Progestins as inhibitors of the human 20-ketosteroid reductases, AKR1C1 and AKR1C3

Development of new steroid-based hydrazide and (thio)semicarbazone compounds with anticancer properties

Most breast and prostate cancers are caused by abnormal production or action of steroidal hormones. Hormonal drugs based on steroid scaffolds represent a significant class of chemotherapeutics that are routinely used in chemotherapy. In this study, the synthesis of new 17a-homo lactone and 17α-(pyridine-2-ylmethyl) androstane derivatives with hydrazide and semicarbazone motifs is presented. All compounds were screened for their effect on cell viability against a panel of five cancer cell lines and one healthy cell line. Two compounds showed significant cytotoxicity against cancer cells, with low toxicity against healthy cells. The relative binding affinities of compounds for the ligand-binding domains of estrogen receptor α, estrogen receptor β, androgen receptor and glucocorticoid receptor were tested using a fluorescence screen in yeast. Potential for inhibition of aldo-keto reductase 1C3 and 1C4 activity was measured in vitro. Experimental results are analyzed in the context of molecular docking simulations. Our results could help guide design of steroid compounds with improved anticancer properties against androgen- and estrogen-dependent cancers.

Metabolism of progestogens used for contraception and menopausal hormone therapy

A variety of progestogens are widely used by women for contraception and menopausal hormone therapy. The progestogens undergo extensive metabolism by oral and parenteral routes of administration to form many metabolites. Although a small number of metabolites have been shown to be biologically active, most have not been tested for biologic activity. The present review shows that we know most about progesterone metabolism, followed by the metabolism of levonorgestrel and norethindrone. Very few studies have been carried out on metabolism of most of the progestogens. The clinical significance of this deficiency is that those progestogen metabolites that bind to the progesterone receptors may also bind to other steroid receptors and be responsible for some of the well-documented side effects of administered progestogens. We also discuss how obesity and genetic polymorphisms alter progestogen metabolism, and how development of oral progestogen formulations that are targeted to the colon, where the concentration of steroid-metabolizing enzymes is much lower than in the proximal gut, may have a beneficial effect on progestogen metabolism.

Research progress of dydrogesterone in the treatment of endometriosis

Endometriosis is a common gynecological disease among women of reproductive age. It is a chronic estrogen and progestin related inflammatory disease. At present, the main treatments for endometriosis are drug therapy and surgery. In drug therapy, progesterone is listed as the first-line recommendation in multinational guidelines. Dydrogesterone, as an oral reversal progesterone, can slow down the metabolism of progesterone, inhibit angiogenesis and extracellular matrix degradation to inhibit the proliferation of the ectopic endometrium, induce the atrophy of the ectopic endometrium through the pro-apoptotic pathway, and treat endometriosis through multiple mechanisms of regulating inflammatory factors to reduce inflammation. Clinically, dydrogesterone treatment of endometriosis can relieve patients' symptoms, promote fertility, be used in combination, and is safe. This article will review the mechanism and clinical application of dydrogesterone in the treatment of endometriosis.

Steroid metabolites as overlooked emerging contaminants: Insights from multimedia partitioning and source-sink simulation in an estuarine environment

Steroids have been attracting global attention given potential carcinogenic and endocrine-disrupting effects, yet the environmental status of steroids, especially their metabolites, in estuarine environment remain largely unexplored. This study investigated 31 steroids and metabolites in suspended particulate matter (SPM), water phase and sediments of the Pearl River Estuary (PRE) during the dry and wet seasons to elucidate their spatiotemporal patterning, partitioning behavior, and environmental fate. The results showed that natural steroids predominated in SPM and sediments while the metabolites predominated in water. The spatial distribution of steroids and metabolites varied seasonally, with hydrophobicity and environmental factors influencing phase partitioning in the estuary. Furthermore, a natural steroid, progesterone (P) could serve as a trustworthy chemical indicator to estimate the concentrations of steroids and metabolites in the PRE. Importantly, the mass budget of P was estimated using an improved multi-box mass balance model, revealing that outflow to the South China Sea was the primary sink of P in water (∼87%) and degradation was the primary sink of P in sediments (∼68%) of the PRE. Overall, this study offers insightful information about the distribution and environmental fate of steroids and metabolites in estuarine environment, with implications for future management strategies.

The serum steroid signature of PCOS hints at the involvement of novel pathways for excess androgen biosynthesis

CONTEXT

Polycystic ovary syndrome (PCOS) is defined by androgen excess and ovarian dysfunction in the absence of a specific physiological diagnosis. The best clinical marker of androgen excess is hirsutism, while the best biochemical parameter is still a matter of debate. Current consensus guidelines recommend, among other hormones, serum free testosterone as an important serum parameter to measure androgen excess. Recently, however, novel active androgens and androgen metabolic pathways have been discovered.

