Rituximab‐mediated Raf kinase inhibitor protein induction modulates NF‐κB in Sjögren syndrome

Primary Sjögren syndrome (pSS) is an autoimmune disorder characterized by an epithelial injury surrounded by dense lymphocytic infiltrates. The conditions for the long‐term maintenance of human salivary gland epithelial cells from pSS patients and a co‐culture system with pSS lymphocytes were used to assess the effect of Rituximab (RTX) on the inflammatory condition and progression in pSS. Quantitative real‐time PCR, genes and protein array analysis, Western blot, flow cytometry, small interfering RNA transfection and nuclear factor‐κB (NF‐κB) DNA binding assays were used as methods. Supporting the benefits of RTX, this study demonstrates that RTX decreases NF‐κB activity and interrupts the NF‐κB signalling pathway through the up‐regulation of the Raf‐1 kinase inhibitor protein (RKIP). Over‐expression of RKIP down‐regulates interleukins, their receptors and the expression of genes encodes proteins that attracted lymphocytes. Silencing of the RKIP gene leads to significantly increased expression and release of pro‐inflammatory mediators supporting that RKIP expression could be involved in the suppression of NF‐κB activation in pSS salivary gland epithelial cells.