Microbial recognition and danger signals in sepsis and trauma

Early identification and diagnosis, pathophysiology, and treatment of sepsis-related acute lung injury: a narrative review

Background and Objective

Sepsis is a life-threatening organ dysfunction, and the most common and vulnerable organ is the lungs, with sepsis-related acute respiratory distress syndrome (ARDS) increasing mortality. In recent years, an increasing number of studies have improved our understanding of sepsis-related ARDS in terms of epidemiology, risk factors, pathophysiology, prognosis, and other aspects, as well as our ability to prevent, detect, and treat sepsis-related ARDS. However, sepsis-related lung injury remains an important issue and clinical burden. Therefore, a literature review was conducted on sepsis-related lung injury in order to further guide clinical practice in reducing the acute and chronic consequences of this condition.

Methods

This study conducted a search of the MEDLINE and PubMed databases, among others for literature published from 1991 to 2023 using the following keywords: definition of sepsis, acute lung injury, sepsis-related acute lung injury, epidemiology, risk factors, early diagnosis of sepsis-related acute lung injury, sepsis, ARDS, pathology and physiology, inflammatory imbalance caused by sepsis, congenital immune response, and treatment.

Key Content and Findings

This review explored the risk factors of sepsis, sepsis-related ARDS, early screening and diagnosis, pathophysiology, and treatment and found that in view of the high mortality rate of ARDS associated with sepsis. In response to the high mortality rate of sepsis-related ARDS, some progress has been made, such as rapid identification of sepsis and effective antibiotic treatment, early fluid resuscitation, lung-protective ventilation, etc.

Conclusions

Sepsis remains a common and challenging critical illness to cure. In response to the high mortality rate of sepsis-related ARDS, progress has been made in rapid sepsis identification, effective antibiotic treatment, early fluid resuscitation, and lung-protective ventilation. However, further research is needed regarding long-term effects such as lung recruitment, prone ventilation, and the application of neuromuscular blocking agents and extracorporeal membrane oxygenation.

Enhancing acute inflammatory and sepsis treatment: superiority of membrane receptor blockade

Conditions such as acute pancreatitis, ulcerative colitis, delayed graft function and infections caused by a variety of microorganisms, including gram-positive and gram-negative organisms, increase the risk of sepsis and therefore mortality. Immune dysfunction is a characterization of sepsis, so timely and effective treatment strategies are needed. The conventional approaches, such as antibiotic-based treatments, face challenges such as antibiotic resistance, and cytokine-based treatments have shown limited efficacy. To address these limitations, a novel approach focusing on membrane receptors, the initiators of the inflammatory cascade, is proposed. Membrane receptors such as Toll-like receptors, interleukin-1 receptor, endothelial protein C receptor, μ-opioid receptor, triggering receptor expressed on myeloid cells 1, and G-protein coupled receptors play pivotal roles in the inflammatory response, offering opportunities for rapid regulation. Various membrane receptor blockade strategies have demonstrated efficacy in both preclinical and clinical studies. These membrane receptor blockades act as early stage inflammation modulators, providing faster responses compared to conventional therapies. Importantly, these blockers exhibit immunomodulatory capabilities without inducing complete immunosuppression. Finally, this review underscores the critical need for early intervention in acute inflammatory and infectious diseases, particularly those posing a risk of progressing to sepsis. And, exploring membrane receptor blockade as an adjunctive treatment for acute inflammatory and infectious diseases presents a promising avenue. These novel approaches, when combined with antibiotics, have the potential to enhance patient outcomes, particularly in conditions prone to sepsis, while minimizing risks associated with antibiotic resistance and immune suppression.

Mechanism and therapeutic potential of traditional Chinese medicine extracts in sepsis

Sepsis is a complex syndrome characterized by multi-organ dysfunction, due to the presence of harmful microorganisms in blood which could cause mortality. Complications associated with sepsis involve multiple organ dysfunction. The pathogenesis of sepsis remains intricate, with limited treatment options and high mortality rates. Traditional Chinese medicine (TCM) has consistently demonstrated to have a potential on various disease management. Its complements include reduction of oxidative stress, inhibiting inflammatory pathways, regulating immune responses, and improving microcirculation. Traditional Chinese medicine can mitigate or even treat sepsis in a human system. This review examines progress on the use of TCM extracts for treating sepsis through different pharmacological action and its mechanisms. The potential targets of TCM extracts and active ingredients for the treatment of sepsis and its complications have been elucidated through molecular biology research, network pharmacology prediction, molecular docking analysis, and visualization analysis. Our aim is to provide a theoretical basis and empirical support for utilizing TCM in the treatment of sepsis and its complications while also serving as a reference for future research and development of sepsis drugs.

Ribonuclease inhibitor 1 emerges as a potential biomarker and modulates inflammation and iron homeostasis in sepsis

Sepsis, marked by organ dysfunction, necessitates reliable biomarkers. Ribonuclease inhibitor 1 (RNH1), a ribonuclease (RNase) inhibitor, emerged as a potential biomarker for acute kidney injury and mortality in thoracoabdominal aortic aneurysm patients. Our study investigates RNH1 dynamics in sepsis, its links to mortality and organ dysfunction, and the interplay with RNase 1 and RNase 5. Furthermore, we explore RNH1 as a therapeutic target in sepsis-related processes like inflammation, non-canonical inflammasome activation, and iron homeostasis. We showed that RNH1 levels are significantly higher in deceased patients compared to sepsis survivors and correlate with creatine kinase, aspartate and alanine transaminase, bilirubin, serum creatinine and RNase 5, but not RNase 1. RNH1 mitigated LPS-induced TNFα and RNase 5 secretion, and relative mRNA expression of ferroptosis-associated genes HMOX1, FTH1 and HAMP in PBMCs. Monocytes were identified as the predominant type of LPS-positive PBMCs. Exogenous RNH1 attenuated LPS-induced CASP5 expression, while increasing IL-1β secretion in PBMCs and THP-1 macrophages. As RNH1 has contradictory effects on inflammation and non-canonical inflammasome activation, its use as a therapeutic agent is limited. However, RNH1 levels may play a central role in iron homeostasis during sepsis, supporting our clinical observations. Hence, RNH1 shows promise as biomarkers for renal and hepatic dysfunction and hepatocyte injury, and may be useful in predicting the outcome of septic patients.

Design, synthesis, and anti-inflammatory activity of indole-2-formamide benzimidazole[2,1-b]thiazole derivatives

Molecular hybridization is a widely employed technique in medicinal chemistry for drug modification, aiming to enhance pharmacological activity and minimize side effects. The combination of an indole ring and imidazole[2,1-b]thiazole has shown promising potential as a group that exhibits potent anti-inflammatory effects. In this study, we designed and synthesized a series of derivatives comprising indole-2-formamide benzimidazole[2,1-b]thiazole to evaluate their impact on LPS-induced production of pro-inflammatory cytokines NO, IL-6, and TNF-α release, as well as iron death in RAW264.7 cells. The findings revealed that most compounds effectively inhibited LPS-induced production of pro-inflammatory cytokines NO, IL-6, and TNF-α release in RAW264.7 cells. Compound 13b exhibited the most potent anti-inflammatory activity among the tested compounds. The results of the cytotoxicity assay indicated that compound 13b was nontoxic. Additionally, compound 13b was found to elevate the levels of ROS, MDA, and Fe2+, while reducing GSH content, thereby facilitating the iron death process. Consequently, compound 13b showed promise for future development as an anti-inflammatory drug.

High-dose Vitamin C injection ameliorates against sepsis-induced myocardial injury by anti-apoptosis, anti-inflammatory and pro-autophagy through regulating MAPK, NF-κB and PI3K/AKT/mTOR signaling pathways in rats

AIMS

This study aimed to evaluate the effects of VC on SIMI in rats.

METHODS

In this study, the survival rate of high dose VC for SIMI was evaluated within 7 days. Rats were randomly assigned to three groups: Sham group, CLP group, and high dose VC (500 mg/kg i.v.) group. The animals in each group were treated with drugs for 1 day, 3 days or 5 days, respectively. Echocardiography, myocardial enzymes and HE were used to detect cardiac function. IL-1β, IL-6, IL-10 and TNF-α) in serum were measured using ELISA kits. Western blot was used to detect proteins related to apoptosis, inflammation, autophagy, MAPK, NF-κB and PI3K/Akt/mTOR signaling pathways.

RESULTS

High dose VC improved the survival rate of SIMI within 7 days. Echocardiography, HE staining and myocardial enzymes showed that high-dose VC relieved SIMI in rats in a time-dependent manner. And compared with CLP group, high-dose VC decreased the expressions of pro-apoptotic proteins, while increased the expression of anti-apoptotic protein. And compared with CLP group, high dose VC decreased phosphorylation levels of Erk1/2, P38, JNK, NF-κB and IKK α/β in SIMI rats. High dose VC increased the expression of the protein Beclin-1 and LC3-II/LC3-I ratio, whereas decreased the expression of P62 in SIMI rats. Finally, high dose VC attenuated phosphorylation of PI3K, AKT and mTOR compared with the CLP group.

