DAMPs, PAMPs, and the origins of SIRS in bacterial sepsis

Exosome-Derived microRNA: Potential Target for Diagnosis and Treatment of Sepsis

Exosome-derived microRNAs (miRNAs) are emerging as pivotal players in the pathophysiology of sepsis, representing a new frontier in both the diagnosis and treatment of this complex condition. Sepsis, a severe systemic response to infection, involves intricate immune and nonimmune mechanisms, where exosome-mediated communication can significantly influence disease progression and outcomes. During the progress of sepsis, the miRNA profile of exosomes undergoes notable alterations, is reflecting, and may affect the progression of the disease. This review comprehensively explores the biology of exosome-derived miRNAs, which originate from both immune cells (such as macrophages and dendritic cells) and nonimmune cells (such as endothelial and epithelial cells) and play a dynamic role in modulating pathways that affect the course of sepsis, including those related to inflammation, immune response, cell survival, and apoptosis. Taking into account these dynamic changes, we further discuss the potential of exosome-derived miRNAs as biomarkers for the early detection and prognosis of sepsis and advantages over traditional biomarkers due to their stability and specificity. Furthermore, this review evaluates exosome-based therapeutic miRNA delivery systems in sepsis, which may pave the way for targeted modulation of the septic response and personalized treatment options.

Effect of ethanol exposure on innate immune response in sepsis

Alcohol use disorder, reported by 1 in 8 critically ill patients, is a risk factor for death in sepsis patients. Sepsis, the leading cause of death, kills over 270,000 patients in the United States alone and remains without targeted therapy. Immune response in sepsis transitions from an early hyperinflammation to persistent inflammation and immunosuppression and multiple organ dysfunction during late sepsis. Innate immunity is the first line of defense against pathogen invasion. Ethanol exposure is known to impair innate and adaptive immune response and bacterial clearance in sepsis patients. Specifically, ethanol exposure is known to modulate every aspect of innate immune response with and without sepsis. Multiple molecular mechanisms are implicated in causing dysregulated immune response in ethanol exposure with sepsis, but targeted treatments have remained elusive. In this article, we outline the effects of ethanol exposure on various innate immune cell types in general and during sepsis.

The Role of Biomarkers in Diagnosis of Sepsis and Acute Kidney Injury

Sepsis and acute kidney injury (AKI) are two major public health concerns that contribute significantly to illness and death worldwide. Early diagnosis and prompt treatment are essential for achieving the best possible outcomes. To date, there are no specific clinical, imaging, or biochemical indicators available to diagnose sepsis, and diagnosis of AKI based on the KDIGO criterion has limitations. To improve the diagnostic process for sepsis and AKI, it is essential to continually evolve our understanding of these conditions. Delays in diagnosis and appropriate treatment can have serious consequences. Sepsis and AKI often occur together, and patients with kidney dysfunction are more prone to developing sepsis. Therefore, identifying potential biomarkers for both conditions is crucial. In this review, we talk about the main biomarkers that evolve the diagnostic of sepsis and AKI, namely neutrophil gelatinase-associated lipocalin (NGAL), proenkephalin (PENK), and cell-free DNA.

Apoptosis dysfunction: unravelling the interplay between ZBP1 activation and viral invasion in innate immune responses

Apoptosis plays a pivotal role in pathogen elimination and maintaining homeostasis. However, viruses have evolved strategies to evade apoptosis, enabling their persistence within the host. Z-DNA binding protein 1 (ZBP1) is a potent innate immune sensor that detects cytoplasmic nucleic acids and activates the innate immune response to clear pathogens. When apoptosis is inhibited by viral invasion, ZBP1 can be activated to compensate for the effect of apoptosis by triggering an innate immune response. This review examined the mechanisms of apoptosis inhibition and ZBP1 activation during viral invasion. The authors outlined the mechanisms of ZBP1-induced type I interferon, pyroptosis and necroptosis, as well as the crosstalk between ZBP1 and the cGAS-STING signalling pathway. Furthermore, ZBP1 can reverse the suppression of apoptotic signals induced by viruses. Intriguingly, a positive feedback loop exists in the ZBP1 signalling pathway, which intensifies the innate immune response while triggering a cytokine storm, leading to tissue and organ damage. The prudent use of ZBP1, which is a double-edged sword, has significant clinical implications for treating infections and inflammation.

Sepsis Management in the Cardiac Intensive Care Unit

Septic shock management in the cardiac intensive care unit (CICU) is challenging due to the complex interaction of pathophysiology between vasodilatory and cardiogenic shock, complicating how to optimally deploy fluid resuscitation, vasopressors, and mechanical circulatory support devices. Because mixed shock portends high mortality and morbidity, familiarity with quality, contemporary clinical evidence surrounding available therapeutic tools is needed to address the resultant wide range of complications that can arise. This review integrates pathophysiology principles and clinical recommendations to provide an organized, topic-based review of the nuanced intricacies of managing sepsis in the CICU.

Investigating the link between miR-34a-5p and TLR6 signaling in sepsis-induced ARDS

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) are lung complications diagnosed by impaired gaseous exchanges leading to mortality. From the diverse etiologies, sepsis is a prominent contributor to ALI/ARDS. In the present study, we retrieved sepsis-induced ARDS mRNA expression profile and identified 883 differentially expressed genes (DEGs). Next, we established an ARDS-specific weighted gene co-expression network (WGCN) and picked the blue module as our hub module based on highly correlated network properties. Later we subjected all hub module DEGs to form an ARDS-specific 3-node feed-forward loop (FFL) whose highest-order subnetwork motif revealed one TF (STAT6), one miRNA (miR-34a-5p), and one mRNA (TLR6). Thereafter, we screened a natural product library and identified three lead molecules that showed promising binding affinity against TLR6. We then performed molecular dynamics simulations to evaluate the stability and binding free energy of the TLR6-lead molecule complexes. Our results suggest these lead molecules may be potential therapeutic candidates for treating sepsis-induced ALI/ARDS. In-silico studies on clinical datasets for sepsis-induced ARDS indicate a possible positive interaction between miR-34a and TLR6 and an antagonizing effect on STAT6 to promote inflammation. Also, the translational study on septic mice lungs by IHC staining reveals a hike in the expression of TLR6. We report here that miR-34a actively augments the effect of sepsis on lung epithelial cell apoptosis. This study suggests that miR-34a promotes TLR6 to heighten inflammation in sepsis-induced ALI/ARDS.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03700-1.

The Molecular Basis and Clinical Consequences of Chronic Inflammation in Prostatic Diseases: Prostatitis, Benign Prostatic Hyperplasia, and Prostate Cancer

Chronic inflammation is now recognized as one of the major risk factors and molecular hallmarks of chronic prostatitis, benign prostatic hyperplasia (BPH), and prostate tumorigenesis. However, the molecular mechanisms by which chronic inflammation signaling contributes to the pathogenesis of these prostate diseases are poorly understood. Previous efforts to therapeutically target the upstream (e.g., TLRs and IL1-Rs) and downstream (e.g., NF-κB subunits and cytokines) inflammatory signaling molecules in people with these conditions have been clinically ambiguous and unsatisfactory, hence fostering the recent paradigm shift towards unraveling and understanding the functional roles and clinical significance of the novel and relatively underexplored inflammatory molecules and pathways that could become potential therapeutic targets in managing prostatic diseases. In this review article, we exclusively discuss the causal and molecular drivers of prostatitis, BPH, and prostate tumorigenesis, as well as the potential impacts of microbiome dysbiosis and chronic inflammation in promoting prostate pathologies. We specifically focus on the importance of some of the underexplored druggable inflammatory molecules, by discussing how their aberrant signaling could promote prostate cancer (PCa) stemness, neuroendocrine differentiation, castration resistance, metabolic reprogramming, and immunosuppression. The potential contribution of the IL1R-TLR-IRAK-NF-κBs signaling molecules and NLR/inflammasomes in prostate pathologies, as well as the prospective benefits of selectively targeting the midstream molecules in the various inflammatory cascades, are also discussed. Though this review concentrates more on PCa, we envision that the information could be applied to other prostate diseases. In conclusion, we have underlined the molecular mechanisms and signaling pathways that may need to be targeted and/or further investigated to better understand the association between chronic inflammation and prostate diseases.

