Olfactomedin 4-Positive Neutrophils Are Upregulated after Hemorrhagic Shock

Dysregulation of iron transport-related biomarkers in blood leukocytes is associated with poor prognosis of early trauma

Objective

The early targeted and effective diagnosis and treatment of severe trauma are crucial for patients' outcomes. Blood leukocytes act as significant effectors during the initial inflammation and activation of innate immunity in trauma. This study aims to identify hub genes related to patients' prognosis in blood leukocytes at the early stages of trauma.

Methods

The expression profiles of Gene Expression Omnibus (GEO) Series (GSE) 36809 and GSE11375 were downloaded from the GEO database. R software, GraphPad Prism 9.3.1 software, STRING database, and Cytoscape software were used to process the data and identify hub genes in blood leukocytes of early trauma.

Results

Gene Ontology (GO) analysis showed that the differentially expressed genes (DEGs) of blood leukocytes at the early stages of trauma (0-4 h, 4-8 h, and 8-12 h) were mainly involved in neutrophil activation and neutrophil degranulation, neutrophil activation involved in immune response, neutrophil mediated immunity, lymphocyte differentiation, and cell killing. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the DEGs were mainly involved in Osteoclast differentiation and Hematopoietic cell lineage. Sixty-six down-regulated DEGs and 148 up-regulated DEGs were identified and 37 hub genes were confirmed by Molecular Complex Detection (MCODE) of Cytoscape. Among the hub genes, Lipocalin 2 (LCN2), Lactotransferrin (LTF), Olfactomedin 4 (OLFM4), Resistin (RETN), and Transcobalamin 1 (TCN1) were related to prognosis and connected with iron transport closely. LCN2 and LTF were involved in iron transport and had a moderate predictive value for the poor prognosis of trauma patients, and the AUC of LCN2 and LTF was 0.7777 and 0.7843, respectively.

Conclusion

As iron transport-related hub genes in blood leukocytes, LCN2 and LTF can be used for prognostic prediction of early trauma.

Beyond host defense and tissue injury: the emerging role of neutrophils in tissue repair

Neutrophils, the most abundant immune cells in human blood, play a fundamental role in host defense against invading pathogens and tissue injury. Neutrophils carry potentially lethal weaponry to the affected site. Inadvertent and perpetual neutrophil activation could lead to nonresolving inflammation and tissue damage, a unifying mechanism of many common diseases. The prevailing view emphasizes the dichotomy of their function, host defense versus tissue damage. However, tissue injury may also persist during neutropenia, which is associated with disease severity and poor outcome. Numerous studies highlight neutrophil phenotypic heterogeneity and functional versatility, indicating that neutrophils play more complex roles than previously thought. Emerging evidence indicates that neutrophils actively orchestrate resolution of inflammation and tissue repair and facilitate return to homeostasis. Thus, neutrophils mobilize multiple mechanisms to limit the inflammatory reaction, assure debris removal, matrix remodeling, cytokine scavenging, macrophage reprogramming, and angiogenesis. In this review, we will summarize the homeostatic and tissue-reparative functions and mechanisms of neutrophils across organs. We will also discuss how the healing power of neutrophils might be harnessed to develop novel resolution and repair-promoting therapies while maintaining their defense functions.

The double-edged role of neutrophil heterogeneity in inflammatory diseases and cancers

Neutrophils are important immune cells act as the body's first line of defense against infection and respond to diverse inflammatory cues. Many studies have demonstrated that neutrophils display plasticity in inflammatory diseases and cancers. Clarifying the role of neutrophil heterogeneity in inflammatory diseases and cancers will contribute to the development of novel treatment strategies. In this review, we have presented a review on the development of the understanding on neutrophil heterogeneity from the traditional perspective and a high-resolution viewpoint. A growing body of evidence has confirmed the double-edged role of neutrophils in inflammatory diseases and tumors. This may be due to a lack of precise understanding of the role of specific neutrophil subsets in the disease. Thus, elucidating specific neutrophil subsets involved in diseases would benefit the development of precision medicine. Thusly, we have summarized the relevance and actions of neutrophil heterogeneity in inflammatory diseases and cancers comprehensively. Meanwhile, we also discussed the potential intervention strategy for neutrophils. This review is intended to deepen our understanding of neutrophil heterogeneity in inflammatory diseases and cancers, while hold promise for precise treatment of neutrophil-related diseases.

Combination of transcriptional biomarkers and clinical parameters for early prediction of sepsis indued acute respiratory distress syndrome

Objective

As a common yet intractable complication of severe sepsis, acute respiratory distress syndrome (ARDS) is closely associated with poor clinical outcomes and elevated medical expenses. The aim of the current study is to generate a model combining transcriptional biomarkers and clinical parameters to alarm the development of ARDS in septic patients.