OBJECTIVE

To assess the contribution of novel androgens and related steroid biosynthetic pathways to the serum steroid pool in PCOS women in comparison to healthy controls.

DESIGN

This is a case control study, wherein PCOS was diagnosed according to the AE-PCOS 2009 criteria. Serum steroid profiling was performed by liquid chromatography high-resolution mass spectrometry.

SETTING

Yeditepe University and associated clinics in Istanbul, Turkey, together with Bern University Hospital Inselspital, Bern, Switzerland.

PARTICIPANTS

42 PCOS women and 42 matched, healthy control women.

MAIN OUTCOME MEASURES

Assessment of 34 steroids compartmentalized in four androgen related pathways: the classic androgen pathway, the backdoor pathway, the C11-oxy backdoor pathway, and the C11-oxy (11β-hydroxyandrostenedione) pathway.

RESULTS

Metabolites of all four pathways were identified in healthy and PCOS women. Highest concentrations were found for progesterone in controls and androstenedione in PCOS. Lowest levels were found for 11-ketotestosterone in controls compared to PCOS, and for 20α-hydroxyprogesterone in PCOS compared to controls. PCOS also had higher serum testosterone levels compared to the controls. PCOS women had overall higher levels of steroid metabolites of all four androgen pathways compared to healthy controls.

CONCLUSIONS

Novel alternative pathways contribute to the androgen production in healthy and PCOS women. Hyperandrogenism in PCOS is characterized by an overall increase of serum androgens in the classic, backdoor and C11-oxy pathways. While monogenetic disorders of steroid biosynthesis can be recognized by a specific pattern in the steroid profile, no diagnostic pattern or classifier was found in the serum for PCOS.

Progesterone signaling in the regulation of luteal steroidogenesis

The corpus luteum is the major source of progesterone, the essential hormone for female reproductive function. While progesterone activity has been the subject of extensive research for decades, characterization of non-canonical progesterone receptor/signaling pathways provided a new perspective for understanding the complex signal transduction mechanisms exploited by the progesterone hormone. Deciphering these mechanisms has significant implications in the management of luteal phase disorders and early pregnancy complications. The purpose of this review is to highlight the complex mechanisms through which progesterone-induced signaling mediates luteal granulosa cell activity in the corpus luteum. Here, we review the literature and discuss the up-to-date evidence on how paracrine and autocrine effects of progesterone regulate luteal steroidogenic activity. We also review the limitations of the published data and highlight future research priorities.

Differential Activation of NRF2 Signaling Pathway in Renal-Cell Carcinoma Caki Cell Lines

Renal-cell carcinoma (RCC) is a heterogeneous disease consisting of several subtypes based on specific genomic profiles and histological and clinical characteristics. The subtype with the highest prevalence is clear-cell RCC (ccRCC), next is papillary RCC (pRCC), and then chromophobe RCC (chRCC). The ccRCC cell lines are further subdivided into prognostic expression-based subtypes ccA or ccB. This heterogeneity necessitates the development, availability, and utilization of cell line models with the correct disease phenotypic characteristics for RCC research. In this study, we focused on characterizing proteomic differences between the Caki-1 and Caki-2 cell lines that are commonly used in ccRCC research. Both cells are primarily defined as human ccRCC cell lines. Caki-1 cell lines are metastatic, harboring wild-type VHL, whereas Caki-2 are considered as the primary ccRCC cell lines expressing wild-type von Hippel–Lindau protein (pVHL). Here, we performed a comprehensive comparative proteomic analysis of Caki-1 and Caki-2 cells using tandem mass-tag reagents together with liquid chromatography mass spectrometry (LC/MS) for the identification and quantitation of proteins in the two cell lines. Differential regulation of a subset of the proteins identified was validated using orthogonal methods including western blot, q-PCR, and immunofluorescence assays. Integrative bioinformatic analysis identifies the activation/inhibition of specific molecular pathways, upstream regulators, and causal networks that are uniquely regulated and associated with the two cell lines and RCC subtypes, and potentially the disease stage. Altogether, we have identified multiple molecular pathways, including NRF2 signaling, which is the most significantly activated pathway in Caki-2 versus Caki-1 cells. Some of the differentially regulated molecules and signaling pathways could serve as potential diagnostic and prognostic biomarkers and therapeutic targets amongst ccRCC subtypes.

