The New HNO Donor, 1-Nitrosocyclohexyl Acetate, Increases Contractile Force in Normal and Β-Adrenergically Desensitized Ventricular Myocytes

Contractile dysfunction and diminished response to β-adrenergic agonists are characteristics for failing hearts. Chemically donated nitroxyl (HNO) improves contractility in failing hearts and thus may have therapeutic potential. Yet, there is a need for pharmacologically suitable donors. In this study we tested whether the pure and long acting HNO donor, 1-nitrosocyclohexyl acetate (NCA), affects contractile force in normal and pathological ventricular myocytes (VMs) as well as in isolated hearts. VMs were isolated from mice either subjected to isoprenaline-infusion (ISO; 30 μg/g per day) or to vehicle (0.9% NaCl) for 5 days. Sarcomere shortening and Ca2+ transients were simultaneously measured using the IonOptix system. Force of contraction of isolated hearts was measured by a Langendorff-perfusion system. NCA increased peak sarcomere shortening by+40-200% in a concentration-dependent manner (EC50 ∼55 μM). Efficacy and potency did not differ between normal and chronic ISO VMs, despite the fact that the latter displayed a markedly diminished inotropic response to acute β-adrenergic stimulation with ISO (1 μM). NCA (60 μM) increased peak sarcomere shortening and Ca2+ transient amplitude by ∼200% and ∼120%, respectively, suggesting effects on both myofilament Ca2+ sensitivity and sarcoplasmic reticulum (SR) Ca2+ cycling. Importantly, NCA did not affect diastolic Ca2+ or SR Ca2+ content, as assessed by rapid caffeine application. NCA (45 μM) increased force of contraction by 30% in isolated hearts. In conclusion, NCA increased contractile force in normal and β-adrenergically desensitized VMs as well as in isolated mouse hearts. This profile warrants further investigations of this HNO donor in the context of heart failure.