Low-density neutrophil heterogeneity and spleen tyrosine kinase as therapeutic targets in sepsis
Heather L. Teague, Lauren Knabe, Raquel S. Da Cruz, Xianglan Yao, Kiana C. Allen, Trenton Williams, Cumhur Y. Demirkale, Merte Woldehanna, Ernest Evans, Amir Hobson, Jared D. Wilkinson, Steven D. Nathan, Christopher S. King, Jeffrey R. Strich
Heather L. Teague, Lauren Knabe, Raquel S. Da Cruz, Xianglan Yao, Kiana C. Allen, Trenton Williams, Cumhur Y. Demirkale, Merte Woldehanna, Ernest Evans, Amir Hobson, Jared D. Wilkinson, Steven D. Nathan, Christopher S. King, Jeffrey R. Strich
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Research Article Immunology Inflammation

Low-density neutrophil heterogeneity and spleen tyrosine kinase as therapeutic targets in sepsis

Abstract

Sepsis is a leading cause of death for which host-directed therapies are urgently needed. We performed high-dimensional flow cytometry, measurement of soluble biomarkers, and lipopolysaccharide (LPS) stimulation of neutrophils to characterize neutrophil heterogeneity and function in patients with sepsis. We observed that in patients with sepsis, low-density neutrophils (LDNs) are elevated and phenotypically diverse populations of innate immune cells with varying degrees of maturity and myeloperoxidase expression. Spleen tyrosine kinase (SYK) expression was found to be higher in whole blood neutrophils and LDNs of patients with sepsis compared with healthy donors. Importantly, SYK+ LDNs associated with increased levels of intracellular myeloperoxidase (MPO) and soluble biomarkers. Furthermore, SYK+ LDNs correlated with clinical outcomes of sepsis disease severity, including sequential organ failure assessment score, mechanical ventilation, and vasopressors. Functionally, the SYK inhibitor R406 suppressed changes in neutrophil features of activation from normal-density neutrophils and LDNs, including the SYK+ and SYK– neutrophil subsets, and MPO release from LDNs following LPS stimulation of sepsis neutrophils. Combined, these results establish LDNs as a heterogenous population of neutrophils that express high levels of SYK and support SYK inhibition as a potentially novel therapeutic target aimed at suppressing overactive neutrophils in sepsis.

Authors

Heather L. Teague, Lauren Knabe, Raquel S. Da Cruz, Xianglan Yao, Kiana C. Allen, Trenton Williams, Cumhur Y. Demirkale, Merte Woldehanna, Ernest Evans, Amir Hobson, Jared D. Wilkinson, Steven D. Nathan, Christopher S. King, Jeffrey R. Strich

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Figure 7

Correlations of WBNs, LDNs, SYK+ WBNs, and SYK+ LDNs with soluble biomarkers and clinical outcomes.

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Correlations of WBNs, LDNs, SYK+ WBNs, and SYK+ LDNs with soluble biomar...
(A) Bubble plot demonstrating the correlations of WBNs, LDNs, SYK+ WBNs, and SYK+ LDNs with soluble biomarkers. The color of the circle represents the strength of the correlations (r value), and size represents the statistical significance (P value). (B) Circos plot visualizing the correlation of the lower outer ring flow cytometry data quantifying WBNs, LDNs, SYK+ WBNs, and SYK+ LDNs with upper outer ring clinical outcomes and laboratory values. The ribbon width represents the strength of the association between 2 variables, with those that are statistically significant outlined in black. (C) Feature importance plot of clinical data, neutrophil populations, and biomarkers that distinguish patients on mechanical ventilation. The x axis is the mean accuracy of each variable in predicting mechanical ventilation. Red indicates a positive association and blue a negative association. Associations for Circos plot were performed with Spearman’s correlations for continuous variables and point-biserial for dichotomous outcomes. SYK, spleen tyrosine kinase; WBNs, whole blood neutrophils; LDNs, low-density neutrophils; MFI, mean fluorescence intensity; ICU, intensive care unit; SOFA, sequential organ failure assessment; LOS, length of stay; WBC, white blood cell; PLT, platelet count; SCr, serum creatinine; NE, elastase-2; LTF, lactoferrin; SAA, serum amyloid A.