Brusatol sensitizes endometrial hyperplasia and cancer to progestin by suppressing NRF2-TET1-AKR1C1-mediated progestin metabolism

Progestin resistance is the main obstacle for the conservative therapy to maintain fertility in women with endometrial cancer. Brusatol was identified as an inhibitor of the NRF2 pathway; however, its impact on progestin resistance and the underlying mechanism remains unclear. Here, we found that brusatol sensitized endometrial cancer to progestin by suppressing NRF2-TET1-AKR1C1-mediated progestin metabolism. Brusatol transcriptionally suppressed AKR1C1 via modifying the hydroxymethylation status in its promoter region through TET1 inhibition. Suppression of AKR1C1 by brusatol resulted in decreased progesterone catabolism and maintained potent progesterone to inhibit endometrial cancer growth. This inhibition pattern has also been found in the established xenograft mouse and organoid models. Aberrant overexpression of AKR1C1 was found in paired endometrial hyperplasia and cancer samples from the same individuals with progestin resistance, whereas attenuated or loss of AKR1C1 was observed in post-treatment samples with well progestin response as compared with paired pre-treatment tissues. Our findings suggest that AKR1C1 expression pattern may serve as an important biomarker of progestin resistance in endometrial cancer.

Overview of human 20 alpha-hydroxysteroid dehydrogenase (AKR1C1): Functions, regulation, and structural insights of inhibitors

Human aldo-keto reductase family 1C1 (AKR1C1) is an important enzyme involved in human hormone metabolism, which is mainly responsible for the metabolism of progesterone in the human body. AKR1C1 is highly expressed and has an important relationship with the occurrence and development of various diseases, especially some cancers related to hormone metabolism. Nowadays, many inhibitors against AKR1C1 have been discovered, including some synthetic compounds and natural products, which have certain inhibitory activity against AKR1C1 at the target level. Here we briefly reviewed the physiological and pathological functions of AKR1C1 and the relationship with the disease, and then summarized the development of AKR1C1 inhibitors, elucidated the interaction between inhibitors and AKR1C1 through molecular docking results and existing co-crystal structures. Finally, we discussed the design ideals of selective AKR1C1 inhibitors from the perspective of AKR1C1 structure, discussed the prospects of AKR1C1 in the treatment of human diseases in terms of biomarkers, pre-receptor regulation and single nucleotide polymorphisms, aiming to provide new ideas for drug research targeting AKR1C1.

Aldo-keto reductase family 1 member C1 regulates the osteogenic differentiation of human ASCs by targeting the progesterone receptor

BACKGROUND

As a promising way to repair bone defect, bone tissue engineering has attracted a lot of attentions from researchers in recent years. Searching for new molecular target to modify the seed cells and enhance their osteogenesis capacity is one of the hot topics in this field. As a member of aldo-keto reductase family, aldo-keto reductase family 1 member C1 (AKR1C1) is reported to associate with various tumors. However, whether AKR1C1 takes part in regulating differentiation of adipose-derived mesenchymal stromal/stem cells (ASCs) and its relationship with progesterone receptor (PGR) remain unclear.

METHODS

Lost-and-gain-of-function experiments were performed using knockdown and overexpression of AKR1C1 to identify its role in regulating osteogenic and adipogenic differentiation of hASCs in vitro. Heterotypic bone and adipose tissue formation assay in nude mice were used to conduct the in vivo experiment. Plasmid and siRNA of PGR, as well as western blot, were used to clarify the mechanism AKR1C1 regulating osteogenesis.

RESULTS

Our results demonstrated that AKR1C1 acted as a negative regulator of osteogenesis and a positive regulator of adipogenesis of hASCs via its enzyme activity both in vitro and in vivo. Mechanistically, PGR mediated the regulation of AKR1C1 on osteogenesis.

CONCLUSIONS

Collectively, our study suggested that AKR1C1 could serve as a regulator of osteogenic differentiation via targeting PGR and be used as a new molecular target for ASCs modification in bone tissue engineering.

Occurrence and mass balance of sixty-two progestins in a municipal sewage treatment plant

Progestins (PGs) are a group of steroid hormones known to have endocrine-disrupting effects. These compounds can enter the aquatic environment via the discharge of treated or untreated wastewater and the disposal of sludge from sewage treatment plants (STPs); thus, their removal in STPs are of great importance. The present study simultaneously investigated the occurrences and fates of 62 PGs in a municipal STP in Beijing, China. Progesterone (P) and its metabolites were found to be the predominant compounds, with total dissolved concentrations of 1866 ng/L in the influent. About 11 P metabolites were newly detected, accounting for 25-55% and 75-91% of the total concentrations in wastewater and sludge, respectively. For the other three groups of PGs derived from different parent compounds, P derivatives were first detected in the STP with the highest concentration in the wastewater and sludge, followed by 19-nortestosterone (NT) derivatives and 17α-hydroxyprogesterone (17α-OHP) derivatives. The removal efficiencies in the dissolved phase of wastewater were relatively high for P and its metabolites (95-99%) and P derivatives (91-99%). And the relative persistence of NT (68-99%) and 17α-OHP derivatives (79-99%) was observed during the wastewater treatment processes. Mass balance analysis showed that the lost mass proportions were as high as 41-99%, the mass fractions in sludge were in the range of 0-55%, and 0.24-25% of the initial mass loadings was present in the effluent. These results indicated that biodegradation was the major removal mechanism of PGs in the STP.

