Background and Aims Plasma microparticles (PMPs) are small (0.1 to 1.0 µm) membrane bound vesicles, released from plasma membrane during cell activation and apoptosis. The cytoplasmic and surface contents of PMPs vary according to the parental cell’s lineage and physiological state. Altered numbers and profiles have been associated with thrombotic and inflammatory disorders including rheumatic diseases.
There have been variable reports on PMPs levels and profiles in Systemic Lupus Erythematosus (SLE). Some studies have reported higher levels while others showed similar or lower numbers with altered profiles. We compared PMPs in a multi-ethnic SLE cohort with a healthy control group, and explored their role in pathophysiology of SLE
Methods Clinical data and blood samples were collected from 56 consented SLE patients (median 45 years, 95% females) who fulfilled the ACR criteria, and 39 healthy adults. PMP pellet was obtained by high speed centrifugation. Flow cytometry was used to enumerate and profile the PMPs, utilising fluorescent polystyrene nanobeads, lipophilic dyes and fluorescent-labelled antibodies. HL60, a promyelocytic cell line, was utilised to study functional effects of PMPs in a smaller subgroup of samples (8 from each arm).
Results SLE patients have lower PMP numbers compared to healthy controls (median: 12 925 vs 26 490 respectively, p=0.01, Figure 1). SLE PMPs also exhibited significantly higher proportions of leukocyte, and endothelial markers (Figure 2). SLE PMPs induced significantly higher p38 phosphorylation in HL60 cells compared to control PMPs (p=0.04, Figure 3)
Conclusions Our data suggest that there are quantitative and functional differences in PMPs between SLE patients and healthy controls
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