Possible Role of Fibrinogen in the Aggregation of White Blood Cells

AK03, a new recombinant fibrinogenase prevents abdominal adhesions in a rat model without systemic side effects

BACKGROUND

Abdominal adhesions are one of the most common complications after abdominal surgery, and fibrin is suspected to be a crucial component. The aim of the current study was an in vivo evaluation of a new recombinant fibrinogenase (AK03) in two animal models.

METHODS

Sixty-four rats were randomly divided into four groups (sodium chloride [NaCl], icodextrin, AK03 low dose, and AK03 high dose) and evaluated at two time endpoints. Adhesion model comprised both a visceral defect (terminal ileum) and parietal defect. Test (AK03) and control substances (NaCl and icodextrin) were administered intraperitoneally after setting the intraabdominal defects. A second dose was administered 24 h after surgery. Plasma fibrinogen values were taken at baseline and after 7 and 21 d, respectively. Rats were sacrificed after 7 or 21 d for macroscopic (Diamond score) and immunohistochemical investigations.

RESULTS

After 7 and 21 d, the Diamond score of postsurgical adhesions were significantly lower in both AK03-treated groups compared with NaCl control group (P = 0.02). There were no unspecific systemic side effects in both treatment groups and no decrease in plasma fibrinogen concentration. In none of the four groups was there any evidence for impaired wound repair. Microscopically in the area of the parietal defect, we saw less cluster of differentiation 3⁺ T-lymphocytes and cluster of differentiation 68⁺ macrophages in both groups receiving AK03 compared with the NaCl and icodextrin control groups.

CONCLUSIONS

The results of this study indicate that the new recombinant fibrinogenase AK03 effectively prevents peritoneal adhesions without causing side effects, notably systemic fibrinogen depletion, bleeding, or impaired wound repair. Due to these results, future clinical studies may be promising.

Increased adhesiveness of white blood cells in patients with unstable angina: additional evidence for an involvement of the immune-inflammatory system

BACKGROUND

Data are being accumulated on the presence of inflammatory response in patients with acute coronary syndromes.

HYPOTHESIS

The study was undertaken to confirm that the adhesive state of the peripheral blood leukocytes can provide information on an inflammatory process in patients with unstable angina pectoris.

METHODS

The study included 21 patients with unstable angina, 32 patients with stable angina, and 13 patients with chest pain and no evidence of coronary artery disease.

RESULTS

The percentage of aggregated leukocytes in patients with unstable angina (5.8 +/- 3.2%) was significantly (p < 0.02) increased compared with that of patients with no evidence of active coronary disease (3.2 +/- 2.6%).

CONCLUSION

Additional evidence for an existing smoldering inflammatory process in unstable angina pectoris can be provided by testing the percentage of aggregated leukocytes in peripheral blood.

Serum amyloid type A may be a predictor of restenosis

BACKGROUND

Elevation of acute phase proteins [C-reactive protein (CRP) and serum amyloid type A (SAA)] has been demonstrated in unstable angina with an adverse clinical prognosis.

HYPOTHESIS

The study was undertaken to determine the effect of angioplasty on the levels of SAA and the correlation with postangioplasty restenosis.

METHODS

In a university-affiliated tertiary medical center, a prospective case study was undertaken in 55 patients who underwent successful percutaneous transluminal coronary angioplasty (PTCA) of a single coronary lesion for angina pectoris. Three groups of patients were clinically characterized according to Braunwald's classification of anginal syndrome: Group A: class III; Group B: class I; Group C: stable angina. Serum amyloid type A was measured by an ELISA method before PTCA and after 24 h, 1, and 3 months. Patients were followed clinically for 12 months. A thallium stress perfusion scan was performed 3 months after PTCA and coronary angiography was repeated in patients with an abnormal thallium perfusion scan.

RESULTS

Serum amyloid type A levels > 100 micrograms/ml could identify Group A patients with a high sensitivity and specificity (r = 0.85 and 0.86, respectively). Of the patients studied, 75% increased their SAA level 24 h after angioplasty. An increase of SAA by > 100% was associated with an increased risk of restenosis, with a relative risk of 6.4 (p < 0.05).

CONCLUSION

Increased levels of SAA characterize patients with unstable angina pectoris with a high specificity and sensitivity. Levels of SAA that increase > 100% 24 h after angioplasty may serve as a marker of restenosis.

