Toll-like receptor 3 plays a central role in cardiac dysfunction during polymicrobial sepsis

The Impact of Extracellular Histones and Absence of Toll-like Receptors on Cardiac Functional and Electrical Disturbances in Mouse Hearts

In polymicrobial sepsis, the extracellular histones, mainly released from activated neutrophils, significantly contribute to cardiac dysfunction (septic cardiomyopathy), as demonstrated in our previous studies using Echo-Doppler measurements. This study aims to elucidate the roles of extracellular histones and their interactions with Toll-like receptors (TLRs) in cardiac dysfunction. Through ex vivo assessments of ECG, left ventricle (LV) function parameters, and in vivo Echo-Doppler studies in mice perfused with extracellular histones, we aim to provide comprehensive insights into the mechanisms underlying sepsis-induced cardiac dysfunction. Langendorff-perfused hearts from both wild-type and TLR2, TLR3, or TLR4 knockout (KO) mice were examined. Paced mouse hearts were perfused with histones to assess contractility and relaxation. Echo-Doppler studies evaluated cardiac dysfunction after intravenous histone injection. Histone perfusion caused defects in contractility and relaxation, with TLR2 and TLR3 KO mice being partially protected. Specifically, TLR2 KO mice exhibited the greatest reduction in Echo-Doppler abnormalities, while TLR4 KO exacerbated cardiac dysfunction. Among individual histones, H1 induced the most pronounced abnormalities in cardiac function, apoptosis of cardiomyocytes, and LDH release. Our data highlight significant interactions between histones and TLRs, providing insights into histones especially H1 as potential therapeutic targets for septic cardiomyopathy. Further studies are needed to explore specific histone-TLR interactions and their mechanisms.

Unraveling the immune functions of large yellow croaker Tmem208 in response to Pseudomonas plecoglossicida: Insights from cloning, expression profiling, and transcriptome analysis

Pseudomonas plecoglossicida, the causative agent of Visceral White Spot Disease, poses substantial risks to large yellow croaker (Larimichthys crocea) aquaculture. Previous genome-wide association studies (GWAS), directed towards elucidating the resistance mechanisms of large yellow croaker against this affliction, suggested that the transmembrane protein 208 (named Lctmem208) may confer a potential advantage. TMEM proteins, particularly TMEM208 located in the endoplasmic reticulum, plays significant roles in autophagy, ER stress, and dynamics of cancer cell. However, research on TMEM's function in teleost fish immunity remains sparse, highlighting a need for further study. This study embarks on a comprehensive examination of LcTmem208, encompassing cloning, molecular characterization, and its dynamics in immune function in response to Pseudomonas plecoglossicida infection. Our findings reveal that LcTmem208 is highly conserved across teleost species, exhibiting pronounced expression in immune-relevant tissues, which escalates significantly upon pathogenic challenge. Transcriptome analysis subsequent to LcTmem208 overexpression in kidney cells unveiled its pivotal role in modulating immune-responsive processes, notably the p53 signaling pathway and cytokine-mediated interactions. Enhanced phagocytic activity in macrophages overexpressing LcTmem208 underscores its importance in innate immunity. Taken together, this is the first time reported the critical involvement of LcTmem208 in regulating innate immune responses of defensing P. plecoglossicida, thereby offering valuable insights into teleost fish immunity and potential strategies for the selective breeding of disease-resistant strains of large yellow croaker in aquaculture practices.

Nucleolin myocardial-specific knockout exacerbates glucose metabolism disorder in endotoxemia-induced myocardial injury

Background

Sepsis-induced myocardial injury, as one of the important complications of sepsis, can significantly increase the mortality of septic patients. Our previous study found that nucleolin affected mitochondrial function in energy synthesis and had a protective effect on septic cardiomyopathy in mice. During sepsis, glucose metabolism disorders aggravated myocardial injury and had a negative effect on septic patients.

Objectives

We investigated whether nucleolin could regulate glucose metabolism during endotoxemia-induced myocardial injury.

Methods

The study tested whether the nucleolin cardiac-specific knockout in the mice could affect glucose metabolism through untargeted metabolomics, and the results of metabolomics were verified experimentally in H9C2 cells. The ATP content, lactate production, and oxygen consumption rate (OCR) were evaluated.

Results

The metabolomics results suggested that glycolytic products were increased in endotoxemia-induced myocardial injury, and that nucleolin myocardial-specific knockout altered oxidative phosphorylation-related pathways. The experiment data showed that TNF-α combined with LPS stimulation could increase the lactate content and the OCR values by about 25%, and decrease the ATP content by about 25%. However, interference with nucleolin expression could further decrease ATP content and OCR values by about 10-20% and partially increase the lactate level in the presence of TNF-α and LPS. However, nucleolin overexpression had the opposite protective effect, which partially reversed the decrease in ATP content and the increase in lactate level.

Conclusion

Down-regulation of nucleolin can exacerbate glucose metabolism disorders in endotoxemia-induced myocardial injury. Improving glucose metabolism by regulating nucleolin was expected to provide new therapeutic ideas for patients with septic cardiomyopathy.

NLRP6 negatively regulates host defense against polymicrobial sepsis

Introduction

Sepsis remains a major cause of death in Intensive Care Units. Sepsis is a life-threatening multi-organ dysfunction caused by a dysregulated systemic inflammatory response. Pattern recognition receptors, such as TLRs and NLRs contribute to innate immune responses. Upon activation, some NLRs form multimeric protein complexes in the cytoplasm termed "inflammasomes" which induce gasdermin d-mediated pyroptotic cell death and the release of mature forms of IL-1β and IL-18. The NLRP6 inflammasome is documented to be both a positive and a negative regulator of host defense in distinct infectious diseases. However, the role of NLRP6 in polymicrobial sepsis remains elusive.

Methods

We have used NLRP6 KO mice and human septic spleen samples to examine the role of NLRP6 in host defense in sepsis.

Results

NLRP6 KO mice display enhanced survival, reduced bacterial burden in the organs, and reduced cytokine/chemokine production. Co-housed WT and KO mice following sepsis show decreased bacterial burden in the KO mice as observed in singly housed groups. NLRP6 is upregulated in CD3, CD4, and CD8 cells of septic patients and septic mice. The KO mice showed a higher number of CD3, CD4, and CD8 positive T cell subsets and reduced T cell death in the spleen following sepsis. Furthermore, administration of recombinant IL-18, but not IL-1β, elicited excessive inflammation and reversed the survival advantages observed in NLRP6 KO mice.

Conclusion

These results unveil NLRP6 as a negative regulator of host defense during sepsis and offer novel insights for the development of new treatment strategies for sepsis.

Research progress of hexokinase 2 in inflammatory-related diseases and its inhibitors

Hexokinase 2 (HK2) is a crucial enzyme involved in glycolysis, which converts glucose into glucose-6-phosphate and plays a significant role in glucose metabolism. HK2 can mediate glycolysis, which is linked to the release of inflammatory factors. The over-expression of HK2 increases the production of pro-inflammatory cytokines, exacerbating the inflammatory reaction. Consequently, HK2 is closely linked to various inflammatory-related diseases affecting multiple systems, including the digestive, nervous, circulatory, respiratory, reproductive systems, as well as rheumatoid arthritis. HK2 is regarded as a novel therapeutic target for inflammatory-related diseases, and this article provides a comprehensive review of its roles in these conditions. Furthermore, the development of potent HK2 inhibitors has garnered significant attention in recent years. Therefore, this review also presents a summary of potential HK2 inhibitors, offering promising prospects for the treatment of inflammatory-related diseases in the future.

Role of toll-like receptor-mediated pyroptosis in sepsis-induced cardiomyopathy

Sepsis, a life-threatening dysregulated status of the host response to infection, can cause multiorgan dysfunction and mortality. Sepsis places a heavy burden on the cardiovascular system due to the pathological imbalance of hyperinflammation and immune suppression. Myocardial injury and cardiac dysfunction caused by the aberrant host responses to pathogens can lead to cardiomyopathy, one of the most critical complications of sepsis. However, many questions about the specific mechanisms and characteristics of this complication remain to be answered. The causes of sepsis-induced cardiac dysfunction include abnormal cardiac perfusion, myocardial inhibitory substances, autonomic dysfunction, mitochondrial dysfunction, and calcium homeostasis dysregulation. The fight between the host and pathogens acts as the trigger for sepsis-induced cardiomyopathy. Pyroptosis, a form of programmed cell death, plays a critical role in the progress of sepsis. Toll-like receptors (TLRs) act as pattern recognition receptors and participate in innate immune pathways that recognize damage-associated molecular patterns as well as pathogen-associated molecular patterns to mediate pyroptosis. Notably, pyroptosis is tightly associated with cardiac dysfunction in sepsis and septic shock. In line with these observations, induction of TLR-mediated pyroptosis may be a promising therapeutic approach to treat sepsis-induced cardiomyopathy. This review focuses on the potential roles of TLR-mediated pyroptosis in sepsis-induced cardiomyopathy, to shed light on this promising therapeutic approach, thus helping to prevent and control septic shock caused by cardiovascular disorders and improve the prognosis of sepsis patients.