SIGNIFICANCE

Our results showed that high dose VC has a good protective effect on SIMI after continuous treatment, which may be mediated by inhibiting apoptosis and inflammatory, and promoting autophagy through regulating MAPK, NF-κB and PI3K/AKT/mTOR pathway.

Sepsis-Related Lung Injury and the Complication of Extrapulmonary Pneumococcal Pneumonia

Globally, sepsis and pneumonia account for significant mortality and morbidity. A complex interplay of immune-molecular pathways underlies both sepsis and pneumonia, resulting in similar and overlapping disease characteristics. Sepsis could result from unmanaged pneumonia. Similarly, sepsis patients have pneumonia as a common complication in the intensive care unit. A significant percentage of pneumonia is misdiagnosed as septic shock. Therefore, our knowledge of the clinical relationship between pneumonia and sepsis is imperative to the proper management of these syndromes. Regarding pathogenesis and etiology, pneumococcus is one of the leading pathogens implicated in both pneumonia and sepsis syndromes. Growing evidence suggests that pneumococcal pneumonia can potentially disseminate and consequently induce systemic inflammation and severe sepsis. Streptococcus pneumoniae could potentially exploit the function of dendritic cells (DCs) to facilitate bacterial dissemination. This highlights the importance of pathogen-immune cell crosstalk in the pathophysiology of sepsis and pneumonia. The role of DCs in pneumococcal infections and sepsis is not well understood. Therefore, studying the immunologic crosstalk between pneumococcus and host immune mediators is crucial to elucidating the pathophysiology of pneumonia-induced lung injury and sepsis. This knowledge would help mitigate clinical diagnosis and management challenges.

Complementary and alternative medicine on cognitive defects and neuroinflammation after sepsis

Sepsis-associated encephalopathy (SAE) is a common manifestation of sepsis, ranging from mild confusion and delirium to severe cognitive impairment and deep coma. SAE is associated with higher mortality and long-term outcomes, particularly substantial declines in cognitive function. The mechanisms of SAE probably include neuroinflammation that is mediated by systemic inflammation and ischemic lesions in the brain, a disrupted blood-brain barrier, oxidative stress, neurotransmitter dysfunction, and severe microglial activation. Increasing evidence suggests that complementary and alternative medicine, especially Traditional Chinese Medicine (TCM), is favorable in alleviating cognitive decline after sepsis. Here, we summarized the studies of traditional herbal remedies, TCM formulas and acupuncture therapy in animal models of neurological dysfunctions after sepsis in recent decades and reviewed their potential mechanisms.

Liensinine alleviates mouse intestinal injury induced by sepsis through inhibition of oxidative stress, inflammation, and cell apoptosis

Sepsis is a clinical syndrome triggered by an imbalanced host response to pathogens that can lead to multiple organ dysfunction. The immune response and barrier function of the gut play an important role in the pathogenesis and progression of sepsis. This study aimed to explore the potential role of natural alkaloid Liensinine in the treatment of intestinal injury caused by sepsis and its possible molecular mechanism. In this study, a mouse model of sepsis was established by injecting LPS to explore the protective effect of Liensinine on intestinal injury in sepsis. The results showed that Liensinine could reduce the intestinal damage caused by LPS and increase the number of goblet cells. Furthermore, it decreased the release of inflammatory cytokines by inhibiting NF-kB phosphorylation and NLRP3 inflammasome synthesis. Liensinine also reduced the oxidative stress and ROS accumulation caused by LPS, and played an anti-oxidative stress role by regulating the Nrf2/keap1 signaling pathway. In addition, Liensinine alleviated the inhibition of intestinal autophagy caused by LPS by inhibiting the PI3K/Akt/mTOR pathway. And then it reduced the excessive apoptosis of intestinal cells. This study provides valuable insights for sepsis prevention and treatment, offering a potential therapeutic candidate to protect against intestinal injury and regulate the inflammatory response in sepsis.

Identifying biomarkers deciphering sepsis from trauma-induced sterile inflammation and trauma-induced sepsis

Objective

The purpose of this study was to identify a panel of biomarkers for distinguishing early stage sepsis patients from non-infected trauma patients.

Background

Accurate differentiation between trauma-induced sterile inflammation and real infective sepsis poses a complex life-threatening medical challenge because of their common symptoms albeit diverging clinical implications, namely different therapies. The timely and accurate identification of sepsis in trauma patients is therefore vital to ensure prompt and tailored medical interventions (provision of adequate antimicrobial agents and if possible eradication of infective foci) that can ultimately lead to improved therapeutic management and patient outcome. The adequate withholding of antimicrobials in trauma patients without sepsis is also important in aspects of both patient and environmental perspective.

Methods

In this proof-of-concept study, we employed advanced technologies, including Matrix-Assisted Laser Desorption/Ionization (MALDI) and multiplex antibody arrays (MAA) to identify a panel of biomarkers distinguishing actual sepsis from trauma-induced sterile inflammation.

Results

By comparing patient groups (controls, infected and non-infected trauma and septic shock patients under mechanical ventilation) at different time points, we uncovered distinct protein patterns associated with early trauma-induced sterile inflammation on the one hand and sepsis on the other hand. SYT13 and IL1F10 emerged as potential early sepsis biomarkers, while reduced levels of A2M were indicative of both trauma-induced inflammation and sepsis conditions. Additionally, higher levels of TREM1 were associated at a later stage in trauma patients. Furthermore, enrichment analyses revealed differences in the inflammatory response between trauma-induced inflammation and sepsis, with proteins related to complement and coagulation cascades being elevated whereas proteins relevant to focal adhesion were diminished in sepsis.

Conclusions

Our findings, therefore, suggest that a combination of biomarkers is needed for the development of novel diagnostic approaches deciphering trauma-induced sterile inflammation from actual infective sepsis.

The Value of Neutrophil-to-Lymphocyte Ratio to Identify Bacterial Infection and Predict Short-Term Mortality in Patients with Acutely Decompensated Cirrhosis

Liver cirrhosis patients are highly susceptible to infections, affecting survival, but current parameters for detecting infection are not reliable enough in this population. We investigated the ability of white blood cell (WBC), ∆WBC, neutrophil and ∆neutrophil counts, neutrophil-to-lymphocyte (NLR) and ∆NLR ratios and C-reactive protein (CRP) and procalcitonin (PCT) levels to identify infection and predict short-term mortality in liver cirrhosis patients. We recruited 233 patients with liver cirrhosis hospitalized with acute decompensation (AD) who had an outpatient visit within 1 month (baseline laboratory data) and followed them for 90 days. Difference between laboratory values at baseline and the AD episode was defined as delta (∆) values of the parameters. Delta values did not increase the diagnostic and predictive ability of investigated parameters. The CRP level was found to be the best diagnostic marker for infection in patients with cirrhosis. However, NLR seems to be superior for short-term mortality prediction, better than the WBC count. Distinguishing inflammations of different origin is a remaining clinical challenge in acutely decompensated cirrhosis. Based on our results, NLR might be more suitable for predicting short-term mortality in patients with AD than the WBC count currently included in the CLIF-C AD score.

PSTPIP2 is associated with disease severity in patients with pressure ulcer sepsis and has anti-inflammatory effects

BACKGROUND

One of the common adverse reactions in patients with pressure ulcers (PU) is sepsis, which is mainly related to microbial infections caused by pathogenic organisms. The activation of nuclear factor kappa-B (NF-κB) frequently occurs in conjunction with pathogenic microbial infections. Proline-serine-threonine-phosphatase-interacting protein 2 (PSTPIP2) is closely related to inflammatory disorders. The role and mechanism of PSTPIP2 in sepsis because of pressure ulcers is unclear. In this study, we discovered that PSTPIP2 was lowly expressed in peripheral blood of patients with sepsis induced by pressure ulcers.

METHODS

Peripheral blood was collected from 20 patients with sepsis due to pressure ulcers and 10 healthy controls, and the expression of PSTPIP2 in peripheral blood was discovered by polymerase chain reaction and Western blot analysis. Information on the clinical characteristics of patients was summarized, and the expression data of PSTPIP2 were correlated with the patients' acute physiology and chronic health evaluation (APACHE) II score, sequential organ failure assessment (SOFA) score, and C-reactive protein (CRP) and procalcitonin (PCT) scores by Spearman's correlation analysis. One of the main mediators of Gram-negative sepsis is lipopolysaccharide (LPS). In order to establish an in vitro sepsis model, THP-1 cells were treated with LPS, and the cells were transfected with PSTPIP2. Contents of interleukin 6 (IL-6), interleukin 1β (IL-1β), and tumor necrosis factor-α (TNF-α) in each group of cells were detected by enzyme-linked--immunosorbent serologic assay, and NF-κB-related proteins were detected by Western blot analysis.

