Epidemiology and impact of frailty in patients with atrial fibrillation in Europe

BACKGROUND

Frailty is a medical syndrome characterised by reduced physiological reserve and increased vulnerability to stressors. Data regarding the relationship between frailty and atrial fibrillation (AF) are still inconsistent.

OBJECTIVES

We aim to perform a comprehensive evaluation of frailty in a large European cohort of AF patients.

METHODS

A 40-item frailty index (FI) was built according to the accumulation of deficits model in the AF patients enrolled in the ESC-EHRA EORP-AF General Long-Term Registry. Association of baseline characteristics, clinical management, quality of life, healthcare resources use and risk of outcomes with frailty was examined.

RESULTS

Among 10,177 patients [mean age (standard deviation) 69.0 (11.4) years, 4,103 (40.3%) females], 6,066 (59.6%) were pre-frail and 2,172 (21.3%) were frail, whereas only 1,939 (19.1%) were considered robust. Baseline thromboembolic and bleeding risks were independently associated with increasing FI. Frail patients with AF were less likely to be treated with oral anticoagulants (OACs) (odds ratio 0.70, 95% confidence interval 0.55-0.89), especially with non-vitamin K antagonist OACs and managed with a rhythm control strategy, compared with robust patients. Increasing frailty was associated with a higher risk for all outcomes examined, with a non-linear exponential relationship. The use of OAC was associated with a lower risk of outcomes, except in patients with very/extremely high frailty.

CONCLUSIONS

In this large cohort of AF patients, there was a high burden of frailty, influencing clinical management and risk of adverse outcomes. The clinical benefit of OAC is maintained in patients with high frailty, but not in very high/extremely frail ones.

In patients with paroxysmal atrial fibrillation left atrial strain paramethers, left atrial function index and poor glycaemic control can be predictors of arrhythmia recurrence

Funding Acknowledgements

Type of funding sources: None.

Introduction

Left atrial (LA) systolic dysfunction is present in early stages of atrial fibrillation (AFib) prior to left anatomical changes and is influenced by left ventricular systolic function. We evaluate weather left atrial function index (LAFI), left atrial strain parameters (LASP) and glycemic control can be a predictor of AFib recurrence after medical or electrical conversion patients with paroxysmal AFib.

Material and method

We evaluate 150 patients who underwent medical or electrical conversion for paroxysmal AFIb, for a period of 2 years. LA systolic function was appreciated with the echocardiography determined LA emptying volume = Maximum LA volume (LAV max)-minimum LA volume (LAV min), LA emptying fraction= {[LAV max-LAV min]/LAV max]x100}, and LAFI = LA emptying fraction x LVOT-VTILA max index. Left atrial strain (LAS) was assessed as reservoir strain[normal value(NV) 39%], conduit strain(NV 23%) and contractile strain(NV 17%). Flow mediated vasodilation was recorded at the level of brachial artery. Recurrent AFib was recorded in 75 patients (50%), time11,5 ± 10 month.

Results

Univariate analysis revealed as markers for arrhythmia recurrence low LAFI, reduced LA ejection force, altered LASP, high BMI, poor glycemic control (cut-off value for hemoglobin HbA1C 7%), high BMI, decreased index of flow mediated vasodilatation (FMD). On multivariate analysis poor glycemic control, reduced LAFI, altered LASP and larger LA diameter had a higher risk of AFib than patients with higher LAFI and good glycemic control (p < 0,004).

Conclusion

In patients with paroxysmal atrial fibrillation, reduced left atrial function index, altered left atrial strain parameters, larger left atrium, altered endothelial dysfunction appreciated by flow mediated vasodilatation, and poor glycemic control can be predictors of arial fibrillation recurrence.

1054 Improving Sleep By Reducing Allergy Symptoms

Introduction

Allergies can impact sleep quality and, in turn, quality of life. Sleep is affected because allergens irritate nasal passages, which can make breathing more difficult, start an immune response, and directly interfere with sleep. Nasal congestion often is worse at night, and during the night some anti-allergic control processes of the body dip, which can lead to increased symptoms. We tested if an air purifier in the bedroom would improve sleep and reduce allergy symptoms.

