Role of cellular events in the pathophysiology of sepsis

Blimp-1 orchestrates macrophage polarization and metabolic homeostasis via purine biosynthesis in sepsis

Sepsis is a life-threatening condition characterized by a dysregulated immune response to infection, leading to systemic inflammation and organ dysfunction. Macrophage polarization plays a critical role in pathogenesis of sepsis, and the influence of B lymphocyte-induced maturation protein-1 (Blimp-1) on this polarization is an underexplored yet pivotal aspect. This study aimed to elucidate the role of Blimp-1 in macrophage polarization and metabolism during sepsis. Using a murine cecal ligation and puncture model, we observed elevated Blimp-1 expression in M2 macrophages. Knockdown of Blimp-1 by macrophage-targeted adeno-associated virus in this model resulted in decreased survival rates, exacerbated tissue damage, and impaired M2 polarization, underscoring its protective role in sepsis. In vitro studies with bone marrow-derived macrophage (BMDM), RAW264.7, and THP-1 cells further demonstrated Blimp-1 promotes M2 polarization and modulates key metabolic pathways. Metabolomics and dual-luciferase assays revealed Blimp-1 significantly influences purine biosynthesis and the downstream Ornithine cycle, which are essential for M2 macrophage polarization. In vitro studies with BMDM further suggested that the purine biosynthesis and Ornithine cycle metabolic regulation is involved in Blimp-1's effects on M2 macrophage polarization, and mediates Blimp-1's impact on septic mice. Our findings unveil a novel mechanism by which Blimp-1 modulates macrophage polarization through metabolic regulation, presenting potential therapeutic targets for sepsis. This study highlights the significance of Blimp-1 in orchestrating macrophage responses and metabolic adaptations in sepsis, offering valuable insights into its role as a critical regulator of immune and metabolic homeostasis.

The Modulation of Septic Shock: A Proteomic Approach

Sepsis poses a significant challenge due its lethality, involving multiple organ dysfunction and impaired immune responses. Among several factors affecting sepsis, monocytes play a crucial role; however, their phenotype, proteomic profile, and function in septic shock remain unclear. Our aim was to fully characterize the subpopulations and proteomic profiles of monocytes seen in septic shock cases and discuss their possible impact on the disease. Peripheral blood monocyte subpopulations were phenotype based on CD14/CD16 expression by flow cytometry, and proteins were extracted from the monocytes of individuals with septic shock and healthy controls to identify changes in the global protein expression in these cells. Analysis using 2D-nanoUPLC-UDMSE identified 67 differentially expressed proteins in shock patients compared to controls, in which 44 were upregulated and 23 downregulated. These proteins are involved in monocyte reprogramming, immune dysfunction, severe hypotension, hypo-responsiveness to vasoconstrictors, vasodilation, endothelial dysfunction, vascular injury, and blood clotting, elucidating the disease severity and therapeutic challenges of septic shock. This study identified critical biological targets in monocytes that could serve as potential biomarkers for the diagnosis, prognosis, and treatment of septic shock, providing new insights into the pathophysiology of the disease.

A synthetic bioactive peptide of the C-terminal fragment of adhesion protein Fibulin7 attenuates the inflammatory functions of innate immune cells in LPS-induced systemic inflammation

OBJECTIVE

Systemic inflammation is associated with improper localization of hyperactive neutrophils and monocytes in visceral organs. Previously, a C-terminal fragment of adhesion protein Fibulin7 (Fbln7-C) was shown to regulate innate immune functionality during inflammation. Recently, a shorter bioactive peptide of Fbln7-C, FC-10, via integrin binding was shown to reduce ocular angiogenesis. However, the role of FC-10 in regulating the neutrophils and monocyte functionality during systemic inflammatory conditions is unknown. The study sought to explore the role of FC-10 peptide on the functionality of innate immune cells during inflammation and endotoxemic mice.

METHODS

Neutrophils and monocytes were isolated from healthy donors and septic patient clinical samples and Cell adhesion assay was performed using a UV spectrophotometer. Gene expression studies were performed using qPCR. Protein level expression was measured using ELISA and flow cytometry. ROS assay, and activation markers analysis in vitro, and in vivo were done using flow cytometry.

TREATMENT

Cells were stimulated with LPS (100 ng/mL) and studied in the presence of peptides (10 μg, and 20 μg/mL) in vitro. In an in vivo study, mice were administered with LPS (36.8 mg/kg bw) and peptide (20 μg).

RESULTS

This study demonstrates that human neutrophils and monocytes adhere to FC-10 via integrin β1, inhibit spreading, ROS, surface activation markers (CD44, CD69), phosphorylated Src kinase, pro-inflammatory genes, and protein expression, compared to scrambled peptide in cells isolated from healthy donors and clinical sample. In line with the in vitro data, FC-10 (20 μg) administration significantly decreases innate cell infiltration at inflammatory sites, improves survival in endotoxemia animals & reduces the inflammatory properties of neutrophils and monocytes isolated from septic patients.

CONCLUSION

FC-10 peptide can regulate neutrophils and monocyte functions and has potential to be used as an immunomodulatory therapeutic in inflammatory diseases.

Pediatric sepsis inflammatory blood biomarkers that correlate with clinical variables and severity of illness scores

BACKGROUND

Sepsis is a dysregulated systemic inflammatory response triggered by infection, resulting in organ dysfunction. A major challenge in clinical pediatrics is to identify sepsis early and then quickly intervene to reduce morbidity and mortality. As blood biomarkers hold promise as early sepsis diagnostic tools, we aimed to measure a large number of blood inflammatory biomarkers from pediatric sepsis patients to determine their predictive ability, as well as their correlations with clinical variables and illness severity scores.

METHODS

Pediatric patients that met sepsis criteria were enrolled, and clinical data and blood samples were collected. Fifty-eight inflammatory plasma biomarker concentrations were determined using immunoassays. The data were analyzed with both conventional statistics and machine learning.

RESULTS

Twenty sepsis patients were enrolled (median age 13 years), with infectious pathogens identified in 75%. Vasopressors were administered to 85% of patients, while 55% received invasive ventilation and 20% were ventilated non-invasively. A total of 24 inflammatory biomarkers were significantly different between sepsis patients and age/sex-matched healthy controls. Nine biomarkers (IL-6, IL-8, MCP-1, M-CSF, IL-1RA, hyaluronan, HSP70, MMP3, and MMP10) yielded AUC parameters > 0.9 (95% CIs: 0.837-1.000; p < 0.001). Boruta feature reduction yielded 6 critical biomarkers with their relative importance: IL-8 (12.2%), MCP-1 (11.6%), HSP70 (11.6%), hyaluronan (11.5%), M-CSF (11.5%), and IL-6 (11.5%); combinations of 2 biomarkers yielded AUC values of 1.00 (95% CI: 1.00-1.00; p < 0.001). Specific biomarkers strongly correlated with illness severity scoring, as well as other clinical variables. IL-3 specifically distinguished bacterial versus viral infection (p < 0.005).

CONCLUSIONS

Specific inflammatory biomarkers were identified as markers of pediatric sepsis and strongly correlated to both clinical variables and sepsis severity.

Silenced-C5ar1 improved multiple organ injury in sepsis rats via inhibiting neutrophil extracellular trap

Sepsis has a systemic inflammatory response syndrome caused by infection. While neutrophils play contradictory roles in different stages of sepsis. Neutrophils have been proven to play an antibacterial role by producing neutrophil extracellular traps (NETs). Although the NET is beneficial to bacteria resistance, abnormal NET increases tissue damage. The complement C5a receptor 1 (C5ar1) is a gene related to strong inflammatory reactions and is found to be associated with inflammatory factors. This study found that there were 45 down-regulated genes and 704 up-regulated genes in sepsis rats by transcriptome sequencing. And those genes were significantly related to inflammation and immunity by GO and KEGG enrichment analysis involving the chemokine signaling pathway, the Toll-like receptor (TLR) signaling pathway, and the Fc gamma R-mediated phagocytosis. Additionally, the C5ar1 gene was significantly upregulated with interesting potential in sepsis and used for further study. This study used cecum ligation and puncture (CLP) rats that were respectively injected intravenously with PBS or the lentivirus vector to explore the effect of C5ar1 on CLP rats. It demonstrated that silenced- C5ar1 inhibited the ALT, AST, BUN, and CREA levels, improved the lung and spleen injury, and reduced the TNF-α, IL-6, IL-1β, IL-10, cf-DNA, and cfDNA/MPO levels. Additionally, silenced C5ar1 inhibited the TLR2, TLR4, and peptidylarginine deiminase 4 expression levels, which suggested the improvement of silenced C5ar1 on sepsis via inhibiting NETs and the TLR signaling pathway. This study provides a basis and new direction for the study of treatment on sepsis.