Aldo-keto reductase 1C3-Assessment as a new target for the treatment of endometriosis

Endometriosis is a common gynecological disorder, which is treated surgically and/ or pharmacologically with an unmet clinical need for new therapeutics. A completed phase I trial and a recent phase II trial that investigated the steroidal aldo-keto reductase 1C3 (AKR1C3) inhibitor BAY1128688 in endometriosis patients prompted this critical assessment on the role of AKR1C3 in endometriosis. This review includes an introduction to endometriosis with emphasis on the roles of prostaglandins and progesterone in its pathophysiology. This is followed by an overview of the major enzymatic activities and physiological functions of AKR1C3 and of the data published to date on the expression of AKR1C3 in endometriosis at the mRNA and protein levels. The review concludes with the rationale for using AKR1C3 inhibitors, a discussion of the effects of AKR1C3 inhibition on the pathophysiology of endometriosis and a brief overview of other drugs under clinical investigation for this indication.

Oral dydrogesterone for luteal phase support in fresh in vitro fertilization cycles: a new standard?

Oral dydrogesterone has been used for luteal phase support on an empirical basis since the early days of in vitro fertilization (IVF) treatment. Systematic comparisons of oral dydrogesterone with vaginal progesterone, so far considered to be the standard of care, started to appear in the middle 2000s. Recently, a large, randomized, double-blind, double-dummy phase III trial on the use of daily 30 mg oral dydrogesterone versus daily 600 mg micronized vaginal progesterone for LPS in IVF was published. This company-sponsored trial confirmed the efficacy findings from previous independent researchers and firmly established the noninferiority of daily 30 mg oral dydrogesterone for luteal phase support. Despite oral administration and first pass through the liver, dydrogesterone was as well tolerated as vaginal progesterone in safety analyses. Moreover, no new fetal safety concerns have arisen from that trial. Given the widespread preference of women for an oral compound, dydrogesterone may well become the new standard for luteal phase support in fresh embryo transfer IVF cycles.

Aldo-keto reductase activity after diethylhexyl phthalate exposure in eutopic and ectopic endometrial cells

OBJECTIVE

Endometriosis is a multifactorial gynaecological disease in reproductive-age women. Endometriotic tissue is characterized by high prostaglandin levels and progesterone resistance. Human aldo-keto reductases (AKRs) convert progesterone to a less potent metabolite and cause progesterone resistance. Therefore, in this study, we evaluated whether diethylhexyl phthalate (DEHP) alters AKR expression in human ectopic and eutopic endometrium.

STUDY DESIGN

We used microarrays and western blotting to study the effects of DEHP, and checked the presence of AKR in endometriosis patients by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Cultured human endometrial cells from normal endometrium of women without endometriosis (NE), eutopic endometrium from endometriosis patients (EE), and ectopic endometrium from endometriosis patients (EC) differed in genetic expression changes after DEHP treatment. DEHP upregulated AKR1C1, AKR1C2, AKR1C3, and AKR1B10 expression in EE, while EC showed continuously increased AKR1C3 expression before and after DEHP exposure. In western blot analysis, before and after DEHP exposure, the AKR1B10 protein band was detected in NE, EE, and EC, whereas the AKR1C3 band was detected only in EC. AKR1B10 and AKR1C3 expression levels in the blood of the enrolled patients were evaluated using ELISA. AKR1B10 expression did not differ between groups (without endometriosis [N=13], 0.10 vs. with endometriosis [N=20], 0.11; P=0.27). AKR1C3 expression was significantly higher in the blood of endometriosis patients than in that of patients without endometriosis (without endometriosis, 9.1 vs. with endometriosis, 10.1; P=0.02). Analysis according to menstrual period showed significantly increased AKR1C3 levels in patients with endometriosis only during the secretory phase and not the proliferative phase (P<0.05).

CONCLUSION

DEHP induces AKR activity in the endometrium of endometriosis patients, and AKR1C3 might influence the development of endometriosis.

Aldo-Keto Reductase AKR1C1-AKR1C4: Functions, Regulation, and Intervention for Anti-cancer Therapy

Aldo-keto reductases comprise of AKR1C1-AKR1C4, four enzymes that catalyze NADPH dependent reductions and have been implicated in biosynthesis, intermediary metabolism, and detoxification. Recent studies have provided evidences of strong correlation between the expression levels of these family members and the malignant transformation as well as the resistance to cancer therapy. Mechanistically, most studies focus on the catalytic-dependent function of AKR1C isoforms, like their impeccable roles in prostate cancer, breast cancer, and drug resistance due to the broad substrates specificity. However, accumulating clues showed that catalytic-independent functions also played critical roles in regulating biological events. This review summarizes the catalytic-dependent and -independent roles of AKR1Cs, as well as the small molecule inhibitors targeting these family members.

