Endothelial cells release nitric oxide, prostaglandin I2 and endothelium-derived hyperpolarizing factor (EDHF) that reduce vascular tone and counteract vasoconstriction. Ischemic heart disease, heart failure and hyperten- sion are associated with vasoconstriction that is attributed, in part, to reductions in endothelium-dependent di- lation. Therapeutic approaches restoring endothelial function represent promising new treatments for cardio- vascular diseases with a major impact on health. We have identified a 15-lipoxygenase (LO) metabolite of ara- chidonic acid, 11(R),12(S),15(S)-trihydroxy-eicosatrienoic acid (11,12,15-THETA), that acts as an EDHF. It relax arteries, in part, by activating apamin-sensitive, small conductance, calcium-activated potassium (SKCa) channels and hyperpolarizing smooth muscle cells (SMCs). It also acts by inhibition of RhoA activation. 11,12,15-THETA mediates a portion of the endothelium-dependent relaxations to acetylcholine (ACh), in- creases in flow and AA and opposes the action of vasoconstrictors. We will test the hypothesis that 11,12,15- THETA mediates relaxations to ACh and AA by a unique combination of mechanisms: (1) activating a hetero- trimeric guanine nucleotide binding protein (G protein) that opens SKCa channels resulting in hyperpolarization of SMCs and (2) inhibiting the activation of the small GTPase RhoA reducing the calcium sensitivity of contrac- tile proteins. These studies will indicate that 11,12,15-THETA is an EDHF and an endothelium-derived calcium (Ca) desensitizer. 11(R),12(S),15(S)-THETA increases GTP335S binding to rabbit arterial membranes implicat- ing a G protein-coupled binding site/receptor. Using biochemical and molecular methods, we will identify the G protein(s) that is coupled to 11,12,15-THETA action. Using patch clamp and bioassay methods, we will char- acterize the role of the G protein in the regulation of SKCa channel activity, hyperpolarization and dilation by 11,12,15-THETA. These studies will provide new insights into the molecular mechanism of action of 11,12,15- THETA and the regulation of vascular SKCa channel activity. Agonists such as norepinephrine and angiotensin promote constriction by activating the RhoA-Rho kinase cascade that sensitizes contractile proteins to Ca. 11,12,15-THETA decreases the formation of the active form of RhoA, RhoA-GTP. These studies will test the hypothesis that 11,12,15-THETA causes relaxation by inhibiting RhoA activation resulting in decreased Rho kinase activity increasing myosin light chain phosphatase activity and decreasing phosphorylated myosin light chain. These studies will access the effect of 11,12,15-THETA on RhoA activity in SMCs and arteries and de- termine the contribution of RhoA inhibition to the relaxations to 11,12,15-THETA. The role of a G protein in RhoA inhibition by 11,12,15-THETA will be determined. These studies will identify two new mechanisms of action for the endothelium-derived relaxing factor 11,12,15-THETA and provide a new therapeutic approach to enhancing endothelial function.

Public Health Relevance

The local regulation of the dilation and constriction of blood vessels is important in normal blood pressure control and contributes to pathological conditions as hypertension, diabetes and angina. These studies have defined a new class of vasodilators that are formed by the blood vessel wall. Knowledge of the mechanisms of action of these new endogenous vasodilators will help our understanding of the regulation of vascular tone and blood pressure.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL103673-02
Application #
8269815
Study Section
Hypertension and Microcirculation Study Section (HM)
Program Officer
Gao, Yunling
Project Start
2011-06-01
Project End
2015-05-31
Budget Start
2012-06-01
Budget End
2013-05-31
Support Year
2
Fiscal Year
2012
Total Cost
$382,500
Indirect Cost
$132,500
Name
Medical College of Wisconsin
Department
Pharmacology
Type
Schools of Medicine
DUNS #
937639060
City
Milwaukee
State
WI
Country
United States
Zip Code
53226
Nithipatikom, Kasem; Endsley, Michael P; Pfeiffer, Adam W et al. (2014) A novel activity of microsomal epoxide hydrolase: metabolism of the endocannabinoid 2-arachidonoylglycerol. J Lipid Res 55:2093-102
Kriska, Tamas; Cepura, Cody; Gauthier, Kathryn M et al. (2014) Role of macrophage PPARýý in experimental hypertension. Am J Physiol Heart Circ Physiol 306:H26-32
Ohta, Masanori; Toyama, Kazuyoshi; Gutterman, David D et al. (2013) Ecto-5'-nucleotidase, CD73, is an endothelium-derived hyperpolarizing factor synthase. Arterioscler Thromb Vasc Biol 33:629-36
Kriska, Tamas; Cepura, Cody; Siangjong, Lawan et al. (2013) Effect of human 15-lipoxygenase-1 metabolites on vascular function in mouse mesenteric arteries and hearts. Prostaglandins Other Lipid Mediat 106:8-15
Siangjong, Lawan; Gauthier, Kathryn M; Pfister, Sandra L et al. (2013) Endothelial 12(S)-HETE vasorelaxation is mediated by thromboxane receptor inhibition in mouse mesenteric arteries. Am J Physiol Heart Circ Physiol 304:H382-92
Campbell, William B; Gauthier, Kathryn M (2013) Inducible endothelium-derived hyperpolarizing factor: role of the 15-lipoxygenase-EDHF pathway. J Cardiovasc Pharmacol 61:176-87
Jennings, Brett L; Anderson, Larry J; Estes, Anne M et al. (2012) Cytochrome P450 1B1 contributes to renal dysfunction and damage caused by angiotensin II in mice. Hypertension 59:348-54
Nithipatikom, Kasem; Gomez-Granados, Ana Doris; Tang, Alan T et al. (2012) Cannabinoid receptor type 1 (CB1) activation inhibits small GTPase RhoA activity and regulates motility of prostate carcinoma cells. Endocrinology 153:29-41
Tang, Alan T; Campbell, William B; Nithipatikom, Kasem (2012) ROCK1 feedback regulation of the upstream small GTPase RhoA. Cell Signal 24:1375-80
Aggarwal, Nitin T; Gauthier, Kathryn M; Campbell, William B (2012) Endothelial nitric oxide and 15-lipoxygenase-1 metabolites independently mediate relaxation of the rabbit aorta. Vascul Pharmacol 56:106-12

Showing the most recent 10 out of 11 publications