The new normal: immunomodulatory agents against sepsis immune suppression

Maresins as novel anti-inflammatory actors and putative therapeutic targets in sepsis

Sepsis, a complex clinical syndrome characterized by an exaggerated host response to infection, often necessitates hospitalization and intensive care unit admission. Delayed or inaccurate diagnosis of sepsis, coupled with suboptimal treatment strategies, can result in unfavorable outcomes, including mortality. Maresins, a newly discovered family of lipid mediators synthesized from docosahexaenoic acid by macrophages, have emerged as key players in promoting inflammation resolution and the termination of inflammatory processes. Extensive evidence has unequivocally demonstrated the beneficial effects of maresins in modulating the inflammatory response associated with sepsis; however, their bioactivity and functions exhibit remarkable diversity and complexity. This article presents a comprehensive review of recent research on the role of maresins in sepsis, aiming to enhance our understanding of their effectiveness and elucidate the specific mechanisms underlying their actions in sepsis treatment. Furthermore, emerging insights into the management of patients with sepsis are also highlighted.

PD-L1 Expression Is Increased in LPS-Induced Acute Respiratory Distress Syndrome by PI3K-AKT-Egr-1/C/EBPδ Signaling Pathway

The role of programmed death ligand 1 (PD-L1) has been extensively investigated in adaptive immune system. However, increasing data show that innate immune responses are also affected by the immune checkpoint molecule. It has been demonstrated that regulation of PD-L1 signaling in macrophages may be a potential therapeutic method for acute respiratory distress syndrome (ARDS). However, the PD-L1 expression pattern in local macrophages and whole lung tissues remains mysterious, hindering optimization of the potential treatment program. Therefore, we aim to determine the PD-L1 expression pattern during ARDS. Our findings show that PD-L1 levels are markedly increased in lipopolysaccharide (LPS)-stimulated lung tissues, which might be attributable to an increase in the gene expression by immune cells, including macrophages and neutrophils. In vitro experiments are performed to explore the mechanism involved in LPS-induced PD-L1 production. We find that PD-L1 generation is controlled by transcription factors early growth response 1 (Egr-1) and CCAAT/enhancer binding protein delta (C/EBPδ). Strikingly, PD-L1 production is enhanced by phosphoinositide-3 kinase (PI3K)-protein kinase B (AKT) signaling pathway via up-regulation of Egr-1 and C/EBPδ expressions. Additionally, we observe that expressions of Egr-1 and C/EBPδ mutually reinforce each other. Moreover, we observe that PD-L1 is protective for ARDS due to its regulatory role in macrophage-associated inflammatory response. In summary, during LPS-induced ARDS, PD-L1 expression, which is beneficial for the disease, is increased via the PI3K-AKT1-Egr-1/C/EBPδ signaling pathway, providing theoretical basis for application of methods controlling PD-L1 signaling in macrophages for ARDS treatment in clinic.

Shift in risk factors for mortality by period of the bloodstream infection timeline

BACKGROUND

This study was designed to determine changes in risk factors on the prognosis of patients during each period of the bloodstream infection (BSI) timeline.

METHODS

Through an integrated study of multivariable regressions with machine learning techniques, the risk factors for mortality during each period of BSI were analyzed.

RESULTS

A total of 302,303 inpatients who underwent blood cultures during 2011-2021 were enrolled. More than 8 % of BSI cases progressed to subsequent BSI, and risk factors were identified as gut colonization with vancomycin-resistant enterococci (aOR 1.82; 95 % CI 1.47-2.24), intensive care unit admission (aOR 3.37; 95 % CI 3.35-4.28), and current cancer chemotherapy (aOR 1.54; 95 % CI 1.36-1.74). The mean SOFA score of the deceased patients during the first 7 days was 10.6 (SD 4.3), which was significantly higher than those on days 8-30 (7.0 ± 4.2) and after Day 30 (4.0 ± 3.5). BSIs caused by Acinetobacter baumannii and Candida albicans were more likely to result in deaths of patients for all time periods (all, P < 0.001). BSIs caused by Enterococcus faecalis and Enterococcus faecium were associated with a poor outcome in the period after Day 30 (both, P < 0.001). Nonsusceptible phenotypes to β-lactam/β-lactamase inhibitors of Escherichia coli and Klebsiella pneumoniae influenced the prognoses of patients with BSI in terms of high mortality rates during both days 8-30 and after Day 30.

CONCLUSION

Influence of microbiological factors on mortality, including BSI-causative microorganisms and their major antimicrobial resistance, was emphasized in both periods of days 8-30 and after Day 30.

Navigating the Cytokine Storm: A Comprehensive Review of Chemokines and Cytokines in Sepsis

This comprehensive review thoroughly explores the intricate relationship between chemokines, cytokines, and the cytokine storm in sepsis, offering a nuanced understanding of the molecular mechanisms underpinning this life-threatening syndrome. Beginning with examining sepsis stages and immune response dynamics, the review emphasizes the dysregulation leading to the cytokine storm, where pro- and anti-inflammatory cytokines disrupt the delicate immune equilibrium. Delving into chemokines, the discussion encompasses subfamilies, receptors, and functions, highlighting their critical roles in immune cell migration and activation during sepsis. The implications for clinical practice are substantial, suggesting avenues for targeted diagnostics and therapeutic interventions. The review identifies areas for future research, including the search for novel biomarkers, deeper insights into cytokine regulation, and the pursuit of personalized medicine approaches. This comprehensive exploration aims to guide clinicians, researchers, and policymakers in navigating the complexities of sepsis, fostering a foundation for transformative advancements in understanding and managing this formidable clinical challenge.

CTLA-4 Checkpoint Inhibition Improves Sepsis Survival in Alcohol-Exposed Mice

Chronic alcohol use increases morbidity and mortality in the setting of sepsis. Both chronic alcohol use and sepsis are characterized by immune dysregulation, including overexpression of T cell coinhibitory molecules. We sought to characterize the role of CTLA-4 during sepsis in the setting of chronic alcohol exposure using a murine model of chronic alcohol ingestion followed by cecal ligation and puncture. Results indicated that CTLA-4 expression is increased on CD4+ T cells isolated from alcohol-drinking septic mice as compared with either alcohol-drinking sham controls or water-drinking septic mice. Moreover, checkpoint inhibition of CTLA-4 improved sepsis survival in alcohol-drinking septic mice, but not water-drinking septic mice. Interrogation of the T cell compartments in these animals following pharmacologic CTLA-4 blockade, as well as following conditional Ctla4 deletion in CD4+ T cells, revealed that CTLA-4 deficiency promoted the activation and proliferation of effector regulatory T cells and the generation of conventional effector memory CD4+ T cells. These data highlight an important role for CTLA-4 in mediating mortality during sepsis in the setting of chronic alcohol exposure and may inform future approaches to develop targeted therapies for this patient population.

A Robust In Vitro Culture Model and Generation of Memory Monocytes

Innate monocytes can be trained or reprogrammed to adopt distinct memory states, such as low-grade inflammation and immune exhaustion, bearing fundamental relevance to the pathogenesis of both acute diseases such as sepsis as well as chronic diseases such as atherosclerosis. Therefore, it is critically important to develop a regimen for generating memory monocytes in vitro in order to better define key monocyte memory states with diverse potentials for proliferation, differentiation, and activation, as well as underlying mechanisms. Here, we describe an efficient in vitro system to propagate a large number of highly purified murine memory monocytes through sustaining bone marrow-derived monocytes with macrophage colony-stimulating factor (M-CSF, 10 ng/mL)-containing medium, together with other polarization agents such as lipopolysaccharide (LPS) for a 5-day period. This method can yield high-purity monocytes, capable of exhibiting dynamic memory behaviors upon training with various polarizing agents.

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

Objective

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

Methods

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

Results

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

Conclusions

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

Dapagliflozin alleviates renal inflammation and protects against diabetic kidney diseases, both dependent and independent of blood glucose levels

Introduction

Diabetic kidney disease (DKD) has become the leading cause of end-stage renal disease worldwide. Therefore, efforts to understand DKD pathophysiology and prevent its development at the early phase are highly warranted.

Methods

Here, we analyzed kidneys from healthy mice, diabetic mice, and diabetic mice treated with the sodium-glucose cotransporter 2 inhibitor dapagliflozin using ATAC and RNA sequencing. The findings were verified at the protein levels and in cultured cells.

Results

Our combined method of ATAC and RNA sequencing revealed Csf2rb, Btla, and Isg15 as the key candidate genes associated with hyperglycemia, azotemia, and albuminuria. Their protein levels were altered together with multiple other inflammatory cytokines in the diabetic kidney, which was alleviated by dapagliflozin treatment. Cell culture of immortalized renal tubular cells and macrophages unraveled that dapagliflozin could directly effect on these cells in vitro as an anti-inflammatory agent independent of glucose concentrations. We further proved that dapagliflozin attenuated ischemia/reperfusion-induced chronic kidney injury and renal inflammation in mice.

Discussion

Overall, our data emphasize the importance of inflammatory factors to the pathogenesis of DKD, and provide valuable mechanistic insights into the renoprotective role of dapagliflozin.

Reconditioned monocytes are immunomodulatory and regulate inflammatory environment in sepsis

Sepsis is caused by dysregulated immune response to severe infection and hyper inflammation plays a central role in worsening the disease. The immunomodulatory properties of mesenchymal stem cells (MSCs) have been evaluated as a therapeutic candidate for sepsis. Reconditioned monocytes (RM), generated from healthy human peripheral blood mononuclear cells (PBMCs) exhibit both macrophage and MSCs-like properties. RM were administered at different stages of sepsis in a mouse model. It reduced serum levels of IL6, MCP-1, IL-10, improved hypothermia, increased survival, and recovery from 0 to 66% when combined with antibiotics in the mouse model. The reduced human leucocyte antigen DR molecules expression on RM enables their co-culture with PBMCs of sepsis patients which resulted in reduced ROS production, and up-regulated TGF-β while down-regulating IL6, IL8, and IL-10 in-vitro. RM are potentially immunomodulatory, enhance survival in sepsis mouse model and modulate inflammatory behaviour of sepsis patient's PBMCs.

SPLENIC INVARIANT NATURAL KILLER T CELLS PLAY A SIGNIFICANT ROLE IN THE RESPONSE TO POLYMICROBIAL SEPSIS

ABSTRACT

Background: Sepsis is marked by a dysregulated immune response to an infection. Invariant natural killer T cells ( i NKT cells) are a pluripotent lymphocyte subpopulation capable of affecting and coordinating the immune response to sepsis. The spleen is an important site of immune interactions in response to an infection. Splenic i NKT cells have emerged as important potential frontline mediators of chronic immune response. There are few data addressing the role splenic of i NKT cells in response to intra-abdominal polymicrobial sepsis. Methods: The cecal ligation and puncture model was used to create intra-abdominal sepsis in 8- to 12-week-old wild-type, i NKT -/- , or programmed cell death receptor-1 (PD-1) -/- mice. Twenty-four hours later, spleens were harvested. Flow cytometry was used for phenotyping using monoclonal antibodies. Cell sort was used to isolate i NKT cells. A macrophage cell line was used to assess i NKT cell-phagocyte interactions. Enzyme-linked immunosorbent assay was used for cytokine analysis. Results: Splenic i NKT-cell populations rapidly declined following induction of sepsis. Within i NKT-cell -/- mice, a distinct baseline hyperinflammatory environment was noted. Within wild type, sepsis induced an increase in splenic IL-6 and IL-10, whereas in i NKT -/- mice, there was no change in elevated IL-6 levels and a noted decrease in IL-10 expression. Further, following sepsis, PD-1 expression was increased upon spleen i NKT cells. With respect to PD-1 ligands upon phagocytes, PD-1 ligand expression was unaffected, whereas PD-L2 expression was significantly affected by the presence of PD-1. Conclusions: Invariant natural killer T cells play a distinct role in the spleen response to sepsis, an effect mediated by the checkpoint protein PD-1. Given that modulators are available in clinical trials, this offers a potential therapeutic target in the setting of sepsis-induced immune dysfunction.

Specific Clearance of Lipopolysaccharide from Blood Based on Peptide Bottlebrush Polymer for Sepsis Therapy

Lipopolysaccharide (LPS) is the primary bacterial toxin that is vital to the pathogenesis and progression of sepsis associated with extremely high morbidity and mortality worldwide. However, specific clearance of LPS from circulating blood is highly challenging because of the structural complexity and its variation between/within bacterial species. Herein, a robust strategy based on phage display screening and hemocompatible peptide bottlebrush polymer design for specific clearance of targeted LPS from circulating blood is proposed. Using LPS extracted from Escherichia coli as an example, a novel peptide (HWKAVNWLKPWT) with high affinity (KD < 1.0 nм), specificity, and neutralization activity (95.9 ± 0.1%) against the targeted LPS is discovered via iterative affinity selection coupled with endotoxin detoxification screening. A hemocompatible bottlebrush polymer bearing the short peptide [poly(PEGMEA-co-PEP-1)] exhibits high LPS selectivity to reduce circulating LPS level from 2.63 ± 0.01 to 0.78 ± 0.05 EU mL-1 in sepsis rabbits via extracorporeal hemoperfusion (LPS clearance ratio > 70%), reversing the LPS-induced leukocytopenia and multiple organ damages significantly. This work provides a universal paradigm for developing a highly selective hemoadsorbent library fully covering the LPS family, which is promising to create a new era of precision medicine in sepsis therapy.

Skewing cPLA2α activity toward oxoeicosanoid production promotes neutrophil N2 polarization, wound healing, and the response to sepsis

Uncontrolled inflammation is linked to poor outcomes in sepsis and wound healing, both of which proceed through distinct inflammatory and resolution phases. Eicosanoids are a class of bioactive lipids that recruit neutrophils and other innate immune cells. The interaction of ceramide 1-phosphate (C1P) with the eicosanoid biosynthetic enzyme cytosolic phospholipase A2 (cPLA2) reduces the production of a subtype of eicosanoids called oxoeicosanoids. We investigated the effect of shifting the balance in eicosanoid biosynthesis on neutrophil polarization and function. Knockin mice expressing a cPLA2 mutant lacking the C1P binding site (cPLA2αKI/KI mice) showed enhanced and sustained neutrophil infiltration into wounds and the peritoneum during the inflammatory phase of wound healing and sepsis, respectively. The mice exhibited improved wound healing and reduced susceptibility to sepsis, which was associated with an increase in anti-inflammatory N2-type neutrophils demonstrating proresolution behaviors and a decrease in proinflammatory N1-type neutrophils. The N2 polarization of cPLA2αKI/KI neutrophils resulted from increased oxoeicosanoid biosynthesis and autocrine signaling through the oxoeicosanoid receptor OXER1 and partially depended on OXER1-dependent inhibition of the pentose phosphate pathway (PPP). Thus, C1P binding to cPLA2α suppresses neutrophil N2 polarization, thereby impairing wound healing and the response to sepsis.

Shikonin inhibits immune checkpoint PD-L1 expression on macrophage in sepsis by modulating PKM2

Sepsis, a life-threatening condition whereby immune dysregulation develops, is one of the major causes of death worldwide. To date, there is still no clinically effective therapeutic method for sepsis. As a natural product from traditional Chinese medicine, Shikonin has been demonstrated to have pleiotropic medical effects, including anti-tumor, anti-inflammation, and relieving sepsis. PD-L1, as the receptor of PD-1, was also involved in exacerbating sepsis by inducing immunosuppression, but the relationship between them is still unclear. In this study, we aimed to evaluate the effect of Shikonin on modulating PD-L1 expression and its contact with PKM2. The results showed that Shikonin significantly decreased the levels of sepsis mice serum inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interferon-γ (IFN-γ), interleukin-1β (IL-1β) and maintain the percentage of T cells from the spleen and significantly reduce the apoptosis of splenocytes in LPS-induced sepsis mice. Our data also demonstrated that Shikonin significantly decreased PD-L1 expression on macrophages, not PD-1 expression on T cells in vivo and in vitro. Additionally, we revealed that Shikonin attenuated PD-L1 expression on macrophages and was associated with downregulating phosphorylation and nuclear import of PKM2, which could bind to the HRE-1 and HRE-4 sites of the PD-L1 promoter. As the present research was conducted in sepsis mice model and macrophage cell line, further study is required to evaluate Shikonin to regulate PD-L1 by targeting PKM2 in clinical samples.

