Inflammation In Abdominal Aortic Aneurysm Research Articles

MiR-195 suppresses abdominal aortic aneurysm through the TNF-α/NF-κB and VEGF/PI3K/Akt pathway.

In the present study, the function of microRNA (miR)‑195 on abdominal aortic aneurysm (AAA) andits possible mechanism were investigated. Reverse transcription‑quantitative polymerase chain reaction analysis was used to detect the expression of miR‑195 in patients with AAA. The expression levels of miR‑195 in patients with AAA were effectively increased. The present study also used miR‑195 mimics to increase the expression of miR‑195, and ELISA kits and western blot analysis were used to analyze the levels of interleukin (IL)‑1β and IL‑6, and the protein expression levels of matrix metalloproteinase (MMP)‑2, MMP‑9, tumor necrosis factor (TNF)‑α, nuclear factor (NF)‑κB, vascular endothelial growth factor (VEGF), phosphoinositide 3‑kinase (PI3K) and phosphorylated (p‑)Akt. The overexpression of miR‑195 promoted the levels of IL‑1β and IL‑6, induced the protein expression of MMP‑2 and MMP‑9, upregulated the protein expression ofTNF‑α and NF‑κB, and suppressed the protein expression levels of VEGF, PI3K and p‑Akt in angiotensin II‑vascular smooth muscle cells. In addition, TNF‑α promoted the pre‑inflammatory effect of miR‑195 on the protein expression levels of TNF‑α and NF‑κB, levels of IL‑1β and IL‑6, and protein expression levels of MMP‑2 and MMP‑9 in the angiotensin II‑vascular smooth muscle cells. Suppression of PI3K promoted the pre‑inflammatory effect of miR‑195 on the protein expression of PI3K, p‑Akt and VEGF, the levels of IL‑1β and IL‑6, and the protein expression of MMP‑2 and MMP‑9 in angiotensin II‑vascular smooth muscle cells. Combined, these results suggested that miR‑195 suppressed AAA inflammation through the TNF‑α/NF‑κB and VEGF/PI3K/Akt pathways.

Down-regulation of Fibulin-5 is associated with aortic dilation: role of inflammation and epigenetics.

Destructive remodelling of extracellular matrix (ECM) and inflammation lead to dilation and ultimately abdominal aortic aneurysm (AAA). Fibulin-5 (FBLN5) mediates cell-ECM interactions and elastic fibre assembly and is critical for ECM remodelling. We aimed to characterize FBLN5 regulation in human AAA and analyse the underlying mechanisms. FBLN5 expression was significantly decreased in human aneurysmatic aortas compared with healthy vessels. Local FBLN5 knockdown promoted aortic dilation and enhanced vascular expression of inflammatory markers in Ang II-infused C57BL/6J mice. Inflammatory stimuli down-regulated FBLN5 expression and transcriptional activity in human aortic vascular smooth muscle cells (VSMC). Further, aortic FBLN5 expression was reduced in LPS-challenged mice. A SOX response element was critical for FBLN5 promoter activity. The SOX9 expression pattern in human AAA parallels that of FBLN5, and like FBLN5, it was reduced in TNFα-stimulated VSMC. Interestingly, SOX9 over-expression prevented the cytokine-mediated reduction of FBLN5 expression and transcription. The inhibition of Class I histone deacetylases (HDACs) by MS-275 or gene silencing attenuated the inflammation-mediated decrease of FBLN5 expression in VSMC and in the vascular wall. Consistently, HDAC inhibition counteracted the reduction of SOX9 expression induced by inflammatory stimuli and prevented the TNFα-mediated decrease in the binding of SOX9 to FBLN5 promoter normalizing FBLN5 expression. We evidence the deregulation of FBLN5 in human AAA and identify a SOX9/HDAC-dependent mechanism involved in the down-regulation of FBLN5 by inflammation. HDAC inhibitors or pharmacological approaches that aimed to preserve FBLN5 could be useful to prevent the disorganization of ECM induced by inflammation in AAA.