RESULTS

When compared to healthy controls, the peripheral blood of patients with pressure sepsis had lower PSTPIP2 expression, which had a negative correlation with the APACHE II, SOFA, CRP, and PCT scores. LPS-induced THP-1 cells expressed less PSTPIP2 than the untreated control cells, and PSTPIP2 transfection decreased IL-6, IL-1β, and TNF-α levels and inhibited the activation of NF-κB pathway.

CONCLUSION

PSTPIP2 is associated with disease severity in patients with pressure ulcer sepsis and has anti-inflammatory effects.

Lipid oxidation dysregulation: an emerging player in the pathophysiology of sepsis

Sepsis is a life-threatening organ dysfunction caused by abnormal host response to infection. Millions of people are affected annually worldwide. Derangement of the inflammatory response is crucial in sepsis pathogenesis. However, metabolic, coagulation, and thermoregulatory alterations also occur in patients with sepsis. Fatty acid mobilization and oxidation changes may assume the role of a protagonist in sepsis pathogenesis. Lipid oxidation and free fatty acids (FFAs) are potentially valuable markers for sepsis diagnosis and prognosis. Herein, we discuss inflammatory and metabolic dysfunction during sepsis, focusing on fatty acid oxidation (FAO) alterations in the liver and muscle (skeletal and cardiac) and their implications in sepsis development.

Damage-mediated macrophage polarization in sterile inflammation

Most of the leading causes of death, such as cardiovascular diseases, cancer, dementia, neurodegenerative diseases, and many more, are associated with sterile inflammation, either as a cause or a consequence of these conditions. The ability to control the progression of inflammation toward tissue resolution before it becomes chronic holds significant clinical potential. During sterile inflammation, the initiation of inflammation occurs through damage-associated molecular patterns (DAMPs) in the absence of pathogen-associated molecules. Macrophages, which are primarily localized in the tissue, play a pivotal role in sensing DAMPs. Furthermore, macrophages can also detect and respond to resolution-associated molecular patterns (RAMPs) and specific pro-resolving mediators (SPMs) during sterile inflammation. Macrophages, being highly adaptable cells, are particularly influenced by changes in the microenvironment. In response to the tissue environment, monocytes, pro-inflammatory macrophages, and pro-resolution macrophages can modulate their differentiation state. Ultimately, DAMP and RAMP-primed macrophages, depending on the predominant subpopulation, regulate the balance between inflammatory and resolving processes. While sterile injury and pathogen-induced reactions may have distinct effects on macrophages, most studies have focused on macrophage responses induced by pathogens. In this review, which emphasizes available human data, we illustrate how macrophages sense these mediators by examining the expression of receptors for DAMPs, RAMPs, and SPMs. We also delve into the signaling pathways induced by DAMPs, RAMPs, and SPMs, which primarily contribute to the regulation of macrophage differentiation from a pro-inflammatory to a pro-resolution phenotype. Understanding the regulatory mechanisms behind the transition between macrophage subtypes can offer insights into manipulating the transition from inflammation to resolution in sterile inflammatory diseases.

The role of the microcirculation and integrative cardiovascular physiology in the pathogenesis of ICU-acquired weakness

Skeletal muscle dysfunction after critical illness, defined as ICU-acquired weakness (ICU-AW), is a complex and multifactorial syndrome that contributes significantly to long-term morbidity and reduced quality of life for ICU survivors and caregivers. Historically, research in this field has focused on pathological changes within the muscle itself, without much consideration for their in vivo physiological environment. Skeletal muscle has the widest range of oxygen metabolism of any organ, and regulation of oxygen supply with tissue demand is a fundamental requirement for locomotion and muscle function. During exercise, this process is exquisitely controlled and coordinated by the cardiovascular, respiratory, and autonomic systems, and also within the skeletal muscle microcirculation and mitochondria as the terminal site of oxygen exchange and utilization. This review highlights the potential contribution of the microcirculation and integrative cardiovascular physiology to the pathogenesis of ICU-AW. An overview of skeletal muscle microvascular structure and function is provided, as well as our understanding of microvascular dysfunction during the acute phase of critical illness; whether microvascular dysfunction persists after ICU discharge is currently not known. Molecular mechanisms that regulate crosstalk between endothelial cells and myocytes are discussed, including the role of the microcirculation in skeletal muscle atrophy, oxidative stress, and satellite cell biology. The concept of integrated control of oxygen delivery and utilization during exercise is introduced, with evidence of physiological dysfunction throughout the oxygen delivery pathway - from mouth to mitochondria - causing reduced exercise capacity in patients with chronic disease (e.g., heart failure, COPD). We suggest that objective and perceived weakness after critical illness represents a physiological failure of oxygen supply-demand matching - both globally throughout the body and locally within skeletal muscle. Lastly, we highlight the value of standardized cardiopulmonary exercise testing protocols for evaluating fitness in ICU survivors, and the application of near-infrared spectroscopy for directly measuring skeletal muscle oxygenation, representing potential advancements in ICU-AW research and rehabilitation.

Recent Advances in Monoclonal Antibody-Based Approaches in the Management of Bacterial Sepsis

Sepsis is a life-threatening condition characterized by an uncontrolled inflammatory response to an infectious agent and its antigens. Immune cell activation against the antigens causes severe distress that mediates a strong inflammatory response in vital organs. Sepsis is responsible for a high rate of morbidity and mortality in immunosuppressed patients. Monoclonal antibody (mAb)-based therapeutic strategies are now being explored as a viable therapy option for severe sepsis and septic shock. Monoclonal antibodies may provide benefits through two major strategies: (a) monoclonal antibodies targeting the pathogen and its components, and (b) mAbs targeting inflammatory signaling may directly suppress the production of inflammatory mediators. The major focus of mAb therapies has been bacterial endotoxin (lipopolysaccharide), although other surface antigens are also being investigated for mAb therapy. Several promising candidates for mAbs are undergoing clinical trials at present. Despite several failures and the investigation of novel targets, mAb therapy provides a glimmer of hope for the treatment of severe bacterial sepsis and septic shock. In this review, mAb candidates, their efficacy against controlling infection, with special emphasis on potential roadblocks, and prospects are discussed.

Extracellular Histone-Induced Protein Kinase C Alpha Activation and Troponin Phosphorylation Is a Potential Mechanism of Cardiac Contractility Depression in Sepsis

Reduction in cardiac contractility is common in severe sepsis. However, the pathological mechanism is still not fully understood. Recently it has been found that circulating histones released after extensive immune cell death play important roles in multiple organ injury and disfunction, particularly in cardiomyocyte injury and contractility reduction. How extracellular histones cause cardiac contractility depression is still not fully clear. In this work, using cultured cardiomyocytes and a histone infusion mouse model, we demonstrate that clinically relevant histone concentrations cause significant increases in intracellular calcium concentrations with subsequent activation and enriched localization of calcium-dependent protein kinase C (PKC) α and βII into the myofilament fraction of cardiomyocytes in vitro and in vivo. Furthermore, histones induced dose-dependent phosphorylation of cardiac troponin I (cTnI) at the PKC-regulated phosphorylation residues (S43 and T144) in cultured cardiomyocytes, which was also confirmed in murine cardiomyocytes following intravenous histone injection. Specific inhibitors against PKCα and PKCβII revealed that histone-induced cTnI phosphorylation was mainly mediated by PKCα activation, but not PKCβII. Blocking PKCα also significantly abrogated histone-induced deterioration in peak shortening, duration and the velocity of shortening, and re-lengthening of cardiomyocyte contractility. These in vitro and in vivo findings collectively indicate a potential mechanism of histone-induced cardiomyocyte dysfunction driven by PKCα activation with subsequent enhanced phosphorylation of cTnI. These findings also indicate a potential mechanism of clinical cardiac dysfunction in sepsis and other critical illnesses with high levels of circulating histones, which holds the potential translational benefit to these patients by targeting circulating histones and downstream pathways.

