Neutrophil dysregulation during sepsis: an overview and update

CD177+ neutrophils exacerbate septic lung injury via the NETs/AIM2 pathway: An experimental and bioinformatics study

BACKGROUND

Acute lung injury (ALI) is one of the most common complications of sepsis. However, the underlying mechanisms and effective treatment strategies remain poorly understood. Immune cells are crucial in sepsis-induced lung injury, yet the heterogeneity of the immune cell populations involved in this context is not well characterized.

METHODS

This study established a Cecal Ligation and Puncture (CLP) mouse model and employed single-cell sequencing along with molecular biology experimental methods to identify the primary functional subgroups of immune cells associated with sepsis-induced ALI, thereby elucidating the key mechanisms related to sepsis-induced ALI.

RESULTS

Our analysis revealed that, in comparison to normal mice, the top 100 differentially expressed genes (DEGs) in septic lung tissue during the acute phase predominantly originate from neutrophils. Cd177 antigen (Cd177)+ neutrophils represent the predominant subpopulation of neutrophils in septic lung tissue. These cells exhibit unique pro-inflammatory and oxidative stress characteristics, and they are capable of producing excessive neutrophil extracellular traps (NETs). NETs can aggravate ALI by activating Absent in Melanoma 2 (AIM2) inflammasome. Furthermore, we discovered that melatonin could effectively inhibit the infiltration of Cd177+ neutrophils in septic lung tissue, reduce the expression levels of NETs, and diminish the activation of AIM2, thereby improving lung injury.

CONCLUSION

Our research provides novel insights and potential therapeutic targets for the treatment of sepsis-induced ALI.

Neutralization of IL-17 and CXCR1 Protects Septic Arthritis by Regulating CXCL8-CXCR1 Pathway Along With Functional Activities in Neutrophils

AIM

The main objective of this study is to elucidate the role of CXCR1 Ab, IL-17 Ab, and gentamicin in protecting septic arthritis by regulating neutrophil functional responses while evaluating the contribution of the CXCL8-CXCR1 pathway.

METHODS

Eighty-four experimental swiss albino mice were utilized to study septic arthritis. They were divided into eight groups. After developing sepsis, respective mice groups were treated with CXCR1 Ab, IL-17 Ab, and gentamicin doses. Doses were administered on days 1, 8, and 13 of the experimental schedule. At the early, middle, and late phases of the experiment i.e. at 3, 10, and 15 DPI (Days Post Infection), mice were sacrificed and blood and tissues were collected for further experimental evaluations. Different functional studies were performed on isolated blood neutrophils, spleen, and synovial tissues. Histological evaluation, immunofluorescence study, sepsis profile, and downstream signaling pathway analysis were done to obtain data.

RESULTS

Infected mice group exhibited high inflammatory responses while treatment helped to mitigate them. IL-17 neutralization helped to lower bacterial burden, neutrophil ROS activity, MPO activity, and ALP activity. However, the combined neutralization of CXCR1 and IL-17 greatly influenced PMN chemotactic activity and lysozyme activity. At the early phase of the experiment, IL-17 neutralization's impact was more prominent, while later, CXCR1 neutralization gained the upper hand.

CONCLUSIONS

We can conclude that IL-17 Ab in combination with gentamicin is potent in modulating neutrophil activities positively to cure sepsis, while CXCR1 Ab, through the CXCL8/CXCR1 pathway, regulates neutrophil functional activities by impacting different downstream signaling cascades.

Relationship between preoperative neutrophil to high-density lipoprotein ratio and postoperative systemic inflammatory response syndrome in elderly patients: a retrospective cohort study

BACKGROUND

Systemic inflammatory response syndrome (SIRS) remains a serious health problem that consumes a large amount of medical resources. The objective of the study was to investigate whether older patients with a high neutrophil to high-density lipoprotein ratio (NHR) before surgery were more susceptible to postoperative SIRS.

METHODS

This retrospective cohort study was conducted on patients older than 65 years admitted to the two campuses of the Third Affiliated Hospital of Sun Yat-sen University between January 2015 and September 2020. Patient baseline characteristics such as demographic information, medical history, laboratory test results, and variables related to postoperative SIRS were obtained from the electronic health record system. The main outcome was the occurrence of postoperative SIRS during the initial three days after surgery. The main exposure was the NHR, divided into two groups according to the optimal receiver operating characteristic (ROC) cut-off value: NHR < 4.82 and NHR ≥ 4.82.

RESULTS

The study involved 5696 older patients, among whom 1419 (24.91%) developed SIRS. The ROC analysis showed that the NHR had the largest curve area for predicting postoperative SIRS. The NHR ≥ 4.82 was independently linked to a higher risk of postoperative SIRS (aOR = 1.29, 95% CI: 1.10-1.52, P = 0.002). This association remained robust in various sensitivity and subgroup analyses. The NHR ≥ 4.82 was correlated with an elevated risk of hospital mortality, prolonged postoperative hospital stays, and increased direct medical expenses.

CONCLUSIONS

The study found that older patients undergoing general anesthesia with NHR ≥ 4.82 were associated with an increased risk of postoperative SIRS.

Single-Cell Landscape of Bronchoalveolar Lavage Fluid Identifies Specific Neutrophils during Septic Immunosuppression

Sepsis-induced immunosuppression is related to increased susceptibility to secondary infections and death. Lung is the most vulnerable target organ in sepsis, but the understanding of the pulmonary immunosuppression state is still limited. Here, single-cell RNA sequencing of bronchoalveolar lavage fluid (BALF) is performed to map the landscape of immune cells, revealing a neutrophil-driven immunosuppressive program in the lungs of patients with immunosuppressive sepsis. Although immunosuppressive genes are upregulated in different immune cells, only neutrophils dramatically increase in the BALF of patients in immunosuppressive phase of sepsis. Five neutrophil subpopulations in BALF are identified, among which CXCR2+ and CD274 (PD-L1 coding gene)+IL1RN+ neutrophil subpopulations increased significantly during septic immunosuppression. Interestingly, a developmental trajectory from CXCR2+ to CD274+IL1RN+ neutrophil subpopulation is disclosed. Moreover, the therapeutic effect of CXCR2 blockade is observed on the survival of septic mice, along with a decreased number of PD-L1+ neutrophils. Taken together, the CXCR2+ neutrophil subpopulation is discovered as a contributor to immunosuppression in sepsis and identified it as a potential therapeutic target in sepsis treatment.

The Protective Effect of Octanoic Acid on Sepsis: A Review

Sepsis, a systemic inflammation that occurs in response to a bacterial infection, is a significant medical challenge. Research conducted over the past decade has indicated strong associations among a patient's nutritional status, the composition of their gut microbiome, and the risk, severity, and prognosis of sepsis. Octanoic acid (OA) plays a vital role in combating sepsis and has a protective effect on both animal models and human patients. In this discussion, the potential protective mechanisms of OA in sepsis, focusing on its regulation of the inflammatory response, immune system, oxidative stress, gastrointestinal microbiome and barrier function, metabolic disorders and malnutrition, as well as organ dysfunction are explored. A comprehensive understanding of the mechanisms by which OA act may pave the way for new preventive and therapeutic approaches to sepsis.

Polyethyleneimine/fucoidan polyplexes as vaccine carriers for enhanced antigen loading and dendritic cell activation

Vaccination is one of the most effective strategies for preventing infectious diseases. Recently, most research has centered on the development of protein subunit vaccines due to their safety. However, their low immunogenicity remains a challenge. Nanoparticle vaccines offer advantages by protecting proteins from degradation and acting as adjuvants to stimulate the immune system. Herein, a polyplexe (OVA@PEI/Fu) formed by the electrostatic interaction between positively charged polyethyleneimine (PEI) and negatively charged fucoidan was prepared for the encapsulation of a model antigen, ovalbumin (OVA). Experimental results revealed that the incorporation of fucoidan in the polyplexes not only enhanced OVA loading efficiency but also contributed adjuvant effects, significantly boosting dendritic cell activation and maturation in vitro compared to OVA@PEI polyplexes. In vivo experiments showed that the OVA@PEI/Fu can induce strong anti-OVA specific antibody responses, as well as OVA-specific CD4+ and CD8+ T cell responses. The carrier developed in the present study shows promise as a platform for protein-based subunit vaccines.

Dysregulation of neutrophil in sepsis: recent insights and advances

Sepsis remains the leading cause of death in intensive care units. Despite newer antimicrobial and supportive therapies, specific treatments are still lacking. Neutrophils are pivotal components of the effector phase of the host immune defense against pathogens and play a crucial role in the control of infections under normal circumstances. In addition to its anti-infective effects, the dysregulation and overactivation of neutrophils may lead to severe inflammation or tissue damage and are potential mechanisms for poor prognosis in sepsis. This review focuses on recent advancements in the understanding of the functional status of neutrophils across various pathological stages of sepsis to explore the mechanisms by which neutrophils participate in sepsis progression and provide insights for the treatment of sepsis by targeting neutrophils.