4-octyl itaconate ameliorates alveolar macrophage pyroptosis against ARDS via rescuing mitochondrial dysfunction and suppressing the cGAS/STING pathway

Acute respiratory distress syndrome (ARDS) is a high-mortality pulmonary disorder characterized by an intense inflammatory response and a cytokine storm. As of yet, there is no proven effective therapy for ARDS. Itaconate, an immunomodulatory derivative accumulated during inflammatory macrophage activation, has attracted widespread attention for its potent anti-inflammatory and anti-oxidative properties. This study pointed to explore the protective impacts of 4-octyl itaconate (4-OI) on ARDS. The results showed that lung injury was attenuated markedly after 4-OI pre-treatment, as represented by decreased pulmonary edema, inflammatory cell infiltration, and production of inflammatory factors. LPS stimulation induced NLRP3-mediated pyroptosis in vitro and in vivo, as represented by the cleavage of gasdermin D (GSDMD), IL-18 and IL-1β release, and these changes could be prevented by 4-OI pretreatment. Mechanistically, 4-OI eliminated mitochondrial reactive oxygen species (mtROS) and mtDNA escaping to the cytosol through the opening mitochondrial permeability transition pore (mPTP) in alveolar macrophages (AMs) under oxidative stress. In addition, 4-OI pretreatment markedly downregulated cyclic GMP-AMP synthase (cGAS), stimulator of interferon genes (STING) expression, and interferon regulatory factor 3 (IRF3) phosphorylation in vitro and in vivo. Meanwhile, inhibition of STING/IRF3 pathway alleviated NLRP3-mediated pyroptosis induced by LPS in vitro. Taken together, this study indicated that 4-OI ameliorated ARDS by rescuing mitochondrial dysfunction and inhibiting NLRP3-mediated macrophage pyroptosis in a STING/IRF3-dependent manner, which further revealed the potential mechanism of itaconate in preventing inflammatory diseases.

The leaky gut and the gut microbiome in sepsis - targets in research and treatment

Both a leaky gut (a barrier defect of the intestinal surface) and gut dysbiosis (a change in the intestinal microbial population) are intrinsic to sepsis. While sepsis itself can cause dysbiosis, dysbiosis can worsen sepsis. The leaky gut syndrome refers to a status with which there is an increased intestinal permeability allowing the translocation of microbial molecules from the gut into the blood circulation. It is not just a symptom of gastrointestinal involvement, but also an underlying cause that develops independently, and its presence could be recognized by the detection, in blood, of lipopolysaccharides and (1→3)-β-D-glucan (major components of gut microbiota). Gut-dysbiosis is the consequence of a reduction in some bacterial species in the gut microbiome, as a consequence of intestinal mucosal immunity defect, caused by intestinal hypoperfusion, immune cell apoptosis, and a variety of enteric neuro-humoral-immunity responses. A reduction in bacteria that produce short-chain fatty acids could change the intestinal barriers, leading to the translocation of pathogen molecules, into the circulation where it causes systemic inflammation. Even gut fungi might be increased in human patients with sepsis, even though this has not been consistently observed in murine models of sepsis, probably because of the longer duration of sepsis and also antibiotic use in patients. The gut virobiome that partly consists of bacteriophages is also detectable in gut contents that might be different between sepsis and normal hosts. These alterations of gut dysbiosis altogether could be an interesting target for sepsis adjuvant therapies, e.g., by faecal transplantation or probiotic therapy. Here, current information on leaky gut and gut dysbiosis along with the potential biomarkers, new treatment strategies, and future research topics are mentioned.

Infection as an under-recognized precipitant of acute heart failure: prognostic and therapeutic implications

As the prevalence of heart failure (HF) continues to rise, prompt diagnosis and management of various medical conditions, which may lead to HF exacerbation and result in poor patient outcomes, are of paramount importance. Infection has been identified as a common, though under-recognized, precipitating factor of acute heart failure (AHF), which can cause rapid development or deterioration of HF signs and symptoms. Available evidence indicates that infection-related hospitalizations of patients with AHF are associated with higher mortality, protracted length of stay, and increased readmission rates. Understanding the intricate interaction of both clinical entities may provide further therapeutic strategies to prevent the occurrence of cardiac complications and improve prognosis of patients with AHF triggered by infection. The purpose of this review is to investigate the incidence of infection as a causative factor in AHF, explore its prognostic implications, elucidate the underlying pathophysiological mechanisms, and highlight the basic principles of the initial diagnostic and therapeutic interventions in the emergency department.

Hematological Parameters and Procalcitonin as Discriminants between Bacterial Pneumonia-Induced Sepsis and Viral Sepsis Secondary to COVID-19: A Retrospective Single-Center Analysis

Bacterial and viral sepsis induce alterations of all hematological parameters and procalcitonin is used as a biomarker of infection and disease severity. Our aim was to study the hematological patterns associated with pulmonary sepsis triggered by bacteria and Severe Acute Respiratory Syndrome-Coronavirus-type-2 (SARS-CoV-2) and to identify the discriminants between them. We performed a retrospective, observational study including 124 patients with bacterial sepsis and 138 patients with viral sepsis. Discriminative ability of hematological parameters and procalcitonin between sepsis types was tested using receiver operating characteristic (ROC) analysis. Sensitivity (Sn%), specificity (Sp%), positive and negative likelihood ratios were calculated for the identified cut-off values. Patients with bacterial sepsis were older than patients with viral sepsis (p < 0.001), with no differences regarding gender. Subsequently to ROC analysis, procalcitonin had excellent discriminative ability for bacterial sepsis diagnosis with an area under the curve (AUC) of 0.92 (cut-off value of >1.49 ng/mL; Sn = 76.6%, Sp = 94.2%), followed by RDW% with an AUC = 0.87 (cut-off value >14.8%; Sn = 80.7%, Sp = 85.5%). Leukocytes, monocytes and neutrophils had good discriminative ability with AUCs between 0.76-0.78 (p < 0.001), while other hematological parameters had fair or no discriminative ability. Lastly, procalcitonin value was strongly correlated with disease severity in both types of sepsis (p < 0.001). Procalcitonin and RDW% had the best discriminative ability between bacterial and viral sepsis, followed by leukocytes, monocytes and neutrophils. Procalcitonin is a marker of disease severity regardless of sepsis type.

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.

Protective effects of S100A8 on sepsis mortality: Links to sepsis risk in obesity and diabetes

Obesity and diabetes are independent risk factors for death during sepsis. S100A8, an alarmin, is related to inflammation, obesity, and diabetes. Here, we examine the role of S100A8 in sepsis of obesity and diabetes models. Injection of S100A8 prolongs the survival of septic mice induced by lethal endotoxemia, Escherichia coli injection, or cecal ligation and puncture. S100A8 decrease the LPS-induced expression of proinflammatory cytokines in peritoneal macrophages by inhibiting TLR4-mediated signals in an autocrine manner. db/db, ob/ob, and western diet-fed mice demonstrate reduced upregulation of S100A8 induced by LPS treatment in both serum and peritoneal cells. These mice also show shorter survival after LPS injection, and S100A8 supplementation prolonged the survival. While myelomonocytic cells-specific S100A8-deficient mice (Lyz2 ^cre :S100A8 ^{floxed/floxed} ) exhibit shorter survival after LPS treatment, S100A8 supplementation prolonged the survival. Thus, myelomonocytic cell-derived S100A8 is crucial for protection from sepsis, and S100A8 supplementation improves sepsis, particularly in mice with obesity and diabetes.

