Correction to "C-3 Steroidal Hemiesters as Inhibitors of 17ß-Hydroxysteroid Dehydrogenase Type 10".

[This corrects the article DOI: 10.1021/acsomega.3c10148.].

C-3 Steroidal Hemiesters as Inhibitors of 17ß-Hydroxysteroid Dehydrogenase Type 10.

17ß-HSD10 is a mitochondrial enzyme that catalyzes the steroidal oxidation of a hydroxy group to a keto group and, thus, is involved in maintaining steroid homeostasis. The druggability of 17ß-HSD10 is related to potential treatment for neurodegenerative diseases, for example, Alzheimer's disease or cancer. Herein, steroidal derivatives with an acidic hemiester substituent at position C-3 on the skeleton were designed, synthesized, and evaluated by using pure recombinant 17ß-HSD10 converting 17ß-estradiol to estrone. Compounds 22 (IC50 = 6.95 ± 0.35 µM) and 23 (IC50 = 5.59 ± 0.25 µM) were identified as the most potent inhibitors from the series. Compound 23 inhibited 17ß-HSD10 activity regardless of the substrate. It was found not cytotoxic toward the HEK-293 cell line and able to inhibit 17ß-HSD10 activity also in the cellular environment. Together, these findings support steroidal compounds as promising candidates for further development as 17ß-HSD10 inhibitors.

5ß-reduced neuroactive steroids as modulators of growth and viability of postnatal neurons and glia.

Endogenous neurosteroids (NS) and their synthetic analogs, neuroactive steroids (NAS), are potentially useful drug-like compounds affecting the pathophysiology of miscellaneous central nervous system disorders (e.g. Alzheimer´s disease, epilepsy, depression, etc.). Additionally, NS have been shown to promote neuron viability and neurite outgrowth upon injury. The molecular, structural and physicochemical basis of the NS effect on neurons is so far not fully understood, and the development of new, biologically relevant assays is essential for their comparative analysis and for assessment of their mechanism of action. Here, we report the development of a novel, plate-based, high-content in vitro assay for screening of NS and newly synthesized, 5ß-reduced NAS for the promotion of postnatal neuron survival and neurite growth using fluorescent, postnatal mixed cortical neuron cultures isolated from thy1-YFP transgenic mice. The screen allows a detailed time course analysis of different parameters, such as the number of neurons or neurite lengths of 7-day, in vitro neuron cultures. Using the screen, we identify a new NAS, compound 42, that promotes the survival and growth of postnatal neurons significantly better than several endogenous NS (dehydroepiandrosterone, progesterone, and allopregnanolone). Interestingly, we demonstrate that compound 42 also promotes the proliferation of glia (in particular oligodendrocytes) and that the glial function is critical for its neuron growth support. Computational analysis of the biological data and calculated physicochemical properties of tested NS and NAS demonstrated that their biological activity is proportional to their lipophilicity. Together, the screen proves useful for the selection of neuron-active NAS and the comparative evaluation of their biologically relevant structural and physicochemical features.

Identification of N-methyl-D-aspartate receptor antagonists using the rat postnatal mixed cortical and hippocampal neurons.

The goal of this study was to evaluate mixed cortical and hippocampal primary rat postnatal neuronal culture as in vitro tool for identification of N-methyl-D-aspartate receptor (NMDAR) antagonists and to find out, whether this model is comparable with other commonly used primary rat neuronal models differing in their origin (pure cortical vs. mixed cortical and hippocampal) and differentiation state (embryonal vs. postnatal). Induced pluripotent stem cell (iPSC) - derived human glutamatergic neurons have been included in this study as well. First, the cultures were characterized by their neuron/astrocyte composition, the mRNA expression of NR2B/NR2A NMDAR subunit ratios, and the expression of glutamate transporters (GLT1, GLAST). Then, selected endogenous steroids and synthetic neuroactive steroids that have been previously identified as negative allosteric modulators of recombinant GluN1/GluN2B NMDA receptors, were evaluated for their ability to prevent an NMDA or glutamate-induced Ca2+ influx (acute effect) and excitotoxicity over 24 h. Though the neuroprotective potential against excitotoxic stimuli varied among the models studied, postnatal mixed cortical and hippocampal culture proved to be a convenient and robust tool for NMDAR antagonist screening. The most widely used embryonal (E18) cultures offered higher cell yields but at the expense of a higher sensitivity to compounds' cytotoxicity. iPSC-derived neurons were not found to be superior to rat cultures for screening purposes.

