Tammy L Strawn

C-Reactive Protein Enhances Tissue Factor Expression by Vascular Smooth Muscle Cells. Mechanisms and In Vivo Significance

Objective—We examined the impact of C-reactive protein (CRP) on vascular smooth muscle cell (VSMC) expression of tissue factor (TF) and TF pathway inhibitor (TFPI). Methods and Results—TF mRNA, protein, and activity levels were significantly higher in VSMCs isolated from CRP-transgenic (Tg) mice than from wild-type (WT) mice. TFPI expression was significantly downregulated in CRP-Tg versus WT VSMCs. Transfection of human VSMCs with CRP expression plasmid significantly increased TF expression and decreased TFPI expression. Gene silencing of Fc&ggr; receptor IIIa (Fc&ggr;RIIIa) blocked the effect of CRP on VSMC TF expression. CRP activated p44/42, but not p38 or JNK MAP kinase (MAPK), and the effect of CRP on TF expression was blocked by pharmacological inhibitor of p44/42, but not p38 or JNK MAPK. Reactive oxygen species (ROS) scavengers blocked CRP-induced upregulation of VSMC TF expression. In vivo analyses revealed significant increases in TF expression and decreases in TFPI expression in carotid arteries of CRP-Tg mice versus WT mice. Conclusion—CRP increases TF and decreases TFPI expression by VSMCs in vitro and in vivo. Induction of TF expression by CRP is mediated by Fc&ggr;RIIIa, p44/42 MAPK, and ROS generation. These data offer important insights into the role of CRP in the pathogenesis of arterial thrombosis.

Plasminogen activator inhibitor‐1 and vitronectin expression level and stoichiometry regulate vascular smooth muscle cell migration through physiological collagen matrices

Summary.  Background:  Vascular smooth muscle cell (VSMC) migration is a critical process in arterial remodeling. Purified plasminogen activator inhibitor‐1 (PAI‐1) is reported to both promote and inhibit VSMC migration on two‐dimensional (D) surfaces.

Multifaceted Role of Plasminogen Activator Inhibitor-1 in Regulating Early Remodeling of Vein Bypass Grafts

Objective—The role of plasminogen activator inhibitor-1 (PAI-1) in vein graft (VG) remodeling is undefined. We examined the effect of PAI-1 on VG intimal hyperplasia and tested the hypothesis that PAI-1 regulates VG thrombin activity. Methods and Results—VGs from wild-type (WT), Pai1−/−, and PAI-1-transgenic mice were implanted into WT, Pai1−/−, or PAI-1-transgenic arteries. VG remodeling was assessed 4 weeks later. Intimal hyperplasia was significantly greater in PAI-1-deficient mice than in WT mice. The proliferative effect of PAI-1 deficiency was retained in vitronectin-deficient mice, suggesting that PAI-1s antiproteolytic function plays a key role in regulating intimal hyperplasia. Thrombin-induced proliferation of PAI-1-deficient venous smooth muscle cells (SMC) was significantly greater than that of WT SMC, and thrombin activity was significantly higher in PAI-1-deficient VGs than in WT VGs. Increased PAI-1 expression, which has been associated with obstructive VG disease, did not increase intimal hyperplasia. Conclusion—Decreased PAI-1 expression (1) promotes intimal hyperplasia by pathways that do not require vitronectin and (2) increases thrombin activity in VG. PAI-1 overexpression, although it promotes SMC migration in vitro, did not increase intimal hyperplasia. These results challenge the concept that PAI-1 drives nonthrombotic obstructive disease in VG and suggest that PAI-1s antiproteolytic function, including its antithrombin activity, inhibits intimal hyperplasia.

C-reactive protein induces expression of tissue factor and plasminogen activator inhibitor-1 and promotes fibrin accumulation in vein grafts

C‐reactive protein (CRP) promotes tissue factor (TF) and plasminogen activator inhibitor‐1 (PAI‐1) expression in vitro, and an elevated plasma CRP concentration is associated with an increased risk of vein graft (VG) thrombosis after coronary artery bypass surgery. However, little is known about the effects of CRP on VG TF and PAI‐1 expression in vivo, or on VG thrombosis.

Pharmacological Targeting of Plasminogen Activator Inhibitor-1 Decreases Vascular Smooth Muscle Cell Migration and Neointima Formation.

