Factor Xa inhibitor rivaroxaban suppresses experimental abdominal aortic aneurysm progression via attenuating aortic inflammation

OBJECTIVE

Rivaroxaban is a specific factor Xa (FXa) inhibitor for venous thromboembolism treatment. Recently, increasing evidence have reported the beneficial effects of rivaroxaban on treating cardiovascular disorders such as coronary and peripheral artery disease. However, its potential influence on abdominal aortic aneurysm (AAA) remains unclear. This study aims to investigate whether rivaroxaban treatment could attenuate experimental AAA progression and its related mechanisms.

APPROACHES AND RESULTS

In human aneurysmal aorta, FXa protein expression was significantly upregulated. Further investigations identified a positive correlation among plasma FXa level, AAA severity (the maximal aortic diameter), and intra-aneurysmal thrombus percentage. In Ang II (angiotensin II)-infused ApoE-/- mice, the administration of high dose rivaroxaban (15 mg/kg/d) for 14 days significantly reduced the maximal aortic diameter, while low dose rivaroxaban (5 mg/kg/d) did not display such a protective role. Although rivaroxaban treatments reduced the incidence of AAA and thrombus formation, these differences did not reach statistical significance. Immunohistochemistry revealed a pronounced aortic remodeling including increased collagen content and enhanced elastin degradation in Ang II-induced AAAs, which was inhibited by high dose rivaroxaban treatment. Further analysis demonstrated that rivaroxaban exerted its protective effects by decreasing leukocyte infiltration, inflammatory cytokines expression, and matrix metalloproteinases (MMPs) expression in the aortic wall. The inhibitory effect of rivaroxaban on aneurysm development was also observed in calcium chloride-induced AAA model. Mechanistically, in human aortic endothelial cells, FXa stimulation increased the expression of inflammatory cytokines (interleukin (IL)-1β, IL-6, IL-8, monocyte chemoattractant protein-1) and adhesive molecules, which were all reversed by the cotreatment of rivaroxaban. Subsequent monocyte-endothelial cell interaction was enhanced after FXa stimulation and was alleviated by rivaroxaban cotreatment. In addition, FXa induced a significantly heightened expression of MMP2 in human aortic endothelial cells, which was ameliorated by rivaroxaban coadministration.

CONCLUSIONS

Rivaroxaban attenuated both angiotensin II- and calcium chloride-induced abdominal aortic aneurysm (AAA) progressions, through inhibiting aortic remodeling and inflammation. Rivaroxaban could be a promising therapeutic agent in attenuating AAA development by counteracting FXa-induced aortic wall inflammation.

Effect of irradiation and bone marrow transplantation on angiotensin II-induced aortic inflammation in ApoE knockout mice

BACKGROUND AND AIMS

Angiotensin II (Ang II) infusion promotes the development of aortic aneurysms and accelerates atherosclerosis in ApoE^-/- mice. In order to elucidate the role of hematopoietic cells in these pathologies, irradiation and bone marrow transplantation (BMT) are commonly utilized. The aim of this study was to investigate the effects of irradiation and BMT on abdominal and thoracic aortic aneurysm formation and acute leukocyte recruitment in the aortic root and descending aorta, in an experimental mouse model of aortic aneurysm formation.

METHODS

ApoE^-/- mice were either lethally irradiated and reconstituted with ApoE^-/- bone marrow or non-irradiated. Following engraftment, mice were treated with Ang II to induce aortic inflammation and accelerate atherosclerosis.

RESULTS

Ang II infusion (0.8 mg/kg/day) in BMT mice resulted in reduced aortic aneurysms and atherosclerosis with decreased leukocyte infiltration in the aorta compared to non-BMT mice, when receiving the same dose of Ang II. Furthermore, the reduced aortic infiltration in BMT mice was accompanied by increased levels of monocytes in the spleen and bone marrow. A dose of 3 mg/kg/day Ang II was required to achieve a similar incidence of aneurysm formation as achieved with 0.8 mg/kg/day in non-BMT mice.

CONCLUSIONS

This study provides evidence that BMT can alter inflammatory cell recruitment in experimental mouse models of aortic aneurysm formation and atherosclerosis and suggests that irradiation and BMT have a considerably more complex effect on vascular inflammation, which should be evaluated.

Sulforaphane reduces advanced glycation end products (AGEs)-induced inflammation in endothelial cells and rat aorta

BACKGROUND AND AIMS

Advanced glycation end products (AGEs)-receptor RAGE interaction evokes oxidative stress and inflammatory reactions, thereby being involved in endothelial cell (EC) damage in diabetes. Sulforaphane is generated from glucoraphanin, a naturally occurring isothiocyanate found in widely consumed cruciferous vegetables, by myrosinase. Sulforaphane has been reported to protect against oxidative stress-mediated cell and tissue injury. However, effects of sulforaphane on AGEs-induced vascular damage remain unclear.

