Elastase inhibitor AZD9668 treatment prevented progression of experimental abdominal aortic aneurysms.

OBJECTIVE: Abdominal aortic aneurysm (AAA) is a particular form of arterial disease characterized by the dilation of the aortic wall and the presence of an intraluminal thrombus linked to a high proteolytic activity. The aim of this study was to investigate the effect of an elastase inhibitor (AZD9668 from AstraZeneca) on aneurysm progression. METHODS: For this purpose, we have used a rat model of elastase perfusion followed by repeated injection of Porphyromonas gingivalis (Pg), a weak periodontal pathogen recently reported to enhance AAA thrombus formation. Pg (1.10(7) colony-forming units) was injected through the jugular vein once a week for 4 weeks, and AZD9668, incorporated in the food, was delivered concomitantly. RESULTS: Our results show a beneficial effect of AZD9668 treatment on AAA progression and composition. The increased AAA diameter induced by Pg was significantly reduced by AZD9668 treatment. Histologic analyses allowed us to observe the persistence of a neutrophil-rich luminal thrombus associated with calcifications in Pg-injected rats and the presence of a healing process in the Pg/AZD9668-treated group. The enhanced concentrations of markers of neutrophil activation, cell-free DNA, and myeloperoxidase and elastase activity in Pg-injected rats were significantly reduced both in the conditioned medium of AAA tissue samples and in plasma of rats injected with Pg and treated with AZD9668. CONCLUSIONS: AZD9668 treatment could therefore constitute a new therapeutic tool for treatment of AAA.

Discs large 1 (Dlg1) scaffolding protein participates with clathrin and adaptator protein complex 1 (AP-1) in forming Weibel-Palade bodies of endothelial cells.

Weibel-Palade bodies (WPBs) are specific cigar-shaped granules that store von Willebrand factor (VWF) for its regulated secretion by endothelial cells. The first steps of the formation of these granules at the trans-Golgi network specifically require VWF aggregation and an external scaffolding complex that contains the adaptator protein complex 1 (AP-1) and clathrin. Discs large 1 (Dlg1) is generally considered to be a modular scaffolding protein implicated in the control of cell polarity in a large variety of cells by specific recruiting of receptors, channels, or signaling proteins to specialized zones of the plasma membrane. We propose here that in endothelial cells, Dlg1, in a complex with AP-1 and clathrin, participates in the biogenesis of WPBs. Supporting data show that Dlg1 colocalizes with microtubules, intermediate filaments, and Golgi markers. Tandem mass spectrometry experiments led to the identification of clathrin as an Dlg1-interacting partner. Interaction was confirmed by in situ proximity ligation assays. Furthermore, AP-1 and VWF immunoprecipitate and colocalize with Dlg1 in the juxtanuclear zone. Finally, Dlg1 depletion by siRNA duplexes disrupts trans-Golgi network morphology and WPB formation. Our results provide the first evidence for an unexpected role of Dlg1 in controlling the formation of specific secretory granules involved in VWF exocytosis in endothelial cells.

Syndromic and non-syndromic aneurysms of the human ascending aorta share activation of the Smad2 pathway.

Common features such as elastic fibre destruction, mucoid accumulation, and smooth muscle cell apoptosis are co-localized in aneurysms of the ascending aorta of various aetiologies. Recent experimental studies reported an activation of TGF-beta in aneurysms related to Marfan (and Loeys-Dietz) syndrome. Here we investigate TGF-beta signalling in normal and pathological human ascending aortic wall in syndromic and non-syndromic aneurysmal disease. Aneurysmal ascending aortic specimens, classified according to aetiology: syndromic MFS (n = 15, including two mutations in TGFBR2), associated with BAV (n = 15) or degenerative forms (n = 19), were examined. We show that the amounts of TGF-beta1 protein retained within and released by aneurysmal tissue were greater than for control aortic tissue, whatever the aetiology, contrasting with an unchanged TGF-beta1 mRNA level. The increase in stored TGF-beta1 was associated with enhanced LTBP-1 protein and mRNA levels. These dysregulations of the extracellular ligand are associated with higher phosphorylated Smad2 and Smad2 mRNA levels in the ascending aortic wall from all types of aneurysm. This activation correlated with the degree of elastic fibre fragmentation. Surprisingly, there was no consistent association between the nuclear location of pSmad2 and extracellular TGF-beta1 and LTBP-1 staining and between their respective mRNA expressions. In parallel, decorin was focally increased in aneurysmal media, whereas biglycan was globally decreased in aneurysmal aortas. In conclusion, this study highlights independent dysregulations of TGF-beta retention and Smad2 signalling in syndromic and non-syndromic aneurysms of the ascending aorta.