The Relationship between Complements and Age-Related Macular Degeneration and Its Pathogenesis

Age-related macular degeneration is a retinal disease that causes permanent loss of central vision in people over the age of 65. Its pathogenesis may be related to mitochondrial dysfunction, inflammation, apoptosis, autophagy, complement, intestinal flora, and lipid disorders. In addition, the patient's genes, age, gender, cardiovascular disease, unhealthy diet, and living habits may also be risk factors for this disease. Complement proteins are widely distributed in serum and tissue fluid. In the early 21st century, a connection was found between the complement cascade and age-related macular degeneration. However, little is known about the effect of complement factors on the pathogenesis of age-related macular degeneration. This article reviews the factors associated with age-related macular degeneration, the relationship between each factor and complement, the related functions, and variants and provides new ideas for the treatment of this disease.

Purinergic P2X7 receptor expression increases in leukocytes from intra-abdominal septic patients

Inflammation is a tightly coordinated response of the host immune system to bacterial and viral infections, triggered by the production of inflammatory cytokines. Sepsis is defined as a systemic inflammatory response followed by immunosuppression of the host and organ dysfunction. This imbalance of the immune response increases the risk of mortality of patients with sepsis, making it a major problem for critical care units worldwide. The P2X7 receptor plays a crucial role in activating the immune system by inducing the activation of peripheral blood mononuclear cells. In this study, we analyzed a cohort of abdominal origin septic patients and found that the expression of the P2X7 receptor in the plasma membrane is elevated in the different subsets of lymphocytes. We observed a direct relationship between the percentage of P2X7-expressing lymphocytes and the early inflammatory response in sepsis. Additionally, in patients whose lymphocytes presented a higher percentage of P2X7 surface expression, the total lymphocytes populations proportionally decreased. Furthermore, we found a correlation between elevated soluble P2X7 receptors in plasma and inflammasome-dependent cytokine IL-18. In summary, our work demonstrates that P2X7 expression is highly induced in lymphocytes during sepsis, and this correlates with IL-18, along with other inflammatory mediators such as IL-6, IL-8, and procalcitonin.

Synthesis and protective effect of pyrazole conjugated imidazo[1,2-a]pyrazine derivatives against acute lung injury in sepsis rats via attenuation of NF-κB, oxidative stress, and apoptosis

The current work was conducted to elucidate the pharmacological effect of pyrazole-conjugated imidazo[1,2-a]pyrazine derivatives against acute lung injury in rats in sepsis and their mechanism of action. Various pyrazole-conjugated imidazo[1,2-a]-pyrazine derivatives have been synthesized in a straightforward synthetic route. They exhibited a diverse range of inhibitory activity against NF-ĸB with IC 50 ranging from 1 to 94 µmol L-1. Among them, compound 3h [(4-(4-((4-hydroxyphenyl)sulfonyl) phenyl)-5-(4-methoxyphenyl)-4,5-dihydro-1H-pyrazol-1-yl) (8-(methylamino)imidazo[1,2-a]pyrazin-2-yl)methanone] was identified as the most potent NF-κB inhibitor with IC 50 of 1.02 µmol L-1. None of the synthesized compounds was found cytotoxic to normal cell-line MCF-12A. The pharmacological activity of the most potent NF-ĸB inhibitor 3h was also investigated in cecal ligation and puncture (CLP)-induced sepsis injury of the lung in rats. Compound 3h was administered to rats after induc tion of lung sepsis, and various biochemical parameters were measured. Results suggested that compound 3h significantly reduced lung inflammation and membrane permeability, as evidenced by H&E staining of lung tissues. It substantially reduced the generation of pro-inflammatory cytokines (TNF-α, IL-1B, IL-6) and oxidative stress (MPO, MDA, SOD). It showed attenuation of NF-ĸB and apoptosis in Western blot and annexin--PI assay, resp. Compound 3h also reduced the production of bronchoalveolar lavage fluid from the lung and provided a protective effect against lung injury. Our study showed the pharmacological significance of pyrazole-conjugated imidazo[1,2-a] pyrazine derivative 3h against acute lung injury in sepsis rats.

Identification and validation of a novel mitochondrion-related gene signature for diagnosis and immune infiltration in sepsis

Background

Owing to the complex pathophysiological features and heterogeneity of sepsis, current diagnostic methods are not sufficiently precise or timely, causing a delay in treatment. It has been suggested that mitochondrial dysfunction plays a critical role in sepsis. However, the role and mechanism of mitochondria-related genes in the diagnostic and immune microenvironment of sepsis have not been sufficiently investigated.

Methods

Mitochondria-related differentially expressed genes (DEGs) were identified between human sepsis and normal samples from GSE65682 dataset. Least absolute shrinkage and selection operator (LASSO) regression and the Support Vector Machine (SVM) analyses were carried out to locate potential diagnostic biomarkers. Gene ontology and gene set enrichment analyses were conducted to identify the key signaling pathways associated with these biomarker genes. Furthermore, correlation of these genes with the proportion of infiltrating immune cells was estimated using CIBERSORT. The expression and diagnostic value of the diagnostic genes were evaluated using GSE9960 and GSE134347 datasets and septic patients. Furthermore, we established an in vitro sepsis model using lipopolysaccharide (1 µg/mL)-stimulated CP-M191 cells. Mitochondrial morphology and function were evaluated in PBMCs from septic patients and CP-M191 cells, respectively.

Results

In this study, 647 mitochondrion-related DEGs were obtained. Machine learning confirmed six critical mitochondrion-related DEGs, including PID1, CS, CYP1B1, FLVCR1, IFIT2, and MAPK14. We then developed a diagnostic model using the six genes, and receiver operating characteristic (ROC) curves indicated that the novel diagnostic model based on the above six critical genes screened sepsis samples from normal samples with area under the curve (AUC) = 1.000, which was further demonstrated in the GSE9960 and GSE134347 datasets and our cohort. Importantly, we also found that the expression of these genes was associated with different kinds of immune cells. In addition, mitochondrial dysfunction was mainly manifested by the promotion of mitochondrial fragmentation (p<0.05), impaired mitochondrial respiration (p<0.05), decreased mitochondrial membrane potential (p<0.05), and increased reactive oxygen species (ROS) generation (p<0.05) in human sepsis and LPS-simulated in vitro sepsis models.

Conclusion

We constructed a novel diagnostic model containing six MRGs, which has the potential to be an innovative tool for the early diagnosis of sepsis.

Inflammatory mechanisms and intervention strategies for sepsis-induced myocardial dysfunction

Sepsis-induced myocardial dysfunction (SIMD) is the leading cause of death in patients with sepsis in the intensive care units. The main manifestations of SIMD are systolic and diastolic dysfunctions of the myocardium. Despite our initial understanding of the SIMD over the past three decades, the incidence and mortality of SIMD remain high. This may be attributed to the large degree of heterogeneity among the initiating factors, disease processes, and host states involved in SIMD. Previously, organ dysfunction caused by sepsis was thought to be an impairment brought about by an excessive inflammatory response. However, many recent studies have shown that SIMD is a consequence of a combination of factors shaped by the inflammatory responses between the pathogen and the host. In this article, we review the mechanisms of the inflammatory responses and potential novel therapeutic strategies in SIMD.

