Self-determined motivation and physical activity in patients with rheumatoid arthritis: a cross-sectional study

OBJECTIVE

To identify factors associated with two self-reported measures of physical activity (PA) in patients with rheumatoid arthritis (RA).

METHOD

Hospital outpatients with RA from central Norway filled in questionnaires about symptoms, psychological factors, and PA. Outcomes were two alternative self-reported measures of PA: (i) fulfilling the aerobic PA recommendations of ≥ 150 min/week at moderate intensity or ≥ 75 min/week at vigorous intensity; or (ii) being in the PA maintenance stage of the Stages of Exercise Behaviour Change framework. Logistic regression was applied to identify factors associated with PA. Step 1 included the independent variables sex, age, and smoking habits. Step 2a added self-reported function, joint pain during the past 6 months, and fatigue to Step 1. Step 2b added Exercise Self-Efficacy and the Relative Autonomy Index (RAI), calculated from the Behavioural Regulation in Exercise Questionnaire-2, to Step 1. Step 3 included all the mentioned independent variables. Steps 1-3 were analysed for each PA measure.

RESULTS

In total, 227 patients participated. The RAI had a statistically significant positive association with being physically active according to both PA definitions. Joint pain had a significant negative association with meeting the aerobic PA recommendations but was not associated with being in the PA maintenance stage.

CONCLUSION

The degree of self-determined motivation was the most consistent variable associated with self-reported PA behaviour. Joint pain was associated with one of the two PA measures. Motivation and joint pain may be useful targets for intervention in clinical practice to improve PA engagement among patients with RA.

POS0313 THE ASSOCIATION BETWEEN BODY COMPOSITION AND PHYSICAL ACTIVITY IN PATIENTS WITH PSORIATIC ARTHRITIS: THE TRØNDELAG HEALTH STUDY

Background

Persons with psoriatic arthritis (PsA) have an altered body composition compared to the general population, including overweight, which may increase the risk of several comorbidities. However, the associations of physical activity (PA) with body composition among persons with PsA is not well described.

Objectives

The aim of the study was to investigate the relationship between visceral fat mass (VFM) and percentage body fat (PBF), respectively, with PA in persons with PsA.

Methods

The study utilized data from the population-based Trøndelag Health Study (HUNT4, 2017-2019), where all inhabitants ≥ 20 years of age in northern Trøndelag were invited. Data comprised questionnaires, measurements, and blood sample analyses. Persons with PsA (n=291, CASPAR criteria) were identified from hospital case notes. The remaining participants with complete data for relevant variables (n=38 955) were used as controls.

Body composition was measured using bioelectrical bioimpedance including 30 values for 5 body segments. The primary outcomes were VFM (Model 1) and PBF (Model 2). PA was quantified using an index based on self-reported frequency, duration, and intensity (1), and categorized as low, moderate, or high.

Data were analyzed with multivariable linear regression including PsA and PA as exposures. The models were adjusted for age (<40, 40-59 >60 years), sex, alcohol consumption (once a week/more vs. less/none), smoking status (present/former vs. never smoker), diabetes, hypertension, heart disease, lung disease and cancer; and height (Model 1 only). To achieve appropriate model fit, an interaction term between age and PsA was included.

Results

Persons with PsA had higher weight, body mass index, VFM and PBF than controls, and they were less physically active (Table 1). The interaction term between PsA and age was statistically significant in both models (p<0.05), showing that the difference in VFM and PBF with PsA compared to controls was relatively larger in persons < 40 years (VMF difference: 3.6kg (95% CI 1.4, 5.9 kg) vs. ~1.1 kg in older age groups, PBF difference: 5.2% (1.9, 8.5%) vs. ~1.5% in older age groups).

Table 1.

Demographic and clinical characteristics

VariablePsA (n=291)Controls(n=38 955)p-valueAge (years), mean (±SD)58 (12)53 (17)p<0.001Male, n (%)174 (59.8)21 875 (56.2)p =0.21Diabetes, n (%)28 (9.7)1 876 (4.8)p<0.001Cardiovascular disease, n (%)11 (3.8)1 349 (3.5)p=0.77Lung disease, n (%)45 (15.5)4 904 (12.6)p=0.14Cancer, n (%)29 (10.0)2 746 (7.1)p=0.053Alcohol (once a week/more), n (%)71 (24.4)8 234 (21.1)p=0.18Smoking (present/former), n (%)208 (71.5)20 915 (53.7)p<0.001Education (college or higher), n (%)164 (56.4)25 166 (64.6)p=0.003Height (cm), mean (±SD)171 (9.1)171 (9.2)p=0.31Weight (kg), mean (±SD)83 (16.5)79 (15.7)p<0.001Body mass index (kg/m2), mean (±SD)28.3 (4.7)26.9 (4.5)p<0.001Percentage body fat, mean (±SD)33.7 (8.8)30.5(9.3)p<0.001Visceral fat mass (kg), mean (±SD)13.5 (5.5)11.4 (5.4)p<0.001Physical activityp=0.004  Low139 (47.8)16 648 (42.8)  Moderate104 (35.7)14 491 (37.2)  High48 (16.5)7 816 (20.1)

The associations between PA and VFM or PBF were similar with and without PsA. In Model 1 (R2=0.17), moderate or high physical activity was significantly associated with lower VFM. The moderate activity group had 0.8 kg (0.7, 0.9 kg, p<0.001) and the high activity group had 2.6 kg (2.5, 2.7, p<0.001) lower VFM compared to the low physical activity group. In Model 2 (R2=0.38), moderate or high physical activity was significantly associated with lower PBF. The moderate activity group had 1.4% (1.2, 1.5%, p<0.001) and the high activity group had 4.3% (4.1, 4.5%, p<0.001) lower PBF compared to the low physical activity group.

Conclusion

Patients with PsA had increased PBF and VFM, and moderate or high physical activity was associated with significant reductions in both endpoints. Physical activity may reduce the comorbidity burden among persons with PsA and should be a focus in clinical treatment plans.

References

[1]Nes BM et al. Med Sci Sports Exerc. 2011 43(11):2024-30.

Disclosure of Interests

None declared

POS0594 FACTORS ASSOCIATED WITH THE 6-MINUTE WALK TEST AMONG PERSONS WITH RHEUMATOID ARTHRITIS

Background

Persons with rheumatoid arthritis (RA) are less physically active than the general population. A 6-minute walk test (6MWT) measures how far a person can walk in 6 minutes, testing overall functional capacity. This can inform clinicians before initiating potential interventions.

Objectives

To assess psychological, patient- and disease-related factors associated with 6MWT results among persons with RA.

Methods

Patients were recruited in 2019 and 2021 from the Rheumatology outpatient clinics at St. Olavs Hospital and Levanger Hospital, Norway (n=225). They answered questionnaires, and a subgroup (n=86) performed a 6MWT according to guidelines from the American Thoracic Society (1). Diagnostic characteristics and medical history were collected from hospital records. Participants with data for 6MWT but missing data for other variables in the main model were excluded (n=7).

Physical function was measured with the Modified Stanford Health Assessment Questionnaire (mHAQ, range 0-3, lower score indicating better physical function). For the patient global assessment (PGA) patients rated their overall disease activity in the past week on a 100 mm visual analogue scale; higher score indicates more symptoms. Presence of depressive symptoms was measured with the Hospital Anxiety Depression Index Depression score (HADS-D, range 0-21, higher value implying more depressive symptoms). Perceived stress was measured with Cohen’s Perceived Stress Scale (range 0-40, higher score indicates more stress). The belief in one’s ability to be physically active under different circumstances was measured by the Self-Efficacy for Exercise score (range 5-35, higher score indicates higher self-efficacy).

Data were analyzed with multiple regression with 6MWT as dependent variable. Model 1 included age (categorized into tertiles to improve model fit: <59, 59-69, or ≥70 years), sex, mHAQ, PGA, HADS-D, Cohen’s Perceived Stress Scale, Self-Efficacy for Exercise, smoking habit and body mass index (BMI, categorized ≤25 or >25 kg/m2). Model 2 included only the variables significantly associated with 6MWT in Model 1, but keeping adjustment for sex. The regression coefficients of Model 2 were standardized.

Results:

Table 1.