Methods

29 adults with self-reported allergy complaints participated in an 8-week field study, using a non-counterbalanced pre-post intervention design. Intervention consisted of the use of an Alen BreatheSmart 45i air purifier at home for 24 hours a day during the duration of the test period. Sleep was measured with self-report and objectively with ResMed S+ every night. Allergy symptoms were measured using self-report. Paired t-tests and multilevel regression were used to test for statistical significance.

Results

28 individuals reported a reduction in allergy symptoms and 27 reported better sleep during the intervention. Overall, participants reported a 38% improvement in allergy symptoms and a 59% improvement in sleep continuity. Moreover, participants felt they fell asleep faster (20% faster), experienced better sleep quality (14% better), and felt more rested in the morning (14% more rested). Objective data showed an 11% improvement of Wake After Sleep Onset and a 1.1% increase in sleep efficiency during intervention (all ps < 0.05), but only in the subgroup (n = 11) of participants with the poorest sleep at baseline.

Conclusion

Using an air purifier in the bedroom can reduce allergy symptoms and improve sleep. Objectively measured sleep improvements supported the self-reported improvements, but only in the subset of participants who showed compromised sleep at baseline.

Support

Alen Corporation

Continuous long-term immunomodulatory therapy in relapsing multiple sclerosis: results from the 15-year analysis of the US prospective open-label study of glatiramer acetate

The ongoing US Glatiramer Acetate (GA) Trial is the longest evaluation of continuous immunomodulatory therapy in relapsing-remitting multiple sclerosis (RRMS). The objective of this study was to evaluate up to 15 years of GA as a sole disease-modifying therapy. Two hundred and thirty-two patients received at least one GA dose since study initiation in 1991 (mITT cohort), and 100 (43%, Ongoing cohort) continued as of February 2008. Patients were evaluated every 6 months using the Expanded Disability Status Scale (EDSS). Mean GA exposures were 8.6 +/- 5.2, 4.81 +/- 3.69, and 13.6 +/- 1.3 years and mean disease durations were 17, 13, and 22 years for mITT, Withdrawn and Ongoing cohorts, respectively. For Ongoing patients, annual relapse rates (ARRs) maintained a decline from 1.12 +/- 0.82 at baseline to 0.25 +/- 0.34 per year; 57% had stable/improved EDSS scores (change < or = 0.5 points); 65% had not transitioned to secondary progressive multiple sclerosis (SPMS); 38%, 18%, and 3% reached EDSS 4, 6, and 8. For all patients on GA therapy (the mITT cohort), ARRs declined from 1.18 +/- 0.82 to 0.43 +/- 0.58 per year; 54% had stable/improved EDSS scores; 75% had not transitioned to SPMS; 39%, 23%, and 5% reached EDSS 4, 6, and 8. In conclusion, multiple sclerosis patients with mean disease duration of 22 years administering GA for up to 15 years had reduced relapse rates, and decreased disability progression and transition to SPMS. There were no long-term safety issues.

Mechanisms of signal transduction activated by sublytic assembly of terminal complement complexes on nucleated cells

The sublytic assembly of C5b-7, C5b-8, and C5b-9, activates membrane phospholipases through heterotrimeric G proteins and stimulates a variety of cellular activities including prostanoids, leukotrienes, and cytokines synthesis. Activation of mitotic signaling through Ras, Raf-1, ERK1, and phosphatidylinositol-3 kinase (PI3-K) was induced in B lymphocytes, endothelial, and smooth muscle cells. PI3-K activation by C5b-9 induced STAT3 phosphorylation and translocation from cytoplasm to nucleus. This complex signaling mechanism is directly involved in many biological functions such as endo- and exocytosis, cell cycle progression, activation of transcription, and protein synthesis. The key role of this signaling pathway is reflected on cell survival and proliferation in acute and chronic inflammation where complement activation is an ubiquitous event.

The complement system in central nervous system diseases

The activation of complement system is an important factor participating in inflammatory, neurodegenerative, and cerebrovascular diseases. Astrocytes and neurons are able to synthesize complement components. Myelin and oligodendrocyte (OLG) activate the classical pathway of complement in vitro in the absence of antibodies. Sublytic C5b-9 in the absence of cell death induces proto-oncogenes, activates cell cycle, and enhances cell survival in OLG. In addition, C5b-9 reverses the differentiation phenotype in OLG and enhances cell survival. beta amyloid protein is an activator of the complement system and neurons are susceptible to bystander complement mediated damage. These findings indicate that complement activation and membrane assembly of C5b-9 play an important role in pathogenesis of central nervous system (CNS) disorders.

