S100A1 in human heart failure: lack of recovery following left ventricular assist device support

Structural insights into the regulation of RyR1 by S100A1

S100A1, a small homodimeric EF-hand Ca2+-binding protein (~21 kDa), plays an important regulatory role in Ca2+ signaling pathways involved in various biological functions including Ca2+ cycling and contractile performance in skeletal and cardiac myocytes. One key target of the S100A1 interactome is the ryanodine receptor (RyR), a huge homotetrameric Ca2+ release channel (~2.3 MDa) of the sarcoplasmic reticulum. Here, we report cryoelectron microscopy structures of S100A1 bound to RyR1, the skeletal muscle isoform, in absence and presence of Ca2+. Ca2+-free apo-S100A1 binds beneath the bridging solenoid (BSol) and forms contacts with the junctional solenoid and the shell-core linker of RyR1. Upon Ca2+-binding, S100A1 undergoes a conformational change resulting in the exposure of the hydrophobic pocket known to serve as a major interaction site of S100A1. Through interactions of the hydrophobic pocket with RyR1, Ca2+-bound S100A1 intrudes deeper into the RyR1 structure beneath BSol than the apo-form and induces sideways motions of the C-terminal BSol region toward the adjacent RyR1 protomer resulting in tighter interprotomer contacts. Interestingly, the second hydrophobic pocket of the S100A1-dimer is largely exposed at the hydrophilic surface making it prone to interactions with the local environment, suggesting that S100A1 could be involved in forming larger heterocomplexes of RyRs with other protein partners. Since S100A1 interactions stabilizing BSol are implicated in the regulation of RyR-mediated Ca2+ release, the characterization of the S100A1 binding site conserved between RyR isoforms may provide the structural basis for the development of therapeutic strategies regarding treatments of RyR-related disorders.

Elevated serum levels of S100A1 and zinc α2-glycoprotein in patients with heart failure

BACKGROUND AND AIMS

Heart failure (HF) is a growing concern worldwide. S100A1 and zinc α2-glycoprotein (ZAG) play an important role in heart function. We examined serum levels of S100A1 and ZAG in HF patients and their association with anthropometric indices and body composition.

METHODS AND RESULTS

Sixty-four patients with HF, mean age 56.2, 48 male and 16 females, with ejection fraction <30-35%, were recruited from Shahid Madani Heart Hospital in Tabriz, Iran, from April to October 2019. Two groups, cachexia (n = 32) and non-cachexia (n = 32), which were divided based on weight loss of at least 7.5% in the last six months, were compared with the control group (n = 26). S100A1 and ZAG serum levels were determined by ELISA. Serum median (min-max) levels of S100A1 and ZAG were significantly greater in HF patients [326 (184.8-635.2) and 150.4 (61.5-520.7)] than healthy controls [265.4 (43.6-658.8) and 119.8 (16.7-533)], both p = 0.001. S100A1 Serum levels in cachexia group was significantly higher than non-cachexia group [331 (245.6-469.6) vs. 318 (184.8-635.2), p = 0.03]. A strong positive association was observed between S100A1 and ZAG serum levels in patients (r = 0.70, p < 0.0001). Serum levels of these two proteins negatively and significantly associated with BMI (r = -0.25, p = 0.044 and r = -0.28, p = 0.024, respectively) and arm circumference (r = -0.26, p = 0.037 and r = -0.25, p = 0.047, respectively).

CONCLUSION

The results indicate that S100A1 and ZAG are likely to contribute to the pathogenesis of HF disease and weight loss, as well as the strong association between S100A1 and ZAG possibly indicating a similar mechanism of action for these two proteins.

