Evidence of myocardial hibernation in the septic heart*

ITGAM: A Pivotal Regulator in Macrophage Dynamics and Cardiac Function During Sepsis-Induced Cardiomyopathy

BACKGROUND

Sepsis-induced cardiomyopathy (SIC) is a critical complication arising from sepsis characterized by reversible myocardial dysfunction. Despite the increasing attention to SIC in research, the underlying molecular mechanisms remain poorly comprehended.

METHODS

In this study, we utilized bioinformatics to analyze RNA-sequencing (RNA-seq) and single-cell RNA-sequencing (scRNA-seq) data from the Gene Expression Omnibus (GEO) database to identify key immune cell populations and molecular markers associated with SIC. Our experimental approach combined in vitro and in vivo studies to investigate the roles of integrin alpha M (ITGAM) and intracellular adhesion molecule-1 (ICAM-1) in macrophage recruitment and phenotypic polarization, as well as their impact on cardiac function during SIC.

RESULTS

The bioinformatics analysis disclosed significant alterations in gene expression and immune cell composition within the cardiac tissue during SIC, where macrophages emerged as the predominant immune cell type. Notably, ITGAM was identified as a key regulatory molecule that modulates macrophage function, driving the pathogenesis of SIC through its influence on the recruitment and functional reprogramming of these cells. In vitro experiments revealed that lipopolysaccharide (LPS) stimulation triggered an upregulation of ITGAM in macrophages and ICAM-1 in endothelial cells, underscoring their critical roles in immune cell mobilization and intercellular communication. The strategic administration of ITGAM-neutralizing antibodies to SIC mice resulted in a marked decrease in macrophage infiltration within the cardiac tissue, which was initially associated with an improvement in cardiac function. However, this intervention paradoxically resulted in an increased mortality rate during the later phases of SIC, underscoring the complex and dualistic function of ITGAM.

CONCLUSION

This study provides new insights into the complex dynamics of immune cells within the cardiac environment during SIC, with a particular emphasis on the modulatory role of ITGAM in shaping macrophage behavior. The findings shed light on the reversible nature of myocardial dysfunction in SIC and emphasize the importance of targeted therapeutic strategies for the effective management of SIC.

A novel speckle-tracking echocardiography parameter assessing left ventricular afterload

BACKGROUND

Left ventricular stroke work index (LVSWI) and afterload-related cardiac performance (ACP) consider left ventricular (LV) afterload and could be better prognosticators in septic cardiomyopathy. However, their invasive nature prevents their routine clinical applications. This study aimed to investigate (1) whether a proposed speckle-tracking echocardiography parameter, Pressure-Strain Product (PSP), can non-invasively predict catheter-based LVSWI, ACP and serum lactate in an ovine model of septic cardiomyopathy; and (2) whether PSP can distinguish the sub-phenotypes of acute respiratory distress syndrome (ARDS) with or without sepsis-like conditions.

METHODS

Sixteen sheep with ARDS were randomly assigned to either (1) sepsis-like (n = 8) or (2) non-sepsis-like (n = 8) group. Each ARDS and sepsis-like condition was induced by intravenous infusion of oleic acid and lipopolysaccharide, respectively. Pulmonary artery catheter-based LVSWI (the product of stroke work index, mean arterial pressure and .0136), ACP (the percentage of cardiac output measured to cardiac output predicted as normal) and serum lactate were measured simultaneously with transthoracic echocardiography. Two PSP indices were calculated by multiplying the mean arterial blood pressure and either global circumferential strain (PSPcirc) or radial strain (PSPrad).

RESULTS

PSPcirc showed a significant correlation with LVSWI (r2  = .66, p < .001) and ACP (r2  = .82, p < .001) in the sepsis-like group. Although PSP could not distinguish subphenotypes, PSPcirc predicted LVSWI (AUC .86) and ACP (AUC .88), and PSPrad predicted serum lactate (AUC .75) better than LV ejection fraction, global circumferential and radial strain.

CONCLUSIONS

A novel PSP has the potential to non-invasively predict catheter-based LVSWI and ACP, and was associated with serum lactate in septic cardiomyopathy.

Extending the 'host response' paradigm from sepsis to cardiogenic shock: evidence, limitations and opportunities

Recent clinical and research efforts in cardiogenic shock (CS) have largely focussed on the restoration of the low cardiac output state that is the conditio sine qua non of the clinical syndrome. This approach has failed to translate into improved outcomes, and mortality has remained static at 30-50%. There is an unmet need to better delineate the pathobiology of CS to understand the observed heterogeneity of presentation and treatment effect and to identify novel therapeutic targets. Despite data in other critical illness syndromes, specifically sepsis, the role of dysregulated inflammation and immunity is hitherto poorly described in CS. High-dimensional molecular profiling, particularly through leukocyte transcriptomics, may afford opportunity to better characterise subgroups of patients with shared mechanisms of immune dysregulation. In this state-of-the-art review, we outline the rationale for considering molecular subtypes of CS. We describe how high-dimensional molecular technologies can be used to identify these subtypes, and whether they share biological features with sepsis and other critical illness states. Finally, we propose how the identification of molecular subtypes of patients may enrich future clinical trial design and identification of novel therapies for CS.

Melatonin as a potential treatment for septic cardiomyopathy

Septic cardiomyopathy (SCM) is a common complication of sepsis contributing to high mortality rates. Its pathophysiology involves complex factors, including inflammatory cytokines, mitochondrial dysfunction, oxidative stress, and immune dysregulation. Despite extensive research, no effective pharmacological agent has been established for sepsis-induced cardiomyopathy. Melatonin, a hormone with diverse functions in the body, has emerged as a potential agent for SCM through its anti-oxidant, anti-inflammatory, anti-apoptotic, and cardioprotective roles. Through various molecular levels of its mechanism of action, it counterattacks the adverse event of sepsis. Experimental studies have mentioned that melatonin protects against many cardiovascular diseases and exerts preventive effects on SCM. Moreover, melatonin has been investigated in combination with other drugs such as antibiotics, resveratrol, and anti-oxidants showing synergistic effects in reducing inflammation, anti-oxidant, and improving cardiac function. While preclinical studies have demonstrated positive results, clinical trials are required to establish the optimal dosage, route of administration, and treatment duration for melatonin in SCM. Its safety profile, low toxicity, and natural occurrence in the human body provide a favorable basis for its clinical use. This review aims to provide an overview of the current evidence of the use of melatonin in sepsis-induced cardiomyopathy (SICM). Melatonin appears to be promising as a possible treatment for sepsis-induced cardiomyopathy and demands further investigation.

Mitochondria in health, disease, and aging

Mitochondria are well known as organelles responsible for the maintenance of cellular bioenergetics through the production of ATP. Although oxidative phosphorylation may be their most important function, mitochondria are also integral for the synthesis of metabolic precursors, calcium regulation, the production of reactive oxygen species, immune signaling, and apoptosis. Considering the breadth of their responsibilities, mitochondria are fundamental for cellular metabolism and homeostasis. Appreciating this significance, translational medicine has begun to investigate how mitochondrial dysfunction can represent a harbinger of disease. In this review, we provide a detailed overview of mitochondrial metabolism, cellular bioenergetics, mitochondrial dynamics, autophagy, mitochondrial damage-associated molecular patterns, mitochondria-mediated cell death pathways, and how mitochondrial dysfunction at any of these levels is associated with disease pathogenesis. Mitochondria-dependent pathways may thereby represent an attractive therapeutic target for ameliorating human disease.

