Session Information
Session Title: Rheumatoid Arthritis: Human Etiology and Pathogenesis II
Session Type: Abstract Submissions (ACR)
Background/Purpose:
To investigate whether in vivo synovial hypoxia and TNF blocking therapy determine expression of Nicotinamide Adenine Dinucleotide Phosphate Oxidase (Nox2) – a key source of Reactive Oxygen Species (ROS) in vasculature – and its relationship with macroscopic and microscopic markers of angiogenesis in inflammatory arthritis.
Methods:
Fifty four patients with active inflammatory arthritis (RA n=33 and PsA n=21) were recruited prior to starting biological treatment and underwent arthroscopy, clinical assessment and synovial tissue oxygen (tpO2) measurements. A subgroup of 16 patients pre/post-TNFi therapy was also recruited. Synovial tissue biopsies were obtained for immunohistochemical and ex vivo explant cultures. Paired peripheral blood samples were collected and peripheral blood mononuclear cells (PBMCs) were isolated for mRNA Nox2 analysis. Macroscopic synovitis/vascularity was measured by visual analogue scale. Synovial levels of Nox2, angiogenic markers (VEGF, Ang2, Factor VIII, NCAM and α-SMA), proinflammatory cytokine (TNF-α) and redox signaling factors (NF-κB) were quantified by immunohistology/immunofluorescence. Using RA synovial explant cultures ex-vivo, the effect of the Nox2 activators (4-HNE and TNF-α) and inhibitor (DPI) on IL-8 release was measured by ELISA.
Results:
The median tpO2 was 26.59 mmHg (range 3.2-63 mmHg), equivalent to an ambient oxygen tension 3.5% (range 0.42-8.28%). Nox2 was expressed both in lining layer (LL), sublining layer (SL) and vascular region (BV) of synovial tissue with a cytoplasmic pattern of staining. Microscopic Nox2 synovial levels and Nox2 mRNA expression in PBMC were increased in patients with tpO2< 20mmHg compared to patients with tpO2 >20mmHg (in LL, BV and PBMC p<0.05; in SL p=0.07). High synovial Nox2 expression correlated with greater macroscopic vascularity, synovitis, and angiogenic markers: VEGF, Ang2, Factor VIII, NCAM, and α-SMA (all p<0.05) and was co-localized with VEGF, Ang2, Factor VIII, TNF-α and NFκB. In biologic responders there was a significant reduction in cytoplasmic Nox2 positivity in synovial tissue (p<0.05), which was paralleled by a significant increase in tpO2 levels (p<0.05) before and after starting TNFi. In contrast, in patients whose tpO2levels remained the same or reduced after TNFi, no significant change in Nox2 expression was observed. 4-HNE and TNF-α significantly increased IL-8 spontaneous release from synovial tissue explants compared to unstimulated (p<0.05) and DPI inhibited TNF-α induced IL-8 secretion (p<0.001).
Conclusion:
Synovial tissue hypoxia activates expression of Nox2 protein and Nox2-derived ROS may promote angiogenic processes in the inflamed joint. Following successful TNFi biologic therapy, a significant decrease in synovial Nox2 expression was coupled with higher in vivo tpO2. These effects may in part be mediated through hypoxic activation of downstream redox sensitive signaling events.
Disclosure:
M. Biniecka,
None;
C. T. Ng,
None;
E. Balogh,
AbbVie, Pfizer, MSD, Roche,
2;
D. J. Veale,
AbbVie, Pfizer, MSD, Roche,
2,
Pfizer, Roche,
5,
Abbott, Pfizer, MSD, Roche,
8;
U. Fearon,
AbbVie, Pfizer, MSD, Roche,
2.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/redox-mediated-angiogenesis-in-the-hypoxic-joint-of-inflammatory-arthritis/