Cytosolic phospholipase A2α gene silencing in the myeloid lineage alters development of Th1 responses and reduces disease severity in collagen-induced arthritis
✍ Scribed by G. Courties; M. Baron; J. Presumey; V. Escriou; P. van Lent; D. Scherman; A. Cantagrel; W. B. van den Berg; C. Jorgensen; F. Apparailly; J.-L. Davignon
- Publisher
- John Wiley and Sons
- Year
- 2011
- Tongue
- English
- Weight
- 652 KB
- Volume
- 63
- Category
- Article
- ISSN
- 0004-3591
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✦ Synopsis
Objective. Several lines of evidence implicate cytosolic phospholipase A 2 ␣ (cPLA 2 ␣) as a critical enzyme in inflammatory disorders, including rheumatoid arthritis. Since cells from the myeloid compartment regulate local and systemic disease pathogenesis, the present study was undertaken to examine the effect of cPLA 2 ␣ inhibition in experimental arthritis, using a delivery system tailored to target monocyte functions by RNA interference (RNAi).
Methods. Mice with collagen-induced arthritis (CIA) were injected intravenously with an anti-cPLA 2 ␣ small interfering RNA (siRNA) sequence (siPLA2) formulated as lipoplexes with the RPR209120/DOPE cationic liposome and a carrier DNA. The clinical course of joint inflammation was assessed, and the immunologic balance was analyzed by measuring T helper cell frequencies and cytokine expression. Biodistribution studies of siRNA were also performed.
Results. Weekly systemic injection of siPLA2 lipoplexes significantly reduced the incidence and severity of CIA, in both preventive and curative settings, as compared with findings in control animals. Histologic scores for inflammation and cartilage damage were reduced. The clinical effect was associated with local inhibition of tumor necrosis factor ␣ secretion and lower cPLA 2 ␣ expression and activity. The siPLA2 lipoplexes enabled triggering of in vivo RNAi-mediated gene silencing of cPLA 2 ␣ in CD11bϩ cells recovered from the spleen. While the treatment had no effect on anti-type II collagen (anti-CII) antibodies, CII-specific T helper cells producing interferon-␥, but not interleukin-17, in draining lymph node cells were decreased.
Conclusion.
Our findings indicate that systemic RNAi-mediated cPLA 2 ␣ gene silencing in CD11bϩ cells is effective in the treatment of CIA, and Th1 suppression is one of the potential underlying mechanisms, whereas Th17 suppression is not.
Rheumatoid arthritis (RA) is an autoimmune disease of unknown etiology, characterized by chronic systemic inflammation that predominantly affects articular tissue. Among the immune cells infiltrating RA joints, monocytes are abundantly represented in the synovial fluid and tissue and are considered to be major effectors of synovial inflammation. Monocytes play a key role in both the systemic and the local progression of RA, by producing molecules that participate in the inflammatory and catabolic events in the disease (1). It was recently shown that the spleen contributes to the regulation of inflammation, through monocytes that are