Low-Dose Endotoxin Induces Late Preconditioning, Increases Peroxynitrite Formation, and Activates STAT3 in the Rat Heart

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.

The pro-inflammatory signature of lipopolysaccharide in spontaneous contracting embryoid bodies differentiated from mouse embryonic stem cells

Embryonic stem (ES) cells differentiate towards all three germ layers, including cardiac cells and leukocytes, and may be therefore suitable to model inflammatory reactions in vitro. In the present study, embryoid bodies differentiated from mouse ES cells were treated with increasing doses of lipopolysaccharide (LPS) to mimic infection with gram-negative bacteria. LPS treatment dose-dependent increased contraction frequency of cardiac cell areas and calcium spikes and increased protein expression of α-actinin. LPS treatment increased the expression of the macrophage marker CD68 and CD69, which is upregulated after activation on T cells, B cells and NK cells. LPS dose-dependent increased protein expression of toll-like receptor 4 (TLR4). Moreover, upregulation of NLR family pyrin domain containing 3 (NLRP3), IL-1ß and cleaved caspase 1 was observed, indicating activation of inflammasome. In parallel, generation of reactive oxygen species (ROS), nitric oxide (NO), and expression of NOX1, NOX2, NOX4 and eNOS occurred. ROS generation, NOX2 expression and NO generation were downregulated by the TLR4 receptor antagonist TAK-242 which abolished the LPS-induced positive chronotropic effect of LPS. In conclusion, our data demonstrate that LPS induced a pro-inflammatory cellular immune response in tissues derived from ES cells, recommending the in vitro model of embryoid bodies for inflammation research.

A Two-Photon Fluorescent Probe for the Visual Detection of Peroxynitrite in Living Cells and Zebrafish

Peroxynitrite (ONOO−), as an important reactive oxygen species (ROS), holds great potential to react with a variety of biologically active substances, leading to the occurrence of various diseases such as cancer and neurodegenerative diseases. In this work, we developed a novel mitochondria-localized fluorescent probe, HDBT-ONOO−, which was designed as a mitochondria-targeting two-photon fluorescence probe based on 1,8-naphthylimide fluorophore and the reactive group of 4-(bromomethyl)-benzene boronic acid pinacol ester. More importantly, the probe exhibited good biocompatibility, sensitivity, and selectivity, enabling its successful application in imaging the generation of intracellular and extracellular ONOO−. Furthermore, exogenous and endogenous ONOO− products in live zebrafish were visualized. It is greatly expected that the designed probe can serve as a useful imaging tool for clarifying the distribution and pathophysiological functions of ONOO− in cells and zebrafish.

Inflammatory mediators of cytokines and chemokines in sepsis: From bench to bedside

Background: Sepsis is a serious clinical condition characterized by damage to the immune system as a result of an uncontrolled response to infection. Septic patients show complications such as fever, cardiovascular shock, and/or systemic organ failure. Acute organ failure formed in sepsis mostly affects the respiratory and cardiovascular systems. In sepsis, responses including pro-inflammatory and anti-inflammatory processes in addition to the Toll-Like Receptor 4 (TLR4) signals leading to the release of inflammatory mediators have been suggested to be fundamental pathways in the pathophysiology of sepsis. Purpose: In this context, unregulated levels of sepsis-associated inflammatory mediators may increase the risk of mortality. In sepsis, infection-induced pathogens lead to a systemic inflammatory response. These systemic responses may contribute to septic shock and organ dysfunction. In the unfavorable clinical course of sepsis, an uncontrolled inflammatory response is observed. Accordingly, the mechanism of inflammatory mediators such as cytokines and chemokines in sepsis might increase. Neurotransmitters and gene regulators affect inflammatory mediators and control the inflammatory response. In this review, we aimed to show the new therapeutic targets in sepsis treatment with current studies. New clinical implications targeting inflammatory mediators in high mortality affected by the uncontrolled inflammatory response in sepsis can contribute to the understanding of the symptoms.

Stellaria media tea protects against diabetes-induced cardiac dysfunction in rats without affecting glucose tolerance

Background and aim

Common chickweed (Stellaria media) tea has traditionally been applied for treatment of various metabolic diseases including diabetes in folk medicine; however, experimental evidence to support this practice is lacking. Therefore, we aimed to assess the effect of Stellaria media tea on glucose homeostasis and cardiac performance in a rat model of diabetes.

Experimental procedure

Hot water extract of Stellaria media herb were analyzed and used in this study, where diabetes was induced by fructose-enriched diet supplemented with a single injection of streptozotocin. Half of the animals received Stellaria media tea (100 mg/kg) by oral gavage. At the end of the 20-week experimental period, blood samples were collected and isolated working heart perfusions were performed.

