Abstract
Tripterine, also known as celastrol, is a main natural ingredient in Tripterygium wilfordii. Tripterine has a variety of pharmacological functions, and the therapeutic potential of tripterine in many kinds of inflammation-linked diseases has been revealed. However, the function of tripterine on osteoarthritis still remains unclear. The objective of this study was to study the function of tripterine (TPR) on lipopolysaccharide (LPS)-injured chondrocyte. ATDC5 cells were treated with tripterine after LPS stimulation and then cell survival, the release of pro-inflammatory cytokines, and the expression of chondrogenic differentiation-associated proteins were assessed by performing CCK-8, flow cytometry, reverse transcription quantitative polymerase chain reaction (RT-qPCR), enzyme-linked immunosorbent assay (ELISA), and Western blot. Moreover, the expression of miR-223 and core factors in PI3K/AKT and nuclear factor kappa B (NF-κB) signaling was tested by RT-qPCR/Western blot. LPS stimulation significantly reduced ATDC5 cells viability, induced apoptosis, and increased the release of interleukin (IL)-6 and tumor necrosis factor (TNF)-α. Tripterine protected ATDC5 cells against LPS-induced chondrocyte loss and the release of IL-6 and TNF-α. miR-223 was down-regulated by LPS, while was up-regulated by tripterine. The protective actions of tripterine were eliminated when miR-223 was silenced. Besides, tripterine inhibited hypertrophic differentiation induced by LPS, and the inhibitory effects of tripterine on hypertrophic differentiation could be abolished when miR-223 was silenced. Furthermore, tripterine activated PI3K/AKT pathway and deactivated NF-κB pathway. And the regulatory effects of tripterine on these two pathways were abolished by miR-223 silence. This study revealed that tripterine protected ATDC5 cells against LPS-induced cell damage possibly via up-regulation of miR-223 and modulation of NF-κB and PI3K/AKT pathways.