N-Glycans on the extracellular domain of the Notch1 receptor control Jagged-1 induced Notch signalling and myogenic differentiation of S100β resident vascular stem cells

Notch signalling, critical for development and postnatal homeostasis of the vascular system, is highly regulated by several mechanisms including glycosylation. While the importance of O-linked glycosylation is widely accepted, the structure and function of N-glycans has yet to be defined. Here, we take advantage of lectin binding assays in combination with pharmacological, molecular, and site-directed mutagenetic approaches to study N-glycosylation of the Notch1 receptor. We find that several key oligosaccharides containing bisecting or core fucosylated structures decorate the receptor, control expression and receptor trafficking, and dictate Jagged-1 activation of Notch target genes and myogenic differentiation of multipotent S100β vascular stem cells. N-glycans at asparagine (N) 1241 and 1587 protect the receptor from accelerated degradation, while the oligosaccharide at N888 directly affects signal transduction. Conversely, N-linked glycans at N959, N1179, N1489 do not impact canonical signalling but inhibit differentiation. Our work highlights a novel functional role for N-glycans in controlling Notch1 signalling and differentiation of vascular stem cells.

Alcohol and vascular endothelial function: Biphasic effect highlights the importance of dose

BACKGROUND

Alcohol (ethanol) consumption has different influences on arterial disease, being protective or harmful depending on the amount and pattern of consumption. The mechanisms mediating these biphasic effects are unknown. Whereas endothelial cells play a critical role in maintaining arterial health, this study compared the effects of moderate and high alcohol concentrations on endothelial cell function.

METHODS

Human coronary artery endothelial cells (HCAEC) were treated with levels of ethanol associated with either low-risk/moderate drinking (i.e., 25 mM) or high-risk/heavy drinking (i.e., 50 mM) after which endothelial function was assessed. The effect of ethanol's primary metabolite acetaldehyde (10 and 25 μM) was also determined.

RESULTS

Moderate ethanol exposure (25 mM) improved HCAEC barrier integrity as determined by increased transendothelial electrical resistance (TEER), inhibited cell adhesion molecule (CAM) mRNA expression, decreased inflammatory cytokine (interferon-γ and interleukin 6) production, inhibited monocyte chemotactic protein-1 (MCP-1) expression and monocyte adhesion, and increased homeostatic Notch signaling. In contrast, exposure to high-level ethanol (50 mM) decreased TEER, increased CAM expression and inflammatory cytokine production, and stimulated MCP-1 and monocyte adhesion, with no effect on Notch signaling. Reactive oxygen species (ROS) generation and endothelial nitric oxide synthase activity were increased by both alcohol treatments, and to a greater extent in the 50 mM ethanol group. Acetaldehyde-elicited responses were generally the same as those of the high-level ethanol group.

CONCLUSIONS

Ethanol has biphasic effects on several endothelial functions such that a moderate level maintains the endothelium in a nonactivated state, whereas high-level ethanol causes endothelial dysfunction, as does acetaldehyde. These data show the importance of dose when considering ethanol's effects on arterial endothelium, and could explain, in part, the J-shaped relationship between alcohol concentration and atherosclerosis reported in some epidemiologic studies.

Caveolin-1 inhibition mediates the opposing effects of alcohol on γ-secretase activity in arterial endothelial and smooth muscle cells

Notch is important to vessel homeostasis. We investigated the mechanistic role of caveolin-1 (Cav-1) in mediating the effects of alcohol (Ethanol/EtOH) on the γ-secretase proteolytic activity necessary for Notch signaling in vascular cells. Human coronary artery endothelial cells (HCAEC) were treated with EtOH (0-50 mM), Notch ligand delta-like ligand 4 (Dll4), and the γ-secretase inhibitor DAPT. EtOH stimulated Notch signaling in HCAEC as evidenced by increased Notch receptor (N1, N4) and target gene (hrt2, hrt3) mRNA levels with the most robust response achieved at 25 mM EtOH. Ethanol (25 mM) stimulated γ-secretase proteolytic activity, to the same extent as Dll4, in HCAEC membranes. Ethanol inhibited Cav-1 mRNA and protein levels in HCAEC. Caveolin-1 negatively regulated γ-secretase activity in HCAEC as Cav-1 knockdown stimulated it, while Cav-1 overexpression inhibited it. Moreover, Cav-1 overexpression blocked the stimulatory effect of EtOH on γ-secretase activity in HCAEC. Although EtOH also inhibited Cav-1 expression in human coronary artery smooth muscle cells (HCASMC), EtOH inhibited γ-secretase activity in HCASMC in contrast to its effect in HCAEC. The inhibitory effect of EtOH on γ-secretase in HCASMC was mimicked by Cav-1 knockdown and prevented by Cav-1 overexpression, suggesting that in these cells Cav-1 positively regulates γ-secretase activity. In conclusion, EtOH differentially regulates γ-secretase activity in arterial EC and SMC, being stimulatory and inhibitory, respectively. These effects are both mediated by caveolin-1 inhibition which itself has opposite effects on γ-secretase in the two cell types. This mechanism may underlie, in part, the effects of moderate drinking on atherosclerosis.

Exosomal Composition, Biogenesis and Profiling Using Point-of-Care Diagnostics—Implications for Cardiovascular Disease

Arteriosclerosis is an important age-dependent disease that encompasses atherosclerosis, in-stent restenosis (ISR), pulmonary hypertension, autologous bypass grafting and transplant arteriosclerosis. Endothelial dysfunction and the proliferation of vascular smooth muscle cell (vSMC)-like cells is a critical event in the pathology of arteriosclerotic disease leading to intimal-medial thickening (IMT), lipid retention and vessel remodelling. An important aspect in guiding clinical decision-making is the detection of biomarkers of subclinical arteriosclerosis and early cardiovascular risk. Crucially, relevant biomarkers need to be good indicators of injury which change in their circulating concentrations or structure, signalling functional disturbances. Extracellular vesicles (EVs) are nanosized membraneous vesicles secreted by cells that contain numerous bioactive molecules and act as a means of intercellular communication between different cell populations to maintain tissue homeostasis, gene regulation in recipient cells and the adaptive response to stress. This review will focus on the emerging field of EV research in cardiovascular disease (CVD) and discuss how key EV signatures in liquid biopsies may act as early pathological indicators of adaptive lesion formation and arteriosclerotic disease progression. EV profiling has the potential to provide important clinical information to complement current cardiovascular diagnostic platforms that indicate or predict myocardial injury. Finally, the development of fitting devices to enable rapid and/or high-throughput exosomal analysis that require adapted processing procedures will be evaluated.

Moderate dose alcohol protects against serum amyloid protein A1-induced endothelial dysfunction via both notch-dependent and notch-independent pathways

BACKGROUND

Arterial endothelium plays a critical role in maintaining vessel homeostasis and preventing atherosclerotic cardiovascular disease (CVD). Low-to-moderate alcohol (EtOH) consumption is associated with reduced atherosclerosis and stimulates Notch signaling in endothelial cells. The aim of this study was to determine whether EtOH protects the endothelium against serum amyloid A1 (SAA1)-induced activation/injury, and to determine whether this protection is exclusively Notch-dependent.

METHODS AND RESULTS

Human coronary artery endothelial cells (HCAEC) were stimulated or not with "pro-atherogenic" SAA1 (1 μM) in the absence or presence of EtOH (25 mM), the Notch ligand DLL4 (3 μg/ml), or the Notch inhibitor DAPT (20 μM). EtOH stimulated Notch signaling in HCAEC, as evidenced by increased expression of the Notch receptor and hrt target genes. Treatment with EtOH alone or stimulation of Notch signaling by DLL4 increased eNOS activity and enhanced HCAEC barrier function as assessed by trans-endothelial electrical resistance. Moreover, EtOH and DLL4 both inhibited SAA1-induced monolayer leakiness, cell adhesion molecule (ICAM, VCAM) expression, and monocyte adhesion. The effects of EtOH were Notch-dependent, as they were blocked with DAPT and by Notch receptor (N1, N4) knockdown. In contrast, EtOH's inhibition of SAA1-induced inflammatory cytokines (IL-6, IFN-γ) and reactive oxygen species (ROS) was Notch-independent, as these effects were unaffected by DAPT or by N1 and/or N4 knockdown.

CONCLUSIONS

EtOH at moderate levels protects against SAA1-induced endothelial activation via both Notch-dependent and Notch-independent mechanisms. EtOH's maintenance of endothelium in a nonactivated state would be expected to preserve vessel homeostasis and protect against atherosclerosis development.

The calcium binding protein S100β marks hedgehog-responsive resident vascular stem cells within vascular lesions

A hallmark of subclinical atherosclerosis is the accumulation of vascular smooth muscle cell (SMC)-like cells leading to intimal thickening. While medial SMCs contribute, the participation of hedgehog-responsive resident vascular stem cells (vSCs) to lesion formation remains unclear. Using transgenic eGFP mice and genetic lineage tracing of S100β vSCs in vivo, we identified S100β/Sca1 cells derived from a S100β non-SMC parent population within lesions that co-localise with smooth muscle α-actin (SMA) cells following iatrogenic flow restriction, an effect attenuated following hedgehog inhibition with the smoothened inhibitor, cyclopamine. In vitro, S100β/Sca1 cells isolated from atheroprone regions of the mouse aorta expressed hedgehog signalling components, acquired the di-methylation of histone 3 lysine 4 (H3K4me2) stable SMC epigenetic mark at the Myh11 locus and underwent myogenic differentiation in response to recombinant sonic hedgehog (SHh). Both S100β and PTCH1 cells were present in human vessels while S100β cells were enriched in arteriosclerotic lesions. Recombinant SHh promoted myogenic differentiation of human induced pluripotent stem cell-derived S100β neuroectoderm progenitors in vitro. We conclude that hedgehog-responsive S100β vSCs contribute to lesion formation and support targeting hedgehog signalling to treat subclinical arteriosclerosis.

Moderate Alcohol Consumption Targets S100β+ Vascular Stem Cells and Attenuates Injury-Induced Neointimal Hyperplasia

BACKGROUND

Stem cells present in the vessel wall may be triggered in response to injurious stimuli to undergo differentiation and contribute to vascular disease development. Our aim was to determine the effect of moderate alcohol (EtOH) exposure on the expansion and differentiation of S100 calcium-binding protein B positive (S100β⁺ ) resident vascular stem cells and their contribution to pathologic vessel remodeling in a mouse model of arteriosclerosis.

