Early prolonged neutrophil activation in critically ill patients with sepsis

Sepsis after middle cerebral artery occlusion exacerbates peripheral oxidative stress in a sex-specific manner

Ischemic stroke occurs due a blockage in the blood flow to the brain, leading to damage to the nervous system. The prevalent morbidities resulting from stroke include post-stroke infection, as sepsis. Additionally, oxidative stress is recognized for inducing functional deficits in peripheral organs during sepsis. Therefore, sex differences in stroke exist and we aimed to investigate the peripheral oxidative stress caused by sepsis after stroke in male and female rats. Wistar rats (male and female) were divided into sham+sham, middle cerebral artery occlusion (MCAO) + sham, sham+ cecal ligation and perforation (CLP) and MCAO+CLP groups to males and female rats. Animals were subjected to MCAO or sham and after 7 days, were subjected to sepsis by CLP or sham. After 24 h, serum, total brain, lung, liver, heart, and spleen were collected. Brain edema, myeloperoxidase (MPO) activity, nitrite/nitrate (N/N) concentration, oxidative damage to lipids and proteins, and catalase activity were evaluated. Brain edema was observed only in male rats in MCAO+CLP group compared to MCAO+sham. Regarding MPO activity, an increase was verified in male in different organs and serum in MCAO+CLP group. For N/N levels, the increase was more pronounced in females submitted to MCAO+CLP. In general, to oxidative stress, an increase was only observed in animals exposed to MCAO+CLP, or with a greater increase in this group compared to the others. The findings provided the first indication that animals exposed to MCAO exhibit a heightened vulnerability to the harmful impacts of sepsis, as evidenced by brain edema and peripheral oxidative stress, and this susceptibility is dependent of sex.

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.

Heparin-binding protein as a biomarker of severe sepsis in the pediatric intensive care unit: A multicenter, prospective study

OBJECTIVES

The aim of this study is to assess Heparin-binding protein (HBP) as a diagnostic and prognostic biomarker of severe sepsis in the pediatric intensive care unit (PICU).

METHODS

A multicenter, prospective study was conducted among children with sepsis in nine PICUs in China from October 2019 to June 2021. Plasma levels of HBP, procalcitonin (PCT), C-reactive protein (CRP), lactate, and white blood cell (WBC) count were determined at enrollment and 72 h after enrollment.

RESULTS

Of 355 included patients, 132 patients were diagnosed with non-severe sepsis (referred to as sepsis), 223 patients had severe sepsis. Patients with severe sepsis had significantly elevated levels of HBP compared with sepsis (median 170.5 vs. 74.1 ng/mL, P < 0.001). Adding HBP to a diagnostic model with PCT and lactate could significantly improve the diagnostic capability for severe sepsis. The plasma levels of HBP correlated positively with the number of dysfunctional organs. After adjusting for confounding factors, the declined levels of HBP at 72 h had a significant association with decreased in-hospital mortality (adjusted odds ratio (aOR) 0.242, P < 0.001). The levels of HBP showed weak positive correlations with PCT, CRP, WBC, and no correlation to lactate.

CONCLUSIONS

HBP at enrollment can be an independent indicator for severe sepsis and the dynamic changes at 72 h can be a predictor for in-hospital mortality in PICU.

[Value of heparin-binding protein in the diagnosis of severe adenovirus pneumonia in children]

OBJECTIVES

To study the value of serum heparin-binding protein (HBP) in the early diagnosis of severe adenovirus pneumonia in children.

METHODS

A total of 80 children who were admitted to the Department of Pediatrics, Changsha Central Hospital Affiliated to University of South China, from February 2019 to August 2021 and were diagnosed with adenovirus pneumonia were enrolled as subjects. According to the diagnostic criteria for severe pneumonia, they were divided into two groups: severe adenovirus pneumonia (40 children) and non-severe adenovirus pneumonia (40 children). The two groups were compared in terms of the serum levels of inflammatory markers within 24 hours after admission, such as HBP, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), white blood cell count, platelet count (PLT), and C-reactive protein. The receiver operating characteristic (ROC) curve was plotted to identify the value of these inflammatory markers in the early diagnosis of severe adenovirus pneumonia.

