Elsevier

Atherosclerosis

Volume 212, Issue 2, October 2010, Pages 398-405
Atherosclerosis

Gax gene transfer inhibits vascular remodeling induced by adventitial inflammation in rabbits

https://doi.org/10.1016/j.atherosclerosis.2010.06.001Get rights and content

Abstract

Aims

Adventitial fibroblasts (AFs) and inflammation play an important role in neointimal formation and vascular remodeling. The present study was aimed to investigate the therapeutic effects and underlying mechanisms of transcriptional regulator Gax gene transfection in aortic remodeling induced by adventitial inflammation.

Methods and results

Fifty rabbits fed a chow diet were randomly divided into a normal control group (n = 10) and experimental group (n = 40). All rabbits in the experimental group underwent collar placement around the abdominal aorta and intra-collar injection of lipopolysaccharide (LPS) to induce adventitial inflammation and they were further divided into model control group, saline-treated group, green fluorescence protein (Ad-GFP)-treated group and Gax gene (Ad-Gax)-treated group, respectively. Four weeks after treatment, the model control group, saline-treated group and Ad-GFP-treated group showed thickened neointima and adventitia, reduced lumen size and increased eccentricity and remodeling index of the abdominal aorta in comparison with the normal control group, whereas Ad-Gax-treated group exhibited attenuated neointimal formation and vascular remodeling (P < 0.01–0.05) .The vascular expression levels of interleukin (IL)-1β, IL-6, IL-8, monocyte chemoattractant protein (MCP)-1, matrix metalloproteinase (MMP)-1, MMP-2, MMP-9, vascular cell adhesion molecule (VCAM)-1 and intercellular adhesion molecule (ICAM)-1, Smads, mitogen-activated protein kinases (MAPKs), integrins and nuclear factor kappa B (NF-kB) were significantly higher in the model control group, saline-treated group and Ad-GFP-treated group than those in the normal control group (P < 0.01–0.05). In contrast, the local expression levels of these cytokines were substantially reduced by Ad-Gax gene transfer (P < 0.01–0.05). Similarly, the serum levels of inflammatory cytokines including C-reactive protein (CRP), transforming growth factor (TGF)-β1, IL-1, IL-6, IL-8, tumor necrosis factor (TNF)-α, MCP-1, VCAM-1 and ICAM-1 were significantly higher in the model control group, saline-treated group and Ad-GFP-treated group than those of the Ad-Gax-treated group (P < 0.01–0.05). In vitro studies showed that Gax overexpression diminished inflammatory cytokine expression in LPS-stimulated arterial fibroblasts.

Conclusions

Adventitial inflammation induces vascular remodeling via the interactions of multiple inflammatory cytokines and local Gax gene transfer in vivo can significantly inhibit these interactions and thereby attenuate local inflammation and vascular remodeling.

Introduction

It has been recognized that excessive proliferation of adventitial cells in response to vessel wall injury contributes to vascular remodeling or restenosis that occurs in 30–50% of patients after angioplasty [1]. Almost three-quarters (73%) of the late lumen loss are due to a decrease in external elastic membrane area and only 27% are due to an increase in intimal and medial thickness [1]. Accumulative evidence indicates that vascular remodeling is closely associated with adventitial inflammation [2], [3] as local inflammatory response may result in increased cytokine/growth factor production that in turn promotes adventitial cell proliferation and migration. Our recent work revealed that cross-talk among Smad, MAPK and integrin signaling pathways were essential in regulating adventitial fibroblast function and vascular remodeling [4], although the exact mechanisms by which inflammation induces vascular remodeling remain to be elucidated.

Homeobox genes encode transcription factors and with a highly conserved DNA-binding domain regulate cell growth, differentiation and migration [5], [6]. Among nuclear transcription inhibitors, growth arrest-specific homeobox (Gax) is a unique homeobox gene and acts as a negative regulator of mesodermal tissue proliferation [7], [8]. Gax is mainly expressed in adult cardiovascular tissues and exerts remarkable inhibitory effects on proliferation of vascular endothelial and smooth muscle cells in vitro and in vivo[6], [9], [10]. Recent study in our laboratory demonstrated a significant inhibitory effect of Gax gene transfer on adventitial fibroblast bioactivities in vitro[4]. However, whether Gax can effectively inhibit adventitial cell bioactivities and vascular remodeling in vivo is still unknown. Therefore, the present study was undertaken to test the hypothesis that adenovirus-mediated Gax gene transfer may effectively inhibit vascular remodeling via interrupting the cross-talk among multiple signaling pathways regulating adventitial cell bioactivities in a rabbit model of adventitial inflammation-induced vascular remodeling.

Section snippets

Materials and methods

Detailed materials and methods are described in the Supplementary data.

Biochemical measurements in vivo

During the experiment in vivo, three rabbits died of anesthetic accident, vessel rupture or intestine rupture and the remaining 47 rabbits (10 rabbits in the normal control group and 37 in the experimental group) completed the study.

In comparison with the normal control group, serum levels of CRP, TGF-β1, IL-1β, IL-6, IL-8, MCP-1, TNF-α, VCAM-1 and ICAM-1 were significantly increased in the model control, saline-treated and Ad-GFP-treated groups (all P < 0.01, Supplementary Table II). The

Discussion

The major finding of the present study was that by applying a peri-aortic collar and local injection of LPS in rabbits, an animal model of vascular remodeling induced by adventitial inflammation can be established, and adenovirus-mediated Gax gene transfer may effectively inhibit vascular remodeling via interrupting the cross-talk among multiple signaling pathways regulating adventitial cell bioactivities in these rabbits. To the best of our knowledge, this is the first study to report the

Disclosure

None declared.

Acknowledgments

We thank Prof. Wei Cheng Hu at Shandong University, China and Prof. Qingbo Xu at St. George's, University of London, UK for their excellent advice. This study was supported by the National 973 Basic Research Program of China (No. 2009CB521900), the National High-tech Research and Development Program of China (No. 2006AA02A406), the Program of Introducing Talents of Discipline to Universities (No. B07035), the State Key Program of National Natural Science of China (No. 60831003) and grants from

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    These authors contributed to this work equally.

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