Low molecular weight xanthan gum suppresses oxidative stress-induced apoptosis in rabbit chondrocytes.

We have previously reported the application of low molecular weight XG(LM-XG), with molecular weights ranging from 1×106 Da to 1.5×106 Da for treating osteoarthritis. In this study, we investigated the anti-apoptotic activity of LM-XG under oxidative stress conditions, activated by hydrogen peroxide (H2 O2 )-treated chondrocytes in vitro. Chondrocytes were pretreated with various doses of LM-XG (0, 10, 100, 500, or 1000μg/mL) or 1000μg/mL sodium hyaluronate for 12h, and then exposed to 0.5mmol/L H2 O2 for another 12h. After treatment, chondrocyte viability was evaluated using a cell counting kit-8; DNA fragmentation was detected using Hoechst33258 staining; the percentage of DNA fragmentation was evaluated using the diphenylamine DNA assay kit; the apoptosis rate was evaluated using flow cytometry; chondrocyte ultra-microscopic morphology was observed using transmission electron microscopy; intracellular reactive oxygen species levels were observed and quantified using 2,7-dichlorofuorescin diacetate, mitochondrial permeability transition analysis was performed using MitoTracker Red CMXRos and 4',6-diamidino-2-phenylindole staining; and finally, caspase-3 activity was detected by western blot. The results showed that, compared with H2 O2 -treated chondrocytes, LM-XG improved cell viability, decreased the percentage of DNA fragmentation, reduced the apoptosis rate, decreased the levels of intracellular reactive oxygen species and mitochondrial permeability transition, reverted the morphological damage, and downregulated cleaved caspase-3 levels. These results demonstrate that LM-XG has anti-apoptotic activity in H2 O2 -treated chondrocytes.