Neutral endopeptidase inhibitors blunt kidney fibrosis by reducing myofibroblast formation.

Kidney fibrosis is the common pathophysiological mechanism in end-stage renal disease characterized by excessive accumulation of myofibroblast-derived extracellular matrix. Natriuretic peptides have been demonstrated to have cyclic guanosine monophosphate (cGMP)-dependent anti-fibrotic properties likely due to interference with pro-fibrotic tissue growth factor ß (TGF-ß) signaling. However, in vivo, natriuretic peptides are rapidly degraded by neutral endopeptidases (NEP). In a unilateral ureteral obstruction (UUO) mouse model for kidney fibrosis we assessed the anti-fibrotic effects of SOL1, an orally active compound that inhibits NEP and endothelin-converting enzyme (ECE). Mice (n=10 per group) subjected to UUO were treated for 1 week with either solvent, NEP-/ECE-inhibitor SOL1 (two doses), reference NEP-inhibitor candoxatril or the angiotensin II receptor type 1 (AT1)-antagonist losartan. While NEP-inhibitors had no significant effect on blood pressure, they did increase urinary cGMP levels as well as endothelin-1 (ET-1) levels. Immunohistochemical staining revealed a marked decrease in renal collagen (∼55% reduction, P<0.05) and α-smooth muscle actin (α-SMA; ∼40% reduction, P<0.05). Moreover, the number of α-SMA positive cells in the kidneys of SOL1-treated groups inversely correlated with cGMP levels consistent with a NEP-dependent anti-fibrotic effect. To dissect the molecular mechanisms associated with the anti-fibrotic effects of NEP inhibition, we performed a 'deep serial analysis of gene expression (Deep SAGE)' transcriptome and targeted metabolomics analysis of total kidneys of all treatment groups. Pathway analyses linked increased cGMP and ET-1 levels with decreased nuclear receptor signaling (peroxisome proliferator-activated receptor [PPAR] and liver X receptor/retinoid X receptor [LXR/RXR] signaling) and actin cytoskeleton organization. Taken together, although our transcriptome and metabolome data indicate metabolic dysregulation, our data support the therapeutic potential of NEP inhibition in the treatment of kidney fibrosis via cGMP elevation and reduced myofibroblast formation.

Age-dependent changes of the antioxidant system in rat livers are accompanied by altered MAPK activation and a decline in motor signaling.

Aging is characterized by a progressive decrease of cellular functions, because cells gradually lose their capacity to respond to injury. Increased oxidative stress is considered to be one of the major contributors to age-related changes in all organs including the liver. Our study has focused on elucidating whether important antioxidative enzymes, the mTOR pathway, and MAPKs exhibit age-dependent changes in the liver of rats during aging. We found an age-dependent increase of GSH in the cytosol and mitochondria. The aged liver showed an increased SOD enzyme activity, while the CAT enzyme activity decreased. HO-1 and NOS-2 gene expression was lower in adult rats, but up-regulated in aged rats. Western blot analysis revealed that SOD1, SOD2, GPx, GR, γ-GCL, and GSS were age-dependent up-regulated, while CAT remained constant. We also demonstrated that the phosphorylation of Akt, JNK, p38, and TSC2(Ser1254) decreased while ERK1/2 and TSC2(Thr1462) increased age-dependently. Furthermore, our data show that the mTOR pathway seems to be activated in livers of aged rats, and hence stimulating cell proliferation/regeneration, as confirmed by an age-dependent increase of PCNA and p-eIF4E(Ser209) protein expression. Our data may help to explain the fact that liver cells only proliferate in cases of necessity, like injury and damage. In summary, we have demonstrated that, age-dependent changes of the antioxidant system and stress-related signaling pathways occur in the livers of rats, which may help to better understand organ aging.

Assessment of impaired vascular reactivity in a rat model of diabetic nephropathy: effect of nitric oxide synthesis inhibition on intrarenal diffusion and oxygenation measured by magnetic resonance imaging.