Cardiac Troponin I and Electrocardiographic Evaluation in Hospitalized Cats with Systemic Inflammatory Response Syndrome

Several studies conducted on humans demonstrate the increase in cardiac troponins and the onset of arrhythmias in the course of systemic inflammatory response syndrome (SIRS). The aim of the current study was to assess the blood concentration of cardiac troponin I (cTnI) and electrocardiographic findings in SIRS-affected cats. Seventeen shorthair cats hospitalized with SIRS were enrolled (Group 1). SIRS diagnosis was performed based on the detection of at least two of the four criteria such as abnormal body temperature, abnormal heart rate (i.e., tachycardia or bradycardia), abnormal respiratory rate (i.e., tachypnea or bradypnea), and alterations of white blood cell number (i.e., leukocytes or band neutrophils). Ten cats screened for elective surgery such as neutering or dental procedures were evaluated as a control population (Group 2). They were considered healthy based on history, physical examination, hematological and biochemical profile, urinalysis, coprological exam, thyroxine assay, blood pressure measurement, and echocardiography. A physical examination, complete blood cell count, biochemistry test (including an electrolyte panel), electrocardiographic examination, and cTnI assay were carried out in each cat enrolled. Traumatic events, gastrointestinal, neoplastic, respiratory, and neurological disorders were identified as causes of SIRS in Group 1. In Group 1, a significantly higher concentration of cTnI than that in Group 2 was recorded (p = 0.004). In 37.5% of cats with SIRS, ventricular premature complexes occurring in couplets with multiform configuration were detected. Similarly, to humans, data herein reported would indicate possible cardiac damage present in cats with SIRS diagnosis.

RIGHT VENTRICULAR DYSFUNCTION IN SEPSIS: AN UPDATED NARRATIVE REVIEW

ABSTRACT

Sepsis is a multisystem disease process, which constitutes a significant public health challenge and is associated with high morbidity and mortality. Among other systems, sepsis is known to affect the cardiovascular system, which may manifest as myocardial injury, arrhythmias, refractory shock, and/or septic cardiomyopathy. Septic cardiomyopathy is defined as the reversible systolic and/or diastolic dysfunction of one or both ventricles. Left ventricle dysfunction has been extensively studied in the past, and its prognostic role in patients with sepsis is well documented. However, there is relatively scarce literature on right ventricle (RV) dysfunction and its role. Given the importance of timely detection of septic cardiomyopathy and its bearing on prognosis of patients, the role of RV dysfunction has come into renewed focus. Hence, through this review, we sought to describe the pathophysiology of RV dysfunction in sepsis and what have we learnt so far about its multifactorial nature. We also elucidate the roles of different biomarkers for its detection and prognosis, along with appropriate management of such patient population.

Infection as an under-recognized precipitant of acute heart failure: prognostic and therapeutic implications

As the prevalence of heart failure (HF) continues to rise, prompt diagnosis and management of various medical conditions, which may lead to HF exacerbation and result in poor patient outcomes, are of paramount importance. Infection has been identified as a common, though under-recognized, precipitating factor of acute heart failure (AHF), which can cause rapid development or deterioration of HF signs and symptoms. Available evidence indicates that infection-related hospitalizations of patients with AHF are associated with higher mortality, protracted length of stay, and increased readmission rates. Understanding the intricate interaction of both clinical entities may provide further therapeutic strategies to prevent the occurrence of cardiac complications and improve prognosis of patients with AHF triggered by infection. The purpose of this review is to investigate the incidence of infection as a causative factor in AHF, explore its prognostic implications, elucidate the underlying pathophysiological mechanisms, and highlight the basic principles of the initial diagnostic and therapeutic interventions in the emergency department.

Increasing illness severity is associated with global myocardial dysfunction in the first 24 hours of sepsis admission

Background

Septic cardiomyopathy was recognized more than 30 years ago, but the early phase remains uncharacterized as no existing studies captured patients at the time of Emergency Department (ED) presentation, prior to resuscitation. Therapeutic interventions alter cardiac function, thereby distorting the relationship with disease severity and outcomes. The goal of this study was to assess the impact of illness severity on cardiac function during the first 24 h of sepsis admission.

Methods

This was a pre-planned secondary analysis of a prospective observational study of adults presenting to the ED with suspected sepsis (treatment for infection plus either lactate > 2 mmol/liter or systolic blood pressure < 90 mm/Hg) who received < 1L IV fluid before enrollment. Patients had 3 echocardiograms performed (presentation, 3, and 24 h). The primary outcome was the effect of increasing sepsis illness severity, defined by ED Sequential Organ Failure Assessment (SOFA) score, on parameters of cardiac function, assessed using linear mixed-effects models. The secondary goal was to determine whether cardiac function differed between survivors and non-survivors, also using mixed-effects models.

Results

We enrolled 73 patients with a mean age of 60 (SD 16.1) years and in-hospital mortality of 23%. For the primary analysis, we found that increasing ED SOFA score was associated with worse cardiac function over the first 24 h across all assessed parameters of left-ventricular systolic and diastolic function as well as right-ventricular systolic function. While baseline strain and E/e' were better in survivors, in the mixed models analysis, the trajectory of Global Longitudinal Strain and septal E/e′ over the first 24 h of illness differed between survivors and non-survivors, with improved function at 24 h in non-survivors.

Conclusions

In the first study to capture patients prior to the initiation of resuscitation, we found a direct relationship between sepsis severity and global myocardial dysfunction. Future studies are needed to confirm these results, to identify myocardial depressants, and to investigate the link with adverse outcomes so that therapeutic interventions can be developed.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13089-022-00282-6.

Electrocardiographic Findings and Cardiac Troponin I Assay in Dogs with SIRS Diagnosis

Several studies performed in humans have demonstrated that the onset of systemic inflammatory response syndrome (SIRS) represents a high risk condition to develop myocardial damage and arrhythmias. Therefore, we also hypothesized cardiac involment for dogs affected by SIRS. To assess this hypothesis, 24 dogs with a diagnosis of SIRS (13 entire males, 7 entire females, and 4 spayed females) with an age ranging from 4 to 11 years (mean 5.6 years) and an average weight of 24 kg (range from 5 to 47 kg) were enrolled. The dogs were divided into two groups according to their prognosis: Survivors (G1) and not survivors (G2), composed by 13 and 11 dogs, respectively. Moreover, healthy dogs were included as the control group (CTR). All the dogs with a history of cardiac or renal disease were excluded. At the inclusion, each patient underwent a physical examination and a complete cell count, and a biochemistry panel (including electrolyte profile) was performed; moreover, the blood cardiac Troponin I (cTnI) was measured. For each clinical variable indicative of SIRS, a score between 0 (absence) and 1 (presence) was applied. Furthermore, an electrocardiographic examination was recorded. Seventeen out of 24 (70.8%) dogs with SIRS showed arrhythmias, of which n. 6 belonged to the G1, while n. 11 belonged to the G2. Most represented findings were sinus tachycardia (7/17; 41.1%), followed by monomorphic premature ventricular beats (6/17; 35.3%), less common were first-degree atrioventricular block (2/17; 11.7%) and sinus bradycardia 1/17; 5.8%). Notably, in G1 dogs, only sinus tachycardia and premature ventricular beats were observed. G2 dogs presented a number of total and banded leukocytes significantly higher than those of G1 (p = 0.002 and 0.049), in the same manner, the clinical score suggestive of SIRS (3 vs. 2.1) was significantly higher in G2 than in G1 dogs (p = 0.01). Moreover, a significantly higher value of cTnI was observed in the G2 group compared to the G1 group (p = 0.006). Data presented here suggested a cardiac involvement in dogs with SIRS, analogously to humans, that may significantly influence the patient's prognosis.

