Background/Purpose:  The aim of this study was to evaluate whether alterations in the splicing-machinery could influence the development and activity of the disease and the atherothrombotic profile of SLE patients.

Methods: An array of selected components of the major- (n=12) and minor-spliceosome (n=4) and associated splicing factors (n=28) was developed, and their expression levels were evaluated using a Fluidigm methodology, in purified leukocytes (monocytes, lymphocytes and neutrophils) from 14 SLE patients and 14 healthy donors. In parallel, an extensive clinical/serological evaluation was performed. Carotid intimate media thickness (CIMT) was used as atherosclerosis marker. Endothelial activity was monitored by laser-doppler flowmetry, netosis was analyzed by fluorescence microscopy, and pro-inflammatory and oxidative stress markers were quantified by flow cytometry and RT-PCR. Then, association of these splicing components with clinical and analytical features were investigated.

Results: As a general feature, a significant reduction in relevant splicing factors and spliceosome components was found in all the leukocyte subtypes of SLE patients. Interestingly, we found a specific altered profile of splicing factors and spliceosome components when compared monocytes (i.e. U2AF1, FBP11, SRSF6), lymphocytes (i. e. RBM22, RB17, SRSF6) and neutrophils (i. e. SRSF10, SND1). Association studies showed that the reduced levels of some components of spliceosome in both monocytes and neutrophils were linked to the occurrence of thrombotic events. In lymphocytes those reduced levels were strongly related to the positivity for anti-dsDNA antibodies in SLE patients, thus suggesting that reduced spliceosome machinery would contribute to increase in altered autoantigen assembly, to which autorreactive T helper cells might react, inducing increased autoantibody production. In addition, reduced spliceosome machinery might derive of the described over-expression of specific anti-spliceosomal autoantibodies in SLE patients. Correlation studies demonstrated an inverse relationship among reduced levels of spliceosome components/splicing factors and high activity of the disease (measured as SLEDAI), endothelial dysfunction, netosis, and increased expression levels of peroxides and peroxynitrites, as well as of altered mitochondrial membrane potential in monocytes and neutrophils. Concomitantly, a direct relationship among reduced levels of spliceosome components/splicing factors in monocytes and neutrophils and low levels of serum complement factors C3 and C4 was established.

Conclusion: These results reveal the existence of SLE-associated spliceosome alterations, which could be related to the development and activity of this autoimmune condition and have influence on the induction of mechanisms that drive atherothrombosis in this disorder.Ongoing studies would clarify the potential physiological implications of these findings, which may provide novel diagnostic-biomarkers and therapeutic-tools to treat SLE. Funded by CTS7940, PI15/01333.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/dysregulation-of-the-splicing-machinery-components-in-leukocytes-from-patients-with-systemic-lupus-erythematosus-influence-on-autoimmune-and-atherothrombotic-mechanisms/