Role of endogenous Fas (CD95/Apo-1) ligand in balloon-induced apoptosis, inflammation, and neointima formation

G6PD maintains the VSMC synthetic phenotype and accelerates vascular neointimal hyperplasia by inhibiting the VDAC1-Bax-mediated mitochondrial apoptosis pathway

BACKGROUND

Glucose-6-phosphate dehydrogenase (G6PD) plays an important role in vascular smooth muscle cell (VSMC) phenotypic switching, which is an early pathogenic event in various vascular remodeling diseases (VRDs). However, the underlying mechanism is not fully understood.

METHODS

An IP‒LC‒MS/MS assay was conducted to identify new binding partners of G6PD involved in the regulation of VSMC phenotypic switching under platelet-derived growth factor-BB (PDGF-BB) stimulation. Co-IP, GST pull-down, and immunofluorescence colocalization were employed to clarify the interaction between G6PD and voltage-dependent anion-selective channel protein 1 (VDAC1). The molecular mechanisms involved were elucidated by examining the interaction between VDAC1 and apoptosis-related biomarkers, as well as the oligomerization state of VDAC1.

RESULTS

The G6PD level was significantly elevated and positively correlated with the synthetic characteristics of VSMCs induced by PDGF-BB. We identified VDAC1 as a novel G6PD-interacting molecule essential for apoptosis. Specifically, the G6PD-NTD region was found to predominantly contribute to this interaction. G6PD promotes VSMC survival and accelerates vascular neointimal hyperplasia by inhibiting VSMC apoptosis. Mechanistically, G6PD interacts with VDAC1 upon stimulation with PDGF-BB. By competing with Bax for VDAC1 binding, G6PD reduces VDAC1 oligomerization and counteracts VDAC1-Bax-mediated apoptosis, thereby accelerating neointimal hyperplasia.

CONCLUSION

Our study showed that the G6PD-VDAC1-Bax axis is a vital switch in VSMC apoptosis and is essential for VSMC phenotypic switching and neointimal hyperplasia, providing mechanistic insight into early VRDs.

Apoptosis and Cell Proliferation Markers in Inflammatory-Fibroproliferative Diseases of the Vessel Wall (Review)

Apoptosis is the main feature of inflammatory-fibroproliferative disorders of the vessel wall. Studies in animal models have shown that smooth muscle cells (SMCs) cultured from endarterectomy specimens from the affected area proliferate more slowly and display higher apoptotic indices than SMCs derived from the normal vessel wall. Apoptotic cells were found in the destabilized atherosclerotic plaques, as well as in the samples with restenosis of the reconstruction area.

Injury to the vessel wall causes two waves of apoptosis. The first wave is the rapid apoptosis in the media that occurs within a few hours after injury and leads to a marked reduction in the number of vascular wall cells. The second wave of apoptosis occurs much later (from several days to weeks) and is limited by the SMCs within the developing neointima. Up to 14% of the neointimal SMCs undergo apoptosis 20 days after balloon angioplasty. Ligation of the external carotid artery in a rabbit model led to a marked decrease in blood flow in the common carotid artery, which correlated with the increased apoptosis of endothelial cells and SMCs.

Angioplasty-induced death of SMCs is regulated by a redox-sensitive signaling pathway, and topical administration of antioxidants can minimize vascular cell loss. On the whole, studies show that apoptosis is prevalent in vascular lesions, controlling the viability of both inflammatory and vascular cells, determining the cellular composition of the vessel wall. The main markers of apoptosis (Fas, Fas ligand, p53, Bcl-2, Bax) and cell proliferation (toll receptor) have been considered in the current review.

A new Mfn-2 related synthetic peptide promotes vascular smooth muscle cell apoptosis via regulating the mitochondrial apoptotic pathway by inhibiting Akt signaling

Background

Restenosis after angioplasty is a major challenge for the treatment of coronary artery diseases. Facilitation of vascular smooth muscle cell (VSMC) apoptosis may be an attractive approach to decrease the incidence of restenosis. We synthesized a 16-amino acid mitofusin-2 (Mfn-2) gene related peptide (MRSP) based on the sequence of the p21^ras signature motif, the smallest functional sequence of the Mfn-2 gene with proapoptotic properties in VSMC. We investigated whether MRSP enhanced apoptotic activities to inhibit VSMC accumulation and neointimal hyperplasia in rats with carotid balloon injury.

Methods

VSMCs were treated with different concentrations of MRSP, the PI3K agonist 740 Y-P and the inhibitor LY294002. Cell apoptosis and related pathway molecules were assessed. MRSP was also given to rats with carotid artery balloon injury. Neointimal hyperplasia and cell apoptotic pathways were detected.

