Project description:Systemic lupus erythematosus is a chronic autoimmune disease with multifactorial ethiopathogenesis. The complement system is involved in both the early and late stages of disease development and organ damage. To better understand autoantibody mediated complement consumption the GAPAID consortium examined ex vivo immune complex formation on autoantigen arrays. We recruited patients with SLE (n=211), with other systemic autoimmune diseases (n=65) and non-autoimmune control subjects (n=149) in two rheumatology tertiary care centers. Standard clinical and laboratory data were collected from all subjects and serum complement levels were determined in SLE patients. The genotype of SNP rs1143679 in the ITGAM gene was also determined. On-chip formation of immune complexes was examined using a functional immunoassay on autoantigen microarray. The amount of antigen-bound IgM, IgG and complement C4 and C3 was quantified on autoantigens comprising nucleic acids, proteins and lipids. Our results show that the relatively high complement consumption of nucleic acids is further increased upon binding of IgM and IgG. This is true even when serum complement levels are decreased due to complement consumption in SLE patients. A negative correlation between serum complement levels and ex vivo complement deposition on nucleic acid autoantigens is demonstrated. On the contrary, most protein and lipid autoantigens show positive correlation with C4 and C3 levels. Genetic analysis reveals that the non-synonymous variant rs1143679 in complement receptor type 3 is associated with an increased production of anti-dsDNA IgG antibodies. Notwithstanding, homozygous carriers of the previously reported susceptible allele (AA) have lower levels of dsDNA specific IgM among SLE patients. Regarding organ involvement we find that besides anti-C1q IgG, low levels of dsDNA specific IgM and low complement C4 binding to C1q are also associated with renal injury. In summary, nucleic acids maintain a skewed complement deposition balance when bound by IgG and IgM, depleting the early classical complement pathway from other physiological processes. Dysfunction of the receptor responsible for complement-mediated apoptotic debris removal promotes the development of autoantibodies targeting nucleic acids. These observations provide serological and genetic evidence for complement-mediated clearance deficiency of apoptotic debris in lupus.

Project description:Background: Bortezomib (Bz) is a proteasome inhibitor that directly targets antibody-producing plasma cells. We recently reported the first randomized control trial that evaluated the effects of Bz in patients with systemic lupus erythematosus (SLE). In that study, we demonstrated that Bz treatment is associated with many adverse reactions in patients with refractory disease. In the present study, we examine the therapeutic and toxic effects of Bz on MRL/MpJ-lpr/lpr (MRL/lpr) mice with severe disease activity. Methods: Female MRL/lpr mice at 10 and 14 weeks of age were treated with phosphate-buffered saline (PBS) (n = 13), Bz (750 μg/kg twice weekly) (n = 12), and cyclophosphamide (Cyc) (1 mg/body, once in 2 weeks) (n = 15). Cellular subsets, serum immunoglobulin, anti-double stranded deoxyribonucleic acid (anti-dsDNA) antibody titer, and a pathological index of glomerulonephritis were then analyzed at 22 weeks of age. Survival curves of the 10 and 14 weeks-Bz-treated groups were compared. Blood counts, creatinine, liver enzymes, and serum cytokine levels were measured 1 week after Bz treatment. Gene expression profiling of spleens from Bz and Cyc treatment mice were compared with those from control mice. Results: The anti-dsDNA antibody levels were significantly higher in 14- than in 10-week-old mice, indicating a higher disease activity at 14 weeks. A significant decrease in the number of splenic cells and glomerulonephritis index was observed in Bz- and Cyc-treated mice. Bz, but not Cyc, significantly decreased serum immunoglobulin and anti-dsDNA antibody titer levels. Survival curve analysis revealed a significantly higher mortality rate in 14- than in 10-week-old Bz-treated and control groups. Following two injections of Bz, serum IL-6 and TNF-α levels were significantly more elevated in 14- than in 10-week-old mice. Potentially immunogenic molecules, such as heat shock proteins and calreticulin, were specifically upregulated in spleens of Bz- but not Cyc-treated mice. Conclusions: In spite of its therapeutic effect, Bz treatment had more toxic effects associated with increased pro-inflammatory cytokine levels in mice with a higher disease activity. Understanding the mechanism of the toxicity and developing preventive strategies against it is important for the safe clinical application of Bz in human SLE.

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Plasma DNA aberrations in systemic lupus erythematosus revealed by genomic and methylomic sequencing

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Plasma DNA aberrations in systemic lupus erythematosus revealed by genomic and methylomic sequencing.

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