PubMed Health⌕ Search

Biomedical subjects

Patrick Most

Publications and source records attributed to Patrick Most.

16 recordsLinked to original sources
PubMed2006

Cardiac S100A1 protein levels determine contractile performance and propensity toward heart failure after myocardial infarction.

BACKGROUND: Diminished cardiac S100A1 protein levels are characteristic of ischemic and dilated human cardiomyopathy. Because S100A1 has recently been identified as a Ca2+-dependent inotropic factor in the heart, this study sought to explore the pathophysiological relevance of S100A1 levels in development and progression of postischemic heart failure (HF). METHODS AND RESULTS: S100A1-transgenic (STG) and S100A1-knockout (SKO) mice were subjected to myocardial infarction (MI) by surgical left anterior descending coronary artery ligation, and survival, cardiac function, and remodeling were compared with nontransgenic littermate control (NLC) and wild-type (WT) animals up to 4 weeks. Although MI size was similar in all groups, infarcted S100A1-deficient hearts (SKO-MI) responded with acute contractile decompensation and accelerated transition to HF, rapid onset of cardiac remodeling with augmented apoptosis, and excessive mortality. NLC/WT-MI mice, displaying a progressive decrease in cardiac S100A1 expression, showed a later onset of cardiac remodeling and progression to HF. Infarcted S100A1-overexpressing hearts (STG-MI), however, showed preserved global contractile performance, abrogated apoptosis, and prevention from cardiac hypertrophy and HF with superior survival compared with NLC/WT-MI and SKO-MI. Both Gq-protein-dependent signaling and protein kinase C activation resulted in decreased cardiac S100A1 mRNA and protein levels, whereas Gs-protein-related signaling exerted opposite effects on cardiac S100A1 abundance. Mechanistically, sarcoplasmic reticulum Ca2+ cycling and beta-adrenergic signaling were severely impaired in SKO-MI myocardium but preserved in STG-MI. CONCLUSIONS: Our novel proof-of-concept study provides evidence that downregulation of S100A1 protein critically contributes to contractile dysfunction of the diseased heart, which is potentially responsible for driving the progressive downhill clinical course of patients with HF.

Animals↗
PubMed2006

S100A1 decreases calcium spark frequency and alters their spatial characteristics in permeabilized adult ventricular cardiomyocytes.

S100A1, a Ca2+-sensor protein of the EF-hand type, exerts positive inotropic effects in the heart via enhanced cardiac ryanodine receptor (RyR2) activity. Here we report that S100A1 protein (0.1microM) interacts with the RyR2 in resting permeabilized cardiomyocytes at free Ca2+-levels comparable to diastolic Ca2+-concentrations ( approximately 150nM). Alterations of RyR2 function due to S100A1 binding was assessed via analysis of Ca2+-spark characteristics. Ca2+-spark frequency, amplitude and duration were all reduced upon perfusion with 0.1microM S100A1 protein by 38%, 14% and 18%, respectively. Most likely, these effects were conveyed through the S100A1 C-terminus (S100A1-ct; amino acids 75-94) as the corresponding S100A1-ct peptide (0.1microM) inhibited S100A1 protein binding to the RyR2 and similarly attenuated frequency, amplitude and duration of Ca2+-sparks by 52%, 8% and 26%, respectively. Accordingly, the sarcoplasmic reticulum (SR) Ca2+-content was slightly increased but the stoichiometry of other accessory RyR2 modulators (sorcin/FKBP12.6) remained unaltered by S100A1. Hence, we propose S100A1 as a novel inhibitory modulator of RyR2 function at diastolic Ca2+-concentrations in rabbit ventricular cardiomyocytes.

Animals↗
PubMed2006

Increased proinflammatory endothelial response to S100A8/A9 after preactivation through advanced glycation end products.

