Stereoselective binding of levosimendan to cardiac troponin C causes Ca2+-sensitization

Levosimendan versus dobutamine for sepsis-induced cardiac dysfunction: a systematic review and meta-analysis

Levosimendan and dobutamine are extensively used to treat sepsis-associated cardiovascular failure in ICU. Nevertheless, the role and mechanism of levosimendan in patients with sepsis-induced cardiomyopathy remains unclear. Moreover, previous studies on whether levosimendan is superior to dobutamine are still controversial. More importantly, these studies did not take changes (before-after comparison to the baseline) in quantitative parameters such as ejection fraction into account with the baseline level. Here, we aimed to determine the pros and cons of the two medicines by assessing the changes in cardiac function and blood lactate, mortality, with the standardized mean difference used as a summary statistic. Relevant studies were obtained by a thorough and disciplined literature search in several notable academic databases, including Google Scholar, PubMed, Cochrane Library and Embase until November 2020. Outcomes included changes in cardiac function, lactic acid, mortality and length of hospital stay. A total of 6 randomized controlled trials were included in this study, including 192 patients. Compared with dobutamine, patients treated with levosimendan had a greater improvement of cardiac index (ΔCI) (random effects, SMD = 0.90 [0.20,1.60]; I2 = 76%, P < 0.01) and left ventricular stroke work index (ΔLVSWI) (random effects, SMD = 1.56 [0.90,2.21]; I2 = 65%, P = 0.04), a significant decrease of blood lactate (Δblood lactate) (random effects, MD =  - 0.79 [- 1.33, - 0.25]; I2 = 68%, P < 0.01) at 24-h after drug intervention, respectively. There was no significant difference between levosimendan and dobutamine on all-cause mortality in ICU (fixed effect, OR = 0.72 [0.39,1.33]; I2 = 0%, P = 0.99). We combine effect sizes related to different measurement parameters to evaluate cardiac function, which implied that septic patients with myocardial dysfunction might have a better improvement of cardiac function by levosimendan than dobutamine (random effects, SMD = 1.05 [0.69,1.41]; I2 = 67%, P < 0.01). This study suggested a significant improvement of CI, LVSWI, and decrease of blood lactate in septic patients with myocardial dysfunction in ICU after 24-h administration of levosimendan than dobutamine. However, the administration of levosimendan has neither an impact on mortality nor LVEF. Septic patients with myocardial dysfunction may partly benefit from levosimendan than dobutamine, mainly embodied in cardiac function improvement.

Effect of Levosimendan Treatment in Pediatric Patients With Cardiac Dysfunction: An Update of a Systematic Review and Meta-Analysis of Randomized Controlled Trials

Levosimendan increasingly has been used to treat heart failure and cardiac dysfunction in pediatric patients. Currently, there is only limited evidence that this drug positively affects outcomes. The authors' aim was to investigate the effects of levosimendan on hemodynamic parameters and outcomes in pediatric patients in all clinical settings. The study design was a systematic review of randomized and nonrandomized studies. Randomized clinical trials (RCTs) were included in a meta-analysis. The primary outcome of the meta-analysis was the effect of levosimendan on central venous oxygen saturation (ScvO₂) and lactate values as surrogate markers of low-cardiac-output syndrome. The study setting was any acute care setting. Study participants were pediatric patients (age <18 years) receiving levosimendan, and the intervention was levosimendan versus any control treatment. The authors identified 44 studies published from 2004 to 2020, including a total of 1,131 pediatric patients. Nine studies (enrolling 547 patients) were RCTs, all performed in a pediatric cardiac surgery setting. Three RCTs were judged to carry a low risk of bias. In the RCTs, levosimendan administration was associated with a significant improvement of ScvO₂ (p = 0.03) and a trend toward lower postoperative lactate levels (p = 0.08). No differences could be found for secondary outcomes. Levosimendan use in pediatric patients is not associated with major side effects and may lead to hemodynamic improvement after cardiac surgery. However, its impact on major clinical outcomes remains to be determined. Overall, the quality of evidence for levosimendan use in pediatric patients is low, and further high-quality RCTs are needed.

An update on levosimendan in acute cardiac care: applications and recommendations for optimal efficacy and safety

Introduction: In the 20 years since its introduction to the palette of intravenous hemodynamic therapies, the inodilator levosimendan has established itself as a valuable asset for the management of acute decompensated heart failure. Its pharmacology is notable for delivering inotropy via calcium sensitization without an increase in myocardial oxygen consumption.Areas covered: Experience with levosimendan has led to its applications expanding into perioperative hemodynamic support and various critical care settings, as well as an array of situations associated with acutely decompensated heart failure, such as right ventricular failure, cardiogenic shock with multi-organ dysfunction, and cardio-renal syndrome. Evidence suggests that levosimendan may be preferable to milrinone for patients in cardiogenic shock after cardiac surgery or for weaning from extracorporeal life support and may be superior to dobutamine in terms of short-term survival, especially in patients on beta-blockers. Positive effects on kidney function have been noted, further differentiating levosimendan from catecholamines and phosphodiesterase inhibitors.Expert opinion:Levosimendan can be a valuable resource in the treatment of acute cardiac dysfunction, especially in the presence of beta-blockers or ischemic cardiomyopathy. When attention is given to avoiding or correcting hypovolemia and hypokalemia, an early use of the drug in the treatment algorithm is preferred.

Levosimendan in patients with reduced left ventricular function undergoing isolated coronary or valve surgery

OBJECTIVE

In the Levosimendan in Patients with Left Ventricular Systolic Dysfunction Undergoing Cardiac Surgery Requiring Cardiopulmonary Bypass (LEVO-CTS) trial, no differences in clinical outcomes were observed between levosimendan and placebo in a broad population of patients undergoing cardiac surgery. In previous studies, the benefits of levosimendan were most clearly evident in patients undergoing isolated coronary artery bypass grafting (CABG) surgery. In a prespecified analysis of LEVO-CTS, we compared treatment-related outcomes and costs across types of cardiac surgical procedures.

