Yttrium Oxide Nanoparticle-Loaded, Self-Assembled Peptide Gel with Antibacterial, Anti-Inflammatory, and Proangiogenic Properties for Wound Healing

Chronic wounds are a major healthcare challenge owing to their complex healing mechanism and number of impediments to the healing process, like infections, unregulated inflammation, impaired cellular functions, poor angiogenesis, and enhanced protease activity. Current topical care strategies, such as surgical debridement, absorption of exudates, drug-loaded hydrogels for infection and inflammation management, and exogenous supply of growth factors for angiogenesis and cell proliferation, slow the progression of wounds and reduce patient suffering but suffer from low overall cure rates. Therefore, we have developed a proteolytically stable, multifunctional nanoparticle loaded-peptide gel with inherent anti-inflammatory, antibacterial, and pro-angiogenic properties to provide a favorable wound healing milieu by restoring impaired cellular functions. We have fabricated a self-assembled, lauric acid-peptide conjugate gel, LA-LLys-DPhe-LLys-NH2, loaded with yttrium oxide (Y2O3) nanoparticles (NLG). Gel formed a nanofibrous structure, and nanoparticles were passively entrapped within the network. The surface morphology, stability, viscoelastic, and self-healing characteristics of gels were characterized. It showed a high stability against degradation by proteolytic enzymes and highly potent antibacterial activities against E. coli and S. aureus due to the presence of positively charged side chains of lysine in the peptide chain. It also exhibited an excellent antioxidant activity as well as ability to stimulate cell proliferation in murine fibroblast (L929) cells and human umbilical vein endothelial cells (HUVECs). The incorporation of nanoparticles promoted angiogenesis by upregulating pro-angiogenic genes, vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF2), and epidermal growth factor (EGFR), and the gel caused complete wound closure in cells. In summary, the Y2O3 nanoparticle-loaded lauric acid-peptide conjugate gel is able to elicit the desired tissue regeneration responses and, therefore, has a strong potential as a matrix for the treatment of chronic wounds.

Synthesis of dihydrotestosterone derivatives modified in the A-ring with (hetero)arylidene, pyrazolo[1,5-a]pyrimidine and triazolo[1,5-a]pyrimidine moieties and their targeting of the androgen receptor in prostate cancer

One of the main directions of steroid research is the preparation of modified derivatives in which, in addition to changes in physicochemical properties, receptor binding is significantly altered, thus a bioactivity different from that of the parent compound predominates. In the frame of this work, 2-arylidene derivatives were first synthesized by regioselective modification of the A-ring of natural sex hormone, 5α-dihydrotestosterone (DHT). After Claisen-Schmidt condensations of DHT with (hetero)aromatic aldehydes in alkaline EtOH, heterocyclizations of the α,β-enones were performed with 3-amino-1,2,4-triazole, 3-aminopyrazole and 3-amino-5-methylpyrazole in the presence of t-BuOK in DMF to afford 7'-epimeric mixtures of A-ring-fused azolo-dihydropyrimidines, respectively. Depending on the electronic demand of the substituents of the arylidene moiety, spontaneous or 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ)-induced oxidation of the heteroring led to triazolo[1,5-a]pyrimidines and pyrazolo[1,5-a]pyrimidines in good yields, while, using the Jones reagent as a strong oxidant, 17-oxidation also occurred. The crystal structures of an arylidene and a triazolopyrimidine product have been determined by single crystal X-ray diffraction and both were found to crystallize in the monoclinic crystal system at P2₁ space group. Most derivatives were found to diminish the transcriptional activity of androgen receptor (AR) in reporter cell line. The candidate compound (17β-hydroxy-2-(4-chloro)benzylidene-5α-androstan-3-one, 2f) showed to suppress androgen-mediated AR transactivation in a dose-dependent manner. We confirmed the cellular interaction of 2f with AR, described the binding in AR-binding cavity by the flexible docking and showed the ability of the compound to suppress the expression of AR-regulated genes in two prostate cancer cell lines.

Mechanistic Insights into the Regio- and Stereoselectivities of Testosterone and Dihydrotestosterone Hydroxylation Catalyzed by CYP3A4 and CYP19A1

The hydroxylation of nonreactive C-H bonds can be easily catalyzed by a variety of metalloenzymes, especially cytochrome P450s (P450s). The mechanism of P450 mediated hydroxylation has been intensively studied, both experimentally and theoretically. However, understanding the regio- and stereoselectivities of substrates hydroxylated by P450s remains a great challenge. Herein, we use a multi-scale modeling approach to investigate the selectivity of testosterone (TES) and dihydrotestosterone (DHT) hydroxylation catalyzed by two important P450s, CYP3A4 and CYP19A1. For CYP3A4, two distinct binding modes for TES/DHT were predicted by dockings and molecular dynamics simulations, in which the experimentally identified sites of metabolism of TES/DHT can access to the catalytic center. The regio- and stereoselectivities of TES/DHT hydroxylation were further evaluated by quantum mechanical and ONIOM calculations. For CYP19A1, we found that sites 1β, 2β and 19 can access the catalytic center, with the intrinsic reactivity 2β>1β>19. However, our ONIOM calculations indicate that the hydroxylation is favored at site 19 for both TES and DHT, which is consistent with the experiments and reflects the importance of the catalytic environment in determining the selectivity. Our study unravels the mechanism underlying the selectivity of TES/DHT hydroxylation mediated by CYP3A4 and CYP19A1 and is helpful for understanding the selectivity of other substrates that are hydroxylated by P450s.

Molecular insights into how SHBG dimerization exerts changes on ligand molecular recognition

Sex hormone binding globulin (SHBG) is a homodimeric glycoprotein and is the major carrier protein for sex steroids in plasma, regulating sex hormone availability in most vertebrate groups. Although it was initially thought that human dimeric SHBG bound a single ligand at the homodimer interface, studies demonstrated that dimeric SHBG binds a ligand to each subunit with similar affinity. In fact, the findings from recent experimental studies suggest that ligand binding to the SHBG dimer involves a complex allosteric mechanism involving conformational changes that limit observations of the presence of allosteric regulation. Therefore, we combined structural data with molecular dynamics simulations using Molecular Mechanics Generalized-Born Surface Area (MMGBSA) to dissect the structural and energetic basis for molecular recognition between five ligands whose affinities and binding positions on SHBG are known, i.e., 3β,17α-diol; 3β,17β-diol; DHT; norgestrel (NOG); and estradiol (E2), and monomeric and dimeric SHBG. Protein-ligand complexes, involving dimeric SHBG saturated with two ligands on each subunit, reproduce the experimental affinity tendency and allow the observation that dimerization exerts disparate effects on binding affinity, characteristic of negative cooperativity for E2, DHT, and NOG, whereas 3β-17α-diol and 3β-17β-diol lack allostery.

Formation of 5α-dihydrotestosterone from 5α-androstane-3α,17β-diol in prostate cancer LAPC-4 cells - Identifying inhibitors of non-classical pathways producing the most potent androgen

5α-Dihydrotestosterone (5α-DHT) possesses a great affinity for the androgen receptor (AR), and its binding to AR promotes the proliferation of prostate cancer (PC) cells in androgen-dependent PC. Primarily synthesized from testosterone (T) in testis, 5α-DHT could also be produced from 5α-androstane-3α,17β-diol (3α-diol), an almost inactive androgen, following non-classical pathways. We reported the chemical synthesis of non-commercially available [4-¹⁴C]-3α-diol from [4-¹⁴C]-T, and the development of a biological assay to identify inhibitors of the 5α-DHT formation from radiolabeled 3α-diol in LAPC-4 cell PC model. We measured the inhibitory potency of 5α-androstane derivatives against the formation of 5α-DHT, and inhibition curves were obtained for the most potent compounds (IC₅₀ = 1.2-14.1 μM). The most potent inhibitor 25 (IC₅₀ = 1.2 μM) possesses a 4-(4-CF₃-3-CH₃O-benzyl)piperazinyl methyl side chain at C3β and 17β-OH/17α-CCH functionalities at C17 of a 5α-androstane core.

Fluorine-18 Labeled Fluorofuranylnorprogesterone ([18F]FFNP) and Dihydrotestosterone ([18F]FDHT) Prepared by "Fluorination on Sep-Pak" Method

To further explore the scope of our recently developed “fluorination on Sep-Pak” method, we prepared two well-known positron emission tomography (PET) tracers 21-[¹⁸F]fluoro-16α,17α-[(R)-(1′-α-furylmethylidene)dioxy]-19-norpregn-4-ene-3,20-dione furanyl norprogesterone ([¹⁸F]FFNP) and 16β-[¹⁸F]fluoro-5α-dihydrotestosterone ([¹⁸F]FDHT). Following the “fluorination on Sep-Pak” method, over 70% elution efficiency was observed with 3 mg of triflate precursor of [¹⁸F]FFNP. The overall yield of [¹⁸F]FFNP was 64–72% (decay corrected) in 40 min synthesis time with a molar activity of 37–81 GBq/µmol (1000–2200 Ci/mmol). Slightly lower elution efficiency (~55%) was observed with the triflate precursor of [¹⁸F]FDHT. Fluorine-18 labeling, reduction, and deprotection to prepare [¹⁸F]FDHT were performed on Sep-Pak cartridges (PS-HCO₃ and Sep-Pak plus C-18). The overall yield of [¹⁸F]FDHT was 25–32% (decay corrected) in 70 min. The molar activity determined by using mass spectrometry was 63–148 GBq/µmol (1700–4000 Ci/mmol). Applying this quantitative measure of molar activity to in vitro assays [¹⁸F]FDHT exhibited high-affinity binding to androgen receptors (K_d~2.5 nM) providing biological validation of this method.