Roles of ginsenosides in sepsis

The herbal medication Panax ginseng Meyer has widespread use in China, Korea, and other parts of the world. The main constituents of ginseng are ginsenosides, which include over 30 different triterpene saponins. It has been found that ginsenosides and their metabolites including Rg1, compound K, Rb1, Re, Rg3, and Rg5 exert anti-inflammatory activities by binding to the glucocorticoid receptor, modulating inflammation-related signaling, including NF-κB and MAPK signaling, and reducing levels of pro-inflammatory cytokines. Here, we review the recent literature on the molecular actions of ginsenosides in sepsis, suggesting ways in which they may be used to prevent and treat the disease.

Phenotypic and functional characterisation of synovial fluid-derived neutrophils in knee osteoarthritis and knee infection

OBJECTIVE

An increase in the number of neutrophils (NEUs) has long been associated with infections in the knee joints; however, their impact on knee osteoarthritis (KOA) pathophysiology remains largely unexplored.

DESIGN

This study compared the phenotypic and functional characteristics of synovial fluid (SF)-derived NEUs in KOA and knee infection (INF).

RESULTS

KOA NEUs were characterised by a lower expression of CD11b, CD54, and CD64 and higher expression of CD62L, TLR2, and TLR4 compared with INF NEUs. Except for CCL2, lower levels of inflammatory mediators and proteases were detected in KOA SF than in INF SF. Functionally, KOA NEUs displayed increased reactive oxygen species production and phagocytic activity compared with INF NEUs. Moreover, KOA and INF NEUs differed in cell sizes, histological characteristics of the surrounding synovial tissues, and their effects on the endothelial cells assessed by human umbilical vein endothelial cells. When KOA patients were subdivided based on the SF NEU abundance, patients with high NEUs (10%-60%) were characterised by i) elevated SF protein levels of TNF-α, IL-1RA, MMP-9, sTREM-1, VILIP-1 and ii) lower CD54, CD64, TLR2 and TLR4 expression compared to patients with low NEUs (<10%). Analysis of paired SF samples suggests that low or high NEU percentages, respectively, persist throughout the course of disease.

CONCLUSIONS

Our findings suggest that NEU may play a significant role in KOA pathophysiology. Further studies should explore the mechanisms that contribute to the increased number of NEUs in SF and the clinical consequences of neutrophilic phenotype in KOA.

Comparison enteral superoxide dismutase 1 IU and 5 IU from Cucumis melo L.C extract combined with gliadin as an antioxidant and anti-inflammatory in LPS-Induced sepsis model rats

Sepsis is a major cause of death in intensive care units whose development is supported by an imbalance of oxidative stress and antioxidant. Superoxide dismutase (SOD) is a primer endogen antioxidant that prevents reactive oxygen species (ROS). Extensive studies on animals and humans have examined Cucumis melo L.C, a cantaloupe rich in SOD, and its combination with gliadin. The studies aimed to determine the effect of enteral administration of Cucumis melo L.C. gliadin (CME-gliadin) 28 days before inducing sepsis in rats. This experimental study aimed to compare four groups of male Wistar rats, including negative and positive control rats and those supplemented with SOD CME-gliadin 1 IU/day and SOD CME-gliadin 5 IU/day. All rats were given the same standard, except the supplementation for 28 days. Sepsis was induced by intraperitoneal injection of LPS 10 mg/kg. Enteral administration of SOD – gliadin extract of CME-gliadin for 28 days was used as antioxidant prophylaxis against oxidative stress due to sepsis. The results showed that enteral administration of CME-gliadin of 1 IU/day and 5 IU/day significantly increased SOD levels based on examination after 14 and 28 days. Also, it significantly decreased MDA (p < 0.001), TNF-α (p < 0.001), and lactate levels in rats induced by sepsis. However, the increase in lactate levels was above >1.64 mmol/l, indicating a high mortality rate. There was no significant difference in SOD, MDA, TNF-α, and Lactate levels between SOD 1 IU and SOD 5 IU. This descriptive data show that SOD 5 IU has a better result in MDA, TNF-α, and Lactate levels than SOD 1 IU.

mTOR Modulates the Endoplasmic Reticulum Stress-Induced CD4+ T Cell Apoptosis Mediated by ROS in Septic Immunosuppression

Introduction

When sepsis attacks the body, the excessive reactive oxygen species (ROS) production can result to endoplasmic reticulum stress (ERS) and eventually cause lymphocyte apoptosis. The mammalian target of rapamycin (mTOR) is essential for regulating lymphocyte apoptosis; we hypothesized that it mediates CD4⁺ T cell apoptosis during ROS-related ERS.

Method

We, respectively, used ROS and ERS blockers to intervene septic mice and then detected ERS protein expression levels to verify the relationship between them. Additionally, we constructed T cell-specific mTOR and TSC1 gene knockout mice to determine the role of mTOR in ROS-mediated, ERS-induced CD4⁺ T cell apoptosis.

Results

Blocking ROS significantly suppressed the CD4⁺ T cell apoptosis associated with the reduction in ERS, as revealed by lower levels of GRP78 and CHOP. ERS rapidly induced mTOR activation, leading to the induction of CD4⁺ T cell apoptosis. However, mTOR knockout mice displayed reduced expression of apoptotic proteins and less ER vesiculation and expansion than what was observed in the wild-type sepsis controls.

Conclusion

By working to alleviate ROS-mediated, ERS-induced CD4⁺ T cell apoptosis, the mTOR pathway is vital for CD4⁺ T cell survival in sepsis mouse model.

Low-dose mycophenolate mofetil improves survival in a murine model of Staphylococcus aureus sepsis by increasing bacterial clearance and phagocyte function

Regulators of TLRs signaling pathways play an important role in the control of the pro-inflammatory response that contributes to sepsis-induced tissue injury. Mycophenolate mofetil, an immunosuppressive drug inhibiting lymphocyte proliferation, has been reported to be a regulator of TLRs signaling pathways. Whether MMF used at infra-immunosuppressive doses has an impact on survival and on innate immune response in sepsis is unknown.

C57BL/6J mice were infected intraperitoneally with 108 CFU Staphylococcus aureus, and treated or not with low-dose of MMF (20mg/kg/day during 4 days). Survival rate and bacterial clearance were compared. Cytokine levels, quantitative and qualitative cellular responses were assessed. S. aureus – infected mice treated with MMF exhibited improved survival compared to non-treated ones (48% vs 10%, p&lt;0.001). With the dose used for all experiments, MMF did not show any effect on lymphocyte proliferation. MMF treatment also improved local and systemic bacterial clearance, improved phagocytosis activity of peritoneal macrophages resulting in decreased inflammatory cytokines secretion. MMF-treated mice showed enhanced activation of NF-κB seemed with a suspected TLR4-dependent mechanism. These results suggest that infra-immunosuppressive doses of MMF improve host defense during S. aureus sepsis and protects infected mice from fatal outcome by regulating innate immune responses. The signaling pathways involved could be TLR4-dependent. This work brings new perspectives in pathogenesis and therapeutic approaches of severe infections.

Identification of Immune-Related Key Genes as Potential Diagnostic Biomarkers of Sepsis in Children

Objective

The pathogenesis of sepsis is still unclear due to its complexity, especially in children. This study aimed to analyse the immune microenvironment and regulatory networks related to sepsis in children at the molecular level and to identify key immune-related genes to provide a new basis for the early diagnosis of sepsis.

Methods

The GSE145227 and GSE26440 datasets were downloaded from the Gene Expression Omnibus. The analyses included differentially expressed genes (DEGs), functional enrichment, immune cell infiltration, the competing endogenous RNA (ceRNA) interaction network, weighted gene coexpression network analysis (WGCNA), protein–protein interaction (PPI) network, key gene screening, correlation of sepsis molecular subtypes/immune infiltration with key gene expression, the diagnostic capabilities of key genes, and networks describing the interaction of key genes with transcription factors and small-molecule compounds. Finally, real-time quantitative PCR (RT–qPCR) was performed to verify the expression of key genes.

