Duhuo Jisheng Decoction regulates intracellular zinc homeostasis by enhancing autophagy via PTEN/Akt/mTOR pathway to improve knee cartilage degeneration

Abstract

Background Articular cartilage and cartilage matrix degradation are key pathological changes occurring in the early stage of knee osteoarthritis (KOA). However, currently, there are limited strategies for early prevention and treatment of KOA. Duhuo Jisheng Decoction (DHJSD) is a formula quoted in Bei Ji Qian jin Yao Fang, which was compiled by Sun Simiao in the Tang Dynasty of China. As a complementary therapy, it is widely used to treat early-stage KOA in China; however, its mechanism has not been completely elucidated. Objective This study investigated the potential role of DHJSD in preventing cartilage degradation and the underlying mechanism. Methods A rat model of KOA model was established via the Hulth method. Subsequently, 25 rats were randomized into sham (saline), model control (saline), high-DHJSD (1.9g/mL of DHJSD), medium-DHJSD (1.2g/mL of DHJSD), and low-DHJSD groups (0.6g/mL of DHJSD). After 4 weeks of treatment, all rats were sacrificed and the severity of the cartilage degeneration was evaluated by a series of histological methods. The autophagosome was observed using transmission electron microscopy, and the related functional proteins were detected by the western blotting and real-time polymerase chain reaction. Next, the mechanism by which DHJSD improves knee cartilage degeneration was further clarified the in vitro by gene silencing technology combined with a series of functional experiments. The proteins levels of PTEN, Akt, p-Akt, mTOR, and p-mTOR, as well as the marker proteins of autophagy and apoptosis were determined. Zinc levels in chondrocytes were determined using inductively coupled plasma mass spectrometry. Results Histopathological staining revealed that DHJSD had a protective effect on the cartilage. DHJSD increased autophagosome synthesis and the expression of autophagy proteins LC3 and Beclin-1 in chondrocytes. Moreover, it reduced the phosphorylation levels of Akt and mTOR and the levels of zinc, MMP-13, Bax, and Bcl-2. Following PTEN silencing, this DHJSD-mediated reduction in Akt and mTOR phosphorylation and Bax, Bcl-2, and zinc levels were further decreased; in addition, DHJSD-mediated increase in LC3 and Beclin-1 levels was decreased. Conclusion DHJSD inhibits the Akt/mTOR signaling pathway by targeting PTEN to promote autophagy in chondrocytes, which may help reduce MMP-13 production by regulating zinc levels in chondrocytes.