Experimental models of systemic lupus erythematosus: anti-dsDNA in murine lupus

(NZW × BXSB) F1 male mice: An unusual, severe and fatal mouse model of lupus erythematosus

Background

Systemic lupus erythematosus (SLE) is a chronic autoimmune/inflammatory disease. The heterogeneity and complexity of clinical presentation has made it challenging to study or treat this syndrome. The (NZW×BXSB) F1 lupus-prone male mouse model of this disease is potentially useful to study mechanism and treatment modalities, but there is a lack of information about this model’s characterization and disease progression. Therefore, the aim was to examine this lupus model’s physical/clinical disease presentation and its immunological status.

Materials and methods

Clinical and physical status were observed in 8- and 16-week-old male and female (± 1 week) (NZW/LacJ x BXSB/MpJ) F1 mice (n = 8 per group). Young males (8 ± 1 week) without disease and female (16 ± 1 week) mice served as controls. Physical changes, quantitative values of autoantibodies, and blood cell parameters were determined. Necropsy and post-mortem histopathology were also performed.

Results

With aging (≥ 12 weeks), significant increases in severe abdominal distension/swelling, inability to walk, paleness of paws and significant weight increase were observed compared to controls (p < 0.05). The necropsy examination showed abdominal distension associated with serous effusion and histological examination identified severe edema and multi-organ abnormalities (spleen, lymph nodes, and kidney). Significant increases in anti-double-stranded DNA antibody (anti-dsDNA) was seen in old/sick compared to female (p = 0.0002) or young male (p = 0.0036) mice. Old mice developed immune thrombocytopenia compared to female (p = 0.0056) and young male (p = 0.0007) mice. Anti-platelet was detectable in old, sick mice. The mortality rate increased with aging; more than 35% of male mice died during this study between the ages of 13-18 weeks.

Conclusion

We found that the (NZW/LacJ x BXSB/MpJ) F1 male mice spontaneously exhibit, over varying lengths of time, extremely severe and fatal clinical disease symptoms. This model may be too severe to be helpful in investigating SLE and testing potential treatment modalities.

Altered patterns of epigenetic changes in systemic lupus erythematosus and auto-antibody production: is there a link?

The prominent feature of immunological defects in systemic lupus erythematosus (SLE) is the production of autoantibodies (auto-Abs) to nuclear antigens including DNA, histones and RNP. In addition, there is growing evidence that epigenetic changes play a key role in the pathogenesis of SLE. Autoreactive CD4(+) T cells and B cells in patients with SLE have evidence of altered patterns of DNA methylation as well as post-translational modifications of histones and ribonucleoproteins (RNP). A key question that has emerged from these two characteristic features of SLE is whether the two processes are linked. New data provide support for such a link. For example, there is evidence that hypomethylated DNA is immunogenic, that anti-histone auto-Abs in patients with SLE bind epigenetic-sensitive hot spots and that epigenetically-modified RNP-derived peptides can modulate lupus disease. All in all, the available evidence indicates that a better understanding of dysregulation in epigenetics in SLE may offer opportunities to develop new biomarkers and novel therapeutic strategies.

Rosiglitazone decreases blood pressure and renal injury in a female mouse model of systemic lupus erythematosus

Women with systemic lupus erythematosus (SLE) exhibit a high prevalence of hypertension and renal injury. Rosiglitazone (Rosi), a peroxisome proliferator activator receptor gamma (PPARgamma) agonist, has renal protective and antihypertensive effects. We tested whether Rosi ameliorates hypertension and renal injury in a female mouse model of SLE (NZBWF1). Thirty-week-old SLE and control (NZW/LacJ) mice (n > or = 6/group) were fed Rosi (5 mg.kg(-1).day(-1) in standard chow) or standard chow for 4 wk. SLE mice had increased blood pressure (BP in mmHg) compared with controls (139 +/- 4 vs. 111 +/- 4, P < 0.05). Rosi treatment lowered BP in SLE mice (127 +/- 4, P < 0.05) but not in controls (111 +/- 4). Urinary albumin (mug/mg creatinine) was increased in SLE mice compared with controls (12,396 +/- 6,525 vs. 50 +/- 6) and reduced with Rosi treatment (148 +/- 117). Glomerulosclerosis (% of glomeruli with sclerosis) was reduced in Rosi-treated SLE mice (4.2 +/- 1.6 vs. 0.4 +/- 0.3, P < 0.05). Renal monocyte/macrophage numbers (cell number/1,320 points counted) were reduced in SLE mice treated with Rosi (32.6 +/- 11.0 vs. 10.6 +/- 3.6, P < 0.05) but unchanged in controls (3.7 +/- 1.6 vs. 3.7 +/- 2.0). Renal osteopontin expression, a cytokine-regulating macrophage recruitment, was reduced in Rosi-treated SLE mice. Urinary endothelin (in pg/mg creatinine) was increased in SLE mice compared with controls (1.9 +/- 0.59 vs. 0.6 +/- 0.04, P < 0.05) and reduced in SLE mice treated with Rosi (0.8 +/- 0.11, P < 0.05). PPARgamma protein expression in the renal cortex was significantly lower in SLE mice compared with controls and was unaffected by Rosi. These data suggest that Rosi may be an important therapeutic option for the treatment of SLE hypertension and renal injury.

Targeting Toll-like receptor signaling in plasmacytoid dendritic cells and autoreactive B cells as a therapy for lupus

This review focuses on the role of Toll-like receptors (TLRs) in lupus and on possibilities to treat lupus using TLR modulating inhibitory oligodeoxynucleotides (INH-ODNs). TLRs bridge innate and adaptive immune responses and may play an important role in the pathogenesis of systemic lupus erythematosus. Of particular interest are TLR3, -7, -8, and -9, which are localized intracellularly. These TLRs recognize single-stranded or double-stranded RNA or hypomethylated CpG-DNA. Exposure to higher order CpG-DNA ligands or to immune complexed self-RNA triggers activation of autoreactive B cells and plasmacytoid dendritic cells. INH-ODNs were recently developed that block all downstream signaling events in TLR9-responsive cells. Some of these INH-ODNs can also target TLR7 signaling pathways. Based on their preferential cell reactivity, we classify INH-ODNs into class B and class R. Class B ('broadly reactive') INH-ODNs target a broad range of TLR-expressing cells. Class R ('restricted') INH-ODNs easily form DNA duplexes or higher order structures, and are preferentially recognized by autoreactive B cells and plasmacytoid dendritic cells, rather than by non-DNA specific follicular B cells. Both classes of INH-ODNs can block animal lupus. Hence, therapeutic application of these novel INH-ODNs in human lupus, particularly class R INH-ODNs, may result in more selective and disease-specific immunosuppression.