Delayed neutrophil apoptosis in sepsis is associated with maintenance of mitochondrial transmembrane potential and reduced caspase-9 activity*

Caspase-8 in inflammatory diseases: a potential therapeutic target

Caspase-8, a renowned cysteine-aspartic protease within its enzyme family, initially garnered attention for its regulatory role in extrinsic apoptosis. With advancing research, a growing body of evidence has substantiated its involvement in other cell death processes, such as pyroptosis and necroptosis, as well as its modulatory effects on inflammasomes and proinflammatory cytokines. PANoptosis, an emerging concept of cell death, encompasses pyroptosis, apoptosis, and necroptosis, providing insight into the often overlapping cellular mortality observed during disease progression. The activation or deficiency of caspase-8 enzymatic activity is closely linked to PANoptosis, positioning caspase-8 as a key regulator of cell survival or death across various physiological and pathological processes. Aberrant expression of caspase-8 is closely associated with the development and progression of a range of inflammatory diseases, including immune system disorders, neurodegenerative diseases (NDDs), sepsis, and cancer. This paper delves into the regulatory role and impact of caspase-8 in these conditions, aiming to elucidate potential therapeutic strategies for the future intervention.

Congential nasolacrimal duct obstruction: investigating the role of systemic inflammation through novel biomakers

OBJECTIVE

Congenital nasolacrimal duct obstruction (CNLDO) is a common lacrimal system anomaly in newborns and infants. We aimed to evaluate the role of inflammation in the pathogenesis of persistent CNLDO and its potential use in diagnosis and follow up, focusing on novel inflammatory biomarkers: Systemic Immune-Inflammation Index (SII), Neutrophil-to-lymphocyte ratio (NLR), Platelet-to-lymphocyte ratio (PLR), Red cell distribution width (RDW), and Mean platelet volume (MPV).

METHODS

A retrospective case-control study involving 76 CNLDO patients and 47 age-matched healthy controls was conducted. Complete blood count parameters were analyzed to calculate SII, NLR, PLR, RDW, and MPV. Receiver Operating Characteristic (ROC) analysis determined the diagnostic efficacy of these markers.

RESULTS

SII, RDW, and neutrophil count were significantly elevated in the CNLDO group (p < 0.05). An elevated SII (cutoff > 200.9) demonstrated a sensitivity of 63.2% and a specificity of 63.8%. ROC analysis (AUC = 61.7%, p = 0.029) indicated that SII is a more significant marker for diagnosing CNLDO compared to NLR and PLR.

CONCLUSION

Elevated SII, indicative of systemic inflammation may serve as a significant biomarker in the diagnosis of CNLDO that does not resolve spontaneously and requires probing. SII > 200.9 acts as a threshold that aids in the diagnosis of persistent CNLDO. Being a valuable biomarker, SII can be used in monitoring patients with CNLDO and in identifying those who will require advanced treatment like probing. Prospective studies are essential to validate these findings.

Effect of ethanol exposure on innate immune response in sepsis

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

MNDA, a PYHIN factor involved in transcriptional regulation and apoptosis control in leukocytes

Inflammation control is critical during the innate immune response. Such response is triggered by the detection of molecules originating from pathogens or damaged host cells by pattern-recognition receptors (PRRs). PRRs subsequently initiate intra-cellular signalling through different pathways, resulting in i) the production of inflammatory cytokines, including type I interferon (IFN), and ii) the initiation of a cascade of events that promote both immediate host responses as well as adaptive immune responses. All human PYRIN and HIN-200 domains (PYHIN) protein family members were initially proposed to be PRRs, although this view has been challenged by reports that revealed their impact on other cellular mechanisms. Of relevance here, the human PYHIN factor myeloid nuclear differentiation antigen (MNDA) has recently been shown to directly control the transcription of genes encoding factors that regulate programmed cell death and inflammation. While MNDA is mainly found in the nucleus of leukocytes of both myeloid (neutrophils and monocytes) and lymphoid (B-cell) origin, its subcellular localization has been shown to be modulated in response to genotoxic agents that induce apoptosis and by bacterial constituents, mediators of inflammation. Prior studies have noted the importance of MNDA as a marker for certain forms of lymphoma, and as a clinical prognostic factor for hematopoietic diseases characterized by defective regulation of apoptosis. Abnormal expression of MNDA has also been associated with altered levels of cytokines and other inflammatory mediators. Refining our comprehension of the regulatory mechanisms governing the expression of MNDA and other PYHIN proteins, as well as enhancing our definition of their molecular functions, could significantly influence the management and treatment strategies of numerous human diseases. Here, we review the current state of knowledge regarding PYHIN proteins and their role in innate and adaptive immune responses. Emphasis will be placed on the regulation, function, and relevance of MNDA expression in the control of gene transcription and RNA stability during cell death and inflammation.

The unexpected effect of parathyroid adenoma on inflammation

Primary hyperparathyroidism (PHPT) is an endocrinological disease that affects systemic inflammation. This study is aimed to investigate the preoperative and postoperative effect of PHPT on systemic inflammation. A total of 203 patients who were successfully operated for PHPT and 98 healthy controls were included in the study. The blood tests of the patients in the last month preoperatively and in the postoperative 6th month were compared. In addition, preoperative and postoperative tests were compared with the healthy control group. When the preoperative neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), lymphocyte-to-monocyte ratio (LMR), and systemic inflammation index (SII) values of the patients who were operated for parathyroid adenoma were compared with the control group (p values were < 0.05, 0.01, 0.19, < 0.05), the NLR, PLR, and SII values were significantly lower in the patient group with parathyroid adenoma than in the control group. When the preoperative and postoperative 6th month NLR, PLR, LMR, and SII values of the patients were compared (p values: 0.026, 0.56, 0.023, 0.016, respectively), there was a significant increase in NLR and SII values after excision, while a significant decrease was observed in the LMR value. When the postoperative 6th month NLR, PLR, LMR, SII values were compared with the healthy control group (p values: 0.22, 0.29, 0.19, 0.29, respectively), no significant difference was observed between all values. We found that the immune system was suppressed in PHPT and this returned to normal levels after a successful surgery.

Predictive value of the neutrophil-to-lymphocyte ratio in the prognosis and risk of death for adult sepsis patients: a meta-analysis

Background

The neutrophil-to-lymphocyte ratio (NLR) is a commonly used biomarker for acute inflammation that often rises during sepsis, making it a valuable diagnostic indicator for clinical practice. However, no consensus has been reached on the prognostic value of NLR for predicting the prognosis and mortality risk in adult sepsis patients. In light of this controversy, we conducted a meta-analysis to clarify the prognostic significance of NLR in adult sepsis patients. The meta-analysis was registered in the PROSPERO database (registration number CRD42023433143).

Methods

We performed a comprehensive literature search in PubMed, Cochrane Library, Ovid, and Springer databases, using retrieval terms "sepsis" or "septic shock" and "prognosis" or "mortality" for studies published between January 1, 2000, and May 31, 2023. Children and neonates with sepsis were excluded from our research. Two independent researchers conducted the literature search and data extraction. Consensus was reached when discrepancies occurred, and in case of persistent discrepancies, the final decision was made by the research supervisor. The hazard ratio (HR) and its corresponding 95% confidence interval (95% CI) were extracted from each study included in the analysis. A random-effects model was used to synthesize all HRs and their 95% CIs. Sensitivity analysis was performed to investigate heterogeneity. Sensitivity analysis was conducted to identify studies that had a significant impact on the overall results of the meta-analysis. Subgroup analysis and meta-regression were performed to explore sources of heterogeneity. Egger's test was also used to investigate publication bias in this meta-analysis.

Results

After a comprehensive literature search and screening, we included 12 studies comprising 10,811 patients for the meta-analysis. The pooled results indicated that patients with a higher NLR level were associated with a poor prognosis (Random-effects model, HR: 1.6273, 95% CI: 1.3951-1.8981). Heterogeneity testing showed significant heterogeneity (I2 = 87.2%, 95% CI: 79.5-92, p<0.0001). Sensitivity analysis was performed to investigate the sources of heterogeneity, which revealed that the omission of one highly sensitive study significantly reduced the I2 value. After removing this study, a strong association was found between a higher NLR level and poor prognosis and risk of death in adult sepsis patients (Random-effects model, HR: 1.6884, 95% CI: 1.4338-1.9882). Both subgroup analysis and meta-regression indicated that the study design and testing time of NLR were sources of heterogeneity. Egger's test showed no obvious publication bias in this meta-analysis.