MECHANISMS OF CARDIAC DYSFUNCTION IN SEPSIS

ABSTRACT

Studies in animal models of sepsis have elucidated an intricate network of signaling pathways that lead to the dysregulation of myocardial Ca 2+ handling and subsequently to a decrease in cardiac contractile force, in a sex- and model-dependent manner. After challenge with a lethal dose of LPS, male animals show a decrease in cellular Ca 2+ transients (ΔCa i ), with intact myofilament function, whereas female animals show myofilament dysfunction, with intact ΔCa i . Male mice challenged with a low, nonlethal dose of LPS also develop myofilament desensitization, with intact ΔCa i . In the cecal ligation and puncture (CLP) model, the causative mechanisms seem similar to those in the LPS model in male mice and are unknown in female subjects. ΔCa i decrease in male mice is primarily due to redox-dependent inhibition of sarco/endoplasmic reticulum Ca 2+ ATP-ase (SERCA). Reactive oxygen species (ROS) are overproduced by dysregulated mitochondria and the enzymes NADPH/NADH oxidase, cyclooxygenase, and xanthine oxidase. In addition to inhibiting SERCA, ROS amplify cardiomyocyte cytokine production and mitochondrial dysfunction, making the process self-propagating. In contrast, female animals may exhibit a natural redox resilience. Myofilament dysfunction is due to hyperphosphorylation of troponin I, troponin T cleavage by caspase-3, and overproduction of cGMP by NO-activated soluble guanylate cyclase. Depleted, dysfunctional, or uncoupled mitochondria likely synthesize less ATP in both sexes, but the role of energy deficit is not clear. NO produced by NO synthase (NOS)-3 and mitochondrial NOSs, protein kinases and phosphatases, the processes of autophagy and sarco/endoplasmic reticulum stress, and β-adrenergic insensitivity may also play currently uncertain roles.

CARDIOMYOCYTE REPROGRAMMING IN ANIMAL MODELS OF SEPTIC SHOCK

ABSTRACT

Cardiomyocyte reprogramming plays a pivotal role in sepsis-induced cardiomyopathy through the induction or overexpression of several factors and enzymes, ultimately leading to the characteristic decrease in cardiac contractility. The initial trigger is the binding of LPS to TLR-2, -3, -4, and -9 and of proinflammatory cytokines, such as TNF, IL-1, and IL-6, to their respective receptors. This induces the nuclear translocation of nuclear factors, such as NF-κB, via activation of MyD88, TRIF, IRAK, and MAPKs. Among the latter, ROS- and estrogen-dependent p38 and ERK 1/2 are proinflammatory, whereas JNK may play antagonistic, anti-inflammatory roles. Nuclear factors induce the synthesis of cytokines, which can amplify the inflammatory signal in a paracrine fashion, and of several effector enzymes, such as NOS-2, NOX-1, and others, which are ultimately responsible for the degradation of cardiomyocyte contractility. In parallel, the downregulation of enzymes involved in oxidative phosphorylation causes metabolic reprogramming, followed by a decrease in ATP production and the release of fragmented mitochondrial DNA, which may augment the process in a positive feedback loop. Other mediators, such as NO, ROS, the enzymes PI3K and Akt, and adrenergic stimulation may play regulatory roles, but not all signaling pathways that mediate cardiac dysfunction of sepsis do that by regulating reprogramming. Transcription may be globally modulated by miRs, which exert protective or amplifying effects. For all these mechanisms, differentiating between modulation of cardiomyocyte reprogramming versus systemic inflammation has been an ongoing but worthwhile experimental challenge.

Effect of thymoquinone on sepsis-induced cardiac damage via anti-inflammatory and anti-apoptotic mechanisms

Objective

Sepsis is a systemic and deleterious host reaction to severe infection. Cardiac dysfunction is an established serious outcome of multiorgan failure associated with this condition. Therefore, it is important to develop drugs targeting sepsis-induced cardiac damage and inflammation. Thymoquinone (TQ) has anti-inflammatory, anti-oxidant, anti-fibrotic, anti-tumor, and anti-apoptotic effects. This study examined the effects of thymoquinone on sepsis-induced cardiac damage.

Methods

Male BALB/c mice were randomly segregated into four groups: control, TQ, cecal ligation and puncture (CLP), and CLP + TQ groups. CLP was performed after gavaging the mice with TQ for 2 weeks. After 48 hours, we estimated the histopathological changes in the cardiac tissue and the serum levels of cardiac troponin-T. We evaluated the expression of factors associated with inflammation, apoptosis, oxidative stress, and the PI3K/AKT pathway.

Results

TQ significantly reduced intestinal histological alterations and inhibited the upregulation of interleukin-6, tumor necrosis factor-α, Bax, NOX4, p-PI3K, and p-AKT. TQ also increased Bcl-2, HO-1, and NRF2 expression.

Conclusion

These results suggest that TQ effectively modulates pro-inflammatory, apoptotic, oxidative stress, and PI3K/AKT pathways, making it indispensable in the treatment of sepsis-induced cardiac damage.

Sex as Biological Variable in Cardiac Mitochondrial Bioenergetic Responses to Acute Stress

Cardiac dysfunction/damage following trauma, shock, sepsis, and ischemia impacts clinical outcomes. Acute inflammation and oxidative stress triggered by these injuries impair mitochondria, which are critical to maintaining cardiac function. Despite sex dimorphisms in consequences of these injuries, it is unclear whether mitochondrial bioenergetic responses to inflammation/oxidative stress are sex-dependent. We hypothesized that sex disparity in mitochondrial bioenergetics following TNFα or H2O2 exposure is responsible for reported sex differences in cardiac damage/dysfunction. Methods and Results: Cardiomyocytes isolated from age-matched adult male and female mice were subjected to 1 h TNFα or H2O2 challenge, followed by detection of mitochondrial respiration capacity using the Seahorse XF96 Cell Mito Stress Test. Mitochondrial membrane potential (ΔΨm) was analyzed using JC-1 in TNFα-challenged cardiomyocytes. We found that cardiomyocytes isolated from female mice displayed a better mitochondrial bioenergetic response to TNFα or H2O2 than those isolated from male mice did. TNFα decreased ΔΨm in cardiomyocytes isolated from males but not from females. 17β-estradiol (E2) treatment improved mitochondrial metabolic function in cardiomyocytes from male mice subjected to TNFα or H2O2 treatment. Conclusions: Cardiomyocyte mitochondria from female mice were more resistant to acute stress than those from males. The female sex hormone E2 treatment protected cardiac mitochondria against acute inflammatory and oxidative stress.

Activation of STIM1/Orai1‑mediated SOCE in sepsis‑induced myocardial depression

Unbalanced Ca2⁺ homeostasis serves an essential role in the occurrence and development of septic myocardial injury. However, the mechanism of Ca2⁺ homeostasis in septic myocardial depression is poorly understood due to the complexity of Ca2⁺ transporters in excitable cells. It was therefore hypothesized that cardiac dysfunction, myocardial injury and cardiac apoptosis in septic myocardial depression are associated with elevated intracellular Ca2⁺ concentrations caused by stromal interaction molecule 1 (STIM1)/Orai calcium release‑activated calcium modulator 1 (Orai1)‑mediated store‑operated Ca2⁺ entry (SOCE). A septic myocardial depression model was established using the cecal ligation and puncture operation (CLP) in mice and was simulated in H9C2 cells via lipopolysaccharide (LPS) stimulation. Cardiac function, myocardial injury, cardiac apoptosis and the expression levels of Bax, Bcl‑2, STIM1 and Orai1 were quantified in vivo at 6, 12 and 24 h. Changes in the intracellular Ca2⁺ concentration, SOCE and the distribution of STIM1 were assessed in vitro within 6 h. The morphological changes of heart tissue were observed by hematoxylin‑eosin staining. Myocardial cellular apoptosis was determined by TUNEL method. The expression of Bax, Bcl‑2, STIM1 and Orai1 were visualized by western blot. Cytosolic calcium concentration and SOCE were evaluated by confocal microscopy. The results demonstrated that cardiac contractile function was significantly reduced at 6 h and morphological changes in cardiac tissues, as well as the myocardial apoptosis rate, were markedly increased at 6, 12 and 24 h following CLP. mRNA and protein expression levels of Bax/Bcl‑2 were significantly enhanced at 6 and 12 h and glycosylation of Orai1 in the myocardium of septic mice was significantly increased at 6 h following CLP. The intracellular Ca2⁺ concentration, SOCE, was significantly increased at 1‑2 h and the clustering and distribution of STIM1 were markedly changed in H9C2 cells at 1 and 2 h. These findings suggested that myocardial dysfunction, cardiac injury and myocardial depression may be related to increased intracellular Ca2⁺ concentration resulting from STIM1/Orai1‑mediated SOCE, which may provide a potential method to alleviate septic myocardial depression.

A new approach to sepsis treatment by rasagiline: a molecular, biochemical and histopathological study

AIM

We aimed to investigate the effects of rasagiline on acute lung injury that develops in the sepsis model induced with the cecal ligation and puncture in rats.

MAIN METHODS

The rats were separated into the following six groups, Group 1: Sham, Group 2: Sham + Rasagiline 4 mg/kg, Group 3: Sepsis, Group 4: Sepsis + Rasagiline 1 mg/kg, Group 5: Sepsis + Rasagiline 2 mg/kg, Group 6: Sepsis + Rasagiline 4 mg/kg. A total of four holes were opened with a 16-gauge needle through the cecum distal to the point of ligation.