C5b-9 terminal complement complex protects oligodendrocytes from death by regulating Bad through phosphatidylinositol 3-kinase/Akt pathway

Apoptosis of oligodendrocytes is induced by serum growth factor deprivation. We showed that oligodendrocytes and progenitor cells respond to serum withdrawal by a rapid decline of Bcl-2 mRNA expression and caspase-3-dependent apoptotic death. Sublytic assembly of membrane-inserted terminal complement complexes consisting of C5b, C6, C7, C8, and C9 proteins (C5b-9) inhibits caspase-3 activation and apoptotic death of oligodendrocytes. In this study, we examined an involvement of the mitochondria in oligodendrocyte apoptosis and the role of C5b-9 on this process. Decreased phosphatidylinositol 3-kinase and Akt activities occurred in association with cytochrome c release and caspase-9 activation when cells were placed in defined medium. C5b-9 inhibited the mitochondrial pathway of apoptosis in oligodendrocytes, as shown by decreased cytochrome c release and inhibition of caspase-9 activation. Phosphatidylinositol 3-phosphate kinase and Akt activities were also induced by C5b-9, and the phosphatidylinositol 3-phosphate kinase inhibitor LY294002 reversed the protective effect of C5b-9. Phosphatidylinositol 3-phosphate kinase activity was also responsible for the phosphorylation of Bad at Ser112 and Ser136. This phosphorylation resulted in dissociation of Bad from the Bad/Bcl-xL complex in a G(i)alpha-dependent manner. The mitochondrial pathway of oligodendrocyte apoptosis is, therefore, inhibited by C5b-9 through post-translational regulation of Bad. This mechanism may be involved in the promotion of oligodendrocyte survival in inflammatory demyelinating disorders affecting the CNS.

Terminal complement complexes concomitantly stimulate proliferation and rescue of Schwann cells from apoptosis

The consequences of sublytic terminal complement complex (TCC) assembly on Schwann cell proliferation and apoptosis were examined by using purified complement proteins (C5*-9) or antibody-sensitized Schwann cells in the presence of a serum that was depleted of the seventh component of complement (C7dHS) and reconstituted with purified C7. Stimulation of cultured Schwann cells with antibody plus 10% C7dHS and C7 or C5*-9 induced DNA synthesis over antibody plus 10% C7dHS alone or in Schwann cells in which C5*-9 insertion was inhibited by heat inactivation, respectively. Cell cycle analysis with propidium iodide showed that, at 24 h, viable Schwann cells in defined medium were synchronized in G1/G0 phase. C5*-9 shifted 64% of these cells into S or G2/M phases in a manner similar to beta-neuregulin (beta-NRG), a known Schwann cell mitogen. Furthermore, antibody with 10% C7dHS and C7 or purified C5*-9 induced proliferation of viable Schwann cells. These effects were mediated by signal-transduction pathways involving p44 ERK1 (extracellular-regulated kinase 1), Gi proteins, and protein kinase C. Culturing in defined medium for 24 h resulted in apoptosis of up to 50% of Schwann cells that was prevented by treatment with beta-NRG or TCC. Sublytic C5*-9 significantly inhibited apoptosis 41% by 24 h, as determined by a terminal deoxyuridine triphosphate-biotin nick end labeling assay, and also decreased annexin-V binding at 4 h. Collectively, these data suggest that sublytic TCC, like beta-NRG, is a potent Schwann cell trophic factor that is capable of stimulating mitogenesis and apoptotic rescue. TCC assembly on Schwann cells during inflammatory demyelination of peripheral nerves may promote survival of mature cells to enhance repair and remyelination processes.