METHODS AND RESULTS

Lineage tracing analysis of S100β⁺ cells was performed in male and female S100β-eGFP/Cre/ERT2-dTomato transgenic mice treated daily with or without EtOH by oral gavage (peak BAC: 15 mM or 0.07%) following left common carotid artery ligation for 14 days. Carotid arteries (ligated or sham-operated) were harvested for morphological analysis and confocal assessment of fluorescent-tagged S100 β ⁺ cells in FFPE carotid cross sections. Ligation-induced carotid remodeling was more robust in males than in females. EtOH-gavaged mice had less adventitial thickening and markedly reduced neointimal formation compared to controls, with a more pronounced inhibitory effect in males compared to females. There was significant expansion of S100β⁺ -marked cells in vessels postligation, primarily in the neointimal compartment. EtOH treatment reduced the fraction of S100β⁺ cells in carotid cross sections, concomitant with attenuated remodeling. In vitro, EtOH attenuated Sonic Hedgehog-stimulated myogenic differentiation (as evidenced by reduced calponin and myosin heavy chain expression) of isolated murine S100β⁺ vascular stem cells.

CONCLUSIONS

These data highlight resident vascular S100β⁺ stem cells as a novel target population for alcohol and suggest that regulation of these progenitors in adult arteries, particularly in males, may be an important mechanism contributing to the antiatherogenic effects of moderate alcohol consumption.

Reactive Oxygen Species (ROS), Intimal Thickening, and Subclinical Atherosclerotic Disease

Arteriosclerosis causes significant morbidity and mortality worldwide. Central to this process is the development of subclinical non-atherosclerotic intimal lesions before the appearance of pathologic intimal thickening and advanced atherosclerotic plaques. Intimal thickening is associated with several risk factors, including oxidative stress due to reactive oxygen species (ROS), inflammatory cytokines and lipid. The main ROS producing systems in-vivo are reduced nicotinamide dinucleotide phosphate (NADPH) oxidase (NOX). ROS effects are context specific. Exogenous ROS induces apoptosis and senescence, whereas intracellular ROS promotes stem cell differentiation, proliferation, and migration. Lineage tracing studies using murine models of subclinical atherosclerosis have revealed the contributory role of medial smooth muscle cells (SMCs), resident vascular stem cells, circulating bone-marrow progenitors and endothelial cells that undergo endothelial-mesenchymal-transition (EndMT). This review will address the putative physiological and patho-physiological roles of ROS in controlling vascular cell fate and ROS contribution to vascular regeneration and disease progression.

Label-Free Multi Parameter Optical Interrogation of Endothelial Activation in Single Cells using a Lab on a Disc Platform

Cellular activation and inflammation leading to endothelial dysfunction is associated with cardiovascular disease (CVD). We investigated whether a single cell label-free multi parameter optical interrogation system can detect endothelial cell and endothelial progenitor cell (EPC) activation in vitro and ex vivo, respectively. Cultured human endothelial cells were exposed to increasing concentrations of tumour necrosis factor alpha (TNF-α) or lipopolysaccharide (LPS) before endothelial activation was validated using fluorescence-activated cell sorting (FACS) analysis of inflammatory marker expression (PECAM-1, E-selectin and ICAM-1). A centrifugal microfluidic system and V-cup array was used to capture individual cells before optical measurement of light scattering, immunocytofluorescence, auto-fluorescence (AF) and cell morphology was determined. In vitro, TNF-α promoted specific changes to the refractive index and cell morphology of individual cells concomitant with enhanced photon activity of fluorescently labelled inflammatory markers and increased auto-fluorescence (AF) intensity at three different wavelengths, an effect blocked by inhibition of downstream signalling with Iκβ. Ex vivo, there was a significant increase in EPC number and AF intensity of individual EPCs from CVD patients concomitant with enhanced PECAM-1 expression when compared to normal controls. This novel label-free 'lab on a disc' (LoaD) platform can successfully detect endothelial activation in response to inflammatory stimuli in vitro and ex vivo.

Abstract 648: Resident S100β + /Sca1 + Multipotent Vascular Stem Cells Undergo Myogenic and Vasculogenic Differentiation In Vitro

Arteriosclerosis is an important age-dependent disease that encompasses atherosclerosis, in-stent restenosis, autologous bypass grafting and transplant arteriosclerosis. Vascular smooth muscle (vSMC)-like accumulation is a key event leading to intimal-medial thickening (IMT), vessel remodelling and an important marker of subclinical disease. Vascular stem cell progeny in addition to de-differentiated SMC and SMC derived from endothelial-mesenchymal transition (EndoMT) are all reported to contribute to IMT as they become activated/dysfunctional, differentiate down vascular and myeloid lineages and subsequently dictate, in-part, vessel remodelling. In this study we examined the multipotent potential of a specialised population of rat adult resident multipotent vascular stem cells (rMVSC) located within the vessel wall and their capability to differentiate down both myogenic (muscle) and vasculogenic (endothelial) lineages when given the appropriate stimulus. Using Sca1-eGFP transgenic mice, in vivo , there was a significant increase in the number of Sca1 + cells within the intima of the left carotid artery (LCA) following partial carotid artery ligation-induced injury after 3 days that co-localised with endothelial nitic oxide synthase (eNOS) and CD31 + positive cells, when compared to the sham-operated control vessels and the contralateral right carotid artery (RCA). The number of Sca1-eGFP + cells significantly increased over time within the adventitial, medial and neointimal layers following ligation-induced injury after 7 and 14 days, respectively. In vitro, S100β/Sca1 + rat MVSCs cultured in vasculogenic inductive media for 7 days underwent differentiation to an endothelial cell phenotype characterised by the appearance of a cobblestone morphology and increased eNOS expression. In contrast, MVSC exposed to media supplemented with TGF-β1 for 7 days underwent myogenic differentiation to SMC. These data suggest that resident S100β/Sca1 + MVSCs are capable of both myogenic and vasculogenic differentiation depending on the inductive stimulus and may contribute in part to intimal medial thickening (IMT) and endothelial regeneration following injury in vivo.

Abstract 480: Injury-Activated Vascular Cells Share a Common Photonic Fingerprint with Stem Cell-Derived Myogenic Progeny Following Interrogation Using a Lab-on-a-Disc (Load) Platform

The accumulation of vascular smooth muscle (SMC)-like cells within the intima contributes significantly to intimal medial thickening (IMT) and vascular remodeling typical of arteriosclerotic disease. Light has emerged as a powerful tool to interrogate cells label-free and facilitates discriminant observations both in vitro and in vivo . The auto-fluorescence (AF) profile of individual cells isolated from arteriosclerotic vessels, captured on V-cup array and interrogated across five wavelengths using a novel Lab-on-a-Disc platform, was significantly increased at the 565 ± 20nm wavelength concomitant with a reduction in Myh11 expression, when compared to differentiated vascular smooth muscle (SMC) cells from control vessels. In vitro, TGF-β1 promoted myogenic differentiation of murine bone-marrow derived Sca1 + /CD44 + mesenchymal stem cells (MSC) and murine Sca1 + C3H 10T1/2 cells concomitant with enrichment of the specific SMC epigenetic histone mark, H3K4me2 at the Myh11 promoter, Myh11 promoter transactivation and increased SMC differentiation marker mRNA and protein expression. Myogenic differentiation resulted in a significant increase in the AF intensity across 565 ± 20nm wavelength, an effect not observed for TGF-β1 treated RAMOS human B lymphocytes but mimicked by Notch activation of resident Sca1 + multipotent vascular stem cells (MVSCs) with Jagged1 and inhibited following elastin and collagen III depletion, respectively. Moreover, the temporal increase in the AF intensity at 565 ± 20nm wavelength during myogenic differentiation was similar to the AF profile of dissociated cells from arteriosclerotic vessels at this same wavelength. These data suggest that an AF photonic fingerprint of stem cell-derived myogenic progeny in vitro mimics that of vascular cells ex vivo following injury.

Abstract 651: Hedgehog Responsive S100β + /Stem Cell Antigen-1 + Vascular Stem Cells Contribute to Neointimal Formation

Intimal medial thickening (IMT) and vascular remodeling are hallmarks of arteriosclerotic disease. However, the origin of neointimal cells and the signaling molecules that dictate their fate and function remains controversial. Herein, we examined whether Hedgehog (Hh) responsive S100β + /Sca1 + stem cells contribute to IMT within carotid arteries of transgenic mice following ligation-induced injury in vivo and myogenic differentiation of undifferentiated multipotent S100β + /Sca1 + stem cells in vitro . Using Sca1-eGFP and S100β-eGFP transgenic mice, we demonstrated a significant accumulation in the number of eGFP + cells within the intima and medial layers of injured arteries following ligation concomitant with enhanced expression of Hh signaling components (ptch1 and Gli). Genetic lineage tracing analysis using S100β-eGFP/Cre/ERT2–dTomato transgenic mice to mark S100β + resident vascular stem cells before injury confirmed that S100β + progeny that are Sca1 + significantly contribute to IMT, an effect significantly attenuated following treatment with the Hh smoothened inhibitor, cylopamine. In vitro, recombinant SHh (rSHh) treatment of multipotent S100β + /Sca1 + resident stem cells increased Hh target gene Gli expression, decreased telomerase activity and promoted myogenic differentiation and cell growth; effects significantly attenuated following Hh inhibition. In human arteriosclerotic lesions, Hh components were upregulated concomitant with enhanced expression of S100β. Together, these findings suggest that S100β + /Sca1 + stem cells are a major source of neointimal cells contributing to IMT and suggest that this cohort may be a relevant therapeutic target to prevent arteriosclerosis.