A new predictive tool consolidating CURB-65 with procalcitonin and albumin to assess short-term mortality in hospitalized elderly patients with infectious disease: A retrospective study of a patient cohort

BACKGROUND

Hospitalized elderly patients are often at risk of life-threatening infectious diseases such as pneumonia and urinary tract infection, thus diagnostic tools for bacterial infections are demanded. We developed a new predictive tool consolidating modified CURB-65, procalcitonin (PCT) and albumin (Alb).

METHOD

This is a retrospective study. Modified CURB-65 (mCURB-65) score, PCT, Alb, and various cardiovascular/respiratory/renal functions were measured. Survival analyses were conducted to assess 30-days mortality of elderly patients using mCURB-65 score, PCT and Alb. The consolidated scores were compared with the number of patients died.

RESULTS

There were 445 elderly patients included. Kaplan-Meier survival curves showed significant differences between the high and low groups of mCURB-65, PCT and Alb (log-rank test, P < .001). Cox proportional regression showed that the hazard ratios (95% confidence intervals) for high mCURB-65, high Alb, and high PCT were all significant, 1.95 (1.24-3.05), 0.50 (0.32-0.77), and 2.09 (1.32-3.31), respectively. The consolidated scores showed tendency of increase with proportion of the number of patients died.

CONCLUSIONS

The consolidated score consisted of mCURB-65, PCT and Alb can be a useful tool to predict short-term mortality of the hospitalized elderly patients with infectious disease.

Role of released mitochondrial DNA in acute lung injury

Acute lung injury(ALI)/acute respiratory distress syndrome(ARDS) is a form of acute-onset hypoxemic respiratory failure characterised by an acute, diffuse, inflammatory lung injury, and increased alveolar-capillary permeability, which is caused by a variety of pulmonary or nonpulmonary insults. Recently, aberrant mitochondria and mitochondrial DNA(mtDNA) level are associated with the development of ALI/ARDS, and plasma mtDNA level shows the potential to be a promising biomarker for clinical diagnosis and evaluation of lung injury severity. In mechanism, the mtDNA and its oxidised form, which are released from impaired mitochondria, play a crucial role in the inflammatory response and histopathological changes in the lung. In this review, we discuss mitochondrial outer membrane permeabilisation (MOMP), mitochondrial permeability transition pore(mPTP), extracellular vesicles (EVs), extracellular traps (ETs), and passive release as the principal mechanisms for the release of mitochondrial DNA into the cytoplasm and extracellular compartments respectively. Further, we explain how the released mtDNA and its oxidised form can induce inflammatory cytokine production and aggravate lung injury through the Toll-like receptor 9(TLR9) signalling, cytosolic cGAS-stimulator of interferon genes (STING) signalling (cGAS-STING) pathway, and inflammasomes activation. Additionally, we propose targeting mtDNA-mediated inflammatory pathways as a novel therapeutic approach for treating ALI/ARDS.

EARLY DIFFERENTIATION BETWEEN SEPSIS AND STERILE INFLAMMATION VIA URINARY GENE SIGNATURES OF METABOLIC DYSREGULATION

ABSTRACT

Objective: The aim of this study was to characterize early urinary gene expression differences between patients with sepsis and patients with sterile inflammation and summarize in terms of a reproducible sepsis probability score. Design: This was a prospective observational cohort study. Setting: The study was conducted in a quaternary care academic hospital. Patients: One hundred eighty-six sepsis patients and 78 systemic inflammatory response syndrome (SIRS) patients enrolled between January 2015 and February 2018. Interventions: Whole-genome transcriptomic analysis of RNA was extracted from urine obtained from sepsis patients within 12 hours of sepsis onset and from patients with surgery-acquired SIRS within 4 hours after major inpatient surgery. Measurements and Main Results: We identified 422 of 23,956 genes (1.7%) that were differentially expressed between sepsis and SIRS patients. Differentially expressed probes were provided to a collection of machine learning feature selection models to identify focused probe sets that differentiate between sepsis and SIRS. These probe sets were combined to find an optimal probe set (UrSepsisModel) and calculate a urinary sepsis score (UrSepsisScore), which is the geometric mean of downregulated genes subtracted from the geometric mean of upregulated genes. This approach summarizes the expression values of all decisive genes as a single sepsis score. The UrSepsisModel and UrSepsisScore achieved area under the receiver operating characteristic curves 0.91 (95% confidence interval, 0.86-0.96) and 0.80 (95% confidence interval, 0.70-0.88) on the validation cohort, respectively. Functional analyses of probes associated with sepsis demonstrated metabolic dysregulation manifest as reduced oxidative phosphorylation, decreased amino acid metabolism, and decreased oxidation of lipids and fatty acids. Conclusions: Whole-genome transcriptomic profiling of urinary cells revealed focused probe panels that can function as an early diagnostic tool for differentiating sepsis from sterile SIRS. Functional analysis of differentially expressed genes demonstrated a distinct metabolic dysregulation signature in sepsis.

Active Release of eCIRP via Gasdermin D Channels to Induce Inflammation in Sepsis

Extracellular cold-inducible RNA binding protein (eCIRP) is an inflammatory mediator that causes inflammation and tissue injury in sepsis. Gasdermin D (GSDMD) is a protein that, when cleaved, forms pores in the cell membrane, releasing intracellular contents into the extracellular milieu to exacerbate inflammation. We hypothesize that eCIRP is released actively from viable macrophages via GSDMD pores. We found that LPS induced eCIRP secretion from macrophages into the extracellular space. LPS significantly increased the expression of caspase-11 and cleavage of the GSDMD, as evidenced by increased N-terminal GSDMD expression in RAW 264.7 cells and mouse primary peritoneal macrophages. GSDMD inhibitor disulfiram decreased eCIRP release in vitro. Treatment with glycine to prevent pyroptosis-induced cell lysis did not significantly decrease eCIRP release from LPS-treated macrophages, indicating that eCIRP was actively released and was independent of pyroptosis. Downregulation of GSDMD gene expression by siRNA transfection suppressed eCIRP release in vitro after LPS stimulation. Moreover, GSDMD^-/- peritoneal macrophages and mice had decreased levels of eCIRP in the culture supernatants and in blood treated with LPS in vitro and in vivo, respectively. GSDMD inhibitor disulfiram inhibited serum levels of eCIRP in endotoxemia and cecal ligation and puncture-induced sepsis. We conclude that eCIRP release from living macrophages is mediated through GSDMD pores, suggesting that targeting GSDMD could be a novel and potential therapeutic approach to inhibit eCIRP-mediated inflammation in sepsis.

[Corticosteroids and metabolic resuscitation (hydrocortisone, ascorbic acid and thiamine) in sepsis and septic shock]

In accordance with the recommendations of, among others, the Surviving Sepsis Campaign, adjunctive therapies may play a role in the treatment and the prognosis in sepsis patients. Corticosteroids, ascorbic acid, and thiamine has been identified as a potential therapy for septic shock alone or in combination. Since many years, low-dosis corticosteroids has been proposed as adjuvant therapies for these patients. However, there are still many controversies regarding the role of systemic low-dose corticosteroids as a part of the treatment of septic shock. In recent clinical and experimental investigations, mitochondrion-target therapy bic acid and thiamine) for sepsis has been suggested to reduce MODS severity and mortality although their clinical results are not yet convincing for their use. In the present article, we have performed a narrative review of the current literature including pathophysiologic rationale and the current evidence for such therapies in septic patients.

