Arthritis & Rheumatism, Volume 63,
November 2011 Abstract Supplement
Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Chicago, Illinois November 4-9, 2011.
Increased Expression of Ribonuclease Prolongs Survival in Murine Lupus.
Sun1, Xizhang, Agrawal1, Nalini, Tanaka1, Lena, Hayden-Ledbetter1, Martha, Hudkins1, Kelly L., Alpers1, Charles E., Bolland2, Silvia
Systemic Lupus Erythematosus (SLE) is a multisystem autoimmune disease characterized by the presence of high titer autoantibodies directed against self nucleoproteins. These antibodies interact with antigens to form immune complexes (ICs) that deposit in the kidneys, skin and vasculature. In addition to directly inducing tissue injury, nucleoprotein containing ICs are endocytosed by plamacytoid dendritic cells (pDC) and, following activation of intracellular TLR 7 and 9, stimulate the production of type 1 interferon (IFN). Evidence supporting the pre-eminence of TLR7 as the main inducer of IFN-a in mice include increased expression of TLR7 in BXSB mice and amelioration of disease in MRL/lpr mice deficient in TLR7 but not TLR9. In humans with SLE, the importance of TLR7 is also evident because the IFN signature is best correlated with anti-RNP containing autoantibodies and polymorphisms associated with increased TLR7 expression are observed in males with SLE.
Since i) RNA is the critical component of ICs that stimulate TLR7 to induce IFN-a and ii) degradation of RNA with RNase attenuates IFN-a production in an in vitro bioassay, we asked whether increasing RNase concentrations in vivo would be effective in ameliorating disease in lupus-prone mice.
C57BL/6 (B6) mice that overexpress TLR7 (TLR7 transgenic (Tg) mice) develop a lupus-like disease with autoantibodies and the deposition of ICs in the kidneys. They have a median survival of ~ 6 months). We created a mouse strain, JLC, on the B6 background that overexpressed bovine RNase. The mice were healthy and exhibited no apparent changes in lymphoid composition in the spleen or lymph nodes. We then crossed the JLC mice to TLR7 transgenic mice (TLR7 Tg) to create RNase × TLR7 doubleTg (DTg) mice. Two cohorts were studied: Cohort A was sacrificed at 34 months for immunological studies and cohort B was a survival study (n = 20 in each group) that was terminated at 12 months. Kidneys were examined by light microscopy, Mac2 staining as well as indirect immunofluorescence for IgG and C3 deposition.
In both single RNAse Tg as well as DTg mice, RNase was secreted into the serum and increased expression levels were detected by an ELISA as well as by a functional enzyme assay in RNA coated agar gels (serum enzyme diffusion or SRED). In Cohort A mice sacrificed at 34 months, we observed statistically significant reductions in PAS staining, glomerular tuft size as well as less macrophage infiltration (all p <0.05) in the kidneys. In Cohort B, there was a statistically significant increase in survival in DTg as compared to TLR7 Tg mice (mean survival of 6 and 9 months for single versus DTg respectively, p<0.01). When the study was terminated at 12 months, examination of the kidneys revealed that there was reduced IgG and C3 deposition in DTg as opposed to single TLR7 Tg mice in surviving mice (p<0.05).
Our results indicate that increased expression of RNase significantly attenuates kidney damage in a lupus mouse model and also significantly improves survival. This novel form of treatment encourages nuclease based therapies to be considered for ameliorating SLE in the future.
To cite this abstract, please use the following information:
Sun, Xizhang, Agrawal, Nalini, Tanaka, Lena, Hayden-Ledbetter, Martha, Hudkins, Kelly L., Alpers, Charles E., et al; Increased Expression of Ribonuclease Prolongs Survival in Murine Lupus. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :559