|
|
||||||||
Eur J Cardiothorac Surg 1999;16:150-155
© 1999 Elsevier Science NL
a Department of Cardiothoracic Surgery, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
b Department of Physiology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
c Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
d Department of Cardiovascular Surgery, Yuksek Ihtisas Hospital of Turkey, Istanbul, Turkey
e Department of Thoracic Surgery, Marmara University, Istanbul, Turkey
Corresponding author. N. Tandogan cad., 5/6 Kavaklidere, 06540 Ankara, Turkey. Tel.: +90-312-4267574; fax: +90-312-4266181
e-mail: kvural{at}tr-net.net.tr
| Abstract |
|---|
|
|
|---|
Key Words: Saphenous Vein graft Adhesion molecule Reoperation Membrane stabilizer Nitric oxide
| 1. Introduction |
|---|
|
|
|---|
Leukocyte adhesion to vascular endothelium is a primary step in the early stages of atherosclerosis, which is mediated by the interaction of cellular adhesion molecules expressed on the surfaces of both endothelial cells and leukocytes. Cellular elements of the blood, especially monocytes and lymphocytes, are known to signal adhesion receptor expression on endothelial cell surface by releasing mediators such as histamine [1]. Histamine is in fact a potent stimulus for neutrophil accumulation in tissues; histamine triggers leukocyte rolling by promoting the expression of P-selectin on the endothelial cell surface, enhances ICAM-1 expression through its actions on H1 receptors, and also induces the upregulation of E-selectin expression [1,2]. Endothelial cells also release nitric oxide (NO) which influences endothelial cell-leukocyte interactions.
Ketotifen, a second generation histamine H1-receptor antagonist, has long been used in the management of allergic disorders. In addition to histamine receptor antagonism, ketotifen reduces mast-cell degranulation and decreases the release of histamine, mast cell proteases, myeloperoxidase, leukotrienes, platelet activating factor (PAF), various prostaglandins, and inhibits polymorphonuclear aggregation and migration [3]. Ketotifen also enhances the expression of NO synthase [4]. In toto, these actions attenuate inflammatory responses. The current study was designed to determine the in vitro effects of this mast cell membrane-stabilizing agent on saphenous vein grafts in terms of inhibiting endothelial reactivity when added to the storage solution.
| 2. Materials and methods |
|---|
|
|
|---|
2.1. Immunostaining
To demonstrate the fact that adhesion molecule expression can increase during the storage period, samples were obtained fresh or after 1 h of storage in heparinized blood. These samples were then fixed in formaldehyde. Fixed specimens were immunostained using a P-selectin antibody (Research Diagnostics Inc., Flanders, NJ) at 1:100 dilution for 1 h at 37°C. After subsequent washes with phosphate buffered saline (PBS), a second antibody, an anti-rabbit IgG-alkaline phosphatase conjugate (Sigma Chemical Co.) was added and incubated for 30 min at 37°C and then stained by Fast Insoluble Alkaline Phosphatase Substrate (Sigma Chemical Co.). Counterstaining was applied as Mayer's hematoxylin dye for 5 min at room temperature. The specimen was then washed, dried and mounted with a cover glass. This study was performed to demonstrate that endothelial expression of cellular adhesion receptors may occur even during short storage periods after harvesting saphenous vein grafts.
