Quantification and location of Chlamydia pneumoniae-specific antigen in the walls of abdominal aortic aneurysms

The elevated expression of TLR4 and MMP9 in human abdominal aortic aneurysm tissues and its implication

Background

Toll-like receptor 4 (TLR4) and matrix metalloproteinase 9 (MMP9) have been investigated to play significant roles in the formation of abdominal aortic aneurysm (AAA). But the reports on the expression pattern of TLR4 and MMP9 in human AAA specimens were relatively scant. The aim of this study was to make a detailed analysis of TLR4 and MMP9 expression in situ and their association with clinical parameters involved in human AAA.

Methods

40 AAA specimens were obtained from full-thickness aneurysmal tissues at the maximal dilation area during the open surgical repair, and 8 non-aneurysmal abdominal aortas from transplant donors served as controls. Expression of TLR4 and MMP9 protein was determined by immunohistochemistry.

Results

There were increased levels of TLR4 and MMP9 expression in human AAA tissues. Compared with macrophages or SMCs, lymphocytes showed a higher positive rate of TLR4 and MMP9 staining, and an elevated ratio of high MMP9 expression (all P < 0.05). There existed a significant association between TLR4 and MMP9 expression (r = 0.767, P < 0.001), and both TLR4 and MMP9 levels were statistically related to circulating CRP. Moreover, TLR4 expression in situ indicated a positive correlation with its serum level (r = 0.654, P = 0.006). Multiple analysis revealed that high TLR4 expression in situ was associated with the risk of large AAA (OR = 6.211, 95%CI = 1.226–31.480, P = 0.027), while high MMP9 expression was correlated to the presence of thrombus within AAA (OR = 5.494, 95%CI = 1.181–25.562, P = 0.030), separately compared with their low expression.

Conclusions

This study confirmed the overexpression of TLR4 and MMP9 in human AAA tissues, and their close relationship implying in the pathogenesis of AAA. We further provided evidence that TLR4 had a potential effect on AAA size and MMP9 could influence the occurrence of thrombus within AAA.

Abdominal aortic aneurysm and virus infection: A potential causative role for cytomegalovirus infection?

An abdominal aortic aneurysm (AAA) is a multifactorial disease with a variety of genetic and environmental risk factors, but the exact mechanism of AAA formation and progression is still not well understood. The present study investigated the frequency of cytomegalovirus (CMV), Epstein-Barr virus (EBV), and papillomavirus types 6 and 11 (HPV6 and HPV11), their impact on clinical manifestations of cardiovascular diseases, and their possible association with inflammation in patients with AAA and healthy volunteers. Genotyping of CMV UL75, EBV LMP-1, and HPV6, and HPV11 E6 was performed by polymerase chain reaction (PCR), while the viral DNA loads were measured by quantitative real-time PCR. Cytokine levels were determined by enzyme-linked immunosorbent assays. The CMV UL75 was detected more frequently in the blood of patients with AAA than in the blood of healthy volunteers (32.7% vs. 6.3%, p < .0001). Neither EBV LMP-1 nor HPV6 E6 was found in blood and aortic wall biopsies, while the HPV11 E6 was detected in 36.4% of AAA walls. The CMV infection in patients with AAA was associated with an increased risk of hypertension and coronary artery disease (OR, 9.057; 95% CI, 1.141-71.862; p = .037; and OR, 2.575; 95% CI, 1.002-6.615; p = .049, respectively). Additionally, CMV-infected patients with AAA had higher tumor necrosis factor-α levels compared with noninfected subjects (p = .017). Our findings suggest that CMV infection can stimulate local inflammation in the aorta but is not a direct cause of most abdominal aortic aneurysms.

Correlation of bacterial coinfection versus matrix metalloproteinase 9 and tissue inhibitor of metalloproteinase 1 expression in aortic aneurysm and atherosclerosis

BACKGROUND

We searched for any relationship between Chlamydophila pneumoniae, Mycoplasma pneumoniae, matrix metalloproteinase 9 (MMP-9), and tissue inhibitor of metalloproteinase 1 (TIMP-1) in aneurysmatic atherosclerotic lesions, and whether this relationship differed from that in atherosclerotic nonaneurysmatic lesions.

METHODS

Twenty-eight tissue samples paired by age and sex were grouped as follows: group 1 included 14 nonaneurysmal atherosclerotic fragments obtained from abdominal aortas collected from necropsies; group 2 included 14 aneurysmatic atherosclerotic aortic fragments obtained from patients during corrective surgery. Immunohistochemistry reactions were evaluated for C pneumoniae, M pneumoniae, MMP-9, and TIMP-1 antigens. Both groups were compared using the Mann-Whitney test, and the correlations among variables were obtained using the Spearman correlation test. P ≤ 0.05 was considered statistically significant.

RESULTS

C pneumoniae and M pneumoniae antigens were detected in 100% of cases. A higher amount of C pneumoniae (P = 0.005), M pneumoniae (P = 0.002), and MMP-9 (P = 0.021) was found in adventitia of group 2 with aneurysm. A positive correlation was found in the aneurysm group, as follows: intima C pneumoniae versus adventitia thickness (r = 0.70; P = 0.01), media C pneumoniae versus adventitia C pneumoniae (r = 0.75; P = 0.002), intima C pneumoniae versus media C pneumoniae (r = 0.8; P = 0.00), and adventitia C pneumoniae versus intima M pneumoniae (r = 0.54; P = 0.05); negative correlations were as follows: adventitia thickness and adventitia M pneumoniae (r = -0.65; P = 0.01), media MMP-9 and media thickness (r = -0.55; P = 0.04), TIMP-1 media versus adventitia C pneumoniae (r = -0.86; P = 0.00), and TIMP-1 media versus M pneumoniae intima (r = -0.67; P = 0.03). Nonaneurysmal atherosclerotic group 1 results are as follows: adventitia C pneumoniae versus TIMP-1 media (r = 0.75; P = 0.01) and media C pneumoniae and adventitia C pneumoniae (r = 0.59; P = 0.03).

CONCLUSIONS

The present work favors a role for coinfection of both M pneumoniae and C pneumoniae in the development of aortic atherosclerotic aneurysm, with increased adventitial inflammation, inhibition of TIMP-1 activity, and increased collagen degradation.

Cathepsins: a new culprit behind abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a fatal disease defined as an abdominal aortic diameter of 3.0 cm or more, where the abdominal aorta exceeds the normal diameter by more than 50%. Histopathological changes of AAA mainly include extracellular matrix (ECM) remodeling at the abdominal aorta wall, but there is lack of specific drugs to treat AAA. Recent studies have reported that lysosomal cathepsins could induce vascular remodeling and AAA formation by regulating vascular inflammation, medial smooth muscle cell apoptosis, neovascularization, and protease expression. Thus, cathepsins are expected to become a new therapeutic target for AAA treatment.

Emerging role of mast cells and macrophages in cardiovascular and metabolic diseases

Mast cells are essential in allergic immune responses. Recent discoveries have revealed their direct participation in cardiovascular diseases and metabolic disorders. Although more sophisticated mechanisms are still unknown, data from animal studies suggest that mast cells act similarly to macrophages and other inflammatory cells and contribute to human diseases through cell-cell interactions and the release of proinflammatory cytokines, chemokines, and proteases to induce inflammatory cell recruitment, cell apoptosis, angiogenesis, and matrix protein remodeling. Reduced cardiovascular complications and improved metabolic symptoms in animals receiving over-the-counter antiallergy medications that stabilize mast cells open another era of mast cell biology and bring new hope to human patients suffering from these conditions.