Refining the reproducibility of a murine model of stress-induced reversible cardiomyopathy

Proteomics of stress-induced cardiomyopathy: insights from differential expression, protein interaction networks, and functional pathway enrichment in an isoproterenol-induced TTC mouse model

Backgrounds

Takotsubo cardiomyopathy (TTC), also known as stress-induced cardiomyopathy, is a condition characterized by transient left ventricular dysfunction without coronary artery obstruction.

Methods

We utilized label-free quantitative proteomics to analyze protein expression in a murine model of TTC, induced by a high dose of isoproterenol (ISO) injection.

Results

We found that a single high dose of ISO injection in mice could induce stress-related cardiac dysfunction.The proteomic analysis revealed 81 differentially expressed proteins (DEPs) between the ISO and control groups-39 were upregulated, and 42 were downregulated. Key pathways enriched by Gene Ontology (GO) analysis included collagen fibril organization, cholesterol biosynthesis, and elastic fiber assembly. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment indicated significant changes in unsaturated fatty acid biosynthesis, glutathione metabolism, steroid biosynthesis, and ferroptosis. Key hub proteins identified by the protein-protein interaction (PPI) network included Ntrk2, Fdft1, Serpine1, and Cyp1a1. Gene set enrichment analysis (GSEA) showed upregulation in terpenoid backbone biosynthesis, oxidative phosphorylation, and ferroptosis, with downregulation in pathways such as systemic lupus erythematosus and Rap1 signaling.

Conclusions

This study employed high-throughput liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify key proteins associated with energy metabolism, oxidative stress, inflammation, and cell death in TTC. These findings provide new insights into the molecular mechanisms of stress-induced myocardial injury and may offer potential therapeutic targets for mitigating cardiovascular damage under stress conditions.

Lipopolysaccharide Induces Trained Innate Immune Tolerance in the Heart Through Interferon Signaling in a Model of Stress-Induced Cardiomyopathy

Background

Although the ability of the heart to adapt to environmental stress has been studied extensively, the molecular and cellular mechanisms responsible for cardioprotection are not yet fully understood.

Methods

We administered Toll-like receptor (TLR) agonists or a diluent to wild-type mice and assessed their potential to induce cardiac protection against injury from a high intraperitoneal dose of isoproterenol (ISO) administered 7 days later. Cardioprotective effects were analyzed through serum cardiac troponin I levels, immune cell profiling via flow cytometry, echocardiography, and multiomic single-nuclei RNA and ATAC sequencing.

Results

Pretreatment with the TLR4 agonist lipopolysaccharide (LPS), but not TLR1/2 or TLR3 agonists, conferred cardioprotection against ISO, as demonstrated by reduced cardiac troponin I leakage, decreased inflammation, preservation of cardiac structure and function, and improved survival. Remarkably, LPS-induced tolerance was reversed by β-glucan treatment. Multiomic analysis showed that LPS-tolerized hearts had greater chromatin accessibility and upregulated gene expression compared to hearts treated with LPS and β-glucan (reverse-tolerized). The LPS tolerance was associated with upregulation of interferon response pathways across various cell types, including cardiac myocytes and stromal cells. Blocking both type 1 and type 2 interferon signaling eliminated LPS-induced tolerance against ISO, while pretreatment with recombinant type 1 and 2 interferons conferred cardiac protection. Multiomic sequencing further revealed enhanced cytoprotective signaling in interferon-treated hearts. Analysis of cell-cell communication networks indicated increased autocrine signaling by cardiac myocytes, as well as greater paracrine signaling between stromal cells and myeloid cells, in LPS-tolerized versus reverse-tolerized hearts.

Conclusions

LPS pretreatment confers cardiac protection against ISO-induced injury through TLR4 mediated type 1 and 2 interferon signaling, consistent with trained innate immune tolerance. The observation that LPS-induced protection in cardiac myocytes involves both cell-autonomous and non-cell-autonomous mechanisms underscores the complexity of innate immune tolerance in the heart, warranting further investigation into this cardioprotective phenotype.

Clinical Perspective

What is new?: The Toll-like receptor 4 (TLR4) agonist lipopolysaccharide (LPS) confers cardiac protection against isoproterenol-mediated injury in a manner consistent with trained innate immune tolerance, which is reversed by β-glucan treatment.Activation of type 1 and 2 interferon signaling, which is downstream of Toll-like receptor 4, is necessary and sufficient for LPS-induced cardiac protection.LPS-tolerized hearts show heightened autocrine signaling by cardiac myocytes and, to a greater degree, increased cell-cell communication between cardiac myocytes and stromal and myeloid cells compared to reverse-tolerized hearts.What are the clinical implications?: TLR4 and interferon signaling play key roles in the establishment of cardiac protection and LPS-induced trained innate immune tolerance.The protective effects of LPS are mediated by cell-autonomous and non-cell-autonomous mechanisms, suggesting that a deeper understanding of the molecular and cellular signatures of innate immune tolerance is required for the development of targeted approaches to modulate trained innate immunity, and consequently cytoprotection, in the heart.

