Background/Purpose

Rheumatoid arthritis (RA) is a perpetuating disease, which affects approximately 1% of the population. Until now, the pathogenic mechanisms of RA remain elusive and currently no cure for the disease. Animal models of arthritis have provided valuable platforms to investigate the potential mechanisms of RA and test new therapeutic principles before initiating clinical trials in humans. Based on the well-known K/BxN model, a spontaneous arthritis mouse model, we have established glucose-6-phosphate isomerase (G6PI) peptide induced arthritis in mice. Since the G6PI peptide used in this model has two cysteines inside, therefore, we focus on how redox balance could affect antigen recognition and thereby affect the pathogenesis of autoimmunity.

Methods

G6PI peptide-induced arthritis is established by immunizing C57Bl/6N.Q (B6N.Q) mice or Ncf1*/* mice with single injection of G6PI peptide emulsified in complete freund’s adjuvant. Cysteine(s) in the peptide is substituted with serine to test whether redox can influence peptide itself.  APCs from both wild type and Ncf1*/* mice are isolated, loaded with G6PI peptide or substituted peptide and cocultured with peptide-specific T cell hybridoma for 24hr. Supernatants are collected then to compare the IL-2 secretion level.

Results

Immunized B6N.Q mice start to develop arthritis on day 10-12, reach to the peak value of severity on day 14-20 and then recover during following 7-10 days. Moreover, both female and male B6N.Q mice could be induced arthritic diseases by G6PI peptide and the incidence is over 80%. Obviously, this peptide-induced arthritis mouse model represents an acute arthritic disease progression. To establish a chronic mouse model with this peptide, we inject pertussis toxin together with G6PI emulsion. It turns out that pertussis toxin not only increases the severity of the disease but also prolong the disease progression over two months. To investigate whether cysteine inside of the peptide is regulated by redox, Ncf1 mutant mice were used. Ncf1 encodes p47^phox subunit, which is an essential cytosolic subunit of NADPH oxidase 2 (Nox2). The mutation of Ncf1 results in the deficiency of ROS production. The in vitro assay suggest that APCs from Ncf1*/* mice show higher capability to present G6PI peptide. However, when either one or both of the cysteine substituted with serine, there is no difference at all in antigen presenting between wild type and Ncf1*/* mice. Furthermore, peptide immunized Ncf1*/* mice exhibit more severe and chronic disease comparing with immunized wild type mice. 

Conclusion

Taken together, we have established a peptide-induced arthritis mouse model. The model is induced with a defined peptide, leading to a high reproducibility and allowing a more precise investigation of the pathogenicity. Since the peptide per se is sensitive to ROS level, therefore, this model provides unique possibility to investigate redox regulation in autoimmune disease including RA.

 

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/redox-regulation-of-a-new-autoimmune-mouse-model-glucose-6-phosphate-isomerase-peptide-induced-arthritis-in-mice/