Direct modulation of rheumatoid inflammatory mediator expression in retinoblastoma protein–dependent and –independent pathways by cyclin‐dependent kinase 4/6

Abstract

Objective. It is known that the cyclin-dependent kinase inhibitor (CDKI) gene p21 Cip1 suppresses rheumatoid inflammation by down-modulating type I interleukin-1 receptor (IL-1RI) expression and inhibiting JNK activity. The purpose of this study was to determine whether CDK activity directly modulates the production of inflammatory molecules in patients with rheumatoid arthritis (RA).Methods. Genes for the CDKIs p16 INK4a and p18 INK4c , a constitutively active form of retinoblastoma (RB) gene product, cyclin D1, and CDK-4, were transferred into RA synovial fibroblasts (RASFs). RASFs were also treated with a synthetic CDK-4/6 inhibitor (CDK4I). Levels of matrix metalloproteinase 3 (MMP-3), monocyte chemoattractant protein 1 (MCP-1), and IL-1RI expression were determined by Northern blotting, real-time polymerase chain reaction analysis, and enzyme-linked immunosorbent assay. CDKIs were immunoprecipitated to reveal their association with JNK. Conclusion. CDK-4/6 modulated the production of MMP-3 and MCP-1. MMP-3 production was regulated primarily at the mRNA level in an RBindependent manner, whereas MCP-1 production was controlled posttranscriptionally by RB. These results show that cell cycle proteins are associated with control of mediators of inflammation through multiple pathways. Results. Transfer of the p16

MicroRNA‐124a is a key regulator of proliferation and monocyte chemoattractant protein 1 secretion in fibroblast‐like synoviocytes from patients with rheumatoid arthritis

“…RA is characterized by pronounced synovial hyperplasia and by synovial fibroblasts that appear to be transformed (27,28). In animal models of RA, this transformed appearance of RA synoviocytes could be mitigated by transferring the CDK inhibitor genes p16 INK4a and p21 Cip1 into inflamed joints (29,30). CDK-2, which is inhibited by p21 Cip1 and p27 Kip1 , is another key CDK: CDK-2/cyclin E complexes are required for the G 1 -to-S phase transition and initiation of DNA synthesis, whereas CDK-2/cyclin A complexes function during the progression of cells through S phase (31).…”

p16INK4a Exerts an Anti-Inflammatory Effect through Accelerated IRAK1 Degradation in Macrophages

“…(7). A separate series of our experiments disclosed that cell-cycle progression is not the only function of CDK (8). CDK kinase activity also regulates production of inflammatory molecules in a pRbindependent manner.…”

“…RA was diagnosed according to the 1988 criteria of the American College of Rheumatology (16). Human synovial cells were prepared as described previously (8). Human acute monocytic leukemia cell line THP-1 cells were cultured and differentiated to macrophages as described elsewhere (17).…”

“…Replication-defective adenoviruses containing a human p16 gene (AxCAp16) and LacZ gene (AxCA-LacZ) were prepared as described previously (8).…”

“…Our previous study demonstrated that p16 INK4a inhibited matrix metalloproteinase (MMP)-3 expression in RSF by suppressing CDK4/6 kinase activity (8). To determine if the inhibitory effect of p16 INK4a on LPS-induced IL-6 production in BMM depends on CDK4/6 kinase activity, CDK4/6 selective inhibitor (PD0332991) was added to the BMM culture.…”