Downregulated miR-29a promotes B cell overactivation by upregulating Crk-like protein in systemic lupus erythematosus

Abstract

Systemic lupus erythematosus (SLE) is an autoimmune disorder; however, the pathogenesis is not fully understood. Accumulating evidence suggested an important role of microRNA s (miRNA /miR) in autoimmunity. The present study aimed therefore to determine the miRNA expression patterns in the B cells from the peripheral blood of 66 patients with SLE and 10 healthy controls (HCs) by using an Affymetrix GeneChip® miRNA 2.0 array. In addition, next-generation sequencing was used to obtain the peripheral blood mononuclear cell (PBMC) miRNA profiles from three patients with SLE and three HCs. Candidate miRNA s that were considered to contribute to the pathogenesis of SLE were obtained based on the intersection of miRNA profiles. The analysis revealed a significant downregulation in miR-29a expression levels in B cells from patients with SLE, which was subsequently verified using reverse transcription-quantitative PCR . Based on these results, the expression pattern of miR- 29a in SLE was further investigated and its role in the hyperactivity of B cells was determined. miR- 29a inhibitors and mimics were transfected into PBMCs obtained from HCs and patients with SLE, and an ELI SA was used to demonstrate that miR- 29a inhibition increased the production of IgG. Bioinformatics analysis predicted Crk-like protein (CR KL) as a target gene of miR- 29a in patients with SLE . Therefore, CR KL expression levels were compared between patients with SLE and HCs by using western blotting, and its direct transcriptional regulation by miR- 29a was determined using a dual-luciferase reporter assay. Low expression levels of miR- 29a were revealed to upregulate the expression levels of CR KL in B cells, and the protein expression levels of CR KL in patients with SLE were significantly upregulated compared with the HCs. In conclusion, the results from the present study suggested that miR- 29a may affect IgG antibody secretion in B cells by regulating CR KL, thereby contributing to the development and progression of SLE, which offers a novel candidate target for treatment.