PKCδ Is Necessary for Smad3 Expression and Transforming Growth Factor β–Induced Fibronectin Synthesis in Vascular Smooth Muscle Cells

The Microenvironment of the Pathogenesis of Cardiac Hypertrophy

Pathological cardiac hypertrophy is a key risk factor for the development of heart failure and predisposes individuals to cardiac arrhythmia and sudden death. While physiological cardiac hypertrophy is adaptive, hypertrophy resulting from conditions comprising hypertension, aortic stenosis, or genetic mutations, such as hypertrophic cardiomyopathy, is maladaptive. Here, we highlight the essential role and reciprocal interactions involving both cardiomyocytes and non-myocardial cells in response to pathological conditions. Prolonged cardiovascular stress causes cardiomyocytes and non-myocardial cells to enter an activated state releasing numerous pro-hypertrophic, pro-fibrotic, and pro-inflammatory mediators such as vasoactive hormones, growth factors, and cytokines, i.e., commencing signaling events that collectively cause cardiac hypertrophy. Fibrotic remodeling is mediated by cardiac fibroblasts as the central players, but also endothelial cells and resident and infiltrating immune cells enhance these processes. Many of these hypertrophic mediators are now being integrated into computational models that provide system-level insights and will help to translate our knowledge into new pharmacological targets. This perspective article summarizes the last decades' advances in cardiac hypertrophy research and discusses the herein-involved complex myocardial microenvironment and signaling components.

Transcription factor GATA6 promotes migration of human coronary artery smooth muscle cells in vitro

Vascular smooth muscle cell plasticity plays a pivotal role in the pathophysiology of vascular diseases. Despite compelling evidence demonstrating the importance of transcription factor GATA6 in vascular smooth muscle, the functional role of GATA6 remains poorly understood. The aim of this study was to elucidate the role of GATA6 on cell migration and to gain insight into GATA6-sensitive genes in smooth muscle. We found that overexpression of GATA6 promotes migration of human coronary artery smooth muscle cells in vitro, and that silencing of GATA6 in smooth muscle cells resulted in reduced cellular motility. Furthermore, a complete microarray screen of GATA6-sensitive gene transcription resulted in 739 upregulated and 248 downregulated genes. Pathways enrichment analysis showed involvement of transforming growth factor beta (TGF-β) signaling which was validated by measuring mRNA expression level of several members. Furthermore, master regulators prediction based on microarray data revealed several members of (mitogen activated protein kinase) MAPK pathway as a master regulators, reflecting involvement of MAPK pathway also. Our findings provide further insights into the functional role of GATA6 in vascular smooth muscle and suggest that targeting GATA6 may constitute as a new approach to inhibit vascular smooth muscle migration.

Antifibrotic TSG-6 Expression Is Synergistically Increased in Both Cells during Coculture of Mesenchymal Stem Cells and Macrophages via the JAK/STAT Signaling Pathway

The pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-1β upregulate TNF-α-stimulated gene 6 (TSG-6); however, current knowledge about the optimal conditions for TSG-6 expression in mesenchymal stem cells (MSCs) is limited. Here, we investigated whether TSG-6 expression varies depending on the polarization state of macrophages co-cultured with adipose tissue-derived stem cells (ASCs) and analyzed the optimal conditions for TSG-6 expression in ASCs. TSG-6 expression increased in ASCs co-cultured with M0, M1, and M2 macrophages indirectly; among them, M1 macrophages resulted in the highest increase in TSG-6 expression in ASCs. TSG-6 expression in ASCs dramatically increased by combination (but not single) treatment of TNF-α, IL-1β, interferon-gamma (IFN-γ), and lipopolysaccharide (LPS). In addition, phosphorylation of signal transducer and activator of transcription (STAT) 1/3 was observed in response to IFN-γ and LPS treatment but not TNF-α and/or IL-1β. STAT1/3 activation synergistically increased TNF-α/IL-1β-dependent TSG-6 expression, and JAK inhibitors suppressed TSG-6 expression both in ASCs and macrophages. In LX-2 hepatic stellate cells, TSG-6 inhibited TGF-β-induced Smad3 phosphorylation, resulting in decreased α-smooth muscle actin (SMA) expression. Moreover, fibrotic activities of LX-2 cells induced by TGF-β were dramatically decreased after indirect co-culture with ASCs and M1 macrophages. These results suggest that a comprehensive inflammatory microenvironment may play an important role in determining the therapeutic properties of ASCs by increasing TSG-6 expression through STAT1/3 activation.

Endothelial-Smooth Muscle Cell Interactions in a Shear-Exposed Intimal Hyperplasia on-a-Dish Model to Evaluate Therapeutic Strategies

Intimal hyperplasia (IH) represents a major challenge following cardiovascular interventions. While mechanisms are poorly understood, the inefficient preventive methods incentivize the search for novel therapies. A vessel-on-a-dish platform is presented, consisting of direct-contact cocultures with human primary endothelial cells (ECs) and smooth muscle cells (SMCs) exposed to both laminar pulsatile and disturbed flow on an orbital shaker. With contractile SMCs sitting below a confluent EC layer, a model that successfully replicates the architecture of a quiescent vessel wall is created. In the novel IH model, ECs are seeded on synthetic SMCs at low density, mimicking reendothelization after vascular injury. Over 3 days of coculture, ECs transition from a network conformation to confluent 2D islands, as promoted by pulsatile flow, resulting in a "defected" EC monolayer. In defected regions, SMCs incorporated plasma fibronectin into fibers, increased proliferation, and formed multilayers, similarly to IH in vivo. These phenomena are inhibited under confluent EC layers, supporting therapeutic approaches that focus on endothelial regeneration rather than inhibiting proliferation, as illustrated in a proof-of-concept experiment with Paclitaxel. Thus, this in vitro system offers a new tool to study EC-SMC communication in IH pathophysiology, while providing an easy-to-use translational disease model platform for low-cost and high-content therapeutic development.

An Overview of Investigational and Experimental Drug Treatment Strategies for Marfan Syndrome

Marfan syndrome (MFS) is a heritable connective tissue disorder caused by pathogenic variants in the gene coding for the extracellular matrix protein fibrillin-1. While the disease affects multiple organ systems, the most life-threatening manifestations are aortic aneurysms leading to dissection and rupture. Other cardiovascular complications, including mitral valve prolapse, primary cardiomyopathy, and arrhythmia, also occur more frequently in patients with MFS. The standard medical care relies on cardiovascular imaging at regular intervals, along with pharmacological treatment with β-adrenergic receptor blockers aimed at reducing the aortic growth rate. When aortic dilatation reaches a threshold associated with increased risk of dissection, prophylactic surgical aortic replacement is performed. Although current clinical management has significantly improved the life expectancy of patients with MFS, no cure is available and fatal complications still occur, underscoring the need for new treatment options. In recent years, preclinical studies have identified a number of potentially promising therapeutic targets. Nevertheless, the translation of these results into clinical practice has remained challenging. In this review, we present an overview of the currently available knowledge regarding the underlying pathophysiological processes associated with MFS cardiovascular pathology. We then summarize the treatment options that have been developed based on this knowledge and are currently in different stages of preclinical or clinical development, provide a critical review of the limitations of current studies and highlight potential opportunities for future research.

Honokiol protects against epidural fibrosis by inhibiting fibroblast proliferation and extracellular matrix overproduction in rats post‑laminectomy

Epidural fibrosis (EF)‑induced failed back surgery syndrome (FBSS) in patients post‑laminectomy remains a medical challenge. Although the scarring mechanisms remain unclear, the majority of aetiological studies have reported fibroblast dysfunction. Honokiol, the major bioactive constituent of the magnolia tree, exerts a variety of pharmacological effects, including anti‑proliferative and anti‑fibrotic effects, on various cell types. The present study investigated whether honokiol attenuates EF progression. In vitro, it was found that honokiol inhibited excessive fibroblast proliferation induced by transforming growth factor‑β1 (TGF‑β1) and the synthesis of extracellular matrix (ECM) components, including fibronectin and type I collagen, in a dose‑dependent manner. These effects were attributed to the ability of honokiol to suppress the activity of connective tissue growth factor (CTGF), which is indispensable for the progression of fibrosis. Mechanistically, honokiol attenuated the TGF‑β1‑induced activation of the Smad2/3 and mitogen‑activated protein kinase (MAPK) signalling pathways in fibroblasts. In vivo, honokiol reduced the proliferation of fibroblasts and the synthesis of ECM components, thus ameliorating EF in a rat model post‑laminectomy. Taken together, these preclinical findings suggest that honokiol deserves further consideration as a candidate therapeutic agent for EF.