Septic Cardiomyopathy: From Pathophysiology to the Clinical Setting

The onset of cardiomyopathy is a common feature in sepsis, with relevant effects on its pathophysiology and clinical care. Septic cardiomyopathy is characterized by reduced left ventricular (LV) contractility eventually associated with LV dilatation with or without right ventricle failure. Unfortunately, such a wide range of ultrasonographic findings does not reflect a deep comprehension of sepsis-induced cardiomyopathy, but rather a lack of consensus about its definition. Several echocardiographic parameters intrinsically depend on loading conditions (both preload and afterload) so that it may be challenging to discriminate which is primitive and which is induced by hemodynamic perturbances. Here, we explore the state of the art in sepsis-related cardiomyopathy. We focus on the shortcomings in its definition and point out how cardiac performance dynamically changes in response to different hemodynamic clusters. A special attention is also given to update the knowledge about molecular mechanisms leading to myocardial dysfunction and that recall those of myocardial hibernation. Ultimately, the aim of this review is to highlight the unsolved issue in the field of sepsis-induced cardiomyopathy as their implementation would lead to improve risk stratification and clinical care.

Cardiorenal syndrome in the pediatric population: A systematic review

The concept of cardiorenal syndrome (CRS) is derived from the crosstalk between the heart and kidneys in pathological conditions. Despite the rising importance of CRS, there is a paucity of information on the understanding of its pathophysiology and management, increasing both morbidity and mortality for patients. This review summarizes the existing conceptual pathophysiology of different types of CRS and delves into the associated therapeutic modalities with a focus on pediatric cases. Prospective or retrospective observational studies, comparative studies, case reports, case-control, and cross-sectional studies that include pediatric patients with CRS were included in this review. Literature was searched using PubMed, EMBASE, and Google Scholar with keywords including "cardio-renal syndrome, type," "reno-cardio syndrome," "children," "acute kidney injury," and "acute decompensated heart failure" from January 2000 to January 2021. A total of 14 pediatric studies were ultimately included and analyzed, comprising a combined population of 3608 children of which 32% had CRS. Of the 14 studies, 57% were based on type 1 CRS, 14% on types 2 and 3 CRS, and 7% were on types 4 and 5 CRS. The majority of included studies were prospective cohort, although a wide spectrum was observed in terms of patient age, comorbidities, etiologies, and treatment strategies. Commonly observed comorbidities in CRS type 1 were hematologic, oncologic, cardiology-related side effects, muscular dystrophy, and pneumonia/bronchiolitis. CRS, particularly type 1, is prevalent in children and has a significant risk of mortality. The current treatment regimen primarily involves diuretics, extracorporeal fluid removal, and treatment of underlying etiologies and comorbidities.

COVID-19 and Long-Term Outcomes: Lessons from Other Critical Care Illnesses and Potential Mechanisms

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus that is currently causing a pandemic and has been termed coronavirus disease (COVID-19). The elderly or those with preexisting conditions like diabetes, hypertension, coronary heart disease, chronic obstructive pulmonary disease, cerebrovascular disease, or kidney dysfunction are more likely to develop severe cases when infected. Patients with COVID-19 admitted to the ICU have higher mortality than non-ICU patients. Critical illness has consistently posed a challenge not only in terms of mortality but also in regard to long-term outcomes of survivors. Patients who survive acute critical illness including, but not limited to, pulmonary and systemic insults associated with acute respiratory distress syndrome, pneumonia, systemic inflammation, and mechanical ventilation, will likely suffer from post-ICU syndrome, a phenomenon of cognitive, psychiatric, and/or physical disability after treatment in the ICU. Post-ICU morbidity and mortality continue to be a cause for concern when considering large-scale studies showing 12-month mortality risks of 11.8-21%. Previous studies have demonstrated that multiple mechanisms, including cytokine release, mitochondrial dysfunction, and even amyloids, may lead to end-organ dysfunction in patients. We hypothesize that COVID-19 infection will lead to post-ICU syndrome via potentially similar mechanisms as other chronic critical illnesses and cause long-term morbidity and mortality in patients. We consider a variety of mechanisms and questions that not only consider the short-term impact of the COVID-19 pandemic but its long-term effects that may not yet be imagined.

Early echocardiographic assessment of cardiac function may be prognostically informative in unresuscitated patients with sepsis: A prospective observational study

Purpose

The goal of this study was to explore the association cardiac function at Emergency Department (ED) presentation prior to the initiation of resuscitation, and its change at 3-hours, with adverse outcomes in patients with sepsis.

Methods

This was a prospective observational study of patients presenting to an urban ED with suspected sepsis. Patients had a point-of-care echocardiogram performed prior to initiation of resuscitation and again 3 hours later. Left-ventricular (LV) parameters recorded included e’, and E/e’, and ejection fraction (EF); right-ventricular (RV) function was evaluated using tricuspid annular plane systolic excursion (TAPSE). Logistic and generalized linear regression were used to assess the association of echocardiographic parameters and ≥ 2-point increase in SOFA score at 24 hours (primary outcome) and 24-hours SOFA score and in-hospital mortality (secondary outcomes).

Results

For ΔSOFA ≥ 2 and 24-hour SOFA score, declining LVEF was associated with better outcomes in patients with greater baseline SOFA scores, but worse outcomes in patients with lower baseline scores. A similar relationship was found for ΔTAPSE at 3 hours. Reduced LVEF at presentation was associated with increased mortality after adjusting for ED SOFA score (odds-ratio (OR) 0.76 (CI 0.60–0.96). No relationship between diastolic parameters and outcomes was found. IVF administration was similar across ΔLVEF/TAPSE sub-groups.

Conclusions

Our results suggest that early change in LV and RV systolic function are independently prognostic of sepsis illness severity at 24-hours. Further study is needed to determine if this information can be used to guide treatment and improve outcomes.

Mitochondrial Sirt3 serves as a biomarker for sepsis diagnosis and mortality prediction

The purpose of this study is to determine whether the levels of serum Sirt3 correlate with disease severity and perfusion indicators in septic patients, as well as to assess the clinical value of Sirt3 as a potential novel marker for sepsis diagnosis and mortality prediction. A total of 79 patients in the ICU were included in the study, of which 28 were postoperatively noninfectious and the remaining 51 patients were all diagnosed with sepsis during the study period. The levels of Sirt3 were detected and dynamically monitored by enzyme-linked adsorption method, Pearson or Spearman coefficient for correlation analysis between Sirt3 and clinical indicators, ROC curve for evaluation of diagnosis and mortality prediction, Kaplan-Meier method for the significance of Sirt3 in 28-day survival. The serum levels of Sirt3 were lower in the sepsis patients on day 1 (P < 0.0001), and the septic shock group had lower Sirt3 levels than the sepsis group (P = 0.013). Sirt3 had good negative correlations with SOFA scores both in sepsis and septic shock groups (Pearson: r² = - 0.424, - 0.518; P = 0.011, 0.040), and Sirt3 correlated strongly with ScvO₂ in the septic shock group (Pearson: r² = - 0.679, P = 0.004) and with PCT in the sepsis group (Pearson: r² = - 0.409, P = 0.015). Sirt3 not only performed well in identifying sepsis (AUC = 0.995, 95% CI 0.987-1, P < 0.0001) but also greatly enhanced lactate's specificity in detecting septic shock (from 91.43 to 94.29%). Patients in the low Sirt3 group had higher ScvO₂, lactate, APACHE II score, SOFA score, longer ICU stays, and worse indicators of inflammation (TNF-α, IL-6) and infection (PCT) than those in the high Sirt3 group (P < 0.05). Additionally, Sirt3 can predict mortality of sepsis (AUC = 0.746, 95% CI 0.571-0.921, P = 0.022), patients with serum Sirt3 < 10.07 pg/ml have a lower 28-day survival (log-rank P = 0.008). Low serum levels of Sirt3 are significantly correlated with the disease severity. At the same time, Sirt3 increases the sensitivity of lactate to detect "cellular hypoxia" in septic shock. Sirt3 is a promising biomarker for the diagnosis of sepsis and predicting mortality risk in septic patients.

