The ATP-binding cassette transporter ABCG2 protects against pressure overload-induced cardiac hypertrophy and heart failure by promoting angiogenesis and antioxidant response.

OBJECTIVE: ATP-binding cassette transporter subfamily G member 2 (ABCG2), expressed in microvascular endothelial cells in the heart, has been suggested to regulate several tissue defense mechanisms. This study was performed to elucidate its role in pressure overload-induced cardiac hypertrophy. METHODS AND RESULTS: Pressure overload was induced in 8- to 12-week-old wild-type and Abcg2-/- mice by transverse aortic constriction (TAC). Abcg2-/- mice showed exaggerated cardiac hypertrophy and ventricular remodeling after TAC compared with wild-type mice. In the early phase after TAC, functional impairment in angiogenesis and antioxidant response in myocardium was found in Abcg2-/- mice. In vitro experiments demonstrated that ABCG2 regulates transport of glutathione, an important endogenous antioxidant, from microvascular endothelial cells. Besides, glutathione transported from microvascular endothelial cells in ABCG2-dependent manner ameliorated oxidative stress-induced cardiomyocyte hypertrophy. In vivo, glutathione levels in plasma and the heart were increased in wild-type mice but not in Abcg2-/- mice after TAC. Treatment with the superoxide dismutase mimetic ameliorated cardiac hypertrophy in Abcg2-/- mice after TAC to the same extent as that in wild-type mice, although cardiac dysfunction with impaired angiogenesis was observed in Abcg2-/- mice. CONCLUSION: ABCG2 protects against pressure overload-induced cardiac hypertrophy and heart failure by promoting angiogenesis and antioxidant response.

The ATP-binding cassette transporter BCRP1/ABCG2 plays a pivotal role in cardiac repair after myocardial infarction via modulation of microvascular endothelial cell survival and function.

OBJECTIVE: To clarify the impact of breast cancer resistance protein 1 (BCRP1)/ATP-binding cassette transporter subfamily G member 2 (ABCG2) expression on cardiac repair after myocardial infarction (MI). METHODS AND RESULTS: The ATP-binding cassette transporter BCRP1/ABCG2 is expressed in various organs, including the heart, and may regulate several tissue defense mechanisms. BCRP1/ABCG2 was mainly expressed in endothelial cells of microvessels in the heart. MI was induced in 8- to 12-week-old wild-type (WT) and Bcrp1/Abcg2 knockout (KO) mice by ligating the left anterior descending artery. At 28 days after MI, the survival rate was significantly lower in KO mice than in WT mice because of cardiac rupture. Echocardiographic, hemodynamic, and histological assessments showed that ventricular remodeling was more deteriorated in KO than in WT mice. Capillary, myofibroblast, and macrophage densities in the peri-infarction area at 5 days after MI were significantly reduced in KO compared with WT mice. In vitro experiments demonstrated that inhibition of BCRP1/ABCG2 resulted in accumulation of intracellular protoporphyrin IX and impaired survival of microvascular endothelial cells under oxidative stress. Moreover, BCRP1/ABCG2 inhibition impaired migration and tube formation of endothelial cells. CONCLUSIONS: BCRP1/ABCG2 plays a pivotal role in cardiac repair after MI via modulation of microvascular endothelial cell survival and function.

Decorin overexpression reduces atherosclerosis development in apolipoprotein E-deficient mice.

