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Mechanisms for Arsenic-Stimulated Sinusoidal Endothelial Cell Capillarization

Straub, Adam C. (2009) Mechanisms for Arsenic-Stimulated Sinusoidal Endothelial Cell Capillarization. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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The vascular effects of arsenic in drinking water are a global public health concern that contribute to disease in millions of people worldwide. However, the cellular and molecular mechanisms for these pathogenic effects of arsenic are not well defined. This thesis examined the hypothesis that arsenic stimulates pathogenic signals through surface receptors on liver sinusoidal endothelial cells (LSECs) to stimulate NADPH oxidase (NOX) activity that is required for arsenic-stimulated LSEC capillarization. In mice and isolated LSECs, we demonstrated that exposure to arsenic promoted capillarization and increased expression of platelet endothelial cell adhesion molecule (PECAM-1) through a time and dose dependent mechanism. Superoxide generating NOX enzyme complexes participate in vascular remodeling and angiogenesis and are central to arsenic stimulated cell signaling. LSEC arsenic exposure increased NOX dependent superoxide generation that was inhibited using gp91ds-tat protein, NSC23766, a Rac1-GTPase inhibitor, or quenched by the intracellular superoxide scavenger, Tempol. These inhibitors also blocked arsenic-stimulated LSEC PECAM-1 expression and defenestration. In vivo arsenic exposures failed to promote LSEC capillarization in p47phox knockout mice. These data demonstrated that arsenic stimulates capillarization through a NOX dependent mechanism. Given that arsenic rapidly activates NOX in vascular cells, we hypothesized that signaling for these responses was receptor mediated. Since arsenic-stimulated LSEC defenestration and capillarization is Rac1 and NOX dependent, we examined whether a g-protein coupled receptor (GPCR) upstream of Rac1 initiated these effects. Pre-treatment LSECs with Pertussis toxin (PTX), an inhibitor of Gi/o, prevented arsenic-stimulated defenestration. Since capillarization is a gain in barrier function, LSEC expression of the sphingosine-1-phosphate type 1 (S1P1) receptor, a major Gi/o linked regulator of endothelial barrier function, and its role in arsenic-stimulated defenestration were investigated. S1P1 was highly expressed in LSECs relative to large vessels. In ex vivo studies, inhibiting LSEC S1P1 with a selective antagonist, VPC23109, blocked arsenic-stimulated superoxide generation, defenestration, and PECAM-1 expression. These data demonstrated that arsenic targets a specific LSEC GPCR to promote vascular remodeling, and the first demonstrating that S1P1 regulates oxidant-dependent LSEC capillarization. Taken together, these data demonstrate that S1P1 activated NOX stimulates LSEC capillarization, which aids in our understanding of mechanisms underlying arsenic-induced liver disease.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Straub, Adam
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairBarchowsky, Aaronaab20@pitt.eduAAB20
Committee CoChairPitt, Brucebrucep@pitt.eduBRUCEP
Committee MemberSt Croix, Claudette Mariecls13@pitt.eduCLS13
Committee MemberStolz, Donnadstolz@pitt.eduDSTOLZ
Date: 29 January 2009
Date Type: Completion
Defense Date: 4 September 2008
Approval Date: 29 January 2009
Submission Date: 1 October 2008
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: School of Public Health > Environmental and Occupational Health
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: NADPH oxidase; arsenic; liver sinusoidal endothelial cell
Other ID:, etd-10012008-162057
Date Deposited: 10 Nov 2011 20:02
Last Modified: 15 Nov 2016 13:50


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