The immunology of sepsis

Dynamic expression analysis of peripheral blood derived small extracellular vesicle miRNAs in sepsis progression

Immune disorders caused by sepsis have recently drawn much attention. We sought to dynamically monitor the expression of small extracellular vesicle (sEV) miRNAs in peripheral blood during sepsis to explore these miRNAs as potential biomarkers for monitoring immune function in sepsis patients. This study included patients with sepsis. Blood samples were obtained from 10 patients on the first through 10th days, the 12th day and the 14th day since sepsis onset, resulting in 120 collected samples. Serum sEVs were extracted from peripheral venous blood, and levels of MIR497HG, miR-195, miR-497, and PD-L1 in serum sEVs were detected by qPCR, and clinical information was recorded. Our study revealed that the levels of MIR497HG, miR-195, miR-497 and PD-L1 in serum sEVs showed periodic changes; the time from peak to trough was approximately 4-5 days. The levels of sEV MIR497HG and miR-195 had a positive linear relationship with SOFA score (r values were -0.181 and -0.189; p values were 0.048 and 0.039, respectively). The recorded quantities of sEV MIR497HG, miR-195 and PD-L1 showed a substantial correlation with ARDS. ROC curve analysis revealed that sEV MIR497HG, miR-195 and miR-497 could predict the 28-day mortality of sepsis patients with an AUC of 0.66, 0.68 and 0.72, respectively. Levels of sEVs MIR497HG, miR-195, miR-497 and PD-L1 showed periodic changes with the immune status of sepsis, which provides a new exploration direction for immune function biomarkers and immunotherapy timing in sepsis patients.

Analysis of comprehensive biomolecules in critically ill patients via bioinformatics technologies

Each patient with a critical illness such as sepsis and severe trauma has a different genetic background, comorbidities, age, and sex. Moreover, pathophysiology changes dynamically over time even in the same patient. Therefore, individualized treatment is necessary to account for heterogeneity in patient backgrounds. Recently, the analysis of comprehensive biomolecular information using clinical specimens has revealed novel molecular pathological classifications called subtypes. In addition, comprehensive biomolecular information using clinical specimens has enabled reverse translational research, which is a data-driven approach to the identification of drug target molecules. The development of these methods is expected to visualize the heterogeneity of patient backgrounds and lead to personalized therapy.

Free Radicals, Mitochondrial Dysfunction and Sepsis-induced Organ Dysfunction: A Mechanistic Insight

Sepsis is a complex clinical condition and a leading cause of death worldwide. During Sepsis, there is a derailment in the host response to infection, which can progress to severe sepsis and multiple organ dysfunction or failure, which leads to death. Free radicals, including reactive oxygen species (ROS) generated predominantly in mitochondria, are one of the key players in impairing normal organ function in sepsis. ROS contributing to oxidative stress has been reported to be the main culprit in the injury of the lung, heart, liver, kidney, gastrointestinal, and other organs. Here in the present review, we describe the generation, and essential properties of various types of ROS, their effect on macromolecules, and their role in mitochondrial dysfunction. Furthermore, the mechanism involved in the ROS-mediated pathogenesis of sepsis-induced organ dysfunction has also been discussed.

The pathophysiology of sepsis and precision-medicine-based immunotherapy

Sepsis remains a major cause of morbidity and mortality in both low- and high-income countries. Antibiotic therapy and supportive care have significantly improved survival following sepsis in the twentieth century, but further progress has been challenging. Immunotherapy trials for sepsis, mainly aimed at suppressing the immune response, from the 1990s and 2000s, have largely failed, in part owing to unresolved patient heterogeneity in the underlying immune disbalance. The past decade has brought the promise to break this blockade through technological developments based on omics-based technologies and systems medicine that can provide a much larger data space to describe in greater detail the immune endotypes in sepsis. Patient stratification opens new avenues towards precision medicine approaches that aim to apply immunotherapies to sepsis, on the basis of precise biomarkers and molecular mechanisms defining specific immune endotypes. This approach has the potential to lead to the establishment of immunotherapy as a successful pillar in the treatment of sepsis for future generations.

Yantiao Formula Intervention in Rats with Sepsis: Network Pharmacology and Experimental Analysis

AIM AND OBJECTIVE

Traditional Chinese Medicine prescribes Yantiao Formula (YTF; peach kernel, mirabilite, Angelica sinensis, Radix Scrophulariae, raw rhubarb, Radix Paeoniae, Flos Lonicerae, Forsythia and Ophiopogon japonicus) to treat sepsis. Clinically, it reduced the inflammatory response of sepsis. It also reduced lung damage by decreasing the level of TNF-α in septic rats' serum. Using network pharmacology analysis, we investigated the efficacy network and mechanism of YTF in treating sepsis.

MATERIALS AND METHODS

We used the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) and a Bioinformatics Analysis Tool for Molecular Mechanisms of Traditional Chinese Medicine (BATMAN-TCM) combined with literature to collect the main components in YTF and their targets. DisGeNET and GENECARDS databases were used for sepsis-related targets. Cytoscape 3.7.1 software was used to construct the herbcomponent- target and ingredient-target-disease interaction protein-protein interaction networks of YTF. The jvenn was used to perform the intersection of YTF targets and sepsis targets. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed． We also created a sepsis rat model using cecal ligation and perforation and stimulated alveolar macrophages (NR8383) with endotoxin to investigate the mechanisms of YTF.

RESULTS

GO, and KEGG enrichment analysis revealed that these targets involved mineralocorticoid secretion, aldosterone secretion, active regulation of chronic inflammatory response, the exogenous coagulation pathway, and other pathophysiology. It was linked to various inflammatory factors and the MAPK pathway. YTF inhibits the p38MAPK pathway and decreases TNF- α, IL-6, and CXCL8 levels.

CONCLUSION

YTF has a multi-component, multi-target, and multi-channel role in treating sepsis. The primary mechanisms may involve inhibiting the p38MAPK pathway to reduce the inflammatory response.

Use of cardiac troponin I, lactic acid, procalcitonin, and serum complement C3 as prognostic indicators in patients with sepsis

Sepsis is a heterogeneous syndrome caused by the immune response to severe infection. This study aimed to investigate the value of cardiac troponin I, lactic acid, procalcitonin, and serum complement C3 levels for predicting death in patients with sepsis. Patients with sepsis who were hospitalized in the Department of Critical Care Medicine at our hospital between June 2017 and October 2022 were included in this retrospective study and divided into a survival group and a death group according to their survival status after 28 days. The Acute Physiology and Chronic Health Evaluation II (APACHE II) and Sequential Organ Failure Assessment (SOFA) scores, and levels of cardiac troponin I, lactic acid, procalcitonin, and serum complement C3 were measured. A total of 516 patients were included in the analysis. Multivariable analysis showed that the APACHE II score (P < .001), SOFA score (P < .001), and cardiac troponin I (P < .001), lactic acid (P = .002), procalcitonin (P < .001), and serum complement C3 (P = .01) levels were independent predictors of sepsis death. The area under the receiver operating characteristic curve (AUC) was 0.882 (95% CI: 0.794-0.941) in patients with sepsis predicted using a combination of cardiac troponin I, lactic acid, procalcitonin, and serum complement C3 levels, which was better than the predictive value of cardiac troponin I (AUC: 0.734, 95% CI: 0.628-0.824), lactic acid (AUC: 0.686, 95% CI: 0.576-0.781), procalcitonin (AUC: 0.727, 95% CI: 0.620-0.817), or serum complement C3 (AUC: 0.684, 95% CI: 0.575-0.780) alone. Cardiac troponin I, lactic acid, and procalcitonin levels are independent predictors of death, whereas serum complement C3 protects against death in patients with sepsis. The combination of cardiac troponin I, lactic acid, procalcitonin, and serum complement C3 levels has a better predictive value for death than any single measure alone in patients with sepsis.

Changes in Early T-Cell Subsets and Their Impact on Prognosis in Patients with Sepsis: A Single-Center Retrospective Study

Objective

To analyze the early changes in CD3+, CD4+, and CD8+T-cell subset counts in patients with sepsis and their correlation with prognosis to provide a feasible basis for clinical immunomodulation in sepsis.

