Non-invasive assessment of locally overexpressed human adenosine 2A receptors in the heart of transgenic mice


Non-invasive assessment of locally overexpressed human adenosine 2A receptors in the heart of transgenic mice

Gündel, D.; Lai, T. H.; Dukic-Stefanovic, S.; Teodoro, R.; Deuther-Conrad, W.; Toussaint, M.; Moldovan, R.-P.; Kopka, K.; Boknik, P.; Hofmann, B.; Gergs, U.; Neumann, J.; Brust, P.

Abstract: A2A adenosine receptors (A2A-AR) have a cardio-protective function upon ischemia and reperfusion, but on the other hand, their stimulation could lead to arrhythmias. Our aim was to investigate the potential use of the PET radiotracer [18F]FLUDA to determine the A2A-AR availability non-invasively for diagnosis of the A2AR status. Therefore, we compared mice with a cardiomyocyte-specific overexpressing of the human A2A-AR (A2A-AR TG) with the respective wild type (WT). We determined: (1) the functional impact of FLUDA on the contractile function of atrial mouse samples, (2) the binding parameters (Bmax and KD) of [18F]FLUDA on mouse and additionally on human atrial tissue samples by autoradiographic studies, and investigated (3) the in vivo uptake of the radiotracer by dynamic PET imaging in the two A2A-AR TG and WT. After A2A-AR stimulation by CGS 21680 in isolated atrial preparations antagonistic effects of FLUDA were found in A2A-AR-TG animals but not in WT mice. Radiolabeled [18F]FLUDA exhibited a KD of 5.9 ± 1.6 nM and a Bmax of 455 ± 78 fmol/mg protein in cardiac samples of A2A-AR TG, whereas in WT, as well as in human atrial preparations only low specific binding could was found. Dynamic PET studies revealed a significantly higher initial uptake of [18F]FLUDA into the myocardium of A2A-AR TG compared to WT. The hA2A-AR-specific binding of [18F]FLUDA in vivo was verified by pre-administration of the highly affine A2AAR-specific antagonist istradefylline.
Conclusion: [18F]FLUDA is a promising PET probe for the non-invasive assessment of the A2A-AR as a marker for pathologies linked to an increased A2A-AR density in the heart, as shown in patients with heart failure.

Keywords: [18F]FLUDA; A2A adenosine receptor; PET; myocardium

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Publ.-Id: 33505