KEY FINDINGS

Rasagiline treatment increased glutathione level and superoxide dismutase activity while decreased the malondialdehyde level after the sepsis. There was a statistically significant improvement in the doses of 2 mg/kg and 4 mg/kg. Rasagiline also increased Tnf-α, IL1β, IL6, NF-κβand HMGB1 gene expressions in dose-dependent at 2 mg/kg and 4 mg/kg doses. In increased doses, rasagiline prevent the development of edema, the formation of inflammation, and hemorrhage.

SIGNIFICANCE

Rasagiline exerts both antioxidant and anti-inflammatory effects on the cecal ligation and puncture induced acute lung injury in rats.

Opioids and Sepsis: Elucidating the Role of the Microbiome and microRNA-146

Sepsis has recently been defined as life-threatening organ dysfunction caused by the dysregulated host response to an ongoing or suspected infection. To date, sepsis continues to be a leading cause of morbidity and mortality amongst hospitalized patients. Many risk factors contribute to development of sepsis, including pain-relieving drugs like opioids, which are frequently prescribed post-operatively. In light of the opioid crisis, understanding the interactions between opioid use and the development of sepsis has become extremely relevant, as opioid use is associated with increased risk of infection. Given that the intestinal tract is a major site of origin of sepsis-causing microbes, there has been an increasing focus on how alterations in the gut microbiome may predispose towards sepsis and mediate immune dysregulation. MicroRNAs, in particular, have emerged as key modulators of the inflammatory response during sepsis by tempering the immune response, thereby mediating the interaction between host and microbiome. In this review, we elucidate contributing roles of microRNA 146 in modulating sepsis pathogenesis and end with a discussion of therapeutic targeting of the gut microbiome in controlling immune dysregulation in sepsis.

Systematic analysis of myocardial immune progression in septic cardiomyopathy: Immune-related mechanisms in septic cardiomyopathy

Background

The immune infiltration and molecular mechanisms underlying septic cardiomyopathy (SC) have not been completely elucidated. This study aimed to identify key genes related to SC and elucidate the potential molecular mechanisms.

Methods

The weighted correlation network analysis (WGCNA), linear models for microarray analysis (LIMMA), protein-protein interaction (PPI) network, CIBERSORT, Kyoto Encyclopedia of Genes and Genomes pathway (KEGG), and gene set enrichment analysis (GSEA) were applied to assess the key pathway and hub genes involved in SC.

Results

We identified 10 hub genes, namely, LRG1, LCN2, PTX3, E LANE, TCN1, CLEC4D, FPR2, MCEMP1, CEACAM8, and CD177. Furthermore, we used GSEA for all genes and online tools to explore the function of the hub genes. Finally, we took the intersection between differential expression genes (DEGs) and hub genes to identify LCN2 and PTX3 as key genes. We found that immune-related pathways played vital roles in SC. LCN2 and PTX3 were key genes in SC progression, which mainly showed an anti-inflammatory effect. The significant immune cells in cardiomyocytes of SC were neutrophils and M2 macrophages.

Conclusion

These cells may have the potential to be prognostic and therapeutic targets in the clinical management of SC. Excessive anti-inflammatory function and neutrophil infiltration are probably the primary causes of SC.

Novel Insights Into the Potential Mechanisms of N6-Methyladenosine RNA Modification on Sepsis-Induced Cardiovascular Dysfunction: An Update Summary on Direct and Indirect Evidences

Sepsis is a life-threatening organ dysfunction caused by a host’s dysfunctional response to infection. As is known to all, septic heart disease occurs because pathogens invading the blood stimulate the activation of endothelial cells, causing a large number of white blood cells to accumulate and trigger an immune response. However, in severe sepsis, the hematopoietic system is inhibited, and there will also be a decline in white blood cells, at which time the autoimmune system will also be suppressed. During the immune response, a large number of inflammatory factors are released into cells to participate in the inflammatory process, which ultimately damages cardiac myocytes and leads to impaired cardiac function. N6-methyladenosine (m6A) is a common RNA modification in mRNA and non-coding RNA that affects RNA splicing, translation, stability, and epigenetic effects of some non-coding RNAs. A large number of emerging evidences demonstrated m6A modification had been involved in multiple biological processes, especially for sepsis and immune disorders. Unfortunately, there are limited results provided to analyze the association between m6A modification and sepsis-induced cardiovascular dysfunction (SICD). In this review, we firstly summarized current evidences on how m6A mediates the pathophysiological process in cardiac development and cardiomyopathy to emphasize the importance of RNA methylation in maintaining heart biogenesis and homeostasis. Then, we clarified the participants of m6A modification in extended inflammatory responses and immune system activation, which are the dominant and initial changes secondary to sepsis attack. After that, we deeply analyzed the top causes of SICD and identified the activation of inflammatory cytokines, endothelial cell dysfunction, and mitochondrial failure. Thus, the highlight of this review is that we systematically collected all the related potential mechanisms between m6A modification and SICD causes. Although there is lack of direct evidences on SICD, indirect evidences had been demonstrated case by case on every particular molecular mechanism and signal transduction, which require further explorations into the potential links among the listed mechanisms. This provides novel insights into the understanding of SICD.

Targeting Toll-Like Receptors in Sepsis: From Bench to Clinical Trials

Significance: Sepsis is a critical clinical syndrome with life-threatening organ dysfunction induced by a dysregulated host response to infection. Despite decades of intensive research, sepsis remains a leading cause of in-hospital mortality with few specific treatments. Recent Advances: Toll-like receptors (TLRs) are a part of the innate immune system and play an important role in host defense against invading pathogens such as bacteria, virus, and fungi. Using a combination of genetically modified animal models and pharmacological agents, numerous preclinical studies during the past two decades have demonstrated that dysregulated TLR signaling may contribute to sepsis pathogenesis. However, many clinical trials targeting inflammation and innate immunity such as TLR4 have yielded mixed results. Critical Issues: Here we review various TLRs and the specific molecules these TLRs sense-both the pathogen-associated and host-derived stress molecules, and their converging signaling pathways. We critically analyze preclinical investigations into the role of TLRs in animal sepsis, the complexity of targeting TLRs for sepsis intervention, and the disappointing clinical trials of the TLR4 antagonist eritoran. Future Directions: Future sepsis treatments will depend on better understanding the complex biological mechanisms of sepsis pathogenesis, the high heterogeneity of septic humans as defined by clinical presentations and unique immunological biomarkers, and improved stratifications for targeted interventions.

CRISPLD2 attenuates pro-inflammatory cytokines production in HMGB1-stimulated monocytes and septic mice

HMGB1 has been identified as a pro-inflammatory mediator which leads to sepsis lethality. Previous studies suggested that CRISPLD2 had anti-inflammatory property and might severe as a therapeutic agent in sepsis. In the present study, we first conducted bioinformatic analysis to explore the expression profile of HMGB1 in septic survivors and non-survivors. We found that the serum HMGB1 level of septic non-survivors was significantly higher than that of septic survivors, and there was a positive correlation between CRISPLD2 and HMGB1 in mRNA expression in most of the cancer and normal tissue types, revealing a co-expression or dependency relationship between the two genes. In vitro, using cultured THP-1 cells, we confirmed that HMGB1 can induce the expression of CRISPLD2 in a time dependent manner through TLR4-dependent pathway. Given that CRISPLD2 and HMGB1 shared a wide range of time scales in gene expression and the anti-inflammatory property of CRISPLD2, we further verified that HMGB1 induced cytokines production might be partially reversed by CRISPLD2. In vivo, intravenously treatment of CRISPLD2 failed to rescue septic mice, although the serum levels of inflammatory cytokines were decreased. In conclusion, our study demonstrated that HMGB1 can act as stimuli to up-regulate the expression of CRISPLD2 in THP-1 cells, and in turn, increased CRISPLD2 can curtail HMGB1 induced pro-inflammatory cytokines production. Unfortunately, the anti-inflammatory effects of CRISPLD2 did not translate into survival benefit in mice with sepsis.

Long non-coding RNA CRNDE and toll-like receptor 3 correlate with disease severity, inflammation, and mortality in sepsis

Objective

This study aimed to assess the interaction between long non‐coding RNA colorectal neoplasia differentially expressed (lncRNA CRNDE) and toll‐like receptor 3 (TLR3), and assess their correlations with disease severity, inflammation, and 28‐days mortality in sepsis patients.

Methods

We consecutively enrolled 146 sepsis patients and 146 healthy controls (HCs), and collected their peripheral blood mononuclear cells to detect lncRNA CRNDE and TLR3 expressions using reverse transcription quantitative polymerase chain reaction. LncRNA CRNDE and TLR3 in sepsis patients were classified into four clusters according to quantile expressions (Quantile 1 (0%‐24%), Quantile 2 (25%‐50%), Quantile 3 (50%‐74%), and Quantile 4 (75%‐100%)) for correlation analysis.

Results

LncRNA CRNDE was upregulated in sepsis patients compared with HCs, and it showed good value in differentiating sepsis patients form HCs by receiver operating characteristic curve analysis. In sepsis patients, lncRNA CRNDE positively correlated with acute pathologic and chronic health evaluation II (APACHE II) score and sequential organ failure assessment (SOFA) score, as well as serum creatinine (Scr). As for inflammation, lncRNA CRNDE positively correlated with C‐reactive protein (CRP), tumor necrosis factor‐α (TNF‐α), interleukin (IL)‐1β, IL‐6, and IL‐8. Regarding mortality, lncRNA CRNDE positively correlated with 28‐days mortality. Furthermore, lncRNA CRNDE positively correlated with TLR3, and TLR3 positively associated with APACHE II score, SOFA score, Scr, albumin, CRP, TNF‐α, IL‐1β, IL‐6, IL‐8, and 28‐days mortality in sepsis patients.

