Shear stress downregulation of platelet-derived growth factor receptor-beta and matrix metalloprotease-2 is associated with inhibition of smooth muscle cell invasion and migration

Adipose tissue-derived mesenchymal stem cells acquire bone cell-like responsiveness to fluid shear stress on osteogenic stimulation

To engineer bone tissue, mechanosensitive cells are needed that are able to perform bone cell-specific functions, such as (re)modeling of bone tissue. In vivo, local bone mass and architecture are affected by mechanical loading, which is thought to provoke a cellular response via loading-induced flow of interstitial fluid. Adipose tissue is an easily accessible source of mesenchymal stem cells for bone tissue engineering, and is available in abundant amounts compared with bone marrow. We studied whether adipose tissue-derived mesenchymal stem cells (AT-MSCs) are responsive to mechanical loading by pulsating fluid flow (PFF) on osteogenic stimulation in vitro. We found that ATMSCs show a bone cell-like response to fluid shear stress as a result of PFF after the stimulation of osteogenic differentiation by 1,25-dihydroxyvitamin D3. PFF increased nitric oxide production, as well as upregulated cyclooxygenase-2, but not cyclooxygenase-1, gene expression in osteogenically stimulated AT-MSCs. These data suggest that AT-MSCs acquire bone cell-like responsiveness to pulsating fluid shear stress on 1,25-dihydroxyvitamin D3-induced osteogenic differentiation. ATMSCs might be able to perform bone cell-specific functions during bone (re)modeling in vivo and, therefore, provide a promising new tool for bone tissue engineering.

Effect of Fluid Shear Stress on Migration of Vascular Smooth Muscle Cells in Cocultured Model

Migration of smooth muscle cells (SMCs) in hyperplasia is thought to have a correlation with blood flow conditions. In this study, the effect of shear stress applied to endothelial cells (ECs) on SMC migration was examined using a newly designed EC-SMC coculture model (CM), in which bovine SMCs and ECs were separated by a collagen layer and a membrane filter. After exposing the CM to shear stresses of 0.5, 1.0, or 1.5 Pa for 48 h, the number of SMCs migrating into the collagen layer was counted. Under static conditions, the migration of SMCs in the CM increased compared with SMCs cultured alone. Shear stress of 1.5 Pa significantly suppressed the SMC migration (p < 0.05) compared with the static CM. Media conditioned with the CM exposed to shear stress of 1.0 Pa (p < 0.05) and 1.5 Pa (p < 0.005) exhibited reduction in activated matrix metalloproteinase-2 (MMP-2) compared with the static CM, as analyzed by zymography. Addition of an inhibitor of nitric oxide (NO) synthase, N (omega)-nitro-L: -arginine methyl ester, to the media inhibited the effect of 1.5 Pa shear stress on SMC migration but MMP-2 activity was unaffected. These results suggest that physiological shear stress has protective roles in atherosclerogenesis.

Inhibition of sphingosine-1-phosphate- and vascular endothelial growth factor-induced endothelial cell chemotaxis by red grape skin polyphenols correlates with a decrease in early platelet-activating factor synthesis

Vascular endothelial growth factor (VEGF) and platelet-derived lipid sphingosine-1-phosphate (S1P) are two proinflammatory mediators which contribute to angiogenesis, in part through the synthesis of platelet-activating factor (PAF). The red grape skin polyphenolic extract (SGE) both prevents and inhibits angiogenesis in the Matrigel model, decreases the basal motility of endothelial and cancer cells, and reverses the chemotactic effect of S1P and VEGF on bovine aortic endothelial cells (BAECs) as well as the chemotactic effect of conditioned medium on human HT-1080 fibrosarcoma, human U-87 glioblastoma, and human DAOY medulloblastoma cells. Inhibition of VEGF- and S1P-mediated chemotaxis by SGE is associated with a down-regulation of ERK and p38/MAPK phosphorylation and a decreased in acute PAF synthesis. Notably, as do extracellular inhibitors of PAF receptor, SGE prevents S1P-induced PAF synthesis and the resulting activation of the S1P/endothelial differentiation gene-1 cascade. Given the key role of VEGF and S1P in inflammation, angiogenesis, and tumor invasion, SGE may therefore contribute to prevent (or to delay) the development of diseases associated with angiogenesis dysregulation, including cancer. The dual inhibition of S1P- and VEGF-mediated migration of endothelial cell and of serum-stimulated migration of U-87 cells suggests a usefulness of SGE against highly invasive human glioblastoma.