Effect of blocking platelet activation with AZD6140 on development of abdominal aortic aneurysm in a rat aneurysmal model.

BACKGROUND: Platelet activation and thrombus renewal are keys to intraluminal thrombus formation and progression of abdominal aortic aneurysms (AAA). This study explored the ability of AZD6140, a P2Y(12) receptor antagonist, to inhibit platelet activation and prevent aneurysm development in a rat experimental model of AAA. METHOD: Aortic aneurysms were induced by implanting a segment of sodium dodecyl sulfate-decellularized guinea pig aorta in rat aortas. One day later, rats were randomized to AZD6140 (10 mg/kg twice daily by mouth) or diluent (n = 23 per group) for either 10 (n = 18) or 42 days (n = 28). Adenosine diphosphate (ADP)-mediated platelet aggregation, aneurysm expansion, intraluminal thrombus formation, inflammatory infiltration, matrix metalloproteinase-9 (MMP-9) expression, and smooth muscle cell colonization were measured. RESULTS: AZD6140 inhibited ADP-induced platelet aggregation in vivo for 12 hours, justifying twice-daily administration in rats. The spontaneous increase in aortic diameter shown in the aneurysmal model (2.22 +/- 0.56 mm at day 10 vs 5.21 +/- 1.22 mm at day 42) was reduced with AZD6140 (3.61 +/- 1.46 mm at day 42, P < .01). This beneficial effect was associated with a significant reduction of thrombus development, platelet CD41 expression (P < .05), and leukocyte infiltration of the mural thrombus at days 10 and 42 (P < .01). MMP-9 expression correlated with mural thrombus area and was significantly reduced by AZD6140 (P < .05). AZD6140 limited elastic fiber degradation (P < .05) and enhanced progressive colonization of the thrombus by smooth muscle cells at day 42 (P < .01). CONCLUSIONS: These data suggest that inhibition of platelet activation limits intraluminal thrombus biologic activities, thereby impairing aneurysm development.

Involvement of intraplaque hemorrhage in atherothrombosis evolution via neutrophil protease enrichment.

The pathological remodeling of the arterial wall in atherosclerosis involves protease activities, which play a major role in complications via plaque rupture. Circulating leukocytes and particularly neutrophils have been shown to be an independent predictor of recurrent ischemic events. However, neutrophils are poorly documented within atherosclerotic plaques. We hypothesized that intraplaque hemorrhage could convey neutrophils into the lesion, spreading into the necrotic core, thus participating in its protease enrichment. One hundred human carotid endarterectomy specimens were dissected into culprit-stenosing plaques (CPs) and adjacent noncomplicated plaques. Half of CPs exhibited hemorrhage, which was confirmed by the release of hemoglobin. Pro- and active forms of matrix metalloproteinase-9 (MMP-9) were increased in media conditioned by hemorrhagic plaques. Higher levels of lipocalin [neutrophil gelatinase-associated lipocalin (NGAL)]/MMP-9 complexes, specifically released by neutrophils, were also found in conditioned media from plaques with hemorrhage. Immunohistochemical analysis of the corresponding carotid samples showed that neutrophil markers such as elastase, NGAL/MMP-9, CD66b, and proteinase 3 colocalized with blood constituents (i.e., hemoglobin, plasminogen). All markers of neutrophil degranulation were positively correlated in CP-conditioned media (alpha1-antitrypsin/elastase complexes, myeloperoxidase, and alpha-defensins), and higher levels came from CPs containing intraplaque hemorrhages. Addition of an elastase inhibitor at the time of incubation led to a decrease in the proMMP-9 activation in CPs, suggesting cross-talk between proteases released by neutrophils. Finally, we found that neovessels observed at the interface between cap and core exhibit an activated endothelium, which may favor leukocyte diapedesis. Our study thus provides evidence for the involvement of neutrophils in plaque vulnerability.