Vitamin D receptor (VDR) on the cell membrane of mouse macrophages participates in the formation of lipopolysaccharide tolerance: mVDR is related to the effect of artesunate to reverse LPS tolerance

It is unclear whether membrane vitamin D receptor (mVDR) exists on the macrophage membrane or whether mVDR is associated with lipopolysaccharide (LPS) tolerance. Herein, we report that interfering with caveolae and caveolae-dependent lipid rafts inhibited the formation of LPS tolerance. VDR was detected as co-localized with membrane molecular markers. VDR was detected on the cell membrane and its level was higher in LPS-tolerant cells than that in only LPS treatment cells. Anti-VDR antibodies could abolish the effect of artesunate (AS) to reverse LPS tolerance, and the wild-type peptides (H397 and H305) of VDR, but not the mutant peptide (H397D and H305A), led to the loss of AS's effect. AS decreased the mVDR level in LPS-tolerant cells. In vivo, AS significantly reduced VDR level in the lung tissue of LPS-tolerant mice. In summary, mVDR exists on the cell membrane of macrophages and is closely associated with the formation of LPS tolerance and the effects of AS. Video Abstract.

Treatment Advances in Sepsis and Septic Shock: Modulating Pro- and Anti-Inflammatory Mechanisms

Sepsis is currently defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection, and it affects over 25 million people every year. Even more severe, septic shock is a subset of sepsis defined by persistent hypotension, and hospital mortality rates are higher than 40%. Although early sepsis mortality has greatly improved in the past few years, sepsis patients who survive the hyperinflammation and subsequent organ damage often die from long-term complications, such as secondary infection, and despite decades of clinical trials targeting this stage of the disease, currently, no sepsis-specific therapies exist. As new pathophysiological mechanisms have been uncovered, immunostimulatory therapy has emerged as a promising path forward. Highly investigated treatment strategies include cytokines and growth factors, immune checkpoint inhibitors, and even cellular therapies. There is much to be learned from related illnesses, and immunotherapy trials in oncology, as well as the recent COVID-19 pandemic, have greatly informed sepsis research. Although the journey ahead is a long one, the stratification of patients according to their immune status and the employment of combination therapies represent a hopeful way forward.

Predictive value of peripheral lymphocyte subsets for the disease progression in patients with sepsis

OBJECTIVE

To investigate the predictive value of peripheral lymphocyte subsets for sepsis progression.

METHODS

Patients with sepsis were divided into the improved group (n = 46) and severe group (n = 39) according to disease progression. Flow cytometric analysis was performed to enumerate absolute counts of peripheral lymphocyte subsets. Logistic regression analyses were conducted to identify clinical factors linked to sepsis progression.

RESULTS

The absolute counts of peripheral lymphocyte subsets were markedly decreased in septic patients compared with healthy controls. After treatment, the absolute counts of lymphocytes, CD3⁺ T cells, and CD8⁺ T cells were restored in the improved group, and reduced in the severe group. Logistic regression analysis indicated that a low CD8⁺ T cells count was a risk factor for sepsis progression. Receiver operating characteristic curve analysis revealed that CD8⁺ T cells count had the greatest ability to predict sepsis progression.

CONCLUSIONS

The absolute counts of CD3⁺ T cells, CD4⁺ T cells, CD8⁺ T cells, B cells, and natural killer cells were significantly higher in the improved group than the severe group. CD8⁺ T cells count was predictive of sepsis progression. Lymphopenia and CD8⁺ T cells depletion were associated with the clinical outcomes of sepsis, suggesting that CD8⁺ T cells have potential as a predictive biomarker and therapeutic target for patients with sepsis.

Fucoxanthin Alleviates Lipopolysaccharide-Induced Inflammation and Immunosuppression in RAW264.7 Macrophages

Fucoxanthin (FX) has been reported to reduce mortality in mouse models of sepsis, but its exact cause remains to be determined. In the present study, we evaluated the immunomodulatory properties of FX in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Our results showed that FX could not only suppress the immune activation responses caused by LPS primary stimulation, but also antagonize LPS restimulation-induced immunosuppression in macrophages. The immunomodulatory capabilities of FX was mainly demonstrated by regulating the production of the inflammatory mediator under different LPS stimuli. Furthermore, we found that adenosine monophosphate-activated protein kinase (AMPK) activation was required for FX's anti-inflammatory and anti-immunosuppressive activities. Our results complement existing data supporting the clinical potential for FX in treating sepsis.

A signature of immune-related genes correlating with clinical prognosis and immune microenvironment in sepsis

BACKGROUND

Immune-related genes (IRGs) remain poorly understood in their function in the onset and progression of sepsis.

METHODS

GSE65682 was obtained from the Gene Expression Omnibus database. The IRGs associated with survival were screened for subsequent modeling using univariate Cox regression analysis and least absolute shrinkage and selection operator in the training cohort. Then, we assessed the reliability of the 7 IRGs signature's independent predictive value in the training and validation cohorts following the creation of a signature applying multivariable Cox regression analysis. After that, we utilized the E-MTAB-4451 external dataset in order to do an independent validation of the prognostic signature. Finally, the CIBERSORT algorithm and single-sample gene set enrichment analysis was utilized to investigate and characterize the properties of the immune microenvironment.

RESULTS

Based on 7 IRGs signature, patients could be separated into low-risk and high-risk groups. Patients in the low-risk group had a remarkably increased 28-day survival compared to those in the high-risk group (P < 0.001). In multivariable Cox regression analyses, the risk score calculated by this signature was an independent predictor of 28-day survival (P < 0.001). The signature's predictive ability was confirmed by receiver operating characteristic curve analysis with the area under the curve reaching 0.876 (95% confidence interval 0.793-0.946). Moreover, both the validation set and the external dataset demonstrated that the signature had strong clinical prediction performance. In addition, patients in the high-risk group were characterized by a decreased neutrophil count and by reduced inflammation-promoting function.

CONCLUSION

We developed a 7 IRGs signature as a novel prognostic marker for predicting sepsis patients' 28-day survival, indicating possibilities for individualized reasonable resource distribution of intensive care unit.

Analysis of signature genes and association with immune cells infiltration in pediatric septic shock

Background

Early diagnosis of septic shock in children is critical for prognosis. This study committed to investigate the signature genes and their connection with immune cells in pediatric septic shock.

Methods

We screened a dataset of children with septic shock from the GEO database and analyzed differentially expressed genes (DEGs). Functional enrichment analysis was performed for these DEGs. Weighted gene co-expression network analysis (WCGNA) was used to screen the key modules. Least absolute shrinkage and selection operator (LASSO) and random forest analysis were finally applied to identify the signature genes. Then gene set enrichment analysis (GSEA) was exerted to explore the signaling pathways related to the hub genes. And the immune cells infiltration was subsequently classified via using CIBERSORT.

Results

A total of 534 DEGs were screened from GSE26440. The data then was clustered into 17 modules via WGCNA, which MEgrey module was significantly related to pediatric septic shock (cor=-0.62, p<0.0001). LASSO and random forest algorithms were applied to select the signature genes, containing UPP1, S100A9, KIF1B, S100A12, SLC26A8. The receiver operating characteristic curve (ROC) of these signature genes was 0.965, 0.977, 0.984, 0.991 and 0.989, respectively, which were verified in the external dataset from GSE13904. GSEA analysis showed these signature genes involve in positively correlated fructose and mannose metabolism and starch and sucrose metabolism signaling pathway. CIBERSORT suggested these signature genes may participate in immune cells infiltration.