Dydrogesterone metabolism in human liver by aldo-keto reductases and cytochrome P450 enzymes

1. The metabolism of dydrogesterone was investigated in human liver cytosol (HLC) and human liver microsomes (HLM). Enzymes involved in dydrogesterone metabolism were identified and their relative contributions were estimated. 2. Dydrogesterone clearance was clearly higher in HLC compared to HLM. The major active metabolite 20α-dihydrodydrogesterone (20α-DHD) was only produced in HLC. 3. The formation of 20α-DHD by cytosolic aldo-keto reductase 1C (AKR1C) was confirmed with isoenzyme-specific AKR inhibitors. 4. Using recombinantly expressed human cytochrome P450 (CYP) isoenzymes, dydrogesterone was shown to be metabolically transformed by CYP3A4 and CYP2C19. 5. A clear contribution of CYP3A4 to microsomal metabolism of dydrogesterone was demonstrated with HLM and isoenzyme-specific CYP inhibitors, and confirmed by a significant correlation between dydrogesterone clearance and CYP3A4 activity. 6. Contribution of CYP2C19 was shown to be clearly less than CYP3A4 and restricted to a small group of human individuals with very high CYP2C19 activity. Therefore, it is expected that CYP2C19 genetic variations will not affect dydrogesterone pharmacokinetics in man. 7. In conclusion, dydrogesterone metabolism in the liver is dominated primarily by cytosolic enzymes (particularly AKR1C) and secondarily by CYP3A4, with the former exclusively responsible for 20α-DHD formation.

Selective AKR1C3 Inhibitors Potentiate Chemotherapeutic Activity in Multiple Acute Myeloid Leukemia (AML) Cell Lines

We report the design, synthesis, and evaluation of potent and selective inhibitors of aldo-keto reductase 1C3 (AKR1C3), an important enzyme in the regulatory pathway controlling proliferation, differentiation, and apoptosis in myeloid cells. Combination treatment with the nontoxic AKR1C3 inhibitors and etoposide or daunorubicin in acute myeloid leukemia cell lines, elicits a potent adjuvant effect, potentiating the cytotoxicity of etoposide by up to 6.25-fold and the cytotoxicity of daunorubicin by >10-fold. The results validate AKR1C3 inhibition as a common adjuvant target across multiple AML subtypes. These compounds in coadministration with chemotherapeutics in clinical use enhance therapeutic index and may avail chemotherapy as a treatment option to the pediatric and geriatric population currently unable to tolerate the side effects of cancer drug regimens.

The other side of progestins: effects in the brain

Progestins are a broad class of progestational agents widely differing in their chemical structures and pharmacological properties. Despite emerging data suggest that progestins, besides their action as endometrial protection, can also have multiple nonreproductive functions, much remains to be discovered regarding the actions exerted by these molecules in the nervous system. Here, we report the role exerted by different progestins, currently used for contraception or in postmenopausal hormone replacement therapies, in regulating cognitive functions as well as social behavior and mood. We provide evidence that the effects and mechanisms underlying their actions are still confusing due to the use of different estrogens and progestins as well as different doses, duration of exposure, route of administration, baseline hormonal status and age of treated women. We also discuss the emerging issue concerning the relevant increase of these substances in the environment, able to deeply affect aquatic wildlife as well as to exert a possible influence in humans, which may be exposed to these compounds via contaminated drinking water and seafood. Finally, we report literature data showing the neurobiological action of progestins and in particular their importance during neurodegenerative events. This is extremely interesting, since some of the progestins currently used in clinical practice exert neuroprotective and anti-inflammatory effects in the nervous system, opening new promising opportunities for the use of these molecules as therapeutic agents for trauma and neurodegenerative disorders.

Important roles of the AKR1C2 and SRD5A1 enzymes in progesterone metabolism in endometrial cancer model cell lines