RESULTS

Compared with the non-severe adenovirus pneumonia group, the severe adenovirus pneumonia group had a significantly higher serum level of HBP [(46±16) ng/mL vs (28±13) ng/mL, P<0.05], as well as significantly higher levels of TNF-α, IL-6, and PLT (P<0.05). HBP had an area under the ROC curve (AUC) of 0.804 in the early diagnosis of severe adenovirus pneumonia, with a sensitivity of 80.0% and a specificity of 70.0% at the optimal cut-off value of 31.76 ng/mL. The ROC curve analysis of HBP combined with other indicators for the early diagnosis of severe adenovirus pneumonia showed that HBP+TNF-α, HBP+PLT, HBP+IL-6, HBP+TNF-α+IL-6, and HBP+TNF-α+IL-6+PLT had an AUC of 0.866, 0.850, 0.863, 0.886, and 0.894, respectively.

CONCLUSIONS

Serum HBP may be used as a biomarker for the early diagnosis of severe adenovirus pneumonia, and its combination with TNF-α, IL-6, and PLT can improve its diagnostic value.

Kynurenine Pathway-An Underestimated Factor Modulating Innate Immunity in Sepsis-Induced Acute Kidney Injury?

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection, and it accounts for about half of the cases of acute kidney injury (AKI). Although sepsis is the most frequent cause of AKI in critically ill patients, its pathophysiological mechanisms are not well understood. Sepsis has the ability to modulate the function of cells belonging to the innate immune system. Increased activity of indoleamine 2,3-dioxygenase 1 (IDO1) and production of kynurenines are the major metabolic pathways utilized by innate immunity cells to maintain immunological tolerance. The activation of the kynurenine pathway (KP) plays a dual role in sepsis—in the early stage, the induction of IDO1 elicits strong proinflammatory effects that may lead to tissue damage and septic shock. Afterwards, depletion of tryptophan and production of kynurenines contribute to the development of immunosuppression that may cause the inability to overpower opportunistic infections. The presented review provides available data on the various interdependencies between elements of innate immunity and sepsis-induced AKI (SAKI) with particular emphasis on the immunomodulatory significance of KP in the above processes. We believe that KP activation may be one of the crucial, though underestimated, components of a deregulated host response to infection during SAKI.

Value of heparin-binding protein in the diagnosis of severe infection in children: a prospective study

OBJECTIVES

To study the value of heparin-binding protein (HBP) in the diagnosis of severe infection in children.

METHODS

This study was a prospective observational study. The medical data of children who were admitted to the pediatric intensive care unit due to infection from January 2019 to January 2020 were collected. According to the diagnostic criteria for severe sepsis and sepsis, the children were divided into a severe sepsis group with 49 children, a sepsis group with 82 children, and a non-severe infection group with 33 children. The three groups were compared in terms of related biomarkers such as plasma HBP, serum C-reactive protein, serum procalcitonin, and platelet count. The receiver operating characteristic (ROC) curve was plotted to investigate the value of plasma HBP level in the diagnosis of severe infection (including severe sepsis and sepsis).

RESULTS

The severe sepsis and sepsis groups had a significantly higher plasma HBP level on admission than the non-severe infection group (P<0.05). Compared with the sepsis and non-severe groups, the severe sepsis group had significantly higher serum levels of C-reactive protein and procalcitonin and a significantly lower platelet count (P<0.05). Plasma HBP level had an area under the ROC curve of 0.590 in determining severe infection, with a sensitivity of 38.0% and a specificity of 82.4% (P<0.05).

CONCLUSIONS

There is an increase in plasma HBP level in children with severe infection, and plasma HBP level has a lower sensitivity but a higher specificity in the diagnosis of severe infection and can thus be used as one of the markers for the judgment of severe infection in children.

Colorimetric Detection of Sepsis-Derived Hyperdegranulation with Plasmonic Nanosensors

Hyperdegranulation of neutrophilic granulocytes is a common finding in sepsis that directly contributes to the heightened immune response leading to organ dysfunction. Currently, cell degranulation is detected by flow cytometry, which requires large infrastructure that is not always available at the point of care. Here, we propose a plasmonic assay for detecting the degranulation status of septic cells colorimetrically. It is based on triggering the aggregation of gold nanoparticles with cationic granule proteins. Cells from septic patients contain fewer granules and therefore release less cationic proteins than healthy cells. This results in red-colored assays than can be easily detected by eye. The assay can selectively detect cationic granule proteins even in the presence of an excess of unrelated proteins, which is key to detect degranulation with high specificity. Coupling this signal generation mechanism with a magnetic purification step enabled the identification of septic cells with the same performance as flow cytometry. This makes the proposed method a promising alternative for diagnosing sepsis in decentralized healthcare schemes.

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.