Leukocyte aggregation-related pseudoleukopenia in pediatrics: a sporadic event or a systematic error?

OBJECTIVE

To determine whether electronic counter-related pseudoleukopenia is a rare phenomenon or a systematic underestimation in children with acute infection/inflammation.

METHODS

We have used a simple slide test and image analysis to reveal the number of white blood cells and their degree of aggregation. The number of leukocytes counted by an electronic cell analyzer was divided by the number of cells counted on the slides creating an electronic cell-to-slide leukocyte count ratio.

RESULTS

A significant (P < 0.0005) negative (r = -0.314) correlation between the above mentioned ratios and the percent of aggregated leukocytes in the peripheral blood was found in a group of 239 children with various acute infections. Thus elevated leukocyte aggregation is associated with a relatively lower electronic analyzer cell count.

CONCLUSIONS

The appearance of aggregated leukocytes in the peripheral blood during acute infections might be associated with pseudoleukopenia. This phenomenon has been extensively described in the adult population and seems to exist in children as well.

Rheological determinants in patients with Gaucher disease and internal inflammation

The purpose of this study was to determine whether the inflammatory response in patients with Gaucher disease (GD) is accompanied by enhanced adhesiveness/aggregation of both red and white blood cells. Sixty patients with GD and matched controls were included. The degree of erythrocyte and leukocyte adhesiveness/aggregation was determined by using a simple slide test and image analysis. Patients with GD had significantly elevated concentrations of fibrinogen (328 vs. 262 mg/dl, P < 0.0001) and accelerated erythrocyte sedimentation rates (27 vs. 13 mm/H, P < 0.005). This was accompanied by a significantly enhanced degree of erythrocyte (75 vs. 85, P < 0.0001) and leukocyte (3.5 vs. 1.3, P < 0.002) adhesiveness/aggregation. The low-grade, smoldering, and subclinical internal inflammation in individuals with GD is accompanied by an increased degree of erythrocyte and leukocyte adhesiveness/aggregation. These findings might have rheological consequences in terms of microcirculatory slow flow and tissue hypoxemia.

New cell attachment peptide sequences from conserved epitopes in the carboxy termini of fibrinogen

Fibrinogen seems to contribute significantly to cell binding and recruitment into wounds besides its major role in clot formation. We describe 19- to 21-mer cell-binding (haptotactic) peptides from the C-termini of fibrinogen beta-chain (Cbeta), the extended alphaE chain, and near the C-terminal of the gamma-chain. When these peptides were covalently bound to a biologically inert matrix such as Sepharose beads (SB), they elicited beads attachment to cells, mostly of mesenchymal origin (including fibroblasts, endothelial cells, and smooth muscle cells) as well as some transformed cell lines. Based on such haptotactic activity, these peptides were termed "haptides." By contrast, peptides homologous to fibrinogen C-termini alpha- and gamma-chains elicited no such activity. The haptide Cbeta could not block the interaction of fibroblasts with antibodies directed against integrins beta(1), alpha(v), alpha(v)beta(1), alpha(v)beta(3), and alphaIIbeta(3). Moreover, GRGDS peptide could not inhibit enhanced cell binding to SB-Cbeta, as expected from an integrin-mediated process. In soluble form the haptides were accumulated in cells with nonsaturable kinetics without any toxic or proproliferative effects in concentrations up to 80 microM. These findings suggest that the conserved haptidic sequences within fibrin(ogen) can be associated with the adhesion and migration of cells into fibrin clots and may have a significant role in normal wound healing and in various pathological conditions.

The leukocyte adhesiveness/aggregation test (LAAT) conveys information of biological relevance and is not a result of chance collision. Something more than another hypothesis

The leukocyte adhesiveness/aggregation test is a sensitive marker for the detection of inflammation and for the assessment of its intensity. This has been convincingly shown by several independent groups as well as in various models of infection/inflammation. However, it has not been settled whether the concomitant appearance of leukocytosis and aggregation is a result of chance collision or not. We recently examined a group of individuals with proven acute infection/inflammation who had absolutely the same number of white blood cells in the peripheral blood and found significantly enhanced leukocyte adhesiveness/aggregation in patients as opposed to control. These findings clearly demonstrate that the phenomenon of leukocyte adhesiveness/aggregation does not result from a simple chance collision. It probably conveys a message of biological relevance reflecting both the appearance of cell adhesive molecules during activation as well as the contribution of plasmatic sticky proteins.

