Persistent Mitochondrial Dysfunction Linked to Prolonged Organ Dysfunction in Pediatric Sepsis

Association of inflammatory biomarkers with new functional morbidity at hospital discharge in children who survive severe sepsis

Objective

New functional morbidity is common in critically ill children who survive sepsis; yet, the underlying biological mechanisms, particularly the impact of inflammation, remain unknown. We sought to test the hypothesis that increased levels of inflammatory biomarkers during the acute phase of pediatric sepsis are associated with new functional morbidity at hospital discharge.

Methods

We conducted a post hoc secondary analysis of the MitoPSe clinical study, including N = 119 critically ill children who survived sepsis. Data collected included demographic and clinical variables and 31 inflammatory biomarkers collected at three distinct timepoints (within days 1-2 of PICU admission, days 3-5, and days 8-14). The primary outcome was new functional morbidity, defined as at least a one-point increase in the pediatric overall performance category from baseline to hospital discharge.

Results

New functional morbidity occurred in 38 children (32%) and was associated with increased plasma levels of interleukin (IL)-6, IL-18, sIL-2Ra, MCP1, IL-8 (CXCL8), sIL-1RII, IL-10, MIP1a, and IL-2r and decreased RANTES (CCL5) (p < .001) at all three timepoints. However, after adjusting for differences in chronic comorbid conditions, hospital length of stay, number of organ dysfunctions, and severity of illness, absolute biomarker levels, and trajectories were not significantly different between patients with or without new functional morbidity at hospital discharge.

Conclusions

In this sample of critically ill children treated for sepsis, increased inflammatory biomarker levels and the trajectory of change during the acute phase of pediatric sepsis were not independently associated with new functional morbidity at hospital discharge. Inflammatory biomarker levels likely reflect illness severity and other clinical variables associated with illness. However, these biomarkers may still be useful in identifying patients at risk of developing functional morbidity, despite the lack of causation within this study.

Unlocking the full potential of memory T cells in adoptive T cell therapy for hematologic malignancies

In recent years, immune cell therapy, particularly adoptive cell therapy (ACT), has shown superior therapeutic effects on hematologic malignancies. However, a challenge lies in ensuring that genetically engineered specific T cells maintain lasting anti-tumor effects within the host. The enduring success of ACT therapy hinges on the persistence of memory T (TM) cells, a diverse cell subset crucial for tumor immune response and immune memory upkeep. Notably, TM cell subsets at varying differentiation stages exhibit distinct biological traits and anti-tumor capabilities. Poorly differentiated TM cells are pivotal for favorable clinical outcomes in ACT. The differentiation of TM cells is influenced by multiple factors, including metabolism and cytokines. Consequently, current research focuses on investigating the differentiation patterns of TM cells and enhancing the production of poorly differentiated TM cells with potent anti-tumor properties in vitro, which is a prominent area of interest globally. This review delves into the differentiation features of TM cells, outlining their distribution in patients and their impact on ACT treatment. It comprehensively explores cutting-edge strategies to boost ACT efficacy through TM cell differentiation induction, aiming to unlock the full potential of TM cells in treating hematologic malignancies and offering novel insights for tumor immune cell therapy.

Effect of sodium butyrate on kidney and liver mitochondrial dysfunction in a lipopolysaccharide mouse model

Sodium butyrate can reduce inflammation, but it is not known if butyrate can improve mitochondrial dysfunction during sepsis. We tested butyrate to prevent or reverse lipopolysaccharide (LPS)-induced mitochondrial dysfunction in murine kidney and liver. C57BL/6 mice were grouped as control (n = 9), intraperitoneal (IP) LPS (n = 8), pretreatment with IP butyrate 600 (n = 3) or 1200 mg/kg (n = 8) followed 2 h later by LPS, posttreatment with IP butyrate 600 (n = 3) or 1200 mg/kg (n = 7) 1 h after LPS, or butyrate 1200 mg/kg only (n = 8). Kidney and liver tissue were collected at 24 h to measure mitochondrial respiration, electron transport system (ETS) complex activity and subunit expression, and content (citrate synthase [CS] activity and mtDNA/nDNA). Kidney mitochondrial respiration was decreased after LPS compared to controls. Pretreatment with butyrate 1200 mg/kg increased kidney OXPHOSCI+II, ETSCI+II, ETSCII, and CIV respiration compared to LPS; posttreatment did not achieve significant increases except for OXPHOSCI. Liver mitochondrial respiration exhibited a similar pattern as in kidney, but differences were not significant. ETS complex and CS activity did not differ between groups, but CI and CII subunit expression trended higher with butyrate in kidney. Changes in mtDNA/nDNA followed a similar pattern as respiration in kidney and liver with a decrease after LPS that was not present with butyrate pretreatment. These data show that butyrate can prevent-but not significantly reverse-the LPS-induced decrease in kidney mitochondrial respiration without a clear effect in liver. Mitochondrial protection was not attributable to changes in ETS complex activity but may reflect maintenance of ETS subunit expression.

Obeticholic acid ameliorates sepsis-induced renal mitochondrial damage by inhibiting the NF-κb signaling pathway

Acute kidney injury (AKI), a common complication of sepsis, might be caused by overactivated inflammation, mitochondrial damage, and oxidative stress. However, the mechanisms underlying sepsis-induced AKI (SAKI) have not been fully elucidated, and there is a lack of effective therapies for AKI. To this end, this study aimed to investigate whether obeticholic acid (OCA) has a renoprotective effect on SAKI and to explore its mechanism of action. Through bioinformatics analysis, our study confirmed that the mitochondria might be a critical target for the treatment of SAKI. Thus, a septic rat model was established by cecal ligation puncture (CLP) surgery. Our results showed an evoked inflammatory response via the NF-κB signaling pathway and NLRP3 inflammasome activation in septic rats, which led to mitochondrial damage and oxidative stress. OCA, an Farnesoid X Receptor (FXR) agonist, has shown anti-inflammatory effects in numerous studies. However, the effects of OCA on SAKI remain unclear. In this study, we revealed that pretreatment with OCA can inhibit the inflammatory response by reducing the synthesis of proinflammatory factors (such as IL-1β and NLRP3) via blocking NF-κB and alleviating mitochondrial damage and oxidative stress in the septic rat model. Overall, this study provides insight into the excessive inflammation-induced SAKI caused by mitochondrial damage and evidence for the potential use of OCA in SAKI treatment.

Progress of heparanase in septic cardiomyopathy: A review

Septic cardiomyopathy (SCM) is a severe complication caused by sepsis, resulting in a high mortality rate. The current understanding of the pathogenic mechanism of SCM primarily involves endocardial injury, microcirculation disturbance, mitochondrial dysfunction and fibrosis. Heparanase (HPA), an endo-β-D-glucuronidase, has been implicated in inflammation, immune response, coagulation promotion, microcirculation disturbance, mitochondrial dysfunction and fibrosis. Therefore, it was hypothesized that HPA may play an important role in the pathogenesis of SCM. The present study provides a summary of various pathophysiological changes and mechanisms behind the involvement of HPA in SCM. It also presents a novel perspective on the pathogenic mechanism, diagnosis and treatment of SCM.

Distinct mitochondrial respiration profiles in pediatric patients with febrile illness versus sepsis

OBJECTIVE

Mitochondrial dysfunction, linked to sepsis-related organ failure, is unknown in febrile illness.

METHODS

Prospective study of children in an Emergency Department (ED) with febrile illness or without infection (ED controls); secondary analysis of ICU patients with sepsis or without infection (ICU controls). Mitochondrial oxygen consumption measured in peripheral blood mononuclear cells using respirometry, with primary outcome of spare respiratory capacity (SRC). Mitochondrial content measured as citrate synthase (CS: febrile illness and ED controls) and mitochondrial to nuclear DNA ratio (mtDNA:nDNA: all groups).

RESULTS

SRC was lower in febrile illness (6.7 ± 3.0 pmol/sec/106 cells) and sepsis (5.7 ± 4.7) than ED/PICU controls (8.5 ± 3.7; both p < 0.05), but not different between febrile illness and sepsis (p = 0.26). Low SRC was driven by increased basal respiration in febrile illness and decreased maximal uncoupled respiration in sepsis. Differences were no longer significant after adjustment for patient demographics. Febrile illness demonstrated lower CS activity than ED controls (p = 0.07) and lower mtDNA:nDNA than both ED/PICU controls and sepsis (both p < 0.05).

