Expression of endothelial cell adhesion molecules on heart valves: up-regulation in degeneration as well as acute endocarditis

Transcriptional regulation of α5β1 integrin, fibronectin, VCAM-1, MCSF-1/c-fms, and MCP-1 in atrioventricular valves after valvular surgery and Staphylococcus aureus bacteremia

OBJECTIVE

The primary event in the development of infective endocarditis (IE) is bacterial adherence to damaged heart valves. This includes capture, adhesion and internalization of bacteria into host cells.

METHODS

We determined in an experimental rabbit model for IE whether a transient bacteremia caused by Staphylococcus aureus and/or endothelial heart valve lesions induce transcriptional regulation of alpha(5)beta(1) integrin, fibronectin, vascular cell adhesion molecule-1 (VCAM-1), macrophage colony-stimulating factor-1 (MCSF-1), c-fms proto-oncogene (MCSF-1 receptor), and macrophage chemoattractant protein-1 (MCP-1) in mitral and tricuspid valves.

RESULTS

No significant upregulation was found after isolated bacteremia. Six hours after surgical manipulation valvular endothelial lesions led to a distinct modulation in the mRNA expression of proinflammatory cytokines (MCSF-1 and MCP-1), VCAM-1 and alpha(5)beta(1) integrin. The most evident differences between the mitral and tricuspid valves were seen in the significant upregulation of VCAM-1 mRNA on the tricuspid valve in the surgical groups, whereas there was no effect on the mitral valve. MCSF-1 and MCP-1 were dramatically upregulated in both valves after surgery.

CONCLUSIONS

During the host defence mechanisms in the development of IE proinflammatory cytokines, cellular adhesion molecules, and molecules of the fibronectin/integrin axis are activated, showing distinct differences in right- and left-sided heart valves.

Endothelial cell reaction on a biological material

The successful clinical application of materials should involve detailed investigations on interaction between them and tissue with which they will contact. We examined herein the behavior of endothelial cells (ECs) on a collagen material, using histological and immunohistochemical methods. We used isolated human umbilical cord vein cells (HUVECs) identified by means of endothelial-specific antibodies. Cells were seeded in a standard density on a collagen membrane (Lycoll, Resorba, Nuernberg, Germany) and on gelatin-coated, control plastic surfaces, after two passages. These were then maintained for periods of 1, 7, or 14 days. The cells adhered, spread, and proliferated, and within 24 h started forming a subconfluent monolayer. We observed that the cultured cells expressed integrins (alpha5beta1 and alpha(v)beta3) and synthesized fibronectin. After 14 days, we could observe a confluent layer of ECs. We could conclude that the collagen material supported growth and attachment of endothelial cells. In addition, the attachment seemed to be most related to the fibronectin synthesized by the cells and to its highly expressed receptor (the alpha5beta1 integrin); even though this is not the only protein related to this adhesion, we observed that our cultured HUVECs did not synthesize vitronectin.

Mechanisms of aortic valve calcification

The calcified aortic valve lesion develops in the setting of endothelial injury and inflammation and displays hallmarks of atherosclerosis, including lipids accumulation, matrix metalloproteinase activation, and interaction with renin-angiotensin system. Current evidence indicates that modification of atherosclerotic risk factors will slow the progression of aortic valve calcification, and valve risk factors should be addressed in all patients who have aortic valve calcification.

Venous Hypertension, Inflammation and Valve Remodeling

OBJECTIVES

To identify possible mechanisms for destruction of valves in chronic venous hypertension and the results of treatment with an anti-inflammatory micronized purified flavonoid fraction.

MATERIAL AND METHODS

The saphenous vein valves in a rat model of venous hypertension caused by a femoral arterial-venous fistula were studied. Studies included femoral venous pressure, valve morphology, femoral venous reflux and selected molecular inflammatory markers as examined by immunohistochemistry. The effects of treatment with the anti-inflammatory micronized purified flavonoid fraction (S 5628, Servier, 50 and 100 mg/kg/day) were investigated.

RESULTS

The femoral venous pressure was elevated close to arterial values for a period of 3 weeks. We then examined the morphology of the veins and selected molecular inflammatory markers were assessed. The results show that in this model venous reflux develops in response to venous hypertension. This can be inhibited by the administration of the anti-inflammatory micronized purified flavonoid fraction (S 5628, Servier, 50 and 100 mg/kg/day). The valve becomes incompetent by a combination of venous dilation and shortening of the valve leaflets. This is not inhibited by treatment with S 5628. The valve leaflets are infiltrated with granulocytes, monocytes and T-lymphocytes, and the endothelial cells express enhanced levels of P-selectin and ICAM-1. Cells in the valves are subject to extensive apoptosis although no enhancement of MMP 2,9 expression could be detected at the three-week time point examined in this study.

