Single-cell transcriptome profiling of sepsis identifies HLA-DR^(low)S100A^(high)monocytes with immunosuppressive function

Background Sustained yet intractable immunosuppression is commonly observed in septic patients,resulting in aggravated clinical outcomes.However,due to the substantial heterogeneity within septic patients,precise indicators in deciphering clinical trajectories and immunological alterations for septic patients remain largely lacking.Methods We adopted cross-species,single-cell RNA sequencing(scRNA-seq)analysis based on two published datasets containing circulating immune cell profile of septic patients as well as immune cell atlas of murine model of sepsis.Flow cytometry,laser scanning confocal microscopy(LSCM)imaging and Western blotting were applied to identify the presence of S100A9^(+)monocytes at protein level.To interrogate the immunosuppressive function of this subset,splenic monocytes isolated from septic wild-type or S100a9^(–/–)mice were co-cultured with naive CD4^(+)T cells,followed by proliferative assay.Pharmacological inhibition of S100A9 was implemented using Paquinimod via oral gavage.Results scRNA-seq analysis of human sepsis revealed substantial heterogeneity in monocyte compartments following the onset of sepsis,for which distinct monocyte subsets were enriched in disparate subclusters of septic patients.We identified a unique monocyte subset characterized by high expression of S100A family genes and low expression of human leukocyte antigen DR(HLA-DR),which were prominently enriched in septic patients and might exert immunosuppressive function.By combining single-cell transcriptomics of murine model of sepsis with in vivo experiments,we uncovered a similar subtype of monocyte significantly associated with late sepsis and immunocompromised status of septic mice,corresponding to HLA-DR^(low)S100A^(high)monocytes in human sepsis.Moreover,we found that S100A9^(+)monocytes exhibited profound immunosuppressive function on CD4^(+)T cell immune response and blockade of S100A9 using Paquinimod could partially reverse sepsis-induced immunosuppression.Conclusions This study identifies HLA-DR^(low)S100A^(high)monocytes correlated with immunosuppressive state upon septic challenge,inhibition of which can markedly mitigate sepsis-induced immune depression,thereby providing a novel therapeutic strategy for the management of sepsis.

Novel insights for high mobility group box 1 proteinmediated cellular immune response in sepsis:A systemic review

BACKGROUND:High mobility group box 1 protein(HMGB1) is a highly conserved,ubiquitous protein in the nuclei and cytoplasm of nearly all cell types.HMGB1 is secreted into the extracellular milieu and acts as a proinflammatory cytokine.In this article we reviewed briefly the cellular immune response mediated by HMGB1 in inflammation and sepsis.METHODS:This systemic review is mainly based on our own work and other related reports.RESULTS:HMGB1 can actively affect the immune functions of many types of cells including T lymphocytes,regulatory T cells(Tregs),dendritic cells(DCs),macrophages,and natural killer cells(NK cells).Various cellular responses can be mediated by HMGB1 which binds to cell-surface receptors[e.g.,the receptor for advanced glycation end products(RAGE),Toll-like receptor(TLR)2,and TLR4].Anti-HMGB1 treatment,such as anti-HMGB1 polyclonal or monoclonal antibodies,inhibitors(e.g.,ethyl pyruvate) and antagonists(e.g.,A box),can protect against sepsis lethality and give a wider window for the treatment opportunity.CONCLUSION:HMGB1 is an attractive target for the development of new therapeutic strategies in the treatment of patients with septic complications.

Advances in the management of acute liver failure

Acute liver failure(ALF)is an uncommon but dramatic clinical syndrome characterized by hepatic encephalopathy and a bleeding tendency due to abrupt loss of liver function caused by massive or submassive liver necrosis in a patient with a previously healthy liver.The causes of ALF encompass a wide variety of toxic,viral,metabolic,vascular and autoimmune insults to the liver,and identifying the correct cause can be difficult or even impossible.Many patients with ALF develop a cascade of serious complications involving almost every organ system,and death is mostly due to multi-organ failure,hemorrhage,infection,and intracranial hypertension.Fortunately,the outcome of ALF has been improved in the last 3 decades through the specific treatment for the disease of certain etiology,and the advanced intensive care management.For most severely affected patients who fail to recover after treatment,rapid evaluation for transfer to a transplantation center and consideration for liver transplantation is mandatory so that transplantation can be applied before contraindications develop.This review focuses on the recent advances in the understanding of various contributing etiologies,the administration of etiology-specific treatment to alleviate the liver injury,and the management of complications(e.g.,encephalopathy,coagulopathy,cardiovascular instability,respiratory failure,renal failure,sepsis and metabolic disturbance)in patients with ALF.Assessment of the need for liver transplantation is also presented.

