Sepsis-Induced myocardial dysfunction: heterogeneity of functional effects and clinical significance

Mechanisms of the septic heart: From inflammatory response to myocardial edema

Sepsis-induced myocardial dysfunction (SIMD), also known as sepsis-induced cardiomyopathy (SICM), is linked to significantly increased mortality. Despite its clinical importance, effective therapies for SIMD remain elusive, largely due to an incomplete understanding of its pathogenesis. Over the past five decades, research involving both animal models and human studies has highlighted several pathogenic mechanisms of SICM, yet many aspects remain unexplored. Initially thought to be primarily driven by inflammatory cytokines, current research indicates that these alone are insufficient for the development of cardiac dysfunction. Recent studies have brought attention to additional mechanisms, including excessive nitric oxide production, mitochondrial dysfunction, and disturbances in calcium homeostasis, as contributing factors in SICM. Emerging clinical evidence has highlighted the significant role of myocardial edema in the pathogenesis of SICM, particularly its association with cardiac remodeling in septic shock patients. This review synthesizes our current understanding of SIMD/SICM, focusing on myocardial edema's contribution to cardiac dysfunction and the critical role of the bradykinin receptor B1 (B1R) in altering myocardial microvascular permeability, a potential key player in myocardial edema development during sepsis. Additionally, this review briefly summarizes existing therapeutic strategies and their challenges and explores future research directions. It emphasizes the need for a deeper understanding of SICM to develop more effective treatments.

Virus-Induced Acute Respiratory Distress Syndrome Causes Cardiomyopathy Through Eliciting Inflammatory Responses in the Heart

BACKGROUND

Viral infections can cause acute respiratory distress syndrome (ARDS), systemic inflammation, and secondary cardiovascular complications. Lung macrophage subsets change during ARDS, but the role of heart macrophages in cardiac injury during viral ARDS remains unknown. Here we investigate how immune signals typical for viral ARDS affect cardiac macrophage subsets, cardiovascular health, and systemic inflammation.

METHODS

We assessed cardiac macrophage subsets using immunofluorescence histology of autopsy specimens from 21 patients with COVID-19 with SARS-CoV-2-associated ARDS and 33 patients who died from other causes. In mice, we compared cardiac immune cell dynamics after SARS-CoV-2 infection with ARDS induced by intratracheal instillation of Toll-like receptor ligands and an ACE2 (angiotensin-converting enzyme 2) inhibitor.

RESULTS

In humans, SARS-CoV-2 increased total cardiac macrophage counts and led to a higher proportion of CCR2+ (C-C chemokine receptor type 2 positive) macrophages. In mice, SARS-CoV-2 and virus-free lung injury triggered profound remodeling of cardiac resident macrophages, recapitulating the clinical expansion of CCR2+ macrophages. Treating mice exposed to virus-like ARDS with a tumor necrosis factor α-neutralizing antibody reduced cardiac monocytes and inflammatory MHCIIlo CCR2+ macrophages while also preserving cardiac function. Virus-like ARDS elevated mortality in mice with pre-existing heart failure.

CONCLUSIONS

Our data suggest that viral ARDS promotes cardiac inflammation by expanding the CCR2+ macrophage subset, and the associated cardiac phenotypes in mice can be elicited by activating the host immune system even without viral presence in the heart.

Songorine ameliorates LPS-induced sepsis cardiomyopathy by Wnt/β-catenin signaling pathway-mediated mitochondrial biosynthesis

Septic cardiomyopathy (SCM) is manifested by impairment of cardiac contractile function with myocardial mitochondrial dysregulation. Natural product, songorine (SGR), a diterpenoid alkaloid derived from the lateral root of Aconitum carmichaeli, has been reported for the treatment of heart failure. Here, the protective role of SGR in heart injury of SCM was investigated and its underlying action of mechanism was explored. Firstly, the mouse and cardiomyocytes (H9C2 cell) SCM model induced by LPS were established to evaluate the therapeutic effect of SGR. The in vivo results exhibited that SGR rescued the survival rate of SCM mice, restored the loss of ejection fraction (EF) and fractional shortening (FS), and reduced left ventricular systolic diameter and left ventricular diastole diameter (LVIDs, LVIDd) by echocardiography. SGR improved the mitochondrial biosynthesis and myocardial fiber structure and arranged them neatly by transmission electron microscope (TEM). Further, SGR inhibited inflammatory targets myeloperoxidase (MPO) and tumor necrosis factor (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and plasminogen activator inhibitor-1 (PAI-1). And SGR activated the mitochondrial biosynthesis-related peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), β-catenin, and matrix metallopeptidase 2 (MMP2) proteins. Meanwhile, the in vitro results showed that SGR promoted the increased the myocardial H9C2 cell viability, and mitochondrial biosynthesis and structure. SGR also blocked the inflammatory factors and reversed PGC-1α, β-catenin, and MMP2 in vitro, while SGR alleviated the myocardial cell apoptosis via flow cytometry. The findings indicate that SGR mitigates sepsis-caused myocardial damage by Wnt/β-catenin signaling pathway-mediated mitochondrial biosynthesis. SGR may be a promising candidate for treatment of SCM.