The usefulness of telemedicine for the detection of infection/inflammation at the point of care

The objective of this study is to examine the possibility of using Telemedicine to diagnose the presence of the inflammatory response and to assess its intensity at the point of care. One drop of citrated peripheral venous blood from 15 patients with infection/inflammation and 15 controls were used to prepare the slides. Unstained pictures were analyzed using a microscope, video camera and image analyzer (INFLAMETTM, Biovision, Tel Aviv, Israel). The jpg-compressed images were transferred via telephone to a physician in a remote location. A significant correlation was noted between the white blood cell count and the number of leukocytes per square mm by image analysis (r = 0.67 p < 0.0001 n = 30), between the degree of leukocyte adhesiveness/aggregation and the concentration of C-reactive protein (r = 0.42 p = 0.02 n = 29) and between the degree of erythrocyte aggregation and either fibrinogen concentrations (r = 0.73 p < 0.0001) or erythrocyte sedimentation (r = 0.83, p < 0.0001). No problems occurred during file transmission and there were no transfer errors. Physicians can successfully estimate the presence of an inflammatory response and its intensity using a simple slide test, image analysis, and Telemedicine technology.

Protein adsorption to oligo(ethylene glycol) self-assembled monolayers: experiments with fibrinogen, heparinized plasma, and serum

Low protein adsorption is believed advantageous for blood-contacting materials and ethylene glycols (EG)-based polymeric compounds are often attached to surfaces for this purpose. In the present study, the adsorption of fibrinogen, serum, and plasma were studied by ellipsometry on a series of well-defined oligo(EG) terminated alkane-thiols self-assembled on gold. The layers were prepared with compounds of the general structure HS-(CH2)15-CONH-EGn, where n = 2, 4, and 6. Methoxy-terminated tri(EG) undecanethiol and hydroxyl-terminated hexadecanethiol self-assembled monolayers (SAMs) were used as references. The results clearly demonstrate that the adsorption depends on the experimental conditions with small amounts of fibrinogen adsorbing from a single protein solution, but larger amounts of proteins from serum and plasma. The adsorption of fibrinogen and blood plasma decreased with an increasing number of EG repeats and was temperature-dependent. Significantly less serum adsorbed to methoxy tri(EG) than to hexa(EG) and more proteins remained on the latter surface after incubation in a sodium dodecyl sulfate (SDS) solution, indicating a looser protein binding to the methoxy-terminated surface. All surfaces adsorbed complement factor 3 (C3) from serum and plasma, although no surface-mediated complement activation was observed. The present study points to the importance of a careful choice of the protein model system before general statements regarding the protein repellant properties of potential surfaces can be made.

The usefulness of an inflammation meter to detect the presence of infection/inflammation in elderly patients

BACKGROUND

Medical personnel who work in small geriatric institutions most frequently do not have access to realtime laboratory facilities.

METHODS

In order to present a new method to determine the presence of an inflammatory response and for the assessment of its intensity, 118 patients aged 77 +/- 6 years with various bacterial infections were evaluated as well as 129 elderly individuals with various stressful conditions but no acute infections who served as controls. The leukocyte and erythrocyte adhesiveness/aggregation tests were performed by using a simple slide test and image analysis. The availability of the CD11b/CD18 and CD62L antigen on the leukocytes' surface was measured by whole blood flow cytometry, and the quantitative C-reactive protein by using laser nephelometry and specific antihuman C-reactive protein antibodies.

RESULTS

A significant difference was noted between patients and controls for all variables obtained by the slide test and image analysis. In addition, a highly significant correlation was noted between the number of leukocytes counted on the slides and white blood cell count, between the leukocyte adhesiveness/aggregation test and quantitative C-reactive protein, and between the degree of erythrocyte adhesiveness/aggregation and either the Westergren sedimentation or fibrinogen concentration.

CONCLUSIONS

By using our low-cost and real-time slide test, any medical or paramedical personnel can get relevant information regarding the presence of an acute phase response at the point of care.

Combined leukocyte and erythrocyte aggregation in patients with acute myocardial infarction

OBJECTIVES

To determine whether the increased aggregability of both white and red blood cells previously reported in acute myocardial infarction (aMI) correlates with each other.