METHODS

Overall, 563 (66.4%) patients underwent isolated CABG, 97 (11.4%) isolated valve, and 188 (22.2%) combined CABG/valve surgery. Outcomes included the co-primary 4-component composite (30-day mortality, 30-day renal replacement, 5-day myocardial infarction, or 5-day mechanical circulatory support), the 2-component composite (30-day mortality or 5-day mechanical circulatory support), 90-day mortality, low cardiac output syndrome (LCOS), and 30-day medical costs.

RESULTS

The 4- and 2-component outcomes were not significantly different with levosimendan and placebo in patients undergoing CABG (15.2% vs 19.3% and 7.8% vs 10.4%), valve (49.0% vs 33.3% and 22.4% vs 2.1%), or combined procedures (39.6% vs 35.9% and 24.0% vs 19.6%). Ninety-day mortality was lower with levosimendan in isolated CABG (2.1% vs 7.9%; hazard ratio [HR], 0.26; 95% confidence interval [CI], 0.11-0.64), but not significantly different in valve (8.3% vs 2.0%; HR, 4.10; 95% CI, 0.46-36.72) or combined procedures (10.4% vs 7.6%; HR, 1.39; 95% CI, 0.53-3.64; interaction P = .011). LCOS (12.0% vs 22.1%; odds ratio, 0.48; 95% CI, 0.30-0.76; interaction P = .118) was significantly lower in levosimendan-treated patients undergoing isolated CABG. Excluding study drug costs, median and mean 30-day costs were $53,707 and $65,852 for levosimendan and $54,636 and $67,122 for placebo, with a 30-day mean difference (levosimendan - placebo) of -$1270 (bootstrap 95% CI, -$8722 to $6165).

CONCLUSIONS

Levosimendan was associated with lower 90-day mortality and LCOS in patients undergoing isolated CABG, but not in those undergoing isolated valve or combined CABG/valve procedures.

Use of levosimendan in acute and advanced heart failure: short review on available real-world data

Published data have shown potential advantages of levosimendan in the management of acute decompensated heart failure and advanced heart failure when standard medical therapies threaten hemodynamics and organ perfusion are unable to alleviate clinical symptoms. Levosimendan distinguishes itself from other catecholaminergic inotropes by its three mechanisms of action: positive inotropy, vasodilation, and cardioprotection. In addition, its pharmacokinetics allow for a longer duration of action from the metabolite OR1896 allowing for further cardiovascular therapeutic effects for several days, even after discontinuation of the parent drug.

Short-term effects of levosimendan on strain/strain rate markers in patients with nonischemic dilated cardiomyopathy

OBJECTIVE

To investigate whether repetitive measurements of speckle tracking echocardiography (STE)-derived strain (S) and strain rate (SR) could reveal changes in left ventricular function in patients with nonischemic dilated cardiomyopathy treated with levosimendan.

METHODS

We included 22 consecutive patients (age 53 ±12 years) with an ejection fraction (EF) below 35% and New York Heart Association (NYHA) class III-IV symptoms that required intravenous inotropic support despite optimal medical therapy. The absence of any occlusive coronary artery disease was identified via previous coronary angiography in all patients. Echocardiographic variables, including strain/strain rate, and NYHA functional class, were evaluated before and after levosimendan infusion at the 72nd hour and one month.

RESULTS

The strain and strain rate values for both left and right ventricles were observed to be increased NYHA functional class and left ventricular EF (P <.05).

CONCLUSION

STE can successfully completed conventional echocardiography in the evaluation of patients with decompensated heart failure who were treated with levosimendan.

Intermittent levosimendan infusions in advanced heart failure: a real world experience

Objective

To analyse the effects of levosimendan infusions in advanced heart failure.

Methods

Patients with advanced heart failure treated with repeated levosimendan infusions were retrospectively compared with controls. Clinical, blood and echocardiographic parameters were obtained at baseline and after 12 months, and before and after each levosimendan infusion. Hospitalizations for heart failure and in-hospital length of stay in the 6 months before enrolment and after 6 and 12 months were recorded, along with 1-year mortality.

Results

Twenty-five patients treated with levosimendan and 25 controls were studied. After each levosimendan infusion, ventricular function and various clinical and metabolic parameters were improved. After 12 months, left ventricular ejection fraction (LVEF) had improved compared with baseline in the levosimendan group. The 1-year mortality rate was similar in both groups. During the 6 months before enrolment, hospitalizations were fewer in controls compared with the levosimendan group; after 6 and 12 months they increased in controls and decreased in the levosimendan group. Seven patients were super-responders to levosimendan, with LVEF improving more than 20% and hospitalizations being reduced at 12 months compared with the rest of the levosimendan group.

Conclusion

Intermittent levosimendan improved LVEF and decreased hospitalizations in advanced heart failure and represents a therapeutic option for patients whose disease is worsening.

Levosimendan Administration in Limb Ischemia: Multicomponent Signaling Serving Kidney Protection

Aims and Objectives

Acute renal failure is a severe complication of lower extremity major arterial reconstructions, which could even be fatal. Levosimendan is a dual-acting positive inotropic and vasodilatory agent, which is suspected to have protective effects against cardiac ischemia. However, there is no data available on lower limb or remote organ ischemic injuries therefore the aim of the study was to investigate the effect of levosimendan on lower limb ischemia-reperfusion injury and the corollary renal dysfunction.

Methods

Male Wistar rats underwent 180 min bilateral lower limb ischemia followed by 4 or 24 hours of reperfusion. Intravenous Levosimendan was administered continuously (0.2μg/bwkg/min) throughout the whole course of ischemia and the first 3h of reperfusion. Results were compared with sham-operated and ischemia-reperfusion groups. Hemodynamic monitoring was performed by invasive arterial blood pressure measurement. Kidney and lower limb muscle microcirculation was registered by a laser Doppler flowmeter. After 4h and 24h of reperfusion, serum, urine and histological samples were collected.