Extracellular CIRP Induces Novel Nectin-2+ (CD112+) Neutrophils to Promote Th1 Differentiation in Sepsis

Neutrophil heterogeneity represents different subtypes, states, phenotypes, and functionality of neutrophils implicated in sepsis pathobiology. Extracellular cold-inducible RNA-binding protein (eCIRP) is a damage-associated molecular pattern that promotes inflammation and alters neutrophil phenotype and function through TLR4. Nectin-2 or CD112 is an Ig-like superfamily member. CD112 serves as the ligand for DNAM-1 (CD226), which induces Th1 differentiation in naive CD4+ T cells. Th1 cells produce IFN-γ to fuel inflammation. CD112 is expressed mainly on APCs, but its expression in neutrophils is unknown. We hypothesize that eCIRP induces CD112 expression in neutrophils, promoting Th1 differentiation in sepsis. Incubation of neutrophils with recombinant murine (rm)CIRP significantly increased the gene and protein expression of CD112 in neutrophils. Anti-TLR4 Ab-treated neutrophils significantly decreased CD112+ neutrophils compared with controls upon rmCIRP stimulation. After 4 h of rmCIRP injection in mice, CD112+ neutrophils were significantly increased in the blood and spleen. At 20 h after cecal ligation and puncture-induced sepsis, CD112+ neutrophils were also significantly increased. Blood and splenic CD112+ neutrophils in septic CIRP-/- mice were much lower than in septic wild-type mice. Coculture of naive CD4 T cells with rmCIRP-treated (CD112+) neutrophils significantly increased IFN-γ-producing Th1 cells compared with coculture with PBS-treated neutrophils. CD112 Ab significantly attenuated Th1 differentiation induced by rmCIRP-treated neutrophils. Thus, eCIRP increases CD112 expression in neutrophils via TLR4 to promote Th1 differentiation in sepsis. Targeting eCIRP may attenuate sepsis by reducing Th1-promoting CD112+ neutrophils.

Extracellular Vesicles: New Players in the Mechanisms of Sepsis- and COVID-19-Related Thromboinflammation

Sepsis and COVID-19 patients often manifest an imbalance in inflammation and coagulation, a complex pathological mechanism also named thromboinflammation, which strongly affects patient prognosis. Extracellular vesicles (EVs) are nanoparticles released by cells into extracellular space that have a relevant role in cell-to-cell communication. Recently, EVs have been shown to act as important players in a variety of pathologies, including cancer and cardiovascular disease. The biological properties of EVs in the mechanisms of thromboinflammation during sepsis and COVID-19 are still only partially known. Herein, we summarize the current experimental evidence on the role of EVs in thromboinflammation, both in bacterial sepsis and in COVID-19. A better understanding of EV involvement in these processes could be useful in describing novel diagnostic and therapeutic applications of EVs in these diseases.

Activated autophagy of innate immune cells during the early stages of major trauma

Background

Trauma-induced immune dysfunction has been a major barrier to achieving reduced mortality, which is poorly understood. Autophagy is a crucial catabolic mechanism of immune cells during times of stress. Few studies have investigated the immune regulatory effects induced by autophagy after trauma. Here, we use single-cell transcriptomics analysis in a major trauma cohort to demonstrate the dominant role of autophagy in innate immune cells during the early stages of major trauma.

Method

Single-cell transcriptional profiling of peripheral blood mononuclear cells (PBMCs) was performed, which were sampled from three control participants and five major trauma patients within 6 hours of injury. In detail, after single-cell RNA-sequence data processing, cell type annotation and cluster marker identification were performed. A genetic toolbox with 604 autophagy-related genes was used to monitor the autophagy levels in immune cells. In addition, all transcriptome RNA sequencing data obtained from PBMCs in a cohort of 167 major trauma patients were downloaded from gene expression omnibus (GEO) datasets (GSE36809). Key deregulated biological processes and important autophagic hub genes involved in immune cells were identified by weighted gene co-expression network analysis and gene ontology enrichment analysis.

Results

A total of 20,445 differentially expressed genes were identified and five co-expression modules were constructed. Enrichment analysis indicated that activated autophagy is the most important biological process during the early stages of major trauma, and JMY (autophagy-related genes) were identified as hub genes. The single-cell transcriptional profiling of PBMCs demonstrated that all components of adaptive immune cells were significantly decreased, whereas components of innate immune cells (monocytes and neutrophils) were significantly increased in major trauma patients compared with control participants. Activated autophagy was detected in monocytes and neutrophils by monitoring the dynamic transcriptional signature of the autophagy-related genetic toolbox. Biological process analysis shows that antigen uptake, processing presentation, and major histocompatibility complex (MHC) class II protein complex assembly pathways were up-regulated in autophagy-positive monocytes, whereas antigen processing and presentation of endogenous antigen and type I interferon signaling pathways were up-regulated in autophagy-positive neutrophils during the early stages of major trauma.

Conclusion

Our study demonstrated that autophagy is a biological process crucial to the development of immune disorders in the early stages of major trauma. Furthermore, the results of our study generated a comprehensive single-cell immune landscape for major trauma patients, in which we determined that autophagy profoundly affects the main functions of innate immune cells and provides insight into the cellular basis of immune dysregulation after major trauma.

Coagulation Disorders in Sepsis and COVID-19-Two Sides of the Same Coin? A Review of Inflammation-Coagulation Crosstalk in Bacterial Sepsis and COVID-19

Sepsis is a major cause of morbidity and mortality worldwide. Sepsis-associated coagulation disorders are involved in the pathogenesis of multiorgan failure and lead to a subsequently worsening prognosis. Alongside the global impact of the COVID-19 pandemic, a great number of research papers have focused on SARS-CoV-2 pathogenesis and treatment. Significant progress has been made in this regard and coagulation disturbances were once again found to underlie some of the most serious adverse outcomes of SARS-CoV-2 infection, such as acute lung injury and multiorgan dysfunction. In the attempt of untangling the mechanisms behind COVID-19-associated coagulopathy (CAC), a series of similarities with sepsis-induced coagulopathy (SIC) became apparent. Whether they are, in fact, the same disease has not been established yet. The clinical picture of CAC shows the unique feature of an initial phase of intravascular coagulation confined to the respiratory system. Only later on, patients can develop a clinically significant form of systemic coagulopathy, possibly with a consumptive pattern, but, unlike SIC, it is not a key feature. Deepening our understanding of CAC pathogenesis has to remain a major goal for the research community, in order to design and validate accurate definitions and classification criteria.

Roles of ginsenosides in sepsis

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

Immunopathophysiology of human sepsis

Sepsis is an ill-defined syndrome yet is a leading cause of morbidity and mortality worldwide. The most recent consensus defines sepsis as life-threatening organ dysfunction caused by a dysregulated host response to infection. However, this definition belies the complexity and breadth of immune mechanisms involved in sepsis, which are characterized by simultaneous hyperinflammation and immune suppression. In this review, we describe the immunopathogenesis of sepsis and highlight some recent pathophysiological findings that have expanded our understanding of sepsis. Sepsis endotypes can be used to divide sepsis patients in different groups with distinct immune profiles and outcomes. We also summarize evidence on the role of the gut microbiome in sepsis immunity. The challenge of the coming years will be to translate our increasing knowledge about the molecular mechanisms underlying sepsis into therapies that improve relevant patient outcomes.

Pain management in surgical intensive care patients: A retrospective observational research

Sepsis and septic shock are the most common causes of death in non-cardiac surgical intensive care units (ICU). Adequate analgesia is essential to achieve positive outcomes. There were differences in pain management between patients with and without sepsis or septic shock. The release of inflammatory mediators, especially cytokines, in sepsis or septic shock decreases the pain threshold. Septic intensive care patients probably require higher doses of opioids than do non-septic patients. A retrospective observational study was carried out in an anesthesiologic intensive care unit from January 1, 2014 to June 30, 2016. Patients were divided into 4 groups according to the following criteria: sepsis ("yes/no" and communication ability "yes/no"). After adjusting for the number of cases using the pairing method, a total of 356 patients were recruited. The endpoint of our study was defined as the "total opioid dose". Statistical evaluations were performed using t tests and 2-factor analysis of variance. There was a significant difference in opioid doses between communicative and non-communicative ICU patients F(1, 352) = 55.102, P < .001). This effect was observed in the ICU patients with and without sepsis. The mean sufentanil dose was significantly higher in non-communicative patients than in communicative patients group (E(1, 352) = 51.435, P < .001, partial ƞ2 = 0.144). The effect of higher opioid- (F(1, 352) = 1.941, P = .161) and sufentanil (F(1, 352) = 1.798, P = .342) requirement was not statistically significant due to sepsis. The hypothesis that sepsis decreases the pain threshold could not be proven in this study. The effect of a higher opioid requirement is not directly caused by sepsis but by communication ability. Furthermore, we were able to show through our investigations and especially through the data of the pain recording instruments that the septic and non-septic intensive care patients receive sufficient pain therapy treatment in our ICU. Regular pain evaluations should be performed on patients in the ICUs who are able to communicate and those who are not.

