-Arrestin-2 Deficiency Attenuates Abdominal Aortic Aneurysm Formation in Mice

1National Institute of Environmental Health Sciences, 111 T.W. Alexander Drive, MD C4-09, Durham, New York, 27709, UNITED STATES.
Circulation Research (Impact Factor: 11.02). 03/2013; 112(9). DOI: 10.1161/CIRCRESAHA.112.280399
Source: PubMed


Abdominal aortic aneurysms (AAAs) are a chronic inflammatory vascular disease for which pharmacological treatments are not available. A mouse model of AAA formation involves chronic infusion of angiotensin II (AngII), and previous studies indicated a primary role for the AngII type 1a receptor in AAA formation. β-arrestin (βarr)-2 is a multifunctional scaffolding protein that binds G-protein-coupled receptors such as AngII type 1a and regulates numerous signaling pathways and pathophysiological processes. However, a role for βarr2 in AngII-induced AAA formation is currently unknown.

To determine whether βarr2 played a role in AngII-induced AAA formation in mice.

Methods and results:
Treatment of βarr2(+/+) and βarr2(-/-) mice on the hyperlipidemic apolipoprotein E-deficient (apoE(-/-)) background or on normolipidemic C57BL/6 background with AngII for 28 days indicated that βarr2 deficiency significantly attenuated AAA formation. βarr2 deficiency attenuated AngII-induced expression of cyclooxygenase-2, monocyte chemoattractant protein-1, macrophage inflammatory protein 1α, and macrophage infiltration. AngII also increased the levels of phosphorylated extracellular signal-regulated kinase 1/2 in apoE(-/-)/βarr2(+/+) aortas, whereas βarr2 deficiency diminished this increase. Furthermore, inhibition of extracellular signal-regulated kinase 1/2 activation with CI1040 (100 mg/kg per day) reduced the level of AngII-induced cyclooxygenase-2 expression in apoE(-/-)/βarr2(+/+) mice to the level observed in apoE(-/-)/βarr2(-/-) mice. AngII treatment also increased matrix metalloproteinase expression and disruption of the elastic layer in apoE(-/-)/βarr2(+/+) aortas, and βarr2 deficiency reduced these effects.

βarr2 contributes to AngII-induced AAA formation in mice by phosphorylated extracellular signal-regulated kinase 1/2-mediated cyclooxygenase-2 induction and increased inflammation. These studies suggest that for the AngII type 1a receptor, G-protein-independent, βarr2-dependent signaling plays a major role in AngII-induced AAA formation.

