PMC

Effect of two isoquinoline derivatives on flow cytometry-based efflux assay. Calcein fluorescence of KB-V1 cells treated with 1, 5, 10 μmol/L of isoquinoline 1 (A) or isoquinoline 2 (B). The fluorescence intensities (mean ± SD) at 1, 5, 10 μmol/L of isoquinoline 1 were 433 ± 988, 2318 ± 1832, and 4200 ± 2588, respectively. Similarly, the fluorescence intensities at 1, 5, 10 μmol/L of isoquinoline 2 were 452 ± 867, 2498 ± 1773, and 4206 ± 2158, respectively. As a reference, the calcein fluorescence with 10 μmol/L cyclosporin A (4867 ± 2942) and control (83 ± 871) is included (A and B). Calcein fluorescence of parental KB-3–1 cells in the presence of 10 μmol/L of isoquinoline 1 (7527 ± 4431) (C) or isoquinoline 2 (7454 ± 3664) (D), and control (6261 ± 3518). Calcein fluorescence of HCT-15 cells treated with 0.1, 1, 10 μmol/L of isoquinoline 2 (E). The fluorescence intensities (mean ± SD) at 0.1, 1, 10 μmol/L of isoquinoline 2 were 1518 ± 1435, 3750 ± 2381, and 4669 ± 2886, respectively, and that of control was 786 ± 921. Rhodamine 123 fluorescence of KB-V1 cells treated with 1, 5, 10 μmol/L of isoquinoline 2; the fluorescence intensities (mean ± SD) at 1, 5, 10 μmol/L of isoquinoline 2 were 65 ± 245, 658 ± 504, and 1470 ± 739, respectively, and the control was 79 ± 251 (F). The representative data of three independent experiments are shown. P values were determined with the two-tailed Student’s t test (*, P < 0.05 compared with control).

Reaction scheme of the conversion of isoquinoline to isoquinoline-1-one, catalyzed by isoquinoline 1-oxidoreductase (IOR).

Effect of isoquinoline 2 on ATPase activity of ABCB1 and [¹²⁵I]IAAP photolabeling of ABCB1. A, ABCB1 expressing membrane vesicles was incubated with varying concentrations of isoquinoline 2 in the presence or absence of 0.25 mmol/L vanadate. The ABCB1-specific activity was recorded as the vanadate-sensitive ATPase activity. The result is a typical experiment of three independent experiments. Data are mean ± SE of three independent experiments performed in duplicate. B, Membrane vesicles from Hi-five cells overexpressing human ABCB1 were incubated with varying concentrations of isoquinoline 2 and treated with 3 nmol/L [¹²⁵I]IAAP (2,200 Ci/mmol). The autoradiogram and quantification of incorporation of IAAP into the ABCB1 band from three independent experiments. Points, mean (n = 3); bars, SE. C, KB-V1/ Isoquinoline 2 and HCT-15/ Isoquinoline 2 cells were cultured with 1 μmol/L isoquinoline 2 for 10 days. KB-V1/ Isoquinoline 2 cells were compared with KB-V1 cells cultured without vinblastine. mRNA expression levels of ABCB1 were measured by RT-qPCR relative to the cells in the absence of isoquinoline 2. Data are mean ± SE (n = 3).

Isoquinoline alkaloids of bisbenzylisoquinoline- and pavinane-types and simple isoquinoline alkaloids with interesting biological activity in connection with AD.