Methods

This is a single-center retrospective study. The study enrolled sepsis patients (meeting SEPSIS 3.0 definition) who were admitted to the Department of Intensive Care Unit at the First Hospital of Jilin University from July 5th, 2018 to December 5th, 2019 and were aged 18 years or above. In addition, these patients underwent cellular immune testing (CD3+, CD4+, CD8+ T lymphocyte counts, and CD4+/CD8+ ratio) within 24 hours of ICU admission. Patient's clinical data including age, gender, infection site, APACHE II score, SOFA score, length of ICU stay, mechanical ventilation time, ICU mortality, 28-day mortality, and 3-year survival status were collected. The prognostic indicators and survival of the decreased and nondecreased groups of different subsets of T lymphocyte counts and CD4+/CD8+ ratio were compared.

Results

A total of 206 patients were enrolled, with 76.7% having a decrease in CD3+ T lymphocyte count, 76.7% having a decrease in CD4+ T lymphocyte count, and 63.6% having a decrease in CD8+ T lymphocyte count. Furthermore, 21.8% had a lower CD4+/CD8+ ratio. Analysis showed that the CD3+ T lymphocyte count decreased group had a longer length of ICU stay [11 d (4, 21) vs. 7 d (4, 17), P=0.03], increased percentage of mechanical ventilation (67.5% vs. 51.0%, P=0.04), and extended mechanical ventilation time [144 h (48, 360) vs. 96 h (48, 144), P=0.04] compared to the nondecreased group. The 28-day mortality was higher in the decreased group of CD4+/CD8+ ratio compared to the nondecreased group (33.3% vs. 25.5%, P=0.29); however, the difference did not reach statistical significance. Logistic regression analysis revealed no significant correlation between the decrease in CD4+/CD8+ ratio and 28-day mortality (P=0.11). The 3-year follow-up revealed that the CD4+/CD8+ decreased group had a lower survival rate than the nondecreased group (33.3% vs. 53.4%, P=0.01).

Conclusions

In the early stage of sepsis, most patients showed a decrease in CD3+, CD4+, and CD8+T-cell subsets, as well as in the CD4+/CD8+ ratio. The decrease in CD3+ and CD4+/CD8+ was related to some poor prognosis.

Recovering intestinal redox homeostasis to resolve systemic inflammation for preventing remote myocardial injury by oral fullerenes

The unbalanced immune state is the dominant feature of myocardial injury. However, the complicated pathology of cardiovascular diseases and the unique structure of cardiac tissue lead to challenges for effective immunoregulation therapy. Here, we exploited oral fullerene nanoscavenger (OFNS) to maintain intestinal redox homeostasis to resolve systemic inflammation for effectively preventing distal myocardial injury through bidirectional communication along the heart-gut immune axis. Observably, OFNS regulated redox microenvironment to repair cellular injury and reduce inflammation in vitro. Subsequently, OFNS prevented myocardial injury by regulating intestinal redox homeostasis and recovering epithelium barrier integrity in vivo. Based on the profiles of transcriptomics and proteomics, we demonstrated that OFNS balanced intestinal and systemic immune homeostasis for remote cardioprotection. Of note, we applied this principle to intervene myocardial infarction in mice and mini-pigs. These findings highlight that locally addressing intestinal redox to inhibit systemic inflammation could be a potent strategy for resolving remote tissue injury.

A comprehensive analysis of immune features and construction of an immune gene diagnostic model for sepsis

Sepsis is a life-threatening syndrome resulting from immune system dysfunction that is caused by infection. It is of great importance to analyze the immune characteristics of sepsis, identify the key immune system related genes, and construct diagnostic models for sepsis. In this study, the sepsis transcriptome and expression profiling data were merged into an integrated dataset containing 277 sepsis samples and 117 non-sepsis control samples. Single-sample gene set enrichment analysis (ssGSEA) was used to assess the immune cell infiltration. Two sepsis immune subtypes were identified based on the 22 differential immune cells between the sepsis and the healthy control groups. Weighted gene co-expression network analysis (WCGNA) was used to identify the key module genes. Then, 36 differentially expressed immune-related genes were identified, based on which a robust diagnostic model was constructed with 11 diagnostic genes. The expression of 11 diagnostic genes was finally assessed in the training and validation datasets respectively. In this study, we provide comprehensive insight into the immune features of sepsis and establish a robust diagnostic model for sepsis. These findings may provide new strategies for the early diagnosis of sepsis in the future.

Dexmedetomidine alleviates renal tubular ferroptosis in sepsis-associated AKI by KEAP1 regulating the degradation of GPX4

Sepsis-associated acute kidney injury (SA-AKI) has a high mortality rate and lacks effective targeted treatment. We applied lipopolysaccharides-induced injury models in human and mouse renal tubular epithelial cells, and at the same time, we selected a commonly used sedative drug, dexmedetomidine, to investigate its potential for renal protection. We found a significant increase in the expression level of HSP90, and the interaction with glutathione peroxidase 4 (GPX4) led to autophagic degradation of GPX4, triggering ferroptosis. Dexmedetomidine reduced the degradation of GPX4 by increasing the binding of KEAP1 and HSP90 in the cytoplasm. Therefore, lipid peroxidation and ferroptosis were reduced. Similarly, dexmedetomidine showed renal protective effects in C57BL/6J male mice with SA-AKI induced by cecal ligation. Our study reveals a new mechanism of renal tubular epithelial cell ferroptosis in SA-AKI treated with dexmedetomidine.

[Value of the expression levels of complement-3a receptor 1 and neutrophil extracellular traps in predicting sepsis-induced coagulopathy]

OBJECTIVES

To investigate the clinical value of complement-3a receptor 1 (C3aR1) and neutrophil extracellular traps (NETs) in predicting sepsis-induced coagulopathy (SIC).

METHODS

A prospective study was conducted among 78 children with sepsis who attended Xuzhou Children's Hospital Affiliated to Xuzhou Medical University from June 2022 to June 2023. According to the presence or absence of SIC, they were divided into two groups: SIC (n=36) and non-SIC (n=42) . The two groups were compared in terms of clinical data and the levels of C3aR1 and NETs. The factors associated with the occurrence of SIC were analyzed. The receiver operating characteristic (ROC) curve was used to evaluate the performance of C3aR1 and NETs in predicting SIC.

RESULTS

Compared with the non-SIC group, the SIC group had significantly higher levels of C-reactive protein, interleukin-6 (IL-6), interleukin-10, C3aR1, and NETs (P<0.05). The multivaiate logistic regression analysis showed that the increases in C3aR1, NETs, and IL-6 were closely associated with the occurrence of SIC (P<0.05). The ROC curve analysis showed that C3aR1 combined with NETs had an area under the curve (AUC) of 0.913 in predicting SIC (P<0.05), which was significantly higher than the AUC of C3aR1 or IL-6 (P<0.05), while there was no significant difference in AUC between C3aR1 combined with NETs and NETs alone (P>0.05).

CONCLUSIONS

There are significant increases in the expression levels of C3aR1 and NETs in the peripheral blood of children with SIC, and the expression levels of C3aR1 and NETs have a high clinical value in predicting SIC.

Prior Evaluation of Nutritional Status and Mortality in Patients with Sepsis in South Korea

Our objective was to determine whether nutritional status correlates with mortality in sepsis patients. Data from a nationwide registration database were utilized for this population-based cohort study. The study subjects comprised adults who received standard health examinations before being admitted to the hospital for sepsis and were diagnosed with sepsis between 2018 and 2020. Nutrition scores were evaluated using the Nutritional Lifestyle Assessment Tool in South Korea. Overall, 2482 patients with sepsis were included in this study. The 90-day and 1-year mortality rates in patients with sepsis were 26.8% (664/2482) and 34.2% (848/2482), respectively. In the covariate-adjusted multivariable logistic regression model, a 1-point increase in nutrition score was associated with a decrease in 90-day mortality in patients with sepsis (odds ratio [OR]: 0.98, 95% confidence interval [CI]: 0.97, 0.98; p = 0.025). In the covariate-adjusted multivariable Cox regression model, a 1-point increase in nutrition score was associated with a decrease in 1-year mortality in patients with sepsis (hazard ratio [H.R.]: 0.99, 95% CI: 0.98, 0.99; p = 0.035). Our results suggest that adequate dietary intake and healthy eating habits might protect against mortality among sepsis patients.

Novel tripeptide RKH derived from Akkermansia muciniphila protects against lethal sepsis

OBJECTIVE

The pathogenesis of sepsis is complex, and the sepsis-induced systemic proinflammatory phase is one of the key drivers of organ failure and consequent mortality. Akkermansia muciniphila (AKK) is recognised as a functional probiotic strain that exerts beneficial effects on the progression of many diseases; however, whether AKK participates in sepsis pathogenesis is still unclear. Here, we evaluated the potential contribution of AKK to lethal sepsis development.