METHODS AND RESULTS

In this study, we investigated whether and how sulforaphane could inhibit inflammation in AGEs-exposed human umbilical vein ECs (HUVECs) and AGEs-injected rat aorta. Sulforaphane treatment for 4 or 24 h dose-dependently inhibited the AGEs-induced increase in RAGE, monocyte chemoattractant protein-1 (MCP-1), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecular-1 (VCAM-1) gene expression in HUVECs. AGEs significantly stimulated MCP-1 production by, and THP-1 cell adhesion to, HUVECs, both of which were prevented by 1.6 μM sulforaphane. Sulforaphane significantly suppressed oxidative stress generation and NADPH oxidase activation evoked by AGEs in HUVECs. Furthermore, aortic RAGE, ICAM-1 and VCAM-1 expression in AGEs-injected rats were increased, which were suppressed by simultaneous infusion of sulforaphane.

CONCLUSION

The present study demonstrated for the first time that sulforaphane could inhibit inflammation in AGEs-exposed HUVECs and AGEs-infused rat aorta partly by suppressing RAGE expression through its anti-oxidative properties. Inhibition of the AGEs-RAGE axis by sulforaphane might be a novel therapeutic target for vascular injury in diabetes.

Toll-like receptors 2 and 4 mediate hyperglycemia induced macrovascular aortic endothelial cell inflammation and perturbation of the endothelial glycocalyx

OBJECTIVES

Hyperglycemia-induced inflammation is central to the vascular complications in diabetes. Toll-like receptors (TLRs) are key players in regulating inflammatory responses. There are sparse data on the role of TLR2 and TLR4 in regulating human macrovascular aortic endothelial cells (HMAECs) inflammation and glycocalyx dysfunction under hyperglycemia. We examined the role of TLR2/4 in the above dysfunctions in HMAEC under high glucose (HG) conditions.

METHODS

HMAECs were treated with high or normal glucose and TLR-2, TLR-4, MyD88, IRF3, TRIF, nuclear NF-κB p65, IL-8, IL-1β, TNF-α, MCP-1, ICAM-1, sVCAM-1, monocyte adhesion to HMAECs, heparan sulfate and hyaluronic acid were measured.

RESULTS

HG upregulated TLR2 and TLR4 mRNA and protein and increased both MyD88 and non-MyD88 pathways, NF-κB p65, inflammatory biomediators, and monocyte adhesion to HMAECs. Heparan sulfate protein expression was reduced and hyaluronic acid secretion was increased on HG exposure. Inhibition of TLR2 and TLR4 signaling by inhibitory peptides and knockdown of TLR-2 and TLR-4 gene expression by siRNA attenuated HG induced inflammation, leukocyte adhesion and glycocalyx dysfunction. An increase in ROS paralleled the increase in TLR-2/4 and antioxidants treatment reduced TLR-2/4 expression and downstream inflammatory biomediators.

CONCLUSION

Thus hyperglycemia induces HMAEC inflammation and glycocalyx dysfunction through TLR-2/4 pathway activation via increased ROS.

Atypical chemokine receptor 1 deficiency reduces atherogenesis in ApoE-knockout mice

AIMS

Atypical chemokine receptor 1 (Ackr1; previously known as the Duffy antigen receptor for chemokines or Darc) is thought to regulate acute inflammatory responses in part by scavenging inflammatory CC and CXC chemokines; however, evidence for a role in chronic inflammation has been lacking. Here we investigated the role of Ackr1 in chronic inflammation, in particular in the setting of atherogenesis, using the apolipoprotein E-deficient (ApoE(-/-)) mouse model.

METHODS AND RESULTS

Ackr1(-/-)ApoE(-/-) and Ackr1(+/+)ApoE(-/-) littermates were obtained by crossing ApoE(-/-) mice and Ackr1(-/-) mice on a C57BL/6J background. Ackr1 (+/+)ApoE(-/-)mice fed a Western diet up-regulated Ackr1 expression in the aorta and had markedly increased atherosclerotic lesion size compared with Ackr1(-/-)ApoE(-/-) mice. This difference was observed in both the whole aorta and the aortic root in both early and late stages of the model. Ackr1 deficiency did not affect serum cholesterol levels or macrophage, collagen or smooth muscle cell content in atherosclerotic plaques, but significantly reduced the expression of Ccl2 and Cxcl1 in the whole aorta of ApoE(-/-) mice. In addition, Ackr1 deficiency resulted in a modest decrease in T cell subset frequency and inflammatory mononuclear phagocyte content in aorta and blood in the model.

CONCLUSIONS

Ackr1 deficiency appears to be protective in the ApoE knockout model of atherogenesis, but it is associated with only modest changes in cytokine and chemokine expression as well as T-cell subset frequency and inflammatory macrophage content.

