https://doi.org/10.1007/s00392-024-02526-y
1Deutsches Herzzentrum der Charite (DHZC) Klinik für Kardiologie, Angiologie und Intensivmedizin | CVK Berlin, Deutschland; 2Deutsches Herzzentrum der Charite (DHZC) experimentelle Kardiologie Berlin, Deutschland; 3Charité - Universitätsmedizin Berlin Berlin, Deutschland; 4Deutsches Herzzentrum der Charite (DHZC) Klinik für Kardiologie, Angiologie und Intensivmedizin | CBF Berlin, Deutschland; 5Städtisches Klinikum Dresden II. Medizinische Klinik Dresden, Deutschland
Background:
HFpEF has been associated with a reduced adrenergic functional reserve. Recently, we have reported a loss of adrenergic functional reserve in HFpEF related to an augmented myocardial contractility at rest (Semmler et al., 2024). The present study explores the effects of therapeutic modulation of β-adrenergic signaling on adrenergic and frequency-dependent stress on sarcomere shortening and intracellular calcium in a murine HFpEF model.
HFpEF has been associated with a reduced adrenergic functional reserve. Recently, we have reported a loss of adrenergic functional reserve in HFpEF related to an augmented myocardial contractility at rest (Semmler et al., 2024). The present study explores the effects of therapeutic modulation of β-adrenergic signaling on adrenergic and frequency-dependent stress on sarcomere shortening and intracellular calcium in a murine HFpEF model.
Methods:
12 weeks old male C57BL6/N mice were fed with high-fat diet and L-NAME (0.5g/l, via drinking water) for 19 weeks (HFpEF) or standard diet (Control). From weeks 15 to 19, HFpEF animals were given either salbutamol (HFpEF-sal) via subcutaneous injection or bisoprolol (HFpEF-biso) orally, both at a dose of 5 mg/kg/day. HFpEF and Sham mice remained untreated. Adult murine left ventricular cardiomoycytes (AMVM) were isolated by enzymatic digestion. Cellular calcium transients and sarcomere shortening were recorded (IonOptix CytoCypher). Experiments in all four groups (Sham, HFpEF, HFpEF-sal, HFpEF-biso) were conducted under incremental rate-dependent stress at frequencies of 1Hz, 3Hz, and 5Hz, both without and with 100nM Isoprenaline (following a 3-minute preincubation). Multiple comparisons were performed using linear mixed models (analyzed by animal), with a significance level set at p<0.05.
12 weeks old male C57BL6/N mice were fed with high-fat diet and L-NAME (0.5g/l, via drinking water) for 19 weeks (HFpEF) or standard diet (Control). From weeks 15 to 19, HFpEF animals were given either salbutamol (HFpEF-sal) via subcutaneous injection or bisoprolol (HFpEF-biso) orally, both at a dose of 5 mg/kg/day. HFpEF and Sham mice remained untreated. Adult murine left ventricular cardiomoycytes (AMVM) were isolated by enzymatic digestion. Cellular calcium transients and sarcomere shortening were recorded (IonOptix CytoCypher). Experiments in all four groups (Sham, HFpEF, HFpEF-sal, HFpEF-biso) were conducted under incremental rate-dependent stress at frequencies of 1Hz, 3Hz, and 5Hz, both without and with 100nM Isoprenaline (following a 3-minute preincubation). Multiple comparisons were performed using linear mixed models (analyzed by animal), with a significance level set at p<0.05.
Results:
Mice with high fat diet and L-NAME developed typical HFpEF characteristics with increased E/E`, preserved LVEF and reduced exercise tolerance. HFpEF cardiomyocytes exhibited enhanced cardiomyocyte function at baseline 1Hz, characterized by numerically higher sarcomere shortening amplitude, significantly accelerated time to 90% relaxation and time to 90% cytosolic Calcium removal compared to Sham. At baseline, HFpEF-biso cardiomyocytes were similarly hypercontractile as HFpEF despite an increased Calcium amplitude vs HFpEF. HFpEF-Sal lead to a significant further increase in contractility and Calcium amplitude vs. HFpEF. Isoprenaline increased sarcomere and calcium amplitude and accelerated kinetics compared to baseline in most groups and frequencies. However, HFpEF, HFpEF-biso and HFpEF-Sal showed a reduced ß-adrenergic response in sarcomere shortening and calcium amplitude compared to Sham. Sham cells showed a significant frequency-dependent increase in sarcomere amplitude (positive frequency response) both without and with isoprenaline, associated with a numerical increase in Calcium transient amplitude. In contrast, no positive frequency-dependent changes in sarcomere amplitude were observed in HFpEF. In fact, in the presence of Iso, HFpEF and HFpEF-Sal cells showed a significant decrease in Calcium amplitude between 1Hz and 5Hz compared to Sham.
Conclusion:
Our study reveals that chronic treatment with bisoprolol does not attenuate and salbutamol even further augments hypercontractile cardiomyocyte function in HFpEF. In HFpEF combined frequency and adrenergic physiological stress is associated with an abolished functional reserve and significantly reduced Calcium release at higher frequencies. Salbutamol or bisoprolol did not restore the functional reserve in HFpEF cardiomyocytes.