Conclusion

UPP1, S100A9, KIF1B, S100A12, SLC26A8 emerge remarkable diagnostic performance in pediatric septic shock and involved in immune cells infiltration.

Immune Modulation in Sepsis, ARDS, and Covid-19 - The Road Traveled and the Road Ahead

Immune Modulation in Sepsis, ARDS, and Covid-19Leligdowicz et al. consider the history and future of immunomodulating therapies in sepsis and ARDS, including ARDS due to Covid-19, and remark on the larger challenge of clinical research on therapies for syndromes with profound clinical and biologic heterogeneity.

Gentamicin promoted the production of CD4+CD25+ Tregs via the STAT5 signaling pathway in mice sepsis

Background

Increasing studies have reported that gentamicin (GNT) plays an essential role in sepsis; however, its underlying mechanism is still unclear. In this study, we investigated the mechanism of GNT in sepsis.

Results

We observed that GNT enhanced survival and alleviated inflammatory injuries of the lungs, liver, kidneys, and intestines in mice with sepsis. Furthermore, regulatory T cells (Tregs) showed enhanced inhibitory function, and pro-inflammatory cytokines IL-1β, TNF-α, and IL-2 and anti-inflammatory cytokine IL-10 showed decreased and increased peritoneal fluid levels, respectively, after treatment with GNT. GNT showed enhanced phosphorylation of signal transducer and activator of transcription 5 (p-STAT5) in Tregs in vivo and in vitro. The STAT5 inhibitor restrained the increased functional changes of Tregs and reduced inflammatory responses induced by GNT in vitro. Moreover, the STAT5 inhibitor reversed GNT-mediated impacts on survival and inflammation, and the percentage, apoptosis, and phenotypic and functional changes of Tregs in neonatal sepsis.

Conclusions

Our study revealed that GNT regulates the function of Tregs via the STAT5 signaling pathway, alleviating inflammatory injuries, and provides novel evidence in the treatment of neonatal sepsis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-022-00521-4.

Immune hyporeactivity to bacteria and multiple TLR-ligands, yet no response to checkpoint inhibition in patients just after meeting Sepsis-3 criteria

Rationale

The immune profile of sepsis patients is incompletely understood and hyperinflammation and hypoinflammation may occur concurrently or sequentially. Immune checkpoint inhibition (ICI) may counter hypoinflammation but effects are uncertain. We tested the reactivity of septic whole blood to bacteria, Toll-like receptor (TLR) ligands and to ICI.

Methods

Whole blood assays of 61 patients’ samples within 24h of meeting sepsis-3 criteria and 12 age and sex-matched healthy volunteers. Measurements included pattern/danger-associated molecular pattern (P/DAMP), cytokine concentrations at baseline and in response to TLR 2, 4, and 7/8 ligands, heat-inactivated Staphylococcus aureus or Escherichia coli, E.coli lipopolysaccharide (LPS), concentration of soluble and cellular immune checkpoint molecules, and cytokine concentrations in response to ICI directed against programmed-death receptor 1 (PD1), PD1-ligand 1, or cytotoxic T-lymphocyte antigen 4, both in the absence and presence of LPS.

Main results

In sepsis, concentrations of P/DAMPs and inflammatory cytokines were increased and the latter increased further upon incubation ex vivo. However, cytokine responses to TLR 2, 4, and 7/8 ligands, heat-inactivated S. aureus or E. coli, and E. coli LPS were all depressed. Depression of the response to LPS was associated with increased in-hospital mortality. Despite increased PD-1 expression on monocytes and T-cells, and monocyte CTLA-4 expression, however, addition of corresponding checkpoint inhibitors to assays failed to increase inflammatory cytokine concentrations in the absence and presence of LPS.

Conclusion

Patients first meeting Sepsis-3 criteria reveal 1) depressed responses to multiple TLR-ligands, bacteria, and bacterial LPS, despite concomitant inflammation, but 2) no response to immune checkpoint inhibition.

Electroacupuncture at Zusanli (ST36), Guanyuan (CV4), and Qihai (CV6) Acupoints Regulates Immune Function in Patients with Sepsis via the PD-1 Pathway

Objective

The present study is aimed at investigating the biochemical and clinical effects of electroacupuncture in patients with sepsis.

Methods

Patients with sepsis treated at Guangdong Provincial Hospital of Chinese Medicine from July 2019 to December 2020 were included. Patients were randomly assigned to treatment with routine Western medicine (WM group) or treatment with Western medicine plus electroacupuncture based on Western medicine (EA group). Indices associated with immune function and clinical efficacy were determined before and at 3 and 5 days after treatment. Indicators of immune function included the percentage of T lymphocyte subsets, natural killer (NK) cells, and soluble programmed death protein 1 (sPD-1) levels. Indicators of clinical efficacy included infection-related indicators in whole blood; levels of tumor necrosis factor-α (TNF-α), C-reactive protein (CRP), and interferon-γ (INF-γ); and assessments using acute physiology and chronic health evaluation-II (APACHE-II) and sequential organ failure assessment (SOFA) scores.

Results

Baseline data were not different between WM (N = 30) and EA groups (N = 30). At day 5 following treatment, the level of sPD-1 in the EA group was lower than that in the WM group. Proportions of CD3 + T lymphocytes, CD4 + T lymphocytes, and NK cells, the percentage of lymphocytes, and INF-γ levels in the EA group were significantly higher than those in the WM group. Compared with the WM group, the white blood cell count (WBC), percentage and count of neutrophils, ratio of neutrophils to lymphocytes, and levels of CRP and TNF-α were significantly decreased in the EA group 5 days after treatment. The APACHE-II score of the EA group was significantly lower than that of the WM group 5 days after treatment.

Conclusion

Electroacupuncture may regulate the immune function of patients with sepsis through the PD-1 pathway to achieve an anti-inflammatory state and improve clinical symptoms.

The Pathophysiology of Sepsis-Associated AKI

Sepsis-associated AKI is a life-threatening complication that is associated with high morbidity and mortality in patients who are critically ill. Although it is clear early supportive interventions in sepsis reduce mortality, it is less clear that they prevent or ameliorate sepsis-associated AKI. This is likely because specific mechanisms underlying AKI attributable to sepsis are not fully understood. Understanding these mechanisms will form the foundation for the development of strategies for early diagnosis and treatment of sepsis-associated AKI. Here, we summarize recent laboratory and clinical studies, focusing on critical factors in the pathophysiology of sepsis-associated AKI: microcirculatory dysfunction, inflammation, NOD-like receptor protein 3 inflammasome, microRNAs, extracellular vesicles, autophagy and efferocytosis, inflammatory reflex pathway, vitamin D, and metabolic reprogramming. Lastly, identifying these molecular targets and defining clinical subphenotypes will permit precision approaches in the prevention and treatment of sepsis-associated AKI.

Dendrobium officinale polysaccharides attenuate uropathogenic Escherichia coli (UPEC)-induced pyroptosis in macrophage cells

Urinary tract infections (UTI) are recognized as one of the most common infectious diseases worldwide, and uropathogenic Escherichia coli (UPEC) is the main causative agent of UTI. Dendrobium officinale polysaccharides (DOPs), the main effective ingredient in Dendrobium officinale, have been reported to possess an anti-inflammatory role. Whether DOPs can attenuate the inflammatory injury (pyroptosis) induced by UPEC remains unknown. The present study aimed to assess the protective effect and potential mechanism of DOPs in UPEC-induced pyroptosis. Cell viability of THP-1 differentiated macrophage cells with DOPs was determined using MTT assay. Pyroptosis by UPEC in macrophage cells with or not DOPs pre-treatment was evaluated with flow cytometry analysis, lactate dehydrogenase (LDH) assay, and proinflammatory cytokines secretion. Expression level of key proteins in the NLRP3/Caspase-1/GSDMD pyroptotic pathway was analyzed with western blot. Furthermore the effect of DOPs on ROS activation was investigated. Results indicated that DOPs attenuated UPEC-induced cell damage in macrophage cells, inhibited the activation of NLRP3 mediated inflammasome, subsequently decreased induction and activation of caspase-1/GSDMD, and reduced the secretion of pro-inflammatory cytokine (IL-1β et al.). Moreover, pretreatment with DOPs significantly reduces ROS production, an important/putative pyroptosis stimulus signal. These results suggested that DOPs successfully mitigate UPEC-promoted pyroptosis in macrophage cells. The protective effects of DOPs are associated with the inhibition of the NLRP3/Caspase-1/GSDMD pathway and ROS signal activation.