2.2. Western blotting
Tissue samples were homogenized for 30 s at 4°C with a Polytron (Kinematica, GmbH, Krienz-Luzerne, Switzerland) with ice-cold 20 mM TrisHCl, pH 7.4, containing 100 mM NaCl, 2 mM phenylmethylsulphonyl fluoride (PMSF), 0.5 mg/l leupeptin and 0.7 mg/l pepstatin. Homogenates were shaken at 4°C for 3 h, then centrifuged at 13 000 rev./min for 10 min at 4°C and, the supernatant was collected as the source of sample protein. Samples were run in a 7.5% polyacrylamide gel (Fisher Scientific, Pittsburgh, PA) and then transferred to a nitrocellulose membrane (Bio-Rad Laboratories, Hercules, CA). The membrane was blocked for non-specific binding using 1% bovine serum albumin (BSA) in PBS for 12 h at 4°C. The membrane was then incubated in 0.05% BSA and 0.05% Tween 20 in PBS containing an anti-human ICAM-1 antibody (R&D Systems Inc., Minneapolis, MN) at a concentration of 1:1000 for 1 h. After subsequent washes, membrane was incubated with an anti-goat IgG-peroxidase conjugate (Sigma Chemical Co.) at 1:2000 concentration in PBS, 0.5% BSA and 0.05% Tween 20 for 45 min. Then the membrane was washed twice before continued processing for enhanced chemiluminescence (ECL) detection (Amersham, Piscataway, NJ). The staining intensity of specific bands was quantified by densitometric scanning by a computer software (Molecular Analyst, Bio-Rad Laboratories, Hercules, CA). Calculated densities were then statistically compared. The same procedure was repeated for the detection of E-selectin, P-selectin and VCAM-1 using corresponding antibodies (R&D Systems Inc.) and a rabbit derived anti-NOS 2 antibody (Santa Cruz Biotechnology Inc., Santa Cruz, CA) for the detection of inducible nitric oxide synthase (NOS-2).
2.3. Enzyme-linked immunosorbent assay
Tissue homogenates in PBS were added to 5% trichloroacetic acid and kept on ice for 30 min. Those homogenates were then centrifuged at 4 000 rev./min for 15 min. Supernatants were collected and washed three times with ether. After storing the homogenates at 20°C for 5 min, cGMP content of nitroglycerin-treated vein segments was measured by an enzyme-linked immunosorbent assay (ELISA) kit (R&D Systems Inc.). This assay is based on the competitive binding technique in which cGMP present in a sample competes with a fixed amount of alkaline phosphatase-labeled cGMP for sites on a rabbit polyclonal antibody. This primary antibody binds to a goat anti-rabbit antibody coated onto the microplate. The absorbance was read at 405 nm using a Biokinetics microplate reader Model EL 340 (Biotek Instruments, Winooski, VT).
2.4. Statistical analysis
Means are presented ±SD. For each outcome variable exactly one sample per patient and per group was used (i.e. there are seven pairs of numbers used for each statistical test. All statistics were obtained by Wilcoxon Matched-Pairs Signed Ranks Test using SPSS statistical software (release 8.0; SPSS Inc., Chicago, IL).
| 3. Results |
|---|
|
|
|---|
|
|
|
|
3.4. cGMP content
ELISA assay of homogenates demonstrated that tissue cGMP levels were higher in Group B upon stimulation with nitroglycerin than they were for Group A (2.2±0.6 pmol/ml vs. 5.7±1.7 pmol/ml, respectively, P=0.03; Fig. 5).
|
| 4. Discussion |
|---|
|
|
|---|
Human blood monocytes and lymphocytes contain substantial amounts of histamine which may be released upon stimulation with either substance-P, C5a or the calcium ionophore [8]. Histamine release from activated mast cells is attenuated by exogenous NO and exacerbated by NO synthesis inhibitors. Moreover, the mast cell produces a nitric oxide-like factor that can directly feed back to decrease histamine release [9]. NO is an endogenous inhibitor of leukocyte adhesion, activation and chemotaxis. NO activates guanylate cyclase and increases the conversion of GTP to cGMP, which in turn reacts with cGMP-dependent protein kinase and causes a cascade of changes in protein phosphorylation, including dephosphorylation of myosin light chain, leading to cell relaxation. Therefore, a reduction in cGMP may cause endothelial cell contraction and increase the size of interendothelial junctions, resulting in a leaky endothelial barrier. Reduced levels of NO synthesis may also lead to superoxide accumulation, which could directly cause an increase in endothelial permeability and the release of various mast cell- derived chemical agents, including PAF and histamine [9]. NO modulates mast cell degranulation by competing with superoxide anion, a potent activator of mast cell activation and degranulation [10]. On the other hand, endothelial free radical generation plays an important role in regulation of intercellular adhesion molecules and leukocyte recruitment. Therefore, the suppression of ICAM-1 expression on the endothelial cells by endogenous NO might contribute to suppressing inflammation in vivo.