CONCLUSION

Mitochondrial SRC was reduced in both febrile illness and sepsis, but due to distinct mitochondrial profiles and impacted by demographics. Further work is needed to determine if mitochondrial profiles could differentiate febrile illness from early sepsis.

IMPACT STATEMENT

Mitochondrial dysfunction has been linked to organ failure in sepsis, but whether mitochondrial alterations are evident in febrile illness without sepsis is unknown. In our study, while mitochondrial spare respiratory capacity (SRC), an index of cellular bioenergetic reserve under stress, was reduced in children with both febrile illness and sepsis compared to children without infections, low SRC was driven by increased basal respiration in febrile illness compared with decreased maximal uncoupled respiration in sepsis. Additional research is needed to understand if distinct mitochondrial profiles could be used to differentiate febrile illness from early sepsis in children.

Clinical drug interactions between linezolid and other antibiotics: For adverse drug event monitoring

Detailed data on safety associated with drug-drug interactions (DDIs) between Linezolid (LZD) and other antibiotics are limited. The aim of this study was to investigate the safety signals related to these DDIs and to provide a reference for clinically related adverse drug event monitoring. Adverse event (AE) information from 1 January 2004 to 16 June 2022 of the target antibiotics including LZD using alone or in combination with LZD was extracted from the OpenVigil FDA data platform for safety signal analysis. The combined risk ratio model, reporting ratio method, Ω shrinkage measure model, and chi-square statistics model were used to analyze the safety signals related to DDIs. Meanwhile, we evaluated the correlation and the influence of sex and age between the drug(s) and the target AE detected. There were 18991 AEs related to LZD. There were 2293, 1726, 4449, 821, 2431, 1053, and 463 AE reports when LZD was combined with amikacin, voriconazole, meropenem, clarithromycin, levofloxacin, piperacillin-tazobactam, and azithromycin, respectively. Except for azithromycin, there were positive safety signals related to DDIs between LZD and these antibiotics. These DDIs might influence the incidence of 13, 16, 7, 7, 6, and 15 types of AEs, respectively, and is associated with higher reporting rates of AEs compared with use alone. Moreover, sex and age might influence the occurrence of AEs. We found that the combinations of LZD and other antibiotics are related to multiple AEs, such as hepatotoxicity, drug resistance and electrocardiogram QT prolonged, but further research is still required to investigate their underlying mechanisms. This study can provide a new reference for the safety monitoring of LZD combined with other antibiotics in clinical practice.

Extracellular release of damaged mitochondria induced by prehematopoietic stem cell transplant conditioning exacerbates GVHD

ABSTRACT

Despite therapeutic advancements, graft-versus-host disease (GVHD) is a major complication of hematopoietic stem cell transplantation (HSCT). In current models of GVHD, tissue injury induced by cytotoxic conditioning regimens, along with translocation of microbes expressing pathogen-associated molecular patterns, result in activation of host antigen-presenting cells (APCs) to stimulate alloreactive donor T lymphocytes. Recent studies have demonstrated that in many pathologic states, tissue injury results in the release of mitochondria from the cytoplasm to the extracellular space. We hypothesized that extracellular mitochondria, which are related to archaebacteria, could also trigger GVHD by stimulation of host APCs. We found that clinically relevant doses of radiation or busulfan induced extracellular release of mitochondria by various cell types, including cultured intestinal epithelial cells. Conditioning-mediated mitochondrial release was associated with mitochondrial damage and impaired quality control but did not affect the viability of the cells. Extracellular mitochondria directly stimulated host APCs to express higher levels of major histocompatibility complex II (MHC-II), costimulatory CD86, and proinflammatory cytokines, resulting in increased donor T-cell activation, and proliferation in mixed lymphocyte reactions. Analyses of plasma from both experimental mice and a cohort of children undergoing HSCT demonstrated that conditioning induced extracellular mitochondrial release in vivo. In mice undergoing MHC-mismatched HSCT, administration of purified syngeneic extracellular mitochondria increased host APC activation and exacerbated GVHD. Our data suggest that pre-HSCT conditioning results in extracellular release of damaged mitochondria, which increase alloreactivity and exacerbate GVHD. Therefore, decreasing the extracellular release of damaged mitochondria after conditioning could serve as a novel strategy for GVHD prevention.

Dysregulated STAT3 signaling and T cell immunometabolic dysfunction define a targetable, high mortality subphenotype of critically ill children

Sepsis is the leading cause of death of hospitalized children worldwide. Despite the established link between immune dysregulation and mortality in pediatric sepsis, it remains unclear which host immune factors contribute causally to adverse sepsis outcomes. Identifying modifiable pathobiology is an essential first step to successful translation of biologic insights into precision therapeutics. We designed a prospective, longitudinal cohort study of 88 critically ill pediatric patients with multiple organ dysfunction syndrome (MODS), including patients with and without sepsis, to define subphenotypes associated with targetable mechanisms of immune dysregulation. We first assessed plasma proteomic profiles and identified shared features of immune dysregulation in MODS patients with and without sepsis. We then employed consensus clustering to define three subphenotypes based on protein expression at disease onset and identified a strong association between subphenotype and clinical outcome. We next identified differences in immune cell frequency and activation state by MODS subphenotype and determined the association between hyperinflammatory pathway activation and cellular immunophenotype. Using single cell transcriptomics, we demonstrated STAT3 hyperactivation in lymphocytes from the sickest MODS subgroup and then identified an association between STAT3 hyperactivation and T cell immunometabolic dysregulation. Finally, we compared proteomics findings between patients with MODS and patients with inborn errors of immunity that amplify cytokine signaling pathways to further assess the impact of STAT3 hyperactivation in the most severe patients with MODS. Overall, these results identify a potentially pathologic and targetable role for STAT3 hyperactivation in a subset of pediatric patients with MODS who have high severity of illness and poor prognosis.

Potential biomarkers used for risk estimation of pediatric sepsis-associated organ dysfunction and immune dysregulation

Pediatric sepsis is a serious issue globally and is a significant cause of illness and death among infants and children. Refractory septic shock and multiple organ dysfunction syndrome are the primary causes of mortality in children with sepsis. However, there is incomplete understanding of mechanistic insight of sepsis associated organ dysfunction. Biomarkers present during the body's response to infection-related inflammation can be used for screening, diagnosis, risk stratification/prognostication, and/or guidance in treatment decision-making. Research on biomarkers in children with sepsis can provide information about the risk of poor outcomes and sepsis-related organ dysfunction. This review focuses on clinically used biomarkers associated with immune dysregulation and organ dysfunction in pediatric sepsis, which could be useful for developing precision medicine strategies in pediatric sepsis management in the future. IMPACT: Sepsis is a complex syndrome with diverse clinical presentations, where organ dysfunction is a key factor in morbidity and mortality. Early detection of organ complications is vital in sepsis management, and potential biomarkers offer promise for precision medicine in pediatric cases. Well-designed studies are needed to identify phase-specific biomarkers and improve outcomes through more precise management.

Association between intracellular adenosine triphosphate content of CD4+ T lymphocytes and mortality in sepsis patients: A prospective observational study

OBJECTIVE

This study aimed to link intracellular adenosine triphosphate content in CD4+ T lymphocytes (CD4+ iATP) with sepsis patient mortality, seeking a new predictive biomarker for outcomes and enhanced management.

METHODS

61 sepsis patients admitted to the Intensive Care Unit between October 2021 and November 2022 were enrolled. iATP levels were gauged using whole blood CD4+ T cells stimulated with mitogen PHA-L. Based on CD4+ iATP levels (<132.24 and ≥132.24 ng/mL), patients were categorized into two groups. The primary endpoint was all-cause mortality. To identify factors associated with mortality, both univariate and multivariate Cox proportional hazard analyses were conducted.

RESULTS

Of the patients, 40 had high CD4+ iATP levels (≥132.24 ng/mL) and 21 had low levels (<132.24 ng/mL). In a 28-day follow-up, 21 (34.4%) patients perished. Adjusting for confounders like SOFA score, APACHE II score, lactic acid, and albumin, those with low CD4+ iATP had three- to fivefold higher mortality risk compared to high CD4+ iATP patients (61.9% vs. 20.0%; hazard ratio [95% confidence interval], Model 1: 4.515 [1.276-15.974], p = .019, Model 2: 3.512 [1.197-10.306], p = .022). CD4+ iATP correlated positively with white blood cell and neutrophil counts but not with lymphocytes, CD3, and CD4 counts.