Gypenoside XLIX Activates the Sirt1/Nrf2 Signaling Pathway to Inhibit NLRP3 Inflammasome Activation to Alleviate Septic Acute Lung Injury

Currently, treatment options for acute lung injury (ALI) are limited. Gypenoside XLIX (Gyp-XLIX) is known for its anti-inflammatory properties, but there is a lack of extensive research on its effects against ALI. This study induced ALI in mice through cecal ligation and puncture surgery and investigated the biological activity and potential mechanisms of Gypenoside XLIX (40 mg/kg) by intraperitoneal injection. The in vitro ALI model was established using mouse lung epithelial (MLE-12) cells stimulated with lipopolysaccharide (LPS) and adenosine triphosphate (ATP). Various methods, including Hematoxylin and Eosin (H&E) staining, biochemical assay kits, Quantitative Polymerase Chain Reaction (qPCR) analysis, Western blotting, Terminal deoxynucleotidyl transferase dUTP Nick End Labeling (TUNEL) assay, immunofluorescence, and flow cytometry, were employed for this research. The results indicated that pretreatment with Gypenoside XLIX significantly alleviated pathological damage in mouse lung tissues and reduced the expression levels of inflammatory factors. Additionally, Gypenoside XLIX inhibited ROS levels and NLRP3 inflammasome, possibly mediated by the Sirt1/Nrf2 signaling pathway. Moreover, Gypenoside XLIX significantly inhibited sepsis-induced lung cell apoptosis and excessive autophagy of mitochondria. Specifically, it suppressed mitochondrial pathway apoptosis and the Pink1/Parkin pathway of mitochondrial autophagy. These findings reveal the multifaceted effects of Gypenoside XLIX in anti-inflammatory, antioxidative, and inhibition of cell apoptosis and autophagy. This provides strong support for its therapeutic potential in sepsis-related lung injuries.

Sepsis Diagnosis Based on a Parylene Matrix Chip Using LPC16:0 as a Biomarker in Comparison with Colorimetry of Total Phospholipid

For the medical diagnosis of sepsis, it is crucial to differentiate infectious inflammation from noninfectious symptoms to prevent acute aggravation. Herein, a diagnosis for early stage sepsis was performed using LPC 16:0 and total phospholipids as small molecular biomarkers. The measurement of LPC 16:0 was conducted using a parylene matrix chip, which was developed to effectively detect small molecules in laser desorption/ionization mass spectrometry (LDI-MS). Meanwhile, the total phospholipid level was measured using colorimetry, following an enzymatic assay. Next, the two biomarkers were analyzed in serum samples from healthy volunteers, systemic inflammatory response syndrome (SIRS) patients, and sepsis patients. Diagnostic criteria were established based on the biomarker intensities observed in each patient group. After the measurements were conducted, the interference in phospholipid analysis due to hemoglobin contamination was considered. Additionally, the analytical parameters from biomarker detection were statistically interpreted and compared with those of conventional diagnostic standards. Finally, the diagnostic performance of each biomarker was evaluated by analyzing the biomarker levels between patient groups and examining their overlapping extents in box plots to distinguish sepsis from noninfectious inflammatory symptoms.

IL-6 and PD-1 antibody blockade combination therapy regulate inflammation and T lymphocyte apoptosis in murine model of sepsis

BACKGROUND

Interleukin-6 (IL-6) plays a central role in sepsis-induced cytokine storm involving immune hyperactivation and early neutrophil activation. Programmed death protein-1 (PD-1) is associated with sepsis-induced immunosuppression and lymphocyte apoptosis. However, the effects of simultaneous blockade of IL-6 and PD-1 in a murine sepsis model are not well understood.

RESULTS

In this study, sepsis was induced in male C57BL/6 mice through cecal ligation and puncture (CLP). IL-6 blockade, PD-1 blockade, or combination of both was administered 24 h after CLP. Peripheral blood count, cytokine level, lymphocyte apoptosis in the spleen, neutrophil infiltration in the lungs and liver, and survival rate were measured. The mortality rate of the IL-6/PD-1 group was lower, though not statistically significant (p = 0.164), than that of CLP mice (75.0% vs. 91.7%). The IL-6/PD-1 group had lower neutrophil percentage and platelet count compared with the CLP group; no significant difference was observed in other cytokine levels. The IL-6/PD-1 group also showed reduced T lymphocyte apoptosis in the spleen and decreased neutrophil infiltration in the liver and lungs.

CONCLUSIONS

IL-6/PD-1 dual blockade reduces neutrophil infiltration, lymphocyte apoptosis, and bacterial burden while preserving tissue integrity in sepsis. Although the improvement in survival was not statistically significant, these findings highlight its potential as a therapeutic approach in sepsis.

Identification of potential crucial genes and biomarkers from neutrophils in sepsis using bioinformatics analysis

Sepsis is a complex series of immune responses to infection and is commonly associated with acquired immunodeficiency. The current study aimed to identify the biomarkers of sepsis. Differential expression analysis and protein-protein interaction analysis were conducted to explore potential biomarkers. Gene Ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes analysis were performed to explore potential mechanisms. The Immune Cell Abundance Identifier website was utilized to evaluate immune cell infiltration in the whole blood. Receiver operating characteristic curve and area under the curve were applied to compare the prognostic accuracy of hub genes. Six genes were selected via differentially expressed gene analysis and protein-protein interaction analysis. Furthermore, CTSD, GADD45A, MAPK14, MMP9, and VIM were selected via validation analysis of independent datasets. Immune infiltration analysis showed that CTSD, GADD45A, MAPK14, MMP9, and VIM may regulate immune cells via neutrophils. Patients with sepsis had a significantly higher expression of CTSD, GADD45A, MAPK14, MMP9, and VIM than normal health controls. The area under the curve of CTSD, GADD45A, MAPK14, MMP9, and VIM were 0.90 (0.83-0.97), 0.89 (0.81-0.96), 0.91 (0.84-0.87), 0.95 (0.91-1.00), and 0.95 (0.91-1.00), respectively. According to the validation result of RT-PCR, only MAPK14 was significantly upregulated compared with controls, which was concordant with the bioinformatics analysis results. This study identified several potential diagnostic genes including CTSD, GADD45A, MAPK14, MMP9, and VIM. These genes may regulate the expression of immune cells via neutrophils in the development of sepsis.

Bacteria and host: what does this mean for sepsis bottleneck?

BACKGROUND

Sepsis is a life-threatening inflammatory condition in which the invading pathogen avoids the host's defense mechanisms and continuously stimulates and damages host cells. Consequently, many immune responses initially triggered for protection become harmful because of the failure to restore homeostasis, resulting in ongoing hyperinflammation and immunosuppression.

METHODS

A literature review was conducted to address bacterial sepsis, describe advances in understanding complex immunological reactions, critically assess diagnostic approaches, and emphasize the importance of studying bacterial bottlenecks in the detection and treatment of sepsis.

RESULTS

Diagnosing sepsis via a single laboratory test is not feasible; therefore, multiple key biomarkers are typically monitored, with a focus on trends rather than absolute values. The immediate interpretation of sepsis-associated clinical signs and symptoms, along with the use of specific and sensitive laboratory tests, is crucial for the survival of patients in the early stages. However, long-term mortality associated with sepsis is now recognized, and alongside the progression of this condition, there is an in vivo selection of adapted pathogens.

CONCLUSION

Bacterial sepsis remains a significant cause of mortality across all ages and societies. While substantial progress has been made in understanding the immunological mechanisms underlying the inflammatory response, there is growing recognition that the ongoing host-pathogen interactions, including the emergence of adapted virulent strains, shape both the acute and long-term outcomes in sepsis. This underscores the urgent need for novel high-throughput diagnostic methods and a shift toward more pre-emptive, rather than reactive, treatment strategies in sepsis care.

N6-methyladenosine (m6A) modification in inflammation: a bibliometric analysis and literature review

N6-methyladenosine (m6A) is the most abundant internal messenger RNA modification in eukaryotes, influencing various physiological and pathological processes by regulating RNA metabolism. Numerous studies have investigated the role of m6A in inflammatory responses and inflammatory diseases. In this study, VOSviewer and Citespace were used to perform bibliometric analysis to systematically evaluating the current landscape of research on the association between m6A and inflammation. The literature was sourced from the Web of Science Core Collection, with characteristics including year, country/region, institution, author, journal, citation, and keywords. According to the bibliometric analysis results of keywords, we present a narrative summary of the potential mechanisms by which m6A regulates inflammation. The results showed that the key mechanisms by which m6A modulates inflammation include apoptosis, autophagy, oxidative stress, immune cell dysfunction, and dysregulation of signaling pathways.