Septic encephalopathy: When cytokines interact with acetylcholine in the brain

Sepsis-associated encephalopathy(SAE) is a brain dysfunction that occurs secondary to infection in the bo characterized by alteration of consciousness, ranging from delirium to coma, seizure or focal neurological signs. S involves a number of mechanisms, including neuroinflammation, in which the interaction between cytokines a acetylcholine results in neuronal loss and alterations in cholinergic signaling. Moreover, the interaction also occurs the periphery, accelerating a type of immunosuppressive state. Although its diagnosis is not specific in biochemis and imaging tests, it could potentiate severe outcomes, including increased mortality, cognitive decline, progress immunosuppression, cholinergic anti-inflammatory deficiency, and even metabolic and hydroelectrolyte imbalan Therefore, the bilateral communication between SAE and the multiple peripheral organs and especially the immu system should be emphasized in sepsis management.

Roles of Tregs in development of hepatocellular carcinoma:A meta-analysis

AIM:To assess systematically the association between regulatory T cells(Tregs)and hepatocellular carcinoma(HCC).METHODS:We searched Medline,Embase and Wanfang databases for literature on the populations of Tregs in HCC patients and controls,using the pooled OR and 95%CIs for assessment.There were no limitations with respect to publication date or language.The references of qualifying articles were also searched.We excluded studies with unclear data or overlapping studies.Twenty-three studies met our criteria,and the quality of these studies was assessed using the Scottish Intercollegiate Guidelines Network(SIGN).The meta-analysis of association between Tregs and HCC was undertaken using the random-effects approach,as described by DerSimonian and Laird.Subgroup analysis was performed when at least three studies were available.Potential publication bias was assessed by visual inspection of the funnel plot,and an asymmetric plot suggested possible publication bias.RESULTS:Twenty-three studies with a total of 1279HCC patients and 547 healthy volunteers as controls were enrolled.The frequency of circulating Tregs in HCC patients was 87%higher than in healthy controls(OR=1.87,95%CI:1.49-2.34).The frequency of Tregs in the HCC tumor microenvironment was significantly higher than that in tumor-surrounding tissue and biopsy specimens from healthy livers(OR=4.04,95%CI:2.10-7.79,P=0.000;OR=2.869,95%CI:2.16-3.82,P=0.000).However,subgroup analyses based on the different types of tumors or patient characteristics such as tumor size,tumor number orαfetoprotein(AFP)levels in HCC patients,showed that populations of Tregs as a whole were not significantly changed between groups(P>0.05 for all).CONCLUSION:There is an obvious association between Tregs and pathogenesis of HCC.Further welldesigned clinical studies are warranted to illustrate the potential role of Tregs in HCC.

Comparison of clinical laboratory tests between bacterial sepsis and SARS-CoV-2-associated viral sepsis

Sepsis is a life-threatening condition that is characterized by multiple organ dysfunction due to abnormal host response to various pathogens,like bacteria,fungi and virus.The differences between viral and bacterial sepsis are indeed of great significance to deepen the understanding of the pathogenesis of sepsis,especially under pandemics of SARS-CoV-2 infection.

Development of septic shock and prognostic assessment in critically ill patients with coronavirus disease outside Wuhan, China

BACKGROUND: The study aims to illustrate the clinical characteristics and development of septic shock in intensive care unit(ICU) patients confirmed with severe acute respiratory syndrome coronavirus 2(SARS-Co V-2) infection, and to perform a comprehensive analysis of the association between septic shock and clinical outcomes in critically ill patients with coronavirus disease(COVID-19).METHODS: Patients confirmed with SARS-Co V-2 infection, who were admitted to the ICU of the Third People's Hospital of Shenzhen from January 1 to February 7, 2020, were enrolled. Clinical characteristics and outcomes were compared between patients with and without septic shock.RESULTS: In this study, 35 critically ill patients with COVID-19 were included. Among them, the median age was 64 years(interquartile range [IQR] 59-67 years), and 10(28.4%) patients were female. The median ICU length of stay was 16 days(IQR 8-23 days). Three(8.6%) patients died during hospitalization. Nine(25.7%) patients developed septic shock in the ICU, and these patients had a significantly higher incidence of organ dysfunction and a worse prognosis than patients without septic shock.CONCLUSIONS: Septic shock is associated with a poor outcome in critically ill COVID-19 patients and is one of the hallmarks of the severity of patients receiving ICU care. A dysregulated immune response, uncontrolled infl ammation, and coagulation disorders are strongly associated with the development and progression of COVID-19-related septic shock.

