Levosimendan-induced venodilation is mediated by opening of potassium channels

A roadmap for therapeutic discovery in pulmonary hypertension associated with left heart failure. A scientific statement of the Heart Failure Association (HFA) of the ESC and the ESC Working Group on Pulmonary Circulation & Right Ventricular Function

Pulmonary hypertension (PH) associated with left heart failure (LHF) (PH-LHF) is one of the most common causes of PH. It directly contributes to symptoms and reduced functional capacity and negatively affects right heart function, ultimately leading to a poor prognosis. There are no specific treatments for PH-LHF, despite the high number of drugs tested so far. This scientific document addresses the main knowledge gaps in PH-LHF with emphasis on pathophysiology and clinical trials. Key identified issues include better understanding of the role of pulmonary venous versus arteriolar remodelling, multidimensional phenotyping to recognize patient subgroups positioned to respond to different therapies, and conduct of rigorous pre-clinical studies combining small and large animal models. Advancements in these areas are expected to better inform the design of clinical trials and extend treatment options beyond those effective in pulmonary arterial hypertension. Enrichment strategies, endpoint assessments, and thorough haemodynamic studies, both at rest and during exercise, are proposed to play primary roles to optimize early-stage development of candidate therapies for PH-LHF.

OR-1896 increases force of contraction in the isolated human atrium

OR-1896 ((R)-N-(4-(4-methyl-6-oxo-1,4,5,6-tetrahydropyridazin-3-yl)phenyl)acetamide) is the main active metabolite of levosimendan. However, nobody has reported a positive inotropic effect of OR-1896 in isolated human cardiac preparations. The mechanism of action of OR-1896 remains controversial. Hence, we wanted to know whether OR-1896 exerts a positive inotropic effect in humans and what might be the underlying mechanism. Therefore, we measured the contractile effects of OR-1896 (0.01-10 µM cumulatively applied) in isolated electrically stimulated (1 Hz) human right atrial preparations (HAP) obtained during cardiac surgery. OR-1896, given alone, exerted time- and concentration-dependent positive inotropic effects; 1-µM OR-1896 increased force by 72 ± 14.7% (p < 0.05, n = 6) and shortened the time of relaxation by 10.6 ± 3.6% (p < 0.05, n = 11) in HAP started at 0.1 µM, plateaued at 1-µM OR-1896, and was antagonized by 1-µM propranolol. The maximum positive inotropic effect of OR-1896 in human right atrial preparations was less than that of 10-µM isoprenaline. EMD 57033 (10 µM), a calcium sensitizer, enhanced the force of contraction further in the additional presence of 1-µM OR-1896 by 109 ± 19% (p < 0.05, n = 4). Cilostamide (10 µM), an inhibitor of phosphodiesterase III given before OR-1896 (1 µM), blocked the positive inotropic effect of OR-1896 in HAP. Our data suggest that OR-1896 is, indeed, a positive inotropic agent in the human heart. OR-1896 acts as a PDE III inhibitor. OR-1896 is unlikely to act as a calcium sensitizer in the human heart.

Levosimendan Reverses Cardiac Malfunction and Cardiomyocyte Ferroptosis During Heart Failure with Preserved Ejection Fraction via Connexin 43 Signaling Activation

PURPOSE

In recent decades, the occurrence of heart failure with preserved ejection fraction (HFpEF) has outweighed that of heart failure with reduced ejection fraction by degrees, but few drugs have been demonstrated to improve long-term clinical outcomes in patients with HFpEF. Levosimendan, a calcium-sensitizing cardiotonic agent, improves decompensated heart failure clinically. However, the anti-HFpEF activities of levosimendan and underlying molecular mechanisms are unclear.

METHODS

In this study, a double-hit HFpEF C57BL/6N mouse model was established, and levosimendan (3 mg/kg/week) was administered to HFpEF mice aged 13 to 17 weeks. Different biological experimental techniques were used to verify the protective effects of levosimendan against HFpEF.

RESULTS

After four weeks of drug treatment, left ventricular diastolic dysfunction, cardiac hypertrophy, pulmonary congestion, and exercise exhaustion were significantly alleviated. Junction proteins in the endothelial barrier and between cardiomyocytes were also improved by levosimendan. Among the gap junction channel proteins, connexin 43, which was especially highly expressed in cardiomyocytes, mediated mitochondrial protection. Furthermore, levosimendan reversed mitochondrial malfunction in HFpEF mice, as evidenced by increased mitofilin and decreased ROS, superoxide anion, NOX4, and cytochrome C levels. Interestingly, after levosimendan administration, myocardial tissue from HFpEF mice showed restricted ferroptosis, indicated by an increased GSH/GSSG ratio; upregulated GPX4, xCT, and FSP-1 expression; and reduced intracellular ferrous ion, MDA, and 4-HNE levels.

CONCLUSION

Regular long-term levosimendan administration can benefit cardiac function in a mouse model of HFpEF with metabolic syndromes (namely, obesity and hypertension) by activating connexin 43-mediated mitochondrial protection and sequential ferroptosis inhibition in cardiomyocytes.

Use of Levosimendan in Patients with Pulmonary Hypertension: What is the Current Evidence?

Pulmonary hypertension, defined as an increase in mean arterial pressure > 20 mmHg, is a chronic and progressive condition with high mortality and morbidity. Drug therapy of patients with pulmonary hypertension is based on the distinctive pathophysiologic aspect that characterizes the different groups. However, recently, levosimendan, a calcium-sensitizing agent with inotropic, pulmonary vasodilator, and cardioprotective properties, has been shown to be an effective and safe therapeutic strategy for patients with pulmonary arterial hypertension (in addition to specific drugs) and pulmonary hypertension associated with left heart disease (as possible treatment). This review provides a comprehensive overview of the current evidence on the use of levosimendan in patients with pulmonary hypertension.

Use of Levosimendan in Patients with Advanced Heart Failure: An Update

Levosimendan is an inodilator drug that, given its unique pharmacological actions and safety profile, represents a viable therapeutic option in patients with heart failure with reduced ejection fraction in the advanced stage of the disease (advHFrEF). Pulsed levosimendan infusion in patients with advHFrEF improves symptoms and clinical and hemodynamic status, prevents recurrent hospitalizations, and enables optimization of guidelines-directed medical therapy. Furthermore, considering its proprieties on right ventricular function and pulmonary circulation, levosimendan could be helpful for the prevention and treatment of the right ventricular dysfunction post-implanting a left ventricular assist device. However, to date, evidence on this issue is scarce and has yielded mixed results. Finally, preliminary experiences indicate that treatment with levosimendan at scheduled intervals may serve as a “bridge to transplant” strategy in patients with advHFrEF. In this review, we summarized the clinical pharmacology of levosimendan, the available evidence in the treatment of patients with advHFrEF, as well as a hypothesis for its use in patients with advanced heart failure with preserved ejection fraction.

Hydrogen Sulfide-Induced Vasodilation: The Involvement of Vascular Potassium Channels

Hydrogen sulfide (H₂S) has been highlighted as an important gasotransmitter in mammals. A growing number of studies have indicated that H₂S plays a key role in the pathophysiology of vascular diseases and physiological vascular homeostasis. Alteration in H₂S biogenesis has been reported in a variety of vascular diseases and H₂S supplementation exerts effects of vasodilation. Accumulating evidence has shown vascular potassium channels activation is involved in H₂S-induced vasodilation. This review aimed to summarize and discuss the role of H₂S in the regulation of vascular tone, especially by interaction with different vascular potassium channels and the underlying mechanisms.