Anti-Cancer Activity of Novel Dihydrotestosterone-Derived Ring A-Condensed Pyrazoles on Androgen Non-Responsive Prostate Cancer Cell Lines

Regioselective synthesis of novel ring A-fused arylpyrazoles of dihydrotestosterone (DHT) was carried out in two steps under facile reaction conditions. Aldol condensation of DHT with acetaldehyde afforded a 2-ethylidene derivative regio- and stereo-selectively, which was reacted with different arylhydrazines in the presence of iodine via microwave-assisted oxidative cyclization reactions. The 17-keto analogs of steroidal pyrazoles were also synthesized by simple oxidation in order to enlarge the compound library available for pharmacological studies and to obtain structure–activity relationship. The antiproliferative activities of the structurally related heteroaromatic compounds were tested in vitro on human cervical and breast adenocarcinoma cell lines (HeLa, MCF-7 and MDA-MB-231) and on two androgen-independent malignant prostate carcinoma cell lines (PC-3 and DU 145). Based on primary cytotoxicity screens and IC₅₀ assessment, a structure-function relationship was identified, as derivatives carrying a hydroxyl group on C-17 exhibit stronger activity compared to the 17-one counterparts. Cancer cell selectivity of the derivatives was also determined using non-cancerous MRC-5 cells. Furthermore, the proapoptotic effects of some selected derivatives were verified on androgen therapy refractive p53-deficient PC-3 cells. The present study concludes that novel DHT-derived arylpyrazoles exert cancer cell specific antiproliferative activity and activate apoptosis in PC-3 cells.

Loss of dihydrotestosterone-inactivation activity promotes prostate cancer castration resistance detectable by functional imaging

Androgens such as testosterone and dihydrotestosterone are a critical driver of prostate cancer progression. Cancer resistance to androgen deprivation therapies ensues when tumors engage metabolic processes that produce sustained androgen levels in the tissue. However, the molecular mechanisms involved in this resistance process are unclear, and functional imaging modalities that predict impending resistance are lacking. Here, using the human LNCaP and C4-2 cell line models of prostate cancer, we show that castration treatment-sensitive prostate cancer cells that normally have an intact glucuronidation pathway that rapidly conjugates and inactivates dihydrotestosterone and thereby limits androgen signaling, become glucuronidation deficient and resistant to androgen deprivation. Mechanistically, using CRISPR/Cas9-mediated gene ablation, we found that loss of UDP glucuronosyltransferase family 2 member B15 (UGT2B15) and UGT2B17 is sufficient to restore free dihydrotestosterone, sustained androgen signaling, and development of castration resistance. Furthermore, loss of glucuronidation enzymatic activity was also detectable with a nonsteroid glucuronidation substrate. Of note, glucuronidation-incompetent cells and the resultant loss of intracellular conjugated dihydrotestosterone were detectable in vivo by 18F-dihydrotestosterone PET. Together, these findings couple a mechanism with a functional imaging modality to identify impending castration resistance in prostate cancers.

Another cat and mouse game: Deciphering the evolution of the SCGB superfamily and exploring the molecular similarity of major cat allergen Fel d 1 and mouse ABP using computational approaches

The mammalian secretoglobin (SCGB) superfamily contains functionally diverse members, among which the major cat allergen Fel d 1 and mouse salivary androgen-binding protein (ABP) display similar subunits. We searched for molecular similarities between Fel d 1 and ABP to examine the possibility that they play similar roles. We aimed to i) cluster the evolutionary relationships of the SCGB superfamily; ii) identify divergence patterns, structural overlap, and protein-protein docking between Fel d 1 and ABP dimers; and iii) explore the residual interaction between ABP dimers and steroid binding in chemical communication using computational approaches. We also report that the evolutionary tree of the SCGB superfamily comprises seven unique palm-like clusters, showing the evolutionary pattern and divergence time tree of Fel d 1 with 28 ABP paralogs. Three ABP subunits (A27, BG27, and BG26) share phylogenetic relationships with Fel d 1 chains. The Fel d 1 and ABP subunits show similarities in terms of sequence conservation, identical motifs and binding site clefts. Topologically equivalent positions were visualized through superimposition of ABP A27:BG27 (AB) and ABP A27:BG26 (AG) dimers on a heterodimeric Fel d 1 model. In docking, Fel d 1-ABP dimers exhibit the maximum surface binding ability of AG compared with that of AB dimers and the several polar interactions between ABP dimers with steroids. Hence, cat Fel d 1 is an ABP-like molecule in which monomeric chains 1 and 2 are the equivalent of the ABPA and ABPBG monomers, respectively. These findings suggest that the biological and molecular function of Fel d 1 is similar to that of ABP in chemical communication, possibly via pheromone and/or steroid binding.

Transport of steroid 3-sulfates and steroid 17-sulfates by the sodium-dependent organic anion transporter SOAT (SLC10A6)

The sodium-dependent organic anion transporter SOAT/Soat shows highly specific transport activity for sulfated steroids. SOAT substrates identified so far include dehydroepiandrosterone sulfate, 16α-hydroxydehydroepiandrosterone sulfate, estrone-3-sulfate, pregnenolone sulfate, 17β-estradiol-3-sulfate, and androstenediol sulfate. Apart from these compounds, many other sulfated steroids occur in mammals. Therefore, we aimed to expand the substrate spectrum of SOAT and analyzed the SOAT-mediated transport of eight different sulfated steroids by combining in vitro transport experiments in SOAT-transfected HEK293 cells with LC-MS/MS analytics of cell lysates. In addition, we aimed to better understand the structural requirements for SOAT substrates and so selected structural pairs varying only at specific positions: 3α/3β-sulfate, 17α/17β-sulfate, mono-sulfate/di-sulfate, and 17α-hydroxylation. We found significant and sodium-dependent SOAT-mediated transport of 17α-hydroxypregnenolone sulfate, 17β-estradiol-17-sulfate, androsterone sulfate, epiandrosterone sulfate, testosterone sulfate, epitestosterone sulfate, and 5α-dihydrotestosterone sulfate. However, 17β-estradiol-3,17-disulfate was not transported by SOAT.

IN CONCLUSION

SOAT substrates from the group of sulfated steroids are characterized by a planar and lipophilic steroid backbone in trans-trans-trans conformation of the rings and a negatively charged mono-sulfate group at positions 3' or 17' with flexibility for α- or β- orientation. Furthermore, 5α-reduction, 16α-hydroxylation, and 17α-hydroxylation are acceptable for SOAT substrate recognition, whereas addition of a second negatively charged sulfate group seems to abolish substrate binding to SOAT, and so 17β-estradiol-3,17-disulfate is not transported by SOAT.

Stability of compounded trilostane suspension in cod liver oil

Trilostane is a synthetic steroid analog used to treat canine hyperadrenocorticism. For small dogs, the dose found in commercially available dosage forms of trilostane is sometimes too high. Compounding trilostane in a liquid diluent provides an option for more precise dosing and adjustments, and can be easier to administer, versus a tablet or capsule. Trilostane suspends well in cod liver oil, which is generally palatable to dogs. The stability of a compounded trilostane suspension in cod liver oil stored at room temperature was investigated for 90 days. Compounded trilostane retained stability, defined as maintaining 90-105% labeled value, for 60 days when stored in amber glass bottles. However, drug potency fell >10% below the labeled value when stored in amber plastic bottles after 7 days.

DHRS7 (SDR34C1) - A new player in the regulation of androgen receptor function by inactivation of 5α-dihydrotestosterone?

DHRS7 (SDR34C1) has been associated with potential tumor suppressor effects in prostate cancer; however, its function remains largely unknown. Recent experiments using purified recombinant human DHRS7 suggested several potential substrates, including the steroids cortisone and Δ4-androstene-3,17-dione (androstenedione). However, the substrate and cofactor concentrations used in these experiments were very high and the physiological relevance of these observations needed to be further investigated. In the present study, recombinant human DHRS7 was expressed in intact HEK-293 cells in order to investigate whether glucocorticoids and androgens serve as substrates at sub-micromolar concentrations and at physiological cofactor concentrations. Furthermore, the membrane topology of DHRS7 was revisited using redox-sensitive green-fluorescent protein fusions in living cells. The results revealed that (1) cortisone is a substrate of DHRS7; however, it is not reduced to cortisol but to 20β-dihydrocortisone, (2) androstenedione is not a relevant substrate of DHRS7, (3) DHRS7 catalyzes the oxoreduction of 5α-dihydrotestosterone (5αDHT) to 3α-androstanediol (3αAdiol), with a suppressive effect on androgen receptor (AR) transcriptional activity, and (4) DHRS7 is anchored in the endoplasmic reticulum membrane with a cytoplasmic orientation. Together, the results show that DHRS7 is a cytoplasmic oriented enzyme exhibiting 3α/20β-hydroxysteroid dehydrogenase activity, with a possible role in the modulation of AR function. Further research needs to address the physiological relevance of DHRS7 in the inactivation of 5αDHT and AR regulation.

