PRKACB Attenuates Chondrocyte Loss and Inflammation in Osteoarthritis.

BACKGROUND: Previous work revealed that protein kinase cAMP-dependent catalytic β (PRKACB) may play a crucial role in osteoarthritis (OA) development. However, the mechanism by which PRKACB plays a role in OA still needs to be further investigated. Our aim was to explore the mechanism of PRKACB in a human chondrocyte inflammatory injury model. METHODS: Human CHON-001 chondrocytes were treated with 10 ng/mL IL-1β for 12 h to establish an in vitro model of chondrocyte inflammatory injury. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Flow cytometry (FCM) was conducted to assess apoptosis. Western blot assays were carried out to measure cleaved caspase-3, caspase-3, PRKACB, collagen II, aggrecan, phosphorated protein kinase A (p-PKA), PKA, cAMP response element-binding protein (CREB) and p-CREB protein expression levels. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) assay was used to measure PRKACB gene expression. Interleukin 6 (IL-6), IL-1β, and tumor necrosis factor alpha (TNF-α) levels were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: PRKACB expression was decreased in IL-1β-treated CHON-001 cells. Transfection of a PRKACB plasmid increased PRKACB expression in CHON-001 cells. IL-1β significantly inhibited CHON-001 cell viability; induced apoptosis; increased cleaved caspase-3 expression and the cleaved caspase-3/caspase-3 ratio; promoted TNF-α, IL-6 and IL-8 secretion; and decreased the expression levels of collagen II and aggrecan. However, these effects could be suppressed by the PRKACB plasmid. Moreover, we also found that PRKACB activated the PKA/CREB signaling pathway. H89 (a PKA inhibitor) distinctly reversed the effect of PRKACB on IL-1β-induced CHON-001 cells. CONCLUSION: PRKACB can increase cell viability and reduce inflammation by activating the PKA/CREB signaling pathway, and PRKACB is a novel target for OA treatment.