[Show abstract][Hide abstract] ABSTRACT: Abdominal aortic aneurysms (AAAs), which commonly occur among elderly individuals, are accompanied by a risk of rupture and subsequent high mortality. Establishment of medical therapies for the prevention of AAAs requires further understanding of the molecular pathogenesis of this condition. This report details the possible involvement of Osteoprotegerin (OPG) in the prevention of AAAs through inhibition of Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). In CaCl2-induced AAA models, both internal and external diameters were significantly increased with destruction of elastic fibers in the media in Opg knockout (KO) mice, as compared to wild-type mice. Moreover, up-regulation of TRAIL expression was observed in the media by immunohistochemical analyses. Using a culture system, both the TRAIL-induced expression of matrix metalloproteinase-9 in smooth muscle cells (SMCs) and the chemoattractive effect of TRAIL on SMCs were inhibited by OPG. These data suggest that Opg may play a preventive role in the development of AAA through its antagonistic effect on Trail.
[Show abstract][Hide abstract] ABSTRACT: HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase inhibitors (statins) have been suggested to attenuate abdominal aortic aneurysm (AAA) growth. However, the effects of statins in human AAA tissues are not fully elucidated. The aim of this study was to investigate the direct effects of statins on proinflammatory molecules in human AAA walls in ex vivo culture. Simvastatin strongly inhibited the activation of nuclear factor (NF)-κB induced by tumor necrosis factor (TNF)-α in human AAA walls, but showed little effect on c-jun N-terminal kinase (JNK) activation. Simvastatin, as well as pitavastatin significantly reduced the secretion of matrix metalloproteinase (MMP)-9, monocyte chemoattractant protein (MCP)-2 and epithelial neutrophil-activating peptide (CXCL5) under both basal and TNF-α-stimulated conditions. Similar to statins, the Rac1 inhibitor NSC23766 significantly inhibited the activation of NF-κB, accompanied by a decreased secretion of MMP-9, MCP-2 and CXCL5. Moreover, the effect of simvastatin and the JNK inhibitor SP600125 was additive in inhibiting the secretion of MMP-9, MCP-2 and CXCL5. These findings indicate that statins preferentially inhibit the Rac1/NF-κB pathway to suppress MMP-9 and chemokine secretion in human AAA, suggesting a mechanism for the potential effect of statins in attenuating AAA progression.
Preview · Article · May 2015 · International Journal of Molecular Sciences
[Show abstract][Hide abstract] ABSTRACT: Toll-like receptor 4 (TLR4) and angiotensin II (AngII) induce vascular remodeling through the production of reactive oxygen species (ROS). AngII has also been shown to increase antioxidant enzyme extracellular superoxide dismutase (ecSOD). However, the roles of TLR4 in Ang II-induced ROS production, vascular remodeling and hypertension remain unknown. Mice lacking TLR4 function showed significant inhibition of vascular remodeling in response to chronic AngII infusion, with no impact on blood pressure. The increases in ROS level and NADPH oxidase activity in response to AngII infusion were markedly blunted in TLR4-deficient mice. Similar effects were observed in wild-type (WT) mice treated with a sub-depressor dose of the AT1 receptor antagonist irbesartan, which had no effects on TLR4-deficient mice. Intriguingly, the AngII infusion-induced increases in ecSOD activity and expression were rather enhanced in TLR4-deficient mice compared with WT mice, whereas the expression of the proinflammatory chemokine MCP-1 was decreased. Importantly, AngII-induced vascular remodeling was positively correlated with NADPH oxidase activity, ROS levels and MCP-1 expression levels. Notably, chronic norepinephrine infusion, which elevates blood pressure without increasing ROS production, did not induce significant vascular remodeling in WT mice. Taken together, these findings suggest that ROS elevation is required for accelerating vascular remodeling but not for hypertensive effects in this model. We demonstrated that TLR4 plays a pivotal role in regulating AngII-induced vascular ROS levels by inhibiting the expression and activity of the antioxidant enzyme ecSOD, as well as by activating NADPH oxidase, which enhances inflammation to facilitate the progression of vascular remodeling.Hypertension Research advance online publication, 9 April 2015; doi:10.1038/hr.2015.55.
