Nebivolol Desensitizes Myofilaments of a Hypertrophic Cardiomyopathy Mouse Model

Abstract

Background: Hypertrophic cardiomyopathy (HCM) patients often present with diastolic dysfunction and a normal to supranormal systolic function. To counteract this hypercontractility, guideline therapies advocate treatment with beta-adrenoceptor and Ca2+ channel blockers. One well established pathomechanism for the hypercontractile phenotype frequently observed in HCM patients and several HCM mouse models is an increased myofilament Ca2+ sensitivity. Nebivolol, a commonly used beta-adrenoceptor antagonist, has been reported to lower maximal force development and myofilament Ca2+ sensitivity in rabbit and human heart tissues. The aim of this study was to evaluate the effect of nebivolol in cardiac muscle strips of an established HCM Mybpc3 mouse model. Furthermore, we investigated actions of nebivolol and epigallocatechin-gallate, which has been shown to desensitize myofilaments for Ca2+ in mouse and human HCM models, in cardiac strips of HCM patients with a mutation in the most frequently mutated HCM gene MYBPC3.Methods and Results: Nebivolol effects were tested on contractile parameters and force-Ca2+ relationship of skinned ventricular muscle strips isolated from Mybpc3-targeted knock-in (KI), wild-type (WT) mice and cardiac strips of three HCM patients with MYBPC3 mutations. At baseline, KI strips showed no difference in maximal force development compared to WT mouse heart strips. Neither 1 nor 10 μM nebivolol had an effect on maximal force development in both genotypes. 10 μM nebivolol induced myofilament Ca2+ desensitization in WT strips and to a greater extent in KI strips. Neither 1 nor 10 μM nebivolol had an effect on Ca2+ sensitivity in cardiac muscle strips of three HCM patients with MYBPC3 mutations, whereas epigallocatechin-gallate induced a right shift in the force-Ca2+ curve.Conclusion: Nebivolol induced a myofilament Ca2+ desensitization in both WT and KI strips, which was more pronounced in KI muscle strips. In human cardiac muscle strips of three HCM patients nebivolol had no effect on myofilament Ca2+ sensitivity.

Analysis of Contractile Function of Permeabilized Human Hypertrophic Cardiomyopathy Multicellular Heart Tissue

“…The observation of an increased myofilament Ca 2+ sensitivity has mainly been made in HCM transgenic mouse models, reconstituted myofilament systems, and isolated cardiomyocytes, but data from multicellular tissues from HCM patients with mutations in different HCM genes have not been reported before (Morimoto et al., 1998; Tardiff et al., 1999; Cazorla et al., 2006; Pohlmann et al., 2007; Robinson et al., 2007; Jacques et al., 2008; Morimoto, 2008; van Dijk et al., 2009, 2012; Vignier et al., 2009; Huke and Knollmann, 2010; Kimura, 2010; Fraysse et al., 2012; Moore et al., 2012; Barefield et al., 2014; Flenner et al., 2016; Wijnker et al., 2016; Stucker et al., 2017; Ren et al., 2018). We therefore investigated force development and myofilament Ca 2+ sensitivity in multicellular cardiac muscle strips derived from septal myectomies of patients with different HCM gene mutations and evaluated the potential use of epigallocatechin-3-gallate (EGCg), a known Ca 2+ -desensitizer, for myofilament Ca 2+ desensitization.…”

“…Therefore, after mounting strips between a force transducer and a length controller and stretching until slack length, they were stretched another 10% of length. For maximum force measurements, strips were kept in pCa 9 to achieve full relaxation and were then moved to pCa 4.5 until maximal force development was reached, as reported before (Friedrich et al., 2016; Stucker et al., 2017). For force-Ca 2+ curves, strips were exposed to increasing Ca 2+ concentrations from pCa 9 to pCa 4.5 in EGTA-buffer, and force development was measured in each pCa solution.…”

“…For force-Ca 2+ curves, strips were exposed to increasing Ca 2+ concentrations from pCa 9 to pCa 4.5 in EGTA-buffer, and force development was measured in each pCa solution. Measurements were repeated in the presence of 30 μM epigallocatechin-3-gallate (EGCg, Sigma Life Sciences) after 5 min preincubation in pCa 9 (Flenner et al., 2016; Friedrich et al., 2016; Stucker et al., 2017). To exclude time-dependent loss of force, EGCg was tested first and a control measurement was performed 5 min after EGCg washout in every second measurement.…”

“…We previously reported that EGCg decreased Ca 2+ sensitivity of mouse and human cardiac myofilaments with MYBPC3 mutations (Friedrich et al., 2016; Stucker et al., 2017). To assess whether the grade of desensitization is similar between HCM strips, we measured force-Ca 2+ relationships in skinned ventricular muscle strips at baseline and after the application of 30 μM EGCg.…”

Approaches to High-Throughput Analysis of Cardiomyocyte Contractility

“…Nebivolol and EGCG both increased TTB90 by about 20% but only the Nebivolol effect was consistently found. Nebivolol, ECG, and EGCG have been proposed as desensitizers, but may also have additional actions (Nebivolol as a beta blocker and EGCG as an inotrope; Feng et al, 2012;Stücker et al, 2017). None of these compounds showed a reduction of% shortening or reduction of TTB90 indicative of enhanced relaxation in our study.…”