Aloe-emodin plus TIENAM ameliorate cecal ligation and puncture-induced sepsis in mice by attenuating inflammation and modulating microbiota

Despite the high sepsis-associated mortality, effective and specific treatments remain limited. Using conventional antibiotics as TIENAM (imipenem and cilastatin sodium for injection, TIE) is challenging due to increasing bacterial resistance, diminishing their efficacy and leading to adverse effects. We previously found that aloe-emodin (AE) exerts therapeutic effects on sepsis by reducing systemic inflammation and regulating the gut microbiota. Here, we investigated whether administering AE and TIE post-sepsis onset, using a cecal ligation and puncture (CLP)-induced sepsis model, extends survival and improves physiological functions. Survival rates, inflammatory cytokines, tissue damage, immune cell populations, ascitic fluid microbiota, and key signaling pathways were assessed. Combining AE and TIE significantly enhanced survival rates, and reduced inflammation and bacterial load in septic mice, indicating potent antimicrobial properties. Moreover, substantial improvements in survival rates of AE + TIE-treated mice (10% to 60%) within 168 h were observed relative to the CLP group. This combination therapy also effectively modulated inflammatory marker (interleukin [IL]-6, IL-1β, and tumor necrosis factor [TNF]-α) levels and immune cell counts by decreasing those of B, NK, and TNFR2+ Treg cells, while increasing that of CD8+ T cells; alleviated tissue damage; reduced bacterial load in the peritoneal cavity; and suppressed the NF-κB signaling pathway. We also observed a significantly altered peritoneal cavity microbiota composition post-treatment, characterized by reduced pathogenic bacteria (Bacteroides) abundance. Our findings underscore the potential of AE + TIE in treating sepsis, and encourage further research and possible clinical implementations to surmount the limitations of TIE and amplify the therapeutic potential of AE.

Could P2X7 receptor be a potencial target in neonatal sepsis?

The United Nations Inter-Agency Group for Child Mortality Estimation (UNIGME) estimates that every year 2.5 million neonates die in their first month of life, accounting for nearly one-half of deaths in children under 5 years of age. Neonatal sepsis is the third leading cause of neonatal mortality. The worldwide burden of bacterial sepsis is expected to increase in the next decades due to the lack of effective molecular therapies to replace the administration of antibiotics whose efficacy is compromised by the emergence of resistant strains. In addition, prolonged exposure to antibiotics can have negative effects by increasing the risk of infection by other organisms. With the global burden of sepsis increasing and no vaccine nor other therapeutic approaches proved efficient, the World Health Organization (WHO) stresses the need for new therapeutic targets for sepsis treatment and infection prevention (WHO, A73/32). In response to this unresolved clinical issue, the P2X7 receptor (P2X7R), a key component of the inflammatory cascade, has emerged as a potential target for treating inflammatory/infection diseases. Indeed numerous studies have demonstrated the relevance of the purinergic system as a pharmacological target in addressing immune-mediated inflammatory diseases by regulating immunity, inflammation, and organ function. In this review, we analyze key features of sepsis immunopathophysiology focusing in neonatal sepsis and on how the immunomodulatory role of P2X7R could be a potential pharmacological target for reducing the burden of neonatal sepsis.

CMTM3 regulates neutrophil activation and aggravates sepsis through TLR4 signaling

Regulation of neutrophil activation plays a significant role in managing sepsis. CKLF-like MARVEL transmembrane domain containing (CMTM)3 is a membrane protein involved in immune response. Here, we find that CMTM3 expression is elevated in sepsis and plays a crucial role in mediating the imbalance of neutrophil migration. Cmtm3 knockout improves the survival rate of septic mice, mitigate inflammatory responses, and ameliorate organ damage. Mechanistically, the deletion of Cmtm3 reduced the expression of Toll-like receptor 4 (TLR4) on neutrophils, leading to a decrease in the expression of C-X-C motif chemokine receptor 2 (CXCR2) on the cell membrane. This resulted in a reduced migration of neutrophils from the bone marrow to the bloodstream, thereby attenuating their recruitment to vital organs. Our findings suggest that targeting CMTM3 holds promise as a therapeutic approach to ameliorate the dysregulation of neutrophil migration and multi-organ damage associated with sepsis.

The toxic effects of neutrophil extracellular traps on mesenchymal stem cells

Sepsis, a systemic inflammatory response syndrome resulting from an uncontrolled inflammatory reaction to infection, remains without a definitive cure despite therapeutic advancements. Mesenchymal stem cells (MSCs), renowned for their capacity to alleviate inflammation and modulate the immune system, have emerged as a potential treatment avenue for sepsis. In sepsis pathophysiology, hyperactivated neutrophils release extracellular neutrophil traps (NETs). NETs are essential for eradicating pathogens; however, excessive formation leads to tissue damage. Given the limited knowledge regarding the impact of NETs on MSCs used in sepsis therapy and the established interaction between MSCs and NETs, this study investigates the effects of NETs on MSCs in vitro. NETs were isolated from stimulated neutrophils, and MSCs were sourced from umbilical cord blood. After co-culturing MSCs with isolated NETs, MSCs' viability, migration, intracellular antioxidant capacity, and changes in gene expression were analyzed. Following exposure to NETs, MSCs exhibited obvious apoptosis and necrosis. NETs disrupt MSCs' mitochondrial activity. Also, NETs upregulate the pro-apoptotic gene BAX and downregulate the anti-apoptotic gene BCL2 in MSCs. Additionally, NETs reduce MSCs' intracellular antioxidant capacity. Furthermore, MSC migration is significantly impaired by NETs. This study collectively demonstrates that NETs have toxic and detrimental effects on MSCs. These effects on MSCs indicate a potential barrier to their functionality and therapeutic efficacy. Therefore, it appears that reducing the undesirable effects of NETs could serve as a novel target to enhance the therapeutic efficacy of MSCs in septic patients.

Recruitment of neutrophils in glomeruli in early mouse sepsis is associated with E-selectin expression and activation of endothelial nuclear factor kappa-light-chain-enhancer of activated B cells and mitogen-activated protein kinase pathways

Sepsis is a dysregulated systemic inflammatory response to an infection, which can lead to multiple organ dysfunction syndrome that includes the kidney. Leukocyte recruitment is an important process of the host immune defense in response to sepsis. Endothelial cells (EC) actively regulate leukocyte recruitment by expressing adhesion molecules following the activation of dedicated intracellular signal transduction pathways. Previous studies reported that the expression of adhesion molecules was associated with the activation of endothelial nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65 and mitogen-activated protein kinase (MAPK) c-Jun pathways in vitro in response to conditions that mimic processes that occur in inflammation. This study aimed to investigate the spatiotemporal patterns of leukocyte recruitment, expression of adhesion molecules, and endothelial nuclear p65 and c-Jun localization in renal microvascular beds of septic mice. Here, we used a cecal ligation and puncture (CLP) sepsis mouse model and RT-qPCR and immunohistochemical staining. We showed that neutrophils, macrophages, and T lymphocytes were all present in the kidney, yet only neutrophils accumulated in a spatiotemporally discernible pattern, mainly in glomeruli at 4 h after CLP sepsis initiation. E-selectin, not vascular cell adhesion molecule-1 (VCAM-1), was expressed in glomeruli at the same time point. In a subset of mice at 72 h after CLP sepsis started, VCAM-1 expression was prominent in glomerular EC, which was not related to changes in mmu-microRNA(miR)-126a-3p levels, a short noncoding microRNA previously shown to inhibit the translation of VCAM-1 mRNA into protein. Nuclear localization of p65 and c-Jun occurred in EC of all microvascular segments at 4 and 7 h after CLP sepsis initiation. In summary, sepsis-induced recruitment of neutrophils, E-selectin expression, and NF-κB p65 and MAPK c-Jun pathway activation coincided in glomeruli at the early stage of the disease. In the other microvascular beds, sepsis led to NF-κB p65 and MAPK c-Jun pathway activation with limited expression of E-selectin and no association with VCAM-1 expression or leukocyte recruitment.

Combining Aloin with TIENAM ameliorates cecal ligation and puncture-induced sepsis in mice by attenuating inflammation and modulating abdominal cavity microbiota

Despite the high mortality rate, sepsis lacks specific and effective treatment options. Conventional antibiotics, such as TIENAM (TIE; imipenem and cilastatin sodium for injection), face challenges owing to the emergence of bacterial resistance, which reduces their effectiveness and causes adverse effects. Addressing resistance and judicious drug use is crucial. Our research revealed that aloin (Alo) significantly boosts survival rates and reduces inflammation and bacterial load in mice with sepsis, demonstrating strong antimicrobial activity. Using a synergistic Alo + TIE regimen in a cecal ligation and puncture (CLP)-induced sepsis model, we observed a remarkable increase in survival rates from 10 % to 75 % within 72 h compared with the CLP group alone. This combination therapy also modulated inflammatory markers interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α, mitigated tissue damage, regulated immune cells by lowering NK, activated CD8+ and CD4+ T cells while increasing peritoneal macrophages, and decreased the bacterial load in the peritoneal cavity. We noted a significant shift in the abdominal cavity microbiota composition post-treatment, with a decrease in harmful bacteria, such as Lachnospiraceae_NK4A136_group, Klebsiella, Bacillus, and Escherichia, and an increase in beneficial bacteria, such as Lactobacillus and Mucispirillum. Our study emphasizes the efficacy of combining Alo with TIE to combat sepsis, and paves the way for further investigations and potential clinical applications aiming to overcome the limitations of TIE and enhance the therapeutic prospects of Alo.