Results

In vitro experiments revealed that MRSP treatment significantly increased VSMC apoptosis and induced increases in procaspase-9 cleavage, caspase-3 activation, cytochrome c release from mitochondria to the cytoplasm and the Bax/Bcl-2 ratio but not caspase-8 expression, indicating that the mitochondrial apoptotic cascade was activated by MRSP, which might be attributed to suppression of the PI3K/Akt signaling pathway. We further found that the PI3K agonist 740 Y-P prevented and that the inhibitor LY294002 strengthened the proapoptotic effects of MRSP. MRSP strongly inhibited neointimal hyperplasia and VSMC accumulation, but increased VSMC apoptosis in the vascular wall after balloon injury. Moreover, MRSP substantially enhanced Bax and cleaved caspase-3 expression and decreased Bcl-2 levels in intima, accompanied by decreased levels of phosphorylated Akt and PI3K in vivo.

Conclusions

Taken together, the present study showed that MRSP treatment results in a strong proapoptotic effect by activating the mitochondrial apoptotic cascade through suppression of the PI3K/Akt pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03064-1.

Galectin-3 Modulates Macrophage Activation and Contributes Smooth Muscle Cells Apoptosis in Abdominal Aortic Aneurysm Pathogenesis

Galectin-3 (Gal-3) is a 26-kDa lectin that regulates many aspects of inflammatory cell behavior. We assessed the hypothesis that increased levels of Gal-3 contribute to abdominal aortic aneurysm (AAA) progression by enhancing monocyte chemoattraction through macrophage activation. We analyzed the plasma levels of Gal-3 in 76 patients with AAA (AAA group) and 97 controls (CTL group) as well as in angiotensin II (Ang-II)-infused ApoE knockout mice. Additionally, conditioned media (CM) were used to polarize THP-1 monocyte to M1 macrophages with or without Gal-3 inhibition through small interfering RNA targeted deletion to investigate whether Gal-3 inhibition could attenuate macrophage-induced inflammation and smooth muscle cell (SMC) apoptosis. Our results showed a markedly increased expression of Gal-3 in the plasma and aorta in the AAA patients and experimental mice compared with the CTL group. An in vitro study demonstrated that the M1 cells exhibited increased Gal-3 expression. Gal-3 inhibition markedly decreased the quantity of macrophage-induced inflammatory regulators, including IL-8, TNF-α, and IL-1β, as well as messenger RNA expression and MMP-9 activity. Moreover, Gal-3-deficient CM weakened SMC apoptosis through Fas activation. These findings prove that Gal-3 may contribute to AAA progression by the activation of inflammatory macrophages, thereby promoting SMC apoptosis.

Synthetic E-selectin prevents postoperative vascular restenosis by inhibiting nuclear factor κB in rats

During the development of postoperative vascular restenosis, the aberrant proliferation of vascular smooth muscle cells (VSMCs) is a critical event resulting in intimal hyperplasia. Inflammatory responses involving the activation of nuclear factor (NF)-κB are among the major molecular processes underlying restenosis. The present study aimed to investigate the roles of NF-κB in VSMC proliferation and restenosis following vascular anastomosis, as well as to evaluate the potential of synthetic E-selectin to downregulate NF-κB and thus inhibit vascular hyperplasia. A total of 72 adult male Sprague-Dawley rats were randomly assigned to three groups: Control, operation and treatment groups. Rats in the operation and treatment groups received longitudinal incisions in the right carotid arteries, which were closed using interrupted sutures. Following vascular anastomosis, synthetic E-selectin (10 mg/kg), or an equal volume of saline, was immediately injected into the right femoral vein of rats in the treatment and operation groups, respectively. Following surgery, the mRNA and protein expression levels of NF-κB at the site of anastomosis, the levels of tumor necrosis factor-α and interleukin-6 in the serum, NF-κB binding activity, and the presence of proliferating cell nuclear antigen (PCNA)-positive cells were evaluated by western blotting, reverse transcription-quantitative polymerase chain reaction, ELISA, electrophoretic mobility shift assay and immunofluorescence staining. The present results demonstrated that following treatment with synthetic E-selectin, the levels of NF-κB and the inflammatory response, as well as the presence of PCNA-positive cells, were significantly reduced (P<0.01). In conclusion, the results of the present study suggested that synthetic E-selectin may exert anti-inflammatory and anti-restenotic effects following vascular anastomosis in vivo.

C1q/TNF-related protein 1 prevents neointimal formation after arterial injury

BACKGROUND AND AIMS

Obesity contributes to the progression of vascular disorders. C1q/TNF-related protein (CTRP) 1 is a circulating adipokine, which is upregulated in obese complications including coronary artery disease. Here, we investigated the role of CTRP1 in regulation of vascular remodeling after mechanical injury and evaluated its potential mechanism.

METHODS

Mice were subjected to wire-induced injury of left femoral arteries. An adenoviral vector encoding CTRP1 (Ad-CTRP1) or β-galactosidase as a control was injected into the jugular vein of mice 3 days prior to surgery.