Abstract 478: Resident Multipotent Vascular Stem Cells Isolated From Susceptible and Non-susceptible Arteriosclerotic Regions of the Mouse Aorta Are Sca1/s100β/nestin + and Respond Similarly to the Same Myogenic Inductive Stimulus

Vascular remodeling leading to arterial obstruction is a hallmark of arteriosclerosis and in-stent restenosis and is due in part to the accumulation of vascular smooth muscle (SMC)-like cells within the vessel wall. The source of these vascular cells has been controversial with many studies providing compelling evidence for a putative role for stem cell-derived myogenic progeny. It is known that neuroectoderm-derived vascular regions (ascending aorta, aortic arch, carotid artery) are more susceptible to arteriosclerotic lesion formation in comparison with mesoderm derived regions (descending and abdominal aorta, femoral artery). Our aim was to isolate and characterize stem cells from arteriosclerotic-susceptible and non-susceptible regions and determine their differential responsiveness to discrete myogenic inductive stimuli. A population of myosin heavy chain (Myh11 - ) negative, Sca1/S100β/Nestin + multipotent vascular stem cells (MVSCs) was first shown to accumulate within the intima of murine carotid arteries following injury using Sca1 and S100β e-GFP transgenic mice. Resident MVSCs were isolated from mouse aorta arch (susceptible) and descending aorta (non-susceptible) by enzymatic dissociation and initial seeding on non-adherent plates for 48 h before suspended cells were re-seeded on adherent plates and grown in B27 supplemented maintenance media. Cells were characterized by fluorescent immunocytochemistry using stem (Sca1/S100β/Nestin) and vascular SMC cell markers (CNN1 and Myh11). MVSCs from both aortic arch and descending aorta were positive for stem cell markers but negative for Myh11 and Cnn1. Treatment of both cell populations with TGF-β1 or the Notch ligand, Jagged-1 for 7 days promoted myogenic differentiation by increasing the number of cells expressing SMC markers concomitant with increased Myh11 and CNN1 mRNA levels, respectively. There was no difference in the responsiveness of stem cells from either arteriosclerotic-prone and non-prone regions. We conclude that the aortic arch and descending aortic region both house a neuroectoderm-derived Sca1/S100β/Nestin + stem cell population that responds similarly to myogenic inductive stimulation.

Differential effects of alcohol and its metabolite acetaldehyde on vascular smooth muscle cell Notch signaling and growth

Alcohol (EtOH) consumption can variously affect cardiovascular disease. Our aim was to compare the effects of EtOH and its primary metabolite acetaldehyde (ACT) on vascular smooth muscle Notch signaling and cell growth, which are important for atherogenesis. Human coronary artery smooth muscle cells (HCASMCs) were treated with EtOH (25 mM) or ACT (10 or 25 μM). As previously reported, EtOH inhibited Notch signaling and growth of HCASMCs. In contrast, ACT treatment stimulated HCASMC proliferation (cell counts) and increased proliferating cell nuclear antigen expression, concomitant with stimulation of Notch signaling, as determined by increased Notch receptor (N1 and N3) and target gene (Hairy-related transcription factor 1-3) mRNA levels. Interaction of the ligand with the Notch receptor initiates proteolytic cleavage by α- and γ-secretase, resulting in the release of the active Notch intracellular domain. Neither EtOH nor ACT had any significant effect on α-secretase activity. A fluorogenic peptide cleavage assay demonstrated almost complete inhibition by EtOH of Delta-like ligand 4-stimulated γ-secretase activity in solubilized HCASMCs (similar to the effect of the control inhibitor DAPT) but no effect of ACT treatment. EtOH, but not ACT, affected the association and distribution of the γ-secretase catalytic subunit presenilin-1 with lipid rafts, as determined by dual fluorescent labeling and confocal microscopic visualization. In conclusion, ACT stimulates vascular smooth muscle cell Notch signaling and growth, effects opposite to those of EtOH. These differential actions on vascular smooth muscle cells of EtOH and its metabolite ACT may be important in mediating the ultimate effects of drinking on cardiovascular disease. NEW & NOTEWORTHY Acetaldehyde stimulates, in a Notch-dependent manner, the vascular smooth muscle cell growth that contributes to atherogenesis; effects opposite to those of ethanol. These data suggest that in addition to ethanol itself, its metabolite acetaldehyde may also mediate some of the effects of alcohol consumption on vascular cells and, thus, cardiovascular health.

Alcohol Reduces Arterial Remodeling by Inhibiting Sonic Hedgehog-Stimulated Stem Cell Antigen-1 Positive Progenitor Stem Cell Expansion

BACKGROUND

Cell and molecular mechanisms mediating the cardiovascular effects of alcohol are not fully understood. Our aim was to determine the effect of moderate ethanol (EtOH) on sonic hedgehog (SHh) signaling in regulating possible stem cell antigen-1 positive (Sca1⁺ ) progenitor stem cell involvement during pathologic arterial remodeling.

METHODS

Partial ligation or sham operation of the left carotid artery was performed in transgenic Sca1-enhanced green fluorescent protein (eGFP) mice gavaged with or without "daily moderate" EtOH.

RESULTS

The EtOH group had reduced adventitial thickening and less neointimal formation, compared to ligated controls. There was expansion of eGFP-expressing (i.e., Sca1⁺ ) cells in remodeled vessels postligation (day 14), especially in the neo intima. EtOH treatment reduced the number of Sca1⁺ cells in ligated vessel cross-sections concomitant with diminished remodeling, compared to control ligated vessels. Moreover, EtOH attenuated SHh signaling in injured carotids as determined by immunohistochemical analysis of the target genes patched 1 and Gli2, and RT-PCR of whole-vessel Gli2 mRNA levels. Intraperitoneal injection of ligated Sca1-eGFP mice with the SHh signaling inhibitor cyclopamine diminished SHh target gene expression, reduced the number of Sca1⁺ cells, and ameliorated carotid remodeling. EtOH treatment of purified Sca1⁺ adventitial progenitor stem cells in vitro inhibited SHh signaling, and their rSHh-induced differentiation to vascular smooth muscle cells.

CONCLUSIONS

EtOH reduces SHh-responsive Sca1⁺ progenitor cell myogenic differentiation/expansion in vitro and during arterial remodeling in response to ligation injury in vivo. Regulation of vascular Sca1⁺ progenitor cells in this way may be an important novel mechanism contributing to alcohol's cardiovascular protective effects.

Abstract 386: Sonic Hedgehog Promotes Stem Cell Differentiation to Vascular Smooth Muscle in vitro

Background: The morphogen Sonic Hedgehog (SHh) and its signaling pathway components are significantly up-regulated within adventitial and medial segments from arteriosclerotic vessels in mice concomitant with enhanced accumulation of SMCs. This vessel remodelling is attenuated in vivo following Hh receptor, Patched 1, depletion. There is evidence supporting a role for stem cell-derived vascular smooth muscle (vSMCs) in contributing to arteriosclerotic vascular disease. In this context, SHh signaling may be an important regulator of stem cell self-renewal and differentiation to SMC in vitro.

Aim: Determine the effects of SHh on bone-marrow derived mesenchymal stem cell (MSC) differentiation to SMC in vitro.

Methods: Murine CD44+ bone-marrow derived MSCs and Sca1+ rat adventitial progenitor stem cells (APCs) were examined for SHh components and their capacity to differentiate to SMCs before and after treatment with sonic hedgehog (rSHh, 0.5 μg/ml) for 7 d, in the absence or presence of Hh inhibitors cyclopamine (10μM) or HPI-4 (50μM). The transition to SMC was determined be examining intermediate (calponin1, CNN1) and late (myosin heavy chain, Myh11) SMC differentiation marker expression by western blot analysis and immunocytochemistry, respectively.

Results: Hh signaling components were present on MSCs and APCs. Stem cell growth was unaffected by treatment with Hh inhibitors cyclopamine or HPI-4 at concentrations that inhibited Gli signalling in vitro. Recombinant SHh increased SMC differentiation marker protein protein expression after 7 days, an effect that was inhibited following SHh inhibition with smoothened inhibitors cyclopamine and HPI-4.

Conclusion: in the absence of any effect on cell growth, Sonic Hedgehog controls mesenchymal stem-like cell differentiation to SMC.

Abstract 143: Enrichment of Dimethylation of Lysine 4 on Histone 3 and Resident Vascular Stem Cell Transition to Vascular Smooth Muscle Cells

Data support a role for stem cell-derived vascular smooth muscle cells (SMC) in arteriosclerosis. Epigenetics play a critical role in SMC differentiation where histone proteins associated with the myosin heavy chain (Myh11) promoter are post-translationally modified by dimethylation of lysine 4 on histone 3 (H3K4me2). Studies report that ‘de-differentiated’ SMC do not exhibit loss of H3K4me2 at the Myh11 promoter even when mRNA levels decrease thereby allowing this modification to be used to track differentiated SMC.

Our aim was to determine the level of H3K4me2 and H3K27me3 methylation of differentiated SMCs and compare to resident vascular stem cells and stem cell-derived SMC.

Murine adventitial Sca1 + stem cells (APCs), rat medial Sox10 + multipotent vascular stem cells (MVSCs) and CD44 + bone-marrow derived mesenchymal stem cells (MSCs) were all examined for methylation of lysine 4 (H3K4me2) and lysine 27 (H3K27me3) on histone 3 associated with the Myh11 promoter, before and after SMC differentiation and compared to fresh aortic differentiated SMC and sub-cultured de-differentiated SMC in vitro by Chromatin Immunoprecipitation (ChIP) assay. Cells were also examined for Myh11 expression, stemness (telomerase activity) and multipotentcy.

Differentiated rat and murine SMC were enriched for H3K4Me2 at the Myh11 promoter, compared to H3K27me3. Phenotypically de-differentiated sub-cutured rat and murine SMC were enriched for H3K4Me2 when compared to H3K27me3, but to a much lesser extent when compared to differentiated aortic SMC. In contrast, resident APCs and MVSCs, and bone-marrow derived MSCs, were all enriched for H3K27me3, concomitant with significant telomerase activity and multipotent differentiation capacity. The levels of enrichment of H3K27me3 dropped significantly after SMC differentiation with TGF-βeta1 concomitant with a significant enrichment of H3K4me2 to levels that mimicked the level of enrichment in de-differentiated SMC when compared to aortic differentiated SMC.

De-differentiated SMC exhibit reduced enrichment of H3K4me2 at the Myh11 promoter region when compared to differentiated aortic SMCs, but mimic the level of enrichment of H3K4me2 observed following resident vascular stem cell differentiation to SMCs.

Abstract 61: Hedgehog-Responsive Stem Cell Antigen 1 Positive Cells Contribute To Vascular Smooth Muscle Cell Accumulation Following Vascular Injury

Background: Cardiovascular disease such as atherosclerosis is associated with the formation of an neointimal layer and medial hyperplasia as a result of the accumulation of vascular smooth muscle cells (vSMC) in the artery wall (i.e., intimal medial thickening, IMT). There is strong, albeit controversial, evidence indicating a putative role for stem cell antigen 1 positive (Sca1 + ) progenitor cell-derived vSMC in contributing to IMT. Interestingly, the Hedgehog (Hh) signaling receptor Patched 1 is present in the adventitial boundary and co-localizes with both Sca1 and Patched 1, the ligand for sonic hedgehog (SHh). The aim of our study was to determine the effect of Hh signaling on Sca1+ stem cells and their contribution to vSMC accumulation and IMT following vascular injury.