Antibodies against malondialdehyde-acetaldehyde adducts can help identify patients with abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a pathologic dilation of the aorta. Inflammation of the aortic wall has been shown to be involved in AAA formation. Malondialdehyde-acetaldehyde (MAA) adducts are MAA/protein hybrids with immunogenic, proinflammatory, and profibrotic properties. Levels of MAA adducts are elevated in patients with coronary artery disease; however, the role of MAA adducts in AAA is unclear. We hypothesize that levels of circulating antibodies against MAA adducts are increased in patients with AAA. Plasma samples were collected from mice and patients with AAA and control patients with atherosclerosis but not AAA. AAA was induced in mice by a standard CaCl2 protocol, with matching sham mice. Plasma levels of anti-MAA antibodies were quantified by enzyme-linked immunosorbent assay. Patients with AAA exhibited higher levels of immunoglobulin G and immunoglobulin A anti-MAA antibody subtypes (P = .049 and .026, respectively) compared with control patients. Conversely, immunoglobulin M anti-MAA antibodies in AAA patients were lower compared with control patients (P = .018). In CaCl2-treated mice, immunoglobulin G anti-MAA antibodies were elevated after AAA formation (P = .006). The pattern of anti-MAA antibodies is able to distinguish between patients with AAA and patients with atherosclerosis but no AAA. These results demonstrate that MAA adducts are associated with AAA and suggest that they may play a role in either initiating or propagating chronic inflammation in AAA.

ACE inhibitors potently reduce vascular inflammation, results of an open proof-of-concept study in the abdominal aortic aneurysm.

BackgroundIndependent of their blood pressure lowering effect, ACE inhibitors are thought to reduce vascular inflammation. The clinical relevance of this effect is unclear with the current knowledge. Abdominal aortic aneurysms (AAA) are characterized by a broad, non-specific inflammatory response, and thus provide a clinical platform to evaluate the anti-inflammatory potential of ACE inhibitors.Methods and ResultsEleven patients scheduled for open AAA repair received ramipril (5 mg/day) during 2–4 weeks preceding surgery. Aortic wall samples were collected during surgery, and compared to matched samples obtained from a biobank. An anti-inflammatory potential was evaluated in a comprehensive analysis that included immunohistochemistry, mRNA and protein analysis. A putative effect of ACE inhibitors on AAA growth was tested separately by comparing 18-month growth rate of patients on ACE inhibitors (n = 82) and those not taking ACE inhibitors (n = 204). Ramipril reduces mRNA expression of multiple pro-inflammatory cytokines such as IL-1β, IL-6, IL-8, TNF -α, Interferon-, and MCP-1, as well as aortic wall IL-8 and MCP-1 (P = 0.017 and 0.008, respectively) protein content. The is followed by clear effects on cell activation that included a shift towards anti-inflammatory macrophage (M2) subtype. Evaluation of data from the PHAST cohort did not indicate an effect of ACE inhibitors on 18-month aneurysm progression (mean difference at 18 months: −0.24 mm (95% CI: −0.90–0.45, P = NS).ConclusionsACE inhibition quenches multiple aspects of vascular inflammation in AAA. However, this does not translate into reduced aneurysm growth.Trial RegistrationNederlands Trial Register 1345.

Atherosclerotic risk factors and atherosclerotic postoperative events are associated with low inflammation in abdominal aortic aneurysms

ObjectiveEvidence is emerging that abdominal aortic aneurysm (AAA) formation cannot completely be explained by systemic atherosclerosis and is in part due to other pathophysiological mechanisms such as local immune reactions. The aim of the present study was to study variance in AAA wall inflammation, and relate that to clinical patient characteristics. MethodsVentral walls from 201 patients with intact AAAs undergoing open repair were prospectively collected and processed for histology and protein measurements. Patients were monitored for 3 years postoperatively. ResultsThe amount of lymphocytic infiltrate was used to distinguish 96 lymphocyte-poor AAAs from 105 lymphocyte-rich AAAs. The walls of lymphocyte-rich AAAs had higher concentrations of various inflammatory markers, including interleukin (IL) 6, IL8, matrix metalloproteinase (MMP) 8; however, MMP9 levels were comparable. Patients with lymphocyte-poor AAAs had more atherosclerotic risk factors: type 2 diabetes (22% vs. 9%, P = .008), hypertension (81% vs 66%, P = .019), and serum cholesterol levels (mean[SD] 5.2[2.5] vs. 4.2[1.0] mmol/L, P = .023). Intimal lesions in the AAAs revealed more frequently an extracellular lipid pool in lymphocyte-poor AAAs (66% vs. 52%, P = .026). Lymphocyte poor AAAs were associated with a worse survival during 3 years of follow-up, although this association did not reach statistical significance when correcting for other cardiovascular predictors (24% vs. 14%; HR 1.9–2.3). ConclusionLow amount of inflammation in AAAs is associated with more atherosclerotic risk factors, more advanced local atherosclerotic lesions and more postoperative atherosclerotic adverse events. This observation supports the view that AAA development is a multi-factorial process in which part of the patient population has a closer relation with systemic atherosclerotic disease, while in other patients local inflammatory reactions might play a larger role.

