Oxidized LDL autoantibodies, endothelial dysfunction, and transplant-associated arteriosclerosis.
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OBJECTIVE: Impaired flow-mediated dilation (FMD) occurs in disease states associated with atherosclerosis, including SLE. The primary hemodynamic determinant of FMD is wall shear stress, which is critically dependent on the forearm microcirculation. We explored the relationship between FMD, diastolic shear stress (DSS), and the forearm microcirculation in 32 patients with SLE and 19 controls. METHODS AND RESULTS: DSS was calculated using (mean diastolic velocity x 8 x blood viscosity)/baseline brachial artery diameter. Doppler velocity envelopes from the first 15 seconds of reactive hyperemia were analyzed for resistive index (RI), and interrogated in the frequency domain to assess forearm microvascular hemodynamics. FMD was significantly impaired in SLE patients (median, 2.4%; range, -2.1% to 10.7% versus median 5.8%; range, 1.9% to 14%; P<0.001). DSS (dyne/cm2) was significantly reduced in SLE patients (median, 18.5; range, 3.9 to 34.0 versus median 21.8; range, 14.1 to 58.7; P=0.037). A strong correlation between FMD and DSS, r(s)=0.65, P=0.01 was found. Postischemic RI was not significantly different between the 2 groups; however, there were significant differences in the power-frequency spectrums of the Doppler velocity envelopes (P<0.05). CONCLUSIONS: These data suggest that in SLE, altered structure and function of the forearm microcirculation contributes to impaired FMD through a reduction in shear stress stimulus.
OBJECTIVE: Angiotensin II (AngII) disrupts the regulation of the cerebral circulation through superoxide, a reactive oxygen species (ROS) generated by a nox2-containing NADPH oxidase. We tested the hypothesis that AngII-derived superoxide reacts with nitric oxide (NO) to form peroxynitrite, which, in turn, contributes to the vascular dysfunction. METHODS AND RESULTS: Cerebral blood flow (CBF) was monitored by laser Doppler flowmetry in the neocortex of anesthetized mice equipped with a cranial window. AngII (0.25+/-0.02 microg/kg/min; intravenous for 30 to 45 minutes) attenuated the cerebral blood flow (CBF) increase produced by topical application of the endothelium-dependent vasodilator acetylcholine (-43+/-1%) and by whisker stimulation (-47+/-1%). AngII also increased the nitration marker 3-nitrotyrosine (3-NT) in cerebral blood vessels, an effect dependent on NO and nox2-derived ROS. Both the cerebrovascular effects of AngII and the nitration were attenuated by pharmacological inhibition or genetic inactivation of NO synthase. The nitration inhibitor uric acid or the peroxynitrite decomposition catalyst FeTPPS abolished AngII-induced cerebrovascular nitration and prevented the cerebrovascular effects of AngII. CONCLUSIONS: These findings provide evidence that peroxynitrite, formed from NO and nox2-derived superoxide, contributes to the deleterious cerebrovascular effects of AngII. Inhibitors of peroxynitrite action may be valuable tools to counteract the deleterious cerebrovascular effects of AngII-induced hypertension.
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