P-glycoprotein (P-gp) is a transmembrane efflux pump that has been associated with ineffective cancer chemotherapy and multidrug resistance (MDR). Chemical inhibitors of P-gp could have potential cancer therapeutic applications by preventing or reversing MDR. To exploit this, we designed twenty-five tetrahydroquinolinone analogs bearing pyridyl methyl carboxylate at C₃ and different substituents at C₄ as MDR reversal agents. The inhibitory effects of the synthesized compounds against P-gp were assessed by flow cytometric determination of rhodamine 123 accumulation in P-gp over-expressing MES-SA/DX5 cells. Fluorescence imaging of intracellular rhodamine 123 accumulation in MES-SA/DX5 cells was also performed. Furthermore, the effect of active derivatives on the reduction of doxorubicin's IC₅₀ in MES-SA/DX5 cells was evaluated using MTT assay. Molecular docking was used to confirm the binding mode of some of the synthesized compounds. Five compounds in group A, bearing a 2-pyridyl methyl ester substituent at the C₃ position, significantly increased rhodamine accumulation at 25 μM comparable to verapamil, a well-established P-gp inhibitor, while only 2 compounds in group B bearing 3-pyridyl methyl ester at the same position had this effect. This study shows that tetrahydroquinolinones containing methyl pyridine esters could represent an attractive scaffold for the discovery of P-gp inhibitors as MDR reversal agents in cancer cells.

中文翻译：

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四氢喹啉酮衍生物作为有效的P-糖蛋白抑制剂：设计，合成，生物学评估和分子对接分析

P-糖蛋白（P-gp）是跨膜外排泵，与无效的癌症化疗和多药耐药性（MDR）相关。P-gp的化学抑制剂通过预防或逆转MDR可能具有潜在的癌症治疗应用。为了利用这一点，我们设计了二十五个四氢喹啉酮类似物，其在C ₃处带有吡啶甲基羧酸盐，在C ₄处具有不同的取代基。作为MDR逆转代理。通过流式细胞术测定过表达P-gp的MES-SA / DX5细胞中若丹明123的积累来评估合成化合物对P-gp的抑制作用。还进行了MES-SA / DX5细胞中细胞内若丹明123积累的荧光成像。此外，使用MTT分析评估了活性衍生物对MES-SA / DX5细胞中阿霉素IC ₅₀减少的影响。分子对接用于确认某些合成化合物的结合模式。A组中的5种化合物，在C ₃处带有2-吡啶基甲基酯取代基与有效的P-gp抑制剂维拉帕米相比，在25μM的位置上若丹明累积量显着增加，而B组中只有2个在相同位置带有3-吡啶基甲基酯的化合物具有这种作用。这项研究表明，含有甲基吡啶酯的四氢喹啉酮可能是发现P-gp抑制剂作为癌细胞MDR逆转剂的诱人支架。