Results

Systemic hemodynamic parameters and microcirculation of kidney and the lower limb significantly improved in the Levosimendan treated group. Muscle viability was significantly preserved 4 and 24 hours after reperfusion. At the same time, renal functional laboratory tests and kidney histology demonstrated significantly less expressive kidney injury in Levosimendan groups. TNF-α levels were significantly less elevated in the Levosimendan group 4 hours after reperfusion.

Conclusion

The results claim a protective role for Levosimendan administration during major vascular surgeries to prevent renal complications.

Fluorescence Based Characterization of Calcium Sensitizer Action on the Troponin Complex

Calcium sensitizers enhance the transduction of the Ca(2+) signal into force within the heart and have found use in treating heart failure. However the mechanisms of action for most Ca(2+) sensitizers remain unclear. To address this issue an efficient fluorescence based approach to Ca(2+) sensitizer screening was developed which monitors cardiac troponin C's (cTnC's) hydrophobic cleft. This approach was tested on four common Ca(2+) -sensitizers, EMD 57033, levosimendan, bepridil and pimobendan with the aim of elucidating the mechanisms of action for each as well as proving the efficacy of the new screening method. Ca(2+) -titration experiments were employed to determine the effect on Ca(2+) sensitivity and cooperativity of cTnC opening, while stopped flow experiments were used to investigate the impact on cTnC relaxation kinetics. Bepridil was shown to increase the sensitivity of cTnC for Ca(2+) under all reconstitution conditions, sensitization by the other drugs was context dependent. Levosimendan and pimobendan reduced the rate of cTnC closing consistent with a stabilization of cTnC's open conformation while bepridil increased the rate of relaxation. Experiments were also run on samples containing cTnT(T204E), a known Ca(2+) -desensitizing phosphorylation mimic. Levosimendan, bepridil, and pimobendan were found to elevate the Ca(2+) -sensitivity of cTnT(T204E) containing samples in this context.

Inotropes and inodilators for acute heart failure: sarcomere active drugs in focus

Acute heart failure (AHF) emerges as a major and growing epidemiological concern with high morbidity and mortality rates. Current therapies in patients with acute heart failure rely on different strategies. Patients with hypotension, hypoperfusion, or shock require inotropic support, whereas diuretics and vasodilators are recommended in patients with systemic or pulmonary congestion. Traditionally inotropic agents, referred to as Ca²⁺ mobilizers load the cardiomyocyte with Ca²⁺ and thereby increase oxygen consumption and risk for arrhythmias. These limitations of traditional inotropes may be avoided by sarcomere targeted agents. Direct activation of the cardiac sarcomere may be achieved by either sensitizing the cardiac myofilaments to Ca²⁺ or activating directly the cardiac myosin. In this review, we focus on sarcomere targeted inotropic agents, emphasizing their mechanisms of action and overview the most relevant clinical considerations.

Molecular and functional consequences of mutations in the central helix of cardiac troponin C

The objective of this work was to investigate the role of acidic residues within the exposed middle segment of the central helix of cTnC in (1) cTnC-cTnI interactions, (2) Ca(2+) binding and exchange with the regulatory N-domain of cTnC in increasingly complex biochemical systems, and (3) ability of the cTn complex to regulate actomyosin ATPase. In order to achieve this objective, we introduced the D87A/D88A and E94A/E95A/E96A mutations into the central helix of cTnC. The D87A/D88A and E94A/E95A/E96A mutations decreased affinity of cTnC for the regulatory region of cTnI. The Ca(2+) sensitivity of the regulatory N-domain of isolated cTnC was decreased by the D87A/D88A, but not E94A/E95A/E96A mutation. However, both the D87A/D88A and E94A/E95A/E96A mutations desensitized the cTn complex and reconstituted thin filaments to Ca(2+). Decreases in the Ca(2+) sensitivity of the cTn complex and reconstituted thin filaments were, at least in part, due to faster rates of Ca(2+) dissociation. In addition, the D87A/D88A and E94A/E95A/E96A mutations desensitized actomyosin ATPase to Ca(2+), and decreased maximal actomyosin ATPase activity. Thus, our results indicate that conserved acidic residues within the exposed middle segment of the central helix of cTnC are important for the proper regulatory function of the cTn complex.

Intermittent levosimendan improves mid-term survival in chronic heart failure patients: meta-analysis of randomised trials

AIMS

Standard inotropic treatment is often necessary in end-stage heart failure but may be harmful. We performed a meta-analysis of randomized controlled trials to investigate the effect of repeated administration of levosimendan on survival in patients with chronic heart failure.

METHODS AND RESULTS

Four investigators independently searched in CENTRAL, Google Scholar MEDLINE/PubMed, Scopus and the Cochrane Central Register of clinical trials to identify any randomized study ever performed with intermittent levosimendan intravenous administration in adult patients with chronic heart failure with no restrictions on dose or time of administration. Data from a total of 326 patients from six randomized controlled studies using intermittent levosimendan in a cardiological setting were included in the analysis. Levosimendan was associated with a significant reduction in mortality at the longest follow-up available [32 of 168 (19 %) in the levosimendan group 46 of 133 (35 %) in the control arm, RR = 0.55 (95 % CI 0.37-0.84), p for effect = 0 0.005, p for heterogeneity = 0.3, I (2) = 23.4 %, NNT = 6 with 5 studies included]. Brain natriuretic peptide values, ejection fraction and number of patients with New York Heart Association ≥ III status were similar in survivors of both groups.

CONCLUSIONS

A large randomized trial is necessary to confirm the promising beneficial effects of intermittent levosimendan administration on the mid-term survival of patients with chronic heart failure.