Methods

Gene expression profile (GSE66890) was downloaded from the Gene Expression Omnibus database and clinical data were extracted. Differentially expressed genes (DEGs) from whole blood leukocytes were identified between patients with sepsis alone and septic patients who develop ARDS. ARDS prediction model was constructed using backward stepwise regression and Akaike Information Criterion (AIC). Meanwhile, a nomogram based on this model was established, with subsequent internal validation.

Results

A total of 57 severe septic patients were enrolled in this study, and 28 (49.1%) developed ARDS. Based on the differential expression analysis, six DEGs (BPI, OLFM4, LCN2, CD24, MMP8 and MME) were screened. According to the outcome prediction model, six valuable risk factors (direct lung injury, shock, tumor, BPI, MME and MMP8) were incorporated into a nomogram, which was used to predict the onset of ARDS in septic patients. The calibration curves of the nomogram showed good consistency between the probabilities and observed values. The decision curve analysis also revealed the potential clinical usefulness of the nomogram. The area under the receiver operating characteristic (AUROC) for the prediction of ARDS occurrence in septic patients by the nomogram was 0.86 (95% CI = 0.767-0.952). A sensitivity analysis showed that the AUROC for the prediction of ARDS development in septic patients without direct lung injury was 0.967 (95% CI = 0.896-1.0).

Conclusions

The nomogram based on transcriptional biomarkers and clinical parameters showed a good performance for the prediction of ARDS occurrence in septic patients.

Olfactomedin-4-Positive Neutrophils in Neonates: Link to Systemic Inflammation and Bronchopulmonary Dysplasia

INTRODUCTION

Little is known about the interplay between neutrophil heterogeneity in neonates in health and disease states. Olfactomedin-4 (OLFM4) marks a subset of neutrophils that have been described in adults and pediatric patients but not neonates, and this subset is thought to play a role in modulating the host inflammatory response.

METHODS

This is a prospective cohort of neonates who were born between June 2020 and December 2021 at the University of Cincinnati Medical Center NICU. Olfactomedin-4-positive (OLFM4+) neutrophils were identified in the peripheral blood using flow cytometry.

RESULTS

OLFM4+ neutrophil percentage was not correlated with gestational age or developmental age. Neonates with sepsis had a higher percentage than those without the condition, 66.9% (IQR 24.3-76.9%) versus 21.5% (IQR 10.6-34.7%), respectively, p = 0.0003. At birth, a high percentage of OLFM4+ neutrophils was associated with severe chorioamnionitis at 49.1% (IQR 28.2-61.5%) compared to those without it at 13.7% (IQR 7.7-26.3%), p < 0.0001. Among neonates without sepsis, the percentages of OLFM4+ neutrophils were lower in the BPD/early death group compared to those without BPD, 11.8% (IQR 6.3-29.0%) versus 32.5% (IQR 18.5-46.1%), p = 0.003, and this retained significance in a multiple logistic regression model that included gestational age, birthweight, and race.

CONCLUSION

This is the first study describing OLFM4+ neutrophils in neonates and it shows that this neutrophil subpopulation is not influenced by gestational age but is elevated in inflammatory conditions such as sepsis and severe chorioamnionitis, and lower percentage at birth is associated with developing bronchopulmonary dysplasia.

The Olfactomedin-4-Defined Human Neutrophil Subsets Differ in Proteomic Profile in Healthy Individuals and Patients with Septic Shock

The specific granule glycoprotein olfactomedin-4 (Olfm4) marks a subset (1-70%) of human neutrophils and the Olfm4-high (Olfm4-H) proportion has been found to correlate with septic shock severity. The aim of this study was to decipher proteomic differences between the subsets in healthy individuals, hypothesizing that Olfm4-H neutrophils have a proteomic profile distinct from that of Olfm4 low (Olfm4-L) neutrophils. We then extended the investigation to septic shock. A novel protocol for the preparation of fixed, antibody-stained, and sorted neutrophils for LC-MS/MS was developed. In healthy individuals, 39 proteins showed increased abundance in Olfm4-H, including the small GTPases Rab3d and Rab11a. In Olfm4-L, 52 proteins including neutrophil defensin alpha 4, CXCR1, Rab3a, and S100-A7 were more abundant. The data suggest differences in important neutrophil proteins that might impact immunological processes. However, in vitro experiments revealed no apparent difference in the ability to control bacteria nor produce oxygen radicals. In subsets isolated from patients with septic shock, 24 proteins including cytochrome b-245 chaperone 1 had significantly higher abundance in Olfm4-H and 30 in Olfm4-L, including Fc receptor proteins. There was no correlation between Olfm4-H proportion and septic shock severity, but plasma Olfm4 concentration was elevated in septic shock. Thus, the Olfm4-H and Olfm4-L neutrophils have different proteomic profiles, but there was no evident functional significance of the differences in septic shock.

