Activities of proteases in parietal thrombus of aortic aneurysm

Neutrophil to lymphocyte ratio: a novel marker for predicting hospital mortality of patients with acute type A aortic dissection

Introduction:

The inflammatory process has been reported to be associated with aortic dissection (AD) from the development to the prognosis. The aim of the study was to investigate a relationship between the neutrophil to lymphocyte ratio (NLR) and in-hospital outcomes in patients with acute aortic dissection (AAD) who underwent surgical repair.

Methods:

One hundred and eighty-four patients who were admitted with the diagnosis of type A AAD who underwent surgical repair at two large tertiary hospitals. According to their NLR, 91 patients had high NLR (>6.0) and 93 patients had low NLR (⩽6.0).

Results:

The frequency of major bleeding, hospital-related infection, multi-organ dysfunction and mortality in hospital were higher in the high NLR group compared to the low NLR group. NLR, WBC count and operation duration were found to be independent predictors for in-hospital mortality.

Conclusions:

The novel inflammatory marker NLR may be used to predict worse outcomes and hospital mortality in patients with AAD treated by surgical repair.

Giant coronary aneurysms exceeding 5 cm in size

Giant coronary artery aneurysms (gCAAs) with a diameter exceeding 5 cm are extremely rare. The pathomechanisms and therapeutical measures in such cases have been controversial topics of discussion. Twenty-seven patients with gCAAs exceeding 5 cm in size described in the literature were evaluated. A case with multiple gCAAs at our department was included in the analysis. Apart from atherosclerosis of all coronary arteries, a large (1.5 2.5 cm) left anterior descending coronary artery aneurysm (CAA) and a gCAA (10.6 9.2 cm) originating from the right coronary artery, the latter causing recurrent myocardial ischaemia with the occlusion of the peripheral right coronary artery and compressing the right cardiac cavities, were the pathological findings in our 43-year old male patient. gCAAs predominantly develop at the proximal right coronary artery. The majority of these aneurysms develop secondary to atherosclerotic lesions in young patients. We performed a successful surgical excision of the right gCAA, tightening of the left anterior descending artery aneurysm and concomitant coronary artery bypass grafting. A pathological examination confirmed advanced atherosclerosis. Microbiological examinations could find no signs of infectious causes. CAAs bear a significant risk of severe complications and have a high risk of mortality. A more aggressive surgical approach should be recommended.

Early fatal hemorrhage after endovascular cerebral aneurysm treatment with a flow diverter (SILK-Stent): do we need to rethink our concepts?

A 69-year-old woman presenting with short lasting recent episodes of visual impairment was treated uneventfully with a flow diverter covering the neck of a large paraophthalmic aneurysm. As angiography showed immediate flow reduction we abstained from additional coiling which was initially planned. Eleven days later CT demonstrated nearly complete thrombosis of the aneurysm. Twenty days after treatment the patient suffered a lethal subarachnoid hemorrhage after rupture of the aneurysm. All available data were reviewed and beside hemodynamic factors instability of the intra-aneurysmal thrombus is discussed as a possible cofactor leading to this disastrous event.

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/α₁-antitrypsin and MMP9/NGAL complexes, myeloperoxidase (MPO), and α-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.

Caspase-3 activation triggers extracellular cathepsin L release and endorepellin proteolysis

Proteolysis of extracellular matrix components and the production of cryptic bioactive factors play key roles in vascular remodeling. We showed previously that extracellular matrix proteolysis is triggered by the apoptosis of endothelial cells (EC), resulting in the release of an anti-apoptotic C-terminal fragment of endorepellin (LG3). Here, we characterize the endorepellin-cleaving proteases released by apoptotic EC using a multifaceted proteomics strategy. Cathepsin L (CathL), a cysteine protease known to be associated with cardiovascular disease progression in animal models and humans, was isolated from medium conditioned by apoptotic EC. CathL cleaved recombinant endorepellin in vitro, leading to LG3 release. Inhibition of CathL activity in EC exposed to pro-apoptotic stimuli prevented LG3 release without modulating the development of apoptosis in EC. Inhibition of caspase-3 activation in EC with the biochemical inhibitor DEVD-fluoromethyl ketone or small interfering RNAs concomitantly prevented CathL release by EC, LG3 production, and the development of paracrine anti-apoptotic activity. These data demonstrate that caspase-3 activation is a novel pathway of importance for triggering extracellular CathL release and the cleavage of extracellular matrix components.

Cathepsin cysteine proteases in cardiovascular disease

Extracellular matrix (ECM) remodeling is one of the underlying mechanisms in cardiovascular diseases. Cathepsin cysteine proteases have a central role in ECM remodeling and have been implicated in the development and progression of cardiovascular diseases. Cathepsins also show differential expression in various stages of atherosclerosis, and in vivo knockout studies revealed that deficiency of cathepsin K or S reduces atherosclerosis. Furthermore, cathepsins are involved in lipid metabolism. Cathepsins have the capability to degrade low-density lipoprotein and reduce cholesterol efflux from macrophages, aggravating foam cell formation. Although expression studies also demonstrated differential expression of cathepsins in cardiovascular diseases like aneurysm formation, neointima formation, and neovascularization, in vivo studies to define the exact role of cathepsins in these processes are lacking. Evaluation of the feasibility of cathepsins as a diagnostic tool revealed that serum levels of cathepsins L and S seem to be promising as biomarkers in the diagnosis of atherosclerosis, whereas cathepsin B shows potential as an imaging tool. Furthermore, cathepsin K and S inhibitors showed effectiveness in (pre) clinical evaluation for the treatment of osteoporosis and osteoarthritis, suggesting that cathepsin inhibitors may also have therapeutic effects for the treatment of atherosclerosis.

Metalloproteinases, insulin-like growth factor-I and its binding proteins in aortic aneurysm

Abdominal aortic aneurysm is accompanied by the impairment of collagen metabolism in arterial wall. Metalloproteinases and collagen-stimulating factors play an important role in the maintenance of balance between collagen biosynthesis and degradation in tissues. Insulin-like growth factor-I (IGF-I) plays a major role in the stimulation of collagen biosynthesis. Its activity and bioavailability to target cells are modulated by IGF binding proteins (IGFBPs). The potential role of these factors in the mechanism of collagen metabolism deregulation in aortic aneurysm is the purpose of this study. Therefore, we have compared the content of collagen, gelatinolytic activity, IGF-I, IGFBP-1 and IGFBP-3 in normal human aorta and aortic aneurysm. The content of hydroxyproline (representing collagen content) in the proteins of aortic aneurysm was found to be similar to that found in normal aorta. Taking into account that some of the hydroxyproline may be derived from collagen degradation products (CDPs), they were separated and hydroxyproline was determined. It has been found that CDP-derived hydroxyproline content in aortic aneurysm was increased as compared with normal aorta, suggesting an increased collagen degradation. In contrast, zymography showed a decrease of collagenolytic activity in aortic aneurysm tissue, but an increase in mural thrombus, compared to respective controls. IGF-I concentration in aortic aneurysm was decreased, while the concentrations of BP-1 and BP-3 were both increased compared to control. The data suggest that increased collagen degradation in aortic aneurysm is due to the increase in collagenolytic activity in mural thrombus accompanying aneurysm tissue. It suggests that the mural thrombus may play a critical role in the pathogenesis of abdominal aortic aneurysm.