RESULTS

Systemic administration of Ad-CTRP1 to wild-type mice led to reduction of the neointimal thickening after wire-induced arterial injury and the number of bromodeoxyuridine-positive cells in injured vessels as compared with treatment with control vectors. Treatment of vascular smooth muscle cells (VSMCs) with CTRP1 protein attenuated proliferative activity and ERK phosphorylation in response to PDGF-BB. CTRP1 treatment increased cyclic AMP (cAMP) levels in VSMCs, and inhibition of adenylyl cyclase reversed the inhibitory effect of CTRP1 on VSMC growth and ERK phosphorylation. Antagonization of sphingosine-1-phosphaterote (S1P) receptor 2 blocked the effects of CTRP1 on cAMP production and VSMC growth. Furthermore, CTRP1-knockout mice had enhanced neointimal thickening following injury and increased numbers of proliferating cells in neointima compared to control WT mice.

CONCLUSIONS

These findings indicate that CTRP1 functions to prevent the development of pathological vascular remodeling by reducing VSMC growth through the cAMP-dependent pathway.

Vascular Proteomics Reveal Novel Proteins Involved in SMC Phenotypic Change: OLR1 as a SMC Receptor Regulating Proliferation and Inflammatory Response

Neointimal hyperplasia of vascular smooth muscle cells (VSMC) plays a critical role in atherosclerotic plaque formation and in-stent restenosis, but the underlying mechanisms are still incompletely understood. We performed a proteomics study to identify novel signaling molecules organizing the VSMC hyperplasia. The differential proteomics analysis in a balloon-induced injury model of rat carotid artery revealed that the expressions of 44 proteins are changed within 3 days post injury. The combination of cellular function assays and a protein network analysis further demonstrated that 27 out of 44 proteins constitute key signaling networks orchestrating the phenotypic change of VSMC from contractile to epithelial-like synthetic. Among the list of proteins, the in vivo validation specifically revealed that six proteins (Rab15, ITR, OLR1, PDHβ, PTPε) are positive regulators for VSMC hyperplasia. In particular, the OLR1 played dual roles in the VSMC hyperplasia by directly mediating oxidized LDL-induced monocyte adhesion via NF-κB activation and by assisting the PDGF-induced proliferation/migration. Importantly, OLR1 and PDGFRβ were associated in close proximity in the plasma membrane. Thus, this study elicits the protein network organizing the phenotypic change of VSMC in the vascular injury diseases such as atherosclerosis and discovers OLR1 as a novel molecular link between the proliferative and inflammatory responses of VSMCs.

Inhibition of neointimal hyperplasia in rats treated with atorvastatin after carotid artery injury may be mainly associated with down-regulation of survivin and Fas expression

CONTEXT

Atorvastatin is a member of the drug class known as statins, which is used for lowering blood cholesterol.

OBJECTIVE

The present study investigates the effect and mechanism of atorvastatin on neointimal hyperplasia after carotid artery injury (CAI) of rat.

MATERIALS AND METHODS

Fifty male rats were randomly divided into four groups: control group, sham-operated group, model group, and atorvastatin treatment group. The treatment group was fed with atorvastatin (10 mg/kg) with gastro-gavage at 5 p.m. every day for 28 d after surgery. The control group, model group, and sham-operated group were fed with the same volume of distilled water instead. The proliferations of intimal and medial layers were evaluated by hematoxylin & eosin (H&E) staining. The apoptosis of vascular smooth muscle cells (VSMCs) was determined by terminal deoxynucleotidyl transferased UTP nick end labeling (TUNEL) staining. Plasma concentrations of survivin and sFas were detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Atorvastatin reduced neointimal formation and increased apoptosis of VSMCs in neointima. VSMCs apoptosis emerged at 3 d (8.42 ± 0.449 μm) and the intimal proliferation peaked by the end of 14 d (41.58 ± 1.64 μm). The plasma levels of survivin and sFas were gradually increased with the neointimal hyperplasia and increasingly decreased after atorvastatin treatment. The plasma levels of survivin and sFas in rats were elevated at 3 d (464.80 ± 105.27 pg/ml and 3256.00 ± 478.20 pg/ml, respectively), reached the peak of survivin at 14 d (1089.20 ± 232.32 pg/ml) and sFas at 7 d (4362.00 ± 639.92 pg/ml) and decreased at 28 d (562.00 ± 90.11 pg/ml and 2148.00 ± 257.14 pg/ml, respectively) in the model group. Compared with the model group, the atorvastatin treatment group has significantly less neointimal hyperplasia and more apoptosis of VSMCs.

CONCLUSIONS

Atorvastatin can inhibit neointimal hyperplasia and promote SMCs apoptosis in neointimal layers, which may be mainly associated with down-regulation of survivin and Fas expression after CAI of rat.

Apoptosis and inflammation associated gene expressions in monocrotaline-induced pulmonary hypertensive rats after bosentan treatment

Background and Objectives

Vascular wall remodeling in pulmonary hypertension can be caused by an aberration in the normal balance between proliferation and apoptosis of endothelial cell in the pulmonary artery. The objective of this study was to evaluate the effect of bosentan on apoptosis in monocrotaline (MCT)-induced pulmonary hypertension.