Beneficial Immune Regulation by Biological Response Modifier Glucans in COVID-19 and Their Envisaged Potentials in the Management of Sepsis

Sepsis is a life-threatening condition caused by an abnormal immune response induced by infection with no approved or specific therapeutic options. We present our perspectives for the therapeutic management of sepsis through a four-way approach: (1) infection control through immune enhancement; (2) immune suppression during the initial hyper-inflammatory phase; (3) balanced immune-modulation to counter the later immune-paralysis phase; and (4) advantageous effects on metabolic and coagulation parameters throughout. COVID-19 is a virus-triggered, accelerated sepsis-like reaction that is associated with the rapid progress of an inflammatory cascade involving a cytokine storm and multiorgan failure. Here, we discuss the potential of the biological response modifiers, β-glucans (BRMGs), in the management of sepsis based on their beneficial effects on inflammatory-immune events in COVID-19 clinical studies. In COVID-19 patients, apart from metabolic regulation, BRMGs, derived from a black yeast, Aureobasidium pullulans strain AFO-202, have been reported to stimulate immune responses. BRMGs, produced by another strain (N-163) of A. pullulans, have been implicated in the beneficial regulation of inflammatory markers and immunity, namely IL-6, C-reactive protein (CRP), D-Dimer, ferritin, neutrophil-to-lymphocyte ratio (NLR), lymphocyte-to-C-reactive protein ratio (LCR), leucocyte-to-C-reactive protein ratio (LeCR), and leukocyte-to-IL-6 ratio (LeIR). Agents such as these β-glucans, which are safe as they have been widely consumed by humans for decades, have potential as adjuncts for the prevention and management of sepsis as they exert their beneficial effects across the spectrum of processes and factors involved in sepsis pathology, including, but not limited to, metabolism, infection, inflammation, immune modulation, immune enhancement, and gut microbiota.

A new indicator: The diagnostic value of CD8+T/B lymphocyte ratio in sepsis progression

Objective

To reveal the value of single lymphocyte subpopulation and their ratios in the progression of sepsis.

Methods

From January 2019 to March 2021, 39 sepsis patients, 16 septic shock patients, and 50 healthy volunteers were recruited in the Second Xiangya Hospital for this cross-sectional study. The absolute quantitation of CD4+T, CD8+T, B lymphocytes, and NK cells in peripheral blood were determined by flow cytometry. SPSS Software was used to analyze the results.

Results

On the whole, the numbers of lymphocytes in the sepsis group and in the septic shock group were lower than that in the healthy control group. Surprisingly, the percentage of CD8+T lymphocytes in the septic shock group was slightly higher than that in the sepsis group. The percentage of B lymphocytes in the sepsis group was higher than that in the healthy control group. The AUC of CD8+T/B was 0.724, with the sensitivity and specificity being 75.00% and 71.79%, respectively.

Conclusion

The immune expression pattern of patients with sepsis was not a simple decrease in the number of lymphocytes. The change in the ratios of lymphocyte subpopulation might be more meaningful along the development and progression of sepsis. The ratio of CD8+T/B could be used to diagnose the progression of sepsis and reduce the misdiagnosis rate to a certain extent.

Pediatric sepsis biomarkers for prognostic and predictive enrichment

Sepsis is a major public health problem in children throughout the world. Given that the treatment guidelines emphasize early recognition, there is interest in developing biomarkers of sepsis, and most attention is focused on diagnostic biomarkers. While there is a need for ongoing discovery and development of diagnostic biomarkers for sepsis, this review will focus on less well-known applications of sepsis biomarkers. Among patients with sepsis, the biomarkers can give information regarding the risk of poor outcome from sepsis, risk of sepsis-related organ dysfunction, and subgroups of patients with sepsis who share underlying biological features potentially amenable to targeted therapeutics. These types of biomarkers, beyond the traditional concept of diagnosis, address the important concepts of prognostic and predictive enrichment, which are key components of bringing the promise of precision medicine to the bedside of children with sepsis.

Concomitant Assessment of Monocyte HLA-DR Expression and Ex Vivo TNF-α Release as Markers of Adverse Outcome after Various Injuries—Insights from the REALISM Study

Intensive care unit (ICU) patients develop an altered host immune response after severe injuries. This response may evolve towards a state of persistent immunosuppression that is associated with adverse clinical outcomes. The expression of human leukocyte antigen DR on circulating monocytes (mHLA-DR) and ex vivo release of tumor necrosis factor α (TNF-α) by lipopolysaccharide-stimulated whole blood are two related biomarkers offered to characterize this phenomenon. The purpose of this study was to concomitantly evaluate the association between mHLA-DR and TNF-α release and adverse clinical outcome (i.e., death or secondary infection) after severe trauma, sepsis or surgery in a cohort of 353 ICU patients. mHLA-DR and TNF-α release was similarly and significantly reduced in patients whatever the type of injury. Persistent decreases in both markers at days 5–7 (post-admission) were significantly associated with adverse outcomes. Overall, mHLA-DR (measured by flow cytometry) appears to be a more robust and standardized parameter. Each marker can be used individually as a surrogate of immunosuppression, depending on center facilities. Combining these two parameters could be of interest to identify the most immunosuppressed patients presenting with a high risk of worsening. This last aspect deserves further exploration.

Detecting Critical Functional Ingredients Group and Mechanism of Xuebijing Injection in Treating Sepsis

Sepsis is a systemic inflammatory reaction caused by various infectious or noninfectious factors, which can lead to shock, multiple organ dysfunction syndrome, and death. It is one of the common complications and a main cause of death in critically ill patients. At present, the treatments of sepsis are mainly focused on the controlling of inflammatory response and reduction of various organ function damage, including anti-infection, hormones, mechanical ventilation, nutritional support, and traditional Chinese medicine (TCM). Among them, Xuebijing injection (XBJI) is an important derivative of TCM, which is widely used in clinical research. However, the molecular mechanism of XBJI on sepsis is still not clear. The mechanism of treatment of "bacteria, poison and inflammation" and the effects of multi-ingredient, multi-target, and multi-pathway have still not been clarified. For solving this issue, we designed a new systems pharmacology strategy which combines target genes of XBJI and the pathogenetic genes of sepsis to construct functional response space (FRS). The key response proteins in the FRS were determined by using a novel node importance calculation method and were condensed by a dynamic programming strategy to conduct the critical functional ingredients group (CFIG). The results showed that enriched pathways of key response proteins selected from FRS could cover 95.83% of the enriched pathways of reference targets, which were defined as the intersections of ingredient targets and pathogenetic genes. The targets of the optimized CFIG with 60 ingredients could be enriched into 182 pathways which covered 81.58% of 152 pathways of 1,606 pathogenetic genes. The prediction of CFIG targets showed that the CFIG of XBJI could affect sepsis synergistically through genes such as TAK1, TNF-α, IL-1β, and MEK1 in the pathways of MAPK, NF-κB, PI3K-AKT, Toll-like receptor, and tumor necrosis factor signaling. Finally, the effects of apigenin, baicalein, and luteolin were evaluated by in vitro experiments and were proved to be effective in reducing the production of intracellular reactive oxygen species in lipopolysaccharide-stimulated RAW264.7 cells, significantly. These results indicate that the novel integrative model can promote reliability and accuracy on depicting the CFIGs in XBJI and figure out a methodological coordinate for simplicity, mechanism analysis, and secondary development of formulas in TCM.