Endovascular Treatment of Aneurysms: Gene Expression of Neointimal Cells Recruited on the Embolic Agent and Evolution with Recurrence in an Experimental Model

PURPOSE

The authors attempted to identify genes associated with healing or recurrence after embolization in an aneurysm model in which neointima formation at the neck varies according to flow zones. A better understanding of the relationship between blood flow, molecular events, and healing or recurrence may provide future avenues to improve results of endovascular treatment of aneurysms.

METHODS

Bilateral carotid venous pouch aneurysms were constructed in 36 dogs and embolized with gelatin sponges. Angiography and pathological studies were performed at T0 and/or 3 weeks (n=22). Angiographic results and neointima formation were scored using a qualitative index applied to the distal (inflow) and proximal (outflow) zones of the neck. In 14 animals, mRNA expression 1 to 14 days after embolization at the proximal or distal segment of the sponge was analyzed by RT-PCR, attempting to correlate flow zones, gene expression, and neointima formation.

RESULTS

Aneurysms recurred at 3 weeks, as shown by significantly worse angiographic scores as compared to T0 (P<.01). Neointimal scores differed at pathology, with a more complete neointima at the proximal as compared to the distal aspect of the sponge at 3 weeks (P=.027). Embolization was followed by migration of CD31+, CD14+, smooth muscle alpha-actin+ (SMA+) cells that progressively expressed metalloproteinases (MMP-9,-12,-14), but stable or lesser, retarded expression of inhibitors (TIMP1-4). Growth factors (PDGF-BB, TGF-beta1, TNF-alpha, MCP-1 and Ang-1) were expressed at increasing levels, maximal at 7 to 14 days. Differences between distal and proximal zones were limited to increased expression of MMP-2 proximally (P<.035).

CONCLUSION

Gene expression after embolization is compatible with patterns associated with neointima formation. The authors have not identified key factors involved in recurrence.

Pathophysiologic mechanisms of persistent pulmonary hypertension of the newborn

Persistent pulmonary hypertension of the newborn (PPHN), among the most rapidly progressive and potentially fatal of vasculopathies, is a disorder of vascular transition from fetal to neonatal circulation, manifesting as hypoxemic respiratory failure. PPHN represents a common pathway of vascular injury activated by numerous perinatal stresses: hypoxia, hypoglycemia, cold stress, sepsis, and direct lung injury. As with other multifactorial diseases, a single inciting event may be augmented by multiple concurrent/subsequent phenomena that result in differing courses of disease progression. I review the various mechanisms of vascular injury involved in neonatal pulmonary hypertension: endothelial dysfunction, inflammation, hypoxia, and mechanical strain, in the context of downstream effects on pulmonary vascular endothelial-myocyte interactions and myocyte phenotypic plasticity.

Shear stress inhibits smooth muscle cell migration via nitric oxide-mediated downregulation of matrix metalloproteinase-2 activity

Vascular smooth muscle cell (SMC) migration is a hallmark of intimal hyperplasia (IH), the progression of which is affected by hemodynamic conditions at the diseased site. The realization that SMCs are exposed to blood flow in both denuded vessels (direct blood flow) and intact vessels (interstitial blood flow) motivated this study of the effects of fluid flow shear stress (SS) on SMC migration. Rat aortic SMCs were seeded onto Matrigel-coated cell culture inserts, and their migratory activity toward PDGF-BB when exposed to SS in a rotating disk apparatus was quantified. Four hours of either 10 or 20 dyn/cm2 SS significantly inhibited SMC migration to the bottom side of the insert. This inhibition was associated with downregulation of SMC matrix metalloproteinase (MMP)-2 activation. Four hours of 10 dyn/cm2 SS also drastically increased SMC production of NO. A NO synthase inhibitor (N(G)-nitro-L-arginine methyl ester; 100 microM) abolished the shear-induced increase in SMC NO production as well as the inhibition of migration and MMP-2 activity. A NO donor (S-nitroso-N-acetyl-penicillamine; 500 microM) suppressed SMC migration via the reduction of both total and active MMP-2 levels. Addition of 10 microM MMP-2 inhibitor I to inserts significantly reduced SMC migration. Western blots showed no effect of 4 h of 20 dyn/cm2 SS on SMC production of PDGF-AA, another chemical known to suppress SMC migration. Thus it appears that SS acts to suppress SMC migration by upregulating the cellular production of NO, which in turn inhibits MMP-2 activity.

Segmental vessel wall shear stress and neointimal formation after sirolimus-eluting stent implantation: physiological insights in a porcine coronary model

BACKGROUND

Low vessel-wall shear stress promotes atherosclerosis and restenosis. We conducted serial analysis of vessel-wall shear stress following placement of metal and sirolimus (SRL) stents to determine the relationship between shear stress and neointima.

METHODS

Serial quantitative coronary angiography, intracoronary ultrasound (IVUS), and Doppler flow analysis were performed at baseline, immediately poststent, and at 30 and 90 days on 16 stents (metal, n = 8; SRL, n = 8) implanted in the coronary arteries of eight miniswine. Segmental vessel-wall shear stress (dyn/cm2) was calculated at 10 sections within the stent and normalized to the average proximal and distal reference vessel shear stress using IVUS and hyperemic average peak flow velocity. At 90 days, histological analysis was completed to determine vessel-wall morphometry on corresponding sections from each stent.

RESULTS

Stent placement resulted in a similar degree of in-stent stenosis (-5% to 25%) and immediate post-in-stent shear stress. At 30 days, the IVUS neointimal cross-sectional area and percentage of area stenosis were significantly less in SRL (1.2+/-0.8 mm2; 12.7+/-8.5%) versus metal stents (2.3+/-0.4 mm2; 28.2+/-3.4%, P < .003). In-stent normalized shear stress was less for SRL (0.93+/-0.07) versus metal (1.07+/-0.08, P = .002) stents. At 90 days, the mean neointimal area was similar for the SRL (2.50+/-0.47 mm2) and metal stents (2.72+/-1.15 mm2). Linear regression documented a negative correlation between poststent shear stress and neointima for metal stents (r = .61, P < .0001). In the SRL stents, however, the post-in-stent shear stress had a positive correlation with neointima (r = .40, P = .0002).

CONCLUSIONS

The placement of oversized stents causes alteration of segmental vessel-wall shear stress, which appears to be an important physiological stimulus for neointimal formation, and may influence the pharmacodynamics of SRL-eluting stent in the porcine coronary model.

Laminar shear stress inhibits CXCR4 expression on endothelial cells: functional consequences for atherogenesis

Laminar shear stress (LSS) represents a major athero-protective stimulus. However, the mechanisms for this effect are poorly characterized. As chemokine receptors modulate endothelial cell functions, we hypothesized that at least some LSS effects on endothelial cells (ECs) may be due to LSS-dependent changes in chemokine receptor expression and function. Exposure of Human umbilical vein endothelial cells (HUVECs) to 15 dynes/cm2/sec(-1) LSS strongly inhibited CXC chemokine receptor 4 (CXCR4) expression at the transcriptional level and impaired stromal-derived factor (SDF)-1/CXCL12-driven chemotaxis. On the contrary, low shear stress (SS; 4 dynes/cm2/sec(-1)) only marginally affected CXCR4 expression when compared with static control cells. Differently from CXCR4, the expression of SDF-1 mRNA was not affected by LSS treatment. CXCR4 overexpression induced a dose-dependent endothelial cell apoptosis that was enhanced by SDF-1 treatment and was caspase-dependent. CXCR4 overexpression inhibited the LSS-mediated antiapoptotic effect on ECs and was associated to impairment of LSS-induced ERK1/2 phosphorylation. These findings suggest that LSS-induced CXCR4 down-regulation may contribute to endothelial cell survival. Interestingly, the expression of the proatherogenic chemokines MCP-1 and IL-8 was induced by SDF-1 treatment and by CXCR4 overexpression in HUVECs. Further, the known LSS-induced inhibition of MCP-1 expression was impaired in CXCR4 overexpressing ECs. Finally, CXCR4 was abundantly expressed by human atherosclerotic plaque endothelium that is exposed to low/absent shear stress, while it was poorly expressed by minimally diseased carotid artery endothelium. In conclusion, LSS-dependent CXCR4 down-regulation may contribute to atheroprotection by favoring the integrity of the endothelial barrier and by inhibiting MCP-1 and IL-8 expression.

Activation of MMP-2 in response to vascular injury is mediated by phosphatidylinositol 3-kinase-dependent expression of MT1-MMP

Phosphatidylinositol 3-kinase (PI3K) is required for smooth muscle cell (SMC) proliferation. This study reports that inhibitors of PI3K also prevent SMC migration and block neointimal hyperplasia in an organ culture model of restenosis. Inhibition of neointimal formation by LY-294002 was concentration and time dependent, with 10 muM yielding the maximal effect. Continuous exposure for at least the first 4-7 days of culture was essential for significant inhibition. To assess the role of matrix metalloproteinases (MMPs) in this process, we monitored MMP secretion by injured vessels in culture. Treatment with LY-294002 selectively reduced active MMP-2 in media samples according to zymography and Western blot analysis without concomitant changes in latent MMP-2. Parallel results with wortmannin indicate that MMP-2 activation is PI3K dependent. Previous research has shown a role for both furin and membrane-type 1 (MT1)-MMP (MMP-14) in the activation of MMP-2. The furin inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethylketone did not prevent MMP-2 activation after balloon angioplasty. In contrast, balloon angioplasty induced a significant increase in the levels of MT1-MMP, which was suppressed by LY-294002. No change in MT1-MMP mRNA was observed with LY-294002, because equivalent amounts of this mRNA were present in both injured and noninjured vessels. These results implicate PI3K-dependent regulation of MT1-MMP protein synthesis and subsequent activation of latent MMP-2 as critical events in neointimal hyperplasia after vascular injury.

Stent design properties and deployment ratio influence indexes of wall shear stress: a three-dimensional computational fluid dynamics investigation within a normal artery

Restenosis limits the effectiveness of stents, but the mechanisms responsible for this phenomenon remain incompletely described. Stent geometry and expansion during deployment produce alterations in vascular anatomy that may adversely affect wall shear stress (WSS) and correlate with neointimal hyperplasia. These considerations have been neglected in previous computational fluid dynamics models of stent hemodynamics. Thus we tested the hypothesis that deployment diameter and stent strut properties (e.g., number, width, and thickness) influence indexes of WSS predicted with three-dimensional computational fluid dynamics. Simulations were based on canine coronary artery diameter measurements. Stent-to-artery ratios of 1.1 or 1.2:1 were modeled, and computational vessels containing four or eight struts of two widths (0.197 or 0.329 mm) and two thicknesses (0.096 or 0.056 mm) subjected to an inlet velocity of 0.105 m/s were examined. WSS and spatial WSS gradients were calculated and expressed as a percentage of the stent and vessel area. Reducing strut thickness caused regions subjected to low WSS (<5 dyn/cm2) to decrease by ∼87%. Increasing the number of struts produced a 2.75-fold increase in exposure to low WSS. Reducing strut width also caused a modest increase in the area of the vessel experiencing low WSS. Use of a 1.2:1 deployment ratio increased exposure to low WSS by 12-fold compared with stents implanted in a 1.1:1 stent-to-vessel ratio. Thinner struts caused a modest reduction in the area of the vessel subjected to elevated WSS gradients, but values were similar for the other simulations. The results suggest that stent designs that reduce strut number and thickness are less likely to subject the vessel to distributions of WSS associated with neointimal hyperplasia.

CCN5 modulates the antiproliferative effect of heparin and regulates cell motility in vascular smooth muscle cells

Background

Vascular smooth muscle cell (VSMC) hyperplasia plays an important role in both chronic and acute vascular pathologies including atherosclerosis and restenosis. Considerable work has focused on the mechanisms regulating VSMC proliferation and motility. Earlier work in our lab revealed a novel growth arrest-specific (gas) gene induced in VSMC exposed to the antiproliferative agent heparin. This gene is a member of the CCN family and has been given the name CCN5. The objective of the present study is to elucidate the function of CCN5 protein and to explore its mechanism of action in VSMC.

Results

Using RNA interference (RNAi), we first demonstrate that CCN5 is required for the antiproliferative effect of heparin in VSMC. We also use this gene knockdown approach to show that CCN5 is an important negative regulator of motility. To explore the mechanism of action of CCN5 on VSMC motility, we use RNAi to demonstrate that knock down of CCN5 up regulates expression of matrix metalloproteinase-2 (MMP-2), an important stimulator of motility in VSMC. In addition, forced expression of CCN5 via adenovirus results in reduced MMP-2 activity, this also corroborates the gene knock down results. Finally, we show that loss of CCN5 expression in VSMC causes changes in VSMC morphology and cytoskeletal organization, including a reduction in the amount and macromolecular assembly of smooth muscle cell α-actin.

Conclusions

This work provides important new insights into the regulation of smooth muscle cell proliferation and motility by CCN5 and may aid the development of therapies for vascular diseases.

Pattern formation of vascular smooth muscle cells subject to nonuniform fluid shear stress: mediation by gradient of cell density

Smooth muscle cells (SMCs) are organized in various patterns in blood vessels. Whereas straight blood vessels mainly contain circumferentially aligned SMCs, curved blood vessels are composed of axially aligned SMCs in regions with vortex blood flow. The vortex flow-dependent feature of SMC alignment suggests a role for nonuniform fluid shear stress in regulating the pattern formation of SMCs. Here, we demonstrate that, in experimental models with vascular polymer implants designed for the observation of neointima formation and SMC migration under defined fluid shear stress, nonuniform shear stress possibly plays a role in regulating the direction of SMC migration and alignment in the neointima of the vascular implant. It was found that fluid shear stress inhibited cell growth, and the presence of nonuniform shear stress influenced the distribution of total cell density and induced the formation of cell density gradients, which in turn directed SMC migration and alignment. In contrast, uniform fluid shear stress in a control model influenced neither the distribution of total cell density nor the direction of SMC migration and alignment. In both the uniform and nonuniform shear models, the gradient of total cell density was consistent with the alignment of SMCs. These observations suggest that nonuniform shear stress may regulate the pattern formation of SMCs, possibly via mediating the gradient of cell density in the neointima of vascular polymer implants.

Pattern formation of vascular smooth muscle cells subject to nonuniform fluid shear stress: role of PDGF-beta receptor and Src

Blood vessels are subject to fluid shear stress, a hemodynamic factor that inhibits the mitogenic activities of vascular cells. The presence of nonuniform shear stress has been shown to exert graded suppression of cell proliferation and induces the formation of cell density gradients, which in turn regulate the direction of smooth muscle cell (SMC) migration and alignment. Here, we investigated the role of platelet-derived growth factor (PDGF)-beta receptor and Src in the regulation of such processes. In experimental models with vascular polymer implants, SMCs migrated from the vessel media into the neointima of the implant under defined fluid shear stress. In a nonuniform shear model, blood shear stress suppressed the expression of PDGF-beta receptor and the phosphorylation of Src in a shear level-dependent manner, resulting in the formation of mitogen gradients, which were consistent with the gradient of cell density as well as the alignment of SMCs. In contrast, uniform shear stress in a control model elicited an even influence on the activity of mitogenic molecules without modulating the uniformity of cell density and did not significantly influence the direction of SMC alignment. The suppression of the PDGF-beta receptor tyrosine kinase and Src with pharmacological substances diminished the gradients of mitogens and cell density and reduced the influence of nonuniform shear stress on SMC alignment. These observations suggest that PDGF-beta receptor and Src possibly serve as mediating factors in nonuniform shear-induced formation of cell density gradients and alignment of SMCs in the neointima of vascular polymer implants.

Oscillatory shear stress increases smooth muscle cell proliferation and Akt phosphorylation

PURPOSE

Hemodynamic forces affect smooth muscle cell (SMC) proliferation and migration both in vitro and in vivo. However, the effects of oscillatory shear stress (SS) on SMC proliferation and signal transduction pathways that control survival are not well described.