Endometrial cancer is the most frequently diagnosed gynecological malignancy. It is associated with prolonged exposure to estrogens that is unopposed by progesterone, whereby enhanced metabolism of progesterone may decrease its protective effects, as it can deprive progesterone receptors of their active ligand. Furthermore, the 5α-pregnane metabolites formed can stimulate proliferation and may thus contribute to carcinogenesis. The aims of our study were to: (1) identify and quantify progesterone metabolites formed in the HEC-1A and Ishikawa model cell lines of endometrial cancer; and (2) pinpoint the enzymes involved in progesterone metabolism, and delineate their roles. Progesterone metabolism studies combined with liquid chromatography-tandem mass spectrometry enabled identification and quantification of the metabolites formed in these cells. Further quantitative PCR analysis and small-interfering-RNA-mediated gene silencing identified individual progesterone metabolizing enzymes and their relevant roles. In Ishikawa and HEC-1A cells, progesterone was metabolized mainly to 20α-hydroxy-pregn-4-ene-3-one, 20α-hydroxy-5α-pregnane-3-one, and 5α-pregnane-3α/β,20α-diol. The major difference between these cell lines was rate of progesterone metabolism, which was faster in HEC-1A cells. In the Ishikawa and HEC-1A cells, expression of AKR1C2 was 110-fold and 6800-fold greater, respectively, than expression of AKR1C1, which suggests that 20-ketosteroid reduction of 5α-pregnanes and 4-pregnenes is catalyzed mainly by AKR1C2. AKR1C1/AKR1C2 gene silencing showed decreased progesterone metabolism in both cell lines, thus further supporting the significant role of AKR1C2. SRD5A1 was also expressed in these cells, and its silencing confirmed that 5α-reduction is catalyzed by 5α-reductase type 1. Silencing of SRD5A1 also had the most pronounced effects, with decreased rate of progesterone metabolism, and consequently higher concentrations of unmetabolized progesterone. Our data confirm that in model cell lines of endometrial cancer, AKR1C2 and SRD5A1 have crucial roles in progesterone metabolism, and may represent novel targets for treatment.

Isoquinoline alkaloids as a novel type of AKR1C3 inhibitors

AKR1C3 is an important human enzyme that participates in the reduction of steroids and prostaglandins, which leads to proliferative signalling. In addition, this enzyme also participates in the biotransformation of xenobiotics, such as drugs and procarcinogens. AKR1C3 is involved in the development of both hormone-dependent and hormone-independent cancers and was recently demonstrated to confer cell resistance to anthracyclines. Because AKR1C3 is frequently upregulated in various cancers, this enzyme has been suggested as a therapeutic target for the treatment of these pathological conditions. In this study, nineteen isoquinoline alkaloids were examined for their ability to inhibit a recombinant AKR1C3 enzyme. As a result, stylopine was demonstrated to be the most potent inhibitor among the tested compounds and exhibited moderate selectivity towards AKR1C3. In the follow-up cellular studies, stylopine significantly inhibited the AKR1C3-mediated reduction of daunorubicin in intact cells without considerable cytotoxic effects. This inhibitor could therefore be used as a model AKR1C3 inhibitor in research or evaluated as a possible therapeutic anticancer drug. Furthermore, based on our results, stylopine can serve as a model compound for the design and future development of structurally related AKR1C3 inhibitors.

Role of aldo-keto reductase family 1 (AKR1) enzymes in human steroid metabolism

Human aldo-keto reductases AKR1C1-AKR1C4 and AKR1D1 play essential roles in the metabolism of all steroid hormones, the biosynthesis of neurosteroids and bile acids, the metabolism of conjugated steroids, and synthetic therapeutic steroids. These enzymes catalyze NADPH dependent reductions at the C3, C5, C17 and C20 positions on the steroid nucleus and side-chain. AKR1C1-AKR1C4 act as 3-keto, 17-keto and 20-ketosteroid reductases to varying extents, while AKR1D1 acts as the sole Δ(4)-3-ketosteroid-5β-reductase (steroid 5β-reductase) in humans. AKR1 enzymes control the concentrations of active ligands for nuclear receptors and control their ligand occupancy and trans-activation, they also regulate the amount of neurosteroids that can modulate the activity of GABAA and NMDA receptors. As such they are involved in the pre-receptor regulation of nuclear and membrane bound receptors. Altered expression of individual AKR1C genes is related to development of prostate, breast, and endometrial cancer. Mutations in AKR1C1 and AKR1C4 are responsible for sexual development dysgenesis and mutations in AKR1D1 are causative in bile-acid deficiency.

Regulation of progesterone signaling during pregnancy: implications for the use of progestins for the prevention of preterm birth

