Modulation of 11 beta-hydroxysteroid dehydrogenase type 2 activity in Ishikawa cells is associated with changes in cellular proliferation

Synthesis of Novel 2-(Isopropylamino)thiazol-4(5H)-one Derivatives and Their Inhibitory Activity of 11β-HSD1 and 11β-HSD2 in Aspect of Carcinogenesis Prevention

Glucocorticoid metabolism at the tissue level is regulated by two isoenzymes 11β-hydroxysteroid dehydrogenase (11β-HSD), which mutually convert biologically active cortisol and inactive cortisone. Recent research is focused on the role of 11β-HSD1 and 11β-HSD2 as autocrine factors of tumor cell proliferation and differentiation. Herein, we report the synthesis of novel 2-(isopropylamino)thiazol-4(5H)-one derivatives and their inhibitory activity for 11β-HSD1 and 11β-HSD2. The derivative containing the spiro system of thiazole and cyclohexane rings shows the highest degree of 11β-HSD1 inhibition (54.53% at 10 µM) and is the most selective inhibitor of this enzyme among the tested compounds. In turn, derivatives containing ethyl and n-propyl group at C-5 of thiazole ring inhibit the activity of 11β-HSD2 to a high degree (47.08 and 54.59% at 10 µM respectively) and are completely selective. Inhibition of the activity of these enzymes may have a significant impact on the process of formation and course of tumors. Therefore, these compounds can be considered as potential pharmaceuticals supporting anti-cancer therapy.

Insulin, CCAAT/enhancer-binding proteins and lactate regulate the human 11β-hydroxysteroid dehydrogenase type 2 gene expression in colon cancer cell lines

11β-Hydroxysteroid dehydrogenases (11beta-HSD) modulate mineralocorticoid receptor transactivation by glucocorticoids and regulate access to the glucocorticoid receptor. The isozyme 11beta-HSD2 is selectively expressed in mineralocorticoid target tissues and its activity is reduced in various disease states with abnormal sodium retention and hypertension, including the apparent mineralocorticoid excess. As 50% of patients with essential hypertension are insulin resistant and hyperinsulinemic, we hypothesized that insulin downregulates the 11beta-HSD2 activity. In the present study we show that insulin reduced the 11beta-HSD2 activity in cancer colon cell lines (HCT116, SW620 and HT-29) at the transcriptional level, in a time and dose dependent manner. The downregulation was reversible and required new protein synthesis. Pathway analysis using mRNA profiling revealed that insulin treatment modified the expression of the transcription factor family C/EBPs (CCAAT/enhancer-binding proteins) but also of glycolysis related enzymes. Western blot and real time PCR confirmed an upregulation of C/EBP beta isoforms (LAP and LIP) with a more pronounced increase in the inhibitory isoform LIP. EMSA and reporter gene assays demonstrated the role of C/EBP beta isoforms in HSD11B2 gene expression regulation. In addition, secretion of lactate, a byproduct of glycolysis, was shown to mediate insulin-dependent HSD11B2 downregulation. In summary, we demonstrate that insulin downregulates HSD11B2 through increased LIP expression and augmented lactate secretion. Such mechanisms are of interest and potential significance for sodium reabsorption in the colon.

11β-hydroxysteroid dehydrogenases: intracellular gate-keepers of tissue glucocorticoid action

Glucocorticoid action on target tissues is determined by the density of "nuclear" receptors and intracellular metabolism by the two isozymes of 11β-hydroxysteroid dehydrogenase (11β-HSD) which catalyze interconversion of active cortisol and corticosterone with inert cortisone and 11-dehydrocorticosterone. 11β-HSD type 1, a predominant reductase in most intact cells, catalyzes the regeneration of active glucocorticoids, thus amplifying cellular action. 11β-HSD1 is widely expressed in liver, adipose tissue, muscle, pancreatic islets, adult brain, inflammatory cells, and gonads. 11β-HSD1 is selectively elevated in adipose tissue in obesity where it contributes to metabolic complications. Similarly, 11β-HSD1 is elevated in the ageing brain where it exacerbates glucocorticoid-associated cognitive decline. Deficiency or selective inhibition of 11β-HSD1 improves multiple metabolic syndrome parameters in rodent models and human clinical trials and similarly improves cognitive function with ageing. The efficacy of inhibitors in human therapy remains unclear. 11β-HSD2 is a high-affinity dehydrogenase that inactivates glucocorticoids. In the distal nephron, 11β-HSD2 ensures that only aldosterone is an agonist at mineralocorticoid receptors (MR). 11β-HSD2 inhibition or genetic deficiency causes apparent mineralocorticoid excess and hypertension due to inappropriate glucocorticoid activation of renal MR. The placenta and fetus also highly express 11β-HSD2 which, by inactivating glucocorticoids, prevents premature maturation of fetal tissues and consequent developmental "programming." The role of 11β-HSD2 as a marker of programming is being explored. The 11β-HSDs thus illuminate the emerging biology of intracrine control, afford important insights into human pathogenesis, and offer new tissue-restricted therapeutic avenues.