Results and conclusion

Compared to the animals receiving standard chow, serum fasting glucose level was increased and glucose tolerance was diminished in diabetic rats. Stellaria media tea did not affect significantly fasting hyperglycemia and glucose intolerance; however, it attenuated diabetes-induced deterioration of cardiac output and cardiac work. Analysis of the chemical composition of Stellaria media tea suggested the presence of rutin and various apigenin glycosides which have been reported to alleviate diabetic cardiomyopathy. Moreover, Stellaria media prevented diabetes-induced increase in cardiac STAT3 phosphorylation. We demonstrated for the first time that Stellaria media tea may beneficially affect cardiac dysfunction induced by diabetes without improvement of glucose homeostasis. Rutin and/or apigenin glycosides as well as modulation of STAT3 signaling may be implicated in the protection of Stellaria media tea against diabetic cardiomyopathy.

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Stellaria media (SM) tea attenuates diabetic deterioration of cardiac performance.

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SM tea contains apigenin glycosides and presumably rutin which have been reported to alleviate diabetic cardiomyopathy.

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SM tea restores diabetes-induced cardiac STAT3 phosphorylation.

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SM tea does not affect fasting hyperglycemia and glucose intolerance.

Prediabetes Induced by Fructose-Enriched Diet Influences Cardiac Lipidome and Proteome and Leads to Deterioration of Cardiac Function prior to the Development of Excessive Oxidative Stress and Cell Damage

Prediabetes is a condition affecting more than 35% of the population. In some forms, excessive carbohydrate intake (primarily refined sugar) plays a prominent role. Prediabetes is a symptomless, mostly unrecognized disease which increases cardiovascular risk. In our work, we examined the effect of a fructose-enriched diet on cardiac function and lipidome as well as proteome of cardiac muscle. Male Wistar rats were divided into two groups. The control group received a normal diet while the fructose-fed group received 60% fructose-supplemented chow for 24 weeks. Fasting blood glucose measurement and oral glucose tolerance test (OGTT) showed slightly but significantly elevated values due to fructose feeding indicating development of a prediabetic condition. Both echocardiography and isolated working heart perfusion performed at the end of the feeding protocol demonstrated diastolic cardiac dysfunction in the fructose-fed group. Mass spectrometry-based, high-performance lipidomic and proteomic analyses were executed from cardiac tissue. The lipidomic analysis revealed complex rearrangement of the whole lipidome with special emphasis on defects in cardiolipin remodeling. The proteomic analysis showed significant changes in 75 cardiac proteins due to fructose feeding including mitochondria-, apoptosis-, and oxidative stress-related proteins. Nevertheless, just very weak or no signs of apoptosis induction and oxidative stress were detected in the hearts of fructose-fed rats. Our results suggest that fructose feeding induces marked alterations in the cardiac lipidome, especially in cardiolipin remodeling, which leads to mitochondrial dysfunction and impaired cardiac function. However, at the same time, several adaptive responses are induced at the proteome level in order to maintain a homeostatic balance. These findings demonstrate that even very early stages of prediabetes can impair cardiac function and can result in significant changes in the lipidome and proteome of the heart prior to the development of excessive oxidative stress and cell damage.

Selective Heart Irradiation Induces Cardiac Overexpression of the Pro-hypertrophic miR-212

Background: A deleterious, late-onset side effect of thoracic radiotherapy is the development of radiation-induced heart disease (RIHD). It covers a spectrum of cardiac pathology including also heart failure with preserved ejection fraction (HFpEF) characterized by left ventricular hypertrophy (LVH) and diastolic dysfunction. MicroRNA-212 (miR-212) is a crucial regulator of pathologic LVH via FOXO3-mediated pathways in pressure-overload-induced heart failure. We aimed to investigate whether miR-212 and its selected hypertrophy-associated targets play a role in the development of RIHD. Methods: RIHD was induced by selective heart irradiation (50 Gy) in a clinically relevant rat model. One, three, and nineteen weeks after selective heart irradiation, transthoracic echocardiography was performed to monitor cardiac morphology and function. Cardiomyocyte hypertrophy and fibrosis were assessed by histology at week 19. qRT-PCR was performed to measure the gene expression changes of miR-212 and forkhead box O3 (FOXO3) in all follow-up time points. The cardiac transcript level of other selected hypertrophy-associated targets of miR-212 including extracellular signal-regulated kinase 2 (ERK2), myocyte enhancer factor 2a (MEF2a), AMP-activated protein kinase, (AMPK), heat shock protein 40 (HSP40), sirtuin 1, (SIRT1), calcineurin A-alpha and phosphatase and tensin homolog (PTEN) were also measured at week 19. Cardiac expression of FOXO3 and phospho-FOXO3 were investigated at the protein level by Western blot at week 19. Results: In RIHD, diastolic dysfunction was present at every time point. Septal hypertrophy developed at week 3 and a marked LVH with interstitial fibrosis developed at week 19 in the irradiated hearts. In RIHD, cardiac miR-212 was overexpressed at week 3 and 19, and FOXO3 was repressed at the mRNA level only at week 19. In contrast, the total FOXO3 protein level failed to decrease in response to heart irradiation at week 19. Other selected hypertrophy-associated target genes failed to change at the mRNA level in RIHD at week 19. Conclusions: LVH in RIHD was associated with cardiac overexpression of miR-212. However, miR-212 seems to play a role in the development of LVH via FOXO3-independent mechanisms in RIHD. As a central regulator of pathologic remodeling, miR-212 might become a novel target for RIHD-induced LVH and heart failure.