PEGylated Polyethylenimine Derivative-Mediated Local Delivery of the shSmad3 Inhibits Intimal Thickening after Vascular Injury

Intimal hyperplasia is a complex process which contributes to several clinical problems such as atherosclerosis and postangioplasty restenosis. Inhibition of Smad3 expression inhibits intimal thickening. Our previous study has modified biscarbamate cross-linked polyethylenimine derivative (PEI-Et) through PEGylation thus obtained polyethylene glycol-graft-polyethylenimine derivative (PEG-Et 1:1), which has lower cytotoxicity and higher gene transfection efficiency compared with PEI-Et. In this study, PEG-Et 1:1 was employed in Smad3 shRNA (shSmad3) delivery for preventing intimal hyperplasia after vascular injury. It was observed that PEG-Et 1:1 could condense shSmad3 gene into nanoparticles with particle size of 115–168 nm and zeta potential of 3–6 mV. PEG-Et 1:1 displayed remarkably lower cytotoxicity, higher transfection efficiency, and shRNA silencing efficiency than PEI-Et and PEI 25 kDa in vascular smooth muscle cells (VSMCs). Moreover, PEG-Et 1:1/shSmad3 polyplex treatment significantly inhibited collagen, matrix metalloproteinase 1 (MMP1), MMP2 and MMP9 expression, and upregulated tissue inhibitor of metalloproteinase 1 (TIMP1) expression both in vitro and in vivo. Furthermore, intravascular delivery of shSmad3 with PEG-Et 1:1 polyplex efficiently reduced Smad3 expression and inhibited intimal thickening 14 days after vascular injury. Ultimately, this study indicated that PEG-Et 1:1-mediated local delivery of shSmad3 is a promising strategy for preventing intimal thickening.

Dietary Sodium Restriction Reduces Arterial Stiffness, Vascular TGF-β-Dependent Fibrosis and Marinobufagenin in Young Normotensive Rats

High salt (HS) intake stimulates the production of marinobufagenin (MBG), an endogenous steroidal Na/K-ATPase ligand, which activates profibrotic signaling. HS is accompanied by a blood pressure (BP) increase in salt-sensitive hypertension, but not in normotensive animals. Here, we investigated whether HS stimulates MBG production and activates transforming growth factor-beta (TGF-β) profibrotic signaling in young normotensive rats, and whether these changes can be reversed by reducing salt to a normal salt (NS) level. Three-month old male Sprague–Dawley rats received NS for 4 and 8 weeks (0.5% NaCl; NS4 and NS8), or HS for 4 and 8 weeks (4% NaCl; HS4 and HS8), or HS for 4 weeks followed by NS for 4 weeks (HS4/NS4), n = 8/group. Systolic BP (SBP), pulse wave velocity (PWV), MBG excretion, aortic collagen 1α2, collagen 4α1 and TGF-β, Smad2, Smad3, Fli-1 mRNA, and total collagen abundance were measured at baseline (BL), and on weeks 4 and 8. Statistical analysis was performed using one-way ANOVA. SBP was not affected by HS (125 ± 5 and 126 ± 6 vs. 128 ± 7 mmHg, HS4 and HS8 vs. BL, p > 0.05). HS increased MBG (164 ± 19 vs. 103 ± 19 pmol/24 h/kg, HS4 vs. BL, p < 0.05) and PWV (3.7 ± 0.2 vs. 2.7 ± 0.2 m/s, HS4 vs. NS4, p < 0.05). HS8 was associated with a further increase in MBG and PWV, with an increase in aortic Col1a2 80%), Col4a1 (50%), Tgfb1 (30%), Smad2 (30%) and Smad3 (45%) mRNAs, and aortic wall collagen (180%) vs. NS8 (all p < 0.05). NS following HS downregulated HS-induced factors: in HS4/NS4, the MBG level was 91 ± 12 pmol/24 h/kg (twofold lower than HS8, p < 0.01), PWV was 3.7 ± 0.3 vs. 4.7 ± 0.2 m/s (HS4/NS4 vs. HS8, p < 0.05), aortic wall Tgfb1, Col1a2, Col4a1, Smad2, Smad3 mRNAs, and collagen abundance were reversed by salt reduction to the BL levels (p < 0.05). HS was associated with an activation of TGF-β signaling, aortic fibrosis and aortic stiffness accompanied by an MBG increase in the absence of SBP changes in young normotensive rats. The reduction of dietary salt following HS decreased MBG, PWV, aortic wall collagen and TGF-β. Thus, HS-induced aortic stiffness in normotensive animals occurred in the context of elevated MBG, which may activate SMAD-dependent TGF-β pro-fibrotic signaling. This data suggests that a decrease in salt consumption could help to restore aortic elasticity and diminish the risk of cardiovascular disease by reducing the production of the pro-fibrotic factor MBG.

Formononetin protects against balloon injury‑induced neointima formation in rats by regulating proliferation and migration of vascular smooth muscle cells via the TGF‑β1/Smad3 signaling pathway

The present study investigated the effects of formononetin (FMN) against balloon injury‑induced neointima formation in vivo and platelet‑derived growth factor (PDGF)‑BB‑induced proliferation and migration of vascular smooth muscle cells (VSMCs) in vitro, and explored the underlying mechanisms. A rat model of carotid artery injury was established, in order to examine the effects of FMN on balloon injury‑induced neointima formation. Histological observation of the carotid artery tissues was conducted by hematoxylin and eosin staining. VSMC proliferation during neointima formation was observed by proliferating cell nuclear antigen staining. Subsequently, rat aortic VSMCs were isolated, and the effects of FMN on PDGF‑BB‑induced VSMC proliferation and migration were determined using Cell Counting Kit‑8 and Transwell/wound healing assays, respectively. Immunohistochemical and immunocytochemical staining was applied to measure the expression of transforming growth factor (TGF)‑β in carotid artery tissues and VSMCs, respectively. SMAD family member 3 (Smad3)/phosphorylated (p)‑Smad3 expression was examined by western blotting. FMN treatment significantly inhibited the abnormal proliferation of smooth muscle cells in neointima, and alterations to the vascular structure were attenuated. In addition, pretreatment with FMN effectively inhibited the proliferation of PDGF‑BB‑stimulated VSMCs (P<0.05). FMN also reduced the number of cells that migrated to the lower surface of the Transwell chamber and decreased wound‑healing percentage (P<0.05). The expression levels of TGF‑β were decreased by FMN treatment in vivo and in vitro, and Smad3/p‑Smad3 expression was also markedly inhibited. In conclusion, FMN significantly protected against balloon injury‑induced neointima formation in the carotid artery of a rat model; this effect may be associated with the regulation of VSMC proliferation and migration through altered TGF‑β1/Smad3 signaling.

TGF-β1 in Vascular Wall Pathology: Unraveling Chronic Venous Insufficiency Pathophysiology

Chronic venous insufficiency and varicose veins occur commonly in affluent countries and are a socioeconomic burden. However, there remains a relative lack of knowledge about venous pathophysiology. Various theories have been suggested, yet the molecular sequence of events is poorly understood. Transforming growth factor-beta one (TGF-β1) is a highly complex polypeptide with multifunctional properties that has an active role during embryonic development, in adult organ physiology and in the pathophysiology of major diseases, including cancer and various autoimmune, fibrotic and cardiovascular diseases. Therefore, an emphasis on understanding its signaling pathways (and possible disruptions) will be an essential requirement for a better comprehension and management of specific diseases. This review aims at shedding more light on venous pathophysiology by describing the TGF-β1 structure, function, activation and signaling, and providing an overview of how this growth factor and disturbances in its signaling pathway may contribute to specific pathological processes concerning the vessel wall which, in turn, may have a role in chronic venous insufficiency.