11β-Hydroxysteroid Dehydrogenase Type II is a Potential Target for Prevention of Colorectal Tumorigenesis

Colorectal cancer (CRC) is a leading cause of cancer death, yet primary prevention remains the best approach to reducing overall morbidity and mortality. There is a clear molecular link between cyclooxygenase-2 (COX-2)-derived prostaglandin E₂ (PGE₂) production and CRC progression. Although selective COX-2 inhibitors as well as non-steroidal anti-inflammatory drugs (NSAIDs) reduce the number and sizes of colonic adenomas, increased cardiovascular risks of selective COX-2 inhibitors and increased gastrointestinal side-effects of NSAIDs limit their use in chemoprevention of CRC. Glucocorticoids induce apoptosis and are endogenous, potent COX-2 inhibitors. Glucocorticoids have been used for the treatment of hematologic malignancies, but not for solid tumors due to adverse side-effects such as immunosuppression and osteoporosis. In tissues, glucocorticoid actions are down-regulated by t y p e 2 1 1 β-hydroxysteroid dehydrogenase (11βHSD2), and inhibition of 11βHSD2 activity will elevate intracellular active glucocorticoid to levels that effectively suppress COX-2 expression. Both COX-2 and 11βHSD2 increase in Apc^+/min mouse intestinal adenomas and human colonic adenomas and either pharmacologic or genetic 11βHSD2 inhibition leads to decreases in COX-2-mediated PGE₂ production in tumors and prevents adenoma formation, tumor growth, and metastasis. 11βHSD2 inhibition may represent a novel approach for CRC chemoprevention by increasing tumor cell intracellular glucocorticoid activity, which in turn inhibits tumor growth by suppressing the COX-2-derived PGE₂ pathway, as well as other pathways, without potential side-effects relating to chronic application of COX-2 inhibitors, NSAIDs and glucocorticoids.

Inhibitory effect of 18beta-glycyrrhetinic acid on 12-O-tetradecanoyl phorbol-13-acetate-induced cutaneous oxidative stress and tumor promotion in mice

Glycyrrhetinic acid is an aglycone of glycyrrhizic acid, another major active component of licorice roots. Licorice root extract has been used for a long time as a medicine and a natural sweetening additive. In the present study, we found that glycyrrhetinic acid inhibits 12-O-tetradecanoylphorbol-13-acetate (TPA) mediated oxidative stress and tumor promotion in murine skin. Topical application of TPA alone in mouse skin enhances ornithine decarboxylase activity and also increases [3H]-thymidine incorporation in DNA. Topical application of TPA also resulted in the depletion of glutathione, activities of glutathione metabolizing and antioxidant enzymes. Application of glycyrrhetinic acid prior to TPA treatment reduces this enhanced ODC activity, [3H]-thymidine incorporation in DNA and oxidative stress. Glycyrrhetinic acid was also found to inhibit DMBA/TPA-induced skin tumor formation at doses of 1.25 and 2.5 mg by reducing the number of tumors per mouse by 24% (P < 0.05) and 62% (P < 0.05), respectively. These results suggest that glycyrrhetinic acid, an antioxidant, is a potential chemopreventive agent that can inhibit DMBA/TPA-induced cutaneous oxidative stress and tumor promotion.

NAD Dependent 11β-Hydroxysteroid Dehydrogenase Activity in Human Endometrium and Endometrial Tumors

BACKGROUND

The isoforms of 11beta-hydroxysteroid dehydrogenase (11beta-HSD) types 1 and 2, regulated by ovarian steroids, catalyze the interconversion of glucocorticoids and their 11-keto metabolites. The role of these enzymes in malignancies of human endometrium is unknown. We compare NAD dependent 11beta-HSD (type 2) activity levels among normal human endometrium and endometrial carcinomas of differing grades and histologies.

METHODS

NAD dependent 11beta-HSD activity was determined in endometrial tissue obtained from patients undergoing hysterectomy for benign or malignant disease (endometroid, serous and carcinosarcomas). Student's t test was utilized with p < 0.05 considered significant. Data are presented as mean +/- SD.

RESULTS

NAD dependent 11beta-HSD activity was present in all endometrial samples. The activities were 0.61+/- 0.27 in normal (n = 9), 0.43 +/- 0.29 in endometrioid endometrial carcinoma (n = 14), 0.50 +/- 0.26 in uterine serous carcinoma (n = 6) and 0.25 +/- 0.37 in carcinosarcomas (n = 9). NAD dependent 11beta-HSD activity was lower in the carcinosarcoma group as compared to normal endometrial tissue (p = 0.03).

CONCLUSIONS

NAD dependent type 2 11beta-HSD activity was demonstrated in all normal and endometrial tumors. Enzyme activity in endometroid and uterine serious carcinoma tumors was similar to enzyme activity in normal endometrium. In contrast, carcinosarcomas show significantly lower enzyme activity compared to normal tissue.