Splenic T lymphocytes induce the formation of immunosuppressive neutrophils through IFN-γ in sepsis

BACKGROUND

Despite many advances in treatment, the prognosis of patients with sepsis still remains poor. Polymorphonuclear leukocytes (PMNs) are the first line of defense against infection. This study aimed to reveal the reason and mechanism of the production of PD-L1⁺ PMNs in sepsis.

METHODS

Cecal ligation and perforation mouse model was established to simulate sepsis. And PMNs were treated for 4 h, 12 h with or without 100 ng/mL (IFN-γ) for further gene sequencing. PD-L1, PD-1, Ly6G, and CD3 were detected by multiplexed immunofluorescence. In addition, expression of PD-L1 and function of PMNs were assessed by flow cytometry. Serum and cell culture supernatant were measured with ELISA assays. Western blot was used to verify the JAK2/STAT1 pathway.

RESULTS

Our study demonstrates that PMNs are the main immune cells with high expression of PD-L1 during sepsis, and these cells, therefore, play a critical role in immunosuppression. In vivo studies demonstrated a specific interaction between PD-L1⁺ PMNs and PD-1⁺ T cells. In vitro studies further demonstrated that IFN-γ induced the production of PD-L1⁺ PMNs through the JAK2/STAT1 pathway. In addition, Fedratinib, an inhibitor of Jak2, was shown to significantly reduce the expression of PD-L1 in neutrophils.

CONCLUSIONS

These data demonstrate that secretion of IFN-γ by splenic T lymphocytes induces the production of PD-L1 + PMNs through the JAK2/STAT1 pathway in sepsis.

Development of Exhausted Memory Monocytes and Underlying Mechanisms

Pathogenic inflammation and immuno-suppression are cardinal features of exhausted monocytes increasingly recognized in septic patients and murine models of sepsis. However, underlying mechanisms responsible for the generation of exhausted monocytes have not been addressed. In this report, we examined the generation of exhausted primary murine monocytes through prolonged and repetitive challenges with high dose bacterial endotoxin lipopolysaccharide (LPS). We demonstrated that repetitive LPS challenges skew monocytes into the classically exhausted Ly6Chi population, and deplete the homeostatic non-classical Ly6Clo population, reminiscent of monocyte exhaustion in septic patients. scRNAseq analyses confirmed the expansion of Ly6Chi monocyte cluster, with elevation of pathogenic inflammatory genes previously observed in human septic patients. Furthermore, we identified CD38 as an inflammatory mediator of exhausted monocytes, associated with a drastic depletion of cellular NAD+; elevation of ROS; and compromise of mitochondria respiration, representative of septic monocytes. Mechanistically, we revealed that STAT1 is robustly elevated and sustained in LPS-exhausted monocytes, dependent upon the TRAM adaptor of the TLR4 pathway. TRAM deficient monocytes are largely resistant to LPS-mediated exhaustion, and retain the non-classical homeostatic features. Together, our current study addresses an important yet less-examined area of monocyte exhaustion, by providing phenotypic and mechanistic insights regarding the generation of exhausted monocytes.

Two-phase releasing immune-stimulating composite orchestrates protection against microbial infections

Sepsis, a syndrome of acute organ dysfunction induced by various infections, could lead to a very high mortality in hospitals despite the development of advanced medical technologies. Herein, a type of two-phase releasing immune-stimulating composite is developed by mixing alginate (ALG) with muramyl dipeptide (MDP) and the nanoparticle formulation of monophosphoryl lipid A (MPLA), the latter two are immunomodulatory agents with different release rates from the formed ALG hydrogel. The obtained two phase-releasing composite could provide instantaneous sepsis protection by the rapid release of MDP to enhance the phagocytic and bactericidal function of macrophages. Later on, such composite could further offer long-term sepsis protection by the sustained release of MPLA to continuously activate the immune system, via up-regulating the production of various pro-inflammatory cytokines, promoting the polarization of macrophages, and increasing the percent of natural killer (NK) cells in the lesion after sepsis challenge. Mice survived from sepsis challenge after such treatment could resist a second infection. Notably, treatment with our composite could increase the mouse survival rate in a cecal ligation and puncture (CLP) induced polymicrobial sepsis model. This work provides an easy-translatable immune-stimulating formulation for effective protection against sepsis under various triggering causes. Our strategy may be promising for long-term broad prevention against various infections, and could potentially be used to protect medical workers under a new pandemic before a reliable vaccine is available.

Pseudomonas aeruginosa Pneumonia Causes a Loss of Type-3 and an Increase in Type-1 Innate Lymphoid Cells in the Gut

BACKGROUND

Sepsis induces gut barrier dysfunction characterized by increased gut epithelial apoptosis and increased intestinal permeability. The cytokine IL-22 has been demonstrated to regulate gut barrier function. Type-3 innate lymphoid cells (ILC3) are the predominate source of IL-22 in the GI tract. We hypothesized that sepsis may cause changes to the gut ILC3/IL-22 axis.

MATERIALS AND METHODS

Sepsis was induced in WT and IL-22 KO mice by Pseudomonas aeruginosa pneumonia. Changes in gut-associated leukocyte populations were determined by flow-cytometry and ILC-associated transcripts were measured by RT-PCR. The effect of sepsis on gut permeability, pulmonary microbial burden, gut epithelial apoptosis, and survival was compared between WT and IL-22-/- mice.

RESULTS

Sepsis resulted in a significant decrease in the number of ILC3 in the gut, with a reciprocal increase in type-1 ILC (ILC1). Consistent with prior reports, sepsis was associated with increased gut permeability; however there was no difference in gut permeability, gut epithelial apoptosis, pulmonary microbial burden, or survival between WT and IL-22-/- mice.

CONCLUSIONS

Septic pneumonia causes a decrease in gut-associated ILC3 and an associated reciprocal increase in ILC1. This may reflect inflammation-induced conversion of ILC3 to ILC1. Constitutive systemic IL-22 deficiency does not alter sepsis-induced gut barrier dysfunction.

High-Affinity Anti-VISTA Antibody Protects against Sepsis by Inhibition of T Lymphocyte Apoptosis and Suppression of the Inflammatory Response

Background

B7 family members and ligands have been identified as critical checkpoints in orchestrating the immune response during sepsis. V-domain Ig suppressor of T cell activation (VISTA) is a new inhibitory immune checkpoint involved in restraining T cell response. Previous studies demonstrated that VISTA engagement on T cells and myeloid cells could transmit inhibitory signals, resulting in reduced activation and function. The current study was designed to determine the potential therapeutic effects of a high-affinity anti-VISTA antibody (clone MH5A) in a murine model of sepsis.

Methods

Polymicrobial sepsis was induced in male C57BL/6 mice via cecal ligation and puncture. Expression profiles of VISTA on T lymphocytes and macrophage were examined at 24 and 72 h postsurgery. The effects of anti-VISTA mAb on the 7-day survival, lymphocyte apoptosis, cytokine expression, bacterial burden, and vital organ damage were determined. Furthermore, the effects of anti-VISTA mAb on CD3⁺ T cell apoptosis and macrophage activation were determined in vitro.

Results

VISTA was substantially expressed on T cells and macrophages in sham-operated mice; septic peritonitis did not induce significant changes in the expression profiles. Treatment with MH5A improved the survival of septic mice, accompanied by reduced lymphocyte apoptosis, decreased cytokine expression, and enhanced bacterial clearance. Engagement of VISTA receptor with MH5A mitigated CD3⁺ T cell apoptosis cultured from CLP mice and suppressed LPS-induced cytokine production by macrophage in vitro.

Conclusion

The present study identified VISTA as a novel immune checkpoint in the regulation of T cell and macrophage response during sepsis. Modulation of the VISTA pathway might offer a promising opportunity in the immunotherapy for sepsis.