Prevention of early vascular graft infection using regional antibiotic release

BACKGROUND

Infections after prosthetic replacement of the aorta remain a serious and life-threatening complication. The only appropriate treatment is the surgical removal of the infected prosthesis. Accordingly, there is a need for new procedures to prevent the infection of vascular prostheses. This in vitro experiment investigated the effect of the pretreatment of vascular prostheses with antibiotics (daptomycin or baneocin) and the effect of antibiotics combined with fibrin sealant as possible prophylaxis of perioperative graft infection.

METHODS

Untreated prostheses served as controls. Pretreated prostheses of double woven velour vascular grafts were contaminated with Staphylococcus epidermidis, and colony-forming units were counted each day (CFU/mL).

RESULTS

The period of sterility differed significantly as a function of the pretreatment. Uncoated prostheses were immediately non-sterile and exhibited 2.63 ± 0.61 × 10(5) CFU/mL. Baneocin pretreatment resulted in sterility for 1.7 ± 0.6 (95% confidence interval (CI) 1.0-2.4) d before we detected 2.14 ± 0.57 × 10(5) CFU/mL on the prostheses. Pretreatment with daptomycin yielded 2.9 ± 0.4 (CI 2.6-3.2) and fibrin sealant/baneocin compound yielded 3.1 ± 0.3 (CI 2.9-3.3) d of sterility, after which 1.81 ± 0.86 × 10(5) CFU/mL and 1.04 ± 0.77 × 10(5) CFU/mL were recorded. Finally, pretreatment with fibrin sealant/daptomycin led to sterility for 7.1 ± 0.3 (CI 6.9-7.3) d, after which 0.77 ± 0.60 × 10(5) CFU/mL were observed on the prostheses.

CONCLUSIONS

The risk of vascular graft infection is reduced by pretreating the prostheses with antibiotics. The antibiotic/fibrin compound exhibited an effect of delayed antibiotic release. Vascular prostheses should therefore be pretreated with antibiotic solution to reduce bacterial adhesion. This procedure might be an effective prophylaxis for perioperative vascular graft infection and provides suitable protection for the prosthetic material.

Comparison of experimental microvascular end-to-end anastomosis via VCS-Clips versus conventional suture technique in an animal model

In this experimental study on 96 CD rats, microvascular end-to-end anastomoses created via suture or alternatively by means of a VCS-Clip-Application-System, were compared. The aorta abdominalis of the animals, with a diameter of 1.5 +/- 0.2 mm, was experimentally dissected, and the free ends of the vessel then anastomosed. The results were evaluated using sonography, microangiography, histologic examination, and vascular imprints. Postoperative examination was carried out after 1, 3, 7, 14, or 30 days. Major advantages of the VCS-Clip technique over suturing were that it was easy to learn, significantly faster to perform (execution of anastomosis 10.9 +/- 2.6 min versus 19.4 +/- 5.0 min), and produced significantly more favorable histologic results in terms of less inflammatory response, foreign body reaction, necrosis of the tunica media, hyperplasia of the intima, and thrombosis of the vessel lumen. The main disadvantage of the clip technique was a significantly higher rate of stenoses (15.8 +/- 6.0 versus 4.1 +/- 6.6 percent).

Viral chemokine-binding proteins inhibit inflammatory responses and aortic allograft transplant vasculopathy in rat models

BACKGROUND

Both CC and CXC chemokines direct monocyte and T-cell migration and activation at sites of vascular injury, but the relative contributions of each chemokine class to transplant vasculopathy development have not been defined. The nonselective C, CC, and CXC chemokine binding protein, M-T7, inhibits vasculopathy development after angioplasty and after renal transplant. We have assessed the effects of three viral chemokine-binding proteins with differing ranges of chemokine inhibition on plaque growth in rats after aortic allograft transplant.

METHODS

One of two myxomaviral chemokine binding proteins, (1). M-T1, a selective CC chemokine inhibitor, or (2). M-T7, a nonselective chemokine-binding protein, was given immediately after transplant. A separate group was treated with the gamma68-herpesvirus protein, M3, a C, CC, CXC, and CX3C binding protein, with preferential CC binding.

RESULTS

Intimal hyperplasia was significantly reduced at late times posttransplant after infusion of each chemokine-binding protein (P <0.05). Early inhibition of macrophage and T-cell invasion was associated with a late decrease in vasculopathy development. Infusion of an inactive myxomavirus protein did not inhibit plaque growth. Combined high-dose M-T1 and M-T7 did not reduce plaque growth or early cell invasion to a greater extent than either protein alone. Coinfusion of the CC chemokines macrophage chemoattractant protein-1 and macrophage inflammatory protein-1alpha neutralized M-T1 and M-T7 inhibition of monocyte invasion, respectively, suggesting a key role for CC chemokine-mediated cellular influx.

CONCLUSION

Viral chemokine-modulating proteins effectively reduce aortic allograft vasculopathy, acting predominantly through inhibition of a CC chemokine-mediated response.