Combining ulinastatin with TIENAM improves the outcome of sepsis induced by cecal ligation and puncture in mice by reducing inflammation and regulating immune responses

Despite the high mortality associated with sepsis, effective and targeted treatments remain scarce. The use of conventional antibiotics such as TIENAM (imipenem and cilastatin sodium for injection, TIE) is challenging because of the increasing bacterial resistance, which diminishes their efficacy and leads to adverse effects. Our previous studies demonstrated that ulinastatin (UTI) exerts a therapeutic impact on sepsis by reducing systemic inflammation and modulating immune responses. In this study, we examined the possibility of administering UTI and TIE after inducing sepsis in a mouse model using cecal ligation and puncture (CLP). We assessed the rates of survival, levels of inflammatory cytokines, the extent of tissue damage, populations of immune cells, microbiota in ascites, and important signaling pathways. The combination of UTI and TIE significantly improved survival rates and reduced inflammation and bacterial load in septic mice, indicating potent antimicrobial properties. Notably, the survival rates of UTI+TIE-treated mice increased from 10 % to 75 % within 168 h compared to those of mice that were subjected to CLP. The dual treatment successfully regulated the levels of inflammatory indicators (interleukin [IL]-6, IL-1β, and tumor necrosis factor [TNF]-α) and immune cell numbers by reducing B cells, natural killer cells, and TNFR2+ Treg cells and increasing CD8+ T cells. Additionally, the combination of UTI and TIE alleviated tissue damage, reduced bacterial load in the peritoneal cavity, and suppressed the NF-κB signaling pathway. Our findings indicate that UTI and TIE combination therapy can significantly enhance sepsis outcomes by reducing inflammation and boosting the immune system. The results offer a promising therapeutic approach for future sepsis treatment.

Deciphering sepsis: An observational bioinformatic analysis of gene expression in granulocytes from GEO dataset GSE123731

Sepsis triggers severe inflammatory responses leading to organ dysfunction and demands early diagnostic and therapeutic intervention. This study identifies differentially expressed genes (DEGs) in sepsis patients using the Gene Expression Omnibus database to find potential diagnostic and therapeutic markers. We analyzed the dataset GSE123731 via GEO2R to detect DEGs, constructed protein-protein interaction networks, and performed transcription factor analyses using Cytoscape. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses were conducted using R and FunRich software. Key genes were validated by Quantitative Reverse Transcription Polymerase Chain and co-immunoprecipitation assays in granulocytes from sepsis patients. We identified 59 DEGs significantly involved in neutrophil degranulation and immune system activation. Cytokine signaling pathways were highlighted in Kyoto Encyclopedia of Genes and Genomes analysis. Co-immunoprecipitation assays confirmed interactions involving matrix metallopeptidase 8, matrix metallopeptidase 9, and arginase 1, supporting their roles as biomarkers. The identified DEGs and validated interactions reveal crucial molecular mechanisms in sepsis, offering new avenues for diagnostic and therapeutic strategies, potentially enhancing patient outcomes.

Neutrophil response to Porphyromonas gingivalis is modulated by low-level laser application

OBJECTIVES

Neutrophil response is critical in inflammatory regulation and immune response to bacterial infections. During periodontal disease, pathogenic bacteria lead to exaggerated neutrophil responses. We hypothesized that low-level laser application (LLLT), therapeutic strategy for dampening inflammatory processes, will regulate neutrophil activity in response to periodontopathogens.

MATERIALS AND METHODS

The impact of LLLT on neutrophil responses was measured by light delivered at wavelength of 850 nm. The direct effect of LLLT on P. gingivalis A7436 was determined by flow cytometry using LIVE/DEADTM Cell Vitality kit. The phagocytosis of P. gingivalis A7436 by human neutrophils was measured using flow cytometry. Superoxide generation was measured by cytochrome-C-reduction in the presence of N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP; 1 mM). Cytokine release by neutrophils was measured by multiplex immunoassay.

RESULTS

The phagocytosis of P. gingivalis by primary human neutrophils was significantly reduced in response to LLLT (p < 0.05). While LLLT led to increased superoxide production in neutrophils that were not challenged by P. gingivalis, it dampened the increased superoxide and IL-6 release by the neutrophils in response to P. gingivalis. LLLT did not directly affect the viability of P. gingivalis.

CONCLUSION

These results suggested that LLLT can provide therapeutic strategy in periodontal disease, regulating the neutrophil response to P. gingivalis.

The Promise of a Pointillist Perspective for Comparative Immunology

Most studies in comparative immunology involve investigations into the detailed mechanisms of the immune system of a nonmodel organism. Although this approach has been insightful, it has promoted a deep understanding of only a handful of species, thus inhibiting the recognition of broad taxonomic patterns. Here, we call for investigating the immune defenses of numerous species within a pointillist framework, that is, the meticulous, targeted collection of data from dozens of species and investigation of broad patterns of organismal, ecological, and evolutionary forces shaping those patterns. Without understanding basic immunological patterns across species, we are limited in our ability to extrapolate and/or translate our findings to other organisms, including humans. We illustrate this point by focusing predominantly on the biological scaling literature with some integrations of the pace of life literature, as these perspectives have been the most developed within this framework. We also highlight how the more traditional approach in comparative immunology works synergistically with a pointillist approach, with each approach feeding back into the other. We conclude that the pointillist approach promises to illuminate comprehensive theories about the immune system and enhance predictions in a wide variety of domains, including host-parasite dynamics and disease ecology.

Microfluidic device reveals new insights into impairment of neutrophil transmigration in patients with sepsis

Neutrophils need to migrate through tight tissue spaces to eliminate pathogens, but their movement is often hindered by their large and stiff nuclei. Neutrophil migration is impaired in sepsis patients, but it is unclear whether this defect is related to the deformability of their nuclei. Herein, we designed microfluidic devices with micron-scale narrow slits to simulate biological barriers. This setup allowed us to observe and record neutrophil movement and nuclear deformation in real-time. We also developed a method for morphological analysis to quantify nucleus deformation in numerous individual cells. Our studies showed that neutrophils from healthy individuals could adjust their nuclear shape to squeeze through these constrictions, whereas those from sepsis patients demonstrated less flexibility. Neutrophils with rigid nuclei struggled to pass through narrow gaps and were more likely to rupture under pressure. These findings suggest that the migration defects of neutrophils observed in sepsis may be attributed to the inability of neutrophils to deform their nuclei, highlighting the crucial role of microfluidic technologies in offering new insights into migration defects under pathological conditions.

R406 reduces lipopolysaccharide-induced neutrophil activation

Modulating SYK has been demonstrated to have impacts on pathogenic neutrophil responses in COVID-19. During sepsis, neutrophils are vital in early bacterial clearance but also contribute to the dysregulated immune response and organ injury when hyperactivated. Here, we evaluated the impact of R406, the active metabolite of fostamatinib, on neutrophils stimulated by LPS. We demonstrate that R406 was able to effectively inhibit NETosis, degranulation, ROS generation, neutrophil adhesion, and the formation of CD16low neutrophils that have been linked to detrimental outcomes in severe sepsis. Further, the neutrophils remain metabolically active, capable of releasing cytokines, perform phagocytosis, and migrate in response to IL-8. Taken together, this data provides evidence of the potential efficacy of utilizing fostamatinib in bacterial sepsis.

Administration of turmeric kombucha ameliorates lipopolysaccharide-induced sepsis by attenuating inflammation and modulating gut microbiota

Our research team previously reported the immunomodulatory effects of kombucha fermentation liquid. This study investigated the protective effects of turmeric kombucha (TK) against lipopolysaccharide (LPS)-induced sepsis and its impact on the intestinal microbiota of mice. A turmeric culture medium without kombucha served as the control (TW). Non-targeted metabolomics analysis was employed to analyze the compositional differences between TK and TW. Qualitative analysis identified 590 unique metabolites that distinguished TK from TW. TK improved survival from 40 to 90%, enhanced thermoregulation, and reduced pro-inflammatory factor expression and inflammatory cell infiltration in the lung tissue, suppressing the NF-κB signaling pathway. TK also altered the microbiome, promoting Allobaculum growth. Our findings shed light on the protective effects and underlying mechanisms of TK in mitigating LPS-induced sepsis, highlighting TK as a promising anti-inflammatory agent and revealing new functions of kombucha prepared through traditional fermentation methods.