Patient characteristic

Rheumatoid arthritis patients (N=79)Female sex, n (%)60 (76)Age (years), median (IQR)65 (55, 71)Ever smoker, n (%)49 (62)Body mass index (kg/m2), median (IQR)26.3 (23.6, 28.9)Rheumatoid arthritis duration (years), median (IQR)10 (5, 23)Seropositive (anti-CCP and/or RF), n (%)68 (86)Uses conventional DMARDs, n (%)67 (85)Uses biological DMARDs, n (%)42 (53)Uses corticosteroids, n (%)21 (27)Cardiovascular disease (HT, angina, MI, arrhythmia or stroke), n (%)38 (48)Respiratory disease (COPD, CRPD or asthma), n (%)21 (27)DAS28-CRP2.3 (1.8, 2.9)Modified Health Assessment Questionnaire, median (IQR)0.38 (0.13, 0.63)Patient global assessment (mm), median (IQR)27 (12, 40)Hospital Anxiety Depression Scale Depression score, median (IQR)3 (1, 4)Cohen’s Perceived Stress Scale, median (IQR)15 (9, 19)Self-Efficacy for Exercise, median (IQR)25 (17, 30)6-Minute Walk Test (m), mean (±SD)507 (±88)

In model 1, the variables associated with 6MWT were mHAQ (p=0.04), Self-Efficacy for Exercise (p=0.001), BMI (p=0.01) and age (oldest versus youngest age tertile p<0.001, middle versus youngest age tertile p=0.11). Sex was not significantly associated with 6MWT (p=0.82).

The standardized coefficients in Model 2 were: mHAQ -0.27 (p=0.002), Self-Efficacy 0.27 (p=0.002), categorized BMI -0.27 (p-value=0.002), middle age group versus youngest age group -0.17 (p=0.08), oldest age group versus youngest age group -0.55 (p<0.001), male gender 0.08 (p=0.33). The R2 of Model 1 and Model 2 were 0.54 and 0.52 respectively.

Conclusion

Self-Efficacy for Exercise, mHAQ, BMI and age had the largest impact on 6MWT, explaining 52 % of the observed variation in 6MWT in a model adjusted for sex.

References

[1]ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med 166(1), 111-117 (2002).

Disclosure of Interests

None declared

Genetic risk score associations for myocardial infarction are comparable in persons with and without rheumatoid arthritis: the population-based HUNT study

Persons with rheumatoid arthritis (RA) have increased risk of myocardial infarction (MI). Overlapping associations with MI of weighted genetic risk scores (wGRS) for coronary artery disease (CAD) and RA is unknown in a population-based setting. Data from the prospective Nord-Trøndelag Health Study (HUNT2: 1995–1997 and HUNT3: 2006–2008) were used. wGRS added each participant’s carriage of all risk variants weighted by the coefficient from published association studies. Published wGRS for CAD and RA were analysed in Cox regression with MI as outcome, age as analysis time, and censoring at the first MI, death, or 31.12.2017. 2609 of 61,465 participants developed MI during follow-up (mean 17.7 years). The best-fitting wGRS for CAD and RA included 157 and 27 single-nucleotide polymorphisms, respectively. In multivariable analysis including traditional CAD risk factors, the CAD wGRS was associated with MI [hazard ratio = 1.23 (95% CI 1.18–1.27) for each SD increase, p < 0.0001] in RA patients (n = 433) and controls. The RA wGRS was not significant (p = 0.06). Independently from traditional risk factors, a CAD wGRS was significantly associated with the risk for MI in RA patients and controls, whereas an RA wGRS was not. The captured genetic risk for RA contributed little to the risk of MI.

Comparison of methods to construct a genetic risk score for prediction of rheumatoid arthritis in the population-based Nord-Trøndelag Health Study, Norway

Objectives

To evaluate selection methods among published single-nucleotide polymorphisms (SNPs) associated with RA to construct predictive genetic risk scores (GRSs) in a population-based setting.

Methods

The Nord-Trøndelag Health (HUNT) Study is a prospective cohort study among the whole adult population of northern Trøndelag, Norway. Participants in HUNT2 (1995–1997) and HUNT3 (2006–2008) were included (489 RA cases, 61 584 controls). The initial SNP selection from relevant genome-wide studies included 269 SNPs from 30 studies. Following different selection criteria, SNPs were weighted by published odds ratios. The sum of each person’s carriage of all weighted susceptibility variants was calculated for each GRS.

Results

The best-fitting risk score included 27 SNPs [weighted genetic risk score 27 (wGRS27)] and was identified using P-value selection criterion ≤5 × 10−8, the largest possible SNP selection without high linkage disequilibrium (r2 &lt; 0.8), and lasso regression to select for positive coefficients. In a logistic regression model adjusted for gender, age and ever smoking, wGRS27 was associated with RA [odds ratio 1.86 (95% CI 1.71, 2.04) for each s.d. increase, P &lt; 0.001]. The AUC was 0.76 (95% CI 0.74, 0.78). The positive and negative predictive values were 1.6% and 99.7%, respectively, and the positive predictive value was not improved in sensitivity analyses subselecting participants to illustrate settings with increased RA prevalences. Other schemes selected more SNPs but resulted in GRSs with lower predictive ability.

Conclusion

Constructing a wGRS based on a smaller selection of informative SNPs improved predictive ability. Even with a relatively high AUC, the low PPV illustrates that there was a large overlap in risk variants among RA patients and controls, precluding clinical usefulness.

Reduced Th22 cell proportion and prevention of atopic dermatitis in infants following maternal probiotic supplementation

BACKGROUND

In the randomized, controlled study Probiotics in the Prevention of Allergy among Children in Trondheim (ProPACT), maternal probiotic supplementation reduced the incidence of atopic dermatitis (AD) in the offspring. In the current study, we hypothesized that the effect was mediated by a shift in the T helper (Th) cells in the children.

OBJECTIVE

To examine whether Th cell proportions were affected by maternal probiotic supplementation and thus could mediate the preventive effect of probiotics on AD.

METHODS

A total of 415 pregnant women were randomized to ingest a combination of Lactobacillus rhamnosus GG (LGG), Bifidobacterium animalis subsp. lactis Bb-12 (Bb-12) and Lactobacillus acidophilus La-5 (La-5) or placebo, and their offspring were assessed for AD during the first 2 years of life. Peripheral blood collected at 3 months of age was analysed for regulatory T cells (n=140) and Th subsets (n=77) including Th1, Th2, Th9, Th17 and Th22.

RESULTS

The proportion of Th22 cells was reduced in children in the probiotic group compared to the placebo group (median 0.038% vs 0.064%, P=.009). The difference between the probiotic and placebo groups was also observed in the children who did not develop AD during the 2-year follow-up. The proportion of Th22 cells was increased in children who developed AD compared to the children who did not develop AD (0.090% vs 0.044%, P<.001). Mediation analysis indicated that the preventive effect of probiotics was partially mediated through the reduction in Th22 cells.

CONCLUSION

Perinatal maternal probiotic supplementation with a combination of LGG, Bb-12 and La-5 reduced the proportion of Th22 cells in 3-month-old children. This may partially explain the preventive effect of probiotics on AD.

Fine-mapping the MHC locus in juvenile idiopathic arthritis (JIA) reveals genetic heterogeneity corresponding to distinct adult inflammatory arthritic diseases

Objectives

Juvenile idiopathic arthritis (JIA) is a heterogeneous group of diseases, comprising seven categories. Genetic data could potentially be used to help redefine JIA categories and improve the current classification system. The human leucocyte antigen (HLA) region is strongly associated with JIA. Fine-mapping of the region was performed to look for similarities and differences in HLA associations between the JIA categories and define correspondences with adult inflammatory arthritides.

Methods

Dense genotype data from the HLA region, from the Immunochip array for 5043 JIA cases and 14 390 controls, were used to impute single-nucleotide polymorphisms, HLA classical alleles and amino acids. Bivariate analysis was performed to investigate genetic correlation between the JIA categories. Conditional analysis was used to identify additional effects within the region. Comparison of the findings with those in adult inflammatory arthritic diseases was performed.

Results

We identified category-specific associations and have demonstrated for the first time that rheumatoid factor (RF)-negative polyarticular JIA and oligoarticular JIA are genetically similar in their HLA associations. We also observe that each JIA category potentially has an adult counterpart. The RF-positive polyarthritis association at HLA-DRB1 amino acid at position 13 mirrors the association in adult seropositive rheumatoid arthritis (RA). Interestingly, the combined oligoarthritis and RF-negative polyarthritis dataset shares the same association with adult seronegative RA.