Emodin relieves the inflammation and pyroptosis of lipopolysaccharide-treated 1321N1 cells by regulating methyltransferase-like 3 -mediated NLR family pyrin domain containing 3 expression

Sepsis brain injury (SBI) is a major cause of death in critically ill patients. The present study aimed to investigate the role of emodin in SBI development. Human astrocyte 1321N1 cells were stimulated with 100 ng/mL lipopolysaccharide (LPS) to establish an SBI model in vitro. Flow cytometry was performed to measure the cell pyroptosis. The protein expression levels of syndecan-1 (SDC-1), NLR family pyrin domain containing 3 (NLRP3), Caspase-1, and the N-terminal fragment of gasdermin D (GSDMD-N) were measured using Western blotting. Interleukin (IL)-1β, IL-6, IL-10, and tumor necrosis factor (TNF)-α levels in cells were measured using enzyme-linked immunosorbent assay kits. The N⁶-methyladenosine (m⁶A) modification was analyzed using the methylated RNA immunoprecipitation assay. NLRP3 activator, nigericin, was used to overexpress NLRP3. LPS treatment significantly enhanced the pyroptosis in 1321N1 cells, increased the levels of TNF-α, IL-1β, and IL-6, and decreased the levels of IL-10. The protein expression levels of NLRP3, SDC-1, GSDMD-N, and Caspase-1 were also increased. Emodin treatment decreased the levels of TNF-α, IL-1β, IL-6, NLRP3, SDC-1, GSDMD-N, and Caspase-1, while increasing the levels of IL-10 in LPS-treated 1321N1 cells. Nigericin reversed the effects of emodin. Furthermore, emodin upregulated m⁶A levels in NLRP3 by increasing the expression of methyltransferase-like 3 (METTL3). Meanwhile, knockdown of METTL3 reversed the effects of emodin on the mRNA expression and stability of NLRP3. Therefore, emodin inhibits the inflammation and pyroptosis of LPS-treated 1321N1 cells by inactivating METTL3-mediated NLRP3 expression.

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.

STING1 in sepsis: Mechanisms, functions, and implications

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

Targeting the "sweet spot" in septic shock - A perspective on the endothelial glycocalyx regulating proteins Heparanase-1 and -2

Sepsis is a life-threatening syndrome caused by a pathological host response to an infection that eventually, if uncontrolled, leads to septic shock and ultimately, death. In sepsis, a massive aggregation of pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) cause a cytokine storm. The endothelial glycocalyx (eGC) is a gel like layer on the luminal side of the endothelium that consists of proteoglycans, glycosaminoglycans (GAG) and plasma proteins. It is synthesized by endothelial cells and plays an active role in the regulation of inflammation, permeability, and coagulation. In sepsis, early and profound injury of the eGC is observed and circulating eGC components correlate directly with clinical severity and outcome. The activity of the heparan sulfate (HS) specific glucuronidase Heparanase-1 (Hpa-1) is elevated in sepsis, resulting in shedding of heparan sulfate (HS), a main GAG of the eGC. HS induces endothelial barrier breakdown and accelerates systemic inflammation. Lipopolysaccharide (LPS), a PAMP mainly found on the surface of gram-negative bacteria, activates TLR-4, which results in cytokine production and further activation of Hpa-1. Hpa-1 shed HS fragments act as DAMPs themselves, leading to a vicious cycle of inflammation and end-organ dysfunction such as septic cardiomyopathy and encephalopathy. Recently, Hpa-1's natural antagonist, Heparanase-2 (Hpa-2) has been identified. It has no intrinsic enzymatic activity but instead acts by reducing inflammation. Hpa-2 levels are reduced in septic mice and patients, leading to an acquired imbalance of Hpa-1 and Hpa-2 paving the road towards a therapeutic intervention. Recently, the synthetic antimicrobial peptide 19-2.5 was described as a promising therapy protecting the eGC by inhibition of Hpa-1 activity and HS shed fragments in animal studies. However, a recombinant Hpa-2 therapy does not exist to the present time. Therapeutic plasma exchange (TPE), a modality already tested in clinical practice, effectively removes injurious mediators, e.g., Hpa-1, while replacing depleted protective molecules, e.g., Hpa-2. In critically ill patients with septic shock, TPE restores the physiological Hpa-1/Hpa-2 ratio and attenuates eGC breakdown. TPE results in a significant improvement in hemodynamic instability including reduced vasopressor requirement. Although promising, further studies are needed to determine the therapeutic impact of TPE in septic shock.

Microbial transformation of pentacyclic triterpenes for anti-inflammatory agents on the HMGB1 stimulated RAW 264.7 cells by Streptomyces olivaceus CICC 23628

High mobility group box-1 protein (HMGB1) is a typical Damage-Associated Molecular Patterns (DAMPs) released in response to cellular inflammation. The pentacyclic triterpenes (PTs) are considered to be the natural inhibitors against HMGB1-related inflammation. To explore new lead compounds of PTs as anti-inflammatory agents, biotransformation of four PTs by Streptomyces olivaceus CICC 23628 was investigated in this study. As a result, thirteen unique 3,4-seco-triterpenes metabolites were isolated and twelve of them were first identified and reported. Structures of metabolites were determined based on HR-ESI-MS, 1D/2D NMR, and single-crystal X-ray diffraction. Furthermore, all compounds were subjected to the bioassay on the model of HMGB1-stimulated RAW 264.7 cells to evaluate their anti-inflammatory activity through nitric oxide (NO) inhibition activity. Compounds 3b (3,4-seco-olean-12-en-4,21α,22β,24-tetrahydroxy-ol-3-oic acid) and 2b (3,4-seco-olean-12-en-4,21β,22β,24,29-pentahydroxy-ol-3-oic acid) exhibited NO inhibitory activity with IC₅₀ values of 15.94 μM and 36.00 μM, respectively. Thus, indicating their potential as HMGB1 inhibitors and in developing potent anti-inflammatory agents. This work provides an operationally simple, efficient method for the rapid diversification of the PTs scaffold for a variety of distinctive 3,4-seco-triterpenes to facilitate the discovery of potential anti-inflammatory compounds.

Peptide VSAK maintains tissue glucose uptake and attenuates pro-inflammatory responses caused by LPS in an experimental model of the systemic inflammatory response syndrome: a PET study

The present investigation using Positron Emission Tomography shows how peptide VSAK can reduce the detrimental effects produced by lipopolysaccharides in Dutch dwarf rabbits, used to develop the Systemic Inflammatory Response Syndrome (SIRS). Animals concomitantly treated with lipopolysaccharides (LPS) and peptide VSAK show important protection in the loss of radiolabeled-glucose uptake observed in diverse organs when animals are exclusively treated with LPS. Treatment with peptide VSAK prevented the onset of changes in serum levels of glucose and insulin associated with the establishment of SIRS and the insulin resistance-like syndrome. Treatment with peptide VSAK also allowed an important attenuation in the circulating levels of pro-inflammatory molecules in LPS-treated animals. As a whole, our data suggest that peptide VSAK might be considered as a candidate in the development of new therapeutic possibilities focused on mitigating the harmful effects produced by lipopolysaccharides during the course of SIRS.