Results

A total of 236 immune-related DEGs, most of which were enriched in immune-related biological functions, were found. Further analysis of immune cell infiltration showed that M0 macrophages and neutrophils infiltrated more in the sepsis group, while fewer activated memory CD4⁺ T cells, resting memory CD4⁺ T cells, and CD8⁺ T cells did. The interaction network of ceRNA was successfully constructed. Six key genes (FYN, FBL, ATM, WDR75, FOXO1 and ITK) were identified by WGCNA and PPI analysis. We found strong associations between key genes and constructed septic molecular subtypes or immune cell infiltration. Receiver operating characteristic analysis showed that the area under the curve values of the key genes for diagnosis were all greater than 0.84. Subsequently, we successfully constructed an interaction network of key genes and transcription factors/small-molecule compounds. Finally, the key genes in the samples were verified by RT–qPCR.

Conclusion

Our results offer new insights into the pathogenesis of sepsis in children and provide new potential diagnostic biomarkers for the disease.

Signal-Strength and History-Dependent Innate Immune Memory Dynamics in Health and Disease

Innate immunity exhibits memory characteristics, reflected not only in selective recognition of external microbial or internal damage signals, but more importantly in history and signal-strength dependent reprogramming of innate leukocytes characterized by priming, tolerance, and exhaustion. Key innate immune cells such as monocytes and neutrophils can finely discern and attune to the duration and intensity of external signals through rewiring of internal signaling circuitries, giving rise to a vast array of discreet memory phenotypes critically relevant to managing tissue homeostasis as well as diverse repertoires of inflammatory conditions. This review will highlight recent advances in this rapidly expanding field of innate immune programming and memory, as well as its translational implication in the pathophysiology of selected inflammatory diseases.

Inflammatory Monocytes and Subsets of Macrophages with Distinct Surface Phenotype Correlate with Specific Integrin Expression Profile during Murine Sepsis

Monocytes and macrophages participate in both pro- and anti-inflammatory responses during sepsis. Integrins are the cell adhesion receptors that mediate leukocyte migration and functions. To date, it is not known whether integrin profiles correlate with their trafficking, differentiation, and polarization during sepsis. In this study, using endotoxemia and cecal ligation and puncture model of murine sepsis, we have analyzed the role of surface integrins in tissue-specific infiltration, distribution of monocytes and macrophages, and their association with inflammation-induced phenotypic and functional alterations postinduction (p.i.) of sepsis. Our data show that Ly-6C^hi inflammatory monocytes infiltrated into the peritoneum from blood and bone marrow within a few hours p.i. of sepsis, with differential distribution of small (Ly-6C^loCD11b^loF4/80^lo) and large peritoneal macrophages (Ly-6C^loCD11b^hiF4/80^hi) in both models. The results from flow cytometry studies demonstrated a higher expression of integrin α₄β₁ on the Ly-6C^hi monocytes in different tissues, whereas macrophages in the peritoneum and lungs expressed higher levels of integrin α₅β₁ and α_vβ₃ in both models. Additionally, F4/80⁺ cells with CD206^hiMHCII^lo phenotype increased in the lungs of both models by six hours p.i. and expressed higher levels of integrin α_vβ₃ in both lungs and peritoneum. The presence of such cells correlated with higher levels of IL-10 and lower levels of IL-6 and IL-1β transcripts within six hours p.i. in the lungs compared with the mesentery. Furthermore, bioinformatic analysis with its experimental validation revealed an association of integrin α₄ and α₅ with inflammatory (e.g., p-SRC) and integrin α_v with regulatory molecules (e.g., TGFBR1) in macrophages during sepsis.

Circulating Complement C3-Alpha Chain Levels Predict Survival of Septic Shock Patients

BACKGROUND

Circulating complement C3 fragments released during septic shock might contribute to the development of complications such as profound hypotension and disseminated intravascular coagulation. The role of C3 in the course of septic shock varies in the literature, possibly because circulating C3 exists in different forms indistinguishable via traditional ELISA-based methods. We sought to test the relationship between C3 forms, measured by Western blotting with its associated protein size differentiation feature, and clinical outcomes.

METHODS

Secondary analysis of two prospective cohorts of patients with septic shock: a discovery cohort of 24 patents and a validation cohort of 181 patients. C3 levels were measured by Western blotting in both cohorts using blood obtained at enrollment. Differences between survivors and non-survivors were compared, and the independent prognostic values of C3 forms were assessed.

RESULTS

In both cohorts there were significantly lower levels of the C3-alpha chain in non-survivors than in survivors, and persisted after controlling for sequential organ failure assessment score. Area under the receiver operating characteristics to predict survival was 0.65 (95% confidence interval: 0.56-0.75). At a best cutoff value (Youden) of 970.6 μg/mL, the test demonstrated a sensitivity of 68.5% and specificity of 61.5%. At this cutoff point, Kaplan-Meier survival analysis showed that patients with lower levels of C3-alpha chain had significantly lower survival than those with higher levels (P < 0.001).

CONCLUSION

Circulating C3-alpha chain levels is a significant independent predictor of survival in septic shock patients.

Oxidative burst and phagocytic activity of phagocytes in canine parvoviral enteritis

Canine parvoviral enteritis (CPE) is a severe disease characterized by systemic inflammation and immunosuppression. The function of circulating phagocytes (neutrophils and monocytes) in affected dogs has not been fully investigated. We characterized the functional capacity of canine phagocytes in CPE by determining their oxidative burst and phagocytic activities using flow cytometry. Blood was collected from 28 dogs with CPE and 11 healthy, age-matched, control dogs. Oxidative burst activity was assessed by stimulating phagocytes with opsonized Escherichia coli or phorbol 12-myristate 13-acetate (PMA) and measuring the percentage of phagocytes producing reactive oxygen species and the magnitude of this production. Phagocytosis was measured by incubating phagocytes with opsonized E. coli and measuring the percentage of phagocytes containing E. coli and the number of bacteria per cell. Complete blood counts and serum C-reactive protein (CRP) concentrations were also determined. Serum CRP concentration was negatively and positively correlated with segmented and band neutrophil concentrations, respectively. Overall, no differences in phagocyte function were found between dogs with CPE and healthy control dogs. However, infected dogs with neutropenia or circulating band neutrophils had decreased PMA-stimulated oxidative burst activity compared to healthy controls. Additionally, CPE dogs with neutropenia or circulating band neutrophils had decreased PMA- and E. coli-stimulated oxidative burst activity and decreased phagocytosis of E. coli compared to CPE dogs without neutropenia or band neutrophils. We conclude that phagocytes have decreased oxidative burst and phagocytic activity in neutropenic CPE dogs and in CPE dogs with circulating band neutrophils.

Protective Effects of Idebenone against Sepsis Induced Acute Lung Damage

BACKGROUND/AIMS

Sepsis is an uncontrolled systemic infection, withcomplex pathophysiology that may result in acute lung organ damage and cause multiple organ failure. Although much research has been conducted to illuminate sepsis's complex pathophysiology, sepsis treatment protocols are limited, and sepsis remains an important cause of mortality andmorbidity in intensive care units.Various studies have shown that idebenone (IDE) possesses strong antioxidant properties, which inhibit lipid peroxidation and protect cells from oxidative damage. The present study aimed to evaluate the protective effects of IDE against lung injury in a cecal ligation and puncture (CLP)-induced sepsis rat model.

METHODS

Male albino Wistar rats were used. The animals were divided into a healthy control (no treatment), CLP, IDE control (200 mg/kg), and CLP + IDE subgroups (50 mg/kg, 100 mg/kg, and 200 mg/kg), with nine rats in each group.IDE was administered 1 h after CLP induction.To evaluate the protective effects of IDE, lung tissues were collected 16 h after sepsis for biochemical, immunohistochemical staining, and histopathological examination.

RESULTS

IDE significantly ameliorated sepsis-induced disturbances in oxidative stress-related factors, with its effects increasing in accordance with the dose.IDE also abolished histopathological changes in lung tissues associated with CLP.Furthermore, interleukin 1 beta (IL-1β)and tumor necrosis factor-alpha (TNF-α) immunopositivity markedly decreased in the septic rats following IDE treatment.

CONCLUSIONS

IDE largely mitigated the inflammatory response in sepsis-induced lung injury by decreasing free radicals and preventing lipid peroxidation. The results suggest that IDE may represent a potential novel therapeutic drug for sepsis treatment.

