typical peroxisome proliferators, hepatocarcinogenesis induced by DHEA is probably due to the same mechanisms as that induced by general peroxisome proliferators.

Dehydroepiandrosterone antiestrogenic action through androgen receptor in MCF-7 human breast cancer cell line

The possible mechanisms of the inhibitory effect of Dehydroepiandrosterone (DHEA) on the estrogen-induced growth of MCF-7 human breast cancer cells were explored. The impairment of metabolic pathways, via the inhibition of glucose-6-phosphate dehydrogenase (G6PD) activity, was excluded: G6PD activity in MCF-7 homogenate was reduced by DHEA only at a very high concentration (50 microM), while no inhibitory action on the enzyme activity was detected when DHEA was added at the antimitotic concentrations (0.02-0.5 microM). A steroid receptor mediated effect was explored: DHEA might either activate androgen receptors (AR) or partially displace E2 from estrogen receptor (ER). The pure antiandrogens Flutamide and Hydroxyflutamide reversed the inhibitory effect of DHEA on MCF-7 cell growth, whereas both the nonsteroidal estrogen Diethylstilbestrol and the antiestrogen Tamoxifen were ineffective. Results demonstrate that the AR activation plays a pivotal role in the inhibitory action of DHEA on the E2-induced MCF-7 growth.

Genetic susceptibility for C19 androgen induction of ovarian granulosa cell tumorigenesis in SWXJ strains of mice

Susceptibility to pubertal onset, malignant granulosa cell (GC) tumors of the ovary is inherited in SWR/Bm and certain SWR-related SWXJ recombinant inbred strains of mice. In some SWXJ strains, GC tumors occur spontaneously (spontaneous strains), and in others GC tumors can only be induced by treatment with dehydroepiandrosterone (DHEA-dependent strains). A gene controlling susceptibility to both spontaneous and DHEA-induced GC tumorigenesis, Gct, has been assigned to Chromosome 4. Additional research on the role of steroids in GC tumorigenesis has revealed a second gene controlling response to C19 androgenic steroids. Spontaneous strains showed increased tumor frequency after treatment with testosterone (T), whereas DHEA-dependent strains showed no GC tumors following T treatment. Within treatment groups, serum steroid data from DHEA, T, and control treated mice showed no consistent differences between spontaneous and DHEA-dependent strains with respect to progesterone, DHEA, androstenedione, dihydrotestosterone, T, estrone, or estradiol. Thus, observed differences in GC tumor responsiveness to exogenous steroids were not due to different patterns of steroid metabolism among spontaneous and DHEA-dependent strains. Further studies on the range of effective C19 steroids were conducted using one spontaneous and one DHEA-dependent strain. The spontaneous strain showed increased GC tumor frequency in response to dihydrotestosterone and androsterone treatment, whereas the DHEA-dependent strain showed no response. This result suggests that spontaneous strains may be sensitive to a broad range of C19 steroids. To determine whether genetic differences in endogenous steroid levels have a role in spontaneous GC tumorigenesis, serum steroid levels were measured in SWR/Bm and SJL/Bm progenitor strains during the developmental period of risk between 22 and 38 days of age. With the exception of transiently increased DHEA at 22 days, there were no consistent differences in steroid levels analyzed. Thus, serum steroid profiles were not reliably prognostic for GC tumorigenesis. In conclusion, GC tumor induction in response to T treatment has co-segregated with susceptibility to spontaneous GC tumors in the SWXJ recombinant inbred strains. Thus, the second gene in our ovarian granulosa cell tumor model regulates responsiveness to T. We propose to name this gene spontaneous ovarian tumorigenesis (Sot), with alleles for susceptibility (s) carried by spontaneous strains and resistance (r) carried by DHEA-dependent strains.

Hepatocarcinogenicity of dehydroepiandrosterone in the rat

Dehydroepiandrosterone, a major secretory steroid hormone of the human adrenal gland, possesses mitoinhibitory and anticarcinogenic properties. It also induces peroxisome proliferation in the livers of rats and mice. Because peroxisome proliferators exhibit hepatocarcinogenic potential, it is necessary to examine the long term hepatic effects of dehydroepiandrosterone since this hormone is contemplated for use as a potential cancer chemopreventive agent in humans. Dehydroepiandrosterone was administered in the diet at a concentration of 0.45% to F-344 rats for up to 84 weeks. At the termination of the experiment, 14 of 16 rats developed hepatocellular carcinomas. Liver tumors induced by dehydroepiandrosterone lacked gamma-glutamyl transpeptidase and glutathione S-transferase (placental form); these phenotypic properties are identical to the features exhibited by liver tumors induced by other peroxisome proliferators. Dehydroepiandrosterone was also shown to markedly inhibit liver cell [3H]thymidine labeling indices, suggesting that cell proliferation is not a critical feature in liver tumor development with this agent. These results show that although dehydroepiandrosterone exerts anticarcinogenic effects in a variety of tissues, the peroxisome-proliferative property makes it a hepatocarcinogen.