Conclusions

The findings suggest the value of using genetic data in helping to classify the categories of this heterogeneous disease. Mapping JIA categories to adult counterparts could enable shared knowledge of disease pathogenesis and aetiology and facilitate transition from paediatric to adult services.

Pre-operative and intraoperative determinants for prolonged ventilation following adult cardiac surgery

BACKGROUND

Prolonged ventilation is a serious complication after cardiac surgery, but few risk prediction models exist. Our objectives were to develop a specific risk prediction model based on pre-operative variables, to identify whether selected intraoperative variables could improve prediction, and to compare our model with the EuroSCORE.

METHODS

Data from 5027 patients undergoing open-heart surgery in 2000-2007 were used for logistic regression model development. Internal validation was performed by bootstrapping. Discrimination and calibration were assessed with areas under the receiver operating characteristic curve (AUC) and the Hosmer-Lemeshow test. Our pre-operative model was compared with predictions based on the additive and logistic EuroSCORE.

RESULTS

Age, previous cardiac surgery, peripheral arterial disease, left ventricular hypertrophy, chronic pulmonary disease, renal insufficiency, pre-operative hemoglobin concentration, urgent or emergency operation, and operation other than isolated coronary artery bypass grafting were identified as pre-operative predictors for prolonged ventilation (model I). Discrimination and accuracy were excellent (AUC: 0.848 and shrinkage factor: 94%). Calibration was good (Hosmer-Lemeshow test: P = 0.43). Inclusion of a few intraoperative variables somewhat improved the model, increasing shrinkage factors (96%) and discrimination ability (AUC model II = 0.870 and model III = 0.875 for two alternative such models). Our pre-operative model showed better performance than the logistic or additive EuroSCORE.

CONCLUSIONS

The pre-operative risk prediction model for prolonged ventilation with easily obtainable variables in routine clinical work performed well and was only slightly improved by inclusion of intraoperative variables. Performance was better than with the EuroSCORE.

Mortality risk prediction in cardiac surgery: comparing a novel model with the EuroSCORE

BACKGROUND

Several models for prediction of early mortality after open-heart surgery have been developed. Our objectives were to develop a local mortality risk prediction model, compare it with the European System for Cardiac Operative Risk Evaluation (EuroSCORE), and investigate whether the addition of intra-operative variables could enhance the accuracy of risk prediction.

METHODS

All 5029 patients undergoing open-heart surgery in 2000-2007 were included in the study. Logistic regression with bootstrap methods was used to develop a pre-operative risk prediction model for in-hospital mortality. Next, several intra-operative variables were added to the pre-operative model. Calibration and discrimination were assessed, and the model was internally validated for prediction in future datasets. We thereafter compared the pre-operative model with the additive and logistic EuroSCOREs.

RESULTS

Our pre-operative model included eight risk factors that are routinely registered in our department: age, gender, degree of urgency, operation type, previous cardiac surgery, and renal, cardiac, and pulmonary dysfunction. The model estimated mortality accurately throughout the dataset except in the 1% of patients at extremely high risk, in which mortality was somewhat overestimated. The estimated shrinkage factor was 0.930. The areas under the receiver operating characteristic curve for our pre-operative model and the logistic EuroSCORE were 0.857(0.823-0.891) and 0.821(0.785-0.857) (P=0.02). There was no significant difference in performance between the pre-operative and the intra-operative model (P>0.10).

CONCLUSION

Our pre-operative model was simple and easy to use, and showed good predictive ability in our population. Internal validation indicated that it would accurately predict mortality in a future dataset.

Biocompatibility and pathways of initial complement pathway activation with Phisio- and PMEA-coated cardiopulmonary bypass circuits during open-heart surgery

A randomized open-heart surgery study comprising 30 patients was undertaken to compare the biocompatibility of Phisio-(phosphorylcholine) and PMEA-(poly-2-methoxyethyl acrylate) coated cardiopulmonary bypass (CPB) circuits and to assess the initial complement pathway activation during open-heart surgery. Blood samples were obtained at five time points, from the start of surgery to 24 hours postoperatively. The following analyses were performed: haemoglobin, lactate dehydrogenase, leukocyte and platelet counts, myeloperoxidase and neutrophil-activating peptide-2, thrombin-anti-thrombin complexes, syndecan-1 and the complement activation products C1rs-C1-inhibitor complexes, C4bc, C3bc, C3bBbP and the terminal complement complex (TCC). No significant inter-group difference was found in any parameters, except for the concentration of TCC which was moderately lower in the PMEA group at termination of CPB. Complement activation during open-heart surgery was mainly mediated through the alternative pathway. In conclusion, PMEA- and Phisio-coated circuits displayed similar biocompatibility with respect to inflammatory and haemostatic responses during and after open-heart surgery.

Comparable biocompatibility of Phisio- and Bioline-coated cardiopulmonary bypass circuits indicated by the inflammatory response

Background: The biocompatibility of cardiopulmonary bypass surfaces has been improved by heparin and polymer surface modifications. The present study compared the effect of two such coatings on the inflammatory reactions after open heart surgery.

Methods:Thirty patients undergoing elective heart surgery were randomly assigned to receive one of two types of coated circuits: Bioline (n=15) or phosphorylcholine (Phisio, n=15). The platelet and leukocyte counts, neutrophil activation (myeloperoxidase), complement activation (C3a and TCC), concentrations of lactate dehydrogenase, 27 cytokines (including interleukins, chemokines and growth factors), thrombin-antithrombin complexes, and the endothelial cell marker syndecan-1 were analyzed at five predetermined time points until 24 hrs post operatively.

Results: Most measurements were comparable in both groups. However, myeloperoxidase was significantly higher in the Bioline group (p < 0.001). Postoperative lactate dehydrogenase concentrations were significantly higher in the Phisio group (p<0.01) and the maximal concentration of thrombin-antithrombin complexes 2 hours postoperatively tended to be higher in the Phisio group (p=0.08), consistent with a longer aortic cross-clamp and cardiopulmonary bypass time. Conclusions: The two circuits exhibited a comparable degree of in vivo biocompatibility.

The additive contribution from inflammatory genetic markers on the severity of cardiovascular disease

Inflammation plays a key role in the development of atherosclerosis. Genetic differences in molecules related to inflammation have therefore been linked to the susceptibility for and severity of atherosclerosis. We hypothesized that the additive contribution from different genes of importance for inflammation would enhance the severity of cardiovascular disease. Blood samples were collected from 230 adults admitted for elective coronary angiography. A total of 130 patients had significant (>50%) stenosis in at least one main coronary artery branch and 100 had not. Six polymorphisms in five different genes were analysed: myeloperoxidase (MPO) -129G/A and -463G/A, toll-like receptor 4 (TLR4) Asp299Gly, interleukin-6 (IL6) -174G/C, surfactant protein D (SFTPD) Met11Thr and regulated upon normal T-cell expressed and secreted (CCL5) -403G/A. The IL6 polymorphism was significantly associated (P = 0.017) to angiographic significant coronary artery disease, and this relation remained after adjustment for age, gender, smoking and hypercholesterolaemia (P = 0.007). The TLR4 (P = 0.050) and SFTPD (P = 0.058) polymorphisms were also associated with the presence of coronary stenosis in univariate but not in multivariate analyses. For MPO and CCL5 no associations were found. There was a significant linear association between the number of high-risk gene variants (IL6-174CC, SFTPD 11CC and TLR4 299AA) and the proportion of patients with coronary artery disease (P < 0.0005). Inherited factors related to inflammation may increase susceptibility for severe coronary artery disease. Furthermore, the additive contribution from different inflammatory genetic markers strongly enhances the individual severity of cardiovascular disease.