Conclusion

LncRNA CRNDE interacts with TLR3, both of which correlate with advanced disease severity, inflammation, and higher 28‐days mortality in sepsis patients.

Novel Role of Endothelial Derived Exosomal HSPA12B in Regulating Macrophage Inflammatory Responses in Polymicrobial Sepsis

Endothelial cell dysfunction contributes to sepsis induced initiate immune response and the infiltration of immune cells into organs, resulting in organ injury. Heat shock protein A12B (HSPA12B) is predominantly expressed in endothelial cells. The present study investigated whether endothelial HSPA12B could regulate macrophage pro-inflammatory response during sepsis. Wild type (WT) and endothelial cell-specific HSPA12B deficient (HSPA12B^-/-) mice were subjected to CLP sepsis. Mortality and cardiac function were monitored. Higher mortality, worsened cardiac dysfunction, and greater infiltrated macrophages in the myocardium and spleen were observed in HSPA12B^-/- septic mice compared with the WT septic mice. The serum levels of TNF-α and IL-1β were higher and the levels of IL-10 were lower in HSPA12B^-/- septic mice than in WT septic mice. Importantly, endothelial exosomes contain HSPA12B which can be uptaken by macrophages. Interestingly, endothelial exosomal HSPA12B significantly increases IL-10 levels and decreases TNF-α and IL-1β production in LPS-stimulated macrophages. Mechanistic studies show that endothelial exosomal HSPA12B downregulates NF-κB activation and nuclear translocation in LPS stimulated macrophages. These data suggest that endothelial HSPA12B plays a novel role in the regulation of macrophage pro-inflammatory response via exosomes during sepsis and that sepsis induced cardiomyopathy and mortality are associated with endothelial cell deficiency of HSPA12B.

Endothelial HSPA12B Exerts Protection Against Sepsis-Induced Severe Cardiomyopathy via Suppression of Adhesion Molecule Expression by miR-126

Heat shock protein A12B (HSPA12B) is predominately expressed in endothelial cells (ECs) and has been reported to protect against cardiac dysfunction from endotoxemia or myocardial infarction. This study investigated the mechanisms by which endothelial HSPA12B protects polymicrobial sepsis–induced cardiomyopathy. Wild-type (WT) and endothelial HSPA12B knockout (HSPA12B^–/–) mice were subjected to polymicrobial sepsis induced by cecal ligation and puncture (CLP). Cecal ligation and puncture sepsis accelerated mortality and caused severe cardiac dysfunction in HSPA12B^–/– mice compared with WT septic mice. The levels of adhesion molecules and the infiltrated immune cells in the myocardium of HSPA12B^–/– septic mice were markedly greater than in WT septic mice. The levels of microRNA-126 (miR-126), which targets adhesion molecules, in serum exosomes from HSPA12B^–/– septic mice were significantly lower than in WT septic mice. Transfection of ECs with adenovirus expressing HSPA12B significantly increased miR-126 levels. Increased miR-126 levels in ECs prevented LPS-stimulated expression of adhesion molecules. In vivo delivery of miR-126 carried by exosomes into the myocardium of HSPA12B^–/– mice significantly attenuated CLP sepsis increased levels of adhesion molecules, and improved CLP sepsis–induced cardiac dysfunction. The data suggest that HSPA12B protects against sepsis-induced severe cardiomyopathy via regulating miR-126 expression which targets adhesion molecules, thus decreasing the accumulation of immune cells in the myocardium.

Complement as a Major Inducer of Harmful Events in Infectious Sepsis

There is abundant evidence that infectious sepsis both in humans and mice with polymicrobial sepsis results in robust activation of complement. Major complement activation products involved in sepsis include C5a anaphylatoxin and its receptors (C5aR1 and C5aR2) and, perhaps, the terminal complement activation product, C5b-9. These products (and others) also cause dysfunction of the innate immune system, with exaggerated early proinflammatory responses, followed by decline of the innate immune system, leading to immunosuppression and multiorgan dysfunction. Generation of C5a during sepsis also leads to activation of neutrophils and macrophages and ultimate appearance of extracellular histones, which have powerful proinflammatory and prothrombotic activities. The distal complement activation product, C5b-9, triggers intracellular Ca fluxes in epithelial and endothelial cells. Histones activate the NLRP3 inflammasome, products of which can damage cells. C5a also activates MAPKs and Akt signaling pathways in cardiomyocytes, causing buildup of [Ca]i, defective action potentials and substantial cell dysfunction, resulting in cardiac and other organ dysfunction. Cardiac dysfunction can be quantitated by ECHO-Doppler parameters. In vivo interventions that block these complement-dependent products responsible for organ dysfunction in sepsis reduce the intensity of sepsis. The obvious targets in sepsis are C5a and its receptors, histones, and perhaps the MAPK pathways. Blockade of C5 has been considered in sepsis, but the FDA-approved antibody (eculizumab) is known to compromise defenses against neisseria and pneumonococcal bacteria, and requires immunization before the mAb to C5 can be used clinically. Small molecular blocking agents for C5aRs are currently in development and may be therapeutically effective for treatment of sepsis.

Attenuation of Sepsis-Induced Cardiomyopathy by Regulation of MicroRNA-23b Is Mediated Through Targeting of MyD88-Mediated NF-κB Activation

Myocardial cell injury or cardiomyopathy is associated with excessive inflammatory response and apoptosis of cardiac myocytes during sepsis. MicroRNA-23b (miR-23b) is a multifunctional miRNA that is considered to regulate immunosuppression in sepsis. The aim of this study was to examine the effect of miR-23b on cardiomyopathy induced by sepsis and to explore the potential mechanism involved. Sprague-Dawley rats were subjected to cecal ligation and puncture (CLP), and the level of miR-23b at different time points was measured by quantitative real-time polymerase chain reaction (qPCR). Then, we overexpressed miR-23b in vivo and in vitro. The rats were subjected to CLP 7 days after transfection. Cardiac function, inflammatory response, and heart tissues were examined 3 days thereafter. In an in vitro experiment, H9C2 cardiomyoblasts were stimulated with lipopolysaccharide (LPS) after transfection of miR-23b, following which apoptosis and the level of NF-κB were analyzed. The expression of miR-23b was upregulated during polymicrobial sepsis, and transfection of miR-23b lentivirus improved the outcome of sepsis-induced cardiomyopathy by attenuating inflammatory responses and protecting against histopathological damage. In in vitro experiments, elevated miR-23b inhibited excessive apoptosis of cardiomyocytes, which may be because activation of the NF-κB signaling pathway was inhibited by the decreased levels of TRAF6 and IKKβ. Therefore, miR-23b improved sepsis-induced cardiomyopathy by attenuating the inflammatory response, suppressing apoptosis, and preventing NF-κB activation via targeted inhibition of TRAF6 and IκκB. These results indicated that miR-23b may represent a novel therapeutic approach for clinical treatment of sepsis-induced cardiomyopathy.

miR-146a targeted to splenic macrophages prevents sepsis-induced multiple organ injury

Development of a novel agent against life-threatening sepsis requires the in-depth understanding of the relevant pathophysiology and therapeutic targets. Given the function of microRNAs (miRNAs) as potent oligonucleotide therapeutics, here we investigated the pathophysiological role of exogenously applied miRNA in sepsis-induced multiple organ injury. In vitro, miR-16, miR-126, miR-146a, and miR-200b suppressed the production of pro-inflammatory cytokines in RAW264.7 macrophage cells after lipopolysaccharide (LPS) stimulation. Of these, miR-146a displayed the most highly suppressive effect, wherein the transcriptional activity of nuclear factor kappa B (NF-κB) was decreased via targeting of interleukin 1 receptor-associated kinase 1 and tumor necrosis receptor-associated factor 6. Sepsis was induced in mice via cecal ligation and puncture (CLP) and an intravenous injection of a complex of miR-146a-expressing plasmid and polyethyleneimine. Treatment with this complex significantly decreased the level of serum inflammatory cytokines, attenuated organ injury including kidney injury, and led to increased survival from polymicrobial sepsis induced by CLP. miR-146a-expressing plasmid was abundantly distributed in splenic macrophages, but not in renal parenchymal cells. CLP mice treated with miR-146a displayed significantly decreased NF-κB activation and splenocyte apoptosis. Splenectomy diminished the anti-inflammatory effects of miR-146a. The collective results support the conclusion that the induction of miR-146a expression in splenic macrophages prevents excessive inflammation and sepsis-induced multiple organ injury. This study establishes a novel and critical pathophysiological role for splenic macrophage interference in sepsis-related organ injury.

