Exploring new chemical functionalities to improve aromatase inhibition of steroids.

In this work, new potent steroidal aromatase inhibitors both in microsomes and in breast cancer cells have been found. The synthesis of the 3,4-(ethylenedioxy)androsta-3,5-dien-17-one (12), a new steroid containing a heterocycle dioxene fused in the A-ring, led to the discovery of a new reaction for which a mechanism is proposed. New structure-activity relationships were established. Some 5ß-steroids, such as compound 4ß,5ß-epoxyandrostan-17-one (9), showed aromatase inhibitory activity, because they adopt a similar A-ring conformation as those of androstenedione, the natural substrate of aromatase. Moreover, new chemical features to increase planarity were disclosed, specifically the 3α,4α-cyclopropane ring, as in 3α,4α-methylen-5α-androstan-17-one (5) (IC50=0.11µM), and the Δ(9-11) double bond in the C-ring, as in androsta-4,9(11)-diene-3,17-dione (13) (IC50=0.25µM). In addition, induced-fit docking (IFD) simulations and site of metabolism (SoM) predictions helped to explain the recognition of new potent steroidal aromatase inhibitors within the enzyme. These insights can be valuable tools for the understanding of the molecular recognition process by the aromatase and for the future design of new steroidal inhibitors.

Lipidomic approach towards deciphering anandamide effects in rat decidual cell.

Altered phospholipid (PL) metabolism has been associated with pregnancy disorders. Moreover, lipid molecules such as endocannabinoids (eCBs) and prostaglandins (PGs) are important mediators of reproductive events. In humans, abnormal decidualization has been linked with unexplained infertility, miscarriage and endometrial pathologies. Anandamide (AEA), the major eCB, induces apoptosis in rat decidual cells. In this study, the PL profile of rat decidual cells was characterized by a Mass spectrometry (MS) based lipidomic approach. Furthermore, we analyzed a possible correlation between changes in PL of rat decidual cells' membrane and AEA-induced apoptosis. We found an increase in phosphatidylserine and a reduction of cardiolipin and phophatidylinositol relative contents. In addition, we observed an increase in the content of alkyl(alkenyl) acylPL, plasmalogens, and of long chain fatty acids especially with high degrees of unsaturation, as well as an increase in lipid hydroperoxides in treated cells. These findings provide novel insights on deregulation of lipid metabolism by anandamide, which may display further implications in decidualization process.

Synthetic cannabinoids JWH-018, JWH-122, UR-144 and the phytocannabinoid THC activate apoptosis in placental cells.

The increasing use of synthetic cannabinoids (SCBs) in recreational settings is becoming a new paradigm of drug abuse. Although SCBs effects mimic those of the Cannabis sativa plant, these drugs are frequently more potent and hazardous. It is known that endocannabinoid signalling plays a crucial role in diverse reproductive events such as placental development. Moreover, the negative impact of the phytocannabinoid Δ9-tetrahydrocannabinol (THC) in pregnancy outcome, leading to prematurity, intrauterine growth restriction and low birth weight is well recognized, which makes women of childbearing age a sensitive group to developmental adverse effects of cannabinoids. Placental trophoblast turnover relies on regulated processes of proliferation and apoptosis for normal placental development. Here, we explored the impact of the SCBs JWH-018, JWH-122 and UR-144 and of the phytocannabinoid THC in BeWo cell line, a human placental cytotrophoblast cell model. All the cannabinoids caused a significant decrease in cell viability without LDH release, though this effect was only detected for the highest concentrations of THC. Moreover, a cell cycle arrest at the G2/M phase was also observed. JWH-018 and JWH-122 increased reactive oxygen species (ROS) production and THC, UR-144 and JWH-122 caused loss of mitochondrial membrane potential. All the compounds were able to induce caspase-9 activation. The involvement of apoptotic pathways was further confirmed through the significant increase in caspase -3/-7 activities. For UR-144, this effect was reversed by the CB1 antagonist AM281, for JWH-018 and THC this effect was mediated by both cannabinoid receptors CB1 and CB2 while for JWH-122 it was cannabinoid receptor-independent. This work demonstrates that THC and SCBs are able to induce apoptotic cell death. Although they may act through different mechanisms and potencies, the studied cannabinoids have the potential to disrupt gestational fundamental events.