CONCLUSIONS

Low CD4+ iATP levels were associated with a higher risk of mortality in sepsis patients. Measurement of CD4+ iATP may serve as a useful tool for identifying patients at a higher risk of mortality and could potentially provide a basis for clinical treatment. Further research is warranted to fully elucidate the underlying mechanisms of this association.

ALTERED PROFILES OF EXTRACELLULAR MITOCHONDRIAL DNA IN IMMUNOPARALYZED PEDIATRIC PATIENTS AFTER THERMAL INJURY

ABSTRACT

Background: Thermal injury is a major cause of morbidity and mortality in the pediatric population worldwide with secondary infection being the most common acute complication. Suppression of innate and adaptive immune function is predictive of infection in pediatric burn patients, but little is known about the mechanisms causing these effects. Circulating mitochondrial DNA (mtDNA), which induces a proinflammatory signal, has been described in multiple disease states but has not been studied in pediatric burn injuries. This study examined the quantity of circulating mtDNA and mtDNA mutations in immunocompetent (IC) and immunoparalyzed (IP) pediatric burn patients. Methods: Circulating DNA was isolated from plasma of pediatric burn patients treated at Nationwide Children's Hospital Burn Center at early (1-3 days) and late (4-7 days) time points postinjury. These patients were categorized as IP or IC based on previously established immune function testing and secondary infection. Three mitochondrial genes, D loop, ND1, and ND4, were quantified by multiplexed qPCR to assess both mtDNA quantity and mutation load. Results: At the early time point, there were no differences in plasma mtDNA quantity; however, IC patients had a progressive increase in mtDNA over time when compared with IP patients (change in ND1 copy number over time 3,880 vs. 87 copies/day, P = 0.0004). Conversely, the IP group had an increase in mtDNA mutation burden over time. Conclusion: IC patients experienced a significant increase in circulating mtDNA quantity over time, demonstrating an association between increased mtDNA release and proinflammatory phenotype in the burn patients. IP patients had significant increases in mtDNA mutation load likely representative of degree of oxidative damage. Together, these data provide further insight into the inflammatory and immunological mechanisms after pediatric thermal injury.

Deubiquitinase BAP1 regulates stability of BRCA1 protein and inactivates the NF-κB signaling to protect mice from sepsis-induced acute kidney injury

Sepsis and its associated organ dysfunction syndrome is a leading cause of death in critically ill patients. Breast cancer susceptibility protein 1 (BRCA1)-associated protein 1 (BAP1) is a potential regulator in immune regulation and inflammatory responses. This study aims to investigate the function of BAP1 in sepsis-induced acute kidney injury (AKI). A mouse model with sepsis-induced AKI was induced by cecal ligation and puncture, and renal tubular epithelial cells (RTECs) were treated with lipopolysaccharide (LPS) to mimic an AKI condition in vitro. BAP1 was significantly poorly expressed in the kidney tissues of model mice and the LPS-treated RTECs. Artificial upregulation of BAP1 ameliorated the pathological changes, tissue injury and inflammatory responses in kidney tissues of the mice, and it reduced the LPS-induced injury and apoptosis of the RTECs. BAP1 was found to interact with BRCA1 and enhance stability of BRCA1 protein through deubiquitination modification. Further downregulation of BRCA1 activated the nuclear factor-kappa B (NF-κB) signaling pathway and blocked the protective roles of BAP1 in sepsis-induced AKI. In conclusion, this study demonstrates that BAP1 protects mice from sepsis-induced AKI through enhancing stability of BRCA1 protein and inactivating the NF-κB signaling.

Troponin I as an Independent Biomarker of Outcome in Children with Systemic Inflammatory Response

Cardiac troponin-I (cTnI) is a biomarker of myocardial injury with implications for clinical outcomes. May other contributing factors that could affect outcomes have not been uniformly considered in pediatric studies. We hypothesized that there is an association between admission serum cTnI and outcomes in critically ill children taking into account the magnitude of the acute systemic inflammatory response syndrome (SIRS), serum lactate concentrations, and nutritional status. Second, we tested for potential factors associated with elevated serum cTnI. This was a prospective cohort study in 104 children (median age: 21.3 months) consecutively admitted to a pediatric intensive care unit (PICU) of a teaching hospital with SIRS and without previous chronic diseases. Primary outcome variables were PICU-free days, ventilator-free days, and 30-day mortality. Exposure variables were serum cTnI concentration on admission, revised pediatric index of mortality (PIM2), pediatric logistic organ dysfunction (PELOD-2), hypotensive shock, C-reactive protein, procalcitonin, and serum lactate on admission, and malnutrition. Elevated cTnI (>0.01 μg/L) was observed in 24% of patients, which was associated with the reduction of ventilator-free days (β coefficient = - 4.97; 95% confidence interval [CI]: -8.03; -1.91) and PICU-free days (β coefficient = - 5.76; 95% CI: -8.97; -2.55). All patients who died had elevated serum cTnI. The increase of 0.1 μg/L in cTnI concentration resulted in an elevation of 2 points in the oxygenation index (β coefficient = 2.0; 95% CI: 1.22; 2.78, p  < 0.001). The PIM2 score, hypotensive shock in the first 24 hours, and serum lactate were independently associated with elevated cTnI on admission. We conclude that elevated serum cTnI on admission is independently associated with adverse outcomes in children with SIRS and without associated chronic diseases.

Peripheral blood mononuclear cells exhibit increased mitochondrial respiration after adjuvant chemo- and radiotherapy for early breast cancer

BACKGROUND

Adjuvant chemo- and radiotherapy cause cellular damage to tumorous and healthy dividing cells. Chemotherapy has been shown to cause mitochondrial respiratory dysfunction in non-tumorous tissues, but the effects on human peripheral blood mononuclear cells (PBMCs) remain unknown.

AIM

We aimed to investigate mitochondrial respiration of PBMCs before and after adjuvant chemo- and radiotherapy in postmenopausal patients with early breast cancer (EBC) and relate these to metabolic parameters of the patients.

METHODS

Twenty-three postmenopausal women diagnosed with EBC were examined before and shortly after chemotherapy with (n = 18) or without (n = 5) radiotherapy. Respiration (O2 flux per million PBMCs) was assessed by high-resolution respirometry of intact and permeabilized PBMCs. Clinical metabolic characteristics and mitochondrial DNA (mtDNA) content of PBMCs (mtDN relative to nuclear DNA) were furthermore assessed.

RESULTS

Respiration of intact and permeabilized PBMCs from EBC patients significantly increased with adjuvant chemo- and radiotherapy (p = 6 × 10-5 and p = 1 × 10-7 , respectively). The oxygen flux attributed to specific mitochondrial complexes and respiratory states increased by 17-43% compared to before therapy initiation. Similarly, PBMC mtDNA content increased by 40% (p = 0.002). Leukocytes (p = 0.0001), hemoglobin (p = 0.0003), and HDL cholesterol (p = 0.003) concentrations decreased whereas triglyceride (p = 0.01) and LDL (p = 0.02) concentrations increased after treatment suggesting a worsened metabolic state. None of the metabolic parameters or the mtDNA content of PBMCs correlated significantly with PBMC respiration.

CONCLUSION

This study shows that mitochondrial respiration and mtDNA content in circulating PBMCs increase after adjuvant chemo- and radiotherapy in postmenopausal patients with EBC. Besides the increased mtDNA content, a shift in PBMC subpopulation proportions towards cells relying on oxidative phosphorylation, who may be less sensitive to chemotherapy, might influence the increased mitochondrial respiration observed iafter chemotherapy.

An Fgr kinase inhibitor attenuates sepsis-associated encephalopathy by ameliorating mitochondrial dysfunction, oxidative stress, and neuroinflammation via the SIRT1/PGC-1α signaling pathway

BACKGROUND

Sepsis-associated encephalopathy (SAE) is characterized by diffuse brain dysfunction, long-term cognitive impairment, and increased morbidity and mortality. The current treatment for SAE is mainly symptomatic; the lack of specific treatment options and a poor understanding of the underlying mechanism of disease are responsible for poor patient outcomes. Fgr is a member of the Src family of tyrosine kinases and is involved in the innate immune response, hematologic cancer, diet-induced obesity, and hemorrhage-induced thalamic pain. This study investigated the protection provided by an Fgr kinase inhibitor in SAE and the underlying mechanism(s) of action.