Evaluation and Application of Dimethylated Amino Acids as Isobaric Tags for Quantitative Proteomics of the TGF-β/Smad3 Signaling Pathway

Isobaric labeling has become a widespread tool for quantitative proteomic studies. Here, we report the development and evaluation of several dimethylated amino acids as novel isobaric tags for quantitative proteomics. Four-plex dimethylated alanine (DiAla), valine (DiVal), and leucine (DiLeu) have been synthesized, sharing common features of peptide tagging and reporter ion production. DiAla and DiLeu are shown to achieve complete labeling. These two tags' impacts on peptide fragmentation and quantitation are further evaluated using HEK293 cell lysate. DiAla labeling generates more abundant backbone fragmentation whereas DiLeu labeling produces more intense reporter ions. Nonetheless, both tags enable accurate quantitative analysis of HEK293 cell proteomes. DiAla and DiLeu tags are then applied to study the TGF-β/Smad3 pathway with four differentially treated mouse vascular smooth muscle (MOVAS) cells. Our MS data reveal proteome-wide changes of AdSmad3 as compared to the GFP control, consistent with previous findings of causing smooth muscle cell (SMC) dedifferentiation.1 Additionally, the other two novel mutations on the hub protein Smad3, Y226A, and D408H, show compromised TGF-β/Smad3-dependent gene transcription and reversed phenotypic switch. These results are further corroborated with Western blotting and demonstrate that the novel DiAla and DiLeu isobaric tagging reagents provide useful tools for multiplex quantitative proteomics.

Local CXCR4 Upregulation in the Injured Arterial Wall Contributes to Intimal Hyperplasia

CXCR4 is a stem/progenitor cell surface receptor specific for the cytokine stromal cell‐derived factor‐1 (SDF‐1α). There is evidence that bone marrow‐derived CXCR4‐expressing cells contribute to intimal hyperplasia (IH) by homing to the arterial subintima which is enriched with SDF‐1α. We have previously found that transforming growth factor‐β (TGFβ) and its signaling protein Smad3 are both upregulated following arterial injury and that TGFβ/Smad3 enhances the expression of CXCR4 in vascular smooth muscle cells (SMCs). It remains unknown, however, whether locally induced CXCR4 expression in SM22 expressing vascular SMCs plays a role in neointima formation. Here, we investigated whether elevated TGFβ/Smad3 signaling leads to the induction of CXCR4 expression locally in the injured arterial wall, thereby contributing to IH. We found prominent CXCR4 upregulation (mRNA, 60‐fold; protein, 4‐fold) in TGFβ‐treated, Smad3‐expressing SMCs. Chromatin immunoprecipitation assays revealed a specific association of the transcription factor Smad3 with the CXCR4 promoter. TGFβ/Smad3 treatment also markedly enhanced SDF‐1α‐induced ERK1/2 phosphorylation as well as SMC migration in a CXCR4‐dependent manner. Adenoviral expression of Smad3 in balloon‐injured rat carotid arteries increased local CXCR4 levels and enhanced IH, whereas SMC‐specific depletion of CXCR4 in the wire‐injured mouse femoral arterial wall produced a 60% reduction in IH. Our results provide the first evidence that upregulation of TGFβ/Smad3 in injured arteries induces local SMC CXCR4 expression and cell migration, and consequently IH. The Smad3/CXCR4 pathway may provide a potential target for therapeutic interventions to prevent restenosis. Stem Cells2016;34:2744–2757

A crosstalk between TGF-β/Smad3 and Wnt/β-catenin pathways promotes vascular smooth muscle cell proliferation

RATIONALE

Endovascular interventions performed for atherosclerotic lesions trigger excessive vascular smooth muscle cell (SMC) proliferation leading to intimal hyperplasia. Our previous studies show that following endovascular injury, elevated TGF-β/Smad3 promotes SMC proliferation and intimal hyperplasia. Furthermore in cultured SMCs, elevated TGF-β/Smad3 increases the expression of several Wnt genes. Here we investigate a crosstalk between TGF-β/Smad3 and Wnt/β-catenin signaling and its role in SMC proliferation.

METHODS AND RESULTS

To mimic TGF-β/Smad3 up-regulation in vivo, rat aortic SMCs were treated with Smad3-expressing adenovirus (AdSmad3) or AdGFP control followed by stimulation with TGF-β1 (or solvent). AdSmad3/TGF-β treatment up-regulated Wnt2b, Wnt4, Wnt5a, Wnt9a, and Wnt11 (confirmed by qRT-PCR and ELISA), and also increased β-catenin protein as detected by Western blotting. Blocking Wnt signaling using a Frizzled receptor inhibitor (Niclosamide) abolished TGF-β/Smad3-induced β-catenin stabilization. Increasing β-catenin through degradation inhibition (using SKL2001) or by adenoviral expression enhanced SMC proliferation. Furthermore, application of recombinant Wnt2b, Wnt4, Wnt5a, or Wnt9a, but not Wnt11, stabilized β-catenin and stimulated SMC proliferation as well. In addition, increased β-catenin was found in the neointima of injured rat carotid artery where TGF-β and Smad3 are known to be up-regulated.

CONCLUSIONS

These results suggest a novel mechanism whereby elevated TGF-β/Smad3 stimulates the secretion of canonical Wnts which in turn enhances SMC proliferation through β-catenin stabilization. This crosstalk between TGF-β/Smad3 and Wnt/β-catenin canonical pathways provides new insights into the pathophysiology of vascular SMCs linked to intimal hyperplasia.

A deleterious gene-by-environment interaction imposed by calcium channel blockers in Marfan syndrome

Calcium channel blockers (CCBs) are prescribed to patients with Marfan syndrome for prophylaxis against aortic aneurysm progression, despite limited evidence for their efficacy and safety in the disorder. Unexpectedly, Marfan mice treated with CCBs show accelerated aneurysm expansion, rupture, and premature lethality. This effect is both extracellular signal-regulated kinase (ERK1/2) dependent and angiotensin-II type 1 receptor (AT1R) dependent. We have identified protein kinase C beta (PKCβ) as a critical mediator of this pathway and demonstrate that the PKCβ inhibitor enzastaurin, and the clinically available anti-hypertensive agent hydralazine, both normalize aortic growth in Marfan mice, in association with reduced PKCβ and ERK1/2 activation. Furthermore, patients with Marfan syndrome and other forms of inherited thoracic aortic aneurysm taking CCBs display increased risk of aortic dissection and need for aortic surgery, compared to patients on other antihypertensive agents.

DOI:http://dx.doi.org/10.7554/eLife.08648.001

Marfan syndrome is a disorder that affects the body's connective tissues, which maintain the structure of the body and support organs and other tissues. People with Marfan syndrome have connective tissues that can stretch more than those of other people, which put them at increased risk of a life-threatening tear in their aorta (the main artery in the body), muscle weakness and other problems.

A cell communication pathway called TGFβ signaling is involved in cell growth and many other important processes. TGFβ signaling is more active in patients with Marfan syndrome due to mutations in a gene called FBN1. Drugs that block TGFβ signaling—which are also used to treat high blood pressure—can reduce the symptoms of the disorder. Unfortunately, not all people with Marfan disease can tolerate these drugs and other medications called calcium channel blockers, which also lower blood pressure, are often used as an alternative. It is thought that calcium channel blockers help reduce stress on blood vessels, but there is little data to show whether these drugs are safe and helpful for patients with Marfan syndrome.

