Renal expression of adhesion molecules in anca-associated disease

Gene Expression Pathways across Multiple Tissues in Antineutrophil Cytoplasmic Antibody-associated Vasculitis Reveal Core Pathways of Disease Pathology

OBJECTIVE

To identify commonalities in gene expression data across all antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) tissues thus far characterized.

METHODS

Gene expression data were collected from the 3 AAV tissues thus far characterized (orbit, peripheral leukocytes, and sinus brushings). These data were analyzed to identify commonly expressed genes and disease pathways. The pathways data were adjusted for multiple comparisons using a combined local false discovery rate, which estimates the probability of a false discovery of a given pathway in all 3 tissues analyzed.

RESULTS

Only 4 genes were upregulated in all 3 tissues - IL1RN, TLR2, SLC11A1, and MMP9. After multiple comparison adjustments, the network pathway analysis revealed 28 pathways associated with all 3 tissues. The most strongly associated pathway for all 3 tissues was the neutrophil degranulation pathway [multidimensional local false discovery (md-locfdr) = 1.05 × 10-12], followed by the osteoclast differentiation (md-locfdr = 3.8 × 10-05), cell surface interactions at the vascular wall (md-locfdr = 4.2 × 10-04), signaling by interleukins (md-locfdr = 6.1 × 10-04), and phagosome (md-locfdr = 0.003) pathways. There were no downregulated genes or pathways common to all 3 tissues.

CONCLUSION

This analysis identified individual genes and pathways of disease common to all AAV tissues thus far characterized. The use of a network pathway analysis allowed us to identify pathologic mechanisms that were not readily apparent in the commonly expressed genes alone. Many of these pathways are consistent with current theories about infectious drivers and the crossroads of innate and adaptive immune mechanisms. In addition, this analysis highlights novel pathways, such as vessel wall interactions and platelet activation, which require further investigation.

Endothelium-neutrophil interactions in ANCA-associated diseases

The two salient features of ANCA-associated vasculitis (AAV) are the restricted microvessel localization and the mechanism of inflammatory damage, independent of vascular immune deposits. The microvessel localization of the disease is due to the ANCA antigen accessibility, which is restricted to the membrane of neutrophils engaged in β2-integrin-mediated adhesion, while these antigens are cytoplasmic and inaccessible in resting neutrophils. The inflammatory vascular damage is the consequence of maximal proinflammatory responses of neutrophils, which face cumulative stimulations by TNF-α, β2-integrin engagement, C5a, and ANCA by the FcγRII receptor. This results in the premature intravascular explosive release by adherent neutrophils of all of their available weapons, normally designed to kill IgG-opsonized bacteria after migration in infected tissues.

Dysregulated neutrophil--endothelial interaction in antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitides: implications for pathogenesis and disease intervention

The interplay between neutrophils and endothelial cells allows ANCA to become pathogenic and results in uncontrolled inflammation in the vessel wall. This review presents an overall view on neutrophil-endothelial interaction during inflammation with a focus on ANCA-associated vasculitis, and summarizes the effector mechanisms which cause vascular damage in AAV. In addition, potential elements for disease intervention based on this process are discussed.