Non-invasive assessment of the A2A adenosine receptor expression in the murine heart with [18F]FLUDA by positron-emission tomography (PET)


Non-invasive assessment of the A2A adenosine receptor expression in the murine heart with [18F]FLUDA by positron-emission tomography (PET)

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

Question
We have shown that A2A adenosine receptors (A2A-AR) are functionally active in human hearts. Moreover, we generated a transgenic mouse model with heart specific overexpression of the human A2A-AR (TG), which responded to agonists with a positive inotropic effect in vitro. Overexpressed A2A-AR were cardioprotective but also proarrhythmic in TG (Boknik et al. Front Pharmacol 2018, 2019). Here, we focused on the question if a cardiac A2A-AR expression could be assessed in vivo utilizing PET imaging in this model.

Methods
The impact of FLUDA (7-(3-(4-(2-(fluoro)ethoxy-1,1,2,2-d4)phenyl)propyl)-2-(furan-2-yl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidin-5-amine; patent: DE 10 2019 116 986.0) on the force of contraction (FOC) in isolated electrically driven (1 Hz) atrial preparation after stimulation with the A2A–AR-agonist CGS 2180 (10 µM, in the presence of the A1A-AR antagonist DPCPX 1 µM) was measured. On cryosections of mouse hearts the KD and Bmax values of [18F]FLUDA were determined by autoradiography. A small animal PET/MRI scanner (nanoscan, Mediso) was used for in vivo imaging of mice under isoflurane anaesthesia. [18F]FLUDA (7.4±3.4 MBq) was applied via the tail vein 20 s after starting the 90-minute PET measurement. A2A-AR specificity of [18F]FLUDA was determined by application of 2.5 mg/kg body weight Tozadenant 10 minutes prior to tracer administration.

Results
FLUDA was able to reduce (p<0.05) the increase of FOC after CGS 2180 stimulation by about 20 % (p<0.05) in isolated electrically driven atrial preparation in TG (but not WT), indicating a functional antagonism of FLUDA at the human cardiac A2A-AR. By in vitro autoradiography of [18F]FLUDA a KD (5.9±1.6 nM) and Bmax (455±78 fmol/mg protein) could be determined in the A2A-AR-TG hearts, whereas in the control hearts the receptor density was below the detection limit. Using PET/MR, an SUV ratio (SUVR) myocardial/cardiac ventricle of ≥1,0 was determined for the A2A-AR-TG animals at 15-30 min p.i.. Tozadenant reduced SUVR by 6 % (p<0.05).

Conclusion
These data suggest that A2A-AR can be in principle quantified in vivo in the heart.

Keywords: A2A-AR; [18F]FLUDA; adenosine; heart

  • Poster
    5th German Pharm-Tox Summit, 02.-05.03.2020, Leipzig, Deutschland

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Publ.-Id: 30040