Objective—Plasminogen activator inhibitor-1 (PAI-1), a serine protease inhibitor that promotes and inhibits cell migration, plays a complex and important role in adverse vascular remodeling. Little is known about the effects of pharmacological PAI-1 inhibitors, an emerging drug class, on migration of vascular smooth muscle cells (SMCs) and endothelial cells (ECs), crucial mediators of vascular remodeling. We investigated the effects of PAI-039 (tiplaxtinin), a specific PAI-1 inhibitor, on SMC and EC migration in vitro and vascular remodeling in vivo. Approach and Results—PAI-039 inhibited SMC migration through collagen gels, including those supplemented with vitronectin and other extracellular matrix proteins, but did not inhibit migration of PAI-1-deficient SMCs, suggesting that its antimigratory effects were PAI-1-specific and physiologically relevant. However, PAI-039 did not inhibit EC migration. PAI-039 inhibited phosphorylation and nuclear translocation of signal transducers and activators of transcription-1 in SMCs, but had no discernable effect on signal transducer and activator of transcription-1 signaling in ECs. Expression of low-density lipoprotein receptor–related protein 1, a motogenic PAI-1 receptor that activates Janus kinase/signal transducers and activators of transcription-1 signaling, was markedly lower in ECs than in SMCs. Notably, PAI-039 significantly inhibited intimal hyperplasia and inflammation in murine models of adverse vascular remodeling, but did not adversely affect re-endothelialization after endothelium-denuding mechanical vascular injury. Conclusions—PAI-039 inhibits SMC migration and intimal hyperplasia, while having no inhibitory effect on ECs, which seems to be because of differences in PAI-1-dependent low-density lipoprotein receptor–related protein 1/Janus kinase/signal transducer and activator of transcription-1 signaling between SMCs and ECs. These findings suggest that PAI-1 may be an important therapeutic target in obstructive vascular diseases characterized by neointimal hyperplasia.

Recombinant Soluble Apyrase APT102 Inhibits Thrombosis and Intimal Hyperplasia in Vein Grafts without Adversely Affecting Hemostasis or Re-endothelialization.

Essentials New strategies are needed to inhibit thrombosis and intimal hyperplasia (IH) in vein grafts (VG). We studied effects of apyrase (APT102) on VGs and smooth muscle and endothelial cells (SMC/EC). APT102 inhibited thrombosis, SMC migration, and IH without impairing hemostasis or EC recovery. Apyrase APT102 is a single‐drug approach to inhibit multiple processes that cause VG failure.

247. Expressing Full-Length Dystrophin in 50% Cardiomyocytes Corrects Cardiomyopathy in the Mdx Mouse Model for Duchenne Muscular Dystrophy

Cardiomyopathy is a major determinant of the clinical outcome in Duchenne and Becker muscular dystrophy (DMD, BMD). Nearly every DMD and BMD patient suffers from some degree of cardiomyopathy. More then one tenth of DMD patients eventually die of heart failure. Clinical success of DMD gene therapy will depend upon functional improvement in both skeletal and cardiac muscle. Substantial progress has been made in DMD skeletal muscle disease gene therapy. However, few studies have been done in DMD cardiomyopathy gene therapy. We recently reported that micro-dystrophin was equally efficient in restoring the dystrophin-glycoprotein complex and maintaining sarcolemma integrity in the mdx heart (Yue et al Circulation 108:1626,2003). The minimal number of dystrophin expressing cells needed for cardiomyopathy therapy has not been determined however. In this study, we used female heterozygous mice (F1 from BL10 and mdx crossing) as an experimental model to evaluate whether dystrophin expression in half of the cardiomyocytes was enough to improve heart function in mdx mice. Consistent with the random X-chromosome inactivation theory, we found that 51.22% and 55.40% of the heart cells were expression dystrophin in maternal and paternal heterozygous mice respectively. The mdx mouse hearts were heavier than the BL10 hearts. Interestingly, weights of the heterozygous mice hearts were similar to those of the BL10. In contrast to previous reports of the benign histology in the mdx hearts, we detected fibrosis in 85.71% of the mdx hearts (N=42). More than half of the fibrosis was in the range of medium-to-large size. Only 43.59% of the heterozygous mice had hearts that contained fibrous regions, and the majority of the fibrosis was localized to small areas. To determine whether full-length dystrophin expression in half of the cardiomyocytes can protect the heart from mechanical-stress induced injury, we challenged the hearts with the inotrope b-isoproterenol. After administrating a vital dye, Evans blue (EBD), we found that 11.26 3.40% of the heart area was EBD positive in mdx mice. In the heterozygous mouse hearts, the EBD positive area was reduced to 2.37 0.70%. This result suggests that a significant improvement in cardiomyocyte sarcolemma integrity has been achieved in the heterozygous mouse hearts. In summary, our results suggest that a 50% correction in the mdx heart is sufficient to ameliorate cardiomyopathy in mdx mice.