Low density neutrophils and neutrophil extracellular traps (NETs) are new inflammatory players in heart failure

Abstract

BackgroundHeart failure with reduced (HFrEF) or preserved ejection fraction (HFpEF) is characterized by low-grade chronic inflammation. Circulating neutrophils regroup two subtypes termed high- and low-density neutrophils (HDNs and LDNs). LDNs represent less than 2% of total neutrophil under physiological conditions, but their count increase in multiple pathologies, releasing more inflammatory cytokines and neutrophil extracellular traps (NETs).ObjectivesAssess the differential count and role of HDNs, LDNs and NETs-related activities in HF patients.MethodsHDNs and LDNs were isolated from human blood by density gradient and purified by FACS and their counts obtained by flow cytometry. NETs formation (NETosis) was quantified by confocal microscopy. Circulating inflammatory and NETosis biomarkers were measured by ELISA. Neutrophil adhesion onto human extracellular matrix (hECM) was assessed by optical microscopy.ResultsA total of 140 individuals were enrolled, including 33 healthy volunteers (HV), 41 HFrEF (19 stable patients and 22 presenting acute decompensated HF; ADHF) and 66 HFpEF patients (36 stable patients and 30 presenting HF decompensation). HDNs and LDNs counts were significantly increased up to 39% and 2740% respectively in HF patients compared to HV. In HF patients, the correlations between LDNs counts and circulating inflammatory (CRP, IL-6 and -8), Troponin T, NT-proBNP and NETosis components were all significant. In vitro, LDNs expressed more H3Cit and NETs and were more pro-adhesive, with ADHFpEF patients presenting the highest pro-inflammatory profile.ConclusionsHFpEF patients present higher levels of circulating LDNs and NETs related activities, which are the highest in the context of acute HF decompensation.Clinical PerspectiveIn comparison to HFrEF, HFpEF patients have higher levels of circulation LDNs and NETs-associated inflammatory cytokines, peaking in acute decompensated clinical condition.Furthermore, LDNs are producing more NETs and are more adhesive than HDNs, which can contribute to pro-thrombogenesis status described in HF patientsMeasurement of circulating NETs-associated biomarkers could become a novel tool to assess the the risk of acute thrombogenesis in hospitalized ADHFpEF patients.These measurements could lead to future clinical treatments using NETosis inhibitors alone or combined with NETs degradation enzymes (e.g. DNase I).At this time, additional preclinical studies are required to determine specific cell surface markers that could distinguish LDNs from HDNs in whole blood.Once available, circulating LDNs levels would be routinely measured and integrated in the complete blood count analysis to better assess patients’ inflammatory status.