DESIGN

Relative abundance of gut microbial AKK in septic patients was evaluated. Cecal ligation and puncture (CLP) surgery and lipopolysaccharide (LPS) injection were employed to establish sepsis in mice. Non-targeted and targeted metabolomics analysis were used for metabolites analysis.

RESULTS

We first found that the relative abundance of gut microbial AKK in septic patients was significantly reduced compared with that in non-septic controls. Live AKK supplementation, as well as supplementation with its culture supernatant, remarkably reduced sepsis-induced mortality in sepsis models. Metabolomics analysis and germ-free mouse validation experiments revealed that live AKK was able to generate a novel tripeptide Arg-Lys-His (RKH). RKH exerted protective effects against sepsis-induced death and organ damage. Furthermore, RKH markedly reduced sepsis-induced inflammatory cell activation and proinflammatory factor overproduction. A mechanistic study revealed that RKH could directly bind to Toll-like receptor 4 (TLR4) and block TLR4 signal transduction in immune cells. Finally, we validated the preventive effects of RKH against sepsis-induced systemic inflammation and organ damage in a piglet model.

CONCLUSION

We revealed that a novel tripeptide, RKH, derived from live AKK, may act as a novel endogenous antagonist for TLR4. RKH may serve as a novel potential therapeutic approach to combat lethal sepsis after successfully translating its efficacy into clinical practice.

Targeting the host response in sepsis: current approaches and future evidence

Sepsis, a dysregulated host response to infection characterized by organ failure, is one of the leading causes of death worldwide. Disbalances of the immune response play an important role in its pathophysiology. Patients may develop simultaneously or concomitantly states of systemic or local hyperinflammation and immunosuppression. Although a variety of effective immunomodulatory treatments are generally available, attempts to inhibit or stimulate the immune system in sepsis have failed so far to improve patients' outcome. The underlying reason is likely multifaceted including failure to identify responders to a specific immune intervention and the complex pathophysiology of organ dysfunction that is not exclusively caused by immunopathology but also includes dysfunction of the coagulation system, parenchymal organs, and the endothelium. Increasing evidence suggests that stratification of the heterogeneous population of septic patients with consideration of their host response might led to treatments that are more effective. The purpose of this review is to provide an overview of current studies aimed at optimizing the many facets of host response and to discuss future perspectives for precision medicine approaches in sepsis.

Host factor TIMP1 sustains long-lasting myeloid-biased hematopoiesis after severe infection

Infection is able to promote innate immunity by enhancing a long-term myeloid output even after the inciting infectious agent has been cleared. However, the mechanisms underlying such a regulation are not fully understood. Using a mouse polymicrobial peritonitis (sepsis) model, we show that severe infection leads to increased, sustained myelopoiesis after the infection is resolved. In post-infection mice, the tissue inhibitor of metalloproteinases 1 (TIMP1) is constitutively upregulated. TIMP1 antagonizes the function of ADAM10, an essential cleavage enzyme for the activation of the Notch signaling pathway, which suppresses myelopoiesis. While TIMP1 is dispensable for myelopoiesis under the steady state, increased TIMP1 enhances myelopoiesis after infection. Thus, our data establish TIMP1 as a molecular reporter of past infection in the host, sustaining hyper myelopoiesis and serving as a potential therapeutic target for modulating HSPC cell fate.

S100A8/A9: An emerging player in sepsis and sepsis-induced organ injury

Sepsis, the foremost contributor to mortality in intensive care unit patients, arises from an uncontrolled systemic response to invading infections, resulting in extensive harm across multiple organs and systems. Recently, S100A8/A9 has emerged as a promising biomarker for sepsis and sepsis-induced organ injury, and targeting S100A8/A9 appeared to ameliorate inflammation-induced tissue damage and improve adverse outcomes. S100A8/A9, a calcium-binding heterodimer mainly found in neutrophils and monocytes, serves as a causative molecule with pro-inflammatory and immunosuppressive properties, which are vital in the pathogenesis of sepsis. Therefore, improving our comprehension of how S100A8/A9 acts as a pathological player in the development of sepsis is imperative for advancing research on sepsis. Our review is the first-to the best of our knowledge-to discuss the biology of S100A8/A9 and its release mechanisms, summarize recent advances concerning the vital roles of S100A8/A9 in sepsis and the consequential organ damage, and underscore its potential as a promising diagnostic biomarker and therapeutic target for sepsis.

Study of Phospholipase A2 Levels and Its Comparison With Procalcitonin Levels in Patients With Sepsis Admitted in a Tertiary Care Hospital, Karnataka, India

INTRODUCTION

Sepsis is a complicated host response to infection involving organ failure which ultimately causes death of the host. Procalcitonin (PCT) is an effective marker used to diagnose sepsis but until now, there has been no ideal marker for sepsis. Phospholipase A2 (PLA2) also increases infections; however, only a few studies have assessed its capacity as a biomarker to diagnose sepsis. Thus, we aimed to examine PLA2 and compare its diagnostic capacity and accuracy with PCT as a biomarker of sepsis.

MATERIAL AND METHODS

Our study was a hospital-oriented cross-sectional study. Our study group included 80 patients of both sexes older than 18 years, meeting the quick sequential organ failure assessment (qSOFA) or systemic inflammatory response syndrome (SIRS) criteria of ≥2, hospitalized in a tertiary care hospital in Karnataka, India from January 2021 to December 2021. Out of them, 59 were found to have sepsis. Samples of all the patients were evaluated for relevant parameters, and data were statistically analyzed using SPSS v21 running on Windows 10. The statistical significance was set at p-value <0.05.

RESULTS

The mean PCT and PLA2 were significantly raised in sepsis patients compared to non-sepsis patients. Out of 59 septic patients, 45.76% had positive blood cultures, and 16.95% had positive urine culture reports. In blood cultures, the most common Gram-positive organism found was Staphylococcus, and the most common Gram-negative organism was Enterobacter. In urine cultures, Escherichia coli was the most common species. PLA2 was significantly higher in patients with bacterial etiology and Gram-positive cultures. The diagnostic capability, sensitivity, specificity, and accuracy of PLA2 were demonstrably higher than those of PCT.

CONCLUSION

Our study proves that PLA2 is a much better and more efficient biomarker in sepsis than PCT. The diagnostic capacity and accuracy of PLA2 clearly surpass PCT, so using PLA2 in sepsis as a biomarker can help clinicians in deciding on timely and appropriate management to speed the recovery of patients.

Flot2 deficiency facilitates B cell-mediated inflammatory responses and endotoxic shock

Sepsis is a life-threatening disease characterized by multiple organ dysfunction. B cells play a pivotal role in sepsis. Here, we first observed the significantly reduced Flot2 gene expression in B cells from patients with bacterial sepsis and endotoxin-induced septic mice. However, the effects of Flot2 on sepsis and B-cell immunity remain unknown. Thus, we sorted B cells from Flot2 knockout (Flot2-/- ) mice, RNA-seq revealed significantly upregulated effector B cell (Beff) cytokines such as Il6, Il1b and Cxcl10 after Flot2 deficiency, while it showed no effect on the expression of regulatory B cell (Breg) cytokines such as Il10, Tgfb. Consistently, elevated Beff cytokine IL-6 and unchanged Breg cytokine IL-10 were shown in B cells from Flot2-/- mice. Similar results were subsequently observed in B cell-specific Flot2 knockout chimeric mice. Notably, Flot2 deficiency aggravated sepsis with increased lung injury and shortened survival time in vivo by facilitating Beffs but not Bregs. Taken together, our data identify Flot2 as a novel controller of B cells, Flot2 deficiency amplifies inflammation by affecting Beffs to participate in the pathogenesis and progression of sepsis.

High-dimensional phenotyping of the peripheral immune response in community-acquired pneumonia

Background

Community-acquired pneumonia (CAP) represents a major health burden worldwide. Dysregulation of the immune response plays an important role in adverse outcomes in patients with CAP.

Methods

We analyzed peripheral blood mononuclear cells by 36-color spectral flow cytometry in adult patients hospitalized for CAP (n=40), matched control subjects (n=31), and patients hospitalized for COVID-19 (n=35).

Results

We identified 86 immune cell metaclusters, 19 of which (22.1%) were differentially abundant in patients with CAP versus matched controls. The most notable differences involved classical monocyte metaclusters, which were more abundant in CAP and displayed phenotypic alterations reminiscent of immunosuppression, increased susceptibility to apoptosis, and enhanced expression of chemokine receptors. Expression profiles on classical monocytes, driven by CCR7 and CXCR5, divided patients with CAP into two clusters with a distinct inflammatory response and disease course. The peripheral immune response in patients with CAP was highly similar to that in patients with COVID-19, but increased CCR7 expression on classical monocytes was only present in CAP.