METHODS

A cecal ligation and puncture (CLP)-induced mouse sepsis model was established. Mice were treated with or without an Fgr inhibitor and a PGC-1α inhibitor/activator. An open field test, a novel object recognition test, and an elevated plus maze were used to assess neurobehavioral changes in the mice. Western blotting and immunofluorescence were used to measure protein expression, and mRNA levels were measured using quantitative PCR (qPCR). An enzyme-linked immunosorbent assay was performed to quantify inflammatory cytokines. Mitochondrial membrane potential and morphology were measured by JC-1, electron microscopy, and the MitoTracker Deep Red probe. Oxidative stress and mitochondrial dysfunction were analyzed. In addition, the regulatory effect of Fgr on sirtuin 1 (SIRT1) was assessed.

RESULTS

CLP-induced sepsis increased the expression of Fgr in the hippocampal neurons. Pharmacological inhibition of Fgr attenuated CLP-induced neuroinflammation, the survival rate, cognitive and emotional dysfunction, oxidative stress, and mitochondrial dysfunction. Moreover, Fgr interacted with SIRT1 and reduced its activity and expression. In addition, activation of SIRT1/PGC-1α promoted the protective effects of the Fgr inhibitor on CLP-induced brain dysfunction, while inactivation of SIRT1/PGC-1α counteracted the benefits of the Fgr inhibitor.

CONCLUSIONS

To our knowledge, this is the first report of Fgr kinase inhibition markedly ameliorating SAE through activation of the SIRT1/PGC-1α pathway, and this may be a promising therapeutic target for SAE.

DIAGNOSTIC VALUE OF MITOCHONDRIAL DNA AND PERIPHERAL BLOOD MONONUCLEAR CELL RESPIROMETRY FOR BURN-RELATED SEPSIS

ABSTRACT

Background: Sepsis is the leading cause of mortality among burn patients that survive acute resuscitation. Clinical criteria have poor diagnostic value for burn-induced sepsis, making it difficult to diagnose. Protein biomarkers (e.g., procalcitonin) have been examined with limited success. We aimed to explore other biomarkers related to mitochondria (mitochondrial DNA [mtDNA]) and mitochondrial function of peripheral blood mononuclear cells (PBMCs) for sepsis diagnosis in burn patients. Methods: We conducted a follow-up analysis of a single center, prospective observational study of subjects (n = 10 healthy volunteers, n = 24 burn patients) to examine the diagnostic value of mtDNA and PBMC respirometry. Patients were enrolled regardless of sepsis status and followed longitudinally. Patient samples were classified as septic or not based on empiric clinical criteria. Isolated PBMCs were loaded into a high-resolution respirometer, and circulating mtDNA was measured with a PCR-based assay. Sequential Organ Failure Assessment (SOFA) criteria were also compared. Results: The SOFA criteria comparing septic versus before/nonseptic patients revealed significantly higher heart rate ( P = 0.012) and lower mean arterial pressure ( P = 0.039) in burn sepsis. MtDNA was significantly elevated in septic burn patients compared with healthy volunteers ( P < 0.0001) and nonseptic patients ( P < 0.0001), with no significant difference between healthy volunteers and nonseptic burn patients ( P = 0.187). The area under the ROC curve (AUC) for mtDNA was 0.685 (95% confidence interval = 0.50-0.86). For PBMC respirometry, burn patients exhibited increased routine and maximal respiration potential compared with healthy volunteers. However, no difference was found between nonseptic and septic patient samples. A subanalysis revealed a significant mortality difference in PBMC respirometry after sepsis diagnosis, wherein survivors had higher routine respiration ( P = 0.003) and maximal respiration ( P = 0.011) compared with nonsurvivors. Conclusion: Our findings reveal that mtDNA may have diagnostic value for burn sepsis, whereas PBMC respirometry is nonspecifically elevated in burns, but may have value in mortality prognosis. A larger, multisite study is warranted for further validity of the diagnostic value of mtDNA and PBMC respirometry as biomarkers for prognosis of sepsis and outcomes in burn patients.

Protective effect of endothelial progenitor cell-derived exosomal microRNA-382-3p on sepsis-induced organ damage and immune suppression in mice

OBJECTIVE

To explore the role of endothelial progenitor cell (EPC)-derived exosomal microRNA-382-3p (miR-382-3p) in septic injury in mice.

METHODS

A murine model of sepsis was introduced by cecal ligation and puncture (CLP). The model mice were treated with EPC-derived exosomes (Exos). The lung, kidney and liver tissues of mice were collected and stained with hematoxylin and eosin. The lymphocytes in murine spleen tissues, and the proportion and phenotype of the T helper cells (Ths) were examined by flow cytometry. The exosomal miRNAs were screened using a microarray analysis. The expressions of miR-382-3p and beta-transducin repeat containing E3 ubiquitin protein ligase (BTRC) were measured to explore possible mechanism of Exos in septic injury in mice.

RESULTS

EPC-derived Exos alleviated CLP-induced tissue damage in the lung, kidney and liver tissues in septic mice. They also restored the number of lymphocytes and the concentration of Ths, and reduced the imbalance in Th1 and Th2 cells in mice. The Exos mainly contained miR-382-3p, and miR-382-3p directly targeted BTRC mRNA. Either downregulation of miR-382-3p or upregulation of BTRC blocked the protective roles of Exos in septic injury and immune suppression. Overexpression of BTRC increased the phosphorylation of nuclear factor kappa B (NF-κB) inhibitor α (IκBα) and NF-κB.

CONCLUSION

EPC-derived exosomal miR-382-3p alleviates sepsis-induced organ damage and immune suppression in septic mice through regulating BTRC and the IκBα/NF-κB axis.

Outcomes Associated With Timing of Neurologic Dysfunction Onset Relative to Pediatric Sepsis Recognition

OBJECTIVES

To compare outcomes associated with timing-early versus late-of any neurologic dysfunction during pediatric sepsis.

DESIGN

Secondary analysis of a cross-sectional point prevalence study.

SETTING

A total of 128 PICUs in 26 countries.

PATIENTS

Less than 18 years with severe sepsis on 5 separate days (2013-2014).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients were categorized as having either no neurologic dysfunction or neurologic dysfunction (i.e., present at or after sepsis recognition), which was defined as Glasgow Coma Scale score less than 5 and/or fixed dilated pupils. Our primary outcome was death or new moderate disability (i.e., Pediatric Overall [or Cerebral] Performance Category score ≥3 and change ≥1 from baseline) at hospital discharge, and 87 of 567 severe sepsis patients (15%) had neurologic dysfunction within 7 days of sepsis recognition (61 at sepsis recognition and 26 after sepsis recognition). Primary site of infection varied based on presence of neurologic dysfunction. Death or new moderate disability occurred in 161 of 480 (34%) without neurologic dysfunction, 45 of 61 (74%) with neurologic dysfunction at sepsis recognition, and 21 of 26 (81%) with neurologic dysfunction after sepsis recognition (p < 0.001 across all groups). On multivariable analysis, in comparison with those without neurologic dysfunction, neurologic dysfunction whether at sepsis recognition or after was associated with increased odds of death or new moderate disability (adjusted odds ratio, 4.9 [95% CI, 2.3-10.1] and 10.7 [95% CI, 3.8-30.5], respectively). We failed to identify a difference between these adjusted odds ratios of death or new moderate disability that would indicate a differential risk of outcome based on timing of neurologic dysfunction (p = 0.20).

CONCLUSIONS

In this severe sepsis international cohort, the presence of neurologic dysfunction during sepsis is associated with worse outcomes at hospital discharge. The impact of early versus late onset of neurologic dysfunction in sepsis on outcome remains unknown, and further work is needed to better understand timing of neurologic dysfunction onset in pediatric sepsis.