Diabetes is associated with impaired vascular reactivity and the development of diabetic nephropathy. In a rat model of streptozotocin-induced diabetic nephropathy, the effects of systemic nitric oxide (NO) synthesis inhibition on intrarenal diffusion and oxygenation were determined by noninvasive magnetic resonance diffusion tensor imaging and blood O2 level-dependent (BOLD) imaging, respectively. Eight weeks after the induction of diabetes, 21 rats [n = 7 rats each in the untreated control group, diabetes mellitus (DM) group, and DM with uninephrectomy (DM UNX) group] were examined by MRI. Diffusion tensor imaging and BOLD sequences were acquired before and after NO synthesis inhibition with N-nitro-L-arginine methyl ester (L-NAME). In the same rats, mean arterial pressure and vascular conductance were determined with and without the influence of L-NAME. In control animals, NO synthesis inhibition was associated with a significant increase of mean arterial pressure of 33.8 ± 4.3 mmHg (P < 0.001) and a decrease of vascular conductance of -17.8 ± 2.0 µl·min(-1)·100 mmHg(-1) (P < 0.001). These changes were attenuated in both DM and DM UNX groups with no significant difference between before and after L-NAME measurements in DM UNX animals. Similarly, L-NAME challenge induced a significant reduction of renal transverse relaxation time (T2*) at MRI in control animals, indicating reduced renal oxygenation after L-NAME injection compared with baseline. DM UNX animals did not show a significant T2* reduction after NO synthesis inhibition in the renal cortex and attenuated T2* reduction in the outer medulla. MRI parameters of tissue diffusion were not affected by L-NAME in all groups. In conclusion, BOLD imaging proved valuable to noninvasively measure renal vascular reactivity upon NO synthesis inhibition in control animals and to detect impaired vascular reactivity in animals with diabetic nephropathy.

Magnetic resonance diffusion tensor imaging for evaluation of histopathological changes in a rat model of diabetic nephropathy.

OBJECTIVES: The aim of this study was to investigate whether magnetic resonance (MR) diffusion tensor imaging (DTI) allows assessment of renal pathologies in a rat model of diabetic nephropathy. MATERIALS AND METHODS: Twenty-one male Sprague-Dawley rats were divided into 3 groups: (1) untreated controls, (2) diabetes (DM), (3) diabetes with uninephrectomy (DM UNX) to accelerate renal impairment. Eight weeks after diabetes induction with streptozotocin, MR imaging was performed in a 1.5-T scanner using an 8-channel wrist coil. Morphological proton density images and echoplanar DTI were obtained (b = 0 and 300 s/mm, 6 diffusion directions). Renal apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were calculated for each of the different anatomical layers of the kidney. Imaging results, laboratory parameters of diabetic state and kidney function, and renal histopathological changes (glomerulosclerosis, tubular dilatation, and renal fibrosis) were compared between groups. Correlations between FA and histopathological changes were evaluated. RESULTS: All diabetic animals developed hyperglycemia and hypoinsulinemia. Uremia, albuminuria, and histopathological changes were most pronounced in DM UNX animals. Fractional anisotropy was significantly reduced in DM UNX animals in the cortex (CO) (0.167; confidence interval [CI], 0.151-0.184; P < 0.001), outer stripe of the outer medulla (OS) (0.254; CI, 0.225-0.283; P = 0.038), and inner medulla (IM) (0.459; CI, 0.395-0.523; P = 0.008) compared with control animals (CO, 0.251; CI, 0.224-0.277; OS, 0.309; CI, 0.267-0.350; IM, 0.559; CI, 0.515-0.603). In DM-without-UNX animals, only cortical FA was significantly lower than in controls (P < 0.001). Between groups, ADC values were not different, except for cortical ADC, which was higher in DM UNX animals than in controls. Significant negative correlations were observed between the FA of different anatomical layers and the extent of glomerulosclerosis (CO, P = 0.003, r = -0.65; and OS, P = 0.022, r = -0.52), tubulointerstitial fibrosis (IM, P = 0.028, r = -0.50), and tubular dilatation (CO, P = 0.015, r = -0.55; and IM, P = 0.006, r = -0.61), respectively. CONCLUSIONS: Magnetic resonance DTI by reduction of FA identified renal pathologies of diabetic nephropathy such as glomerulosclerosis, interstitial fibrosis, and tubular damage. Representing different stages of disease, DM and DM UNX animals could be differentiated. Thus, MR DTI may be valuable for noninvasive detection and monitoring of renal pathology in patients with diabetes.

Novel estrogen-related genes and potential biomarkers of ovarian endometriosis identified by differential expression analysis.

