Change of walking distance in intermittent claudication: impact on inflammation, oxidative stress and mononuclear cells: a pilot study.

BACKGROUND: Atherosclerosis is a chronic inflammatory process involving the immune system and formation of reactive oxygen species (ROS). We investigated changes of mononuclear blood cells and ROS production in relation to the walking distance of patients with intermittent claudication during home-based exercise training. METHODS: Forty patients with intermittent claudication were asked to perform a home-based exercise training for a mean time of 12 months. ROS formation was measured using the luminol analogue L-012. Peripheral blood leucocytes [monocytes, polymorphonuclear neutrophils (PMN) and dendritic cells (DC)] were analysed by flow cytometry and analysed for the expression of major inflammatory surface molecules. RESULTS: At follow-up, patients showed an increased walking distance and reduced ROS production upon stimulation with a phorbol ester derivative (PDBu) (p < 0.01). Monocytes changed their inflammatory phenotype towards an increased anti-inflammatory CD14(++)CD16(-) subpopulation (p < 0.0001). Adhesion molecules CD11b, CD11c and TREM-1 on monocytes and PMN decreased (all p < 0.01). On DC expression of HLA-DR, CD86 or CD40 decreased at follow-up. Inflammatory markers like fibrinogen, C-reactive protein or soluble TREM-1 (sTREM-1) decreased over the observation period. Finally, we found a close relation of sTREM-1 with the walking distance, fibrinogen and ROS production. CONCLUSIONS: We observed an amelioration of the proinflammatory phenotype on monocytes, DC and PMN, as well as a reduced ROS production in PAD patients under home-based exercise, paralleled by an increased walking distance. Our data suggest that a reduced inflammatory state might be achieved by regular walking exercise, possibly in a dimension proportionately to changes in walking distance.

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

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.

Phenotypic characterisation of pro-inflammatory monocytes and dendritic cells in peripheral arterial disease.

Atherosclerosis is a chronic inflammatory process involving antigen-presenting cells like monocytes and dendritic cells (DC). The aim of this study was to perform a phenotypic characterisation of these cell types in patients with different degrees of peripheral arterial disease (PAD). Sixty patients with PAD [N= 30 intermittent claudication (IC), N= 30 critical limb ischemia (CLI)] and 30 controls were included. Peripheral blood leucocytes were analysed from peripheral blood by flow cytometry using different gating strategies to directly identify and analyse monocytes, myeloid DC, (mDC) and plasmacytoid DC (pDC). PAD patients showed a significantly higher proportion of proinflammatory CD14++CD16+ monocytes (p<0.0001) compared with healthy individuals. We found an increased number of mDC/ml and a reduced number of pDC/ml (both p<0.01) in PAD patients, leading to a shift in the mDC/pDC ratio (p<0.01). As compared to patients with intermittent claudication, CLI patients presented a reduced expression of HLA-DR (p<0.01), CD86 and CD40 on both mDCs and pDCs (p<0.01). Peripheral blood monocytes show a proinflammatory phenotype in PAD patients compared to controls. In contrast, CLI patients show a reduced expression of proinflammatory markers. We hypothesise that severe ischaemia and/or prolonged inflammation in CLI might lead to a paradoxical attenuation in the proinflammatory membrane pattern of circulating mononuclear cells, possibly hindering an adequate regulatory function of mDCs and pDCs and favouring the progression of disease.