ICU and Sepsis: Role of Myeloid and Lymphocyte Immune Cells

Sepsis is a severe immune system reaction to infection and a major cause of ICU-related fatalities. Because of the high mortality, high cost of treatment, and complex aetiology of sepsis, sepsis has a huge impact on healthcare. Some of the health complications in sepsis are abnormal cardiac functions, hypoperfusion, hypotension, tissue damage, multiple organ failure, and ultimately death. Individuals with weak immune systems and chronic medical conditions are highly vulnerable to sepsis. In sepsis, a patient shows the extreme immune response in the initial stage while prolonged immunosuppression in the later stages. Sepsis-driven immunosuppression ushers in death because sepsis cases develop secondary infections postrecovery. The later immunocompromised state in sepsis is attributed myeloid-derived suppressor cell upregulation and reduced immune activity displayed by lymphocytes (lymphocyte anergy). As a result, it is currently suggested that regulating the immune response is a better therapeutic approach than focusing on inflammation to improve the immune system's capacity to fight infections. Moreover, finding novel and accurate prognostic biomarkers that can help in rapid sepsis diagnoses and deciding better therapeutic strategies will significantly lower clinical case mortality rates.

When does hepatitis B virus meet long-stranded noncoding RNAs?

Hepatitis B virus (HBV) infection in humans and its associated diseases are long-standing problems. HBV can produce a large number of non-self-molecules during its life cycle, which acts as targets for innate immune recognition and initiation. Among these, interferon and its large number of downstream interferon-stimulated gene molecules are important early antiviral factors. However, the development of an effective antiviral immune response is not simple and depends not only on the delicate regulation of the immune response but also on the various mechanisms of virus-related immune escape and immune tolerance. Therefore, despite there being a relatively well-established consensus on the major pathways of the antiviral response and their component molecules, the complete clearance of HBV remains a challenge in both basic and clinical research. Long-noncoding RNAs (lncRNAs) are generally >200 bp in length and perform different functions in the RNA strand encoding the protein. As an important part of the IFN-inducible genes, interferon-stimulated lncRNAs are involved in the regulation of several HBV infection-related pathways. This review traces the basic elements of such pathways and characterizes the various recent targets of lncRNAs, which not only complement the regulatory mechanisms of pathways related to chronic HBV infection, fibrosis, and cancer promotion but also present with new potential therapeutic targets for controlling HBV infection and the malignant transformation of hepatocytes.

Multi-Omics Techniques Make it Possible to Analyze Sepsis-Associated Acute Kidney Injury Comprehensively

Sepsis-associated acute kidney injury (SA-AKI) is a common complication in critically ill patients with high morbidity and mortality. SA-AKI varies considerably in disease presentation, progression, and response to treatment, highlighting the heterogeneity of the underlying biological mechanisms. In this review, we briefly describe the pathophysiology of SA-AKI, biomarkers, reference databases, and available omics techniques. Advances in omics technology allow for comprehensive analysis of SA-AKI, and the integration of multiple omics provides an opportunity to understand the information flow behind the disease. These approaches will drive a shift in current paradigms for the prevention, diagnosis, and staging and provide the renal community with significant advances in precision medicine in SA-AKI analysis.

Oleuropein ameliorated lung ischemia-reperfusion injury by inhibiting TLR4 signaling cascade in alveolar macrophages

Lung ischemia-reperfusion (I/R) injury is a common postoperative complication in patients with lung transplantation, pulmonary embolism, and cardiopulmonary bypass. Lung I/R injury is a sterile inflammatory process that leads to lung dysfunction, and is an important cause of patient death. Effectively alleviating lung I/R injury can thus improve the prognosis of patients. In this study, we created a mouse model of lung I/R injury by transient unilateral left pulmonary artery occlusion. 6-8 weeks male C57BL/6 mice were randomly assigned to four groups: Sham, I/R, I/R + oleuropein (OLE) and OLE. OLE (50 mg/kg) was orally 24 h and 30 min before anesthesia. Measurement of lung pathohistological, isolated alveolar macrophages (AMs), inflammatory mediators, TLR4 and its downstream factors (MyD88, NF-κB) were performed. We then evaluated the ability of oleuropein (OLE) to ameliorate I/R-induced lung injury and explored the possible molecular mechanisms. OLE ameliorated I/R-induced lung injury and edema and decreased inflammatory factors in lung tissue and bronchoalveolar lavage fluid. This protection required toll-like receptor 4 (TLR4). OLE significantly inhibited I/R-induced expression of TLR4 and its downstream factors in lung tissue and alveolar macrophages. In addition, hypoxia-inducible factor 1α protein accumulated in TLR4-mediated lung I/R injury, and further induced the production of inflammatory factors. Collectively, these data suggest that OLE ameliorates I/R-induced lung injury. The mechanism responsible for its protective effect may involve inhibition of the I/R-induced inflammatory response by downregulating the TLR4 signaling cascade in AMs.

Streptococcus pyogenes Hijacks Host Glutathione for Growth and Innate Immune Evasion

The nasopharynx and the skin are the major oxygen-rich anatomical sites for colonization by the human pathogen Streptococcus pyogenes (group A Streptococcus [GAS]). To establish infection, GAS must survive oxidative stress generated during aerobic metabolism and the release of reactive oxygen species (ROS) by host innate immune cells. Glutathione is the major host antioxidant molecule, while GAS is glutathione auxotrophic. Here, we report the molecular characterization of the ABC transporter substrate binding protein GshT in the GAS glutathione salvage pathway. We demonstrate that glutathione uptake is critical for aerobic growth of GAS and that impaired import of glutathione induces oxidative stress that triggers enhanced production of the reducing equivalent NADPH. Our results highlight the interrelationship between glutathione assimilation, carbohydrate metabolism, virulence factor production, and innate immune evasion. Together, these findings suggest an adaptive strategy employed by extracellular bacterial pathogens to exploit host glutathione stores for their own benefit.

Functional Characterization of Neutrophils Allows Source Control Evaluation in a Murine Sepsis Model

INTRODUCTION

Current surgical guidelines for the treatment of intra-abdominal sepsis recommend interventional source control as the key element of therapy, alongside resuscitation and antibiotic administration. Past trials attempted to predict the success of interventional source control to assess whether further interventional therapy is needed. However, no predictive score could be developed.

MATERIALS AND METHODS

We utilized an established murine abdominal sepsis model, the cecal ligation and puncture (CLP), and performed a successful surgical source control intervention after full development of sepsis, the CLP-excision (CLP/E). We then sought to evaluate the success of the source control by characterizing circulating neutrophil phenotype and functionality 24 h postintervention.

RESULTS

We showed a significant relative increase of neutrophils and a significant absolute and relative increase of activated neutrophils in septic mice. Source control with CLP/E restored these numbers back to baseline. Moreover, main neutrophil functions, the acidification of cell compartments, such as lysosomes, and the production of Tumor Necrosis Factor-alpha (TNF-α), were impaired in septic mice but restored after CLP/E intervention.

CONCLUSIONS

Neutrophil characterization by phenotyping and evaluating their functionality indicates successful source control in septic mice and can serve as a prognostic tool. These findings provide a rationale for the phenotypic and functional characterization of neutrophils in human patients with infection. Further studies will be needed to determine whether a predictive score for the assessment of successful surgical source control can be established.

Sepsis-associated brain injury: underlying mechanisms and potential therapeutic strategies for acute and long-term cognitive impairments

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. Sepsis causes cerebral dysfunction in the short and long term and induces disruption of the blood–brain barrier (BBB), neuroinflammation, hypoperfusion, and accumulation of amyloid β (Aβ) and tau protein in the brain. White matter changes and brain atrophy can be detected using brain imaging, but unfortunately, there is no specific treatment that directly addresses the underlying mechanisms of cognitive impairments in sepsis. Here, we review the underlying mechanisms of sepsis-associated brain injury, with a focus on BBB dysfunction and Aβ and tau protein accumulation in the brain. We also describe the neurological manifestations and imaging findings of sepsis-associated brain injury, and finally, we propose potential therapeutic strategies for acute and long-term cognitive impairments associated with sepsis. In the acute phase of sepsis, we suggest using antibiotics (such as rifampicin), targeting proinflammatory cytokines, and preventing ischemic injuries and hypoperfusion. In the late phase of sepsis, we suggest targeting neuroinflammation, BBB dysfunction, Aβ and tau protein phosphorylation, glycogen synthase kinase-3 beta (GSK3β), and the receptor for advanced glycation end products (RAGE). These proposed strategies are meant to bring new mechanism-based directions for future basic and clinical research aimed at preventing or ameliorating acute and long-term cognitive impairments in patients with sepsis.

TRDMT1 exhibited protective effects against LPS-induced inflammation in rats through TLR4-NF-κB/MAPK-TNF-α pathway

Background

Inflammation is a complex physiological and pathological process. Although many types of inflammation are well characterized, their physiological functions are largely unknown. tRNA aspartic acid methyltransferase 1 (TRDMT1) has been implicated as a stress‐related protein, but its intrinsic biological role is unclear.