Sodium butyrate reverses lipopolysaccharide-induced mitochondrial dysfunction in lymphoblasts

Butyrate is a short-chain fatty acid that is produced by commensal microbes within the intestinal microbiome through fermentation of dietary fibre. Microbial-derived butyrate has been shown to promote immunologic and metabolic homeostasis, in part through its beneficial effects on mitochondrial function, and thus has been proposed as a possible anti-inflammatory therapy. We tested the hypothesis that butyrate could mitigate the decrease in mitochondrial respiration in immune cells under septic conditions as a preliminary step towards better understanding the potential for butyrate as a novel therapy in sepsis. Mitochondrial respiration and content (measured as citrate synthase activity) were compared within four Epstein-Barr virus-transformed lymphoblast (LB) cell lines exposed to either control media or lipopolysaccharide (LPS) 100 ng/ml. Both co-incubation of LBs with LPS + butyrate and treatment with butyrate after LPS stimulation reversed the decrease in mitochondrial respiration observed in LBs exposed to LPS without butyrate. Neither LPS nor butyrate led to significant changes in citrate synthase activity. The preliminary findings support further investigation of a potential mitochondrial-based mechanism through which butyrate may help to mitigate the immuno-inflammatory response in sepsis.

Drp1/Fis1-Dependent Pathologic Fission and Associated Damaged Extracellular Mitochondria Contribute to Macrophage Dysfunction in Endotoxin Tolerance

OBJECTIVES

Recent publications have shown that mitochondrial dynamics can govern the quality and quantity of extracellular mitochondria subsequently impacting immune phenotypes. This study aims to determine if pathologic mitochondrial fission mediated by Drp1/Fis1 interaction impacts extracellular mitochondrial content and macrophage function in sepsis-induced immunoparalysis.

DESIGN

Laboratory investigation.

SETTING

University laboratory.

SUBJECTS

C57BL/6 and BALB/C mice.

INTERVENTIONS

Using in vitro and murine models of endotoxin tolerance (ET), we evaluated changes in Drp1/Fis1-dependent pathologic fission and simultaneously measured the quantity and quality of extracellular mitochondria. Next, by priming mouse macrophages with isolated healthy mitochondria (MC) and damaged mitochondria, we determined if damaged extracellular mitochondria are capable of inducing tolerance to subsequent endotoxin challenge. Finally, we determined if inhibition of Drp1/Fis1-mediated pathologic fission abrogates release of damaged extracellular mitochondria and improves macrophage response to subsequent endotoxin challenge.

MEASUREMENTS AND MAIN RESULTS

When compared with naïve macrophages (NMs), endotoxin-tolerant macrophages (ETM) demonstrated Drp1/Fis1-dependent mitochondrial dysfunction and higher levels of damaged extracellular mitochondria (Mitotracker-Green + events/50 μL: ETM = 2.42 × 106 ± 4,391 vs NM = 5.69 × 105 ± 2,478; p < 0.001). Exposure of NMs to damaged extracellular mitochondria (MH) induced cross-tolerance to subsequent endotoxin challenge, whereas MC had minimal effect (tumor necrosis factor [TNF]-α [pg/mL]: NM = 668 ± 3, NM + MH = 221 ± 15, and NM + Mc = 881 ± 15; p < 0.0001). Inhibiting Drp1/Fis1-dependent mitochondrial fission using heptapeptide (P110), a selective inhibitor of Drp1/Fis1 interaction, improved extracellular mitochondrial function (extracellular mitochondrial membrane potential, JC-1 [R/G] ETM = 7 ± 0.5 vs ETM + P110 = 19 ± 2.0; p < 0.001) and subsequently improved immune response in ETMs (TNF-α [pg/mL]; ETM = 149 ± 1 vs ETM + P110 = 1,150 ± 4; p < 0.0001). Similarly, P110-treated endotoxin tolerant mice had lower amounts of damaged extracellular mitochondria in plasma (represented by higher extracellular mitochondrial membrane potential, TMRM/MT-G: endotoxin tolerant [ET] = 0.04 ± 0.02 vs ET + P110 = 0.21 ± 0.02; p = 0.03) and improved immune response to subsequent endotoxin treatment as well as cecal ligation and puncture.

CONCLUSIONS

Inhibition of Drp1/Fis1-dependent mitochondrial fragmentation improved macrophage function and immune response in both in vitro and in vivo models of ET. This benefit is mediated, at least in part, by decreasing the release of damaged extracellular mitochondria, which contributes to endotoxin cross-tolerance. Altogether, these data suggest that alterations in mitochondrial dynamics may play an important role in sepsis-induced immunoparalysis.

Impaired Lymphocyte Responses in Pediatric Sepsis Vary by Pathogen Type and are Associated with Features of Immunometabolic Dysregulation

BACKGROUND

Sepsis is the leading cause of death in hospitalized children worldwide. Despite its hypothesized immune-mediated mechanism, targeted immunotherapy for sepsis is not available for clinical use.

OBJECTIVE

To determine the association between longitudinal cytometric, proteomic, bioenergetic, and metabolomic markers of immunometabolic dysregulation and pathogen type in pediatric sepsis.

METHODS

Serial peripheral blood mononuclear cell (PBMC) samples were obtained from 14 sepsis patients (34 total samples) and 7 control patients for this observational study. Flow cytometry was used to define immunophenotype, including T cell subset frequency and activation state, and assess intracellular cytokine production. Global immune dysfunction was assessed by tumor necrosis factor-α (TNF-α) production capacity and monocyte human leukocyte antigen DR (HLA-DR) expression. Mitochondrial function was assessed by bulk respirometry. Plasma cytokine levels were determined via Luminex assay. Metabolites were measured by liquid chromatography-mass spectrometry. Results were compared by timepoint and pathogen type.

RESULTS

Sepsis patients were older (15.9 years vs. 10.4 years, P = 0.02) and had higher illness severity by PRISM-III (12.0 vs. 2.0, P < 0.001) compared to controls; demographics were otherwise similar, though control patients were predominately male. Compared to controls, sepsis patients at timepoint 1 demonstrated lower monocyte HLA-DR expression (75% vs. 92%, P = 0.02), loss of peripheral of non-naïve CD4+ T cells (62.4% vs. 77.6%, P = 0.04), and reduced PBMC mitochondrial spare residual capacity (SRC; 4.0 pmol/s/106 cells vs. 8.4 pmol/s/106 cells, P = 0.01). At sepsis onset, immunoparalysis (defined as TNF-α production capacity < 200 pg/mL) was present in 39% of sepsis patients and not identified among controls. Metabolomic findings in sepsis patients were most pronounced at sepsis onset and included elevated uridine and 2-dehydrogluconate and depleted citrulline. Loss of peripheral non-naïve CD4+ T cells was associated with immune dysfunction and reduced cytokine production despite increased T cell activation. CD4+ T cell differentiation and corresponding pro- and anti-inflammatory cytokines varied by pathogen.

CONCLUSION

Pediatric sepsis patients exhibit a complex, dynamic physiologic state characterized by impaired T cell function and immunometabolic dysregulation which varies by pathogen type.

Temperature Trajectory Sub-phenotypes and the Immuno-Inflammatory Response in Pediatric Sepsis

OBJECTIVE

Heterogeneity has hampered sepsis trials, and sub-phenotyping may assist with enrichment strategies. However, biomarker-based strategies are difficult to operationalize. Four sub-phenotypes defined by distinct temperature trajectories in the first 72 h have been reported in adult sepsis. Given the distinct epidemiology of pediatric sepsis, the existence and relevance of temperature trajectory-defined sub-phenotypes in children is unknown. We aimed to classify septic children into de novo sub-phenotypes derived from temperature trajectories in the first 72 h, and compare cytokine, immune function, and immunometabolic markers across subgroups.

METHODS

This was a secondary analysis of a prospective cohort of 191 critically ill septic children recruited from a single academic pediatric intensive care unit. We performed group-based trajectory modeling using temperatures over the first 72 h of sepsis to identify latent profiles. We then used mixed effects regression to determine if temperature trajectory-defined sub-phenotypes were associated with cytokine levels, immune function, and mitochondrial respiration.

RESULTS

We identified four temperature trajectory-defined sub-phenotypes: hypothermic, normothermic, hyperthermic fast-resolvers, and hyperthermic slow-resolvers. Hypothermic patients were less often previously healthy and exhibited lower levels of pro- and anti-inflammatory cytokines and chemokines. Hospital mortality did not differ between hypothermic children (17%) and other sub-phenotypes (3-11%; P = 0.26).

CONCLUSIONS

Critically ill septic children can be categorized into temperature trajectory-defined sub-phenotypes that parallel adult sepsis. Hypothermic children exhibit a blunted cytokine and chemokine profile. Group-based trajectory modeling has utility for identifying subtypes of clinical syndromes by incorporating readily available longitudinal data, rather than relying on inputs from a single timepoint.