In the search for novel biomarkers of endometriosis, we selected 152 genes from the GeneLogic database based on results of genome-wide expression analysis of ovarian endometriosis, plus 20 genes related to estrogen metabolism and action. We then performed low-density array analysis of these 172 genes on 11 ovarian endometriosis samples and 9 control endometrium samples. Principal component analysis of the gene expression levels showed clear separation between the endometriosis and control groups. We identified 78 genes as differentially expressed. Based on Ingenuity pathway analysis, these differentially expressed genes were arranged into groups according to biological function. These analyses revealed that 32 differentially expressed genes are estrogen related, 23 of which have not been reported previously in connection with endometriosis. Functional annotation showed that 25 and 22 genes are associated with the biological terms "secreted" and "extracellular region", respectively. Differential expression of 4 out of 5 genes related to estrogen metabolism and action (ESR1, ESR2, PGR and BGN) was also confirmed by immunohistochemistry. Our study thus reveals differential expression of several genes that have not previously been associated with endometriosis and that encode potential novel biomarkers and drug targets.

Selectivity and potency of the retroprogesterone dydrogesterone in vitro.

Dydrogesterone is widely used for menstrual disorders, endometriosis, threatened and habitual abortion and postmenopausal hormone replacement therapy. Although progestins have a promiscuous nature, dydrogesterone does not have clinically relevant androgenic, estrogenic, glucocorticoid or mineralocorticoid activities. To date, systematic biochemical characterization of this progestin and its active main metabolite, 20α-dihydrodydrogesterone, has not been performed in comparison to progesterone. The objective of this study was to evaluate the selectivity and potential androgenic/antiandrogenic effects of dydrogesterone and its metabolite in comparison to progesterone and medroxyprogesterone acetate by analyzing their interference with AR signaling in vitro. We characterized dydrogesterone and its metabolite for their binding and transactivation of androgen and other steroid hormone receptors and for their potential inhibitory effects against androgen biosynthetic enzymes, 17ß-hydroxysteroid dehydrogenase types 3 and 5 and 5α-reductase types 1 and 2. We found that dydrogesterone resembled progesterone mainly in its progestogenic effects and less in its androgenic, anti-androgenic, glucocorticoid and antiglucocorticoid effects; whereas, 20α-dihydrodydrogesterone showed reduced progestogenic potency with no androgenic, glucocorticoid and mineralocorticoid effects. Effects on the androgen and glucocorticoid receptor differed depending on the technology used to investigate transactivation. Progesterone, but not dydrogesterone and 20α-dihydrodydrogesterone, exerted anti-androgenic effects at the pre-receptor level by inhibiting 5α-reductase type 2. Dydrogesterone, 20α-dihydrodydrogesterone and progesterone inhibited the biosynthesis of testosterone catalyzed by 17ß-hydroxysteroid dehydrogenase types 3 and 5; however, due to their micromolar K(i) values, these activities appeared to be not of relevance at therapeutic levels. Overall, our data show that the anti-androgenic potential of dydrogesterone and 20α-dihydrodydrogesterone is less pronounced compared to progesterone.

Species used for drug testing reveal different inhibition susceptibility for 17beta-hydroxysteroid dehydrogenase type 1.

Steroid-related cancers can be treated by inhibitors of steroid metabolism. In searching for new inhibitors of human 17beta-hydroxysteroid dehydrogenase type 1 (17beta-HSD 1) for the treatment of breast cancer or endometriosis, novel substances based on 15-substituted estrone were validated. We checked the specificity for different 17beta-HSD types and species. Compounds were tested for specificity in vitro not only towards recombinant human 17beta-HSD types 1, 2, 4, 5 and 7 but also against 17beta-HSD 1 of several other species including marmoset, pig, mouse, and rat. The latter are used in the processes of pharmacophore screening. We present the quantification of inhibitor preferences between human and animal models. Profound differences in the susceptibility to inhibition of steroid conversion among all 17beta-HSDs analyzed were observed. Especially, the rodent 17beta-HSDs 1 were significantly less sensitive to inhibition compared to the human ortholog, while the most similar inhibition pattern to the human 17beta-HSD 1 was obtained with the marmoset enzyme. Molecular docking experiments predicted estrone as the most potent inhibitor. The best performing compound in enzymatic assays was also highly ranked by docking scoring for the human enzyme. However, species-specific prediction of inhibitor performance by molecular docking was not possible. We show that experiments with good candidate compounds would out-select them in the rodent model during preclinical optimization steps. Potentially active human-relevant drugs, therefore, would no longer be further developed. Activity and efficacy screens in heterologous species systems must be evaluated with caution.

