title: Overexpression of angiopoietin-2 impairs myocardial angiogenesis and exacerbates cardiac fibrosis in the diabetic db/db mouse model.
abstract: The angiopoietins/Tie-2 system is essential for the maintenance of vascular integrity and angiogenesis. The functional role of angiopoietin-2 (Ang-2) in the regulation of angiogenesis is dependent on other growth factors such as VEGF and a given physiopathological conditions. This study investigates the potential role of Ang-2 in myocardial angiogenesis and fibrosis formation in the diabetic db/db mouse. Diabetic db/db mice received intramyocardial administration of either adenovirus Ang-2 (Ad-CMV-Ang-2) or Ad-β-gal. The levels of Tie-2, VEGF, caspase-3, Wnt7b, fibroblast-specific protein-1 (FSP-1), and adhesion molecules (ICAM-1 and VCAM-1) expression were measured. Apoptosis, capillary density, and cardiac fibrosis were also analyzed in the db/db mouse hearts. Overexpression of Ang-2 suppressed Tie-2 and VEGF expression in db/db mouse hearts together with significant upregulation of Wnt7b expression. Overexpression of Ang-2 also sensitizes ICAM-1 and VCAM-1 expression in db/db mouse hearts. Immunohistochemical analysis revealed that overexpression of Ang-2 resulted in a gradual apoptosis as well as interstitial fibrosis formation, these leading to a significant loss of capillary density. Data from these studies were confirmed in cultured mouse heart microvascular endothelial cells (MHMEC) exposed to excessive Ang-2. Exposure of MHMEC to Ang-2 resulted in increased caspase-3 activity and endothelial apoptosis. Knockdown of Ang-2 attenuated high glucose-induced endothelial cell apoptosis. Further, counterbalance of Ang-2 by overexpression of Ang-1 reversed loss of capillary density and fibrosis formation in db/db mouse hearts. Our data demonstrate that Ang-2 increases endothelial apoptosis, sensitizes myocardial microvascular inflammation, and promotes cardiac fibrosis and thus contributes to loss of capillary density in diabetic diseases.
authors.affiliation: Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, MS 39216, USA. JChen3@umc.edu
authors.forename: Jian-Xiong
authors.initials: JX
authors.lastname: Chen
authors.forename: Heng
authors.initials: H
authors.lastname: Zeng
authors.forename: Jeff
authors.initials: J
authors.lastname: Reese
authors.forename: Judy L
authors.initials: JL
authors.lastname: Aschner
authors.forename: Barbara
authors.initials: B
authors.lastname: Meyrick
mesh_terms: D042702:Angiopoietin-2 / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000503:physiopathology*; D003920:Diabetes Mellitus / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology*; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D005355:Fibrosis; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D008297:Male; D051379:Mice; D008817:Mice, Mutant Strains; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology*; D009389:Neovascularization, Pathologic / Q000503:physiopathology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D042787:Receptor, TIE-2 / Q000378:metabolism; D015854:Up-Regulation / Q000502:physiology; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D051153:Wnt Proteins / Q000378:metabolism
chemical_list: D042702:Angiopoietin-2; D011518:Proto-Oncogene Proteins; D019010:Vascular Cell Adhesion Molecule-1; D042461:Vascular Endothelial Growth Factor A; D051153:Wnt Proteins; C095937:Wnt7b protein, mouse; D018799:Intercellular Adhesion Molecule-1; D042787:Receptor, TIE-2; D053148:Caspase 3