Early Hyperdynamic Sepsis Alters Coronary Blood Flow Regulation in Porcine Fecal Peritonitis

Background: Sepsis is a common condition known to impair blood flow regulation and microcirculation, which can ultimately lead to organ dysfunction but such contribution of the coronary circulation remains to be clarified. We investigated coronary blood flow regulatory mechanisms, including autoregulation, metabolic regulation, and endothelial vasodilatory response, in an experimental porcine model of early hyperdynamic sepsis.

Methods: Fourteen pigs were randomized to sham (n = 7) or fecal peritonitis-induced sepsis (n = 7) procedures. At baseline, 6 and 12 h after peritonitis induction, the animals underwent general and coronary hemodynamic evaluation, including determination of autoregulatory breakpoint pressure and adenosine-induced maximal coronary vasodilation for coronary flow reserve and hyperemic microvascular resistance calculation. Endothelial-derived vasodilatory response was assessed both in vivo and ex vivo using bradykinin. Coronary arteries were sampled for pathobiological evaluation.

Results: Sepsis resulted in a right shift of the autoregulatory breakpoint pressure, decreased coronary blood flow reserve and increased hyperemic microvascular resistance from the 6th h after peritonitis induction. In vivo and ex vivo endothelial vasomotor function was preserved. Sepsis increased coronary arteries expressions of nitric oxide synthases, prostaglandin I₂ receptor, and prostaglandin F_2α receptor.

Conclusion: Autoregulation and metabolic blood flow regulation were both impaired in the coronary circulation during experimental hyperdynamic sepsis, although endothelial vasodilatory response was preserved.

Echocardiographic Assessment of Left Ventricular Systolic and Diastolic Functions in Dogs with Severe Sepsis and Septic Shock; Longitudinal Study

Simple Summary

Sepsis is associated with cardiovascular changes. The aim of the study was to determine sepsis-induced myocardial dysfunction in dogs with severe sepsis and septic shock using transthoracic echocardiography. Clinical, laboratory and cardiologic examinations for the septic dogs were performed at admission, 6 and 24 h, and on the day of discharge from the hospital. Left ventricular (LV) systolic dysfunction, LV diastolic dysfunction, and both types of the dysfunction were present in 13%, 70%, and 9% of dogs with sepsis, respectively. Dogs with LV diastolic dysfunction had a worse outcome and short-term mortality. Transthoracic echocardiography can be used for monitoring cardiovascular dysfunction in dogs with sepsis.

Abstract

The purpose of this study was to monitor left ventricular systolic dysfunction (LVSD) and diastolic dysfunction (LVDD) using transthoracic echocardiography (TTE) in dogs with severe sepsis and septic shock (SS/SS). A prospective longitudinal study using 23 dogs with SS/SS (experimental group) and 20 healthy dogs (control group) were carried out. All the clinical, laboratory and cardiologic examinations for the experimental dogs were performed at admission, 6 and 24 h after the start of treatment and on the day of discharge. LVSD was described as LV ejection fraction (LVEF) < 50%. LVDD was determined when the septal mitral annulus early diastolic velocity (LVEm) was <8 cm/s. LVSD and LVDD were present in 3 and 16 dogs with SS/SS, respectively, with both types of dysfunction present in 2 of the dogs. Although all the dogs with LVSD survived, 8 dogs with LVDD did not. The survival period was significantly shorter in dogs with an LVEm < 8 cm/s (1.3 ± 1.4 days). In conclusion, LVDD, rather than LVSD, was a common cardiovascular abnormality in the septic dogs, and this may be a negative prognostic factor. TTE is a useful tool for the identifying and monitoring of myocardial dysfunction in the dogs with SS/SS.

Cardiac Glucose and Fatty Acid Transport After Experimental Mono- and Polytrauma

OBJECTIVE

The aim of this study was to define the influence of trauma on cardiac glucose and fatty acid transport. The effects were investigated in vivo in a porcine mono- and polytrauma model and in vitro in human cardiomyocytes, which were treated simultaneously with different inflammatory substances, mimicking posttraumatic inflammatory conditions.

METHODS AND RESULTS

In the porcine fracture- and polytrauma model, blood glucose concentrations were measured by blood gas analysis during an observation period of 72 h. The expression of cardiac glucose and fatty acid transporters in the left ventricle was determined by RT-qPCR and immunofluorescence. Cardiac and hepatic glycogen storage was examined. Furthermore, human cardiomyocytes were exposed to a defined trauma-cocktail and the expression levels of glucose- and fatty acid transporters were determined. Early after polytrauma, hyperglycemia was observed. After 48 and 72 h, pigs with fracture- and polytrauma developed hypoglycemia. The propofol demand significantly increased posttrauma. The hepatic glycogen concentration was reduced 72 h after trauma. Cardiac glucose and fatty acid transporters changed in both trauma models in vivo as well as in vitro in human cardiomyocytes in presence of proinflammatory mediators.

CONCLUSIONS

Monotrauma as well as polytrauma changed the cardiac energy transport by altering the expression of glucose and fatty acid transporters. In vitro data suggest that human cardiomyocytes shift to a state alike myocardial hibernation preferring glucose as primary energy source to maintain cardiac function.

Pathophysiology of sepsis-induced cardiomyopathy

Sepsis is the life-threatening organ dysfunction caused by a dysregulated host response to infection and is the leading cause of death in intensive care units. Cardiac dysfunction caused by sepsis, usually termed sepsis-induced cardiomyopathy, is common and has long been a subject of interest. In this Review, we explore the definition, epidemiology, diagnosis and pathophysiology of septic cardiomyopathy, with an emphasis on how best to interpret this condition in the clinical context. Advances in diagnostic techniques have increased the sensitivity of detection of myocardial abnormalities but have posed challenges in linking those abnormalities to therapeutic strategies and relevant clinical outcomes. Sophisticated methodologies have elucidated various pathophysiological mechanisms but the extent to which these are adaptive responses is yet to be definitively answered. Although the indications for monitoring and treating septic cardiomyopathy are clinical and directed towards restoring tissue perfusion, a better understanding of the course and implications of septic cardiomyopathy can help to optimize interventions and improve clinical outcomes.

The Surviving Sepsis Campaign: Basic/Translational Science Research Priorities

Objectives:

Expound upon priorities for basic/translational science identified in a recent paper by a group of experts assigned by the Society of Critical Care Medicine and the European Society of Intensive Care Medicine.

Data Sources:

Original paper, search of the literature.

Study Selection:

By several members of the original task force with specific expertise in basic/translational science.

Data Extraction:

None.

Data Synthesis:

None.

Conclusions:

In the first of a series of follow-up reports to the original paper, several members of the original task force with specific expertise provided a more in-depth analysis of the five identified priorities directly related to basic/translational science. This analysis expounds on what is known about the question and what was identified as priorities for ongoing research. It is hoped that this analysis will aid the development of future research initiatives.

The Role of Long Non-coding RNAs in Sepsis-Induced Cardiac Dysfunction

Sepsis is a syndrome with life-threatening organ dysfunction induced by a dysregulated host response to infection. The heart is one of the most commonly involved organs during sepsis, and cardiac dysfunction, which is usually indicative of an extremely poor clinical outcome, is a leading cause of death in septic cases. Despite substantial improvements in the understanding of the mechanisms that contribute to the origin and responses to sepsis, the prognosis of sepsis-induced cardiac dysfunction (SICD) remains poor and its molecular pathophysiological changes are not well-characterized. The recently discovered group of mediators known as long non-coding RNAs (lncRNAs) have presented novel insights and opportunities to explore the mechanisms and development of SICD and may provide new targets for diagnosis and therapeutic strategies. LncRNAs are RNA transcripts of more than 200 nucleotides with limited or no protein-coding potential. Evidence has rapidly accumulated from numerous studies on how lncRNAs function in associated regulatory circuits during SICD. This review outlines the direct evidence of the effect of lncRNAs on SICD based on clinical trials and animal studies. Furthermore, potential functional lncRNAs in SICD that have been identified in sepsis studies are summarized with a proven biological function in research on other cardiovascular diseases.