Lithocholic acid inhibits P2X2 and potentiates P2X4 receptor channel gating.

The family of ATP-gated purinergic P2X receptors comprises seven bunits (P2X1-7) that are unevenly distributed in the central and peripheral nervous systems as well as other organs. Endogenous modulators of P2X receptors are phospholipids, steroids and neurosteroids. Here, we analyzed whether bile acids, which are natural products derived from cholesterol, affect P2X receptor activity. We examined the effects of primary and secondary bile acids and newly synthesized derivatives of lithocholic acid on agonist-induced responses in HEK293T cells expressing rat P2X2, P2X4 and P2X7 receptors. Electrophysiology revealed that low micromolar concentrations of lithocholic acid and its structural analog 4-dafachronic acid strongly inhibit ATP-stimulated P2X2 but potentiate P2X4 responses, whereas primary bile acids and other secondary bile acids exhibit no or reduced effects only at higher concentrations. Agonist-stimulated P2X7 responses are significantly potentiated by lithocholic acid at moderate concentrations. Structural modifications of lithocholic acid at positions C-3, C-5 or C-17 abolish both inhibitory and potentiation effects to varying degrees, and the 3α-hydroxy group contributes to the ability of the molecule to switch between potentiation and inhibition. Lithocholic acid allosterically modulates P2X2 and P2X4 receptor sensitivity to ATP, reduces the rate of P2X4 receptor desensitization and antagonizes the effect of ivermectin on P2X4 receptor deactivation. Alanine-scanning mutagenesis of the upper halve of P2X4 transmembrane domain-1 revealed that residues Phe48, Val43 and Tyr42 are important for potentiating effect of lithocholic acid, indicating that modulatory sites for lithocholic acid and ivermectin partly overlap. Lithocholic acid also inhibits ATP-evoked currents in pituitary gonadotrophs expressing native P2X2, and potentiates ATP currents in nonidentified pituitary cells expressing P2X4 receptors. These results indicate that lithocholic acid is a bioactive steroid that may help to further unveil the importance of the P2X2, and P2X4 receptors in many physiological processes.

Synthetic testosterone derivatives modulate rat P2X2 and P2X4 receptor channel gating.

P2X receptors (P2XRs) are ATP-gated cationic channels that are allosterically modulated by numerous compounds, including steroids and neurosteroids. These compounds may both inhibit and potentiate the activity of P2XRs, but sex steroids such as 17ß-estradiol or progesterone are reported to be inactive. Here, we tested a hypothesis that testosterone, another sex hormone, modulates activity of P2XRs. We examined actions of native testosterone and a series of testosterone derivatives on the gating of recombinant P2X2R, P2X4R and P2X7R and native channels expressed in pituitary cells and hypothalamic neurons. The 17ß-ester derivatives of testosterone rapidly and positively modulate the 1 µM ATP-evoked currents in P2X2R- and P2X4R-expressing cells, but not agonist-evoked currents in P2X7R-expressing cells. In general, most of the tested testosterone derivatives are more potent modulators than endogenous testosterone. The comparison of chemical structures and whole-cell recordings revealed that their interactions with P2XRs depend on the lipophilicity and length of the alkyl chain at position C-17. Pre-treatment with testosterone butyrate or valerate increases the sensitivity of P2X2R and P2X4R to ATP by several fold, reduces the rate of P2X4R desensitization, accelerates resensitization, and enhances ethidium uptake by P2X4R. Native channels are also potentiated by testosterone derivatives, while endogenously expressed GABA receptors type A are inhibited. The effect of ivermectin, a P2X4R-specific allosteric modulator, on deactivation is antagonized by testosterone derivatives in a concentration-dependent manner. Together, our results provide evidence for potentiation of particular subtypes of P2XRs by testosterone derivatives and suggest a potential role of ivermectin binding site for steroid-induced modulation. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.