Impact of Sex Differences on Mortality in Patients With Sepsis After Trauma: A Nationwide Cohort Study

Objective

Sepsis is the leading cause of death in intensive care units, and sepsis after trauma is associated with increased mortality rates. However, the characteristics of sepsis after trauma remain unknown, and the influence of sex on mortality remains controversial. This study aimed to assess the role of sex in in-hospital mortality in patients with sepsis after trauma.

Methods

We performed a retrospective cohort study involving several emergency hospitals (n=288) in Japan. The data of patients with trauma who developed sepsis after admission from 2004 to 2019 were obtained from the Japan Trauma Data Bank. We divided the patients into two groups according to sex and compared their in-hospital mortality. We also performed subgroup analysis limited to the elderly population (age ≥ 65 years) and evaluated in-hospital mortality between men and women.

Results

A total of 1935 patients met the inclusion criteria during the study period. Of these, 1204 (62.2%) were allocated to the male group and 731 (37.8%) to the female group. Multivariable Cox proportional-hazards analysis showed a significantly lower risk of in-hospital mortality in the female group than in the male group (hazard ratio (HR): 0.74, 95% confidence interval (CI): 0.62–0.89; p=0.001). In the subgroup analysis, multivariable Cox proportional hazards still showed significantly lower risks of in-hospital mortality in the female group than in the male group (HR: 0.72, 95% CI: 0.58–0.88; p=0.002).

Conclusion

The present study shows a significantly increased survival in the female group when compared to that in the male group of patients with sepsis after trauma. The underlying mechanism remains unclear, and further investigations are required.

Narciclasine attenuates sepsis-induced myocardial injury by modulating autophagy

Acute myocardial injury (AMI) is often secondary to sepsis, which is a life-threatening disease associated with severe cardiac inflammation. Narciclasine, a plant alkaloid isolated from different members of the Amaryllidaceae family, has been extensively characterized as an antitumor and anti-inflammatory compound. In addition, autophagy is critical for sepsis-induced myocardial injury. However, the role and mechanism of autophagy by which narciclasine confers cardioprotection are still unclear. The present study aimed to investigate the underlying mechanism by which narciclasine affects the pathogenesis of sepsis-induced myocardial injury. Narciclasine effectively attenuated LPS-induced myocardial inflammation in vitro and in vivo. In addition, narciclasine protected cardiac function and suppressed the expression of inflammatory cytokines in LPS-induced heart tissue. Furthermore, narciclasine upregulated LPS-induced autophagic activity, and the autophagy inhibitor 3-MA abrogated narciclasine-mediated protection against LPS-induced AMI. Importantly, narciclasine exerted an inhibitory effect on the JNK signaling pathway, and JNK activity was tightly associated with narciclasine-induced autophagy and the consequent protective effects during AMI. Taken together, our findings indicate that narciclasine protects against LPS-induced AMI by inducing JNK-dependent autophagic flux; hence, narciclasine may be an effective and novel agent for the clinical treatment of sepsis-induced myocardial injury.

Role of Damage-Associated Molecular Patterns in Septic Acute Kidney Injury, From Injury to Recovery

Damage-associated molecular patterns (DAMPs) are a group of immunostimulatory molecules, which take part in inflammatory response after tissue injury. Kidney-specific DAMPs include Tamm-Horsfall glycoprotein, crystals, and uromodulin, released by tubular damage for example. Non-kidney-specific DAMPs include intracellular particles such as nucleus [histones, high-mobility group box 1 protein (HMGB1)] and cytosol parts. DAMPs trigger innate immunity by activating the NRLP3 inflammasome, G-protein coupled class receptors or the Toll-like receptor. Tubular necrosis leads to acute kidney injury (AKI) in either septic, ischemic or toxic conditions. Tubular necrosis releases DAMPs such as histones and HMGB1 and increases vascular permeability, which perpetuates shock and hypoperfusion via Toll Like Receptors. In acute tubular necrosis, intracellular abundance of NADPH may explain a chain reaction where necrosis spreads from cell to cell. The nature AKI in intensive care units does not have preclinical models that meet a variation of blood perfusion or a variation of glomerular filtration within hours before catecholamine infusion. However, the dampening of several DAMPs in AKI could provide organ protection. Research should be focused on the numerous pathophysiological pathways to identify the relative contribution to renal dysfunction. The therapeutic perspectives could be strategies to suppress side effect of DAMPs and to promote renal function regeneration.

Cytokine Storm as a Cellular Response to dsDNA Breaks: A New Proposal

Pathogenesis of cytokine storm is poorly understood. In this article we propose a new mechanism and suggest innovative therapeutic avenues for its prevention. We have reported that particles of cell-free chromatin (cfCh) that are released from the billions of cells that die in the body everyday can illegitimately integrate into genomes of healthy cells to trigger dsDNA breaks. The latter leads to apoptosis and/or intense activation of inflammatory cytokines in the affected cells. We hypothesise that a similar phenomenon of dsDNA breaks and inflammation is involved in cytokine storm. The abundant cfCh particles that are released from dying host cells following viral/microbial invasion initiate a cascading effect of more cell death resulting in a vicious cycle of further DNA damage, apoptosis and hyper-inflammation which culminate in cytokine storm. We propose that this unrelenting vicious cycle of cellular DNA damage and cytokine storm may be the underlying cause of high mortality from severe COVID-19. We discuss results of our preclinical studies wherein we have shown that endotoxin induced cytokine storm in mice can be reversed by three different agents that have the ability to inactivate cfCh. These agents may be worthy of investigation in clinical trials to reduce mortality from COVID-19.

Single-cell deconstruction of post-sepsis skeletal muscle and adipose tissue microenvironments

BACKGROUND

Persistent loss of skeletal muscle mass and function as well as altered fat metabolism are frequently observed in severe sepsis survivors. Studies examining sepsis-associated tissue dysfunction from the perspective of the tissue microenvironment are scarce. In this study, we comprehensively assessed transcriptional changes in muscle and fat at single-cell resolution following experimental sepsis induction.

METHODS

Skeletal muscle and visceral white adipose tissue from control mice or mice 1 day or 1 month following faecal slurry-induced sepsis were used. Single cells were mechanically and enzymatically prepared from whole tissue, and viable cells were further isolated by fluorescence activated cell sorting. Droplet-based single-cell RNA-sequencing (scRNA-seq; 10× Genomics) was used to generate single-cell gene expression profiles of thousands of muscle and fat-resident cells. Bioinformatics analyses were performed to identify and compare individual cell populations in both tissues.

RESULTS

In skeletal muscle, scRNA-seq analysis classified 1438 single cells into myocytes, endothelial cells, fibroblasts, mesenchymal stem cells, macrophages, neutrophils, T-cells, B-cells, and dendritic cells. In adipose tissue, scRNA-seq analysis classified 2281 single cells into adipose stem cells, preadipocytes, endothelial cells, fibroblasts, macrophages, dendritic cells, B-cells, T-cells, NK cells, and gamma delta T-cells. One day post-sepsis, the proportion of most non-immune cell populations was decreased, while immune cell populations, particularly neutrophils and macrophages, were highly enriched. Proportional changes of endothelial cells, neutrophils, and macrophages were validated using faecal slurry and cecal ligation and puncture models. At 1 month post-sepsis, we observed persistent enrichment/depletion of cell populations and further uncovered a cell-type and tissue-specific ability to return to a baseline transcriptomic state. Differential gene expression analyses revealed key genes and pathways altered in post-sepsis muscle and fat and highlighted the engagement of infection/inflammation and tissue damage signalling. Finally, regulator analysis identified gonadotropin-releasing hormone and Bay 11-7082 as targets/compounds that we show can reduce sepsis-associated loss of lean or fat mass.

CONCLUSIONS

These data demonstrate persistent post-sepsis muscle and adipose tissue disruption at the single-cell level and highlight opportunities to combat long-term post-sepsis tissue wasting using bioinformatics-guided therapeutic interventions.

Oxidation-Specific Epitopes (OSEs) Dominate the B Cell Response in Murine Polymicrobial Sepsis

In murine abdominal sepsis by colon ascendens stent peritonitis (CASP), a strong increase in serum IgM and IgG antibodies was observed, which reached maximum values 14 days following sepsis induction. The specificity of this antibody response was studied in serum and at the single cell level using a broad panel of bacterial, sepsis-unrelated as well as self-antigens. Whereas an antibacterial IgM/IgG response was rarely observed, studies at the single-cell level revealed that IgM antibodies, in particular, were largely polyreactive. Interestingly, at least 16% of the IgM mAbs and 20% of the IgG mAbs derived from post-septic mice showed specificity for oxidation-specific epitopes (OSEs), which are known targets of the innate/adaptive immune response. This identifies those self-antigens as the main target of B cell responses in sepsis.

The Critical Roles and Mechanisms of Immune Cell Death in Sepsis

Sepsis was first described by the ancient Greek physicians over 2000 years ago. The pathophysiology of the disease, however, is still not fully understood and hence the mortality rate is still unacceptably high due to lack of specific therapies. In the last decade, great progress has been made by shifting the focus of research from systemic inflammatory response syndrome (SIRS) to multiple organ dysfunction syndrome (MODS). Sepsis has been re-defined as infection-induced MODS in 2016. How infection leads to MODS is not clear, but what mediates MODS becomes the major topic in understanding the molecular mechanisms and developing specific therapies. Recently, the mechanism of infection-induced extensive immune cell death which releases a large quantity of damage-associated molecular patterns (DAMPs) and their roles in the development of MODS as well as immunosuppression during sepsis have attracted much attention. Growing evidence supports the hypothesis that DAMPs, including high-mobility group box 1 protein (HMGB1), cell-free DNA (cfDNA) and histones as well as neutrophil extracellular traps (NETs), may directly or indirectly contribute significantly to the development of MODS. Here, we provide an overview of the mechanisms and consequences of infection-induced extensive immune cell death during the development of sepsis. We also propose a pivotal pathway from a local infection to eventual sepsis and a potential combined therapeutic strategy for targeting sepsis.

Coronavirus (Covid-19) sepsis: revisiting mitochondrial dysfunction in pathogenesis, aging, inflammation, and mortality

Background

Decline in mitochondrial function occurs with aging and may increase mortality. We discuss mitochondrial contribution to Covid-19 sepsis, specifically the complex interaction of innate immune function, viral replication, hyper-inflammatory state, and HIF-α/Sirtuin pathways.

Methods

Articles from PubMed/Medline searches were reviewed using the combination of terms “SARS-CoV-2, Covid-19, sepsis, mitochondria, aging, and immunometabolism”.

Results

Evidence indicates that mitochondria in senescent cells may be dysfunctional and unable to keep up with hypermetabolic demands associated with Covid-19 sepsis. Mitochondrial proteins may serve as damage-associated molecular pattern (DAMP) activating innate immunity. Disruption in normal oxidative phosphorylation pathways contributes to elevated ROS which activates sepsis cascade through HIF-α/Sirtuin pathway. Viral–mitochondrial interaction may be necessary for replication and increased viral load. Hypoxia and hyper-inflammatory state contribute to increased mortality associated with Covid-19 sepsis.

Conclusions

Aging is associated with worse outcomes in sepsis. Modulating Sirtuin activity is emerging as therapeutic agent in sepsis. HIF-α, levels of mitochondrial DNA, and other mitochondrial DAMP molecules may also serve as useful biomarker and need to be investigated. These mechanisms should be explored specifically for Covid-19-related sepsis. Understanding newly discovered regulatory mechanisms may lead to the development of novel diagnostic and therapeutic targets.

Targeting of G-protein coupled receptors in sepsis

The Third International Consensus Definitions (Sepsis-3) define sepsis as life-threatening multi-organ dysfunction caused by a dysregulated host response to infection. Sepsis can progress to septic shock-an even more lethal condition associated with profound circulatory, cellular and metabolic abnormalities. Septic shock remains a leading cause of death in intensive care units and carries a mortality of almost 25%. Despite significant advances in our understanding of the pathobiology of sepsis, therapeutic interventions have not translated into tangible differences in the overall outcome for patients. Clinical trials of antagonists of various pro-inflammatory mediators in sepsis have been largely unsuccessful in the past. Given the diverse physiologic roles played by G-protein coupled receptors (GPCR), modulation of GPCR signaling for the treatment of sepsis has also been explored. Traditional pharmacologic approaches have mainly focused on ligands targeting the extracellular domains of GPCR. However, novel techniques aimed at modulating GPCR intracellularly through aptamers, pepducins and intrabodies have opened a fresh avenue of therapeutic possibilities. In this review, we summarize the diverse roles played by various subfamilies of GPCR in the pathogenesis of sepsis and identify potential targets for pharmacotherapy through these novel approaches.

Intravenous Immunoglobulin G Modulates the Expression of Sepsis-Induced Coagulopathy Factors and Increases Serum IgM Levels: A Prospective, Single-Center Intervention Study

Sepsis and sepsis-related multiple organ failure are major causes of mortality in intensive care unit (ICU) settings. This study aimed to determine the effect of intravenous immunoglobulin G (IVIgG) on different types of immunoglobulin and anti-coagulant factor types in sepsis patients. A single-center observational study of patients with sepsis, severe sepsis, or septic shock was conducted from August 2008 to March 2013. Patients were divided into the IVIgG (immunoglobulin G [IgG] <870 mg/dL; lower normal range) and non-IVIgG (IgG ≥870 mg/dL) groups. The IVIgG group received IVIgG for three days, and other standard medications. Serial measurements were taken of serum IgG, immunoglobulin A (IgA), immunoglobulin M (IgM), total plasminogen activator inhibitor 1 (tPAI-1), and protein C. Patients in the IVIgG treatment group had significantly higher serum IgM level on Days 4 and 7 than on Day 1, but no significant changes in IgM levels were observed in patients in the non-IVIgG group. Patients in the IVIgG treatment had lower tPAI-1 levels on Days 4 and 7 than on Day 1 and increased protein C levels on Day 7 compared to those on Days 1 and 4. There were no significant differences in tPAI-1 levels or protein C levels in the non-IVIgG group, although a similar trend was observed. IVIgG administration increased patients' serum IgM and protein C levels and decreased their serum tPAI-1 levels. IVIgG has potential application for preventing sepsis-induced coagulopathy and disseminated intravascular coagulation.

DAMPs and NETs in Sepsis

Sepsis is a deadly inflammatory syndrome caused by an exaggerated immune response to infection. Much has been focused on host response to pathogens mediated through the interaction of pathogen-associated molecular patterns (PAMPs) and pattern recognition receptors (PRRs). PRRs are also activated by host nuclear, mitochondrial, and cytosolic proteins, known as damage-associated molecular patterns (DAMPs) that are released from cells during sepsis. Some well described members of the DAMP family are extracellular cold-inducible RNA-binding protein (eCIRP), high mobility group box 1 (HMGB1), histones, and adenosine triphosphate (ATP). DAMPs are released from the cell through inflammasome activation or passively following cell death. Similarly, neutrophil extracellular traps (NETs) are released from neutrophils during inflammation. NETs are webs of extracellular DNA decorated with histones, myeloperoxidase, and elastase. Although NETs contribute to pathogen clearance, excessive NET formation promotes inflammation and tissue damage in sepsis. Here, we review DAMPs and NETs and their crosstalk in sepsis with respect to their sources, activation, release, and function. A clear grasp of DAMPs, NETs and their interaction is crucial for the understanding of the pathophysiology of sepsis and for the development of novel sepsis therapeutics.