Sepsis and the evolution of human increased sensitivity to lipopolysaccharide

Among mammals, humans are exquisitely sensitive to lipopolysaccharide (LPS), an environmentally pervasive bacterial cell membrane component. Very small doses of LPS trigger powerful immune responses in humans and can even initiate symptoms of sepsis. Close evolutionary relatives such as African and Asian monkeys require doses that are an order of magnitude higher to do the same. Why humans have evolved such an energetically expensive antimicrobial strategy is a question that biological anthropologists are positioned to help address. Here we compare LPS sensitivity in primate/mammalian models and propose that human high sensitivity to LPS is adaptive, linked to multiple immune tactics against pathogens, and part of multi-faceted anti-microbial strategy that strongly overlaps with that of other mammals. We support a notion that LPS sensitivity in humans has been driven by microorganisms that constitutively live on us, and has been informed by human behavioral changes over our species' evolution (e.g., meat eating, agricultural practices, and smoking).

Systemic and local cardiac inflammation after experimental long bone fracture, traumatic brain injury and combined trauma in mice

Background

Trauma is the leading cause of death and disability worldwide, especially in the young population. Cardiac injuries are an independent predictor for a poor overall outcome after trauma. The aim of the present study was to analyze systemic inflammation as well as local cardiac inflammation after experimental limb-, neuro- and combined trauma in mice.

Methods

Male C57BL/6 mice received either a closed tibia fracture (Fx), isolated traumatic brain injury (TBI) or a combination of both (Fx ​+ ​TBI). Control animals underwent sham procedure. After 6 and 24 ​h, systemic levels of inflammatory mediators were analyzed, respectively. Locally, cardiac inflammation and cardiac structural alterations were investigated in left ventricular tissue of mice 6 and 24 ​h after trauma.

Results

Mice showed enhanced systemic inflammation after combined trauma, which was manifested by increased levels of KC, MCP-1 and G-CSF. Locally, mice exhibited increased expression of inflammatory cytokines (IL-1β, TNF) in heart tissue, which was probably mediated via toll-like receptor (TLR) signaling. Furthermore, mice demonstrated a redistribution of connexin 43 in cardiac tissue, which appeared predominantly after combined trauma. Besides inflammation and structural cardiac alterations, expression of glucose transporter 4 (GLUT4) mRNA was increased in the heart early after TBI and after combination of TBI and limb fracture, indicating a modification of energy metabolism. Early after combination of TBI and tibia fracture, nitrosative stress was increased, manifested by elevation of nitrotyrosine in cardiac tissue. Finally, mice showed a trend of increased systemic levels of cardiac troponin I and heart-fatty acid binding protein (HFABP) after combined trauma, which was associated with a significant decrease of troponin I and HFABP mRNA expression in cardiac tissue after TBI and combination of TBI and limb fracture.

Conclusion

Mice exhibited early cardiac alterations as well as alterations in cardiac glucose transporter expression, indicating a modification of energy metabolism, which might be linked to increased systemic- and local cardiac inflammation after limb-, neuro- and combined trauma. These cardiac alterations might predispose individuals for secondary cardiac damage after trauma that might compromise cardiac function after TBI and long bone fracture.

Translational potential statement

Injuries to the head and extremities frequently occur after severe trauma. In our study, we analyzed the effects of closed tibia fracture, isolated TBI, and the combination of both injuries with regard to the development of post-traumatic secondary cardiac injuries.

Trauma, a Matter of the Heart-Molecular Mechanism of Post-Traumatic Cardiac Dysfunction

Trauma remains a leading global cause of mortality, particularly in the young population. In the United States, approximately 30,000 patients with blunt cardiac trauma were recorded annually. Cardiac damage is a predictor for poor outcome after multiple trauma, with a poor prognosis and prolonged in-hospitalization. Systemic elevation of cardiac troponins was correlated with survival, injury severity score, and catecholamine consumption of patients after multiple trauma. The clinical features of the so-called "commotio cordis" are dysrhythmias, including ventricular fibrillation and sudden cardiac arrest as well as wall motion disorders. In trauma patients with inappropriate hypotension and inadequate response to fluid resuscitation, cardiac injury should be considered. Therefore, a combination of echocardiography (ECG) measurements, echocardiography, and systemic appearance of cardiomyocyte damage markers such as troponin appears to be an appropriate diagnostic approach to detect cardiac dysfunction after trauma. However, the mechanisms of post-traumatic cardiac dysfunction are still actively being investigated. This review aims to discuss cardiac damage following trauma, focusing on mechanisms of post-traumatic cardiac dysfunction associated with inflammation and complement activation. Herein, a causal relationship of cardiac dysfunction to traumatic brain injury, blunt chest trauma, multiple trauma, burn injury, psychosocial stress, fracture, and hemorrhagic shock are illustrated and therapeutic options are discussed.

Reaming of femoral fractures with different reaming irrigator aspirator systems shows distinct effects on cardiac function after experimental polytrauma

Cardiac injuries are recorded after multiple trauma and are associated with a poor patient outcome. Reaming prior to locked intramedullary nailing is a frequently used technique to stabilize femoral diaphysis fractures. However, in polytraumatized patients, complications such as fat emboli and acute respiratory distress syndrome have been associated with reaming. The reaming irrigator aspirator (RIA) system provides concomitant irrigation and suction of the intramedullary contents, and should, therefore, reduce reaming-associated complications. The aim of the study was to investigate cardiac function after multiple trauma with regard to two different RIA devices (RIAI vs RIAII). 15 male pigs were included in the study. Pigs received either sham treatment or multiple trauma (chest trauma, femur fracture, liver laceration, and hemorrhagic shock), followed by intramedullary nailing after reaming with either the RIAI or RIAII system (RIAII: reduced diameter of the reamer, improved control of irrigation and suction). Cardiac function was assessed by transesophageal echocardiography and systemic inflammation as well as local cardiac damage examined. Pigs of both treatment groups showed impaired cardiac function, valvular insufficiency, and cardiac damage. Systemic inflammation and local cardiac alterations were observed which might contribute to early myocardial damage in vivo. Multiple trauma including long-bone fracture and subsequent intramedullary reaming induces cardiac dysfunction and valvular insufficiency, which might be linked to both mechanical cardiac injury and increased systemic inflammation. 6 hours after trauma there are less differences between RIAI and RIAII treatment with regard to post-traumatic cardiac consequences in multiple injured pigs, indicating no beneficial effect of RIAII over RIAI.

The surviving sepsis campaign: basic/translational science research priorities

Objectives

Expound upon priorities for basic/translational science identified in a recent paper by a group of experts assigned by the Society of Critical Care Medicine and the European Society of Intensive Care Medicine.

Data sources

Original paper, search of the literature.

Study selection

This study is selected by several members of the original task force with specific expertise in basic/translational science. Data extraction and data synthesis are not available.

Conclusions

In the first of a series of follow-up reports to the original paper, several members of the original task force with specific expertise provided a more in-depth analysis of the five identified priorities directly related to basic/translational science. This analysis expounds on what is known about the question and what was identified as priorities for ongoing research. It is hoped that this analysis will aid the development of future research initiatives.

