Angiotensin II Signaling Mechanisms Involved in the Elevation of Arginase Activity/Expression and Vascular Dysfunction

Hdl Handle:
http://hdl.handle.net/10675.2/319903
Title:
Angiotensin II Signaling Mechanisms Involved in the Elevation of Arginase Activity/Expression and Vascular Dysfunction
Authors:
Shatanawi, Alia
Abstract:
Vascular endothelial dysfunction is a major cause of morbidity and mortality in patients with cardiovascular diseases such as hypertension, atherosclerosis and diabetes. Nitric oxide (NO) produced by endothelial nitric oxide synthase (NOS) is needed for normal vascular function. During hypertension, diabetes or atherosclerosis, elevated levels of arginase can compete with NOS for available L-arginine thus reducing vascular NO production. Elevated angiotensin II (Ang II) is a key participant of endothelial dysfunction in many cardiovascular diseases and has been linked to elevated arginase activity. In this study we explored the signaling pathway leading to increased arginase expression/activity in responses to Ang II in bovine aortic endothelial cells (BAEC). Treatment of BAEC with Ang II (10-7 M, 24 hrs) caused a 40±6% increase in arginase activity. This was accompanied by 30±8% decrease in NO production. Our studies indicate involvement of the RhoA/ROCK-p38 mitogen activated protein kinase (MAPK) in Ang II-induced arginase upregulation and reduced NO production, as inhibitors of ROCK or p38 MAPK prevented the Ang II-induced increase in arginase activity. Our studies in mice also show involvement of p38 MAPK in Ang II-induced vascular dysfunction associated with elevated arginase activity and expression. Ang II (42 μg/kg/h) caused impaired EC-dependent vasorelaxation in mouse aorta (55±7% vs. 75±8% for control). This impairment was prevented by treatment with p38 inhibitor SB203580 (5 μg/kg/day). Ang II also caused a 6.2 fold increase in vascular arginase activity/expression that was completely prevented by p38 MAPK inhibition. Additionally, treatment of BAEC with Ang II causes phosphorylation of activating transcription factor-2 (ATF-2) and enhancement of the binding of ATF-2 to arginase promotor through an AP-1 site as evident from electrophoretic mobility shift assay experiments. Transfection of BAEC with ATF-2 siRNA prevents Ang II-induced increases in arginase activity/expression and maintains NO production. These results indicate that ATF-2 is necessary for enhanced expression of arginase by Ang II. Collectively, our results indicate that Ang II increases endothelial arginase activity/expression through a RhoA/ROCK-p38 MAPK-ATF-2 pathway leading to reduced NO production and endothelial dysfunction. Targeting these signaling steps might be therapeutic points for preventing vascular endothelial dysfunction associated with elevated arginase activity/expression.
Affiliation:
Department of Pharmacology and Toxicology
Issue Date:
Nov-2011
URI:
http://hdl.handle.net/10675.2/319903
Additional Links:
http://ezproxy.augusta.edu/login?url=http://search.proquest.com/docview/920882425?accountid=12365
Type:
Dissertation
Language:
en
Appears in Collections:
Department of Pharmacology and Toxicology Theses and Dissertations; Theses and Dissertations

Full metadata record

DC FieldValue Language
dc.contributor.authorShatanawi, Aliaen
dc.date.accessioned2014-06-05T22:44:36Z-
dc.date.available2014-06-05T22:44:36Z-
dc.date.issued2011-11-
dc.identifier.urihttp://hdl.handle.net/10675.2/319903-
dc.description.abstractVascular endothelial dysfunction is a major cause of morbidity and mortality in patients with cardiovascular diseases such as hypertension, atherosclerosis and diabetes. Nitric oxide (NO) produced by endothelial nitric oxide synthase (NOS) is needed for normal vascular function. During hypertension, diabetes or atherosclerosis, elevated levels of arginase can compete with NOS for available L-arginine thus reducing vascular NO production. Elevated angiotensin II (Ang II) is a key participant of endothelial dysfunction in many cardiovascular diseases and has been linked to elevated arginase activity. In this study we explored the signaling pathway leading to increased arginase expression/activity in responses to Ang II in bovine aortic endothelial cells (BAEC). Treatment of BAEC with Ang II (10-7 M, 24 hrs) caused a 40±6% increase in arginase activity. This was accompanied by 30±8% decrease in NO production. Our studies indicate involvement of the RhoA/ROCK-p38 mitogen activated protein kinase (MAPK) in Ang II-induced arginase upregulation and reduced NO production, as inhibitors of ROCK or p38 MAPK prevented the Ang II-induced increase in arginase activity. Our studies in mice also show involvement of p38 MAPK in Ang II-induced vascular dysfunction associated with elevated arginase activity and expression. Ang II (42 μg/kg/h) caused impaired EC-dependent vasorelaxation in mouse aorta (55±7% vs. 75±8% for control). This impairment was prevented by treatment with p38 inhibitor SB203580 (5 μg/kg/day). Ang II also caused a 6.2 fold increase in vascular arginase activity/expression that was completely prevented by p38 MAPK inhibition. Additionally, treatment of BAEC with Ang II causes phosphorylation of activating transcription factor-2 (ATF-2) and enhancement of the binding of ATF-2 to arginase promotor through an AP-1 site as evident from electrophoretic mobility shift assay experiments. Transfection of BAEC with ATF-2 siRNA prevents Ang II-induced increases in arginase activity/expression and maintains NO production. These results indicate that ATF-2 is necessary for enhanced expression of arginase by Ang II. Collectively, our results indicate that Ang II increases endothelial arginase activity/expression through a RhoA/ROCK-p38 MAPK-ATF-2 pathway leading to reduced NO production and endothelial dysfunction. Targeting these signaling steps might be therapeutic points for preventing vascular endothelial dysfunction associated with elevated arginase activity/expression.en
dc.language.isoenen
dc.relation.urlhttp://ezproxy.augusta.edu/login?url=http://search.proquest.com/docview/920882425?accountid=12365en
dc.rightsCopyright protected. Unauthorized reproduction or use beyond the exceptions granted by the Fair Use clause of U.S. Copyright law may violate federal law.-
dc.subjectAngiotensin IIen
dc.subjectArginaseen
dc.subjectNitric Oxideen
dc.subjectVascular Endothelial Dysfunctionen
dc.subjectL-arginineen
dc.subjectEndothelial Cellen
dc.subjectRhoAen
dc.subjectROCKen
dc.subjectp38 MAPKen
dc.subjectActivator Protein-1en
dc.subjectActivating Transcription Factor-2en
dc.subjectATF-2en
dc.subjectAP-1en
dc.titleAngiotensin II Signaling Mechanisms Involved in the Elevation of Arginase Activity/Expression and Vascular Dysfunctionen
dc.typeDissertationen
dc.contributor.departmentDepartment of Pharmacology and Toxicologyen
dc.description.advisorCaldwell, R. Williamen
dc.description.committeeCaldwell, Ruth; Fulton, David; Johnson, John; White, Richarden
dc.description.degreeDoctor of Philosophy (Ph.D.)-
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