Inhibition of oligodendrocyte apoptosis by sublytic C5b-9 is associated with enhanced synthesis of bcl-2 and mediated by inhibition of caspase-3 activation

We have previously shown that generation of sublytic C5b-9, the membrane attack complex of complement, induces oligodendrocytes to enter cell cycle and reduces apoptotic cell death in vitro. In the present study, the cellular factors involved in apoptosis of oligodendrocyte progenitor cells and oligodendrocytes, and the inhibitory effect of C5b-9 on apoptotic process were investigated. Oligodendrocyte progenitor cells identified by mAb A2B5 that were isolated from neonatal rat brains were differentiated into oligodendrocytes in serum-free defined medium. The differentiation, which occurs simultaneously with apoptotic cell death, was associated with a rapid loss of bcl-2 mRNA and increased expression of caspase-3 mRNA. Activation of caspase-3 in differentiating cells was demonstrated by the generation of 17- and 12-kDa fragments of caspase-3 proenzyme and by cleavage of poly(ADP-ribose) polymerase, a specific caspase-3 substrate. Cell death associated with differentiation was inhibited by the caspase-3 inhibitor DEVD-CHO in a dose-dependent manner. Assembly of sublytic C5b-9 resulted in inhibition of caspase-3 activation. In addition, synthesis of BCL-2 protein in oligodendrocytes was significantly increased by C5b-9. The TNF-alpha-induced apoptosis of oligodendrocytes was also inhibited by C5b-9. These results indicate that up-regulation of BCL-2 protein and inhibition of caspase-3 activation are potential mechanisms by which C5b-9 increases survival of oligodendrocyte in vitro and possibly in vivo during inflammation and immune-mediated demyelination affecting the CNS.

Complement activation and atherosclerosis

Atherosclerosis is an inflammatory disease mediated through the action of monocyte/macrophages, complement and T-lymphocytes. C5a and monocyte chemotactic factor released during complement activation in the arterial wall may participate in the initial monocyte recruitment. Assembly of C5b-9 on cells of the arterial wall may also induce cell lysis. On the other hand, sublytic assembly of C5b-9 on smooth muscle cells (SMC) and endothelial cells (EC) induces cell activation and proliferation. Analysis of mitogen activated protein kinases (MAPK) pathways induced by C5b-9 in aortic SMC revealed that extracellular signal regulated kinase (ERK) 1, c-jun NH2-terminal kinase (JNK) 1, and p38 MAPK are all activated by C5b-9. ERK1 activity was inhibited by wortmannin suggesting that ERK1 pathway is activated through phosphatidyl inositol -3 (PI 3-) kinase. Sublytic C5b-9 assembly on the plasma membrane was also able to activate Janus kinase (JAK) 1, signal transducer and activator (STAT) 3 and STAT4 in EC. JAK1 but not STAT3 activation induced by C5b-9 is dependent on Gi protein activation. New evidence accumulated during the last decade support the role of complement activation in both initiation and progression of the atherosclerotic lesions. Complement system activation is a major component of the chronic inflammatory process associated with atherosclerosis.

Tyrosine phosphorylation and activation of Janus kinase 1 and STAT3 by sublytic C5b-9 complement complex in aortic endothelial cells

The pathway involving Janus kinase (JAK) and signal transducers and activators of transcription (STATs) plays an important role in differentiation and proliferation of cells initiated by receptor activation. In the present study we identified the JAK and STAT proteins activated by C5b-9 in human aortic endothelial cells (AEC). JAK1 but not JAK2 was tyrosine phosphorylated in response to sublytic C5b-9. STAT3 was rapidly tyrosine phosphorylated also by C5b-9. Pertussis toxin inhibited the C5b-9 induced JAK1 activation. However, phosphorylation of STAT3 was not inhibited by Pertussis toxin, although C5b-9 induced a time-dependent nuclear translocation of STAT3. These observations indicated that JAK1 is phosphorylated by C5b-9 through activation of trimeric G proteins of the Gi/Go family. Raf-1 and ERK1 were also activated by C5b-9 in human AEC in a G protein dependent manner. Therefore, JAK1 activity may be involved in activation of Raf-1 and ERK1 via G proteins activated by C5b-9. This study demonstrates the ability of membrane-inserted C5b-9 to activate JAK1 and STAT3 proteins, thus defining new signalling pathway by which C5b-9 may regulate gene activation.

