CKLF1 interference alleviates IL-1β-induced inflammation, apoptosis and degradation of the extracellular matrix in chondrocytes via CCR5

Osteoarthritis (OA) is a type of joint disease with a rising prevalence and incidence among the elderly across the global population. Chemokine-like factor 1 (CKLF1) is a human cytokine, which has been demonstrated to be involved in the progression of multiple human diseases. However, little attention has been paid to the impact of CKLF1 on OA. The present study was designed to identify the role of CKLF1 in OA and to clarify the regulatory mechanism. The expression levels of CKLF1 and its receptor CC chemokine receptor 5 (CCR5) were examined by reverse transcription-quantitative PCR (RT-qPCR) and western blotting. A Cell Counting Kit-8 assay was used to estimate cell viability. The levels and expression of inflammatory factors were determined by ELISA and RT-qPCR, respectively. Apoptosis was investigated by TUNEL assays and the protein levels of apoptosis-related factors were analyzed by western blotting. RT-qPCR and western blotting were used to examine the expression of extracellular matrix (ECM) degradation-associated proteins and ECM components. Dimethylmethylene blue analysis was used to analyze the production of soluble glycosamine sulfate additive. A co-immunoprecipitation assay was used to confirm the protein interaction between CKLF1 and CCR5. The results revealed that CKLF1 expression was increased in IL-1 beta-exposed murine chondrogenic ATDC5 cells. Furthermore, CKLF1 silencing enhanced the viability of IL-1 beta-induced ATDC5 cells, while inflammation, apoptosis and degradation of the ECM were reduced. Additionally, CKLF1 knockdown led to decreased CCR5 expression in IL-1 beta-challenged ATDC5 cells, and CKLF1 bound with CCR5. The enhanced viability, as well as the suppressed inflammation, apoptosis and degradation of the ECM, following CKLF1 knockdown in the IL-1 beta-induced ATDC5 cells were all restored after CCR5 was overexpressed. In conclusion, CKLF1 might serve a detrimental role in the development of OA by targeting its receptor CCR5.