Influence of Immune Cell Subtypes on Mitochondrial Measurements in Peripheral Blood Mononuclear Cells From Children with Sepsis

INTRODUCTION

Peripheral blood mononuclear cells (PBMCs) are commonly used to compare mitochondrial function in patients with versus without sepsis, but how these measurements in this mixed cell population vary by composition of immune cell subtypes is not known, especially in children. We determined the effect of changing immune cell composition on PBMC mitochondrial respiration and content in children with and without sepsis.

METHODS

PBMC mitochondrial respiration and citrate synthase (CS) activity, a marker of mitochondrial content, were measured in 167 children with sepsis at three timepoints (day 1-2, 3-5, and 8-14) and once in 19 nonseptic controls. The proportion of lymphocytes and monocytes and T, B, and NK cells was measured using flow cytometry. More specific CD4+ and CD8+ T cell subsets were measured from 13 sepsis patients and 6 controls. Spearman's correlation and simple and mixed effects linear regression were used to determine the association of PBMC mitochondrial measures with proportion of immune cell subtypes.

RESULTS

PBMC mitochondrial respiration and CS activity were correlated with proportion of monocytes, lymphocytes, T B, and NK cells in controls, but not in sepsis patients. PBMC mitochondrial respiration was correlated with CD4+ and CD8+ T cell subsets in both groups. After controlling for differences in immune cell composition between groups using linear regression models, PBMC respiration and CS activity remained lower in sepsis patients than controls.

CONCLUSIONS

Mitochondrial measurements from PBMCs varied with changes in immune cell composition in children with and without sepsis. However, differences in PBMC mitochondrial measurements between sepsis patients and controls were at least partially attributable to the effects of sepsis rather than solely an epiphenomena of variable immune cell composition.

Association of mitochondrial respiratory chain enzymes with the risk and mortality of sepsis among Chinese children

BACKGROUND

Sepsis is a leading cause of pediatric morbidity and mortality worldwide. The aim of this study was to explore the association of decreased mitochondrial respiratory chain enzyme activities with the risk for pediatric sepsis, and explore their association with mortality among affected children.

METHODS

A total of 50 incident cases with sepsis and 49 healthy controls participated in this study. The level of serum coenzyme Q10 was measured by high-performance liquid chromatography, and selected mitochondrial respiratory chain enzymes in WBC were measured using spectrophotometric. Logistic regression models were used to estimate odds ratio (OR) and 95% confidence interval (CI).

RESULTS

The levels of CoQ10, complex II, complex I + III and FoF1-ATPase were significantly higher in healthy controls than in children with sepsis (p < 0.001, = 0.004, < 0.001 and < 0.001, respectively). In children with sepsis, levels of CoQ10 and complex I + III were significantly higher in survived cases than in deceased cases (p < 0.001). Per 0.05 μmol/L, 50 nmol/min.mg and 100 nmol/min.mg increment in CoQ10, complex I + III and FoF1-ATPase were associated with significantly lowered risk of having sepsis, even after adjusting for confounding factors (OR = 0.85, 0.68 and 0.04, p = 0.001, < 0.001 and < 0.001, respectively). Per 0.05 μmol/L and 50 nmol/min.mg increment in CoQ10 and complex I + III was associated with significantly lowered risk of dying from sepsis during hospitalization, and significance retained after adjustment (OR = 0.73 and 0.76, 95% CI: 0.59 to 0.90 and 0.64 to 0.89, p = 0.004 and 0.001, respectively) in children with sepsis.

CONCLUSIONS

Our findings indicate the promising predictive contribution of low serum CoQ10 and complex I + III to the risk of pediatric sepsis and its associated mortality during hospitalization among Chinese children. Trial registration The trial was registered with www.chictr.org.cn , number ChiCTR-IOR-15006446 on May 05, 2015. Retrospectively registered.

Refining the Pediatric Multiple Organ Dysfunction Syndrome

Since its introduction into the medical literature in the 1970s, the term multiple organ dysfunction syndrome (or some variant) has been applied broadly to any patient with >1 concurrent organ dysfunction. However, the epidemiology, mechanisms, time course, and outcomes among children with multiple organ dysfunction vary substantially. We posit that the term pediatric multiple organ dysfunction syndrome (or MODS) should be reserved for patients with a systemic pathologic state resulting from a common mechanism (or mechanisms) that affects numerous organ systems simultaneously. In contrast, children in whom organ injuries are attributable to distinct mechanisms should be considered to have additive organ system dysfunctions but not the syndrome of MODS. Although such differentiation may not always be possible with current scientific knowledge, we make the case for how attempts to differentiate multiple organ dysfunction from other states of additive organ dysfunctions can help to evolve clinical and research priorities in diagnosis, monitoring, and therapy from largely organ-specific to more holistic strategies.

STING1 in sepsis: Mechanisms, functions, and implications

Sepsis is a life-threatening clinical syndrome and one of the most challenging health problems in the world. Pathologically, sepsis and septic shock are caused by a dysregulated host immune response to infection, which can eventually lead to multiple organ failure and even death. As an adaptor transporter between the endoplasmic reticulum and Golgi apparatus, stimulator of interferon response cGAMP interactor 1 (STING1, also known as STING or TMEM173) has been found to play a vital role at the intersection of innate immunity, inflammation, autophagy, and cell death in response to invading microbial pathogens or endogenous host damage. There is ample evidence that impaired STING1, through its immune and non-immune functions, is involved in the pathological process of sepsis. In this review, we discuss the regulation and function of the STING1 pathway in sepsis and highlight it as a suitable drug target for the treatment of lethal infection.

Mitochondrial gene mutations in pediatric septic shock

BACKGROUND

There has been a growing interest in the association between mitochondrial dysfunction and sepsis. However, most studies have focused on mitochondrial structural damage, functional aspects, or the clinical phenotypes in sepsis. The purpose of this study was to evaluate mitochondrial DNA (mtDNA) gene mutations in critically ill pediatric patients with septic shock.

METHOD

Thirteen patients with severe sepsis or septic shock admitted to the pediatric intensive care unit (PICU) of a tertiary children's hospital were enrolled in this prospective observational study. Clinical data from electronic medical records were obtained. Whole-blood samples were collected within 24 h of PICU admission to perform PBMC isolation, mtDNA extraction, and mtDNA sequencing using next-generation sequencing.

RESULTS

mtDNA sequencing revealed mutations in 9 of the 13 patients, presenting 27 point mutations overall, with 15 (55.6%) located in the locus related to adenosine triphosphate production and superoxide metabolism, including electron transport.

CONCLUSION

In this pilot study, significant numbers of mtDNA point mutations were detected in critically ill pediatric patients with septic shock. These mutations could provide promising evidence for mitochondrial dysfunction in sepsis and a basis for further large-scale studies.

IMPACT

This study is the first to examine mitochondrial DNA mutations in pediatric patients with septic shock using next-generation sequencing. A high frequency of mitochondrial DNA mutations was detected in these patients indicating an association with septic shock. This pilot study may provide a potential explanation for the association between mitochondrial dysfunction and septic shock on a genetic basis.

Mitochondrial Dysfunction is Associated With an Immune Paralysis Phenotype in Pediatric Sepsis

OBJECTIVE

Immune dysregulation is a defining feature of sepsis, but the role for mitochondria in the development of immunoparalysis in pediatric sepsis is not known. We sought to determine if mitochondrial dysfunction measured in peripheral blood mononuclear cells (PBMCs) is associated with immunoparalysis and systemic inflammation in children with sepsis.

DESIGN

Prospective observational study.

SETTING

Single-academic pediatric intensive care unit (PICU).

PATIENTS

One hundred sixty-one children with sepsis/septic shock and 18 noninfected PICU controls.

MEASUREMENTS AND MAIN RESULTS

Mitochondrial respiration in PBMCs, markers of immune function, and plasma cytokines were measured on days 1 to 2 (T1), 3 to 5 (T2), and 8 to 14 (T3) after sepsis recognition, and once for controls. Immunoparalysis was defined as whole-blood ex vivo lipopolysaccharide-induced tumor necrosis factor-alpha (TNF-α) ≤200 pg/mL or monocyte human leukocyte antigen-DR ≤30%. Mitochondrial respiration was lower in children with versus without immunoparalysis measured at the same timepoint. Mitochondrial respiration measured early (at T1 and T2) was also lower in those with immunoparalysis at T2 and T3, respectively. Although most patients with immunoparalysis exhibited low mitochondrial respiration, this metabolic finding was not specific to the immunoparalysis phenotype. Plasma cytokines, including IL-8, IL-10, TNF-α, and MCP-1, were highest in the subset of sepsis patients with immune paralysis or low mitochondrial respiration at T1.