Methods: Sca1 + stem cells were treated with differentiation inductive stimuli in the absence or presence of recombinant SHh (rSHh), with or without the Hh inhibitor cyclopamine, before the cells were examined for their stemness (telomerase activity), differentiation capacity (SMC differentiation) and epigenetic profile. In parallel, Sca1-eGFP transgenic mice were subjected to carotid injury (i.e., partial ligation), with or without cyclopamine, before IMT, Sca1 expression and SMC phenotype was assessed.

Results: Sonic Hedgehog stimulated Sca1 + stem cell differentiation capacity, as demonstrated by enhanced expression of SMC differentiation markers in addition to their altered stemness, epigenetic profile (H3K4me2:H3K27me3) and proliferative status. In parallel studies, Hh signaling components were elevated in ligated carotids when compared to sham-operated controls, concomitant with increased Sca1 expression and SMC accumulation. Moreover, there was a significant attenuation of SMC accumulation and intimal medial thickening of injured carotids following Hh inhibition with cyclopamine.

Conclusion: Sca1 + stem cells are Hh-responsive and they contribute to vSMC accumulation in the carotid following ligation injury.

Ethanol inhibits γ-secretase proteolytic activity in vascular smooth muscle cells

BACKGROUND

Ethanol (EtOH) inhibits Notch-mediated vascular smooth muscle cell (SMC) proliferation, an event that is key in vessel remodeling and atherogenesis. The object of this study was to determine whether EtOH inhibits Notch signaling in SMC at the level of γ-secretase, a protease that in concert with α-secretase catalyzes the release of the intracellular domain of the Notch receptor necessary for signaling.

METHODS

Human coronary artery SMCs (HCASMCs) were treated with a recombinant soluble Notch ligand, Delta-like ligand 4 (DLL4) (2 μg/ml), or transfected with a constitutively active Notch 1 intracellular domain (N1ICD), in the absence or presence of EtOH. EtOH (25 mM) treatment inhibited DLL4-stimulated CBF-1/RBP-Jk-dependent promoter activity (determined by luciferase assay) and downstream target gene HRT-3 mRNA levels. In contrast, EtOH had no effect on N1ICD-driven CBF-1/RBP-Jk-dependent promoter activity or HRT-3 expression.

RESULTS

These data suggest that EtOH inhibits Notch signaling at, or prior to, Notch intracellular domain (NICD) generation. γ-Secretase activity was determined in solubilized membrane preparations from HCASMC treated with/without EtOH (25 mM) or the γ-secretase inhibitor DAPT (20 μM) using (i) a fluorometric assay and (ii) Western blot detection of cleavage products using a Flag-tagged Notch-based substrate, N100Flag. EtOH inhibited basal and DLL4-stimulated γ-secretase activity, and SMC growth to a similar extent as DAPT, whereas it had no effect on α-secretase (TACE/ADAM17) activity also determined by fluorometric assay. Moreover, EtOH treatment inhibited the expression of caveolin-1, a lipid raft protein implicated in regulating γ-secretase activity, and altered its cellular distribution in HCASMC.

CONCLUSIONS

EtOH inhibits Notch signaling in vascular SMCs at the level of γ-secretase activity, possibly by affecting lipid raft function. Such a response might be expected to result in attenuation of pathologic vessel remodeling and thus may contribute to moderate alcohols' cardioprotective effects.

Flk-1/KDR mediates ethanol-stimulated endothelial cell Notch signaling and angiogenic activity

We previously reported that ethanol (EtOH) stimulates endothelial angiogenic activity mediated via a notch- and angiopoietin-1 (Ang-1) pathway. As crosstalk exists between notch and vascular endothelial growth factor (VEGF) signaling, we examined whether the VEGF receptor (VEGFR) Flk-1 (fetal liver kinase 1) mediates EtOH-stimulated notch signaling and angiogenic activity.

METHODS AND RESULTS

Treatment of human coronary artery endothelial cells (HCAECs) with EtOH (1-50 mM, 24 h) dose-dependently increased Flk-1 expression with a maximum increase observed at 25 mM EtOH. Ethanol treatment activated both Flk-1 and Flt-1 (FMS-like tyrosine kinase 1) as indicated by their phosphorylation, and subsequent stimulation of Akt. EtOH activation of Flk-1 was inhibited by the VEGFR inhibitor SU5416. Gene silencing of Flk-1 using small interfering RNA inhibited the EtOH-induced increase in notch receptors 1 and 4 and notch target gene (hairy enhancer of split-related transcription factor 1) mRNA. Knockdown of Flk-1 inhibited EtOH-induced Ang-1/Tie-2 mRNA expression and blocked EtOH-induced HCAEC network formation on Matrigel, a response that was restored by notch ligand, notch ligand delta-like ligand 4, treatment. In vivo, moderate alcohol feeding increased vascular remodeling in mouse ischemic hindlimbs.

CONCLUSIONS

These data demonstrate that EtOH activates Flk-1 and Flt-1 receptors in HCAECs and promotes angiogenic activity via an Flk-1/notch pathway. These effects of EtOH may be relevant to the influence of moderate alcohol consumption on cardiovascular health.

Glucose attenuates hypoxia-induced changes in endothelial cell growth by inhibiting HIF-1α expression

Hyperglycaemia and hypoxia play essential pathophysiological roles in diabetes. We determined whether hyperglycaemia influences endothelial cell growth under hypoxic conditions in vitro. Using a Ruskinn Invivo₂ 400 Hypoxia Workstation, bovine aortic endothelial cells (BAEC) were exposed to high glucose concentrations (25 mM glucose) under normoxic or hypoxic conditions before cell growth (balance of proliferation and apoptosis) was assessed by fluorescence-activated cell sorting (FACS) analysis, proliferating cell nuclear antigen (pCNA), Bcl-x_L and caspase-3 protein expression and activity. Hypoxia increased hypoxia response element (HRE) transactivation and induced hypoxia-inducible factor-1α (HIF-1α) expression when compared to normoxic controls concomitant with a significant decrease in cell growth. High glucose (25 mM) concentrations attenuated HRE transactivation and HIF-1α protein expression while concurrently reducing hypoxia-induced changes in BAEC growth. Knockdown of HIF-1α expression significantly decreased hypoxia-induced changes in growth and attenuated the modulatory effects of glucose. These results provide evidence that hypoxia-induced control of BAEC growth can be altered by the presence of glucose via inhibition of HIF-1α expression and activation.

Abstract 518: Differential Effects of Alcohol and Its Primary Metabolite Acetaldehyde on Vascular Smooth Muscle Cell Notch Signaling and Growth

Moderate consumption of alcohol (ethanol/EtOH) is a negative risk factor for atherosclerosis while binge drinking and chronic alcohol abuse is associated with increased cardiovascular disease and mortality. As the balance between the levels of EtOH itself and its primary metabolite, acetaldehyde, is likely different in these two drinking groups, we assessed the hypothesis that differential effects of EtOH and acetaldehyde on vascular smooth muscle cell (SMC) Notch signaling and growth may be key in mediating the effects of various drinking patterns on cardiovascular disease.

Human coronary artery smooth muscle cells (HCASMC) were treated (24 h) with either EtOH (25 mM) or acetaldehyde (10 or 25 μM). We confirmed our previously reported inhibitory effects of EtOH on Notch signaling and subsequently on the growth of HCASMC. In contrast, acetaldehyde treatment stimulated HCASMC proliferation (determined by cell counts) and increased proliferating cell nuclear antigen expression, concomitant with stimulation of Notch signaling as determined by increased Notch target gene (HRT 1-3) mRNA levels. Interaction of a ligand (e.g., Dll4) with the Notch receptor initiates proteolytic cleavage by γ-secretase, resulting in the release of the active Notch-intracellular domain (NICD). A fluorogenic peptide cleavage assay demonstrated almost complete inhibition by EtOH of Dll4-stimulated γ-secretase activity in a solubilized membrane fraction from HCASMC (similar to the effect of the control inhibitor, DAPT), but no effect of acetaldehyde treatment. Similarly, EtOH, but not acetaldehyde, affected the association and distribution of the γ-secretase catalytic subunit, presenilin-1, with lipid rafts as determined by dual fluorescent labeling and confocal microscopic visualization (Alexa 488-conjugated cholera toxin B subunit for lipid rafts, and Alexa 594-conjugated anti-presenilin-1 antibody).

In conclusion, EtOH and acetaldehyde have opposite effects on SMC Notch signaling and growth. These differential effects of alcohol and its metabolite may be relevant in mediating the opposing effects of different drinking patterns (e.g., daily moderate vs weekend binge) on cardiovascular disease.

Abstract 294: Differential Expression of Hedgehog/Notch and Transforming Growth Factor-ß in Human Abdominal Aortic Aneurysms

Objective: The molecular mechanisms leading to the development of Adnominal Aortic Aneurysms (AAA) remain poorly understood. The aim of this study was to determine the expression of Sonic Hedgehog (SHh), Transforming Growth Factor Beta (TGF-β) and Notch signaling components in aneurysmal and non-aneurysmal aorta in vivo and demonstrate SHh control of Notch, TGF- β1 and SMC differentiation in vitro.

Methods: Paired tissue samples were obtained from aneurysmal and non-aneurysmal (control) segments of the aortic wall of at least 8 patients with suitable anatomy undergoing open repair of infrarenal AAA. Protein and mRNA expression levels were determined by western blot analysis and quantitative Real-time PCR.

Results: Aneurysm development resulted in a significant reduction in vascular smooth muscle (vSMC) differentiation gene protein and mRNA levels for α-actin and SMC22α, respectively. In parallel, significant reductions in Hh and Notch signaling component expression was observed in aneurysmal tissue when compared to control, concurrent with increased TGF-β1 expression. In vitro, Hh signaling inhibition with cyclopamine (40μmol/L) treatment for 24 h in human aortic smooth muscle cells (HASMC), resulted in decreased Hh/Notch signaling component and vSMC differentiation gene expression. Moreover, cyclopamine significantly increased TGF-β1 mRNA expression.