Heart Dysfunction in Sepsis

Cardiac involvement during sepsis frequently occurs. A series of molecules induces a set of changes at the cellular level that result in the malfunction of the myocardium. The understanding of these molecular alterations has simultaneously promoted the implementation of diagnostic strategies that are much more precise and allowed the advance of the therapeutics. The heart is a vital organ for survival. Its well-being ensures the adequate supply of essential elements for organs and tissues.

Sepsis-induced cardiac dysfunction: a review of pathophysiology

It is well known that cardiac dysfunction in sepsis is associated with significantly increased mortality. The pathophysiology of sepsis-induced cardiac dysfunction can be summarized as involving impaired myocardial circulation, direct myocardial depression, and mitochondrial dysfunction. Impaired blood flow to the myocardium is associated with microvascular dysfunction, impaired endothelium, and ventriculo-arterial uncoupling. The mechanisms behind direct myocardial depression consist of downregulation of β-adrenoceptors and several myocardial suppressants (such as cytokine and nitric oxide). Recent research has highlighted that mitochondrial dysfunction, which results in energy depletion, is a major factor in sepsis-induced cardiac dysfunction. Therefore, the authors summarize the pathophysiological process of cardiac dysfunction in sepsis based on the results of recent studies.

Toll-Like Receptor-Mediated Cardiac Injury during Experimental Sepsis

Sepsis is associated with global cardiac dysfunction and with high mortality rate. The development of septic cardiomyopathy is due to complex interactions of damage-associated molecular patters, cytokines, and complement activation products. The aim of this study was to define the effects of sepsis on cardiac structure, gap junction, and tight junction (TJ) proteins. Sepsis was induced by cecal ligation and puncture in male C57BL/6 mice. After a period of 24 h, the expression of cardiac structure, gap junction, and TJ proteins was determined. Murine HL-1 cells were stimulated with LPS, and mRNA expression of cardiac structure and gap junction proteins, intracellular reactive oxygen species, and troponin I release was analyzed. Furthermore, pyrogenic receptor subtype 7 (P2X7) expression and troponin I release of human cardiomyocytes (iPS) were determined after LPS exposure. In vivo, protein expression of connexin43 and α-actinin was decreased after the onset of polymicrobial sepsis, whereas in HL-1 cells, mRNA expression of connexin43, α-actinin, and desmin was increased in the presence of LPS. Expression of TJ proteins was not affected in vivo during sepsis. Although the presence of LPS and nigericin resulted in a significant troponin I release from HL-1 cells. Sepsis affected cardiac structure and gap junction proteins in mice, potentially contributing to compromised cardiac function.

Complement Activation and Organ Damage After Trauma-Differential Immune Response Based on Surgical Treatment Strategy

Background: The complement system is part of the innate immunity, is activated immediately after trauma and is associated with adult respiratory distress syndrome, acute lung injury, multiple organ failure, and with death of multiply injured patients. The aim of the study was to investigate the complement activation in multiply injured pigs as well as its effects on the heart in vivo and in vitro. Moreover, the impact of reamed vs. non-reamed intramedullary nailing was examined with regard to the complement activation after multiple trauma in pigs.

Materials and Methods: Male pigs received multiple trauma, followed by femoral nailing with/without prior conventional reaming. Systemic complement hemolytic activity (CH-50 and AH-50) as well as the local cardiac expression of C3a receptor, C5a receptors1/2, and the deposition of the fragments C3b/iC3b/C3c was determined in vivo after trauma. Human cardiomyocytes were exposed to C3a or C5a and analyzed regarding calcium signaling and mitochondrial respiration.

Results: Systemic complement activation increased within 6 h after trauma and was mediated via the classical and the alternative pathway. Furthermore, complement activation correlated with invasiveness of fracture treatment. The expression of receptors for complement activation were altered locally in vivo in left ventricles. C3a and C5a acted detrimentally on human cardiomyocytes by affecting their functionality and their mitochondrial respiration in vitro.

Conclusion: After multiple trauma, an early activation of the complement system is triggered, affecting the heart in vivo as well as in vitro, leading to complement-induced cardiac dysfunction. The intensity of complement activation after multiple trauma might correlate with the invasiveness of fracture treatment. Reaming of the femoral canal might contribute to an enhanced “second hit” response after trauma. Consequently, the choice of fracture treatment might imply the clinical outcome of the critically injured patients and might be therefore crucial for their survival.

Prognostic importance of tissue Doppler imaging of systolic and diastolic functions in dogs with severe sepsis and septic shock

The goal of this study was to determine the distribution of left ventricular (LV) systolic and diastolic dysfunctions and their prognostic value in canine parvovirus-infected dogs suffering from severe sepsis and septic shock (SS/SS). Twenty dogs with SS/SS (experimental group) and 18 healthy dogs (control group) were used in the study. Systolic and diastolic dysfunction was present in three (15%) and 14 (70%) diseased dogs, respectively, with both types of dysfunction present in two (10%) of the patients. These dogs were split into two groups: survivors (Sv, n = 14) and non-survivors (non-Sv, n = 6). The pulsed wave tissue Doppler (PW-TDI) septal mitral annulus systolic velocity (LVS'), an index of systolic dysfunction, had a high sensitivity and specificity to differentiate Sv and non-Sv animals, with values of 83.3% (95% CI: 41.6-98.4) and 83.3% (95% CI: 59.8-94.8), respectively, at an optimum cut-off point of ≥ 9.90. The PW-TDI septal early mitral annulus early-diastolic peak velocity (E'), an index of diastolic dysfunction, had the best sensitivity and specificity to differentiate Sv and non-Sv dogs, with values of 100% (95% CI: 55.2-100) and 100% (95% CI: 78.9-100), respectively, at an optimum cut-off point of ≤ 6.50. Therefore, diastolic dysfunction determined by E' is a good independent outcome predictor.

Mitochondrial dysfunction is associated with long-term cognitive impairment in an animal sepsis model

Background: Several different mechanisms have been proposed to explain long-term cognitive impairment in sepsis survivors. The role of persisting mitochondrial dysfunction is not known. We thus sought to determine whether stimulation of mitochondrial dynamics improves mitochondrial function and long-term cognitive impairment in an experimental model of sepsis.

Methods: Sepsis was induced in adult Wistar rats by cecal ligation and perforation (CLP). Animals received intracerebroventricular injections of either rosiglitazone (biogenesis activator), rilmenidine, rapamycin (autophagy activators), or n-saline (sham control) once a day on days 7–9 after the septic insult. Cognitive impairment was assessed by inhibitory avoidance and object recognition tests. Animals were killed 24 h, 3 and 10 days after sepsis with the hippocampus and prefrontal cortex removed to determine mitochondrial function.

Results: Sepsis was associated with both acute (24 h) and late (10 days) brain mitochondrial dysfunction. Markers of mitochondrial biogenesis, autophagy and mitophagy were not up-regulated during these time points. Activation of biogenesis (rosiglitazone) or autophagy (rapamycin and rilmenidine) improved brain ATP levels and ex vivo oxygen consumption and the long-term cognitive impairment observed in sepsis survivors.

Conclusion: Long-term impairment of brain function is temporally related to mitochondrial dysfunction. Activators of autophagy and mitochondrial biogenesis could rescue animals from cognitive impairment.

Alprostadil attenuates LPS-induced cardiomyocyte injury by inhibiting the Wnt5a/JNK/NF-κB pathway

Background

Clinical research has demonstrated that alprostadil has an anti-inflammatory effect; however, to date, its molecular mechanisms remain unclear. This study aimed to examine the anti-inflammatory activity and related mechanisms of alprostadil in lipopolysaccharide (LPS)-treated H9c2 cells.