Soluble ICAM-1 and VCAM-1 as markers of endothelial activation

Activated endothelium releases the soluble adhesion molecules vascular cell adhesion molecule-1 (sVCAM-1) and intercellular adhesion molecule-1 (sICAM-1). Measurement of fluid-phase adhesion molecules is therefore used to quantify endothelial activation, but it is unclear which is the better marker. The aims of the study were to compare the relationships between mRNA, surface and total expression and released VCAM-1 and ICAM-1 in endothelial cell cultures during activation, and to compare human umbilical vein endothelial cells (HUVEC) with the microvascular cell line HMEC-1. sVCAM-1 better represented mRNA and surface expression changes in HUVEC undergoing endotoxin stimulation than did sICAM-1. Very little VCAM-1 was released from endotoxin-stimulated HMEC-1, and sICAM-1 seemed a better activation marker for these cells. During incubation of HUVEC in media with glucose concentrations of 5.6, 10.6 or 20.6 mM, VCAM-1 was released to the media in a dose-dependent way without changes in surface expression. ICAM-1 was not influenced by the glucose concentration. There are situations when VCAM-1 concentrations in the media do not mirror the surface expression on HUVEC in culture, indicating that measurements of soluble adhesion molecules may not necessarily be representative of the conditions on the cell surface. Endothelium from different locations showed varying responses with respect to VCAM-1 and ICAM-1 liberation upon endotoxin stimulation. Thus, both sVCAM-1 and sICAM-1 should be quantified in clinical studies of endothelial activation until their characteristics are better clarified.

Complement activation by neutrophil granulocytes

Complement plays a vital role in the body's defence systems. Cardiopulmonary bypass induces a detrimental inflammatory reaction in which the complement system is known to participate through direct effects as well as through activation of neutrophils, platelets and endothelial cells. On the other hand, it has been suggested that in the setting of cardiopulmonary bypass, complement may be activated by neutrophils, perhaps due to fragmentation caused by the heart-lung machine. We therefore investigated whether intact or fragmented neutrophils were able to activate the complement system, and whether neutrophil-platelet interaction could influence such complement activation. Lepirudin-anticoagulated plasma was incubated at 37 degrees C with resting or activated intact neutrophils or neutrophils combined with platelets, or increasing amounts of fragmented neutrophils. Complement activation was evaluated by measurement of C1rs-C1 inhibitor complexes, C4bc, C3bBbP, C3bc, C5a and sC5b-9. We found significant activation of complement only by unphysiological doses of fragmented neutrophils or supernatant from fragmented neutrophils, consistent with a limited clinical significance related to neutrophil destruction during cardiopulmonary bypass. Unstimulated neutrophils induced C3bPBb formation but little formation of other activation products, indicating an increased C3 hydrolysis which was kept under control by regulatory mechanisms. Neutrophils and platelets combined increased classical activation and decreased alternative activation, similar to the findings with platelets alone. Our data confirm that in the setting of acute neutrophil fragmentation or activation, complement activation is much more important in the inflammatory network as an event upstream to neutrophil activation than vice versa.

The inflammatory response to stent grafting of the thoracic aorta

AIM

The aim of this study was to evaluate the inflammatory reactions in patients with thoracic aortic aneurysms before, during and after stent graft treatment and to relate markers of leukocyte activation to the use of radiographic contrast media.

METHODS

Blood samples were drawn from 7 patients undergoing elective stent graft treatment for thoracic aneurysms. The samples were analyzed for leukocyte and platelet counts and the concentrations of iohexol (radiographic contrast medium), myeloperoxidase, lactoferrin, neutrophil activating peptide-2 (NAP-2), soluble intercellular adhesion molecule-1, soluble vascular cell adhesion molecule-1 (sVCAM-1), the complement activation products C3bc and the terminal complement complex (TCC). The preoperative results were compared with 10 healthy blood donors of similar age.

RESULTS

Preoperatively, the aneurysm patients had significantly elevated concentrations of myeloperoxidase, neopterin and complement activation products compared to controls. Myeloperoxidase and lactoferrin increased after the first contrast dose and peaked at 8 h postoperatively. Platelet counts decreased, while NAP-2, sVCAM-1 and TCC increased from 8 h postoperatively.

CONCLUSION

We conclude that patients with thoracic aneurysms have a low-grade inflammation prior to intervention. Stent graft treatment induces further activation, and markers of endothelial, platelet, and complement activation were increased for several days after the procedure. Radiographic contrast media could be an important contributor to the activation of neutrophil leukocytes.

Changes in neutrophil surface-receptor expression after stimulation with FMLP, endotoxin, interleukin-8 and activated complement compared to degranulation

Neutrophil activation induces changes in the expression of surface receptors and may lead to degranulation. Surface expression of beta2-integrins, l-selectin, complement receptor 1 (CR-1), decay-accelerating factor (DAF), C5a receptor, intercellular adhesion molecule-1 (ICAM-1) and ICAM-3 was compared by flow cytometry on isolated neutrophils stimulated with phorbol 12-myristate 13-acetate (PMA), N-formyl-methionyl-leucyl-phenylalanine (FMLP), endotoxin or interleukin-8 and on neutrophils in whole blood anti-coagulated with the thrombin inhibitor lepirudin and stimulated with cobra venom factor to induce complement activation. Myeloperoxidase and lactoferrin in the supernatants were quantified in enzyme immunoassays. With high enough doses, all stimulants induced significant upregulation of beta2-integrins, CR-1 and DAF and downregulation of l-selectin. ICAM-3 was either unchanged or somewhat downregulated. Only FMLP and PMA induced significant upregulation of ICAM-1. Combined measurement of beta2-integrins and l-selectin permitted graded evaluation of early neutrophil activation. Measurement of degranulation showed no differences compared to unstimulated controls due to substantial spontaneous degranulation of isolated neutrophils by rewarming from 4 degrees C and incubation at 37 degrees C. Spontaneous activation was less in ethylenediaminetetraacetic acid-anti-coagulated blood, but calcium chelation may also inhibit the stimulated responses. There was large activation of unstimulated neutrophils in lepirudin-anti-coagulated blood at 37 degrees C, obscuring changes induced by stimulation, which may render this anti-coagulant unsuitable for studies of neutrophils.

Increased concentrations of soluble CD40 ligand, RANTES and GRO-alpha in preeclampsia--possible role of platelet activation

Activated platelets may release inflammatory mediators that activate leukocytes and trigger inflammatory reactions in endothelial cells. We examined the concentrations of soluble CD40 ligand (sCD40L) and the chemokines RANTES and GRO-alpha in platelet-free plasma (PFP), and unstimulated and SFLLRN-stimulated platelet-rich plasma (PRP), as well as in platelet pellets before stimulation using enzyme immunoassays. Nineteen women with normal and twenty-one with preeclamptic pregnancies were studied, and several differences between these two groups of pregnancies were revealed (1). Women with preeclampsia had significantly increased concentrations of sCD40L and GRO-alpha in PFP (2). Platelets from these patients spontaneously released larger quantities of CD40L and RANTES ex vivo (3). When further activated ex vivo by SFLLRN, platelets from preeclamptic women released lower amounts per platelet of CD40L, RANTES and GRO-alpha (4). The platelet pellets in preeclamptic women contained decreased amounts of CD40L, RANTES and GRO-alpha per platelet. Our findings suggest enhanced platelet activation in vivo during preeclampsia resulting in increased release of inflammatory mediators, possibly contributing to inflammation, leukocyte activation and endothelial dysfunction in this disorder.

Chemokines and leukocyte activation in the fetal circulation during preeclampsia

Preeclampsia is a potentially life-threatening disease for both mother and fetus. Endothelial dysfunction is pivotal in the pathogenesis of this disorder, possibly reflecting a state of persistent inflammation. In the present study, we examined whether signs of inflammation with production of chemokines and leukocyte activation were present in the fetal circulation during preeclampsia. Venous cord blood was sampled during cesarean sections from 36 neonates born after uncomplicated pregnancies and from 35 born after severe preeclamptic pregnancies with premature newborns. The expression of adhesion molecules on neutrophils and monocytes was analyzed by flow cytometry, and plasma levels of chemokines and soluble adhesion molecules were analyzed by enzyme immunoassay. Newborns of preeclamptic mothers had increased expression of CD15s (P=0.003), CD49d/CD29 (P=0.01/0.005), and CD31 (P=0.007) on neutrophils and CD15s (P<0.001), CD11c (P=0.009), and CD54 (P=0.001) on monocytes. This activation of neutrophils and monocytes was accompanied by raised plasma levels of the CXC chemokines interleukin-8 (P=0.007) and growth-related oncogene-alpha (P=0.01) and decreased plasma levels of soluble E-selectin (P=0.001) and L-selectin (P=0.002). Although raised levels of adhesion molecules on leukocytes or decreased levels of soluble adhesion molecules in plasma were not related to prematurity or the degree of preeclampsia, raised interleukin-8 levels were found only in neonates of preeclamptic mothers with the highest blood pressures. Our findings suggest the activation of neutrophils and monocytes in the fetus during preeclampsia involving enhanced chemokine activation, possibly contributing to the fetal morbidity of this disorder.