Progestins inhibit expression of MMPs and of angiogenic factors in human ectopic endometrial lesions in a mouse model.

Progestins are successfully used in the treatment of endometriosis; however, the exact mechanisms of their action are still unsolved. We here focused on the effect of different progestins on parameters of extracellular matrix degradation and angiogenesis involved in the establishment and maintenance of ectopic endometrial lesions. Human endometrium was intraperitoneally transplanted into nude mice. After 7 and 28 days of treatment with progesterone, dydrogesterone, or its metabolite dihydrodydrogesterone, respectively, ectopic lesions were evaluated for proliferation and apoptosis. Expression of estrogen receptor alpha, progesterone receptor-AB, the angiogenetic factors, cysteine-rich angiogenic inducer (CYR61), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGFA) and the matrix metalloproteinase (MMP)-2, -3, -7 and -9 was investigated. Functional impact on angiogenesis was evaluated by density of microvessels and of vessels stabilized by pericytes within the ectopic lesions. Although dydrogesterone significantly reduced proliferation of endometrial stromal cells after 28 days, suppression of apoptosis was independent from progestins. Expression of MMP-2 was significantly reduced by all progestins and MMP-3 by dydrogesterone. In the grafted endometrial tissue, transcription of bFGF was suppressed by progesterone and dihydrodydrogesterone, and VEGFA and CYR61 by dihydrodydrogesterone and dydrogesterone. In parallel, microvessel density was slightly suppressed by progestins, whereas number of stabilized vessels increased. Thus, progestins regulate factors important for the establishment and maintenance of ectopic endometrial lesions.

Relaxin supports implantation and early pregnancy in the marmoset monkey.

To test the hypothesis that relaxin is an important factor supporting implantation, two approaches have been carried out using a human-relevant animal model, the marmoset monkey. First, uterine mRNA transcription and protein expression during the implantation phase in the conceptive and nonconceptive cycles were examined. Second, functional parameters were analyzed to assess the in vivo effects of exogenous applied relaxin throughout implantation. Relaxin and its receptor, RXFP1, were highly upregulated shortly before and during the physical process of implantation, indicating that relaxin is an important factor for remodeling and immunotolerance. The action of relaxin on the uterus was accompanied by an increase of estrogen-associated factors and macrophage infiltration, suggesting redundant systems necessary for successful implantation. The data from relaxin-treated animals supported those obtained from naive tissues in terms of increases in angiogenesis as well as earlier and faster growth of the uterus and placenta in the relaxin-treated marmoset monkey group, resulting in parturition 7-10 days earlier than the control group, but not pathological. In general, relaxin is very effective in preparing the endometrium for implantation. These findings should encourage further clinical research regarding introducing relaxin for pathological pregnancies, such as early pregnancy failure or insufficient placenta.

In vivo mouse model for analysis of hydroxysteroid (17beta) dehydrogenase 1 inhibitors.

Hydroxysteroid (17beta) dehydrogenase 1 (HSD17B1) catalyzes the reaction between the low active 17-ketosteroids and the highly active 17beta-hydroxysteroids. In the present study, we have generated transgenic (TG) mice expressing human (h) HSD17B1 under mouse mammary tumor virus (MMTV) promoter (MMTV-hHSD17B1TG mice). The MMTV-hHSD17B1TG mice were used to characterize HSD17B1 enzyme activity and properties of HSD17B1 inhibitor in vivo. Expression of the transgene was detected by enzyme activity and RT-PCR analysis. Increased HSD17B1 activity in the TG mice was detected in vivo by applying estrone as a substrate via an intravenous injection. The developed enzyme activity measurement was then applied to analyze the efficacy of HSD17B1 inhibitor in vivo. The results indicated that the MMTV-hHSD17B1TG mouse model is a valuable novel tool to test human HSD17B1 inhibition by various compounds in vivo. With the potent hHSD17B1 inhibitor compound tested, at highest an 85% and 33% inhibition of the enzyme activity in males and in females, respectively, was observed.