Single-cell transcriptome profiling reveals heterogeneous neutrophils with prognostic values in sepsis

Neutrophils constitute the largest proportion of nucleated peripheral blood cells, and neutrophils have substantial heterogeneity. We profiled nearly 300,000 human peripheral blood cells in this study using single-cell RNA sequencing. A large proportion (>50%) of these cells were annotated as neutrophils. Neutrophils were further clustered into four subtypes, including Neu1, Neu2, Neu3, and Neu4. Neu1 is characterized by high expression of MMP9, HP, and RGL4. Neu1 was associated with septic shock and significantly correlated with the sequential organ failure assessment (SOFA) score. A gene expression module in Neu1 named Neu1_C (characterized by expression of NFKBIA, CXCL8, G0S2, and FTH1) was highly predictive of septic shock with an area under the curve of 0.81. The results were extensively validated in external bulk datasets by using single-cell deconvolution methods. In summary, our study establishes a general framework for studying neutrophil-related mechanisms, prognostic biomarkers, and potential therapeutic targets for septic shock.

•

Neutrophils were clustered into four subtypes, including Neu1, Neu2, Neu3, and Neu4

•

Neu1 was associated with septic shock

•

Neu1 was correlated with the sequential organ failure assessment (SOFA) score

•

A gene expression module in Neu1 named Neu1_C was highly predictive of septic shock

Qinbaohong Zhike Oral Liquid Attenuates LPS-Induced Acute Lung Injury in Immature Rats by Inhibiting OLFM4

Acute respiratory infections (ARIs) are a common public safety threat with high morbidity and mortality in pediatric patients worldwide. Qinbaohong Zhike oral liquid (QBH), a marketed traditional Chinese medicine product, has been widely used to cure respiratory diseases. QBH is reported to have antitussive, expectorant, and antiasthmatic properties. However, its treatment effect against ARIs is not elucidated. This study aimed to explore the therapeutic efficacy of QBH in the treatment of ARIs-induced pneumonia. Network pharmacology was used to predict the possible targets of QBH against ARIs. Next, the tracheal lipopolysaccharide (LPS-)-induced acute lung injury (ALI) immature rat model was constructed to evaluate the therapeutic effect of QBH. Tandem mass tag (TMT-)-based quantitative proteomics was then used to screen the in-depth disease targets of QBH. QBH exerted a protective effect against LPS-induced ALI by inhibiting pulmonary pathological damage. QBH also reduced the levels of interleukin (IL)-6, tumor necrosis factor (TNF)-α, interferon (IFN)-γ, and granulocyte macrophage colony-stimulating factor (GM-CSF) in the serum and IL-1β, IL-6, IL-8, TNF-α, IFN-γ, and GM-CSF in the lung tissue. Based on proteomic data, olfactomedin 4 (OLFM4) related to immunity and inflammation was selected as a potential target. Western blot analysis further confirmed the moderating effect of QBH downregulation on OLFM4 in the lung tissue. Our findings demonstrated that QBH alleviated lung tissue damage and inflammatory reaction via inhibiting OLFM4 expression in LPS-challenged immature rats. Our research indicates that QBH may have therapeutic potential for treating ARIs-related ALI in pediatric patients, which also serves as a candidate target for drug therapy of ALI by intervening OLFM-related signaling pathways.

Neutrophils, functions beyond host defense

Neutrophils are the most abundant, ephemeral cell type in human blood. As the first line of defense in the host immune system, neutrophils mature in the bone marrow after undergoing multiple stages of development and then are released into the peripheral blood and conduct a surveillance function. Recent advances in cutting-edge techniques such as single-cell sequencing have uncovered the complexity and plasticity of neutrophils under homeostatic and inflammatory conditions. The exploration of neutrophil heterogeneity and function under disease and homeostasis settings has revealed many unexpected roles of neutrophils beyond a phagocyte. Furthermore, neutrophils are known to actively communicate with innate and adaptive immunocytes via direct or indirect interactions, allowing the modulation of various immune cells. In this review, we will discuss the versatile identities of neutrophils that have been discovered in recent decades, as well as the interplay between neutrophils and other cells.

