Session Information
Session Type: Abstract Submissions (ACR)
Background/Purpose: Angiopoietin (Ang) -1 and -2 signalling to the Tie2 tyrosine kinase receptor has an essential role in blood vessel remodeling and angiogenesis. Ang-1, Ang-2 and Tie2 are all expressed in rheumatoid arthritis (RA) synovial tissue. Activated Tie2 is prominently observed in RA synovial macrophages, both Ang-1 and Ang-2 can cooperate with TNF to induce macrophage IL-6 production, and Ang-1 signaling to Tie2 promotes disease persistence and progression in early RA. Here, we examined how macrophage differentiation regulates expression of Tie2 and macrophage responses to Ang-1 and Ang-2, as well as the impact of Tie2 signalling on macrophage production of secreted products elevated in the synovial fluid (SF) of early RA patients.
Methods: Human healthy donor peripheral blood mononuclear cells were isolated from buffy coats and differentiated into macrophages in the presence of Ang-1 and Ang-2, the pro-inflammatory/classically activating cyokines GM-CSF and IFN-γ, or in the presence of the anti-inflammatory/alternatively activating cytokines M-CSF or IL-10. The expression of macrophage polarization markers and Tie2 was analyzed by flow cytometry and quantitative (q)-PCR. Macrophages were stimulated with TNF in the presence or absence of Ang-1 or Ang-2 and effects on gene expression assessed using low density q-PCR arrays, ELISA and luminex. Monocyte chemotactic responses were assessed using 96-well transwell systems.
Results: Macrophage Tie2 protein and mRNA expression was observed under all conditions, but failed to correspond to pro- or anti-inflammatory phenotypes, as it was highest in macrophages differentiated in IL-10 and IFN-g. Ang-1 and Ang-2 failed to induce macrophage polarization. Each polarization condition displayed a distinct expression profile of angiogenic factors. Ang-1 and Ang-2 alone failed to influence gene expression. Ang-1, and to a lesser extent Ang-2, synergized with TNF to stimulate expression of similar gene profiles regardless of macrophage polarization conditions. Significantly enhanced TNF-induced CXCL2, CXCL-3, CXCL-9, IL-6 mRNA expression was observed. Neither Ang-1 nor Ang-2 stimulated monocyte chemotaxis. However, conditioned medium from macrophages stimulated with TNF in combination with Ang-1 or Ang-2 demonstrated significantly enhanced chemotactic activity for monocytes, compared to conditioned medium from macrophages stimulated with TNF alone. Ang-1, but not Ang-2, significantly cooperated with TNF to induce macrophage production of cytokines elevated in the SF of early RA patients, including TGFalpha, FGF2, and IL-12B.
Conclusion: Our results demonstrate that Tie2 is functionally expressed in macrophages, regardless of macrophage polarization conditions. Stimulation of macrophage Tie2 with Ang-1, and to a lesser extent Ang-2, enhances TNF induced pro-inflammatory cytokine and chemokine expression. These results suggest that Tie2 signaling, in combination with TNF, induce a pro-inflammatory and pro-angiogenic profile in differentiated macrophages, and provide a molecular basis for the role of Tie2 in promoting disease progression in both early and established RA.
Disclosure:
S. Garcia,
None;
S. Krausz,
None;
C. A. Ambarus,
None;
B. Malvar Fernandez,
None;
D. L. Baeten,
None;
P. P. Tak,
Employee of GlaxoSmithKline,
3;
K. A. Reedquist,
None.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/tie2-signalling-induces-a-pro-inflammatory-and-pro-angiogenic-phenotype-in-differentiated-macrophages-independently-of-macrophage-polarization-conditions-and-contributes-to-production-of-cytokines/