Anti-inflammatory activity of β-caryophyllene combined with docosahexaenoic acid in a model of sepsis induced by Staphylococcus aureus in mice

BACKGROUND

Sepsis is a set of serious organic manifestations caused by an infection, whose progression culminates in exacerbated inflammation and oxidative stress, poor prognosis, and high hospital costs. Antioxidants used against sepsis have been evaluated, including essential oils such as β-caryophyllene (BCP), and polyunsaturated fatty acids, such as docosahexaenoic acid (DHA). The aim of this study was to evaluate the anti-inflammatory activity of the association of these two compounds.

RESULTS

Treatment with BCP-DHA, at a dose of 200 μL/animal, significantly inhibited the migration of neutrophils in a Cg-induced peritonitis model. After Staphylococcus aureus infection, in the groups treated with BCP-DHA there was a significant decrease in the total and differential count of leukocytes, increased expression of cytokines TNF-α and IFN-γ in treated groups, an increase of IL-4 and IL-5 in B/D and B/D + SA groups, and an augmentation of IL-6 and IL-12 groups in B/D + SA groups. Histological and bacterial analysis revealed lower neutrophil migration and lower bacterial load in the infected and treated groups.

CONCLUSION

In general, the BCP-DHA association presented anti-inflammatory activity against two different models of acute inflammation and infection, showing promising potential as a therapeutic adjuvant in sepsis. © 2019 Society of Chemical Industry.

Extracellular Mitochondrial DNA and N-Formyl Peptides in Trauma and Critical Illness: A Systematic Review

OBJECTIVES

Extracellular mitochondrial DNA and N-formyl peptides released following tissue damage may contribute to systemic inflammation through stimulation of the innate immune system. In this review, we evaluate existing in vivo human data regarding a role for mitochondrial DNA and N-formyl peptides in producing systemic inflammation in trauma and critical illness, investigate the utility of these molecules in risk prediction and clinical decision support, and provide suggestions for standardization of future research.

DATA SOURCES

PubMed, Embase (1971-2017).

STUDY SELECTION

Studies measuring extracellular mitochondrial DNA and/or N-formyl peptides in acutely ill patients.

DATA EXTRACTION

Fifty-four studies were analyzed. Data extracted included article characteristics, methods, results, and performance in clinical prediction.

DATA SYNTHESIS

The most common patient types investigated were trauma (19 studies) and sepsis (eight). In studies comparing patient mitochondrial DNA or N-formyl peptide levels to healthy controls, 38 (90.5%) reported significantly elevated mitochondrial DNA levels in patients at first reported time point, as did the one study making this comparison for N-formyl peptides. Nine studies (81.8%) reported significantly elevated plasma/serum mitochondrial DNA levels in at least one time point in patients who developed inflammatory complications of their primary pathology compared with patients without inflammatory complications. For the ability of mitochondrial DNA to predict complications or outcomes, the area under the curve was 0.7 or greater in 84.6% of receiver operating characteristic curves, and 92.9% of odds, adjusted odds, risk, and hazard ratios were statistically significant.

CONCLUSIONS

Extracellular mitochondrial DNA levels are elevated early in patients' hospital courses in many acute illnesses and are higher in patients who develop inflammatory complications. Elevated mitochondrial DNA levels may be clinically useful in risk prediction and clinical decision support systems. Further research is needed to determine the role of extracellular N-formyl peptides in systemic inflammation and their possible clinical utility.

Immune Modulation and Immune-Mediated Pathogenesis of Emerging Tickborne Banyangviruses

In the last decade, the emergence of several, novel tickborne viruses have caused significant disease in humans. Of interest are the tickborne banyangviruses: Severe fever with thrombocytopenia syndrome virus (SFTSV), Heartland virus (HRTV), and Guertu virus (GTV). SFTSV and HRTV infection in humans cause viral hemorrhagic fever-like disease leading to mortality rates ranging from 6–30% of the cases. The systemic inflammatory response syndrome (SIRS) associated with SFTSV infection is hypothesized to contribute significantly to pathology seen in patients. Despite the severe disease caused by HRTV and SFTSV, there are no approved therapeutics or vaccines. Investigation of the immune response during and following infection is critical to the generation of fully protective vaccines and/or supportive treatments, and overall understanding of viral immune evasion mechanisms may aid in the development of a new class of therapeutics.

Dialysate cell-free mitochondrial DNA fragments as a marker of intraperitoneal inflammation and peritoneal solute transport rate in peritoneal dialysis

BACKGROUND

Mitochondrial DNA (mtDNA) released into extracellular subsequent to cell injury and death can promote inflammation in patients and animal models. However, the effects of peritoneal dialysate cell-free mtDNA on intraperitoneal inflammation and peritoneal solute transport rate (PSTR) in peritoneal dialysis (PD) patients remain unclear.

METHODS

We select the incident patients who began PD therapy between January 1, 2009, and December 30, 2010. Peritoneal dialysate was collected at the time of peritoneal equilibration test. The cell-free mtDNA, IL-6, IL-17A, TNF-α and IFN-γ were measured. All patients were followed till December 2017. The results were compared with PSTR and patient survival.

RESULTS

One hundred and eighty-nine patients were included in the study. The average age was 47.1 ± 13.5 years, 55.6% of the patients were males. The average PSTR was 0.66 ± 0.12, the median dialysate mtDNA levels were 4325 copies/ul. The median concentrations of IL-6, IL-17A, TNF-α and IFN-γ were 25.9, 10.8, 25.8 and 17.9 pg/ml, respectively. We found that dialysate mtDNA was significantly correlated with PSTR (r = 0.461, P < 0.001), IL-6 (r = 0.568, P < 0.001), TNF-α (r = 0.454, P < 0.001) and IFN-γ (r = 0.203, P = 0.005). After adjustment for multiple covariates, dialysate mtDNA levels were independently correlated with IL-6 and PSTR. Dialysate mtDNA levels were not associated with patient survival.

CONCLUSIONS

We found that dialysate mtDNA levels correlated with the degree of intraperitoneal inflammatory status in PD patients. Peritoneal effluent mtDNA was an independent determinant of PSTR but did not affect patient survival.

Mitochondrial integrity in neurodegeneration

The mitochondrion is a unique organelle with a diverse range of functions. Mitochondrial dysfunction is a key pathological process in several neurodegenerative diseases. Mitochondria are mostly important for energy production; however, they also have roles in Ca²⁺ homeostasis, ROS production, and apoptosis. There are two major systems in place, which regulate mitochondrial integrity, mitochondrial dynamics, and mitophagy. These two processes remove damaged mitochondria from cells and protect the functional mitochondrial population. These quality control systems often become dysfunctional during neurodegenerative diseases, such as Parkinson's and Alzheimer's disease, causing mitochondrial dysfunction and severe neurological symptoms.

A pro-inflammatory role of Fcα/μR on marginal zone B cells in sepsis

Fc receptors play important roles for a wide array of immune responses. In contrast to the well-defined Fcγ and Fcε receptors, the molecular and functional characteristics of Fc receptors for IgA and IgM have remained incompletely understood for years. Recent progress has unveiled the characteristics of Fc receptors for IgA and IgM, including Fcα/μ receptor (Fcα/μR) (CD351), polymeric immunoglobulin receptor (poly-IgR), Fcα receptor (FcαRI) (CD89) and Fcμ receptor (FcμR). In this review, we summarize the molecular and functional characteristics of Fcα/μR in comparison with poly-IgR, FcμR and FcαRI, and focus particularly on the pro-inflammatory function of Fcα/μR expressed on marginal zone B cells in sepsis.