SS5. Antibodies Against Malondialdehyde-Acetaldehyde Adducts Can Identify Patients With Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a pathologic dilation of the aorta. Inflammation of the aortic wall has been shown to be involved in AAA formation. Malondialdehyde-acetaldehyde (MAA) adducts are MAA/protein hybrids with immunogenic, proinflammatory, and profibrotic properties. Levels of MAA adducts are elevated in patients with coronary artery disease; however, the role of MAA adducts in AAA is unclear. We hypothesize that levels of circulating antibodies against MAA adducts are increased in patients with AAA. Plasma samples were collected from mice and patients with and without AAA. AAA was induced in mice by a standard CaCl2 protocol, with matching sham mice. Plasma levels of anti-MAA antibodies were quantified by enzyme-linked immunosorbent assay. Patients with AAA exhibited higher levels of immunoglobulin G (IgG) and IgA anti-MAA antibody subtypes (P = .049 and P = .026, respectively) compared with control patients. Conversely, IgM anti-MAA antibodies in AAA patients were lower compared with control patients (P = .018). In CaCl2 treated mice IgG anti-MAA antibodies were elevated after AAA formation (P = .006). The pattern of anti-MAA antibodies is able to distinguish between patients with AAA and patients with atherosclerosis but no AAA. These results demonstrate that MAA adducts are associated with AAA and suggest they may play a role in either initiating or propagating chronic inflammation in AAA.

Abstract 109: IL-1ß-Induced Ceramide Synthesis Accentuates NETosis and Inflammation in Abdominal Aortic Aneurysms

Objective: We have previously shown that circulating neutrophils are required for experimental aortic aneurysm (AA) formation via a non-MMP2/9-mediated mechanism. In other experiments we documented that IL-1β signaling is required for AA formation. Therefore, we hypothesized that increased levels of IL-1β in AA triggers inflammatory ceramide synthesis and thus extracellular trap (NET) formation (NETosis) by neutrophils, thereby augmenting inflammation. Methods: Immunohistochemical techniques were used to identify neutrophils and NETs. Ceramides from human AA and control aortas from transplant donors were quantified using liquid chromatography/tandem mass spectrometry (LC-MS/MS). Neutrophils isolated from human blood were treated with IL-1β to determine if IL-1β induces ceramide synthesis and NETosis in vitro. Experimental AAs were induced by elastase perfusion in C57BL/6 wild-type (WT) and IL-1β knock-out (KO) mice and cellular content of AA was analyzed using flow cytometry. Groups were compared using two-tailed unpaired t-test. Results: Immunohistochemical staining showed that neutrophils were scattered or grouped near lymphoid-like structures in the adventitia of human AA. Three-dimensional confocal imaging showed NETs in the adventitia of human AA. Importantly, the levels of long chain ceramides C16 and C24:1 were higher (2.6 and 1.8-fold, respectively), whereas, the levels of short chain ceramides C4, C6 and C8 were lower (4.3, 3.9 and 3.5-fold, respectively) in human AA compared to controls. In isolated neutrophils, IL-1β treatment induced synthesis of long chain ceramides and discharge of NETs. Neutrophils and NETs were also detected in aortic media at day 7 after induction of AA in WT mice. On day 7 following elastase perfusion, despite the increase in number of circulating immune cells, AA size was smaller (91.08±11.7% vs 53.8±5.4%, p=0.03), and, infiltration of neutrophils (12179±2697 vs 3046±628, p=0.01) and B cells was lower in the aorta of IL-1β KO mice compared to WT mice. Conclusions: These data document for the first time the presence of NETs in human AAs. Furthermore, the data suggests that neutrophils augment inflammation in AA by increasing pro-inflammatory long chain ceramide synthesis and NETosis in response to IL-1β.