Veno-venous bypass in liver transplantation: heparin-coated perfusion circuits reduce the activation of humoral defense systems in an in vitro model

We studied the effects of bypass circuit surface heparinization on kallikrein-kinin, coagulation, fibrinolytic and complement activation in a closed model system for simulating veno-venous bypass (WBP) in orthotopic liver transplantation (OLT). The circuits were identical to those in routine use during clinical OLT in our institution. Fresh whole human blood diluted 1:2 with Ringer's acetate was circulated at a non-pulsatile flow (2 l/min) and at a constant temperature (37.5 degrees C) for 12 h. In 10 experiments, the entire inner surface of the circuits was coated with end-point attached heparin (HC). In the remaining 10, non-treated PVC tubing was used (NC). Components of the plasma kallikrein-kinin, coagulation, fibrinolytic and complement systems were analyzed using functional techniques (chromogenic peptide substrate assays) and enzyme immunoassays at baseline, 3 and 12 h. Significant activation of the initial (C3bc) and terminal (TCC) components of the complement system were found in both the NC and HC groups after 3 and 12 h: C3bc: NC: baseline = 4 (3.5-7.7), 3 h = 17.3* (12.5-27), 12h = 31* (17.7-63.6), HC: baseline = 4.9 (3.2-6.8), 3h = 9* (6-14.4), 12h = 13.7* (7.4-18.1). TCC: NC: baseline = 0.4 (0.2-0.6), 3h = 5*(0.8-11.9), 12 h: 13.1* (4.2-25.7). HC: baseline = 0.5 (0.1-0.6), 3 h = 0.6* (0.1-0.8), 12 h = 1.2* (0.3-2) AU/ml; median and range (*: p < 0.05). The C3bc and TCC concentrations were significantly higher in the NC group at 3 and 12 h, compared to the HC group: C3bc (NC vs. HC group): 3 h, p < 0.001; 12 h, p < 0.001. TCC (NC vs. HC group): 3h, p < 0.001; 12 h, p < 0.001. Significant increases in the values of thrombin-antithrombin complexes (p = 0.003), prothrombin fragment 1 + 2 (p = 0.006) and plasmin-alpha2-antiplasmin complexes (p = 0.016) were found in the non-coated group, but not in the heparin-coated group during the observation period, showing that the coagulation and fibrinolytic systems were activated in the non-coated circuits. We conclude that heparin-coating of the internal surface of the extracorporeal perfusion circuit used for WBP reduces activation of the plasma cascade systems in a closed venous system in vitro.

Increased systemic activation of neutrophils but not complement in preeclampsia

OBJECTIVE

To investigate whether neutrophils and systemic complement are activated in pregnancies complicated by preeclampsia more than in normal pregnancies.

METHODS

We measured native complement components and activation products in plasma by enzyme immunoassays in 19 women with uncomplicated pregnancies, 15 with preeclampsia before cesarean deliveries, and 16 nonpregnant women. Neutrophil activation was measured by specific enzyme immunoassays for myeloperoxidase and lactoferrin.

RESULTS

Myeloperoxidase was significantly higher in women with preeclampsia (197 microg/L, 95% confidence interval [CI] 94, 646) than in women with uncomplicated pregnancies (124 microg/L, 95% CI 70, 289; P =.009), whereas lactoferrin did not differ between groups. C4 was decreased in preeclamptic women (0.16 g/L, 95% CI 0.07, 0.48) compared with women with uncomplicated pregnancies (0.21, 95% CI 0.10, 0.30, P <.001). There were no differences for the other native complement components. There was a significant decrease in C1rs-C1 inhibitor, 13 AU/mL (95% CI 9, 34) versus 19 (95% CI 13, 38) (P < or =.001) in normal pregnant women compared with nonpregnant women. There also was an increase in C3, C4, C9 (data not shown), C4bp, 132% (95% CI 94%, 161%) versus 91% (95% CI 57%, 128%); C3bc (7.4 AU/mL, 95% CI 4.2, 10.7) versus 4.8 AU/mL (95% CI 3.2, 7.3) and C4bc (8.6 AU/mL, 95% CI 5.7, 14.0) versus 3.5 AU/mL (95% CI 2.2, 6.7) in normal pregnant women compared with nonpregnant women (P < or =.001).

CONCLUSION

Neutrophil activation in preeclampsia was shown by systemic increases in myeloperoxidase. Except for a decrease in C4, systemic complement activation could not be detected in preeclampsia.

Donor neutrophil function after plateletpheresis

BACKGROUND

Neutrophils are important mediators of inflammation and may be activated by foreign surfaces in apheresis systems. Because most of the WBCs are returned to the donor, it was investigated whether artificial activation leads to altered donor neutrophil function.

STUDY DESIGN AND METHODS

Three apheresis systems (Amicus, Autopheresis-C, and CS-3000; all: Baxter Fenwal) were investigated. Preapheresis and postapheresis blood samples were drawn from 10 volunteer donors, with all three apheresis systems used in random order for each donor. Changes in neutrophil phagocytic ability, oxidative burst, and expression of L-selectin and CD11b were measured by flow cytometry, and plasma concentrations of myeloperoxidase and lactoferrin were measured by EIA. Complement activation was evaluated by quantification of C3bc and the terminal complement complex by EIA.

RESULTS

Neutrophil expression of L-selectin increased after apheresis (p = 0.02), and the production of oxygen radicals was reduced (p = 0.01). This effect was possibly a result of priming. Complement was not activated. There were no significant differences in neutrophil function after apheresis with any of the three apheresis systems.

CONCLUSIONS

Neutrophil function was altered after apheresis, although to a very small extent, and contact between neutrophils and the foreign surface in the apheresis systems is found to be a biotolerant procedure.

Plasma endotoxin concentrations during cardiac surgery may be related to atherosclerosis

Systemic endotoxemia develops during cardiopulmonary bypass, probably due to intestinal ischaemia. Differences in endotoxaemia among various cardiac operations and the relationship between endotoxemia and postoperative complications were studied in high-risk patients. Blood samples were obtained at termination of bypass in 136 adults undergoing elective cardiac surgery. Postoperative complications were registered prospectively. Plasma endotoxin was quantified by a kinetic limulus amebocyte lysate assay. Mean endotoxin concentrations were significantly lower in patients undergoing isolated valve replacement (89 ng/l) than in patients undergoing coronary artery bypass grafting alone (234 ng/l), or combined with valve replacement (278 ng/l) or carotid artery surgery (321 ng/l) (p < 0.05). In multivariate linear regression, only the number of grafts (0, 1-3, 4-5) was significantly correlated to endotoxin concentrations (p < 0.0005). Endotoxin concentrations were related to development of gastrointestinal dysfunction (p = 0.03), but not to mortality (p = 0.24) or other complications (p = 0.62).

An ex vivo perfusion model to evaluate hyperacute rejection in a discordant pig-to-human combination

Inadequate supplies of human organs for transplantation have evoked an escalating interest in human xenotransplantation. Hyperacute rejection precludes use of discordant organs. We have developed an ex vivo perfusion model in order to evaluate hyperacute rejection in a pig-to-human combination. Pig kidneys (n = 6) perfused with human blood deteriorated rapidly and rejection was seen after 70 (60–87) min (median, 95% confidence interval). Kidneys perfused with pig blood survived 300 (216–360) min, corresponding to the upper time limit of the model. Increases in prostaglandin E₂ and 6-keto-prostaglandin F_1α indicated endothelial activation. Sequential blood samples revealed a strong progressive inflammatory response with reduced leukocyte and platelet counts, granulocyte activation indicated by increased myeloperoxidase, and complement activation, shown by an increase in C3 activation products and the terminal SC5b-9 complement complex. A significant role for classical pathway activation was indicated by formation of C1rs-C1 inhibitor complexes and activation of C4, whereas factor B was not significantly activated. Biopsies at rejection demonstrated hyperacute rejection with inflammatory changes involving the vessels as well as the nephrons. Where the inflammatory markers could be studied in pig blood, activation was less than in human blood. The present discordant xenotransplant model is a valuable adjunct for evaluation of changes occurring in the human blood perfusate as well as in the pig kidney during hyperacute rejection.

