Benzothiazolyl Ureas are Low Micromolar and Uncompetitive Inhibitors of 17β-HSD10 with Implications to Alzheimer's Disease Treatment

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

17β-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 17β-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 17β-HSD10 converting 17β-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 17β-HSD10 activity regardless of the substrate. It was found not cytotoxic toward the HEK-293 cell line and able to inhibit 17β-HSD10 activity also in the cellular environment. Together, these findings support steroidal compounds as promising candidates for further development as 17β-HSD10 inhibitors.

Involvement of Type 10 17β-Hydroxysteroid Dehydrogenase in the Pathogenesis of Infantile Neurodegeneration and Alzheimer's Disease

Type 10 17β-hydroxysteroid dehydrogenase (17β-HSD10) is the HSD17B10 gene product playing an appreciable role in cognitive functions. It is the main hub of exercise-upregulated mitochondrial proteins and is involved in a variety of metabolic pathways including neurosteroid metabolism to regulate allopregnanolone homeostasis. Deacetylation of 17β-HSD10 by sirtuins helps regulate its catalytic activities. 17β-HSD10 may also play a critical role in the control of mitochondrial structure, morphology and dynamics by acting as a member of the Parkin/PINK1 pathway, and by binding to cyclophilin D to open mitochondrial permeability pore. 17β-HSD10 also serves as a component of RNase P necessary for mitochondrial tRNA maturation. This dehydrogenase can bind with the Aβ peptide thereby enhancing neurotoxicity to brain cells. Even in the absence of Aβ, its quantitative and qualitative variations can result in neurodegeneration. Since elevated levels of 17β-HSD10 were found in brain cells of Alzheimer's disease (AD) patients and mouse AD models, it is considered to be a key factor in AD pathogenesis. Since data underlying Aβ-binding-alcohol dehydrogenase (ABAD) were not secured from reported experiments, ABAD appears to be a fabricated alternative term for the HSD17B10 gene product. Results of this study would encourage researchers to solve the question why elevated levels of 17β-HSD10 are present in brains of AD patients and mouse AD models. Searching specific inhibitors of 17β-HSD10 may find candidates to reduce senile neurodegeneration and open new approaches for the treatment of AD.

Nanomolar Benzothiazole-Based Inhibitors of 17β-HSD10 with Cellular Bioactivity

Multifunctional mitochondrial enzyme 17β-hydroxysteroid dehydrogenase type 10 (17β-HSD10) is a potential drug target for the treatment of various pathologies. The most discussed is the pathology associated with Alzheimer's disease (AD), where 17β-HSD10 overexpression and its interaction with amyloid-β peptide contribute to mitochondrial dysfunction and neuronal stress. In this work, a series of new benzothiazole-derived 17β-HSD10 inhibitors were designed based on the structure-activity relationship analysis of formerly published inhibitors. A set of enzyme-based and cell-based methods were used to evaluate the inhibitory potency of new compounds, their interaction with the enzyme, and their cytotoxicity. Most compounds exhibited significantly a higher inhibitory potential compared to published benzothiazolyl ureas and good target engagement in a cellular environment accompanied by low cytotoxicity. The best hits displayed mixed-type inhibition with half maximal inhibitory concentration (IC50) values in the nanomolar range for the purified enzyme (3-7, 15) and/or low micromolar IC50 values in the cell-based assay (6, 13-16).

Frentizole derivatives with mTOR inhibiting and senomorphic properties

Frentizole is immunosuppressive drug with low acute toxicity and lifespan-prolonging effect. Recently, frentizole´s potential to disrupt toxic amyloid β (Aβ) - Aβ-binding alcohol dehydrogenase (ABAD) interaction in mitochondria in Alzheimer´s brains has been revealed. Another broadly studied drug with anti-aging and immunosuppressive properties is an mTOR inhibitor - rapamycin. Since we do not yet precisely know what is behind the lifespan-prolonging effect of rapamycin and frentizole, whether it is the ability to inhibit the mTOR signaling pathway, reduction in mitochondrial toxicity, immunosuppressive effect, or a combination of all of them, we have decided within our previous work to dock the entire in-house library of almost 240 Aβ-ABAD modulators into the FKBP-rapamycin-binding (FRB) domain of mTOR in order to interlink mTOR-centric and mitochondrial free radical-centric theories of aging and thus to increase the chances of success. Based on the results of the docking study, molecular dynamic simulation and MM-PBSA calculations, we have selected nine frentizole-like compounds (1 - 9). Subsequently, we have determined their real physical-chemical properties (logP, logD, pKa and solubility in water and buffer), cytotoxic/cytostatic, mTOR inhibitory, and in vitro anti-senescence (senolytic and senomorphic) effects. Finally, the three best candidates (4, 8, and 9) have been forwarded for in vivo safety studies to assess their acute toxicity and pharmacokinetic properties. Based on obtained results, only compound 4 demonstrated the best results within in vitro testing, the ability to cross the blood-brain barrier and the lowest acute toxicity (LD50 in male mice 559 mg/kg; LD50 in female mice 575 mg/kg).