An analytical observational study for diagnostic accuracy of volume, conductivity & scatter (VCS) indices of neutrophils for diagnosis of sepsis in an emergency hospital setting

Background & objectives The newer technique using an innovative volume conductivity scatter (VCS) technology is emerging as a surrogate for sepsis diagnosis. The VCS technology offers a more objective method to measure cell volume (V), characterize conductivity (C) and light scatter (S) directly from more than 8,000 white blood cells (WBCs). However, diagnostic performance of VCS parameters in sepsis has not been extensively tested in routine hospital emergency settings. Therefore, the present study aimed to investigate the diagnostic and prognostic performance of VCS markers of neutrophils in our local hospital emergency setting. Methods It was an observational analytical study with 41 cases of sepsis and 43 healthy controls aged above 18 yr. Individuals with acute coronary syndrome and individuals with already diagnosed Human Immunodeficiency Virus (HIV) infection were excluded from the study. Results The mean neutrophil volume (MNV) values were not significantly different between cases and controls (P 0.138) whereas mean neutrophil conductance (MNC) and mean neutrophil scatter (MNS) measurements were significantly higher among cases as compared to controls (both P-values <0.001). According to Receiver Operating Characteristics (ROCs) curve analysis, MNV in our study failed to show statistically significant discriminatory ability in sepsis (AUC 0.54) whereas MNC (AUC 0.98) and MNS (AUC 0.95) showed marked discriminatory ability in diagnosing sepsis in this study cohort. Interpretation & conclusions Among VCS parameters, MNV failed as a standalone biomarker of sepsis in routine emergency setting whereas MNC and MNS had statistically significant diagnostic and discriminatory accuracies among hospitalized affected individuals with sepsis.

Phage therapy combats pan drug-resistant Acinetobacter baumannii infection safely and efficiently

Phage therapy offers a promising approach to combat the growing threat of antimicrobial resistance. Yet, key questions remain regarding dosage, administration routes, combination therapy, and the causes of therapeutic failure. In this study, we focused on a novel lytic phage, ФAb4B, which specifically targeted the Acinetobacter baumannii strains with KL160 capsular polysaccharide, including the pan-drug resistant A. baumannii YQ4. ФAb4B exhibited the ability to effectively inhibit biofilm formation and eradicate mature biofilms independently of dosage. Additionally, it demonstrated a wide spectrum of antibiotic-phage synergy and did not show any cytotoxic or haemolytic effects. Continuous phage injections, both intraperitoneally and intravenously over 7 d, showed no acute toxicity in vivo. Importantly, phage therapy significantly improved neutrophil counts, outperforming ciprofloxacin. However, excessive phage injections suppressed neutrophil levels. The combinatorial treatment of phage-ciprofloxacin rescued 91% of the mice, a superior outcome compared to phage alone (67%). The efficacy of the combinatorial treatment was independent of phage dosage. Notably, prophylactic administration of the combinatorial regimen provided no protection, but even when combined with a delayed therapeutic regimen, it saved all the mice. Bacterial resistance to the phage was not a contributing factor to treatment failure. Our preclinical study systematically describes the lytic phage's effectiveness in both in vitro and in vivo settings, filling in crucial details about phage treatment against bacteriemia caused by A. baumannii, which will provide a robust foundation for the future of phage therapy.

A synthetic bioactive peptide of the C-terminal fragment of adhesion protein Fibulin7 attenuates the inflammatory functions of innate immune cells in LPS-induced systemic inflammation

OBJECTIVE

Systemic inflammation is associated with improper localization of hyperactive neutrophils and monocytes in visceral organs. Previously, a C-terminal fragment of adhesion protein Fibulin7 (Fbln7-C) was shown to regulate innate immune functionality during inflammation. Recently, a shorter bioactive peptide of Fbln7-C, FC-10, via integrin binding was shown to reduce ocular angiogenesis. However, the role of FC-10 in regulating the neutrophils and monocyte functionality during systemic inflammatory conditions is unknown. The study sought to explore the role of FC-10 peptide on the functionality of innate immune cells during inflammation and endotoxemic mice.

METHODS

Neutrophils and monocytes were isolated from healthy donors and septic patient clinical samples and Cell adhesion assay was performed using a UV spectrophotometer. Gene expression studies were performed using qPCR. Protein level expression was measured using ELISA and flow cytometry. ROS assay, and activation markers analysis in vitro, and in vivo were done using flow cytometry.

TREATMENT

Cells were stimulated with LPS (100 ng/mL) and studied in the presence of peptides (10 μg, and 20 μg/mL) in vitro. In an in vivo study, mice were administered with LPS (36.8 mg/kg bw) and peptide (20 μg).

RESULTS

This study demonstrates that human neutrophils and monocytes adhere to FC-10 via integrin β1, inhibit spreading, ROS, surface activation markers (CD44, CD69), phosphorylated Src kinase, pro-inflammatory genes, and protein expression, compared to scrambled peptide in cells isolated from healthy donors and clinical sample. In line with the in vitro data, FC-10 (20 μg) administration significantly decreases innate cell infiltration at inflammatory sites, improves survival in endotoxemia animals & reduces the inflammatory properties of neutrophils and monocytes isolated from septic patients.

CONCLUSION

FC-10 peptide can regulate neutrophils and monocyte functions and has potential to be used as an immunomodulatory therapeutic in inflammatory diseases.

Sided Stimulation of Endothelial Cells Modulates Neutrophil Trafficking in an In Vitro Sepsis Model

While the role of dysregulated polymorphonuclear leukocyte (PMN) transmigration in septic mediated tissue damage is well documented, strategies to mitigate aberrant transmigration across endothelium have yet to yield viable therapeutics. Recently, microphysiological systems (MPS) have emerged as novel in vitro mimetics that facilitate the development of human models of disease. With this advancement, aspects of endothelial physiology that are difficult to assess with other models can be directly probed. In this study, the role of endothelial cell (EC) apicobasal polarity on leukocyte trafficking response is evaluated with the µSiM-MVM (microphysiological system enabled by a silicon membrane - microvascular mimetic). Here, ECs are stimulated either apically or basally with a cytokine cocktail to model a septic-like challenge before introducing healthy donor PMNs into the device. Basally oriented stimulation generated a stronger PMN transmigratory response versus apical stimulation. Importantly, healthy PMNs are unable to migrate towards a bacterial peptide chemoattractant when ECs are apically stimulated, which mimics the attenuated PMN chemotaxis seen in sepsis. Escalating the apical inflammatory stimulus by a factor of five is necessary to elicit high PMN transmigration levels across endothelium. These results demonstrate that EC apicobasal polarity modulates PMN transmigratory behavior and provides insight into the mechanisms underlying sepsis.

Mechanism and therapeutic potential of traditional Chinese medicine extracts in sepsis

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

Development and validation of an ensemble learning risk model for sepsis after abdominal surgery

Introduction

Although their importance has gained attention, the clinical applications of methods for screening patients at high risk of sepsis after abdominal surgery have been restricted. Therefore, we aimed to develop and validate models for screening patients at high risk of sepsis after abdominal surgery based on machine learning with routine variables.

Material and methods

The whole dataset was composed of three representative academic hospitals in China and the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. Routine clinical variables were implemented for model development. The Boruta algorithm was applied for feature selection. Afterwards, ensemble learning and eight other conventional algorithms were used for model fitting and validation based on all features and selected features. The area under the receiver operating characteristic curves (ROC AUC), sensitivity, specificity, F1 score, accuracy, net reclassification index (NRI), integrated discrimination improvement (IDI), decision curve analysis (DCA), and calibration curves were used for model evaluation.

Results

A total of 955 patients undergoing abdominal surgery were finally analyzed (sepsis: 285, non-sepsis: 670). After feature selection, the ensemble learning model constructed by integrating k-Nearest Neighbor (KNN) and Support Vector Machine (SVM) yielded the ROC AUC of 0.892 (0.841-0.944) and accuracy of 85.0% on the test data, and the ROC AUC of 0.782 (0.727-0.838) and accuracy of 68.1% on the validation data, which performed best. Albumin, ASA score, neutrophil-lymphocyte ratio, age, and glucose were the top features associated with postoperative sepsis by KNN and SVM.

Conclusions

We developed a new and potential generalizable model to preoperatively screen patients at high risk of sepsis after abdominal surgery, with the advantages of a representative training cohort and routine variables.