Conclusion: These results suggest that SHh/Notch and TGFβ signaling are differentially regulated in aneurysmal tissue, compared with non-aneurysmal tissue. Changes in these signaling pathways and the resulting changes in vSMC content may play a causative role in the development of AAA.

Differential expression of Hedgehog/Notch and transforming growth factor-β in human abdominal aortic aneurysms

OBJECTIVE

The molecular mechanisms leading to the development of abdominal aortic aneurysms (AAAs) remain poorly understood. The aim of this study was to determine the expression of Sonic Hedgehog (SHh), transforming growth factor β (TGF-β), and Notch signaling components in human aneurysmal and nonaneurysmal aorta in vivo.

METHODS

Paired tissue samples were obtained from aneurysmal and nonaneurysmal (control) segments of the aortic wall of eight patients with suitable anatomy undergoing open repair of infrarenal AAAs. Protein and messenger RNA (mRNA) expression levels were determined by Western blot and quantitative real-time polymerase chain reaction analysis.

RESULTS

Aneurysm development resulted in a significant reduction in vascular smooth muscle (vSMC) differentiation genes α-actin and SMC22α at both mRNA and protein levels. In parallel experiments, an 80.0% ± 15% reduction in SHh protein expression was observed in aneurysmal tissue compared with control. SHh and Ptc-1 mRNA levels were also significantly decreased, by 82.0% ± 10% and 75.0% ± 5%, respectively, in aneurysmal tissue compared with nonaneurysmal control tissue. Similarly, there was a 50.0% ± 9% and 60.0% ± 4% reduction in Notch receptor 1 intracellular domain and Hrt-2 protein expression, respectively, in addition to significant reductions in Notch 1, Notch ligand Delta like 4, and Hrt-2 mRNA expression in aneurysmal tissue compared with nonaneurysmal tissue. There was no change in Hrt-1 expression observed in aneurysmal tissue compared with control. In parallel experiments, we found a 2.2 ± 0.2-fold and a 5.6 ± 2.2-fold increase in TGF-β mRNA and protein expression, respectively, in aneurysmal tissue compared with nonaneurysmal tissue. In vitro, Hedgehog signaling inhibition with cyclopamine in human aortic SMCs resulted in decreased Hedgehog/Notch signaling component and vSMC differentiation gene expression. Moreover, cyclopamine significantly increased TGF-β1 mRNA expression by 2.6 ± 0.9-fold.

CONCLUSIONS

These results suggest that SHh/Notch and TGF-β signaling are differentially regulated in aneurysmal tissue compared with nonaneurysmal tissue. Changes in these signaling pathways and the resulting changes in vSMC content may play a causative role in the development of AAAs.

Inhibition of patched-1 prevents injury-induced neointimal hyperplasia

OBJECTIVE

To determine the role of patched receptor (Ptc)-1 in mediating pulsatile flow-induced changes in vascular smooth muscle cell growth and vascular remodeling.

APPROACH AND RESULTS

In vitro, human coronary arterial smooth muscle cells were exposed to normal or pathological low pulsatile flow conditions for 24 hours using a perfused transcapillary flow system. Low pulsatile flow increased vascular smooth muscle cell proliferation when compared with normal flow conditions. Inhibition of Ptc-1 by cyclopamine attenuated low flow-induced increases in Notch expression while concomitantly decreasing human coronary arterial smooth muscle cell growth to that similar under normal flow conditions. In vivo, ligation injury-induced low flow increased vascular smooth muscle cell growth and vascular remodeling, while increasing Ptc-1/Notch expression. Perivascular delivery of Ptc-1 small interfering RNA by pluronic gel inhibited the pathological low flow-induced increases in Ptc-1/Notch expression and markedly reduced the subsequent vascular remodeling.

CONCLUSIONS

These results suggest that pathological low flow stimulates smooth muscle cell growth in vitro and vascular remodeling in vivo via Ptc-1 regulation of Notch signaling.

Abstract 96: Aberrations in the Sonic Hedgehog/Notch Signaling Pathway in Abdominal Aortic Aneurysms

Objectives: The molecular mechanisms leading to the development of Adnominal Aortic Aneurysms (AAA) remain poorly understood. Vascular Smooth Muscle Cells (VSMCs) are fundamental to maintaining a healthy arterial wall and changes in VSMC phenotype may be pivotal to aneurysm development. We have recently determined a role for a Hedgehog (Hh)/Notch signaling cascade in regulating adult VSMC phenotype. The aim of this study was to investigate Hh/Notch signaling components in aneurysmal and non-aneurysmal aorta. As crosstalk between Notch and Transforming Growth Factor Beta (TGFβ) has been postulated we also investigated expression of this growth factor.

Methods: Tissue samples were obtained from aneurysmal and non-aneurysmal segments of the aortic wall of at least 5 patients with suitable anatomy undergoing open repair of infrarenal AAA. All samples analyzed were paired from the same patient with aneurysmal and non-aneurysmal specimens. Protein and mRNA expression levels were determined by western blot analysis and quantitative Real-time PCR respectively.

Results: SHh, Notch 1 and 3 IC protein expression was decreased by at least 50% in aneurysmal tissue when compared to non-aneurysmal tissue. In addition, SHh mRNA expression was also decreased by 65%, while there was a decrease in Dll4, Notch 1 and Notch 3 by 66%, 57% and 54% respectively. In contrast, aneurysmal tissue had significantly increased expression of TGFβ and MMP9. TGFB protein and mRNA expression was significantly increased by 5.45±2.13 and 2.5±.2 fold respectively in aneurysmal tissue when compared to non-aneurysmal tissue. Furthermore, MMP9 mRNA expression was significantly increased by 4.7±1.6 fold. In parallel experiments, SMC alpha actin protein expression was significantly decreased by 90% in aneurysmal tissue when compared to non-aneurysmal tissue.

Conclusion: These results suggest that SHH/Notch and TGFβ signaling is altered in aneurysmal tissue, compared with non-aneurysmal tissue. Changes in these signaling pathways and resulting changes in VSMC phenotype may play a role in the development of AAA.

Alcohol and cardiovascular disease--modulation of vascular cell function

Alcohol is a commonly used drug worldwide. Epidemiological studies have identified alcohol consumption as a factor that may either positively or negatively influence many diseases including cardiovascular disease, certain cancers and dementia. Often there seems to be a differential effect of various drinking patterns, with frequent moderate consumption of alcohol being salutary and binge drinking or chronic abuse being deleterious to one’s health. A better understanding of the cellular and molecular mechanisms mediating the many effects of alcohol consumption is beginning to emerge, as well as a clearer picture as to whether these effects are due to the direct actions of alcohol itself, or caused in part by its metabolites, e.g., acetaldehyde, or by incidental components present in the alcoholic beverage (e.g., polyphenols in red wine). This review will discuss evidence to date as to how alcohol (ethanol) might affect atherosclerosis that underlies cardiovascular and cerebrovascular disease, and the putative mechanisms involved, focusing on vascular endothelial and smooth muscle cell effects.

Investigational Notch and Hedgehog inhibitors--therapies for cardiovascular disease

INTRODUCTION

During the past decade, a variety of Notch and Hedgehog pathway inhibitors have been developed for the treatment of several cancers. An emerging paradigm suggests that these same gene regulatory networks are often recapitulated in the context of cardiovascular disease and may now offer an attractive target for therapeutic intervention.

AREAS COVERED

This article briefly reviews the profile of Notch and Hedgehog inhibitors that have reached the preclinic and clinic for cancer treatment and discusses the clinical issues surrounding targeted use of these inhibitors in the treatment of vascular disorders.

EXPERT OPINION

Preclinical and clinical data using pan-Notch inhibitors (γ-secretase inhibitors) and selective antibodies to preferentially target notch receptors and ligands have proven successful but concerns remain over normal organ homeostasis and significant pathology in multiple organs. By contrast, the Hedgehog-based drug pipeline is rich with more than a dozen Smoothened (SMO) inhibitors at various stages of development. Overall, refined strategies will be necessary to harness these pathways safely as a powerful tool to disrupt angiogenesis and vascular proliferative phenomena without causing prohibitive side effects already seen with cancer models and patients.

Differential effects of daily-moderate versus weekend-binge alcohol consumption on atherosclerotic plaque development in mice

OBJECTIVES

We examined the effect of daily-moderate (2 drinks/day, 7 days/week) and weekend-binge (7 drinks/day, 2 days/week) patterns of alcohol consumption on plasma lipid levels and physiological parameters of atherosclerotic plaque development.

METHODS

ApoE k/o mouse were fed (1) 'daily-moderate' (blood alcohol content: 0.07%) or (2) 'weekend-binge' (blood alcohol content: 0.23%), or (3) an isocaloric cornstarch mix. Then, to induce atherosclerotic plaque formation, all groups underwent partial carotid artery ligation, started on an atherogenic diet and continued on the alcohol feeding regimen. After 2 weeks plasma lipid levels and atherosclerotic plaque formation were assessed.

RESULTS

While there was an increase in HDL-C levels in both binge and moderate groups, LDL-C levels were significantly decreased in the daily-moderate drinking mice and significantly elevated in the weekend-binge drinking mice. In the daily-moderate alcohol group there was a decrease in atherosclerotic plaque volume, concomitant with an increase in lumen volume and decreased macrophage accumulation, when compared to no alcohol mice. In contrast, after 4 weeks of weekend-binge alcohol there was an increase in plaque volume, concomitant with a decrease in lumen volume and increased deposition of macrophages.

CONCLUSION

These findings demonstrate for the first time a differential effect of daily-moderate vs. weekend-binge alcohol consumption on atherosclerotic plaque development and highlight the importance of patterns of alcohol consumption, as opposed to total amount consumed, in relation to the cardiovascular effects of alcohol.

Microvascular retinal endothelial and pericyte cell apoptosis in vitro: role of hedgehog and Notch signaling

PURPOSE

Aberrant retinal blood flow is a hallmark of retinopathies and may be a causative factor in their pathophysiology. In this study, the effects of pulsatile flow on hedgehog and Notch control of retinal endothelial cell and pericyte apoptosis were examined.

METHODS

The levels of hedgehog and Notch signaling components in bovine retinal endothelial cells (BRECs) and pericytes (BRPs) were examined in vitro under static conditions and after exposure to pulsatile flow, with a perfused transcapillary co-culture system. Notch and hedgehog signaling was examined by immunocytochemistry, immunoblot, and real-time PCR.