Effect of miR-412-5p-loaded exosomes in H9c2 cardiomyocytes via the MAPK pathway

Objectives

MicroRNAs (miRNAs) are small non-coding RNAs that function in all biological processes. Recent findings suggest that exosomes, which are small vesicles abundantly secreted by various cell types, can transport miRNAs to target cells. Here, we elucidated the effect of miRNA-loaded exosomes on lipopolysaccharide (LPS)-induced inflammation in H9c2 cardiomyocytes.

Materials and Methods

Exosomes were isolated from mesenchymal stem cells (MSC) and loaded with miR-412-5p. Additionally, the effect of the miR-412-5p-loaded exosomes on LPS-induced inflammation in H9c2 cardiomyocytes was evaluated by assessing the levels of nitric oxide (NO), reactive oxygen species (ROS), and prostaglandin E2 (PGE2). The expression of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), inflammatory cytokines, and mitogen-activated protein kinase (MAPK) signaling factors was evaluated using reverse transcription-quantitative PCR and western blotting.

Results

miR-412-5p-loaded exosomes inhibited LPS-induced secretion of inflammatory mediators (NO, PGE2, and ROS), pro-inflammatory cytokines (IL-1β and IL-6), and COX-2 and iNOS expression. Additionally, miR-412-5p-loaded exosomes significantly decreased the expression of MAPK signaling molecules, including p-extracellular signal-regulated kinase (ERK), p-p38, and p-Jun kinase (JNK), in H9c2 cardiomyocytes.

Conclusion

These findings showed that miR-412-5p-loaded exosomes ameliorated LPS-induced inflammation in H9c2 cardiomyocytes by inhibiting COX-2 and iNOS expression, inflammatory mediators, and pro-inflammatory cytokines via the MAPK pathway. The findings indicate that miR-412-5p-loaded exosomes may be effective for the prevention of myocardial injury.

Therapeutic S100A8/A9 blockade inhibits myocardial and systemic inflammation and mitigates sepsis-induced myocardial dysfunction

BACKGROUND AND AIMS

The triggering factors of sepsis-induced myocardial dysfunction (SIMD) are poorly understood and are not addressed by current treatments. S100A8/A9 is a pro-inflammatory alarmin abundantly secreted by activated neutrophils during infection and inflammation. We investigated the efficacy of S100A8/A9 blockade as a potential new treatment in SIMD.

METHODS

The relationship between plasma S100A8/A9 and cardiac dysfunction was assessed in a cohort of 62 patients with severe sepsis admitted to the intensive care unit of Linköping University Hospital, Sweden. We used S100A8/A9 blockade with the small-molecule inhibitor ABR-238901 and S100A9-/- mice for therapeutic and mechanistic studies on endotoxemia-induced cardiac dysfunction in mice.

RESULTS

In sepsis patients, elevated plasma S100A8/A9 was associated with left-ventricular (LV) systolic dysfunction and increased SOFA score. In wild-type mice, 5 mg/kg of bacterial lipopolysaccharide (LPS) induced rapid plasma S100A8/A9 increase and acute LV dysfunction. Two ABR-238901 doses (30 mg/kg) administered intraperitoneally with a 6 h interval, starting directly after LPS or at a later time-point when LV dysfunction is fully established, efficiently prevented and reversed the phenotype, respectively. In contrast, dexamethasone did not improve cardiac function compared to PBS-treated endotoxemic controls. S100A8/A9 inhibition potently reduced systemic levels of inflammatory mediators, prevented upregulation of inflammatory genes and restored mitochondrial function in the myocardium. The S100A9-/- mice were protected against LPS-induced LV dysfunction to an extent comparable with pharmacologic S100A8/A9 blockade. The ABR-238901 treatment did not induce an additional improvement of LV function in the S100A9-/- mice, confirming target specificity.

CONCLUSION

Elevated S100A8/A9 is associated with the development of LV dysfunction in severe sepsis patients and in a mouse model of endotoxemia. Pharmacological blockade of S100A8/A9 with ABR-238901 has potent anti-inflammatory effects, mitigates myocardial dysfunction and might represent a novel therapeutic strategy for patients with severe sepsis.