Sepsis in elderly patients: the role of neutrophils in pathophysiology and therapy

Sepsis is among the most important causes of mortality, particularly within the elderly population. Sepsis prevalence is on the rise due to different factors, including increasing average population age and the concomitant rise in the prevalence of frailty and chronic morbidities. Recent investigations have unveiled a "trimodal" trajectory for sepsis-related mortality, with the ultimate zenith occurring from 60 to 90 days until several years after the original insult. This prolonged temporal course ostensibly emanates from the sustained perturbation of immune responses, persevering beyond the phase of clinical convalescence. This phenomenon is particularly associated with the aging immune system, characterized by a broad dysregulation commonly known as "inflammaging." Inflammaging associates with a chronic low-grade activation of the innate immune system preventing an appropriate response to infective agents. Notably, during the initial phases of sepsis, neutrophils-essential in combating pathogens-may exhibit compromised activity. Paradoxically, an overly zealous neutrophilic reaction has been observed to underlie multi-organ dysfunction during the later stages of sepsis. Given this scenario, discovering treatments that can enhance neutrophil activity during the early phases of sepsis while curbing their overactivity in the later phases could prove beneficial in fighting pathogens and reducing the detrimental effects caused by an overactive immune system. This narrative review delves into the potential key role of neutrophils in the pathological process of sepsis, focusing on how the aging process impacts their functions, and highlighting possible targets for developing immune-modulatory therapies. Additionally, the review includes tables that outline the principal potential targets for immunomodulating agents.

Neutrophils cultured ex vivo from CD34+ stem cells are immature and genetically tractable

BACKGROUND

Neutrophils are granulocytes with essential antimicrobial effector functions and short lifespans. During infection or sterile inflammation, emergency granulopoiesis leads to release of immature neutrophils from the bone marrow, serving to boost circulating neutrophil counts. Steady state and emergency granulopoiesis are incompletely understood, partly due to a lack of genetically amenable models of neutrophil development.

METHODS

We optimised a method for ex vivo production of human neutrophils from CD34+ haematopoietic progenitors. Using flow cytometry, we phenotypically compared cultured neutrophils with native neutrophils from donors experiencing emergency granulopoiesis, and steady state neutrophils from non-challenged donors. We carry out functional and proteomic characterisation of cultured neutrophils and establish genome editing of progenitors.

RESULTS

We obtain high yields of ex vivo cultured neutrophils, which phenotypically resemble immature neutrophils released into the circulation during emergency granulopoiesis. Cultured neutrophils have similar rates of ROS production and bacterial killing but altered degranulation, cytokine release and antifungal activity compared to mature neutrophils isolated from peripheral blood. These differences are likely due to incomplete synthesis of granule proteins, as demonstrated by proteomic analysis.

CONCLUSION

Ex vivo cultured neutrophils are genetically tractable via genome editing of precursors and provide a powerful model system for investigating the properties and behaviour of immature neutrophils.

The Prospect of Biomimetic Immune Cell Membrane-Coated Nanomedicines for Treatment of Serious Bacterial Infections and Sepsis

Invasive bacterial infections and sepsis are persistent global health concerns, complicated further by the escalating threat of antibiotic resistance. Over the past 40 years, collaborative endeavors to improve the diagnosis and critical care of septic patients have improved outcomes, yet grappling with the intricate immune dysfunction underlying the septic condition remains a formidable challenge. Anti-inflammatory interventions that exhibited promise in murine models failed to manifest consistent survival benefits in clinical studies through recent decades. Novel therapeutic approaches that target bacterial virulence factors, for example with monoclonal antibodies, aim to thwart pathogen-driven damage and restore an advantage to the immune system. A pioneering technology addressing this challenge is biomimetic nanoparticles-a therapeutic platform featuring nanoscale particles enveloped in natural cell membranes. Borne from the quest for a durable drug delivery system, the original red blood cell-coated nanoparticles showcased a broad capacity to absorb bacterial and environmental toxins from serum. Tailoring the membrane coating to immune cell sources imparts unique characteristics to the nanoparticles suitable for broader application in infectious disease. Their capacity to bind both inflammatory signals and virulence factors assembles the most promising sepsis therapies into a singular, pathogen-agnostic therapeutic. This review explores the ongoing work on immune cell-coated nanoparticle therapeutics for infection and sepsis. SIGNIFICANCE STATEMENT: Invasive bacterial infections and sepsis are a major global health problem made worse by expanding antibiotic resistance, meaning better treatment options are urgently needed. Biomimetic cell-membrane-coated nanoparticles are an innovative therapeutic platform that deploys a multifaceted mechanism to action to neutralize microbial virulence factors, capture endotoxins, and bind excessive host proinflammatory cytokines, seeking to reduce host tissue injury, aid in microbial clearance, and improve patient outcomes.

Assessing the clinical utility of abdominal computed tomography in sepsis patients with unknown origin: A retrospective cohort study

Early identification of the sources of infection in emergency department (ED) patients of sepsis remains challenging. Computed tomography (CT) has the potential to identify sources of infection. This retrospective study aimed to investigate the role of CT in identifying sources of infection in patients with sepsis without obvious infection foci in the ED. A retrospective chart review was conducted on patients with fever and sepsis visiting the ED of Linkou Chang Gung Memorial Hospital between July 1, 2020 and June 30, 2021. Data on patient demographics, vital signs, clinical symptoms, underlying medical conditions, laboratory results, administered interventions, length of hospital stay, and mortality outcomes were collected and analyzed. Of 218 patients included in the study, 139 (63.8%) had positive CT findings. The most common sources of infection detected by CT included liver abscesses, acute pyelonephritis, and cholangitis. Laboratory results showed that patients with positive CT findings had higher white blood cell and absolute neutrophil counts and lower hemoglobin levels. Positive blood culture results were more common in patients with positive CT findings. Additionally, the length of hospital stay was longer in the group with positive CT findings. Multivariate logistic regression analysis revealed that hemoglobin levels and positive blood culture results independently predicted positive CT findings in patients with fever or sepsis without an obvious source of infection. In patients with sepsis with an undetermined infection focus, those presenting with leukocytosis, anemia, and elevated absolute neutrophil counts tended to have positive findings on abdominal CT scans. These patients had high rates of bacteremia and longer lengths of stay. Abdominal CT remains a valuable diagnostic tool for identifying infection sources in carefully selected patients with sepsis of undetermined infection origins.

GPX4, ferroptosis, and diseases

GPX4 (Glutathione peroxidase 4) serves as a crucial intracellular regulatory factor, participating in various physiological processes and playing a significant role in maintaining the redox homeostasis within the body. Ferroptosis, a form of iron-dependent non-apoptotic cell death, has gained considerable attention in recent years due to its involvement in multiple pathological processes. GPX4 is closely associated with ferroptosis and functions as the primary inhibitor of this process. Together, GPX4 and ferroptosis contribute to the pathophysiology of several diseases, including sepsis, nervous system diseases, ischemia reperfusion injury, cardiovascular diseases, and cancer. This review comprehensively explores the regulatory roles and impacts of GPX4 and ferroptosis in the development and progression of these diseases, with the aim of providing insights for identifying potential therapeutic strategies in the future.

SIRT1 downregulation in pneumonia is associated with an immature neutrophil response and increased disease severity

BACKGROUND

Pneumonia remains a common complication in trauma patients. Sirtuin 1 (SIRT1) is an anti-inflammatory NAD + -dependent deacetylase that has been shown to reduce the severity of ARDS in polymicrobial sepsis. The impact of SIRT1 in acute pneumonia, however, remains unknown. We hypothesized that SIRT1 deletion in pneumonia would worsen the inflammatory response and clinical severity, and that increased SIRT1 expression would be protective.

METHODS

Ten- to 14-week-old male and female SIRT1 knockout (S1KO) mice, SIRT1 overexpressor (S1OE) mice, and their wildtype (WT) littermates underwent intra-tracheal inoculation with Pseudomonas aeruginosa . Rectal temperature was recorded, SIRT1 lung protein was quantified by western blotting, Sirt1 mRNA was measured by qPCR, and lung leukocyte subpopulations were analyzed by flow cytometry. Data were analyzed by one-way ANOVA using Prism software.

RESULTS

Pneumonia created a functional SIRT1 knockdown in the lungs of WT mice by 4 hours, resulting in comparable SIRT1 levels and temperatures to the S1KO mice by 12 hours. Pneumonia also partially reduced SIRT1expression in S1OE mice, but S1OE mice still had improved thermoregulation 12 hours after pneumonia. In all groups, Sirt1 mRNA expression was not affected by infection. Sirtuin 1 deletion was associated with decreased neutrophil infiltration in the lung, as well as a shift toward a more immature neutrophil phenotype. SIRT1 deletion was also associated with decreased myeloperoxidase-positive neutrophils in the lungs following pneumonia, indicating decreased neutrophil activity. S1OE mice had no change in lung leukocyte subpopulations when compared to WT.

