Ryoji Koshida

Angiostatin A Negative Regulator of Endothelial-Dependent Vasodilation

Background—Angiostatin is known to inhibit certain aspects of endothelial function, eg, angiogenesis. Here we investigated the effects of angiostatin on another aspect of endothelial function, vasodilation, and examined mechanisms of inhibition—namely, association of heat-shock protein 90 (hsp90) with endothelial nitric oxide synthase (eNOS) and endothelial generation of nitric oxide (·NO) and superoxide anion (&OV0151;). This avenue of investigation was based on recent reports suggesting that hsp90 modulates NOS production of ·NO and &OV0151;. Methods and Results—Effects of angiostatin on vasodilation were determined in arterioles with the use of videomicroscopy in response to endothelium- and ·NO-dependent vasodilators, acetylcholine (ACh) and vascular endothelial growth factor (VEGF), and an endothelium-independent agonist, papaverine. Association of hsp90 with eNOS was determined in rat aortas and bovine aortic endothelial cells (BAECs). Effects of angiostatin on ·NO and &OV0151; generation by BAECs were determined by ozone chemiluminescence and superoxide dismutase (SOD)–inhibitable ferricytochrome c reduction, respectively. Angiostatin impaired vasodilation mediated by ACh and VEGF but not papaverine. Pretreating arterioles with polyethylene glycolated–SOD (PEG-SOD) improved vasodilation to ACh and VEGF. Angiostatin decreased the association of hsp90 with eNOS in aortas and BAEC cultures and increased &OV0151; generation in stimulated BAECs by an L&ggr;-nitroargininemethylester (L-NAME)–inhibitable mechanism. Conclusions—These data indicate angiostatin alters endothelial function by allowing eNOS to generate &OV0151; on activation. Such changes in enzyme function begin to explain, in part, why angiostatin is antiangiogenic and impairs endothelium-dependent vasodilation.

Role of Focal Adhesion Kinase in Flow-Induced Dilation of Coronary Arterioles

Backgound—Flow-induced regulation of endothelial NO synthase (eNOS) depends on integrin signaling and tyrosine kinase activation. Integrins cluster in focal adhesion complexes, where the extracellular matrix is connected to the cytoskeleton and where focal adhesion kinase (FAK) is located. FAK plays a central role in integrin signaling and Src activation. Accordingly, we hypothesized that FAK plays an important role in flow-induced dilation (FID). Methods and Results—To inactivate FAK-dependent signaling, anti-FAK, phosphospecific (Tyr397) antibody (FAKab), which binds against the FAK autophosphorylation site, was incorporated into endothelium of rat coronary arterioles using liposomal transfection. The responses to flow, acetylcholine (Ach), or the NO donor MAHAMANONOate (NOC-9) were observed before and after FAKab. In control and vehicles (denatured antibody or transfecting reagent alone), flow produced progressive dilation to a maximal value of 35% increase in diameter, which was inhibited by N&ohgr;-nitro-l-arginine methyl ester (l-NAME). However, FAKab prevented FID (P<0.01 versus control). Combined treatment with FAKab and l-NAME did not produce inhibition greater than FAKab alone. FAKab did not blunt Ach- or NOC-9–induced dilation. Western analysis demonstrated that FAKab prevented flow-induced phosphorylation of FAK (pY397-FAK), Akt (pS473-Akt), and eNOS (pS1179-eNOS). Conclusion—Our study demonstrates the pivotal role of FAK in NO-mediated FID. Inhibition of FAK signaling with FAKab impaired FID and phosphorylation of Akt and eNOS. Our data suggest that the activation of FAK is central to the mechanotransduction of FID via regulation of activation of Akt and eNOS.