RESULTS

Notch and hedgehog proteins were present in BRECs and BRPs in vitro and in human retinal vasculature in vivo. Inhibition of hedgehog with cyclopamine and Notch with DAPT decreased hedgehog target gene levels and Notch intracellular receptor expression, respectively, concomitant with an increase in BREC and BRP apoptosis. Sonic hedgehog (Shh) mediated upregulation of Notch1 receptor levels was attenuated after cyclopamine treatment in both cell types. Exposure of co-cultured BRECs and BRPs to pulsatile flow increased apoptosis in the BRPs while concurrently decreasing apoptosis in the BRECs. These changes were concomitant with increased expression of Notch and hedgehog signaling components in the BRECs and reduced expression in the BRPs. The flow-induced decrease in apoptosis in the BRECs was associated with increased Notch receptor expression and was reversed after inhibition of hedgehog signaling with cyclopamine and inhibition of Notch signaling after ectopic expression of the CBF-1/RBP-Jκ-binding protein, RPMS-1.

CONCLUSIONS

Pulsatile flow promotes BREC survival and enhances BRP apoptosis through modulation of Notch and hedgehog pathways. These interactions have important implications for the pathogenesis of retinopathies.

Endothelial Grb2-associated binder 1 is crucial for postnatal angiogenesis

OBJECTIVE

Grb2-associated binder 1 (Gab1), a scaffolding adaptor protein, plays an important role in transmitting key signals that control cell growth, differentiation, and function from multiple tyrosine kinase receptors. The study was designed to investigate the role of endothelial Gab1 in angiogenesis and its underlying molecular mechanisms.

METHODS AND RESULTS

Using Cre-Lox recombination technology, we generated endothelial-specific Gab1 knockout (Gab1-ecKO) mice. Gab1-ecKO mice are viable and showed no obvious developmental defects in the vascular system. To analyze the role of Gab1 in postnatal angiogenesis, we used hindlimb ischemia and Matrigel plug models. We found that loss of endothelial Gab1 in mice dramatically impaired postnatal angiogenesis. Gab1-ecKO mice had impaired ischemia-initiated blood flow recovery, exhibited reduced angiogenesis, and were associated with marked limb necrosis. We further observed significant endothelial cell (EC) death in the ischemic hindlimb of Gab1-ecKO mice. Matrigel plug assay showed that hepatocyte growth factor (HGF)-mediated angiogenesis was inhibited in Gab1-ecKO mice. In vitro studies showed that Gab1 was required for HGF-induced EC migration, tube formation, and microvessel sprouting. Mechanistically, HGF stimulated Gab1 tyrosine phosphorylation in ECs, leading to activation of extracellular regulated MAP kinase 1/2 and Akt, which are angiogenic and survival signaling.

CONCLUSIONS

Gab1 is essential for postnatal angiogenesis through mediating angiogenic and survival signaling.

Heat shock protein 27 differentiates tolerogenic macrophages that may support human breast cancer progression

Tumor cells release several factors that can help the progression of the tumor by directly supporting tumor growth and/or suppressing host antitumor immunity. Here, we report that human primary breast tumor cells not only express elevated levels of heat shock protein 27 (Hsp27) at the intracellular level but also release extremely high levels of Hsp27 compared with the same patients' serum Hsp27 levels, predicting an acutely increased concentration of soluble Hsp27 in the human breast tumor microenvironment (HBTM). We demonstrate that Hsp27 levels in the HBTM can be extremely elevated as evidenced by high soluble Hsp27 levels in patients' tumor interstitial fluid. Because increasing numbers of tumor-associated macrophages (TAM) in the HBTM negatively correlate to patients' clinical outcomes and we have previously reported the immunoregulatory activity of soluble Hsp27, here, we tested for any specific effects of soluble Hsp27 on human monocyte to macrophage differentiation. We demonstrate that soluble Hsp27 causes the differentiation of monocytes to macrophages with immuno-tolerizing phenotypes (HLA-DRlow, CD86low, PD-L1high, ILT2high, and ILT4high). We detected the presence of TAMs with similar phenotypes in breast cancer patients. Hsp27-differentiated macrophages induce severe unresponsiveness/anergy in T cells. Moreover, these macrophages lose tumoricidal activity but become extremely proangiogenic, inducing significant neovascularization, a process that is critically important for tumor growth. Thus, our data demonstrate a novel immune escape and tumor growth-supporting mechanism mediated by soluble Hsp27 that may be operative in human breast cancer.

Alcohol inhibits smooth muscle cell proliferation via regulation of the Notch signaling pathway

OBJECTIVE

To determine the role of Notch signaling in mediating alcohol's inhibition of smooth muscle cell (SMC) proliferation.

METHODS AND RESULTS

Treatment of human coronary artery SMCs with ethanol (EtOH) decreased Notch 1 mRNA and Notch 1 intracellular domain protein levels, in the absence of any effect on Notch 3. EtOH treatment also decreased C-promoter binding factor-1 (CBF-1)/recombination signal-binding protein (RBP)-jk promoter activity and Notch target gene (hairy related transcription factor [HRT-1] or HRT-2) expression. These effects were concomitant with an inhibitory effect of EtOH on SMC proliferation. Overexpression of constitutively active Notch 1 intracellular domain or human hairy related transcription factor-1 (hHRT-1) prevented the EtOH-induced inhibition of SMC proliferation. In vivo, Notch 1 and HRT-1 mRNA expression was increased after ligation-induced carotid artery remodeling. The vessel remodeling response was inhibited in mice that received "moderate" amounts of alcohol by gavage daily; intimal-medial thickening was markedly reduced, and medial and neointimal SMC proliferating cell nuclear antigen expression was decreased. Moreover, Notch 1 and HRT-1 expression, induced after ligation injury, was inhibited by moderate alcohol consumption.

CONCLUSIONS

EtOH inhibits Notch signaling and, subsequently, SMC proliferation, in vitro and in vivo. The modulation of Notch signaling in SMCs by EtOH may be relevant to the cardiovascular protective effects of moderate alcohol consumption purported by epidemiological studies.

Sonic Hedgehog induces Notch target gene expression in vascular smooth muscle cells via VEGF-A

OBJECTIVE

Notch, VEGF, and components of the Hedgehog (Hh) signaling pathway have been implicated in vascular morphogenesis. The role of Notch in mediating hedgehog control of adult vascular smooth muscle cell (SMC) growth and survival remains unexplored.

METHODS AND RESULTS

In cultured SMCs, activation of Hh signaling with recombinant rShh (3.5 mug/mL) or plasmid encoded Shh increased Ptc1 expression, enhanced SMC growth and survival and promoted Hairy-related transcription factor (Hrt) expression while concomitantly increasing VEGF-A levels. These effects were significantly reversed after Hh inhibition with cyclopamine. Shh-induced stimulation of Hrt-3 mRNA and SMC growth and survival was attenuated after inhibition of Notch-mediated CBF-1/RBP-Jk-dependent signaling with RPMS-1 while siRNA knockdown of Hrt-3 inhibited SMC growth and survival. Recombinant VEGF-A increased Hrt-3 mRNA levels while siRNA knockdown abolished rShh stimulated VEGF-A expression while concomitantly inhibiting Shh-induced increases in Hrt-3 mRNA levels, proliferating cell nuclear antigen (PCNA), and Notch 1 IC expression, respectively. Hedgehog components were expressed within intimal SMCs of murine carotid arteries after vascular injury concomitant with a significant increase in mRNA for Ptc1, Gli(2), VEGF-A, Notch 1, and Hrts.

CONCLUSIONS

Hedgehog promotes a coordinate regulation of Notch target genes in adult SMCs via VEGF-A.

Notch and Vascular Smooth Muscle Cell Phenotype

The Notch signaling pathway is critical for cell fate determination during embryonic development, including many aspects of vascular development. An emerging paradigm suggests that the Notch gene regulatory network is often recapitulated in the context of phenotypic modulation of vascular smooth muscle cells (VSMC), vascular remodeling, and repair in adult vascular disease following injury. Notch ligand receptor interactions lead to cleavage of receptor, translocation of the intracellular receptor (Notch IC), activation of transcriptional CBF-1/RBP-Jκ–dependent and –independent pathways, and transduction of downstream Notch target gene expression. Hereditary mutations of Notch components are associated with congenital defects of the cardiovascular system in humans such as Alagille syndrome and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). Recent loss- or gain-of-function studies have provided insight into novel Notch-mediated CBF-1/RBP-Jκ–dependent and –independent signaling and cross-regulation to other molecules that may play a critical role in VSMC phenotypic switching. Notch receptors are critical for controlling VSMC differentiation and dictating the phenotypic response following vascular injury through interaction with a triad of transcription factors that act synergistically to regulate VSMC differentiation. This review focuses on the role of Notch receptor ligand interactions in dictating VSMC behavior and phenotype and presents recent findings on the molecular interactions between the Notch components and VSMC-specific genes to further understand the function of Notch signaling in vascular tissue and disease.

Acetaldehyde stimulates monocyte adhesion in a P-selectin- and TNFalpha-dependent manner

OBJECTIVE

The aim of this study was to determine the effects of acetaldehyde on various steps of the monocyte recruitment cascade.

METHODS

Human umbilical venous endothelial cells (HUVEC), primary blood monocytes (PBM) and THP-1 monocytes, were treated with acetaldehyde (0.1-0 microM) for 6h. Monocyte adherence experiments were performed using 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein-acetoxymethylester labeled PBM or (3)H-thymidine labeled THP-1 cells. HUVEC TNFalpha mRNA and protein levels were determined by quantitative real-time PCR and immunoassay, respectively, and HUVEC P-selectin and monocyte CCR2 expression were determined by FACS analysis.

RESULTS

Acetaldehyde dose-dependently increased the number of CCR2 positive THP-1 monocytes, with a maximal increase of approximately 50% observed in the presence of 10 microM acetaldehyde. There was a significant increase in both the number of P-selectin positive cells and P-selectin receptor density when HUVEC were incubated with acetaldehyde. HUVEC TNFalpha mRNA expression and secretion were enhanced by acetaldehyde. Moreover, acetaldehyde increased THP-1 and PBM adhesion to HUVEC. Inhibition of P-selectin or TNFalpha, using antibodies or siRNA-directed gene knockdown, attenuated acetaldehyde-induced monocyte adhesion. In conclusion, acetaldehyde increased the number of CCR2 positive monocytes and stimulated endothelial cell P-selectin and TNFalpha expression. Moreover, acetaldehyde increased monocyte adhesion to endothelial cells, an effect that was both P-selectin- and TNFalpha-dependent.