Wnt/β-Catenin Antagonist Pyrvinium Exerts Cardioprotective Effects in Polymicrobial Sepsis Model by Attenuating Calcium Dyshomeostasis and Mitochondrial Dysfunction

Calcium dysregulation and mitochondrial dysfunction are key elements in the development of sepsis-induced cardiac dysfunction. Evidences have suggested that inhibition of Wnt/β-Catenin signalling prevents cardiac dysfunction and remodelling in surgical, hypertension and pressure overload models. The present study investigated the effects of Wnt/β-Catenin inhibitor on calcium overload and mitochondrial dysfunction in rat sepsis model of cardiomyopathy. Induction of sepsis by cecal ligation puncture (CLP) resulted in the up-regulation of cardiac β-catenin transcriptional levels and cardiac dysfunction depicted by increased serum lactate dehydrogenase, CK-MB levels reduced maximum (dp/dt max.) and minimum developed pressure (dp/dt min.), increased LVEsDP and relaxation constant tau values. Moreover, oxidative and inflammatory stress, immune cell infiltration, increased myeloperoxidase activity, enhanced caspase-3 activity and fibronectin protein levels were observed in septic rat's heart. Also, septic rat's heart displayed mitochondrial dysfunction due to mPTP opening, increased calcium up-regulation in left ventricular apex tissues and whole heart, increased collagen staining, necrosis and structural damage. Pre-treatment with Wnt/β-Catenin antagonist attenuated sepsis-induced serum and tissue biochemical changes, cardiac dysfunction and structural alterations by inhibiting mitochondrial mPTP opening and restricting calcium overloading in cardiac tissue.

Bicentric evaluation of stabilizing sampling tubes for assessment of monocyte HLA-DR expression in clinical samples

BACKGROUND

Diminished expression of human leukocyte antigen DR on circulating monocytes (mHLA-DR), measured by standardized flow cytometry procedure, is a reliable indicator of immunosuppression in severely injured intensive care unit patients. As such, it is used as stratification criteria in clinical trials evaluating novel immunostimulating therapies. Preanalytical constraints relative to the short delay between blood sampling and flow cytometry staining have nevertheless limited its use in multicentric studies. The objective of the present work was to compare mHLA-DR expression between whole blood samples simultaneously drawn in EDTA or Cyto-Chex BCT tubes.

METHODS

In two university hospitals, mHLA-DR was assessed in fresh whole blood from septic patients (n = 12) and healthy donors (n = 6) simultaneously sampled on EDTA and Cyto-Chex BCT tubes. Staining was performed immediately after sampling and after blood storage at room temperature.

RESULTS

We confirmed that samples collected in Cyto-Chex tube had substantially enhanced stability for mHLA-DR results (48-72 h) over those collected in EDTA. On baseline values, despite good correlation between tubes (r = 0.98, p < 0.001), mHLA-DR expression was systematically lower with Cyto-Chex BCT.

CONCLUSION

The present reports confirms the potential of Cyto-Chex BCT tubes to stabilize mHLA-DR expression before staining and extends the work of Quadrini et al. [Cytometry B 2021;100:103-114]. In centers without rapid access to flow cytometry facilities, it enables to tolerate delays in mHLA-DR staining. However, a 30% gap exists between results obtained with EDTA and Cyto-Chex BCT tubes. As current thresholds for clinical decisions were obtained with EDTA samples, further studies are needed to confirm clinical thresholds with Cyto-Chex BCT tubes.

Exosome: The Regulator of the Immune System in Sepsis

Sepsis is a syndrome comprised of a series of life-threatening organ dysfunctions caused by a maladjusted body response to infection with no effective treatment. There is growing evidence that the immune system plays a core role in sepsis. Pathogens cause abnormal host immune response and eventually lead to immunosuppression, which is an important cause of death in patients with sepsis. Exosomes are vesicles derived from double invagination of plasma membrane, associating with immune responses closely. The cargos delivered by exosomes into recipient cells, especially immune cells, effectively alter their response and functions in sepsis. In this review, we focus on the effects and mechanisms of exosomes on multiple immune cells, as well as the role of immune cell-derived exosomes in sepsis. This is helpful for us to have an in-depth understanding of the mechanism of immune disorders in sepsis. Exosomes is also expected to become a novel target and therapeutic approach for sepsis.

Immunomodulatory Effect of Doxycycline Ameliorates Systemic and Pulmonary Inflammation in a Murine Polymicrobial Sepsis Model

Acute lung injury is an inflammatory condition developed after severe sepsis in response to excessive secretion of pro-inflammatory cytokines. Doxycycline is widely reported to possess immunomodulatory activity through inhibition of various inflammatory pathways. Considering the broad spectrum of anti-inflammatory activity, protective effect of doxycycline was evaluated in clinically relevant murine polymicrobial sepsis model induced by caecal ligation and puncture (CLP). In this model, sepsis is accompanied with infection and therefore ceftriaxone at sub-protective dose was combined to retard the bacterial growth. Three hours after CLP challenge, mice were administered vehicle, ceftriaxone (100 mg/kg subcutaneously) alone and in combination with immunomodulatory dose of doxycycline (50 mg/kg, intraperitoneal) and survival were monitored for 5 days. Bacterial count in blood and peritoneal fluid along with cytokines [interleukin (IL)-6, IL-1β, tumour necrosis factor (TNF)-α] and myeloperoxidase (MPO) in plasma and lung homogenate were measured at 18 h post-CLP. Plasma glutathione (GSH) was also determined. Doxycycline in presence of ceftriaxone improved survival of septic mice by significantly reducing the plasma and lung pro-inflammatory cytokines and MPO levels. It also increased plasma GSH levels. Doxycycline did not improve antibacterial effect of ceftriaxone in combination, suggesting that the protective effect of doxycycline was due to its immunomodulatory activity. Doxycycline in the presence of ceftriaxone demonstrated improved survival of septic mice by modulating the immune response.

From sepsis to acute respiratory distress syndrome (ARDS): emerging preventive strategies based on molecular and genetic researches

A healthy body activates the immune response to target invading pathogens (i.e. viruses, bacteria, fungi, and parasites) and avoid further systemic infection. The activation of immunological mechanisms includes several components of the immune system, such as innate and acquired immunity. Once any component of the immune response to infections is aberrantly altered or dysregulated, resulting in a failure to clear infection, sepsis will develop through a pro-inflammatory immunological mechanism. Furthermore, the severe inflammatory responses induced by sepsis also increase vascular permeability, leading to acute pulmonary edema and resulting in acute respiratory distress syndrome (ARDS). Apparently, potential for improvement exists in the management of the transition from sepsis to ARDS; thus, this article presents an exhaustive review that highlights the previously unrecognized relationship between sepsis and ARDS and suggests a direction for future therapeutic developments, including plasma and genetic pre-diagnostic strategies and interference with proinflammatory signaling.

Tripterygium glycoside improves regulatory T cells and attenuates acute organ dysfunction in septic mice

Sepsis is a fatal infectious disease accompanied by multiple organ failure. Immune dysfunction and inflammatory response play an important role in the progression of the disease. Tripterygium glycoside (TG) has immune suppression and anti-inflammatory effects. Here, we investigated the effects of TG on cecal ligation and puncture (CLP)-induced sepsis. Septic mice model was induced by cecal ligation and puncture(CLP), after administration of TG, specimens are collected at designated time points. Histopathology changes of lung tissues and Kidney tissues were observed under light microscope, magnetic microbeads were used to isolate splenic CD4+CD25+ regulatory T cells (Tregs), and phenotypes were then analyzed by flow cytometry. ELISA method was employed to detect the concentrations of plasma TNF-α, IL-6, and IL-10. Nuclear p-NF-κB and Cytoplasmic IkB-a was detected by western blot. TG administration significantly alleviated lung and kidney inflammatory injury and improved the survival of septic mice. Furthermore, the suppressive function of regulatory T cells was enhanced and plasma expression of IL-10 was increased following TG treatment. The NF-B signaling pathway and secretion of plasma TNF-α and IL-6 was notably inhibited in septic mice treated with TG. TG exerts protective effects through improving regulatory T cells and attenuating pro-inflammatory cytokines in septic mice.