Potential therapy strategy: targeting mitochondrial dysfunction in sepsis

Recently, the definition of sepsis was concluded to be a life-threatening organ dysfunction caused by a dysregulated host response to infection. Severe patients always present with uncorrectable hypotension or hyperlactacidemia, which is defined as septic shock. The new definition emphasizes dysregulation of the host response and multiple organ dysfunction, which is partially attributed to metabolic disorders induced by energy crisis and oxidative stress. Mitochondria are a cellular organelle that are well known as the center of energy production, and mitochondrial damage or dysfunction is commonly induced in septic settings and is a predominant factor leading to a worse prognosis. In the present review, we determine the major mitochondrial disorders from morphology to functions in sepsis. In the following, several clinical or pre-clinical assays for monitoring mitochondrial function are demonstrated according to accumulated evidence, which is the first step of specific therapy targeting to modulate mitochondrial function. Accordingly, various reagents used for regulating mitochondrial enzyme activities and promoting biogenesis have been documented, among which mitochondriatargeted cation, TPP-conjugated antioxidants are the most valuable for future trials and clinical treatment to improve mitochondrial function as they may take advantage of the prognosis associated with septic complications.

Better therapy for combat injury

In modern warfare,therapy for combat injury is a critical issue to improve personnel survival and battle effectiveness.Be limited to the severe circumstance in the distant battlefield,quick and effective treatment cannot be supplied that leads infections,sepsis,multiple organ dysfunction syndrome(MODS)and high mortality.To get a better therapy for combat injury,we summarized several reports that associated with the mechanisms of sepsis and MODS,those published on MMR recently.Chaudry and colleagues reported gender difference in the outcomes of trauma,shock and sepsis.The advantageous outcome in female is due to their hormone milieu.Their accumulating reports indicated estrogen as a beneficial factor for multiple system and organs,including the central nervous system,the cardiopulmonary system,the liver,the kidneys,the immune system,and leads to better survival from sepsis.Thompson et al.reviewed the underlying mechanisms in trauma induced sepsis,which can be concluded as an imbalance of immune response triggered by damage-associated molecular patterns(DAMPs)and other immune modifying agents.They also emphasize immunomodulation as a better therapeutic strategy that might be a potential benefit in regulating the host immune response.Fan et al.have revealed a crucial mechanism underlying lung epithelial and macrophage crosstalk,which involves IL-25 as a mediator.After the injury,lung epithelial secreted IL-25 promotes TNF-αproduction in macrophage leading to acute lung injury(ALI).In addition to a mountain of cytokines,mitochondrial dysfunction in immune cell is another critical risk factor for immune dysfunction during sepsis.Both morphology and function alterations in mitochondria are closely associated with inadequate ATP production,insufficient metabolism process and overloaded ROS production,which lead harm to immune cells and other tissues by triggering oxidative stress.All the above reports discussed mechanisms of sepsis induction after trauma and provided evidence to improve better therapy strategies targeting diverse risk factors.

Effect of high mobility group box-1 protein on immune cells and its regulatory mechanism

High mobility group box-1 protein(HMGB1),which is a nuclear protein,participates in chromatin architecture and transcriptional regulation.When released from cells,HMGB1 also plays a well-established role as a pro-inflammatory mediator during innate immune responses to injury.In the initial stage of injury,there is a release of large quantities of early pro-inflammatory mediators to initiate or perpetuate immune responses against pathogens,but this pro-inflammatory period is transient,and it is followed by a prolonged period of immune suppression.At present,several lines of evidences have suggested that HMGB1 is a late cytokine provoking delayed endotoxin morbidity,which may enhance the production of early proinflammatory mediators,and it can contribute potently to the activation of different immune cells and play a role in the development of host cell-mediated immunity.The biology of HMGB1 has been extensively studied as a pro-inflammatory cytokine of systemic inflammation,however,this review will attempt to provide a summary of the effects of HMGB1 on different immune cells and its regulatory mechanism in acute insults.