CONCLUSIONS

These results indicate that in this model chronic elevation of venous pressure is associated with an inflammatory reaction in venous valves, a process that may lead to their dysfunction, reflux, and upstream elevation of venous pressure. These effects are mitigated by the anti-inflammatory micronized purified flavonoid fraction in a dose dependent manner.

Angiogenic activation of valvular endothelial cells in aortic valve stenosis

Here, we demonstrate the angiogenic response of valvular endothelial cells to aortic valve (AV) stenosis using a new ex vivo model of aortic leaflets. Histological analysis revealed neovascularization within the cusps of stenotic but not of non-stenotic aortic valves. Correspondingly, the number of capillary-like outgrowth in 3D collagen gel was significantly higher in stenotic than in non-stenotic valves. Capillary-like sprouting was developed significantly faster in stenotic than in non-stenotic valves. New capillary sprouts from stenotic aortic valves exhibited the endothelial cell markers CD31, CD34 and von-Willebrand factor (vWF) as well as carcinoembryonic antigen cell adhesion molecule-1 (CEACAM1), Tie-2 and angiogenesis inhibitor endostatin. Western blot analyses revealed a significant increase of CEACAM1 and endostatin in stenotic aortic valve tissue. Electron microscopic examinations demonstrate that these capillary-like tubes are formed by endothelial cells containing Weibel-Palade bodies. Remarkably, inter-endothelial junctions are established and basement membrane material is partially deposited on the basal side of the endothelial tubes. Our data demonstrate the capillary-like sprout formation from aortic valves and suggest a role of angiogenesis in the pathogenesis of aortic valve stenosis. These data provide new insights into the mechanisms of valvular disorders and open new perspectives for prevention and early treatment of calcified aortic stenosis.

Nε-(Carboxymethyl)lysine depositions in human aortic heart valves: similarities with atherosclerotic blood vessels

Recent studies indicate a role of atherosclerosis-like changes involved in the pathogenesis of aortic valve stenosis. Interestingly, one of the major advanced glycation end products (AGEs), N(omega)-(carboxymethyl)lysine (CML) has been related to the process of atherosclerosis in blood vessels. In the present study, we have analyzed the presence of CML in degenerative altered aortic valves with atherosclerosis-like changes, and in degenerated mitral valves without atherosclerosis-like changes, derived from patients suffering from acute rheumatism during childhood. Degenerated and non-degenerated valves were derived from autopsy or obtained during cardiac surgery. The presence of CML was examined by immunohistochemistry. CML was found on the endothelium and fibroblasts in control aortic and mitral valves. Minor differences in CML staining were observed between control and degeneratively affected mitral valves. In contrast, in degenerated aortic valves, CML accumulation was found in macrophages and on calcification sites, comparable to that in atherosclerotic arteries, while the presence of CML staining on the endothelium and fibroblasts was significantly less as compared with control aortic valves. Our data support the hypothesis that the process of degeneration of aortic valves resembles that of atherosclerosis in blood vessels. They suggest that CML also plays a role in the process of atherosclerosis in aortic valves.

Percutaneous Transluminal Mitral Valvuloplasty Reduces Circulating Vascular Cell Adhesion Molecule-1 in Rheumatic Mitral Stenosis

BACKGROUND

The circulating levels of adhesion molecules, such as vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1), have been demonstrated to be elevated in patients with rheumatic mitral stenosis (MS). However, the impact of percutaneous transluminal mitral valvuloplasty (PTMV) on the elevated circulating levels of VCAM-1 and ICAM-1 in patients with MS has never been investigated.

METHODS

and results: A total of 19 patients with symptomatic MS undergoing PTMV were studied (group 1) [15 patients in chronic atrial fibrillation, and 4 patients in sinus rhythm]. The plasma levels of soluble VCAM-1 and ICAM-1 in the femoral vein and artery, and right and left atria before PTMV, and those in the peripheral venous blood at the 1-week and 4-week follow-ups after PTMV were determined by solid-phase sandwich enzyme-linked immunosorbent assay. The mitral valve area was calculated by means of the Doppler pressure half-time method. In addition, we measured plasma concentrations of soluble VCAM-1 and ICAM-1 in the peripheral venous blood samples obtained from 22 control patients (including 14 healthy volunteers in sinus rhythm [group 2] and 8 patients in chronic lone atrial fibrillation [group 3]). The plasma level of soluble VCAM-1 was significantly elevated in group 1 patients (1,205.4 +/- 462.4 ng/mL [mean +/- SD]) compared with group 2 (580.9 +/- 208.0 ng/mL) and group 3 patients (716.4 +/- 221.6 ng/mL) [p < 0.0001]. In group 1 patients, the plasma levels of soluble VCAM-1 and ICAM-1 in the left atrium did not differ from those in the right atrium, femoral vein, or femoral artery (p = 0.668 for VCAM-1, and p = 0.232 for ICAM-1). The area of mitral valve increased significantly after PTMV (1.08 +/- 0.14 cm(2) vs 1.48 +/- 0.33 cm(2), p < 0.0001). The mean left atrial pressure fell significantly after PTMV (22.9 +/- 5.2 mm Hg vs 17.7 +/- 6.0 mm Hg, p < 0.0001). The peripheral venous plasma level of soluble VCAM-1 obtained before PTMV fell significantly after PTMV (before, 1,205.4 +/- 462.4 ng/mL; 1 week after PTMV, 915.7 +/- 280.2 ng/mL; 4 weeks after PTMV, 859.0 +/- 298.7 ng/mL; p < 0.0001).