Several lines of evidence from both in vitro and in vivo studies have recently suggested a role of NO as an antiatherogenic autocoid. Accumulating evidence suggests that NO also influences endothelial cell-leukocyte interactions [10]. In addition, NO suppresses T-cell proliferation and inhibits migration of neutrophils and monocytes [11]. Among its immunological functions, NO has cytotoxic and cytostatic actions and therefore often is considered a hallmark of macrophage activation [12]. Recent evidence suggests that increased levels of NO impair leukocyte-endothelium interaction, inhibit atherosclerotic intimal thickening [13], and inhibits vasomotor reactivity [14]. Therefore, the suppression of ICAM-1 and VCAM-1 expression on saphenous vein endothelial cells by endogenous NO could prevent development of atherosclerotic lesions in vivo.
Ketotifen, a second generation histamine H1 receptor antagonist has long been used in the management of allergic disorders. In addition to histamine receptor antagonism, some of these effects may be related to the inhibition of the release of mast-cell and neutrophil-derived proinflammatory mediators. In various experimental and clinical conditions ketotifen was noted to reduce mast-cell degranulation and to decrease the release of histamine, mast-cell proteases, myeloperoxidase, leukotrienes, platelet activating factor (PAF), and various prostaglandins [3]. Ketotifen also stimulates NO synthase activity by mechanisms other than H1-receptor antagonism and, administration of this drug causes a modest decline in blood pressure and reduces vascular resistance [4]. Ketotifen stabilizes the cell membrane and/or alters its properties with respect to calcium permeability. It causes a dose related decrease in acetyl-CoA acetyltransferase stimulation and antigen-induced PAF release. Ketotifen also blocks the decline in cAMP levels in leukocytes caused by antigenic challenge [15].
In this study, we investigated any beneficial effect of ketotifen by means of graft reactivity when added to the storage solution (heparinized blood for most instances) of saphenous vein grafts before their implantation to arterial system as graft conduits. Although ketotifen did not reduce ICAM-1, E-selectin and P-selectin expression in vitro, ketotifen treated segments expressed less VCAM-1 and more NOS-2. This may be due to either a different mechanism of action for ketotifen in which VCAM-1 and NOS-2 involved or a possible NOS-2 induction pathway inversely related to VCAM-1 receptor activation. However current data did not provide a scientific explanation for this observation and further studies in this area are certainly needed to go beyond speculation. From a functional standpoint, ketotifen treatment was associated with increased cGMP production in response to nitroglycerin and vein segments exhibited a greater degree of relaxation. Taken together, these data show that venous endothelium may be activated by the ex vivo storage period, and that the storage period presents an opportunity to modulate vascular properties. Mast cell stabilizing agents such as ketotifen represent one potential means of treating ex vivo venous segments to help preserve vascular homeostatic properties. Studies such as these may help to establish this class of agents as being potentially useful for organ storage and for settings of anticipated reperfusion injury, such as occurs during cardiac surgical procedures.
| Acknowledgments |
|---|
| References |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
K. Hinokiyama, G. Valen, S. Tokuno, J. B. Vedin, and J. Vaage Vein graft harvesting induces inflammation and impairs vessel reactivity. Ann. Thorac. Surg., October 1, 2006; 82(4): 1458 - 1464. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Kaplan, J. A. Morgan, G. Bisleri, F. H. Cheema, H. O. Akman, V. K. Topkara, and M. C. Oz Effects of Resveratrol in Storage Solution on Adhesion Molecule Expression and Nitric Oxide Synthesis in Vein Grafts Ann. Thorac. Surg., November 1, 2005; 80(5): 1773 - 1778. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. Sakaguchi, T. Asai, D. Belov, M. Okada, D. J. Pinsky, A. M. Schmidt, and Y. Naka Influence of ischemic injury on vein graft remodeling: Role of cyclic adenosine monophosphate second messenger pathway in enhanced vein graft preservation J. Thorac. Cardiovasc. Surg., January 1, 2005; 129(1): 129 - 137. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. P Vallely, P. G Bannon, C. F Hughes, and L. Kritharides Endothelial Cell Adhesion Molecules and Cardiopulmonary Bypass Asian Cardiovasc Thorac Ann, December 1, 2001; 9(4): 349 - 355. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |