4-Hydroxynonenal (HNE) altered redox status and energy metabolism in osteoarthritis chondrocytes. Chondrocytes were treated for 16 hours with 30 μM HNE, and cellular extracts were subjected to different analysis to determine (a) GSSG/(GSSG+GSH) and NADP/(NADPH+NADP) ratios, (b) mNADP+-ICDH activity, (c) glucose uptake, and (d) ATP level. Data are mean ± standard error of the mean and expressed as a percentage of untreated cells. Statistics: Student unpaired t test; **P < 0.01, ***P < 0.001. GSH, glutathione; GSSG, oxidized glutathione; mNADP+-ICDH, mitochondrial NADP+-dependent isocitrate dehydrogenase.