PLCγ1 inhibition‐driven autophagy of IL‐1β‐treated chondrocyte confers cartilage protection against osteoarthritis, involving AMPK, Erk and Akt

Abstract

Previous studies identified the involvement of phosphoinositide‐specific phospholipase C (PLC) γ1 in some events of chondrocytes. This study aims to investigate whether and how PLCγ1 modulates autophagy to execute its role in osteoarthritis (OA) progression. Rat normal or human OA chondrocytes were pretreated with IL‐1β for mimicking or sustaining OA pathological condition. Using Western blotting, immunoprecipitation, qPCR, immunofluorescence and Dimethylmethylene blue assays, and ELISA and transmission electron microscope techniques, we found that PLCγ1 inhibitor U73122 enhanced Collagen II, Aggrecan and GAG levels, accompanied with increased LC3B‐II/I ratio and decreased P62 expression level, whereas autophagy inhibitor Chloroquine partially diminished its effect. Meanwhile, U73122 dissociated Beclin1 from Beclin1‐IP3R‐Bcl‐2 complex and blocked mTOR/ULK1 axis, in which the crosstalk between PLCγ1, AMPK, Erk and Akt were involved. Additionally, by haematoxylin and eosin, Safranin O/Fast green, and immunohistochemistry staining, we observed that intra‐articular injection of Ad‐shPLCγ1‐1/2 significantly enhanced Collagen and Aggrecan levels, accompanied with increased LC3B and decreased P62 levels in a rat OA model induced by anterior cruciate ligament transection and medial meniscus resection. Consequently, PLCγ1 inhibition‐driven autophagy conferred cartilage protection against OA through promoting ECM synthesis in OA chondrocytes in vivo and in vitro, involving the crosstalk between PLCγ1, AMPK, Erk and Akt.

The role of EDIL3 in maintaining cartilage extracellular matrix and inhibiting osteoarthritis development

“…Previous studies have already addressed the involvement of phosphokinase protein in OA chondrocyte events, such as phospholipase C gamma 1 (PLCγ1), glycogen synthase kinase 3 alpha/beta (GSK-3β), STAT, and Src. 51 - 54 PLCγ1 and GSK-3β inhibition conferred cartilage protection against OA through promotion of ECM synthesis in OA chondrocytes. 51 , 52 Thus, we collected intracellular proteins from IL-1β-treated chondrocytes and performed phosphokinase protein arrays to measure the phosphorylation profiles of kinases ( Figure 6d ).…”

Corosolic Acid Protects Rat Chondrocytes Against IL-1β-Induced ECM Degradation by Activating Autophagy via PI3K/AKT/mTOR Pathway and Ameliorates Rat Osteoarthritis

“…Our data showed that IL-1β significantly decreased the autophagy flux marker LC3-II/LC3-I ratio and increased the expression of P62, indicating that IL-1β played a negative role in the regulation of chondrocyte autophagy, which was consistent with the results of previous studies. 39 , 40 However, the administration of CRA could partly reverse the IL-1β–induced autophagy downregulation. Chondrocyte autophagy was not affected when CRA was administered alone.…”

The Role of Autophagy in Osteoarthritic Cartilage

“…Ansari et al observed that butein, an organic compound belongs to the polyphenol family (found to be useful in OA management), triggers autophagic flux through phosphorylation of AMPKα threonine-172 and ULK1 serine-317, and suppresses mTOR in OA-like chondrocytes [ 76 ]. Then, there is one research about PLCγ1 (Phospholipase C gamma 1) speaking about the indirect reaction of AMPK and ULK1 with the utilization of AMPK activator metformin decreasing the level of p-PLCγ1 and blocking mTOR/ULK1 axis, eventually encouraging the synthesis of cartilage extracellular matrix [ 77 ].…”