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PEP-1-SIRT2 causes dedifferentiation and COX-2 expression via the MAPK pathways in rabbit articular chondrocytes
Seong-Hui Eo1, Dae Won Kim2, Soo Young Choi3
1Department of Biological Sciences, College of Natural Sciences, Kongju National University, 182 Shinkwan-Dong, Gongju, Chungnam 314-701, Republic of Korea.
Abstract:
SIRT2 is a member of the mammalian sirtuin protein family, primarily found in the cytoplasm. It regulates numerous cellular processes including aging, DNA repair, cell cycle, and survival under stress conditions. However, the biological function and mechanism of the SIRT2 protein was not well understood in normal cells such as primary chondrocytes. In this study, we examined the effects of SIRT2 on differentiation and inflammation in rabbit articular chondrocytes by using a cell-permeative PEP-1-SIRT2 protein. Our results indicate that PEP-1-SIRT2-induced a loss of type II collagen and decreased sulfate proteoglycan levels in a dose- and time-dependent manner, as examined by Western blotting, alcian blue staining, and immunohistochemistry. Furthermore, PEP-1-SIRT2 caused an inflammatory response by inducing the expression of cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2). In addition, after treatment with PEP-1-SIRT2, phosphorylation of both p38 and ERK was observed. Inhibition of ERK with PD98059 (PD) suppressed PEP-1-SIRT2-induced dedifferentiation and COX-2 expression. Reduction in PEP-1-SIRT2-induced inflammatory response was observed upon inhibition of p38 by SB203580 (SB). The same pattern was demonstrated in PEP-1-SIRT2-induced dedifferentiation and inflammatory response during culture with serial passages. During expansion to four passages, levels of type II collagen decreased, whereas levels of COX-2 and SIRT2 increased and activated ERK and p38. Furthermore, PEP-1-SIRT2 enhances dedifferentiation through the ERK pathway and inflammatory response through the ERK and p38 pathways in rabbit chondrocytes in vitro. These findings suggest that PEP-1-SIRT2 induces dedifferentiation via the ERK pathway and inflammation through the p38 and ERK pathways in rabbit articular chondrocytes.
Insights
SIRT2 protein promotes dedifferentiation and inflammation in rabbit chondrocytes by activating ERK and p38 pathways. This study reveals SIRT2
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Sirtuin 2 (SIRT2) is a key protein regulating cellular processes like aging and DNA repair.
- Its specific role in normal cells, such as primary chondrocytes, remains unclear.
- Understanding SIRT2's function in chondrocytes is crucial for cartilage biology.
Purpose of the Study:
- To investigate the effects of SIRT2 on differentiation and inflammation in rabbit articular chondrocytes.
- To elucidate the molecular pathways involved in SIRT2-mediated cellular changes.
- To assess the impact of a cell-permeative PEP-1-SIRT2 protein on chondrocyte function.
Main Methods:
- Treatment of rabbit articular chondrocytes with a cell-permeative PEP-1-SIRT2 protein.
- Analysis of type II collagen and proteoglycan levels using Western blotting, alcian blue staining, and immunohistochemistry.
- Measurement of cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2) expression.
- Assessment of p38 and ERK phosphorylation.
- Pharmacological inhibition of ERK and p38 pathways using PD98059 and SB203580, respectively.
- Evaluation of SIRT2 effects during serial passages of chondrocyte cultures.
Main Results:
- PEP-1-SIRT2 treatment dose- and time-dependently decreased type II collagen and proteoglycan levels.
- PEP-1-SIRT2 induced chondrocyte inflammation by increasing COX-2 and PGE2 expression.
- SIRT2 activation led to p38 and ERK phosphorylation.
- ERK inhibition partially reversed PEP-1-SIRT2-induced dedifferentiation and COX-2 expression.
- p38 inhibition reduced PEP-1-SIRT2-induced inflammatory responses.
- Serial passaging of chondrocytes showed decreased type II collagen and increased COX-2 and SIRT2, with activated ERK and p38.
Conclusions:
- PEP-1-SIRT2 induces dedifferentiation in rabbit articular chondrocytes primarily through the ERK pathway.
- SIRT2 promotes inflammation in these cells via both ERK and p38 pathways.
- These findings highlight SIRT2's role in regulating chondrocyte phenotype and inflammatory responses in vitro.
- SIRT2 may be a potential therapeutic target for cartilage-related inflammatory conditions.