A novel enzyme immunoassay for plasma thrombospondin. Comparison with beta-thromboglobulin as platelet activation marker in vitro and in vivo

A novel enzyme immunoassay for plasma thrombospondin (TSP) based on commercially available monoclonal antibodies was established. The following conditions for correct collection and preservation of blood samples were required: venipuncture directly into a vacutainer containing citrate, theophylline, adenosine and dipyridamole, storage on ice, and separation of plasma within 30 minutes. Thereafter, the plasma TSP concentration remained constant at room temperature and after five times of freezing and thawing. Both inter- and intraassay variation coefficients were 5%. The lower detection limit was 20 microg/L. Median TSP concentration among 40 healthy blood donors was 43 microg/L, slightly lower than previously published. The assay is valid, reliable, and has certain advantages compared with previously published methods. TSP and beta-thromboglobulin (BTG) were then compared as platelet activation and biocompatibility markers in vivo: 23 patients undergoing cardiopulmonary bypass (CPB); and in vitro: effect of coating polyvinyl chloride with heparin. The kinetic patterns of TSP and BTG were markedly different in vivo but virtually identical in vitro, explained by different in vivo clearance mechanisms during CPB. We conclude that BTG is superior to TSP for evaluation of platelet activation during in vivo CPB, whereas TSP and BTG are virtually identical as markers in vitro.

The inflammatory response following treatment of abdominal aortic aneurysms: a comparison between open surgery and endovascular repair

OBJECTIVES

to compare the inflammatory response following endovascular and conventional AAA repair.

DESIGN

prospective study.

PATIENTS AND METHODS

ten patients were selected for open surgery (OPEN) and ten for endovascular (ENDO) AAA repair. Leukocytes, platelets, myeloperoxidase, lactoferrin, beta-thromboglobulin, C-reactive protein (CRP), interleukin 6 (IL-6), tumour necrosis factor alpha (TNF-alpha) and complement activation products were measured before, during and after surgery.

RESULTS

in the OPEN group the median hospital stay was longer (6 vs. 12 days, p=0.001) and more patients required transfusion (p=0.02). IL-6 and CRP increased postoperatively, most in OPEN (p<0.01). Platelet counts decreased after the first angiography in ENDO (p<0.01) and before aortic cross-clamping in OPEN (p<0.05). The decrease was larger in OPEN (p=0.02). Leukocyte counts decreased after the first angiography in ENDO, and thereafter increased (p=0.001). An equivalent increase was observed in OPEN after declamping (p=0.001). Leukocyte and platelet degranulation products increased after the first angiography in ENDO and after declamping in OPEN. Changes in complement activation products were small. TNF-alpha did not change significantly.

CONCLUSION

endovascular AAA repair caused significant leukocyte and platelet activation. Based on the timing of activation this could be caused by radiographic contrast media.

Inhibition of platelet aggregation by the GPIIb/IIIa antagonist reopro does not significantly prolong xenograft survival in an ex vivo model

Effects on hyperacute rejection were studied in a discordant model with the platelet GPIIb/IIIa antagonist Reopro. Pig kidneys perfused with human blood survived median 118 min in the Reopro group and 103 min in the controls (P = 0.22). Platelet and leukocyte counts decreased, whereas plasma thrombospondin and soluble as well as platelet membrane P-selectin increased significantly in both groups without significant intergroup differences. beta-Thromboglobulin and myeloperoxidase increased significantly more in the control group than in the Reopro group (P = 0.009 and P = 0.02, respectively). The classical complement pathway was substantially and similarly activated in both groups. Light and electron microscopy revealed arterial thrombi and numerous glomerular platelet aggregates in the control group in contrast to the Reopro group. In conclusion, Reopro reduced platelet aggregation, and platelet and leukocyte activation to some extent, but had no effect on complement activation and did not significantly prolong xenograft survival, even though better preservation of morphology was shown.

Platelet compatibility of an artificial surface modified with functionally active heparin

Platelet compatibility after coating an artificial material with functionally active heparin was investigated. Blood was circulated in uncoated or heparin coated PVC tubing. In one hour platelet counts decreased from 155 (113-184)x10(9)/l to 124 (100-148)x10(9)/l with uncoated compared to 164 (132-192)x10(9)/l with heparin coated tubing (intergroup p = 0.02). Beta-thromboglobulin increased from 116 (80-148) microg/l to 1039 (757-1298) microg/l with uncoated and to 352 (229-638) microg/l with heparin coated tubing (intergroup p = 0.005). Platelet counts and beta-thromboglobulin correlated closely with complement activation. Solid-phase enzyme immunoassay demonstrated substantial deposition of CD42a/GPIbIX and CD61/GPIIIa on uncoated, but not on heparin coated tubing (intergroup p<0.0005). Scanning electron microscopy demonstrated activated platelets and aggregates on uncoated in contrast to heparin coated tubing, where scattered, unactivated platelets were found. Changes in P-selectin and microparticles were minor. In conclusion, this heparin surface substantially improved platelet compatibility. Markers of choice for in vitro evaluation were platelet counts, beta-thromboglobulin and platelet deposition.

C1-inhibitor attenuates hyperacute rejection and inhibits complement, leukocyte and platelet activation in an ex vivo pig-to-human perfusion model

Xenotransplantation may be a future alternative due to increased shortage of organs. Classical complement activation is central in hyperacute rejection in pig-to-human combinations. We investigated the effects of C1-inhibitor (C1-INH), a regulator of the complement and contact systems, on hyperacute rejection. Pig kidneys were perfused with fresh human blood to which either C1-INH (n = 6) or human serum albumin (n = 6) was added. The survival of the C1-INH perfused kidneys (mean 327 min) was significantly longer (p < 0.00001) than the controls (79 min). C1-INH substantially inhibited complement activation (C1rs-C1-INH complexes, C4bc, C3bc and terminal complement complex) (p < 0.001 for all) compared with the marked complement activation in the controls. No contact activation was found. Leukocytes and platelets were substantially activated (counts, myeloperoxidase, beta-thromboglobulin, thrombospondin, soluble P-selectin) in the control group, and this activation was markedly reduced by C1-INH (p < 0.02 for all). Immunohistochemistry showed less C1q, C3, TCC, IgG and fibrin deposition in the C1-INH group. C1-INH may be useful to attenuate hyperacute rejection, probably through inhibition of complement. The reduced activation of neutrophils and platelets may mainly be secondary to inhibition of complement.

Heparin-coated cardiopulmonary bypass equipment. I. Biocompatibility markers and development of complications in a high-risk population

OBJECTIVES

1. To study possible clinical benefits of heparin-coated cardiopulmonary bypass in patients with a broad range of preoperative risk factors. 2. To evaluate the correlation between the terminal complement complex and clinical outcome. 3. To identify clinical predictors of complement activation and correlates of granulocyte activation during cardiac surgery.

METHODS

Blood samples from adults undergoing elective cardiac surgery with Duraflo II heparin-coated (n = 81) or uncoated (n = 75) cardiopulmonary bypass sets (Duraflo coating surface; Baxter International, Inc, Deerfield, Ill) were analyzed for activation of complement (C3 activation products, terminal complement complex), granulocytes (myeloperoxidase, lactoferrin), and platelets (beta-thromboglobulin) by enzyme immunoassays. Preoperative risk was assessed by means of the "Higgins' score." Complications (cardiac, renal, pulmonary, gastrointestinal, and central nervous system dysfunction, infections, death) were registered prospectively. Data were analyzed by analysis of variance, logistic regression, and linear regression.

RESULTS AND CONCLUSIONS

Sixty-seven percent of the patients had predefined risk factors. Complications developed in 53 patients (34%), equivalently with and without heparin-coated bypass sets (P =. 44-.82), despite a significant reduction in complement and granulocyte activation by heparin coating. No clear-cut relationship between the terminal complement complex and outcome was found, even if it was significant in the models for renal and central nervous system dysfunction and infections (P =.006). The Higgins' score was significantly related to complement activation (P <.05). Approximately 50% of the variation in granulocyte activation was explained by complement (P </=.01) and platelet activation (P <.05), heparin/protamine dose ratio (P =.02), duration of cardiopulmonary bypass (P <.01), and gender (P <.05). Therefore measures reducing complement activation alone will not necessarily reduce granulocyte activation sufficiently for clinical significance.

Heparin-coated cardiopulmonary bypass equipment. II. Mechanisms for reduced complement activation in vivo

OBJECTIVE

Our objective was to study mechanisms for reduced complement activation by heparin coating of cardiopulmonary bypass equipment in clinical heart surgery.