BACKGROUND: Atherosclerosis is an inflammatory disease in which a perpetuated activation of NFkappaB via the RAGE (receptor for advanced glycation end products)-MAPK signalling pathway may play an important pathogenetic role. As recently S100 proteins have been identified as ligands of RAGE, we sought to determine the effects of the proinflammatory heterodimer of S100A8/S100A9 on the RAGE-NFkappaB mediated induction of proinflammatory gene expression. METHODS: Human umbilical vein endothelial cells (HUVEC) were preincubated for 72 h with AGE-albumin or unmodified albumin for control, whereas AGE-albumin induction resulted in an upregulation of RAGE. Following this preactivation, cells were stimulated for 48 h with heterodimeric human recombinant S100A8/S100A9. RESULTS: Heterodimeric S100A8/S100A9 enhanced secretion of IL-6, ICAM-1, VCAM-1 and MCP1 in AGE-albumin pretreated HUVEC in a dose dependent manner. These effects could not be detected after stimulation with the homodimeric proteins S100A8, S100A9, S100A1 and S100B. The effects of heterodimeric S100A8/S100A9 were reduced by inhibition of the MAP-kinase pathways ERK1/2 and p38 by PD 98059 and SB 203580, respectively. CONCLUSION: The heterodimeric S100A8/S100A9 might therefore play a hitherto unknown role in triggering atherosclerosis in diabetes and renal failure, pathophysiological entities associated with a high AGE burden. Thus, blocking heterodimeric S100A8/S100A9 might represent a novel therapeutic modality in treating atherosclerosis.

Calgranulin A↗
PubMed2005

S100A1 gene therapy preserves in vivo cardiac function after myocardial infarction.

Myocardial infarction (MI) represents an enormous clinical challenge as loss of myocardium due to ischemic injury is associated with compromised left ventricular (LV) function often leading to acute cardiac decompensation or chronic heart failure. S100A1 was recently identified as a positive inotropic regulator of myocardial contractility in vitro and in vivo. Here, we explore the strategy of myocardial S100A1 gene therapy either at the time of, or 2 h after, MI to preserve global heart function. Rats underwent cryothermia-induced MI and in vivo intracoronary delivery of adenoviral transgenes (4 x 10(10) pfu). Animals received saline (MI), the S100A1 adenovirus (MI/AdS100A1), a control adenovirus (MI/AdGFP), or a sham operation. S100A1 gene delivery preserved global in vivo LV function 1 week after MI. Preservation of LV function was due mainly to S100A1-mediated gain of contractility of the remaining, viable myocardium since contractile parameters and Ca(2+) transients of isolated MI/AdS100A1 myocytes were significantly enhanced compared to myocytes isolated from both MI/AdGFP and sham groups. Moreover, S100A1 gene therapy preserved the cardiac beta-adrenergic inotropic reserve, which was associated with the attenuation of GRK2 up-regulation. Also, S100A1 overexpression reduced cardiac hypertrophy 1 week post-MI. Overall, our data indicate that S100A1 gene therapy provides a potential novel treatment strategy to maintain contractile performance of the post-MI heart.

Adenoviridae↗
PubMed2005

VEGF-PLCgamma1 pathway controls cardiac contractility in the embryonic heart.

The strength of the heart beat can accommodate in seconds to changes in blood pressure or flow. The mechanism for such homeostatic adaptation is unknown. We sought the cause of poor contractility in the heart of the embryonic zebrafish with the mutation dead beat. We find through cloning that this is due to a mutation in the phospholipase C gamma1 (plcgamma1) gene. In mutant embryos, contractile function can be restored by PLCgamma1 expression directed selectively to cardiac myocytes. In other situations, PLCgamma1 is known to transduce the signal from vascular endothelial growth factor (VEGF), and we show here that abrogation of VEGF also interferes with cardiac contractility. Somewhat unexpectedly, FLT-1 is the responsible VEGF receptor. We show that the same system functions in the rat. Blockage of VEGF-PLCgamma1 signaling decreases calcium transients in rat ventricular cardiomyocytes, whereas VEGF imposes a positive inotropic effect on cardiomyocytes by increasing calcium transients. Thus, the muscle of the heart uses the VEGF-PLCgamma1 cascade to control the strength of the heart beat. We speculate that this paracrine system may contribute to normal and pathological regulation of cardiac contractility.

Animals↗
PubMed2005

Distinct subcellular location of the Ca2+-binding protein S100A1 differentially modulates Ca2+-cycling in ventricular rat cardiomyocytes.

