Therapeutic Effects of Total Saponins From Dioscorea nipponica Makino on Gouty Arthritis Based on the MAPK-PPARγ Signaling Pathway: An In Vitro Study

Gouty arthritis (GA) is an inflammatory disease caused by the deposition of monosodium urate in the synovial membrane and cartilage due to a high concentration of uric acid in the blood. Dioscorea nipponica Makino is widely used in the clinic to treat GA. Total saponins are its main components and showed an anti-inflammatory effect on GA in a previous study. The mitogen-activated protein kinase (MAPK)-peroxisome proliferator-activated receptor γ (PPARγ) signaling pathway plays a key role during the onset of GA; however, little is known about its potential mechanism. Based on in vitro experiments, this study aims to determine the mechanism of total saponins from Dioscorea nipponica Makino (TDN) in treating GA by regulating the MAPK-PPARγ signaling pathway. Fibroblast-like synoviocytes were divided into 3 groups: the model group, which was given 10 µg/L IL-1β to induce proliferation; TDN group (10 µg/L IL-1β + 100 µg/L TDN); and indomethacin group (10 µg/L IL-1β + 100 µg/L indomethacin). Seventy-two hours after treatment, the real-time PCR method was used to detect the mRNA expression levels of extracellular signal regulated kinase 1/2 (ERK1/2), p-38, c-Jun N-terminal kinase (JNK), IKKα, c-Jun, MAPK phosphatase (MKP), vascular cell adhesion molecule 1 (VCAM1), intercellular adhesion molecule 1 (ICAM1), C-X-C motif chemokine ligand 1 (CXCL1), PPARγ, and Adipor2. The Western blot method was used to detect the protein expression of ERK1/2, p-ERK1/2, p-38, p-P38, JNK, p-JNK, IKKα, p-IKKα, c-Jun, p-c-Jun, MKP, p-MKP, VCAM1, ICAM1, CXCL1, PPARγ, and Adipor2. Compared with the model group, the TDN group displayed significantly increased mRNA expression of c-Jun, MKP, CXCL1, PPARγ, and Adipor2 and significantly decreased mRNA expression of ICAM1. Compared with the model group, the TDN group exhibited significantly increased protein expression of MKP and significantly decreased protein expression of p-ERK1/2, p-38, p-JNK, p-IKKα, p-c-Jun, VCAM1, ICAM1, and PPARγ. Our results indicated that TDN could treat GA by influencing the MAPK-PPARγ signaling pathway.