Vascular homeostasis is critically dependent upon factors released from the endothelium, the most prominent of which are nitric oxide (NO), prostacyclin (PGI2), and a class of endothelium-derived hyperpolarizing factors. The presence of vascular disease and its risk factors can change the balance of these endothelial factors. Our previous studies have demonstrated that such a change in human coronary arterioles (HCAs) from subjects with coronary artery disease (CAD), where the physiological stimulus of laminar flow or shear induces endothelial production of hydrogen peroxide (H2O2) to elicit dilation; in the absence of disease, however, the same stimulus releases NO as the main dilator factor. How shear induces the release of two distinct factors in flow-mediated dilation (FMD) remains incompletely understood. While both H2O2 and NO dilate HCAs, each has different or opposing non-vasomotor effects on vessel wall homeostasis and propensity for atherosclerosis. The overall goal of this project is to elucidate the intracellular pathways responsible for the releaseof these two mediators of FMD, expanding upon published and preliminary data indicating a crucial role for transient receptor potential vanilloid (TRPV) channels in endothelial production o vasodilator factors. The overall hypothesis of this proposal is that FMD of HCAs involves a functional switch of TRPV channels from health (TRPV1/2; TRPV type 1 and 2) to disease (TRPV4; TRPV type 4). As a result of this switch, the mediator of dilation changes from NO to H2O2. We propose three specific aims to test this hypothesis.
Aim 1 will determine the spectrum of endothelial TRPV channel involvement in FMD of coronary arteries in the absence and presence of CAD.
Aim 2 attempts to define the signaling pathways responsible for flow-induced TRPV activation and production of disparate endothelial dilator factors in non-CAD versus CAD. We will pursue preliminary data suggesting that arachidonic acid (AA) serves as an endogenous activator of TRPV4 in FMD of HCAs, likely via a potentially novel arachidonate recognition sequence (ARS) on TRPV4 protein. We will also test the innovative hypothesis that NO- and H2O2-mediated allosteric regulation of TRPV channels reinforces two distinct pathways of vasodilator release in non-CAD versus CAD. Finally, aim 3 will determine whether TRPV4 serves as a molecular switch contributing to the change of endothelial dilator factors and redox balance. Studies will be conducted on freshly isolated human coronary vessels and endothelial cells using a multifaceted approach incorporating isolated vessel reactivity, Ca2+ imaging, patch-clamping recording of TRP channel activity, biochemical methods such as ligand binding assays, and molecular techniques including gene overexpression and protein mutagenesis. Genetically engineered mice will also be used to corroborate human data and to support causality and in vivo significance. We expect that success of the proposed work will provide new translational and mechanistic insights into the pathways responsible for the transition of dilator factors and vascular oxidative stress in CAD and impact our understanding of coronary atherosclerosis.
Coronary artery disease (CAD) is the leading cause of death for both men and women in the US. Accumulating clinical trials indicate that coronary microvascular dysfunction contributes to myocardial ischemia and angina and predicts outcomes of patients with CAD. Our application addresses a change in mechanism of endothelium-mediated dilation in the human coronary microcirculation as an underlying cause of coronary microvascular dysfunction.
|Xu, Suowen; Liu, Bin; Yin, Meimei et al. (2016) A novel TRPV4-specific agonist inhibits monocyte adhesion and atherosclerosis. Oncotarget 7:37622-37635|
|Nishijima, Yoshinori; Cao, Sheng; Chabowski, Dawid S et al. (2016) Contribution of KV1.5 Channel to H2O2-Induced Human Arteriolar Dilation and its Modulation by Coronary Artery Disease. Circ Res :|
|Baumgardt, Shelley L; Paterson, Mark; Leucker, Thorsten M et al. (2016) Chronic Co-Administration of Sepiapterin and L-Citrulline Ameliorates Diabetic Cardiomyopathy and Myocardial Ischemia/Reperfusion Injury in Obese Type 2 Diabetic Mice. Circ Heart Fail 9:e002424|
|Ho, W S V; Zheng, X; Zhang, D X (2015) Role of endothelial TRPV4 channels in vascular actions of the endocannabinoid, 2-arachidonoylglycerol. Br J Pharmacol 172:5251-64|
|Lakshmikanthan, Sribalaji; Zheng, Xiaodong; Nishijima, Yoshinori et al. (2015) Rap1 promotes endothelial mechanosensing complex formation, NO release and normal endothelial function. EMBO Rep 16:628-37|
|Nishijima, Yoshinori; Zheng, Xiaodong; Lund, Hayley et al. (2014) Characterization of blood pressure and endothelial function in TRPV4-deficient mice with l-NAME- and angiotensin II-induced hypertension. Physiol Rep 2:e00199|
|Lakshmikanthan, Sribalaji; Zieba, Bartosz J; Ge, Zhi-Dong et al. (2014) Rap1b in smooth muscle and endothelium is required for maintenance of vascular tone and normal blood pressure. Arterioscler Thromb Vasc Biol 34:1486-94|
|Rahaman, Shaik O; Grove, Lisa M; Paruchuri, Sailaja et al. (2014) TRPV4 mediates myofibroblast differentiation and pulmonary fibrosis in mice. J Clin Invest 124:5225-38|
|Zheng, Xiaodong; Zinkevich, Natalya S; Gebremedhin, Debebe et al. (2013) Arachidonic acid-induced dilation in human coronary arterioles: convergence of signaling mechanisms on endothelial TRPV4-mediated Ca2+ entry. J Am Heart Assoc 2:e000080|
|Zhang, David X; Borbouse, Lena; Gebremedhin, Debebe et al. (2012) H2O2-induced dilation in human coronary arterioles: role of protein kinase G dimerization and large-conductance Ca2+-activated K+ channel activation. Circ Res 110:471-80|
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