Effects of 17β-HSD2 inhibition in bones on osteoporosis based on an animal rat model

Recent advances in the development of 17beta-hydroxysteroid dehydrogenase inhibitors

The family of 17β-hydroxysteroid dehydrogenases (17β-HSDs) occupies a prominent place due to its number of isoforms, which carry out a bidirectional transformation (reduction of a steroid carbonyl to alcohol and oxidation of a steroid alcohol to ketone) depending on the nature of the cofactor present. Involved in the activation or inactivation of key estrogens and androgens, 17β-HSDs are therefore therapeutic targets whose selective inhibition would make it possible to be considered for the treatment of several diseases, such as breast cancer, prostate cancer, endometriosis, Alzheimer's disease and osteoporosis. This review article is a continuation of those having reported the great diversity of inhibitors developed over the last years but focusses on inhibitors recently developed. Work to obtain more effective inhibitors that target the first known isoforms (types 1, 2, 3, 5 and 7) has continued, among others, but new inhibitors that target the isoforms more recently reported in the literature (types 10, 12, 13 and 14) are now being reported. Dual inhibitors of two enzymes (17β-HSD1 and steroid sulfatase) were also reported. These inhibitors were grouped according to the 17β-HSD type inhibited and their backbone (steroidal or non-steroidal) when necessary. They were also reported in chronological order and according to the research group.

Psoralen prevents the inactivation of estradiol and treats osteoporosis via covalently targeting HSD17B2

ETHNOPHARMACOLOGICAL RELEVANCE

Psoralea corylifolia L. seeds (P. corylifolia), popularly known as Buguzhi in traditional Chinese medicine, are often used to treat osteoporosis in China. Psoralen (Pso) is the key anti-osteoporosis constituent in P. corylifolia, however, its targets and mechanism of action are still unclear.

AIM OF THE STUDY

The purpose of this study was to explore the interaction between Pso and 17-β hydroxysteroid dehydrogenase type 2 (HSD17B2), an estrogen synthesis-related protein that inhibits the inactivation of estradiol (E2) to treat osteoporosis.

MATERIALS AND METHODS

Tissue distribution of Pso was analyzed by in-gel imaging after oral administration of an alkynyl-modified Pso probe (aPso) in mice. The target of Pso in the liver was identified and analyzed using chemical proteomics. Co-localization and cellular thermal shift assays (CETSA) were used to verify the key action targets. To detect the key pharmacophore of Pso, the interaction of Pso and its structural analogs with HSD17B2 was investigated by CETSA, HSD17B2 activity assay, and in-gel imaging determination. Target competitive test, virtual docking, mutated HSD17B2 activity, and CETSA assay were used to identify the binding site of Pso with HSD17B2. A mouse model of osteoporosis was established by ovariectomies, and the efficacy of Pso in vivo was confirmed by micro-CT, H&E staining, HSD17B2 activity, and bone-related biochemical assays.

RESULTS

Pso regulated estrogen metabolism by targeting HSD17B2 in the liver, with the α, β-unsaturated ester in Pso being the key pharmacophore. Pso significantly suppressed HSD17B2 activity by irreversibly binding to Lys236 of HSD17B2 and preventing NAD⁺ from entering the binding pocket. In vivo studies in ovariectomized mice revealed that Pso could inhibit HSD17B2 activity, prevent the inactivation of E2, increase levels of endogenous estrogen, improve bone metabolism-related indices, and play a role in anti-osteoporosis.

CONCLUSIONS

Pso covalently binds to Lys236 of HSD17B2 in hepatocytes to prevent the inactivation of E2, thereby aiding in the treatment of osteoporosis.

Androstenedione (a Natural Steroid and a Drug Supplement): A Comprehensive Review of Its Consumption, Metabolism, Health Effects, and Toxicity with Sex Differences

Androstenedione is a steroidal hormone produced in male and female gonads, as well as in the adrenal glands, and it is known for its key role in the production of estrogen and testosterone. Androstenedione is also sold as an oral supplement, that is being utilized to increase testosterone levels. Simply known as "andro" by athletes, it is commonly touted as a natural alternative to anabolic steroids. By boosting testosterone levels, it is thought to be an enhancer for athletic performance, build body muscles, reduce fats, increase energy, maintain healthy RBCs, and increase sexual performance. Nevertheless, several of these effects are not yet scientifically proven. Though commonly used as a supplement for body building, it is listed among performance-enhancing drugs (PEDs) which is banned by the World Anti-Doping Agency, as well as the International Olympic Committee. This review focuses on the action mechanism behind androstenedione's health effects, and further side effects including clinical features, populations at risk, pharmacokinetics, metabolism, and toxicokinetics. A review of androstenedione regulation in drug doping is also presented.