CONCLUSION

These effects of acetaldehyde may contribute, in part, to the increase in coronary heart disease that is associated with binge patterns of alcohol consumption.

Ethanol stimulates endothelial cell angiogenic activity via a Notch- and angiopoietin-1-dependent pathway

AIMS

Our aims were to determine the effect of alcohol (EtOH) on endothelial angiogenic activity and to delineate the cell signalling mechanisms involved.

METHODS AND RESULTS

Treatment of human umbilical vein endothelial cells (HUVECs) with EtOH (1-100 mM, 24 h) dose-dependently increased their network formation on Matrigel (an index of angiogenesis) with a maximum response (2.5- to 3-fold increase) at 25 mM. Ethanol also stimulated the proliferation (by cell count and proliferating cell nuclear antigen expression) and migration (by scratch wound assay) of HUVECs. In parallel cultures, EtOH stimulated Notch receptor (1 and 4) and Notch target gene (hrt-1, -2, and -3) mRNA and protein expression and enhanced CBF-1/RBP-Jk promoter activity. EtOH also stimulated, at the mRNA and protein level, the expression of angiopoietin-1 (Ang1) and its Tie2 receptor in these cells. Knockdown of Notch 1 or 4 by siRNA or inhibition of Notch-mediated, CBF-1/RBP-Jk-regulated gene expression by the Epstein-Barr virus-encoded protein RPMS-1 inhibited both ethanol-induced Ang1/Tie2 expression in HUVECs and their network formation on Matrigel. Moreover, knockdown of Ang1 or Tie2 by siRNA inhibited ethanol-induced endothelial network formation.

CONCLUSION

These data demonstrate that ethanol, at levels consistent with moderate consumption, enhances endothelial angiogenic activity in vitro by stimulating a novel Notch/CBF-1/RBP-JK-Ang1/Tie2-dependent pathway. These actions of ethanol may be relevant to the cardiovascular effects of alcohol consumption purported by epidemiological studies.

Resveratrol inhibits expression and binding activity of the monocyte chemotactic protein-1 receptor, CCR2, on THP-1 monocytes

Monocyte chemotactic protein-1 and its receptor, CCR2, play a key role in atherosclerosis. We determined the effect of the polyphenol, resveratrol, on CCR2 and the mechanisms involved. Resveratrol treatment inhibited 125I-MCP-1 binding to THP-1 cells; 31, 56, 84% decrease for 10, 50 and 100 microM resveratrol, in the absence of any effect on receptor affinity. The inhibitory effect of resveratrol on 125I-MCP-1 binding to THP-1 cells and on CCR2 protein expression determined by FACS analysis was attenuated by treatment with L-NAME (NOS inhibitor), PD98059 (MAPK inhibitor) and LY294002 (PI3K inhibitor), whereas neither X/XO (reactive oxygen species generator) nor ICI182780 (estrogen receptor antagonist) had any effect. Concomitant with a decrease in CCR2 protein expression, resveratrol inhibited THP-1 CCR2 mRNA levels, in the absence of any effect on its stability; 26 and 45% inhibition at 10 and 50 microM resveratrol, respectively. This effect was not altered by co-treatment with L-NAME, PD98059 or ICI182780, but was potentiated by LY294002 and X/XO.

CONCLUSIONS

Resveratrol inhibits monocyte CCR2 binding activity in an NO-, MAPK- and PI3K-dependent manner, whereas it inhibits CCR2 mRNA in an NO- and MAPK-independent, PI3K-dependent manner. These inhibitory effects of resveratrol on chemokine receptor binding and expression may contribute, in part, to its cardiovascular protective activity in vivo.

Cyclic strain regulates the Notch/CBF-1 signaling pathway in endothelial cells: role in angiogenic activity

OBJECTIVE

The purpose of this study was to determine the effect of cyclic strain on Notch signaling in endothelial cells.

METHODS AND RESULTS

Exposure of human endothelial cells (ECs) to cyclic strain (10%) resulted in temporal upregulation of Notch receptors (1 and 4) at the mRNA and protein level. Cyclic strain significantly increased EC network formation on Matrigel (an index of angiogenesis); network AU=775+/-127 versus 3928+/-400 for static and strained ECs, respectively. In addition, Angiopoietin 1 (Ang1), Tie1, and Tie2 expression were increased and knockdown of Ang1/Tie1,2 by siRNAs decreased cyclic strain-induced network formation. Knockdown of Notch 1 and 4 by siRNA, or inhibition of Notch mediated CBF-1/RBP-Jk regulated gene expression by RPMS-1, caused a significant decrease in cyclic strain-induced network formation and in Tie1 and Tie2 mRNA expression. Notch 1 or Notch 4 siRNA, but not RPMS-1, inhibited cyclic strain-induced Ang1. Constitutive overexpression of Notch IC resulted in increased network formation, and Ang1 and Tie2 mRNA expression, under both static and strain conditions.

CONCLUSIONS

These data suggest that cyclic strain-stimulated EC angiogenesis is mediated in part through a Notch-dependent, Ang1/Tie2 signaling pathway. This pathway may represent a novel therapeutic target for disease states in which hemodynamic force-induced angiogenesis occurs.

Biomechanical regulation of hedgehog signaling in vascular smooth muscle cells in vitro and in vivo

Hedgehog (Hh) signaling has recently been shown to be both responsive to mechanical loading in vitro and to control vascular development in vivo. We investigated the role of cyclic strain and pulsatile flow in modulating Hh signaling and growth of adult rat vascular smooth muscle cells (SMC) in culture. Exposure of SMC to defined equibiaxial cyclic strain (0% and 10% stretch, 60 cycles/min, for 24 h) significantly decreased sonic hedgehog (Shh) and patched 1 (Ptc1) expression while concurrently inhibiting Gli2-dependent promoter activity and mRNA expression, respectively. Cyclic strain significantly decreased SMC proliferation (cell counts and proliferating cell nuclear antigen expression) concomitant with a marked increase in SMC apoptosis (fluorescence-activated cell sorter analysis, acridine orange staining of apoptotic nuclei and Bax/Bcl-xL ratio). These strain-induced changes in proliferation and apoptosis were significantly attenuated following addition of either recombinant Shh (3.5 μg/ml) or overexpression of the Notch 3 intracellular domain (Notch IC). Further studies using a perfused transcapillary culture system demonstrated a significant decrease in Hh signaling in SMC following exposure of cells to increased pulsatile flow concomitant with a decrease in proliferation and an increase in apoptosis. Finally, the pulsatile flow-induced decreases in Hh signaling were validated in vivo following flow-induced rat carotid arterial remodeling after 28 days. These data suggest that Hh expression is diminished by biomechanical stimulation in vitro and in vivo and thus may play a fundamental role in arterial remodeling and atherogenesis in vivo.

Resveratrol, a Polyphenolic Phytostilbene, Inhibits Endothelial Monocyte Chemotactic Protein-1 Synthesis and Secretion

BACKGROUND/AIMS

Resveratrol is a naturally occurring polyphenol phytoestrogen and one of several constituents of red wine thought to be cardioprotective. We investigated the effect of resveratrol on the expression of the atherogenic chemokine, monocyte chemotactic protein-1 (MCP-1).

METHODS

Human umbilical vein endothelial cells were stimulated with interleukin-1beta (IL-1beta) in the absence or presence of resveratrol. MCP-1 levels were determined by ELISA and MCP-1 mRNA was measured.

RESULTS

Resveratrol (1-100 microM) dose-dependently inhibited IL-1beta-stimulated MCP-1 secretion, with approximately 45% inhibition at 50 microM resveratrol. This was a Gi-protein- and NO-dependent effect. Resveratrol also significantly inhibited MCP-1 gene expression in a Gi-protein-dependent but NO-independent manner. While resveratrol had no effect on MCP-1 mRNA degradation, it inhibited MCP-1 promoter activity and reduced nuclear factor kappaB and activator protein-1 binding activity induced by IL-1beta. Moreover, while hemoxygenase-1 (HO-1) expression was induced by resveratrol in human umbilical vein endothelial cells, neither treatment with the HO-1 inhibitor tin-protoporphyrin IX nor siRNA-directed knockdown of HO-1 had any effect on the inhibition of MCP-1 mRNA or protein secretion by resveratrol.

CONCLUSION

These data demonstrate an inhibitory effect of resveratrol on MCP-1 synthesis and secretion, mediated via distinct signaling pathways. The inhibition of MCP-1 may represent a novel cardioprotective mechanism of resveratrol.

Cyclic strain-mediated matrix metalloproteinase regulation within the vascular endothelium: a force to be reckoned with

The vascular endothelium is a dynamic cellular interface between the vessel wall and the bloodstream, where it regulates the physiological effects of humoral and biomechanical stimuli on vessel tone and remodeling. With respect to the latter hemodynamic stimulus, the endothelium is chronically exposed to mechanical forces in the form of cyclic circumferential strain, resulting from the pulsatile nature of blood flow, and shear stress. Both forces can profoundly modulate endothelial cell (EC) metabolism and function and, under normal physiological conditions, impart an atheroprotective effect that disfavors pathological remodeling of the vessel wall. Moreover, disruption of normal hemodynamic loading can be either causative of or contributory to vascular diseases such as atherosclerosis. EC-matrix interactions are a critical determinant of how the vascular endothelium responds to these forces and unquestionably utilizes matrix metalloproteinases (MMPs), enzymes capable of degrading basement membrane and interstitial matrix molecules, to facilitate force-mediated changes in vascular cell fate. In view of the growing importance of blood flow patterns and mechanotransduction to vascular health and pathophysiology, and considering the potential value of MMPs as therapeutic targets, a timely review of our collective understanding of MMP mechanoregulation and its impact on the vascular endothelium is warranted. More specifically, this review primarily summarizes our current knowledge of how cyclic strain regulates MMP expression and activation within the vascular endothelium and subsequently endeavors to address the direct and indirect consequences of this on vascular EC fate. Possible relevance of these phenomena to vascular endothelial dysfunction and pathological remodeling are also addressed.