CONCLUSIONS

Children with sepsis had lower PBMC mitochondrial respiration when immunoparalysis was present compared with those without immunoparalysis. The subsets with immune paralysis and low mitochondrial respiration exhibited the highest levels of systemic inflammation.

Prognostic Significance of the Fission1/Parkin Ratio for Sepsis: A Prospective Cohort Study

Introduction: Fission1 (Fis1) and parkin are key proteins related to mitochondrial fission and mitophagy, respectively. This study aimed to assess the prognostic value of the Fis1/parkin ratio as a biomarker in patients with sepsis.

Methods: Consecutive patients with sepsis (n = 133) or simple infection (n = 24) were enrolled within 24 h of arrival at the intensive care unit (ICU). Serum levels of Fis1, parkin, mitofusin2 (Mfn2), and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) were measured by enzyme-linked immunosorbent assay (ELISA) upon ICU admission. Clinical parameters and standard laboratory test data were also collected. All patients received follow-up for at least 28 days.

Results: Patients with sepsis presented with significantly decreased serum levels of parkin, Mfn2, and PGC-1α, but an increased serum Fis1 level and Fis1/parkin, Fis1/Mfn2, and Fis1/PGC-1α ratios at ICU admission. Relative to patients with simple infections, the ratios were remarkably elevated in septic patients—particularly septic shock patients. The area under the receiver operating characteristic (ROC) curve of the Fis1/parkin ratio was greater than that of Fis1, parkin, Mfn2, and PGC-1α levels as well as that of the Fis1/Mfn2 and Fis1/PGC-1α ratios for prediction of 28-day mortality due to sepsis. All of the ratios were significantly higher in non-survivors than survivors at the 28-day follow-up examination. Fis1/parkin ratio was found to be an independent predictor of 28-day mortality in patients with sepsis.

Conclusions: The Fis1/parkin ratio is valuable for risk stratification in patients with sepsis and is associated with poor clinical outcomes for sepsis in the ICU.

Decreased Intestinal Microbiome Diversity in Pediatric Sepsis: A Conceptual Framework for Intestinal Dysbiosis to Influence Immunometabolic Function

Supplemental Digital Content is available in the text.

Objectives:

The intestinal microbiome can modulate immune function through production of microbial-derived short-chain fatty acids. We explored whether intestinal dysbiosis in children with sepsis leads to changes in microbial-derived short-chain fatty acids in plasma and stool that are associated with immunometabolic dysfunction in peripheral blood mononuclear cells.

Design:

Prospective observational pilot study.

Setting:

Single academic PICU.

Patients:

Forty-three children with sepsis/septic shock and 44 healthy controls.

Measurements and Main Results:

Stool and plasma samples were serially collected for sepsis patients; stool was collected once for controls. The intestinal microbiome was assessed using 16S ribosomal RNA sequencing and alpha- and beta-diversity were determined. We measured short-chain fatty acids using liquid chromatography, peripheral blood mononuclear cell mitochondrial respiration using high-resolution respirometry, and immune function using ex vivo lipopolysaccharide-stimulated whole blood tumor necrosis factor-α. Sepsis patients exhibited reduced microbial diversity compared with healthy controls, with lower alpha- and beta-diversity. Reduced microbial diversity among sepsis patients (mainly from lower abundance of commensal obligate anaerobes) was associated with increased acetic and propionic acid and decreased butyric, isobutyric, and caproic acid. Decreased levels of plasma butyric acid were further associated with lower peripheral blood mononuclear cell mitochondrial respiration, which in turn, was associated with lower lipopolysaccharide-stimulated tumor necrosis factor-α. However, neither intestinal dysbiosis nor specific patterns of short-chain fatty acids were associated with lipopolysaccharide-stimulated tumor necrosis factor-α.

Conclusions:

Intestinal dysbiosis was associated with altered short-chain fatty acid metabolites in children with sepsis, but these findings were not linked directly to mitochondrial or immunologic changes. More detailed mechanistic studies are needed to test the role of microbial-derived short-chain fatty acids in the progression of sepsis.

Targeting the eCIRP/TREM-1 interaction with a small molecule inhibitor improves cardiac dysfunction in neonatal sepsis

Background

Neonatal sepsis and the associated myocardial dysfunction remain a leading cause of infant mortality. Extracellular cold-inducible RNA-binding protein (eCIRP) acts as a ligand of triggering receptor expressed on myeloid cells-1 (TREM-1). M3 is a small CIRP-derived peptide that inhibits the eCIRP/TREM-1 interaction. We hypothesize that the eCIRP/TREM-1 interaction in cardiomyocytes contributes to sepsis-induced cardiac dysfunction in neonatal sepsis, while M3 is cardioprotective.

Methods

Serum was collected from neonates in the Neonatal Intensive Care Unit (NICU). 5–7-day old C57BL/6 mouse pups were used in this study. Primary murine neonatal cardiomyocytes were stimulated with recombinant murine (rm) CIRP with M3. TREM-1 mRNA and supernatant cytokine levels were assayed. Mitochondrial oxidative stress, ROS, and membrane potential were assayed. Neonatal mice were injected with rmCIRP and speckle-tracking echocardiography was conducted to measure cardiac strain. Sepsis was induced by i.p. cecal slurry. Mouse pups were treated with M3 or vehicle. After 16 h, echocardiography was performed followed by euthanasia for tissue analysis. A 7-day survival study was conducted.

Results

Serum eCIRP levels were elevated in septic human neonates. rmCIRP stimulation of cardiomyocytes increased TREM-1 gene expression. Stimulation of cardiomyocytes with rmCIRP upregulated TNF-α and IL-6 in the supernatants, while this upregulation was inhibited by M3. Stimulation of cardiomyocytes with rmCIRP resulted in a reduction in mitochondrial membrane potential (MMP) while M3 treatment returned MMP to near baseline. rmCIRP caused mitochondrial calcium overload; this was inhibited by M3. rmCIRP injection impaired longitudinal and radial cardiac strain. Sepsis resulted in cardiac dysfunction with a reduction in cardiac output and left ventricular end diastolic diameter. Both were improved by M3 treatment. Treatment with M3 attenuated serum, cardiac, and pulmonary levels of pro-inflammatory cytokines compared to vehicle-treated septic neonates. M3 dramatically increased sepsis survival.

Conclusions

Inhibition of eCIRP/TREM-1 interaction with M3 is cardioprotective, decreases inflammation, and improves survival in neonatal sepsis.

Trial registration Retrospectively registered.

Endothelial Biomarkers Are Associated With Indirect Lung Injury in Sepsis-Associated Pediatric Acute Respiratory Distress Syndrome

Supplemental Digital Content is available in the text.

Objectives:

Acute respiratory distress syndrome occurring in the setting of direct versus indirect lung injury may reflect different pathobiologies amenable to different treatment strategies. We sought to test whether a panel of plasma biomarkers differed between children with sepsis-associated direct versus indirect acute respiratory distress syndrome. We hypothesized that a biomarker profile indicative of endothelial activation would be associated with indirect acute respiratory distress syndrome.

Design:

Observational cohort.

Setting:

Academic PICU.

Subjects:

Patients less than 18 years old with sepsis-associated direct (pneumonia, n = 52) or indirect (extrapulmonary sepsis, n = 46) acute respiratory distress syndrome.

Interventions:

None.

Measurements and Main Results:

Of 58 biomarkers examined, 33 differed by acute respiratory distress syndrome subtype. We used classification and regression tree methodology to examine associations between clinical and biochemical markers and acute respiratory distress syndrome subtype. The classification and regression tree model using only clinical variables (age, sex, race, oncologic comorbidity, and Pediatric Risk of Mortality-III score) performed worse than the classification and regression tree model using five clinical variables and 58 biomarkers. The best classification and regression tree model used only four endothelial biomarkers, including elevated angiopoietin-2/angiopoietin-1 ratio, vascular cell-adhesion molecule, and von Willebrand factor, to identify indirect acute respiratory distress syndrome. Test characteristics were 89% (80–97%) sensitivity, 80% (69–92%) specificity, positive predictive value 84% (74–93%), and negative predictive value 86% (76–96%).