Preterm birth is a major cause of neonatal morbidity and mortality. Progesterone plays a critical role in suppressing the inflammatory signals that would induce parturition prior to term. Progesterone signaling is regulated in a variety of ways during pregnancy. Endocrine production of high levels of progesterone by the placenta ensures the availability of high levels of progesterone throughout pregnancy. Paracrine regulation of progesterone metabolism in target tissues, particularly the myometrium and cervix, also determines the amount of progesterone ligand available. Progesterone metabolism can also lead to the formation of metabolites that contribute to its effects. In particular, 5β-dihydroprogesterone formation by aldo-keto reductase 1D1 appears to play an important role in maintaining uterine quiescence. Progesterone signaling can also be regulated at the receptor level through changes in the relative expression of the nuclear progesterone receptor isoforms, reduced expression of membrane receptors, and changes in the expression levels of coactivators and/or corepressors, including nuclear factor κB. Progesterone and 17α-hydroxyprogesterone caproate (17OH-PC) have recently been shown to reduce preterm births in women with previous preterm birth or shortened cervix. It is important to realize that these two progestins are likely to act in significantly different ways, which will likely influence their efficacy. The structural differences and resistance to metabolism exhibited by 17OH-PC means that it will be unable to activate some of the pathways that progesterone activates, but that it also will not be subject to paracrine inactivation. The fact that progesterone therapy works for maintaining pregnancy in some women, indicates that for those women insufficient levels of progesterone ligand in target tissues is a determining factor in early parturition, despite high levels of circulating progesterone. This article is part of a Special Issue entitled 'Pregnancy and Steroids'.

2,3-Diarylpropenoic acids as selective non-steroidal inhibitors of type-5 17β-hydroxysteroid dehydrogenase (AKR1C3)

The aldo-keto reductase AKR1C3 is an important target for the development of new drugs. Selective inhibitors of this enzyme are needed because they should not inhibit other, structurally closely related AKR1C isoforms. A comprehensive series of 2,3-diarylpropenoic acids was synthesized and evaluated for the inhibition of AKR1C1-AKR1C3. We found that the 4-methylsulfonylphenyl substituent at position 2 of these acids is required to exhibit the selective inhibition of AKR1C3. The best results were obtained for the compounds that fulfill the above requirement and possess a 4-bromophenyl, 4-methylthiophenyl, 4-methylphenyl or 4-ethylphenyl substituent at position 3 of the substituted propenoic acids (i.e., acids 28, 29, 37, and 39, respectively). These compounds represent an important step toward the development of drug candidates for a treatment of the hormone-dependent and hormone-independent forms of prostate and breast cancers.

New enzymatic assay for the AKR1C enzymes

The imbalance in expression of the human aldo-keto reductases AKR1C1-AKR1C3 is related to different hormone dependent and independent cancers and some other diseases. The AKR1C1-3 enzymes thus represent emerging targets for the development of new drugs. Currently, various enzymatic assays are used in the search for AKR1C inhibitors, and consequently the results of different research groups are not necessarily comparable. During our recent search for AKR1C inhibitors, we found a cyclopentanol derivative (2-(4-chlorobenzylidene)cyclopentanol, CBCP-ol) and its respective cyclopentanone counterpart (2-(4-chlorobenzylidene)cyclopentanone, CBCP-one) that acted as AKR1C substrates. We determined the kinetic parameters KM, kcat and kcat/KM for oxidation of CBCP-ol and reduction of CBCP-one by AKR1C enzymes in the presence of NAD(+)/NADP(+) and NADH/NADPH, respectively. The catalytic efficiencies for the oxidation of CBCP-ol in the presence of NAD(+) or NADP(+) were in general higher when compared to the catalytic efficiencies for reduction of CBCP-one in the presence of NADH or NADPH. When NADPH was used, as compared to NADH, the reductions of CBCP-one by AKR1C1, AKR1C2 and AKR1C3 were 14-, 51- and 31-fold more efficient, respectively. When comparing to oxidations of the well-known artificial substrates, 1-acenaphthenol and S-tetralol, we observed similar catalytic efficiencies as for CBCP-ol oxidation with NAD(+) and NADP(+). The comparison of CBCP-one reduction with NADPH to reductions of physiological substrates revealed in general higher efficiencies, except for reduction of 9-cis-retinaldehyde by AKR1C3. This NADPH-dependent reduction of CBCP-one was then used to re-evaluate inhibitory potencies of the known inhibitors of the target AKR1C3 and the anti-target AKR1C2, medroxyprogesterone acetate and ursodeoxycholic acid, respectively, showing Ki constants similar to the reported values. Our data thus confirm that the new enzymatic assays with two cyclopentane substrates CBP-ol and CBP-one, and especially reduction of CBCP-one with NADPH, are appropriate for the evaluation of AKR1C inhibitors.

Expression of human aldo-keto reductase 1C2 in cell lines of peritoneal endometriosis: potential implications in metabolism of progesterone and dydrogesterone and inhibition by progestins