Estrone C15 derivatives--a new class of 17beta-hydroxysteroid dehydrogenase type 1 inhibitors.

Lowering local estradiol concentration by inhibition of the estradiol-synthesizing enzyme 17beta-hydroxysteroid dehydrogenase type 1 (17beta-HSD1) has been proposed as a promising new therapeutic option to treat estrogen-dependent diseases like endometriosis and breast cancer. Based on a molecular modelling approach we designed and synthesized novel C15-substituted estrone derivatives. Subsequent biological evaluation revealed that potent inhibitors of human 17beta-HSD1 can be identified in this compound class. The best, compound 21, inhibited recombinant human 17beta-HSD1 with an IC50 of 10nM and had no effect on the activity of recombinant human 17beta-hydroxysteroid dehydrogenase type 2 (17beta-HSD2), the enzyme catalyzing estradiol inactivation. These properties were retained in a cell-based enzyme activity assays. In spite of the estrogen backbone compound 21 did not show estrogen receptor mediated effects in vitro or in vivo. In conclusion, estrone C15 derivative compound 21 can be regarded as a promising lead compound for further development as a 17beta-HSD1 inhibitor.

Disturbed estrogen and progesterone action in ovarian endometriosis.

Endometriosis is a very common disease in pre-menopausal women, where defective metabolism of steroid hormones plays an important role in its development and promotion. In the present study, we have examined the expression of 11 estrogen and progesterone metabolizing enzymes and their corresponding receptors in samples of ovarian endometriomas and control endometrium. Expression analysis revealed significant up-regulation of enzymes involved in estradiol formation (aromatase, sulfatase and all reductive 17beta-hydroxysteroid dehydrogenases) and in progesterone inactivation (AKR1C1 and AKR1C3). Among the estrogen and progesterone receptors, ERalpha was down-regulated, ERbeta was up-regulated, and there was no significant difference in expression of progesterone receptors A and B (PRAB). Our data indicate that several enzymes of estrogen and progesterone metabolism are aberrantly expressed in endometriosis, which can lead to increased local levels of mitogenic estradiol and decreased levels of protective progesterone. Changes in estrogen receptor expression suggest that estradiol may also act via non-estrogen receptor-mediated pathways, while expression of progesterone receptors still needs further investigation.

Expression analysis of the genes involved in estradiol and progesterone action in human ovarian endometriosis.

Endometriosis is defined as the presence of endometrial glands and stroma within extrauterine sites, and it is well known that endometriosis is an estrogen-dependent disease. The defective formation and metabolism of steroid hormones is responsible for the promotion and development of endometriosis. In the present study we examined the mRNA levels of six enzymes that are involved in the metabolism of estrogen and progesterone--aromatase, 17beta-hydroxysteroid dehydrogenase (17beta-HSD) types 1, 2 and 7, sulfatase and sulfotransferase--and of the steroid receptors--estrogen receptors alpha and beta (ERalpha, ERbeta) and progesterone receptors A and B (PRAB)--implicated in human ovarian endometriosis. We analyzed 16 samples of ovarian endometriosis and 9 of normal endometrium. The real-time polymerase chain reaction analyses revealed that six of the nine genes investigated are differentially regulated. Aromatase, 17beta-HSD types 1 and 7, sulfatase and ERbeta were statistically significantly upregulated, while ERalpha was significantly downregulated, in the endometriosis group compared with the control group. There were no significant differences in 17beta-HSD type 2, sulfotransferase and PRAB gene expression. Our results indicate that, in addition to the previously reported upregulation of aromatase, upregulation of 17beta-HSD types 1 and 7 and sulfatase can also increase the local estradiol concentration. This could thus be responsible for the estrogen-dependent growth of endometriotic tissue. Surprisingly ERalpha was downregulated.

Expression and regulation of estrogen-converting enzymes in ectopic human endometrial tissue.