Topology of protease activities reflects atherothrombotic plaque complexity.

The pathological remodeling of the arterial wall in atherosclerosis involves protease activities, which play a major role in complications, through plaque rupture. Here, we investigated the release of active proteases by human carotid plaques in relation to (1) the degree of lesion complexity and (2) their compartmentalization between cap, core and media. Eighty human carotid endarterectomy specimens were dissected into culprit stenosing (CPs) and adjacent non-complicated/non-stenosing plaques (NPs). Thirty-five additional CPs were microdissected into cap, core and media. All specimens were compared to control non-atherosclerotic endarteries for the release of components of the plasminogen/plasmin system and matrix metalloproteinases (MMPs). Results show a greater release of the plasminogen activators (PAs), plasmin and active MMPs by CPs compared to NPs, whereas healthy arteries released even lower levels. Furthermore, we highlight a functional interaction between these proteases in human atherosclerotic tissues and more importantly, we demonstrate that the core constitutes the main source of protease activities within CPs. Together, these results suggest that CPs generate plasmin, mainly in the core, which could in turn participate in MMP activation and the onset of complications.

Transforming growth factor-beta 1 production is correlated with genetically determined ACE expression in congenic rats: a possible link between ACE genotype and diabetic nephropathy.

Genetic background appears to modulate the development of diabetic vascular complications. In particular, polymorphisms in the ACE gene have been associated with diabetic nephropathy and, in some studies, macrovascular complications. However, the links between ACE gene polymorphism and factors implicated in diabetes complications remain unknown. The aim of this study was to determine whether the ACE genotype could modify factors, such as transforming growth factor (TGF)-beta 1, involved in the complications of diabetes. For this purpose, congenic rats (L.BNAce10), differing from the LOU strain in only a small segment of chromosome 10 containing the ACE locus, were generated. These congenic rats have plasma ACE levels twice as high as the donor strain. Diabetes was induced in rats of both strains, and its effects on ACE and TGF-beta 1 expressions were evaluated in lungs and kidneys. In lung, the main source of ACE production, ACE mRNA levels and activity were higher in L.BNAce10 rats than in LOU rats. Diabetes increased ACE lung expression in rats of both strains in a similar manner. TGF-beta 1 expression was also higher in lungs of L.BNAce10 compared with LOU rats and was also increased by diabetes. Furthermore, a strong correlation was found between TGF-beta 1 and ACE expressions. In renal arterioles, ACE and TGF-beta mRNA expressions were higher in L.BNAce10 rats than LOU rats (both diabetic and nondiabetic). In these vessels, there was also a correlation between ACE and TGF-beta 1 expressions. Urine TGF-beta 1 concentration depended on the genotype and was further increased by diabetes. These results show that TGF-beta 1 expression is correlated with ACE expression and suggest that this growth factor could be a link between ACE gene polymorphism and diabetic vascular complications.

Pericellular plasmin induces smooth muscle cell anoikis.

Smooth muscle cell (SMC) rarefaction is involved in the development of several vascular pathologies. We suggest that the plasminogen activation system is a potential extracellular signal that can induce pericellular proteolysis and apoptosis of vascular SMCs. Using primary cultures of arterial SMCs, we show that plasmin generated from plasminogen on the cell surface induces cell retraction and fibronectin fragmentation, leading to detachment and morphological/biochemical changes characteristic of apoptosis (also called anoikis). The generation of cell-bound plasmin mediated by tissue-type plasminogen activator (t-PA), constitutively expressed by VSMCs, requires binding of plasminogen to the cell surface and is inhibited by epsilon-aminocaproic acid (IC50=0.9+/-0.2 mM), a competitor of plasminogen binding to membrane glycoproteins. Conversely, addition of alpha2-antiplasmin, which blocks free plasmin in the cell supernatant, could not fully prevent anoikis. Finally, an MMP inhibitor failed to prevent VSMC anoikis, arguing for a direct involvement of plasmin in this phenomenon. Indeed, similar changes are induced by plasmin directly added to VSMCs or to arterial rings, ex-vivo. We show for the first time that pathological anoikis can be triggered by a process that requires functional assembly of the plasminogen activation system on the surface of VSMCs.