Calcium is a key regulator of cardiac function and is modulated through the Ca2+-sensor protein S100A1. S100 proteins are considered to exert both intracellular and extracellular functions on their target cells. Here we report the impact of an increased intracellular S100A1 protein level on Ca2+-homeostasis in neonatal ventricular cardiomyocytes in vitro. Specifically, we compare the effects of exogenously added recombinant S100A1 to those resulting from the overexpression of a transduced S100A1 gene. Extracellularly added S100A1 enhanced the Ca2+-transient amplitude in neonatal ventricular cardiomyocytes (NVCMs) through a marked decrease in intracellular diastolic Ca2+-concentrations ([Ca2+]i). The decrease in [Ca2+]i was independent of sarcoplasmic reticulum Ca2+-ATPase (SERCA2a) activity and was probably the result of an increased sarcolemmal Ca2+-extrusion through the sodium-calcium exchanger (NCX). At the same time the Ca2+-content of the sarcoplasmic reticulum (SR) decreased. These effects were dependent on the uptake of extracellularly added S100A1 protein and its subsequent routing to the endosomal compartment. Phospholipase C and protein kinase C, which are tightly associated with this subcellular compartment, were found to be activated by endocytosed S100A1. By contrast, adenoviral-mediated intracellular S100A1 overexpression enhanced the Ca2+-transient amplitude in NVCMs mainly through an increase in systolic [Ca2+]i. The increased Ca2+-load in the SR was based on an enhanced SERCA2a activity while NCX function was unaltered. Overexpressed S100A1 colocalized with SERCA2a and other Ca2+-regulatory proteins at the SR, whereas recombinant S100A1 protein that had been endocytosed did not colocalize with SR proteins. This study provides the first evidence that intracellular S100A1, depending on its subcellular location, modulates cardiac Ca2+-turnover via different Ca2+-regulatory proteins.

Animals↗
PubMed2004

Role of Omi/HtrA2 in apoptotic cell death after myocardial ischemia and reperfusion.

BACKGROUND: Omi/HtrA2 is a proapoptotic mitochondrial serine protease involved in caspase-dependent as well as caspase-independent cell death. However, the role of Omi/HtrA2 in the apoptotic cell death that occurs in vivo under pathological conditions remains unknown. The present study was designed to investigate whether Omi/HtrA2 plays an important role in postischemic myocardial apoptosis. METHODS AND RESULTS: Male adult mice were subjected to 30 minutes of myocardial ischemia followed by reperfusion and treated with vehicle or ucf-101, a novel and specific Omi/HtrA2 inhibitor, 10 minutes before reperfusion. Myocardial ischemia/reperfusion significantly increased cytosolic Omi/HtrA2 content and markedly increased apoptosis. Treatment with ucf-101 exerted significant cardioprotective effects, as evidenced by less terminal dUTP nick end-labeling staining, a lower incidence of DNA ladder fragmentation, and smaller infarct size. Furthermore, treatment with ucf-101 before reperfusion attenuated X-linked inhibitor of apoptosis protein degradation and inhibited caspase-9 and caspase-3 activities. CONCLUSIONS: Taken together, these results demonstrate for the first time that ischemia/reperfusion results in Omi/HtrA2 translocation from the mitochondria to the cytosol, where it promotes cardiomyocyte apoptosis via a protease activity-dependent, caspase-mediated pathway.

Animals↗
PubMed2004

S100A1 gene transfer: a strategy to strengthen engineered cardiac grafts.

BACKGROUND: Cardiac tissue replacement therapy, although a promising novel approach for the potential treatment of heart failure, still suffers from insufficient contractile support to the failing myocardium. Here, we explore a strategy to improve contractile properties of engineered heart tissue (EHT) by S100A1 gene transfer. METHODS: EHTs were generated from neonatal rat cardiomyocytes and transfected (MOI 10 PFU) with the S100A1 adenovirus (AdvS100A1, n = 25) while an adenovirus devoid of the S100A1 cDNA served as a control (AdvGFP, n = 30). Contractile properties of transfected EHTs were measured 7 days following gene transfer. RESULTS: Western blot analysis confirmed a 8.7 +/- 3.6-fold S100A1 protein overexpression in AdvS100A1-transfected EHTs (n = 4; P < 0.01) that increased maximal isometric force (mN; AdvGFP 0.175 +/- 0.03 vs. AdvS100A1 0.47 +/- 0.06; P < 0.05) at 0.4 mmol/L extracellular calcium concentration [Ca(2+)](e). In addition, S100A1 overexpression enhanced both maximal Ca(2+)-stimulated force generation (+81%; P < 0.05) and Ca(2+)-sensitivity of EHTs (EC50% [Ca(2+)](e) mM; AdvGFP 0.33 +/- 0.04 vs. AdvS100A1 0.21 +/- 0.0022; P < 0.05). The S100A1-mediated gain in basal graft contractility was preserved throughout a series of isoproterenol interventions (10(-9) to 10(-6) M). Physiological properties of EHTs resembling intact heart preparations were preserved. CONCLUSIONS: S100A1 gene transfer in EHT is feasible and augments contractile performance, while characteristic physiological features of EHT remain unchanged. Thus, specific genetic manipulation of tissue constructs prior to implantation should be part of an improved tissue replacement strategy in heart failure.