Is oxygen therapy beneficial for normoxemic patients with acute heart failure?A propensity score matched study

Background:The clinical efficiency of routine oxygen therapy is uncertain in patients with acute heart failure(AHF)who do not have hypoxemia.The aim of this study was to investigate the association between oxygen therapy and clinical outcomes in normoxemic patients hospitalized with AHF using real-world data.Methods:Normoxemic patients diagnosed with AHF on intensive care unit(ICU)admission from the electronic ICU(eICU)Collaborative Research Database were included in the current study,in which the study population was divided into the oxygen therapy group and the ambient air group.Propensity score matching(PSM)was applied to create a balanced covariate distribution between patients receiving supplemental oxygen and those exposed to ambient air.Linear regression and logistic regression models were performed to assess the associations between oxygen therapy and length of stay(LOS),and all-cause in-hospital as well as ICU mortality rates,respectively.A series of sensitivity and subgroup analyses were conducted to further validate the robustness of our findings.Results:A total of 2922 normoxemic patients with AHF were finally included in the analysis.Overall,42.1%(1230/2922)patients were exposed to oxygen therapy,and 57.9%(1692/2922)patients did not receive oxygen therapy(defined as the ambient air group).After PSM analysis,1122 pairs of patients were matched:each patient receiving oxygen therapy was matched with a patient without receiving supplemental oxygen.The multivariable logistic model showed that there was no significant interaction between the ambient air and oxygen therapy for all-cause in-hospital mortality[odds ratio(OR)=1.30;95%confidence interval(CI)0.92–1.82;P=0.138]or ICU mortality(OR=1.39;95%CI 0.83–2.32;P=0.206)in the post-PSM cohorts.In addition,linear regression analysis revealed that oxygen therapy was associated with prolonged ICU LOS(OR=1.11;95%CI 1.06–1.15;P<0.001)and hospital LOS(OR=1.06;95%CI 1.01–1.10;P=0.009)after PSM.Furthermore,the absence of an effect of supplemental oxygen on mortality was consistent in all subgroups.Conclusions:Routine use of supplemental oxygen in AHF patients without hypoxemia was not found to reduce all cause in-hospital mortality or ICU mortality.

Role of the Ca^2＋-Calcineurin-Nuclear Factor of Activated T cell Pathway in Mitofusin-2-Mediated Immune Function of Jurkat Cells

Background：Mitofusin-2 （MFN2）,a well-known mitochondrial fusion protein,has been shown to participate in innate immunity,but its role in mediating adaptive immunity remains poorly characterized.In this study,we explored the potential role of MFN2 in mediating the immune function of T lymphocytes.Methods：We manipulated MFN2 gone expression in Jurkat cells via lentiviral transduction of MFN2 small interfering RNA （siRNA） or full-length MFN2.After transduction,the immune response and its underlying mechanism were determined in Jurkat cells.One-way analysis of variance and Student＇s t-test were performed to determine the statistical significance between the groups.Results：Overexpression of MFN2 enhanced the immune response of T lymphocytes by upregulating Ca2＋ （359.280 ± 10.130 vs.266.940 ± 10.170,P =0.000）,calcineurin （0.513 ± 0.014 vs.0.403 ± 0.020 nmol/L,P =0.024）,and nuclear factor of activated T cells （NFATs） activation （1.040 ± 0.086 vs.0.700 ± 0.115,P =0.005）,whereas depletion of MFN2 impaired the immune function ofT lymphocytes by downregulating Ca2＋ （141.140 ± 14.670 vs.267.060 ± 9.230,P =0.000）,calcineurin （0.054 ± 0.030 nmol/L vs.0.404 ± 0.063 nmol/L,P =0.000）,and NFAT activation （0.500 ± 0.025 vs.0.720 ± 0.061,P =0.012）.Furthermore,upregulated calcineurin partially reversed the negative effects ofMFN2 siRNA on T cell-mediated immunity evidenced by elevations in T cell proliferation （1.120 ± 0.048 vs.0.580 ± 0.078,P =0.040）,interleukin-2 （IL-2） production （473.300 ± 24.100 vs.175.330 ± 12.900 pg/ml,P =0.000）,and the interferon-γ/IL-4 ratio （3.080 ± 0.156 vs.0.953 ± 0.093,P =0.000）.Meanwhile,calcineurin activity inhibitor depleted the positive effects of overexpressed MFN2 on T cells function.Conclusions：Our findings suggest that MFN2 may regulate T cell immune functions primarily through the Ca2＋-calcineurin-NFAT pathway.MFN2 may represent a potential therapeutic target for T cell immune dysfunction-related diseases.