The serpin protease-nexin 1 is present in rat aortic smooth muscle cells and is upregulated in L-NAME hypertensive rats.

OBJECTIVE: Protease-nexin 1 (PN-1) belongs to the serpin superfamily and behaves as a specific thrombin inhibitor in the pericellular environment. Little is known about PN-1 expression and its regulation in the vascular system. In this study, we examined the expression of functionally active PN-1 in vitro in rat aortic smooth muscle cells and in vivo in rat arterial media and its regulation in hypertensive rats. METHODS AND RESULTS: The vascular PN-1 formed specific covalent complexes with thrombin involving the catalytic site of the protease, and heparin increased the formation of these complexes. We also demonstrated PN-1 in rat arterial media by immunohistochemical staining. Moreover, we examined in vivo vascular expression of PN-1 in a model of chronic hypertension induced by long-term administration of N(G)-nitro-L-arginine methyl ester (L-NAME). Marked increases in PN-1 mRNA (3-fold) and protein (2-fold) were observed after 2 months of hypertension. Increased expression of PN-1 in the vascular wall was associated with an increase in the formation of complexes between radiolabeled-thrombin and PN-1, indicating that PN-1 was functional. CONCLUSIONS: PN-1 may thus participate in the mechanisms that regulate thrombin activity in the vessel wall.

Pulmonary endothelium as a site of synthesis and storage of interleukin-6 in experimental congestive heart failure.

BACKGROUND: Pulmonary endothelium is an early upstream hemodynamic target of left ventricular dysfunction. Interleukin 6 (IL-6) is a pro-inflammatory cytokine reported to increase in congestive heart failure (CHF) patients. AIMS: We sought to determine the origin of IL-6, IL-6 receptor (IL-6R) and gp130 in experimental CHF. METHODS: We used rats with coronary artery ligation as an experimental model of either compensated or decompensated heart failure. Lung and aorta samples were analysed by RT-PCR, ELISA and immunohistochemistry for IL-6 and its receptors. RESULTS: IL-6 mRNA expression increased in the lung of rats with decompensated heart failure and was positively correlated with infarct severity whereas IL-6R mRNA decreased in the lung of myocardial infarction rats and gp130 mRNA remained unchanged. In contrast, there were no changes in IL-6 mRNA expression in the aorta and left ventricular myocardium. IL-6 peptide content as determined by ELISA and Western Blot in lung tissue was 2-fold higher in decompensated heart failure as compared to control rats. These data were confirmed by immunohistochemistry showing a preferential endothelial localization of IL-6 in the CHF lung. IL-6 peptide was also present in the pleural effusion of decompensated heart failure and was positively correlated with IL-6 mRNA expression in the lungs of decompensated HF rats. Pulmonary IL-6 overexpression was associated with nuclear translocation of NF-kappaB and cytosolic degradation of IkappaB. CONCLUSION: Dysfunctional pulmonary endothelium is a source of synthesis and storage of IL-6 in an experimental model of CHF.

Identification of mitogen-activated protein/extracellular signal-responsive kinase kinase 2 as a novel partner of the scaffolding protein human homolog of disc-large.