CONCLUSION

Pneumonia creates a functional SIRT1 knockdown in mice. SIRT1 deletion altered the early inflammatory cell response to pneumonia, resulting in a neutrophil response that would be less favorable for bacterial clearance. Despite overexpression of SIRT1, S1OE mice also developed low SIRT1 levels and exhibited only minimal improvement. This suggests increasing SIRT1 transcription is not sufficient to overcome pneumonia-induced downregulation and has implications for future treatment options. Targeting SIRT1 through increasing protein stability may promote a more efficient inflammatory cell response to pneumonia, thereby preventing subsequent lung injury.

Distinct functional neutrophil phenotypes in sepsis patients correlate with disease severity

Purpose

Sepsis is a clinical syndrome defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Sepsis is a highly heterogeneous syndrome with distinct phenotypes that impact immune function and response to infection. To develop targeted therapeutics, immunophenotyping is needed to identify distinct functional phenotypes of immune cells. In this study, we utilized our Organ-on-Chip assay to categorize sepsis patients into distinct phenotypes using patient data, neutrophil functional analysis, and proteomics.

Methods

Following informed consent, neutrophils and plasma were isolated from sepsis patients in the Temple University Hospital ICU (n=45) and healthy control donors (n=7). Human lung microvascular endothelial cells (HLMVEC) were cultured in the Organ-on-Chip and treated with buffer or cytomix ((TNF/IL-1β/IFNγ). Neutrophil adhesion and migration across HLMVEC in the Organ-on-Chip were used to categorize functional neutrophil phenotypes. Quantitative label-free global proteomics was performed on neutrophils to identify differentially expressed proteins. Plasma levels of sepsis biomarkers and neutrophil extracellular traps (NETs) were determined by ELISA.

Results

We identified three functional phenotypes in critically ill ICU sepsis patients based on ex vivo neutrophil adhesion and migration patterns. The phenotypes were classified as: Hyperimmune characterized by enhanced neutrophil adhesion and migration, Hypoimmune that was unresponsive to stimulation, and Hybrid with increased adhesion but blunted migration. These functional phenotypes were associated with distinct proteomic signatures and differentiated sepsis patients by important clinical parameters related to disease severity. The Hyperimmune group demonstrated higher oxygen requirements, increased mechanical ventilation, and longer ICU length of stay compared to the Hypoimmune and Hybrid groups. Patients with the Hyperimmune neutrophil phenotype had significantly increased circulating neutrophils and elevated plasma levels NETs.

Conclusion

Neutrophils and NETs play a critical role in vascular barrier dysfunction in sepsis and elevated NETs may be a key biomarker identifying the Hyperimmune group. Our results establish significant associations between specific neutrophil functional phenotypes and disease severity and identify important functional parameters in sepsis pathophysiology that may provide a new approach to classify sepsis patients for specific therapeutic interventions.

Identification of RRM2 as a key ferroptosis-related gene in sepsis

OBJECTIVE

Sepsis and sepsis-associated organ failure are devastating conditions for which there are no effective therapeutic agent. Several studies have demonstrated the significance of ferroptosis in sepsis. The study aimed to identify ferroptosis-related genes (FRGs) in sepsis, providing potential therapeutic targets.

METHODS

The weighted gene co-expression network analysis (WGCNA) was utilized to screen sepsis-associated genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were used to explore gene functions. Three machine learning methods were employed to identify sepsis-related hub genes. Survival and multivariate Cox regression analysis allowed further screening for the key gene RRM2 associated with prognosis. The immune infiltration analysis of the screened sepsis key genes was performed. Additionally, a cecum ligation and puncture (CLP)-induced mouse sepsis model was constructed to validate the expression of key gene in the sepsis.

RESULTS

Six sepsis-associated differentially expressed FRGs (RRM2, RPL7A, HNRNPA1, PEBP1, MYL8B and TXNIP) were screened by WGCNA and three machine learning methods analysis. Survival analysis and multivariate Cox regression analysis showed that RRM2 was a key gene in sepsis and an independent prognostic factor associated with clinicopathological and molecular features of sepsis. Immune cell infiltration analysis demonstrated that RRM2 had a connection to various immune cells, such as CD4 T cells and neutrophils. Furthermore, animal experiment demonstrated that RRM2 was highly expressed in CLP-induced septic mice, and the use of Fer-1 significantly inhibited RRM2 expression, inhibited serum inflammatory factor TNF-α, IL-6 and IL-1β expression, ameliorated intestinal injury and improved survival in septic mice.

CONCLUSION

RRM2 plays an important role in sepsis and may contribute to sepsis through the ferroptosis pathway. This study provides potential therapeutic targets for sepsis.

Implications for neutrophils in cardiac arrhythmias

Cardiac arrhythmias commonly occur as a result of aberrant electrical impulse formation or conduction in the myocardium. Frequently discussed triggers include underlying heart diseases such as myocardial ischemia, electrolyte imbalances, or genetic anomalies of ion channels involved in the tightly regulated cardiac action potential. Recently, the role of innate immune cells in the onset of arrhythmic events has been highlighted in numerous studies, correlating leukocyte expansion in the myocardium to increased arrhythmic burden. Here, we aim to call attention to the role of neutrophils in the pathogenesis of cardiac arrhythmias and their expansion during myocardial ischemia and infectious disease manifestation. In addition, we will elucidate molecular mechanisms associated with neutrophil activation and discuss their involvement as direct mediators of arrhythmogenicity.

Systemic inflammation response index as a prognostic factor for patients with sepsis-associated acute kidney injury: a retrospective observational study

OBJECTIVE

To assess the association between the systemic inflammation response index (SIRI) and the prognosis in patients with sepsis-associated acute kidney injury (SA-AKI).

METHODS

In this observational study, adult patients with SA-AKI were categorized into three groups based on SIRI tertiles. Survival outcomes were compared across the three groups using Kaplan-Meier survival curves. Various Cox proportional hazards regression models were developed to determine the association between the SIRI and mortality in patients with SA-AKI. Subgroup analyses were also performed to explore the association between different SIRI tertiles and all-cause mortality.

RESULTS

After adjusting for several confounders, the second SIRI tertile (2.5 < SIRI < 7.6) was found to be an independent risk factor for 30-day mortality [hazard ratio (95% confidence interval): 1.19 (1.01-1.40)], 90-day mortality [1.22 (1.06-1.41)], and 365-day mortality [1.24 (1.09-1.40)]. Furthermore, high SIRI values were associated with increased risks of 30-day, 90-day, and 365-day mortality in patients with SA-AKI across all three models. The third tertile showed a significant association with adverse outcomes in most subgroups.

CONCLUSIONS

The SIRI serves as a comprehensive biomarker for predicting all-cause mortality of critically ill patients with SA-AKI.

Autologous cryo-shocked neutrophils enable targeted therapy of sepsis via broad-spectrum neutralization of pro-inflammatory cytokines and endotoxins

Background: Sepsis is a life-threatening disease characterized by multiple organ failure due to excessive activation of the inflammatory response and cytokine storm. Despite recent advances in the clinical use of anti-cytokine biologics, sepsis treatment efficacy and improvements in mortality remain unsatisfactory, largely due to the mechanistic complexity of immune regulation and cytokine interactions. Methods: In this study, a broad-spectrum anti-inflammatory and endotoxin neutralization strategy was developed based on autologous "cryo-shocked" neutrophils (CS-Neus) for the management of sepsis. Neutrophils were frozen to death using a novel liquid nitrogen "cryo-shock" strategy. The CS-Neus retained the source cell membrane structure and functions related to inflammatory site targeting, broad-spectrum inflammatory cytokines, and endotoxin (LPS) neutralizing properties. This strategy aimed to disable harmful pro-inflammatory functions of neutrophils, such as cytokine secretion. Autologous cell-based therapy strategies were employed to avoid immune rejection and enhance treatment safety. Results: In both LPS-induced sepsis mouse models and clinical patient-derived blood samples, CS-Neus treatment significantly ameliorated cytokine storms by removing inflammatory cytokines and endotoxin. The therapy showed notable anti-inflammatory therapeutic effects and improved the survival rate of mice. Discussion: The results of this study demonstrate the potential of autologous "cryo-shocked" neutrophils as a promising therapeutic approach for managing sepsis. By targeting inflammatory organs and exhibiting anti-inflammatory activity, CS-Neus offer a novel strategy to combat the complexities of sepsis treatment. Further research and clinical trials are needed to validate the efficacy and safety of this approach in broader populations and settings.

A Flow Cytometry-Based High-Throughput Technique for Screening Integrin-Inhibitory Drugs

This protocol aims to establish a method for identifying small molecular antagonists of β2 integrin activation, utilizing conformational-change-reporting antibodies and high-throughput flow cytometry. The method can also serve as a guide for other antibody-based high-throughput screening methods. β2 integrins are leukocyte-specific adhesion molecules that are crucial in immune responses. Neutrophils rely on integrin activation to exit the bloodstream, not only to fight infections but also to be involved in multiple inflammatory diseases. Controlling β2 integrin activation presents a viable approach for treating neutrophil-associated inflammatory diseases. In this protocol, a monoclonal antibody, mAb24, which specifically binds to the high-affinity headpiece of β2 integrins, is utilized to quantify β2 integrin activation on isolated primary human neutrophils. N-formylmethionyl-leucyl-phenylalanine (fMLP) is used as a stimulus to activate neutrophil β2 integrins. A high-throughput flow cytometer capable of automatically running 384-well plate samples was used in this study. The effects of 320 chemicals on β2 integrin inhibition are assessed within 3 h. Molecules that directly target β2 integrins or target molecules in the G protein-coupled receptor-initiated integrin inside-out activation signaling pathway can be identified through this approach.