Conclusion

CAP is associated with profound cellular changes in blood that mainly relate to classical monocytes and largely overlap with the immune response detected in COVID-19.

Dysregulated monocyte-derived macrophage response to Group B Streptococcus in newborns

Introduction

Streptococcus agalactiae (Group B Streptococcus, GBS) is a leading pathogen of neonatal sepsis. The host-pathogen interactions underlying the progression to life-threatening infection in newborns are incompletely understood. Macrophages are first line in host defenses against GBS, contributing to the initiation, amplification, and termination of immune responses. The goal of this study was to compare the response of newborn and adult monocyte-derived macrophages (MDMs) to GBS.

Methods

Monocytes from umbilical cord blood of healthy term newborns and from peripheral blood of healthy adult subjects were cultured with M-CSF to induce MDMs. M-CSF-MDMs, GM-CSF- and IFNγ-activated MDMs were exposed to GBS COH1, a reference strain for neonatal sepsis.

Results

GBS induced a greater release of IL-1β, IL-6, IL-10, IL-12p70 and IL-23 in newborn compared to adult MDMs, while IL-18, IL-21, IL-22, TNF, RANTES/CCL5, MCP-1/CCL2 and IL-8/CXCL8 were released at similar levels. MDM responses to GBS were strongly influenced by conditions of activation and were distinct from those to synthetic bacterial lipopeptides and lipopolysaccharides. Under similar conditions of opsonization, newborn MDMs phagocytosed and killed GBS as efficiently as adult MDMs.

Discussion

Altogether, the production of excessive levels of Th1- (IL-12p70), Th17-related (IL-1β, IL-6, IL-23) and anti-inflammatory (IL-10) cytokines is consistent with a dysregulated response to GBS in newborns. The high responsiveness of newborn MDMs may play a role in the progression of GBS infection in newborns, possibly contributing to the development of life-threatening organ dysfunction.

Immunomodulatory biomaterials against bacterial infections: Progress, challenges, and future perspectives

Bacterial infectious diseases are one of the leading causes of death worldwide. Even with the use of multiple antibiotic treatment strategies, 4.95 million people died from drug-resistant bacterial infections in 2019. By 2050, the number of deaths will reach 10 million annually. The increasing mortality may be partly due to bacterial heterogeneity in the infection microenvironment, such as drug-resistant bacteria, biofilms, persister cells, intracellular bacteria, and small colony variants. In addition, the complexity of the immune microenvironment at different stages of infection makes biomaterials with direct antimicrobial activity unsatisfactory for the long-term treatment of chronic bacterial infections. The increasing mortality may be partly attributed to the biomaterials failing to modulate the active antimicrobial action of immune cells. Therefore, there is an urgent need for effective alternatives to treat bacterial infections. Accordingly, the development of immunomodulatory antimicrobial biomaterials has recently received considerable interest; however, a comprehensive review of their research progress is lacking. In this review, we focus mainly on the research progress and future perspectives of immunomodulatory antimicrobial biomaterials used at different stages of infection. First, we describe the characteristics of the immune microenvironment in the acute and chronic phases of bacterial infections. Then, we highlight the immunomodulatory strategies for antimicrobial biomaterials at different stages of infection and their corresponding advantages and disadvantages. Moreover, we discuss biomaterial-mediated bacterial vaccines' potential applications and challenges for activating innate and adaptive immune memory. This review will serve as a reference for future studies to develop next-generation immunomodulatory biomaterials and accelerate their translation into clinical practice.

Metatranscriptome of human lung microbial communities in a cohort of mechanically ventilated COVID-19 Omicron patients

The Omicron variant of the severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) infected a substantial proportion of Chinese population, and understanding the factors underlying the severity of the disease and fatality is valuable for future prevention and clinical treatment. We recruited 64 patients with invasive ventilation for COVID-19 and performed metatranscriptomic sequencing to profile host transcriptomic profiles, plus viral, bacterial, and fungal content, as well as virulence factors and examined their relationships to 28-day mortality were examined. In addition, the bronchoalveolar lavage fluid (BALF) samples from invasive ventilated hospital/community-acquired pneumonia patients (HAP/CAP) sampled in 2019 were included for comparison. Genomic analysis revealed that all Omicron strains belong to BA.5 and BF.7 sub-lineages, with no difference in 28-day mortality between them. Compared to HAP/CAP cohort, invasive ventilated COVID-19 patients have distinct host transcriptomic and microbial signatures in the lower respiratory tract; and in the COVID-19 non-survivors, we found significantly lower gene expressions in pathways related viral processes and positive regulation of protein localization to plasma membrane, higher abundance of opportunistic pathogens including bacterial Alloprevotella, Caulobacter, Escherichia-Shigella, Ralstonia and fungal Aspergillus sydowii and Penicillium rubens. Correlational analysis further revealed significant associations between host immune responses and microbial compositions, besides synergy within viral, bacterial, and fungal pathogens. Our study presents the relationships of lower respiratory tract microbiome and transcriptome in invasive ventilated COVID-19 patients, providing the basis for future clinical treatment and reduction of fatality.

Gasdermins in sepsis

Sepsis is a hyper-heterogeneous syndrome in which the systemic inflammatory response persists throughout the course of the disease and the inflammatory and immune responses are dynamically altered at different pathogenic stages. Gasdermins (GSDMs) proteins are pore-forming executors in the membrane, subsequently mediating the release of pro-inflammatory mediators and inflammatory cell death. With the increasing research on GSDMs proteins and sepsis, it is believed that GSDMs protein are one of the most promising therapeutic targets in sepsis in the future. A more comprehensive and in-depth understanding of the functions of GSDMs proteins in sepsis is important to alleviate the multi-organ dysfunction and reduce sepsis-induced mortality. In this review, we focus on the function of GSDMs proteins, the molecular mechanism of GSDMs involved in sepsis, and the regulatory mechanism of GSDMs-mediated signaling pathways, aiming to provide novel ideas and therapeutic strategies for the diagnosis and treatment of sepsis.

The noncanonical inflammasome-induced pyroptosis and septic shock

Sepsis remains one of the most common and lethal conditions globally. Currently, no proposed target specific to sepsis improves survival in clinical trials. Thus, an in-depth understanding of the pathogenesis of sepsis is needed to propel the discovery of effective treatment. Recently attention to sepsis has intensified because of a growing recognition of a non-canonical inflammasome-triggered lytic mode of cell death termed pyroptosis upon sensing cytosolic lipopolysaccharide (LPS). Although the consequences of activation of the canonical and non-canonical inflammasome are similar, the non-canonical inflammasome formation requires caspase-4/5/11, which enzymatically cleave the pore-forming protein gasdermin D (GSDMD) and thereby cause pyroptosis. The non-canonical inflammasome assembly triggers such inflammatory cell death by itself; or leverages a secondary activation of the canonical NLRP3 inflammasome pathway. Excessive cell death induced by oligomerization of GSDMD and NINJ1 leads to cytokine release and massive tissue damage, facilitating devastating consequences and death. This review summarized the updated mechanisms that initiate and regulate non-canonical inflammasome activation and pyroptosis and highlighted various endogenous or synthetic molecules as potential therapeutic targets for treating sepsis.

Sepsis-associated encephalopathy: From pathophysiology to clinical management

Sepsis-associated encephalopathy, which presents as delirium and coma, is a significant complication of sepsis characterized by acute brain dysfunction. The presence of inflammatory pathological changes in the brain of sepsis patients and animal models has been recognized since the 1920 s, initially attributed to the entry of microbial toxins into the brain. In the early 2000 s, attention shifted towards the impact of oxidative stress, the cholinergic system, and cytokines on brain function following sepsis onset. More recently, sepsis-associated encephalopathy has been defined as a diffuse brain dysfunction not directly caused by pathogenic infection of the brain. Currently, there is no evidence-based standard for diagnosing sepsis-associated encephalopathy, and clinical management is primarily focused on symptomatic and supportive measures. This review aims to explore the pathophysiology of sepsis-associated encephalopathy and establish the connection between pathophysiological mechanisms and clinical characteristics. We hope that this work will spark the interest of researchers from various fields and contribute to the advancement of sepsis-associated encephalopathy research.

