RECOMBINANT BACTERICIDAL/PERMEABILITY-INCREASING PROTEIN INHIBITS ENDOTOXIN-INDUCED HIGH-MOBILITY GROUP BOX 1 PROTEIN GENE EXPRESSION IN SEPSIS

Decreased Expression of the High Mobility Group Box 1 (HMGB1) Gene in Peripheral Blood in Patients with Mild or Moderate Clostridioides difficile Infection

Cytokines are mediators of inflammation induced in the course of Clostridioides difficile infection (CDI). High Mobility Group Box 1 (HMGB1) is a cytokine playing an important role in the pathogenesis of numerous inflammatory and autoimmune diseases. The aim of the study was to assess the HMGB1 gene expression in the course of CDI. We have performed a prospective case-control study- including 55 adult patients, among them 27 with CDI, who were hospitalized from October 2018 to February 2020 and 28 healthy volunteers. We assessed: a complete blood count with differential leukocyte count, blood creatinine, albumin, and C-reactive protein (CRP) levels. Then, the expression of the HMGB1 gene was evaluated using quantitative Real-Time PCR. Patients with CDI were found to have a significant increase in white blood cells (WBC), neutrophil count, and CRP levels, they also exhibited decreased levels of albumin compared with controls. The HMGB1 gene expression was significantly lower among patients with CDI compared with the control group and significantly, inversely correlated with CRP level in blood. In conclusion, we have observed a decreased expression of the HMGB1 gene in peripheral blood of patients with mild or moderate CDI, which hypothetically could reflect their diminished capability to fight the pathogen.

Cutaneous Burn Injury Modulates Urinary Antimicrobial Peptide Responses and the Urinary Microbiome

OBJECTIVES

Characterization of urinary bacterial microbiome and antimicrobial peptides after burn injury to identify potential mechanisms leading to urinary tract infections and associated morbidities in burn patients.

DESIGN

Retrospective cohort study using human urine from control and burn subjects.

SETTING

University research laboratory.

PATIENTS

Burn patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Urine samples from catheterized burn patients were collected hourly for up to 40 hours. Control urine was collected from "healthy" volunteers. The urinary bacterial microbiome and antimicrobial peptide levels and activity were compared with patient outcomes. We observed a significant increase in urinary microbial diversity in burn patients versus controls, which positively correlated with a larger percent burn and with the development of urinary tract infection and sepsis postadmission, regardless of age or gender. Urinary psoriasin and β-defensin antimicrobial peptide levels were significantly reduced in burn patients at 1 and 40 hours postadmission. We observed a shift in antimicrobial peptide hydrophobicity and activity between control and burn patients when urinary fractions were tested against Escherichia coli and Enterococcus faecalis urinary tract infection isolates. Furthermore, the antimicrobial peptide activity in burn patients was more effective against E. coli than E. faecalis. Urinary tract infection-positive burn patients with altered urinary antimicrobial peptide activity developed either an E. faecalis or Pseudomonas aeruginosa urinary tract infection, suggesting a role for urinary antimicrobial peptides in susceptibility to select uropathogens.

CONCLUSIONS

Our data reveal potential links for urinary tract infection development and several morbidities in burn patients through alterations in the urinary microbiome and antimicrobial peptides. Overall, this study supports the concept that early assessment of urinary antimicrobial peptide responses and the bacterial microbiome may be used to predict susceptibility to urinary tract infections and sepsis in burn patients.