Sublytic C5b-9 induces proliferation of human aortic smooth muscle cells: role of mitogen activated protein kinase and phosphatidylinositol 3-kinase

Proliferation of vascular smooth muscle cells contributes to initimal hyperplasia during atherogenesis, but the factors regulating their proliferation are not well known. In the present study we report that sublytic C5b-9 assembly induced proliferation of differentiated human aortic smooth muscle cells (ASMC) in culture. Cell cycle re-entry occurred through activation of cdk4, cdk2 kinase and the reduction of p21 cell cycle inhibitor. We also investigated if C5b-9 cell cycle induction is mediated through activation of mitogen activated protein kinase (MAPK) pathways. Extracellular signal regulated kinase (ERK) 1 activity was significantly increased, while c-jun NH2-terminal kinase (JNK) 1 and p38 MAPK activity were only transiently increased. Pretreatment with wortmannin inhibits ERK1 activation by C5b-9, suggesting the involvement of phosphatidylinositol 3-kinase (PI 3-kinase). Both PI 3-kinase and p70 S6 kinase were activated by C5b-9 but not by C5b6. C5b-9 induced DNA synthesis was abolished by pretreatment with inhibitors of ERK1 and PI 3-kinase, but not by p38 MAPK. These data indicated that ERK1 and PI 3-kinase play a major role in C5b-9 induced ASMC proliferation.

Molecular cloning and characterization of RGC-32, a novel gene induced by complement activation in oligodendrocytes

Sublytic complement activation on oligodendrocytes (OLG) down-regulates expression of myelin genes and induces cell cycle in culture. Differential display (DD) was used to search for new genes whose expression is altered in response to complement and that may be involved in cell cycle activation. DD bands showing either increased or decreased mRNA expression in response to complement were identified and designated Response Genes to Complement (RGC) 1-32. RGC-1 is identical with heat shock protein 105, RGC-2 with poly(ADP-ribose) polymerase, and RGC-10 with IP-10. A new gene, RGC-32, that encodes a protein of 137 amino acids was cloned. RGC-32 has no homology with other known proteins, and contains no motif that would indicate its function. In OLG, the mRNA expression was increased by complement activation and by terminal complement complex assembly. RGC-32 protein was localized in the cytoplasm and co-immunoprecipitated with cdc2 kinase. Overexpression of RGC-32 increased DNA synthesis in OLGxC6 glioma cell hybrids. These results suggest that RGC-32 may play a role in cell cycle activation.

Terminal complement complexes induce cell cycle entry in oligodendrocytes through mitogen activated protein kinase pathway

Sublytic complement attack through C5b-9 assembly induces oligodendrocytes (OLG) to express proto-oncogenes and to enter the cell cycle from resting G0/G1 phase to S phase. We have investigated whether cell cycle induction by C5b-9 is mediated by mitogen activated protein kinase (MAPK) pathway in OLG. C5b-9 but not C5b6 induced activation of both ERK1 and c-jun NH2 terminal kinases 1 (JNK1) in OLG. The increased ERK1 and JNK1 activities are transient, reaching a maximum around 20 min following exposure to C5b-9. Activation of Raf-1 and MEK1, upstream kinases of ERK1, was shown by increased Raf-1 kinase activity in anti-Raf-1 immunoprecipitates of OLG treated with C5b-9 and ERK1 activity that can be inhibited by PD098,059, a specific MEK1 inhibitor. Requirement for the ERK1 pathway in DNA synthesis was then evaluated using PD098,059. Enhanced DNA synthesis induced by serum complement was completely abolished when OLG were pretreated with PD098,059. On the other hand, c-fos mRNA expression induced by complement was inhibited only 50% by PD098,059, while the c-jun mRNA level was not affected by this MEK1 inhibitor. Interestingly, p70 S6 kinase, an important ribosomal kinase in mitogenesis, was also activated by C5b-9. These findings indicated that the MAPK pathways appears to play a major role in inducing OLG to enter the S phase of the cell cycle from the resting G1/G0 phase.