CT textural analysis of abdominal aortic aneurysms as a biomarker for aneurysm growth

BackgroundSize of abdominal aortic aneurysm (AAA) does not account entirely for rate of expansion or risk of rupture. More accurate methods of risk stratification are needed. Textural analysis of aneurysm CT data (CTTA) provides one approach. CTTA measures heterogeneity within standard CT images. Greater heterogeneity in tumours corresponds with adverse pathological features such as hypoxia and neovascularisation, and predicts reduced survival. In this study, we prospectively tested CTTA in AAA, assessing its association with annual expansion and need for intervention. In addition, we assessed the correlation between CTTA and 18F-fluorodeoxyglucose (FDG) uptake on PET, a marker of AAA inflammation. MethodsPatients with small and medium AAA underwent contrast CT and FDG PET with usual surveillance. CTTA (TexRAD software) was used on CT images from the sac and shoulder of each aneurysm. Fine, medium, and coarse CT textures were quantified with histogram-based parameters (standard deviation [SD], kurtosis, and entropy). Non-parametric statistical testing was used to assess significant correlations. Findings63 patients with a mean AAA diameter of 4·3 cm (SD 0·7) were included. Median annual expansion was 0·1 cm (IQR 0–0·3), with 13 patients requiring surgery across a median follow-up of 2·3 years (1·9–3·3). Shoulder CTTA kurtosis for medium texture was positively correlated with annual AAA growth (r=0·338 p=0·027). Shoulder CTTA entropy was significantly higher in patients who went on to require surgery (unfiltered images p=0·035), suggesting more heterogeneity in these patients. There were significant correlations between CTTA parameters and PET standardised uptake value in both the sac and shoulder—positive correlations with SD (sac, unfiltered r=0·313, p=0·012; shoulder, fine textures r=0·270, p=0·033), and inverse correlations with kurtosis (sac, unfiltered r=−0·330, p=0·008; sac, fine textures r=−3·03, p=0·017; shoulder, fine textures r=−0·247, p=0·051). InterpretationOur findings suggest that CTTA analysis can provide useful prognostic information about AAA. CT heterogeneity might be correlated with corresponding AAA FDG PET signal. CTTA parameters can be derived from standard CT images, potentially providing a straightforward and cost-effective means of risk stratification. FundingNational Institute for Health Research, Higher Education Funding Council for England.

Increased Expression and Activation of Absent in Melanoma 2 Inflammasome Components in Lymphocytic Infiltrates of Abdominal Aortic Aneurysms

Chronic vascular inflammation is a key hallmark in the pathogenesis of abdominal aortic aneurysm (AAA). Recent investigations have suggested that the inflammasome, a cytosolic multiprotein complex that recognizes pathogen-associated molecular patterns, plays a role in atherosclerosis. However, its role in AAA inflammation has not yet been investigated. This pilot study analyzed inflammasome activation and its intramural localization in 24 biopsy samples from 11 patients with asymptomatic AAA versus 12 aortic samples from apparently healthy controls. Using a histological inflammation scale, we identified grade 2/3 inflammatory changes with lymphoid aggregates/tertiary lymphoid organs in 21 out of 24 AAA samples, whereas only 7 of the 12 control samples exhibited local grade 1 inflammatory changes. Strong expression levels of "apoptosis-associated speck-like protein with a caspase recruitment domain" (ASC), caspase-1, caspase-5 and "absent in melanoma 2" (AIM2) were detected by immunohistochemistry in both sporadic infiltrating lymphoid cells and lymphoid aggregates located in the outer media and adventitia of AAA samples. In contrast, inflammasome-positive cells were restricted to cholesterol plaque-associated areas and to single infiltrating cells in control aortas. Analysis of gene expression using real-time polymerase chain reaction (PCR) revealed significantly increased median mRNA levels of the inflammasome core components PYCARD (ASC), CASP1 (Caspase-1) and IL1B (IL-1β) in AAA tissue compared with normal aorta. Moreover, significantly increased median amounts of AIM2 protein and mature caspase-5 (p20) were found in samples associated with high rupture risk compared with paired low rupture risk samples of the same AAA patient. We conclude from our data that AAA-associated lymphoid cells are capable of inflammasome signaling, suggesting that inflammasome activation is involved in the chronic inflammatory process driving AAA progression.

Periostin links mechanical strain to inflammation in abdominal aortic aneurysm.