Regorafenib modulation of the angiopoietin/TIE2 axis in a mouse model of sepsis-induced lung injury

Sepsis, often resulting from an immune response overreaction to microorganisms and their products, can lead to acute lung injury through inflammation mediated by excessive cytokines. This study aimed to investigate the effects of regorafenib on lung injury in mice following the induction of sepsis. We divided mice into four groups (n=6 each): a sham group (undergoing laparotomy without cecal ligation and puncture [CLP]), a CLP group, a vehicle group, and a regorafenib-treated group (30 mg/kg IP, administered one hour before CLP). TNF-α, IL-1β, VEGF, MPO, caspase-11, and Ang-2 levels were significantly increased (p<0.05) in the CLP group compared to the sham group, while the regorafenib group showed significant reductions in these markers versus the CLP group (p< 0.05). In contrast, Ang-1 levels, which were reduced in the CLP group (p<0.05) compared to the sham group, were elevated in the regorafenib group compared to the CLP group. Quantitative real-time PCR revealed a significant decrease in TIE2 and VE-cadherin mRNA expression in the lung tissue of the CLP group compared to the sham group. There were no significant differences in mRNA expression of the TIE2 gene between the regorafenib and CLP group. However, VE-cadherin significantly increased after regorafenib treatment. Regorafenib demonstrated lung-protective effects through its anti-inflammatory and antiangiogenic activities and its influence on lung tissue mRNA expression of the cadherin gene.

Single-cell transcriptional gene signature analysis identifies IL-17 signaling pathway as the key pathway in sepsis

Sepsis is a multiple dysregulated systemic inflammatory response with high mortality and leads to public concern. This study was designed to identify possible critical pathways associated with sepsis clinical severity and outcome, which offer potential biomarkers and therapeutic targets for sepsis diagnosis and treatment. Single-cell transcriptome profiles of human peripheral blood mononuclear (PBMC) in the healthy control population and sepsis patients were downloaded from the sepsis database GSE167363 and performed quality control before subsequent analysis. The bulk-RNA sequencing of blood samples in the sepsis-associated databases GSE100159 and GSE133822 was also used to confirm the association between critical pathways and sepsis pathology after processing raw data. We found there was a total of 18 distinct clusters in PBMC of sepsis, which was identified by the t-SNE and UMAP dimension reduction analysis. Meanwhile, the main cell types including B, NK, T, and monocyte cells were identified via the cell maker website and the "Single R" package cell-type annotation analysis. Subsequently, GO and KEGG enrichment analysis of differential expression genes in each cluster found that DEGs between healthy control and sepsis patients were significantly enriched in the IL-17 signaling pathway in monocyte, NK, and T cells. Finally, GSE100159 and GSE133822 confirmed IL-17 signaling pathway-associated genes including IL-17R, TRAF6, RELB, TRAF5, CEBPB, JUNB, CXCL1, CXCL3, CXCL8, CXCR1, and CXCR2 were significantly up-regulated in sepsis blood samples compared with the age-matched healthy control population. Taken together, we concluded that the IL-17 signaling pathway serves as a significant potential mechanism of sepsis and provides a promising therapeutic target for sepsis treatment. This research will further deepen our understanding of sepsis development.

Depletion of mTOR ameliorates CD4+ T cell pyroptosis by promoting autophagy activity in septic mice

A reduction in the number of CD4+ T cells is a central part of the immunosuppression phase of sepsis and leads to impaired immune defense ability and increased mortality. Pyroptosis, a newly discovered programmed cell death, was confirmed to be an important mechanism of lymphocytopenia in a lot of human diseases and is under the regulation of autophagy. The mammalian target of rapamycin (mTOR) pathway is closely related to CD4+ T-cell survival. Whether the mTOR pathway influences CD4+ T cell pyroptosis by regulating autophagy remains unknown. In this study, a septic mouse model was developed using cecal ligation and puncture (CLP) to explore the degree of pyroptosis and autophagy of CD4+ T cells. T-cell-specific mTOR/TSC1-knockout mice were used to investigate the role of mTOR pathway in the regulation of CD4+ T cell pyroptosis. Bafilomycin, a specific autophagy inhibitor, was used to verify the regulatory effect of autophagy on pyroptosis in septic mice. We observed aggravated pyroptosis in CD4+ T cells in CLP mice accompanied by impaired autophagy activity and an overactivated mTOR signaling pathway. Depletion of mTOR relieved autophagy deficiency and reduced the proportion of pyroptotic CD4+ T cells. In T-cell-specific mTOR-knockout mice treated with bafilomycin, the protective effect of mTOR depletion vanished. This indicated that autophagy negatively regulates CD4+ T cell pyroptosis, which is under the control of the mTOR pathway. Taken together, our findings emphasize the importance of pyroptosis in sepsis-induced lymphopenia and reveal the regulatory effects of the mTOR pathway and the role of autophagy in this regulation.

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

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

Heat shock protein 27 in the pathogenesis of COVID-19 and non-COVID acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a common cause of hypoxemic respiratory failure in intensive care units that has increased dramatically as a result of the COVID-19 pandemic. In both COVID-19 and non-COVID ARDS, the pathogenesis of lung injury involves local (pulmonary) and systemic inflammation, leading to impaired gas exchange, requirement for mechanical ventilation, and a high risk of mortality. Heat shock protein 27 (HSP27) is a chaperone protein expressed in times of cell stress with roles in modulation of systemic inflammation via the NF-κB pathway. Given its important role as a modulator of inflammation, we sought to investigate the role of HSP27 and its associated auto-antibodies in ARDS caused by both SARS-CoV-2 and non-COVID etiologies. A total of 68 patients admitted to the intensive care unit with ARDS requiring mechanical ventilation were enrolled in a prospective, observational study that included 22 non-COVID-19 and 46 COVID-19 patients. Blood plasma levels of HSP27, anti-HSP27 auto-antibody (AAB), and cytokine profiles were measured on days 1 and 3 of ICU admission along with clinical outcome measures. Patients with COVID-19 ARDS displayed significantly higher levels of HSP27 in plasma, and a higher ratio of HSP27:AAB on both day 1 and day 3 of ICU admission. In patients with COVID-19, higher levels of circulating HSP27 and HSP27:AAB ratio were associated with a more severe systemic inflammatory response and adverse clinical outcomes including more severe hypoxemic respiratory failure. These findings implicate HSP27 as a marker of advanced pathogenesis of disease contributing to the dysregulated systemic inflammation and worse clinical outcomes in COVID-19 ARDS, and therefore may represent a potential therapeutic target.

Hyper-inflammatory profile and immunoparalysis in patients with severe Legionnaires' disease

Introduction

Severe Legionnaires' disease (LD) can lead to multi-organ failure or death in 10%-30% of patients. Although hyper-inflammation and immunoparalysis are well described in sepsis and are associated with high disease severity, little is known about the immune response in LD. This study aimed to evaluate the immune status of patients with LD and its association with disease severity.

Methods

A total of 92 hospitalized LD patients were included; 19 plasmatic cytokines and pulmonary Legionella DNA load were measured in 84 patients on the day of inclusion (day 0, D0). Immune functional assays (IFAs) were performed from whole blood samples collected at D2 and stimulated with concanavalin A [conA, n = 19 patients and n = 21 healthy volunteers (HV)] or lipopolysaccharide (LPS, n = 14 patients and n = 9 HV). A total of 19 cytokines (conA stimulation) and TNF-α (LPS stimulation) were quantified from the supernatants. The Sequential Organ Failure Assessment (SOFA) severity score was recorded at D0 and the mechanical ventilation (MV) status was recorded at D0 and D8.

Results

Among the 84 patients, a higher secretion of plasmatic MCP-1, MIP1-β, IL-6, IL-8, IFN-γ, TNF-α, and IL-17 was observed in the patients with D0 and D8 MV. Multiparametric analysis showed that these seven cytokines were positively associated with the SOFA score. Upon conA stimulation, LD patients had a lower secretion capacity for 16 of the 19 quantified cytokines and a higher release of IL-18 and MCP-1 compared to HV. IL-18 secretion was higher in D0 and D8 MV patients. TNF-α secretion, measured after ex vivo LPS stimulation, was significantly reduced in LD patients and was associated with D8 MV status.

Discussion

The present findings describe a hyper-inflammatory phase at the initial phase of Legionella pneumonia that is more pronounced in patients with severe LD. These patients also present an immunoparalysis for a large number of cytokines, except IL-18 whose secretion is increased. An assessment of the immune response may be relevant to identify patients eligible for future innovative host-directed therapies.

