Background Deregulation of endogenous miR155 was observed in many autoimmune conditions, including systemic lupus erythematosus (SLE).
Objectives We herein examined the role of miR155 in the development of systemic manifestations in mice with pristane-induced lupus (PIL).
Methods MiR155-deficient and C57/Bl6 mice were injected with pristane or PBS as control and analyzed after 8 months. Glomerulonephritis and pneumonitis were quantified by using the composite kidney biopsy score (KBS) and by analyzing the numbers of affected lung-vessels and the area of the inflammatory lung-infiltrate, respectively. Specimens were stained with B220 (B), CD3 (T), Neu7/4 (neutrophils) and F4/80 (macrophages) and analyzed by cell-identification algorithms for nuclear segmentation (HistoQuest). Serum levels of anti-dsDNA, anti-histone and anti-chromatin antibodies were measured by ELISA. Frequencies of B cells, activated and regulatory CD4+ T cells as well as Th1, Th2, Th17 cells were measured by flow cytometry. Quantitative real-time polymerase chain reaction was used to measure expression levels of interferon-signature and T-cell subset related as well as miR155-associated genes.
Results All pristane-injected mice showed signs of pneumonitis, while controls did not. Compared to wild types treated with pristane, similarly treated knockouts showed significantly decreased perivascular inflammatory area with B cells being the most prominent inflammatory cell. Wildtypes had a more severe renal involvement in the KBS than knockouts. Corresponding with reduced organ involvement, miR155 deficient mice had significantly lower serum levels of anti-dsDNA antibodies, anti-chromatin and anti-histone antibodies and decreased frequencies of activated CD4+CD25+(Foxp3–) cells. Interestingly, also frequencies of CD4+CD25+Foxp3+ regulatory T cells were lower in these mice. Upon restimulation, CD4+ cells showed a more pronounced Th2 response in wild types, but no significant differences in Th1 and Th17 phenotype. Regarding INF-signature and T-cell subset activation, pristane-treated wild types showed significantly up-regulated gene-expression patterns whereas equivalently treated mutants showed the same levels as PBS-treated controls.
Conclusions MiR155 deficiency in PIL mice did not prevent disease, but was associated with less severe organ involvement, lower serum auto-abs levels, lower frequencies of Th2 cells, whereas lower expressions of genes jointly responsible for disease development may be one key mechanism. Thus, antagonisation of miR155 might be a future approach in treating SLE.
Disclosure of Interest None declared