Early prophylactic anticoagulation with heparin alleviates mortality in critically ill patients with sepsis:a retrospective analysis from the MIMIC-IV database

Background:Minimal data exist on anticoagulation use and timing and the dose of heparin in patients with sepsis,and whether heparin use improves sepsis survival remains largely unclear.This study was performed to assess whether heparin administration would provide a survival advantage in critically ill patients with sepsis.Methods:A retrospective cohort study of patients with sepsis in the Medical Information Mart for Intensive Care(MIMIC)-IV database was conducted.Cox proportional hazards model and propensity score matching(PSM)were used to evaluate the outcomes of prophylactic anticoagulation with heparin administered by subcutaneous injection within 48 h of intensive care unit(ICU)admission.The primary outcome was in-hospital mortality.Secondary outcomes included 60-day mortality,length of ICU stay,length of hospital stay and incidence of acute kidney injury(AKI)on day 7.EValue analysis were used for unmeasured confounding.Results:A total of 6646 adult septic patients were included and divided into an early prophylactic heparin group(n=3211)and a nonheparin group(n=3435).In-hospital mortality in the heparin therapy group was significantly lower than that in the nonheparin group(prematched 14.7 vs 20.0%,hazard ratio(HR)0.77,95%confidence interval(CI)[0.68-0.87],p<0.001,and postmatched 14.9 vs 18.3%,HR 0.78,95%CI[0.68-0.89],p<0.001).Secondary endpoints,including 60-day mortality and length of ICU stay,differed between the heparin and nonheparin groups(p<0.01).Early prophylactic heparin administration was associated with in-hospital mortality among septic patients in different adjusted covariates(HR 0.71-0.78,p<0.001),and only administration of five doses of heparin was associated with decreased in-hospital mortality after PSM(HR 0.70,95%CI 0.56-0.87,p<0.001).Subgroup analysis showed that heparin use was significantly associated with reduced in-hospital mortality in patients with sepsis-induced coagulopathy,septic shock,sequential organ failure assessment score≥10,AKI,mechanical ventilation,gram-positive bacterial infection and gram-negative bacterial infection,with HRs of 0.74,0.70,0.58,0.74,0.73,0.64 and 0.72,respectively(p<0.001).E-Value analysis suggested robustness to unmeasured confounding.Conclusions:This study found an association between early administration prophylactic heparin provided to patients with sepsis and reduced risk-adjusted mortality.A prospective randomizedcontrolled study should be designed to further assess the relevant findings.

Nuclear fragile X mental retardation-interacting protein 1-mediated ribophagy protects T lymphocytes against apoptosis in sepsis

Background:Ribophagy is a selective autophagic process that specifically degrades dysfunctional or superfluous ribosomes to maintain cellular homeostasis.Whether ribophagy can ameliorate the immunosuppression in sepsis similar to endoplasmic reticulum autophagy(ERphagy)and mitophagy remains unclear.This study was conducted to investigate the activity and regulation of ribophagy in sepsis and to further explore the potential mechanism underlying the involvement of ribophagy in T-lymphocyte apoptosis.Methods:The activity and regulation of nuclear fragile X mental retardation-interacting protein 1(NUFIP1)-mediated ribophagy in T lymphocytes during sepsis were first investigated by western blotting,laser confocal microscopy and transmission electron microscopy.Then,we constructed lentivirally transfected cells and gene-defective mouse models to observe the impact of NUFIP1 deletion on T-lymphocyte apoptosis and finally explored the signaling pathway associated with T-cell mediated immune response following septic challenge.Results:Both cecal ligation and perforation-induced sepsis and lipopolysaccharide stimulation significantly induced the occurrence of ribophagy,which peaked at 24 h.When NUFIP1 was knocked down,T-lymphocyte apoptosis was noticeably increased.Conversely,the overexpression of NUFIP1 exerted a significant protective impact on T-lymphocyte apoptosis.Consistently,the apoptosis and immunosuppression of T lymphocytes and 1-week mortality rate in NUFIP1 gene-deficient mice were significantly increased compared with those in wild-type mice.In addition,the protective effect of NUFIP1-mediated ribophagy on T lymphocytes was identified to be closely related to the endoplasmic reticulum stress apoptosis pathway,and PERK-ATF4-CHOP signaling was obviously involved in downregulating T-lymphocyte apoptosis in the setting of sepsis.Conclusions:NUFIP1-mediated ribophagy can be significantly activated to alleviate T lymphocyte apoptosis through the PERK-ATF4-CHOP pathway in the context of sepsis.Thus,targeting NUFIP1-mediated ribophagy might be of importance in reversing the immunosuppression associated with septic complications.