Physiologically relevant fluorescent assay for identification of 17β-hydroxysteroid dehydrogenase type 10 inhibitors

Mitochondrial enzyme 17β-hydroxysteroid dehydrogenase type 10 (HSD10) is a potential molecular target for treatment of mitochondrial-related disorders such as Alzheimer's disease (AD). Its over-expression in AD brains is one of the critical factors disturbing the homeostasis of neuroprotective steroids and exacerbating amyloid beta (Aβ)-mediated mitochondrial toxicity and neuronal stress. This study was focused on revalidation of the most potent HSD10 inhibitors derived from benzothiazolyl urea scaffold using fluorescent-based enzymatic assay with physiologically relevant substrates of 17β-oestradiol and allopregnanolone. The oestradiol-based assay led to the identification of two nanomolar inhibitors (IC50 70 and 346 nM) differing from HSD10 hits revealed from the formerly used assay. Both identified inhibitors were found to be effective also in allopregnanolone-based assay with non-competitive or uncompetitive mode of action. In addition, both inhibitors were confirmed to penetrate the HEK293 cells and they were able to inhibit the HSD10 enzyme in the cellular environment. Both molecules seem to be potential lead structures for further research and development of HDS10 inhibitors.

Development of submicromolar 17β-HSD10 inhibitors and their in vitro and in vivo evaluation

17β-hydroxysteroid dehydrogenase type 10 (17β-HSD10) is a multifunctional mitochondrial enzyme and putative drug target for the treatment of various pathologies including Alzheimer's disease or some types of hormone-dependent cancer. In this study, a series of new benzothiazolylurea-based inhibitors were developed based on the structure-activity relationship (SAR) study of previously published compounds and predictions of their physico-chemical properties. This led to the identification of several submicromolar inhibitors (IC₅₀ ∼0.3 μM), the most potent compounds within the benzothiazolylurea class known to date. The positive interaction with 17β-HSD10 was further confirmed by differential scanning fluorimetry and the best molecules were found to be cell penetrable. In addition, the best compounds weren't found to have additional effects for mitochondrial off-targets and cytotoxic or neurotoxic effects. The two most potent inhibitors 9 and 11 were selected for in vivo pharmacokinetic study after intravenous and peroral administration. Although the pharmacokinetic results were not fully conclusive, it seemed that compound 9 was bioavailable after peroral administration and could penetrate into the brain (brain-plasma ratio 0.56).

Design, Synthesis and Biological Activities of (Thio)Urea Benzothiazole Derivatives

(Thio)ureas ((T)Us) and benzothiazoles (BTs) each have demonstrated to have a great variety of biological activities. When these groups come together, the 2-(thio)ureabenzothizoles [(T)UBTs] are formed, improving the physicochemical as well as the biological properties, making these compounds very interesting in medicinal chemistry. Frentizole, bentaluron and methabenzthiazuron are examples of UBTs used for treatment of rheumatoid arthritis and as wood preservatives and herbicides in winter corn crops, respectively. With this antecedent, we recently reported a bibliographic review about the synthesis of this class of compounds, from the reaction of substituted 2-aminobenzothiazoles (ABTs) with iso(thio)cyanates, (thio)phosgenes, (thio)carbamoyl chlorides, 1,1'-(thio)carbonyldiimidazoles, and carbon disulfide. Herein, we prepared a bibliographic review about those features of design, chemical synthesis, and biological activities relating to (T)UBTs as potential therapeutic agents. This review is about synthetic methodologies generated from 1968 to the present day, highlighting the focus to transform (T)UBTs to compounds containing a range substituents, as illustrated with 37 schemes and 11 figures and concluded with 148 references. In this topic, the scientists dedicated to medicinal chemistry and pharmaceutical industry will find useful information for the design and synthesis of this interesting group of compounds with the aim of repurposing these compounds.

Synthesis and Biological Importance of 2-(thio)ureabenzothiazoles

The (thio)urea and benzothiazole (BT) derivatives have been shown to have a broad spectrum of biological activities. These groups, when bonded, result in the 2-(thio)ureabenzothizoles (TBT and UBT), which could favor the physicochemical and biological properties. UBTs and TBTs are compounds of great importance in medicinal chemistry. For instance, Frentizole is a UBT derivative used for the treatment of rheumatoid arthritis and systemic lupus erythematosus. The UBTs Bentaluron and Bethabenthiazuron are commercial fungicides used as wood preservatives and herbicides in winter corn crops. On these bases, we prepared this bibliography review, which covers chemical aspects of UBTs and TBTs as potential therapeutic agents as well as their studies on the mechanisms of a variety of pharmacological activities. This work covers synthetic methodologies from 1935 to nowadays, highlighting the most recent approaches to afford UBTs and TBTs with a variety of substituents as illustrated in 42 schemes and 13 figures and concluded with 187 references. In addition, this interesting review is designed on chemical reactions of 2-aminobenzothiazoles (2ABTs) with (thio)phosgenes, iso(thio)cyanates, 1,1′-(thio)carbonyldiimidazoles [(T)CDI]s, (thio)carbamoyl chlorides, and carbon disulfide. This topic will provide information of utility for medicinal chemists dedicated to the design and synthesis of this class of compounds to be tested with respect to their biological activities and be proposed as new pharmacophores.