Methods

Cell morphology was observed under an inverted light microscope, while cell viability was assessed with the 3‑(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay. Enzyme-linked immunosorbent assays (ELISA) were conducted to study biochemical indicators of cellular damage, such as released lactate dehydrase (LDH) and troponin, and inflammatory cytokine levels including interleukin-1β (IL-1β), IL-6, IL-17, and tumor necrosis factor-α (TNF-α). The mRNA expression levels of Wnt5a, c‑jun N‑terminal kinase (JNK), and nuclear factor kappa B (NF-κB) were further investigated by real-time quantitative polymerase chain reaction (RT-PCR). The effects of alprostadil on the Wnt5a/JNK/NF-κB pathway in H9c2 cells was examined by Western blotting.

Results

Alprostadil increased the cell viability of LPS-stimulated H9c2 cells, reduced LDH and troponin production, and attenuated IL-1β, IL-6, IL-17, and TNF-α secretion. Moreover, alprostadil reduced the mRNA expression of Wnt5a, JNK, and NF-κB and decreased the expression of Wnt5a, NF-κB, and the ratio of p‑JNK/JNK in H9c2 cells treated with LPS. The siWnt5a or JNK inhibitor SP600125 significantly augmented the inhibitory effects of alprostadil on the Wnt5a/JNK/NF-κB pathway.

Conclusion

Our results show that alprostadil has anti-inflammatory effects and could attenuate LPS-induced injury in H9c2 cardiomyocytes via the Wnt5a/JNK/NF-κB pathway.

Cardiovascular biomarkers in dogs with systemic inflammatory response syndrome

OBJECTIVE

To measure plasma N-terminal fragments of pro-B-type natriuretic peptides (NT-proBNP) and cardiac troponin T (cTnT) concentration in hospitalized dogs and relate these markers to underlying conditions and evaluate their potential as prognostic markers in dogs with systemic inflammatory response syndrome (SIRS).

DESIGN

Prospective, observational, clinical study.

SETTING

Emergency department of a university teaching hospital.

ANIMALS

Sixty-nine dogs with SIRS examined in the emergency department were prospectively studied. Patient age ranged from 5 months to 15 years, and weight ranged from 5.5 to 75 kg.

MEASUREMENTS AND MAIN RESULTS

Blood samples were obtained at presentation, during hospitalization until discharge or death, and at a "control" visit (T1m) at least 1 month after hospital discharge. NT-proBNP was assayed with a commercially available canine ELISA, while cTnT was measured with an automated immunoassay previously used in dogs. A correlation procedure, mixed procedure on a linear model, and a logistic procedure were performed. Forty-four patients survived, 19 of which had control visits. cTnT concentrations were significantly higher than T0 and T1m at T12, T24, and T72. In 28 dogs, cTnT was detected during hospitalization, but cTnT was not detected in any dog at the control visits. Higher concentrations of cTnT were negatively associated with survival, irrespective of disease category. NT-proBNP concentrations were significantly higher than T0, T6, T12, and T1m at T24, T72, and T120, but were not associated with survival.

CONCLUSIONS

NT-proBNP and cTnT increased significantly in dogs with SIRS, regardless of the underlying disease process. Nonsurvivors displayed significantly higher cTnT concentrations during hospitalization.

Myalgic encephalomyelitis or chronic fatigue syndrome: how could the illness develop?

A model of the development and progression of chronic fatigue syndrome (myalgic encephalomyelitis), the aetiology of which is currently unknown, is put forward, starting with a consideration of the post-infection role of damage-associated molecular patterns and the development of chronic inflammatory, oxidative and nitrosative stress in genetically predisposed individuals. The consequences are detailed, including the role of increased intestinal permeability and the translocation of commensal antigens into the circulation, and the development of dysautonomia, neuroinflammation, and neurocognitive and neuroimaging abnormalities. Increasing levels of such stress and the switch to immune and metabolic downregulation are detailed next in relation to the advent of hypernitrosylation, impaired mitochondrial performance, immune suppression, cellular hibernation, endotoxin tolerance and sirtuin 1 activation. The role of chronic stress and the development of endotoxin tolerance via indoleamine 2,3-dioxygenase upregulation and the characteristics of neutrophils, monocytes, macrophages and T cells, including regulatory T cells, in endotoxin tolerance are detailed next. Finally, it is shown how the immune and metabolic abnormalities of chronic fatigue syndrome can be explained by endotoxin tolerance, thus completing the model.

Targeting Complement Pathways in Polytrauma- and Sepsis-Induced Multiple-Organ Dysfunction

Exposure to traumatic or infectious insults results in a rapid activation of the complement cascade as major fluid defense system of innate immunity. The complement system acts as a master alarm system during the molecular danger response after trauma and significantly contributes to the clearance of DAMPs and PAMPs. However, depending on the origin and extent of the damaged macro- and micro -milieu, the complement system can also be either excessively activated or inhibited. In both cases, this can lead to a maladaptive immune response and subsequent multiple cellular and organ dysfunction. The arsenal of complement-specific drugs offers promising strategies for various critical conditions after trauma, hemorrhagic shock, sepsis, and multiple organ failure. The imbalanced immune response needs to be detected in a rational and real-time manner before the translational therapeutic potential of these drugs can be fully utilized. Overall, the temporal-spatial complement response after tissue trauma and during sepsis remains somewhat enigmatic and demands a clinical triad: reliable tissue damage assessment, complement activation monitoring, and potent complement targeting to highly specific rebalance the fluid phase innate immune response.

Challenges in high-sensitive troponin assay interpretation for intensive therapy

Cardiac troponins T and I are considered highly sensitive and specific markers for the diagnosis of acute myocardial infarction. Currently, a series of nonprimary cardiac abnormalities may manifest as an elevation in high-sensitive assays. The reduction in their detection limits has allowed earlier diagnosis and the use of evidence-based therapeutic measures; however, this characteristic has increased the spectrum of detectable noncoronary heart diseases, which poses challenges for characterizing acute coronary syndromes and creates a new role for these tests in known disorders in intensive care units, especially sepsis. Management of patients through a greater understanding of how these markers behave should be re-evaluated to ensure their correct interpretation.

PEDF increases GLUT4-mediated glucose uptake in rat ischemic myocardium via PI3K/AKT pathway in a PEDFR-dependent manner

BACKGROUND

Targeted increase in glucose uptake of ischemic myocardium is a potential therapeutic strategy for myocardial ischemia. PEDF presents a profound moderating effect on glucose metabolism of cells, but its role is still controversial. Here, we try to demonstrate the direct effect of PEDF on glucose uptake in ischemic myocyte and to elucidate its underlying mechanism.

METHODS AND RESULTS

Lentivirus vectors carrying PEDF gene were delivered into the myocardium to locally overexpress PEDF in a myocardial ischemia/reperfusion rat model. PET imaging showed that PEDF local overexpression increased [¹⁸F]-FDG uptake of ischemic myocardium. In vitro, PEDF directly increased the glucose uptake in hypoxic cardiomyocytes. The expression of glucose transporter 4 (GLUT4) on plasma membrane of hypoxic cardiomyocytes was significantly upregulated by PEDF, but its total amount was not changed. The increased glucose uptake and cardioprotective effects induced by PEDF were blocked by the GLUT4 inhibitor indinavir. PEDF-mediated GLUT4 translocation and glucose uptake increase in hypoxic cardiomyocytes were prevented by phosphatidyl-inositol-3 kinase (PI3K) inhibitor or AKT inhibitor. The PEDF-mediated glucose uptake was also diminished when PEDF receptor (PEDFR) was downregulated or potent phospholipase A2 enzymatic activity was inhibited.

CONCLUSIONS

PEDF can increase glucose uptake in ischemic myocardium through a PEDFR-dependent mechanism, involving PI3K/AKT signaling and GLUT4 translocation.

