Figure 4. Effect of CM on oxidative stress induced by IL-1β in OA chondrocytes. The intracellular levels of HNE-modified proteins were quantified by ELISA. OA chondrocytes were incubated with IL-1β and/or CM for the indicated times. Data are shown as mean±standard deviation of N=9 separate experiments with cells from separate donors. ++p<0.01 with respect to non-treated cells; *p<0.05, with respect to IL-1β-treated cells.