Adenoviridae↗
PubMed2004

Hope for a broken heart?

Heart failure affects 23 million people worldwide and results from cardiac dysfunction characterized by decreased responsiveness to beta-adrenergic stimulation. A recent publication by W.J. Koch and colleagues highlights evidence for targeted beta-adrenergic receptor kinase (betaARK1) inhibition by gene transfer to improve contractile function and beta-adrenergic responsiveness in failing human myocardium. This proof-of-concept study has great importance for future heart failure therapy because it provides evidence for the therapeutic effectiveness of betaARK1 inhibition in failing human myocardium.

Adenoviridae↗
PubMed2004

Cardiac adenoviral S100A1 gene delivery rescues failing myocardium.

Cardiac-restricted overexpression of the Ca2+-binding protein S100A1 has been shown to lead to increased myocardial contractile performance in vitro and in vivo. Since decreased cardiac expression of S100A1 is a characteristic of heart failure, we tested the hypothesis that S100A1 gene transfer could restore contractile function of failing myocardium. Adenoviral S100A1 gene delivery normalized S100A1 protein expression in a postinfarction rat heart failure model and reversed contractile dysfunction of failing myocardium in vivo and in vitro. S100A1 gene transfer to failing cardiomyocytes restored diminished intracellular Ca2+ transients and sarcoplasmic reticulum (SR) Ca2+ load mechanistically due to increased SR Ca2+ uptake and reduced SR Ca2+ leak. Moreover, S100A1 gene transfer decreased elevated intracellular Na+ concentrations to levels detected in nonfailing cardiomyocytes, reversed reactivated fetal gene expression, and restored energy supply in failing cardiomyocytes. Intracoronary adenovirus-mediated S100A1 gene delivery in vivo to the postinfarcted failing rat heart normalized myocardial contractile function and Ca2+ handling, which provided support in a physiological context for results found in myocytes. Thus, the present study demonstrates that restoration of S100A1 protein levels in failing myocardium by gene transfer may be a novel therapeutic strategy for the treatment of heart failure.

Adenoviridae↗
PubMed2003

Extracellular S100A1 protein inhibits apoptosis in ventricular cardiomyocytes via activation of the extracellular signal-regulated protein kinase 1/2 (ERK1/2).

S100A1 is a Ca2+-binding protein of the EF-hand type that belongs to the S100 protein family. It is specifically expressed in the myocardium at high levels and is considered to be an important regulator of cardiac contractility. Because the S100A1 protein is released into the extracellular space during ischemic myocardial injury, we examined the cardioprotective potential of the extracellular S100A1 protein on ventricular cardiomyocytes in vitro. In this report we show that extracellularly added S100A1 protein is endocytosed into the endosomal compartment of neonatal ventricular cardiomyocytes via a Ca2+-dependent clathrin-mediated process. S100A1 uptake protects neonatal ventricular cardiomyocytes from 2-deoxyglucose and oxidative stress-induced apoptosis in vitro. S100A1-mediated anti-apoptotic effects involve specific activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) pro-survival pathway, including activation of phospholipase C, protein kinase C, mitogen-activated protein kinase kinase 1, and ERK1/2. In contrast, neither transsarcolemmal Ca2+ influx via the L-type channel nor protein kinase A activity seems to take part in the S100A1-mediated signaling pathway. In conclusion, this study provides evidence for the S100A1 protein serving as a novel cardioprotective factor in vitro. These findings warrant speculation that injury-dependent release of the S100A1 protein from cardiomyocytes may serve as an intrinsic mechanism to promote survival of the myocardium in vivo.

Animals↗
PubMed2003

Transgenic overexpression of the Ca2+-binding protein S100A1 in the heart leads to increased in vivo myocardial contractile performance.