Spatio-temporal expression patterns of anandamide-binding receptors in rat implantation sites: evidence for a role of the endocannabinoid system during the period of placental development.

BACKGROUND: Although there is growing evidence that endocannabinoids play a critical role in early pregnancy, there are no studies describing the possible targets for this system after implantation. The endometrial stroma, which undergoes extensive proliferation and differentiation giving rise to the decidua and the trophoblast cells that invade after the initial stages of implantation, are potential targets. Since high anandamide (AEA) levels, the main endocannabinoid, are detrimental to implantation and in order to gain insight into the role of the endocannabinoid system in the development of the fetoplacental unit, the spatio-temporal pattern of expression of the anandamide-binding receptors, CB1, CB2 and the vanilloid receptor (TRPV1), were investigated by quantitative RT-PCR, western blot and immunohistochemistry. METHODS: Rat uterine maternal tissues from different days of pregnancy were used to investigate the expression of CB1, CB2 and vanilloid receptors by quantitative RT-PCR, western blot and immunohistochemistry. RESULTS: The data indicate that all the three receptors were expressed in decidualized cells and placenta. Interestingly, CB1 and CB2 were also expressed in smooth muscle cells of maternal blood vessels and in endovascular trophoblast cells, whereas TRPV1 was mainly expressed in uterine natural killer (uNK) cells and in the longitudinal muscle layer throughout pregnancy. In all tissues, CB2 protein was present at a lower level than CB1. CONCLUSION: These observations support a role for the endocannabinoid system during the period of decidualization and placental development.

Synthetic cannabinoids and endometrial stromal cell fate: Dissimilar effects of JWH-122, UR-144 and WIN55,212-2.

The emergence of synthetic cannabinoids (SCBs) as drugs of abuse in readily available "Spice" smoking blends has exposed users to much more potent cannabinoids than the phytocannabinoids present in Cannabis sativa L. Increasing reports of adverse reactions are emerging in the clinical literature. SCBs may disrupt the endocannabinoid signalling, which has been shown to be crucial within human endometrium remodelling process. Within this study, a telomerase-immortalised human endometrial stromal cell line (St-T1b) and primary human decidual fibroblasts (HdF) were used to determine the impact of SCBs JWH-122, UR-144 and WIN55,212-2 (WIN) on endometrial stromal cells. Our findings indicate that JWH-122 and UR-144 (0.01-25 µM) induce prompt ROS/RNS formation and endoplasmic reticulum (ER) stress without reduction in cell viability. Disturbances in the normal functions of the ER lead to cell stress response, which is after compensated with the increase in reduced/oxidized glutathione ratio (GSH/GSSG). Instead, WIN induces ER stress, mitochondrial dysfunction and apoptotic cell death. The addition of the CB1 antagonist AM281 significantly reduces the effects on cell viability, suggesting that CB1 plays a key role in WIN-induced apoptosis. Collectively, our data suggests that SCBs have dissimilar effects on human endometrial stromal cells and, thus, may impact human reproductive function through distinct mechanisms that are crucial for the understanding of the pathophysiological outcomes from its abuse.

C-6α- vs C-7α-Substituted Steroidal Aromatase Inhibitors: Which Is Better? Synthesis, Biochemical Evaluation, Docking Studies, and Structure-Activity Relationships.

C-6α and C-7α androstanes were studied to disclose which position among them is more convenient to functionalize to reach superior aromatase inhibition. In the first series, the study of C-6 versus C-7 methyl derivatives led to the very active compound 9 with IC50 of 0.06 µM and Ki = 0.025 µM (competitive inhibition). In the second series, the study of C-6 versus C-7 allyl derivatives led to the best aromatase inhibitor 13 of this work with IC50 of 0.055 µM and Ki = 0.0225 µM (irreversible inhibition). Beyond these findings, it was concluded that position C-6α is better to functionalize than C-7α, except when there is a C-4 substituent simultaneously. In addition, the methyl group was the best substituent, followed by the allyl group and next by the hydroxyl group. To rationalize the structure-activity relationship of the best inhibitor 13, molecular modeling studies were carried out.

New steroidal aromatase inhibitors: suppression of estrogen-dependent breast cancer cell proliferation and induction of cell death.