AimsAbdominal aortic aneurysms (AAAs) are characterized by chronic inflammation, which contributes to the pathological remodeling of the extracellular matrix. Although mechanical stress has been suggested to promote inflammation in AAA, the molecular mechanism remains uncertain. Periostin is a matricellular protein known to respond to mechanical strain. The aim of this study was to elucidate the role of periostin in mechanotransduction in the pathogenesis of AAA.Methods and ResultsWe found significant increases in periostin protein levels in the walls of human AAA specimens. Tissue localization of periostin was associated with inflammatory cell infiltration and destruction of elastic fibers. We examined whether mechanical strain could stimulate periostin expression in cultured rat vascular smooth muscle cells. Cells subjected to 20% uniaxial cyclic strains showed significant increases in periostin protein expression, focal adhesion kinase (FAK) activation, and secretions of monocyte chemoattractant protein-1 (MCP-1) and the active form of matrix metalloproteinase (MMP)-2. These changes were largely abolished by a periostin-neutralizing antibody and by the FAK inhibitor, PF573228. Interestingly, inhibition of either periostin or FAK caused suppression of the other, indicating a positive feedback loop. In human AAA tissues in ex vivo culture, MCP-1 secretion was dramatically suppressed by PF573228. Moreover, in vivo, periaortic application of recombinant periostin in mice led to FAK activation and MCP-1 upregulation in the aortic walls, which resulted in marked cellular infiltration.ConclusionOur findings indicated that periostin plays an important role in mechanotransduction that maintains inflammation via FAK activation in AAA.

Inflammation in abdominal aortic aneurysms: cellular infiltrate and cytokine profiles

Abdominal aortic aneurysm (AAA) pathogenesis occurs as a result of the altered homeostasis of the aortic vessel wall structural proteins. This results in weakening, and subsequent expansion, of the aorta leading to aneurysm formation. Multiple mechanisms are involved in this process, including genetic abnormalities, biomechanical wall stress, apoptosis, and proteolytic degradation of the aortic wall. One key hallmark of this pathology, which orchestrates the interaction of the various pathologic processes, is inflammation. The inflammatory process is characterized by the infiltration of a variety of cells, which leads to the upregulation of multiple cytokines. The balance of the cellular type and resultant cytokine milieu determines the ultimate fate of the aortic wall - healing, atherosclerosis or aneurysm formation. This review highlights some of the known cellular and cytokine inflammatory events that are involved in aortic aneurysm formation.

A Randomised Placebo-controlled Double-blind Trial to Evaluate Lipid-lowering Pharmacotherapy on Proteolysis and Inflammation in Abdominal Aortic Aneurysms

A Randomised Placebo-controlled Double-blind Trial to Evaluate Lipid-lowering Pharmacotherapy on Proteolysis and Inflammation in Abdominal Aortic Aneurysms

A Randomised Placebo-controlled Double-blind Trial to Evaluate Lipid-lowering Pharmacotherapy on Proteolysis and Inflammation in Abdominal Aortic Aneurysms

Objectives: Modulation of abdominal aortic aneurysm (AAA) expansion by HMG-CoA reductase inhibitors (statins) might be linked to reducing IL-6 and MMP-9, which may be consequent on reducing plasma cholesterol. Ezetimibe is a novel cholesterol absorption inhibitor used in combination with statins. This pilot study compared the biological effects of ezetimibe combination therapy with simvastatin alone on parameters relevant to aneurysm expansion including cytokines and proteolytic enzymes. Design: Randomised placebo-controlled double-blind trial. Materials & Methods: Eighteen patients scheduled for elective open AAA repair were randomised to simvastatin 40 mg plus ezetimibe 10 mg (n = 9), or simvastatin 40 mg plus placebo (n = 9), for 32.5 days (IQR 28–50.5) until the day of surgery. Total concentrations of TNF-α, IL-1β, IL-6, IL-8, IL-10, MMPs-1, -2, -3, -8, -9, -12, -13, TIMP-1 and -2 were measured in plasma, aortic wall homogenates and tissue culture explants. Results: Two patients in the placebo arm did not undergo open repair precluding aortic samples. Ezetimibe was associated with a significant reduction in aortic wall MMP-9 (p = 0.02) and aortic wall IL-6 (p = 0.02), associated with a reduction in plasma lipids. Conclusions: These results suggest that ezetimibe combination therapy reduces aortic wall proteolysis and inflammation, key processes that drive AAA expansion. A larger RCT is justified focussing on aneurysm growth rates in small AAA.