Now, Doyle, Doyle et al. studied the effect of two different calcium channel blockers on mice that have a mutation in Fbn1—the mouse equivalent of FBN1—that is similar to those found in humans with Marfan syndrome. The experiments show that the aortas of these mice grew more quickly and were more likely to tear when compared to mice that did not receive these drugs. Many of these aortic tears were fatal. The calcium channel blockers increased the activity of two signaling molecules that are regulated by TGFβ signaling. Treating the Marfan mice with other drugs that lower the activity of these signaling molecules protected the aorta, even if they were also treated with the calcium channel blockers.

Doyle, Doyle et al. examined a registry of human patients. This revealed preliminary evidence that aortic tears and aortic repair surgery were more common in patients with Marfan syndrome who had received calcium channel blockers than patients who had been treated with other drugs. Together, these findings suggest that it may be dangerous to treat patients with Marfan syndrome with calcium channel blockers. Additional work will be needed to confirm this risk, to find out if it extends to other similar conditions, and to explore the therapeutic potential of drugs that target the two enzymes.

DOI:http://dx.doi.org/10.7554/eLife.08648.002

Acute reductions in mechanical wall strain precede the formation of intimal hyperplasia in a murine model of arterial occlusive disease

OBJECTIVE

Intimal hyperplasia (IH) continues to plague the durability of vascular interventions. Employing a validated murine model, ultrasound biomicroscopy, and speckle-tracking algorithms, we tested the hypothesis that reduced cyclic arterial wall strain results in accentuated arterial wall IH.

METHODS

A 9-0 suture was tied around the left mouse (n = 10) common carotid artery and a 35-gauge (outer diameter = 0.14 mm) blunt mandrel. We previously showed that mandrel removal results in a ∼78% reduction in diameter and ∼85% reduction in flow, with subsequent delayed induction of IH by day 28. Preoperative, postoperative day-4 (before measurable IH), and postoperative day-27 circumferential wall strains were measured in locations 1, 2, and 3 mm proximal to the stenosis and in the same locations on the contralateral (nonstenosed) carotid. At postoperative day 28, arteries were perfusion fixed and arterial wall morphology was assessed microscopically in the same regions.

RESULTS

Strains were the same in all locations preoperatively. Wall strain was decreased in all regions proximal to the stenosis by day 4 (0.26 ± 0.01 to 0.11 ± 0.02; P < .001), while strains remained unchanged for the contralateral artery (P = .45). No statistical regional differences in mean strain or IH were noted at any time point for the experimental or contralateral artery. Based on the median, regions were divided into those with low strain (≤0.1) and high strain (>0.1). Average preoperative strains in both groups were the same (0.27 ± 0.09 and 0.27 ± 0.08). All segments in the low-strain group (n = 13) demonstrated significant IH formation by day 28, while only 31% of the high strain group demonstrated any detectable IH at day 28. (Mean low-strain intimal thickness = 32 ± 20 μm, high strain = 8.0 ± 16 μm; P < .01). Changes in cross-sectional area at diastole drove the reduction in strain in the low-strain group, increasing significantly from preoperatively to day 4 (P = .04), while lumen cross-section at systole remained unchanged (P = .46). Cross-sectional area at diastole and systole in the high-strain group remained unchanged from preoperatively to day 4 (P = .67).

CONCLUSIONS

Early reduction in arterial wall strain is associated with subsequent development of hemodynamically induced IH.

AAV2/8-hSMAD3 gene delivery attenuates aortic atherogenesis, enhances Th2 response without fibrosis, in LDLR-KO mice on high cholesterol diet

Background

Inflammation is a key etiologic component in atherogenesis and transforming growth factor beta 1 (TGFβ1) is a well known anti-inflammatory cytokine which potentially might be used to limit it. Yet TGFβ1 is pleiomorphic, causing fibrosis, cell taxis, and under certain circumstances, can even worsen inflammation. SMAD3 is an important member of TGFβ1′s signal transduction pathway, but is a fully intracellular protein.

Objectives

With the hope of attenuating TGFβ1′s adverse systemic effects (eg. fibrosis) and accentuating its anti-inflammatory activity, we proposed the use of human (h)SMAD3 as an intracellular substitute for TGFβ1.

Study design

To test this hypothesis adeno-associated virus type 2/8 (AAV)/hSMAD3 or AAV/Neo (control) was tail vein injected into the low density lipoprotein receptor knockout (LDLR-KO) mice, then placed on a high-cholesterol diet (HCD).

Results

The hSMAD3 delivery was associated with significantly lower atherogenesis as measured by larger aortic cross sectional area, thinner aortic wall thickness, and lower aortic systolic blood velocity compared with Neo gene-treated controls. HSMAD3 delivery also resulted in fewer aortic macrophages by immunohistochemistry for CD68 and ITGAM, and quantitative reverse transcriptase polymerase chain reaction analysis of EMR and ITGAM. Overall, aortic cytokine expression showed an enhancement of Th2 response (higher IL-4 and IL-10); while Th1 response (IL-12) was lower with hSMAD3 delivery. While TGFβ1 is often associated with increased fibrosis, AAV/hSMAD3 delivery exhibited no increase of collagen 1A2 or significantly lower 2A1 expression in the aorta compared with Neo-delivery. Connective tissue growth factor (CTGF), a mediator of TGFβ1/SMAD3-induced fibrosis, was unchanged in hSMAD3-delivered aortas. In the liver, all three of these genes were down-regulated by hSMAD3 gene delivery.

Conclusion

These data strongly suggest that AAV/hSMAD3 delivery gave anti-atherosclerosis therapeutic effect without the expected undesirable effect of TGFβ1-associated fibrosis.

Protein kinase C-δ (PKCδ) regulates proinflammatory chemokine expression through cytosolic interaction with the NF-κB subunit p65 in vascular smooth muscle cells

Proinflammatory chemokines released by vascular smooth muscle cells (VSMCs) play a critical role in vascular inflammation. Protein kinase C-δ (PKCδ) has been shown to be up-regulated in VSMCs of injured arteries. PKCδ knock-out (Prkcd(-/-)) mice are resistant to inflammation as well as apoptosis in models of abdominal aortic aneurysm. However, the precise mechanism by which PKCδ modulates inflammation remains incompletely understood. In this study, we identified four inflammatory chemokines (Ccl2/Mcp-1, Ccl7, Cxcl16, and Cx3cl1) of over 45 PKCδ-regulated genes associated with inflammatory response by microarray analysis. Using CCL2 as a prototype, we demonstrated that PKCδ stimulated chemokine expression at the transcriptional level. Inhibition of the NF-κB pathway or siRNA knockdown of subunit p65, but not p50, eliminated the effect of PKCδ on Ccl2 expression. Overexpressing PKCδ followed by incubation with phorbol 12-myristate 13-acetate resulted in an increase in p65 Ser-536 phosphorylation and enhanced DNA binding affinity without affecting IκB degradation or p65 nuclear translocation. Prkcd gene deficiency impaired p65 Ser-536 phosphorylation and DNA binding affinity in response to TNFα. Results from in situ proximity ligation analysis and co-immunoprecipitation performed on cultured VSMCs and aneurysmal aorta demonstrated physical interaction between PKCδ and p65 that took place largely outside the nucleus. Promoting nuclear translocation of PKCδ with peptide ψδRACK diminished Ccl2 production, whereas inhibition of PKCδ translocation with peptide δV1-1 enhanced Ccl2 expression. Together, these results suggest that PKCδ modulates inflammation at least in part through the NF-κB-mediated chemokines. Mechanistically, PKCδ activates NF-κB through an IκB-independent cytosolic interaction, which subsequently leads to enhanced p65 phosphorylation and DNA binding affinity.