Screening of novel 3α5ß-neurosteroids for neuroprotective activity against glutamate- or NMDA-induced excitotoxicity.

A broad variety of central nervous system diseases have been associated with glutamate induced excitotoxicity under pathological conditions. The neuroprotective effects of neurosteroids can combat this excitotoxicity. Herein, we have demonstrated the neuroprotective effect of novel steroidal N-methyl-D-aspartate receptor inhibitors against glutamate- or NMDA- induced excitotoxicity. Pretreatment with neurosteroids significantly reduced acute L-glutamic acid or NMDA excitotoxicity mediated by Ca2+ entry and consequent ROS (reactive oxygen species) release and caspase-3 activation. Compounds 6 (IC50 = 5.8 µM), 7 (IC50 = 12.2 µM), 9 (IC50 = 7.8 µM), 13 (IC50 = 1.1 µM) and 16 (IC50 = 8.2 µM) attenuated glutamate-induced Ca2+ entry more effectively than memantine (IC50 = 18.9 µM). Moreover, compound 13 shows comparable effect with MK-801 (IC50 = 1.2 µM) and also afforded significant protection without any adverse effect upon prolonged exposure. This drop in Ca2+ level resulted in corresponding ROS suppression and prevented glutamate-induced caspase-3 activation. Therefore, compound 13 has great potential for development into a therapeutic agent for improving glutamate-related nervous system diseases.

Pregn-5-en-3ß-ol and androst-5-en-3ß-ol dicarboxylic acid esters as potential therapeutics for NMDA hypofunction: In vitro safety assessment and plasma stability.

Neurosteroids are endogenous steroidal compounds that can modulate neuronal receptors. N-Methyl-D-aspartate receptors (NMDARs) are glutamate-gated, calcium-permeable ion channels that are of particular interest, as they participate in synaptic transmission and are implicated in various processes, such as learning, memory, or long-term neuronal potentiation. Positive allosteric modulators that increase the activity of NMDARs may provide a therapeutic aid for patients suffering from neuropsychiatric disorders where NMDAR hypofunction is thought to be involved, such as intellectual disability, autism spectrum disorder, or schizophrenia. We recently described a new class of pregn-5-ene and androst-5-ene 3ß-dicarboxylic acid hemiesters (2-24) as potent positive modulators of NMDARs. Considering the recommended guidelines for the early stage development of new, potent compounds, we conducted an in vitro safety assessment and plasma stability screening to evaluate their druglikeness. First, compounds were screened for their hepatotoxicity and mitochondrial toxicity in a HepG2 cell line. Second, toxicity in primary rat postnatal neurons was estimated. Next, the ability of compounds 2-24 to cross a Caco-2 monolayer was also studied. Finally, rat and human plasma stability screening revealed an unforeseen high stability of the C-3 hemiester moiety. In summary, by using potency/efficacy towards NMDARs data along with toxicity profile, Caco-2 permeability and plasma stability, compounds 14 and 15 were selected for further in vivo animal studies.

Strong Inhibitory Effect, Low Cytotoxicity and High Plasma Stability of Steroidal Inhibitors of N-Methyl-D-Aspartate Receptors With C-3 Amide Structural Motif.

