Protective Effects of Annatto Tocotrienol and Palm Tocotrienol-Rich Fraction on Chondrocytes Exposed to Monosodium Iodoacetate

Background: This study aimed to compare the chondroprotective efficacy and mechanism of annatto tocotrienol (AnTT) and palm tocotrienol-rich fraction (PT3) using SW1353 chondrocytes treated with monosodium iodoacetate (MIA). Methods: The chondrocytes were incubated with AnTT or PT3 in advance or concurrently with MIA for 24 h. The viability of the cells was tested with an MTT assay. The 8-isoprostane F2-α, extracellular matrix proteins, metalloproteinase and sex-determining region Y box protein 9 (SOX9) levels were determined using immunoassays. Results: AnTT and PT3 reversed an MIA-induced decrease in chondrocyte viability when incubated together with MIA (p < 0.05). Prior incubation with both mixtures did not produce the same effects. AnTT and PT3 cotreatment could suppress 8-isoprostane F2-α level in chondrocytes exposed to MIA (p < 0.01). Co-exposure to tocotrienols and MIA increased the type II collagen/type I collagen ratio in chondrocytes (p < 0.01). In addition, the co-exposure of AnTT and MIA for 24 h significantly upregulated SOX9, type II collagen and aggrecan levels (p < 0.05), which was not observed with co-exposure of PT3 and MIA, AnTT or PT3 exposure alone. Conclusion: AnTT and PT3 could prevent a reduction in chondrocyte viability following MIA exposure by reducing oxidative stress. In addition, AnTT might induce self-repair and anabolic activities in chondrocytes challenged with MIA.