Critical limb ischaemia is characterised by an increased production of whole blood reactive oxygen species and expression of TREM-1 on neutrophils

Abstract

Background: Atherosclerosis is a chronic inflammatory process involving polymorphonuclear neutrophils (PMN) and formation of reactive oxygen species (ROS). The aim of the present study was to investigate the phenotype of inflammatory cells in regard to the expression of triggering receptor expressed on myeloid cells (TREM)-1 and its soluble form (sTREM-1) as well as its relationship with oxidative stress in peripheral artery disease (PAD) patients.

Methods: In total 90 patients with PAD (N = 30 intermittent claudication (IC) > 300 m absolute walking distance, N = 30 IC < 300 m absolute walking distance, N = 30 critical limb ischaemia (CLI)) and 30 control persons were included. ROS formation was measured at basal or stimulated conditions using the luminol analogue L-012 chemiluminescence. Peripheral blood leucocytes were analysed from whole blood by flow cytometry using different gating strategies to identify PMN and monocytes and analyse TREM-1 expression.

Results: CLI patients showed a significant higher ROS production at basal levels (p < 0.05) and upon stimulation with PDBu (p < 0.0001), LPS (p < 0.05) and zymosan A (p < 0.0001). TREM-1 was expressed significantly more on PMN of CLI patients (p < 0.01) in comparison to all other groups, whereas monocytic expression of TREM-1 was similar between all 4 groups. The serum concentration of its soluble form sTREM-1 however was increased in CLI and IC < 300 m patients (p < 0.0001). sTREM-1 concentrations correlated with basal ROS levels as wells with ROS production upon stimulation. Furthermore, we found the walking distance of IC patients to inversely correlate with sTREM-1 (rs = - 0.29; p = 0.03).

Conclusions: We found an increased oxidative stress as well as an increased expression of TREM-1 and serum levels of sTREM-1 in patients with CLI. IC < 300 m patients showed a similar patter in regard to oxidative stress, TREM-1 expression and sTREM-1 concentration. Thus, sTREM-1 might represent a potential inflammatory biomarker to evaluate the severity of PAD. Whether this implies the potential for therapeutic recommendations, i.e. conservative vs. interventional/operative treatment, or a possibility to monitor the efficacy of interventions, requires further studies.

Keywords: PMN; Peripheral arterial disease; ROS; TREM-1.