Chronic kidney disease induces left ventricular overexpression of the pro-hypertrophic microRNA-212

Chronic kidney disease (CKD) is a public health problem that increases the risk of cardiovascular morbidity and mortality. Heart failure with preserved ejection fraction (HFpEF) characterized by left ventricular hypertrophy (LVH) and diastolic dysfunction is a common cardiovascular complication of CKD. MicroRNA-212 (miR-212) has been demonstrated previously to be a crucial regulator of pathologic LVH in pressure-overload-induced heart failure via regulating the forkhead box O3 (FOXO3)/calcineurin/nuclear factor of activated T-cells (NFAT) pathway. Here we aimed to investigate whether miR-212 and its hypertrophy-associated targets including FOXO3, extracellular signal-regulated kinase 2 (ERK2), and AMP-activated protein kinase (AMPK) play a role in the development of HFpEF in CKD. CKD was induced by 5/6 nephrectomy in male Wistar rats. Echocardiography and histology revealed LVH, fibrosis, preserved systolic function, and diastolic dysfunction in the CKD group as compared to sham-operated animals eight and/or nine weeks later. Left ventricular miR-212 was significantly overexpressed in CKD. However, expressions of FOXO3, AMPK, and ERK2 failed to change significantly at the mRNA or protein level. The protein kinase B (AKT)/FOXO3 and AKT/mammalian target of rapamycin (mTOR) pathways are also proposed regulators of LVH induced by pressure-overload. Interestingly, phospho-AKT/total-AKT ratio was increased in CKD without significantly affecting phosphorylation of FOXO3 or mTOR. In summary, cardiac overexpression of miR-212 in CKD failed to affect its previously implicated hypertrophy-associated downstream targets. Thus, the molecular mechanism of the development of LVH in CKD seems to be independent of the FOXO3, ERK1/2, AMPK, and AKT/mTOR-mediated pathways indicating unique features in this form of LVH.

Polyphenolic Compounds, Antioxidant, and Cardioprotective Effects of Pomace Extracts from Fetească Neagră Cultivar

Grape pomace is a potential source of natural antioxidant agents. Phenolic compounds and antioxidant and cardioprotective properties of fresh and fermented pomace extracts obtained from Vitis vinifera L. red variety Fetească neagră grown in Romania in 2015 were investigated. Grape pomace extracts total phenolic index, total tannins, total anthocyanins, proanthocyanidins, flavan-3-ol monomers, stilbenes, and DPPH free radical scavenger were measured. The effect of a seven-day pretreatment with grape pomace extracts on the isoprenaline-induced infarct-like lesion in rats was assessed by ECG monitoring, serum levels of creatine kinase, aspartate transaminase, and alanine transaminase. Total serum oxidative status, total antioxidant response, oxidative stress index, malondialdehyde, total thiols, and nitric oxide have been also assessed. Higher phenolic content and antioxidant activity were found in fermented pomace extracts when compared to fresh pomace extracts. Pretreatment with grape pomace extracts significantly improved cardiac and oxidative stress parameters. In conclusion, Fetească neagră pomace extracts had a good in vitro antioxidant activity due to an important phenolic content. In vivo, the extracts had cardioprotective effects against isoprenaline-induced infarct-like lesion by reducing oxidative stress, fresh pomace extracts having a better effect.

Antihypertensive effects of Tartary buckwheat flavonoids by improvement of vascular insulin sensitivity in spontaneously hypertensive rats

Tartary buckwheat flavonoids alleviate hypertension through attenuating vascular insulin resistance and oxidative stress.