Crosstalk between TGF-β/Smad3 and BMP/BMPR2 signaling pathways via miR-17-92 cluster in carotid artery restenosis

In the recent decades, carotid angioplasty and stenting (CAS) has been developed into a credible option for the patients with carotid stenosis. However, restenosis remains a severe and unsolved issue after CAS treatment. Restenosis is characterized by neointimal hyperplasia, which is partially caused by vascular smooth muscle cells (VSMC) proliferation. However, the molecular mechanism involved in the restenosis is still unclear. In this study, we demonstrated a functional crosstalk between two TGF-β superfamily signaling pathway members, Smad3 and BMPR2, in VSMC proliferation. Smad3 plays an important role in the TGF-β/Smad3 signaling pathway, and is significantly upregulated in the carotid artery with restenosis to promote VSMC proliferation. In contrast, BMP receptor II (BMPR2), an inhibitor of VSMC proliferation is downregulated in carotid restenosis. We further found that BMPR2 downregulation is mediated by miR-17-92 cluster, which is transcriptionally regulated by Smad3. Thus, Smad3 upregulation and Smad3/miR-17-92 cluster-dependent BMPR2 downregulation are likely to promote VSMC proliferation and restenosis. Taken together, our results may provide novel clues for early diagnosis of carotid restenosis and developing new therapeutic strategy.

PKCδ as a regulator for TGF-β-stimulated connective tissue growth factor production in human hepatocarcinoma (HepG2) cells

CTGF (connective tissue growth factor) is widely regarded as an important amplifier of the profibrogenic action of TGF-β (transforming growth factor β) in a variety of tissues, although the precise mechanism of how the TGF-β signalling pathways modulate CTGF expression remains unclear. In the present study, the role of PKCδ (protein kinase Cδ) in TGF-β1-mediated CTGF expression was investigated using HepG2 cells. TGF-β1 treatment specifically elevated PKCδ activation and CTGF expression. In contrast, blockade of PKCδ by the selective inhibitor Rottlerin or by siRNA knockdown significantly reduced TGF-β1-induced CTGF production. The regulatory mechanism was further demonstrated in HepG2 cells whereby TGF-β1-induced PKCδ activation negatively regulated the nuclear levels of PPM1A (protein phosphatase, Mg2+/Mn2+ dependent, 1A) through the RhoA/ROCK (Rho-associated kinase) pathway. Moreover, we showed that both Smad signalling and the PKCδ pathway appeared to be stimulated by TGF-β1 in parallel. Time course assessments indicated that PKCδ signalling may have a function in maintaining nuclear phospho-Smads at a maximal level. The collective results of the present study demonstrated that PKCδ-stimulated RhoA/ROCK activation resulted in a reduction in PPM1A, thereby up-regulating Smad-dependent gene induction for extended periods. These findings indicated that PKCδ plays a critical role in TGF-β1-induced CTGF production in HepG2 cells.

Suppression of AKT phosphorylation restores rapamycin-based synthetic lethality in SMAD4-defective pancreatic cancer cells

mTOR has been implicated in survival signals for many human cancers. Rapamycin and TGF-β synergistically induce G1 cell-cycle arrest in several cell lines with intact TGF-β signaling pathway, which protects cells from the apoptotic effects of rapamycin during S-phase of the cell cycle. Thus, rapamycin is cytostatic in the presence of serum/TGF-β and cytotoxic in the absence of serum. However, if TGF-β signaling is defective, rapamycin induced apoptosis in both the presence and absence of serum/TGF-β in colon and breast cancer cell lines. Because genetic dysregulation of TGF-β signaling is commonly observed in pancreatic cancers-with defects in the Smad4 gene being most prevalent, we hypothesized that pancreatic cancers would display a synthetic lethality to rapamycin in the presence of serum/TGF-β. We report here that Smad4-deficient pancreatic cancer cells are killed by rapamycin in the absence of serum; however, in the presence of serum, we did not observe the predicted synthetic lethality with rapamycin. Rapamycin also induced elevated phosphorylation of the survival kinase Akt at Ser473. Suppression of rapamycin-induced Akt phosphorylation restored rapamycin sensitivity in Smad4-null, but not Smad4 wild-type pancreatic cancer cells. This study shows that the synthetic lethality to rapamycin in pancreatic cancers with defective TGF-β signaling is masked by rapamycin-induced increases in Akt phosphorylation. The implication is that a combination of approaches that suppress both Akt phosphorylation and mTOR could be effective in targeting pancreatic cancers with defective TGF-β signaling.

A human monoclonal antibody 264RAD targeting αvβ6 integrin reduces tumour growth and metastasis, and modulates key biomarkers in vivo

αvβ6 integrin expression is upregulated on a wide range of epithelial tumours, and is thought to play a role in modulating tumour growth. Here we describe a human therapeutic antibody 264RAD, which binds and inhibits αvβ6 integrin function. 264RAD cross-reacts with human, mouse and cynomolgus monkey αvβ6, and inhibits binding to all ligands including the latency-associated peptide of TGF-β. Screening across a range of integrins revealed that 264RAD also binds and inhibits the related integrin αvβ8, but not the integrins α5β1, αvβ3, αvβ5 and α4β1. In vitro 264RAD inhibited invasion of VB6 and Detroit 562 cells in a Matrigel invasion assay and αvβ6 mediated production of matrix metalloproteinase-9 in Calu-3 cells. It inhibited TGF-β-mediated activation of dermal skin fibroblasts by preventing local activation of TGF-β by NCI-H358 tumour cells in a tumour cell-fibroblast co-culture assay. In vivo 264RAD showed dose-dependent inhibition of Detroit 562 tumour growth, regressing established tumours when dosed at 20 mg/kg once weekly. The reduction in growth associated with 264RAD was related to a dose-dependent inhibition of Ki67 and phospho-ERK and a reduction of αvβ6 expression in the tumour cells, coupled to a reduction in fibronectin and alpha smooth muscle actin expression in stromal fibroblasts. 264RAD also reduced the growth and metastasis of orthotopic 4T1 tumours. At 20 mg/kg growth of both the primary tumour and the number of metastatic deposits in lung were reduced. The data support the conclusion that 264RAD is a potent inhibitor of αvβ6 integrin, with some activity against αvβ8 integrin, that reduces both tumour growth and metastasis.

Role of TGF-β1/Smad3 signaling pathway in secretion of type I and III collagen by vascular smooth muscle cells of rats undergoing balloon injury

Antisense Smad3 adenoviral vectors were used to transfect vascular smooth muscle cells (VSMCs) from rats with balloon injury or infused into the rat balloon-catheter injured carotid arteries, and the role of TGF-β1/Smad3 signaling pathway in the secretion of type I and III collagen by VSMCs following balloon injury was investigated. Antisense Smad3 adenoviral vectors were used to transfect these VSMCs (antisense Smad3 group). A total 90 rats were randomly assigned into blank control group, experiment group, negative control group. In the in vitro study, the expression of type I and III collagen was markedly reduced in the antisense Smad3 group when compared with the control groups (P < 0.05). In the in vivo study, the expression of type I and III collagen was significantly lower than that in the negative control group at 3 days, 1 week and 2 weeks after injury (P < 0.05). At 2 weeks and 3 months after injury, the lumen area in the antisense Smad3 group was markedly increased but the intimal area dramatically reduced when compared with the negative control (P < 0.05). We conclude that transfection of VSMCs with antisense Smad3 can reduce the secretion of type I and III collagen which then inhibit intimal hyperplasia.

Protein kinase C δ regulates the release of collagen type I from vascular smooth muscle cells via regulation of Cdc42

Both gene knockout and chemical inhibition show that PKCδ is critical for efficient secretion of type I collagen by arterial smooth muscle cells. The data suggest that PKCδ regulates trafficking of collagen I by controlling its exit from the trans-Golgi network through a mechanism involving Cdc42.