Toll-like receptor 3 controls QT interval on the electrocardiogram by targeting the degradation of Kv4.2/4.3 channels in the endoplasmic reticulum

TLRs have been proven to be essential mediators for the early innate immune response. Overactivation of TLR-mediated immune signaling promotes deterioration of cardiovascular diseases; however, the role of TLRs in the heart under physiologic conditions remains neglected. Here, we show that Tlr3 deficiency induced the endoplasmic reticulum (ER) retention of Kv4.2/4.3 proteins and consequent degradation via the ubiquitin-proteasome pathway. Knockout of Tlr3 resulted in a prolonged QT interval (the space between the start of the Q wave and the end of the T wave) in mice with no significant signs of inflammation and tissue abnormality in cardiac muscles. Prolongation of action potential duration resulted from the depression of transient outward potassium channel (I_to) currents in Tlr3-deficient ventricular myocytes mirrored the change in QT interval. Mechanistically, we found that Tlr3 was exclusively localized in the ER of cardiomyocytes where it interacted with Kv4.2/4.3 subunits of I_to channel. Thus, our data indicated that TLR3 directly regulates I_to channel protein dynamics to maintain cardiac repolarization, which may implicate a new molecular surveillance system for cardiac electrophysiological homeostasis.-Gao, X., Gao, S., Guan, Y., Huang, L., Huang, J., Lin, L., Liu, Y., Zhao, H., Huang, B., Yuan, T., Liu, Y., Liang, D., Zhang, Y., Ma, X., Li, L., Li, J., Zhou, D., Shi, D., Xu, L., Chen, Y.-H. Toll-like receptor 3 controls QT interval on the electrocardiogram by targeting the degradation of Kv4.2/4.3 channels in the endoplasmic reticulum.

Harmful Roles of TLR3 and TLR9 in Cardiac Dysfunction Developing during Polymicrobial Sepsis

We determined the roles of TLR3 and TLR9 in adverse events of polymicrobial sepsis, with a focus on development of septic cardiomyopathy, progression of which we have recently shown to be complement- and histones-dependent. So Wt, TLR3-knocked out (K.O.), and TLR9-K.O. mice were subjected to polymicrobial sepsis following cecal ligation and puncture (CLP). In the absence of either TLR3 or TLR9, the intensity of echocardiogram (Echo)-Doppler dysfunction during development of cardiomyopathy was substantially reduced in the K.O. mice. Based on our prior studies emphasizing the adverse effects of plasma C5a and histones in the cardiomyopathy of sepsis, in TLR3- and TLR9-K.O. mice, there were striking reductions in plasma levels of C5a and histones as well as reduced levels of cytokines in plasma and heart tissue after CLP. Since we know that histones cause cardiac dysfunction, rat cardiomyocytes (CMs) were exposed in vitro to the histones (purified from calf thymus), which caused bleb formation on the surfaces of CMs, suggesting histones may perturb the cell membrane of CMs. In vitro, exposure of CMs to the histones for 3 hours caused lactate dehydrogenase release from CMs. These data indicate that sepsis-induced cardiac dysfunction requires presence of TLR3 and TLR9 and may be linked to histone-induced damage of CMs.

[Heart in sepsis : Molecular mechanisms, diagnosis and therapy of septic cardiomyopathy]

An impairment of cardiac function is a key feature of cardiovascular failure associated with sepsis; however, its clinical relevance is still underestimated. Recent advancements in echocardiography in patients with septic shock enable a better characterization of septic cardiomyopathy by unmasking a severe, cardiac dysfunction even in the presence of preserved left ventricular ejection fraction. The pathophysiology of septic cardiomyopathy involves a complex mixture of systemic factors and molecular, metabolic, and structural changes of the cardiomyocytes. A better understanding of these factors will enable the discovery of new therapeutic targets for urgently needed disease-modifying therapeutic interventions. To date, the cornerstone of therapeutic management lies in control of the underlying infectious process and hemodynamic stabilization. This review summarizes the pathogenesis, diagnosis, and treatment of septic cardiomyopathy, and highlights the importance of further urgently needed studies aimed at improving diagnosis and treatment for septic cardiomyopathy.

α2A-adrenergic blockade attenuates septic cardiomyopathy by increasing cardiac norepinephrine concentration and inhibiting cardiac endothelial activation

Cardiomyopathy is a common complication associated with increased mortality in sepsis, but lacks specific therapy. Here, using genetic and pharmacological approaches, we explored the therapeutic effect of α_2A-adrenergic receptor (AR) blockade on septic cardiomyopathy. CLP-induced septic rats were treated with BRL44408 (α_2A-AR antagonist), prazosin (α₁-AR antagonist) and/or reserpine. CLP-induced cardiomyopathy, indicated by reduced dP/dt and increased cardiac troponin I phosphorylation, was attenuated by BRL44408, this was associated with reduced cardiac TNF-α and endothelial VCAM-1 expression, cardiomyocyte apoptosis and related signal molecule phosphorylation. BRL44408 increased cardiac norepinephrine (NE) concentration in CLP rats. Pretreatment with reserpine that exhausts cardiac NE without affecting the circulating NE concentration or with prazosin partially abolished the cardioprotection of BRL44408 and reversed its inhibitory effects on myocardial TNF-α, apoptosis and related signal molecule phosphorylation, but not on VCAM-1 expression in septic rats. These effects of BRL44408 were confirmed by α_2A-AR gene deletion in septic mice. Furthermore, α₂-AR agonist not only enhanced LPS-induced TNF-α and VCAM-1 expression in cardiac endothelial cells that express α_2A-AR, but also enhanced LPS-induced cardiac dysfunction in isolated rat hearts. Our data indicate that α_2A-AR blockade attenuates septic cardiomyopathy by promoting cardiac NE release that activates myocardial α₁-AR and suppressing cardiac endothelial activation.

Zymosan-Induced Peritonitis: Effects on Cardiac Function, Temperature Regulation, Translocation of Bacteria, and Role of Dectin-1

Zymosan-induced peritonitis is a model commonly used to study systemic inflammatory response syndrome and multiple organ dysfunction syndrome. However, effects of zymosan on cardiac function have not been reported. We evaluated cardiac responses to zymosan in mice and the role of β-glucan and dectin-1 in mediating these responses. Temperature and cardiac function were evaluated before and after intraperitoneal (i.p.) injection of zymosan (100 or 500 mg/kg) or saline. Chronotropic and dromotropic functions were measured using electrocardiograms (ECGs) collected from conscious mice. Cardiac inotropic function was determined by echocardiography. High-dose zymosan caused a rapid and maintained hypothermia along with visual signs of illness. Baseline heart rate (HR) was unaffected but HR variability (HRV) increased, and there was a modest slowing of ventricular conduction. High-dose zymosan also caused prominent decreases in cardiac contractility at 4 and 24 h. Because zymosan is known to cause gastrointestinal tract pathology, peritoneal wash and blood samples were evaluated for bacteria at 24 h after zymosan or saline injection. Translocation of bacterial occurred in all zymosan-treated mice (n = 3), and two had bacteremia. Purified β-glucan (50 and 125 mg/kg, i.p.) had no effect on temperature or ECG parameters. However, deletion of dectin-1 modified the ECG responses to high-dose zymosan; slowing of ventricular conduction and the increase in HRV were eliminated but a marked bradycardia appeared at 24 h after zymosan treatment. Zymosan-treated dectin-1 knockout mice also showed hypothermia and visual signs of illness. Fecal samples from dectin-1 knockout mice contained more bacteria than wild types, but zymosan caused less translocation of bacteria. Collectively, these findings demonstrate that zymosan-induced systemic inflammation causes cardiac dysfunction in mice. The data suggest that dectin-1-dependent and -independent mechanisms are involved. Although zymosan treatment causes translocation of bacteria, this effect does not have a major role in the overall systemic response to zymosan.

Toll-like receptor 4-induced ryanodine receptor 2 oxidation and sarcoplasmic reticulum Ca2+ leakage promote cardiac contractile dysfunction in sepsis

Studies suggest the potential role of a sarcoplasmic reticulum (SR) Ca²⁺ leak in cardiac contractile dysfunction in sepsis. However, direct supporting evidence is lacking, and the mechanisms underlying this SR leak are poorly understood. Here, we investigated the changes in cardiac Ca²⁺ handling and contraction in LPS-treated rat cardiomyocytes and a mouse model of polymicrobial sepsis produced by cecal ligation and puncture (CLP). LPS decreased the systolic Ca²⁺ transient and myocyte contraction as well as SR Ca²⁺ content. Meanwhile, LPS increased Ca²⁺ spark-mediated SR Ca²⁺ leak. Preventing the SR leak with ryanodine receptor (RyR) blocker tetracaine restored SR load and increased myocyte contraction. Similar alterations in Ca²⁺ handling were observed in cardiomyocytes from CLP mice. Treatment with JTV-519, an anti-SR leak drug, restored Ca²⁺ handling and improved cardiac function. In the LPS-treated cardiomyocytes, mitochondrial reactive oxygen species and oxidative stress in RyR2 were increased, whereas the levels of the RyR2-associated FK506-binding protein 1B (FKBP12.6) were decreased. The Toll-like receptor 4 (TLR4)-specific inhibitor TAK-242 reduced the oxidative stress in LPS-treated cells, decreased the SR leak, and normalized Ca²⁺ handling and myocyte contraction. Consistently, TLR4 deletion significantly improved cardiac function and corrected abnormal Ca²⁺ handling in the CLP mice. This study provides evidence for the critical role of the SR Ca²⁺ leak in the development of septic cardiomyopathy and highlights the therapeutic potential of JTV-519 by preventing SR leak. Furthermore, it reveals that TLR4 activation-induced mitochondrial reactive oxygen species production and the resulting oxidative stress in RyR2 contribute to the SR Ca²⁺ leak.