Conclusion

NLR is a reliable and valuable biomarker for predicting prognosis and the risk of death in adult sepsis patients.

Systematic Review Registration

[https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023433143] PROSPERO, identifier [CRD42023433143].

Association of the neutrophil-lymphocyte ratio with outcome in sick hospitalized neonatal foals

BACKGROUND

The neutrophil-lymphocyte ratio (NLR) in human medicine is an objective biomarker that reflects prognosis. The NLR as an independent biomarker to help predict nonsurvival in hospitalized neonatal foals has not been thoroughly interrogated.

OBJECTIVES/HYPOTHESIS

Retrospectively evaluate if the NLR at admission is associated with nonsurvival in sick hospitalized foals <4 days old. We hypothesized that a lower NLR will be associated with nonsurvival.

ANIMALS

One thousand one hundred ninety-six client-owned foals <4 days old of any breed and sex: 993 hospitalized foals and 203 healthy foals.

METHODS

Retrospective multicenter study. Medical records of foals presenting to 3 equine referral hospitals were reviewed. Foals were included if they had complete CBCs, sepsis scores, and outcome data. The NLR was calculated by dividing the absolute neutrophil count by the absolute lymphocyte count. Data were analyzed by nonparametric methods and univariate analysis.

RESULTS

Of the 993 sick hospitalized foals, 686 were sick nonseptic and 307 were septic. The median NLR was lower in sick hospitalized foals (median [95% confidence interval], 3.55 [0.5-13.9]) compared with healthy foals (6.61 [3.06-18.1]). Septic foals had the lowest NLR (2.00 [0.20-9.71]). The NLR was lower in nonsurviving (1.97 [1.67-2.45]) compared with surviving foals (4.10 [3.76-4.33]). Nonsurviving septic foals had the lowest NLR (1.47 [1.70-3.01]). Foals with a NLR of <3.06 or <1.6 at admission had odds ratio of 3.21 (2.24-4.29) and 4.03 (2.86-5.67) for nonsurvival, respectively.

CONCLUSIONS AND CLINICAL IMPORTANCE

A NLR < 3.06 at admission in sick hospitalized foals is readily available and clinically useful variable to provide prognostic information.

The Construction of Three-Layered Biomimetic Arterial Graft Balances Biomechanics and Biocompatibility for Dynamic Biological Reconstruction

The process of reconstructing an arterial graft is a complex and dynamic process that is subject to the influence of various mechanical factors, including tissue regeneration and blood pressure. The attainment of favorable remodeling outcomes is contingent upon the biocompatibility and biomechanical properties of the arterial graft. A promising strategy involves the emulation of the three-layer structure of the native artery, wherein the inner layer is composed of polycaprolactone (PCL) fibers aligned with blood flow, exhibiting excellent biocompatibility that fosters endothelial cell growth and effectively prevents platelet adhesion. The middle layer, consisting of PCL and polyurethane (PU), offers mechanical support and stability by forming a contractile smooth muscle ring and antiexpansion PU network. The outer layer, composed of PCL fibers with an irregular arrangement, promotes the growth of nerves and pericytes for long-term vascular function. Prioritizing the reconstruction of the inner and outer layers establishes a stable environment for intermediate smooth muscle growth. Our three-layer arterial graft is designed to provide the blood vessel with mechanical support and stability through nondegradable PU, while the incorporation of degradable PCL generates potential spaces for tissue ingrowth, thereby transforming our graft into a living implant.

The implication of targeting PD-1:PD-L1 pathway in treating sepsis through immunostimulatory and anti-inflammatory pathways

Sepsis currently remains a major contributor to mortality in the intensive care unit (ICU), with 48.9 million cases reported globally and a mortality rate of 22.5% in 2017, accounting for almost 20% of all-cause mortality worldwide. This highlights the urgent need to improve the understanding and treatment of this condition. Sepsis is now recognized as a dysregulation of the host immune response to infection, characterized by an excessive inflammatory response and immune paralysis. This dysregulation leads to secondary infections, multiple organ dysfunction syndrome (MODS), and ultimately death. PD-L1, a co-inhibitory molecule expressed in immune cells, has emerged as a critical factor in sepsis. Numerous studies have found a significant association between the expression of PD-1/PD-L1 and sepsis, with a particular focus on PD-L1 expressed on neutrophils recently. This review explores the role of PD-1/PD-L1 in immunostimulatory and anti-inflammatory pathways, illustrates the intricate link between PD-1/PD-L1 and sepsis, and summarizes current therapeutic approaches against PD-1/PD-L1 in the treatment and prognosis of sepsis in preclinical and clinical studies.

Mitochondria in health, disease, and aging

Mitochondria are well known as organelles responsible for the maintenance of cellular bioenergetics through the production of ATP. Although oxidative phosphorylation may be their most important function, mitochondria are also integral for the synthesis of metabolic precursors, calcium regulation, the production of reactive oxygen species, immune signaling, and apoptosis. Considering the breadth of their responsibilities, mitochondria are fundamental for cellular metabolism and homeostasis. Appreciating this significance, translational medicine has begun to investigate how mitochondrial dysfunction can represent a harbinger of disease. In this review, we provide a detailed overview of mitochondrial metabolism, cellular bioenergetics, mitochondrial dynamics, autophagy, mitochondrial damage-associated molecular patterns, mitochondria-mediated cell death pathways, and how mitochondrial dysfunction at any of these levels is associated with disease pathogenesis. Mitochondria-dependent pathways may thereby represent an attractive therapeutic target for ameliorating human disease.

Advances in the Study of Immunosuppressive Mechanisms in Sepsis

Sepsis is a life-threatening disease caused by a systemic infection that triggers a dysregulated immune response. Sepsis is an important cause of death in intensive care units (ICUs), poses a major threat to human health, and is a common cause of death in ICUs worldwide. The pathogenesis of sepsis is intricate and involves a complex interplay of pro- and anti-inflammatory mechanisms that can lead to excessive inflammation, immunosuppression, and potentially long-term immune disorders. Recent evidence highlights the importance of immunosuppression in sepsis. Immunosuppression is recognized as a predisposing factor for increased susceptibility to secondary infections and mortality in patients. Immunosuppression due to sepsis increases a patient's chance of re-infection and increases organ load. In addition, antibiotics, fluid resuscitation, and organ support therapy have limited impact on the prognosis of septic patients. Therapeutic approaches by suppressing excessive inflammation have not achieved the desired results in clinical trials. Research into immunosuppression has brought new hope for the treatment of sepsis, and a number of therapeutic approaches have demonstrated the potential of immunostimulatory therapies. In this article, we will focus on the mechanisms of immunosuppression and markers of immune monitoring in sepsis and describe various targets for immunostimulatory therapy in sepsis.

Evaluating clinical heterogeneity and predicting mortality in severely burned patients through unsupervised clustering and latent class analysis

Burn injuries often result in a high level of clinical heterogeneity and poor prognosis in patients with severe burns. Clustering algorithms, which are unsupervised methods that can identify groups with similar trajectories in patients with heterogeneous diseases, can provide insights into the mechanisms of the disease pathogenesis. This study aimed to analyze routinely collected biomarkers to understand their mortality prediction power, identify the clinical meanings or subtypes, and inform treatment decisions to improve the outcomes of patients with burns. This retrospective cohort study included patients aged ≥ 18 years who were admitted between January 2010 and December 2021. The patients were divided into four subgroups based on the time period of their admission: week 1, 2, 3, and 4. The study revealed that 22 biomarkers were evaluated, and the red blood cell distribution width, bicarbonate level, pH, platelets, and lymphocytes were significantly associated with the mortality risk. Latent class analysis further demonstrated that the pH, platelets, lymphocytes, lactate, and albumin demonstrated the lowest levels in the cluster with the highest risk of mortality, with the lowest levels of pH and lactate being particularly noteworthy in week 1 of the study. During the week 2, the pH and lymphocyte levels were demonstrated to be significant predictors of the mortality risk, whereas the lymphocyte and platelet counts were meaningful predictors in week 3. During week 4, pH, platelet count, and albumin level were important predictors of mortality risk. Analysis of routinely collected biomarkers using clustering algorithms and latent class analysis can provide valuable insights into the heterogeneity of burn injuries and improve the ability to predict disease progression and mortality. Our findings suggest that lactate levels are a better indicator of cellular hypoxia in the early stages of burn shock, whereas platelet and lymphocyte levels are more indicative of infections such as sepsis. Albumin levels are considered a better indicator of reduced nutritional loss with decrease in unhealed burn wounds; however, the pH levels reflect the overall condition of the patient throughout the study period. These findings can be used to inform treatment decisions and improve the outcomes of burn patients.