Methods

We constructed a Trdmt1 knockout rat and adopted the LPS‐induced sepsis model. Survival curve, histopathological examination, expression of inflammatory factors, and protein level of TLR4 pathway were analyzed.

Results

Trdmt1 deletion had no obvious impact on development and growth. Trdmt1 deletion slightly increased the mortality during aging. Our data showed that Trdmt1 strongly responded in LPS‐treated rats, and Trdmt1 knockout rats were vulnerable to LPS treatment with declined survival rate. We also observed more aggravated tissue damage and more cumulative functional cell degeneration in LPS‐treated knockout rats compared with control rats. Further studies showed upregulated TNF‐α level in liver, spleen, lung, and serum tissues, which may be explained by enhanced p65 and p38 phosphorylation.

Conclusions

Our data demonstrated that Trdmt1 plays a protective role in inflammation by regulating the TLR4‐NF‐κB/MAPK‐TNF‐α pathway. This work provides useful information to understand the TRDMT1 function in inflammation.

Pentamidine Alleviates Inflammation and Lipopolysaccharide-Induced Sepsis by Inhibiting TLR4 Activation via Targeting MD2

Toll-like receptor 4 (TLR4) is a pattern-recognition receptor (PRR) that can recognize lipopolysaccharides (LPS) and initiate the immune response, to protect the body from infection. However, excessive activation of TLR4 induced by LPS leads to substantial release of pro-inflammatory factors, which may bring a cytokine storm in the body and cause severe sepsis. Existing molecules specialized in sepsis therapy are either in clinical trials or show mediocre effects. In this study, pentamidine, an approved drug used in the treatment of trypanosomiasis, was identified as a TLR4 antagonist. Saturation transferred difference (STD)-NMR spectra indicated that pentamidine directly interacted with TLR4's co-receptor myeloid differentiation protein 2 (MD2) in vitro. Cellular thermal shift assay (CETSA) showed that pentamidine binding decreased MD2 stability, which was supported by in silico simulations that pentamidine binding rendered most regions of MD2 more flexible. Pentamidine was found to inhibit the formation of the TLR4/MD2/MyD88 complex and the activation of the TLR4 signaling axes of NF-κB and MAPKs, therefore blocking LPS-induced TLR4 signaling downstream of the pro-inflammatory factors NO, TNF-α, and IL-1β. The bioisosteric replacement of the methylene group at the center 13' site of pentamidine by the ether oxygen group significantly decreased its interactions with MD2 and abolished its TLR4 antagonist activity. Furthermore, pentamidine enhanced the survival rate of septic mice and exerted an anti-inflammatory effect on organs. All these data provide strong evidence that pentamidine may be an effective drug in alleviating inflammation and sepsis.

Sepsis-Exacerbated Brain Dysfunction After Intracerebral Hemorrhage

Sepsis susceptibility is significantly increased in patients with intracerebral hemorrhage (ICH), owing to immunosuppression and intestinal microbiota dysbiosis. To date, ICH with sepsis occurrence is still difficult for clinicians to deal with, and the mortality, as well as long-term cognitive disability, is still increasing. Actually, intracerebral hemorrhage and sepsis are mutually exacerbated via similar pathophysiological mechanisms, mainly consisting of systemic inflammation and circulatory dysfunction. The main consequence of these two processes is neural dysfunction and multiple organ damages, notably, via oxidative stress and neurotoxic mediation under the mediation of central nervous system activation and blood-brain barrier disruption. Besides, the comorbidity-induced multiple organ damages will produce numerous damage-associated molecular patterns and consequently exacerbate the severity of the disease. At present, the prospective views are about operating artificial restriction for the peripheral immune system and achieving cross-tolerance among organs via altering immune cell composition to reduce inflammatory damage.

Mitochondrial STAT3 exacerbates LPS-induced sepsis by driving CPT1a-mediated fatty acid oxidation

Rationale: We found that a subset of signal transducer and activator of transcription 3 (STAT3) translocated into mitochondria in phagocytes, including macrophages isolated from individuals with sepsis. However, the role of mitochondrial STAT3 in macrophages remains unclear.

Method: To investigate the function of mitochondrial STAT3 in vivo, we generated inducible mitochondrial STAT3 knock-in mice. A cytokine array analysis, a CBA analysis, flow cytometry, immunofluorescence staining and quantification and metabolic analyses in vivo were subsequently performed in an LPS-induced sepsis model. Single-cell RNA sequencing, a microarray analysis, metabolic assays, mass spectrometry and ChIP assays were utilized to gain insight into the mechanisms of mitochondrial STAT3 in metabolic reprogramming in LPS-induced sepsis.

Results: We found that mitochondrial STAT3 induced NF-κB nuclear localization and exacerbated LPS-induced sepsis in parallel with a metabolic switch from mainly using glucose to an increased reliance on fatty acid oxidation (FAO). Moreover, mitochondrial STAT3 abrogated carnitine palmitoyl transferase 1a (CPT1a) ubiquitination and degradation in LPS-treated macrophages. Meanwhile, an interaction between CPT1a and ubiquitin-specific peptidase 50 (USP50) was observed. In contrast, knocking down USP50 decreased CPT1a expression and FAO mediated by mitochondrial STAT3. The ChIP assays revealed that NF-κB bound the USP50 promoter. Curcumin alleviated LPS-mediated sepsis by suppressing the activities of mitochondrial STAT3 and NF-κB.

Conclusion: Our findings reveal that mitochondrial STAT3 could trigger FAO by inducing CPT1a stabilization mediated by USP50 in macrophages, at least partially.

A Nomogram to Better Predict the In-Hospital Mortality of Trauma Patients with Sepsis in the Intensive Care Unit

BACKGROUND

Trauma has a high incidence and mortality worldwide, and sepsis is one of the main causes of mortality in trauma patients. Therefore, it is essential to identify the risk factors of in-hospital mortality for trauma patients with sepsis.

METHODS

Data were extracted from the Medical Information Mart for Intensive Care III database and divided into a training set and internal validation set, and another Chinese dataset was used as external validation set. Then, risk factors were estimated using univariate and multivariate logistic regression analyses in the training set. Finally, a nomogram was created to predict the probability of in-hospital mortality for trauma patients with sepsis.

RESULTS

A total of 503 patients were enrolled in our study (335 in the training set and 168 in the validation set). Multivariate logistic regression analysis revealed that age (1.047 [1.025-1.071]), respiratory rate (1.258 [1.135-1.394]), PTT (1.026 [1.008-1.044]), ventilation (6.703 [1.528-29.408]), and vasopressor use (3.682 [1.502-9.025]) were independent factors associated with in-hospital mortality. The nomogram for trauma-related sepsis predicted in-hospital mortality with AUC values of 0.8939 in the training set, 0.8200 in the internal validation set, and 0.7779 in the external validation set.

CONCLUSIONS

The new nomogram has a well predicted value for in-hospital mortality for patients with trauma and sepsis in intensive care units.

The role of neutrophil extracellular traps in acute lung injury

Acute lung injury (ALI) is a heterogeneous inflammatory condition associated with high morbidity and mortality. Neutrophils play a key role in the development of different forms of ALI, and the release of neutrophil extracellular traps (NETs) is emerging as a common pathogenic mechanism. NETs are essential in controlling pathogens, and their defective release or increased degradation leads to a higher risk of infection. However, NETs also contain several pro-inflammatory and cytotoxic molecules than can exacerbate thromboinflammation and lung tissue injury. To reduce NET-mediated lung damage and inflammation, DNase is frequently used in preclinical models of ALI due to its capability of digesting NET DNA scaffold. Moreover, recent advances in neutrophil biology led to the development of selective NET inhibitors, which also appear to reduce ALI in experimental models. Here we provide an overview of the role of NETs in different forms of ALI discussing existing gaps in our knowledge and novel therapeutic approaches to modulate their impact on lung injury.