Collagen type I is the most abundant component of extracellular matrix in the arterial wall. Mice knocked out for the protein kinase C δ gene (PKCδ KO) show a marked reduction of collagen I in the arterial wall. The lack of PKCδ diminished the ability of arterial smooth muscle cells (SMCs) to secrete collagen I without significantly altering the intracellular collagen content. Moreover, the unsecreted collagen I molecules accumulate in large perinuclear puncta. These perinuclear structures colocalize with the trans-Golgi network (TGN) marker TGN38 and to a lesser degree with cis-Golgi marker (GM130) but not with early endosomal marker (EEA1). Associated with diminished collagen I secretion, PKCδ KO SMCs exhibit a significant reduction in levels of cell division cycle 42 (Cdc42) protein and mRNA. Restoring PKCδ expression partially rescues Cdc42 expression and collagen I secretion in PKCδ KO SMCs. Inhibition of Cdc42 expression or activity with small interfering RNA or secramine A in PKCδ WT SMCs eliminates collagen I secretion. Conversely, restoring Cdc42 expression in PKCδ KO SMCs enables collagen I secretion. Taken together, our data demonstrate that PKCδ mediates collagen I secretion from SMCs, likely through a Cdc42-dependent mechanism.

TGF-β1 downregulates AT1 receptor expression via PKC-δ-mediated Sp1 dissociation from KLF4 and Smad-mediated PPAR-γ association with KLF4

OBJECTIVE

Cardiovascular effects of angiotensin II are primarily mediated via the angiotensin II type 1 receptor (AT1R). Krüppel-like factor 4 (KLF4), a transcription factor that binds to the transforming growth factor (TGF)-β control element (TCE), regulates a variety of receptor expression in vascular smooth muscle cells. In the present study, we investigated the mechanisms of TGF-β-mediated KLF4 regulation of AT1R expression.

METHODS AND RESULTS

Coimmunoprecipitation, chromatin immunoprecipitation, and luciferase assays were performed, with the results suggesting that Sp1 forms a complex with KLF4 bound to the TCE of the AT1R promoter and cooperatively activates AT1R transcription in vascular smooth muscle cells under basal conditions. On activation of TGF-β1 signaling, Sp1 is dissociated from the KLF4-Sp1 complex through PKC-δ-mediated KLF4 phosphorylation at Thr401, downregulating AT1R expression. Simultaneously, TGF-β1 facilitates KLF4-PPAR-γ complex formation and its binding to the TCE of the AT1R promoter through Smad-mediated KLF4 phosphorylation at Ser470, subsequently leading to inhibition of AT1R transcription.

CONCLUSIONS

KLF4 functions as a protein platform that is able to bind to the TCE of the AT1R promoter. On activation of TGF-β signaling, KLF4 mediates Sp1 dissociation from, and PPAR-γ association with, the AT1R promoter, leading to downregulation of AT1R expression in VSMCs.

Schisandrin B suppresses TGFβ1 signaling by inhibiting Smad2/3 and MAPK pathways

TGFβ1 plays a crucial role in the pathogenesis of vascular fibrotic diseases. Schisandra chinensis (S. chinensis), which is used as an oriental herbal medicine, is effective in the treatment of vascular injuries that cause aberrant TGFβ1 signaling. In this study, we investigated whether S. chinensis extract and its active ingredients inhibit TGFβ1 signaling in A7r5 vascular smooth muscle cells. We found that S. chinensis extract suppressed TGFβ1 signaling via inhibition of Smad2/3 phosphorylation and nuclear translocation. Among the active ingredients of S. chinensis extract, schisandrin B (SchB) most potently inhibited TGFβ1 signaling. SchB inhibited sustained phosphorylation and nuclear translocation of Smad2/3. Moreover, SchB suppressed TGFβ1-induced phosphorylation of p38 and JNK, which contributed to Smad2/3 inactivation. The present study is the first to demonstrate that S. chinensis extract and SchB inhibit TGFβ1 signaling. Our results may help future investigations to understand vascular fibrosis pathogenesis and to develop novel therapeutic strategies for treatment of vascular fibrotic diseases.

Effect of protein kinase C delta (PKC-δ) inhibition on the transcriptome of normal and systemic sclerosis human dermal fibroblasts in vitro

Previous studies demonstrated that protein kinase C- δ (PKC-δ) inhibition with the selective inhibitor, rottlerin, resulted in potent downregulation of type I collagen expression and production in normal human dermal fibroblasts and abrogated the exaggerated type I collagen production and expression in fibroblasts cultured from affected skin from patients with the fibrosing disorder systemic sclerosis (SSc). To elucidate the mechanisms involved in the ability of PKC-δ to regulate collagen production in fibroblasts, we examined the effects of PKC-δ inhibition on the transcriptome of normal and SSc human dermal fibroblasts. Normal and SSc human dermal fibroblasts were incubated with rottlerin (5 µM), and their gene expression was analyzed by microarrays. Pathway analysis and gene ontology analysis of differentially expressed genes in each comparison were performed. Identification of significantly overrepresented transcriptional regulatory elements (TREs) was performed using the Promoter Analysis and Interaction Network Toolset (PAINT) program. PKC-δ activity was also inhibited using RNA interference (siRNA) and by treating fibroblasts with a specific PKC-δ inhibitory cell permeable peptide. Differential gene expression of 20 genes was confirmed using real time PCR. PKC-δ inhibition caused a profound change in the transcriptome of normal and SSc human dermal fibroblasts in vitro. Pathway and gene ontology analysis identified multiple cellular and organismal pathways affected by PKC-δ inhibition. Furthermore, both pathway and PAINT analyses indicated that the transcription factor NFκB played an important role in the transcriptome changes induced by PKC-δ inhibition. Multiple genes involved in the degradation of the extracellular matrix components were significantly reduced in SSc fibroblasts and their expression was increased by PKC-δ inhibition. These results indicate that isoform-specific inhibition of PKC-δ profibrotic effects may represent a novel therapeutic approach for SSc and other fibrotic diseases.

Cellular Interplay between Cardiomyocytes and Nonmyocytes in Cardiac Remodeling

Cardiac hypertrophy entails complex structural remodeling involving rearrangement of muscle fibers, interstitial fibrosis, accumulation of extracellular matrix, and angiogenesis. Many of the processes underlying cardiac remodeling have features in common with chronic inflammatory processes. During these processes, nonmyocytes, such as endothelial cells, fibroblasts, and immune cells, residing in or infiltrating into the myocardial interstitium play active roles. This paper mainly addresses the functional roles of nonmyocytes during cardiac remodeling. In particular, we focus on the communication between cardiomyocytes and nonmyocytes through direct cell-cell interactions and autocrine/paracrine-mediated pathways.

TGF-β and restenosis revisited: a Smad link

Despite novel surgical therapies for the treatment of atherosclerosis, restenosis continues to be a significant impediment to the long-term success of vascular interventions. Transforming growth factor-beta (TGF-β), a family of cytokines found to be up-regulated at sites of arterial injury, has long been implicated in restenosis; a role that has largely been attributed to TGF-β-mediated vascular fibrosis. However, emerging data indicate that the role of TGF-β in intimal thickening and arterial remodeling, the critical components of restenosis, is complex and multidirectional. Recent advancements have clarified the basic signaling pathway of TGF-β, making evident the need to redefine the precise role of this family of cytokines and its primary signaling pathway, Smad, in restenosis. Unraveling TGF-β signaling in intimal thickening and arterial remodeling will pave the way for a clearer understanding of restenosis and the development of innovative pharmacological therapies.

Protein kinase C delta mediates arterial injury responses through regulation of vascular smooth muscle cell apoptosis

AIMS

A balance between apoptosis and proliferation of vascular smooth muscle cells (VSMC) influences the development of intimal hyperplasia. We have previously demonstrated that protein kinase C delta (PKCdelta) regulates both apoptosis and proliferation of VSMC in vitro. Here we investigate the role of PKCdelta in intimal hyperplasia through gene deletion or overexpression in rodent models of arterial injury.