PKM2/STAT1-mediated PD-L1 upregulation on neutrophils during sepsis promotes neutrophil organ accumulation by serving an anti-apoptotic role

BACKGROUND

Delayed neutrophil apoptosis during sepsis may impact neutrophil organ accumulation and tissue immune homeostasis. Elucidating the mechanisms underlying neutrophil apoptosis may help identify potential therapeutic targets. Glycolysis is critical to neutrophil activities during sepsis. However, the precise mechanisms through which glycolysis regulates neutrophil physiology remain under-explored, especially those involving the non-metabolic functions of glycolytic enzymes. In the present study, the impact of programmed death ligand-1 (PD-L1) on neutrophil apoptosis was explored. The regulatory effect of the glycolytic enzyme, pyruvate kinase M2 (PKM2), whose role in septic neutrophils remains unaddressed, on neutrophil PD-L1 expression was also explored.

METHODS

Peripheral blood neutrophils were isolated from patients with sepsis and healthy controls. PD-L1 and PKM2 levels were determined by flow cytometry and Western blotting, respectively. Dimethyl sulfoxide (DMSO)-differentiated HL-60 cells were stimulated with lipopolysaccharide (LPS) as an in vitro simulation of septic neutrophils. Cell apoptosis was assessed by annexin V/propidium iodide (annexin V/PI) staining, as well as determination of protein levels of cleaved caspase-3 and myeloid cell leukemia-1 (Mcl-1) by Western blotting. An in vivo model of sepsis was constructed by intraperitoneal injection of LPS (5 mg/kg) for 16 h. Pulmonary and hepatic neutrophil infiltration was assessed by flow cytometry or immunohistochemistry.

RESULTS

PD-L1 level was elevated on neutrophils under septic conditions. Administration of neutralizing antibodies against PD-L1 partially reversed the inhibitory effect of LPS on neutrophil apoptosis. Neutrophil infiltration into the lung and liver was also reduced in PD-L1-/- mice 16 h after sepsis induction. PKM2 was upregulated in septic neutrophils and promoted neutrophil PD-L1 expression both in vitro and in vivo. In addition, PKM2 nuclear translocation was increased after LPS stimulation, which promoted PD-L1 expression by directly interacting with and activating signal transducer and activator of transcription 1 (STAT1). Inhibition of PKM2 activity or STAT1 activation also led to increased neutrophil apoptosis.

CONCLUSION

In this study, a PKM2/STAT1-mediated upregulation of PD-L1 on neutrophils and the anti-apoptotic effect of upregulated PD-L1 on neutrophils during sepsis were identified, which may result in increased pulmonary and hepatic neutrophil accumulation. These findings suggest that PKM2 and PD-L1 could serve as potential therapeutic targets.

Microbes and the fate of neutrophils

Neutrophils or polymorphonuclear neutrophils (PMNs) are an important component of innate host defense. These phagocytic leukocytes are recruited to infected tissues and kill invading microbes. There are several general characteristics of neutrophils that make them highly effective as antimicrobial cells. First, there is tremendous daily production and turnover of granulocytes in healthy adults-typically 1011 per day. The vast majority (~95%) of these cells are neutrophils. In addition, neutrophils are mobilized rapidly in response to chemotactic factors and are among the first leukocytes recruited to infected tissues. Most notably, neutrophils contain and/or produce an abundance of antimicrobial molecules. Many of these antimicrobial molecules are toxic to host cells and can destroy host tissues. Thus, neutrophil activation and turnover are highly regulated processes. To that end, aged neutrophils undergo apoptosis constitutively, a process that contains antimicrobial function and proinflammatory capacity. Importantly, apoptosis facilitates nonphlogistic turnover of neutrophils and removal by macrophages. This homeostatic process is altered by interaction with microbes and their products, as well as host proinflammatory molecules. Microbial pathogens can delay neutrophil apoptosis, accelerate apoptosis following phagocytosis, or cause neutrophil cytolysis. Here, we review these processes and provide perspective on recent studies that have potential to impact this paradigm.

The role of G protein-coupled receptor in neutrophil dysfunction during sepsis-induced acute respiratory distress syndrome

Sepsis is defined as a life-threatening dysfunction due to a dysregulated host response to infection. It is a common and complex syndrome and is the leading cause of death in intensive care units. The lungs are most vulnerable to the challenge of sepsis, and the incidence of respiratory dysfunction has been reported to be up to 70%, in which neutrophils play a major role. Neutrophils are the first line of defense against infection, and they are regarded as the most responsive cells in sepsis. Normally, neutrophils recognize chemokines including the bacterial product N-formyl-methionyl-leucyl-phenylalanine (fMLP), complement 5a (C5a), and lipid molecules Leukotriene B4 (LTB4) and C-X-C motif chemokine ligand 8 (CXCL8), and enter the site of infection through mobilization, rolling, adhesion, migration, and chemotaxis. However, numerous studies have confirmed that despite the high levels of chemokines in septic patients and mice at the site of infection, the neutrophils cannot migrate to the proper target location, but instead they accumulate in the lungs, releasing histones, DNA, and proteases that mediate tissue damage and induce acute respiratory distress syndrome (ARDS). This is closely related to impaired neutrophil migration in sepsis, but the mechanism involved is still unclear. Many studies have shown that chemokine receptor dysregulation is an important cause of impaired neutrophil migration, and the vast majority of these chemokine receptors belong to the G protein-coupled receptors (GPCRs). In this review, we summarize the signaling pathways by which neutrophil GPCR regulates chemotaxis and the mechanisms by which abnormal GPCR function in sepsis leads to impaired neutrophil chemotaxis, which can further cause ARDS. Several potential targets for intervention are proposed to improve neutrophil chemotaxis, and we hope that this review may provide insights for clinical practitioners.

Intrinsic Apoptotic Pathway Genes of Circulating Blood Neutrophils Triggered during HIV Infection and Remained Stimulated in ART Patients

BACKGROUND

The intrinsic apoptotic pathway of neutrophils in Human Immunodeficiency Virus (HIV) infection results in spontaneous neutrophil death. There is a scarcity of data regarding the gene expression of an intrinsic apoptotic pathway of neutrophils in HIV patients.

OBJECTIVE

The objective of this study was to observe the differential expression of some important genes involved in the intrinsic apoptotic pathway of HIV patients, including those who were receiving antiretroviral therapy (ART).

METHODS

Blood samples were collected from asymptomatic, symptomatic, ART receiver HIV patients, and healthy individuals. Total RNA was extracted from neutrophils and subjected to quantitative real-time PCR assay. CD4+T cells and an automated complete blood count were performed.

RESULTS

Among the asymptomatic, symptomatic, and ART receiver HIV patients (n=20 in each group), median CD4+T counts were 633, 98, and 565 cells/ml, and the length of HIV infection in months (± SD) was 24.06 ± 21.36, 62.05 ± 25.51, and 69.2 ± 39.67, respectively. Compared with healthy controls, intrinsic apoptotic pathway genes, i.e., BAX, BIM, Caspase-3, Caspase-9, MCL-1, and Calpain-1, were upregulated to 1.21 ± 0.33, 1.8 ± 0.25, 1.24 ± 0.46, 1.54 ± 0.21, 1.88 ± 0.30, and 5.85 ± 1.34 fold in the asymptomatic group, and even more significantly, i.e., 1.51 ± 0.43, 2.09 ± 1.13, 1.85 ± 1.22, 1.72 ± 0.85, 2.26 ± 1.34, and 7.88 ± 3.31 fold in symptomatic patients, respectively. Despite CD4+ T-cell levels increased in the ART receiver group, these genes did not approach the level of healthy or asymptomatic and remained significantly upregulated.

CONCLUSION

The genes involved in the intrinsic apoptotic pathway in circulating neutrophils during HIV infection were stimulated in vivo, and ART reduced the expression of those upregulated genes but did not return to the level of asymptomatic or healthy individuals.