METHODS

Adults undergoing elective coronary artery bypass grafting were randomized to cardiopulmonary bypass with Duraflo II heparin-coated (n = 15) or uncoated (n = 14) sets (Duraflo coating surface; Baxter International, Inc, Deerfield, Ill). Blood samples were analyzed with the use of enzyme immunoassays for C1rs-C1 inhibitor complexes and the activation products Bb, C4bc, C3bc, C5a-desArg, and the terminal complement complex. Data were compared by repeated-measures analysis of variance.

RESULTS

C1 was activated during bypass, and increases in C1rs-C1 inhibitor complexes were larger with heparin coating (P =.03). C4bc increased after administration of protamine, without intergroup differences (P =.69). Bb (P =.22) and C5a-desArg (P =.13) tended to increase less with heparin coating. Formation of C3bc (P =.03) and the terminal complement complex (P <.01) was significantly reduced with heparin coating. C5a-desArg increased 2-fold during bypass, whereas the terminal complement complex increased 10- to 20-fold. Maximal terminal complement complex concentrations were significantly correlated to maximal Bb and C3bc (R = 0.6, P <.001), but not to C1rs-C1 inhibitor complexes or C4bc (R < 0.05, P >.8).

CONCLUSIONS

C1 activation during bypass was increased by heparin coating, but further classical pathway activation was held in check until administration of protamine. Heparin coating significantly inhibited C3bc and terminal complement complex formation. Terminal complement complex concentrations were related to alternative pathway activation and may be useful for evaluation of differences in bypass circuitry. Increases and intergroup differences in terminal complement complex concentrations were much larger than those in C5a-desArg.

Leucocyte filtration during cardiopulmonary reperfusion in coronary artery bypass surgery

Postoperative organ dysfunction after cardiac operations has been related to the damaging effects of cardiopulmonary bypass (CPB). These complications are considered to be mediated partly by complement activation and subsequent activation of leucocytes due to the contact between blood and the large nonendothelial surfaces in the bypass circuit. Removal of leucocytes by filtration during the reperfusion period may potentially reduce the postoperative morbidity after CPB. Forty patients undergoing elective, primary coronary artery bypass grafting were randomized to initial identical bypass circuits until the aortic crossclamp was released. Then, the ordinary arterial line filter was closed and either a leucocyte depletion filter (n = 20), or a control filter (n = 20) was incorporated in the circuits during the reperfusion period of CPB. Blood samples were drawn at fixed intervals and analysed for white blood cell and platelet counts, plasma concentration of myeloperoxidase, C3-complement activation products, the terminal complement complex, and interleukins (IL)-6 and -8. The numbers of circulating white blood cells in the leucocyte-depleted group decreased during the reperfusion period from 5.5 (4.8-6.8) to 5.3 (4.4-6.2) x 10(9)/l, and increased in the control group from 6.5 (5.1-8.0) to 7.4 (5.7-9.0) x 10(9)/l. Two hours postoperatively the total white blood cell count in the leucocyte-depleted group was 14.7 (12.1-17.2) x 10(9)/l, and in the control group 17.6 (14.5-20.7) x 10(9)/l. The differences between the groups were statistical significant (p = 0.05). There were no statistically significant differences between the groups with regard to other test parameters or clinical data. We conclude that the use of leucocyte filters during the reperfusion period in elective coronary artery bypass surgery significantly reduced the number of circulating leucocytes, whereas no effects were seen for granulocyte activation measured as myeloperoxidase release, platelet counts, complement activation, or IL-6 and -8 release. The clinical benefit of leucocyte filters in routine or high risk patients remains to be demonstrated and is suggested to be dependent on both the efficacy and the biocompatibility of the filters.

Comparison of three oxygenator-coated and one total-circuit-coated extracorporeal devices

The present study was designed to compare the biocompatibility of three cardiopulmonary bypass setups with different surface coatings, and to determine if coating of the whole circuit with one of the coatings was more beneficial than coating of the oxygenator only. Extracorporeal devices entirely coated with synthetic polymers (Avecor, n = 6) were compared to oxygenators coated with synthetic polymers (Avecor, n = 6), end-point, covalently attached heparin (CBAS, n = 6) or absorbed heparin (Duraflo 2, n = 6) in an in vitro model of a heart lung machine. The circuits were primed with fresh human whole blood and Ringer's acetate and recirculated at 4 l/min at 30 degrees C for 2 h. Test samples were obtained at regular intervals and analysed for myeloperoxidase (MPO), platelet counts, beta-thromboglobulin, heparin, prothrombin fragment 1+2, plasmin anti-plasmin complexes, and complement activation products. The mean MPO concentrations increased in the Avecor-coated oxygenator group (AV) from 247 at the start to 671 microg/l at the termination of the experiments, in the Avecor-coated total circuit group (AV-T) from 116 to 288 microg/l, in the Duraflo 2 coated oxygenator group (DU) from 160 to 332 microg/l, and in the CBAS-coated oxygenator (CA) group from 172 to 311 microg/l. The MPO concentrations increased significantly in all groups (p < 0.03). The increase in group A was significantly higher than in the other three groups (p = 0.007). The mean platelet counts decreased in the Avecor-coated total circuit group from 117 at start to 99 x 10(9)/l at termination of the experiments, in the Avecor-coated oxygenator group from 119 to 103 x 10(9)/l, in the Duraflo 2 group from 96 to 86 x 10(9)/l, and in the CBAS group from 132 to 123 x 10(9)/l. The platelet counts decreased significantly in all groups (p < 0.01), but the intergroup differences were not significant (p = 0.15). The mean beta-thromboglobulin concentrations increased in the Avecor-coated total circuit group from 193 at the start to 754 ng/ml at the termination of the experiments, in the Avecor-coated oxygenator group from 474 to 1654 ng/l, in the Duraflo 2 group from 496 to 1280 ng/l, and in the CBAS group from 418 to 747 ng/l. The beta-thromboglobulin increase was significant in each group (p < 0.01), but not between the groups (p = 0.49). The mean heparin concentrations in the Duraflo 2 group increased from 2460 at the start to 2897 IU/l at termination of the experiments, in the CBAS group from 2468 to 2518 IU/l. In the Avecor-coated oxygenator group heparin concentrations decreased from 2010 to 1968 IU/l, and in the Avecor-coated total circuit group from 2002 to 1927 IU/l. The differences in heparin concentrations were significant between the Duraflo 2 group and the other groups (p < 0.05). The mean prothrombin fragment 1+2 concentrations increased in the CBAS group from 0.4 at the start to 2.1 nmol/l at the end of the experiments, in the Avecor-coated oxygenator group from 0.4 to 0.6 nmol/l, in the Avecor-coated total circuit group from 0.3 to 0.4 nmol/l, and in the Duraflo 2 group from 1.2 to 1.3 nmol/l. The prothrombin fragment 1+2 increase was significant in all groups (p < 0.05), but there were no significant intergroup differences (p = 0.54). There were no significant differences at the termination of the experiments among the four groups regarding complement activation as measured by C3 activation products and the terminal complement complex. In the present in vitro model of a heart-lung machine, none of the three specific setups with different coatings was superior with regard to all test parameters. The CBAS group generated the highest levels of prothrombin fragment 1+2 formation, but least complement activation. The increasing plasma heparin concentrations in the Duraflo 2 group indicated more unstable heparin bonding. The Avecor-coated total circuit group were superior to the Avecor-coated oxygenator group regarding plasma concentrations of MPO, but not compa

Compstatin, a peptide inhibitor of C3, prolongs survival of ex vivo perfused pig xenografts

Compstatin, a newly described C3-binding peptide, inhibits complement activation by blocking C3 convertase-mediated cleavage of C3. As the complement activation is an essential part of the rejection reaction, we evaluated the ability of Compstatin to delay or prevent hyperacute rejection in an ex vivo xenograft model. Pig kidneys were perfused with fresh human blood containing either Compstatin (n=6) or a control agent (n=6). Graft survival and activation of complement, leukocytes and platelets both in the fluid-phase and in the tissue were examined. The survival of the Compstatin-perfused kidneys (median, 380 min) was significantly (P=0.0036) longer than that of the controls (median, 90 min). The classical complement pathway (C1rs-C1inhibitor and C4bc) was significantly and equally activated in both groups during the first 60 min. C3 activation products increased fivefold and terminal complement complex eightfold in the control group, but no increase occurred in the Compstatin group during this period. Immunohistochemistry showed less C3 and fibrin deposition and immune electron microscopy showed less terminal SC5b-9 complement complex deposition in the Compstatin group. A significant change in total white cells, neutrophils, myeloperoxidase, and expression of the surface activation markers CD11b (CR3) and CD35 (CR1) and CD62L (L-selectin) was observed in both groups. Leukocyte activation was lower in the Compstatin group but the difference was not statistically significant. There were no differences in platelet counts, thrombospondin, soluble P-selectin or beta-thromboglobulin between the groups. We conclude that Compstatin prolongs graft survival and suggest that it may be a useful agent for attenuating hyperacute rejection by inhibiting C3 and thus terminal complement pathway activation.

