Chemoprevention by dietary dehydroepiandrosterone against promotion/progression phase of radiation-induced mammary tumorigenesis in rats

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.

Anticarcinogenic activity of alpha-difluoromethylornithine, ginseng, eleutherococcus, and leuzea on radiation-induced carcinogenesis in female rats

PURPOSE

To carry out a comparative study of inhibition of radiation carcinogenesis using alpha-difluoromethylornithine (DFMO), tinctures of ginseng, eleutherococcus and leuzea in female rats.

MATERIALS AND METHODS

Locally bred female LIO-strain rats were subjected to a single whole body γ-irradiation dose of 4 Gy at 12 weeks of age. Modifying drugs were given with drinking water from the 10th day after irradiation until the end of the experiment (for 16 months).

RESULTS

Irradiated rats developed tumors 70.0-79.6% (malignant tumors: 43.7-45.0%) with a multiplicity of 1.48-1.75 (malignant: 0.5-0.58), while in unirradiated animals the incidence of all/malignant tumors was 21.9%/7.7% with multiplicity of 0.22/0.08. In exposed rats tumors most often developed in the mammary gland - 57.3%, reproductive and endocrine organs - 27.2%, and other localizations - 29.1%. All drugs, except leuzea, significantly reduced incidence and multiplicity of tumors, overall or at some localizations in irradiated rats. Highest, and practically equal inhibition, was shown by ginseng and DFMO, while eleutherococcus was clearly inferior. Ginseng reduced overall tumor incidence and multiplicity by 1.5 and 2.4 times, malignant tumor incidence and multiplicity - by 2.5 and 2.9 times, respectively.

CONCLUSIONS

The ginseng extract is the most promising radiation carcinogenesis inhibitor tested.

Molecular Specificity of 5-Androstenediol as a Systemic Radioprotectant in Mice

We compared in vivo radioprotective efficacy of 5-androstenediol (5-AED) to that of ten other steroids: 17alpha-androstenediol, dehydroepiandrosterone, 5-androstenetriol (AET), 4-androstenedione (AND), testosterone, estradiol, fluasterone, 16alpha-bromoepiandrosterone, 16alpha-fluoro-androst-5-en-17alpha-ol (alpha-fluorohydrin, AFH), and 16alpha-fluoro-androst-5-en-17beta-ol (beta-fluorohydrin). Steroids were administered 24 or 48 hr before, or 1 hr after, whole-body gamma-irradiation. Two days after irradiation at 3 Gy, blood elements were counted. In addition, after irradiation at 9-12.5 Gy, survival was recorded for 30 days. The results showed radioprotective efficacy was specific for 5-AED. One other steroid, AFH, demonstrated appreciable survival effects but was less efficacious than 5-AED. AND and AET produced slight enhancement of survival in some experiments. This is the first demonstration that the prophylactic window for survival enhancement by 1 subcutaneous (s.c.) injection of 5-AED is as long as 48 hr in mice. Moreover, the results indicate that 1 s.c. injection of 5-AED 1 hr after irradiation is much less effective than 1 injection 24-48 hr before irradiation. Comparing the molecular features of steroids with radioprotective efficacy leads to the following conclusions: 1) these effects are due to interaction with specific receptors, since s.c. injection of extremely similar molecules with the same physicochemical properties as 5-AED were not radioprotective; 2) the 17-hydroxyl group is essential; 3) this group must be in the beta configuration in the absence of nearby side groups; 4) a halogen atom at 16 changes the 17-hydroxyl specificity to alpha; 5) the 3beta-hydroxyl group is not essential; 6) addition of a 7beta-hydroxyl group is deleterious; and 7) the effects are not due to activation of sex steroid receptors.

Effect of dehydroepiandrosterone on lipopolysaccharide-induced interleukin-6 production in DH82 cultured canine macrophage cells

OBJECTIVE

This study examined the effect of dehydroepiandrosterone (DHEA) on lipopolysaccharide (LPS)-stimulated interleukin-6 (IL-6) production in the DH82 canine macrophage cell line.