The fluorescent two-hybrid assay for live-cell profiling of androgen receptor modulators

The androgen receptor (AR) is an important target for drug therapies combating prostate cancer. However, various acquired mutations within the AR sequence often render this receptor resistant to treatment. Ligand-induced interaction between the N- and C-termini of the AR marks the initial step in the AR signaling cascade and can thus serve as an early read-out for analysis of potential antagonists of wt and mutant AR. To measure changes of the N/C interaction in the wt and mutant AR variants upon the addition of inhibitors, we applied our recently developed Fluorescent Two-Hybrid (F2H) assay. The F2H method enables real-time monitoring and quantitative analysis of the interactions between GFP- and RFP-tagged proteins in live mammalian cells, where GFP-tagged proteins are tethered to a specific nuclear location. This anchoring approach provides a local signal enrichment suitable for direct visualization of protein-protein interactions as co-localizations by conventional epifluorescence microscopy. Since the F2H assay is fully reversible, we could monitor dynamics of AR N/C interactions in living cells in real time upon agonistic, as well as antagonistic treatments. In dose-response F2H experiments, we compared the potencies of abiraterone, bicalutamide, enzalutamide, flutamide, and galeterone/TOK-001 to prevent the dihydrotestosterone-induced N/C interaction in wt AR. We further applied the newly developed F2H assay to analyze how the AR N/C interaction is affected by the clinically relevant mutations W741L, F876L, T877A and F876L/T877A. We conclude that F2H is a reliable and technically undemanding approach for straightforward screening of new AR modulators, as well as for monitoring their activity in real time in living cells.

Studies on Chromatographic Fingerprint and Fingerprinting Profile-Efficacy Relationship of Saxifraga stolonifera Meerb

This work investigated the spectrum-effect relationships between high performance liquid chromatography (HPLC) fingerprints and the anti-benign prostatic hyperplasia activities of aqueous extracts from Saxifraga stolonifera. The fingerprints of S. stolonifera from various sources were established by HPLC and evaluated by similarity analysis (SA), hierarchical clustering analysis (HCA) and principal component analysis (PCA). Nine samples were obtained from these 24 batches of different origins, according to the results of SA, HCA and the common chromatographic peaks area. A testosterone-induced mouse model of benign prostatic hyperplasia (BPH) was used to establish the anti-benign prostatic hyperplasia activities of these nine S. stolonifera samples. The model was evaluated by analyzing prostatic index (PI), serum acid phosphatase (ACP) activity, concentrations of serum dihydrotestosterone (DHT), prostatic acid phosphatase (PACP) and type II 5α-reductase (SRD5A2). The spectrum-effect relationships between HPLC fingerprints and anti-benign prostatic hyperplasia activities were investigated using Grey Correlation Analysis (GRA) and partial least squares regression (PLSR). The results showed that a close correlation existed between the fingerprints and anti-benign prostatic hyperplasia activities, and peak 14 (chlorogenic acid), peak 17 (quercetin 5-O-β-d-glucopyranoside) and peak 18 (quercetin 3-O-β-l-rhamno-pyranoside) in the HPLC fingerprints might be the main active components against anti-benign prostatic hyperplasia. This work provides a general model for the study of spectrum-effect relationships of S. stolonifera by combing HPLC fingerprints with a testosterone-induced mouse model of BPH, which can be employed to discover the principle components of anti-benign prostatic hyperplasia bioactivity.

Hamster SRD5A3 lacks steroid 5α-reductase activity in vitro

According to current knowledge, two steroid 5α-reductases, designated type 1 (SRD5A1) and type 2 (SRD5A2), are present in all species examined to date. These isozymes play a central role in steroid hormone physiology by catalyzing the reduction of 3-keto-4-ene-steroids into more active 5α-reduced derivatives, including the conversion of testosterone (T) to dihydrotestosterone (DHT). A third 5α-reductase (SRD5A3, -type 3), which is overexpressed in hormone-refractory prostate cancer cells, has been identified; however, its enzymatic characteristics are practically unknown. Here, we isolated a cDNA encoding hamster Srd5a3 (hSrd5a3) and performed functional metabolic assays to investigate its biochemical properties. The cloned cDNA encodes a 330 amino acid protein that is 87% identical to the homologous protein in mice and 78% to that in humans. However, hSrd5a3 exhibits low sequence homology with its counterparts hSrd5a1 (19%) and hSrd5a2 (17%). A fusion protein consisting of hSrd5a3 and green fluorescent protein provided evidence for cytoplasmic localization in transfected mammalian cells. Real-time PCR analysis revealed that, Srd5a3 mRNA was present in nearly all hamster tissues, with high expression in the cerebellum, Harderian gland and testis. Functional assays expressing hSrd5a3 cDNA in HEK-293 cells revealed that this isozyme is unable to reduce T into DHT. Further expression assays confirmed that similar to testosterone, progesterone, androstenedione and corticosterone are not reduced by hSrd5a3 or human SRD5A3. Together, these results indicate that hSrd5a3 lacks the catalytic activity to transform 3-keto-4-ene-compounds; therefore 5α-reductase type 3 may not be involved in 5α-reduction of steroids.

Human 3-alpha hydroxysteroid dehydrogenase type 3 (3α-HSD3): the V54L mutation restricting the steroid alternative binding and enhancing the 20α-HSD activity

Human 3-alpha hydroxysteroid dehydrogenase type 3 (3α-HSD3) has an essential role in the inactivation of 5α-dihydrotestosterone (DHT). Notably, human 3α-HSD3 shares 97.8% sequence identity with human 20-alpha hydroxysteroid dehydrogenase (20α-HSD) and there is only one amino acid difference (residue 54) that is located in their steroid binding pockets. However, 20α-HSD displays a distinctive ability in transforming progesterone to 20α-hydroxy-progesterone (20α-OHProg). In this study, to understand the role of residue 54 in the steroid binding and discrimination, the V54L mutation in human 3α-HSD3 has been created. We have solved two crystal structures of the 3α-HSD3·NADP(+)·Progesterone complex and the 3α-HSD3 V54L·NADP(+)·progesterone complex. Interestingly, progesterone adopts two different binding modes to form complexes within the wild type enzyme, with one binding mode similar to the orientation of a bile acid (ursodeoxycholate) in the reported ternary complex of human 3α-HSD3·NADP(+)·ursodeoxycholate and the other binding mode resembling the orientation of 20α-OHProg in the ternary complex of human 20α-HSD·NADP(+)·20α-OHProg. However, the V54L mutation directly restricts the steroid binding modes to a unique one, which resembles the orientation of 20α-OHProg within human 20α-HSD. Furthermore, the kinetic study has been carried out. The results show that the V54L mutation significantly decreases the 3α-HSD activity for the reduction of DHT, while this mutation enhances the 20α-HSD activity to convert progesterone.

Functional mechanism of C-terminal tail in the enzymatic role of porcine testicular carbonyl reductase: a combined experiment and molecular dynamics simulation study of the C-terminal tail in the enzymatic role of PTCR

Porcine testicular carbonyl reductase, PTCR which is one of the short chain dehydrogenases/reductases (SDR) superfamily catalyzes the NADPH-dependent reduction of carbonyl compounds including steroids and prostaglandins. Previously we reported C- terminal tail of PTCR was deleted due to a nonsynonymous single nucleotide variation (nsSNV). Here we identified from kinetic studies that the enzymatic properties for 5α-dihydrotestosterone (5α-DHT) were different between wild-type and C-terminal-deleted PTCRs. Compared to wild-type PTCR, C-terminal-deleted PTCR has much higher reduction rate. To investigate structural difference between wild-type and C-terminal-deleted PTCRs upon 5α-DHT binding, we performed molecular dynamics simulations for two complexes. Using trajectories, molecular interactions including hydrogen bonding patterns, distance between 5α-DHT and catalytic Tyr193, and interaction energies are analyzed and compared. During the MD simulation time, the dynamic behavior of C-terminal tail in wild-type PTCR is also examined using essential dynamics analysis. The results of our simulations reveal that the binding conformation of 5α-DHT in C-terminal-deleted PTCR is more favorable for reduction reaction in PTCR, which shows strong agreement with kinetic data. These structural findings provide valuable information to understand substrate specificity of PTCR and further kinetic properties of enzymes belonging to the SDR superfamily.

