Key result
Oscillatory flow and reduced stretch impair porcine endothelial function, with oscillatory flow driving superoxide production.
Why the study?
Do reduced cyclic stretch and oscillatory shear stress independently induce endothelial dysfunction and oxidative stress in an ex vivo arterial model?
Do reduced cyclic stretch and oscillatory shear stress independently induce endothelial dysfunction and oxidative stress in an ex vivo arterial model?
This ex vivo study demonstrates that shear stress and cyclic stretch independently and differentially modulate endothelial function and oxidative stress in distinct regions of the vascular wall.
Answers are grounded in this paper and cite their sources.
Hypothesis-generating for flow-mediated endothelial impairment; should not yet change clinical practice.
Cyclic circumferential stretch and shear stress caused by pulsatile blood flow work in concert, yet are very different stimuli capable of independently mediating endothelial function by modulating eNOS expression, oxidative stress (via production of superoxide anion) and NO bioavailability. Porcine carotid arteries were perfused using an ex vivo arterial support system for 72 h. Groups we created by combining normal (5%) and reduced (1%) stretch with high shear (6 +/- 3 dynes/cm(2)) and oscillatory shear (0.3 +/- 3 dynes/cm(2)) stress while maintaining a pulse pressure of 80 +/- 10 mm Hg. Oscillatory flow and reduced stretch both proved detrimental to endothelial function, whereas oscillatory flow alone dominated total endogenous vascular wall superoxide anion production. Yet, when superoxide anion production was analyzed in just the endothelial region, we observed that it was modulated more significantly by reduced cyclic stretch than by oscillatory shear, emphasizing an important distinction between shear- and stretch-mediated effects to the vascular wall. Western blotting analysis of eNOS and nitrotyrosine proved that they too are more significantly negatively modulated by oscillatory flow than by reduced stretch. These findings point out how shear and stretch stimulate regions of the vascular wall differently, affecting NO bioavailability and contributing to vascular disease.
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Thacher et al. (2009) studied Endothelial dysfunction and oxidative stress. Combinations of normal/reduced stretch and high/oscillatory shear stress was evaluated on Endothelial function, oxidative stress, and eNOS expression. Oscillatory flow and reduced stretch impaired endothelial function in an ex vivo porcine model, with oscillatory flow dominating total vascular wall superoxide anion production.
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