Chirality and anaesthetic drugs: A review and an update

Many molecules can exist as right-handed and left-handed forms that are non-superimposable mirror images of each other. They are known as enantiomers or substances of opposite shape. Such compounds are also said to be chiral (Greek chiros meaning ‘hand’). Such chiral molecules are of great relevance to anaesthetic theory and practice. This review summarizes the basic concepts, pharmacokinetic and pharmacodynamic aspects of chirality, and some specific examples of their application in anaesthesia, along with recent advances to elucidate the anaesthetic mechanisms. Chirality is relevant to anaesthesia, simply because more than half of the synthetic agents used in anaesthesia practice are chiral drugs. Almost all these synthetic chiral drugs are administered as racemic mixture, rather than as single pure enantiomers. These mixtures are not drug formulations containing two or more therapeutic substances, but combination of isomeric substances, with the therapeutic activity residing mainly in one of the enantiomer. The other enantiomer can have undesirable properties, have different therapeutic activities or be pharmacologically inert. Specific examples of application of chirality in anaesthetic drugs include inhalational general anaesthetics (e.g. isoflurane), intravenous anaesthetics (e.g. etomidate, thiopentone), neuromuscular blocking agents (e.g. cisatracurium), local anaesthetics (e.g. ropivacaine and levobupivacaine) and other agents (e.g. levosimendan, dexmedetomidine, L-cysteine). In the recent advances, chirality study has not only helped new drug development as mentioned above, but has also contributed in a more profound way to the understanding of the mechanism of anaesthesia and anaesthetic drugs.

Levosimendan versus milrinone in neonates and infants after corrective open-heart surgery: a pilot study

OBJECTIVE

Low cardiac output syndrome commonly complicates the postoperative course after open-heart surgery in children. To prevent low cardiac output syndrome, prophylactic administration of milrinone after cardiopulmonary bypass is commonly used in small children. The aim of this study was to compare the effect of prophylactically administered levosimendan and milrinone on cardiac index in neonates and infants after corrective open-heart surgery.

DESIGN

Prospective, single-center, double-blind, randomized pilot study.

SETTING

Tertiary care center, postoperative pediatric cardiac intensive care unit.

PATIENTS

After written informed consent, 40 infants undergoing corrective open-heart surgery were included.

INTERVENTIONS

At weaning from cardiopulmonary bypass, either a 24-hr infusion of 0.1 μg/kg/min levosimendan or of 0.5 μg/kg/min milrinone were administered. Cardiac output was evaluated at 2, 6, 9, 12, 18, 24, and 48 hrs after cardiopulmonary bypass using a transesophageal Doppler technique (Cardio-QP, Deltex Medical, Chichester, UK). Cardiac index was calculated from cardiac output and the patients' respective body surface area.

RESULTS

Intention-to-treat data of 39 patients (19 in the levosimendan and 20 in the milrinone group) were analyzed using analysis of variance for repeated measurements for statistics. Analysis of variance revealed for both, cardiac index and cardiac output, similar results with no significant differences of the factors group and time. A significant interaction for cardiac output (p = .005) and cardiac index (p = .007) was found, which indicates different time courses of cardiac index in the two groups. Both drugs were well tolerated; no death or serious adverse event occurred.

CONCLUSIONS

In our small study, postoperative cardiac index over time was similar in patients with prophylactically administered levosimendan and patients with prophylactically given milrinone. We observed an increase in cardiac output and cardiac index over time in the levosimendan group, whereas cardiac output and cardiac index remained stable in the milrinone group. This pilot study has primarily served to obtain experience using the new drug levosimendan in neonates and infants and to initiate further multicenter trials in pediatric patients.

A structural and functional perspective into the mechanism of Ca2+-sensitizers that target the cardiac troponin complex

The Ca(2+) dependent interaction between troponin I (cTnI) and troponin C (cTnC) triggers contraction in heart muscle. Heart failure is characterized by a decrease in cardiac output, and compounds that increase the sensitivity of cardiac muscle to Ca(2+) have therapeutic potential. The Ca(2+)-sensitizer, levosimendan, targets cTnC; however, detailed understanding of its mechanism has been obscured by its instability. In order to understand how this class of positive inotropes function, we investigated the mode of action of two fluorine containing novel analogs of levosimendan; 2',4'-difluoro(1,1'-biphenyl)-4-yloxy acetic acid (dfbp-o) and 2',4'-difluoro(1,1'-biphenyl)-4-yl acetic acid (dfbp). The affinities of dfbp and dfbp-o for the regulatory domain of cTnC were measured in the absence and presence of cTnI by NMR spectroscopy, and dfbp-o was found to bind more strongly than dfbp. Dfbp-o also increased the affinity of cTnI for cTnC. Dfbp-o increased the Ca(2+)-sensitivity of demembranated cardiac trabeculae in a manner similar to levosimendan. The high resolution NMR solution structure of the cTnC-cTnI-dfbp-o ternary complex showed that dfbp-o bound at the hydrophobic interface formed by cTnC and cTnI making critical interactions with residues such as Arg147 of cTnI. In the absence of cTnI, docking localized dfbp-o to the same position in the hydrophobic groove of cTnC. The structural and functional data reveal that the levosimendan class of Ca(2+)-sensitizers work by binding to the regulatory domain of cTnC and stabilizing the pivotal cTnC-cTnI regulatory unit via a network of hydrophobic and electrostatic interactions, in contrast to the destabilizing effects of antagonists such as W7 at the same interface.