Molecular and structural basis of androgen receptor responses to dihydrotestosterone, medroxyprogesterone acetate and Δ(4)-tibolone

Medroxyprogesterone acetate (MPA) has widely been used in hormone replacement therapy (HRT), and is associated with an increased risk of breast cancer, possibly due to disruption of androgen receptor (AR) signaling. In contrast, the synthetic HRT Tibolone does not increase breast density, and is rapidly metabolized to estrogenic 3α-OH-tibolone and 3β-OH-tibolone, and a delta-4 isomer (Δ(4)-TIB) that has both androgenic and progestagenic properties. Here, we show that 5α-dihydrotestosterone (DHT) and Δ(4)-TIB, but not MPA, stabilize AR protein levels, initiate specific AR intramolecular interactions critical for AR transcriptional regulation, and increase proliferation of AR positive MDA-MB-453 breast cancer cells. Structural modeling and molecular dynamic simulation indicate that Δ(4)-TIB induces a more stable AR structure than does DHT, and MPA a less stable one. Microarray expression analyses confirms that the molecular actions of Δ(4)-TIB more closely resembles DHT in breast cancer cells than either ligand does to MPA.

A new simple and high-yield synthesis of 5α-dihydrotestosterone (DHT), a potent androgen receptor agonist

We have devised an efficient procedure for the synthesis of 5α-dihydrotestosterone (DHT) (1) starting from 3β-hydroxy-5α-androstan-17-one, providing the product in unprecedented 82% yield. A reported method of using toxic Jones reagent is replaced by milder oxidizing agent (NMO/TPAP) in the synthesis of a key intermediate 17β-[(tert-butyldimethylsilyl)oxy]-5α-androstan-3-one (18). This new procedure is simple, does not require special apparatus/precautions or chromatographic purification in most of the steps.

Phylogenetic comparisons implicate sex hormone-binding globulin in "masculinization" of the female spotted hyena (Crocuta crocuta)

Exposures to sex steroids during fetal development are thought to contribute to the unique urogenital anatomy and social dominance of the female spotted hyena: overt phenotypes not shared by other hyenids (i.e. striped hyena, brown hyena, and aardwolf). Because both androgens and estrogens influence development of genitalia and behavior, and because plasma SHBG regulates their access to tissues, we compared the Shbg gene sequences, structures, and steroid-binding properties in the four extant hyenids. We found the hyenid Shbg genes (>95% identical) and mature protein sequences (98% identical) are highly conserved. As in other mammals, the hyenid SHBG all bind 5α-dihydrotestosterone with high affinity (K(d) = 0.62-1.47 nm), but they also bind estrone and dehydroepiandrosterone with similarly high affinity, and this unusual property was attributed to specific amino acids within their SHBG steroid-binding sites. Phylogenetic comparisons also indicated that the spotted hyena SHBG precursor uniquely lacks two leucine residues and has a L15W substitution within its secretion signal polypeptide, the reduced size and hydrophobicity of which markedly decreases the production of SHBG and may therefore explain why serum SHBG concentrations in male and female spotted hyenas are approximately five times lower than in other hyenids. This is important because low plasma SHBG concentrations in spotted hyenas will increase exposure to biologically active androgens and estrogen as well as to their precursors (dehydroepiandrosterone and estrone), which may contribute to the masculinized external genitalia of female spotted hyenas and to female social dominance over males.

Structural features discriminate androgen receptor N/C terminal and coactivator interactions

Human androgen receptor (AR) transcriptional activity involves interdomain and coactivator interactions with the agonist-bound AR ligand binding domain (LBD). Structural determinants of the AR NH(2)- and carboxyl-terminal interaction between the AR NH(2)-terminal FXXLF motif and activation function 2 (AF2) in the LBD were shown previously by crystallography. In this report, we provide evidence for a region in AR LBD helix 12 outside the AF2 binding cleft that facilitates interactions with the FXXLF and LXXLL motifs. Mutagenesis of glutamine 902 to alanine in AR LBD helix 12 (Q902A) disrupted AR FXXLF motif binding to AF2, but enhanced coactivator LXXLL motif binding. Functional compensation for defective FXXLF motif binding by AR-Q902A was suggested by the slower dissociation rate of bound androgen. Functional importance of glutamine 902 was indicated by the charged residue germline mutation Q902R that caused partial androgen insensitivity, and a similar somatic mutation Q902K reported in prostate cancer, both of which increased the androgen dissociation rate and decreased AR transcriptional activity. High affinity equilibrium androgen binding was retained by alanine substitution mutations at Tyr-739 in AR LBD helix 5 or Lys-905 in helix 12 structurally adjacent to AF2, whereas transcriptional activity decreased and the androgen dissociation increased. Deleterious effects of these loss of function mutations were rescued by the helix stabilizing AR prostate cancer somatic mutation H874Y. Sequence NH(2)-terminal to the AR FXXLF motif contributed to the AR NH(2)- and carboxyl-terminal interaction based on greater AR-2-30 FXXLF motif peptide binding to the agonist-bound AR LBD than a shorter AR-20-30 FXXLF motif peptide. We conclude that helix 12 residues outside the AF2 binding cleft modulate AR transcriptional activity by providing flexibility to accommodate FXXLF or LXXLL motif binding.

The functions of key residues in the inhibitor, substrate and cofactor sites of human 3beta-hydroxysteroid dehydrogenase type 1 are validated by mutagenesis

In postmenopausal women, human 3beta-hydroxysteroid dehydrogenase type 1 (3beta-HSD1) is a critical enzyme in the conversion of DHEA to estradiol in breast tumors, while 3beta-HSD2 participates in the production of cortisol and aldosterone in the human adrenal gland. The goals of this project are to determine if Arg195 in 3beta-HSD1 vs. Pro195 in 3beta-HSD2 in the substrate/inhibitor binding site is a critical structural difference responsible for the higher affinity of 3beta-HSD1 for inhibitor and substrate steroids compared to 3beta-HSD2 and whether Asp61, Glu192 and Thr8 are fingerprint residues for cofactor and substrate binding using site-directed mutagenesis. The R195P-1 mutant of 3beta-HSD1 and the P195R-2 mutant of 3beta-HSD2 have been created, expressed, purified and characterized kinetically. Dixon analyses of the inhibition of the R195P-1 mutant, P195R-2 mutant, wild-type 3beta-HSD1 and wild-type 3beta-HSD2 by trilostane has produced kinetic profiles that show inhibition of 3beta-HSD1 by trilostane (K(i)=0.10microM, competitive) with a 16-fold lower K(i) and different mode than measured for 3beta-HSD2 (K(i)=1.60microM, noncompetitive). The R195P-1 mutation shifts the high-affinity, competitive inhibition profile of 3beta-HSD1 to a low-affinity (trilostane K(i)=2.56microM), noncompetitive inhibition profile similar to that of 3beta-HSD2 containing Pro195. The P195R-2 mutation shifts the low-affinity, noncompetitive inhibition profile of 3beta-HSD2 to a high-affinity (trilostane K(i)=0.19microM), competitive inhibition profile similar to that of 3beta-HSD1 containing Arg195. Michaelis-Menten kinetics for DHEA, 16beta-hydroxy-DHEA and 16alpha-hydroxy-DHEA substrate utilization by the R195P-1 and P195R-2 enzymes provide further validation for higher affinity binding due to Arg195 in 3beta-HSD1. Comparisons of the Michaelis-Menten values of cofactor and substrate for the targeted mutants of 3beta-HSD1 (D61N, D61V, E192A, T8A) clarify the functions of these residues as well.

Self-organizing molecular field analysis on pregnane derivatives as human steroidal 5alpha-reductase inhibitors

Normal growth and development of human prostate is regulated by the androgens which balances cell proliferation and apoptosis. Testosterone (T) and dihydrotestosterone (DHT) are the two key androgens that stimulate most of the androgen action in prostate. Testosterone is converted to DHT by the membrane bound NADPH-dependent 5alpha-reductase enzyme. As a consequence of the important observation that progesterone and deoxycortisone inhibits the synthesis of DHT by competing with 4-en-3-one function of the testosterone for the 5alpha-reductase enzyme a number of pregnane derivatives were synthesized and have been reported as inhibitors of human 5alpha-reductase enzyme. Due to lack of information on the crystal structure of human 5alpha-reductase, ligand-based 3D-QSAR study has been performed on pregnane derivatives using self-organizing molecular field analysis (SOMFA) for rationalizing the molecular properties and human 5alpha-reductase inhibitory activities. The statistical results having good cross-validated r(cv)(2) (0.881), non-cross-validated r(2) (0.893) and F-test value (175.527), showed satisfied predictive ability r(pred)(2) (0.777). Analysis of SOMFA models through electrostatic and shape grids provide useful information for the design and optimization of steroidal structure as novel human 5alpha-reductase inhibitors.