STUDY DESIGN

Cultured DH82 cells were stimulated with varying concentrations of LPS with or without DHEA for various times. Supernatant IL-6 levels were measured by enzyme-linked immunosorbent assay, and cellular cytoplasmic IkappaBalpha protein expression measured by Western blot analysis.

RESULTS

LPS dose-dependently stimulated IL-6 production (p=0.016). Cells stimulated with 20 microg LPS showed a time-dependent increase of IL-6 concentration up to 10 h post-treatment (p=0.007). Co-treatment of DH82 cells with 20 microg LPS and various concentrations of DHEA for 14 h showed that up to 10 microM DHEA dose-dependently decreased the IL-6 concentration (p=0.007). Also, addition of 20 microM DHEA to DH82 cells with 20 microg LPS time-dependently decreased the IL-6 concentration for up to 14 h post-treatment (p=0.018). Stimulation of cultured DH82 cells with 20 microg LPS significantly decreased cellular cytoplasmic IkappaBalpha expression, beginning at 30 min post-treatment and persisting to at least 2 h post-treatment (p=0.012). However, co-treatment of cells with 20 microg LPS and 20 microM DHEA abrogated this effect until 2 h post-treatment.

CONCLUSIONS

DHEA decreased the IL-6 concentration in the supernatant of LPS-stimulated DH82 cells by inhibiting the sequestration of IkappaBalpha, which is necessary for the activation of nuclear factor-kappa B. These findings provide new insights into the immunomodulatory effects of DHEA.

Dehydroepiandrosterone affects the expression of multiple genes in rat liver including 11 beta-hydroxysteroid dehydrogenase type 1: a cDNA array analysis

Dehydroepiandrosterone (DHEA) is a C-19 adrenal steroid precursor to the gonadal steroids. In humans, circulating levels of DHEA, as its sulfated conjugate, are high at puberty and throughout early adulthood but decline with age. Dietary supplementation to maintain high levels of DHEA purportedly has beneficial effects on cognitive memory, the immune system, and fat and carbohydrate metabolism. In rodents, DHEA is a peroxisome proliferator that induces genes for the classical peroxisomal and microsomal enzymes associated with this response. These effects are mediated through activation of peroxisome proliferator-activated receptor alpha (PPAR alpha). However, DHEA can affect the expression of genes independently of PPAR alpha, including the gene for the major inducible drug and xenobiotic metabolizing enzyme, cytochrome P450 3A23. To elucidate the biochemistry associated with DHEA treatment, we employed a cDNA gene expression array using liver RNA from rats treated with DHEA or the classic peroxisome proliferator nafenopin. Principal components analysis identified 30 to 35 genes whose expression was affected by DHEA and/or nafenopin. Some were genes previously identified as PPAR-responsive genes. Changes in expression of several affected genes were verified by quantitative reverse transcriptase-polymerase chain reaction. These included aquaporin 3, which was induced by DHEA and to a lesser extent nafenopin, nuclear tyrosine phosphatase, which was induced by both agents, and 11 beta-hydroxysteroid dehydrogenase 1, which was decreased by treatment with DHEA in a dose-dependent fashion. Regulation of 11 beta-hydroxysteroid dehydrogenase 1 expression is important since the enzyme is believed to amplify local glucocorticoid signaling, and its repression may cause some of the metabolic effects associated with DHEA.

Prevention of radiation-induced mammary tumors

The radiation-induced rat mammary tumor model is useful for studying tumor prevention by treatment in the initiation or promotion stage. In anti-initiation experiments, the administration of radical scavengers or spin-trapping agents before or immediately after irradiation reduced the incidence of mammary tumors, suggesting that free radicals produced by exposure are a potent initiator. To evaluate the role of nitric oxide (NO) in the initiation, NO-specific scavengers or NO synthase inhibitors were administered during the initiation. These agents partially prevented the tumorigenesis, suggesting that radiation-induced NO contributes to tumor initiation. The administration of curcumin during irradiation reduced the incidence of the tumors in the presence of tumor promotor. In anti-promotion experiments on preventing diethylstilbestrol (DES)-dependent tumor development from mammary primodial cells exposed to radiation, tamoxifen decreased the tumor incidence. From the results, estrogen itself or prolactin induced by estrogen may be a promoter for the tumorigenesis. Bezafibrate and simvastatin, agents inducing hypolipidemia and hypocholesterolemia respectively, cause a decrease in the DES-dependent promotion of radiation-induced tumorigenesis. The simultaneous administration of curcumin and DES significantly reduces the development of mammary tumors in irradiated rats. In this review, the endocrinologic and pharmacologic significance of the anti-initiation and anti-promotion is discussed.