Survival and Pulmonary Injury After Neonatal Sepsis: PD1/PDL1's Contributions to Mouse and Human Immunopathology

Morbidity and mortality associated with neonatal sepsis remains a healthcare crisis. PD1-/- neonatal mice endured experimental sepsis, in the form of cecal slurry (CS), and showed improved rates of survival compared to wildtype (WT) counterparts. End-organ injury, particularly of the lung, contributes to the devastation set forth by neonatal sepsis. PDL1-/- neonatal mice, in contrast to PD1-/- neonatal mice did not have a significant improvement in survival after CS. Because of this, we focused subsequent studies on the impact of PD1 gene deficiency on lung injury. Here, we observed that at 24 h post-CS (but not at 4 or 12 h) there was a marked increase in pulmonary edema (PE), neutrophil influx, myeloperoxidase (MPO) levels, and cytokine expression sham (Sh) WT mice. Regarding pulmonary endothelial cell (EC) adhesion molecule expression, we observed that Zona occludens-1 (ZO-1) within the cell shifted from a membranous location to a peri-nuclear location after CS in WT murine cultured ECs at 24hrs, but remained membranous among PD1-/- lungs. To expand the scope of this inquiry, we investigated human neonatal lung tissue. We observed that the lungs of human newborns exposed to intrauterine infection had significantly higher numbers of PD1+ cells compared to specimens who died from non-infectious causes. Together, these data suggest that PD1/PDL1, a pathway typically thought to govern adaptive immune processes in adult animals, can modulate the largely innate neonatal pulmonary immune response to experimental septic insult. The potential future significance of this area of study includes that PD1/PDL1 checkpoint proteins may be viable therapeutic targets in the septic neonate.

Emerging therapeutic targets for sepsis

Introduction: Sepsis is characterized by a dysregulated host response to infection. Sepsis-associated morbidity/mortality demands concerted research efforts toward therapeutic interventions which are reliable, broadly effective, and etiologically based. More intensive and extensive investigations on alterations in cellular signaling pathways, gene targeting as a means of modifying the characteristic hyper and/or hypo-immune responses, prevention through optimization of the microbiome, and the molecular pathways underlying the septic immune response could improve outcomes.] Areas covered: The authors discuss key experimental mammalian models and clinical trials. They provide an evaluation of evolving therapeutics in sepsis and how they have built upon past and current treatments. Relevant literature was derived from a PubMed search spanning 1987-2020.Expert opinion: Given the complex nature of sepsis and the elicited immune response, it is not surprising that a single cure-all therapeutic intervention, which is capable of effectively and reliably improving patient outcomes has failed to emerge. Innovative approaches seek to address not only the disease process but modify underlying patient factors. A true improvement in sepsis-associated morbidity/mortality will require a combination of unique therapeutic modalities.

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

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

Immunological Endotyping of Chronic Critical Illness After Severe Sepsis

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

Immune Cell Number, Phenotype, and Function in the Elderly with Sepsis

Sepsis is a form of life-threatening organ dysfunction caused by dysregulated host responses to an infection that can be partly attributed to immune dysfunction. Although sepsis affects patients of all ages, elderly individuals display increased susceptibility and mortality. This is partly due to immunosenescence, a decline in normal immune system function associated with physiological aging that affects almost all cell types in the innate and adaptive immune systems. In elderly patients with sepsis, these alterations in immune cells such as endothelial cells, neutrophils, monocytes, macrophages, natural killer cells, dendritic cells, T lymphocytes, and B lymphocytes, are largely responsible for their poor prognosis and increased mortality. Here, we review recent studies investigating the events affecting both innate and adaptive immune cells in elderly mice and patients with sepsis, including alterations in their number, phenotype, and function, to shed light on possible new therapeutic strategies.

Therapeutic Effect of an Anti-Human Programmed Death-Ligand 1 (PD-L1) Nanobody on Polymicrobial Sepsis in Humanized Mice

BACKGROUND Immunosuppression is regarded as the main cause of death induced by sepsis. Anti-programmed death-ligand 1 (PD-L1) therapy is promising in reversing sepsis-induced immunosuppression but no evidence is available on use of commercially available anti-PD-L1 medications for this indication. The present preclinical study was performed to investigate the therapeutic effect of an anti-PD-L1 nanobody (KN035) in sepsis. MATERIAL AND METHODS The level of expression of PD-L1 in PD-L1 humanized mice was confirmed with flow cytometry. Plasma concentrations of KN035 at different dosages at different time points were detected using an enzyme-linked immunosorbent assay. PD-L1 humanized mice were allocated into 4 groups: sham, cecal ligation and puncture (CLP), isotype (isotype+CLP), and PD-L1 (KN035+CLP). The 7-day survival rate was observed to investigate outcomes in CLP mice. Disease severity was assessed with histopathological scoring of mice lungs and livers. Immune status was assessed based on cell apoptosis in the spleen and bacterial clearance. RESULTS PD-L1 levels were significantly elevated in peripheral lymphocytes, monocytes, and neutrophils after CLP surgery. Blood concentrations of KN035 showed that 2.5 mg/kg had potential to be an ideal dosage for KN035 therapy. Survival analysis demonstrated that KN035 was associated with significantly reduced mortality on Day 7 after surgery (P=0.0083). The histopathological tests showed that KN035 alleviated sepsis-induced injury in the lungs and liver. KN035 reduced the number of apoptotic cells in the spleen and almost eliminated bacterial colonies in the peritoneal lavage fluid from the CLP mice. CONCLUSIONS KN035, an anti-PD-L1 antibody, can improve the rate of survival in CLP mice and alleviate sepsis-induced apoptosis in the spleen.

Incidence and Impact of Healthcare-associated Infections on Patients Primarily Admitted with Sepsis and Non-sepsis Diagnoses

Objectives: To compare the incidence of healthcare-associated infections (HAI) and their outcomes between patients admitted to the ICU with sepsis and those admitted with non-sepsis diagnoses. Materials and methods: We performed a single-center, prospective, observational study of ICU patients at a tertiary level medical-surgical unit from April 2018 to October 2018. All patients admitted to the ICU with a length of stay (LOS) > 48 hours were included. Baseline data including demographics, comorbidities, and severity of illness scores were collected. Index occurrence of HAI in all these patients was noted and data regarding organ support and patient outcomes were recorded. The incidence, complications, ICU LOS, and 30-day mortality of HAI were compared between the patients admitted to ICU originally with sepsis and non-sepsis diagnoses. Results: A total of 271 patients were evaluated in our study (N = 106 for the sepsis group and N = 165 for the non-sepsis group). No significant difference between the groups was found in the incidence of HAI (29.2% in sepsis group vs 24.4% in non-sepsis group; p = 0.07). Complications (acute kidney injury (AKI): 71 vs 45%; p = 0.01, shock: 81 vs 55%; p = 0.05, need for mechanical ventilation (MV): 30 vs 15%; p = 0.04) were more common in sepsis group compared to the non-sepsis group. The ICU LOS (12.2 ± 5.2 days vs 8.8 ± 2.05 days; p = 0.01) was significantly longer in the sepsis group. There was no significant difference in 30-day mortality between the groups (45 vs 25%; p = 0.07). Conclusion: The incidence of HAI seems to be similar between patients admitted with sepsis and non-sepsis diagnoses. However, patients admitted with sepsis develop higher rates of organ failure secondary to HAI and have a longer ICU LOS compared to patients admitted with non-sepsis diagnoses. The mortality rate of HAI did not differ between these two groups. How to cite this article: Chintamani A, Prakash B, Abraham BK, Kumar S, Ramakrishnan N, Venkataraman R. Incidence and Impact of Healthcare-associated Infections on Patients Primarily Admitted with Sepsis and Non-sepsis Diagnoses. Indian J Crit Care Med 2021;25(3): 292-295.