S100A1, a Ca2+-sensing protein of the EF-hand family, is most highly expressed in myocardial tissue, and cardiac S100A1 overexpression in vitro has been shown to enhance myocyte contractile properties. To study the physiological consequences of S100A1 in vivo, transgenic mice were developed with cardiac-restricted overexpression of S100A1. Characterization of two independent transgenic mouse lines with approximately 4-fold overexpression of S100A1 in the myocardium revealed a marked augmentation of in vivo basal cardiac function that remained elevated after beta-adrenergic receptor stimulation. Contractile function and Ca2+ handling properties were increased in ventricular cardiomyocytes isolated from S100A1 transgenic mice. Enhanced cellular Ca2+ cycling by S100A1 was associated both with increased sarcoplasmic reticulum Ca2+ content and enhanced sarcoplasmic reticulum Ca2+-induced Ca2+ release, and S100A1 was shown to associate with the cardiac ryanodine receptor. No alterations in beta-adrenergic signal transduction or major cardiac Ca2+-cycling proteins occurred, and there were no signs of hypertrophy with chronic cardiac S100A1 overexpression. Our findings suggest that S100A1 plays an important in vivo role in the regulation of cardiac function perhaps through interacting with the ryanodine receptor. Because S100A1 protein expression is down-regulated in heart failure, increasing S100A1 expression in the heart may represent a novel means to augment contractility.

Adrenergic beta-Agonists↗
PubMed2003

The C terminus (amino acids 75-94) and the linker region (amino acids 42-54) of the Ca2+-binding protein S100A1 differentially enhance sarcoplasmic Ca2+ release in murine skinned skeletal muscle fibers.

S100A1, a Ca2+-binding protein of the EF-hand type, is most highly expressed in striated muscle and has previously been shown to interact with the skeletal muscle sarcoplasmic reticulum (SR) Ca2+ release channel/ryanodine receptor (RyR1) isoform. However, it was unclear whether S100A1/RyR1 interaction could modulate SR Ca2+ handling and contractile properties in skeletal muscle fibers. Since S100A1 protein is differentially expressed in fast- and slow-twitch skeletal muscle, we used saponin-skinned murine Musculus extensor digitorum longus (EDL) and Musculus soleus (Soleus) fibers to assess the impact of S100A1 protein on SR Ca2+ release and isometric twitch force in functionally intact permeabilized muscle fibers. S100A1 equally enhanced caffeine-induced SR Ca2+ release and Ca2+-induced isometric force transients in both muscle preparations in a dose-dependent manner. Introducing a synthetic S100A1 peptide model (devoid of EF-hand Ca2+-binding sites) allowed identification of the S100A1 C terminus (amino acids 75-94) and hinge region (amino acids 42-54) to differentially enhance SR Ca2+ release with a nearly 3-fold higher activity of the C terminus. These effects were exclusively based on enhanced SR Ca2+ release as S100A1 influenced neither SR Ca2+ uptake nor myofilament Ca2+ sensitivity/cooperativity in our experimental setting. In conclusion, our study shows for the first time that S100A1 augments contractile performance both of fast- and slow-twitch skeletal muscle fibers based on enhanced SR Ca2+ efflux at least mediated by the C terminus of S100A1 protein. Thus, our data suggest that S100A1 may serve as an endogenous enhancer of SR Ca2+ release and might therefore be of physiological relevance in the process of excitation-contraction coupling in skeletal muscle.

Amino Acid Sequence↗
PubMed2002

The small EF-hand Ca2+ binding protein S100A1 increases contractility and Ca2+ cycling in rat cardiac myocytes.

S100A1 is an interesting Ca2+ binding protein with respect to muscle physiology as it is preferentially expressed in cardiac muscle and colocalizes with the sarcolemmal and the sarcoplasmic reticulum membranes as well as with the sarcomere. It is therefore conceivable that S100A1 may play a specific role in the regulation of cardiac Ca2+ homeostasis and contractility. We therefore investigated the impact of adenoviral S100A1 overexpression on fractional shortening (FS%) and systolic Ca2+ transients in adult rat cardiomyocytes as well as of S100A1 protein on SERCA activity in skinned cell preparation. In our setting S100A1 gene transfer increased FS% by 55%, systolic Ca2+ amplitudes by 62%, while S100A1 protein increased SERCA activity by 28%. Importantly, the gain in systolic Ca2+ supply was not only seen on basal conditions but also with isoproterenol-stimulated Ca2+ cycling. Thus, S100A1 enhances cardiac contractility by increasing intracellular Ca2+ fluxes at least in part due to a modulation of SERCA. Since earlier observations demonstrated S100A1 protein levels to be increased in compensatory hypertrophy and significantly downregulated in end stage heart failure, these functional data suggest that S100A1 is a novel determinant of cardiac function whose expression levels are causally related to the prevailing contractile state of the heart.

Adenoviridae↗