Xuebijing Injection Promotes M2 Polarization of Macrophages and Improves Survival Rate in Septic Mice

Xuebijing (XBJ) injection, a concoction of several Chinese herbs, has been widely used as an immunomodulator for the treatment of severe sepsis in China. However, the precise mechanisms responsible for its efficacy have not been fully elucidated. In our study, we determined the flow cytometry markers (F4/80, CD11c, and CD206), the levels of secreted cytokines (TNF-α, IL-6, and IL-10), and the expression of specific proteins of M2 (Ym1, Fizz1, and Arg1) to assess macrophage polarization. Treatment with XBJ lowered M1 associated cytokine levels and increased the level of M2 associated cytokine level. The percentage of M2 phenotype cells of XBJ group was much higher than that of the control group. Expressions of phosphorylated Janus kinase 1 (JAK1) and signal transducer and activator of transcription 6 (STAT6) were markedly enhanced after the administration of XBJ; on the other hand, the M2 associated cytokines and proteins were decreased following treatment with JAK1 or STAT6 inhibitor. In addition, the treatment of XBJ significantly improved the survival rate of septic mice. These studies demonstrate that XBJ can markedly promote M2 polarization and improve the survival rate of septic mice, thereby contributing to therapeutic effect in the treatment of septic complications.

HMGB1 in health and disease

Complex genetic and physiological variations as well as environmental factors that drive emergence of chromosomal instability, development of unscheduled cell death, skewed differentiation, and altered metabolism are central to the pathogenesis of human diseases and disorders. Understanding the molecular bases for these processes is important for the development of new diagnostic biomarkers, and for identifying new therapeutic targets. In 1973, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and termed high-mobility group (HMG) proteins. The HMG proteins include three superfamilies termed HMGB, HMGN, and HMGA. High-mobility group box 1 (HMGB1), the most abundant and well-studied HMG protein, senses and coordinates the cellular stress response and plays a critical role not only inside of the cell as a DNA chaperone, chromosome guardian, autophagy sustainer, and protector from apoptotic cell death, but also outside the cell as the prototypic damage associated molecular pattern molecule (DAMP). This DAMP, in conjunction with other factors, thus has cytokine, chemokine, and growth factor activity, orchestrating the inflammatory and immune response. All of these characteristics make HMGB1 a critical molecular target in multiple human diseases including infectious diseases, ischemia, immune disorders, neurodegenerative diseases, metabolic disorders, and cancer. Indeed, a number of emergent strategies have been used to inhibit HMGB1 expression, release, and activity in vitro and in vivo. These include antibodies, peptide inhibitors, RNAi, anti-coagulants, endogenous hormones, various chemical compounds, HMGB1-receptor and signaling pathway inhibition, artificial DNAs, physical strategies including vagus nerve stimulation and other surgical approaches. Future work further investigating the details of HMGB1 localization, structure, post-translational modification, and identification of additional partners will undoubtedly uncover additional secrets regarding HMGB1's multiple functions.

Presence of neutrophil extracellular traps and citrullinated histone H3 in the bloodstream of critically ill patients

Neutrophil extracellular traps (NETs), a newly identified immune mechanism, are induced by inflammatory stimuli. Modification by citrullination of histone H3 is thought to be involved in the in vitro formation of NETs. The purposes of this study were to evaluate whether NETs and citrullinated histone H3 (Cit-H3) are present in the bloodstream of critically ill patients and to identify correlations with clinical and biological parameters. Blood samples were collected from intubated patients at the time of ICU admission from April to June 2011. To identify NETs, DNA and histone H3 were visualized simultaneously by immunofluorescence in blood smears. Cit-H3 was detected using a specific antibody. We assessed relationships of the presence of NETs and Cit-H3 with the existence of bacteria in tracheal aspirate, SIRS, diagnosis, WBC count, and concentrations of IL-8, TNF-α, cf-DNA, lactate, and HMGB1. Forty-nine patients were included. The median of age was 66.0 (IQR: 52.5-76.0) years. The diagnoses included trauma (7, 14.3%), infection (14, 28.6%), resuscitation from cardiopulmonary arrest (8, 16.3%), acute poisoning (4, 8.1%), heart disease (4, 8.1%), brain stroke (8, 16.3%), heat stroke (2, 4.1%), and others (2, 4.1%). We identified NETs in 5 patients and Cit-H3 in 11 patients. NETs and/or Cit-H3 were observed more frequently in "the presence of bacteria in tracheal aspirate" group (11/22, 50.0%) than in "the absence of bacteria in tracheal aspirate" group (4/27, 14.8%) (p<.01). Multiple logistic regression analysis showed that only the presence of bacteria in tracheal aspirate was significantly associated with the presence of NETs and/or Cit-H3. The presence of bacteria in tracheal aspirate may be one important factor associated with NET formation. NETs may play a pivotal role in the biological defense against the dissemination of pathogens from the respiratory tract to the bloodstream in potentially infected patients.