Atherosclerosis results from accumulation of macrophages and extracellular matrix in the arterial wall. Decorin, a small matrix proteoglycan, is able to regulate cell proliferation, migration and growth factors' activity. We investigated the effect of decorin overexpression on atherosclerosis progression in apolipoprotein E-deficient (ApoE(-/-)) mice. Female ApoE(-/-) mice, 10 weeks old (early treatment, n = 20) and 20 weeks old (delayed treatment, n = 20) were administered intravenously with either an adenovirus (2.5 x 10(9) plaque-forming units/mouse) containing human decorin gene (Ad-Dcn) or beta-galactosidase (LacZ), or PBS. Transgenic decorin was mainly expressed in the liver, and was secreted in the plasma up to 4 weeks. Six weeks after treatment, no significant difference in aortic root lesion size was observed between LacZ- and PBS-control groups. In contrast, Ad-Dcn-treated mice showed significantly reduced atherosclerotic lesions as compared to controls in both early and delayed treatment groups (2.9 +/- 1.1% versus 5.5 +/- 0.4%; p = 0.004 and 13.4 +/- 1.3% versus 19.9 +/- 1.41%; p = 0.009, respectively). In parallel, macrophage, gelatinase activity and collagen plaque content were also reduced. Interestingly, plasma triglycerides were reduced and decorin formed complexes with transforming growth factor-beta1 (TGF-beta1) that resulted in reduced circulating free-TGF-beta1. In conclusion, systemic overexpression of decorin reduces inflammation, triglycerides and fibrosis in atherosclerotic plaques of ApoE(-/-) mice resulting in slowing down of disease progression.

Isolation of "side population" progenitor cells from healthy arteries of adult mice.

OBJECTIVE: Circulating progenitors and stem cells have been reported to contribute to angiogenesis and arterial repair after injury. In the present study, we investigated whether the arterial wall could host permanently residing progenitor cells under physiological context. METHODS AND RESULTS: Using the Hoechst-based flow cytometry method, we identified and isolated progenitor cells termed side population (SP) cells at a prevalence of 6.0+/-0.8% in the tunica media of adult mice aortas. Arterial SP cells expressed the ATP-binding cassette transporter subfamily G member 2, frequently present on SP cell surface, and displayed a Sca-1+ c-kit(-/low) Lin- CD34(-/low) profile. They did not form myeloid or lymphoid hematopoietic colonies after plating in methylcellulose-based medium. Importantly, cultured SP cells were able to acquire the phenotype of endothelial cells (CD31, VE-cadherin, and von Willebrand factor expression) or of smooth muscle cells (alpha-smooth muscle actin, calponin, and smooth muscle myosin heavy chain expression), in presence of either vascular endothelial growth factor or transforming growth factor (TGF)-beta1/PDGF-BB, respectively. Moreover, they generated vascular-like branching structures, composed of both VE-cadherin+ cells and alpha-smooth muscle actin+ cells on Matrigel. CONCLUSIONS: In this study, we provide the first evidence to our knowledge that in the adult mice, the normal arterial wall harbors SP cells with vascular progenitor properties.

Prolonged islet allograft survival by adenovirus-mediated transfer of sICAM-1/Ig immunoadhesin gene.

Administration of monoclonal antibodies directed against the leukocyte function-associated antigen 1 (LFA-1)-intercellular adhesion molecule 1 (ICAM-1) pathway showed that these costimulatory molecules play a key role in allograft rejection. Here, adenoviral gene transfer of an immunoadhesin, sICAM-1/Ig, was used to prolong islet allograft survival in a mouse model, and was compared with anti-LFA-1 antibody administration. A replication-deficient recombinant adenoviral vector encoding a chimeric protein, in which the extracellular domain of ICAM-1 is covalently linked to the C(H)2-C(H)3 domains of an IgG1, was used for gene transfer. C3H murine islets were transplanted under the kidney capsule of streptozotocin-induced diabetic BALB/c mice. Experimental groups underwent adenovirus vector administration either in vivo (intravenous injection) or ex vivo (gene transfer to the graft), and control groups received either an empty vector (Ad.null) or an anti-LFA-1 monoclonal antibody. Graft survival was significantly prolonged by in vivo sICAM-1/Ig gene transfer as compared with both Ad.null and anti-LFA-1 groups, but not by ex vivo gene transfer. Histological examination of the grafts showed the presence of a mononuclear infiltrate within functioning grafts, suggesting that the homing of alloreactive T cells was not altered. In vitro T cell proliferation experiments indicated that sICAM-1/Ig exerted agonist effects on both CD4(+) and CD8(+) T cells.