Protection of carboxymethylated chitosan on chondrocytes from nitric oxide-induced apoptosis by regulating phosphatidylinositol 3-kinase/Akt signaling pathway

Chondrocyte apoptosis is the most important element of development and progression of osteoarthritis (OA). Nitric oxide (NO) was used as the agent to induce chondrocyte apoptosis. Carboxymethylated chitosan (CMCS) has anti-apoptosis effect on many cell types in vitro. This study was designed to investigate the protective effect of CMCS on NO-induced chondrocyte apoptosis and the probable molecular mechanisms. The newborn Sprague-Dawley (SD) rats were used in this study for isolation of chondrocytes. The cell viability was determined by cell counting kit (CCK-8), cell apoptosis was detected by Annexin-V/PI double staining assay kit. The levels of phosphorylated-PI3K (p-PI3K), phosphorylated-Akt (p-Akt), Bcl-2 and Bax were determined by Western blot analysis. The caspase-3 activity was determined by a quantitative colorimetric assay. Results showed that pretreatment with CMCS could inhibit the apoptosis induced by NO. CMCS could decrease the activity of NO and decrease the expression of Bcl-2, p-PI3K and p-Akt, increase the expression of Bax, cytochrome c and caspase-3. CMCS also could reverse the effect of NO that prompted matrix metalloproteinase-13 (MMP-13) and inhibited tissue inhibitor of metalloproteinase-1 (TIMP-1) activity. All the present results indicated that CMCS can protect NO induced chondrocytes apoptosis by activate PI3K/Akt signaling pathway.