Sepsis-Induced Cardiomyopathy: Mechanisms and Treatments

Sepsis is a lethal syndrome with a high incidence and a weighty economy burden. The pathophysiology of sepsis includes inflammation, immune dysfunction, and dysfunction of coagulation, while sepsis-induced cardiomyopathy (SIC), defined as a global but reversible dysfunction of both sides of the heart induced by sepsis, plays a significant role in all of the aspects above in the pathogenesis of sepsis. The complex pathogenesis of SIC involves a combination of dysregulation of inflammatory mediators, mitochondrial dysfunction, oxidative stress, disorder of calcium regulation, autonomic nervous system dysregulation, and endothelial dysfunction. The treatments for SIC include the signal pathway intervention, Chinese traditional medicine, and other specific therapy. Here, we reviewed the latest literatures on the mechanisms and treatments of SIC and hope to provide further insights to researchers and create a new road for the therapy of sepsis.

Enhanced Glycolytic Metabolism Contributes to Cardiac Dysfunction in Polymicrobial Sepsis

Background

Cardiac dysfunction is present in >40% of sepsis patients and is associated with mortality rates of up to 70%. Recent evidence suggests that glycolytic metabolism plays a critical role in host defense and inflammation. Activation of Toll-like receptors on immune cells can enhance glycolytic metabolism. This study investigated whether modulation of glycolysis by inhibition of hexokinase will be beneficial to septic cardiomyopathy.

Methods

Male C57B6/J mice were treated with a hexokinase inhibitor (2-deoxy-d-glucose [2-DG], 0.25-2 g/kg, n = 6-8) before cecal ligation and puncture (CLP) induced sepsis. Untreated septic mice served as control. Sham surgically operated mice treated with or without the 2-DG inhibitor served as sham controls. Cardiac function was assessed 6 hours after CLP sepsis by echocardiography. Serum was harvested for measurement of inflammatory cytokines and lactate.

Results

Sepsis-induced cardiac dysfunction was significantly attenuated by administration of 2-DG. Ejection fraction and fractional shortening in 2-DG-treated septic mice were significantly (P < .05) greater than in untreated CLP mice. 2-DG administration also significantly improved survival outcome, reduced kidney and liver injury, attenuated sepsis-increased serum levels of tumor necrosis factor α and interleukin 1β as well as lactate, and enhanced the expression of Sirt1 and Sirt3 in the myocardium, which play an important role in mitochondrial function and metabolism. In addition, 2-DG administration suppresses sepsis-increased expression of apoptotic inducers Bak and Bax as well as JNK phosphorylation in the myocardium.

Conclusions

Glycolytic metabolism plays an important role in mediating sepsis-induced septic cardiomyopathy. The mechanisms may involve regulation of inflammatory response and apoptotic signaling.

Diminished responsiveness to dobutamine as an inotrope in mice with cecal ligation and puncture-induced sepsis: attribution to phosphodiesterase 4 upregulation

Dobutamine has been used in septic shock for many years as an only inotrope, but its benefit has been questioned. We weighed the effects of dobutamine and milrinone as inotropes in mice with cecal ligation and puncture (CLP)-induced polymicrobial sepsis. CLP-induced septic mice exhibited significant cardiac inflammation, as indicated by greatly increased mRNAs of proinflammatory cytokines and robust infiltration of inflammatory cells in the ventricular myocardium. Elevations of plasma cardiac troponin-I showed cardiac injury in CLP mice. Noninvasive echocardiographic assessment of cardiac function revealed that despite preserved left ventricular function in the presence of fluid replacement, the dobutamine inotropic response was significantly impaired in CLP mice compared with sham-operated controls. By contrast, milrinone exerted inotropic effects in sham-operated and CLP mice in an equally effective manner. Surface expression levels of β₁-adrenoceptors and α-subunits of three main G protein families in the myocardium were unaffected by CLP-induced sepsis. Plasma cAMP levels were significantly elevated in both sham-operated and CLP mice in response to milrinone but only in sham-operated controls in response to dobutamine. Of phosphodiesterase (PDE) isoforms, PDE4D, but not PDE3A, both of which are responsible for cardiac cAMP hydrolysis, was significantly upregulated in CLP mouse myocardium. We define a novel mechanism for the impaired responsiveness to dobutamine as an inotrope in sepsis, and understanding the role of PDE4D in modulating cardiac functional responsiveness in sepsis may open the potential of a PDE4D-targeted therapeutic option in septic patients with low cardiac output who have a need for inotropic support.NEW & NOTEWORTHY Advisability of the usefulness of dobutamine in septic shock management is limited. Here, we reveal that the effect of dobutamine as a positive inotrope is impaired in mice with cecal ligation and puncture-induced sepsis without changes in cardiac β₁-adrenoceptor signaling as a result of cAMP breakdown achieved by upregulated phosphodiesterase 4D.

MicroRNA-125b Prevents Cardiac Dysfunction in Polymicrobial Sepsis by Targeting TRAF6-Mediated Nuclear Factor κB Activation and p53-Mediated Apoptotic Signaling

BACKGROUND

 This study examined the effect of microRNA-125b (miR-125b) on sepsis-induced cardiac dysfunction.

METHODS

 Mouse hearts were transfected with lentivirus expressing miR-125b (LmiR-125b) 7 days before cecal ligation and puncture (CLP)-induced sepsis. Cardiac function was examined by echocardiography before and 6 hours after CLP (n = 6/group). Survival was monitored following CLP-induced sepsis (n = 12/group).

RESULTS

 LmiR-125b transfection significantly attenuated cardiac dysfunction due to CLP-induced sepsis. Fractional shortening and ejection fraction values were significantly (P < .05) higher in the LmiR-125b-treated CLP group than in the untreated CLP group. Survival outcome in LmiR-125b-transfected septic mice was markedly improved, compared with mice with CLP-induced sepsis. Transfection of LmiR-125b into the heart significantly suppressed the expression of ICAM-1 and VCAM-1, decreased the accumulation of macrophages and neutrophils in the myocardium, and decreased serum levels of tumor necrosis factor α and interleukin 1β by targeting tumor necrosis factor receptor-associated factor 6 (TRAF6)-mediated nuclear factor κB (NF-κB) activation. In addition, sepsis-induced myocardial apoptosis was markedly attenuated by LmiR-125b transfection through suppression of p53, Bax, and Bak1 expression. In vitro transfection of endothelial cells with miR-125b mimics attenuate LPS-induced ICAM-1 and VCAM-1 expression by suppressing TRAF6 and NF-κB activation.

CONCLUSIONS

 Increased myocardial miR-125b expression attenuates sepsis-induced cardiac dysfunction and improves survival. miR-125b may be a target for septic cardiomyopathy.

Therapeutic Potential of Cerium Oxide Nanoparticles for the Treatment of Peritonitis Induced by Polymicrobial Insult in Sprague-Dawley Rats

OBJECTIVES

Peritonitis is a life-threatening disease that is associated with high mortality. The purpose of this study was to determine if cerium oxide nanoparticles can be used to diminish intra-abdominal infection-induced mortality and systemic inflammatory response syndrome in the laboratory rat.

DESIGN

Randomized, controlled animal study and cell culture study.

SETTING

University research laboratory.

SUBJECTS

Male Sprague-Dawley rats aged 12 weeks, RAW 246.7 macrophage cell line.

INTERVENTIONS

Intra-abdominal infection or peritonitis was induced by intraperitoneal injection of cecal material (600 mg/kg in 5% sterile dextrose water at a dosage of 5 mL/kg) obtained from healthy donors. Rats in control and peritonitis groups received 200 μL of sterile deionized water IV via the tail vein, whereas rats in cerium oxide-only group and peritonitis+cerium oxide group received cerium oxide nanoparticles (0.5 mg/kg) IV at the time of polymicrobial injection. Survival rate was monitored for 14 days, while in other experiments, animals were killed at 3 and 18 hours after induction of peritonitis for biochemical analysis.

MEASUREMENTS AND MAIN RESULTS

Administration of a single dose (0.5 mg/kg) of cerium oxide nanoparticles IV to rats in the peritonitis group significantly improved survival rates and functioned to restore core body temperature toward baseline. Treatment-induced increases in animal survivability were associated with reduced systemic and hepatic oxidative stress, diminished serum cytokines, and chemokine levels. Changes in serum inflammatory markers with treatment were accompanied by decreased monocyte and lymphocyte extravasation into the peritoneal cavity along with decreased infiltration of macrophages into liver. In the heart, treatment diminished extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase-Stat-3 signaling and attenuated endothelial expression of P-selectin and vascular cell adhesion molecule-1.

CONCLUSIONS

Cerium oxide nanoparticles attenuate the systemic inflammatory response associated with peritonitis, suggesting potential use as a novel therapeutic agent for the treatment of severe intra-abdominal infection.

Attenuation of cardiac dysfunction and remodeling of myocardial infarction by microRNA-130a are mediated by suppression of PTEN and activation of PI3K dependent signaling

OBJECTIVE

Activation of PI3K/Akt signaling protects the myocardium from ischemia/reperfusion injury. MicroRNAs have been demonstrated to play an important role in the regulation of gene expression at the post-transcriptional level. In this study, we examined whether miR-130a will attenuate cardiac dysfunction and remodeling after myocardial infarction (MI) via PI3K/Akt dependent mechanism.

