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Increased smooth muscle cell activation and neointima formation in response to injury in AIF-1 transgenic mice.

ABSTRACT: Allograft Inflammatory Factor-1 (AIF-1) is a calcium binding scaffold protein which is rapidly induced in vascular smooth muscle cells (VSMCs) in response to injury and inflammation. A transgenic mouse in which AIF-1 expression was driven by a VSMC-specific SM22alpha promoter was generated to establish a direct relationship between AIF-1 expression and intimal hyperplasia.Morphological analysis of partially ligated carotid artery demonstrate a significant increase in neointimal area of AIF-1 Tg versus wild-type mice (569+/-64 um versus 256+/-49 um, P=0.004). Immunohistochemistry using antibody to the proliferation marker Ki-67 show a significantly greater number of proliferating cells in the AIF-1 Tg lesion compared with wild-type arteries (10.6%+/-1.0 versus 3.6%+/-.9, P=0.0007). AIF-1 Tg arteries also had a greater number of cells with activated signal transduction kinase p38 (55.4%+/-7.0 versus 22.6%+/-5.4, P=0.002) and PAK1 (67.5%+/-6.7 versus 35.3%+/-10.2, P=0.02) compared with wild-type. Cultured VSMCs explanted from AIF-1 Tg proliferate (55.5+/-3.6x10(3) versus 37.2+/-2.0x10(3) cells/mL, P=0.0001) and migrate more rapidly (39.2+/-3.2 versus 17.1+/-1.5 VSMCs per HPF, P=0.0003) than wild-type, and have significantly greater levels of activated p38 and PAK1 than did VSMCs from wild-type littermates (P<0.05).These data indicate that AIF-1 expression results in increased signal transduction, neointimal formation, and VSMC proliferation in injured mouse carotid arteries.

SUBMITTER: Sommerville LJ

PROVIDER: S-EPMC2664967 | biostudies-literature | 2008 Jan

REPOSITORIES: biostudies-literature

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Increased smooth muscle cell activation and neointima formation in response to injury in AIF-1 transgenic mice.

Sommerville Laura J LJ Kelemen Sheri E SE Autieri Michael V MV

Arteriosclerosis, thrombosis, and vascular biology 20071108 1

<h4>Objective</h4>Allograft Inflammatory Factor-1 (AIF-1) is a calcium binding scaffold protein which is rapidly induced in vascular smooth muscle cells (VSMCs) in response to injury and inflammation. A transgenic mouse in which AIF-1 expression was driven by a VSMC-specific SM22alpha promoter was generated to establish a direct relationship between AIF-1 expression and intimal hyperplasia.<h4>Methods and results</h4>Morphological analysis of partially ligated carotid artery demonstrate a signif ...[more]

PMID: 17991871

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Project description:ObjectiveMitogen-activated protein kinase pathways play an important role in neointima formation secondary to vascular injury, in part by promoting proliferation of vascular smooth muscle cells (VSMC). Mixed-lineage kinase 3 (MLK3) is a mitogen-activated protein kinase kinase kinase that activates multiple mitogen-activated protein kinase pathways and has been implicated in regulating proliferation in several cell types. However, the role of MLK3 in VSMC proliferation and neointima formation is unknown. The aim of this study was to determine the function of MLK3 in the development of neointimal hyperplasia and to elucidate the underlying mechanisms.Approach and resultsNeointima formation was analyzed after endothelial denudation of carotid arteries from wild-type and MLK3-deficient mice. MLK3 deficiency promoted injury-induced neointima formation and increased proliferation of primary VSMC derived from aortas isolated from MLK3-deficient mice compared with wild-type mice. Furthermore, MLK3 deficiency increased the activation of p63Rho guanine nucleotide exchange factor, RhoA, and Rho kinase in VSMC, a pathway known to promote neointimal hyperplasia, and reconstitution of MLK3 expression attenuated Rho kinase activation. Furthermore, cJun NH2-terminal kinase activation was decreased in MLK3-deficient VSMC, and proliferation of wild-type but not MLK3 knockout cells treated with a cJun NH2-terminal kinase inhibitor was attenuated.ConclusionsWe demonstrate that MLK3 limits RhoA activation and injury-induced neointima formation by binding to and inhibiting the activation of p63Rho guanine nucleotide exchange factor, a RhoA activator. In MLK3-deficient cells, activation of p63Rho guanine nucleotide exchange factor proceeds in an unchecked manner, leading to a net increase in RhoA pathway activation. Reconstitution of MLK3 expression restores MLK3/p63Rho guanine nucleotide exchange factor interaction, which is attenuated by feedback from activated cJun NH2-terminal kinase.

Project description:Background3,3'Diindolylmethane (DIM), a natural phytochemical, has shown inhibitory effects on the growth and migration of a variety of cancer cells; however, whether DIM has similar effects on vascular smooth muscle cells (VSMCs) remains unknown. The purpose of this study was to assess the effects of DIM on the proliferation and migration of cultured VSMCs and neointima formation in a carotid injury model, as well as the related cell signaling mechanisms.Methodology/principal findingsDIM dose-dependently inhibited the platelet-derived growth factor (PDGF)-BB-induced proliferation of VSMCs without cell cytotoxicity. This inhibition was caused by a G0/G1 phase cell cycle arrest demonstrated by fluorescence-activated cell-sorting analysis. We also showed that DIM-induced growth inhibition was associated with the inhibition of the expression of cyclin D1 and cyclin-dependent kinase (CDK) 4/6 as well as an increase in p27(Kip1) levels in PDGF-stimulated VSMCs. Moreover, DIM was also found to modulate migration of VSMCs and smooth muscle-specific contractile marker expression. Mechanistically, DIM negatively modulated PDGF-BB-induced phosphorylation of PDGF-recptor? (PDGF-R?) and the activities of downstream signaling molecules including Akt/glycogen synthase kinase(GSK)3?, extracellular signal-regulated kinase1/2 (ERK1/2), and signal transducers and activators of transcription 3 (STAT3). Our in vivo studies using a mouse carotid arterial injury model revealed that treatment with 150 mg/kg DIM resulted in significant reduction of the neointima/media ratio and proliferating cell nuclear antigen (PCNA)-positive cells, without affecting apoptosis of vascular cells and reendothelialization. Infiltration of inflammatory cells was also inhibited by DIM administration.ConclusionThese results demonstrate that DIM can suppress the phenotypic modulation of VSMCs and neointima hyperplasia after vascular injury. These beneficial effects on VSMCs were at least partly mediated by the inhibition of PDGF-R? and the activities of downstream signaling pathways. The results suggest that DIM has the potential to be a candidate for the prevention of restenosis.

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Increased smooth muscle cell activation and neointima formation in response to injury in AIF-1 transgenic mice.

Publications

Increased smooth muscle cell activation and neointima formation in response to injury in AIF-1 transgenic mice.

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