Human disc-large homolog (hDlg), also known as synapse-associated protein 97, is a scaffold protein, a member of the membrane-associated guanylate kinase family, implicated in neuronal synapses and epithelial-epithelial cell junctions whose expression and function remains poorly characterized in most tissues, particularly in the vasculature. In human vascular tissues, hDlg is highly expressed in smooth muscle cells (VSMCs). Using the yeast two-hybrid system to screen a human aorta cDNA library, we identified mitogen-activated protein/extracellular signal-responsive kinase (ERK) kinase (MEK)2, a member of the ERK cascade, as an hDlg binding partner. Site-directed mutagenesis showed a major involvement of the PSD-95, disc-large, ZO-1 domain-2 of hDlg and the C-terminal sequence RTAV of MEK2 in this interaction. Coimmunoprecipitation assays in both human VSMCs and human embryonic kidney 293 cells, demonstrated that endogenous hDlg physically interacts with MEK2 but not with MEK1. Confocal microscopy suggested a colocalization of the two proteins at the inner layer of the plasma membrane of confluent human embryonic kidney 293 cells, and in a perinuclear area in human VSMCs. Additionally, hDlg also associates with the endoplasmic reticulum and microtubules in these latter cells. Taken together, these findings allow us to hypothesize that hDlg acts as a MEK2-specific scaffold protein for the ERK signaling pathway, and may improve our understanding of how scaffold proteins, such as hDlg, differentially tune MEK1/MEK2 signaling and cell responses.

Mediators of neutrophil recruitment in human abdominal aortic aneurysms.

AIMS: Neutrophils/platelet interactions are involved in abdominal aortic aneurysm (AAA). The intraluminal thrombus (ILT) is a human model of platelet/neutrophil interactions. The present study focused on mediators involved in neutrophil recruitment in AAA. METHODS AND RESULTS: Conditioned media from luminal, intermediate, and abluminal layers of 29 human ILTs were analysed for neutrophil markers [elastase/alpha1-antitrypsin and MMP9/NGAL complexes, myeloperoxidase (MPO), and alpha-defensin peptides], RANTES, platelet factor 4 (PF4), and interleukin-8 (IL-8). Their time-dependent release into serum from clots generated in vitro and their plasma concentrations in AAA patients and controls were determined. Immunohistochemistry for neutrophils, platelets, IL-8, PF4, and RANTES on AAA sections was performed; and molecules involved in ILT neutrophil chemotactic function were analysed in vitro. Neutrophils and platelets colocalized in the luminal layer of the thrombus. Consistently, neutrophil markers and platelet-derived RANTES and PF4 were released predominantly by the luminal thrombus pole, where their concentrations were significantly correlated. The luminal ILT layer was also the main source of IL-8, whose immunostaining colocalized with neutrophils. All were also released time dependently from clots and were increased in plasma of AAA patients. Luminal ILT layers displayed potent neutrophil chemotactic activity in vitro, which was inhibited by RANTES- and IL-8-blocking antibodies as well as by reparixin, an antagonist of the IL-8 receptors CXCR1 and CXCR2. CONCLUSION: Taken together, these results suggest that platelet-derived RANTES and neutrophil-derived IL-8 are involved in attracting neutrophils to the luminal layer of AAA ILT.

Tissue diffusion and retention of metalloproteinases in ascending aortic aneurysms and dissections.

Histopathological alterations in human aneurysms and dissections of the thoracic ascending aorta include areas of mucoid degeneration within the medial layer, colocalized with areas of cell disappearance and disruption of extracellular matrix elastic and collagen fibers. We studied the presence of matrix metalloproteinases in relation to their capacity to diffuse through the tissue or to be retained in areas of mucoid degeneration in aneurysms and dissections of the ascending aorta. Ascending aortas from 9 controls, 33 patients with aneurysms, and 14 with acute dissections, all collected at surgery, were analyzed. The morphological aspect was similar whatever the etiology or phenotypic expression of the pathological aortas, involving areas of extracellular matrix breakdown and cell rarefaction associated with mucoid degeneration. Release of proMMP-2, constitutively expressed by smooth muscle cells, was not different between controls and aneurysmal aortas, whereas the aneurysmal aortas released more of the active form. Release of pro and active MMP-9 was also similar between controls and aneurysmal aortas. Immunohistochemical staining of MMP-2 and MMP-9 was weak in both control and pathological aortas. In contrast, released MMP-7 (matrilysin) and MMP-3 (stromelysin-1) could not be detected in conditioned media but were present in tissue extracts with no detectable quantitative difference between controls and pathological aortas. Immunohistochemical staining of MMP-7 and MMP-3 revealed their retention in areas of mucoid degeneration, and semiquantitative evaluation of immunostaining showed more MMP-7 in pathological aortas than in controls. In conclusion, areas of mucoid degeneration, the hallmark of aneurysms, and dissections of thoracic ascending aortas, whatever their etiology, are not inert and can retain specific proteases.