APPROACHES AND RESULTS

To determine the role of miR-130a in the proliferation and migration of endothelial cells, HUVECs were transfected with miR-130a mimics before the cells were subjected to scratch-induced wound injury. Transfection of miR-130a mimics stimulated the migration of endothelial cells into the wound area and increased phospho-Akt levels. To examine the effect of miR-130a on cardiac dysfunction and remodeling after MI, Lentivirus expressing miR-130a (LmiR-130a) was delivered into mouse hearts seven days before the mice were subjected to MI. Cardiac function was assessed by echocardiography before and for up to 21 days after MI. Ejection fraction (EF%) and fractional shortening (FS%) in the LmiR-130a transfected MI hearts were significantly greater than in LmiR-control and untransfected control MI groups. LmiR-130a transfection increased capillary number and VEGF expression, and decreased collagen deposition in the infarcted myocardium. Importantly, LmiR-130a transfection significantly suppressed PTEN expression and increased the levels of phosphorylated Akt in the myocardium. However, treatment of LmiR-130a-transfected mice with LY294002, a PI3K inhibitor, completely abolished miR-130a-induced attenuation of cardiac dysfunction after MI.

CONCLUSIONS

miR-130a plays a critical role in attenuation of cardiac dysfunction and remodeling after MI. The mechanisms involve activation of PI3K/Akt signaling via suppression of PTEN expression.

Blockade of exosome generation with GW4869 dampens the sepsis-induced inflammation and cardiac dysfunction

Sepsis is an infection-induced severe inflammatory disorder that leads to multiple organ failure. Amongst organs affected, myocardial depression is believed to be a major contributor to septic death. While it has been identified that large amounts of circulating pro-inflammatory cytokines are culprit for triggering cardiac dysfunction in sepsis, the underlying mechanisms remain obscure. Additionally, recent studies have shown that exosomes released from bacteria-infected macrophages are pro-inflammatory. Hence, we examined in this study whether blocking the generation of exosomes would be protective against sepsis-induced inflammatory response and cardiac dysfunction. To this end, we pre-treated RAW264.7 macrophages with GW4869, an inhibitor of exosome biogenesis/release, followed by endotoxin (LPS) challenge. In vivo, we injected wild-type (WT) mice with GW4869 for 1h prior to endotoxin treatment or cecal ligation/puncture (CLP) surgery. We observed that pre-treatment with GW4869 significantly impaired release of both exosomes and pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) in RAW264.7 macrophages. At 12h after LPS treatment or CLP surgery, WT mice pre-treated with GW4869 displayed lower amounts of exosomes and pro-inflammatory cytokines in the serum than control PBS-injected mice. Accordingly, GW4869 treatment diminished the sepsis-induced cardiac inflammation, attenuated myocardial depression and prolonged survival. Together, our findings indicate that blockade of exosome generation in sepsis dampens the sepsis-triggered inflammatory response and thereby, improves cardiac function and survival.

Attenuation of Cardiac Dysfunction in Polymicrobial Sepsis by MicroRNA-146a Is Mediated via Targeting of IRAK1 and TRAF6 Expression

Cardiac dysfunction is a major consequence of sepsis/septic shock and contributes to the high mortality of sepsis. Innate and inflammatory responses mediated by TLRs play a critical role in sepsis-induced cardiac dysfunction. MicroRNA-146 (miR-146) was first identified as a negative regulator in innate immune and inflammatory responses induced by LPS. This study examined whether miR-146a will have a protective effect on sepsis-induced cardiac dysfunction. Lentivirus-expressing miR-146a (LmiR-146a) or lentivirus-expressing scrambled miR (LmiR-control) was delivered into the myocardium via the right carotid artery. Seven days after transfection, mice were subjected to cecal ligation and puncture (CLP). Untransfected mice were also subjected to CLP-induced sepsis. Cardiac function was examined by echocardiography before and 6 h after CLP. In vitro studies showed that increased miR-146a levels suppress LPS-induced IκBα phosphorylation and inflammatory cytokine production in both H9C2 cardiomyocytes and J774 macrophages. In vivo transfection of LmiR-146a attenuated sepsis-induced cardiac dysfunction. The values for percent ejection fraction and percent fractional shortening in LmiR-146a-transfected CLP mice were significantly greater than in untransfected CLP control. LmiR-146a transfection prevented sepsis-induced NF-κB activity, suppressed IRAK and TRAF6 expression in the myocardium, and attenuated sepsis-induced inflammatory cytokine production in both plasma and peritoneal fluid. In addition, LmiR-146a transfection decreased sepsis-induced infiltration of neutrophils and macrophages into the myocardium. LmiR-146a can also transfect macrophages in the periphery. We conclude that miR-146a attenuates sepsis-induced cardiac dysfunction by preventing NF-κB activation, inflammatory cell infiltration, and inflammatory cytokine production via targeting of IRAK and TRAF6 in both cardiomyocytes and inflammatory monocytic cells.

Attenuation of Cardiac Dysfunction in Polymicrobial Sepsis by MicroRNA-146a Is Mediated via Targeting of IRAK1 and TRAF6 Expression

Cardiac dysfunction is a major consequence of sepsis/septic shock and contributes to the high mortality of sepsis. Innate and inflammatory responses mediated by TLRs play a critical role in sepsis-induced cardiac dysfunction. MicroRNA-146 (miR-146) was first identified as a negative regulator in innate immune and inflammatory responses induced by LPS. This study examined whether miR-146a will have a protective effect on sepsis-induced cardiac dysfunction. Lentivirus-expressing miR-146a (LmiR-146a) or lentivirus-expressing scrambled miR (LmiR-control) was delivered into the myocardium via the right carotid artery. Seven days after transfection, mice were subjected to cecal ligation and puncture (CLP). Untransfected mice were also subjected to CLP-induced sepsis. Cardiac function was examined by echocardiography before and 6 h after CLP. In vitro studies showed that increased miR-146a levels suppress LPS-induced IκBα phosphorylation and inflammatory cytokine production in both H9C2 cardiomyocytes and J774 macrophages. In vivo transfection of LmiR-146a attenuated sepsis-induced cardiac dysfunction. The values for percent ejection fraction and percent fractional shortening in LmiR-146a-transfected CLP mice were significantly greater than in untransfected CLP control. LmiR-146a transfection prevented sepsis-induced NF-κB activity, suppressed IRAK and TRAF6 expression in the myocardium, and attenuated sepsis-induced inflammatory cytokine production in both plasma and peritoneal fluid. In addition, LmiR-146a transfection decreased sepsis-induced infiltration of neutrophils and macrophages into the myocardium. LmiR-146a can also transfect macrophages in the periphery. We conclude that miR-146a attenuates sepsis-induced cardiac dysfunction by preventing NF-κB activation, inflammatory cell infiltration, and inflammatory cytokine production via targeting of IRAK and TRAF6 in both cardiomyocytes and inflammatory monocytic cells.

Toll-like receptor 4 plays a central role in cardiac dysfunction during trauma hemorrhage shock

Cardiac dysfunction is a major consequence that contributes to the high mortality of trauma-hemorrhage (TH) patients. Recent evidence suggests that innate immune and inflammatory responses mediated by Toll-like receptors (TLRs) play a critical role in the pathophysiologic mechanisms of acute organ dysfunction during TH. This study investigated the role of TLR4 in cardiac dysfunction following TH. Toll-like receptor 4-deficient (TLR4-/-, n = 7/group) and age-matched wild-type (WT, n = 8/group) mice were subjected to TH that was induced by soft tissue injury and blood withdrawal from the jugular vein to a mean arterial pressure of 35 ± 5 mmHg. Cardiac function and mean arterial pressure were measured with a Millar system before, during, and after blood withdrawal. Sham surgical-operated mice served as control (WT, n = 9/group; TLR4-/-, n = 10/group). Cardiac function in WT mice was significantly reduced following TH. However, cardiac function was well preserved in TLR4-/- mice. Administration of a TLR4 antagonist (3 mg/kg) to WT mice also significantly attenuated TH-induced cardiac dysfunction. Western blot showed that either TLR4-/- or TLR4 antagonist markedly attenuated TH-induced decreases in the levels of phosphorylated-Akt in myocardium. In addition, inhibition of TLR4 attenuated TH-induced myocardial nuclear factor κB-binding activity as well as lung myeloperoxidase activity and tumor necrosis factor α production. The data indicate that TLR4 plays a central role in TH-induced cardiac dysfunction. Toll-like receptor 4 deficiency or TLR4 inhibition attenuated cardiac dysfunction following TH, which may involve activation of the phosphoinositide 3-kinase/Akt signaling and decrease in nuclear factor κB-binding activity. Toll-like receptor 4 antagonism may be a new and novel approach for the treatment and management of cardiac dysfunction in TH patients.