Functional and Therapeutic Relevance of Rho GTPases in Innate Immune Cell Migration and Function during Inflammation: An In Silico Perspective

Systematic regulation of leukocyte migration to the site of infection is a vital step during immunological responses. Improper migration and localization of immune cells could be associated with disease pathology as seen in systemic inflammation. Rho GTPases act as molecular switches during inflammatory cell migration by cycling between Rho-GDP (inactive) to Rho-GTP (active) forms and play an essential role in the precise regulation of actin cytoskeletal dynamics as well as other immunological functions of leukocytes. Available reports suggest that the dysregulation of Rho GTPase signaling is associated with various inflammatory diseases ranging from mild to life-threatening conditions. Therefore, it is crucial to understand the step-by-step activation and inactivation of GTPases and the functioning of different Guanine Nucleotide Exchange Factors (GEFs) and GTPase-Activating Proteins (GAPs) that regulate the conversion of GDP to GTP and GTP to GDP exchange reactions, respectively. Here, we describe the molecular organization and activation of various domains of crucial elements associated with the activation of Rho GTPases using solved PDB structures. We will also present the latest evidence available on the relevance of Rho GTPases in the migration and function of innate immune cells during inflammation. This knowledge will help scientists design promising drug candidates against the Rho-GTPase-centric regulatory molecules regulating inflammatory cell migration.

Immunomodulatory and Therapeutic Effects of Mesenchymal Stem Cells on Organ Dysfunction in Sepsis

ABSTRACT

Sepsis is a life-threatening disorder that is caused by a dysregulated inflammatory response during an infection. The disease mostly affects pregnant women, newborns, and patients in intensive care units. Sepsis treatment is a significant part of a country's health budgets. Delay in the therapy causes irreversible failure of various organs due to the lack of blood supply and reduction of oxygen in the tissues and eventually increased mortality. The involvement of four or five organs by sepsis has been attributed to an increased risk of death to over 90%. Although antibiotics are at the first line of sepsis treatment, they do not possess enough potency to control the disease and prevent subsequent organ failure. The immunomodulatory, anti-inflammatory, anti-apoptotic, and anti-microbial properties of mesenchymal stem cells (MSCs) have been reported in various studies. Therefore, the application of MSCs has been considered a potentially promising therapeutic strategy. In preclinical studies, the administration of MSCs has been associated with reduced bacterial load and decreased levels of pro-inflammatory factors as well as the improved function of the different vital organs, including heart, kidney, liver, and lungs. The current study provides a brief review of sepsis and its pathophysiology, and then highlights recent findings in the therapeutic effects of MSCs and MSC-derived secretome in improving sepsis-induced organ dysfunction. Besides, eligible sepsis candidates for MSC-therapy and the latest clinical findings in these areas have been reviewed.

Damage-associated molecular patterns in trauma

In 1994, the "danger model" argued that adaptive immune responses are driven rather by molecules released upon tissue damage than by the recognition of "strange" molecules. Thus, an alternative to the "self versus non-self recognition model" has been provided. The model, which suggests that the immune system discriminates dangerous from safe molecules, has established the basis for the future designation of damage-associated molecular patterns (DAMPs), a term that was coined by Walter G. Land, Seong, and Matzinger. The pathological importance of DAMPs is barely somewhere else evident as in the posttraumatic or post-surgical inflammation and regeneration. Since DAMPs have been identified to trigger specific immune responses and inflammation, which is not necessarily detrimental but also regenerative, it still remains difficult to describe their "friend or foe" role in the posttraumatic immunogenicity and healing process. DAMPs can be used as biomarkers to indicate and/or to monitor a disease or injury severity, but they also may serve as clinically applicable parameters for optimized indication of the timing for, i.e., secondary surgeries. While experimental studies allow the detection of these biomarkers on different levels including cellular, tissue, and circulatory milieu, this is not always easily transferable to the human situation. Thus, in this review, we focus on the recent literature dealing with the pathophysiological importance of DAMPs after traumatic injury. Since dysregulated inflammation in traumatized patients always implies disturbed resolution of inflammation, so-called model of suppressing/inhibiting inducible DAMPs (SAMPs) will be very briefly introduced. Thus, an update on this topic in the field of trauma will be provided.

A C-terminal fragment of adhesion protein Fibulin7 regulates neutrophil migration and functions and improves survival in LPS induced systemic inflammation

Accumulation of hyperactive neutrophils in the visceral organs was shown to be associated with sepsis-induced multi-organ failure. Recently, a C-terminal fragment of secreted glycoprotein Fibulin7 (Fbln7-C) was shown to inhibit angiogenesis and regulate monocyte functions in inflammatory conditions. However, its effects on neutrophil functions and systemic inflammation induced lethality remain unknown. In this study, we show that human peripheral blood neutrophils adhered to Fbln7-C in a dose-dependent manner via integrin β1. Moreover, the presence of Fbln7-C inhibited spreading, and fMLP mediated random migration of neutrophils on fibronectin. Significant reduction in ROS and inflammatory cytokine production (i.e., IL-6, IL-1β) was observed, including a reduction in ERK1⁄2 phosphorylation in neutrophils stimulated with LPS and fMLP in the presence of Fbln7-C compared to untreated controls. In an in vivo model of endotoxemia, the administration of Fbln7-C (10 μg/dose) significantly improved survival and reduced the infiltration of neutrophils to the site of inflammation. Additionally, neutrophils infiltrating into the inflamed peritoneum of Fbln7-C administered animals expressed lower levels CD11b marker, IL-6, and produced lower levels of ROS upon stimulation with PMA compared to untreated controls. In conclusion, our results show that Fbln7-C could bind to the integrin β1 on the neutrophil surface and regulate their inflammatory functions.

Effects of umbelliferone isolated from the Ferulago pauciradiata Boiss. & Heldr. Plant on cecal ligation and puncture-induced sepsis model in rats

Sepsis is a pathophysiological event involving systemic inflammatory response syndrome, multiple organ failure syndromes, and tissue damage. Overproduction of free radicals as a result of tissue damage during sepsis contributes to cellular toxicity, organ failure, and even mortality. Antioxidants, which scavenge free radicals, play a protective role against various diseases. Previous studies have shown that umbelliferone (UF) has antioxidant and anti-inflammatory effects. Since oxidative stress is naturally associated with sepsis-induced organ dysfunction, the application of antioxidant compounds could potentially illuminate the pathophysiology of sepsis, which does not yet have an effective treatment. The sepsis model induced by cecal ligation and puncture (CLP) was applied to rats. Different doses of UF (10░mg/kg, 20░mg/kg, and 40░mg/kg) on oxidant-antioxidant in septic rats, mRNA of inflammatory mediators such as tumor necrosis factor- α (TNF-α) and interleukin (IL)-1 its effects on expression levels were evaluated in lung, kidney, and liver tissues. When the lung, kidney, and liver tissues of septic rats were compared with those of the control group, it was found that UF administration increased dose-dependent superoxide dismutase activity and glutathione levels and significantly decreased malondialdehyde levels. The effects of UF administration on oxidative parameters were dose-dependent. The 40░mg/kg UF dose showed greater anti-oxidative properties than the 20░mg/kg and 10░mg/kg doses for all the evaluated parameters. Further, the TNF- α mRNA expression of the CLP +40░mg/kg group was reduced to a level comparable to that of the control group. UF has been found to be an effective molecule in reducing oxidative stress by supporting endogenous antioxidants and enhancing the scavenging effects of free radicals. The potent antioxidant property of UF may also be related to the suppression of the cytokine cascade during sepsis. The results suggest that UF administration may represent a new treatment for the prevention of lung, kidney and liver damage caused by septic conditions.