CONCLUSIONS

In patients with moderate-to-severe MS, the venous plasma level of soluble VCAM-1 fell significantly after PTMV, and the elevated plasma soluble VCAM-1 concentration was associated with hemodynamic abnormality rather than with rheumatic activity.

Changes in plasma levels of adhesion molecules after percutaneous mitral balloon valvuloplasty

BACKGROUND

Adhesion molecules are expressed on vascular endothelium and on immune and inflammatory cells. Recently increased levels of adhesion molecules have been shown in patients with rheumatic mitral stenosis. This study examined the serum levels of the adhesion molecules intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and E-selectin in patients with rheumatic mitral stenosis and the effects of percutaneous mitral balloon valvuloplasty (PMBV) on these adhesion molecules.

MATERIALS AND METHODS

Thirty five patients (3 men, 32 women, mean age 39+/-5 years) with severe rheumatic mitral stenosis who underwent percutaneous balloon mitral valvuloplasty, and 35 age and sex matched healthy control subjects were included in the study. Serum levels of ICAM-1, VCAM-1, and E-selectin were measured in all patients who underwent PMBV and in all control subjects. Blood samples were taken for measurement of adhesion molecules immediately before and 24 h after the mitral balloon valvuloplasty.

RESULTS

The plasma levels of soluble adhesion molecules E-selectin, ICAM-1 and VCAM-1 were significantly elevated in patients with mitral stenosis compared to control subjects: E-selectin, 97+/-59 vs. 45+/-24 ng/ml (P=.001), sICAM-1, 874+/-301 ng/ml vs. 238+/-82 ng/ml (P<.0001); sVCAM-1, 3056+/-763 ng/ml vs. 985+/-298 ng/ml (P<.0001). Plasma levels of VCAM-1 significantly increased 24 h after the valvuloplasty procedure (3056+/-763 ng/ml vs. 3570+/-1225 ng/ml P=.013). Plasma levels of E-selectin showed a significant decrease after PMBV (97+/-59 vs. 70+/-58 ng/ml, P=.043) and plasma levels of ICAM-1 did not show any change after PMBV (874+/-301 vs. 944+/-377 ng/ml, P=.356).

CONCLUSION

Cellular adhesion molecules, sICAM-1, E-selectin, sVCAM-1 have shown changes in different directions in response to PMBV. These results necessitate further studies to clarify the mechanism underlying the association between adhesion molecules and PMBV as well as rheumatic mitral stenosis.

Endothelium and valvular diseases of the heart

It has become increasingly evident that the endothelium plays a critical role in the pathogenesis of valvular heart disease. The endothelium helps regulate vascular tone, inflammation, thrombosis, and vascular remodeling. Dysfunction of the endothelial cells has been linked to many vascular disorders including atherosclerosis. Common valvular diseases such as senile degenerative valve disease, myxomatous (or floppy) valves, rheumatic valves, and infective endocarditis valves show changes in the synthetic, morphologic, and metabolic functions of the valvular endothelial cells. These diseases are active processes related to endothelial cell dysfunction. Endothelial cell dysfunction is caused by mechanical forces, bacterial infection, autoantibodies, and circulating modulators of endothelial cell function. This study reviews the role of endothelial cell dysfunction in the more common valvular diseases. Continued research on endothelial cell dysfunction is crucial to our understanding of valvular heart diseases and may elucidate novel treatment and prevention strategies.

