Gremlin‐1 promotes IL‐1β‐stimulated chondrocyte inflammation and extracellular matrix degradation via activation of the MAPK signaling pathway

Abstract

AbstractThe role and mechanism of Gremlin‐1 in osteoarthritis (OA) were expected to be probed in this study. Firstly, an in vitro OA model was constructed by stimulating human chondrocyte cell line CHON‐001 with IL‐1β. Next, 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) and quantitative reverse transcriptase polymerase chain reaction (qRT‐PCR) were utilized for assessing the effect of IL‐1β with different concentrations (5, 10, and 20 ng/mL) on the activity and Gremlin‐1 messenger RNA of CHON‐001 cells, respectively. Besides, the influence of knocking down/over‐expressing Gremlin‐1 on the inflammatory factors (IL‐6, TNF‐α, IL‐18 and PGE2), oxidative stress‐related substances (malondialdehyde [MDA]; superoxide dismutase [SOD]; lactate dehydrogenase [LDH]), extracellular matrix (ECM) degradation‐related proteins, and mitogen‐activated protein kinase (MAPK) pathway proteins in IL‐1β‐stimulated CHON‐001 cells were tested by enzyme‐linked immunosorbent assay, related kits, qRT‐PCR, and western blot, respectively. IL‐1β inhibited CHON‐001 cell proliferation and upregulated Gremlin‐1 expression in a concentration‐dependent manner. Overexpression of Gremlin‐1 increased the IL‐6, TNF‐α, IL‐18, PGE2, and MDA levels, enhanced the LDH activity, and decreased the SOD activity in IL‐1β‐induced CHON‐001 cells; while the effect of Gremlin‐1 knockdown on the above factors was in contrast with that of the overexpression. Furthermore, overexpression of Gremlin‐1 upregulated protein expression of matrix metalloproteinase (MMP)‐3, MMP‐13, and ADAMTS4 while downregulated protein expression of collagen III, aggrecan, and SOX‐9 in IL‐1β‐stimulated CHON‐001 cells. Besides, overexpression of Gremlin‐1 increased the p‐p38/p38 value while decreased the p‐JNK/JNK value in L‐1β‐stimulated CHON‐001 cells; however, knockdown of Gremlin‐1 reversed the above results. Gremlin‐1 may promote IL‐1β‐stimulated CHON‐001 cell inflammation and ECM degradation by activating the MAPK signaling pathway.