VEGFR2 regulates p38 but not ERK1/2 in response to shear stress

Increased capillary shear stress in skeletal muscle causes luminal splitting. Signaling mechanisms initiating this form of angiogenesis are not known. We hypothesize that shear stress‐dependent activation of vascular endothelial growth factor receptor 2 (VEGFR2) causes p38 and ERK1/2 phosphorylation. Skeletal muscle endothelial cells were sheared (12 dynes/cm 2 , 2 or 6 hrs) in the presence or absence of 10 μM VEGFR2 kinase inhibitor I or 30 μM LNNA (nitric oxide synthase inhibitor) then lysed. Cells were treated with 20 ng/ml vascular endothelial growth factor 165 (VEGF) for 30 minutes then lysed. Male Sprague‐Dawley rats were administered prazosin (50 mg/L drinking water) to increase shear stress, the extensor digitorum longus was extracted at 2, 4 and 7 days. Lysates were analyzed by Western blot. In vitro, p38 and ERK1/2 phosphorylation increased at 2 hrs of shear stress but only p38 remained phosphorylated at 6 hrs. Sustained phosphorylation of p38 was not blocked by LNNA. VEGFR2 inhibition abrogated p38 but not ERK1/2 phosphorylation. Similarly, VEGF treatment of static cultures increased phosphorylation of p38 but not ERK1/2. In vivo, p38 phosphorylation was increased significantly in muscles exposed to increased shear stress for 7 days. Our data imply that VEGFR2 is a shear stress sensitive receptor necessary for p38 phosphorylation, and it may play a role in luminal splitting. Supported by CIHR.