Herein, we report the synthesis, structure-activity relationship study, and biological evaluation of neurosteroid inhibitors of N-methyl-D-aspartate receptors (NMDARs) receptors that employ an amide structural motif, relative to pregnanolone glutamate (PAG) - a compound with neuroprotective properties. All compounds were found to be more potent NMDAR inhibitors (IC50 values varying from 1.4 to 21.7 µM) than PAG (IC50 = 51.7 µM). Selected compound 6 was evaluated for its NMDAR subtype selectivity and its ability to inhibit AMPAR/GABAR responses. Compound 6 inhibits the NMDARs (8.3 receptors (8.3 ± 2.1 µM) more strongly than it does at the GABAR and AMPARs (17.0 receptors (17.0 ± 0.2 µM and 276.4 ± 178.7 µM, respectively). In addition, compound 6 (10 µM) decreases the frequency of action potentials recorded in cultured hippocampal neurons. Next, compounds 3, 5-7, 9, and 10 were not associated with mitotoxicity, hepatotoxicity nor ROS induction. Lastly, we were able to show that all compounds have improved rat and human plasma stability over PAG.

Positive Modulators of the N-Methyl-d-aspartate Receptor: Structure-Activity Relationship Study of Steroidal 3-Hemiesters.

Here, we report the synthesis of pregn-5-ene and androst-5-ene dicarboxylic acid esters and explore the structure-activity relationship (SAR) for their modulation of N-methyl-d-aspartate receptors (NMDARs). All compounds were positive modulators of recombinant GluN1/GluN2B receptors (EC50 varying from 1.8 to 151.4 µM and Emax varying from 48% to 452%). Moreover, 10 compounds were found to be more potent GluN1/GluN2B receptor modulators than endogenous pregnenolone sulfate (EC50 = 21.7 µM). The SAR study revealed a relationship between the length of the residues at carbon C-3 of the steroid molecule and the positive modulatory effect at GluN1/GluN2B receptors for various D-ring modifications. A selected compound, 20-oxo-pregnenolone hemiadipate, potentiated native NMDARs to a similar extent as GluN1/GluN2A-D receptors and inhibited AMPARs and GABAAR responses. These results provide a unique opportunity for the development of new steroid based drugs with potential use in the treatment of neuropsychiatric disorders involving hypofunction of NMDARs.

Physicochemical and biological properties of novel amide-based steroidal inhibitors of NMDA receptors.

Herein, we report a new class of amide-based inhibitors (1-4) of N-methyl-d-aspartate receptors (NMDARs) that were prepared as analogues of pregnanolone sulfate (PAS) and pregnanolone glutamate (PAG) - the steroidal neuroprotective NMDAR inhibitors. A series of experiments were conducted to evaluate their physicochemical and biological properties: (i) the inhibitory effect of compounds 3 and 4 on NMDARs was significantly improved (IC50=1.0 and 1.4µM, respectively) as compared with endogenous inhibitor - pregnanolone sulfate (IC50=24.6µM) and pregnanolone glutamate (IC50=51.7µM); (ii) physicochemical properties (logP and logD) were calculated; (iii) Caco-2 assay revealed that the permeability properties of compounds 2 and 4 are comparable with pregnanolone glutamate; (iv) compounds 1-4 have minimal or no adverse hepatic effect; (v) compounds 1-4 cross blood-brain-barrier.

Docosahexaenoic Acid-Derived Fatty Acid Esters of Hydroxy Fatty Acids (FAHFAs) With Anti-inflammatory Properties.

