Targeting of GRK5 in heart failure: a promising therapeutic strategy

Johanna Klöcker (Würzburg)1, J. Fender (Würzburg)1, M. Baumann (Dortmund)2, M. Kleindl (Dortmund)3, J. Hatzold (Würzburg)1, J. Engel (Dortmund)2, F. Ballaschk (Dortmund)2, B. Klebl (Dortmund)2, K. Lorenz (Würzburg)1

1Universität Würzburg Institut für Pharmakologie und Toxikologie Würzburg, Deutschland; 2Lead Discovery Center GmbH Dortmund, Deutschland; 3Leibniz-Institut für Analytische Wissenschaften—ISAS e.V. Dortmund, Deutschland


Background: G protein-coupled receptor kinase 5 (GRK5) is a potential target for heart failure therapy. It plays an important role in desensitizing G protein-coupled receptors (GPCRs) but has also been reported to impact on cardiac remodeling via non-canonical signaling pathways. Thus far, no GRK5 inhibitor has been approved for clinical use.
Aim: Here, we aimed to set up a selection process to identify potent and potentially cardio safe GRK5 inhibitors and to examine those in two different mouse models of heart failure. 
Methods and results: To select promising GRK5 inhibitors from a templated library for further investigation, we (i) established a bioluminescence resonance transfer (BRET)-based method to monitor βarrestin2 recruitment to β2-adrenergic receptors in HEK cells, and (ii) an impedance-based method to monitor cell viability, contractility and beating rhythm of neonatal cardiomyocytes. With the help of this approach, we selected GRK5 inhibitors of interest for further investigation of which several not only revealed efficient inhibition of βarrestin2 recruitment to the β-adrenoceptors and the absence of toxic effects on cardiomyocytes but also anti-arrhythmic effects. Two selected compounds were tested in two distinct heart failure models, i.e. transverse aortic constriction (TAC) to induce chronic left ventricular pressure overload and permanent ligation of the left anterior descending artery to simulate a myocardial infarction (MI). Treatment with GRK5 inhibitors one week prior surgery resulted in an improved survival (from 60% up to 100 %), cardiac function (fractional shortening from 24 ± 3.4% up to 42 ± 1.9%), reduction in cardiomyocyte size (up to 19% reduction), and in interstitial fibrosis (up to 66% reduction) after four weeks of TAC and an improved survival (from 64% up to 92%) and cardiac function (ejection fraction from 28 ± 2.6% up to 51 ± 4.5%) in the MI model.
In this study, we validated GRK5 as a promising target in heart failure and evaluated two potentially interesting small molecule compounds in different murine heart failure models. Further studies will show, whether the prevention of cardiac arrhythmias in these cardiac stress models by GRK5 inhibition contributes to the promising data on survival and improved cardiac function. 
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