Validation of a recombinant human bactericidal/permeability-increasing protein (hBPI) expression vector using murine mammary gland tumor cells and the early development of hBPI transgenic goat embryos

Human bactericidal/permeability-increasing protein (hBPI) is the only antibacterial peptide which acts against both gram-negative bacteria and neutralizes endotoxins in human polymorphonuclear neutrophils; therefore, hBPI is of great value in clinical applications. In the study, we constructed a hBPI expression vector (pBC1-Loxp-Neo-Loxp-hBPI) containing the full-length hBPI coding sequence which could be specifically expressed in the mammary gland. To validate the function of the vector, in vitro cultured C127 (mouse mammary Carcinoma Cells) were transfected with the vector, and the transgenic cell clones were selected to express hBPI by hormone induction. The mRNA and protein expression of hBPI showed that the constructed vector was effective and suitable for future application in producing mammary gland bioreactor. Then, female and male goat fibroblasts were transfected with the vector, and two male and two female transgenic clonal cell lines were obtained. Using the transgenic cell lines as nuclear donors for somatic cell nuclear transfer, the reconstructed goat embryos produced from all four clones could develop to blastocysts in vitro. In conclusion, we constructed and validated an efficient mammary gland-specific hBPI expression vector, pBC1-Loxp-Neo-Loxp-hBPI, and transgenic hBPI goat embryos were successfully produced, laying foundations for future production of recombinant hBPI in goat mammary gland.

DUF538 protein super family is predicted to be the potential homologue of bactericidal/permeability-increasing protein in plant system

DUF538 protein super family includes a number of plant proteins that their role is not yet clear. These proteins have been frequently reported to be expressed in plants under various stressful stimuli such as bacteria and elicitors. In order to further understand about this protein family we utilized bioinformatics tools to analyze its structure in details. As a result, plants DUF538 was predicted to be the partial structural homologue of BPI (bactericidal/permeability increasing) proteins in mammalian innate immune system that provides the first line of defense against different pathogens including bacteria, fungi, viruses and parasites. Moreover, on the base of the experimental data, it was identified that exogenously applied purified fused product of Celosia DUF538 affects the bacterial growth more possibly similar to BPI through the binding to the bacterial membranes. In conclusion, as the first ever time report, we nominated DUF538 protein family as the potential structural and functional homologue of BPI protein in plants, providing a basis to study the novel functions of this protein family in the biological systems in the future.

Identification of neutrophil extracellular traps in the blood of patients with systemic inflammatory response syndrome

Objective

Neutrophils are able to form ‘neutrophil extracellular traps’ (NETs), which they use to trap and kill pathogens such as bacteria and fungi at the foci of infection. This observational study investigated the presence of NETs in the blood from critically ill patients and healthy volunteers.

Methods

Fluorescent triple-colour immunocytochemical analysis of blood smears collected from patients with systemic inflammatory response syndrome (SIRS; associated with various clinical conditions) who had been hospitalized in the intensive care unit, and healthy volunteers, was undertaken to identify NETs in the blood. Blood smears were stained for DNA, histone H1 and neutrophil elastase.

Results

NETs were identified in 10 of 21 (47.6%) blood samples from the study group compared with none of the blood samples from eight healthy volunteers.

Conclusion

These data suggest that fluorescent triple-colour immunocytochemical staining of NETs in the blood could be used to simplify the early identification of critically ill patients with SIRS. Larger studies are required to clarify the pathophysiological role of NETs in this specific patient population.