11Beta-hydroxysteroid dehydrogenases in human endometrium

Key reproductive events, such as menstruation and implantation, are considered to be inflammatory processes and glucocorticoids act as anti-inflammatory agents. The balance of expression of types 1 and 2 11beta-hydroxysteroid dehydrogenases (11betaHSD) controls the availability of cortisol to bind to the glucocorticoid receptor (GR) and mineralocorticoid receptor (MR). Expression profiles of glucocorticoid-metabolising enzymes and their cognate receptors have been characterized in the reproductive tract. We propose that factors that peripherally promote glucocorticoid action are part of an anti-inflammatory response to tissue remodelling in human endometrium. Protein and mRNA expression in endometrium were investigated using immunohistochemistry and quantitative real-time PCR. There was up-regulated expression of 11betaHSD-1 at menstruation and in first trimester decidua. 11BetaHSD-2 and GR were expressed across the cycle. The MR expression pattern across the cycle and in decidua implies progesterone may also play a regulatory role. The precise roles and interactions of these proteins require further investigation.

Adrenal gland involvement in the regulation of renal 11beta-hydroxysteroid dehydrogenase 2

Renal 11beta-hydroxysteroid dehydrogenase 2 (HSD2) catalyzes the conversion of active glucocorticoids to inert 11beta-keto compounds, thereby preventing the illicit binding of these hormones to mineralocorticoid receptors (MRs) and, thus, conferring aldosterone specificity. Absence or inhibition of HSD2 activity, originates a hypertensive syndrome with sodium retention and increased potassium elimination. Recent studies from our laboratory reported an increment of HSD2 activity in intact-stressed rats. To evaluate the adrenal involvement in this increase, we analyzed HSD2 activity and protein abundance in Intact, Sham-operated, and adrenalectomized rats under stress situations (gavage with an overload of 200 mM HCl (10 ml) and simulated gavage) or with corticosterone replacement. HSD2 activity was assessed in renal microsomal preparations obtained from different groups of animals. HSD2 protein abundance was measured by Western-blot. Circulating corticosterone was determined by radioimmunoassay. Sham-operated animals showed an increase in HSD2 activity and abundance compared to Intact and adrenalectomized rats suggesting the involvement of stress-related adrenal factors in HSD2 regulation. In the case of acidotic adrenalectomized animals, there was an increase in renal HSD2 activity when, along with the HCl overload, the rats were injected with corticosterone. This increment occurred without an increase in enzyme abundance. These results suggest the importance of circulating levels of glucocorticoids to respond to a metabolic acidosis, through regulation of HSD2 stimulation. The group subjected to a simulated gavage showed an increase in enzyme activity and protein abundance, thus demonstrating the need for both adrenal and extra-factors in the modulation of renal HSD2. The adrenalectomized animals injected with different doses of corticosterone, produced a progressive increase in enzyme activity and abundance, being significant for the dose of 68 microg corticosterone/100 g body weight. The highest dose (308 microg/100 g body weight) did not show any variation in activity and abundance compared to the control group. This biphasic effect of glucocorticoids could be explained taking into account their permissive and suppressive actions, depending on their blood levels. Knowing that stress induces multifactorial responses, it should not be surprising to observe a differential regulation in renal HSD2, confirming that different stressors act through different factors of both, adrenal and extra-adrenal origin.

11beta-hydroxysteroid dehydrogenases, cell proliferation and malignancy

The enzymes 11beta-hydroxysteroid dehydrogenase type 1 and 2 (11beta-HSD1 and 2) have well-defined roles in the tissue-specific metabolism of glucocorticoids which underpin key endocrine mechanisms such as adipocyte differentiation (11beta-HSD1) and mineralocorticoid action (11beta-HSD2). However, in recent studies we have shown that the effects of 11beta-HSD1 and 2 are not restricted to distinct tissue-specific hormonal functions. Studies of normal fetal and adult tissues, as well as their tumor equivalents, have shown a further dichotomy in 11beta-HSD expression and activity. Specifically, most normal glucocorticoid receptor (GR)-rich tissues such as adipose tissue, bone, and pituitary cells express 11beta-HSD1, whereas their fetal equivalents and tumors express 11beta-HSD2. We have therefore postulated that the ability of 11beta-HSD1 to generate cortisol acts as an autocrine anti-proliferative, pro-differentiation stimulus in normal adult tissues. In contrast, the cortisol-inactivating properties of 11beta-HSD2 lead to pro-proliferative effects, particularly in tumors. This proposal is supported by experiments in vitro which have demonstrated divergent effects of 11beta-HSD1 and 2 on cell proliferation. Current studies are aimed at (1) characterizing the underlying mechanisms for a "switch" in 11beta-HSD isozyme expression in tumors; (2) defining the molecular targets for glucocorticoids as regulators of cell proliferation; (3) evaluating the potential for targeting glucocorticoid metabolism as therapy for some cancers. These and other issues are discussed in the present review.