Activation of Ras and mitogen-activated protein kinase pathway by terminal complement complexes is G protein dependent

Assembly of terminal complement complexes (TCC) C5b-7, C5b-8, and C5b-9 on target cells during acute and chronic inflammation induces hydrolysis of plasma membrane phospholipids and heterotrimeric G protein activation. TCC also stimulate a variety of cellular activities, which include cytokine synthesis, proto-oncogene activation, and mitotic signaling. Now we report that sublytic TCC induced Ras, Raf-1, and extracellular signal-regulated kinase (ERK) 1 activation in JY25 B cell line. When cells were exposed to C5b-9, GTP-bound Ras in anti-C5b-9 immunoprecipitates was increased 3.2-fold at 2 min, while GTP-bound Ras in anti-Ras immunoprecipitates was increased 2-fold at 10 min. Both C5b-9 and C5b-7, but not C5b6, increased Raf-1 kinase activity maximum 3.3-fold at 2 min and 2.8-fold at 5 min, respectively. ERK1 activity was 2-fold increased by C5b-9 at 2 min and by C5b-7 at 10 min, over the C5b6 level. The role of mitogen-activated protein kinase (MAPK) pathway on TCC-inducible mitotic signaling was evaluated by assessing DNA synthesis and activator protein 1 (AP-1) DNA-binding activity. The MAPK/ERK-specific inhibitor PD 098,059 abolished the C5b-9-induced DNA synthesis. Involvement of G protein in the activation of MAPK pathway by TCC was indicated by inhibition of Raf-1 and ERK1 kinase activity, as well as the DNA synthesis by pretreatment of cells with pertussis toxin. Overexpression of beta-adrenergic receptor kinase 1 carboxyl-terminal peptide in JY25 cells also inhibited Raf-1 and ERK1 activity, indicating a direct involvement of G betagamma subunits in the signal transduction generated through activation of MAPK pathway by TCC assembly in the plasma membrane.

Activation of Ras and mitogen-activated protein kinase pathway by terminal complement complexes is G protein dependent

Assembly of terminal complement complexes (TCC) C5b-7, C5b-8, and C5b-9 on target cells during acute and chronic inflammation induces hydrolysis of plasma membrane phospholipids and heterotrimeric G protein activation. TCC also stimulate a variety of cellular activities, which include cytokine synthesis, proto-oncogene activation, and mitotic signaling. Now we report that sublytic TCC induced Ras, Raf-1, and extracellular signal-regulated kinase (ERK) 1 activation in JY25 B cell line. When cells were exposed to C5b-9, GTP-bound Ras in anti-C5b-9 immunoprecipitates was increased 3.2-fold at 2 min, while GTP-bound Ras in anti-Ras immunoprecipitates was increased 2-fold at 10 min. Both C5b-9 and C5b-7, but not C5b6, increased Raf-1 kinase activity maximum 3.3-fold at 2 min and 2.8-fold at 5 min, respectively. ERK1 activity was 2-fold increased by C5b-9 at 2 min and by C5b-7 at 10 min, over the C5b6 level. The role of mitogen-activated protein kinase (MAPK) pathway on TCC-inducible mitotic signaling was evaluated by assessing DNA synthesis and activator protein 1 (AP-1) DNA-binding activity. The MAPK/ERK-specific inhibitor PD 098,059 abolished the C5b-9-induced DNA synthesis. Involvement of G protein in the activation of MAPK pathway by TCC was indicated by inhibition of Raf-1 and ERK1 kinase activity, as well as the DNA synthesis by pretreatment of cells with pertussis toxin. Overexpression of beta-adrenergic receptor kinase 1 carboxyl-terminal peptide in JY25 cells also inhibited Raf-1 and ERK1 activity, indicating a direct involvement of G betagamma subunits in the signal transduction generated through activation of MAPK pathway by TCC assembly in the plasma membrane.

Activation of human neutrophils after contact with cellulose-based haemodialysis membranes: intracellular calcium signalling in single cells

PURPOSE OF STUDY

In vitro contact of human leukocytes with cellulose-based dialysis membranes under complement-independent conditions results in activation of various leukocyte functions. To analyse signals involved in the mechanism of cell activation, we measured changes in cytosolic free calcium ([Ca2+]i) in individual human blood neutrophils (PMN) upon contact with flat sheet haemodialysis membranes.