Comments regarding ‘A Randomised Placebo-controlled Double-blind Trial to Evaluate Lipid-lowering Pharmacotherapy on Proteolysis and Inflammation in Abdominal Aortic Aneurysms’

There is great interest in finding an effective pharmacological agent for the treatment of abdominal aortic aneurysms (AAA). Since Schouten et al. published their article in 2006, much hope has been placed on statin treatment to slowdown AAA growth. But evidence of the effects of statins on AAA natural history has been confusing in the last few years. A recentmeta-analysis of clinical controlled studies hasproved a significant association of statins and reduced AAA growth rates. Still, none of the published studies are randomized and not all studies report favourable results. Indeed, a randomized controlled trial seems essential to assess the true impact of statin treatment onAAAevolution but it would find great difficulty given the proven beneficial effect of the medication on overall cardiovascular risk and the massive current demand and prescription,making a potential control group limited and possibly unethical. Dawson et al. found a significant reduction in AAA wall MMP-9 and IL-6 from patients treated with simvastatin 40 mg þ ezetimibe 10 mg compared to simvastatin alone. Concentrations of other inflammatory or proteolytic enzymes

A Randomised Placebo-controlled Double-blind Trial to Evaluate Lipid-lowering Pharmacotherapy on Proteolysis and Inflammation in Abdominal Aortic Aneurysms

Objectives Modulation of abdominal aortic aneurysm (AAA) expansion by HMG-CoA reductase inhibitors (statins) might be linked to reducing IL-6 and MMP-9, which may be consequent on reducing plasma cholesterol. Ezetimibe is a novel cholesterol absorption inhibitor used in combination with statins. This pilot study compared the biological effects of ezetimibe combination therapy with simvastatin alone on parameters relevant to aneurysm expansion including cytokines and proteolytic enzymes. Design Randomised placebo-controlled double-blind trial. Materials & Methods Eighteen patients scheduled for elective open AAA repair were randomised to simvastatin 40 mg plus ezetimibe 10 mg ( n = 9), or simvastatin 40 mg plus placebo ( n = 9), for 32.5 days (IQR 28–50.5) until the day of surgery. Total concentrations of TNF-α, IL-1β, IL-6, IL-8, IL-10, MMPs-1, -2, -3, -8, -9, -12, -13, TIMP-1 and -2 were measured in plasma, aortic wall homogenates and tissue culture explants. Results Two patients in the placebo arm did not undergo open repair precluding aortic samples. Ezetimibe was associated with a significant reduction in aortic wall MMP-9 ( p = 0.02) and aortic wall IL-6 ( p = 0.02), associated with a reduction in plasma lipids. Conclusions These results suggest that ezetimibe combination therapy reduces aortic wall proteolysis and inflammation, key processes that drive AAA expansion. A larger RCT is justified focussing on aneurysm growth rates in small AAA.

Cystatin C Deficiency Promotes Inflammation in Angiotensin II–Induced Abdominal Aortic Aneurisms in Atherosclerotic Mice

An imbalance between cysteinyl cathepsins and their principal endogenous inhibitor cystatin C (CystC) may favor proteolysis in the pathogenesis of human abdominal aortic aneurysms (AAA), yet a direct role of CystC in AAA remains unproven. This study used CystC and apolipoprotein E (ApoE) compound mutant (CystC(-/-)ApoE(-/-)) mice to examine directly the role of cysteine protease/protease inhibitor imbalance in AAA formation in angiotensin II-induced AAA. CystC-deficiency increased lumenal diameter and lesion size compared with control mice. CystC(-/-) ApoE(-/-) lesions also demonstrated enhanced inflammatory cell accumulation, more severe elastin fragmentation, and fewer smooth muscle cells in the tunica media. Macrophage content, measured as percent positive area (23.2 +/- 1.4% versus 11.2 +/- 1.4%; P = 0.0003) and number of the CD4(+) T cells (ninefold; P = 0.048), increased significantly in CystC(-/-)ApoE(-/-) lesions. CystC deficiency increased cathepsin activity (5.5 fold; P = 0.001) in AAA, yielding greater elastin degradation and proangiogenic laminin-5 gamma2 peptide production, which may account for increased microvascularization in CystC(-/-)ApoE(-/-) compared with ApoE(-/-) lesions. Increased leukocyte adhesion molecule VCAM-1 expression and leukocyte proliferation might also promote inflammation in CystC-deficient AAA. These data indicate that CystC contributes to experimental AAA pathogenesis and that enhanced cysteine protease activity, due to the lack of CystC, favors inflammation in AAA lesions induced in atherosclerotic mice by promoting microvascularization and smooth muscle cell apoptosis as well as leukocytes adhesion and proliferation.