On animal pathophysiology-seeking models of takotsubo syndrome

The aim of this viewpoint/commentary on a recent contribution by the Gothenburg takotsubo syndrome (TTS) laboratory, in which the authors provide a comprehensive review/state of the art report on the animal models, currently employed in the elucidation of the pathophysiology of TTS, is to intensify the debate as to what constitutes a suitable TTS animal model with as promising as possible translational potential to the human TTS.

Animal models of Takotsubo syndrome: bridging the gap to the human condition

Modelling human diseases serves as a crucial tool to unveil underlying mechanisms and pathophysiology. Takotsubo syndrome (TS), an acute form of heart failure resembling myocardial infarction, manifests with reversible regional wall motion abnormalities (RWMA) of the ventricles. Despite its mortality and clinical similarity to myocardial infarction, TS aetiology remains elusive, with stress and catecholamines playing central roles. This review delves into current animal models of TS, aiming to assess their ability to replicate key clinical traits and identifying limitations. An in-depth evaluation of published animal models reveals a variation in the definition of TS among studies. We notice a substantial prevalence of catecholamine-induced models, particularly in rodents. While these models shed light on TS, there remains potential for refinement. Translational success in TS research hinges on models that align with human TS features and exhibit the key features, including transient RWMA. Animal models should be comprehensively evaluated regarding the various systemic changes of the applied trigger(s) for a proper interpretation. This review acts as a guide for researchers, advocating for stringent TS model standards and enhancing translational validity.

Recurrent Adrenergic Stress Provokes Persistent Myocarditis in PD-1-Deficient Mice

It is unclear how the immune system initiates effective tissue repair responses without also simultaneously activating adaptive immune responses to self-antigens released by damaged or necrotic cells. We studied the role of repetitive adrenergic mediated stress on cardiac injury wild-type and programmed death-1-deficient (PD-1-/-) mice treated with 3 intraperitoneal low doses of isoproterenol followed by an intraperitoneal injection of high-dose ISO 7 days later (ISOprimed/ISOinjury). Repetitive adrenergic stress in ISOprimed/ISOinjury PD-1-/- mice resulted in a persistent dysregulated myocardial inflammatory response characterized by the expansion of autoreactive effector CD8+ T cells, increased cardiac hypertrophy, mild left ventricular dysfunction, and increased lethality when compared with ISOprimed/ISOinjury wild-type mice.

The Immunology of Takotsubo Syndrome

Takotsubo syndrome (TTS) is a disorder characterized by transient cardiac dysfunction with ventricular regional wall motion abnormalities, primarily thought to be caused by the effects of a sudden catecholamine surge on the heart. Although the majority of patients exhibit prompt recovery of their cardiac dysfunction, TTS remains associated with increased mortality rates acutely and at long-term, and there is currently no cure for TTS. Inflammation has been shown to play a key role in determining outcomes in TTS patients, as well as in the early pathogenesis of the disorder. There are also cases of TTS patients that have been successfully treated with anti-inflammatory therapies, supporting the importance of the inflammatory response in TTS. In this article, we provide a comprehensive review of the available clinical and pre-clinical literature on the immune response in TTS, in an effort to not only better understand the pathophysiology of TTS but also to generate insights on the treatment of patients with this disorder.

A Mouse Model of Dilated Cardiomyopathy Produced by Isoproterenol Acute Exposure Followed by 5-Fluorouracil Administration

Appropriate dilated cardiomyopathy (DCM) animal models are highly desirable considering the pathophysiological and clinical heterogeneity of DCM. Genetically modified mice are the most widely and intensively utilized research animals for DCM. However, to translate discoveries from basic science into new and personalized medical applications, research in non-genetically based DCM models remains a key issue. Here, we characterized a mouse model of non-ischemic DCM induced by a stepwise pharmacologic regime of Isoproterenol (ISO) high dose bolus followed by a low dose systemic injection of the chemotherapy agent, 5-Fluorouracil (5-FU). C57BL/6J mice were injected with ISO and, 3 days after, were randomly assigned to saline or 5-FU. Echocardiography and a strain analysis show that ISO + 5FU in mice induces progressive left ventricular (LV) dilation and reduced systolic function, along with diastolic dysfunction and a persistent global cardiac contractility depression through 56 days. While mice treated with ISO alone recover anatomically and functionally, ISO + 5-FU causes persistent cardiomyocyte death, ensuing in cardiomyocyte hypertrophy through 56 days. ISO + 5-FU-dependent damage was accompanied by significant myocardial disarray and fibrosis along with exaggerated oxidative stress, tissue inflammation and premature cell senescence accumulation. In conclusions, a combination of ISO + 5FU produces anatomical, histological and functional cardiac alterations typical of DCM, representing a widely available, affordable, and reproducible mouse model of this cardiomyopathy.