BACKGROUND: Aromatase, the cytochrome P-450 enzyme (CYP19) responsible for estrogen biosynthesis, is an important target for the treatment of estrogen-dependent breast cancer. In fact, the use of synthetic aromatase inhibitors (AI), which induce suppression of estrogen synthesis, has shown to be an effective alternative to the classical tamoxifen for the treatment of postmenopausal patients with ER-positive breast cancer. New AIs obtained, in our laboratory, by modification of the A and D-rings of the natural substrate of aromatase, compounds 3a and 4a, showed previously to efficiently suppress aromatase activity in placental microsomes. In the present study we have investigated the effects of these compounds on cell proliferation, cell cycle progression and induction of cell death using the estrogen-dependent human breast cancer cell line stably transfected with the aromatase gene, MCF-7 aro cells. RESULTS: The new steroids inhibit hormone-dependent proliferation of MCF-7aro cells in a time and dose-dependent manner, causing cell cycle arrest in G0/G1 phase and inducing cell death with features of apoptosis and autophagic cell death. CONCLUSION: Our in vitro studies showed that the two steroidal AIs, 3a and 4a, are potent inhibitors of breast cancer cell proliferation. Moreover, it was also shown that the antiproliferative effects of these two steroids on MCF-7aro cells are mediated by disrupting cell cycle progression, through cell cycle arrest in G0/G1 phase and induction of cell death, being the dominant mechanism autophagic cell death. Our results are important for the elucidation of the cellular effects of steroidal AIs on breast cancer.

Synthesis and biochemical studies of 17-substituted androst-3-enes and 3,4-epoxyandrostanes as aromatase inhibitors.

A series of 5alpha-androst-3-enes and 3alpha,4alpha-epoxy-5alpha-androstanes were synthesized and tested for their abilities to inhibit aromatase in human placental microsomes. In these series the original C-17 carbonyl group was replaced by hydroxyl, acetyl and hydroxyimine groups. Inhibition kinetic analysis on the most potent steroid of these series revealed that it inhibits the enzyme in a competitive manner (IC(50)=6.5 microM). The achieved data pointed out the importance of the C-17 carbonyl group in the D-ring of the studied steroids as a structural feature required to reach maximum aromatase inhibitory activity. Further, at least one carbonyl group (C-3 or C-17) seems to be essential to effective aromatase inhibition.

Structure-activity relationships of new A,D-ring modified steroids as aromatase inhibitors: design, synthesis, and biological activity evaluation.

Inhibition of aromatase is an efficient approach for the prevention and treatment of breast cancer. New A,D-ring modified steroid analogues of formestane and testolactone were designed and synthesized and their biochemical activity was investigated in vitro in an attempt to find new aromatase inhibitors and to gain insight into their structure-activity relationships (SAR). All compounds tested were less active than formestane. However, the 3-deoxy steroidal olefin 3a and its epoxide derivative 4a proved to be strong competitive aromatase inhibitors (K(i) = 50 and 38 nM and IC50 = 225 and 145 nM, respectively). According to our findings, the C-3 carbonyl group is not essential for anti-aromatase activity, but 5alpha-stereochemistry and some planarity in the steroidal framework is required. Furthermore, modification of the steroidal cyclopentanone D-ring, by construction of a delta-lactone six-membered ring, decreases the inhibitory potency. From the results obtained, it may be concluded that the binding pocket of the active site of aromatase requires planarity in the region of the steroid A,B-rings and the D-ring structure is critical for the binding.

Design, synthesis and biochemical studies of new 7α-allylandrostanes as aromatase inhibitors.

Two series of derivatives of 7α-allylandrostenedione, namely its 3-deoxo and 1-ene analogs, were designed and synthesised and their biochemical activity towards aromatase evaluated. In each of these series, the C-17 carbonyl group was further replaced by the hydroxyl and acetoxyl groups. The attained data pointed out that the absence of the C-3 carbonyl group led to a slightly decrease in the inhibitory activity and the introduction of an additional double bond in C-1 revealed to be a very beneficial structural change in the studied compounds (compound 12, IC50 = 0.47 µM, K(i) = 45.00 nM). Furthermore, the relevance of the C-17 carbonyl group in the D-ring as a structural feature required to achieve maximum aromatase inhibitory activity is also observed for this set of derivatives.

The rat as an animal model for fetoplacental development: a reappraisal of the post-implantation period.

