Shear stress acting on endothelial cells produces vasodilation. This is arguably the most physiologically important endothelial mechanism of dilation and occurs in virtually every vascular bed. Recent data from our laboratory indicate that flow-mediated dilation (FMD) occurs in coronary arterioles from patients with coronary disease however it operates through a novel mechanism involving endothelial production of reactive oxygen species (ROS) including hydrogen peroxide (H2O2). Surprisingly the mitochondrial respiratory chain plays a necessary role in FMD in the human heart, however it is not known how mitochondria are involved in the transduction of mechanical shear stress on the surface of the endothelium to elicit dilation. Our overall hypothesis is that shear acting on endothelial cells through attached cytoskeletal elements stimulates release from the mitochondria ofH2O2, an endothelial derived hyperpolarizing factor (EDHF). We shall test this hypothesis in three ways. First antimycin A and TNFa will be used to determine if pharmacological stimulation of mitochondrial ROS release can elicit dilation of human coronary arterioles. In separate studies, we shall use novel antioxidants targeted to the mitochondrial inner membrane to determine whether H2O2 generated from within the mitochondria is necessary for FMD. A bioassay system will confirm whether H2O2 is indeed an EDHF mediating FMD in the human coronary circulation. Second we will use immunohistochemistry and specific pharmacological and molecular approaches including siRNA to determine whether endothelial cytoskeletal elements play a necessary role in FMD and mitochondrial ROS generation. Third, we shall test the hypothesis that nitric oxide through its inhibitory effect on mitochondrial respiration reduces FMD in the human heart. This will be done using nitric oxide donors, measuring mitochondrial complex activity and ROS generation. These experiments may identify a pathway not previously described by which nitric oxide can inhibit EDHF-mediated dilation;namely, by blocking mitochondrial production of ROS. Collectively these aims address a novel mechanism of endothelium-dependent vasodilation involving mitochondrial generation of ROS, thus far reported only in human hearts. These studies should identify new links among cell processes including mechanotransduction, respiration, and redox signaling that regulate physiological events such as vasodilation.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL080704-05
Application #
7744632
Study Section
Vascular Cell and Molecular Biology Study Section (VCMB)
Program Officer
Mcdonald, Cheryl
Project Start
2006-01-01
Project End
2011-12-31
Budget Start
2010-01-01
Budget End
2011-12-31
Support Year
5
Fiscal Year
2010
Total Cost
$367,766
Indirect Cost
Name
Medical College of Wisconsin
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
937639060
City
Milwaukee
State
WI
Country
United States
Zip Code
53226
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Kizhakekuttu, Tinoy J; Wang, Jingli; Dharmashankar, Kodlipet et al. (2012) Adverse alterations in mitochondrial function contribute to type 2 diabetes mellitus-related endothelial dysfunction in humans. Arterioscler Thromb Vasc Biol 32:2531-9
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Zinkevich, Natalya S; Gutterman, David D (2011) ROS-induced ROS release in vascular biology: redox-redox signaling. Am J Physiol Heart Circ Physiol 301:H647-53
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Widlansky, Michael E; Gutterman, David D (2011) Regulation of endothelial function by mitochondrial reactive oxygen species. Antioxid Redox Signal 15:1517-30

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