Ethanol inhibits pulse pressure-induced vascular smooth muscle cell migration by differentially modulating plasminogen activator inhibitor type 1, matrix metalloproteinase-2 and -9

We investigated the effect of ethanol on the pulse pressure-induced expression of PAI-1 and MMP-2/9 in human smooth muscle cells (SMC). Human SMC were exposed to static or pulse pressure (25 mL/min; pulse pressure 106/50 mm Hg) conditions for 24 h in the absence or presence of ethanol (0.1-100 mM). SMC migration was then measured by Transwell migration assay. SMC exposed to pulse pressure demonstrated a significant increase in PAI-1 mRNA and protein expression (approximately 4-fold and approximately 3-fold) concomitant with a 3- and 8-fold increase in MMP-2 and MMP-9 protein, respectively. Ethanol dose-dependently inhibited the pulse pressure-induced SMC migration with complete inhibition observed at 20 mM. There was no effect of ethanol on basal PAI-1 or MMP-2/9 in SMC under static conditions. However, ethanol significantly enhanced the pulse pressure-induced PAI-1 mRNA and protein expression (2.2 +/- 0.52 fold and 2.5 +/- 0.27 fold, for 10 mM), respectively. In contrast, ethanol dose-dependently inhibited the pulse pressure-induced increases in MMP-9 protein and pro-MMP-9 activity and to a lesser extent MMP-2 mRNA and protein and pro-MMP-2 activity, with significant inhibition observed at 1 mM. These data provide a molecular mechanism mediating the inhibitory effect of ethanol on pulse-pressure-induced SMC migration and may be relevant to the cardioprotective effects of ethanol in vivo.

Notch-mediated CBF-1/RBP-J{kappa}-dependent regulation of human vascular smooth muscle cell phenotype in vitro

Vascular smooth muscle cell (VSMC) phenotypic modulation is a key factor in vascular pathology. We have investigated the role of Notch receptor signaling in controlling human vascular smooth muscle cell (hVSMC) differentiation in vitro and established a role for cyclic strain-induced changes in Notch signaling in promoting this phenotypic response. The expression of alpha-actin, calponin, myosin, and smoothelin was examined by performing immunocytochemistry, Western blot analysis, and quantitative real-time PCR in hVSMCs cultured under static conditions after forced overexpression of constitutively active Notch 1 and 3 receptors, inhibition of endogenous Cp-binding factor 1 (CBF-1)/recombination signal sequence-binding protein-Jkappa (RBP-Jkappa) signaling, and exposure to cyclic strain using a Flexercell Tension Plus unit. Overexpression of constitutively active Notch intracellular (IC) receptors (Notch 1 IC and Notch 3 IC) resulted in a significant downregulation of alpha-actin, calponin, myosin, and smoothelin expression, an effect that was significantly attenuated after inhibition of Notch-mediated, CBF-1/RBP-Jkappa-dependent signaling by coexpression of RPMS-1 (Epstein-Barr virus-encoded gene product) and selective knockdown of basic helix-loop-helix factors [hairy enhancer of split (HES) gene and Hes-related transcription (Hrt) factors Hrt-1, Hrt-2, and Hrt-3] using targeted small interfering RNA. Cells cultured under conditions of defined equibiaxial cyclic strain (10% strain, 60 cycles/min, 24 h) exhibited a significant reduction in Notch 1 IC and Notch 3 IC expression concomitant with a significant increase in VSMC differentiation marker expression. Moreover, this cyclic strain-induced increase was further enhanced after inhibition of CBF-1/RBP-Jkappa-dependent signaling with RPMS-1. These findings suggest that Notch promotes changes in hVSMC phenotype via activation of CBF-1/RBP-Jkappa-dependent pathways in vitro and contributes to the phenotypic response of VSMCs to cyclic strain-induced changes in VSMC differentiation.

Ethanol inhibits monocyte chemotactic protein-1 expression in interleukin-1{beta}-activated human endothelial cells

The aim of this study was to determine the effect of ethanol (EtOH) on endothelial monocyte chemotactic protein-1 (MCP-1) expression. IL-1beta increased the production of MCP-1 by human umbilical vein endothelial cells from undetectable levels to approximately 900 pg/ml at 24 h. EtOH dose-dependently inhibited IL-1beta-stimulated MCP-1 secretion as determined by ELISA: 25 +/- 1%, 35 +/- 7%, and 65 +/- 5% inhibition for 1, 10, and 100 mM EtOH, respectively, concomitant with inhibition of monocyte adhesion to activated endothelial cells. Similarly, EtOH dose-dependently inhibited IL-1beta-stimulated MCP-1 mRNA expression. Experiments with actinomycin D demonstrated that EtOH decreased the stability of MCP-1 mRNA. In addition, EtOH significantly reduced NF-kappaB and AP-1 binding activity induced by IL-1beta and inhibited MCP-1 gene transcription. Binding of (125)I-labeled MCP-1 to its receptor (CCR2) on THP-1 human monocytic cells was not affected by EtOH treatment. Modulation of the expression of MCP-1 represents a mechanism whereby EtOH could inhibit atherogenesis by blocking the crucial early step of monocyte adhesion and subsequent recruitment to the subendothelial space. These actions of EtOH may underlie, in part, its cardiovascular protective effects in vivo.

Cyclic strain-mediated regulation of vascular endothelial cell migration and tube formation

Hemodynamic forces exerted by blood flow (cyclic strain, shear stress) affect the initiation and progression of angiogenesis; however, the precise signaling mechanism(s) involved are unknown. In this study, we examine the role of cyclic strain in regulating bovine aortic endothelial cell (BAEC) migration and tube formation, indices of angiogenesis. Considering their well-documented mechanosensitivity, functional inter-dependence, and involvement in angiogenesis, we hypothesized roles for matrix metalloproteinases (MMP-2/9), RGD-dependent integrins, and urokinase plasminogen activator (uPA) in this process. BAECs were exposed to equibiaxial cyclic strain (5% strain, 1Hz for 24h) before their migration and tube formation was assessed by transwell migration and collagen gel tube formation assays, respectively. In response to strain, both migration and tube formation were increased by 1.83+/-0.1- and 1.84+/-0.1-fold, respectively. Pertussis toxin, a Gi-protein inhibitor, decreased strain-induced migration by 45.7+/-32% and tube formation by 69.8+/-13%, whilst protein tyrosine kinase (PTK) inhibition with genistein had no effect. siRNA-directed attenuation of endothelial MMP-9 (but not MMP-2) expression/activity decreased strain-induced migration and tube formation by 98.6+/-41% and 40.7+/-31%, respectively. Finally, integrin blockade with cRGD peptide and siRNA-directed attenuation of uPA expression reduced strain-induced tube formation by 85.7+/-15% and 84.7+/-31%, respectively, whilst having no effect on migration.

CONCLUSIONS

Cyclic strain promotes BAEC migration and tube formation in a Gi-protein-dependent PTK-independent manner. Moreover, we demonstrate for the first time a putative role for MMP-9 in both strain-induced events, whilst RGD-dependent integrins and uPA appear only to be involved in strain-induced tube formation.

Cyclic Strain Inhibits Notch Receptor Signaling in Vascular Smooth Muscle Cells In Vitro

Notch signaling has been shown recently to regulate vascular cell fate in adult cells. By applying a uniform equibiaxial cyclic strain to vascular smooth muscle cells (SMCs), we investigated the role of strain in modulating Notch-mediated growth of SMCs in vitro. Rat SMCs cultured under conditions of defined equibiaxial cyclic strain (0% to 15% stretch; 60 cycles/min; 0 to 24 hours) exhibited a significant temporal and force-dependent reduction in Notch 3 receptor expression, concomitant with a significant reduction in Epstein Barr virus latency C promoter-binding factor-1/recombination signal-binding protein of the Jkappa immunoglobulin gene-dependent Notch target gene promoter activity and mRNA levels when compared with unstrained controls. The decrease in Notch signaling was Gi-protein- and mitogen-activated protein kinase-dependent. In parallel cultures, cyclic strain inhibited SMC proliferation (cell number and proliferating cell nuclear antigen expression) while significantly promoting SMC apoptosis (annexin V binding, caspase-3 activity and bax/bcl-x(L) ratio). Notch 3 receptor overexpression significantly reversed the strain-induced changes in SMC proliferation and apoptosis to levels comparable to unstrained control cells, whereas Notch inhibition further potentiated the changes in SMC apoptosis and proliferation. These findings suggest that cyclic strain inhibits SMC growth while enhancing SMC apoptosis, in part, through regulation of Notch receptor and downstream target gene expression.

Plasminogen activator inhibitor-1 deficiency enhances flow-induced smooth muscle cell migration

INTRODUCTION

We determined the role of smooth muscle cell (SMC)-derived plasminogen activator inhibitor-1 (PAI-1) in the flow-induced SMC migratory response.

MATERIALS AND METHODS

Wild type (wt) or PAI-1 knockout SMC were cultured in the absence or presence of endothelial cells (EC) under static or pulsatile flow conditions in a perfused culture system. SMC migration was then assessed by Transwell assay.

RESULTS

Pulsatile flow significantly increased SMC PAI-1 mRNA and protein levels, approximately 4- and 3-fold respectively (n = 4, p < 0.05). In the absence, but not in the presence of EC, pulsatile flow significantly increased ( approximately 2.4-fold) the migration of wt SMC when compared to wt SMC cultured under static conditions. PAI-1 -/-SMC migration was significantly increased under flow conditions as compared to wild-type controls (334 +/- 22% vs. 237 +/- 11%, n = 6, p < 0.05). This flow-induced migration was significantly attenuated, but not completely inhibited, when PAI-1 -/-SMC were cultured in the presence of EC (147 +/- 13%, n = 6, p < 0.05). The flow-induced PAI-1 -/-SMC migratory response was partially inhibited by an anti-urokinase plasminogen activator (uPA) antibody (#1189), and completely inhibited by both 1189 and the matrix metalloproteinase (MMP) inhibitor BB3103. In parallel PAI-1 -/-SMC cells, there was a greater flow-induced increase in proMMP-2 activity as compared to wild-type control cells. Moreover, under both static and flow conditions, tissue inhibitors of matrix metalloproteinases (TIMP)-2 activity was reduced in these PAI-1-deficient cells as compared to wild-type controls.

CONCLUSIONS

These results suggest that SMC PAI-1 plays a role in limiting flow-induced SMC migration and thus may be an important mechanism for controlling the process of vascular remodelling.