Following implantation in rodents, the uterine stromal fibroblasts differentiate into densely packed decidual cells. This process, called decidualization, is well-orchestrated and progresses both antimesometrially and mesometrially, creating two regions with distinctive cellular morphologies. In addition, subsequent placental development is dependent on the invasion of the trophoblast, the process intimately linked to the endometrial tissue remodelling and depending largely on the environment created by the decidua; this phenomenon is crucial for the establishment and maintenance of pregnancy. The key mechanisms underlying the maternal tissue remodelling and trophoblast invasion remain poorly understood. The rat, just like human beings, exhibits a highly invasive type of placental development, the haemochorial placentation. For obvious ethical reasons, the studies of endometrial tissue remodelling throughout pregnancy in humans are greatly limited. Although the rat differs somewhat from humans with regards to the implantation process, it is an appropriate model for studying the mechanisms of decidualization as well as subsequent remodelling of the uterine tissues and fetoplacental development. As decidual remodelling is very closely linked to placentation and the maternal-fetal interactions in the rat show several important similarities to human placentation, the morphological alterations occurring during the post-implantation period in the rat have been addressed in the present review.

Characterisation of the endocannabinoid system in rat haemochorial placenta.

Trophoblast cells that comprise the placenta play a crucial role in the complex cross-talk between fetus and maternal tissues. Although anandamide and 2-arachidonoylglycerol, the best studied endocannabinoids, affect trophoblast attachment and outgrowth, the functional significance of the endocannabinoid system in the development of placenta has not been established. We investigated the correlation between endocannabinoid levels and the pattern of expression of the receptors and metabolic enzymes of the endocannabinoid system during rat placental development. Here, we showed that all the endocannabinoid machinery is dynamically expressed in the functionally distinct basal and labyrinth zones of the rat placenta. Indeed, endocannabinoid levels are shown to increase with the progression of pregnancy. Together, these data support a role for the endocannabinoid system in normal placental function and evidence for a potential novel cellular target for the deleterious action of cannabis-derived compounds during the second half of pregnancy.

New structure-activity relationships of A- and D-ring modified steroidal aromatase inhibitors: design, synthesis, and biochemical evaluation.

A- and D-ring androstenedione derivatives were synthesized and tested for their abilities to inhibit aromatase. In one series, C-3 hydroxyl derivatives were studied leading to a very active compound, when the C-3 hydroxyl group assumes 3ß stereochemistry (1, IC(50) = 0.18 µM). In a second series, the influence of double bonds or epoxide functions in different positions along the A-ring was studied. Among epoxides, the 3,4-epoxide 15 showed the best activity (IC(50) = 0.145 µM) revealing the possibility of the 3,4-oxiran oxygen resembling the C-3 carbonyl group of androstenedione. Among olefins, the 4,5-olefin 12 (IC(50) = 0.135 µM) revealed the best activity, pointing out the importance of planarity in the A,B-ring junction near C-5. C-4 acetoxy and acetylsalicyloxy derivatives were also studied showing that bulky substituents in C-4 diminish the activity. In addition, IFD simulations helped to explain the recognition of the C-3 hydroxyl derivatives (1 and 2) as well as 15 within the enzyme.

Molecular mechanisms of aromatase inhibition by new A, D-ring modified steroids.

A recent approach for treatment and prevention of estrogen-dependent breast cancer focuses on the inhibition of aromatase, the enzyme that catalyzes the final step of estrogen biosynthesis. Some synthetic steroids, such as formestane and exemestane, resembling the natural enzyme substrate androstenedione, revealed to be potent and useful aromatase inhibitors (AIs) and were approved for the treatment of estrogen-dependent breast cancer in postmenopausal women. Recently, we found that five newly synthesized steroids with chemical features in the A- and D-rings considered important for drug-receptor interaction efficiently inhibit aromatase derived from human placental microsomes. In this work, these steroids showed a similar pattern of anti-aromatase activity in several aromatase-expressing cell lines. 5alpha-androst-3-en-17-one and 3alpha,4alpha-epoxy-5alpha-androstan-17-one were revealed to be the most potent inhibitors. These compounds induced a time-dependent inhibition of aromatase, showing to be irreversible AIs. The specific interactions of these compounds with aromatase active sites were further demonstrated by site-directed mutagenesis studies and evaluated by computer-aided molecular modeling. Both compounds were able to suppress hormone-dependent proliferation of MCF-7aro cells in a dose-dependent manner. These findings are important for the elucidation of a structure-activity relationship on aromatase, which may help in the development of new AIs.