DESIGN

Cross-sectional study comparing two groups of patients and a group of healthy controls.

SETTING

A tertiary university affiliated hospital (Intensive Cardiac Care Unit and Department of General Internal Medicine).

PATIENTS

Consecutive patients with aMI, patients with chest pain and no infarction, and healthy controls.

MEASUREMENTS AND RESULTS

We adapted a simple slide test and image analysis to reveal the state of both leukocyte and erythrocyte adhesiveness/aggregation in the peripheral blood of patients with aMI. A significant (P=0.0001) increment in the aggregation of both cellular populations was noted in 48 patients with aMI as opposed to the 141 patients with ischemic heart disease and no infarction and in 45 matched controls. In addition, a significant correlation was noted between the various variables of the leukocyte and erythrocyte adhesiveness/aggregation tests.

CONCLUSIONS

The significant correlation between the aggregability of white and red blood cells in patients with aMI is suggestive of there being a commonly shared adhesive protein(s). The prompt identification of patients with increased aggregation might have clinical and therapeutic implications.

Combined leukocyte and erythrocyte aggregation in the peripheral venous blood during sepsis. An indication of commonly shared adhesive protein(s)

We have used a simple slide test and image analysis to reveal the state of leukocyte and erythrocyte adhesiveness/aggregation in the peripheral blood of 28 patients with sepsis and 28 controls. A significant (P<0.00001) increment in both leukocyte and erythrocyte adhesiveness/aggregation was noted in patients compared with controls. Moreover, a significant (r=0.73, n=56, P<0.001) correlation was noted between the two adhesiveness/aggregation variables themselves, suggesting a common mechanism responsible for these adhesive phenomena. The significant correlation with fibrinogen suggests that this protein might be such a "non-specific glue." Our results indicate that a simple slide technique and image analysis can assess the aggregability of both white and red blood cells in septic patients. This might have clinical application when interventions to reduce cell aggregability are planned in order to improve blood flow in the microcirculation.

Fibrinogen promotes neutrophil activation and delays apoptosis

The acute phase of the inflammatory response involves an increase in the concentrations of different plasma proteins that include fibrinogen (Fbg) and multiple proinflammatory mediators. In parallel, neutrophil activation is thought to play a crucial role in several inflammatory conditions, and it has been recently demonstrated that Fbg specifically binds to the alpha-subunit of CD11b/CD18 on neutrophil surface. Although several reports have shown that CD11b engagement modulates neutrophil responses, the effect of human Fbg (hFbg), one of CD11b physiologic ligands, has not been exhaustively investigated. We have now shown that incubation of purified neutrophils with hFbg induces a transient and rapid elevation of free intracellular Ca2+. This early intracellular signal is accompanied by changes in the expression of neutrophil activation markers, including enhancement of CD11b and CD66b, and down-regulation of FcgammaRIII. In addition, we have evaluated the effect of hFbg on two functional events related to expression and resolution of inflammation: cytotoxic capacity and rate of neutrophil apoptosis. We have found that activation of neutrophils by hFbg resulted in both enhancement of phagocytosis and Ab-dependent cellular cytotoxicity, and delay of apoptosis. We conclude that during inflammatory processes, soluble Fbg could influence neutrophil responses, increasing and prolonging their functional capacity.

Trilinolein potentiates the pro-aggregating effect of phorbol-12-myristate 13-acetate in human polymorphonuclear leukocytes

Trilinolein, a triacylglycerol with linoleic acid as the only type of fatty acid residue in all three of the glycerol esterified positions, was recently reported to have an antiplatelet effect, mediated through stimulating nitric oxide and cyclic guanosine monophosphate (GMP) formation. In our study, trilinolein induced aggregation of human polymorphonuclear neutrophils (PMNs) and, pretreatment with 0.1 nM trilinolein enhanced phorbol-12-myristate 13-acetate (PMA) induced aggregation. Further investigation showed that trilinolein at concentrations ranging from 0.1 nM to 10 microM increased cyclic GMP formation after 10 min of incubation with PMNs. Pretreatment of trilinolein with 10 microM d-sphingosine, before being incubated with PMNs, attenuated the stimulatory effect of trilinolein on cyclic GMP formation, and pretreatment of 10 microM d-sphingosine also attenuated the aggregation induced by PMA and trilinolein. We conclude that trilinolein can induce the aggregation of human PMNs, and enhance the aggregation induced by PMA.