Absence of mitochondrial activation during levosimendan inotropic action in perfused paced guinea pig hearts as demonstrated by modular control analysis

Levosimendan is a calcium sensitizer developed for the treatment of heart failure. It increases contractile force by enhancing the sensitivity of myofilaments to calcium. Besides this sensitizing effect, the drug has also been reported to show some inhibitory action on phosphodiesterase 3 (PDE3). The inotropic effects of levosimendan have been studied on guinea pig paced perfused hearts by using modular control analysis (MoCA) (Diolez P, Deschodt-Arsac V, Raffard G, Simon C, Santos PD, Thiaudiere E, Arsac L, Franconi JM. Am J Physiol Regul Integr Comp Physiol 293: R13-R19, 2007.), an integrative approach of heart energetics using noninvasive (31)P NMR. The aim was to evaluate quantitatively the respective effects of this drug on energy supply and demand modules. Under our experimental conditions, 0.7 muM levosimendan induced a 45% increase in paced heart output associated with a 7% decrease in phosphocreatine and a negligible increase in oxygen consumption. Because MoCA allows in situ study of the internal regulations in intact beating heart energetics, it was applied to describe quantitatively by which routes levosimendan exerts its inotropic action. MoCA demonstrated the absence of any significant effect of the drug on the supply module, which is responsible for the lower increase in oxygen consumption, compared with epinephrine, which increases the ratio between myocardial oxygen consumption and cardiac contraction. This result evidences that, under our conditions, a possible effect of levosimendan on PDE3 activity and/or intracellular calcium remains very low on mitochondrial activity and insignificant on integrated cardiac energetics. Thus, levosimendan inotropic effect on guinea pig heart depends almost entirely on the calcium-sensitizing properties leading to myofilament activation and the concomitant activation of energy supply by the decrease in PCr, therefore improving energetic efficiency of contraction.

Effects of levo- and dextrosimendan on NF-kappaB-mediated transcription, iNOS expression and NO production in response to inflammatory stimuli

BACKGROUND AND PURPOSE

Levosimendan is used in the treatment of decompensated heart failure. It increases the contractility of the myocardium by sensitizing troponin C to calcium. In addition, levosimendan has been reported to have beneficial effects in experimental models of septic shock. Because heart failure and sepsis have been associated with excessive nitric oxide (NO) production through inducible NOS (iNOS), we investigated the effects of the simendans on NO production and iNOS expression and on generation of pro-inflammatory cytokines.

EXPERIMENTAL APPROACH

Macrophages and fibroblasts were exposed to inflammatory stimuli to induce iNOS expression. Proteins were measured by western blot and mRNA expression was determined by quantitative RT-PCR. Promoter activity and nuclear factor-kappaB (NF-kappaB) and the gamma-activated site (GAS; binding site for signal transducer and activator of transcription 1; STAT1)-mediated transcription were investigated using luciferase reporter constructs. Cytokines tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were measured by ELISA.

KEY RESULTS

Levosimendan and dextrosimendan decreased NO production in a dose-dependent manner in cells exposed to inflammatory stimuli. The simendans decreased iNOS protein and mRNA expression but did not affect iNOS mRNA decay. These compounds decreased iNOS promoter activity and inhibited NF-kappaB-mediated transcription but not that mediated by STAT1/GAS. The simendans reduced IL-6 production slightly but they had no effect on TNF-alpha synthesis.

CONCLUSIONS AND IMPLICATIONS

The simendans downregulated NF-kappaB-dependent transcription and decreased iNOS promoter activity, iNOS expression and NO production. These mechanisms may contribute to their beneficial clinical effects.

Defining the binding site of levosimendan and its analogues in a regulatory cardiac troponin C-troponin I complex

The interaction of Cardiac Troponin C (cTnC) and Cardiac Troponin I (cTnI) plays a critical role in transmitting the Ca (2+) signal to the other myofilament proteins in the activation of cardiac muscle contraction. As such, the cTnC-cTnI interface is a logical target for cardiotonic agents such as levosimendan that can modulate the Ca (2+) sensitivity of the myofilaments. Evidence indicates that drug candidates may exert their effects by targeting a site formed by binding of the switch region of cTnI to the regulatory N domain of cTnC (cNTnC). In this study, we utilized two-dimensional (1)H- (15)N HSQC NMR spectroscopy to monitor the binding of levosimendan and its analogues, CMDP, AMDP, CI-930, imazodan, and MPDP, to cNTnC.Ca (2+) in complex with two versions of the switch region of cTnI (cTnI 147-163 and cTnI 144-163). Levosimendan, CMDP, AMDP, and CI-930 were found to bind to both cNTnC.Ca (2+).cTnI 147-163 and cNTnC.Ca (2+).cTnI 144-163 complexes. These compounds contain a methyl group that is absent in MPDP or imazodan. Thus, the methyl group is one of the pharmacophores responsible for the action of these pyridazinone drugs on cTnC. Furthermore, the results showed that the cNTnC.Ca (2+).cTnI 144-163 complex presents a higher-affinity binding site for these compounds than the cNTnC.Ca (2+).cTnI 147-163 complex. This is consistent with our observation that the affinity of cTnI 144-163 for cNTnC.Ca (2+) is approximately 10-fold stronger than that of cTnI 147-163, likely a result of electrostatic forces between the N-terminal RRV extension in cTnI 144-163 and the acidic residues in the C and D helices of cNTnC. These results will help in the delineation of the mode of action of levosimendan on the important functional unit of cardiac troponin that constitutes the regulatory domain of cTnC and the switch region of cTnI.

Inoprotection: the perioperative role of levosimendan

Levosimendan is emerging as a novel cardioprotective inotrope. Levosimendan augments myocardial contractility by sensitising contractile myofilaments to calcium without increasing myosin adenosine triphosphatase activity or oxygen consumption. Levosimendan activates cellular adenosine triphosphate-dependent potassium channels, a mechanism which is postulated to protect cells from ischaemia in a manner similar to ischaemic preconditioning. Levosimendan may therefore protect the ischaemic myocardium during ischaemia-reperfusion as well as improve the contractile function of the heart. Adenosine triphosphate-dependent potassium channel activation by levosimendan may also be protective in other tissues, such as coronary vascular endothelium, kidney and brain. Clinical trials in patients with decompensated heart failure and myocardial ischaemia show levosimendan to improve haemodynamic performance and potentially improve survival. This paper reviews the known pharmacology of levosimendan, the clinical experience with the drug to date and the potential use of levosimendan as a cardioprotective agent during surgery.