RESULTS

By confocal laser-scanning microscopy (CLSM), changes in [Ca2+]i were monitored in Fluo-3-labelled cells up to 10 min after contact with a regenerated cellulose (RC) membrane. Multiple [Ca2+]i transients were observed for cells in contact with RC; biostochastic analysis showed that up to 67% of the PMN responded with a high increase in [Ca2+]i, the rest were low- or non-responding cells. After contact with the new synthetic polycarbonate-polyether (PC-PE) membrane only non-responding cells were seen, indicating reduced cellular contact activation. The increase in [Ca2+]i of cells on RC could be inhibited by 5mM L-fucose. This monosaccharide was recently found to be present in cellulose-based polymers in picomolar concentrations.

CONCLUSIONS

The data supports the hypothesis that dialysis-membrane-associated L-fucose residues participate in complement-independent leukocyte activation during haemodialysis therapy.

Receptor-independent activation of guanine nucleotide-binding regulatory proteins by terminal complement complexes

Activation of heterotrimeric guanine nucleotide-binding proteins (G proteins) by terminal complement complexes (TCC) was investigated on human lymphoblastoid B-cell line JY25 and its mutant JY5 deficient in glycosylphosphatidylinositol-anchored proteins. TCC assembly achieved by antibody-dependent activation of C7-deficient serum reconstituted with C7 increased specific guanosine-5'-(gamma-thio)triphosphate (GTP gamma S) binding, 4- and 8-fold, in JY25 and JY5 membranes, respectively, between 2 and 10 min, over the level without C7. TCC also increased GTPase activity 5- and 4-fold in JY25 and JY5, respectively, between 5 and 10 min. Increased GTPase activity was noted first with C5b-7 assembly, which increased further with C5b-8 and C5b-9. The presence of G proteins in anti-TCC immunoprecipitates of cell lysates was investigated by demonstration of G alpha subunit that can be ADP-ribosylated by pertussis toxin (PTX). Immunoprecipitated TCC complexes contained a PTX-sensitive 41-kDa Gi alpha/Go alpha subunit, as shown by SDS-PAGE and Western blotting. These complexes were functionally active as determined by GTP gamma S binding. We have further shown that enhanced TCC elimination from the plasma membrane induced by TCC-generated signals was inhibited by PTX. In conclusion the biological activities induced by TCC in nucleated cells may be mediated in part by activation of PTX-sensitive G proteins.

Generation of diacylglycerol and ceramide during homologous complement activation

Formation of sublytic terminal complement complexes (TCC) on nucleated cells produces transient increase in [Ca2+]i and activates protein kinase C. The present study is to evaluate whether TCC can generate endogenous signal messengers other than Ca2+ that regulate cell activities by measuring mass-levels of sn-1,2-diacylglycerol (DAG) and ceramide. As targets, lymphoblastoid human B cell lines JY25 and its mutant JY5 were used. JY5, cells deficient in glycosylphosphatidylinositol-anchored proteins with higher lytic susceptibility to human complement, are four times more efficient in forming C5b-9. When cells sensitized with limited anti-class II IgG were exposed to human serum to generate sublytic TCC, a sustained increase in DAG and ceramide was observed with a maximum 3.6-fold DAG increase over basal level in JY25 and 2.8-fold in JY5, and 6.3-fold ceramide increase in JY25 and 2.8-fold in JY5. The effect of TCC was evaluated with C7-deficient human serum (C7D) +/- C7 and also with C5b6, C7, C8, and C9 proteins. The DAG and ceramide increase by C7D + C7 over C7D control were 1.6- and 1.8-fold, respectively, in JY25, and 2.3-, and two-fold in JY5. TCC activation also induced an increased hydrolysis of sphyingomyelin and phosphatidylcholine. In addition, DAG increase by TCC was primarily achieved by C5b-7 and preincubation of cells with pertussis toxininhibited DAG increase, suggesting an involvement of a pertussis toxin-sensitive GTP-binding protein. As important signal transduction molecules, DAG and ceramide generated in response to TCC assembly, could participate in cell activation during inflammation and repair.

