Activating CD137 Signaling Promotes Sprouting Angiogenesis via Increased VEGFA Secretion and the VEGFR2/Akt/eNOS Pathway

Figure 7

CD137 signaling increased endothelial secretion of VEGFA. (a) Schematic diagram of different treatments used on CD137-activated ECs. (b) Detection of endothelial p-VEGFR2 (Tyr1173), p-Akt (Ser473), and p-eNOS (Ser1177) proteins by western blot after coculture with VEGFA or condition medium for 3 h. (c) The relative expression level of p-VEGFR2 (Tyr1173), p-Akt (Ser473), and p-eNOS proteins. (d, e) Detection of the VEGFA expression from endothelial extracts in control and CD137L groups. The relative VEGFA protein level was quantified in relation to β-actin. (f, g) The VEGFA expression and relative change of concentrated condition medium in the control and CD137L groups. (h) VEGFA concentration of the condition medium was measured with ELISA detection after treatment with CD137L for 3 h. (i, j) The VEGFA expression in exosomes, which derived from the supernatant of the control and CD137L groups. , , , . The CD137 agonist group was stimulated with TNFα for 24 hours and then CD137L for 3 hours. The Anti-CD137 group was treated with inhibitory CD137 signaling antibody for 30 minutes then CD137L for 3 hours. Condition medium contained the supernatant after the activation of endothelial CD137 signaling for 3 hours.

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