OBJECTIVE: To investigate the regulation of estrogen-converting enzymes in human ectopic endometrial tissue. DESIGN: Animal study. SETTING: Academic medical center. ANIMAL(S): Sixty female nude mice with implanted human endometrial tissue. PATIENT(S): Twenty-two premenopausal women undergoing endometrial biopsy or hysterectomy. INTERVENTION(S): Human endometrial tissue was implanted into the peritoneal cavity of nude mice, and the effect of therapeutic drugs on transcription of steroid receptors and estrogen-converting enzymes was analyzed. MAIN OUTCOME MEASURE(S): Transcript levels of steroid hormone receptors, 17beta-hydroxysteroid dehydrogenase type 1 and 2, aromatase, and steroid sulfatase as well as proliferation rate were analyzed in the human ectopic endometrial tissue. RESULT(S): Steroid receptors and estrogen-converting enzymes were expressed in the ectopic human endometrial fragments. Application of medroxyprogesterone acetate, dydrogesterone, danazol, and the aromatase inhibitor finrozole significantly inhibited aromatase transcription. In addition, danazol caused a significant decrease in transcription of steroid sulfatase, and finrozole, of 17beta-hydroxysteroid dehydrogenase type 1 in parallel to a decrease in proliferation rate in the ectopic human endometrial tissue. CONCLUSION(S): Pharmacological regulation of transcription of estrogen-converting enzymes in human endometrium cultured in nude mice may help to develop new therapeutic concepts based on local regulation of estrogen metabolism in endometriosis.

Gender and gonadal status differences in zona reticularis expression in marmoset monkey adrenals: Cytochrome b5 localization with respect to cytochrome P450 17,20-lyase activity.

Neonatal marmosets express an adrenal fetal zone comparable to humans. While adult males fail to express a functional ZR, with barely detectable blood DHEA levels, females produce higher levels of DHEA than males in adulthood. We investigated the presence of a putative functional ZR in adult female marmosets. In contrast to males, immunohistochemical analysis showed the ZR marker cytochrome b5 was elevated in the innermost zone in cycling females (compared to testis-intact males), further elevated in the adrenals from anovulatory females, and substantially elevated and continuous in ovariectomized females. As a functional test in vivo, following overnight dexamethasone treatment, cycling and anovulatory females showed higher levels of DHEA relative to males, but DHEA failed to increase in response to ACTH. In direct contrast, while ovariectomized females exhibited lower initial DHEA levels, clear increases were detectable after ACTH administration (p<0.05), suggesting an adrenal origin. The apparent differences in cytochrome b5 expression between groups were also further verified by Western blotting of adrenal microsomes, and compared to 17,20-lyase activity; the two parameters were positively correlated (p<0.01) across multiple treatment groups. We conclude that the cycling female marmoset expresses a rudimentary ZR with at least a capacity for DHEA production that becomes significantly ACTH-responsive after anovulation. Expression of cytochrome b5 in this region may be directly or indirectly controlled by gonadal function, and is, at least in part, a critical determinant in the development of an adrenal ZR that is more defined and significantly ACTH-responsive.

Human hydroxysteroid (17-beta) dehydrogenase 1 expression enhances estrogen sensitivity of MCF-7 breast cancer cell xenografts.

Hydroxysteroid (17-beta) dehydrogenase 1 (HSD17B1) catalyzes the conversion between estrone (E1) and estradiol (E2). The reaction is reversible in vitro, but the data in cultured cells suggest that E2 production is the predominant reaction in physiological conditions. However, the hypothesis has not been verified in vivo. In the present study, estrogen-dependent MCF-7 human breast cancer cells were stably transfected with an expression plasmid for human HSD17B1. The enzyme efficiently converted E1 to E2 and enhanced the estrogen-dependent growth of cultured MCF-7 cells in the presence of hormonally less active E1. The HSD17B1-expressing cells also formed estrogen-dependent tumors in immunodeficient nude mice. After treating the mice with an appropriate dose of the substrate (E1, 0.1 micromol/kg x d), a marked difference in tumor growth was observed between nontransfected and HSD17B1-transfected MCF-7 cells, mean tumor weights at the end of E1 treatment being 23.2 and 130.4 mg, respectively. Furthermore, estrogen-dependent growth of the HSD17B1-expressing xenografts in the presence of E1 was markedly inhibited by administering 5 micromol/kg x d of a specific HSD17B1 inhibitor. After a 4-wk treatment, the tumor size was reduced by 59.8% as compared with the nontreated tumors, whereas the uterine growth of the mice was not affected by the HSD17B1 inhibitor used. This was in line with the induction of apoptosis of the tumors. The results evidently show that estrogenic response for E1 is enhanced by the local action of HSD17B1 in vivo, and thus, the enzyme is a potential target for pharmacological inhibition of estrogen action.

