Session Title: Vasculitis
Session Type: Abstract Submissions (ACR)
Background/Purpose: Previous studies from our group suggested that the inflammatory events that occur during relapses in patients with Granulomatosis with Polyangiitis (GPA, Wegener’s) may have a direct role in the pathogenesis of atherosclerosis. We also showed that circulating microparticle (MPs) levels were elevated during relapse and correlated with platelet reactivity. We further elucidated possible mechanisms by which MPs act at the interface between inflammation and atherosclerosis in GPA.
Methods: Human dermal microvascular endothelial cells (huDMVEC, Clonetics CAMBREX) were cultured in EGm-2MV media from Lonza. MPs isolated from plasma from GPA patients, healthy controls or derived from THP-1 human monocytic cells in vitro, were added at various ratios to the huDMVEC and incubated for timed periods. Cells were then detached, washed, and re-suspended in buffer and analyzed by immunofluorescence flow cytometry with anti-ICAM-1 IgG to detect endothelial cell activation. An isotope-matched control IgG was used as control. In addition, fluorescent tagged normal human platelets were incubated with GPA patient-derived MPs (MP/platelet ratio of 10:1) and platelet activation was detected by flow cytometry with PAC-1, an antibody to the activated form of the α2bβ3 integrin.
Results: GPA patient-derived MPs, when incubated for 4h with huDMVEC, induced surface expression of ICAM-1. MP depleted plasma was used as a control and did not influence ICAM-1 expression. ICAM-1 induction by MPs was blocked by cycloheximide indicating a requirement for new protein synthesis and showing that the ICAM-1 was not transferred to the cells by the MPs. MPs isolated from control subjects or from cultured THP-1 cells exerted a similar activating effect on huDMVEC, suggesting that the effect of MP on EC activation was a general feature of MPs. Platelet surface expression of activated α2bβ3 integrin was also significantly enhanced when platelets from healthy donors were pre-incubated with patient-derived MPs and then exposed to low doses of ADP (1μM).
Conclusion: Our findings demonstrate that MPs isolated from plasma of GPA patients can activate platelets and vascular endothelial cells. These findings suggest possible roles for MPs as an interface between inflammation and athero-thrombosis in GPA.
R. L. Silverstein,
G. S. Hoffman,
C. A. Langford,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/pathogenesis-of-atherosclerosis-in-granulomatosis-polyangiitis/