Metabolism of DHEA by cytochromes P450 in rat and human liver microsomal fractions

Administration of dehydroepiandrosterone (DHEA) to rodents produces many unique biological responses, some of which may be due to metabolism of DHEA to more biologically active products. In the current study, DHEA metabolism was studied using human and rat liver microsomal fractions. In both species, DHEA was extensively metabolized to multiple products; formation of these products was potently inhibited in both species by miconazole, demonstrating a principal role for cytochrome P450. In the rat, use of P450 form-selective inhibitors suggested the participation of P4501A and 3A forms in DHEA metabolism. Human liver samples displayed interindividual differences in that one of five subjects metabolized DHEA to a much greater extent than the others. This difference correlated with the level of P4503A activity present in the human liver samples. For one subject, troleandomycin inhibited hepatic microsomal metabolism of DHEA by 78%, compared to 81% inhibition by miconazole, suggesting the importance of P4503A in these reactions. Form-selective inhibitors of P4502D6 and P4502E1 had a modest inhibitory effect, suggesting that these forms may also contribute to metabolism of DHEA in humans. Metabolites identified by LC-MS in both species included 16alpha-hydroxy-DHEA, 7alpha-hydroxy-DHEA, and 7-oxo-DHEA. While 16alpha-hydroxy-DHEA appeared to be the major metabolite produced in rat, the major metabolite produced in humans was a mono-hydroxylated DHEA species, whose position of hydroxylation is unknown.

Radiation-induced tumorigenesis of mammary glands in pituitary transplanted rats ovariectomized before onset of estrous cycle

The role of prolactin in the initiation of mammary tumorigenesis by radiation was evaluated in ovarian hormone-free rats. Rats were bilaterally ovariectomized at 23 days of age, and then, at 2.5 months of age, two pituitaries obtained from mature rats of the same strain were transplanted underneath the kidney capsule as a means of increasing the serum prolactin level to provide stimulation of development of mammary glands. After 2 weeks, the ovariectomized rats with ectopic pituitary glands were exposed to whole body irradiation of 2.6 Gy of gamma-rays from a 60Co source and then treated with diethylstilbestrol as a tumor promoter. For the control, ovariectomized rats without ectopic pituitary glands were exposed and treated in the same way as the experimental group. A significant increase of serum prolactin level was observed at the time of irradiation by the pituitary transplanted rats, and intense immunohistochemical reaction with a specific anti-prolactin antiserum was detected in the ectopic pituitary glands. Also, mammary glands in the pituitary transplanted rats, ovariectomized before puberty, showed lactiferous ducts without alveolar buds at the time of tumor initiation. The pituitary transplanted rats showed a significantly increased incidence of adenocarcinoma and fibroadenoma compared with the control. Many of the mammary tumors induced in the pituitary transplanted rats given radiation were estrogen receptor (ER)(+) progesterone receptor (PgR)(+) and ER(+)PgR(-) tumors, whereas ER(-)PgR(-) tumors were mainly obtained in the control rats. In the experimental group, many of the fibroadenomas had low concentrations of ER and no PgR, while the adenocarcinomas had moderate concentrations of ER and high PgR. These results suggest that hypersecretion of prolactin from the pituitary transplants developed lactiferous ducts and accelerated the tumorigenesis of mammary glands initiated by radiation in the absence of synergism with ovarian hormones.