Functionalized Allopurinols Targeting Amyloid-Binding Alcohol Dehydrogenase Rescue Aβ-Induced Mitochondrial Dysfunction

Alzheimer's disease (AD) is the most common dementia affecting one in nine people over 65. Only a handful of small-molecule drugs and the anti-β amyloid (Aβ) antibody aducanumab are approved to treat AD. However, they only serve to reduce symptoms of advanced disease. Novel treatments administered early in disease progression before the accumulation of Aβ and tau reaches the threshold where neuroinflammation is triggered and irreversible neuronal damage occurs are more likely to provide effective therapy. There is a growing body of evidence implying that mitochondrial dysfunction occurs at an early stage of AD pathology. The mitochondrial enzyme amyloid-binding alcohol dehydrogenase (ABAD) binds to Aβ potentiating toxicity. Moreover, ABAD has been shown to be overexpressed in the same areas of the brain most affected by AD. Inhibiting the Aβ-ABAD protein-protein interaction without adversely affecting normal enzyme turnover is hypothesized to be a potential treatment strategy for AD. Herein, we conduct structure-activity relationship studies across a series of functionalized allopurinol derivatives to determine their ability to inhibit Aβ-mediated reduction of estradiol production from ABAD. The lead compound resulting from these studies possesses potent activity with no toxicity up to 100 μM, and demonstrates an ability to rescue defective mitochondrial metabolism in human SH-SY5Y cells and rescue both defective mitochondrial metabolism and morphology ex vivo in primary 5XFAD AD mouse model neurons.

Benzothiazole-Containing Analogues of Triclocarban with Potent Antibacterial Activity

Triclocarban (TCC) is a polychlorinated, aromatic, antimicrobial agent commercially used since the 1950s in personal care products for the prevention of spoilage and infections. Humans are frequently exposed to TCC due to its widespread use, leading to its substantial release into the aquatic environment. With the recent ban of TCC from some personal care products, implemented in 2016, many replacement antimicrobial compounds have been studied by researchers. Herein, we report the synthesis and biological activity of a series of diarylureas, analogues of TCC that bear the benzothiazole nucleus as one of the two aryl moieties. Among the studied compounds, 2bF and 2eC showed the highest antimicrobial activity against Staphylococcus aureus, being also more active than TCC, with MIC values of 8 µg/mL versus 16 µg/mL of TCC. Moreover, compound 2bB was much more active than TCC against Enterococcus faecalis, a Gram-positive bacterium that is, unfortunately, strongly responsible for nosocomial infections. Finally, interesting results were found for compound 2bG that, even though less active than the others, exerts an interesting bactericidal action.

Synthesis of 17β-hydroxysteroid dehydrogenase type 10 steroidal inhibitors: Selectivity, metabolic stability and enhanced potency

17beta-Hydroxysteroid dehydrogenase type 10 (17β-HSD10) is the only mitochondrial member of 17β-HSD family. This enzyme can oxidize estradiol (E2) into estrone (E1), thus reducing concentration of this neuroprotective steroid. Since 17β-HSD10 possesses properties that suggest a possible role in Alzheimer's disease, its inhibition appears to be a therapeutic strategy. After we identified the androsterone (ADT) derivative 1 as a first steroidal inhibitor of 17β-HSD10, new analogs were synthesized to increase the metabolic stability, to improve the selectivity of inhibition over 17β-HSD3 and to optimize the inhibitory potency. From six D-ring derivatives of 1 (17-CO), two compounds (17β-H/17α-OH and 17β-OH/17α-CCH) were more metabolically stable and did not inhibit the 17β-HSD3. Moreover, solid phase synthesis was used to extend the molecular diversity on the 3β-piperazinylmethyl group of the steroid base core. Eight over 120 new derivatives were more potent inhibitors than 1 for the transformation of E2 to E1, with the 4-(4-trifluoromethyl-3-methoxybenzyl)piperazin-1-ylmethyl-ADT (D-3,7) being 16 times more potent (IC₅₀ = 0.14 μM). Finally, D-ring modification of D-3,7 provided 17β-OH/17α-CCH derivative 25 and 17β-H/17α-OH derivative 26, which were more potent inhibitor than 1 (1.8 and 2.4 times, respectively).

Friend or enemy? Review of 17β-HSD10 and its role in human health or disease

17β-hydroxysteroid dehydrogenase (17β-HSD10) is a multifunctional human enzyme with important roles both as a structural component and also as a catalyst of many metabolic pathways. This mitochondrial enzyme has important functions in the metabolism, development and aging of the neural system, where it is involved in the homeostasis of neurosteroids, especially in regard to estradiol, changes in which make it an essential part of neurodegenerative pathology. These roles therefore, indicate that 17β-HSD10 may be a possible druggable target for neurodegenerative diseases including Alzheimer's disease (AD), and in hormone-dependent cancer. The objective of this review was to provide a summary about physiological functions and pathological roles of 17β-HSD10 and the modulators of its activity.