Reynoutrin Improves Ischemic Heart Failure in Rats Via Targeting S100A1

This study investigated the effects of reynoutrin on the improvement of ischemic heart failure (IHF) and its possible mechanism in rats. The rat heart failure model was established by permanently ligating the left anterior descending coronary artery (LAD) and administering different doses of reynoutrin. Cardiac function, inflammatory factors releasing, oxidative stress, cardiomyocytes apoptosis, and myocardial fibrosis were evaluated. Western blotting was used to determine protein expression levels of S100 calcium-binding protein A1 (S100A1), matrix metallopeptidase 2(MMP2), MMP9, phosphorylated (p-) p65, and transforming growth factor -β1 (TGF-β1) in myocardial tissue of the left ventricle. Results showed that reynoutrin significantly improved cardiac function, suppressed the release of inflammatory factors, reduced oxidative stress, inhibited cardiomyocytes apoptosis, and attenuated myocardial fibrosis in rats with IHF. In rat myocardial tissue, permanent LAD-ligation resulted in a significant down-regulation in S100A1 expression, whereas reynoutrin significantly up-regulated S100A1 protein expression while down-regulating MMP2, MMP9, p-p65, and TGF-β1 expressions. However, when S100A1 was knocked down in myocardial tissue, the above-mentioned positive effects of reynoutrin were significantly reversed. Reynoutrin is a potential natural drug for the treatment of IHF, and its mechanism of action involves the up-regulation of S100A1 expression, thereby inhibiting expressions of MMPs and the transcriptional activity of nuclear factor kappa-B.

LC/MS/MS-based quantitation of pig and human S100A1 protein in cardiac tissues: Application to gene therapy

The S100A1 protein is a target of interest for the treatment of heart failure as it has been previously reported to be depleted in failing cardiomyocytes. A gene therapy approach leading to increased expression levels of the protein directly in the heart could potentially lead to restoration of contractile function and improve overall cell survival. S100A1 is a relatively small soluble protein that is extremely well conserved across species with only a single amino acid difference between the sequences in human and pig, a commonly used pre-clinical model for evaluation of efficacy, biodistribution and safety for cardiac-directed gene therapy approaches. This high homology presents a bioanalytical challenge for the accurate detection and quantitation of both endogenous (pig) and exogenous (human) transduced S100A1 proteins post treatment using a human S100A1 gene therapy in pigs. Here we present a sensitive and selective LC-MS/MS approach that can easily differentiate and simultaneously quantitate both human and pig S100A1 proteins. Additionally, we report on a detailed profiling of S100A1 protein in various pig tissues, a comprehensive evaluation of S100A1 distribution in pig hearts and a comparison to S100A1 levels in human cardiac samples.

B-type natriuretic peptide and its role in altering Ca2+-regulatory proteins in heart failure-mechanistic insights

Heart failure (HF) is a worldwide disease with high levels of morbidity and mortality. The pathogenesis of HF is complicated and involves imbalances in hormone and electrolyte. B-type natriuretic peptide (BNP) has served as a biomarker of HF severity, and in recent years, it has been used to treat the disease, thanks to its cardio-protective effects, such as diuresis, natriuresis, and vasodilatation. In stage C/D HF, symptoms are severe despite elevated BNP. Disturbances in Ca²⁺ homeostasis are often a dominating feature of the disease, causing Ca²⁺-regulatory protein dysfunction, including reduced expression and activity of sarcoplasmic reticulum Ca²⁺-ATPase2a (SERCA2a), impaired ryanodine receptors (RYRs) function, intensive Na⁺-Ca²⁺ exchanger (NCX), and downregulation of S100A1. The relationship between natriuretic peptides (NPs) and Ca²⁺-regulatory proteins has been widely studied and represents important mechanisms in the etiology of HF. In this review, we present evidence that BNP may regulate Ca²⁺-regulatory proteins, in particular, suppressing SERCA2a and S100A1 expression. However, relationships between BNP and other Ca²⁺-regulatory proteins remain vague.

Pathophysiological mechanism and therapeutic role of S100 proteins in cardiac failure: a systematic review

S100 proteins are a family of highly acidic calcium-binding proteins involved in calcium handling in many tissues and organs. Some of these proteins are highly expressed in cardiac tissue, and an impairment of some specific S100 proteins has been related to heart failure. To check this hypothesis, we decided to review the literature since 2008 until May 2015. According to the studies collected, recovering S100A1 levels may enhance contractile/relaxing performance in heart failure, reverse negative force-frequency relationship, improve contractile reserve, reverse diastolic dysfunction and protect against pro-arrhythmic reductions of sarcoplasmic reticulum calcium. The safety profile of gene therapy was also confirmed. Increased S100B protein levels were related to a worse outcome in chronic heart failure. S100A8/A9 complex plasma levels, as well as other inflammatory biomarkers, were significantly higher in chronic heart failure patients. S100A2 seems to increase both contractile and relaxation performance in animal cardiomyocytes. Otherwise, S100A6 cardiac expression seems to have no effects on contractility. S100A4 KO mice showed reduced cardiac interstitial fibrosis. Data collected encourage a potential prospective application in human. These proteins could be exploited as biomarkers in stadiation and prognosis of chronic heart failure, as well as therapeutic target to rescue failing heart. Registration details The study protocol has been registered in PROSPERO ( http://www.crd.york.ac.uk/PROSPERO/ ) under registration number CRD42015027932.

