The effect of IFNα2b on endothelial cell proliferation and nitric oxide (NO) bioavailability. (A) IFNα2b had no effect on the number of HAoECs at 24, 48, or 72 h compared to vehicle control. Bars represent the mean and SE of the mean; combined results from n=3 independent experiments. (B) Cellular proliferation as measured by MTT assay shows a positive effect of vascular endothelial growth factor (VEGF) (20 ng/mL) and a negative effect of the NO scavenger PTIO (10 μM) on proliferation in both HAoEC and human venous endothelial cell (HUVEC) after 24 h. The absorbance values were normalized to vehicle-treated cells. (C) IFNα2b (10 ng/mL) had no effect on proliferation compared to vehicle control in HAoEC at 24, 48, or 72 h. (D) In contrast, IFNα2b significantly increased HUVEC proliferation at 24 h (P=0.047). This effect persisted to 48 h but was not statistically significant (P=0.134) at this time point. (E) The NO bioavailability (as measured by supernatant nitrite concentration) was not changed by IFNα2b (0.1–10 ng/mL) at either 6 or 24 h.