No preview · Article · Apr 2015 · Hypertension Research
[Show abstract][Hide abstract] ABSTRACT: Abdominal aortic aneurysm (AAA) is characterized by chronic inflammation, which leads to pathological remodeling of the extracellular matrix. Decorin, a small leucine-rich repeat proteoglycan, has been suggested to regulate inflammation and stabilize the extracellular matrix. Therefore, the present study investigated the role of decorin in the pathogenesis of AAA. Decorin was localized in the aortic adventitia under normal conditions in both mice and humans. AAA was induced in mice using CaCl2 treatment. Initially, decorin protein levels decreased, but as AAA progressed decorin levels increased in all layers. Local administration of exogenous decorin prevented the development of CaCl2-induced AAA. However, decorin was highly expressed in the degenerative lesions of human AAA walls, and this expression positively correlated with matrix metalloproteinase (MMP)-9 expression. In cell culture experiments, the addition of decorin inhibited secretion of MMP-9 in vascular smooth muscle cells, but had the opposite effect in macrophages. The results suggest that decorin plays a dual role in AAA. Adventitial decorin in normal aorta may protect against the development of AAA, but macrophages expressing decorin in AAA walls may facilitate the progression of AAA by up-regulating MMP-9 secretion.
[Show abstract][Hide abstract] ABSTRACT: Aim:
Angiotensin Ⅱ(Ang Ⅱ) produces reactive oxygen species (ROS), thus contributing to the development of cardiac hypertrophy and subsequent heart failure, and stimulates the expression of monocyte chemoattractant protein-1 (MCP-1). In addition, Toll-like receptor 4 (TLR4) is involved in the upregulation of MCP-1. In order to clarify whether TLR4 is involved in the onset of cardiac dysfunction caused by Ang Ⅱ stimulation, we investigated the effects of TLR4 on oxidative stress, the MCP-1 expression and cardiac dysfunction in mice with Ang Ⅱ-induced hypertension.
TLR4-deficient (Tlr4(lps-d)) and wild-type (WT) mice were randomized into groups treated with Ang Ⅱ, norepinephrine (NE) or a subdepressor dose of the Ang Ⅱreceptor blocker irbesartan (IRB) and Ang Ⅱ for two weeks.
Ang Ⅱ and NE similarly increased systolic blood pressure in all drug-treated groups compared to that observed in the control group among both WT and Tlr4(lps-d) mice (p＜0.05). In the WT mice, Ang Ⅱ induced cardiac hypertrophy as well as vascular remodeling and perivascular fibrosis of the intramyocardial arteries and monocyte/macrophage infiltration in the heart (p＜0.05). Furthermore, Ang Ⅱ treatment decreased the left ventricular diastolic function and resulted in a greater left ventricular end-systolic dimension (p＜0.05) in addition to producing a five-fold increase in the NADPH oxidase activity, ROS content and MCP-1 expression (p＜0.05). In contrast, the Tlr4(lps-d) mice showed little effects of Ang Ⅱ on these indices. In the WT mice, IRB treatment reversed these changes compared to that seen in the mice treated with Ang Ⅱ alone. NE produced little effect on any of the indices in either the WT or Tlr4(lps-d) mice.
TLR4 may be involved in the processes underlying the increased oxidative stress, selectively activated MCP-1 expression and cardiac hypertrophy and dysfunction seen in cases of Ang Ⅱ- induced hypertension.
Preview · Article · Mar 2015 · Journal of atherosclerosis and thrombosis
[Show abstract][Hide abstract] ABSTRACT: Objective:
Abdominal aortic aneurysm (AAA) is considered a chronic inflammatory disease; however, the molecular basis underlying the sterile inflammatory response involved in the process of AAA remains unclear. We previously showed that the inflammasome, which regulates the caspase-1-dependent interleukin-1β production, mediates the sterile cardiovascular inflammatory responses. Therefore, we hypothesized that the inflammasome is a key mediator of initial inflammation in AAA formation.
Approach and results:
Apoptosis-associated speck-like protein containing a caspase recruitment domain is highly expressed in adventitial macrophages in human and murine AAA tissues. Using an established mouse model of AAA induced by continuous infusion of angiotensin II in Apoe(-/-) mice, NLR family pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing a caspase recruitment domain, and caspase-1 deficiency in Apoe(-/-) mice were shown to decrease the incidence, maximal diameter, and severity of AAA along with adventitial fibrosis and inflammatory responses significantly, such as inflammatory cell infiltration and cytokine expression in the vessel wall. NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain, and caspase-1 deficiency in Apoe(-/-) mice also reduced elastic lamina degradation and metalloproteinase activation in the early phase of AAA formation. Furthermore, angiotensin II stimulated generation of mitochondria-derived reactive oxygen species in the adventitial macrophages, and this mitochondria-derived reactive oxygen species generation was inhibited by NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain, and caspase-1 deficiency. In vitro experiments revealed that angiotensin II stimulated the NLRP3 inflammasome activation and subsequent interleukin-1β release in macrophages, and this activation was mediated through an angiotensin type I receptor/mitochondria-derived reactive oxygen species-dependent pathway.