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    • "Both MMP-2 and MMP-9 are also overexpressed in different Ang II infusion induced aortic aneurysm and aortic dissection models [33]. This kind of overexpression is attenuated in β-Arrestin-2 (βarr2) deficiency mice by the interruption of Ang II–AT1a-βarr2- COX2 pathway [34]. Only MMP-9 overexpression is attenuated in AKT2 deficiency mice because AKT2 regulates FOXO1 which bind to the promoters of MMP-9 [35]. "
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    ABSTRACT: To test the hypothesis that angiotensin II (Ang II) could enhance noradrenaline (NA) release from sympathetic nerve endings of the aorta thus contributing to the up-regulation of matrix metalloproteinase 2 (MMP-2) during the formation of aortic dissection (AD). Ang II, NA, MMP-2, MMP-9 of the aorta sample obtained during operation from aortic dissection patients were detected by High Performance Liquid Chromatography and ELISA and compared with controls. Isotope labelling method was used to test the impact of exogenous Ang II and noradrenaline on the NA release and MMP-2, MMP-9 expression on Sprague Dawley (SD) rat aorta rings in vitro. Two kidneys, one clip, models were replicated for further check of that impact in SD rats in vivo. The concentration of Ang II, MMP-2, 9 was increased and NA concentration was decreased in aorta samples from AD patients. Exogenous Ang II enhanced while exogenous NA restrained NA release from aortic sympathetic endings. The Ang II stimulated NA release and the following MMP-2 up-regulation could be weakened by Losartan and chemical sympathectomy. Beta blocker did not influence NA release but down-regulated MMP-2. Long term in vivo experiments confirmed that Ang II could enhance NA release and up-regulate MMP-2. AD is initiated by MMP-2 overexpression as a result of increased NA release from sympathetic nervous endings in response to Ang II. This indicates an interaction of RAS and SAS during the formation of AD.
    PLoS ONE 10/2013; 8(10):e76922. DOI:10.1371/journal.pone.0076922 · 3.23 Impact Factor
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    ABSTRACT: Regulatory mechanisms of the expression of interleukin-10 (IL-10) in brain inflammatory conditions remain elusive. To address this issue, we used multiple primary brain cell cultures to study the expression of IL-10 in lipopolysaccharide (LPS)-elicited inflammatory conditions. In neuron-glia cultures, LPS triggered well-orchestrated expression of various immune factors in the following order: tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2), and lastly IL-10, and these inflammatory mediators were mainly produced from microglia. While exogenous application of individual earlier-released pro-inflammatory factors (e.g., TNF-α, IL-1β, or PGE2) failed to induce IL-10 expression, removal of LPS from the cultures showed the requirement of continuing presence of LPS for IL-10 expression. Interestingly, genetic disruption of tnf-α, its receptors tnf-r1/r2, and cox-2 and pharmacological inhibition of COX-2 activity enhanced LPS-induced IL-10 production in microglia, which suggests negative regulation of IL-10 induction by the earlier-released TNF-α and PGE2. Further studies showed that negative regulation of IL-10 production by TNF-α is mediated by PGE2. Mechanistic studies indicated that PGE2-elicited suppression of IL-10 induction was eliminated by genetic disruption of the PGE2 receptor EP2 and was mimicked by the specific agonist for the EP2, butaprost, but not agonists for the other three EP receptors. Inhibition of cAMP-dependent signal transduction failed to affect PGE2-mediated inhibition of IL-10 production, suggesting that a G protein-independent pathway was involved. Indeed, deficiency in β-arrestin-1 or β-arrestin-2 abolished PGE2-elicited suppression of IL-10 production. In conclusion, we have demonstrated that COX-2-derived PGE2 inhibits IL-10 expression in brain microglia through a novel EP2- and β-arrestin-dependent signaling pathway.
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    ABSTRACT: Transforming growth factor-β (TGF-β) signaling has been significantly implicated in the pathogenesis of aneurysm, prominently the initiation and progression of abdominal aortic aneurysm (AAA). Vascular smooth muscle cell (SMC) is the principal resident cell in aortic wall and is essential for its structure and function. However, the role of TGF-β pathway in SMC for the formation of AAA remains unknown. Therefore, the goal of the present study was to investigate the effect of TGF-β pathway in SMC for AAA pathogenesis, by using a genetical smooth muscle-specific (SM-specific) TGF-βtype II receptor (Tgfbr2) disruption animal model. Mice deficient in the expression of Tgfbr2 (MyhCre.Tgfbr2f/f and MyhCre.Tgfbr2WT/f) and their corresponding wild-type background mice (MyhCre.Tgfbr2WT/WT) underwent AAA induction by infrarenal peri-adventitial application of elastase. Fourteen days after elastase treatment, the aortas were analyzed and indicated that disruption of 1 or 2 alleles of Tgfbr2 in SMC provided markedly step-wise protection from AAA formation. And elastin degradation, medial SMC loss, macrophage infiltration, and matrix metalloproteinases (MMP) expression were all significantly reduced in Tgfbr2 deletion mice. Our study demonstrated, for the first time, that the TGF-β signaling pathway in SMC plays a critical role in AAA and disruption can prevent the aneurysm formation.
    Biochemical and Biophysical Research Communications 10/2014; 454(1). DOI:10.1016/j.bbrc.2014.10.053 · 2.30 Impact Factor
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