The anti-inflammatory effect of the synthetic antimicrobial peptide 19-2.5 in a murine sepsis model: a prospective randomized study

Introduction

Increasing rates of multi-resistant bacteria are a major problem in the treatment of critically ill patients. Furthermore, conventional antibiotics lead to the release of bacterial derived membrane parts initiating pro-inflammatory cascades with potential harm to the patient. Antimicrobial peptides (AMP) may kill bacteria without releasing pro-inflammatory factors. Thus, we compared three newly developed synthetic anti-lipopolysaccharide peptides (SALPs) with a broader range of efficacy to suppress cytokine release in plasma and CD14 mRNA expression in organ tissue in a murine, polymicrobial sepsis model.

Methods

A randomized, experimental trial was conducted in an animal research facility. Male NMRI mice (n = 90; 8- to 12-weeks old) were randomized to the following six groups: (i) sham operation and parenteral vehicle (NaCl 0.9%) administration (sham); (ii) cecal ligation and puncture (CLP) and vehicle infusion (sepsis-control), (iii) CLP and polymyxin B infusion (polyB), or (iv to vi) CLP and infusion of three different synthetic antimicrobial peptides Peptide 19-2.5 (Pep2.5), Peptide 19-4 (Pep4) or Peptide 19-8 (Pep8). All animals underwent arterial and venous catheterization for hemodynamic monitoring 48 hours prior to CLP or sham-operation. Physical appearance and behavior (activity), plasma cytokine levels, and CD14 mRNA expression in heart, lung, liver, spleen and kidney tissue were determined 24 hours after CLP or sham operation.

Results

Only Pep2.5 significantly enhanced the activity after CLP, whereas none of the therapeutic regimens elevated the mean arterial pressure or heart rate. The strongly elevated IL-6, IL-10 and monocyte chemoattractant protein serum levels in septic animals were significantly reduced after Pep2.5 administration (P < 0.001, P < 0.001, and P < 0.001, respectively). Similarly, Pep2.5 significantly reduced the sepsis-induced CD14 mRNA expression in heart (P = 0.003), lung (P = 0.008), and spleen tissue (P = 0.009) but not in kidney and liver.

Conclusions

Structurally variable SALPs exhibit major differences in their anti-inflammatory effect in vivo. Continuous parenteral administration of Pep2.5 is able to reduce sepsis-induced cytokine release and tissue inflammation.

Immunomodulatory therapy for sepsis: an update

Currently the treatment mainstay of sepsis is early and appropriate antibiotic therapy, accompanied by aggressive fluid administration, the use of vasopressors when needed and the prompt initiation of measures to support each failing organ. Activated protein C and hydrocortisone, when used accordingly can affect mortality. As the pathophysiologic events that take place during sepsis are being elucidated, new molecules that target each step of those pathways are being tested. However, a lot of those molecules affect various mediators of the sepsis cascade including inflammatory cytokines, cellular receptors, nuclear transcription factors, coagulation activators and apoptosis regulators. Over the last decade, a multitude of clinical trials and animal studies have investigated strategies that aimed to restore immune homeostasis either by reducing inflammation or by stimulating the innate and adaptive immune responses. Antibiotics, statins and other molecules with multipotent immunomodulatory actions have also been studied in the treatment of sepsis.

Association of high mobility group box-1 protein levels with sepsis and outcome of severely burned patients

BACKGROUND

The study was performed to observe the systemic release and kinetics of high mobility group box-1 protein (HMGB1) in burned patients.

METHODS

106 patients were included, and they were divided into three groups with different burn sizes: group I, group II and group III. Healthy volunteers served as normal controls (n=25). The peripheral blood samples were collected on postburn days (PBD) 1, 3, 7, 14, and 21. The blood samples were used to detect levels of HMGB1 in plasma by ELISA kits for human. Gene expression of HMGB1 in peripheral blood mononuclear cells was assessed by real-time quantitative PCR taking GAPDH as the internal standard.