Antieosinophilic activity of simendans

Simendans are novel agents used in the treatment of decompensated heart failure. They sensitize troponin C to calcium and open ATP-sensitive potassium channels and have been shown to reduce cardiac myocyte apoptosis. The aim of the present study was to evaluate whether simendans reduce pulmonary eosinophilia and regulate eosinophil apoptosis. Bronchoalveolar lavage (BAL) eosinophilia was evaluated in ovalbumin-sensitized mice. Effects of simendans on apoptosis in isolated human eosinophils were assessed by relative DNA fragmentation assay, annexin V-binding, and morphological analysis. Dextrosimendan [(+)-[[4-(1,4,5,6-tetrahydro-4-methyl-6-oxo-3-pyridazinyl)phenyl)hydrazono]propanedinitrile] reduced ovalbumin-induced BAL-eosinophilia in sensitized mice. Levosimendan [(-)-[[4-(1,4,5,6-tetrahydro-4-methyl-6-oxo-3-pyridazinyl)phenyl]hydrazono]propanedinitrile] and dextrosimendan reversed interleukin (IL)-5-afforded survival of human eosinophils by inducing apoptosis in vitro. Even high concentrations of IL-5 were not able to overcome the effect of dextrosimendan. Dextrosimendan further enhanced spontaneous apoptosis as well as that induced by CD95 ligation, without inducing primary necrosis. Dextrosimendan-induced DNA fragmentation was shown to be dependent on caspase and c-Jun NH2-terminal kinase activation, whereas extracellular signal-regulated kinase, p38 mitogen-activated kinase, and ATP-sensitive potassium channels seemed to play no role in its actions. Taken together, our results show that simendans possess antieosinophilic activity and may be useful for the treatment of eosinophilic inflammation.

Levosimendan restores both systolic and diastolic cardiac performance in lipopolysaccharide-treated rabbits: Comparison with dobutamine and milrinone

OBJECTIVE

Current treatment strategies for severe septic conditions (i.e., intravenous fluids, vasopressors, and cardiac inotropes) reestablish fluid balance and improve cardiac systole but do not address diastolic dysfunction. Our study aimed to fully characterize both systolic and diastolic abnormalities of sepsis-associated heart failure and to identify treatment that would support full-cycle cardiac improvement.

DESIGN

Endotoxin-injected rabbits, an animal model of abnormal cardiac function in human sepsis, were used to delineate cardiac abnormalities and to examine effects of drug treatments on heart systolic and diastolic function (n = 30); saline-injected animals served as comparators (n = 17). As treatment, three inotropes commonly used for treatment of cardiac failure were infused for 45 mins in separate animal groups-milrinone, dobutamine, and levosimendan.

MEASUREMENTS

Variables of left ventricular systolic and diastolic function were assessed with a pressure conductance catheter. Measurements were made before and after endotoxin/saline injection and before and after inotrope treatment.

RESULTS

Pressure-volume analyses of the left ventricle showed marked impairment in systolic function and in all indices of diastolic function (isovolumic relaxation time constant, left ventricular end-diastolic pressure, and end-diastolic pressure-volume relationship) in endotoxin-treated rabbits. The inotropes, milrinone, dobutamine, and levosimendan, could each partially or completely restore systolic function in the lipopolysaccharide-treated rabbits. However, only levosimendan therapy led to additional beneficial effects on left ventricular relaxation and diastolic function.

CONCLUSIONS

Cardiac failure in severe sepsis results from impairments in both systolic and diastolic functions. Treatment with the calcium sensitizer levosimendan improved both systolic and diastolic cardiac functions in septic animals, but cyclic adenosine monophosphate-dependent inotropes milrinone and dobutamine only improved systolic function.

Use of levosimendan, a new inodilator, for postoperative myocardial stunning in a premature neonate

OBJECTIVE

To first report the successful use of the new inodilator levosimendan in a premature infant with congestive heart failure (CHF) following cardiac surgery. Although the calcium sensitizer levosimendan improves hemodynamics in adults with CHF, no data are available on the use of levosimendan in premature infants with CHF.

DESIGN

Single case report.

SETTING

Twenty-bed postoperative adult and pediatric cardiac intensive care unit.

PATIENT

A 32 wks gestational age, 1525-g premature male twin with transposition of the great arteries.

INTERVENTIONS

The patient underwent arterial switch operation.

MEASUREMENTS AND MAIN RESULTS

Immediately after operation, the patient developed signs of low cardiac output syndrome. Mixed venous saturation was 56%, serum lactate increased to 14.8 mmol/L, systolic arterial pressure was 40 mm Hg, left atrial pressure was 24 mm Hg, and echocardiography showed reduced left ventricular function with a fractional shortening of 10%. There were no signs of reduced coronary perfusion. Milrinone, dobutamine, and epinephrine did not improve hemodynamics. Levosimendan was initiated at a dose of 0.05 mug.kg.min, increased to 0.1 mug.kg.min, and continuously infused for 24 hrs. Within 6 hrs after starting the levosimendan infusion, left atrial pressure decreased to 7 mm Hg and systolic arterial pressure increased to 60 mm Hg; within 24 hrs after initiation serum lactate level normalized to 1.7 mmol/L and mixed venous saturation increased to 81%. Echocardiography revealed improvement of left ventricular function with a fractional shortening of 25%. No side effects were recognized during administration of levosimendan.

CONCLUSIONS

In this premature neonate with postoperative low cardiac output syndrome due to failing myocardial function, levosimendan was a potent inotropic agent.

