The inhibition of PLCγ1 protects chondrocytes against osteoarthritis, implicating its binding to Akt

Abstract

Previous studies have addressed the involvement of phosphoinositide-specifc phospholipase γ1 (PLCγ1) and protein kinase B (PKB/Akt) in osteoarthritis (OA) pathogenesis, but it is not ascertained the possibility of them to be potential targets for OA therapy. Here, through local intra-articular injection of PLCγ or Akt inhibitor in a rat OA model induced by anterior cruciate ligament transaction plus medial meniscus resection, the architecture of chondrocyte and matrix organization of articular cartilage were observed using histopathological assays and Aggrecan, Col2, PLCγ1, and Akt levels were detected using immunohistochemistry assays. By treatment of Akt or PLCγ inhibitor and transfection of different PLCγ1- or Akt-expressing vectors in rat OA model chondrocytes, Aggrecan, Col2, PLCγ1, p-PLCγ1, Akt, and p-Akt levels were detected using western blotting analysis. The binding between PLCγ1 and Akt was assessed with co-immunoprecipitation assays in human OA chondrocytes. These results showed that PLCγ inhibition protected chondrocytes against OA, but Akt inhibition did not dramatically aggravate OA progression. There were mutual antagonism and binding between PLCγ1 and Akt that could be regulated by their phosphorylation levels. Consequently, the data reveal that the inhibition of PLCγ1 may provide an attractive therapeutic target for OA therapy, implicating its binding to Akt.

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

“…Consistent with previous studies, 10,11,29 our findings displayed that PLCγ1 was expressed at elevated level in cartilage of human OA and rat OA model, as well as both human and rat OA chondrocytes. Furthermore, the data that PLCγ1 inhibitor increased Collagen II and Aggrecan at protein and mRNA levels in IL‐1β‐treated human OA and rat chondrocytes and intra‐articular injection of Ad‐shPLCγ1 decreased OARSI scores and increased levels of Collagen II, Aggrecan and proteoglycans in rat OA model indicated the cartilage protection of PLCγ1 inhibition against OA.…”

“…Besides, the above‐mentioned results illustrated a reciprocal suppression between PLCγ1 and Erk in OA chondrocyte and a reciprocal promotion between PLCγ1 and Akt in OA chondrocyte, which has been demonstrated in previous studies 9,11,29 . Our further data that PD98059 elevated p‐Akt level and TCN reduced p‐Erk level accompanied with alterations of LC3B and P62 indicated that Erk negatively regulated Akt activation and Akt positively regulated Erk activation in IL‐1β‐treated rat chondrocytes exposed to U73122.…”

Characterization of Osteoarthritis in a Medial Meniscectomy-Induced Animal Model Using Contrast-Enhanced X-Ray Microtomography

“…Evaluation of joint cartilage is considered critical since the primary tissue degradation in KOA animal models that mimic human KOA occurs in this tissue; however, many studies have been limited. For example, in some KOA animal studies, only local assessment of the cartilage has been done using tissue sections and staining methods to assess cartilage degeneration quantitatively [4][5][6][7]. In addition, microscopic evaluation using India ink staining to confirm cartilage degradation in KOA animal models has demonstrated localized positive and non-positive areas [8][9][10].…”

Characterization of Osteoarthritis in a Medial Meniscectomy-Induced Animal Model Using Contrast-Enhanced X-ray Microtomography

“…Evaluation of joint cartilage is considered critical as the primary tissue degradation in KOA animal models that mimic human KOA occurs in this tissue; however, many studies have been limited. For example, in some KOA animal studies, only local assessment of the cartilage has been done using tissue sections and staining methods to assess cartilage degeneration quantitatively [4][5][6][7]. In addition, microscopic evaluation using India ink staining to confirm cartilage degradation in KOA animal models has demonstrated localized positive and non-positive areas [8][9][10].…”