ABSTRACT
In patients with dilated cardiomyopathy (DCM), cardiac autoantibodies are able to bind with their Fab fragment to epitopes on cardiomyocytes, but thereafter they crosslink through their Fc fragment to cardiac Fc(gamma)-receptor IIa. Polymorphic variability of the Fc(gamma)-receptor IIa is associated with modified affinity of immunoglobin G (IgG) binding and may influence therapeutic effects. In this study, 103 consecutive DCM patients were treated with immunoadsorption (IA) therapy with subsequent IgG substitution (IA/IgG). Echocardiography was performed at baseline and again at 3 and 6 months after IA/IgG. Fc(gamma)-receptor IIa polymorphism R/H131 was genotyped using a nested sequence-specific primer polymerase chain reaction (PCR). Patients with the Fc(gamma)-receptor IIa genotype R/R131 showed significantly greater improvement in left ventricular (LV) function than patients with the R/H131 or H/H131 genotypes did. Irrespective of the Fc(gamma)-receptor polymorphism, patients with shorter disease duration and a more impaired LV function responded with a greater increase in LV ejection fraction (LVEF). Therefore, the Fc(gamma)-receptor polymorphism influences the efficacy of immunomodulatory therapy involving IA/IgG.
Subject(s)
Cardiomyopathy, Dilated/physiopathology , Immunoglobulin G/immunology , Polymorphism, Genetic , Receptors, IgG/genetics , Autoantibodies/immunology , Cardiomyopathy, Dilated/genetics , Echocardiography , Epitopes , Female , Follow-Up Studies , Genotype , Humans , Immunosorbent Techniques , Male , Middle Aged , Polymerase Chain Reaction , Ventricular Dysfunction, Left/genetics , Ventricular Dysfunction, Left/physiopathologyABSTRACT
BACKGROUND: After ischaemia and during reperfusion, rat hearts release cardiodepressive substances that are putatively cyclooxygenase-2-dependent. The present study analyses the mechanisms by which these substances mediate their effect downstream of cyclooxygenase-2. MATERIALS AND METHODS: After 10 min of global stop-flow ischaemia, isolated rat hearts were reperfused and post-ischaemic coronary effluent was collected over a period of 30 s. Non-ischaemic effluent collected before ischaemia was used as a control. We investigated the effect of the effluents on cell shortening and Ca(++)-metabolism, by application of fluorescence microscopy of field-stimulated adult rat cardiomyocytes incubated with fura-2. Cells were pre-incubated with inhibitors of protein kinase A and C and with antagonists of protein kinase A-dependent prostaglandin receptors. We examined the expression of prostaglandin receptors in cardiomyocytes by Western blotting. RESULTS: In contrast to non-ischaemic effluent, post-ischaemic effluent induced reduction of Ca(++) transient and cell shortening in the cardiomyocytes. In contrast to protein kinase C inhibitor Myr-PKC [19-27], the protein kinase A inhibitor Rp-cAMPS completely blocked the effect of post-ischaemic effluent. Furthermore, we determined a cyclic adenosine monophosphate increase in cardiomyocytes that were pre-incubated with post-ischaemic effluent. The antagonist of prostaglandin E-receptor EP2 AH6809 and the antagonist of receptor subtype EP4 AH23848 attenuated the effect of post-ischaemic effluent in contrast to other antagonists of prostaglandin D and I receptors, which did not influence the effect. In lysates of adherend cardiomyocytes, expression of prostaglandin D, E and I receptors was detected by Western blotting. CONCLUSIONS: The effect of post-ischaemic effluent is mediated by the protein kinase A-dependent prostaglandin-receptor subtypes EP2 and EP4 downstream of cyclooxygenase-2.
Subject(s)
Cyclic AMP-Dependent Protein Kinases/pharmacology , Heart/drug effects , Myocardial Ischemia/metabolism , Myocytes, Cardiac/metabolism , Protein Kinase C/pharmacology , Receptors, Prostaglandin/physiology , Animals , Blotting, Western , Cyclic AMP-Dependent Protein Kinases/antagonists & inhibitors , Cyclic AMP-Dependent Protein Kinases/metabolism , Cyclooxygenase Inhibitors/metabolism , Myocardial Reperfusion , Protein Kinase C/antagonists & inhibitors , Protein Kinase C/metabolism , Rats , Rats, Wistar , Receptors, Prostaglandin/antagonists & inhibitorsABSTRACT
BACKGROUND: Cardiac autoantibodies may play a pathophysiological role in cardiac dysfunction of patients suffering from dilated cardiomyopathy (DCM). Immunoadsorption (IA), which removes antibodies from patients' plasma, may consequently improve cardiac function in DCM. The functional effects of DCM antibodies are only partly understood. MATERIALS AND METHODS: DCM patients (n = 10) were treated with IA by application of antibody columns directed against human immunoglobulin (Ig). IA was also performed with plasma taken from 10 healthy donors (controls). The antibodies eliminated and purified by IA were collected and dialysed. Rat hearts were isolated and perfused retrogradely via the aorta in Langendorff mode. During constant-pressure and constant-volume perfusion of the hearts, the influence of diluted antibodies on contractility, relaxation, and on coronary perfusion was analysed. RESULTS: Antibodies obtained from controls had no effect on contractility and relaxation of isolated perfused hearts during constant-pressure and constant-volume perfusion. In contrast, during constant-pressure perfusion, collected DCM antibodies caused immediate and dose-related reduction of contractility (dLVP/dtmax: dilution -1:32 = -7.1 +/- 1.1%; dilution -1:2 = -20.1 +/- 2.1%; P < 0.001) and diastolic relaxation (dLVP/dtmin: dilution -1:32 = -11.1 +/- 1.5%; dilution -1:2 = -23.9 +/- 2.2%; P < 0.001). The heart rate did not change significantly in either group. The effects of DCM antibodies on contractility and relaxation remained detectable during constant-volume perfusion. The observed reduction of contractility and diastolic relaxation was accompanied by impairment of coronary perfusion. CONCLUSION: In the rat heart, antibodies obtained from DCM patients may impair contractility and relaxation, and thereby probably also coronary perfusion.