Principles in Immunology for the Design and Development of Vaccines

Vaccinology has come a long way from early, empirically developed vaccines to modern vaccines rationally designed and produced. Vaccines are meant to cooperate with the human immune system, the later largely unknown in the early years of vaccine development. In the recent years, a tremendous depth of knowledge has been accumulated in the field of immunology that has provided an opportunity to understand the mechanisms of action of the vaccine components. In parallel, our knowledge in microbiology, molecular biology, infectiology, epidemiology, and furthermore in bioinformatics has fostered our understanding of the interaction of microorganisms with the human immune system. Strategies engaged by pathogens strongly determine the targets of a vaccine, which should be formulated to stimulate potent and efficiently protective immune responses. The improved knowledge of immune response mechanisms has facilitated the development of new vaccines with the capacity to selectively address the key pathogenic mechanisms. The primary goal of a vaccine design might no longer be to mimic the pathogen but to identify the relevant processes of the pathogenic mechanisms to be effectively interrupted by a highly specific immune response, eventually surpassing natural limitations. Vaccines have become complex sets of components meant to orchestrate the fine-tuning of the immune processes leading to a lasting and specific immune memory. In addition to antigenic materials, which are comprised of the most critical immunogenic epitopes, adjuvant components are frequently added to induce a favorable immunological activation. Furthermore, for reasons of production and product stability preservatives, stabilizers, inactivators, antibiotics, or diluents could be present, but need to be evaluated. While on the one hand vaccine effectiveness is a primary goal, on the other hand side effects need to be excluded due to safety and tolerability. Further challenges in vaccinology include variability of the vaccinees, the variability of the pathogen, the population-based settings of vaccine application, and the process technology in vaccine production. Vaccine design has become more tailored and in turn has opened up the potential of extending its application to hitherto not accessible complex microbial pathogens plus providing new immunotherapies to tackle diseases such as cancer, Alzheimer's disease, and autoimmune disease. This chapter gives an overview of the key considerations and processes involved in vaccine design and development. It also describes the basic principles of normal immune responses and in their function in defense of infectious agents by vaccination.

Protective effects of pentoxifylline on T-cell viability under inflammatory conditions

Introduction: Pentoxifylline (PTX) reduces the levels of pro-inflammatory cytokines; however, its effects on immune system is not well understood. The aim of this study was to investigate the effect of PTX on T cells under inflammatory conditions in co-culture with THP-1-derived macrophages.

Methods: Toll-like receptor 4 (TLR4) and macrophage migration inhibitory factor (MIF) levels were measured after addition of PTX to lipopolysaccharide (LPS)-stimulated differentiated THP-1 cells. T cell viability and MIF levels were measured after PTX was added to prostaglandin E2 (PGE2)-stimulated Jurkat T-cell leukemia line. Co-culture was conducted to determine the effect of LPS-stimulated differentiated THP-1 cells that are affected by PTX on Jurkat cells. To prevent the direct effects of LPS and PTX on Jurkat cells, LPS and PTX were washed from THP-1 cells before co-culture. T cell viability and interleukin-2 (IL-2) levels were determined in Jurkat cells. Results: Increase in the MIF concentration and TLR4 expression level in differentiated THP-1 cells stimulated with LPS were reversed after PTX addition. However, PTX did not improve T cell viability in PGE2–stimulated Jurkat cells. Co-culturing Jurkat cell and LPS-stimulated differentiated THP-1 cells resulted in a decreased viability of T cells. The addition of PTX restored T cell viability to normal control levels and IL-2 expression level in Jurkat cells. Conclusion: LPS-stimulated THP-1-derived macrophages reduced the T cell viability under inflammation. However, PTX restored T cells viability and IL-2 back to normal levels. Therefore, the immunomodulatory action of PTX may be mediated by macrophage-T cell interactions.

Maresin 1 Attenuates Lipopolysaccharide-Induced Acute Kidney Injury via Inhibiting NOX4/ROS/NF-κB Pathway

Sepsis-associated acute kidney injury (S-AKI) is a common complication in hospitalized and critically ill patients, which increases the risk of multiple comorbidities and is associated with extremely high mortality. Maresin 1 (MaR1), a lipid mediator derived from the omega-3 fatty acid docosahexaenoic acid has been reported to protect against inflammation and promote the regression of acute inflammation. This study proposed to systematically investigate the renoprotective effects and potential molecular mechanism of MaR1 in septic acute kidney injury. We established a S-AKI animal model by a single intraperitoneal injection of lipopolysaccharide (LPS), 10 mg/kg, on male C57BL/6J mice. LPS-stimulated (100 μg/ml) mouse kidney tubular epithelium cells (TCMK-1) were used to simulate septic AKI in vitro. The results showed that pretreatment with MaR1 significantly reduced serum creatinine and blood urea nitrogen levels as well as tubular damage scores and injury marker neutrophil gelatinase-associated lipocalin in septic AKI mice. Meanwhile, MaR1 administration obviously diminished pro-inflammatory cytokines (TNF-α, IL-6, IL-1β, and MCP-1), downregulated BAX and cleaved caspase-3 expression, and upregulated BCL-2 expression in the injured kidney tissues and TCMK-1 cells. In addition, MaR1 reduced malondialdehyde production and improved the superoxide dismutase activity of renal tissues while inhibiting reactive oxygen species (ROS) production and protecting the mitochondria. Mechanistically, LPS stimulated the expression of the NOX4/ROS/NF-κB p65 signaling pathway in S-AKI kidneys, while MaR1 effectively suppressed the activation of the corresponding pathway. In conclusion, MaR1 attenuated kidney inflammation, apoptosis, oxidative stress, and mitochondrial dysfunction to protect against LPS-induced septic AKI via inhibiting the NOX4/ROS/NF-κB p65 signaling pathway.

Platelets differentially modulate CD4+ Treg activation via GPIIa/IIIb-, fibrinogen-, and PAR4-dependent pathways

CD4⁺FoxP3⁺ regulatory T cells (CD4⁺ Tregs) are known to dampen inflammation following severe trauma. Platelets were shown to augment their posttraumatic activation in burn injury, but the exact mechanisms remain unclear. We hypothesized that platelet activation mechanisms via GPIIb/IIIa, fibrinogen, and PAR4 have an immunological effect and modulate CD4⁺ Treg activation early after trauma. Therefore, C57Bl/6 N mice were injected with tirofiban (GPIIb/IIIa inhibition), ancrod (fibrinogen splitting enzyme), or tcY-NH₂ (selective PAR4 antagonist peptide) before inducing a third-degree burn injury of 25% of the total body surface area. Changes in coagulation, and local and systemic CD4⁺ Treg activity were assessed via rotational thromboelastometry (ROTEM®) and phospho-flow cytometry 1 h post intervention. The inhibition of GPIIb/IIIa and fibrinogen locally led to a higher basic activity of CD4⁺ Tregs compared to non-inhibited animals. In contrast, PAR4 disruption on platelets locally led to an increased posttraumatic activation of CD4⁺ Tregs. Fibrinogen led to complete elimination of coagulation, whereas GPIIb/IIIa or PAR4 inhibition did not. GPIIb/IIIa receptor and fibrinogen inhibition increase CD4⁺ Tregs activity independently of trauma. Both are crucial for thrombus formation. We suggest platelets trapped in thrombi are unable to interact with CD4⁺ Tregs but augment their activity when circulating freely. In contrast, PAR4 seems to reduce CD4⁺ Treg activation following trauma. In summary, GPIIb/IIIa-, PAR4-, and fibrinogen-dependent pathways in platelets modulate CD4⁺ Treg baseline activity, independently from their hemostatic functionality. PAR4-dependent pathways modulate the posttraumatic interplay of platelets and CD4⁺ Tregs.

LBP Protects Hepatocyte Mitochondrial Function Via the PPAR-CYP4A2 Signaling Pathway in a Rat Sepsis Model

OBJECTIVES

To explore the role of LPS binding protein (LBP) in metabolism and optimize sepsis treatment.

DESIGN

A sepsis model was established by injecting LPS into LBP-/- rats and WT rats and observing changes in the liver over time (0, 1, 6, and 24 h).

SETTING

Detecting liver inflammation and injury. Optimizing the treatment of sepsis.

SUBJECTS

WT rats and LBP-/- rats.

INTERVENTIONS

We established a sepsis model by injecting LPS intravenously.

MEASUREMENTS AND MAIN RESULTS

First, we induced sepsis in WT and LBP-/- rats with LPS. The rats were sacrificed, and serum and liver samples were collected at 1, 6, and 24 h after LPS injection. We found that the deletion of LBP reduced LPS-induced liver inflammation and injury at 1 and 6 h. Ballooning degeneration was clearly present in LBP-/- rat livers at 24 h after LPS injection. We found that mitochondrial damage and reactive oxygen species (ROS) levels were higher in LBP-/- rat livers than in WT rat livers at 24 h after LPS injection. According to the transcriptomic results, the peroxisome proliferator-activated receptor (PPAR) pathway may be the reason for lesions in LBP-/- rats. To further investigate the function of PPARα in sepsis, we inhibited mTOR with rapamycin and examined mitochondrial injury and ROS levels. The levels of mitochondrial damage and ROS were reduced after LBP-/- rats were pretreated with rapamycin in the context of LPS-induced sepsis. Inhibiting CYP4a2, one of the PPARα-target gene products, reduced the level of LPS-induced ROS in LBP-/- rats.

CONCLUSION

LBP protects hepatic mitochondria against LPS-induced damage via the LBP-PPARα-CYP4a2 signaling pathway.