Our results demonstrate the importance of the NLRP3 inflammasome in the initial inflammatory responses in AAA formation, indicating its potential as a novel therapeutic target for preventing AAA progression.
No preview · Article · Nov 2014 · Arteriosclerosis Thrombosis and Vascular Biology
[Show abstract][Hide abstract] ABSTRACT: Background
Kawasaki disease (KD) is the most common systemic vasculitis of unknown etiology in children, and can cause the life-threatening complication of coronary artery aneurysm. Although a novel treatment strategy for patients with KD-caused vascular lesions is eagerly awaited, their molecular pathogenesis remains largely unknown. c-Jun N-terminal kinase (JNK) is a signaling molecule known to have roles in inflammation and tissue remodeling. The aim of this study was to elucidate significant involvement of JNK in the development of vascular lesions in a mouse model of KD.
Methods and results
We injected Candida albicans cell wall extract (CAWE) into 4-week-old C57BL/6 mice. Macroscopically, we found that CAWE caused the development of bulging lesions at coronary artery, carotid artery, celiac artery, iliac artery and abdominal aorta. Histological examination of coronary artery and abdominal aorta in CAWE-treated mice showed marked inflammatory cell infiltration, destruction of elastic lamellae, loss of medial smooth muscle cells and intimal thickening, which are similar to histological features of vascular lesions of patients with KD. To find the role of JNK in lesion formation, we evaluated the effects of JNK inhibitor, SP600125, on abdominal aortic lesions induced by CAWE. Interestingly, treatment with SP600125 significantly decreased the incidence of lesions and also protected against vascular inflammation and tissue destruction histologically, compared with the placebo treatment.
Our findings suggest that JNK is crucial for the development of CAWE-induced vascular lesions in mice, and potentially represents a novel therapeutic target for KD.
Full-text · Article · Aug 2014 · Cardiovascular Pathology
[Show abstract][Hide abstract] ABSTRACT: Acute aortic dissection (AAD) is caused by the disruption of intimomedial layer of the aortic walls, which is immediately life-threatening. Although recent studies indicate the importance of proinflammatory response in pathogenesis of AAD, the mechanism to keep the destructive inflammatory response in check is unknown. Here, we report that induction of tenascin-C (TNC) is a stress-evoked protective mechanism against the acute hemodynamic and humoral stress in aorta. Periaortic application of CaCl2 caused stiffening of abdominal aorta, which augmented the hemodynamic stress and TNC induction in suprarenal aorta by angiotensin II infusion. Deletion of Tnc gene rendered mice susceptible to AAD development upon the aortic stress, which was accompanied by impaired TGFβ signaling, insufficient induction of extracellular matrix proteins and exaggerated proinflammatory response. Thus, TNC works as a stress-evoked molecular damper to maintain the aortic integrity under the acute stress.
Full-text · Article · Feb 2014 · Scientific Reports
[Show abstract][Hide abstract] ABSTRACT: Abdominal 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.
We 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.
Our findings indicated that periostin plays an important role in mechanotransduction that maintains inflammation via FAK activation in AAA.
[Show abstract][Hide abstract] ABSTRACT: Background:
The precise pathologic mechanisms underlying human thoracic aortic aneurysms (TAAs) remain uncertain, except that matrix metalloproteinase-9 (MMP-9) is considered a key enzyme for the degradation of extracellular matrix in aneurysm walls. The aim of this study was to elucidate the significance of the angiotensin II (AngII) pathway to MMP-9 production in human TAA walls.
Methods and results:
We examined the activation of Smad2, a common downstream molecule of AngII and transforming growth factor β (TGF-β) pathways, and the expression of MMP-9 in human nonsyndromic TAA walls. We observed significant increases in Smad2 activation and MMP-9 expression, associated with disruption of elastic lamellae. Using human TAA walls in ex vivo culture, we investigated whether AngII and/or TGF-β pathways are essential for MMP-9 production. Unexpectedly, TGF-β receptor inhibitor had no effect on MMP-9 production. We used PD98059, an inhibitor of extracellular signal-regulated kinase (ERK) activation, and demonstrated that PD98059 dramatically reduced MMP-9 production with attenuation of Smad2 activation. Moreover, exogenous AngII resulted in increases in Smad2 activation and MMP-9 production, in an ERK-dependent manner.