Localization of nitric oxide synthases and nitric oxide production in the rat mammary gland

We investigated nitric oxide (NO) production and the presence of nitric oxide synthase (NOS) in the mammary gland by use of an organ culture system of rat mammary glands. Mammary glands were excised from the inguinal parts of female Wistar-MS rats primed by implantation with pellets of 17beta-estradiol and progesterone and were diced into approximately 3-mm cubes. Three of these cubes were cultured with 2 ml of 10% FCS/DMEM plus carboxy-PTIO (an NO scavenger, 100 microM) in the presence or absence of LPS (0.5 microgram/ml) for 2 days. The amount of NO produced spontaneously by the cultured mammary glands was relatively minute at the end of the 2-day culture period, and the NO production was significantly enhanced by the presence of LPS. This enhancement of NO production was completely eliminated by addition of hydrocortisone (3 microM), an inhibitor of inducible NOS (iNOS), to the incubation medium. Immunoblot analyses with specific antisera against NOS isoforms such as iNOS, endothelial NOS (eNOS), and brain NOS (bNOS) showed immunoreactive bands of iNOS (122 +/- 2 kD) and eNOS (152 +/- 3 kD) in extracts prepared from the mammary glands in the culture without LPS. The immunoreactive band of iNOS was highly intense after the treatment of mammary glands with LPS, whereas the corresponding eNOS immunoreactive band was faded. The immunohistochemical study of anti-iNOS antiserum on frozen sections of the cultured mammary glands showed that an immunoreactive substance with the antiserum was localized to the basal layer (composed of myoepithelial cells of alveoli and lactiferous ducts) of the mammary epithelia and to the endothelium of blood vessels that penetrated into the interstitium of the mammary glands. Histochemical staining for NADPH-diaphorase activity, which is identical to NOS, showed localization similar to that of iNOS in the mammary glands. Similar observations were noted in the immunohistochemistry of eNOS. In contrast, the immunoreactive signal with the bNOS antiserum was barely detected in the epithelial parts of alveoli and lactiferous ducts of the mammary glands. These observations demonstrate that three isoforms of NOS are present not only in the endothelium of blood vessels but also in the parenchymal cells (the glandular epithelium) of the rat mammary gland, such as epithelial cells and myoepithelial cells, and suggest that NO may have functional roles in the physiology of the mammary glands.

Distribution of casein-like proteins in various organs of rat

Casein-like proteins were detected in various organs of rat by use of a specific antiserum raised against rat milk caseins. The antiserum specifically recognized alpha 1-, alpha 2-, beta-, and gamma-caseins in rat milk by Western blot analysis, whereas no immunoreactive band was observed in sera of rat and fetal bovine and in bovine caseins. Immunohistochemical studies of this antiserum on formalin-fixed mammary glands showed that immunoreactive caseins were localized to the apical portion of the cytoplasm in lactating mammary epithelial cells and in the luminal secretion, which indicates a directional secretion of caseins to the lumen by the mammary epithelial cells. With this antiserum, immunoreactive substances were detected in various organs, including the pancreatic ducts and islets of Langerhans, the secretory ducts of salivary glands, zona fasciculata cells and ganglion cells of adrenal gland, distal tubules and convoluted collecting tubules of kidney, epithelial cells of bronchioles and large pneumocytes of the lung, hair follicles, sebaceous glands, and the prickle cell layer of skin, uterine glands and epithelium of the endometrium, hepatic bile ducts, and brain. In Western blot analysis, major immunoreactive substances in the above organ extracts showed a similarity in molecular weight to alpha 2-casein of rat milk. Skin was the only tissue that expressed both alpha 2- and beta-caseins. There were no other immunoreactive bands with similarity to beta- and gamma-caseins in the other organ extracts, but higher molecular weight immunoreactive bands (> 100 kD) were detected in some organ extracts, such as salivary gland, kidney, liver, lung, and uterus. These findings suggest that the alpha 2-casein-like substance is localized not only in the mammary gland but also in a variety of organs and may play an important role as a functional molecule in those organs.

Natural products and their derivatives as cancer chemopreventive agents

This review summarizes currently available data on the chemopreventive efficacies, proposed mechanisms of action and relationships between activities and structures of natural products like vitamin D, calcium, dehydroepidandrosterone, coenzyme Q10, celery seed oil, parsley leaf oil, sulforaphane, isoflavonoids, lignans, protease inhibitors, tea polyphenols, curcumin, and polysaccharides from Acanthopanax genus.