METHODS AND RESULTS

Arterial injury was induced in mice and rats by means of carotid ligation or balloon angioplasty, respectively. Overexpression of PKCdelta was achieved by adenovirus-mediated gene transfer immediately after balloon injury in rat carotid arteries. Levels of PKCdelta protein were profoundly increased in the carotid wall 3-7 days after balloon injury, co-localizing to TUNEL-positive medial cells. When subjected to arterial injury, PKCdelta gene-deficient mice responded with an enhanced intimal hyperplasia accompanied by an 80% reduction in the number of TUNEL-positive cells detected in the injured arteries as compared with their wild-type littermates. Conversely, arterial gene transfer of PKCdelta further increased the arterial expression of PKCdelta, which was associated with a marked increase in apoptosis and reduction of intimal hyperplasia. Neither manipulation led to significant alteration in cell proliferation, suggesting that the function of PKCdelta after arterial injury is predominantly pro-apoptotic. This notion is further supported by our observation of high PKCdelta expression in human restenotic lesions that also co-localized with apoptosis.

CONCLUSION

The expression of PKCdelta is upregulated in the arterial wall in response to injury. This induction appears to be a mechanism of arterial response that negatively influences the degree of intimal hyperplasia by stimulating VSMC apoptosis.

Arterial gene transfer of the TGF-beta signalling protein Smad3 induces adaptive remodelling following angioplasty: a role for CTGF

AIMS

Although transforming growth factor-beta (TGF-beta) is believed to stimulate intimal hyperplasia after arterial injury, its role in remodelling remains unclear. We investigate whether Smad3, a TGF-beta signalling protein, might facilitate its effect on remodelling.

METHODS AND RESULTS

Using the rat carotid angioplasty model, we assess Smad3 expression following arterial injury. We then test the effect of arterial Smad3 overexpression on the response to injury, and use a conditioned media experimental design to confirm an Smad3-dependent soluble factor that mediates this response. We use small interfering RNA (siRNA) to identify this factor as connective tissue growth factor (CTGF). Finally, we attempt to replicate the effect of medial Smad3 overexpression through adventitial application of recombinant CTGF. Injury induced medial expression of Smad3; overexpression of Smad3 caused neointimal thickening and luminal expansion, suggesting adaptive remodelling. Smad3 overexpression, though exclusively medial, caused adventitial changes: myofibroblast transformation, proliferation, and collagen production, all of which are associated with adaptive remodelling. Supporting the hypothesis that Smad3 initiated remodelling and these adventitial changes via a secreted product of medial smooth muscle cells (SMCs), we found that media conditioned by Smad3-expressing recombinant adenoviral vector (AdSmad3)-infected SMCs stimulated adventitial fibroblast transformation, proliferation, and collagen production in vitro. This effect was attenuated by pre-treatment of SMCs with siRNA specific for CTGF, abundantly produced by AdSmad3-infected SMCs, and significantly up-regulated in Smad3-overexpressing arteries. Moreover, periadventitial administration of CTGF replicated the effect of medial Smad3 overexpression on adaptive remodelling and neointimal hyperplasia.

CONCLUSION

Medial gene transfer of Smad3 promotes adaptive remodelling by indirectly influencing the behaviour of adventitial fibroblasts. This arterial cell-cell communication is likely to be mediated by Smad3-dependent production of CTGF.

TGF-beta through Smad3 signaling stimulates vascular smooth muscle cell proliferation and neointimal formation

The objective of this study was to better understand the role of transforming growth factor-beta (TGF-beta) and its primary signaling protein Smad3 in the development of intimal hyperplasia. Male Sprague-Dawley rats underwent left carotid balloon injury followed by intra-arterial infection with adenovirus-expressing Smad3 (AdSmad3). In uninfected injured arteries, endogenous Smad3 was upregulated with the expression peaking at 14 days. Moreover, in arteries infected with AdSmad3, we observed an enhancement of intimal hyperplasia and increased vascular smooth muscle cell (VSMC) proliferation. The novel finding, that TGF-beta/Smad3 stimulated rather than inhibited VSMC proliferation, was confirmed in cultured VSMCs infected with AdSmad3 and treated with TGF-beta. To identify the mechanism underlying TGF-beta/Smad3-mediated VSMC proliferation, we studied the cyclin-dependent kinase inhibitor p27. Although the upregulation of Smad3 in VSMCs had no significant effect on total p27 levels, Smad3 did stimulate the phosphorylation of p27 at serine-10 as well as the nuclear export of p27, events associated with cell proliferation. Furthermore, serine-10-phosphorylated p27 was also increased in AdSmad3-infected injured rat carotid arteries, demonstrating the existence of this same mechanism in vivo. In conclusion, our findings identify a novel mechanism for the effect of TGF-beta on intimal hyperplasia. In the presence of elevated levels of Smad3 that develop in response to injury, TGF-beta stimulates smooth muscle cell proliferation through a mechanism involving the phosphorylation and nuclear export of p27.

Characterization of primary and restenotic atherosclerotic plaque from the superficial femoral artery: Potential role of Smad3 in regulation of SMC proliferation

OBJECTIVE

To characterize and compare primary and restenotic lesions of the superficial femoral artery and analyze the contribution of TGF-beta/Smad3 signaling to the pathophysiology of peripheral artery occlusive disease.

METHODS AND RESULTS

Immunohistochemical studies were performed on specimens retrieved from the superficial femoral artery of patients undergoing either atherectomy for primary atherosclerotic or recurrent disease after stenting and/or prior angioplasty. Immunohistochemical analysis revealed a significantly higher smooth muscle cell (SMC) content (alpha-actin+) and expression of Smad3 in restenotic lesions while primary lesions contained significantly more leukocytes (CD45+) and macrophages (CD68+). Further studies demonstrated colocalization of Smad3 with alpha-actin and PCNA, suggesting a role for Smad3 in the proliferation observed in restenotic lesions. To confirm a role for Smad3 in SMC proliferation, we both upregulated Smad3 via adenoviral mediated gene transfer (AdSmad3) and inhibited Smad3 through transfection with siRNA in human aortic SMCs, then assessed cell proliferation with tritiated thymidine. Overexpression of Smad3 enhanced whereas inhibition of Smad3 decreased cell proliferation.

CONCLUSION

Differences in cellular composition and cell proliferation in conjunction with the finding that Smad3 is expressed exclusively in restenotic disease suggest that TGF-beta, through Smad3 signaling, may play an essential role in SMC proliferation and the pathophysiology of restenosis in humans.

Transforming growth factor-beta promotes recruitment of bone marrow cells and bone marrow-derived mesenchymal stem cells through stimulation of MCP-1 production in vascular smooth muscle cells

Bone marrow-derived progenitor cells have recently been shown to be involved in the development of intimal hyperplasia after vascular injury. Transforming growth factor-beta (TGF-beta) has profound stimulatory effects on intimal hyperplasia, but it is unknown whether these effects involve progenitor cell recruitment. In this study we found that although TGF-beta had no direct effect on progenitor cell recruitment, conditioned media derived from vascular smooth muscle cells (VSMC) stimulated with TGF-beta induced migration of both total bone marrow (BM) cells and BM-mesenchymal stem cells (MSC) and also induced MSC differentiation into smooth muscle like cells. Furthermore, overexpression of the signaling molecule Smad3 in VSMC via adenovirus-mediated gene transfer (AdSmad3) enhanced the TGF-beta's chemotactic effect. Microarray analysis of VSMC stimulated by TGF-beta/AdSmad3 revealed monocyte chemoattractant protein-1 (MCP-1) as a likely factor responsible for progenitor cell recruitment. We then demonstrated that TGF-beta through Smad3 phosphorylation induced a robust expression of MCP-1 in VSMC. Recombinant MCP-1 mimicked the stimulatory effect of conditioned media on BM and MSC migration. In the rat carotid injury model, Smad3 overexpression significantly increased MCP-1 expression after vascular injury, consistent with our in vitro results. Interestingly, TGF-beta/Smad3-induced MCP-1 was completely blocked by both Ro-32-0432 and rotterlin, suggesting protein kinase C-delta (PKCdelta) may play a role in TGF-beta/Smad3-induced MCP-1 expression. In summary, our data demonstrate that TGF-beta, through Smad3 and PKCdelta, stimulates VSMC production of MCP-1, which is a chemoattractant for bone marrow-derived cells, specifically MSC. Manipulation of this signaling system may provide a novel approach to inhibition of intimal hyperplasia.