Cellular Immuno-Profile in Septic Human Host: A Scoping Review

Simple Summary

Septic shock is a life-threatening disease caused by a dysregulated host response to infection, affecting millions of people every year and killing more than 25% directly despite advances in modern medicine. This pathology is characterized by apoptosis-induced depletion of immune cells and immunodepression. Many alterations in the expression of surface markers of neutrophils and monocytes have been described in septic patients. There is no specific treatment but the early identification and diagnosis of the pathology as well as timely treatment can greatly improve patient outcomes. The aim of this study was to inspect the recently published literature to inform the clinician about the most up-to-date techniques for the study of immune cell phenotypes and on the function of leukocytes of extracorporeal and non-blood purification treatments proposed for sepsis were also analyzed. The most important alteration observed in septic neutrophils is the activation of a survival program capable of resisting apoptotic death. As regards adaptive immunity, sepsis-induced apoptosis leads to lymphopenia in patients with septic shock and this process involves all types of T cells (CD4, CD8 and Natural Killer), except for regulatory T cells, favoring immunosuppression. Several promising therapies that target the host’s immune response to sepsis are currently under evaluation.

Abstract

Innate and adaptive immune system cells play a critical role in the host response to sepsis. Sepsis is a life-threatening disease characterized by apoptosis-induced depletion of immune cells and immunodepression, which contribute to morbidity and mortality. Many alterations in the expression of surface markers of neutrophils and monocytes have been described in septic patients. The aim of this study was to inspect the recently published literature to inform the clinician about the most up-to-date techniques for the study of circulating leukocytes. The impact on cell phenotypes and on the function of leukocytes of extracorporeal and non-blood purification treatments proposed for sepsis were also analyzed. We conducted a systematic review using Pubmed/Medline, Ovid/Willey, the Cochrane Library, the Cochrane Controlled Trials Register, and EMBASE, combining key terms related to immunological function in sepsis and selected the most relevant clinical trials and review articles (excluding case reports) published in the last 50 years. The most important alteration in neutrophils during sepsis is that they activate an anti-apoptotic survival program. In septic monocytes, a reduced characteristic expression of HLA-DR is observed, but their role does not seem to be significantly altered in sepsis. As regards adaptive immunity, sepsis leads to lymphopenia and immunosuppression in patients with septic shock; this process involves all types of T cells (CD4, CD8 and Natural Killer), except for regulatory T cells, which retain their function. Several promising therapies that target the host immune response are currently under evaluation. During the worldwide pandemic caused by SARS-CoV-2, it was useful to study the “cytokine storm” to find additional treatments, such as the oXiris^® filter. This therapy can decrease the concentration of inflammatory markers that affect the severity of the disease.

Evaluating the Effects of Storage Conditions on Multiple Cell-Free RNAs in Plasma by High-Throughput Sequencing

Background: Plasma cell-free RNAs (cfRNAs) can serve as noninvasive biomarkers for the diagnosis and monitoring of diseases. However, the delay in blood processing may lead to unreliable results. Therefore, an unbiased evaluation based on the whole transcriptome under different storage conditions is needed. Methods: Here, blood samples were collected in ethylenediaminetetraacetic acid tubes and processed immediately (0 hour), or stored at room temperature (RT) or 4°C for different time intervals (2, 6, and 24 hours) before plasma separation. High-throughput sequencing was applied to assess the effects of storage conditions on the transcript profiles and fragment characteristics of plasma cell-free mRNA, long noncoding RNA (lncRNA), and small RNAs. Results: More genes changed their expression levels with time when blood was stored at RT compared with those at 4°C. Cell-free mRNA and lncRNA were relatively stable in blood preserved at 4°C for 6 hours, while cell-free microRNA (miRNA) and piwi-interacting RNA (piRNA) remained stable at 4°C for 24 hours. After 24 hours, more contamination of the leukocyte-derived RNAs occurred at RT, possibly due to apoptosis. Meanwhile, significant changes were also observed regarding the characteristics of the RNA fragments, including fragment size, the proportion of intron, and the pyrimidine frequency of the fragmented 3' end. Fifteen tissue-enriched genes were detected in the plasma but not expressed in leukocytes. The expression level and fragment length of these genes gradually decreased during storage, suggesting the degradation of the cfRNA and the dilution of leukocyte-derived RNA with other tissue-derived cfRNA. Conclusions: Our results suggest that the contamination of leukocyte-derived RNA and the degradation of original cfRNA contribute to the changes in the cfRNA expression profiles and the fragment characteristics during short-term storage. The storage of blood at 4°C for 6 hours allows plasma cfRNA to remain relatively stable, which will be useful for further studies or clinical applications where adequate quantification or the fragment signature of cfRNA is required.

Dysregulation of neutrophil death in sepsis

Sepsis is a prevalent disease that has alarmingly high mortality rates and, for several survivors, long-term morbidity. The modern definition of sepsis is an aberrant host response to infection followed by a life-threatening organ dysfunction. Sepsis has a complicated pathophysiology and involves multiple immune and non-immune mediators. It is now believed that in the initial stages of sepsis, excessive immune system activation and cascading inflammation are usually accompanied by immunosuppression. During the pathophysiology of severe sepsis, neutrophils are crucial. Recent researches have demonstrated a clear link between the process of neutrophil cell death and the emergence of organ dysfunction in sepsis. During sepsis, spontaneous apoptosis of neutrophils is inhibited and neutrophils may undergo some other types of cell death. In this review, we describe various types of neutrophil cell death, including necrosis, apoptosis, necroptosis, pyroptosis, NETosis, and autophagy, to reveal their known effects in the development and progression of sepsis. However, the exact role and mechanisms of neutrophil cell death in sepsis have not been fully elucidated, and this remains a major challenge for future neutrophil research. We hope that this review will provide hints for researches regarding neutrophil cell death in sepsis and provide insights for clinical practitioners.

The relationship between the neutrophil-to-lymphocyte ratio and diabetic retinopathy in adults from the United States: results from the National Health and nutrition examination survey

Background

Diabetic retinopathy (DR) is a common complication of diabetes mellitus (DM). Systemic inflammation is intimately associated with DR. The neutrophil-to-lymphocyte ratio (NLR) index is a relatively new indicator of inflammation.

Methods

This cross-sectional study was carried out among adults with DM based on the National Health and Nutrition Examination Survey (NHANES) from 2009 to 2016. NLR was presented as absolute neutrophil counts/ absolute lymphocyte counts. The relationship of NLR levels to DR was analyzed using multivariable logistic regression.

Results

There were 2772 eligible subjects extracted from the NHANES. In the multivariate analysis, NLR was related to the risk of DR after adjustment for potential confounders. The association between NLR levels and DR was nonlinear, with an inflection point of 4.778. Compared with the baseline values, NLR was not statistically significant on the right side of the inflection point (1.000, 0.914 to 1.094, 0.9974) but was positively associated with DR on the left side (1.236, 1.132 to 1.349, < 0.0001).

Conclusions

NLR reflects systemic inflammation that may increase the risk of DR. NLR positively correlates with DR when its value is less than 4.778.

Nanoporous Gold Ring-Integrated Photothermal Intraocular Lens for Active Prevention of Posterior Capsular Opacification

Posterior capsular opacification (PCO) is the leading complication after cataract surgery, and is mainly induced by the proliferation and migration of residual lens epithelial cells (LECs). Although numerous attempts have been made to reduce the incidence of PCO, this complication remains a critical challenge in postoperative visual recovery. This study aims to report a functionalized intraocular lens (R-IOL) with a region-confined photothermal effect for the active prevention of PCO after implantation. The outer rim of R-IOL (non-optical area) is decorated with a nanoporous gold (NPG) ring, which can effectively eliminate the LECs around R-IOL, ultimately inhibiting the migration of LECs from the periphery to the visual axis center in the initial stage, and preventing the subsequent PCO. Furthermore, the mechanism of LECs elimination can be attributed to apoptosis induced by mild photothermal therapy. After in vivo implantation for 30 days, PCO is rarely observed in the R-IOL group, whereas the considerably higher incidence of PCO (75%) is found in the pristine IOL (P-IOL) group. The region-confined photothermal effect based on NPG not only provides an active strategy to effectively prevent PCO, but also introduces new opportunities for the treatment of undesirable hyperplasia.