Effect of anti-C5a antibody on blood-lung and blood-brain barrier in rabbits after decompression

The complement activation product C5a may be an important mediator of tissue injury after decompression stress. This study investigated whether the administration of anti-C5a antibody may reduce changes after decompression in the lung and in the brain. Two groups of rabbits were used; one receiving anti-C5a monoclonal antibody (n = 7) and the other receiving a sham antibody as control (n = 7) before pressure exposure. Five rabbits (4 in the anti-C5a group and 1 in the control group) died during the 2-h observation period postdive due to massive bubbling. Polymorphonuclear leukocyte (PMN) infiltration of lung tissue and pulmonary edema was observed, but this accumulation was unaffected by anti-C5a pretreatment. However, a significant positive correlation was observed between PMN accumulation and survival time postdive. Brain-specific gravity was lower for the group treated with anti-C5a antibody compared to the control group. Further, it was lower for those rabbits that died early compared to the ones that survived the 2-h period. This study was unable to prove a protective effect on the blood-brain and blood-lung barrier by injecting anti-C5a antibody. A possible beneficial effect of anti-C5a antibody may be masked by the mechanical damage caused by the gas bubbles.

In vitro evaluation of new surface coatings for extracorporeal circulation

Cardiopulmonary bypass (CPB) exposes blood to large, foreign surfaces. This exposure may activate the cellular and humoral inflammatory systems, resulting in inflammatory reactions and organ dysfunction. Coating the inner surfaces of the bypass circuit may help alleviate these side-effects. The objective of this study was to determine the influence of two new surface treatments on blood cell and complement activation. Oxygenator and tubing sets coated with synthetic polymers (n = 7) or heparin (n = 7) were compared to uncoated sets (n = 7) in an in vitro model of CPB. The circuits were run at 4 l/min and recirculated for 120 min. The inflammatory response was assessed at regular intervals by platelet counts, and activation of complement, leucocytes and platelets. We found that the median platelet counts decreased from 127 to 122 x 10(9)/l (not significant, NS) in the synthetic polymer sets, from 96 to 88 x 10(9)/l (NS) in the heparin-coated sets, and from 93 to 54 x 10(9)/l (p < 0.01) in the uncoated sets after 2 h of recirculation. There were significant differences in platelet counts between the coated sets and the uncoated set at end of experiments (p < 0.05). Beta-thromboglobulin (BTG) concentrations increased in the synthetic polymer sets from 166 to 352 ng/ml (p < 0.01), in the heparin coated sets from 336 to 1168 ng/ml (p < 0.01), and in the uncoated sets from 301 to 3149 ng/ml (p < 0.01) after 2 h of recirculation. The differences in BTG at termination of the experiments were significant among all three sets (p < 0.05). Myeloperoxidase (MPO) concentrations in the synthetic polymer sets increased from 63 to 86 micrograms/l (p < 0.01), in the heparin-coated sets from 90 to 208 micrograms/l (p < 0.01), and in the uncoated sets from 122 to 513 micrograms/l (p < 0.01) after 2 h of recirculation. The differences in MPO at termination of the experiments were significant among all three groups (p < 0.01). There were no significant differences at termination of the experiments among the three sets regarding complement activation as measured by C3 activation products and the terminal complement complex. We conclude that in the current in vitro model of a CPB circuit, the synthetic polymer coating and the heparin coating caused significantly less platelet loss and granulocyte and platelet activation than the uncoated surface (p < 0.05). The synthetic polymer coating caused significantly less granulocyte and platelet activation than the heparin coating (p < 0.05). There was moderate complement activation within each group, but no significant differences among the three groups.

Leucocyte filtration during cardiopulmonary bypass hardly changed leucocyte counts and did not influence myeloperoxidase, complement, cytokines or platelets

In some patients, coronary artery bypass surgery induces postoperative organ dysfunction despite an apparently adequate revascularization and good haemodynamic performance. This complication may be caused by activation of the body's inflammatory systems on blood contact with large foreign surfaces in the extracorporeal circuit. Activated leucocytes may play an important role in organ damage, and it is conceivable that leucocyte removal by filtration may decrease the potential side-effects of cardiopulmonary bypass (CPB). The aim of the present study was to investigate possible effects of leucocyte filtration during the whole CPB period in elective coronary artery bypass surgery on biochemical and clinical parameters. Forty patients were randomized to extracorporeal circulation using a leucocyte-depleting filter (group L, n = 20) or to extracorporeal circulation with no leucocyte filter (group C, n = 20). In the leucocyte-depleted group, the mean total white blood cell counts increased from 6.3 (95% confidence interval, 5.5-7.0) x 10(9)/l to 7.0 (5.7-8.3) x 10(9)/l during extracorporeal circulation and in the control group from 6.3 (5.2-7.3) x 10(9)/l to 8.5 (7.2-9.8) x 10(9)/l. The intergroup difference was not statistically significant (p = 0.84). A substantial increase in concentrations of interleukin-6, myeloperoxidase and complement activation products were observed in both groups without statistically significant intergroup differences. It is concluded that the leucocyte-depletion filter did not cause a significant reduction of circulating white blood cells during CPB, and there were no significant differences between the groups with respect to the inflammatory markers studied.

Heparin coating reduces cell activation and mediator release in an in vitro venovenous bypass model for liver transplantation

We used an in vitro model for venovenous bypass in a prospective, randomized study to analyze the effect on leukocytes cell activation after coating the total blood contact surface with covalently bound heparin. In ten experiments heparin-coated circuits were used, and in ten other experiments noncoated circuits were used. Monocyte cytokine production and neutrophil myeloperoxidase release were analyzed. Monocytes were isolated using anti-CD14 paramagnetic beads, and oligo (dT)25 beads were used to isolate mRNA before subsequent reverse transcription and semiquantitative amplification of various cytokines in order to determine time-related changes in expression during bypass. After 2 h, mRNAs for IL-1 beta and IL-6 were highly upregulated in noncoated compared to heparin-coated circuits. Little or no change was seen in the expression of other cytokines. IL-1 beta and IL-6 were measured in plasma after 12 h and reflected the upregulated mRNAs in noncoated circuits. A significantly reduced release of myeloperoxidase was observed in coated versus noncoated circuits. This indicates that heparin-coated surfaces reduce cellular activation and the release of inflammatory mediators.

Immunoglobulin prolongs survival of pig kidneys perfused ex vivo with human blood

Intravenous immunoglobulin (IVIG) (Octagam), was used to determine the effect on hyperacute rejection in an ex vivo xenograft model. Six pig kidneys were perfused with IVIG and fresh human AB blood, and six control pig kidneys were simultaneously perfused with albumin and blood from the same donation. The survival of the IVIG-perfused xenografts (median, 6.5 h) was significantly (P = 0.03) longer than the albumin-perfused xenografts (median, 3.5 h). Complement was activated in both groups. The administration of IVIG to the perfused blood resulted in immediate and significantly higher complement activation in the fluid phase as compared with the albumin group. At rejection the fluid phase complement activation was higher in the IVIG group than in the albumin group for C1rs/C1inh complexes, C4bc, Bb and TCC. At the time of rejection both the albumin and the IVIG group demonstrated interstitial tubular haemorrhage, vasculitis or necrosis of glomerular capillaries and glomerular microthrombi. IgM, C1q, C3c, C4 and fibrin were located in arteries and glomeruli and IgG in the interstitium in both groups at rejection. The fluid phase findings are consistent with a modulatory effect of IVIG on complement activation by deviating the classical pathway activation towards the fluid phase. The prolonged survival of the IVIG-perfused kidneys suggests that IVIG may be useful to dampen hyperacute rejection.