Scar and pulmonary expression and shedding of ACE in rat myocardial infarction.

We examined the topology of angiotensin-converting enzyme (ACE) mRNA expression, activity, and shedding in myocardial infarction-induced heart failure and sought to elucidate the source of the increased plasma ACE activity in this model. Three months after coronary ligature, lung, scar, and remaining viable left ventricular tissues were analyzed for ACE mRNA expression as well as tissue and solubilized ACE activity. ACE mRNA expression increased in the scar with respect to infarct severity, decreased in the lung, and remained unchanged in the left ventricle. ACE activity decreased in the lung and increased in the scar tissue and plasma. Shedding of ACE remained constant in the lung and increased in the scar. This study shows that ACE expression and activity is shifted from the pulmonary endothelium to the infarct scar tissue and that constancy of shedding in the lung and its increase in the scar are the source of the increased plasma ACE in congestive heart failure.

IL-10 inhibits vascular smooth muscle cell activation in vitro and in vivo.

The anti-inflammatory cytokine IL-10 inhibits intimal hyperplasia after stent implantation via a powerful inactivation of monocytes. We tested the hypothesis that IL-10 may also inhibit vascular smooth muscle cell (SMC) activation via the inhibition of the NF-kappaB/I-kappaB system. The IL-10 receptor was detected in rat SMCs in vitro and in vivo. In LPS-stimulated rat SMCs, 1 ng/ml recombinant murine IL-10 (mIL-10) reduced I-kappaBalpha and I-kappaBbeta degradation, NF-kappaB activation, as well as the expression of the NF-kappaB-dependent gene IL-6 by 32%, 31%, 75%, and 19%, respectively (P < 0.05 for all). Similar results were obtained in vivo 6 h and 4 days after balloon abrasion of the rat aorta, a model in which intimal hyperplasia results essentially from SMC activation. Moreover, mIL-10 reduced SMC proliferation and migration in vitro (by 60% for both, P < 0.0001), resulting in reduced SMC proliferation and intimal growth 14 days after balloon abrasion of the rat aorta (by 76% and 75%, respectively; P < 0.005). In conclusion, mIL-10 has a direct inhibitory effect on SMCs in vitro and in vivo. This effect is mediated in part by NF-kappaB inactivation and may participate in the overall protective effect of IL-10 on postangioplasty restenosis.

Hemostasis imbalance in experimental hypertension.

BACKGROUND: The rat model of chronic intoxication by N(G) -nitro-L-arginine methyl ester (L-NAME) induces severe systemic arterial hypertension and progressive ischemic lesions in the central nervous system and kidneys. We investigated the possible molecular basis of these thrombotic events. METHODS AND RESULTS: Administration of L-NAME increased plasma markers of thrombin generation, thrombin-antithrombin complexes, and soluble glycoprotein V, measured by specific ELISA. Thrombin generation in vivo was associated with ex vivo platelet desensitization to adenosine 5'-diphosphate and collagen-induced aggregation. In the aortic layers and renal arterioles, tissue factor mRNA (semi-quantitative RT-PCR) and activity (coagulation assay) were increased. In contrast, tissue factor activity was not modified in glomeruli. In parallel, an impairment of the fibrinolytic system was demonstrated by an increase in plasma levels and arterial secretion of plasminogen activator inhibitor-1. In the arterial wall, plasminogen activator inhibtor-1 mRNA was significantly increased. Moreover, antifibrinolytic activity, studied by fibrin reverse zymography, was increased whereas all tissue-plasminogen activator activity secreted by the hypertensive arterial wall was detected as complexes with its specific inhibitor. In animals treated with the angiotensin-converting enzyme (ACE) inhibitor Zofenil, all of these parameters remained at control levels. CONCLUSIONS: These results indicate that chronic blockade of nitric oxide production in rats results in enhancement of blood markers of thrombin generation associated with tissue factor induction and impairment of fibrinolysis in the vascular wall, which may contribute to the thrombotic complications associated with hypertension.