The association between the neutrophil to lymphocyte ratio and in-hospital mortality among sepsis patients: A prospective study

The Neutrophil to lymphocyte ratio (NLR) was shown to be associated with disease severity, poor prognosis and increased mortality in sepsis. However, the association between NLR and sepsis prognosis remains controversial. Our study aims to prospectively examine the prognostic ability of NLR in predicting in-hospital mortality among sepsis patients and determine the optimal cutoff of NLR that can most accurately predict in-hospital mortality in sepsis patients. This study was a prospective cohort study that included adult sepsis patients that presented to the emergency department of a tertiary care center between September 2018 and February 2021. Receiver operating characteristic curve was used to determine the optimal cutoff of the neutrophil to lymphocyte ratio that predicts in-hospital mortality. Patients were divided into 2 groups: above and below the optimal cutoff. Stepwise logistic regression was performed to assess the magnitude of the association between NLR and in-hospital mortality. A total of 865 patients were included in the study. The optimal cutoff for the neutrophil to lymphocyte ratio that predicts in-hospital mortality was found to be 14.20 with a sensitivity of 44.8% and a specificity of 65.3% (with PPV = 0.27 and NPV = 0.80). The area under the curve for the ratio was 0.552 with a 95% confidence intervals = [0.504-0.599] with a P value = .03. Patients that have a NLR above the cutoff were less likely to survive with time compared to patients below the cutoff based on the Kaplan-Meier curves. In the stepwise logistic regression, the optimal neutrophil to lymphocyte ratio cutoff was not associated with in-hospital mortality (odds ratios = 1.451, 95% confidence intervals = [0.927-2.270], P = .103). In conclusion the optimal cutoff of the NLR that predicts in-hospital mortality among sepsis patients was 14.20. There was no association between the NLR and in-hospital mortality in sepsis patients after adjusting for confounders. Further studies with a larger sample size should be done to determine the optimal NLR cutoff and its prognostic role in septic patients (in-hospital mortality and other clinically significant outcomes).

ACUTE AND SUSTAINED ALTERATIONS TO THE BONE MARROW IMMUNE MICROENVIRONMENT FOLLOWING POLYMICROBIAL INFECTION

ABSTRACT

Sepsis is a highly prevalent cause of death in intensive care units. Characterized by severe immune cell derangements, sepsis is often associated with multiorgan dysfunction. For many sepsis survivors, these deficits can persist long after clinical resolution of the underlying infection. Although many studies report on the impact of sepsis on individual immune cell subtypes, a comprehensive analysis of sepsis-induced alterations within and across the immune cell landscape is lacking. In this study, we used single-cell RNA sequencing to assess sepsis-associated transcriptional changes in immune cells isolated from bone marrow at single-cell resolution. We used a high-survival fecal-induced peritonitis sepsis model using Friend leukemia virus B mice. Single-cell RNA sequencing classified 3402 single cells from control subjects into 14 clusters representing long-term hematopoietic stem cell (HSC), short-term HSC, basophil, dendritic cell, eosinophil, erythroblast, erythrocyte, macrophage, neutrophil, natural killer cell, plasma cell, plasmacytoid dendritic cell, pre-B cell, and T memory cell lineages. One day following experimentally induced sepsis, cell type compositions shifted significantly and included notable decreases in HSC and myeloid cell abundance. In addition to proportional cell composition changes, acute sepsis induced significant transcriptional alterations in most immune cell types analyzed-changes that failed to completely resolve 1 month after sepsis. Taken together, we report widespread and persistent transcriptional changes in diverse immune cells in response to polymicrobial infection. This study will serve as a valuable resource for future work investigating acute and/or long-term sepsis-associated immune cell derangements.

Withaferin A Inhibits Neutrophil Adhesion, Migration, and Respiratory Burst and Promotes Timely Neutrophil Apoptosis

Neutrophils play a major role in many equine conditions, including equine asthma, laminitis, and intestinal ischemia and reperfusion injury, and therefore represent an attractive target for innovative therapeutic approaches. Novel strategies for reducing neutrophilic inflammation include modulation of neutrophil functions and lifespan. Withaferin A (WFA) is a phytochemical with well-established in vitro and in vivo anti-inflammatory properties, but its direct effects on neutrophils are largely unknown. We hypothesized that WFA would inhibit adhesion, migration, and respiratory burst by equine neutrophils and promote timely apoptosis of primed equine neutrophils. Consistent with this hypothesis, our data show that WFA causes a significant, concentration-dependent inhibition of equine neutrophil adhesion, migration, and respiratory burst in response to diverse stimuli. Further, WFA treatment increased apoptosis of equine neutrophils exposed to GM-CSF for 24 h. This pro-apoptotic effect of WFA was not observed in unprimed neutrophils, nor at the 2-h time point relevant to our functional neutrophil experiments. Our data demonstrate that WFA may reduce neutrophil-mediated inflammation through multiple mechanisms, including suppression of inflammatory responses and promotion of apoptosis. Additional research is needed to elucidate the molecular mechanisms for these effects and evaluate the potential clinical use of WFA in veterinary and human patients.

Duchesnea indica Extract Ameliorates LPS-Induced Septic Shock in Mice

Objective

Duchesnea indica has been reported for its anti-inflammatory properties. However, its efficacy in sepsis has yet to be reported. In this study, we studied the ability of Duchesnea indica extract (DIE) to rescue mice from septic shock and sepsis.

Methods

In vitro studies included the measurement of secreted nitric oxide, cell viability, gene and protein expression via real-time polymerase chain reaction and western blot, and confocal microscopy in RAW 264.7 cells. In vivo studies include a model of septic shock and sepsis in BALB/c mice induced by a lethal and sub-lethal dose of lipopolysaccharide (LPS).

Results

DIE suppressed the expression of proinflammatory cytokines induced by LPS and prevented the translocation of NFκB into the nucleus of RAW 264.7 cells. It also prevented reactive oxygen species damage induced by LPS in murine bone marrow-derived macrophages. Models of sepsis and septic shock were established in BALB/c mice and DIE-rescued mice from septic shock. DIE also reversed the increase in tumor necrosis factor-α and nitrite levels in the serum of mice induced with sepsis. DIE also prevented the translocation of NFκB from the cytosol into the nucleus in murine lungs. Histopathological damage induced by sepsis was reversed in the testis, liver, and lungs of mice.

Conclusion

In conclusion, DIE is a suitable candidate for development as a therapeutic agent for sepsis.

The Impact of Cytokines on Neutrophils' Phagocytosis and NET Formation during Sepsis-A Review

Sepsis is an overwhelming inflammatory response to infection, resulting in multiple-organ injury. Neutrophils are crucial immune cells involved in innate response to pathogens and their migration and effector functions, such as phagocytosis and neutrophil extracellular trap (NET) formation, are dependent on cytokine presence and their concentration. In the course of sepsis, recruitment and migration of neutrophils to infectious foci gradually becomes impaired, thus leading to loss of a crucial arm of the innate immune response to infection. Our review briefly describes the sepsis course, the importance of neutrophils during sepsis, and explains dependence between cytokines and their activation. Moreover, we, for the first time, summarize the impact of cytokines on phagocytosis and NET formation. We highlight and discuss the importance of cytokines in modulation of both processes and emphasize the direction of further investigations.

The Actin-Binding Protein Cortactin Promotes Sepsis Severity by Supporting Excessive Neutrophil Infiltration into the Lung

Sepsis is a systemic infection that can lead to multi-organ failure. It is characterised by an uncontrolled immune response with massive neutrophil influx into peripheral organs. Neutrophil extravasation into tissues depends on actin remodeling and actin-binding proteins such as cortactin, which is expressed ubiquitously, except for neutrophils. Endothelial cortactin is necessary for proper regulation of neutrophil transendothelial migration and recruitment to sites of infection. We therefore hypothesised that cortactin plays a crucial role in sepsis development by regulating neutrophil trafficking. Using a murine model of sepsis induced by cecal ligation and puncture (CLP), we showed that cortactin-deficient (KO) mice survive better due to reduced lung injury. Histopathological analysis of lungs from septic KO mice revealed absence of oedema, reduced vascular congestion and mucus deposition, and better-preserved alveoli compared to septic wild-type (WT) mice. Additionally, sepsis-induced cytokine storm, excessive neutrophil infiltration into the lung and oxidative stress were significantly reduced in KO mice. Neutrophil depletion 12 h after sepsis improved survival in WT mice by averting lung injury, similar to both neutrophil-depleted and non-depleted KO mice. Our findings highlight a critical role of cortactin for lung neutrophil infiltration and sepsis severity.

Immunomonitoring of Monocyte and Neutrophil Function in Critically Ill Patients: From Sepsis and/or Trauma to COVID-19

Immune cells and mediators play a crucial role in the critical care setting but are understudied. This review explores the concept of sepsis and/or injury-induced immunosuppression and immuno-inflammatory response in COVID-19 and reiterates the need for more accurate functional immunomonitoring of monocyte and neutrophil function in these critically ill patients. in addition, the feasibility of circulating and cell-surface immune biomarkers as predictors of infection and/or outcome in critically ill patients is explored. It is clear that, for critically ill, one size does not fit all and that immune phenotyping of critically ill patients may allow the development of a more personalized approach with tailored immunotherapy for the specific patient. In addition, at this point in time, caution is advised regarding the quality of evidence of some COVID-19 studies in the literature.

