Endothelial cytoskeletal elements are critical for flow-mediated dilation in human coronary arterioles

Mitochondrial H2O2 contributes to flow-mediated dilation (FMD) in human coronary arterioles (HCA). We examined the hypothesis that the endothelial cytoskeleton plays a critical role in transducing endothelial wall shear stress into a stimulus for releasing mitochondrial ROS. Phallacidin together with alpha-, beta-tubulin antibodies and Mito-Tracker Red showed the proximity of F-actin, microtubules and mitochondria in endothelial cells. Cytochalasin D (CytoD) and nocodazole (Noc) disrupted endothelial F-actin and microtubules in HCA, respectively, concurrent with a reduction in the generation of cytosolic and H2O2 (hydroethidine and dichlorodihydrofluorescein fluorescence) and mitochondrial superoxide (mitoSox) during flow (control: 3.5 +/- 1.6, Cyto D: 0.51 +/- 0.2, Noc: 0.81 +/- 0.6). FMD, but not the dilation to bradykinin or papaverine, was reduced by Cyto D (26 +/- 10% vs. 56 +/- 3%) or Noc (26 +/- 11% vs. 58 +/- 7%). These results suggest that cytoskeletal elements are a critical component of the signaling mechanism linking endothelial shear stress and mitochondrial release of ROS in the human coronary microcirculation.