Cardiac Non-myocyte Cells Show Enhanced Pharmacological Function Suggestive of Contractile Maturity in Stem Cell Derived Cardiomyocyte Microtissues

The immature phenotype of stem cell derived cardiomyocytes is a significant barrier to their use in translational medicine and pre-clinical in vitro drug toxicity and pharmacological analysis. Here we have assessed the contribution of non-myocyte cells on the contractile function of co-cultured human embryonic stem cell derived cardiomyocytes (hESC-CMs) in spheroid microtissue format. Microtissues were formed using a scaffold free 96-well cell suspension method from hESC-CM cultured alone (CM microtissues) or in combination with human primary cardiac microvascular endothelial cells and cardiac fibroblasts (CMEF microtissues). Contractility was characterized with fluorescence and video-based edge detection. CMEF microtissues displayed greater Ca²⁺transient amplitudes, enhanced spontaneous contraction rate and remarkably enhanced contractile function in response to both positive and negative inotropic drugs, suggesting a more mature contractile phenotype than CM microtissues. In addition, for several drugs the enhanced contractile response was not apparent when endothelial cell or fibroblasts from a non-cardiac tissue were used as the ancillary cells. Further evidence of maturity for CMEF microtissues was shown with increased expression of genes that encode proteins critical in cardiac Ca²⁺handling (S100A1), sarcomere assembly (telethonin/TCAP) and β-adrenergic receptor signalling. Our data shows that compared with single cell-type cardiomyocyte in vitro models, CMEF microtissues are superior at predicting the inotropic effects of drugs, demonstrating the critical contribution of cardiac non-myocyte cells in mediating functional cardiotoxicity.

Cardiomyocytes, endothelial cells and cardiac fibroblasts: S100A1's triple action in cardiovascular pathophysiology

Over the past decade, basic and translational research delivered comprehensive evidence for the relevance of the Ca(2+)-binding protein S100A1 in cardiovascular diseases. Aberrant expression levels of S100A1 surfaced as molecular key defects, driving the pathogenesis of chronic heart failure, arterial and pulmonary hypertension, peripheral artery disease and disturbed myocardial infarction healing. Loss of intracellular S100A1 renders entire Ca(2+)-controlled networks dysfunctional, thereby leading to cardiomyocyte failure and endothelial dysfunction. Lack of S100A1 release in ischemic myocardium compromises cardiac fibroblast function, entailing impaired damage healing. This review focuses on molecular pathways and signaling cascades regulated by S100A1 in cardiomyocytes, endothelial cells and cardiac fibroblasts in order to provide an overview of our current mechanistic understanding of S100A1's action in cardiovascular pathophysiology.

The war against heart failure: the Lancet lecture

Heart failure is a global problem with an estimated prevalence of 38 million patients worldwide, a number that is increasing with the ageing of the population. It is the most common diagnosis in patients aged 65 years or older admitted to hospital and in high-income nations. Despite some progress, the prognosis of heart failure is worse than that of most cancers. Because of the seriousness of the condition, a declaration of war on five fronts has been proposed for heart failure. Efforts are underway to treat heart failure by enhancing myofilament sensitivity to Ca(2+); transfer of the gene for SERCA2a, the protein that pumps calcium into the sarcoplasmic reticulum of the cardiomyocyte, seems promising in a phase 2 trial. Several other abnormal calcium-handling proteins in the failing heart are candidates for gene therapy; many short, non-coding RNAs--ie, microRNAs (miRNAs)--block gene expression and protein translation. These molecules are crucial to calcium cycling and ventricular hypertrophy. The actions of miRNAs can be blocked by a new class of drugs, antagomirs, some of which have been shown to improve cardiac function in animal models of heart failure; cell therapy, with autologous bone marrow derived mononuclear cells, or autogenous mesenchymal cells, which can be administered as cryopreserved off the shelf products, seem to be promising in both preclinical and early clinical heart failure trials; and long-term ventricular assistance devices are now used increasingly as a destination therapy in patients with advanced heart failure. In selected patients, left ventricular assistance can lead to myocardial recovery and explantation of the device. The approaches to the treatment of heart failure described, when used alone or in combination, could become important weapons in the war against heart failure.