Tougu Xiaotong capsule promotes chondrocyte autophagy by regulating the Atg12/LC3 conjugation systems

Abstract

Abstract. We have previously reported that Tougu Xiaotong capsule (TXC) inhibits tidemark replication and cartilage degradation by regulating chondrocyte autophagy in vivo. Autophagy, a cell protective mechanism for maintaining cellular homeostasis, has been shown to be a constitutively active and protective process for chondrocyte survival. However, it remains unclear whether TXC promotes chondrocyte autophagy by regulating the autophagy-related (Atg)12/microtubuleassociated protein 1 light chain 3 (LC3) conjugation systems. Thus, in the present study, we investigated the effects of TXC on primary chondrocytes treated with cobalt chloride (CoCl 2 ). We found that CoCl 2 induced a decrease in chondrocyte viability and the autophagosome formation of chondrocytes, indicating that CoCl 2 induced autophagic death in a dose-and time-dependent manner. To determine the effects of TXC on CoCl 2 -exposed chondrocytes, we assessed cell viability by MTT assay. Our results revealed that TXC enhanced the viability of CoCl 2 -exposed chondrocytes. To gain insight into the mechanisms responsible for the enhancing effects of TXC on CoCl 2 -exposed chondrocytes, the expression of Atg genes was assessed in chondrocytes exposed to CoCl 2 and treated with or without TXC. The results revealed that the expression of beclin 1, Atg3, Atg5, Atg7, Atg10, Atg12 and LC3 II/LC3 I in the chondrocytes treated with TXC increased, compared to that in the untreated chondrocytes. In addition, ultrastructural analysis indicated that treated chondrocytes contained more autophagosomes than the untreated cells, suggesting that TXC increased the formation of autophagosomes in the chondrocytes to clear the CoCl 2 -induced autophagic death. Therefore, these data suggest that TXC is a potential therapeutic agent for the reduction of cartilage degradation that occurs in osteoarthritis.

The Role of Autophagy in Osteoarthritis

“…Drugs regulating other targets, such as Tougu Xiaotong Capsule, facilitate autophagy by balancing ATG12/LC3 coupling system (Li et al, 2014). Several autophagosome formation indexes including ATG3, ATG7, ATG12-5 and BECN1 in trehalose treated chondrocytes and the proportion of LC3-II:LC3-I increased as the dose of the drug increases, and the level of SQSTM1 decreased, indicating that trehalose can enhance autophagy flux (Tang et al, 2017).…”

Biomarkers of Chondrocyte Apoptosis and Autophagy in Osteoarthritis

“…Moreover several autophagy-inducing agents are object of recent researches as protective for OA. Among them, Tougu Xiaotong capsule inhibits tidemark replication and cartilage degradation by regulating chondrocyte autophagy and it could be a potential therapeutic agent for the reduction of cartilage degradation that occurs in osteoarthritis [ 77 ]. Manipulation of Hypoxia-inducible factor 1-alpha (HIF-1α) and 2-alpha (HIF-2α) has been suggested as a promising approach to the treatment of OA.…”

Are Kidney-Tonifying and Blood-Activating Medicinal Herbs Better than NSAIDs for Knee Osteoarthritis? A Systematic Review and Meta-Analysis

“…Another study showed that Du-Huo-Ji-Sheng decoction (a KTBAM compound) exerted significant therapeutic effects in osteoarthritic rabbits, probably through inhibiting the expression of VEGF and hypoxia-inducible factor-1 α [15]. Yaotongning capsules (a KTBAM compound) promoted proliferation and glycosaminoglycan synthesis in IL-1 β -induced chondrocytes and may have potential activity in treating chondrocyte degeneration caused by osteoarthritis [69, 70]. A study has found that kidney-tonifying and blood-activating Chinese herbs may suppress the expression of interferon regulatory factor 7 (IRF-7) by regulating the TLR4/MyD88 signaling pathway, resulting in less secretion of interleukin 6 (IL-6) and matrix metallopeptidase 13 (MMP-13), which alleviates inflammation and delays cartilage destruction [71].…”