Upregulation of protein kinase cdelta in vascular smooth muscle cells promotes inflammation in abdominal aortic aneurysm

BACKGROUND

The development of abdominal aortic aneurysms (AAAs) involves a complex interplay of extracellular matrix degradation, inflammation, and apoptosis. We have previously shown that protein kinase Cdelta (PKCdelta) plays a critical role in vascular smooth muscle cell (vSMC) apoptosis in the setting of oxidative stresses. Here, we show that PKCdelta is also involved in the signaling that draws inflammatory cells to aneurismal tissue.

MATERIALS AND METHODS

Immunostaining for monocyte chemotactic factor (MCP)-1 and PKCdelta was performed on paraffin-fixed arterial sections. Enzyme-linked immunosorbent assay to detect MCP-1 produced by vSMCs was performed on media from cultured rat A10 cells after cytokine induction with or without the PKCdelta-specific inhibitor rottlerin. Migration of isolated lymphocytes was evaluated in response to media from activated A10 cells.

RESULTS

Human AAAs show widespread and elevated expression of PKCdelta that is not seen in normal aortic tissues. Cytokine stimulation of cultured vSMCs induced vigorous production of the key chemotactant MCP-1, the expression of which was PKCdelta dependent. Stimulated vSMCs were capable of inducing the migration of leukocytes, and this effect was also dependent on PKCdelta activity. Staining of human AAA tissue for MCP-1 showed an expression pattern that was identical to that of PKCdelta and smooth muscle specific alpha-actin.

CONCLUSIONS

PKCdelta is widely expressed in human AAA vessel walls and mediates MCP-1 expression by vSMCs, which could contribute to the inflammatory process. These findings, coupled with earlier studies of PKCdelta, suggest that PKCdelta plays a central role in the pathogenesis of AAAs and may be a potential target for future therapies.

Biodegradable arginine-based poly(ester-amide)s as non-viral gene delivery reagents

A novel family of synthetic biodegradable poly(ester-amide)s (Arg-PEAs) was evaluated for their biosafety and capability to transfect rat vascular smooth muscle cells, a major cell type participating in vascular diseases. Arg-PEAs showed high binding capacity toward plasmid DNA, and the binding activity was inversely correlated to the number of methylene groups in the diol segment of Arg-PEAs. All Arg-PEAs transfected smooth muscle cells with an efficiency that was comparable to the commercial transfection reagent Superfect. However, unlike Superfect, Arg-PEAs, over a wide range of dosages, had minimal adverse effects on cell morphology, viability or apoptosis. Using rhodamine-labeled plasmid DNA, we demonstrated that Arg-PEAs were able to deliver DNA into nearly 100% of cells under optimal polymer-to-DNA weight ratios, and that such a high level of delivery was achieved through an active endocytosis mechanism. A large portion of DNA delivered, however, was trapped in acidic endocytotic compartments, and subsequently was not expressed. These results suggest that with further modification to enhance their endosome escape, Arg-PEAs can be attractive candidates for non-viral gene carriers owning to their high cellular uptake nature and reliable cellular biocompatibility.

Novel role of protein kinase C-delta Tyr 311 phosphorylation in vascular smooth muscle cell hypertrophy by angiotensin II

We have shown previously that activation of protein kinase C-delta (PKC delta) is required for angiotensin II (Ang II)-induced migration of vascular smooth muscle cells (VSMCs). Here, we have hypothesized that PKC delta phosphorylation at Tyr(311) plays a critical role in VSMC hypertrophy induced by Ang II. Immunoblotting was used to monitor PKC delta phosphorylation at Tyr(311), and cell size and protein measurements were used to detect hypertrophy in VSMCs. PKC delta was rapidly (0.5 to 10.0 minutes) phosphorylated at Tyr(311) by Ang II. This phosphorylation was markedly blocked by an Src family kinase inhibitor and dominant-negative Src but not by an epidermal growth factor receptor kinase inhibitor. Ang II-induced Akt phosphorylation and hypertrophic responses were significantly enhanced in VSMCs expressing PKC delta wild-type compared with VSMCs expressing control vector, whereas the enhancements were markedly diminished in VSMCs expressing a PKC delta Y311F mutant. Also, these responses were significantly inhibited in VSMCs expressing kinase-inactive PKC delta K376A compared with VSMCs expressing control vector. From these data, we conclude that not only PKC delta kinase activation but also the Src-dependent Tyr(311) phosphorylation contributes to Akt activation and subsequent VSMC hypertrophy induced by Ang II, thus signifying a novel molecular mechanism for enhancement of cardiovascular diseases induced by Ang II.

Potent stimulation of large-conductance Ca2+-activated K+ channels by rottlerin, an inhibitor of protein kinase C-delta, in pituitary tumor (GH3) cells and in cortical neuronal (HCN-1A) cells

The effects of rottlerin, a known inhibitor of protein kinase C-delta activation, on ion currents were investigated in pituitary tumor (GH3) cells. Rottlerin (0.3-100 microM) increased the amplitude of Ca2+-activated K+ current (I K(Ca)) in a concentration-dependent manner with an EC50 value of 1.7 microM. In intracellular perfusion with rottlerin (1 microM) or staurosporine (10 microM), phorbol 12-myristate 13-acetate-induced inhibition of I K(Ca) in these cells was abolished. In cell-attached mode, rottlerin applied on the extracellular side of the membrane caused activation of large-conductance Ca2+-activated K+ (BK(Ca)) channels, and a further application of BAPTA-AM (10 microM) to the bath had no effect on rottlerin-stimulated channel activity. When cells were exposed to rottlerin, the activation curve of these channels was shifted to less positive potential with no change in the slope factor. Rottlerin increased BK(Ca)-channel activity in outside-out patches. Its change in kinetic behavior of BK(Ca) channels is primarily due to an increase in mean open time. With the aid of minimal kinetic scheme, a quantitative description of rottlerin stimulation on BK(Ca) channels in GH3 cells was also provided. Under current-clamp configuration, rottlerin (1 microM) decreased the firing of action potentials. I K(Ca) elicited by simulated action potential waveforms was enhanced by this compound. In human cortical HCN-1A cells, rottlerin (1 microM) could also interact with the BK(Ca) channel to stimulate I K(Ca). Therefore, rottlerin may directly activate BK(Ca) channels in neurons or endocrine cells.

Phosphorylation of the cyclic AMP response element binding protein mediates transforming growth factor beta-induced downregulation of cyclin A in vascular smooth muscle cells

Transforming growth factor beta (TGFbeta), a multifunctional cytokine associated with vascular injury, is a potent inhibitor of cell proliferation. The current results demonstrate that the TGFbeta-induced growth arrest of vascular smooth muscle cells (VSMCs) is associated with cyclin A downregulation. TGFbeta represses the cyclin A gene through a cyclic AMP (cAMP) response element, which complexes with the cAMP response element binding protein (CREB). The CREB-cyclin A promoter interaction is hindered by TGFbeta, preceded by a TGFbeta receptor-dependent CREB phosphorylation. Induction of CREB phosphorylation with forskolin or 6bnz-cAMP mimics TGFbeta's inhibitory effect on cyclin A expression. Conversely, inhibition of CREB phosphorylation with a CREB mutant in which the phosphorylation site at serine 133 was changed to alanine (CREB-S133A) upregulated cyclin A gene expression. Furthermore, the CREB-S133A mutant abolished TGFbeta-induced CREB phosphorylation, cyclin A downregulation, and growth inhibition. Since we have previously shown that the novel PKC isoform protein kinase C delta (PKCdelta) is activated by TGFbeta in VSMCs, we tested the role of this kinase in CREB phosphorylation and cyclin A downregulation. Inhibition of PKCdelta by a dominant-negative mutant or by targeted gene deletion blocked TGFbeta-induced CREB phosphorylation and cyclin A downregulation. Taken together, our data indicate that phosphorylation of CREB stimulated by TGFbeta is a critical step leading to the inhibition of cyclin A expression and, thus, VSMC proliferation.