Effects of opiates on blood rheology

To evaluate the possible effect of opiates on blood rheology, the plasma fibrinogen, prothrombin time and leukocyte aggregation were measured in 75 heroin addicts categorized by the time of abstention from heroin and the administration of naltrexone (25 active heroin abusers, 25 abstaining for 1 week, 11 abstaining for at least 5 months and 14 abstaining for 1 month and taking naltrexone during this period). No difference was detected in prothrombin time, but the leukocyte aggregation and fibrinogen were significantly different among the four groups (p = 0.028 and p = 0.0001, respectively). In particular, fibrinogen was 318 +/- 10.9 mg/dL in heroin abusers, significantly higher than that of the remaining three groups; the percentage of aggregated leukocytes was 5.01 +/- 0.77 in heroin users, significantly higher than that of subjects abstaining for at least 5 months. The fibrinogen levels declined sharply with abstention and an additive effect was noted with the administration of naltrexone, but leukocyte aggregation changed more slowly, and the effect of naltrexone (if any) was weaker. These data indicate an adverse effect of opiates on blood rheology and suggest that further studies should be performed to evaluate whether naltrexone may be useful in the prevention of major ischemic syndromes in patients with hyperfibrinogenemia and, perhaps, in those with high levels of leukocyte aggregation.

Cigarette Smoking Increases White Blood Cell Aggregation in Whole Blood

We studied the effect of chronic cigarette smoking on white blood cell aggregation, increased aggregation predisposes to microvascular occlusion and damage. Current smokers had significantly increased white blood cell aggregation when compared with non smokers. The presence of chronically activated white blood cells in current smokers may be relevant in the pathogenesis of ischaemic vascular disease.

The state of leukocyte adhesiveness/aggregation in the peripheral blood is more sensitive than the white blood cell count for the detection of acute mental stress

We determined the state of the leukocyte adhesiveness/aggregation in the peripheral blood by using a simple slide test and found it to be more sensitive than the white blood cell count for the detection of acute mental stress. Included were 71 controls, 64 young athletes examined just before their exercise, 14 volunteers who were examined 10-20 min before engagement in rappelling while an additional group of 20 were examined just before the act as they were facing an abyss from the top of a cliff. The state of leukocyte adhesiveness/aggregation correlated significantly (p less than 0.0005) only with the increasing strain assumed to occur from the first to the fourth group. The state of leukocyte adhesiveness/aggregation was 3.3 x more sensitive than white blood cell count in both rappelling groups and 5 x more sensitive than white blood cell count when evaluated in those examined at the last minute. We concluded that the state of leukocyte adhesiveness/aggregation is a reliable marker of acute mental stress.

Possible role for a plasma factor in the induction and/or maintenance of the state of leukocyte adhesiveness/aggregation in the peripheral blood. A study of mothers and their newborns

The adhesive property of white blood cells is essential for a normal immune response. We examined the state of leukocyte adhesiveness/aggregation (LAA) in the peripheral blood of 31 mothers and their newborns by means of a direct slide test and found it to differ significantly, the respective per cents of aggregated leukocytes found in the peripheral blood being 15 +/- 6.4 and 5 +/- 3.3 (mean +/- SD). However, the particle concentration of white blood cells in the peripheral blood did not differ significantly (14.2 +/- 4.4 and 13.6 +/- x 10(9) l-1). By incubating a mother's plasma with her newborn's whole blood we could induce a significant (p less than 0.0001) increment in the state of LAA. We conclude that deficiency of a plasma factor that does not cross the placenta is responsible for the low LAA in the newborn's peripheral blood.

Fibrinogen as a major risk factor in cardiovascular disease

Evidence has accumulated over the past ten years to implicate elevated plasma fibrinogen levels in cardiovascular disorders such as ischaemic heart disease, stroke and peripheral vascular disease. At a cellular level, insight has been gained into the molecular regulation of fibrinogen biosynthesis and the mechanisms through which fibrinogen may be involved in these disease processes. Here, Nigel Cook and David Ubben summarize this evidence and consider the possibilities for novel therapies targeted at fibrinogen. A variety of structurally diverse pharmacological agents, many of which were developed for their effects on plasma lipids, have serendipitously been found to lower plasma fibrinogen levels.