METHODS

Bovine aortic SMC were exposed to arterial levels of oscillatory SS (14 dyne/cm(2)) with an orbital shaker; control cells were exposed to static conditions (0 dyne/cm(2)). Cell number and (3)[H]thymidine incorporation were measured after 1, 3, or 5 days of SS. Activation of the Akt pathway was assessed with the Western blot technique. Specificity of the phosphatidylinositol 3-kinase (PI3K) pathway was determined with the Western blot technique with the inhibitors LY294002 (10 micromol/L) or wortmannin (25 nmol/L).

RESULTS

Arterial levels of oscillatory SS increased SMC cell number by 20.1 +/- 3.7% and (3)[H]thymidine incorporation by 33.4% +/- 6.8% at 5 days. To identify whether SS increased activity of the SMC survival pathway, Akt activation was measured. SMC exposed to SS demonstrated increased Akt phosphorylation compared with control cells, with maximal phosphorylation at 60 minutes. Both PI3K inhibitors specifically inhibited the increase in Akt phosphorylation in SMC exposed to oscillatory SS.

CONCLUSION

SMC directly respond to oscillatory SS by increasing DNA synthesis, proliferation, and activation of the PI3K-Akt signal transduction pathway. These results suggest a mechanism of SMC survival and proliferation in response to endothelial-denuding arterial injury.

mRNA expression of the five membrane-type matrix metalloproteinases MT1-MT5 in human prostatic cell lines and their down-regulation in human malignant prostatic tissue

BACKGROUND

The aim of this study was to assess the expression of membrane-type matrix metalloproteinases (MT-MMPs) 1-5 in the human prostatic cell lines BPH-1, LNCaP, DU 145, PC-3, in malignant and non-malignant prostatic tissue samples, and in epithelial cells cultured from these tissue samples.

METHODS

Matched malignant and non-malignant tissue specimens were obtained from 12 men with untreated prostate carcinoma after radical prostatectomy. Expression of mRNA for the five MT-MMPs was quantified by real-time PCR technique and normalized to the expression of the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH).

RESULTS

The expression of the five MT-MMPs was distinctly different not only between the prostate cell lines but also varied in the same cell line. There was a general higher expression of all MT-MMPs except for MT3-MMP in the androgen-insensitive cells DU 145 and PC-3 compared with that in the androgen-sensitive LNCaP cells. Their relatively high expression in the benign prostatic cell line BPH-1 and also in the primary cell cultures from malignant and non-malignant tissue samples argues against a simple association between MT-MMP expression and invasiveness. In malignant tissue samples and their corresponding cell cultures, the expression of most MT-MMPs was down-regulated in comparison to the normal counterparts. There was no correlation between tumor classification data and the MT-MMP expression results.

CONCLUSIONS

In contrast to other carcinoma, the down-regulation of most MT-MMPs is typical for prostate carcinoma. It seems to occur mainly in epithelial cells and has to be examined as special characteristic of this tumor entity in further studies.

CCN5 is a growth arrest-specific gene that regulates smooth muscle cell proliferation and motility

Vascular smooth muscle cell (VSMC) hyperplasia plays an important role in both chronic and acute vascular pathologies. Considerable work has focused on the mechanisms regulating VSMC growth and the search for agents that could suppress VSMC hyperproliferation. One of the several inhibitors studied is the glycosaminoglycan heparin, which inhibits VSMC proliferation and migration both in cell culture and in animal models (Mishra-Gorur K, Delmolino LM, Castellot Jr JJ: Biological functions of heparan sulfate and heparan sulfate proteoglycans. Trends Glycosci Glycotechnol 1998, 10:193-210). To aid our understanding of the anti-proliferative mechanism of action of heparin, we used a subtractive hybridization approach to isolate and characterize a novel growth arrest-specific (gas) gene induced in VSMCs exposed to heparin (Delmolino LM, Stearns NA, Castellot Jr JJ: Heparin induces a member of the CCN family which has characteristics of a growth arrest specific gene. Mol Biol Cell 1997, 8:287a and Delmolino LM, Stearns NA, Castellot Jr JJ: COP-1, a member of the CCN family, is a heparin-induced growth arrest specific gene in vascular smooth muscle cells. J Cell Physiol 2001, 188:45-55). This gene is a member of the cysteine-rich 61/connective tissue growth factor/nephroblastoma-overexpressed (CCN) family and has been given the name CCN5. In this report, we provide functional evidence that CCN5 can inhibit VSMC proliferation, motility, and invasiveness. In contrast, adhesion and apoptosis are unaffected by CCN5 in this cell type. We also significantly extend previous data from our laboratory that suggests CCN5 is a growth arrest-specific (gas) gene. Furthermore, we map for the first time the cellular localization of CCN5 protein in cultured VSMCs. We also examine uninjured and balloon-injured rat carotid arteries for CCN5 expression. The results from the in vitro and in vivo localization studies show that CCN5 is temporally and spatially expressed in a manner consistent with a role in regulating proliferation, motility, and invasiveness of VSMCs.