Natriuretic Peptides in Cardiac Anesthesia and Intensive Care

Natriuretic peptides, predominantly B-type, are widely used in cardiology as prognostic and diagnostic biomarkers or, much less often, as a substantive treatment tool. They are hormones that are produced mainly in the myocardium in response to overload and ischemia, and their level quite accurately reflects the degree of myocardial dysfunction. Although their use in cardiac anesthesia and intensive care setting seems to be very beneficial for assessing the risk of acute disturbance of myocardial function or its laboratory monitoring, the actual significance of natriuretic peptides in this area is not yet recognized. This is due to the lack of clear diagnostic and prognostic values for these biomarkers supported by high-quality researches. On the basis of the available data, main advantages, existing difficulties, and most effective ways of using natriuretic peptides for determining the risk of heart surgery and assessing the severity of sepsis, pneumonia, and other critical conditions have been discussed in this review. In addition, the expediency of using natriuretic peptides as target parameters for goal-oriented therapy and as a substantive tool for treatment is considered.

[Viewing sepsis and autoimmune disease in relation with infection and NETs-formation]

Neutrophil has been widely recognized as body's first line of defence against pathogens. NETosis was first reported in 2004 as a programmed cell death of neutrophil and distinguished from apoptosis and necrosis. This phenomenon has been already observed in both basic and clinical research. NETosis is induced by various stimulants such as PMA, IL-8, DAMPs/PAMPs, bacteria, and antigen-antibody complex including self-antibody such as ANCA. It is known that there are two types of NETosis following bacterial infections. Although both of them have the ability to capture and kill bacteria, they also damage the host tissues. The inhibition of the NETs-related enzymes prevents the NETs formation at that time. The production of O₂^- from respiratory burst of neutrophils triggers NETs formation. In the first type of NETosis, neutrophils are completely collapsed, while in the second type, they maintain the morphology and the ability of phagocytosis. However, bacteria can escape from NETs by degrading NETs with their secreting nucleases. Thus the animal models of infection, using these bacteria, oftentimes suffer from severe infectious diseases. Human CGD (Chronic Granulomatosis Disease) patients who do not have Nox2 are immunocompromised, and highly susceptible to infection due to the defect of NETs formation. On the other hand, SLE patients are unable to break down the NETs as their serum inhibits the DNase1 activity, which results in autoantibody generation against NETs as well as self-DNA. It is getting clear that there is a relationship between inflammatory diseases, including infectious diseases, Sepsis and autoimmune diseases, and NETs. Therefore, it is important to re-evaluate the inflammatory disorders from NETs' perspective, and to incorporate the emerging concepts for better understanding the mechanisms involved.

Cellular Stress Responses and Monitored Cellular Activities

To survive, organisms require mechanisms that enable them to sense changes in the outside environment, introduce necessary responses, and resist unfavorable distortion. Consequently, through evolutionary adaptation, cells have become equipped with the apparatus required to monitor their fundamental intracellular processes and the mechanisms needed to try to offset malfunction without receiving any direct signals from the outside environment. It has been shown recently that eukaryotic cells are equipped with a special mechanism that monitors their fundamental cellular functions and that some pathogenic proteobacteria can override this monitoring mechanism to cause harm. The monitored cellular activities involved in the stressed intracellular response have been researched extensively in Caenorhabditis elegans, where discovery of an association between key mitochondrial activities and innate immune responses was named "cellular associated detoxification and defenses (cSADD)." This cellular surveillance pathway (cSADD) oversees core cellular activities such as mitochondrial respiration and protein transport into mitochondria, detects xenobiotics and invading pathogens, and activates the endocrine pathways controlling behavior, detoxification, and immunity. The cSADD pathway is probably associated with cellular responses to stress in human inflammatory diseases. In the critical care field, the pathogenesis of lethal inflammatory syndromes (e.g., respiratory distress syndromes and sepsis) involves the disturbance of mitochondrial respiration leading to cell death. Up-to-date knowledge about monitored cellular activities and cSADD, especially focusing on mitochondrial involvement, can probably help fill a knowledge gap regarding the pathogenesis of lethal inflammatory syndromes in the critical care field.

CIRP increases ICAM-1+ phenotype of neutrophils exhibiting elevated iNOS and NETs in sepsis

Sepsis represents uncontrolled inflammation due to an infection. Cold-inducible RNA-binding protein (CIRP) is a stress-induced damage-associated molecular pattern (DAMP). A subset of neutrophils expressing ICAM-1⁺ neutrophils was previously shown to produce high levels of reactive oxygen species. The role of CIRP for the development and function of ICAM-1⁺ neutrophils during sepsis is unknown. We hypothesize that CIRP induces ICAM-1 expression in neutrophils causing injury to the lungs during sepsis. Using a mouse model of cecal ligation and puncture (CLP)-induced sepsis, we found increased expression of CIRP and higher frequencies and numbers of ICAM-1⁺ neutrophils in the lungs. Conversely, the CIRP^-/- mice showed significant inhibition in the frequencies and numbers of ICAM-1⁺ neutrophils in the lungs compared to wild-type (WT) mice in sepsis. In vitro treatment of bone marrow-derived neutrophils (BMDN) with recombinant murine CIRP (rmCIRP) significantly increased ICAM-1⁺ phenotype in a time- and dose-dependent manner. The effect of rmCIRP on increasing frequencies of ICAM-1⁺ neutrophils was significantly attenuated in BMDN treated with anti-TLR4 Ab or NF-κB inhibitor compared, respectively, with BMDN treated with isotype IgG or DMSO. The frequencies of iNOS producing and neutrophil extracellular traps (NETs) forming phenotypes in rmCIRP-treated ICAM-1⁺ BMDN were significantly higher than those in ICAM-1^- BMDN. Following sepsis the ICAM-1⁺ neutrophils in the lungs showed significantly higher levels of iNOS and NETs compared to ICAM-1^- neutrophils. We further revealed that ICAM-1 and NETs were co-localized in the neutrophils treated with rmCIRP. CIRP^-/- mice showed significant improvement in their survival outcome (78% survival) over that of WT mice (48% survival) in sepsis. Thus, CIRP could be a novel therapeutic target for regulating iNOS producing and NETs forming ICAM-1⁺ neutrophils in the lungs during sepsis.

Cardiovascular dysfunction in sepsis at the dawn of emerging mediators

Subcellular dysfunction and impaired metabolism derived from the complex interaction of cytokines and mediators with cellular involvement are on the basis of the cardiovascular response to sepsis. The lethal consequences of an infection are intimately related to its ability to spread to other organ sites and the immune system of the host. About one century ago, William Osler (1849-1919), a Canadian physician, remarkably defined the sequelae of the host response in sepsis: "except on few occasions, the patient appears to die from the body's response to infection rather than from it." Cardiac dysfunction has received considerable attention to explain the heart failure in patients progressing from infection to sepsis, but our understanding of the processes remains limited. In fact, most concepts are linked to a mechanical concept of the sarcomeric structure, and physiological data seems to be often disconnected. Cytokines, prostanoids, and nitric oxide release are high direct impact factors, but coronary circulation and cardiomyocyte physiology also play a prominent role in modulating the effects of monocyte adhesion and infiltration. Damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs) are involved in the host response. The identification of microRNAs, as well as the cyclic activation of the inflammatory cascade, has further added complexity to the scene. In this review, we delineate the current concepts of cellular dysfunction of the cardiomyocyte in the setting of sepsis and consider potential therapeutic strategies.