Synthesis and Identification of Pregnenolone Derivatives as Inhibitors of Isozymes of 5α-Reductase

Synthesis, In Vitro Biological Evaluation of Antiproliferative and Neuroprotective Effects and In Silico Studies of Novel 16E-Arylidene-5α,6α-epoxyepiandrosterone Derivatives

Steroids constitute an important class of pharmacologically active molecules, playing key roles in human physiology. Within this group, 16E-arylideneandrostane derivatives have been reported as potent anti-cancer agents for the treatment of leukemia, breast and prostate cancers, and brain tumors. Additionally, 5α,6α-epoxycholesterol is an oxysterol with several biological activities, including regulation of cell proliferation and cholesterol homeostasis. Interestingly, pregnenolone derivatives combining these two modifications were described as potential neuroprotective agents. In this research, novel 16E-arylidene-5α,6α-epoxyepiandrosterone derivatives were synthesized from dehydroepiandrosterone by aldol condensation with different aldehydes followed by a diastereoselective 5α,6α-epoxidation. Their cytotoxicity was evaluated on tumoral and non-tumoral cell lines by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Furthermore, the assessment of the neuroprotective activity of these derivatives was performed in a dopaminergic neuronal cell line (N27), at basal conditions, and in the presence of the neurotoxin 6-hydroxydopamine (6-OHDA). Interestingly, some of these steroids had selective cytotoxic effects in tumoral cell lines, with an IC50 of 3.47 µM for the 2,3-dichlorophenyl derivative in the breast cancer cell line (MCF-7). The effects of this functionalized epoxide on cell proliferation (Ki67 staining), cell necrosis (propidium iodide staining), as well as the analysis of the nuclear area and near neighbor distance in MCF-7 cells, were analyzed. From this set of biological studies, strong evidence of the activation of apoptosis was found. In contrast, no significant neuroprotection against 6-OHDA-induced neurotoxicity was observed for the less cytotoxic steroids in N27 cells. Lastly, molecular docking simulations were achieved to verify the potential affinity of these compounds against important targets of steroidal drugs (androgen receptor, estrogen receptor α, and 5α-reductase type 2, 17α-hydroxylase-17,20-lyase and aromatase enzymes). This in silico study predicted a strong affinity between most novel steroidal derivatives and 5α-reductase and 17α-hydroxylase-17,20-lyase enzymes.

Activity of steroid 4 and derivatives 4a-4f as inhibitors of the enzyme 5α-reductase 1

It is known that the growth of prostate metastatic bone tumor depends on androgens, and tumor formation can start from migratory malignant cells produced in that organ. These cells exhibit grater type 1 5α-reductase (5α-R1) activity than type 2 5α-reductase. Noteworthy, both isozymes convert testosterone (T) to the more active androgen dihydrotestosterone (DHT) in the target tissues. Thus, in order to potentially improve the prognosis of this disease, in this work, seven derivatives of 17-(1H-benzimidazol-1-yl)-16-formillandrosta-5,16-dien-3β-yl benzoate (4a-f) and 17-(1H-benzimidazol-1-yl)-3-hydroxy-16-formylandrost-5,16-diene (4) were synthesized, characterized and identified as inhibitors of type 1 5α-reductase (5αR1). These derivatives having the advantage of improved plasma half-life. The inhibitory activity of the compounds towards 5α-R1 isoenzyme was determined by conversion of T into DHT in the presence or absence of compounds 4, 4a-f. Further, in vivo experiments were also carried out, treating gonadectomized hamsters with T and/or 4, 4a-f and evaluating their effect on the diameter of hamster flank organs and on the weight of the prostatic and seminal vesicles. Results indicated that compounds 4, 4b, 4c, served as in vitro inhibitors of the enzyme 5α-R1 and pharmacological experiments showed that 4 and derivatives 4a-f decreased the diameter of the flank glands, the weight of the prostate and seminal vesicles of treated hamsters without any appreciable toxicity during observation. Noteworthy the fact that compound 4 is the product, in all cases, of the hydrolysis of the series of esters 4a-f, thus they can serve as precursors (prodrugs) of the active form 4.

Synthesis and cytotoxic effect of pregnenolone derivatives with one or two α,β-unsaturated carbonyls and an ester moiety at C-21 or C-3

Four series of pregnenolone derivatives having one or two α,β-unsaturated carbonyls and an ester moiety at C-21 or C-3 were synthetized to compare their cytotoxicity effect. The final compounds were evaluated on three human cancer cell lines: PC-3 (prostate cancer), MCF-7 (breast cancer), SKLU-1 (lung cancer) and a noncancerous cell line HGF (human gingival fibroblast). Two steroids with a 4-fluorinated benzoic acid ester at C-21 were the most active against lung cancer cell line with IC₅₀ of 13.1 ± 1.2 and 12.8 ± 0.5 μM and showed a low percentage of cytotoxicity for noncancerous cells (27.63 ± 2.3 and 18.39 ± 1.2% in the screening at 50 μM).