Development of highly sensitive quantification method for testosterone and dihydrotestosterone in human serum and prostate tissue by liquid chromatography-electrospray ionization tandem mass spectrometry

We developed highly sensitive detection of testosterone (T) and 5alpha-dihydrotestosterone (DHT) by liquid chromatography-electrospray ionization tandem mass spectrometry using high proton affinitive derivatization of 17beta-hydroxyl group of T and DHT with picolinic acid, mobile phase consisting of MeCN-MeOH-H(2)O-formic acid and conventional octadecylsilica (ODS) column. Purification of the derivatives was carried out using solid-phase extraction with ODS cartridge. By this method, T and DHT were determined simultaneously with limits of quantification (LOQs) of 1 pg/0.2 ml in serum, and T and DHT with LOQs of 0.5 pg and 1 pg/3mg in prostate tissue, respectively, under acceptable assay performance (intra-assay and inter-assay accuracy and precision). The present method provides reliable and reproducible results for quantification of T and DHT in small volumes of serum and prostate samples for diagnosis in prostatic disorders and male climacteric.

In vivo and in vitro effect of novel 4,16-pregnadiene-6,20-dione derivatives, as 5alpha-reductase inhibitors

In this study, we report the synthesis and biological evaluation of several new 3-substituted pregna-4,16-diene-6,20-dione derivatives (11a-11d). These compounds were prepared from the commercially available 16-dehydropregnenolone acetate. The biological effect of these steroids was demonstrated in in vivo and in vitro experiments. In the in vivo experiments, we measured the activity of the 11a-11d on the weight of the prostate gland of gonadectomized hamsters treated with testosterone plus finasteride or with the new steroids. For the studies in vitro, we determined the IC50 values by measuring the steroid concentration that inhibits 50% of the activity of 5alpha-reductase present in human prostate. In order to study the mechanism of action of 11a-11d, we also determined the capacity of these steroids to bind to the androgen receptor (AR) present in the rat prostate cytosol using labeled mibolerone as a tracer. The results from this work indicated that compounds 11a-11d significantly decreased the weight of the prostate as compared to testosterone treated animals and this reduction of the weight of the prostate was comparable to that produced by the finasteride. On the other hand 11a-11d exhibited a high inhibitory activity for the human 5alpha-reductase enzyme with IC50 values of 1.4 x 10(-8), 1.8 x 10(-9), 1.0 x 10(-8) and 4 x 10(-5) respectively. However the IC50 value of 11a (1.8 x 10(-9)) was the only one lower than that of finasteride (8.5 x 10(-9)). Nevertheless this compound did not show a higher potency in vivo as compared to that of compounds 11b-11d. The competition analysis for the androgen receptor indicated that the IC50 value of non-labeled mibolerone used in this experiment was 1nM, whereas steroids 10, 11a-11d did not inhibit the labeled mibolerone binding to the androgen receptor. On the other hand, steroid 10 did not show any activities in vitro or in vivo, and for this reason these steroidal derivatives (11a-11d) cannot be considered as prodrugs of compound 10. In conclusion, the compounds containing chlorine 11a, bromine 11b, iodine 11c atoms, and 11d (without any substituent in the ester moiety) at C-3 produce a significant decrease of the prostate weight in castrated animals treated with T and inhibits the activity of the 5alpha-reductase. Apparently the presence of the halogen atoms in compounds 11a-11c enhances the inhibitory activity for the 5alpha-reductase enzyme.

Modulation of androgen receptor activation function 2 by testosterone and dihydrotestosterone

The androgen receptor (AR) is transcriptionally activated by high affinity binding of testosterone (T) or its 5alpha-reduced metabolite, dihydrotestosterone (DHT), a more potent androgen required for male reproductive tract development. The molecular basis for the weaker activity of T was investigated by determining T-bound ligand binding domain crystal structures of wild-type AR and a prostate cancer somatic mutant complexed with the AR FXXLF or coactivator LXXLL peptide. Nearly identical interactions of T and DHT in the AR ligand binding pocket correlate with similar rates of dissociation from an AR fragment containing the ligand binding domain. However, T induces weaker AR FXXLF and coactivator LXXLL motif interactions at activation function 2 (AF2). Less effective FXXLF motif binding to AF2 accounts for faster T dissociation from full-length AR. T can nevertheless acquire DHT-like activity through an AR helix-10 H874Y prostate cancer mutation. The Tyr-874 mutant side chain mediates a new hydrogen bonding scheme from exterior helix-10 to backbone protein core helix-4 residue Tyr-739 to rescue T-induced AR activity by improving AF2 binding of FXXLF and LXXLL motifs. Greater AR AF2 activity by improved core helix interactions is supported by the effects of melanoma antigen gene protein-11, an AR coregulator that binds the AR FXXLF motif and targets AF2 for activation. We conclude that T is a weaker androgen than DHT because of less favorable T-dependent AR FXXLF and coactivator LXXLL motif interactions at AF2.

Structural characterization of the human androgen receptor ligand-binding domain complexed with EM5744, a rationally designed steroidal ligand bearing a bulky chain directed toward helix 12

Antiandrogens are commonly used to treat androgen-dependent disorders. The currently used drugs unfortunately possess very weak affinity for the human AR (hAR), thus indicating the need to develop new high-affinity steroidal antiandrogens. Our compounds are specially designed to impede repositioning of the mobile carboxyl-terminal helix 12, which blocks the ligand-dependent transactivation function (AF-2) located in the AR ligand-binding domain (ARLBD). Using crystal structures of the hARLBD, we first found that H12 could be directly reached from the ligand-binding pocket (LBP) by a chain positioned on the C18 atom of an androgen steroid nucleus. A set of 5alpha-dihydrotestosterone-derived molecules bearing various C18 chains were thus synthesized and tested for their capacity to bind hAR and act as antagonists. Although most of those having very high affinity for hAR were agonists, several very potent antagonists were obtained, confirming the structural importance of the C18 chain. To understand the role of the C18 chain in their agonistic/antagonistic properties, the structure of the hARLBD complexed with one of these agonists, EM5744, was determined at a 1.65-A resolution. We have identified new interactions involving Gln(738), Met(742), and His(874) that explain both the high affinity of this compound and the inability of its bulky chain to prevent the repositioning of H12. This structural information will be helpful to refine the structure of the chains placed on the C18 atom to obtain efficient H12-directed steroidal antiandrogens.

Rv1106c from Mycobacterium tuberculosis is a 3beta-hydroxysteroid dehydrogenase

New approaches are required to combat Mycobacterium tuberculosis (Mtb), especially the multi-drug resistant and extremely drug resistant organisms (MDR-TB and XDR-TB). There are many reports that mycobacteria oxidize 3beta-hydroxysterols to 3-ketosteroids, but the enzymes responsible for this activity have not been identified in mycobacterial species. In this work, the Rv1106c gene that is annotated as a 3beta-hydroxysteroid dehydrogenase in Mtb has been cloned and heterologously expressed. The purified enzyme was kinetically characterized and found to have a pH optimum between 8.5 and 9.5. The enzyme, which is a member of the short chain dehydrogenase superfamily, uses NAD+ as a cofactor and oxidizes cholesterol, pregnenolone, and dehydroepiandrosterone to their respective 3-keto-4-ene products. The enzyme forms a ternary complex with NAD+ binding before the sterol. The enzyme shows no substrate preference for dehydroepiandrosterone versus pregnenolone with second-order rate constants (kcat/Km) of 3.2 +/- 0.4 and 3.9 +/- 0.9 microM-1 min-1, respectively, at pH 8.5, 150 mM NaCl, 30 mM MgCl2, and saturating NAD+. Trilostane is a competitive inhibitor of dehydroepiandrosterone with a Ki of 197 +/- 8 microM. The expression of the 3beta-hydroxysteroid dehydrogenase in Mtb is intracellular. Disruption of the 3beta-hydroxysteroid dehydrogenase gene in Mtb abrogates mycobacterial cholesterol oxidation activity. These data are consistent with the Rv1106c gene being the one responsible for 3beta-hydroxysterol oxidation in Mtb.

Exciton self-trapping in tetrafluoro-dimethyl-aminoacridine single crystals

The UV-visible optical spectra of 1,2,3,4-tetrafluoro-7-(N,N)dimethyl-amino-acridine single crystals are reported. The results are discussed on the basis of the molecular transitions and crystal packing in the framework of the theory of molecular excitons under a fluctuating potential field due to dynamic disorder. A strong local geometry distortion is demonstrated by applying the Urbach rule to the absorption tails, which is the amplitude of the local potential fluctuation being larger than the intermolecular transfer energy. The lineshape and linewidth of the emission band and its temperature dependence give further evidence of exciton self-trapping.

Discovery of 7α-substituted dihydrotestosterones as androgen receptor pure antagonists and their structure–activity relationships

A series of 7alpha-substituted dihydrotestosterone derivatives were synthesized and evaluated for androgen receptor (AR) pure antagonistic activity. From reporter gene assay (RGA), the compound with a side chain containing N-n-butyl-N-methyl amide (19a) showed pure antagonistic activity (IC(50)=340nM, FI(5)>10,000nM), whereas known AR antagonists showed partial agonistic activities. The optimization of 19a led to compound 23 (CH4892280), which showed more potent pure antagonistic activity (IC(50)=190nM, FI(5)>10,000nM). The SARs of tested compounds suggested that the length of the side chain and the substituents on the amide nitrogen are important for pure antagonistic activities.

