Vascular endothelial growth factor and angiopoietin-2 play a major role in the pathogenesis of vascular leakage in cirrhotic rats
- 1Biochemistry and Molecular Genetics Service, Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Spain
- 2Liver Unit, CIBERehd, Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Spain
- 3Department of Physiology I, Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Spain
- Dr W Jiménez, Servicio Bioquímica y Genética Molecular, Hospital Clinic Universitari, Villarroel 170, Barcelona 08036, Spain; wjimenez{at}clinic.ub.es
- Revised 2 September 2008
- Accepted 14 October 2008
- Published Online First 31 October 2008
Abstract
Background and aims: The extent and molecular mechanisms governing plasma extravasation and formation of ascites in cirrhosis are unknown. Vascular endothelial growth factor-A (VEGF-A) and angiopoietin-2 (Ang-2) are endogenous substances with powerful vascular permeability effects. We assessed regional blood flow, vascular leakage, mRNA and tissular expression of VEGF-A and Ang-2 and vascular permeability following VEGF receptor 2 blockade in control and cirrhotic rats to define the vascular territories showing altered vascular permeability in cirrhosis and to determine whether VEGF-A and Ang-2 are involved in this phenomenon.
Methods: Arterial blood flow was analysed with the coloured microsphere method. Vascular leakage was measured and visualised with the dye Evan’s Blue and colloidal carbon techniques, respectively. VEGF-A and Ang-2 expression were determined by real-time polymerase chain reaction (RT-PCR), immunohistochemistry and western blot. The effect on vascular permeability induced by VEGFR2 blockade was assessed by administration of the receptor inhibitor SU11248.
Results: Arterial blood flow was increased in the mesentery, pancreas and small intestine but not in the kidney and spleen of cirrhotic rats as compared to controls. Increased vascular leakage was observed in the mesentery and liver, where colloidal carbon spread from microvessels to the adjacent fibrotic tracts. Increased hepatic and mesenteric expression of VEGF-A and Ang-2 was found in cirrhotic rats as compared to controls. Blockade of VEGFR2 markedly reduced hepatic and mesenteric vascular leakage in cirrhotic rats.
Conclusions: Enhanced endothelial permeability is restricted to the hepatic and mesenteric vascular beds in cirrhotic rats with ascites and VEGF-A and Ang-2 are key factors in the signalling pathways regulating this dysfunction.
Footnotes
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Supplementary methods and a figure are published online only at http://gut.bmj.com/content/vol58/issue2
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Funding: This work was supported by grants from Dirección General de Investigación Científica y Técnica (SAF03-02597 and SAF06-07053 to WJ, and SAF07-63069 to MM-R). PM-L had a grant from DGICYT (BES-2004-5186). ST had a grant from IDIBAPS. GF-V had a clinical chemistry fellowship from Siemens Medical Solutions Diagnostics (Tarrytown, New York, USA). SU11248 was generously supplied by Pfizer, South San Francisco, California, USA. CIBERehd is funded by the Instituto de Salud Carlos III, Spain.
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Competing interests: None declared.
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Ethics approval: Approval for this study was obtained from the Investigation and Ethics Committees of the Hospital Clinic on 17 December 2002.