Materials and Methods

Sprague-Dawley rats were divided into three groups: control (C) group, M group (MCT 60 mg/kg) and B group (MCT 60 mg/kg plus bosentan 20 mg/day orally). Gene expressions of Bcl (B cell leukemia/lymphoma)-2, caspase-3, complement component (C)-6, vascular endothelial growth factor (VEGF), interleukin (IL)-6 and tumor necrosis factor-alpha (TNF-α) were analyzed by real time polymerase chain reaction and western blot analysis.

Results

The messenger ribonucleic acid (mRNA) expressions of caspase-3 and VEGF were significantly increased in the M group compared with the C group, and significantly decreased in the B group compared with the M group in week 4. mRNA expression of IL-6 was significantly decreased in weeks 1, 2, and 4 in the B group compared with the M group. mRNA expression of TNF-α was significantly decreased on day 5 and in weeks 1 and 2 in the B group compared with the M group.

Conclusion

Bosentan may have potential for preventing apoptosis and inflammation.

Gene expression in the vascular wall of the aortic arch in spontaneously hypertensive hyperlipidemic model rats using DNA microarray analysis

AIMS

In recent years, there has been an increase in patients with arteriosclerosis and the risk of lifestyle-related diseases. However, the pathogenesis and medication of atherosclerosis have not been elucidated. We developed a rat model of lifestyle-related diseases by feeding a high-fat diet and 30% sucrose solution (HFDS) to spontaneously hypertensive hyperlipidemic rats (SHHR) and reported that this model is a useful model of early atherosclerosis. In order to elucidate the pathogenesis of early atherosclerosis, we searched for atherosclerosis-related genes by microarray analysis using the aortic arch rat model of lifestyle-related diseases.

MAIN METHODS

Four-month-old male Sprague-Dawley rats and SHHR were each divided into two normal diet (ND) groups and two HFDS groups. After a four-month treatment, the expression of mRNA in the aortic arch was detected using the oligo DNA microarray one-color method and quantified using real-time PCR.

KEY FINDINGS

In this study, we detected 39 genes in microarray analysis. Esm1, Retnlb Mkks, and Grem2 showed particularly marked changes in gene expression in the SHHR-HFDS group. Compared with the SD-ND group, the SHHR-HFDS group had an increase in Mkks gene expression of about 26-fold and an approximately 22-fold increase in the expression of Grem2. Similarly, the expression of Esm1 increased by about 12-fold and that of Retnlg by about 10-fold as shown by quantitative real-time PCR.

SIGNIFICANCE

This study suggested that these four genes might be important in early atherosclerosis development.

The sFas/sFasL ratio as a novel marker of inflammation in children with chronic kidney disease

OBJECTIVES

Membrane Fas-FasL binding triggers apoptosis, enhanced in chronic kidney disease (CKD). However, the role of soluble forms, sFas and sFasL, remains unclear. Matrix metalloproteinases (MMPs) are known converters of sFasL from the membrane-bound form, but there are no data on relations between sFas/sFasL, MMPs, their tissue inhibitors (TIMPs) or inflammatory/endothelial factors in CKD patients. We aimed to evaluate correlations between sFas, sFasL, MMP-2, MMP-7, MMP-9, TIMP-1, TIMP-2, and the role of sFas/sFasL as markers of inflammation and endothelial dysfunction.

METHODS

Serum concentrations of sFas, sFasL, MMPs, TIMPs, hsCRP, IL-4 and sE-selectin were assessed by ELISA in 65 CKD children and in 30 controls.

RESULTS

sFas, sFasL, sFas/sFasL ratio, MMPs, TIMPs, sE-selectin and IL-4 levels were significantly enhanced in CKD patients vs. controls. sFas/sFasL ratio correlated with inflammatory/endothelial markers. sE-selectin was the best predictor of sFas and sFas/sFasL ratio. MMP-9, TIMP-1 and IL-4 predicted most accurately the sFasL concentrations.

CONCLUSIONS

CKD children present with progressive sFas/sFasL dysfunction. Relations between sFas/sFasL, MMPs and TIMPs indicate the potential role of metalloproteinases in the sFas/sFasL regulation. Correlations with hsCRP, sE-selectin and IL-4 suggest that sFas/sFasL ratio may become a new marker of inflammation and endothelial dysfunction in children with CKD.