Rhaponticin contained Rheum officinale root extract improved Postmenopause symptom of Ovariectomized Rat

Postmenopausal women have decreased levels of the hormone estrogen. Reduced estrogen levels will often involve many symptoms that reduced quality of life. This research aims to analyze the effects of Rheum officinale root extract on postmenopausal model rats. To this end, thirty rats underwent ovariectomy (OVX) surgery and six rats were operated without having their ovaries removed. The OVX was confirmed by body weight–uterus weight ratio and a vaginal swab. Six groups of the rats were performed: SHAM group and negative control groups are given vehicle; the positive control was assigned tamoxifen; and the extract has been given three doses 7, 35, and 175 mg/200 g BW, respectively, for 30 days. The calcium content of bone ash was measured using atomic absorption spectrophotometer. Blood pressure was evaluated using CODA^®, and the metabolites in the blood were assessed using gas chromatography–mass spectrometry (MS) and high-performance liquid chromatography. As a result, using ultra-performance liquid chromatography (UPLC)-MS, we found that the extract's major component was rhaponticin and its metabolites. The bone calcium levels increased with increasing doses of the extract. In the OVX group, the bone calcium content was decreased significantly 51.56% ± 8.9% g compared with the SHAM group 62.97% ±5.6% g, and the administration of Rheum extract could restore the calcium content of the bone to become 69.27% ± 3.8% g. From the above data, we concluded that Rheum root extracts contain astrigin, rhaponticin, rhapontigenin, and desoxyrhaponticin. Rheum root extract could improve calcium content and lipid profiles of OVX rats by stimulation osteoblastogenesis. Rheum root extracts could control the blood pressure of OVX rats by reducing lipid profiles.

Homology modeling meets site-directed mutagenesis: An ideal combination to elucidate the topology of 17β-HSD2

17β-Hydroxysteroid dehydrogenase type 2 (17β-HSD2) catalyzes the conversion of highly active estrogens and androgens into their less active forms using NAD⁺ as cofactor. Substrate and cofactor specificities of 17β-HSD2 have been reported and potent 17β-HSD2 inhibitors have been discovered in a ligand-based approach. However, the molecular basis and the amino acids involved in the enzymatic functionality are poorly understood, as no crystal structure of the membrane-associated 17β-HSD2 exists. The functional properties of only few amino acids are known. The lack of topological information impedes structure-based drug design studies and limits the design of biochemical experiments. The aim of this work was the determination of the 17β-HSD2 topology. For this, the first homology model of 17β-HSD2 in complex with NAD⁺ and 17β-estradiol was built, using a multi-fragment "patchwork" approach. To confirm the quality of the model, fifteen selected amino acids were exchanged one by one using site directed mutagenesis. The mutants' functional behavior demonstrated that the generated model was of very good quality and allowed the identification of several key amino acids involved in either ligand or internal structure stabilization. The final model is an optimal basis for further experiments like, for example, lead optimization.

Design, Synthesis, and Biological Characterization of Orally Active 17β-Hydroxysteroid Dehydrogenase Type 2 Inhibitors Targeting the Prevention of Osteoporosis

Osteoporosis is predominantly treated with drugs that inhibit further bone resorption due to estrogen deficiency. Yet, osteoporosis drugs that not only inhibit bone resorption but also stimulate bone formation, such as potentially inhibitors of 17β-hydroxysteroid dehydrogenase type 2 (17β-HSD2), may be more efficacious in the treatment of osteoporosis. Blockade of 17β-HSD2 is thought to increase intracellular estradiol and testosterone in bone, thereby inhibiting bone resorption by osteoclasts and stimulating bone formation by osteoblasts, respectively. We here describe the design, synthesis, and biological characterization of a novel bicyclic-substituted hydroxyphenylmethanone 17β-HSD2 inhibitor (compound 24). Compound 24 is a nanomolar potent inhibitor of human 17β-HSD2 (IC₅₀ of 6.1 nM) and rodent 17β-HSD2 with low in vitro cellular toxicity, devoid of detectable estrogen receptor α affinity, displays high aqueous solubility and in vitro metabolic stability, and has an excellent oral pharmacokinetic profile for testing in a rat osteoporosis model. Administration of 24 in a rat osteoporosis model demonstrates its bone-sparing efficacy.