The role of mitochondria in sepsis-induced cardiomyopathy

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. Myocardial dysfunction, often termed sepsis-induced cardiomyopathy, is a frequent complication and is associated with worse outcomes. Numerous mechanisms contribute to sepsis-induced cardiomyopathy and a growing body of evidence suggests that bioenergetic and metabolic derangements play a central role in its development; however, there are significant discrepancies in the literature, perhaps reflecting variability in the experimental models employed or in the host response to sepsis. The condition is characterised by lack of significant cell death, normal tissue oxygen levels and, in survivors, reversibility of organ dysfunction. The functional changes observed in cardiac tissue may represent an adaptive response to prolonged stress that limits cell death, improving the potential for recovery. In this review, we describe our current understanding of the pathophysiology underlying myocardial dysfunction in sepsis, with a focus on disrupted mitochondrial processes.

Pathophysiology, echocardiographic evaluation, biomarker findings, and prognostic implications of septic cardiomyopathy: a review of the literature

BACKGROUND

Sepsis is a common condition encountered by emergency and critical care physicians, with significant costs, both economic and human. Myocardial dysfunction in sepsis is a well-recognized but poorly understood phenomenon. There is an extensive body of literature on this subject, yet results are conflicting and no objective definition of septic cardiomyopathy exists, representing a critical knowledge gap.

OBJECTIVES

In this article, we review the pathophysiology of septic cardiomyopathy, covering the effects of key inflammatory mediators on both the heart and the peripheral vasculature, highlighting the interconnectedness of these two systems. We focus on the extant literature on echocardiographic and laboratory assessment of the heart in sepsis, highlighting gaps therein and suggesting avenues for future research. Implications for treatment are briefly discussed.

CONCLUSIONS

As a result of conflicting data, echocardiographic measures of left ventricular (systolic or diastolic) or right ventricular function cannot currently provide reliable prognostic information in patients with sepsis. Natriuretic peptides and cardiac troponins are of similarly unclear utility. Heterogeneous classification of illness, treatment variability, and lack of formal diagnostic criteria for septic cardiomyopathy contribute to the conflicting results. Development of formal diagnostic criteria, and use thereof in future studies, may help elucidate the link between cardiac performance and outcomes in patients with sepsis.

Critical illness and flat batteries

An exaggerated, dysregulated host response to insults such as infection (i.e. sepsis), trauma and ischaemia-reperfusion injury can result in multiple organ dysfunction and death. While the focus of research in this area has largely centred on inflammation and immunity, a crucial missing link is the precise identification of mechanisms at the organ level that cause this physiological-biochemical failure. Any hypothesis must reconcile this functional organ failure with minimal signs of cell death, availability of oxygen, and (often) minimal early local inflammatory cell infiltrate. These failed organs also retain the capacity to usually recover, even those that are poorly regenerative. A metabolic-bioenergetic shutdown, akin to hibernation or aestivation, is the most plausible explanation currently advanced. This shutdown appears driven by a perfect storm of compromised mitochondrial oxidative phosphorylation related to inhibition by excessive inflammatory mediators, direct oxidant stress, a tissue oxygen deficit in the unresuscitated phase, altered hormonal drive, and downregulation of genes encoding mitochondrial proteins. In addition, the efficiency of oxidative phosphorylation may be affected by a substrate shift towards fat metabolism and increased uncoupling. A lack of sufficient ATP provision to fuel normal metabolic processes will drive downregulation of metabolism, and thus cellular functionality. In turn, a decrease in metabolism will provide negative feedback to the mitochondrion, inducing a bioenergetic shutdown. Arguably, these processes may offer protection against a prolonged inflammatory hit by sparing the cell from initiation of death pathways, thereby explaining the lack of significant morphological change. A narrow line may exist between adaptation and maladaptation. This places a considerable challenge on any therapeutic modulation to provide benefit rather than harm.

Cardiac Depression in Pigs after Multiple Trauma - Characterization of Posttraumatic Structural and Functional Alterations

The purpose of this study was to define the relationship between cardiac depression and morphological and immunological alterations in cardiac tissue after multiple trauma. However, the mechanistic basis of depressed cardiac function after trauma is still elusive. In a porcine polytrauma model including blunt chest trauma, liver laceration, femur fracture and haemorrhage serial trans-thoracic echocardiography was performed and correlated with cellular cardiac injury as well as with the occurrence of extracellular histones in serum. Postmortem analysis of heart tissue was performed 72 h after trauma. Ejection fraction and shortening fraction of the left ventricle were significantly impaired between 4 and 27 h after trauma. H-FABP, troponin I and extracellular histones were elevated early after trauma and returned to baseline after 24 and 48 h, respectively. Furthermore, increased nitrotyrosine and Il-1β generation and apoptosis were identified in cardiac tissue after trauma. Main structural findings revealed alteration of connexin 43 (Cx43) and co-translocation of Cx43 and zonula occludens 1 to the cytosol, reduction of α-actinin and increase of desmin in cardiomyocytes after trauma. The cellular and subcellular events demonstrated in this report may for the first time explain molecular mechanisms associated with cardiac dysfunction after multiple trauma.

Robust suppression of cardiac energy catabolism with marked accumulation of energy substrates during lipopolysaccharide-induced cardiac dysfunction in mice

BACKGROUND

Myocardial contractile dysfunction in sepsis has been attributed mainly to increased inflammatory cytokines, insulin resistance, and impaired oxidative phosphorylation of fatty acids (FAs). However, precise molecular mechanisms underlying the cardiac dysfunction in sepsis remain to be determined. We previously reported major shift in myocardial energy substrates from FAs to glucose, and increased hepatic ketogenesis in mice lacking fatty acid-binding protein 4 (FABP4) and FABP5 (DKO).

PURPOSE

We sought to determine whether a shift of energy substrates from FAs to glucose and increased availability of ketone bodies are beneficial or detrimental to cardiac function under the septic condition.

METHODS

Lipopolysaccharide (LPS, 10mg/kg) was intraperitoneally injected into wild-type (WT) and DKO mice. Twelve hours after injection, cardiac function was assessed by echocardiography and serum and hearts were collected for further analyses.

RESULTS

Cardiac contractile function was more deteriorated by LPS injection in DKO mice than WT mice despite comparable changes in pro-inflammatory cytokine production. LPS injection reduced myocardial uptake of FA tracer by 30% in both types of mice, while uptake of the glucose tracer did not significantly change in either group of mice in sepsis. Storage of glycogen and triacylglycerol in hearts was remarkably increased by LPS injection in both mice. Metabolome analysis revealed that LPS-induced suppression of pool size in the TCA cycle was more enhanced in DKO hearts. A tracing study with ¹³C₆-glucose further revealed that LPS injection substantially reduced glucose-derived metabolites in the TCA cycle and related amino acids in DKO hearts. Consistent with these findings, glucose oxidation in vitro was similarly and markedly reduced in both mice. Serum concentration of β-hydroxybutyrate and cardiac expression of genes associated with ketolysis were reduced in septic mice.

CONCLUSIONS

Our study demonstrated that LPS-induced cardiac contractile dysfunction is associated with the robust suppression of catabolism of energy substrates including FAs, glucose and ketone bodies and accumulation of glycogen and triacylglycerol in the heart. Thus, a fuel shift from FAs to glucose and/or ketone bodies may be detrimental rather than protective under septic conditions.

Mechanisms of Organ Dysfunction in Sepsis

Sepsis-associated organ dysfunction involves multiple responses to inflammation, including endothelial and microvascular dysfunction, immune and autonomic dysregulation, and cellular metabolic reprogramming. The effect of targeting these mechanistic pathways on short- and long-term outcomes depends highly on the timing of therapeutic intervention. Furthermore, there is a need to understand the adaptive or maladaptive character of these mechanisms, to discover phase-specific biomarkers to guide therapy, and to conceptualize these mechanisms in terms of resistance and tolerance.