Cannabinoid receptor CB2 protects against balloon-induced neointima formation

Cannabinoid receptor CB(2) activation inhibits inflammatory proliferation and migration of vascular smooth muscle cells in vitro. The potential in vivo relevance of these findings is unclear. We performed carotid balloon distension injury in hypercholesterolemic apolipoprotein E knockout (ApoE(-/-)) mice receiving daily intraperitoneal injection of the CB(2) agonist JWH133 (5 mg/kg) or vehicle, with the first injection given 30 min before injury. Alternatively, we subjected CB(2)(-/-) and wild-type (WT) mice to balloon injury. We determined CB(2) mRNA and protein expression in dilated arteries of ApoE(-/-) mice. Neointima formation was assessed histologically. We used bone marrow-derived murine CB(2)(-/-) and WT macrophages to study adhesion to plastic, fibronectin, or collagen, and migration was assayed by modified Boyden chamber. Aortic smooth muscle cells were isolated to determine in vitro proliferation rates. We found increased vascular CB(2) expression in ApoE(-/-) mice in response to balloon injury. Seven to twenty-one days after dilatation, injured vessels of JWH133-treated mice had less intimal nuclei numbers as well as intimal and medial areas, associated with less staining for proliferating cells, smooth muscle cells, and macrophages. Complete endothelial repair was observed after 14 days in both JWH133- and vehicle-treated mice. CB(2) deficiency resulted in increased intima formation compared with WT, whereas JWH133 did not affect intimal formation in CB(2)(-/-) mice. Apoptosis rates assessed by in situ terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling staining 1 h postballooning were significantly higher in the CB(2) knockouts. In vitro, bone marrow-derived CB(2)(-/-) macrophages showed enhanced adherence and migration compared with WT cells and elevated mRNA levels of adhesion molecules, chemokine receptors CCR1 and 5, and chemokine CCL2. Proliferation rates were significantly increased in CB(2)(-/-) smooth muscle cells compared with WT. In conclusion, pharmacological activation or genetic deletion of CB(2) receptors modulate neointima formation via protective effects in macrophages and smooth muscle cells.

Matrix metalloproteinases and soluble Fas/FasL system as novel regulators of apoptosis in children and young adults on chronic dialysis

The system of membrane receptor Fas and its ligand FasL compose one of the main pathways triggering apoptosis. However, the role of their soluble forms has not been clarified yet. Although sFasL can be converted from the membrane-bound form by matrix metalloproteinases (MMPs), there are no data on relations between sFas/sFasL, MMPs and their tissue inhibitors (TIMPs) in patients on chronic dialysis—neither children nor adults. The aim of our study was to evaluate serum concentrations of sFas, sFasL, and their potential regulators (MMP-2, MMP-7, MMP-9, TIMP-1, TIMP-2), in children and young adults chronically dialyzed. Twenty-two children on automated peritoneal dialysis (APD), 19 patients on hemodialysis (HD) and 30 controls were examined. Serum concentrations of sFas, sFasL, MMPs and TIMPs were assessed by ELISA. Median values of sFas, sFasL, sFas/sFasL ratio, MMP-2, MMP-7, MMP-9, TIMP-1 and TIMP-2 were significantly elevated in all dialyzed patients vs. controls, the highest values being observed in subjects on HD. A single HD session caused the decrease in values of all parameters to the levels below those seen in children on APD. Regression analysis revealed that MMP-7 and TIMP-1 were the best predictors of sFas and sFasL concentrations. Children and young adults on chronic dialysis are prone to sFas/sFasL system dysfunction, more pronounced in patients on hemodialysis. The correlations between sFas/sFasL and examined enzymes suggest that MMPs and TIMPs take part in the regulation of cell death in the pediatric population on chronic dialysis, triggering both anti- (sFas) and pro-apoptotic (sFasL) mechanisms.

A link between smooth muscle cell death and extracellular matrix degradation during vascular atrophy

OBJECTIVE

High blood flow induces neointimal atrophy in polytetrafluoroethylene (PTFE) aortoiliac grafts and a tight external PTFE wrap of the iliac artery induces medial atrophy. In both nonhuman primate models, atrophy with loss of smooth muscle cells and extracellular matrix (ECM) begins at ≤4 days. We hypothesized that matrix loss would be linked to cell death, but the factors and mechanisms involved are not known. The purpose of this study was to determine commonly regulated genes in these two models, which we hypothesized would be a small set of genes that might be key regulators of vascular atrophy.

METHODS

DNA microarray analysis (Sentrix Human Ref 8; Illumina, San Diego, Calif; ∼23,000 genes) was performed on arterial tissue from the wrap model (n = 9) and graft neointima from the graft model (n = 5) 1 day after wrapping or the switch to high flow, respectively. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) was also performed. Expression of this vascular atrophy gene set was also studied after Fas ligand-induced cell death in cultured smooth muscle cells and organ cultured arteries.

RESULTS

Microarray analysis showed 15 genes were regulated in the same direction in both atrophy models: 9 upregulated and 6 downregulated. Seven of nine upregulated genes were confirmed by qRT-PCR in both models. Upregulated genes included the ECM-degrading enzymes ADAMTS4, tissue plasminogen activator (PLAT), and hyaluronidase 2; possible growth regulatory factors, including chromosome 8 open reading frame 4 and leucine-rich repeat family containing 8; a differentiation regulatory factor (musculoskeletal embryonic nuclear protein 1); a dead cell removal factor (ficolin 3); and a prostaglandin transporter (solute carrier organic anion transporter family member 2A1). Five downregulated genes were confirmed but only in one or the other model. Of the seven upregulated genes, ADAMTS4, PLAT, hyaluronidase 2, solute carrier organic anion transporter family member 2A1, leucine-rich repeat family containing 8, and chromosome 8 open reading frame 4 were also upregulated in vitro in cultured smooth muscle cells or cultured iliac artery by treatment with FasL, which causes cell death. However, blockade of caspase activity with Z-VAD inhibited FasL-mediated cell death, but not gene induction.