Changes in liver structure and function after short-term and long-term treatment of rats with dehydroepiandrosterone

The effects on the liver of feeding a diet containing 0.2% dehydroepiandrosterone were studied after short (7 d) and long (100 d) periods of treatment in rats. The short-term treatment caused hypertrophy of the hepatocytes that, at the ultrastructural level, seemed to be due to proliferation of peroxisomes and (to a minor extent) of mitochondria. The mitochondria seemed to have undergone transition from expanded to condensed configuration; accordingly, after isolation, their rate of coupled respiration was greater than that of control mitochondria. After long-term treatment, the structure of the hepatocytes reverted toward normal. In fact, at the ultrastructural level, the number and the size of peroxisomes was not significantly different from those of the controls, but degenerative phenomena were observed in the mitochondria. Attempts are made to explain the above ultrastructural and biochemical findings in view of the effects of dehydroepiandrosterone on the energy metabolism of liver.

Dehydroepiandrosterone-induced peroxisome proliferation in the rat liver

We have investigated the effect of dehydroepiandrosterone (DHEA), a naturally occurring steroid hormone, on hepatic peroxisomes in the rat. Dietary administration of DHEA at a concentration of 0.45% for 2 weeks resulted in a 200% increase in the liver weight and a more than 5.0-fold increase in the volume density of peroxisomes. SDS-polyacrylamide gel electrophoresis of the postnuclear fraction of livers showed a marked increase in the 80,000-molecular weight polypeptide. Northern blot analysis of total RNA showed 2- and 12-fold increases, respectively, in the levels of catalase and peroxisomal enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase bifunctional enzyme (PBE) mRNA. Administration of a single large dose of DHEA led to a 10- to 40-fold increase in PBE mRNA levels by 24 h. These changes are qualitatively similar to those caused by a variety of structurally different peroxisome proliferators.

Reversal by ribo- and deoxyribonucleosides of dehydroepiandrosterone-induced inhibition of enzyme altered foci in the liver of rats subjected to the initiation--selection process of experimental carcinogenesis

The effect of dehydroepiandrosterone (DHEA) on the activity of NADPH-producing enzymes and the development of enzyme-altered foci has been investigated in the liver of female Wistar rats subjected to an initiating treatment (a necrogenic dose of diethylnitrosamine) followed, 15 days later, by a selection treatment [a 15-day feeding of a diet containing 0.03% 2-acetylaminofluorene (2-AAF), with a partial hepatectomy at the midpoint of this feeding]. At the end of the selection treatment all rat groups received, for 15 days, a basal diet containing, when indicated, 0.05% phenobarbital (PB) and/or 0.6% DHEA. The effect of DHEA on the activity of NADPH-producing enzymes was also studied in normal rats fed, for 15 days, a diet containing 0.6% DHEA and in their pair-fed controls. DHEA caused a 43-58% inhibition of glucose-6-phosphate dehydrogenase (G6PD) and, respectively, 338-420% and 21-24% increases in malic enzyme (ME) and isocitric dehydrogenase activities in all rat groups. This was coupled with a great fall in the production of ribulose-5-phosphate, while no change in NADP+/NADPH ratio occurred. Hepatocytes, isolated from DHEA-treated rats, exhibited a very low activity of hexose monophosphate shunt (HMS), which was not stimulated by methylene blue, an exogenous oxidizing agent that markedly stimulated HMS activity in control hepatocytes. DHEA caused a great fall in the percentage of liver occupied by gamma-glutamyltranspeptidase (GGT)-positive foci, in the rats subjected to the initiation-selection treatments. PB enhanced the development of these foci, an effect which was completely overcome by DHEA. In addition, focal cells no longer expressed a G6PD activity higher than that of surrounding liver in DHEA-treated rats, but exhibited a high histochemical reaction for ME. DHEA also caused a great fall in labelling index of GGT-positive foci. Starting at the end of 2-AAF feeding, a mixture of ribonucleosides (RNs) of adenine, cytosine, guanine and uracil and of deoxyribonucleosides (DRNs) of adenine, cytosine, guanine and thymine were injected i.p. every 8 h for 12 days to the rats subjected to the initiation-selection treatments plus PB. Rats were killed 3 days after the end of RN and DRN treatments. These treatments completely overcome the DHEA effect on the development of GGT-positive foci and DNA synthesis by the focal cells, without affecting G6PD activity of both whole liver and putative preneoplastic foci. Experiments with labeled nucleosides revealed that RNs and DRNs produced derivatives that were incorporated into liver DNA.(ABSTRACT TRUNCATED AT 400 WORDS)

Antimutagenic effects of natural and synthetic hormonal steroids

Among the steroid molecules, bile acids have been shown to have either a co- or an antimutagenic activity toward various direct and indirect acting mutagens in the Ames test. The present report extends such observations to other steroids having hormonal activity. The main effect of the active hormones is an inhibition of the genotoxicity of both direct and indirect acting mutagens. This effect is strictly structure-related. Moreover, both ethinyl oestradiol and mestranol, which are synthetic derivatives of beta-oestradiol largely used in contraceptive pills, are strong inhibitors of the mutagenicity, acting at nanomolar concentrations. The present article emphasizes the possible role of compounds with steroid structure as modulators of genotoxicity.

Alpha-methylene-gamma-lactone fused to steroidal ring D as potential antitumor agent

Steroidal alpha-methylene-gamma-lactone la has been synthesised from 3 beta-hydroxy-5-androsten-17-one 2 and showed to be active against HeLa cells.