The interface of inflammation and subclinical atherosclerosis in granulomatosis with polyangiitis (Wegener's): a preliminary study

Abstract

The objective of this study is to assess the relationship between inflammatory disease in granulomatosis with polyangiitis (GPA, Wegener's) and the development of subclinical atherosclerosis. A total of 46 adult patients with GPA were enrolled. Disease status was measured by Birmingham vasculitis assessment scores as modified for GPA, vasculitis damage index, disease duration, and number of relapses. Classic atherosclerotic risk factors, platelet aggregation responses, and circulating microparticle (MP) levels were recorded. All patients underwent carotid artery intima-media thickness (IMT) measurement as outcome for subclinical atherosclerosis. In univariate analyses, systolic and diastolic blood pressure, creatinine, and age were significantly associated with higher IMT (ρ values 0.37, 0.38, 0.35, and 0.054, respectively [P < 0.02 for all]). In a multiple regression model, greater number of relapses, older age at the onset of disease, and higher diastolic blood pressure were found to be associated with higher IMT (P values 0.003, <0.001, and 0.031, respectively). MP counts and platelet reactivity correlated well with disease activity in GPA. Furthermore, MPs were found to activate vascular endothelial cells and platelets in vitro. The cumulative burden of systemic inflammation in GPA correlated with the development of subclinical atherosclerosis. The correlation with subclinical atherosclerosis could be because of glucocorticoid use and not the inflammatory process in GPA, giving the inherent bias that exits with the use of glucocorticoid with each relapse. The findings of increased levels of circulating leukocyte-derived MPs and enhanced platelet reactivity during relapse suggest possible roles for MPs and platelets in disease pathogenesis and support a growing literature that links inflammation, atherosclerosis, and platelet activation. This hypothesis is further substantiated by our demonstration that MPs isolated from plasma of GPA patients can activate platelets and vascular endothelial cells.

Figure 1

Microparticle counts (A) and platelet aggregation (B) correlate with disease activity in granulomatosis with polyangiitis.

Figure 2

MPs from GPA patients increase platelet reactivity to ADP. (A) Calcein-labeled platelets were exposed to GPA patient-derived MPs at an MP-to-platelet ratio of 10:1 and then treated with ADP (1uM) prior to assessment of activation by PAC-1 immunostaining. Mean fluorescence intensity is shown using 2 patient samples. (B) Flow cytometry scattergrams from the 2 patient sample studies showing PAC-1 fluorescence on X axis and calcein fluorescence on Y-axis. ADP, adenosine diphosphate; FL2-H, fluorescence label; GPA, granulomatosis with polyangiitis; IgM, immunoglobulin M; MP, microparticle; NT, non reated; PAC-1, platelet activation clone.

Figure 3

MPs induce ICAM expression on huDMVECs. (A) Flow cytometry histogram showing ICAM-1 immunostaining of huDMVEC after incubation with MP from GPA patient or MP-depleted plasma from the same patient. Untreated cells are shown as a control. (B) Cells treated as in panel A were pre-incubated with cycloheximide prior to incubation with MP. GPA, granulomatosis with polyangiitis; huDMVECs, human dermal microvascular endothelial cells; ICAM, intercellular adhesion molecule; MPs, microparticles; PPP, platelet-poor plasma.