Anti-Inflammatory Activity of Fucan from Spatoglossum schröederi in a Murine Model of Generalized Inflammation Induced by Zymosan

Fucans from marine algae have been the object of many studies that demonstrated a broad spectrum of biological activities, including anti-inflammatory effects. The aim of this study was to verify the protective effects of a fucan extracted from the brown algae Spatoglossum schröederi in animals submitted to a generalized inflammation model induced by zymosan (ZIGI). BALB/c mice were first submitted to zymosan-induced peritonitis to evaluate the treatment dose capable of inhibiting the induced cellular migration in a simple model of inflammation. Mice were treated by the intravenous route with three doses (20, 10, and 5 mg/kg) of our fucan and, 1 h later, were inoculated with an intraperitoneal dose of zymosan (40 mg/kg). Peritoneal exudate was collected 24 h later for the evaluation of leukocyte migration. Doses of the fucan of Spatoglossum schröederi at 20 and 10 mg/kg reduced peritoneal cellular migration and were selected to perform ZIGI experiments. In the ZIGI model, treatment was administered 1 h before and 6 h after the zymosan inoculation (500 mg/kg). Treatments and challenges were administered via intravenous and intraperitoneal routes, respectively. Systemic toxicity was assessed 6 h after inoculation, based on three clinical signs (bristly hair, prostration, and diarrhea). The peritoneal exudate was collected to assess cellular migration and IL-6 levels, while blood samples were collected to determine IL-6, ALT, and AST levels. Liver tissue was collected for histopathological analysis. In another experimental series, weight loss was evaluated for 15 days after zymosan inoculation and fucan treatment. The fucan treatment did not present any effect on ZIGI systemic toxicity; however, a fucan dose of 20 mg/kg was capable of reducing the weight loss in treated mice. The treatment with both doses also reduced the cellular migration and reduced IL-6 levels in peritoneal exudate and serum in doses of 20 and 10 mg/kg, respectively. They also presented a protective effect in the liver, with a reduction in hepatic transaminase levels in both doses of treatment and attenuated histological damage in the liver at a dose of 10 mg/kg. Fucan from S. schröederi presented a promising pharmacological activity upon the murine model of ZIGI, with potential anti-inflammatory and hepatic protective effects, and should be the target of profound and elucidative studies.

Combination of NK and Other Immune Markers at Early Phase Stratify the Risk of Sepsis Patients: A Retrospective Study

Purpose

Immune dysfunction plays a pivotal role in sepsis pathogenesis. Previous studies have revealed the crucial role of T cells and human leukocyte antigen-DR (HLA-DR) in sepsis. However, the function of natural killer (NK) cells remains unclear. This study aimed to investigate whether NK cells are associated with sepsis prognosis. In addition, we aimed to explore the interrelation and influence between NK and other immunological features in patients with sepsis.

Patients and Methods

This retrospective, observational study included patients with sepsis from two hospitals in mainland China. The clinical characteristics and immune results during the early phase were collected. Patients were classified according to the level of immune cells to analyze the relationship between immunological features and 28-day mortality.

Results

A total of 984 patients were included in this study. Non-survivors were older and had lower levels of lymphocytes, monocytes, NK cells, HLA-DR, and T cells. Patients were classified into eight groups according to their levels of NK cells, HLA-DR, and T cells. Only patients with decreased NK and T cell counts showed a significant increase in 28-day mortality. An increase in CD8+ T cells was correlated with the alleviation of 28-day mortality only among patients with high NK cell levels.

Conclusion

This study provides novel insights into the association between NK cells and 28-day mortality as well as the interrelation between NK cells and other immune cells in sepsis. The relationship between CD8+ T cells and 28-day mortality in sepsis is dependent on NK cell count.

Protein modification by short-chain fatty acid metabolites in sepsis: a comprehensive review

Sepsis is a major life-threatening syndrome of organ dysfunction caused by a dysregulated host response due to infection. Dysregulated immunometabolism is fundamental to the onset of sepsis. Particularly, short-chain fatty acids (SCFAs) are gut microbes derived metabolites serving to drive the communication between gut microbes and the immune system, thereby exerting a profound influence on the pathophysiology of sepsis. Protein post-translational modifications (PTMs) have emerged as key players in shaping protein function, offering novel insights into the intricate connections between metabolism and phenotype regulation that characterize sepsis. Accumulating evidence from recent studies suggests that SCFAs can mediate various PTM-dependent mechanisms, modulating protein activity and influencing cellular signaling events in sepsis. This comprehensive review discusses the roles of SCFAs metabolism in sepsis associated inflammatory and immunosuppressive disorders while highlights recent advancements in SCFAs-mediated lysine acylation modifications, such as substrate supplement and enzyme regulation, which may provide new pharmacological targets for the treatment of sepsis.

Clinical value of droplet digital PCR in the diagnosis and dynamic monitoring of suspected bacterial bloodstream infections

BACKGROUND

Bloodstream infections (BSIs) represent a significant public health challenge due to their high morbidity and mortality. The clinical prognosis of BSIs is closely related to the timely and accurate diagnosis and the rational use of initial antimicrobials. We aimed to evaluate the clinical value of droplet digital PCR (ddPCR) in rapid diagnosis and dynamic monitoring of BSIs.

METHODS

In this prospective study, using a ddPCR-based approach which detects 18 common pathogens, we compared the detection results and clinical concordance rates of ddPCR with blood culture (BC) in 211 patients with suspected BSIs. Further, the inflammatory profile of BSIs with Gram-negative bacteria was analyzed by Olink proteomics platform.

RESULTS

Our data showed that the positive detection rate of ddPCR was 48.82%, which was higher than that of BC (9.48%). For BC-validated BSIs, ddPCR had a sensitivity of 90.00% and a specificity of 55.50%. When considering clinically-validated BSIs, the diagnostic value of ddPCR improved with a sensitivity of 92.59% and a specificity of 78.46%.The bacterial load detected by ddPCR was correlated with traditional clinical inflammatory indicators such as interleukin-6 (IL-6) and C-reactive protein (CRP). In addition, using Olink proteomics platform, we revealed that serological osteoprotegerin (OPG), interleukin-8 (IL-8), interleukin-18 receptor 1 (IL-18R1), C-C motif chemokine 20 (CCL20) and IL-6 were substantially elevated in Gram-negative bacteria-associated BSIs, which could serve as novel auxiliary diagnostic indicators for Gram-negative bacteria BSIs.

CONCLUSION

ddPCR has the potential to provide early pathogen diagnosis, dynamic monitoring, and treatment regimen optimization for patients with BSIs.

ANGPTL2 aggravates LPS-induced septic cardiomyopathy via NLRP3-mediated inflammasome in a DUSP1-dependent pathway

Angiopoietin-like protein 2 (ANGPTL2) was implicated in various cardiovascular diseases; however, its role in lipopolysaccharide (LPS)-related septic cardiomyopathy remains unclear. Herein, mice were exposed to LPS to generate septic cardiomyopathy, and adeno-associated viral vector was employed to overexpress ANGPTL2 in the myocardium. Besides, mice were treated with adenoviral vector to knock down ANGPTL2 in hearts. ANGPTL2 expressions in hearts and cardiomyocytes were upregulated by LPS challenge. ANGPTL2 overexpression aggravated, while ANGPTL2 silence ameliorated LPS-associated cardiac impairment and inflammation. Mechanically, we found that ANGPTL2 activated NLRP3 inflammasome via suppressing DUSP1 signaling, and NLRP3 knockdown abrogated the detrimental role of ANGPTL2 in aggravating LPS-induced cardiac inflammation. Furthermore, DUSP1 overexpression significantly inhibited ANGPTL2-mediated NLRP3 activation, and subsequently improved LPS-related cardiac dysfunction. In summary, ANGPTL2 exacerbated septic cardiomyopathy via activating NLRP3-mediated inflammation in a DUSP1-dependent manner, and our study uncovered a promising therapeutic target in preventing septic cardiomyopathy.

