Effects of DPP-4 on ROS generation (A and B) and RAGE gene expression (D) in HUVECs and (C) representative binding sensorgram of DPP-4 to immobilized M6P/IGF-IIR. HUVEC were treated with or without the indicated concentrations of DPP-4 in the presence or absence of 50 μM M6P, 5 μg/ml M6P/IGF-IIR-Ab, or 10 nM linagliptin for 4 hr. (A and B) Then the cells were incubated with DHE. Upper panel shows typical microphotographs of the cells. Lower panel shows quantitative data of ROS generation evaluated by fluorescent intensity. (A) N = 12 per group. (B) N = 27 per group. (D) Total RNAs were transcribed and amplified by real-time PCR. Data were normalized by the intensity of β-actin mRNA-derived signals and then related to the value obtained with control. N = 3 per group. (C) DPP-4 at 0.1 and 0.3 μM was injected on the sensor chip immobilized M6P/IGF-IIR. N = 3 per group. * and **, p < 0.05 and p < 0.01 compared to the value with control, respectively.