Levosimendan ameliorates cardiomyocyte injury and mitochondrial dysfunction in an Nrf2-dependent manner in mice with sepsis-induced cardiomyopathy

Abstract

Sepsis-induced cardiomyopathy (SIC) is a severe complication of sepsis and septic shock and is characterized by cardiac dysfunction. Levosimendan (LEVO), a calcium sensitizer, has shown therapeutic potential in SIC, although its underlying mechanism remains unclear. Nrf2, a pivotal regulator of antioxidant and anti-inflammatory responses, may represent a potential target for SIC treatment. In this study, we examine the effects of LEVO on SIC and explore the mechanistic role of Nrf2 in mediating its cardioprotective effects. A murine SIC model is established via cecal ligation and puncture (CLP), and cardiomyocyte injury is induced in vitro via lipopolysaccharide (LPS) exposure in HL-1 cells. The CLP procedure significantly elevates serum cTnI and IL-6 levels and reduces the survival rates of mice. Echocardiographic analysis reveals impaired cardiac structure and function, accompanied by mitochondrial morphological and functional damage, in SIC mice. Interestingly, these pathological changes in SIC are markedly attenuated by LEVO treatment. Similarly, LEVO administration restores proliferative capacity; increases mitochondrial ATP, mitochondrial membrane potential (MMP) and NADH levels; and reduces ROS production and intracellular calcium overload. Notably, the protective effects of LEVO on cardiomyocyte viability and mitochondrial function are significantly diminished following Nrf2 inhibition or Nrf2 knockout (KO). Collectively, these findings demonstrate that LEVO mitigates cardiomyocyte injury and mitochondrial dysfunction in SIC through an Nrf2-dependent mechanism.

1. Introduction

Sepsis is a life-threatening condition characterized by organ dysfunction resulting from a dysregulated host response to infection [1]. Among the affected organs, the heart is particularly vulnerable, and cardiac dysfunction caused by sepsis, commonly referred to as sepsis-induced cardiomyopathy (SIC), is a major contributor to sepsis-related morbidity and mortality [2,3]. The reported prevalence of SIC among septic patients varies widely, ranging from 10-70% [4]. Clinically, SIC is typically defined as reversible myocardial dysfunction occurring during the early stages of sepsis and is characterized by features such as a reduced left ventricular ejection fraction (LVEF ≤50%), left ventricular dilation, and subsequent restoration of cardiac function [5]. Multiple risk factors have been implicated in the pathogenesis of SIC, including cytokine storm, oxidative stress, mitochondrial dysfunction, calcium dysregulation, cardiomyocyte apoptosis, and autonomic imbalance [2].

Accounting for approximately 30% of the cardiomyocyte volume, mitochondria are the primary sites of energy production in cardiac muscle. Dysfunction of these genes directly compromises myocardial energy metabolism, forming a critical pathological basis for SIC [6]. Recent studies have shown that disturbances in mitochondrial dynamics (fusion and fission), mitochondrial biogenesis and mitophagy can trigger or exacerbate various cardiac diseases, including SIC [7–9]. However, mitochondrion-targeted strategies remain underutilized in clinical settings. Moreover, the precise molecular mechanisms modulating mitochondrial dynamics and quality control in cardiomyocytes to improve SIC remain incompletely understood.

Levosimendan (LEVO), a calcium sensitizer agent, enhances myocardial contractility and vasodilation [10]. LEVO has been approved for the treatment of decompensated heart failure in many countries and is commonly employed in critical care and emergency medicine [11]. LEVO improves myocardial diastolic function by increasing the affinity of calcium for cardiac troponin C and opening ATP-dependent potassium channels on the cell surface without significantly increasing myocardial oxygen consumption [12]. Evidence has indicated that LEVO may have a therapeutic effect on SIC, although mechanistic studies are still in the early stage [11]. In addition to its positive inotropic effects, LEVO also has anti-inflammatory, antioxidant, and antiapoptotic properties [13]. In addition, it increases nitric oxide synthesis, protects vascular endothelial cells, and inhibits the expression of hypoxia-inducible factor-1α (HIF-1α) in ...