Single-cell RNA sequencing reveals the effects of capsaicin in the treatment of sepsis-induced liver injury

Sepsis is a difficult-to-treat systemic condition in which liver dysfunction acts as both regulator and target. However, the dynamic response of diverse intrahepatic cells to sepsis remains poorly characterized. Capsaicin (CAP), a multifunctional chemical derived from chilli peppers, has recently been shown to potentially possess anti-inflammatory effects, which is also one of the main approaches for drug discovery against sepsis. We performed single-cell RNA transcriptome sequencing on 86,830 intrahepatic cells isolated from normal mice, cecal ligation and puncture-induced sepsis model mice and CAP-treated mice. The transcriptional atlas of these cells revealed dynamic changes in hepatocytes, macrophages, neutrophils, and endothelial cells in response to sepsis. Among the extensive crosstalk across these major subtypes, KC_Cxcl10 shared strong potential interaction with other cells when responding to sepsis. CAP mitigated the severity of inflammation by partly reversing these pathophysiologic processes. Specific cell subpopulations in the liver act collectively to escalate inflammation, ultimately causing liver dysfunction. CAP displays its health-promoting function by ameliorating liver dysfunction induced by sepsis. Our study provides valuable insights into the pathophysiology of sepsis and suggestions for future therapeutic gain.

Sepsis heterogeneity

BACKGROUND

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection, with extremely high mortality. Notably, sepsis is a heterogeneous syndrome characterized by a vast, multidimensional array of clinical and biologic features, which has hindered advances in the therapeutic field beyond the current standards.

DATA SOURCES

We used PubMed to search the subject-related medical literature by searching for the following single and/or combination keywords: sepsis, heterogeneity, personalized treatment, host response, infection, epidemiology, mortality, incidence, age, children, sex, comorbidities, gene susceptibility, infection sites, bacteria, fungi, virus, host response, organ dysfunction and management.

RESULTS

We found that host factors (age, biological sex, comorbidities, and genetics), infection etiology, host response dysregulation and multiple organ dysfunctions can all result in different disease manifestations, progression, and response to treatment, which make it difficult to effectively treat and manage sepsis patients.

CONCLUSIONS

Herein, we have summarized contributing factors to sepsis heterogeneity, including host factors, infection etiology, host response dysregulation, and multiple organ dysfunctions, from the key elements of pathogenesis of sepsis. An in-depth understanding of the factors that contribute to the heterogeneity of sepsis will help clinicians understand the complexity of sepsis and enable researchers to conduct more personalized clinical studies for homogenous patients.

INTERFERING HSA_CIRC_0001226 MITIGATES LPS-INDUCED BEAS-2B CELL INJURY BY REGULATING MIR-940/TGFBR2 PATHWAY

ABSTRACT

Background: Sepsis-associated acute lung injury (SA-ALI) is a serious threat to human health. A growing body of evidence suggested that circular RNAs may be involved in ALI progression. The aim of this study was to investigate the effect and mechanism of circ_0001226 on lipopolysaccharide (LPS)-induced BEAS-2B cells. Methods: BEAS-2B cells were stimulated with LPS to establish a SA-ALI cell model. The expression of circ_0001226, miR-940, and transforming growth factor beta receptor II (TGFBR2) were monitored by quantitative real-time polymerase chain reaction. Cell proliferation and apoptosis were evaluated by the Cell Counting Kit-8, 5-ethynyl-2'-deoxyuridine assay, and flow cytometry. The levels of interleukin-6 (IL-6), IL-1β, and tumor necrosis factor-α were calculated by enzyme-linked immunosorbent assay. Western blot was implemented to test the protein levels of PCNA, Bax, and TGFBR2. Dual-luciferase reporter assay and RNA pull-down assay were adopted to investigate the interaction between circ_0001226 and miR-940, as well as TGFBR2 and miR-940. Results: The levels of circ_0001226 and TGFBR2 were elevated, and miR-940 was decreased in SA-ALI serum specimens and LPS-evoked BEAS-2B cells. Besides that, circ_0001226 interference contributed to cell proliferation and restrained apoptosis and inflammation in LPS-induced BEAS-2B cells. Mechanically, circ_0001226 worked as a molecular sponge of miR-940 to regulate TGFBR2 expression. Conclusion: Circ_0001226 deficiency weakened LPS-mediated proliferation inhibition and inflammatory processes in BEAS-2B cells by binding miR-940 and regulating TGFBR2.

The nano-windmill exerts superior anti-inflammatory effects via reducing choline uptake to inhibit macrophage activation

Macrophages' activation plays a central role during the development and progression of inflammation, while the regulation of metabolic reprogramming of macrophages has been recently identified as a novel strategy for anti-inflammatory therapies. Our previous studies have found that tetrahedral framework nucleic acid (tFNA) plays a mild anti-inflammatory effect by inhibiting macrophage activation, but the specific mechanism remains unclear. Here, by metabolomics and RNA sequencing, choline uptake is identified to be significantly repressed by decreased slc44a1 expression in tFNA-treated activated macrophages. Inspired by this result, combined with the excellent delivery capacities of tFNA, siR-slc44a1 is loaded into the tFNA to develop a new tFNA-based small interfering RNA (siRNA) delivery system named 'nano-windmill,' which exhibits a synergetic role by targeting slc44a1, finally blowing up the anti-inflammatory effects of tFNA to inhibit macrophages activation via reducing choline uptake. By confirming its anti-inflammatory effects in chronic (periodontitis) and acute (sepsis) inflammatory disease, the tFNA-based nanomedicine developed for inflammatory diseases may provide broad prospects for tFNA upgrading and various biological applications such as anti-inflammatory.

Targeting Toll-like receptor-driven systemic inflammation by engineering an innate structural fold into drugs

There is a clinical need for conceptually new treatments that target the excessive activation of inflammatory pathways during systemic infection. Thrombin-derived C-terminal peptides (TCPs) are endogenous anti-infective immunomodulators interfering with CD14-mediated TLR-dependent immune responses. Here we describe the development of a peptide-based compound for systemic use, sHVF18, expressing the evolutionarily conserved innate structural fold of natural TCPs. Using a combination of structure- and in silico-based design, nuclear magnetic resonance spectroscopy, biophysics, mass spectrometry, cellular, and in vivo studies, we here elucidate the structure, CD14 interactions, protease stability, transcriptome profiling, and therapeutic efficacy of sHVF18. The designed peptide displays a conformationally stabilized, protease resistant active innate fold and targets the LPS-binding groove of CD14. In vivo, it shows therapeutic efficacy in experimental models of endotoxin shock in mice and pigs and increases survival in mouse models of systemic polymicrobial infection. The results provide a drug class based on Nature´s own anti-infective principles.

A hub gene signature as a therapeutic target and biomarker for sepsis and geriatric sepsis-induced ARDS concomitant with COVID-19 infection

Background

COVID-19 and sepsis represent formidable public health challenges, characterized by incompletely elucidated molecular mechanisms. Elucidating the interplay between COVID-19 and sepsis, particularly in geriatric patients suffering from sepsis-induced acute respiratory distress syndrome (ARDS), is of paramount importance for identifying potential therapeutic interventions to mitigate hospitalization and mortality risks.

Methods

We employed bioinformatics and systems biology approaches to identify hub genes, shared pathways, molecular biomarkers, and candidate therapeutics for managing sepsis and sepsis-induced ARDS in the context of COVID-19 infection, as well as co-existing or sequentially occurring infections. We corroborated these hub genes utilizing murine sepsis-ARDS models and blood samples derived from geriatric patients afflicted by sepsis-induced ARDS.

Results

Our investigation revealed 189 differentially expressed genes (DEGs) shared among COVID-19 and sepsis datasets. We constructed a protein-protein interaction network, unearthing pivotal hub genes and modules. Notably, nine hub genes displayed significant alterations and correlations with critical inflammatory mediators of pulmonary injury in murine septic lungs. Simultaneously, 12 displayed significant changes and correlations with a neutrophil-recruiting chemokine in geriatric patients with sepsis-induced ARDS. Of these, six hub genes (CD247, CD2, CD40LG, KLRB1, LCN2, RETN) showed significant alterations across COVID-19, sepsis, and geriatric sepsis-induced ARDS. Our single-cell RNA sequencing analysis of hub genes across diverse immune cell types furnished insights into disease pathogenesis. Functional analysis underscored the interconnection between sepsis/sepsis-ARDS and COVID-19, enabling us to pinpoint potential therapeutic targets, transcription factor-gene interactions, DEG-microRNA co-regulatory networks, and prospective drug and chemical compound interactions involving hub genes.

Conclusion

Our investigation offers potential therapeutic targets/biomarkers, sheds light on the immune response in geriatric patients with sepsis-induced ARDS, emphasizes the association between sepsis/sepsis-ARDS and COVID-19, and proposes prospective alternative pathways for targeted therapeutic interventions.