Generation of diacylglycerol and ceramide during homologous complement activation

Formation of sublytic terminal complement complexes (TCC) on nucleated cells produces transient increase in [Ca2+]i and activates protein kinase C. The present study is to evaluate whether TCC can generate endogenous signal messengers other than Ca2+ that regulate cell activities by measuring mass-levels of sn-1,2-diacylglycerol (DAG) and ceramide. As targets, lymphoblastoid human B cell lines JY25 and its mutant JY5 were used. JY5, cells deficient in glycosylphosphatidylinositol-anchored proteins with higher lytic susceptibility to human complement, are four times more efficient in forming C5b-9. When cells sensitized with limited anti-class II IgG were exposed to human serum to generate sublytic TCC, a sustained increase in DAG and ceramide was observed with a maximum 3.6-fold DAG increase over basal level in JY25 and 2.8-fold in JY5, and 6.3-fold ceramide increase in JY25 and 2.8-fold in JY5. The effect of TCC was evaluated with C7-deficient human serum (C7D) +/- C7 and also with C5b6, C7, C8, and C9 proteins. The DAG and ceramide increase by C7D + C7 over C7D control were 1.6- and 1.8-fold, respectively, in JY25, and 2.3-, and two-fold in JY5. TCC activation also induced an increased hydrolysis of sphyingomyelin and phosphatidylcholine. In addition, DAG increase by TCC was primarily achieved by C5b-7 and preincubation of cells with pertussis toxininhibited DAG increase, suggesting an involvement of a pertussis toxin-sensitive GTP-binding protein. As important signal transduction molecules, DAG and ceramide generated in response to TCC assembly, could participate in cell activation during inflammation and repair.

Characterization of circulating immune complexes in heart disease

Circulating immune complexes (CIC) were characterized for the content in IgG, IgA, IgM, C3 and C4 in patients with heart disease. The levels of IgG, IgM and C4 in PEG-precipitates of patients' sera were significantly higher than those found in controls, and the precipitation profile was similar to that of rheumatoid arthritis patients. Differences were observed in the composition of CIC: IgM was highest in association with myocarditis, and C3 predominated in cases of valvular disease. Complex-bound C4 was significantly higher in patients with myocardial infarction which developed pericarditis either early or late in the evolution of the disorder. Antimyocardial antibodies could be detected in sera and in corresponding PEG-precipitates. The bulk of the data suggests that CIC might play a pathogenetic role in various heart diseases.

Localization of the terminal C5b-9 complement complex in the human aortic atherosclerotic wall

The terminal C5b-9 complement complex was investigated in 15 aortic, 2 femoral fibrous plaques and 5 fatty streaks aortic intimae using indirect immunofluorescence and immunoperoxidase. All the fibrous plaques presented C5b-9 deposit-like threads in the fibrous cap and masses in the amorphous areas of the plaque. The deposits were frequently associated with other immune-related proteins such as: IgG, IgA, IgM, Clq, C3c and C4 which were simultaneously investigated. Fatty streaks intimae presented no C5b-9 and complement component deposits. Whereas the demonstration of the complement components could merely reflect a non-specific trapping, the presence of assembled C5b-9 in the damaged tissue is more indicative of the involvement of complement activation in the progression of atherosclerotic lesions.

Comparative behaviour of the components of the factor VIII complex in acute myocardial infarction

The three components of the factor VIII complex: VIII coagulant (VIII:C), VIII related antigen (VIII R:Ag) and the VIII related von Willebrand factor (VIII R:WF) were studied in patients with acute myocardial infarction (AMI). Using a carefully standardized technique for the determination of VIII R:WF, a significantly higher R:WF level was found in 32 patients compared to 19 control subjects, confirming our previous results. However VIII R:AG was increased to an even greater extent, resulting in a VIII R:Ag/VIII R:WF ratio of 1.58 +/- 0.084 in patients, compared to 1.21 +/- 0.045 in controls. A similar increase of the VIII R:AG/VIII:C ratio was noted in the 13 patients in whom VIII:C was investigated. In 7 patients with severe AMI who could be investigated twice the plasma levels of both VIII R:Ag and VIII R:WF were found to be lower a week after the acute event than during the first 48 hours. However the VIII R:Ag/VIII R:WF ratio was not significantly reduced after 7 days. Acute phase reaction and endothelial injury resulting in release of multimers which are less polymerised are probably involved in the above changes.