Fig. 2.

DPPB increases eNOS activity and endothelial NO release. (A) EA.hy926 cells were treated with 10 μM of the indicated compound or solvent vehicle for 24 h. Endothelial NO release of eleven lignan derivatives was measured by incubation with the NO-sensitive fluorescent probe diaminofluorescein-2. Fluorescence values were normalized to the number of viable cells as determined by resazurin staining (*p < 0.05; **p < 0.01) (mean ± SEM, n = 3). (B) EA.hy926 cells were treated with 10 μM of the indicated compound or solvent vehicle for 24 h. Then a [¹⁴C]l-arginine/[¹⁴C]l-citrulline conversion assay was performed as described in Section 2. [¹⁴C]l-citrulline production was normalized to the untreated control (**p < 0.01) (mean ± SEM, n = 4). (C) EA.hy926 cells were incubated with 10 μM DPPB for 24 h. Mevastatin (Mev, 1 μM) was used as positive control. NO release was quantified as in (A) (*p < 0.01) (mean ± SEM, n = 3). (D) EA.hy926 cells were treated with the indicated concentration of DPPB for 24 h. Then a [¹⁴C]l-arginine/[¹⁴C]l-citrulline conversion assay was performed as in (B). Ascorbic acid (Asc, 100 μM) served as a positive control. [¹⁴C]l-citrulline production was normalized to the untreated control (**p < 0.01; ***p < 0.001; n.s., not significant) (mean ± SEM, n = 3). (E) HUVECs were incubated with 10 μM of DPPB for 24 h, and eNOS activity was determined as in (B) (**p < 0.01) (mean ± SEM, n = 3).