The Role of DAMPS in Burns and Hemorrhagic Shock Immune Response: Pathophysiology and Clinical Issues. Review

Severe or major burns induce a pathophysiological, immune, and inflammatory response that can persist for a long time and affect morbidity and mortality. Severe burns are followed by a "hypermetabolic response", an inflammatory process that can be extensive and become uncontrolled, leading to a generalized catabolic state and delayed healing. Catabolism causes the upregulation of inflammatory cells and innate immune markers in various organs, which may lead to multiorgan failure and death. Burns activate immune cells and cytokine production regulated by damage-associated molecular patterns (DAMPs). Trauma has similar injury-related immune responses, whereby DAMPs are massively released in musculoskeletal injuries and elicit widespread systemic inflammation. Hemorrhagic shock is the main cause of death in trauma. It is hypovolemic, and the consequence of volume loss and the speed of blood loss manifest immediately after injury. In burns, the shock becomes evident within the first 24 h and is hypovolemic-distributive due to the severely compromised regulation of tissue perfusion and oxygen delivery caused by capillary leakage, whereby fluids shift from the intravascular to the interstitial space. In this review, we compare the pathophysiological responses to burns and trauma including their associated clinical patterns.

The Ambivalent Role of Skin Microbiota and Adrenaline in Wound Healing and the Interplay between Them

After skin injury, wound healing sets into motion a dynamic process to repair and replace devitalized tissues. The healing process can be divided into four overlapping phases: hemostasis, inflammation, proliferation, and maturation. Skin microbiota has been reported to participate in orchestrating the wound healing both in negative and positive ways. Many studies reported that skin microbiota can impose negative and positive effects on the wound. Recent findings have shown that many bacterial species on human skin are able to convert aromatic amino acids into so-called trace amines (TAs) and convert corresponding precursors into dopamine and serotonin, which are all released into the environment. As a stress reaction, wounded epithelial cells release the hormone adrenaline (epinephrine), which activates the β2-adrenergic receptor (β2-AR), impairing the migration ability of keratinocytes and thus re-epithelization. This is where TAs come into play, as they act as antagonists of β2-AR and thus attenuate the effects of adrenaline. The result is that not only TAs but also TA-producing skin bacteria accelerate wound healing. Adrenergic receptors (ARs) play a key role in many physiological and disease-related processes and are expressed in numerous cell types. In this review, we describe the role of ARs in relation to wound healing in keratinocytes, immune cells, fibroblasts, and blood vessels and the possible role of the skin microbiota in wound healing.

Potential Targets to Mitigate Trauma- or Sepsis-Induced Immune Suppression

In sepsis and trauma, pathogens and injured tissue provoke a systemic inflammatory reaction which can lead to overwhelming inflammation. Concurrent with the innate hyperinflammatory response is adaptive immune suppression that can become chronic. A current key issue today is that patients who undergo intensive medical care after sepsis or trauma have a high mortality rate after being discharged. This high mortality is thought to be associated with persistent immunosuppression. Knowledge about the pathophysiology leading to this state remains fragmented. Immunosuppressive cytokines play an essential role in mediating and upholding immunosuppression in these patients. Specifically, the cytokines Interleukin-10 (IL-10), Transforming Growth Factor-β (TGF-β) and Thymic stromal lymphopoietin (TSLP) are reported to have potent immunosuppressive capacities. Here, we review their ability to suppress inflammation, their dynamics in sepsis and trauma and what drives the pathologic release of these cytokines. They do exert paradoxical effects under certain conditions, which makes it necessary to evaluate their functions in the context of dynamic changes post-sepsis and trauma. Several drugs modulating their functions are currently in clinical trials in the treatment of other pathologies. We provide an overview of the current literature on the effects of IL-10, TGF-β and TSLP in sepsis and trauma and suggest therapeutic approaches for their modulation.

Respiratory Burst and TNF-α Receptor Expression of Neutrophils after Sepsis and Severe Injury-Induced Inflammation in Children

Systemic inflammatory response syndrome (SIRS) is defined as the systemic host response to infection or a non-infectious factor. The purpose of this study was to evaluate the involvement of reactive oxygen species (ROS) in severe inflammation and to assess the discrimination strength of the neutrophil BURSTTEST assay regarding its etiology in three groups of patients (sepsis, burns, and bone fractures) who met the SIRS criteria. The neutrophil activation (respiratory burst of granulocytes as well as p55 and p75 tumor necrosis factor (TNF-α) receptor expression) was evaluated twice using flow cytometry, and the results were compared with healthy controls and among SIRS subjects. A decreased oxygen metabolism in neutrophils after E.coli stimulation and increased TNF-α receptor expression were found in septic and burned patients on admission, while ROS production augmented and TNF-α receptor expression diminished with the applied therapy. The significant differences in neutrophil respiratory burst intensity among septic and burned patients and those with sepsis and bone fractures were found (however, there were not any such differences between patients with thermal and mechanical injuries). This study indicates that the neutrophil BURSTTEST evaluation might be a clinically reliable marker for differentiating the SIRS etiology.

Immunological Endotyping of Chronic Critical Illness After Severe Sepsis

Improved management of severe sepsis has been one of the major health care accomplishments of the last two decades. Due to enhanced recognition and improved management of severe sepsis, in-hospital mortality has been reduced by up to 40%. With that good news, a new syndrome has unfortunately replaced in-hospital multi-organ failure and death. This syndrome of chronic critical illness (CCI) includes sepsis patients who survive the early "cytokine or genomic storm," but fail to fully recover, and progress into a persistent state of manageable organ injury requiring prolonged intensive care. These patients are commonly discharged to long-term care facilities where sepsis recidivism is high. As many as 33% of sepsis survivors develop CCI. CCI is the result, at least in part, of a maladaptive host response to chronic pattern-recognition receptor (PRR)-mediated processes. This maladaptive response results in dysregulated myelopoiesis, chronic inflammation, T-cell atrophy, T-cell exhaustion, and the expansion of suppressor cell functions. We have defined this panoply of host responses as a persistent inflammatory, immune suppressive and protein catabolic syndrome (PICS). Why is this important? We propose that PICS in survivors of critical illness is its own common, unique immunological endotype driven by the constant release of organ injury-associated, endogenous alarmins, and microbial products from secondary infections. While this syndrome can develop as a result of a diverse set of pathologies, it represents a shared outcome with a unique underlying pathobiological mechanism. Despite being a common outcome, there are no therapeutic interventions other than supportive therapies for this common disorder. Only through an improved understanding of the immunological endotype of PICS can rational therapeutic interventions be designed.

Therapeutic approaches targeting renin-angiotensin system in sepsis and its complications

Sepsis, caused by the inappropriate host response to infection, is characterized by excessive inflammatory response and organ dysfunction, thus becomes a critical clinical problem. Commonly, sepsis may progress to septic shock and severe complications, including acute kidney injury (AKI), acute respiratory distress syndrome (ARDS), sepsis-induced myocardial dysfunction (SIMD), liver dysfunction, cerebral dysfunction, and skeletal muscle atrophy, which predominantly contribute to high mortality. Additionally, the global pandemic of coronavirus disease 2019 (COVID-19) raised the concern of development of effectve therapeutic strategies for viral sepsis. Renin-angiotensin system (RAS) may represent as a potent therapeutic target for sepsis therapy. The emerging role of RAS in the pathogenesis of sepsis has been investigated and several preclinical and clinical trials targeting RAS for sepsis treatment revealed promising outcomes. Herein, we attempt to review the effects and mechanisms of RAS manipulation on sepsis and its complications and provide new insights into optimizing RAS interventions for sepsis treatment.

Inhalation Injury: Unmet Clinical Needs and Future Research

Pulmonary and systemic insults from inhalation injury can complicate the care of burn patients and contribute to significant morbidity and mortality. However, recent progress in diagnosis and treatment of inhalation injury has not kept pace with the care of cutaneous thermal injury. There are many challenges unique to inhalation injury that have slowed advancement, including deficiencies in our understanding of its pathophysiology, the relative difficulty and subjectivity of bronchoscopic diagnosis, the lack of diagnostic biomarkers, the necessarily urgent manner in which decisions are made about intubation, and the lack of universal recommendations for the application of mucolytics, anticoagulants, bronchodilators, modified ventilator strategies, and other measures. This review represents a summary of critical shortcomings in our understanding and management of inhalation injury identified by the American Burn Association's working group on Cutaneous Thermal Injury and Inhalation Injury in 2018. It addresses our current understanding of the diagnosis, pathophysiology, and treatment of inhalation injury and highlights topics in need of additional research, including 1) airway repair mechanisms; 2) the airway microbiome in health and after injury; and 3) candidate biomarkers of inhalation injury.