A novel fluorescence method for the rapid detection of functional beta1-adrenergic receptor autoantibodies in heart failure.
OBJECTIVE
This study sought to develop a rapid method for the detection of activating autoantibodies directed against the beta1-adrenoceptor (anti-beta1-Abs) in patients with heart failure.


BACKGROUND
The anti-beta1-Abs are supposed to play a pathophysiological role in heart failure. However, there is no reliable method for their detection. With a complex screening strategy (enzyme-linked immunosorbent assay, immunofluorescence, cyclic adenosine monophosphate [cAMP]-radioimmunoassay) we have previously identified antibodies targeting the second extracellular beta1-receptor loop (anti-beta1-EC(II)) in 13% of patients with ischemic cardiomyopathy (ICM) and in 26% with dilated cardiomyopathy (DCM).


METHODS
To detect anti-beta1-Abs, we measured beta1-receptor-mediated increases in intracellular cAMP by fluorescence resonance energy transfer using a highly sensitive cAMP sensor (Epac1-based fluorescent cAMP sensor).


RESULTS
The immunoglobulin G (IgG) prepared from 77 previously antibody-typed patients (22 ICM/55 DCM) and 50 matched control patients was analyzed. The IgG from all 22 previously anti-beta1-EC(II)-positive patients (5 ICM/17 DCM) induced a marked cAMP increase, indicating receptor activation (49.8 +/- 4.2% of maximal isoproterenol-induced signal). The IgG from control patients and 32 previously anti-beta1-EC(II)-negative patients (17 ICM/15 DCM) did not significantly affect cAMP. Surprisingly, our technology detected anti-beta1-Abs in 23 DCM patients formerly judged antibody-negative, but their cAMP signals were generally lower (31.3 +/- 6.8%) than in the previous group. "Low"-activator anti-beta1-Abs were blocked preferentially by peptides corresponding to the first, and "high"-activator anti-beta1-Abs by peptides corresponding to the second beta1-extracellular loop. Beta-blockers alone failed to fully prevent anti-beta1-EC(II)-induced receptor activation, which could be achieved, however, by the addition of beta1-EC(II) peptides.


CONCLUSIONS
Our novel method of detecting anti-beta1-Abs proved to be fast and highly sensitive. It also revealed an insufficient ability of beta-blockers to prevent anti-beta1-EC(II)-induced receptor activation, which opens new venues for the research on anti-beta1-Abs and eventual treatment options in heart failure.
Institut für Pharmakologie und Toxikologie, University of Würzburg, Würzburg, Germany.
Viacheslav O
VO
Nikolaev
Valérie
V
Boivin
Stefan
S
Störk
Christiane E
CE
Angermann
Georg
G
Ertl
Martin J
MJ
Lohse
Roland
R
Jahns
D058671:Adrenergic beta-1 Receptor Antagonists; D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000368:Aged; D001323:Autoantibodies / Q000032:analysis* / Q000187:drug effects; D015415:Biomarkers / Q000032:analysis; D000939:Epitopes; D005260:Female; D031541:Fluorescence Resonance Energy Transfer / Q000295:instrumentation / Q000379:methods*; D006333:Heart Failure / Q000188:drug therapy / Q000276:immunology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018342:Receptors, Adrenergic, beta-1 / Q000276:immunology*; D012016:Reference Values; D012680:Sensitivity and Specificity
D058671:Adrenergic beta-1 Receptor Antagonists; D000319:Adrenergic beta-Antagonists; D001323:Autoantibodies; D015415:Biomarkers; D000939:Epitopes; D018342:Receptors, Adrenergic, beta-1