Novel styryl-thiazole hybrids as potential anti-Alzheimer's agents

Abstract

In this study, combining the thiazole and cinnamoyl groups into the styryl-thiazole scaffold, a series of novel styryl-thiazole hybrids (6a-p) was rationally designed, synthesized, and evaluated by the multi-target-directed ligands strategy as potential candidates for the treatment of Alzheimer's disease (AD). Hybrids 6e and 6i are the most promising among the synthesized hybrids since they are able to significantly increase cell viabilities in Aβ_1-42-exposed-human neuroblastoma cell line (6i at the concentration of 50 μg mL^-1 and 6e at the concentration of 25 μg mL^-1 resulted in ∼34% and ∼30% increase in cell viabilities, respectively). Compounds 6e and 6i exhibit highly AChE inhibitory properties in the experimental AD model at 375.6 ± 18.425 mU mL^-1 and 397.6 ± 32.152 mU mL^-1, respectively. Moreover, these data were also confirmed by docking studies and in vitro enzyme inhibition assays. Compared to hybrid 6e and according to the results, 6i also has the highest potential against Aβ_1-42 aggregation with over 80% preventive activity. The in silico prediction of the physicochemical properties confirms that 6i possesses a better profile compared to 6e. Therefore, compound 6i presents a promising multi-targeted active molecular profile for treating AD considering the multifactorial nature of AD, and it is reasonable to deepen its mechanisms of action in an in vivo experimental model of AD.

Fig. 1. Design of styryl-thiazole hybrids.

Scheme 1. Synthesis of styryl-thiazole hybrids 6a–p.

Fig. 2. Cell viability assays of 6e and 6i on the human neuroblastoma RA/BDNF differentiated SH-SY-5Y cells. SH-SY-5Y cells were incubated for 24 h with 6e and 6i (12.5–100 μg mL⁻¹) and then the % cell viability was assayed by MTT test. (−) Ctrl: untreated cells. (+) Ctrl: cells treated with 1.0% Triton X-100. Data are presented as the means ± SD for three independent experiments (n = 3). *p < 0.05 and **p < 0.01 significative vs. (+) Ctrl.

Fig. 3. Hoechst 33258 fluorescent staining analysis for genotoxicity assessments. a) Negative control – 20× magnification, b) compound 6e – 20× magnification, and c) compound 6i – 20× magnification. MN, micronucleus; L, lobbed nuclei, N, notched nuclei, and A, apoptotic.

Fig. 4. Neuroprotective properties of 6e and 6i (12.5–100 μg mL⁻¹) against Aβ_1–42-treated SH-SY-5Y cells assayed by MTT assay (−) Ctrl: untreated cells. (+) Ctrl: cells treated with 1.0% Triton X-100. Data are presented as the means ± SD for three independent experiments (n = 3). *p < 0.05 and **p < 0.01 significative vs. (+) Ctrl.

Fig. 5. In vitro AChE inhibitory activity of 6e and 6i.

Fig. 6. BACE1 inhibitory activity of 6e and 6i assessed by BACE1-FRET assay.

Fig. 7. In vitro Aβ_1–42 aggregation analysis in the experimental AD model. Data are presented as the means ± SD for three independent experiments (n = 3). *p < 0.05 and **p < 0.01.

Fig. 8. Flow cytometry analysis of 6e and 6i on the experimental AD model for 24 h. A) Negative control; B) Aβ_1–42 treatment; C) compound 6i (50 μg mL⁻¹); D) compound 6e (25 μg mL⁻¹).

Fig. 9. Binding mode of the best docking conformation of the binding mode of human AChE with 6e obtained by a) PyMol, b) LigPlot, and c) the table of hydrogen-bonds (H-bonds) (with distance Å), binding energy (kcal mol⁻¹), inhibition constant, number of H-bonds (drug–enzyme) and amino acid involved in interaction obtained from Protein–Ligand Interaction Profiler. The blue line and dashed green show the H-bonds in PyMol and LigPlot, respectively.

Fig. 10. Binding mode of the best docking conformation of the binding mode of human AChE with 6i obtained by a) PyMol, b) LigPlot, and c) the table of hydrogen-bonds (H-bonds) (with distance Å), binding energy (kcal mol⁻¹), inhibition constant, number of H-bonds (drug–enzyme) and amino acid involved in interaction obtained from Protein–Ligand Interaction Profiler. The blue line and dashed green show the H-bonds in Pymol and LigPlot, respectively.

Fig. 11. Interaction mode of the best docking conformation of the binding mode of human BACE with 6e obtained by a) PyMol, b) LigPlot, and c) the table of hydrogen-bonds (H-bonds) (with distance Å), binding energy (kcal mol⁻¹), inhibition constant, number of H-bonds (drug–enzyme) and amino acid involved in interaction obtained from Protein–Ligand Interaction Profiler. The blue line and dashed green show the H-bonds in Pymol and LigPlot, respectively.

Fig. 12. Interaction mode of the best docking conformation of the binding mode of human BACE with 6i obtained by a) PyMol, b) LigPlot, and c) the table of hydrogen-bonds (H-bonds) (with distance Å), binding energy (kcal mol⁻¹), inhibition constant, number of H-bonds (drug–enzyme) and amino acid involved in interaction obtained from Protein–Ligand Interaction Profiler. The blue line and dashed green show the H-bonds in Pymol and LigPlot, respectively.