White adipose tissue (WAT) is a complex organ with both metabolic and endocrine functions. Dysregulation of all of these functions of WAT, together with low-grade inflammation of the tissue in obese individuals, contributes to the development of insulin resistance and type 2 diabetes. n-3 polyunsaturated fatty acids (PUFAs) of marine origin play an important role in the resolution of inflammation and exert beneficial metabolic effects. Using experiments in mice and overweight/obese patients with type 2 diabetes, we elucidated the structures of novel members of fatty acid esters of hydroxy fatty acids-lipokines derived from docosahexaenoic acid (DHA) and linoleic acid, which were present in serum and WAT after n-3 PUFA supplementation. These compounds contained DHA esterified to 9- and 13-hydroxyoctadecadienoic acid (HLA) or 14-hydroxydocosahexaenoic acid (HDHA), termed 9-DHAHLA, 13-DHAHLA, and 14-DHAHDHA, and were synthesized by adipocytes at concentrations comparable to those of protectins and resolvins derived from DHA in WAT. 13-DHAHLA exerted anti-inflammatory and proresolving properties while reducing macrophage activation by lipopolysaccharides and enhancing the phagocytosis of zymosan particles. Our results document the existence of novel lipid mediators, which are involved in the beneficial anti-inflammatory effects attributed to n-3 PUFAs, in both mice and humans.

Neurosteroid-like Inhibitors of N-Methyl-d-aspartate Receptor: Substituted 2-Sulfates and 2-Hemisuccinates of Perhydrophenanthrene.

N-Methyl-d-aspartate receptors (NMDARs) display a critical role in various diseases of the central nervous system. The activity of NMDARs can be modulated by neurosteroids. Herein, we report a structure-activity relationship study for perhydrophenanthrene analogues possessing a framework that mimics the steroidal ring system. This study comprises the design, synthesis, and assessment of the biological activity of a library of perhydrophenanthrene 2-sulfates and 2-hemisuccinates (1-10). Their ability to modulate NMDAR-induced currents was tested on recombinant GluN1/GluN2B receptors. Our results demonstrate that such structural optimization leads to compounds that are inhibitors of NMDARs. Notably, compound 9 (IC50 = 15.6 µM) was assessed as a more potent inhibitor of NMDAR-induced currents than the known endogenous neurosteroid, pregnanolone sulfate (IC50 = 24.6 µM).

A New Class of Potent N-Methyl-D-Aspartate Receptor Inhibitors: Sulfated Neuroactive Steroids with Lipophilic D-Ring Modifications.

N-Methyl-D-aspartate receptors (NMDARs) are glutamate-gated ion channels that play a crucial role in excitatory synaptic transmission. However, the overactivation of NMDARs can lead to excitotoxic cell damage/death, and as such, they play a role in numerous neuropathological conditions. The activity of NMDARs is known to be influenced by a wide variety of allosteric modulators, including neurosteroids, which in turn makes them promising therapeutic targets. In this study, we describe a new class of neurosteroid analogues which possess structural modifications in the steroid D-ring region. These analogues were tested on recombinant GluN1/GluN2B receptors to evaluate the structure-activity relationship. Our results demonstrate that there is a strong correlation between this new structural feature and the in vitro activity, as all tested compounds were evaluated as more potent inhibitors of NMDA-induced currents (IC50 values varying from 90 nM to 5.4 µM) than the known endogeneous neurosteroid-pregnanolone sulfate (IC50 = 24.6 µM).

Allopregnanolone and pregnanolone analogues modified in the C ring: synthesis and activity.

(25R)-3ß-Hydroxy-5α-spirostan-12-one (hecogenin) and 11α-hydroxypregn-4-ene-3,20-dione (11α-hydroxyprogesterone) were used as starting materials for the synthesis of a series of 11- and 12-substituted derivatives of 5ξ-pregnanolone (3α-hydroxy-5α-pregnan-20-one and 3α-hydroxy-5ß-pregnan-20-one), the principal neurosteroid acting via γ-aminobutyric acid (GABA). These analogues were designed to study the structural requirements of the corresponding GABAA receptor. Their biological activity was measured by in vitro test with [(3)H]flunitrazepam as radioligand in which allopregnanolone and its active analogues stimulated the binding to the GABAA receptor. Analysis of the SAR data suggests dependence of the flunitrazepam binding activity on the hydrophobic-hydrophilic balance of the groups at the C-ring edge rather than on specific interactions between them and the receptor.

Access of inhibitory neurosteroids to the NMDA receptor.