Upregulation of Protein Kinase Cδ in Vascular Smooth Muscle Cells Promotes Inflammation in Abdominal Aortic Aneurysm

The development of abdominal aortic aneurysms (AAAs) involves a complex interplay of extracellular matrix degradation, inflammation, and apoptosis. We have previously shown that protein kinase Cdelta (PKCdelta) plays a critical role in vascular smooth muscle cell (vSMC) apoptosis in the setting of oxidative stresses. Here, we show that PKCdelta is also involved in the signaling that draws inflammatory cells to aneurismal tissue.Immunostaining for monocyte chemotactic factor (MCP)-1 and PKCdelta was performed on paraffin-fixed arterial sections. Enzyme-linked immunosorbent assay to detect MCP-1 produced by vSMCs was performed on media from cultured rat A10 cells after cytokine induction with or without the PKCdelta-specific inhibitor rottlerin. Migration of isolated lymphocytes was evaluated in response to media from activated A10 cells.Human AAAs show widespread and elevated expression of PKCdelta that is not seen in normal aortic tissues. Cytokine stimulation of cultured vSMCs induced vigorous production of the key chemotactant MCP-1, the expression of which was PKCdelta dependent. Stimulated vSMCs were capable of inducing the migration of leukocytes, and this effect was also dependent on PKCdelta activity. Staining of human AAA tissue for MCP-1 showed an expression pattern that was identical to that of PKCdelta and smooth muscle specific alpha-actin.PKCdelta is widely expressed in human AAA vessel walls and mediates MCP-1 expression by vSMCs, which could contribute to the inflammatory process. These findings, coupled with earlier studies of PKCdelta, suggest that PKCdelta plays a central role in the pathogenesis of AAAs and may be a potential target for future therapies.

Hemodynamic forces regulate mural macrophage infiltration in experimental aortic aneurysms

Blood flow (BF) and wall shear stress (WSS) influence reactive oxygen species production and oxidative stress in abdominal aortic aneurysm (AAA) disease. To gain further insight into the mechanisms of hemodynamic influences on AAA inflammation, we examined aneurysm macrophage density, chemotaxis and survival under varying aortic flow conditions. Rat AAAs were created via porcine pancreatic elastase (PPE) infusion. In selected cohorts, AAA flow was increased via left common femoral arteriovenous fistula (AVF) creation (HF-AAA) or decreased by left common iliac ligation (LF-AAA). WSS was highest in HF-AAA (10.4 ± 2.3 dyn/cm 2 vs. 2.4 ± 0.4 and 0.5 ± 0.2 for NF- and LF-AAA, respectively, P < 0.001) 7 days after PPE infusion, with reduced medial macrophage density and increased apoptosis. Adventitial macrophage density was not significantly influenced by flow. Monocyte chemoattractant protein-1 (MCP-1) and granulocyte-macrophage colony-stimulating factor (GM-CSF) gene expression correlated with observed macrophage densities in the media and adventitia. Luminal flow conditions regulate AAA inflammation in part via influences on medial macrophage density. Hemodynamic forces may modulate AAA inflammation and diameter enlargement via direct regulation of intimal macrophage adhesion, transmural migration or survival.

The Role of Inflammation in Nonspecific Abdominal Aortic Aneurysm Disease

The predominant pathologic feature of abdominal aortic aneurysm is elastin destruction, and elastin destruction may be mediated by inflammation. In this investigation serial sections of abdominal aortic aneurysm specimens were selectively stained to study the relationship between inflammation and elastin degradation. In addition, soluble aortic extracts were examined for the presence of immunoglobulins. An inflammatory infiltrate was present in 8 of 10 of the abdominal aortic aneurysm specimens examined. The infiltrate was mononuclear, commonly located at the junction of the media and adventitia; it did not codistribute with loss of elastin. The presence of an inflammatory component in abdominal aortic aneurysm was associated with a large amount of immunoglobulin in soluble extracts from aneurysmal tissue compared to atherosclerotic and normal control extracts. This study further characterizes the microscopic pathology of abdominal aortic aneurysm and describes the presence of immunoglobulin in soluble tissue extracts. In addition, the possible role of inflammation in abdominal aortic aneurysm as it relates to protease expression is detailed.