Changes Within H3K4me3-Marked Histone Reveal Molecular Background of Neutrophil Functional Plasticity

Neutrophils are a heterogenous population capable of both antimicrobial functions and suppressor ones, however, no specific pattern of transcription factors controlling this plasticity has been identified. We observed rapid changes in the neutrophil status after stimulation with LPS, pre-activating concentration of TNF-α, or IL-10. Chromatin immunoprecipitation sequencing (ChIP-Seq) analysis of histone H3K4me3 allowed us to identify various transcriptional start sites (TSSs) associated with plasticity and heterogeneity of human neutrophils. Gene Ontology analysis demonstrated great variation within target genes responsible for neutrophil activation, cytokine production, apoptosis, histone remodelling as well as NF-κB transcription factor pathways. These data allowed us to assign specific target genes positioned by H3K4me3-marked histone with a different pattern of gene expression related to NF-κB pathways, apoptosis, and a specific profile of cytokines/chemokines/growth factors realised by neutrophils stimulated by LPS, IL-10, or TNF-α. We discovered IL-10-induced apoptotic neutrophils being transcriptionally active cells capable of switching the profile of cytokines/chemokines/growth factors desired in resolving inflammation via non-canonical NF-κB pathway with simultaneous inhibition of canonical NF-κB pathway. As apoptotic/suppressive neutrophils induced by IL-10 via positioning genes within H3K4me3-marked histone were transcriptionally active, newly described DNA binding sites can be considered as potential targets for immunotherapy.

OLFM4 Regulates Lung Epithelial Cell Function in Sepsis-Associated ARDS/ALI via LDHA-Mediated NF-κB Signaling

Background

Acute respiratory distress syndrome (ARDS) is one of the leading causes of death in patients with sepsis. As such, early and accurate identification of sepsis-related ARDS is critical.

Methods

Bioinformatic analysis was used to explore the GEO datasets. ELISA method was used to detect the plasma or cellular supernatant of relevant proteins. Quantitative real-time PCR was used for mRNA measurements and Western blot was applied for protein measurements. Immunohistochemistry staining and Immunofluorescence staining were used to identify the localization of OLFM4. Cecal ligation and puncture (CLP) model was used to establish sepsis model.

Results

The bioinformatic analysis results identified ten genes (CAMP, LTF, RETN, LCN2, ELANE, PGLYRP1, BPI, DEFA4, MPO, and OLFM4) as critical in sepsis and sepsis-related ARDS. OLFM4, LCN2, and BPI were further demonstrated to have diagnostic values in sepsis-related ARDS. Plasma expression of OLFM4 and LCN2 was also upregulated in sepsis-related ARDS patients compared to septic patients alone. OLFM4 expression was significantly increased in the lung tissues of septic mice and was co-localized with Ly6G+ neutrophils, F4/80+ macrophages and pro-surfactant C+ lung epithelial cells. In vitro data showed that OLFM4 expression in lung epithelial cells was downregulated upon LPS stimulation, whereas neutrophil media induced OLFM4 expression in lung epithelial cells. Overexpression of OLFM4 and treatment with recombinant OLFM4 effectively suppressed LPS-induced pro-inflammatory responses in lung epithelial cells. Furthermore, the increased levels of LDHA phosphorylation and the downstream NF-κB activation induced by LPS in epithelial cells were effectively diminished by OLFM4 overexpression and recombinant OLFM4 treatment via a reduction in ROS production and HIF1α expression.

Conclusion

OLFM4 may regulate the pro-inflammatory response of lung epithelial cells in sepsis-related ARDS by modulating metabolic disorders; this result could provide new insights into the treatment of sepsis-induced ARDS.

Neutrophil kinetics and function after major trauma: A systematic review

BACKGROUND

Immune dysfunction following major traumatic injury is complex and strongly associated with significant morbidity and mortality through the development of multiple organ dysfunction syndrome (MODS), persistent inflammation, immunosuppression, and catabolism syndrome and sepsis. Neutrophils are thought to be a pivotal mediator in the development of immune dysfunction.

AIM

To provide a review with a systematic approach of the recent literature describing neutrophil kinetics and functional changes after major trauma in humans and discuss hypotheses as to the mechanisms of the observed neutrophil dysfunction in this setting.

METHODS

Medline, Embase and PubMed were searched on January 15, 2021. Papers were screened by two reviewers and those included had their reference list hand searched for additional papers of interest. Inclusion criteria were adults > 18 years old, with an injury severity score > 12 requiring admission to an intensive care unit. Papers that analysed major trauma patients as a subgroup were included.

RESULTS

Of 107 papers screened, 48 were included in the review. Data were heterogeneous and most studies had a moderate to significant risk of bias owing to their observational nature and small sample sizes. Key findings included a persistently elevated neutrophil count, stereotyped alterations in cell-surface markers of activation, and the elaboration of heterogeneous and immunosuppressive populations of cells in the circulation. Some of these changes correlate with clinical outcomes such as MODS and secondary infection. Neutrophil phenotype remains a promising avenue for the development of predictive markers for immune dysfunction.

CONCLUSION

Understanding of neutrophil phenotypes after traumatic injury is expanding. A greater emphasis on incorporating functional and clinically significant markers, greater uniformity in study design and assessment of extravasated neutrophils may facilitate risk stratification in patients affected by major trauma.