BACKGROUND AND PURPOSE: NMDA receptors are glutamatergic ionotropic receptors involved in excitatory neurotransmission, synaptic plasticity and excitotoxic cell death. Many allosteric modulators can influence the activity of these receptors positively or negatively, with behavioural consequences. 20-Oxo-5ß-pregnan-3α-yl sulphate (pregnanolone sulphate; PA-6) is an endogenous neurosteroid that inhibits NMDA receptors and is neuroprotective. We tested the hypothesis that the interaction of PA-6 with the plasma membrane is critical for its inhibitory effect at NMDA receptors. EXPERIMENTAL APPROACH: Electrophysiological recordings and live microscopy were performed on heterologous HEK293 cells expressing GluN1/GluN2B receptors and cultured rat hippocampal neurons. KEY RESULTS: Our experiments showed that the kinetics of the steroid inhibition were slow and not typical of drug-receptor interaction in an aqueous solution. In addition, the recovery from steroid inhibition was accelerated by ß- and γ-cyclodextrin. Values of IC(50) assessed for novel synthetic C3 analogues of PA-6 differed by more than 30-fold and were positively correlated with the lipophilicity of the PA-6 analogues. Finally, the onset of inhibition induced by C3 analogues of PA-6 ranged from use-dependent to use-independent. The onset and offset of cell staining by fluorescent analogues of PA-6 were slower than those of steroid-induced inhibition of current responses mediated by NMDA receptors. CONCLUSION AND IMPLICATIONS: We conclude that steroid accumulation in the plasma membrane is the route by which it accesses a binding site on the NMDA receptor. Thus, our results provide a possible structural framework for pharmacologically targeting the transmembrane domains of the receptor.

The synthesis of androstane brassinosteroid analogues with alpha-azido acid ester groups in position 17beta.

Androstane brassinosteroid analogues with alpha-azido acid ester groups in position 17beta were synthesized from 2alpha,3alpha,17beta-trihydroxy-5alpha-androstan-6-one after the protection of the 2alpha,3alpha-diols upon treatment with the corresponding alpha-azido acid and the subsequent deprotection of the diol grouping. Six new castasterone analogues were prepared. The biological activities were evaluated in two bioassays: a rice lamina inclination test and bean second internode bioassays. The activities of the new analogues differ in these two bioassays.

Synthesis of fluorinated brassinosteroids based on alkene cross-metathesis and preliminary biological assessment.

Three types of brassinosteroid analogues with perfluoroalkylated side chains were synthesized by using alkene cross-metathesis of a brassinosteroid derivative bearing a terminal alkene moiety with different (perfluoroalkyl)propenes. The presence of the double bonds in the cross-metathesis products allowed a facile one-step double dihydroxylation to provide intermediates that after Baeyer-Villiger oxidation afforded the target compounds. Biological activity of the prepared analogues was tested in GABA(A) receptor, cytotoxic, and brassinolide activity, which reached in some cases the same range as their nonfluorinated analogues.

Allopregnanolone (3alpha-hydroxy-5alpha-pregnan-20-one) derivatives with a polar chain in position 16alpha: synthesis and activity.

The lipophilic nature of allopregnanolone prevents its user-friendly application in human medicine. On inspiration by previously prepared allopregnanolone with a 16alpha-bound tetraethylammonium salt, an attempt was made to produce allopregnanolone analogues with polar groups introduced into position 16alpha with the goal of increasing water solubility, brain accessibility, and potency of neuroactive steroids. The Michael addition to derivatives of pregn-16-en-20-one was the key reaction step. The link between the steroid skeleton and the new side chain was either a methylene group (when diethyl malonate was added) or an oxygen atom (when a hydroxy derivative was added). [(35)S]TBPS displacement was used to evaluate the products. Several carbamates (but not their parent alcohols) displaced TBPS from the picrotoxin binding site on GABA(A) receptors. Although none of them was more potent than the above ammonium salt, which stimulated this study, their nonionic nature should not prevent their passage into the brain.