Pharmacological and x-ray structural characterization of a novel selective androgen receptor modulator: potent hyperanabolic stimulation of skeletal muscle with hypostimulation of prostate in rats

A novel, highly potent, orally active, nonsteroidal tissue selective androgen receptor (AR) modulator (BMS-564929) has been identified, and this compound has been advanced to clinical trials for the treatment of age-related functional decline. BMS-564929 is a subnanomolar AR agonist in vitro, is highly selective for the AR vs. other steroid hormone receptors, and exhibits no significant interactions with SHBG or aromatase. Dose response studies in castrated male rats show that BMS-564929 is substantially more potent than testosterone (T) in stimulating the growth of the levator ani muscle, and unlike T, highly selective for muscle vs. prostate. Key differences in the binding interactions of BMS-564929 with the AR relative to the native hormones were revealed through x-ray crystallography, including several unique contacts located in specific helices of the ligand binding domain important for coregulatory protein recruitment. Results from additional pharmacological studies effectively exclude alternative mechanistic contributions to the observed tissue selectivity of this unique, orally active androgen. Because concerns regarding the potential hyperstimulatory effects on prostate and an inconvenient route of administration are major drawbacks that limit the clinical use of T, the potent oral activity and tissue selectivity exhibited by BMS-564929 are expected to yield a clinical profile that provides the demonstrated beneficial effects of T in muscle and other tissues with a more favorable safety window.

Multiple steps determine the overall rate of the reduction of 5alpha-dihydrotestosterone catalyzed by human type 3 3alpha-hydroxysteroid dehydrogenase: implications for the elimination of androgens

Human type 3 3alpha-hydroxysteroid dehydrogenase, or aldo-keto reductase (AKR) 1C2, eliminates the androgen signal in human prostate by reducing 5alpha-dihydrotestosterone (DHT, potent androgen) to form 3alpha-androstanediol (inactive androgen), thereby depriving the androgen receptor of its ligand. The k(cat) for the NADPH-dependent reduction of DHT catalyzed by AKR1C2 is 0.033 s(-1). We employed transient kinetics and kinetic isotope effects to dissect the contribution of discrete steps to this low k(cat) value. Stopped-flow experiments to measure the formation of the AKR1C2.NADP(H) binary complex indicated that two slow isomerization events occur to yield a tight complex. A small primary deuterium isotope effect on k(cat) (1.5) and a slightly larger effect on k(cat)/K(m) (2.1) were observed in the steady state. In the transient state, the maximum rate constant for the single turnover of DHT (k(trans)) was determined to be 0.11 s(-1) for the NADPH-dependent reaction, which was approximately 4-fold greater than the corresponding k(cat) x k(trans) was significantly reduced when NADPD was substituted for NADPH, resulting in an apparent (D)k(trans) of 3.5. Thus, the effects of isotopic substitution on the hydride transfer step were masked by slow events that follow or precede the chemical transformation. Transient multiple-turnover reactions generated curvilinear reaction traces, consistent with the product formation and release occurring at comparable rates. Global fitting analysis of the transient kinetic data enabled the estimate of the rate constants for the three-step cofactor binding/release model and for the minimal ordered bi-bi turnover mechanism. Results were consistent with a kinetic mechanism in which a series of slow events, including the chemical step (0.12 s(-1)), the release of the steroid product (0.081 s(-1)), and the release of the cofactor product (0.21 s(-1)), combine to yield the overall observed low turnover number.

Comparison of crystal structures of human androgen receptor ligand-binding domain complexed with various agonists reveals molecular determinants responsible for binding affinity

Androgens exert their effects by binding to the highly specific androgen receptor (AR). In addition to natural potent androgens, AR binds a variety of synthetic agonist or antagonist molecules with different affinities. To identify molecular determinants responsible for this selectivity, we have determined the crystal structure of the human androgen receptor ligand-binding domain (hARLBD) in complex with two natural androgens, testosterone (Testo) and dihydrotestosterone (DHT), and with an androgenic steroid used in sport doping, tetrahydrogestrinone (THG), at 1.64, 1.90, and 1.75 A resolution, respectively. Comparison of these structures first highlights the flexibility of several residues buried in the ligand-binding pocket that can accommodate a variety of ligand structures. As expected, the ligand structure itself (dimension, presence, and position of unsaturated bonds that influence the geometry of the steroidal nucleus or the electronic properties of the neighboring atoms, etc.) determines the number of interactions it can make with the hARLBD. Indeed, THG--which possesses the highest affinity--establishes more van der Waals contacts with the receptor than the other steroids, whereas the geometry of the atoms forming electrostatic interactions at both extremities of the steroid nucleus seems mainly responsible for the higher affinity measured experimentally for DHT over Testo. Moreover, estimation of the ligand-receptor interaction energy through modeling confirms that even minor modifications in ligand structure have a great impact on the strength of these interactions. Our crystallographic data combined with those obtained by modeling will be helpful in the design of novel molecules with stronger affinity for the AR.

Solvent effects on infrared spectroscopy of 17beta-hydroxy-17-methyl-2-oxa-5alpha-androstan-3-one in single solvents

Infrared spectroscopy studies of 17beta-hydroxy-17-methyl-2-oxa-5alpha-androstan-3-one (HMOA) in 20 different pure organic solvents were undertaken to investigate the solute-solvent interactions and to correlate solvent properties, such as the KBM equation, the solvent acceptor number (AN), Schleyer's linear free energy equation (G-value), Dimroth and Reichardt's parameter E(T)(30) and Brownstein's parameter S with the frequency shifts of the carbonyl stretching vibration for solute. The result indicated that the KBM relationship is unsuitable to the complicated molecules. These frequencies exhibited a better correlation with the solvent parameters AN and G-value than others.

Radical cross-linked albumin microspheres as potential drug delivery systems: preparation and in vitro studies

The aim of this research is the preparation of acryloylated bovine serum albumin microspheres and the evaluation of their employment in drug delivery. The influence of preparation parameters on albumin microspheres and the chemicophysical properties of loaded drugs were investigated. In particular, we focused our attention on acylation albumin degree, amount of acryloylated albumin against comonomer in the polymerization step, and finally the release profile. We considered on the interaction drug-matrix, the fuctionalization degree of albumin, and the water affinity of matrix.

Pharmacologic Basis for the Enhanced Efficacy of Dutasteride against Prostatic Cancers

PURPOSE

Prostatic dihydrotestosterone (DHT) concentration is regulated by precursors from systemic circulation and prostatic enzymes of androgen metabolism, particularly 5alpha-reductases (i.e., SRD5A1 and SRD5A2). Therefore, the levels of expression SRD5A1 and SRD5A2 and the antiprostatic cancer growth response to finasteride, a selective SRD5A2 inhibitor, versus the dual SRD5A1 and SRD5A2 inhibitor, dutasteride, were compared.

EXPERIMENTAL DESIGN

Real-time PCR and enzymatic assays were used to determine the levels of SRD5A1 and SRD5A2 in normal versus malignant rat and human prostatic tissues. Rats bearing the Dunning R-3327H rat prostate cancer and nude mice bearing LNCaP or PC-3 human prostate cancer xenografts were used as model systems. Tissue levels of testosterone and DHT were determined using liquid chromatography-mass spectrometry.

RESULTS

Prostate cancer cells express undetectable to low levels of SRD5A2 but elevated levels of SRD5A1 activity compared with nonmalignant prostatic tissue. Daily oral treatment of rats with the SRD5A2 selective inhibitor, finasteride, reduces prostate weight and DHT content but did not inhibit R-3327H rat prostate cancer growth or DHT content in intact (i.e., noncastrated) male rats. In contrast, daily oral treatment with even a low 1 mg/kg/d dose of the dual SRD5A1 and SRD5A2 inhibitor, dutasteride, reduces both normal prostate and H tumor DHT content and weight in intact rats while elevating tissue testosterone. Daily oral treatment with finasteride significantly (P < 0.05) inhibits growth of LNCaP human prostate cancer xenografts in intact male nude mice, but this inhibition is not as great as that by equimolar oral dosing with dutasteride. This anticancer efficacy is not equivalent, however, to that produced by castration. Only combination of dutasteride and castration produces a greater tumor inhibition (P < 0.05) than castration monotherapy against androgen-responsive LNCaP cancers. In contrast, no response was induced by dutasteride in nude mice bearing androgen-independent PC-3 human prostatic cancer xenografts.

CONCLUSIONS

These results document that testosterone is not as potent as DHT but does stimulate prostate cancer growth, thus combining castration with dutasteride enhances therapeutic efficacy.