Role of Specialized Pro-Resolving Mediators in Modifying Host Defense and Decreasing Bacterial Virulence

Bacterial infection activates the innate immune system as part of the host’s defense against invading pathogens. Host response to bacterial pathogens includes leukocyte activation, inflammatory mediator release, phagocytosis, and killing of bacteria. An appropriate host response requires resolution. The resolution phase involves attenuation of neutrophil migration, neutrophil apoptosis, macrophage recruitment, increased phagocytosis, efferocytosis of apoptotic neutrophils, and tissue repair. Specialized Pro-resolving Mediators (SPMs) are bioactive fatty acids that were shown to be highly effective in promoting resolution of infectious inflammation and survival in several models of infection. In this review, we provide insight into the role of SPMs in active host defense mechanisms for bacterial clearance including a new mechanism of action in which an SPM acts directly to reduce bacterial virulence.

The Value of a Complete Blood Count (CBC) for Sepsis Diagnosis and Prognosis

Sepsis represents an important global health burden due to its high mortality and morbidity. The rapid detection of sepsis is crucial in order to prevent adverse outcomes and reduce mortality. However, the diagnosis of sepsis is still challenging and many efforts have been made to identify reliable biomarkers. Unfortunately, many investigated biomarkers have several limitations that do not support their introduction in clinical practice, such as moderate diagnostic and prognostic accuracy, long turn-around time, and high-costs. Complete blood count represents instead a precious test that provides a wealth of information on individual health status. It can guide clinicians to early-identify patients at high risk of developing sepsis and to predict adverse outcomes. It has several advantages, being cheap, easy-to-perform, and available in all wards, from the emergency department to the intensive care unit. Noteworthy, it represents a first-level test and an alteration of its parameters must always be considered within the clinical context, and the eventual suspect of sepsis must be confirmed by more specific investigations. In this review, we describe the usefulness of basic and new complete blood count parameters as diagnostic and prognostic biomarkers of sepsis.

Immune System Disequilibrium-Neutrophils, Their Extracellular Traps, and COVID-19-Induced Sepsis

Equilibrium within the immune system can often determine the fate of its host. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the pathogen responsible for the coronavirus disease 2019 (COVID-19) pandemic. Immune dysregulation remains one of the main pathophysiological components of SARS-CoV-2-associated organ injury, with over-activation of the innate immune system, and induced apoptosis of adaptive immune cells. Here, we provide an overview of the innate immune system, both in general and relating to COVID-19. We specifically discuss "NETosis," the process of neutrophil release of their extracellular traps, which may be a more recently described form of cell death that is different from apoptosis, and how this may propagate organ dysfunction in COVID-19. We complete this review by discussing Stem Cell Therapies in COVID-19 and emerging COVID-19 phenotypes, which may allow for more targeted therapy in the future. Finally, we consider the array of potential therapeutic targets in COVID-19, and associated therapeutics.

Usefulness of neutrophil-to-lymphocyte ratio for predicting acute pericarditis outcomes

BACKGROUND

In daily practice, C-reactive protein (CRP) may be used to predict recurrence and treatment response in patients with acute pericarditis; however, the predictive role of CRP might be insufficient for clinical prediction in some patients. In this study, we aimed to investigate the relationship between neutrophil-to-lymphocyte ratio (NLR) and the composite endpoint of pericarditis recurrence and/or tamponade within 1 year in patients with acute pericarditis.

METHODS

A total of 104 patients diagnosed with acute idiopathic pericarditis (mean age 42.8 ± 15.2 years, 55.8% male) were included in the study. Physical examination findings of these patients, electrocardiography, echocardiography, chest X-ray and laboratory findings were evaluated and analysed. During the 1-year follow-up, the composite of cardiac tamponade and/or pericarditis recurrence was investigated as the primary endpoint of the study.

RESULTS

Compared to the group without the composite outcome, the group with the composite outcome had significantly higher rates of moderate and severe pericardial effusion (p < 0.01) and higher white blood cell (WBC) count (p:0.001), platelet count (p = 0.003), NLR (2.14 (1.49-3.02) vs 6.60 (5.50-8.68); p < 0.001) and high-sensitivity C-reactive protein (hs-CRP) (8.01 (5.1-24.5 vs 69.5 (40.8-128); p:0.001). Higher hs-CRP (p < 0.001), WBC (p:0.001), NLR (p < 0.001) and platelets (p:0.02) were associated with pericarditis recurrence. NLR and hs-CRP were independently associated with the composite endpoint (p < 0.001 and p < 0.001, respectively).

CONCLUSION

NLR and hs-CRP were found to be independent predictors for the composite endpoint of tamponade and/or recurrence in acute pericarditis patients during the 1-year follow-up. Similar to hs-CRP, NLR may also be used for risk assessment in patients with idiopathic pericarditis.

Impact of the apelin/APJ axis in the pathogenesis of Parkinson's disease with therapeutic potential

The pathogenesis of Parkinson's disease (PD) remains elusive. There is still no available disease-modifying strategy against PD, whose management is mainly symptomatic. A growing amount of preclinical evidence shows that a complex interplay between autophagy dysregulation, mitochondrial impairment, endoplasmic reticulum stress, oxidative stress, and excessive neuroinflammation underlies PD pathogenesis. Identifying key molecules linking these pathological cellular processes may substantially aid in our deeper understanding of PD pathophysiology and the development of novel effective therapeutic approaches. Emerging preclinical evidence indicates that apelin, an endogenous neuropeptide acting as a ligand of the orphan G protein-coupled receptor APJ, may play a key neuroprotective role in PD pathogenesis, via inhibition of apoptosis and dopaminergic neuronal loss, autophagy enhancement, antioxidant effects, endoplasmic reticulum stress suppression, as well as prevention of synaptic dysregulation in the striatum, excessive neuroinflammation, and glutamate-induced excitotoxicity. Underlying signaling pathways involve phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin, extracellular signal-regulated kinase 1/2, and inositol requiring kinase 1α/XBP1/C/EBP homologous protein. Herein, we discuss the role of apelin/APJ axis and associated molecular mechanisms on the pathogenesis of PD in vitro and in vivo and provide evidence for its challenging therapeutic potential.

Parallels in Sepsis and COVID-19 Conditions: Implications for Managing Severe COVID-19

Sepsis is a life-threatening systemic illness attributed to a dysregulated host response to infection. Sepsis is a global burden killing ~11 million persons annually. In December 2019, a novel pneumonia condition termed coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), emerged and has resulted in more than 1,535,982 deaths globally as of 8^th December 2020. These two conditions share many pathophysiological and clinical features. Notably, both sepsis and COVID-19 patients experience consumptive thrombocytopenia, haemolytic anaemia, vascular microthrombosis, multi-organ dysfunction syndrome, coagulopathy, septic shock, respiratory failure, fever, leukopenia, hypotension, leukocytosis, high cytokine production and high predisposition to opportunistic infections. Considering the parallels in the immunopathogenesis and pathophysiological manifestations of sepsis and COVID-19, it is highly likely that sepsis care, which has a well-established history in most health systems, could inform on COVID-19 management. In view of this, the present perspective compares the immunopathogenesis and pathophysiology of COVID-19 and non-SARS-CoV-2 induced sepsis, and lessons from sepsis that can be applicable to COVID-19 management.

Molecular Mechanisms for Regulation of Neutrophil Apoptosis under Normal and Pathological Conditions

Neutrophils are one of the main cells of innate immunity that perform a key effector and regulatory function in the development of the human inflammatory response. Apoptotic forms of neutrophils are important for regulating the intensity of inflammation and restoring tissue homeostasis. This review summarizes current data on the molecular mechanisms of modulation of neutrophil apoptosis by the main regulatory factors of the inflammatory response-cytokines, integrins, and structural components of bacteria. Disturbances in neutrophil apoptosis under stress are also considered, molecular markers of changes in neutrophil lifespan associated with various diseases and pathological conditions are presented, and data on pharmacological agents for modulating apoptosis as potential therapeutics are also discussed.