Our findings indicate that the AngII/ERK pathway has an important role in the production of MMP-9 in human nonsyndromic TAA walls.
No preview · Article · Jul 2013 · Journal of Surgical Research
[Show abstract][Hide abstract] ABSTRACT: Abdominal aortic aneurysm (AAA) is a common disease causing segmental expansion and rupture of the aorta with a high mortality rate. The lack of nonsurgical treatment represents a large and unmet need in terms of pharmacotherapy. Advances in AAA research revealed that activation of inflammatory signaling pathways through proinflammatory mediators shifts the balance of extracellular matrix (ECM) metabolism toward tissue degradation. This idea is supported by experimental evidence in animal models that pharmacologic intervention at each pathological step can prevent AAA development. Previously, we identified c-Jun N-terminal kinase (JNK), a pro-inflammatory signaling molecule, as a therapeutic target for AAA. Abnormal activation of JNK in AAA tissue regulates multiple pathological processes in a coordinated manner. Pharmacologic inhibition of JNK tips the ECM balance back towards repair rather than degradation. Interventions targeting signaling molecules such as JNK in order to manipulate multiple pathological processes may be an ideal therapeutic strategy for AAA. Furthermore, the development of biomarkers as well as appropriate drug delivery systems is essential to produce clinically practical pharmacotherapy for AAA.
Preview · Article · Aug 2012 · International journal of vascular medicine
[Show abstract][Hide abstract] ABSTRACT: Recently, we reported that angiopoietin-like protein 2 (Angptl2) functions in various chronic inflammatory diseases. In the present study, we asked whether Angptl2 and its associated chronic inflammation contribute to abdominal aortic aneurysm (AAA).
Immunohistochemistry revealed that Angptl2 is abundantly expressed in infiltrating macrophages within the vessel wall of patients with AAA and in a CaCl(2)-induced AAA mouse model. When Angptl2-deficient mice were used in the mouse model, they showed decreased AAA development compared with wild-type mice, as evidenced by reduction in aneurysmal size, less severe destruction of vessel structure, and lower expression of proinflammatory cytokines and matrix metalloproteinase-9. However, no difference in the number of infiltrating macrophages within the aortic aneurysmal vessel wall was observed between genotypes. AAA development was also significantly suppressed in wild-type mice that underwent Angptl2-deficient bone marrow transplantation. Expression levels of proinflammatory cytokines and metalloproteinase-9 in Angptl2-deficient macrophages were significantly decreased, and those decreases were rescued by treatment of Angptl2 deficient macrophages with exogenous Angptl2.
Macrophage-derived Angptl2 contributes to AAA development by inducing inflammation and degradation of extracellular matrix in the vessel wall, suggesting that targeting the Angptl2-induced inflammatory axis in macrophages could represent a new strategy for AAA therapy.
Preview · Article · May 2012 · Arteriosclerosis Thrombosis and Vascular Biology
[Show abstract][Hide abstract] ABSTRACT: The targeting of Ca2+ cycling has emerged as a potential therapy for the treatment of severe heart failure. These approaches include gene therapy directed at overexpressing sarcoplasmic reticulum (SR) Ca2+ ATPase, or ablation of phospholamban (PLN) and associated protein phosphatase 1 (PP1) protein complexes. We previously reported that PP1β, one of the PP1 catalytic subunits, predominantly suppresses Ca2+ uptake in the SR among the three PP1 isoforms, thereby contributing to Ca2+ downregulation in failing hearts. In the present study, we investigated whether heart-failure-inducible PP1β-inhibition by adeno-associated viral-9 (AAV9) vector mediated gene therapy is beneficial for preventing disease progression in genetic cardiomyopathic mice.