Identification of a region of troponin I important in signaling cross-bridge-dependent activation of cardiac myofilaments

Force generating strong cross-bridges are required to fully activate cardiac thin filaments, but the molecular signaling mechanism remains unclear. Evidence demonstrating differential extents of cross-bridge-dependent activation of force, especially at acidic pH, in myofilaments in which slow skeletal troponin I (ssTnI) replaced cardiac TnI (cTnI) indicates the significance of a His in ssTnI that is an homologous Ala in cTnI. We compared cross-bridge-dependent activation in myofilaments regulated by cTnI, ssTnI, cTnI(A66H), or ssTnI(H34A). A drop from pH 7.0 to 6.5 induced enhanced cross-bridge-dependent activation in cTnI myofilaments, but depressed activation in cTnI(A66H) myofilaments. This same drop in pH depressed cross-bridge-dependent activation in both ssTnI myofilaments and ssTnI(H34A) myofilaments. Compared with controls, cTnI(A66H) myofilaments were desensitized to Ca(2+), whereas there was no difference in the Ca(2+)-force relationship between ssTnI and ssTnI(H34A) myofilaments. The mutations in cTnI and ssTnI did not affect Ca(2+) dissociation rates from cTnC at pH 7.0 or 6.5. However, at pH 6.5, cTnI(A66H) had lower affinity for cTnT than cTnI. We also probed cross-bridge-dependent activation in myofilaments regulated by cTnI(Q56A). Myofilaments containing cTnI(Q56A) demonstrated cross-bridge-dependent activation that was similar to controls containing cTnI at pH 7.0 and an enhanced cross-bridge-dependent activation at pH 6.5. We conclude that a localized N-terminal region of TnI comprised of amino acids 33-80, which interacts with C-terminal regions of cTnC and cTnT, is of particular significance in transducing signaling of thin filament activation by strong cross-bridges.

Positive inotropic effect of levosimendan is correlated to its stereoselective Ca2+-sensitizing effect but not to stereoselective phosphodiesterase inhibition

In order to clarify the mechanisms of the positive inotropic actions of levosimendan and its optical isomer, dextrosimendan, we compared their concentration-dependent effects in intact papillary muscles, permeabilized cardiomyocytes and in purified phosphodiesterase enzyme preparations of guinea-pig hearts. In papillary muscles twitch tension increased with EC50 values of 60 nM and 2.8 microM for levosimendan and dextrosimendan, respectively. Hence, the two enantiomers exhibited a 47 times potency difference in their positive inotropic effects in a preparation where theoretically Ca2+-sensitization and phosphodiesterase inhibition could both contribute to the positive inotropic effects. In guinea-pig cardiomyocytes, levosimendan and dextrosimendan increased isometric force production (at pCa 6.2) due to Ca2+-sensitization with EC50 values of 8.4 nM and 0.64 microM, respectively, with a similar relative potency difference of 76. A major difference appeared in their relative pharmacological potencies, however, when the inhibitory effects of the two enantiomers were assayed on phosphodiesterase III, purified from guinea pig left ventricle (i.e. the phosphodiesterase isoenzyme which is dominant in that tissue). Levosimendan was a 427 times more potent phosphodiesterase inhibitor than dextrosimendan, with IC50 values of 7.5 nM, and 3.2 microM, respectively. Taken together, our data support the hypothesis that levosimendan and dextrosimendan exert their positive inotropic effects via a stereoselective Ca2+-sensitizing mechanism and not via stereoselective inhibition of phosphodiesterase III in the myocardium.

Pharmacological Mechanisms Contributing to the Clinical Efficacy of Levosimendan

Acute decompensation of chronic heart failure is a direct life-threatening situation with short-term mortality approaching 30%. A number of maladaptive changes are amplified within the cardiovascular system during the progression of chronic heart failure that makes the decompensation phase difficult to handle. Levosimendan is a new Ca2+-sensitizer for the treatment of acutely decompensated heart failure that has proved to be effective during the decompensation of chronic heart failure and acute myocardial infarction. Levosimendan differs from other cardiotonic agents that are used for acute heart failure in that it utilizes a unique dual mechanism of action: Ca2+-sensitization through binding to troponin C in the myocardium, and the opening of ATP-sensitive K+ channels in vascular smooth muscle. In general, these mechanisms evoke positive inotropy and vasodilation. Clinical studies suggested long-term benefits on mortality following short-term administration. It may, therefore, be inferred that levosimendan has additional effects on the cardiovascular system that are responsible for the prolongation of survival. Results of preclinical and clinical investigations suggest that the combination of levosimendan-induced cardiac and vascular changes has favorable effects on the coronary, pulmonary and peripheral circulations. Redistribution of the circulating blood offers an improved hemodynamic context for the development of a positive inotropic effect through Ca2+-sensitization of the contractile filaments, without a proportionate increase in myocardial oxygen consumption or the development of arrhythmias. Activation of ATP-sensitive K+ channels, both on sarcolemma and mitochondria, may protect against myocardial ischemia, and decreased levels of cytokines may prevent the development of further myocardial remodeling. Collectively, these effects of levosimendan shift the disturbed cardiovascular parameters towards normalization, thereby halting the perpetuation of the vicious cycle of heart failure progression. This may contribute to stabilization of the circulation and improved life expectancy of patients with chronic heart failure.

Pharmacology of new agents for acute heart failure syndromes

Current therapies for acute heart failure syndromes (AHFS) target hemodynamics by decreasing congestion or increasing myocardial contraction. Several new agents for AHFS use novel mechanisms of action that focus on new treatment targets, such as those providing anti-ischemic and anti-stunning effects, blocking vasopressin receptors, or blocking endothelin-1 receptors. For example, levosimendan acts as a calcium sensitizer and adenosine triphosphate-dependent potassium (K(ATP)) channel opener that increases contraction, causes vasodilation, and provides cardioprotective effects. This is accomplished by its dual mechanism of action. Levosimendan binds to cardiac troponin C, thereby enhancing calcium myofilament responsiveness and increasing myocardial contraction without increasing intracellular calcium levels. Thus, contraction is increased with no significant increase in myocardial oxygen consumption. The opening of K(ATP) channels by levosimendan causes vasodilation and exerts anti-ischemic and anti-stunning effects on the myocardium. Other new agents target neurohormonal pathways. Tezosentan is an antagonist of endothelin-1 receptors A and B. By inhibiting endothelin-1 receptors, tezosentan may counteract the activities of endothelin-1, which include vasoconstriction, proarrhythmic activities, potentiation of other neurohormones, and mediation of increased vascular permeability. Tolvaptan is a vasopressin V2-receptor antagonist that functions as an aquaretic (ie, it increases urine volume and serum sodium with little or no sodium loss). Therefore, by using novel mechanisms of action, these agents may provide new opportunities for helping patients with AHFS.