Depletion of pulmonary intravascular macrophages rescues inflammation-induced delayed neutrophil apoptosis in horses

The objective of this study was to determine the effect of pulmonary intravascular macrophage depletion on systemic inflammation and ex vivo neutrophil apoptosis using an experimental model of intestinal ischemia and reperfusion injury in horses. Neutrophils were isolated before and after surgery from horses that were randomized to three treatment groups, namely, sham celiotomy (CEL, n = 4), intestinal ischemia and reperfusion (IR, n = 6), and intestinal ischemia and reperfusion with gadolinium chloride treatment to deplete pulmonary intravascular macrophages (PIMs, IRGC, n = 6). Neutrophil apoptosis was assessed with Annexin V and propidium iodide staining quantified with flow cytometry and caspase-3, caspase-8, and caspase-9 activities in neutrophil lysates. All horses experienced a systemic inflammatory response following surgery. Following surgery, ex vivo neutrophil apoptosis was significantly delayed after 12 or 24 h in culture, except in IRGC horses (12 h: CEL: P = 0.03, IR: P = 0.05, IRGC: P = 0.2; 24 h: CEL: P = 0.001, IR: P = 0.004, IRGC: P = 0.3). Caspase-3, caspase-8, and caspase-9 activities were significantly reduced in neutrophils isolated after surgery and cultured for 12 h in IR horses, but not in IRGC horses (IR caspase-3: P = 0.002, IR caspase-8: P = 0.002, IR caspase-9: P = 0.04). Serum TNF-α concentration was increased in IRGC horses for 6-18 h following jejunal ischemia. Following surgery, ex vivo equine neutrophil apoptosis was delayed via downregulation of caspase activity, which was ameliorated by PIM depletion potentially via upregulation of TNF-α.

Diagnostic Value of Neutrophil to Lymphocyte Ratio and Mean Platelet Volume on Early Onset Neonatal Sepsis on Term Neonate

By setting out from increased neutrophil count, decreased lymphocyte count, and increased mean platelet volume (MPV), which is a result of the effect of inflammation on blood cells, we aimed to investigate whether neutrophil to lymphocyte ratio (NLP) and MPV can be used as an auxiliary parameter for the diagnosis of early-onset neonatal sepsis (EOS). This study was conducted by analyzing term neonates with EOS and physiological jaundice who were admitted to the neonatal intensive care unit of Izmir Katip Celebi University Ataturk Training and Research Hospital. A total of 63 neonate files were examined to include 30 term neonates with EOS, and 77 neonate files were examined to include 30 term neonates with physiological jaundice as a control group. NLR had an area under the curve (AUC) of 0.891 for prediction of EOS. At a cut-off level of 1.42, NLR had a likelihood ratio (LR) of 5.5, sensitivity of 88%, a specificity of 84%, a positive predictive value (PPV) of 84.6%, and a negative predictive value (NPV) of 87.5%. MPV had an AUC of 0.666 for the prediction of EOS and at a cut-off level of 9.3 fL, MPV had an LR of 1.23, sensitivity of 84%, a specificity of 32%, a PPV of 55.2%, and an NPV of 66.6%. In conclusion, this study provides evidence that NLR and MPV can be used in addition to conventional parameters in the diagnosis of EOS.

The Septic Neutrophil-Friend or Foe

ABSTRACT

Neutrophils play a critical role in the eradication of pathogenic organisms, particularly bacteria. However, in the septic patient the prolonged activation and accumulation of neutrophils may augment tissue and organ injury. This review discusses the different activation states and chemotaxis of neutrophils in septic patients. Neutrophil killing of bacteria and the formation of neutrophil extracellular traps represent important components of the innate immune response and they become dysregulated during sepsis, possibly through changes in their metabolism. Delayed neutrophil apoptosis may contribute to organ injury, or allow better clearance of pathogens. Neutrophils provide a friendly immune response to clear infections, but excessive activation and recruitment has the potential to turn them into potent foes.

Defective Neutrophil Function in Patients with Sepsis Is Mostly Restored by ex vivo Ascorbate Incubation

Background

Neutrophil function is essential for effective defence against bacterial infections but is defective in patients with sepsis. Ascorbate or vitamin C, which is low in the plasma of patients with sepsis, is stored inside human neutrophils and is essential for their normal function.

Objective

This study aimed to determine if ascorbate treatment ex vivo improved neutrophil function in patients with sepsis.

Patients and Methods

Human blood neutrophils were isolated from 20 patients with sepsis and 20 healthy age-matched controls. Neutrophils were incubated with or without ascorbate (1, 5, 10, 20 and 40 mM) for periods up to 2h. Chemotaxis was evaluated using a chemotactic chamber in response to the chemoattractant, fMLP. Phagocytosis (uptake of pHrodo red stained S. aureus) and apoptosis (annexin-V/propidium iodide staining) were measured by flow cytometry. Neutrophil extracellular trap (NET) formation was detected and quantified using DAPI, anti-myeloperoxidase and anti-neutrophil elastase immuno-fluorescence staining. Quantifluor detected the amount of dsDNA in NET supernatants, while quantitative PCR identified changes in expression of PADI4 gene.

Results

Chemotactic and phagocytic activities were decreased in patients with sepsis but increased after treatment with the high concentrations of ascorbate. Apoptosis was increased in the sepsis patients but not altered by ascorbate treatment. Spontaneous NET formation was observed in patients with sepsis. A quantity of 1mM ascorbate decreased spontaneous NETosis to that of normal, healthy neutrophils, while high concentrations of ascorbate (>10mM) further promoted NET formation.

Conclusion

Dysregulated neutrophil function was observed in patients with sepsis which could contribute to disease pathology and outcomes. Exposure to ascorbate could reverse some of these changes in function. These novel discoveries raise the possibility that ascorbate treatment could be used as an adjunctive therapy that could result in improved neutrophil function during sepsis.

CIRP Induces Neutrophil Reverse Transendothelial Migration in Sepsis

Extracellular cold-inducible RNA-binding protein (CIRP) exaggerates inflammation in sepsis. Neutrophil reverse transendothelial migration (rTEM) allows neutrophils to migrate from tissues into the circulation. The phenotype of neutrophils after reverse migration is CD54CXCR1. We hypothesize that CIRP induces neutrophil rTEM in sepsis. Sepsis was induced in male C57BL/6 mice by cecal ligation and puncture (CLP), and at 5, 10, or 20 h after CLP the frequencies of reversely migrated (RM) neutrophils were assessed in the blood by flow cytometry. As 20 h of CLP showed highest increase in the frequency of RM neutrophils, we further assessed RM neutrophils in the blood of WT and CIRP mice at this time point. The effect of CIRP on neutrophil rTEM was determined by injecting mice with recombinant mouse CIRP (rmCIRP) intratracheally (i.t.) and assessed the frequencies of RM neutrophils. The expression of neutrophil elastase (NE) and junctional adhesion molecule-C (JAM-C) in the lungs was measured by Western blot. The mean frequency of RM neutrophils in sham mice was 0.4%, whereas the frequencies were significantly increased to 1%, 3%, and 7% at 5, 10, and 20 h of CLP, respectively. The mean frequency of RM neutrophils in the blood of CIRP mice was significantly lower than that of WT mice at 20 h of CLP. The RM neutrophils in the blood was significantly increased after administration of rmCIRP i.t. into mice in a time- and dose-dependent manners. NE expression was upregulated, whereas JAM-C expression was downregulated in the lungs after CLP or rmCIRP administration. For the first time, we have showed that CIRP induces neutrophil rTEM in sepsis by increasing NE and decreasing JAM-C.

Neutrophils in Biomaterial-Guided Tissue Regeneration: Matrix Reprogramming for Angiogenesis

Biomaterial-guided in situ tissue regeneration uses biomaterials to stimulate and guide the body's endogenous, regenerative processes to drive functional tissue repair and regeneration. To be successful, cell migration into the biomaterials is essential, which requires angiogenesis to maintain cell viability. Neutrophils, the first cells responding to an implanted biomaterial, are now known to play an integral part in angiogenesis in multiple tissues and exhibit considerable potential for driving angiogenesis in the context of tissue regeneration. In terms of biomaterial-guided in situ tissue regeneration, harnessing the proangiogenic potential of the neutrophil through its robust secretion of matrix metalloproteinase 9 (MMP-9) may provide a mechanism to improve biomaterial performance by initiating matrix reprogramming. This review will discuss neutrophils as matrix reprogrammers and what is currently known about their ability to create a microenvironment that is more conducive for angiogenesis and tissue regeneration through the secretion of MMP-9. It will first review a set of ground-breaking studies in tumor biology and then present an overview of what is currently known about neutrophils and MMP-9 in biomaterial vascularization. Finally, it will conclude with potential strategies and considerations to engage neutrophils in biomaterial-guided angiogenesis and in situ tissue regeneration. Impact statement This review draws attention to a highly neglected topic in tissue engineering, the role of neutrophils in biomaterial-guided tissue regeneration and angiogenesis. Moreover, it highlights their abundant secretion of matrix metalloproteinase 9 (MMP-9) for matrix reprogramming, a topic with great potential yet to be vetted in the literature. It presents strategies and considerations for designing the next generation of immunomodulatory biomaterials. While there is literature discussing the overall role of neutrophils in angiogenesis, there are a limited number of review articles focused on this highly relevant topic in the context of biomaterial integration and tissue regeneration, making this a necessary and impactful article.