The human aldo-keto reductase AKR1C2 converts 5α-dihydrotestosterone to the less active 3α-androstanediol and has a minor 20-ketosteroid reductase activity that metabolises progesterone to 20α-hydroxyprogesterone. AKR1C2 is expressed in different peripheral tissues, but its role in uterine diseases like endometriosis has not been studied in detail. Some progestins used for treatment of endometriosis inhibit AKR1C1 and AKR1C3, with unknown effects on AKR1C2. In this study we investigated expression of AKR1C2 in the model cell lines of peritoneal endometriosis, and examined the ability of recombinant AKR1C2 to metabolise progesterone and progestin dydrogesterone, as well as its potential inhibition by progestins. AKR1C2 is expressed in epithelial and stromal endometriotic cell lines at the mRNA level. The recombinant enzyme catalyses reduction of progesterone to 20α-hydroxyprogesterone with a 10-fold lower catalytic efficiency than the major 20-ketosteroid reductase, AKR1C1. AKR1C2 also metabolises progestin dydrogesterone to its 20α-dihydrodydrogesterone, with 8.6-fold higher catalytic efficiency than 5α-dihydrotestosterone. Among the progestins that are currently used for treatment of endometriosis, dydrogesterone, medroxyprogesterone acetate and 20α-dihydrodydrogesterone act as AKR1C2 inhibitors with low μM K(i) values in vitro. Their potential in vivo effects should be further studied.

Enzymes of the AKR1B and AKR1C Subfamilies and Uterine Diseases

Endometrial and cervical cancers, uterine myoma, and endometriosis are very common uterine diseases. Worldwide, more than 800,000 women are affected annually by gynecological cancers, as a result of which, more than 360,000 die. During their reproductive age, about 70% of women develop uterine myomas and 10-15% suffer from endometriosis. Uterine diseases are associated with aberrant inflammatory responses and concomitant increased production of prostaglandins (PG). They are also related to decreased differentiation, due to low levels of protective progesterone and retinoic acid, and to enhanced proliferation, due to high local concentrations of estrogens. The pathogenesis of these diseases can thus be attributed to disturbed PG, estrogen, and retinoid metabolism and actions. Five human members of the aldo-keto reductase 1B (AKR1B) and 1C (AKR1C) superfamilies, i.e., AKR1B1, AKR1B10, AKR1C1, AKR1C2, and AKR1C3, have roles in these processes and can thus be implicated in uterine diseases. AKR1B1 and AKR1C3 catalyze the formation of PGF2α, which stimulates cell proliferation. AKR1C3 converts PGD2 to 9α,11β-PGF2, and thus counteracts the formation of 15-deoxy-PGJ2, which can activate pro-apoptotic peroxisome-proliferator-activated receptor γ. AKR1B10 catalyzes the reduction of retinal to retinol, and thus lessens the formation of retinoic acid, with potential pro-differentiating actions. The AKR1C1-AKR1C3 enzymes also act as 17-keto- and 20-ketosteroid reductases to varying extents, and are implicated in increased estradiol and decreased progesterone levels. This review comprises an introduction to uterine diseases and AKR1B and AKR1C enzymes, followed by an overview of the current literature on the AKR1B and AKR1C expression in the uterus and in uterine diseases. The potential implications of the AKR1B and AKR1C enzymes in the pathophysiologies are then discussed, followed by conclusions and future perspectives.

Aldo-keto reductases AKR1C1, AKR1C2 and AKR1C3 may enhance progesterone metabolism in ovarian endometriosis

Endometriosis is a very common disease that is characterized by increased formation of estradiol and disturbed progesterone action. This latter is usually explained by a lack of progesterone receptor B (PR-B) expression, while the role of pre-receptor metabolism of progesterone is not yet fully understood. In normal endometrium, progesterone is metabolized by reductive 20α-hydroxysteroid dehydrogenases (20α-HSDs), 3α/β-HSDs and 5α/β-reductases. The aldo-keto reductases 1C1 and 1C3 (AKR1C1 and AKR1C3) are the major reductive 20α-HSDs, while the oxidative reaction is catalyzed by 17β-HSD type 2 (HSD17B2). Also, 3α-HSD and 3β-HSD activities have been associated with the AKR1C isozymes. Additionally, 5α-reductase types 1 and 2 (SRD5A1, SRD5A2) and 5β-reductase (AKR1D1) are responsible for the formation of 5α- and 5β-reduced pregnanes. In this study, we examined the expression of PR-AB and the progesterone metabolizing enzymes in 31 specimens of ovarian endometriosis and 28 specimens of normal endometrium. Real-time PCR analysis revealed significantly decreased mRNA levels of PR-AB, HSD17B2 and SRD5A2, significantly increased mRNA levels of AKR1C1, AKR1C2, AKR1C3 and SRD5A1, and negligible mRNA levels of AKR1D1. Immunohistochemistry staining of endometriotic tissue compared to control endometrium showed significantly lower PR-B levels in epithelial cells and no significant differences in stromal cells, there were no significant differences in the expression of AKR1C3 and significantly higher AKR1C2 levels were seen only in stromal cells. Our expression analysis data at the mRNA level and partially at the cellular level thus suggest enhanced metabolism of progesterone by SRD5A1 and the 20α-HSD and 3α/β-HSD activities of AKR1C1, AKR1C2 and AKR1C3.