Investigation of Extracellular Matrix Protein Expression Dynamics Using Murine Models of Systemic Inflammation

Extracellular matrix (ECM) proteins form the structural support for migration of leukocytes and provide multiple signals to assist in their functions during inflammatory conditions. Presence of pro-inflammatory mediators in the tissues results in the remodelling of matrices which could modify the functions of extravasated leukocytes. Previous reports have shown changes in the expression of ECM proteins during local inflammatory responses. In this study, we have investigated the time- and tissue-specific expression profile of key ECM proteins in systemic inflammation using lipopolysaccharide (LPS)-induced endotoxemia and cecal ligation and puncture (CLP) mouse models. The results show that compared to naïve tissues, within 12 h following CLP surgery, a 20-30-fold increase was observed in the expression of collagen-IV (Col-IV) transcripts in the mesentery tissues with a 2.4-fold increase in the protein by 24 h. However, Western blot band intensities indicated that vimentin and fibrinogen were remarkably expressed in more quantity compared to Col-IV. Secondly, in CLP group of mice, fibrinogen showed 6-40-fold increase in mRNA level in various tissues with about 2-fold increase in the protein level compared to respective naïve tissues. Similar studies in the LPS-injected mice showed up to 2-3 fold increase in the expression of Col-IV, fibrinogen and vimentin at protein level in the lungs. In such animals, although similar pattern was observed for fibrinogen in kidney and liver tissues, the mesentery showed prominent changes in Col-IV and vimentin mRNA compared to CLP. Further, bioinformatics analysis showed multiple pathways which could be associated with vimentin, Col-IV and fibrinogen under inflammatory conditions both in human and mouse. The current study will help in better understanding of possible signalling from ECM proteins in inflammatory microenvironment and may contribute in development of cell adhesion-based therapeutics.

Crosstalk between Dendritic Cells and Immune Modulatory Agents against Sepsis

Dendritic cells (DCs) play a critical role in the immune system which sense pathogens and present their antigens to prime the adaptive immune responses. As the progression of sepsis occurs, DCs are capable of orchestrating the aberrant innate immune response by sustaining the Th1/Th2 responses that are essential for host survival. Hence, an in-depth understanding of the characteristics of DCs would have a beneficial effect in overcoming the obstacle occurring in sepsis. This paper focuses on the role of DCs in the progression of sepsis and we also discuss the reverse sepsis-induced immunosuppression through manipulating the DC function. In addition, we highlight some potent immunotherapies that could be used as a novel strategy in the early treatment of sepsis.

Long-Chain Acyl-CoA Synthetase 1 Role in Sepsis and Immunity: Perspectives From a Parallel Review of Public Transcriptome Datasets and of the Literature

A potential role for the long-chain acyl-CoA synthetase family member 1 (ACSL1) in the immunobiology of sepsis was explored during a hands-on training workshop. Participants first assessed the robustness of the potential gap in biomedical knowledge identified via an initial screen of public transcriptome data and of the literature associated with ACSL1. Increase in ACSL1 transcript abundance during sepsis was confirmed in several independent datasets. Querying the ACSL1 literature also confirmed the absence of reports associating ACSL1 with sepsis. Inferences drawn from both the literature (via indirect associations) and public transcriptome data (via correlation) point to the likely participation of ACSL1 and ACSL4, another family member, in inflammasome activation in neutrophils during sepsis. Furthermore, available clinical data indicate that levels of ACSL1 and ACSL4 induction was significantly higher in fatal cases of sepsis. This denotes potential translational relevance and is consistent with involvement in pathways driving potentially deleterious systemic inflammation. Finally, while ACSL1 expression was induced in blood in vitro by a wide range of pathogen-derived factors as well as TNF, induction of ACSL4 appeared restricted to flagellated bacteria and pathogen-derived TLR5 agonists and IFNG. Taken together, this joint review of public literature and omics data records points to two members of the acyl-CoA synthetase family potentially playing a role in inflammasome activation in neutrophils. Translational relevance of these observations in the context of sepsis and other inflammatory conditions remain to be investigated.

A nationwide fluidics biobank of polytraumatized patients: implemented by the Network "Trauma Research" (NTF) as an expansion to the TraumaRegister DGU® of the German Trauma Society (DGU)

To decrypt the complexity of the posttraumatic immune responses and to potentially identify novel research pathways for exploration, large-scale multi-center projects including not only in vivo and in vitro modeling, but also temporal sample and material collection along with clinical data capture from multiply injured patients is of utmost importance. To meet this gap, a nationwide biobank for fluidic samples from polytraumatized patients was initiated in 2013 by the task force Network “Trauma Research” (Netzwerk Traumaforschung, NTF) of the German Trauma Society (Deutsche Gesellschaft für Unfallchirurgie e.V., DGU). The NTF-Biobank completes the clinical NTF-Biobank Database and complements the TR-DGU with temporal biological samples from multiply injured patients. The concept behind the idea of the NTF-Biobank was to create a robust interface for meaningful innovative basic, translational and clinical research. For the first time, an integrated platform to prospectively evaluate and monitor candidate biomarkers and/or potential therapeutic targets in biological specimens of quality-controlled and documented patients is introduced, allowing reduction in variability of measurements with high impact due to its large sample size. Thus, the project was introduced to systemically evaluate and monitor multiply injured patients for their (patho-)physiological sequalae together with their clinical treatment strategies applied for overall outcome improval.

Infections after a traumatic brain injury: The complex interplay between the immune and neurological systems

Traumatic brain injury (TBI) is a serious global health issue, being the leading cause of death and disability for individuals under the age of 45, and one of the largest causes of global neurological disability. In addition to the brain injury itself, it is increasingly appreciated that a TBI may also alter the systemic immune response in a way that renders TBI patients more vulnerable to infections in the acute post-injury period. Such infections pose an additional challenge to the patient, increasing rates of mortality and morbidity, and worsening neurological outcomes. Hospitalization, surgical interventions, and a state of immunosuppression induced by injury to the central nervous system (CNS), may all contribute to the high rate of infections seen in the population with TBI. Ongoing research to better understand the immunomodulators that underlie TBI-induced immunosuppression may aid in the development of effective therapeutic strategies to improve the recovery trajectory for patients. This review first describes the clinical scenario, posing the question of whether TBI patients are more susceptible to infections such as pneumonia, and if so, why? We then consider how cross-talk between the injured brain and the systemic immune system occurs, and further, how the additional immune challenge of an acquired infection can contribute to ongoing neuroinflammation and neurodegeneration after a TBI. Experimental models combining TBI with infection are discussed, as well as current treatment options available for this double-barreled insult. The aims of this review are to summarize current understanding of the bidirectional relationship between the CNS and the immune system when faced with a mechanical trauma combined with a concomitant infection, and to highlight key outstanding questions that remain in the field.

Physiology and technology for the ICU in vivo

This paper discusses the physiological and technological concepts that might form the future of critical care medicine. Initially, we discuss the need for a personalized approach and introduce the concept of personalized physiological medicine (PPM), including (1) assessment of frailty and physiological reserve, (2) continuous assessment of organ function, (3) assessment of the microcirculation and parenchymal cells, and (4) integration of organ and cell function for continuous therapeutic feedback control. To understand the cellular basis of organ failure, we discuss the processes that lead to cell death, including necrosis, necroptosis, autophagy, mitophagy, and cellular senescence. In vivo technology is used to monitor these processes. To this end, we discuss new materials for developing in vivo biosensors and drug delivery systems. Such in vivo biosensors will define the diagnostic platform of the future ICU in vivo interacting with theragnostic drugs. In addition to pharmacological therapeutic options, placement and control of artificial organs to support or replace failing organs will be central in the ICU in vivo of the future. Remote monitoring and control of these biosensors and artificial organs will be made using adaptive physiological mathematical modeling of the critically ill patient. The current state of these developments is discussed.