Down-regulation of miR-133a-3p protects lung tissue against sepsis-induced acute respiratory distress syndrome by up-regulating SIRT1

Introduction

MicroRNA-133a-3p (miR-133a-3p) is a potential gene regulator having an important role in the process of inflammation and lung injury. The present work studied the role of miR-133a-3p in sepsis-mediated acute respiratory distress syndrome (ARDS) and the mechanism involved.

Material and methods

C57BL/6 mice were selected for the study. Protein expression of Bcl-2, cleaved caspase-3 and Bax was assessed by western blot analysis. Expression of mRNA was assessed by RT-PCR. Effects of inflammation were studied by myeloperoxidase (MPO) activity. Quantification of albumin was done by measuring the albumin conjugated with Evan's blue. The alveolar macrophages were separated from the lungs of mice by the bronchoalveolar lavage procedure and were submitted to sepsis challenge in vitro; the macrophages were treated with lipopolysaccharide (LPS).

Results

Treatment of LPS resulted in upregulation of miR-133a-3p in alveolar macrophages. Suppression of miR-133a-3p halted the over-expression of inflammatory cytokines in macrophages and caused remission of histopathologic changes. The ARDS lungs showed a decrease in levels of proinflammatory cytokines and an increase in levels of apoptotic protein, establishing the protective role for miR-133a-3p. The results suggested sirtuin 1 (SIRT1) as a potential target of miR-133a-3p in the macrophages, also showing that expression of SIRT1 was inversely associated with expression of miR-133a-3p. The protective effect of miR-133a-3p down-regulation in LPS-mediated alveolar macrophages and sepsis-induced ARDS could be corrected by a SIRT1 inhibitor.

Conclusions

Down-regulation of miR-133a-3p may exert a protective effect on lung tissue against sepsis-mediated ARDS by up-regulating the levels of SIRT1 via suppressing the inflammatory response and inhibiting the cellular apoptosis in lung tissues.

APOL1 Nephropathy Risk Alleles and Risk of Sepsis in Blacks

BACKGROUND AND OBJECTIVES

apo L1 (APOL1) nephropathy risk alleles are associated with CKD in blacks. Although APOL1 has innate immune functions, little is known about the association of APOL1 genotypes with risk of infectious outcomes, such as sepsis. The objective of this study was to examine the associations of APOL1 nephropathy risk alleles with risk of sepsis in black adults.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We assessed the association of APOL1 risk alleles with incident sepsis in 10,366 black participants of the Reasons for Geographic and Racial Differences in Stroke study enrolled between 2003 and 2007 with follow-up through December 31, 2012. In Cox models adjusted for demographics, comorbid conditions, and principal components ancestry, we examined the association of APOL1 risk alleles with incident sepsis using recessive (comparing zero or one versus two risk alleles), dominant (zero versus one or two risk alleles), and additive genetic models. We also examined models stratified by diabetes and CKD status.

RESULTS

A total of 1320 (13%) participants had two APOL1 risk alleles, 4719 (46%) had one risk allele, and 4327 (42%) participants had zero risk alleles. A total of 306 sepsis events occurred over a median 6.5 years (interquartile range, 4.5-8.1). There were no statistically significant associations of APOL1 genotype with sepsis risk under recessive genetic models. APOL1 genotypes were associated with sepsis risk under dominant (hazard ratio, 1.55; 95% confidence interval, 1.13 to 2.11) and additive (hazard ratio per variant allele copy, 1.25; 95% confidence interval, 1.02 to 1.53) genetic models adjusted for covariates and ancestry. These associations did not vary by diabetes or CKD status (Pinteraction>0.10 for both).

CONCLUSIONS

In community-dwelling black adults, carriage of APOL1 nephropathy risk alleles are common and associated with higher risk of sepsis.

Prognostic value of neutrophil-to-lymphocyte ratio in sepsis: A meta-analysis

BACKGROUND

Neutrophil-to-lymphocyte ratio (NLR) has been used to predict the prognosis of patients with sepsis with inconsistent results. This meta-analysis aimed to clarify the prognostic value of NLR in patients with sepsis.

METHODS

A comprehensive literature search for relevant studies, published prior to March 2019, was conducted using PubMed, Web of Science, and the China National Knowledge. Infrastructure database. Standard mean differences (SMDs) with 95% confidence intervals (CI) were used to evaluate the NLR of patients with sepsis retrospectively. Hazard ratios (HRs) with 95% CIs were used to evaluate the prognostic value of NLR in patients with sepsis.

RESULTS

Patients from 14 studies (n = 11,564) were selected for evaluation. Nine studies (1371 patients) analyzed the NLR in these patients. The pooled results showed significantly higher NLR in non-survivors than in survivors (random-effects model: SMD = 1.18, 95% CI; 0.42-1.94). Nine studies (10,685 patients) evaluated the prognostic value of NLR for sepsis; the pooled results showed that higher NLR was associated with poor prognosis in patients with sepsis (fixed-effects model: HR = 1.75, 95% CI; 1.56-1.97). Subgroup analysis revealed that study design, cut-off NLR, or primary outcome did not affect the prognostic value of NLR in patients with sepsis.

CONCLUSION

This meta-analysis indicates that NLR may be a helpful prognostic biomarker of patients with sepsis and that higher NLR values may indicate unfavorable prognoses in these patients.

Delayed Pulmonary Apoptosis of Diet-Induced Obesity Mice following Escherichia coli Infection through the Mitochondrial Apoptotic Pathway

Escherichia coli (E. coli) is one of pathogens causing nosocomial pneumonia and could induce pulmonary excessive apoptosis. Although much has been learned about metabolic diseases induced by obesity, the information linking bacterial pneumonia to obesity is limited. Accordingly, we investigated the apoptosis of normal (lean) and diet-induced obesity (DIO, fed a high-fat diet) mice after nasal instillation with E. coli. Lung tissues were obtained at 0 (preinfection), 12, 24, and 72 h after infection, and acute pulmonary inflammation was observed at 12 h. Elevated cell apoptosis and percentage of pulmonary cells depolarized with collapse of the mitochondrial transmembrane potential (Δψm) occurred in response to bacterial infection. The relative mRNA and protein expressions of Bax, caspase-3, and caspase-9 increased, but Bcl-2 decreased in the lung. Interestingly, the apoptotic percentage and most of apoptosis-associated factors mentioned above peaked at 12 or 24 h in the lean-E. coli group, while at 24 or 72 h in the DIO-E. coli group. Taken together, these findings indicated that the E. coli pneumonia caused excessive pulmonary apoptosis through the mitochondria-mediated pathway, and the apoptosis was delayed in the DIO mice with E. coli pneumonia.

Pathological alteration and therapeutic implications of sepsis-induced immune cell apoptosis

Sepsis is a life-threatening organ dysfunction syndrome caused by dysregulated host response to infection that leads to uncontrolled inflammatory response followed by immunosuppression. However, despite the high mortality rate, no specific treatment modality or drugs with high efficacy is available for sepsis to date. Although improved treatment strategies have increased the survival rate during the initial state of excessive inflammatory response, recent trends in sepsis show that mortality occurs at a period of continuous immunosuppressive state in which patients succumb to secondary infections within a few weeks or months due to post-sepsis “immune paralysis.” Immune cell alteration induced by uncontrolled apoptosis has been considered a major cause of significant immunosuppression. Particularly, apoptosis of lymphocytes, including innate immune cells and adaptive immune cells, is associated with a higher risk of secondary infections and poor outcomes. Multiple postmortem studies have confirmed that sepsis-induced immune cell apoptosis occurs in all age groups, including neonates, pediatric, and adult patients, and it is considered to be a primary contributing factor to the immunosuppressive pathophysiology of sepsis. Therapeutic perspectives targeting apoptosis through various strategies could improve survival in sepsis. In this review article, we will focus on describing the major apoptosis process of immune cells with respect to physiologic and molecular mechanisms. Further, advances in apoptosis-targeted treatment modalities for sepsis will also be discussed.