A novel anoikis-related gene signature predicts prognosis in patients with sepsis and reveals immune infiltration

Sepsis is a common acute and severe medical condition with a high mortality rate. Anoikis, an emerging form of cell death, plays a significant role in various diseases. However, the role of anoikis in sepsis remains poorly understood. Based on the datasets from Gene Expression Omnibus and anoikis-related genes from GeneCards, the differentially expressed anoikis-related genes (DEARGs) were identified. Based on hub genes of DEARGs, a novel prognostic risk model was constructed, and the pattern of immune infiltration was investigated by CIBERSORT algorithm. And small molecule compounds targeting anoikis in sepsis were analyzed using Autodock. Of 23 DEARGs, CXCL8, CFLAR, FASLG and TP53 were significantly associated with the prognosis of sepsis (P < 0.05). Based on the prognostic risk model constructed with these four genes, high-risk population of septic patients had significant lower survival probability than low-risk population (HR = 3.30, P < 0.001). And the level of CFLAR was significantly correlated with the number of neutrophils in septic patients (r = 0.54, P < 0.001). Moreover, tozasertib had low binding energy with CXCL8, CFLAR, FASLG and TP53, and would be a potential compound for sepsis. Conclusively, our results identified a new prognostic model and potential therapeutic molecular for sepsis, providing new insights on mechanism and treatment of sepsis.

Clinical predictive value of the initial neutrophils to lymphocytes and platelets ratio for prognosis of sepsis patients in the intensive care unit: a retrospective study

Background

Neutrophils to lymphocytes and platelets (N/LP) ratio has been confirmed as an indirect marker of inflammation. In this study, we aimed to further evaluate the prognostic significance of the N/LP ratio in sepsis patients admitted to the ICU.

Methods

Sepsis patients from the Affiliated Hospital of Jiangsu University were retrospectively enrolled from January 2015 and July 2023. The primary outcomes were 30/60 days mortality. The secondary outcomes included the incidence of AKI, vasoactive drug, CRRT, invasive ventilation, length of ICU stay, length of hospital stay and ICU mortality.

Results

A total of 1,066 sepsis patients were enrolled with a median age of 75.0 (66.0, 85.0) years, and 62.5% of them being male. The 30 days and 60 days mortality rates were found to be 28.7 and 34.0%, respectively, while the incidence of AKI was 45.2%. Based on their N/LP ratios, we classified the sepsis patients into three groups: low, middle, and high, consisting of 266, 534, and 266 patients, respectively. According the Cox proportional hazard model, the middle and high N/LP groups were associated with a 1.990/3.106-fold increase in 30 days mortality risk and a 2.066/3.046-fold increase in 60 days mortality risk compared with the low N/LP group. Besides, multivariate logistic regression model suggested that the risk of AKI occurrence increased 2.460 fold in the high group compared to the low group. However, through subgroup analyses, we observed substantial variations in the association between N/LP ratios and 30/60 days mortality rates as well as the incidence of AKI among different populations. Notably, the N/LP ratio measured at ICU admission exhibited a higher AUC for predicting 30/60 days mortality (0.684/0.687). Additionally, we observed a good predictive power for the occurrence of AKI (AUC: 0.645) using the N/LP ratio measured at sepsis prognosis. Regarding the other secondary outcomes, the N/LP ratio was associated with disease severity in sepsis patients, including the need for vasoactive drugs, length of ICU stay, and ICU mortality.

Conclusion

The N/LP ratio at ICU admission was found to have a significant independent association with 30/60 days mortality and the incidence of AKI in sepsis patients.

Lactobacillus rhamnosus (LR) ameliorates pulmonary and extrapulmonary acute respiratory distress syndrome (ARDS) via targeting neutrophils

Pulmonary and extrapulmonary acute respiratory distress syndrome (ARDS) is a life-threatening respiratory failure associated with high mortality. Despite progress in our understanding of the pathological mechanism causing the crippling illness, there are currently no targeted pharmaceutical treatments available for it. Recent discoveries have emphasized the existence of a potential nexus between gut and lung health fueling novel approaches including probiotics for the treatment of ARDS. We thus investigated the prophylactic-potential of Lactobacillus rhamnosus-(LR) in lipopolysaccharide (LPS)-induced pulmonary and cecal ligation puncture (CLP) induced extrapulmonary ARDS mice. Our in-vivo findings revealed that pretreatment with LR significantly ameliorated vascular-permeability (edema) of the lungs via modulating the neutrophils along with significantly reducing the expression of inflammatory-cytokines in the BALF, lungs and serum in both pulmonary and extrapulmonary mice-models. Interestingly, our ex-vivo immunofluorescence and flow cytometric data suggested that mechanistically LR via short chain fatty acids (butyrate being the most potent and efficient in ameliorating the pathophysiology of both pulmonary and extra-pulmonary ARDS) targets the phagocytic and neutrophils extracellular traps (NETs) releasing potential of neutrophils. Moreover, our in-vivo data further corroborated our ex-vivo findings and suggested that butyrate exhibits enhanced potential in ameliorating the pathophysiology of ARDS via reducing the infiltration of neutrophils into the lungs. Altogether, our study establishes the prophylactic role of LR and its associated metabolites in the prevention and management of both pulmonary and extrapulmonary ARDS via targeting neutrophils.

Free Radicals, Mitochondrial Dysfunction and Sepsis-induced Organ Dysfunction: A Mechanistic Insight

Sepsis is a complex clinical condition and a leading cause of death worldwide. During Sepsis, there is a derailment in the host response to infection, which can progress to severe sepsis and multiple organ dysfunction or failure, which leads to death. Free radicals, including reactive oxygen species (ROS) generated predominantly in mitochondria, are one of the key players in impairing normal organ function in sepsis. ROS contributing to oxidative stress has been reported to be the main culprit in the injury of the lung, heart, liver, kidney, gastrointestinal, and other organs. Here in the present review, we describe the generation, and essential properties of various types of ROS, their effect on macromolecules, and their role in mitochondrial dysfunction. Furthermore, the mechanism involved in the ROS-mediated pathogenesis of sepsis-induced organ dysfunction has also been discussed.

A comprehensive analysis of immune features and construction of an immune gene diagnostic model for sepsis

Sepsis is a life-threatening syndrome resulting from immune system dysfunction that is caused by infection. It is of great importance to analyze the immune characteristics of sepsis, identify the key immune system related genes, and construct diagnostic models for sepsis. In this study, the sepsis transcriptome and expression profiling data were merged into an integrated dataset containing 277 sepsis samples and 117 non-sepsis control samples. Single-sample gene set enrichment analysis (ssGSEA) was used to assess the immune cell infiltration. Two sepsis immune subtypes were identified based on the 22 differential immune cells between the sepsis and the healthy control groups. Weighted gene co-expression network analysis (WCGNA) was used to identify the key module genes. Then, 36 differentially expressed immune-related genes were identified, based on which a robust diagnostic model was constructed with 11 diagnostic genes. The expression of 11 diagnostic genes was finally assessed in the training and validation datasets respectively. In this study, we provide comprehensive insight into the immune features of sepsis and establish a robust diagnostic model for sepsis. These findings may provide new strategies for the early diagnosis of sepsis in the future.

Immune dysregulation in sepsis: experiences, lessons and perspectives

Sepsis is a life-threatening organ dysfunction syndrome caused by dysregulated host responses to infection. Not only does sepsis pose a serious hazard to human health, but it also imposes a substantial economic burden on the healthcare system. The cornerstones of current treatment for sepsis remain source control, fluid resuscitation, and rapid administration of antibiotics, etc. To date, no drugs have been approved for treating sepsis, and most clinical trials of potential therapies have failed to reduce mortality. The immune response caused by the pathogen is complex, resulting in a dysregulated innate and adaptive immune response that, if not promptly controlled, can lead to excessive inflammation, immunosuppression, and failure to re-establish immune homeostasis. The impaired immune response in patients with sepsis and the potential immunotherapy to modulate the immune response causing excessive inflammation or enhancing immunity suggest the importance of demonstrating individualized therapy. Here, we review the immune dysfunction caused by sepsis, where immune cell production, effector cell function, and survival are directly affected during sepsis. In addition, we discuss potential immunotherapy in septic patients and highlight the need for precise treatment according to clinical and immune stratification.