New inhibitors of 17beta-hydroxysteroid dehydrogenase type 1.

The estradiol-synthesizing enzyme 17beta-hydroxysteroid dehydrogenase type 1 (17betaHSD1) is mainly responsible for the conversion of estrone (E1) to the potent estrogen estradiol (E2). It is a key player to control tissue levels of E2 and is therefore an attractive target in estradiol-dependent diseases like breast cancer or endometriosis. We selected a unique non-steroidal pyrimidinone core to start a lead optimization program. We optimized this core by modulation of R1-R6. Its binding mode at the substrate-binding site of 17betaHSD1 is complex and difficult to predict. Nevertheless, some basic structure-activity relationships could be identified. In vitro, the most active pyrimidinone derivative showed effective inhibition of recombinant human 17betaHSD1 at nanomolar concentrations. In intact cells overexpressing the human enzyme, IC50 values in the lower micromolar range were determined. Furthermore, the pyrimidinone proved its use in vivo by significantly reducing 17betaHSD1-dependent tumor growth in a new nude mouse model.

The common marmoset monkey as a model for implantation and early pregnancy research.

This chapter describes methods used to investigate implantation in the common marmoset monkey, Callithrix jacchus. A reverse-transcriptase polymerase chain reaction-strategy with which to detect transcripts for steroid receptors and enzymes involved in estradiol biosynthesis is described, and an immunohistochemistry approach for detecting proteins within the implantation site is presented.

Closing the gap: identification of human 3-ketosteroid reductase, the last unknown enzyme of mammalian cholesterol biosynthesis.

The protein encoded by the HSD17B7 gene was originally described as a prolactin receptor-associated protein and as 17beta-hydroxysteroid dehydrogenase (HSD) type 7. Its ability to synthesize 17beta-estradiol in vitro has been reported previously. However, we demonstrate that HSD17B7 is the ortholog of the yeast 3-ketosteroid reductase Erg27p and converts zymosterone to zymosterol in vitro, using reduced nicotinamide adenine dinucleotide phosphate as cofactor. Expression of human and murine HSD17B7 in an Erg27p-deficient yeast strain complements the 3-ketosteroid reductase deficiency of the cells and restores growth on sterol-deficient medium. A fusion of HSD17B7 with green fluorescent protein is located in the endoplasmic reticulum, the site of postsqualene cholesterogenesis. Further critical evidence for a role of HSD17B7 in cholesterol metabolism is provided by the observation that its murine ortholog is a member of the same highly distinct embryonic synexpression group as hydroxymethyl-glutaryl-coenzyme A reductase, the rate-limiting enzyme of sterol biogenesis, and is specifically expressed in tissues that are involved in the pathogenesis of congenital cholesterol-deficiency disorders. We conclude that HSD17B7 participates in postsqualene cholesterol biosynthesis, thus completing the molecular cloning of all genes of this central metabolic pathway. In its function as the 3-ketosteroid reductase of cholesterol biosynthesis, HSD17B7 is a novel candidate for inborn errors of cholesterol metabolism.

Immortalisation of ovarian granulosa and Theca cells of the marmoset monkey Calllithrix jacchus.

In view of the increasing need for laboratory primates in biomedical research it is desirable to develop appropriate primate-specific cell culture models that could prevent or significantly reduce the increasing use of primary cultures and experiments with living animals. Follicular granulosa and theca cells are essential for the control of hormone-dependent processes such as the ovarian cycle and pregnancy, but also for the occurrence of hormone-dependent diseases. For this reason it is of great interest to know more about control mechanisms existing in these follicular cell types and the effect of pharmacological or toxicological agents on them. An immortalisation protocol for the two ovarian cell types of the marmoset monkey (Callithrix jacchus) has been developed. All cell lines established so far were examined with regard to the maintenance of known, tissue-specific features (e.g. hormone responsiveness and enzyme expression). The results obtained indicate that it is worth while cloning and characterising the cell lines in more detail so that they could be used after an adequate validation as a defined test system both for basic research as well as for pharmacological or toxicological screening.