RESULTS

The levels of HMGB1 were significantly elevated on PBD 1-21 in patients with various burn sizes compared with normal controls, and there were obvious differences between group I and group III. The HMGB1 levels were significantly higher in septic patients than those without sepsis on PBD 7-21. Among septic patients, the HMGB1 levels in the survival group were markedly lower than those with fatal outcome on PBD 3-21.

CONCLUSIONS

Extensive burn injury could result in significantly increased HMGB1 levels, which appears to be associated with the development of sepsis and fatal outcome of major burns.

Association between regulatory T cell activity and sepsis and outcome of severely burned patients: a prospective, observational study

Introduction

To investigate the significance of changes in regulatory T cells (Tregs) activity and its relationship with sepsis, as well as outcome of patients with major burns.

Methods

The periphery blood samples of 106 patients were collected on post-burn days 1, 3, 7, 14, and 21. Tregs were isolated and their phenotypes (cytotoxic T-lymphocyte-associated antigen 4 and forkhead/winged helix transcription factor p3) were analyzed by flow cytometry, and the contents of cytokines (interleukin-10 and transforming growth factor-β1) released into supernatants by Tregs were also determined by enzyme-linked immunosorbent assay kits. Gene expressions of cytokines were assessed by real-time quantitative polymerase chain reaction.

Results

Expressions of Tregs phenotypes and gene/protein expression of cytokines were all elevated after burn, and there were obvious differences among patients with various burn sizes. They were also higher in septic patients than those without sepsis. Among septic patients, the expressions of Tregs phenotypes and the levels of cytokines were markedly lower in the survival group than those in patients with fatal outcome.

Conclusions

Severe burn injury per se could lead to the changes in Tregs activities. Elevated levels of cytokines produced by Tregs and activation markers on Tregs surface might play an important role in the pathogenesis of sepsis and mortality in burned patients.

Rosmarinic acid protects against experimental sepsis by inhibiting proinflammatory factor release and ameliorating hemodynamics

The present study was to investigate the effects of rosmarinic acid (RA) in cultured RAW264.7 cells and experimental model of sepsis induced by cecal ligation and puncture in rats and the potential mechanism. Results showed that RA concentration dependently down-regulated the levels of TNF-alpha, IL-6, and high-mobility group box 1 protein in LPS-induced RAW264.7 cells, inhibited the IkappaB kinase pathway, and modulated nuclear factor-kappaB. Intravenous injection of RA alone or in combination with imipenem reduced cecal ligation and puncture-induced lethality in rats. In addition, serum levels of TNF-alpha, IL-6, high-mobility group box 1 protein, triggering receptor expressed on myeloid cells, and endotoxin were down-regulated; in contrast, serum level of IL-10 was up-regulated. Amelioration of hemodynamics and decrease in serum enzyme activities and myeloperoxidase in lung, liver, and small intestine were also observed after RA injection. These data indicate that the antisepsis effect of RA was mediated by decreasing local and systemic levels of a wide spectrum of inflammatory mediators. This article provides the first evidence that RA has the capacity to inactivate inflammatory response in sepsis. The anti-inflammatory mechanism of RA may inhibit activation of the nuclear factor- kappaB pathway by inhibiting IkappaB kinase activity.

The clinical value of neutrophil extracellular traps

Neutrophil extracellular traps (NETs) have recently been discovered as a central part of antimicrobial innate immunity. In the meanwhile, evidence accumulated that NETs are also generated upon non-infectious stimuli in various clinical settings. In acute or chronic inflammatory disorders aberrantly enhanced NET formation and/or decreased NET degradation seems to correlate with disease outcome. This review summarizes current knowledge about the relation of NETs in a broad spectrum of clinical settings. Specifically, we focus on the importance of NETs as a predictive marker in severely ill patients and further, we speculate about the potential pathophysiology of NETs.