[Show abstract][Hide abstract] ABSTRACT: Abdominal aortic aneurysm (AAA) is a common disease caused by segmental weakening of the aortic walls and progressive aortic dilation leading to the eventual rupture of the aorta. Currently no biomarkers have been established to indicate the disease status of AAA. Tenascin-C (TN-C) is a matricellular protein that is synthesized under pathological conditions. In the current study, we related TN-C expression to the clinical course and the histopathology of AAA to investigate whether the pattern of TN-C expression could indicate the status of AAA. We found that TN-C and matrix metalloproteinase (MMP)-9 were highly expressed in human AAA. In individual human AAA TN-C deposition associated with the tissue destruction, overlapped mainly with the smooth muscle actin-positive cells, and showed a pattern distinct from macrophages and MMP-9. In the mouse model of AAA high TN-C expression was associated with rapid expansion of the AAA diameter. Histological analysis revealed that TN-C was produced mainly by vascular smooth muscle cells and was deposited in the medial layer of the aorta during tissue inflammation and excessive destructive activities. Our findings suggest that TN-C may be a useful biomarker for indicating the pathological status of smooth muscle cells and interstitial cells in AAA.
No preview · Article · Oct 2011 · Pathology International
[Show abstract][Hide abstract] ABSTRACT: We sought to examine the effect of resveratrol (3,4',5-trihydroxy-trans-stilbene), a plant-derived polyphenolic compound, on the development of abdominal aortic aneurysm (AAA).
AAA was induced in mice by periaortic application of CaCl(2). NaCl (0.9%)-applied mice were used as a sham group. Mice were treated with intraperitoneal injection of PBS (Sham/CON, AAA/CON, n=30 for each) or resveratrol (100 mg/kg/day) (AAA/RSVT, n=30). Six weeks after the operation, aortic tissue was excised for further examinations.
Aortic diameter was enlarged in AAA/CON compared with Sham/CON. Resveratrol treatment reduced the aneurysm size and inflammatory cell infiltration in the aortic wall compared with AAA/CON. Elastica Van Gieson staining showed destruction of the wavy morphology of the elastic lamellae in AAA/CON, while it was preserved in AAA/RSVT. The increased mRNA expression of monocyte chemotactic protein-1, tumor necrosis factor-α, intercellular adhesion molecule-1, CD68, vascular endothelial growth factor-A, p47, glutathione peroxidase (GPX)1 and GPX3 were attenuated by resveratrol treatment (all p<0.05). Administration of resveratrol decreased protein expression of phospho-p65 in AAA. The increased 8-hydroxy-2'-deoxyguanosine-positive cell count and 4-hydroxy-2-nonenal-positive cell count in AAA were also reduced by resveratrol treatment. Zymographic activity of matrix metalloproteinase (MMP)-9 and MMP-2 was lower in AAA/RSVT compared with AAA/CON (both p<0.05). Compared with AAA/CON, Mac-2(+) macrophages and CD31(+) vessels in the aortic wall were decreased in AAA/RSVT (both p<0.05).
Treatment with resveratrol in mice prevented the development of CaCl(2)-induced AAA, in association with reduced inflammation, oxidative stress, neoangiogenesis, and extracellular matrix disruption. These findings suggest therapeutic potential of resveratrol for AAA.
[Show abstract][Hide abstract] ABSTRACT: Increased angiogenesis, chronic inflammation, and extracellular matrix degradation are the major pathological features of abdominal aortic aneurysm (AAA). We sought to elucidate the role of vascular endothelial growth factor (VEGF)-A, a potent angiogenic and proinflammatory factor, in the development of AAA.
Human AAA samples showed increased VEGF-A expression, neovascularization, and macrophage infiltration compared with normal aortic walls. AAA was induced in mice by periaortic application of CaCl(2). AAA mice were treated with soluble VEGF-A receptor (sFlt)-1 or phosphate-buffered saline and sacrificed 6 weeks after the operation. Treatment with sFlt-1 resulted in reduced aneurysm size, restored wavy structure of the elastic lamellae, reduced Mac-2(+) monocytes/macrophages, CD3(+) T-lymphocytes, and CD31(+) vessels, and attenuated matrix metalloproteinase (MMP)-2 and 9 activity in periaortic tissue of AAA. Increased aortic mRNA expression of monocyte chemotactic protein-1, tumour necrosis factor-α, and intercellular adhesion molecule-1 in AAA was attenuated by sFlt-1 treatment.
VEGF-A was overexpressed in the aortic wall of human and experimental AAA. Treatment with sFlt-1 inhibited AAA development in mice, in association with reduced neoangiogenesis, infiltration of inflammatory cells, MMP activity, and extracellular matrix degradation. These findings suggest a crucial role of VEGF-A in the development of AAA.
Preview · Article · Mar 2011 · Cardiovascular Research