Probiotics and Their Bioproducts: A Promising Approach for Targeting Methicillin-Resistant Staphylococcus aureus and Vancomycin-Resistant Enterococcus

Antibiotic resistance is a serious global health problem that poses a threat to the successful treatment of various bacterial infections, especially those caused by methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). Conventional treatment of MRSA and VRE infections is challenging and often requires alternative or combination therapies that may have limited efficacy, higher costs, and/or more adverse effects. Therefore, there is an urgent need to find new strategies to combat antibiotic-resistant bacteria. Probiotics and antimicrobial peptides (AMPs) are two promising approaches that have shown potential benefits in various diseases. Probiotics are live microorganisms that confer health benefits to the host when administered in adequate amounts. AMPs, usually produced with probiotic bacteria, are short amino acid sequences that have broad-spectrum activity against bacteria, fungi, viruses, and parasites. Both probiotics and AMPs can modulate the host immune system, inhibit the growth and adhesion of pathogens, disrupt biofilms, and enhance intestinal barrier function. In this paper, we review the current knowledge on the role of probiotics and AMPs in targeting multi-drug-resistant bacteria, with a focus on MRSA and VRE. In addition, we discuss future directions for the clinical use of probiotics.

Adverse Long-Term Outcomes and an Immune Suppressed Endotype in Sepsis Patients with Reduced Interferon-γELISpot: A Multicenter, Prospective Observational Study

BACKGROUND

Sepsis remains a major clinical challenge for which successful treatment requires greater precision in identifying patients at increased risk of adverse outcomes requiring different therapeutic approaches. Predicting clinical outcomes and immunological endotyping of septic patients has generally relied on using blood protein or mRNA biomarkers, or static cell phenotyping. Here, we sought to determine whether functional immune responsiveness would yield improved precision.

METHODS

An ex vivo whole blood enzyme-linked immunosorbent (ELISpot) assay for cellular production of interferon-γ (IFN-γ) was evaluated in 107 septic and 68 non-septic patients from five academic health centers using blood samples collected on days 1, 4 and 7 following ICU admission.

RESULTS

Compared with 46 healthy subjects, unstimulated and stimulated whole blood IFNγ expression were either increased or unchanged, respectively, in septic and nonseptic ICU patients. However, in septic patients who did not survive 180 days, stimulated whole blood IFNγ expression was significantly reduced on ICU days 1, 4 and 7 (all p<0.05), due to both significant reductions in total number of IFNγ producing cells and amount of IFNγ produced per cell (all p<0.05). Importantly, IFNγ total expression on day 1 and 4 after admission could discriminate 180-day mortality better than absolute lymphocyte count (ALC), IL-6 and procalcitonin. Septic patients with low IFNγ expression were older and had lower ALC and higher sPD-L1 and IL-10 concentrations, consistent with an immune suppressed endotype.

CONCLUSIONS

A whole blood IFNγ ELISpot assay can both identify septic patients at increased risk of late mortality, and identify immune-suppressed, sepsis patients.

Heparanase inhibition leads to improvement in patients with acute gastrointestinal injuries induced by sepsis

BACKGROUND

Patients with sepsis are at high risk for acute gastrointestinal injury (AGI), but the diagnosis and treatment of AGI due to sepsis are unsatisfactory. Heparanase (HPA) plays an important role in septic AGI (S-AGI), but its specific mechanism is not completely understood, and few clinical reports are available.

AIM

To explore the effect and mechanism of HPA inhibition in S-AGI patients.

METHODS

In our prospective clinical trial, 48 patients with S-AGI were randomly assigned to a control group to receive conventional treatment, whereas 47 patients were randomly assigned to an intervention group to receive conventional treatment combined with low molecular weight heparin. AGI grade, sequential organ failure assessment score, acute physiology and chronic health evaluation II score, D-dimer, activated partial thromboplastin time (APTT), anti-Xa factor, interleukin-6, tumour necrosis factor-α, HPA, syndecan-1 (SDC-1), LC3B (autophagy marker), intestinal fatty acid binding protein, D-lactate, motilin, gastrin, CD4/CD8, length of intensive care unit (ICU) stay, length of hospital stay and 28-d survival on the 1st, 3rd and 7th d after treatment were compared. Correlations between HPA and AGI grading as well as LC3B were compared. Receiver operator characteristic (ROC) curves were generated to evaluate the diagnostic value of HPA, intestinal fatty acid binding protein and D-lactate in S-AGI.

RESULTS

Serum HPA and SCD-1 levels were significantly reduced in the intervention group compared with the control group (P < 0.05). In addition, intestinal fatty acid-binding protein, D-lactate, AGI grade, motilin, and gastrin levels and sequential organ failure assessment score were significantly decreased (P < 0.05) in the intervention group. However, LC3B, APTT, anti-Xa factor, and CD4/CD8 were significantly increased (P < 0.05) in the intervention group. No significant differences in interleukin-6, tumour necrosis factor-α, d-dimer, acute physiology and chronic health evaluation II score, length of ICU stay, length of hospital stay, or 28-d survival were noted between the two groups (P > 0.05). Correlation analysis revealed a significant negative correlation between HPA and LC3B and a significant positive correlation between HPA and AGI grade. ROC curve analysis showed that HPA had higher specificity and sensitivity in diagnosis of S-AGI.

CONCLUSION

HPA has great potential as a diagnostic marker for S-AGI. Inhibition of HPA activity reduces SDC-1 shedding and alleviates S-AGI symptoms. The inhibitory effect of HPA in gastrointestinal protection may be achieved by enhanced autophagy.

Analysis of the dynamic changes in gut microbiota in patients with different severity in sepsis

BACKGROUND

The gastrointestinal tract contains a massive microbiota, and targeting the gut could be a potential intervention for sepsis. However, the interaction between sepsis and the intestinal microbiota is defined as an "incompletely understood bidirectional relationship".

METHODS

This retrospective observational cohort study investigated the fecal microbiota of sepsis patients admitted to the Department of Critical Care Medicine of the Central Hospital of Wuhan, China, from May 2019 to January 2020. 14 septic patients were divided into the non-severe group and the severe group according to the Acute Physiology and Chronic Health Evaluation II (APACHE II) score. Herein, fecal samples were serially collected on admission, the third, fourth, and fifth days, and ICU discharge. The fecal microbiota was analyzed by 16S rRNA gene sequencing and its correlation with clinical parameters was evaluated.

RESULTS

Bacteroidetes, Firmicutes, and Proteobacteria were dominant phyla at ICU admission, and fecal biodiversity was not significantly different between the non-severe group (APACHE II < 15) and the severe group (APACHE II > 15). However, the diversity of the gut microbiota was significantly lower at ICU discharge than that at ICU admission with the extension of treatment time. Further significant difference flora analysis (LEfSe) showed that the genera Veillonella and Ruminococcus were the most discriminant biomarkers at ICU admission in non-severe and severe patients, respectively, while Enterococcus was the most discriminant biomarker at ICU discharge in all septic patients. Of note, liver function tests, including ALT, AST, TBIL, and DBIL correlated with the prevalence of various bacterial genera.

CONCLUSIONS

The diversity of the gut microbiota in patients with sepsis decreases dramatically during ICU stay, and there are distinct dynamic changes in gut microbiota among patients with different severity in sepsis.

[Value of complement component 3 in predicting the prognosis of children with sepsis]

OBJECTIVES

To investigate changes in complement component 3 (C3) levels in children with sepsis and its correlation with the severity of sepsis and to explore the significance of C3 in predicting mortality in children with sepsis.

METHODS

A retrospective analysis was conducted on 529 children with sepsis who were admitted to the Pediatric Intensive Care Unit in Hunan Children's Hospital between November 2019 and September 2021. The children were categorized into two groups based on their prognosis at day 28 after sepsis diagnosis: the survival group (n=471) and the death group (n=58). Additionally, the children were divided into normal C3 group (n=273) and reduced C3 group (n=256) based on the median C3 level (0.77 g/L) within 24 hours of admission. Clinical data and laboratory markers were compared between the groups, and assess the predictive value of C3 levels in relation to sepsis-related mortality.

RESULTS

The death group exhibited significantly lower C3 levels compared to the survival group (P<0.05). Multivariate logistic regression analysis revealed that higher pediatric Sequential Organ Failure Assessment (p-SOFA) scores and lower C3 levels were closely associated with sepsis-related mortality (P<0.05). The receiver operating characteristic curve (ROC) analysis demonstrated that combination of p-SOFA scores and C3 levels yielded an area under the ROC curve of 0.852, which was higher than that of each indicator alone (P<0.05).

CONCLUSIONS

C3 can serve as an indicator to assess the severity and prognosis of sepsis in children. The combination of p-SOFA scores and C3 levels holds good predictive value for mortality in children with sepsis.