CONCLUSION

Seven gene products were upregulated in two distinctly different in vivo nonhuman primate vascular atrophy models. Induction of cell death by FasL in vitro induced six of these genes, including the ECM-degrading factors ADAMTS4, hyaluronidase 2, and PLAT, suggesting a mechanism by which the program of tissue atrophy coordinately removes extracellular matrix as cells die. These genes may be key regulators of vascular atrophy.

High soluble Fas and soluble Fas Ligand serum levels before stent implantation are protective against restenosis

Percutaneous coronary intervention (PCI) represents the most important treatment of coronary artery stenosis today. But instent restenosis (ISR) is a limitation for the outcome. Fas and Fas Ligand have been implicated in apoptosis and vessel wall inflammation. Their role in ISR is not known so far. In this prospective study we studied 137 patients with stable coronary artery disease who underwent elective PCI. Blood samples were taken directly before and 24 hours after PCI. Soluble (s)Fas and sFas Ligand serum levels were measured by ELISA. Restenosis was evaluated six to eight months later either by coronary angiography or by exercise testing. During the follow-up period, 18 patients (13%) developed ISR. At baseline, patients with ISR had significantly lower median sFas, as well as sFas Ligand levels compared to patients without ISR (sFAS: ISR 492 pg/ml, no ISR 967 pg/ml, p=0.014; sFAS Ligand: ISR: 26 pg/ml, no ISR: 42 pg/ml, p=0.001). After PCI median sFas levels significantly decreased in patients with ISR compared to patients without ISR [ISR: -152 pg/ml (IQR -36 to -227), no ISR: -38 pg/ml (IQR -173 to +150 pg/ml), p=0.03]. sFas Ligand levels after PCI significantly increased in ISR patients compared to patients without ISR [ISR: 14 pg/ml (IQR -3 to +26 pg/ml), no ISR -6 pg/ml (IQR -22 to +21 pg/ml), p=0.014]. In conclusion, sFas and sFas Ligand seem to be associated with the development of ISR. Determination of serum levels before and after PCI might help identifying patients at higher risk of ISR.

Angiotensin II-inducible smooth muscle cell apoptosis involves the angiotensin II type 2 receptor, GATA-6 activation, and FasL-Fas engagement

RATIONALE

Fas ligand (FasL)-mediated smooth muscle cell (SMC) apoptosis within the vulnerable plaque may lead to plaque instability and rupture, events that underlie myocardial infarction and stroke.

OBJECTIVE

The molecular mechanisms underlying FasL transcription and FasL-dependent SMC apoptosis were investigated in this study in vitro and in vivo.

METHODS AND RESULTS

We demonstrate that GATA-6, the predominant GATA family member expressed in SMCs, stimulates SMC apoptosis in an extracellular FasL-dependent manner. Both GATA-6 and FasL were inducibly and transiently expressed following balloon injury to rat carotid arteries. We identified two potential GATA binding in the FasL promoter and demonstrated using DNA binding and chromatin immunoprecipitation assays that GATA-6 regulates FasL through one ((-298)TTATCA(-303)) but not both these elements. Angiotensin II (Ang II) stimulated expression of both GATA-6 and FasL. Ang II increased SMC apoptosis in an Ang II type 2 receptor-, caspase 8-, and FasL-dependent fashion. GATA-6 activation was MEK-ERK1/2- and JNK-dependent, and GATA-6 small interfering RNA blocked Ang II-inducible FasL expression and SMC apoptosis. Administration of Ang II to rats increased FasL expression and apoptosis in carotid artery SMCs in an Ang II type 2 receptor- and GATA-6-dependent manner.

CONCLUSIONS

This study provides new insights into the transcriptional events underpinning FasL-dependent SMC apoptosis after exposure to Ang II.

Cardiovascular inflammation and lesion cell apoptosis: a novel connection via the interferon-inducible immunoproteasome

OBJECTIVE

Increasing evidence suggests that chronic inflammation contributes to atherogenesis, and that acute inflammatory events cause plaque rupture, thrombosis, and myocardial infarction. The present studies examined how inflammatory factors, such as interferon-gamma (IFNgamma), cause increased sensitivity to apoptosis in vascular lesion cells.