Mdivi-1 Protects CD4+ T Cells against Apoptosis via Balancing Mitochondrial Fusion-Fission and Preventing the Induction of Endoplasmic Reticulum Stress in Sepsis

Apoptosis of CD4⁺ T cells plays a central role in the progression of sepsis because it is associated with subsequent immunosuppression and the lack of specific treatment. Thus, developing therapeutic strategies to attenuate the apoptosis of CD4⁺ T cells in sepsis is critical. Several studies have demonstrated that Mdivi-1, which is a selective inhibitor of the dynamin-related protein 1 (Drp1), attenuates apoptosis of myocardial cells and neurons during various pathologic states. The present study revealed the impact of Mdivi-1 on the apoptosis of CD4⁺ T cells in sepsis and the potential underlying mechanisms. We used lipopolysaccharide (LPS) stimulation and cecal ligation and puncture (CLP) surgery as sepsis models in vitro and in vivo, respectively. Our results showed that Mdivi-1 attenuated the apoptosis of CD4⁺ T cells both in vitro and in vivo. The potential mechanism underlying the protective effect of Mdivi-1 involved Mdivi-1 reestablishing mitochondrial fusion-fission balance in sepsis, as reflected by the expression of the mitofusin 2 (MFN2) and optic atrophy 1 (OPA1) , Drp1 translocation, and mitochondrial morphology, as observed by electron microscopy. Moreover, Mdivi-1 treatment reduced reactive oxygen species (ROS) production and prevented the induction of endoplasmic reticulum stress (ERS) and associated apoptosis. After using tunicamycin to activate ER stress, the protective effect of Mdivi-1 on CD4⁺ T cells was reversed. Our results suggested that Mdivi-1 ameliorated apoptosis in CD4⁺ T cells by reestablishing mitochondrial fusion-fission balance and preventing the induction of endoplasmic reticulum stress in experimental sepsis.

The Central Role of the Inflammatory Response in Understanding the Heterogeneity of Sepsis-3

In sepsis-3, in contrast with sepsis-1, the definition "systemic inflammatory response" has been replaced with "dysregulated host response", and "systemic inflammatory response syndrome" (SIRS) has been replaced with "sequential organ failure assessment" (SOFA). Although the definition of sepsis has changed, the debate regarding its nature is ongoing. What are the fundamental processes controlling sepsis-induced inflammation, immunosuppression, or organ failure? In this review, we discuss the heterogeneity of sepsis-3 and address the central role of inflammation in the pathogenesis of sepsis. An unbalanced pro- and anti-inflammatory response, inflammatory resolution disorder, and persistent inflammation play important roles in the acute and/or chronic phases of sepsis. Moreover, powerful links exist between inflammation and other host responses (such as the neuroendocrine response, coagulation, and immunosuppression). We suggest that a comprehensive evaluation of the role of the inflammatory response will improve our understanding of the heterogeneity of sepsis.

Danger signals in trauma

This review summarizes a short list of currently discussed trauma-induced danger-associated molecular patterns (DAMP). Due to the bivalent character and often pleiotropic effects of a DAMP, it is difficult to describe its "friend or foe" role in post-traumatic inflammation and regeneration, both systemically as well locally in tissues. DAMP can be used as biomarkers to indicate or monitor disease or injury severity, but also may serve as clinically applicable parameters for better indication and timing of surgery. Due to the inflammatory processes at the local tissue level or the systemic level, the precise role of DAMP is not always clear to define. While in vitro and experimental studies allow for the detection of these biomarkers at the different levels of an organism-cellular, tissue, circulation-this is not always easily transferable to the human setting. Increased knowledge exploring the dual role of DAMP after trauma, and concentrating on their nuclear functions, transcriptional targets, release mechanisms, cellular sources, multiple functions, their interactions and potential therapeutic targeting is warranted.

Inhibition of necroptosis attenuates lung injury and improves survival in neonatal sepsis

BACKGROUND

Neonatal sepsis represents a unique therapeutic challenge owing to an immature immune system. Necroptosis is a form of programmed cell death that has been identified as an important mechanism of inflammation-induced cell death. Receptor-interacting protein kinase 1 plays a key role in mediating this process. We hypothesized that pharmacologic blockade of receptor-interacting protein kinase 1 activity would be protective in neonatal sepsis.

METHODS

Sepsis was induced in C57BL/6 mouse pups (5-7 days old) by intraperitoneal injection of adult cecal slurry. At 1 hour after cecal slurry injection, the receptor-interacting protein kinase 1 inhibitor necrostatin-1 (10 µg/g body weight) or vehicle (5% dimethyl sulfoxide in phosphate buffered saline) was administered via retro-orbital injection. At 20 hours after cecal slurry injection, blood and lung tissues were collected for various analyses.

RESULTS

At 20 hours after sepsis induction, vehicle-treated pups showed a marked increase in serum levels of interleukin 6, interleukin 1-beta, and interleukin 18 compared to sham. With necrostatin-1 treatment, serum levels of interleukin 6, interleukin 1-beta, and interleukin 18 were decreased by 77%, 81%, and 63%, respectively, compared to vehicle. In the lungs, sepsis induction resulted in a 232-, 10-, and 2.8-fold increase in interleukin 6, interleukin 1-beta, and interleukin 18 mRNA levels compared to sham, while necrostatin-1 treatment decreased these levels to 40-, 4-, and 0.8-fold, respectively. Expressions of the neutrophil chemokines keratinocyte chemoattractant and macrophage-inflammatory-protein-2 were also increased in the lungs in sepsis, while necrostatin-1 treatment decreased these levels by 81% and 61%, respectively, compared to vehicle. In addition, necrostatin-1 treatment significantly improved the lung histologic injury score and decreased lung apoptosis in septic pups. Finally, treatment with necrostatin-1 increased the 7-day survival rate from 0% in the vehicle-treated septic pups to 29% (P = .11).

CONCLUSION

Inhibition of receptor-interacting protein kinase 1 by necrostatin-1 decreases systemic and pulmonary inflammation, decreases lung injury, and increases survival in neonatal mice with sepsis. Targeting the necroptosis pathway might represent a new therapeutic strategy for neonatal sepsis.

Soluble TREM-1 as a predictive factor of neonatal sepsis: a meta-analysis

BACKGROUND

The efficacy of soluble triggering receptor expressed on myeloid cell-1 (TREM-1) in detecting sepsis in adults has already been proven. To date, however, consensus in the field of neonatal sepsis is lacking. The purpose of the present systematic review is to accumulate current evidence in this field.

SEARCH STRATEGY

We systematically searched Medline (1966-2017), Scopus (2004-2017), Clinicaltrials.gov (2008-2017), EMBASE (1980-2017), Cochrane Central Register of Controlled Trials CENTRAL (1999-2017) and Google Scholar (2004-2017) along with reference lists from included studies.

MAIN RESULTS

Eight studies were finally included in the present analysis, with a total number of 667 neonates. The estimated sensitivity for the summary point was 0.95 [95% CI (0.81-0.99)] and the specificity was 0.87 [95% CI (0.56-0.97)]. The diagnostic odds ratio was calculated at 132.49 [95% CI (6.85-2560.70)]. Fagan's nomogram demonstrated that the post-test probability increased to 71% and decreased to 2%, when the pre-test probability was set at 25%. However, significant discrepancy was observed in terms of the used cut-offs; therefore, the sensitivity and specificity presented in our meta-analysis should be reviewed with caution, as they may present an overestimation of the actual predictive efficacy of this protein.

CONCLUSION

Current evidence suggests that sTREM-1 may become a useful biomarker for the prediction of neonatal sepsis. However, the small number of studies and the variation of the threshold values limit its implementation in clinical practice. Future large-scale studies are needed to determine the optimal cut-off value that may discriminate normal levels from those suggestive of the presence of neonatal sepsis.

Extension of chemotactic pseudopods by nonadherent human neutrophils does not require or cause calcium bursts

Global bursts in free intracellular calcium (Ca²⁺) are among the most conspicuous signaling events in immune cells. To test the common view that Ca²⁺ bursts mediate rearrangement of the actin cytoskeleton in response to the activation of G protein-coupled receptors, we combined single-cell manipulation with fluorescence imaging and monitored the Ca²⁺ concentration in individual human neutrophils during complement-mediated chemotaxis. By decoupling purely chemotactic pseudopod formation from cell-substrate adhesion, we showed that physiological concentrations of anaphylatoxins, such as C5a, induced nonadherent human neutrophils to form chemotactic pseudopods but did not elicit Ca²⁺ bursts. By contrast, pathological or supraphysiological concentrations of C5a often triggered Ca²⁺ bursts, but pseudopod protrusion stalled or reversed in such cases, effectively halting chemotaxis, similar to sepsis-associated neutrophil paralysis. The maximum increase in cell surface area during pseudopod extension in pure chemotaxis was much smaller-by a factor of 8-than the known capacity of adherent human neutrophils to expand their surface. Because the measured rise in cortical tension was not sufficient to account for this difference, we attribute the limited deformability to a reduced ability of the cytoskeleton to generate protrusive force in the absence of cell adhesion. Thus, we hypothesize that Ca²⁺ bursts in neutrophils control a mechanistic switch between two distinct modes of cytoskeletal organization and dynamics. A key element of this switch appears to be the expedient coordination of adhesion-dependent lock or release events of cytoskeletal membrane anchors.