Conclusions:

Indirect lung injury in children with acute respiratory distress syndrome is characterized by a biomarker profile indicative of endothelial activation, excess inflammation, and worse outcomes. A model using four biomarkers has the potential to be useful for more precisely identifying patients with acute respiratory distress syndrome whose pathobiology may respond to endothelial-targeted therapies in future trials.

Systemic Endothelial Activation Is Associated With Early Acute Respiratory Distress Syndrome in Children With Extrapulmonary Sepsis

OBJECTIVES

Systemic endothelial activation may contribute to sepsis-associated organ injury, including acute respiratory distress syndrome. We hypothesized that children with extrapulmonary sepsis with versus without acute respiratory distress syndrome would have plasma biomarkers indicative of increased endothelial activation and that persistent biomarker changes would be associated with poor outcome.

DESIGN

Observational cohort.

SETTING

Academic PICU.

PATIENTS

Patients less than 18 years old with sepsis from extrapulmonary infection with (n = 46) or without (n = 54) acute respiratory distress syndrome and noninfected controls (n = 19).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Endothelial (angiopoietin-1, angiopoietin-2, tyrosine kinase with immunoglobulin-like loop epidermal growth factor homology domain 2, vascular endothelial growth factor, soluble fms-like tyrosine kinase, von Willebrand factor, E-selectin, intercellular adhesion molecule, vascular cell adhesion molecule, thrombomodulin) and inflammatory biomarkers (C-reactive protein, interleukin-6, and interleukin-8) were measured from peripheral plasma collected within 3 days (time 1) of sepsis recognition and at 3-6 days (time 2) and 7-14 days (time 3). Time 1 biomarkers and longitudinal measurements were compared for sepsis patients with versus without acute respiratory distress syndrome and in relation to complicated course, defined as greater than or equal to two organ dysfunctions at day 7 or death by day 28. Angiopoietin-2, angiopoietin-2/angiopoietin-1 ratio, tyrosine kinase with immunoglobulin-like loop epidermal growth factor homology domain 2, vascular endothelial growth factor, von Willebrand factor, E-selectin, intercellular adhesion molecule, vascular cell adhesion molecule, thrombomodulin, endocan, C-reactive protein, interleukin-6, and interleukin-8 were different between sepsis and noninfected control patients at time 1. Among patients with sepsis, those with acute respiratory distress syndrome had higher angiopoietin-2/angiopoietin-1 ratio, vascular endothelial growth factor, vascular cell adhesion molecule, thrombomodulin, endocan, interleukin-6, and interleukin-8 than those without acute respiratory distress syndrome (all p < 0.003). Angiopoietin-2 and angiopoietin-2/angiopoietin-1 ratio remained higher in sepsis with versus without acute respiratory distress syndrome after multivariable analyses. Time 1 measures of angiopoietin-2, angiopoietin-2/-1 ratio, von Willebrand factor, and endocan were indicative of complicated course in all sepsis patients (all area under the receiver operating curve ≥ 0.80). In sepsis without acute respiratory distress syndrome, soluble fms-like tyrosine kinase decreased more quickly and von Willebrand factor and thrombomodulin decreased more slowly in those with complicated course.

CONCLUSIONS

Children with extrapulmonary sepsis with acute respiratory distress syndrome had plasma biomarkers indicative of greater systemic endothelial activation than those without acute respiratory distress syndrome. Several endothelial biomarkers measured near sepsis recognition were associated with complicated course, whereas longitudinal biomarker changes yielded prognostic information only in those without sepsis-associated acute respiratory distress syndrome.

Early label-free analysis of mitochondrial redox states by Raman spectroscopy predicts septic outcomes

•

Resonance Raman spectroscopy was applied to in vivo detection of the mitochondrial redox state in septic mice for the first time.

•

Monitoring mitochondrial redox states using resonance Raman spectroscopy had higher prognostic accuracy for mortality than the lactate level during sepsis and could be a novel diagnostic marker for predicting septic outcomes at an early time point.

•

Resonance Raman spectroscopy could detect mitochondrial dysfunction in sepsis and provide a biomarker that can be a specific target of adjunctive treatment.

Background

Sepsis remains an unacceptably high mortality due to the lack of biomarkers for predicting septic outcomes in the early period. Mitochondrial redox states play a pivotal role in this condition and are disturbed early in the development of sepsis. Here, we hypothesized that visualizing mitochondrial redox states via resonance Raman spectroscopy (RRS) could identify septic outcomes at an early time point. Sepsis was induced by cecal ligation and puncture (CLP). We applied RRS analysis at baseline and 30 min, 1 h, 2 h, 4 h, and 6 h after CLP, and the mitochondrial redox states were identified. The levels of blood lactate as a predictor in sepsis were assessed. Our study is the first to reveal the possibility of in vivo detection of the mitochondrial redox state by using RRS in septic mice. The peak area for the Raman reduced mitochondrial fraction, the indicator of mitochondrial redox states, fluctuated significantly at 2 h after CLP. This fluctuation occurred earlier than the change in lactate level. Moreover, this fluctuation had higher prognostic accuracy for mortality than the lactate level during sepsis and could be a novel diagnostic marker for predicting septic outcomes according to the cutoff value of 1.059, which had a sensitivity of 80% and a specificity of 90%.

Objectives

To explore an effective indicator concerning mitochondrial redox states in the early stage of sepsis and to predict septic outcomes accurately in vivo using non-invasive and label-free Resonance Raman spectroscopy (RRS) analysis.

Methods

Mitochondria, primary skeletal muscle cells andex-vivo muscles harvested from gastrocnemius were detected mitochondrial redox states respectively by using RRS. Sepsis was induced by cecal ligation and puncture (CLP). We applied RRS analysis at baseline and 30 min, 1 h, 2 h, 4 h, and 6 h after CLP, and the mitochondrial redox states were identified. The levels of blood lactate as a predictor in sepsis were assessed. The predictive correlation of mitochondrial redox states on mortality, inflammation and organ dysfunction was further assessed.

Results

Mitochondrial redox states were clearly recognized in ex-vivo gastrocnemius muscles as well as purified mitochondria and primary skeletal muscle cells by using RRS. The peak area for the Raman reduced mitochondrial fraction, the indicator of mitochondrial redox states, fluctuated significantly at 2 h after CLP. This fluctuation occurred earlier than the change in lactate level. Moreover, this fluctuation had higher prognostic accuracy for mortality than the lactate level during sepsis and could be a novel diagnostic marker for predicting septic outcomes according to the cutoff value of 1.059, which had a sensitivity of 80% and a specificity of 90%.

Conclusions

This study demonstrated that monitoring mitochondrial redox states using RRS as early as 2 h could indicate outcomes in septic mice. These data may contribute to developing a non-invasive clinical device concerning mitochondrial redox states by using bedside-RRS.

The Metabolic Basis of Immune Dysfunction Following Sepsis and Trauma

Critically ill, severely injured and high-risk surgical patients are vulnerable to secondary infections during hospitalization and after hospital discharge. Studies show that the mitochondrial function and oxidative metabolism of monocytes and macrophages are impaired during sepsis. Alternatively, treatment with microbe-derived ligands, such as monophosphoryl lipid A (MPLA), peptidoglycan, or β-glucan, that interact with toll-like receptors and other pattern recognition receptors on leukocytes induces a state of innate immune memory that confers broad-spectrum resistance to infection with common hospital-acquired pathogens. Priming of macrophages with MPLA, CPG oligodeoxynucleotides (CpG ODN), or β-glucan induces a macrophage metabolic phenotype characterized by mitochondrial biogenesis and increased oxidative metabolism in parallel with increased glycolysis, cell size and granularity, augmented phagocytosis, heightened respiratory burst functions, and more effective killing of microbes. The mitochondrion is a bioenergetic organelle that not only contributes to energy supply, biosynthesis, and cellular redox functions but serves as a platform for regulating innate immunological functions such as production of reactive oxygen species (ROS) and regulatory intermediates. This review will define current knowledge of leukocyte metabolic dysfunction during and after sepsis and trauma. We will further discuss therapeutic strategies that target leukocyte mitochondrial function and might have value in preventing or reversing sepsis- and trauma-induced immune dysfunction.