Background/Purpose: The aim of this study was to evaluate whether alterations in the splicing machinery of immune cells could influence the development and activity of the disease and the kidney involvement in systemic lupus erythematosus (SLE) patients.

Methods: Monocytes, lymphocytes and neutrophils from 43 SLE patients and 34 healthy donors (HD) were purified by immunomagnetic selection. Then, 45 selected elements of the splicing machinery and a set of 48 genes related to inflammation, renal and cardiovascular disease (including interleukins, adipocytokines, chemokines, and oxidative stress markers, among others) were evaluated using a microfluidic qPCR array (Fluidigm). In parallel, an extensive clinical/serological evaluation was performed, comprising renal and CV involvement along with autoantibodies, and inflammatory molecules. Correlation and association studies and logistic models among those clinical and analytical parameters were developed. Separately, mechanistic in vitro studies were carried out by incubation of HD-leukocytes with purified anti-dsDNA-IgG from SLE patients.

Results: Altered expression of spliceosome components was demonstrated in the 3 leukocyte subsets: 29, 13 and 22 components were differentially expressed in monocytes, lymphocytes and neutrophils, respectively, vs HD. Intriguingly, any spliceosome component was commonly deregulated among the three leucocyte subsets except for PRPB8, a key component of the spliceosome, that acts as a scaffold protein essential for spliceosome assembly.

Correlation studies demonstrated multiple links among altered spliceosome components and the score of disease activity along with a number of inflammatory and oxidative stress mediators. Remarkably, the levels of those altered components were associated to the presence of lupus nephritis in the three leukocyte subsets. Moreover, we could build different logistic models to precisely identify patients with renal involvement, which integrated the concomitant alteration of: RNU12, RNU4ATAC and RNU6ATAC, in monocytes; RNU4, SRRM1 and U2AF2 in lymphocytes; and PRPF8, SF3B1 and KHDRBS1 in neutrophils.

On the other hand, a logistic model combining RNU6, CELF1 and RAVER1 could classify anti-dsDNA positivity in lymphocytes, thus suggesting the involvement of these autoantibodies in the splicing process. Finally, in vitro treatment of HD lymphocytes with anti-dsDNA promoted the decrease of several spliceosome components found altered in vivo in SLE lymphocytes, such as KHDRBS1, SRSF5 and TRA2B.

Conclusion: 1) The splicing machinery is profoundly altered in leukocytes from SLE patients and closely related to the development and activity of the disease. 2) Evaluation of specific components of the spliceosome in leukocytes subsets might be used to clinically typify kidney involvement. Ongoing studies would clarify the physiological implications of these findings, which may provide novel diagnostic-biomarkers and therapeutic-tools to treat SLE.

Funded by ISCIII, PI18/00837 and RIER RD16/0012/0015 co-funded with FEDER

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-role-of-alterations-in-the-splicing-machinery-in-the-pathogenesis-of-lupus-does-it-impact-lupus-nephritis/