Janus face of complement-driven neutrophil activation during sepsis

During local and systemic inflammation, the complement system and neutrophil granulocytes are activated not only by pathogens, but also by released endogenous danger signals. It is recognized increasingly that complement-mediated neutrophil activation plays an ambivalent role in sepsis pathophysiology. According to the current definition, the onset of organ dysfunction is a hallmark of sepsis. The preceding organ damage can be caused by excessive complement activation and neutrophil actions against the host, resulting in bystander injury of healthy tissue. However, in contrast, persistent and overwhelming inflammation also leads to a reduction in neutrophil responsiveness as well as complement components and thus may render patients at enhanced risk of spreading infection. This review provides an overview on the molecular and cellular processes that link complement with the two-faced functional alterations of neutrophils in sepsis. Finally, we describe novel tools to modulate this interplay beneficially in order to improve outcome.

Traumatic Injury

Traumatic injury as one of the world's most relevant but neglected health concerns results in modulated inflammasome activity, which is closely linked to the development of post-injury complications. Cytokine-producing capacity of cells is important for the appropriate immune response to trauma and requires not only synthesis and transcription of inflammasome components but also their activation. Unfortunately, the precise role of inflammasome in trauma is still largely unknown. However, in the following chapter, we provide an overview on the best described inflammasomes in the various settings of trauma, introducing the recent findings on the up-to-date best described NLRP inflammasomes and underlying cytokines in the inflammatory response to trauma.

Activated Protein C Attenuates Severe Inflammation by Targeting VLA-3high Neutrophil Subpopulation in Mice

The host injury involved in multiorgan system failure during severe inflammation is mediated, in part, by massive infiltration and sequestration of hyperactive neutrophils in the visceral organ. A recombinant form of human activated protein C (rhAPC) has shown cytoprotective and anti-inflammatory functions in some clinical and animal studies, but the direct mechanism is not fully understood. Recently, we reported that, during endotoxemia and severe polymicrobial peritonitis, integrin VLA-3 (CD49c/CD29) is specifically upregulated on hyperinflammatory neutrophils and that targeting the VLA-3high neutrophil subpopulation improved survival in mice. In this article, we report that rhAPC binds to human neutrophils via integrin VLA-3 (CD49c/CD29) with a higher affinity compared with other Arg-Gly-Asp binding integrins. Similarly, there is preferential binding of activated protein C (PC) to Gr1highCD11bhighVLA-3high cells isolated from the bone marrow of septic mice. Furthermore, specific binding of rhAPC to human neutrophils via VLA-3 was inhibited by an antagonistic peptide (LXY2). In addition, genetically modified mutant activated PC, with a high affinity for VLA-3, shows significantly improved binding to neutrophils compared with wild-type activated PC and significantly reduced neutrophil infiltration into the lungs of septic mice. These data indicate that variants of activated PC have a stronger affinity for integrin VLA-3, which reveals novel therapeutic possibilities.

Integrative model of leukocyte genomics and organ dysfunction in heart failure patients requiring mechanical circulatory support: a prospective observational study

BACKGROUND

The implantation of mechanical circulatory support devices in heart failure patients is associated with a systemic inflammatory response, potentially leading to death from multiple organ dysfunction syndrome. Previous studies point to the involvement of many mechanisms, but an integrative hypothesis does not yet exist. Using time-dependent whole-genome mRNA expression in circulating leukocytes, we constructed a systems-model to improve mechanistic understanding and prediction of adverse outcomes.

METHODS

We sampled peripheral blood mononuclear cells from 22 consecutive patients undergoing mechanical circulatory support device (MCS) surgery, at 5 timepoints: day -1 preoperative, and postoperative days 1, 3, 5, and 8. Clinical phenotyping was performed using 12 clinical parameters, 2 organ dysfunction scoring systems, and survival outcomes. We constructed a strictly phenotype-driven time-dependent non-supervised systems-representation using weighted gene co-expression network analysis, and annotated eigengenes using gene ontology, pathway, and transcription factor binding site enrichment analyses. Genes and eigengenes were mapped to the clinical phenotype using a linear mixed-effect model, with Cox models also fit at each timepoint to survival outcomes.

RESULTS

We inferred a 19-module network, in which most module eigengenes correlated with at least one aspect of the clinical phenotype. We observed a response of advanced heart failure patients to surgery orchestrated into stages: first, activation of the innate immune response, followed by anti-inflammation, and finally reparative processes such as mitosis, coagulation, and apoptosis. Eigengenes related to red blood cell production and extracellular matrix degradation became predictors of survival late in the timecourse corresponding to multiorgan dysfunction and disseminated intravascular coagulation.

CONCLUSIONS

Our model provides an integrative representation of leukocyte biology during the systemic inflammatory response following MCS device implantation. It demonstrates consistency with previous hypotheses, identifying a number of known mechanisms. At the same time, it suggests novel hypotheses about time-specific targets.

Growth Differentiation Factor-15 Deficiency Augments Inflammatory Response and Exacerbates Septic Heart and Renal Injury Induced by Lipopolysaccharide

Septic acute kidney injury (AKI) and myocardial dysfunction are leading causes of mortality with no accepted method of therapy. In this study we demonstrate the role of growth differentiating factor 15 (GDF15) in septic AKI and myocardial dysfunction using a murine lipopolysaccharide (LPS)-induced sepsis model and an in vitro cell culture system. Data show that GDF15 deficiency augments inflammatory response and exacerbates renal and cardiac injury induced by LPS, while over-expression of GDF15 protects the kidney and heart from LPS-induced organ dysfunction. Therefore, this study highlights the therapeutic potential of GDF15 in the treatment of endotoxin-induced sepsis.

Neutrophil dysregulation during sepsis: an overview and update

Sepsis remains a leading cause of death worldwide, despite advances in critical care, and understanding of the pathophysiology and treatment strategies. No specific therapy or drugs are available for sepsis. Neutrophils play a critical role in controlling infection under normal conditions, and it is suggested that their migration and antimicrobial activity are impaired during sepsis which contribute to the dysregulation of immune responses. Recent studies further demonstrated that interruption or reversal of the impaired migration and antimicrobial function of neutrophils improves the outcome of sepsis in animal models. In this review, we provide an overview of the associated mediators and signal pathways involved which govern the survival, migration and antimicrobial function of neutrophils in sepsis, and discuss the potential of neutrophils as a target to specifically diagnose and/or predict the outcome of sepsis.

Specific Metabolome Profile of Exhaled Breath Condensate in Patients with Shock and Respiratory Failure: A Pilot Study

BACKGROUND

Shock includes different pathophysiological mechanisms not fully understood and remains a challenge to manage. Exhaled breath condensate (EBC) may contain relevant biomarkers that could help us make an early diagnosis or better understand the metabolic perturbations resulting from this pathological situation.

OBJECTIVE

we aimed to establish the metabolomics signature of EBC from patients in shock with acute respiratory failure in a pilot study.

MATERIAL AND METHODS

We explored the metabolic signature of EBC in 12 patients with shock compared to 14 controls using LC-HRMS. We used a non-targeted approach, and we performed a multivariate analysis based on Orthogonal Partial Least Square-Discriminant Analysis (OPLS-DA) to differentiate between the two groups of patients.

RESULTS

We optimized the procedure of EBC collection and LC-HRMS detected more than 1000 ions in this fluid. The optimization of multivariate models led to an excellent model of differentiation for both groups (Q2 > 0.4) after inclusion of only 6 ions.

DISCUSSION AND CONCLUSION

We validated the procedure of EBC collection and we showed that the metabolome profile of EBC may be relevant in characterizing patients with shock. We performed well in distinguishing these patients from controls, and the identification of relevant compounds may be promising for ICC patients.