Role of the alternate pathway of dihydrotestosterone formation in virilization of the Wolffian ducts of the tammar wallaby, Macropus eugenii

Dihydrotestosterone in androgen target tissues is formed under most circumstances by the 5alpha-reduction of testosterone, but an alternate pathway involves the oxidation of androstanediol to dihydrotestosterone. To investigate the mechanism by which androgens virilize the Wolffian ducts in the tammar wallaby, [(3)H]progesterone was incubated with testes from d 10 and 19 pouch young, and radioactivity was recovered in testosterone and androstanediol at both ages. Analysis of the intermediates indicates that androstanediol was formed both from testosterone via 5alpha-reduction and 3alpha-keto reduction and directly from 5alpha-reduced progestogens. 5alpha-Reductase activity was high in minces of mesonephros/epididymis from d 6-21 pouch young. When minces of urogenital tract tissues from d 19 pouch young were incubated with [(3)H]testosterone, [(3)H]dihydrotestosterone, and [(3)H]androstanediol, dihydrotestosterone was the principal androgen formed in the mesonephros/epididymis, urogenital sinus, and urogenital tubercle, whereas androstanediol was the principal androgen formed by the testis. In intact pouch young studied between d 10 and 34, administration of the 5alpha-reductase inhibitor, 17beta-(N,N-diethyl)carbamoyl-4-methyl-4-aza-5alpha-androstan-3-one, blocked virilization of the Wolffian ducts in males, and administration of androstanediol caused virilization of the Wolffian ducts in females. We conclude that dihydrotestosterone, largely formed in the tissue by the oxidation of androstanediol derived from the testes and also the 5alpha-reduction of testosterone, is responsible for Wolffian duct virilization in this species.

HUMAN UDP-GLUCURONOSYLTRANSFERASE, UGT1A8, GLUCURONIDATES DIHYDROTESTOSTERONE TO A MONOGLUCURONIDE AND FURTHER TO A STRUCTURALLY NOVEL DIGLUCURONIDE

We identified human UDP-glucuronosyltransferase (UGT) isoforms responsible for producing dihydrotestosterone (DHT) diglucuronide, a novel glucuronide in which the second glucuronosyl moiety is attached at the C2' position of the first glucuronosyl moiety, leading to diglucuronosyl conjugation of a single hydroxyl group of DHT at the C17 position. Incubation of the DHT monoglucuronide with 12 cDNA-expressed recombinant human UGT isoforms and uridine 5'-diphosphoglucuronic acid resulted in a low but measurable DHT diglucuronidation activity primarily with UGT1A8, a gastrointestinal UGT, and to a lesser extent with UGT1A1 and UGT1A9. In contrast, the activity of DHT monoglucuronidation was high and was found in UGT2B17, UGT2B15, UGT1A8, and UGT1A4 in descending order. Among the 12 UGT isoforms tested, only UGT1A8 was capable of producing DHT diglucuronide from DHT. The kinetics of DHT diglucuronidation by microsomes from human liver and intestine fitted the Michaelis-Menten model, and the V(max)/K(m) value for the intestinal microsomes was approximately 4 times greater than that for the liver microsomes.

Mapping of Steroids Binding to 17β-Hydroxysteroid Dehydrogenase Type 1 Using Monte Carlo Energy Minimization Reveals Alternative Binding Modes

Crystallographic studies of ligand-protein complexes reveal most preferable ligand binding modes, but do not show less populated modes that may contribute to measurable biochemical and biophysical characteristics of the complexes. In some cases, a ligand may bind a protein in essentially different modes. An example is 17beta-hydroxysteroid dehydrogenase type 1 (17beta-HSD1), a steroidogenic enzyme that catalyzes reduction of estrone to estradiol in gonadal and peripheral tissues. The enzyme exhibits a high specificity for estrogens which bind with their C17 atom in the proximity of the NADP(H) cofactor. 17Beta-HSD1 can also bind androgens, but in a reverse binding mode, in which the steroid C3 atom is the closest carbon atom to the cofactor. Here we map the interaction energy of estradiol and dihydrotestosterone binding to 17beta-HSD1. Positions and orientations of the steroids in the ligand-binding tunnel were sampled systematically, and at each combination of these generalized coordinates, the energy was Monte Carlo minimized. The computed maps show energy minima corresponding to the X-ray structures and predict alternative binding modes, in particular, an upside-down orientation in which steroidal face alpha is exposed to protein residues that normally interact with face beta. The methodology can be used for mapping ligand-receptor interactions in various systems, for example, in ion channels and G-protein-coupled receptors that bind elongated ligands in confined space between transmembrane helices.

Engineering lipobeads: properties of the hydrogel core and the lipid bilayer shell

We previously reported on a novel system termed Lipobead that consists of hydrogel beads encased within an anchored lipid bilayer. The hydrogel particles are formed by inverse suspension polymerization of dimethylacrylamide with N,N'-ethylenebis(acrylamide). During the polymerization stage, the water in oil emulsion is interfacially stabilized by small molecule surfactants as well as a small percentage of lipid functionalized with a vinyl group. The functionalized lipid becomes tethered to the bead surface and promotes the assembly of a lipid bilayer on the surface of the hydrogel beads. The presence of the functionalized lipid during polymerization dramatically alters the yield, average size, and size distribution of beads produced. This paper examines the effect of various chemical and physical processing parameters on the average size and size distribution of beads produced when lipid is a component of the surfactant mixture. Relationships between the processing parameters, average bead size, and size distribution were established. Macroscopic properties of the lipid bilayers of Lipobeads were also evaluated including phase transition temperature as well as permeability to the small polar molecule, adenosine triphosphate. It was established that the presence of functionalized lipid improves the organization of the bilayer on the Lipobead surface.

Identification of key amino acids responsible for the substantially higher affinities of human type 1 3beta-hydroxysteroid dehydrogenase/isomerase (3beta-HSD1) for substrates, coenzymes, and inhibitors relative to human 3beta-HSD2

The human type 1 (placenta, breast tumors, and prostate tumors) and type 2 (adrenals and gonads) isoforms of 3beta-hydroxysteroid dehydrogenase/isomerase (3beta-HSD1 and 3beta-HSD2) are encoded by two distinct genes that are expressed in a tissue-specific pattern. Our recent studies have shown that His156 contributes to the 14-fold higher affinity that 3beta-HSD1 exhibits for substrate and inhibitor steroids compared with human 3beta-HSD2 containing Tyr156 in the otherwise identical catalytic domain. Our structural model of human 3beta-HSD localizes His156 or Tyr156 in the subunit interface of the enzyme homodimer. The model predicts that Gln105 on one enzyme subunit has a higher probability of interacting with His156 on the other subunit in 3beta-HSD1 than with Tyr156 in 3beta-HSD2. The Q105M mutant of 3beta-HSD1 (Q105M1) shifts the Michaelis-Menten constant (Km) for 3beta-HSD substrate and inhibition constants (Ki) for epostane and trilostane to the much lower affinity profiles measured for wild-type 3beta-HSD2 and H156Y1. However, the Q105M2 mutant retains substrate and inhibitor kinetic profiles similar to those of 3beta-HSD2. Our model also predicts that Gln240 in 3beta-HSD1 and Arg240 in 3beta-HSD2 may be responsible for the 3-fold higher affinity of the type 1 isomerase activity for substrate steroid and cofactors. The Q240R1 mutation increases the isomerase substrate Km by 2.2-fold to a value similar to that of 3beta-HSD2 isomerase and abolishes the allosteric activation of isomerase by NADH. The R240Q2 mutation converts the isomerase substrate, cofactor, and inhibitor kinetic profiles to the 4-14-fold higher affinity profiles of 3beta-HSD1. Thus, key structural reasons for the substantially higher affinities of 3beta-HSD1 for substrates, coenzymes, and inhibitors have been identified. These structure and function relationships can be used in future docking studies to design better inhibitors of the 3beta-HSD1 that may be useful in the treatment of hormone-sensitive cancers and preterm labor.

Dissection of the physiological interconversion of 5alpha-DHT and 3alpha-diol by rat 3alpha-HSD via transient kinetics shows that the chemical step is rate-determining: effect of mutating cofactor and substrate-binding pocket residues on catalysis

3Alpha-hydroxysteroid dehydrogenases (3alpha-HSDs) catalyze the interconversion between 5alpha-dihydrotestosterone (5alpha-DHT), the most potent androgen, and 3alpha-androstanediol (3alpha-diol), a weak androgen metabolite. To identify the rate-determining step in this physiologically important reaction, rat liver 3alpha-HSD (AKR1C9) was used as the protein model for the human homologues in fluorescence stopped-flow transient kinetic and kinetic isotope effect studies. Using single and multiple turnover experiments to monitor the NADPH-dependent reduction of 5alpha-DHT, it was found that k(lim) and k(max) values were identical to k(cat), indicating that chemistry is rate-limiting overall. Kinetic isotope effect measurements, which gave (D)k(cat) = 2.4 and (D)2(O)k(cat) = 3.0 at pL 6.0, suggest that the slow chemical transformation is significantly rate-limiting. When the NADP(+)-dependent oxidation of 3alpha-diol was monitored, single and multiple turnover experiments showed a k(lim) and burst kinetics consistent with product release as being rate-limiting overall. When NAD(+) was substituted for NADP(+), burst phase kinetics was eliminated, and k(max) was identical to k(cat). Thus with the physiologically relevant substrates 5alpha-DHT plus NADPH and 3alpha-diol plus NAD(+), the slowest event is chemistry. R276 forms a salt-linkage with the phosphate of 2'-AMP, and when it is mutated, tight binding of NAD(P)H is no longer observed [Ratnam, K., et al. (1999) Biochemistry 38, 7856-7864]. The R276M mutant also eliminated the burst phase kinetics observed for the NADP(+)-dependent oxidation of 3alpha-diol. The data with the R276M mutant confirms that the release of the NADPH product is the slow event; and in its absence, chemistry becomes rate-limiting. W227 is a critical hydrophobic residue at the steroid binding site, and when it is mutated to alanine, k(cat)/K(m) for oxidation is significantly depressed. Burst phase kinetics for the NADP(+)-dependent turnover of 3alpha-diol by W227A was also abolished. In the W227A mutant, the slow release of NADPH is no longer observed since the chemical transformation is now even slower. Thus, residues in the cofactor and steroid-binding site can alter the rate-determining step in the NADP(+)-dependent oxidation of 3alpha-diol to make chemistry rate-limiting overall.

