As a calcium sensor protein it co-localizes and interacts with the SERCA2/phospholamban complex and modulates both systolic and diastolic ryanodine receptor function and cardiomyocyte SR calcium release, respectively.26 Failing hearts are characterized by progressively diminished S100A1 protein levels, and these low levels inversely correlate with the severity of the disease.26 These observations suggest that the down-regulation of S100 protein may be pathological. Indeed, S100A1 knock-out mice showed enhanced Inhibitors,research,lifescience,medical susceptibility to functional deterioration in response to chronic cardiac pressure overload stress and ischemic damage.27,28 In contrast, mice with overexpression

of S100A1 are hypercontractile and maintained almost normal left ventricular function following myocardial infarction.28 Studies in a large-animal Inhibitors,research,lifescience,medical model of heart failure suggested that S100A1 may be an attractive target of cardiac gene therapy.29 The calcium leak through the ryanodine receptors is believed to contribute to the abnormal calcium cycling in failing hearts, and therefore this appears to be a target for treatment. In selleck inhibitor addition to reducing the sarcoplasmic reticulum calcium load, Inhibitors,research,lifescience,medical a leak may also trigger arrhythmias and increase energy consumption. A pharmacological agent, JTV519, can

reduce the ryanodine receptor calcium leak, and this was shown to preserve contractile performance in a heart failure animal model.30 JTV519 was originally suggested to increase the binding Inhibitors,research,lifescience,medical of calstabin2 to RyR2. However, the original molecule JTV519 was not entirely specific to the ryanodine receptor and blocked in addition the L-type calcium channels and potassium channels. Another molecule S107 was shown to inhibit arrhythmias in a catecholaminergic polymorphic ventricular tachycardia Inhibitors,research,lifescience,medical mouse model.31 The effects of “type”:”entrez-protein”,”attrs”:S44121″S44121,

a more ryanodine leak-specific agent, is currently being analyzed in patients with congestive heart failure who are at risk for ventricular arrhythmias in a phase 2 clinical study. TARGETING CONTRACTILITY already IN HEART FAILURE The β-adrenoreceptor transduces the signal through Gs protein to adenylate cyclase, which leads to increased generation of cyclic adenosine monophosphate (cAMP), which then interacts with protein kinase A (PKA) and other intracellular effector proteins. Currently, 10 different isoforms of adenylate cyclase have been cloned and characterized in mammals, of which the adult human left ventricle appears to express predominantly adenylate cyclase isoform 6 (AC6). Failing human hearts have reduced amounts of basal cAMP and impaired cAMP generation in response to agonist stimulation.32 However, results of clinical trials that aimed to increase β-adrenoreceptor activation by the agonist dobutamine or to increase the cAMP content through inhibition of the phosphodiesterase that breaks it down by milrinone have been disappointing.