METHODS AND RESULTS

Cells from the fibrous cap of human atherosclerotic lesions were sensitized by interferon-gamma (IFNgamma) to Fas-induced apoptosis, in a Bcl-X(L) reversible manner. Microarray profiling identified 72 INFgamma-induced transcripts with potential relevance to apoptosis. Half could be excluded because they were induced by IRF-1 overexpression, which did not sensitize to apoptosis. IFNgamma treatment strongly reduced Mcl-1, phospho-Bcl-2 (ser70), and phospho-Bcl-X(L) (ser62) protein levels. Candidate transcripts were modulated by siRNA, overexpression, or inhibitors to assess the effect on IFNgamma-induced Fas sensitivity. Surprisingly, siRNA knockdown of PSMB8 (LMP7), an "immunoproteasome" component, reversed IFNgamma-induced sensitivity to Fas ligation and prevented Fas/IFNgamma-induced degradation of Mcl-1, but did not protect p-Bcl-2 or p-Bcl-X(L). Proteasome inhibition markedly increased Mcl-1, p-Bcl-2, and p-Bcl-X(L) levels after IFNgamma treatment.

CONCLUSIONS

Although critical for antigen presentation, the immunoproteasome appears to be a key link between inflammatory factors and the control of vascular cell apoptosis and may thus be an important factor in plaque rupture and myocardial infarction.

Fas-mediated apoptosis is regulated by the extracellular matrix protein CCN1 (CYR61) in vitro and in vivo

Although Fas ligand (FasL) is primarily expressed by lymphoid cells, its receptor Fas (CD95/Apo-1) is broadly expressed in numerous nonlymphoid tissues and can mediate apoptosis of parenchymal cells upon injury and infiltration of inflammatory cells. Here we show that CCN1 (CYR61) and CCN2 (CTGF), matricellular proteins upregulated at sites of inflammation and wound repair, synergize with FasL to induce apoptosis by elevating cellular levels of reactive oxygen species (ROS). CCN1 acts through engagement of integrin alpha(6)beta(1) and cell surface heparan sulfate proteoglycans, leading to ROS-dependent hyperactivation of p38 mitogen-activated protein kinase in the presence of FasL to enhance mitochondrial cytochrome c release. We show that CCN1 activates neutral sphingomyelinase, which functions as a key source of CCN1-induced ROS critical for synergism with FasL. Furthermore, Fas-dependent hepatic apoptosis induced by an agonistic monoclonal anti-Fas antibody or intragastric administration of alcohol is severely blunted in knock-in mice expressing an apoptosis-defective Ccn1 allele. These results demonstrate that CCN1 is a physiologic regulator of Fas-mediated apoptosis and that the extracellular matrix microenvironment can modulate Fas-dependent apoptosis through CCN1 expression.

Identifying fragilities in biochemical networks: robust performance analysis of Fas signaling-induced apoptosis

Proper control of apoptotic signaling is critical to immune response and development in multicellular organisms. Two tools from control engineering are applied to a mathematical model of Fas ligand signaling-induced apoptosis. Structured singular value analysis determines the volume in parameter space within which the system parameters may exist and still maintain efficacious signaling, but is limited to linear behaviors. Sensitivity analysis can be applied to nonlinear systems but is difficult to relate to performance criteria. Thus, structured singular value analysis is used to quantify performance during apoptosis rejection, ensuring that the system remains sensitive but not overly so to apoptotic stimuli. Sensitivity analysis is applied when the system has switched to the death-inducing, apoptotic steady state to determine parameters significant to maintaining the bistability. The analyses reveal that the magnitude of the death signal is fragile to perturbations in degradation parameters (failures in the ubiquitin/proteasome mechanism) while the timing of signal expression can be tuned by manipulating local parameters. Simultaneous parameter uncertainty highlights apoptotic fragility to disturbances in the ubiquitin/proteasome system. Sensitivity analysis reveals that the robust signaling characteristics of the apoptotic network is due to network architecture, and the apoptotic signaling threshold is best manipulated by interactions upstream of the apoptosome.

Death receptors and their ligands in atherosclerosis

Atherosclerosis is characterized by the accumulation of a fibro-fatty plaque consisting of immune cells, vascular smooth muscle cells (VSMCs), vascular endothelial cells (ECs), and extracellular matrix, surrounding a lipid-rich core. The complexity of atherosclerosis is highlighted by the multifaceted effects that apoptosis and proliferation of specific cell types can have on vessels at different stages of the disease. Death receptors are membrane-bound protein complexes that on binding their cognate ligand, activate an intracellular signaling cascade that results in apoptosis. More recently, signaling from these receptors has been shown to activate multiple other processes, including cell proliferation. This review summarizes our current understanding of signaling events after death receptor activation and the role of death receptors and their ligands in atherosclerosis.

PARP1 is required for adhesion molecule expression in atherogenesis

AIMS

Atherosclerosis is the leading cause of death in Western societies and a chronic inflammatory disease. However, the key mediators linking recruitment of inflammatory cells to atherogenesis remain poorly defined. Poly(ADP-ribose) polymerase 1 (PARP1) is a nuclear enzyme, which plays a role in acute inflammatory diseases.