An ongoing search for potential targets and therapies for lethal sepsis

Sepsis, which refers to a systemic inflammatory response syndrome resulting from a microbial infection, represents the leading cause of death in intensive care units. The pathogenesis of sepsis remains poorly understood although it is attributable to dysregulated immune responses orchestrated by innate immune cells that are sequentially released early (e.g., tumor necrosis factor(TNF), interleukin-1(IL-1), and interferon-γ(IFN-γ)) and late (e.g., high mobility group box 1(HMGB1)) pro-inflammatory mediators. As a ubiquitous nuclear protein, HMGB1 can be passively released from pathologically damaged cells, thereby converging infection and injury on commonly dysregulated inflammatory responses. We review evidence that supports extracellular HMGB1 as a late mediator of inflammatory diseases and discuss the potential of several Chinese herbal components as HMGB1-targeting therapies. We propose that it is important to develop strategies for specifically attenuating injury-elicited inflammatory responses without compromising the infection-mediated innate immunity for the clinical management of sepsis and other inflammatory diseases.

A novel 1,2-benzenediamine derivative FC-99 suppresses TLR3 expression and ameliorates disease symptoms in a mouse model of sepsis

BACKGROUND AND PURPOSE

Sepsis is a clinical condition characterized by overwhelming systemic inflammation with high mortality rate and high prevalence, but effective treatment is still lacking. Toll-like receptor 3 (TLR3) is an endogenous sensor, thought to regulate the amplification of immune response during sepsis. Modulators of TLR3 have an advantage in the treatment of sepsis. Here, we aimed to explore the mechanism of a monosubstituted 1,2-benzenediamine derivative FC-99 {N(1) -[(4-methoxy)methyl]-4-methyl-1,2-benzenediamine}on modulating TLR3 expression and its therapeutic potential on mouse model of sepsis.

EXPERIMENTAL APPROACH

Cells were pretreated with FC-99 followed by poly(I:C) or IFN-α stimulation; TLR3 and other indicators were assayed. Female C57BL/6 mice were subjected to sham or caecal ligation puncture (CLP) surgery after i.p. injection of vehicle or FC-99; serum and tissues were collected for further experiments.

KEY RESULTS

FC-99 suppressed inflammatory response induced by poly(I:C) with no effect on cell viability or uptake of poly(I:C). FC-99 also inhibited TLR3 expression induced by not only poly(I:C) but also by exogenous IFN-α. This inhibition of FC-99 was related to the poly(I:C)-evoked IRF3/IFN-α/JAK/STAT1 signalling pathway. In CLP-induced model of sepsis, FC-99 administration decreased mice mortality and serum levels of inflammatory factors, attenuated multiple organ dysfunction and enhanced bacterial clearance. Accordingly, systemic and local expression of TLR3 was reduced by FC-99 in vivo.

CONCLUSION AND IMPLICATIONS

FC-99 reversed TLR3 expression and ameliorate CLP-induced sepsis in mice. Thus, FC-99 will be a potential therapeutic candidate for sepsis.

UVB radiation illuminates the role of TLR3 in the epidermis

UV radiation poses a significant risk to human health. The mechanisms that help repair UV-damaged cells have recently been more clearly defined with the observation that Toll-like receptor 3 can sense self RNA released from necrotic keratinocytes following UV damage. TLR3 activation in the skin induces inflammation and increases expression of genes involved in skin barrier repair. Activation of TLR2 in the skin by commensal microbial products prevents excessive inflammation by blocking downstream TLR3 signaling. This review highlights how UV damage induced inflammation in the skin is propagated by host products and regulated by host inhabitants.

Extracellular Hb enhances cardiac toxicity in endotoxemic guinea pigs: protective role of haptoglobin

Endotoxemia plays a major causative role in the myocardial injury and dysfunction associated with sepsis. Extracellular hemoglobin (Hb) has been shown to enhance the pathophysiology of endotoxemia. In the present study, we examined the myocardial pathophysiology in guinea pigs infused with lipopolysaccharide (LPS), a Gram-negative bacterial endotoxin, and purified Hb. We also examined whether the administration of the Hb scavenger haptoglobin (Hp) could protect against the effects observed. Here, we show that Hb infusion following LPS administration, but not either insult alone, increased myocardial iron deposition, heme oxygenase-1 expression, phagocyte activation and infiltration, as well as oxidative DNA damage and apoptosis assessed by 8-hydroxy-2'-deoxyguanosine (8-OHdG) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) immunostaining, respectively. Co-administration of Hp significantly attenuated the myocardial events induced by the combination of LPS and Hb. These findings may have relevant therapeutic implications for the management of sepsis during concomitant disease or clinical interventions associated with the increased co-exposures to LPS and Hb, such as trauma, surgery or massive blood transfusions.

MicroRNA-125b protects against myocardial ischaemia/reperfusion injury via targeting p53-mediated apoptotic signalling and TRAF6

AIMS

The present study examined the role of microRNA-125b (miR-125b) in myocardial ischaemia/reperfusion (I/R) injury. We constructed lentivirus-expressing miR-125b (LmiR-125b) and developed transgenic mice with overexpression of miR-125b.

METHODS AND RESULTS

LmiR-125b was transfected into mouse hearts through the right common carotid artery. Lentivirus vector (LmiR-Con) served as vector control. Untreated mice served as I/R control. Sham operation served as sham control. Seven days after transfection, the hearts were subjected to ischaemia (45 min) followed by reperfusion (4 h). Myocardial infarct size was analysed by 2,3,5-triphenyltetrazolium chloride staining. In separate experiments, hearts were subjected to ischaemia (45 min) followed by reperfusion for up to 7 days. Cardiac function was measured by echocardiography before, as well as 3 and 7 days after myocardial I/R. Increased expression of miR-125b significantly decreased I/R-induced myocardial infarct size by 60% and prevented I/R-induced decreases in ejection fraction (EF%) and fractional shortening (%FS). Transgenic mice with overexpression of miR-125b also showed the protection against myocardial I/R injury. Increased expression of miR-125b attenuated I/R-induced myocardial apoptosis and caspase-3/7 and -8 activities. Western blot showed that increased expression of miR-125b suppresses p53 and Bak1 expression in the myocardium. In addition, transfection of LmiR-125b decreased the levels of TNF receptor-associated factor 6 (TRAF6) and prevented I/R-induced NF-κB activation.

CONCLUSION

miR-125 protects the myocardium from I/R injury by preventing p53-mediated apoptotic signalling and suppressing TRAF6-mediated NF-κB activation.

Connection between cardiac vascular permeability, myocardial edema, and inflammation during sepsis: role of the α1AMP-activated protein kinase isoform

OBJECTIVE

As adenosine monophosphate (AMP)-activated protein kinase both controls cytoskeleton organization in endothelial cells and exerts anti-inflammatory effects, we here postulated that it could influence vascular permeability and inflammation, thereby counteracting cardiac wall edema during sepsis.

DESIGN

Controlled animal study.

SETTINGS

University research laboratory.

SUBJECTS

C57BL/6J, α1AMPK, and α1AMPK mice.

INTERVENTION

Sepsis was triggered in vivo using a sublethal injection of lipopolysaccharide (O55B5, 10 mg/kg), inducing systolic left ventricular dysfunction. Left ventricular function, edema, vascular permeability, and inflammation were assessed in vivo in both wild-type mice (α1AMPK) and α1AMP-activated protein kinase-deficient mice (α1AMPK). The 5-aminoimidazole-4-carboxamide riboside served to study the impact of AMP-activated protein kinase activation on vascular permeability in vivo. The integrity of endothelial cell monolayers was also examined in vitro after lipopolysaccharide challenge in the presence of aminoimidazole-4-carboxamide riboside and/or after α1AMP-activated protein kinase silencing.

MEASUREMENTS AND MAIN RESULTS

α1AMP-activated protein kinase deficiency dramatically impaired tolerance to lipopolysaccharide challenge. Indeed, α1AMPK exhibited heightened cardiac vascular permeability after lipopolysaccharide challenge compared with α1AMPK. Consequently, an increase in left ventricular mass corresponding to exaggerated wall edema occurred in α1AMPK, without any further decrease in systolic function. Mechanistically, the lipopolysaccharide-induced α1AMPK cardiac phenotype could not be attributed to major changes in the systemic inflammatory response but was due to an increased disruption of interendothelial tight junctions. Accordingly, AMP-activated protein kinase activation by aminoimidazole-4-carboxamide riboside counteracted lipopolysaccharide-induced hyperpermeability in wild-type mice in vivo as well as in endothelial cells in vitro. This effect was associated with a potent protection of zonula occludens-1 linear border pattern in endothelial cells.

CONCLUSIONS

Our results demonstrate for the first time the involvement of a signaling pathway in the control of left ventricular wall edema during sepsis. AMP-activated protein kinase exerts a protective action through the preservation of interendothelial tight junctions. Interestingly, exaggerated left ventricular wall edema was not coupled with aggravated systolic dysfunction. However, it could contribute to diastolic dysfunction in patients with sepsis.

Targeting HMGB1 in the treatment of sepsis

INTRODUCTION

Sepsis refers to the host's deleterious and non-resolving systemic inflammatory response to microbial infections and represents the leading cause of death in the intensive care unit. The pathogenesis of sepsis is complex, but partly mediated by a newly identified alarmin molecule, the high mobility group box 1 (HMGB1).

AREAS COVERED

Here we review the evidence that support extracellular HMGB1 as a late mediator of experimental sepsis with a wider therapeutic window and discuss the therapeutic potential of HMGB1-neutralizing antibodies and small molecule inhibitors (herbal components) in experimental sepsis.

EXPERT OPINION

It will be important to evaluate the efficacy of HMGB1-targeting strategies for the clinical management of human sepsis in the future.