Androgen receptor (AR) NH2- and COOH-terminal interactions result in the differential influences on the AR-mediated transactivation and cell growth

Early reports showed that androgen receptor (AR) NH2- and COOH-terminal (N-C) interaction was important for full AR function. However, the influence of these interactions on the AR in vivo effects remains unclear. Here we tested some AR-associated peptides and coregulators to determine their influences on AR N-C interaction, AR transactivation, and AR coregulator function. The results showed that AR coactivators such as ARA70N, gelsolin, ARA54, and SRC-1 can enhance AR transactivation but showed differential influences on the N-C interaction. In contrast, AR corepressors ARA67 and Rad9 can suppress AR transactivation, with ARA67 enhancing and Rad9 suppressing AR N-C interaction. Furthermore, liganded AR C terminus-associated peptides can block AR N-C interaction, but only selective peptides can block AR transactivation and coregulator function. We found all the tested peptides can suppress prostate cancer LNCaP cell growth at different levels in the presence of 5alpha-dihydrotestosterone, but only the tested FXXLF-containing peptides, not FXXMF-containing peptides, can suppress prostate cancer CWR22R cell growth. Together, these results suggest that the effects of AR N-C interactions may not always correlate with similar effects on AR-mediated transactivation and/or AR-mediated cell growth. Therefore, drugs designed by targeting AR N-C interaction as a therapeutic intervention for prostate cancer treatment may face unpredictable in vivo effects.

5Alpha-reductase inhibition activity of steroids isolated from marine soft corals

The aim of this study is to determine the 5alpha-reductase inhibitory activity of several new steroidal compounds PR-01-PR-07 by measuring the conversion of [3H]T to[3H]DHT in Penicillium crustosum broths. These compounds were obtained from marine soft corals collected on the coasts of Andaman and Nicobar at Hori, Natkal and Kalipur (Diglipur) Islands and identified as Sinularia grandilobata Verseveldt, Sinularia crassa Tixier- Durivault, Sinularia gravis Tixier- Durivault, Sinularia sp., Lobophytum sp., Lobophytum crassum and Cladiella sp. PR-01-PR-04 significantly inhibited the conversion of [3H]T to [3H]DHT (P < 0.05) whereas PR-05 and PR-06 did not show an appreciable difference (P > 0.05) in this model. On the other hand PR-07 stimulated (P < 0.05) the enzymatic reaction.

Chemical Genetic Control of Protein Levels: Selective in Vivo Targeted Degradation

Genetic loss of function analysis is a powerful method for the study of protein function. However, some cell biological questions are difficult to address using traditional genetic strategies often due to the lack of appropriate genetic model systems. Here, we present a general strategy for the design and syntheses of molecules capable of inducing the degradation of selected proteins in vivo via the ubiquitin-proteasome pathway. Western blot and fluorometric analyses indicated the loss of two different targets: green fluorescent protein (GFP) fused with FK506 binding protein (FKBP12) and GFP fused with the androgen receptor (AR), after treatment with PROteolysis TArgeting Chimeric moleculeS (PROTACS) incorporating a FKBP12 ligand and dihydrotestosterone, respectively. These are the first in vivo examples of direct small molecule-induced recruitment of target proteins to the proteasome for degradation upon addition to cultured cells. Moreover, PROTAC-mediated protein degradation offers a general strategy to create "chemical knockouts," thus opening new possibilities for the control of protein function.

Interaction of Androgens with Cardiotonic Drugs in Isolated Left Atrium of Rat

Pharmacological concentrations of androgens are known to elicit a rapid positive inotropism in isolated left atrium of male rats. Upon short-term exposure to androgens, an increase in intracellular cAMP levels has been observed, though delayed with respect to the time course of contraction, suggesting that other mechanisms may participate in initiating the contraction. Therefore, the interaction of positive inotropism elicited by ouabain, an inhibitor of Na(+)-K(+)-ATPase, and androgens was studied in isolated left atrium of rat. Androgens antagonized ouabain-elicited positive inotropism and increased the basal tone. Vanadate, an inhibitor of the Ca(2+) pump, produced a similar effect as androgens on ouabain-elicited positive inotropism. Therefore, androgens might interact with the Ca(2+) pump and this may explain the increase in basal tone. The conjugation of 5 alpha-dihydrotestosterone with bovine serum albumin produced the same effect, suggesting an extracellular interaction of androgens inhibiting the Na(+)-K(+)-ATPase that could increase intracellular Ca(2+) via the Na(+)-Ca(2+) exchange.

Efficient Oxidizing Methods for the Synthesis of Oxandrolone Intermediates

Mild, efficient and eco-friendly oxidation of 17alpha-methylandrostan-3beta-17beta-diol (1) has been studied with three different reagents viz. pentavalent iodine reagent 2-iodoxy benzoic acid (IBX) in DMSO at 65 degrees C, sodium hypochlorite and H2O2/Na2WO4 under phase transfer conditions to give 17beta-hydroxy-17alpha-methylandrostan-3-one (mestanolone 2), a drug intermediate as oxidized product. The H2O2/Na2WO4/PTC gave mestanolone in high yield and purity whereas sodium hypochlorite/PTC system yielded some chlorinated material along with the mestanolone. However, 1 with 2.5 equivalent of IBX gave 17beta-hydroxy-17alpha-methyl-Delta1-androsten-3-one (3) under the similar reaction conditions in good yield and single step reaction.

Human type 3 3alpha-hydroxysteroid dehydrogenase (aldo-keto reductase 1C2) and androgen metabolism in prostate cells

Human aldo-keto reductases (AKRs) of the AKR1C subfamily function in vitro as 3-keto-, 17-keto-, and 20-ketosteroid reductases or as 3alpha-, 17beta-, and 20alpha-hydroxysteroid oxidases. These AKRs can convert potent sex hormones (androgens, estrogens, and progestins) into their cognate inactive metabolites or vice versa. By controlling local ligand concentration AKRs may regulate steroid hormone action at the prereceptor level. AKR1C2 is expressed in prostate, and in vitro it will catalyze the nicotinamide adenine dinucleotide (NAD(+))-dependent oxidation of 3alpha-androstanediol (3alpha-diol) to 5alpha-dihydrotestosterone (5alpha-DHT). This reaction is potently inhibited by reduced NAD phosphate (NADPH), indicating that the NAD(+): NADPH ratio in cells will determine whether AKR1C2 makes 5alpha-DHT. In transient COS-1-AKR1C2 and in stable PC-3-AKR1C2 transfectants, 5alpha-DHT was reduced by AKR1C2. However, the transfected AKR1C2 oxidase activity was insufficient to surmount the endogenous 17beta-hydroxysteroid dehydrogenase (17beta-HSD) activity, which eliminated 3alpha-diol as androsterone. PC-3 cells expressed retinol dehydrogenase/3alpha-HSD and 11-cis-retinol dehydrogenase, but these endogenous enzymes did not oxidize 3alpha-diol to 5alpha-DHT. In stable LNCaP-AKR1C2 transfectants, AKR1C2 did not alter androgen metabolism due to a high rate of glucuronidation. In primary cultures of epithelial cells, high levels of AKR1C2 transcripts were detected in prostate cancer, but not in cells from normal prostate. Thus, in prostate cells AKR1C2 acts as a 3-ketosteroid reductase to eliminate 5alpha-DHT and prevents activation of the androgen receptor. AKR1C2 does not act as an oxidase due to either potent product inhibition by NADPH or because it cannot surmount the oxidative 17beta-HSD present. Neither AKR1C2, retinol dehydrogenase/3alpha-HSD nor 11-cis-retinol dehydrogenase is a source of 5alpha-DHT in PC-3 cells.

Factors that mediate and modulate androgen action

Androgens mediate a wide range of processes during embryogenesis and in the adult. In mammals, although a number of steroids can be shown to exert androgenic effects using in vitro and in vivo assays, testosterone and its 5alpha reduced metabolite, 5alpha-dihydrotestosterone (DHT) are considered to represent the principal physiologic androgens. Furthermore, although the effects that androgens exert differ widely among different tissues and cell types, genetic and biochemical data suggest that these effects are mediated via the protein products of a single androgen receptor gene, which is encoded on the X-chromosome in mammals.