METHODS AND RESULTS

In order to test the role of PARP in atherogenesis, we applied chronic pharmacological PARP inhibition or genetic PARP1 deletion in atherosclerosis-prone apolipoprotein E-deficient mice and measured plaque formation, adhesion molecules, and features of plaque vulnerability. After 12 weeks of high-cholesterol diet, plaque formation in male apolipoprotein E-deficient mice was decreased by chronic inhibition of enzymatic PARP activity or genetic deletion of PARP1 by 46 or 51%, respectively (P < 0.05, n >or= 9). PARP inhibition or PARP1 deletion reduced PARP activity and diminished expression of inducible nitric oxide synthase, vascular cell adhesion molecule-1, and P- and E-selectin. Furthermore, chronic PARP inhibition reduced plaque macrophage (CD68) and T-cell infiltration (CD3), increased fibrous cap thickness, and decreased necrotic core size and cell death (P < 0.05, n >or= 6).

CONCLUSION

Our data provide pharmacological and genetic evidence that endogenous PARP1 is required for atherogenesis in vivo by increasing adhesion molecules with endothelial activation, enhancing inflammation, and inducing features of plaque vulnerability. Thus, inhibition of PARP1 may represent a promising therapeutic target in atherosclerosis.

Resistance to fas-induced apoptosis in cells from human atherosclerotic lesions: elevated Bcl-XL inhibits apoptosis and caspase activation

The inappropriate survival of cells in the neointima contributes to atherosclerotic plaque progression, while apoptosis in the fibrous cap of lesions contributes to myocardial infarction and stroke. Prior genomic-scale transcript profiling of human carotid artery plaque cells with known sensitivity or resistance to fas-induced apoptosis identified candidate genes involved in lesion cell apoptosis. Retroviral overexpression indicated that several candidate factors were not causative, but that Bcl-X(L) conferred complete resistance to apoptosis induced by fas ligation. Resistant cells failed to efficiently activate caspase 8, an effect which was also observed in Bcl-X(L)-transfected cells. Small-molecule Bcl-2/X(L) inhibitors and siRNA knockdown of Bcl-X(L) markedly sensitized resistant cells to apoptosis, and partially restored caspase 8 activation. Caspase 3, 6 and 9 inhibitors reduced caspase 8 activation and blocked apoptosis. Complete knockdown of caspase 9 did not reduce apoptosis, while knockdown of Bid suppressed apoptosis, suggesting that mitochondrial pathways independent of caspase 9, such as Smac/Diablo or AIF, provide a necessary mitochondrial input to efficient caspase activation. Bcl-X(L) appears to modulate lesion cell apoptosis by suppressing mitochondrial amplification of caspase activation loops. The results may have direct implications for controlling plaque instability/progression, and identify a new class of small molecules to inhibit restenosis.

DNA damage, p53, apoptosis and vascular disease

Atherosclerosis is the commonest cause of death in the Western world. The atherosclerotic plaque shows evidence of DNA damage, activation of damage repair pathways, p53 expression and apoptosis, involving a variety of different cell types. This review summarises the evidence for DNA damage in atherosclerosis, the likely stimuli inducing damage, and the increasing role of p53 in mediating apoptosis and its consequences in atherosclerosis.

Impaired apoptosis of pulmonary endothelial cells is associated with intimal proliferation and irreversibility of pulmonary hypertension in congenital heart disease

OBJECTIVES

This study sought to assess the cellular and histologic basis of irreversible pulmonary hypertension (PHT) in the clinical setting of congenital heart disease (CHD).

BACKGROUND

Although many children with CHD develop pulmonary vascular disease, it is unclear why this complication is reversible after complete repair in some cases but irreversible in others. Because failure of endothelial cell apoptosis might lead to intimal proliferation and lack of reversibility of PHT, we investigated this and other key markers of vasoactivity and angiogenesis in subjects with PHT and CHD.

METHODS

We assessed antiapoptotic and proapoptotic markers in vascular and perivascular cells in lung biopsy samples from 18 patients with CHD, 7 with reversible and 11 with irreversible PHT, and 6 control patients. Immunostaining for endothelial nitric oxide synthase, vascular endothelial growth factor, and CD34 (markers of vasoactivity and neoangiogenesis) was also performed.

RESULTS

The antiapoptotic protein Bcl-2 was highly expressed by pulmonary endothelial cells in all cases of irreversible PHT but in no cases of reversible PHT, nor in control patients (p < 0.001). Intimal proliferation was present in 10 of 11 irreversible PHT cases, but never observed in reversible PHT (p < 0.001). Similarly, perivascular inflammatory T-cells expressed more antiapoptotic proteins in irreversible PHT (p < 0.01). Irreversible PHT cases were also more likely to show compensatory upregulation of vascular endothelial growth factor and new small vessel formation at the sites of native vessel stenosis or occlusion (p < 0.001).

CONCLUSIONS

Irreversible PHT is strongly associated with impaired endothelial cell apoptosis and antiapoptotic signaling from perivascular inflammatory cells. These changes are associated with intimal proliferation and vessel narrowing, and thereby may contribute to clinical outcomes associated with pulmonary hypertension.