The Ca2+-sensitizer levosimendan improves oxidative damage, BNP and pro-inflammatory cytokine levels in patients with advanced decompensated heart failure in comparison to dobutamine

AIM

To investigate the effect of a new inotropic drug, levosimendan compared with dobutamine on levels of brain natriuretic peptide (BNP), interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), and malondialdehyde (MDA) in patients with severe decompensated heart failure.

METHODS AND RESULTS

Twenty-nine consecutive patients (22 males and 7 females), mean age 70.5+/-9.9 years, with decompensated heart failure on standard medical therapy, were randomised to receive either a 24 h infusion of levosimendan (n=15) or dobutamine (n=14). Blood samples were drawn at baseline, 48 h and 5 days post infusion. Levosimendan produced a significant reduction in BNP compared to baseline, at both 48 h (744.1+/-100 vs 1136.3+/-93.7 pg/ml, p=0.04) and 5 days (446+/-119.3 vs 1136.3+/-93.7 pg/ml, p=0.03), while IL-6 values decreased after 5 days (4.8+/-1.3 vs 8.6+/-1.5 pg/ml, p=0.01). MDA levels were significantly lower 5 days after levosimendan compared to baseline (2.3+/-0.2 vs 3+/-0.3 microM, p=0.01). TNF-alpha levels did not differ between the groups. The comparison of percentage alteration compared to baseline showed that BNP (-44.5+/-7.6% vs 4.8+/-18.7%, p=0.025), MDA (-21.8+/-5.1% vs 14.9+/-8.5%, p=0.001) and IL-6 (-38.8+/-12.5% vs 70.2+/-24%, p=0.001) levels were significantly lower in the levosimendan group 5 days after treatment compared to the dobutamine group.

CONCLUSIONS

Treatment with levosimendan in advanced decompensated heart failure exerts a beneficial hemodynamic, anti-inflammatory and antioxidant effect. These findings may give an insight into the favourable impact on mortality that levosimendan appears to have in published multicenter trials.

Comparision of the inotropic effects of levosimendan, rolipram, and dobutamine on human atrial trabeculae

The aim of this study was to compare the positive inotropic effects of 3 different agents with 3 different mechanisms of actions-levosimendan, rolipram, and dobutamine-on human atrial trabecular muscles. Samples of right atrial appendage (1 cm, 500-1000 mg) were removed and immersed in preoxygenated and modified Tyrode solution. In oxygenated Tyrode solution, preparations were used to investigate the concentration-effect relationship of levosimendan, dobutamine, and rolipram on percentage developed tension (DT), from 10 to 10 M, each concentration for 15 minutes. All 3 agents produced concentration-dependent increments in DT. We found that levosimendan was the most efficacious positive inotropic agent on isolated human atrial trabeculae. Both the sensitivity (pD2) and maximum response (Emax) of human atrial trabeculae to levosimendan (6.711 +/- 0.26 and 23.2 +/- 2.2 mN, respectively) were significantly greater than those of dobutamine (6.663 +/- 0.19 and 17.6 +/- 2.8 mN) and rolipram (6.497 +/- 0.18 and 15.0 +/- 1.0 mN). pD2 and Emax values for dobutamine were significantly higher than those for rolipram. It was suggested that because of its potential to enhance cardiac performance without predisposition to calcium-induced arrhythmias, levosimendan might be more useful as a positive inotropic agent in clinical practice.

Enatiomeric analysis of simendan by CE with?-CD as chiral selector compared with CMPA-HPLC

The chiral separation of simendan enantiomers using capillary electrophoresis was studied with beta-cyclodextrin (beta-CD) as chiral selector. The influences of the concentration and pH of borate buffer solution, beta-CD concentration and methanol content in the background electrolyte were investigated. These factors were compared with those in an HPLC with beta-CD as chiral mobile phase additive (CMPA-HPLC). The quantification properties of the developed CE method were examined. A baseline separation of simendan enantiomers was achieved in the background electrolyte of 20 mmol/L borate buffer (pH 11.0) containing 12 mmol/L beta-CD-methanol (50:50 in volume ratio). The CE method is comparable with CMPA-HPLC in chiral resolution, although the optimal pH in CE (11.0) is much higher than that (6.0) in CMPA-HPLC. This chiral CE method is applicable to the quantitative ananlysis and enantiomeric excess value determination of L-simendan.

On the Mechanism of Levosimendan-Induced Dopamine Release in the Striatum of Freely Moving Rats

The Ca(2+) sensitizer levosimendan (LEV) improves myocardial contractility by enhancing the sensitivity of the contractile apparatus to Ca(2+). In addition, LEV promotes Ca(2+) entry through L-type channels in human cardiac myocytes. In this study, which was performed using microdialysis, infusion of LEV at 0.25 microM for 160 min increased dopamine (DA) concentrations (up to fivefold baseline) in dialysates from the striatum of freely moving rats. Ca(2+) omission from the perfusion fluid abolished baseline DA release and greatly decreased LEV-induced DA release. Reintroduction of Ca(2+) in the perfusion fluid restored LEV-induced DA release. Chelation of intracellular Ca(2+) by co-infusing 1,2-bis (o-amino-phenoxy)ethane-N,N,N',N'-tetraacetic acid tetra (acetoxymethyl) ester (BAPTA-AM, 0.2 mM) did not affect basal DA release and scarcely affected LEV-induced increases in dialysate DA. In addition, co-infusion of the L-type (Ca(v) 1.1-1.3) voltage-sensitive Ca(2+)-channel inhibitor nifedipine failed to inhibit LEV-induced increases in dialysate DA, which, in contrast, was inhibited by co-infusion of the N-type (Ca(v) 2.2) voltage-sensitive Ca(2+)-channel inhibitor omega-conotoxin GVIA. We conclude that LEV promotes striatal extracellular Ca(2+) entry through N-type Ca(2+) channels with a consequent increase in DA release.