Heterogeneous expression of cell adhesion molecules by endothelial cells in ARDS

ARDS (acute respiratory distress syndrome) can be associated with septic shock and multiple organ failure caused by an uncontrolled systemic inflammatory response to Gram-negative bacterial infection. While in animal models the key role of the endothelial adhesion molecules ICAM-1, E-selectin, and VCAM in ARDS has been extensively studied, there are scarcely any corresponding pathomorphological studies of human lung tissue. Hence, little is known about whether there is a comparable, or even heterogeneous, expression pattern of these molecules in the human pulmonary vasculature. This study was therefore undertaken to investigate the immunohistochemical expression of the constitutively expressed PECAM (CD31) and the inducible molecules ICAM-1, E-selectin, and VCAM in ARDS lungs from patients who had died in septic shock induced by Gram-negative bacteria. While in all specimens (ARDS and normal lungs) there was homogeneous strong expression of PECAM in all vessels, ICAM-1 was clearly up-regulated in ARDS lungs. E-selectin and VCAM were not expressed by endothelial cells (ECs) in normal lungs, but in ARDS lungs there was strong expression of both molecules in larger vessels, while in the capillaries there was only mosaic-like weak expression of a few ECs. This immunohistochemical investigation demonstrates the induction and up-regulation of adhesion molecules in human ARDS lungs, comparable to that described in animal models. There is also markedly heterogeneous expression of E-selectin and VCAM, indicating toporegional differences in the function of pulmonary ECs.

Expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 in human crescentic glomerulonephritis

AIMS

In glomerulonephritis, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) may play important roles in the formation of crescents. These studies are designed to evaluate the expression patterns of ICAM-1 and VCAM-1 in human crescentic glomerulonephritis and to determine the cellular origin of adhesion molecules in the crescentic lesions.

METHODS AND RESULTS

We examined the expression of ICAM-1 and VCAM-1 proteins in renal biopsies with cellular (n=7), fibrocellular (n=9) or fibrous (n=4) crescentic glomerulonephritis, and six controls by immunohistochemistry. mRNA expression of ICAM-1 and VCAM-1 was further evaluated by RNA in-situ hybridization. Cytokeratin or CD68 immunohistochemistry was performed on the same sections, where in-situ hybridization had been carried out. In cellular crescents, ICAM-1 and VCAM-1 proteins were over-expressed to a similar extent. Of the three types of crescents, the extent of ICAM-1 immunopositivity was the greatest in the cellular crescents and decreased towards the fibrous crescents (P < 0.05). Yet the extent of VCAM-1 immunoreactivity was not different between the types. Fibrous crescents still contained some epithelial cells and showed only VCAM-1 expression. In the glomeruli with cellular or fibrocellular crescents, the extent of ICAM-1 immunopositivity in the glomerular tufts was significantly larger than that of VCAM-1 (P < 0.05). In an in-situ hybridization study, the mRNA expression patterns of ICAM-1 and VCAM-1 paralleled their protein expressions. A double-labelling study showed that the signal for ICAM-1 and VCAM-1 mRNAs was mainly present in cytokeratin-positive and CD68-negative cells in the crescentic lesions.

CONCLUSIONS

These results suggest that glomerular parietal epithelial cells in cellular crescents up-regulate both ICAM-1 and VCAM-1, and that some epithelial cells retained in fibrous crescents persistently over-express VCAM-1, but not ICAM-1. They also suggest that ICAM-1 is involved in early leucocyte recruitment into glomeruli in crescentic glomerulonephritis.

Cigarette smoking and hypertension influence nitric oxide release and plasma levels of adhesion molecules

Progression of atherosclerosis is currently believed to involve interactions between leukocytes and vascular endothelium. Epidemiological risk factors for atherosclerosis such as hypertension and smoking are known to cause endothelial dysfunction, which is an early event in the atherosclerotic process; they also may be considered in the light of their effects on adhesion molecule expression and release. Little is known about the additive effect between these two risk factors on endothelial adhesion molecule expression and nitric oxide release. Soluble adhesion molecules and the nitric oxide were quantified in smoking hypertensive patients in comparison to those from patients with hypertension alone. Cotinine, a stable metabolite of nicotine, has been used to identify smokers. One hundred and three hypertensive patients were selected: 51 smokers (plasma cotinine levels >25 ng/ml) and 52 non-smokers. Plasma concentrations of soluble intercellular cell adhesion molecule-1 (sICAM-1), soluble endothelial leukocyte adhesion molecule-1 (sELAM-1) and soluble vascular cell adhesion molecule-1 (sVCAM-I) were quantified with ELISA methods. Plasma concentration of nitric oxide metabolites was measured by HPLC, whilst plasma concentration of cotinine was measured by RIA. Significant increases of sICAM-1 and sVCAM-1 were demonstrated in smokers (p<0.001 and p<0.05, respectively). In the same patients, a positive significant correlation between sVCAM-1 and plasma cotinine levels was observed (p<0.002). Nitric oxide metabolites were reduced significantly (p<0.04) in smokers. In conclusion, our data show that the two risk factors, smoking and hypertension, are additive risk factors in generating endothelial dysfunction and vascular damage, which plays a key role in atherogenesis.