Transcription factor Sp1 phosphorylation induced by shear stress inhibits membrane type 1-matrix metalloproteinase expression in endothelium

Membrane type 1-matrix metalloproteinase (MT1-MMP) plays a key role in endothelial cell migration, matrix remodeling, and angiogenesis. Previous studies demonstrated that a mechanical force, cyclic strain, increases MT1-MMP expression by displacing Sp1 with increased Egr-1 expression and binding to the promoter site. However, the effect of shear stress (SS) on MT1-MMP expression is poorly understood. Although Egr-1 mRNA transcription and protein was induced (7.6-fold) in response to SS (n = 5, 0-8 h, p < 0.05), SS decreased MT1-MMP mRNA transcription and protein levels in a time-dependent fashion (10, 50, and 90% reduction at 1, 4, and 8 h, respectively; n = 5, p < 0.05). Egr-1 protein was increased after SS and cyclic strain, but Sp1 was serine-phosphorylated only after SS. SS increased Sp1 DNA binding (3.8-, 5.8-, and 2.4-fold increase at 1, 4, and 8 h, respectively; n = 5, p < 0.05) that was inhibitable by calf intestinal phosphatase. Thus, SS inhibits MT1-MMP expression despite Egr-1 up-regulation by inducing the serine phosphorylation of Sp1, which in turn increases its binding affinity for its site on the MT1-MMP promoter, reducing the ability of Egr-1 to displace it. These data illustrate the complex control of microvascular endothelial cell MT1-MMP expression in response to distinct environmental stimuli (cyclic strain versus shear stress), consisting of both the modulation of specific transcription factor expression (Egr-1) as well as transcription factor post-translational modification (serine phosphorylation of Sp1).

Soluble Fas ligand and atherosclerosis in hypertensive patients

BACKGROUND

The Fas-Fas ligand (FasL) system is involved in apoptosis in many types of cells. Recently, the expression of FasL on endothelial cells was reported. FasL is cleaved by a metalloproteinase and released in serum as soluble FasL (sFasL). Vasoactive substances, including metalloproteinase, are modulated by endothelial dysfunction. Advanced atherosclerosis and impaired endothelial function are seen in hypertensive patients. The inflammatory response has an important role in the development of atherosclerosis, whereas C-reactive protein (CRP) is associated with the presence and severity of atherosclerosis.

OBJECTIVE

To measure the intima-media thickness of the common carotid artery and evaluate the relationship between atherosclerosis and serum sFasL concentrations in hypertensive patients.

PATIENTS AND MAIN OUTCOME MEASURES

Forty-seven patients with hypertension participated in the study. The intima-media thickness of the common carotid artery was evaluated by ultrasound imaging. Serum concentrations of sFasL were measured by enzyme-linked immunosorbent assay.

RESULTS

Intima-media thickness correlated positively with age (r = 0.362, P = 0.012) and sFasL concentrations (r =0.332, P = 0.022), and negatively with creatinine clearance (r = -0.399, P = 0.0055). A general linear model analysis with atherosclerotic risk factors and sFasL revealed that age, sFasL, high-density lipoprotein-cholesterol and systolic blood pressure were significantly associated with intima-media thickness. Furthermore, we demonstrated that serum sFasL is directly associated with CRP concentration (r = 0.316, P = 0.030).

CONCLUSIONS

These results indicated that serum sFasL concentration is associated with atherosclerosis and inflammatory disease, in patients with hypertension.