Effects of resveratrol and curcumin on IL-1β-induced mitochondrial changes and apoptosis in primary chondrocytes. (a) Transmission electron microscopy was performed to demonstrate the effects of resveratrol and curcumin on IL-1β-stimulated primary chondrocytes in monolayer culture at an ultrastructural level. Untreated control cultures consisted of vital, active chondrocytes containing mitochondria, rough endoplasmic reticulum and many other cell organelles (panel a). In contrast, stimulation of chondrocytes with 10 ng/ml IL-1β for 1, 12, 24, and 48 hours resulted in degenerative changes in the cells. After 1 hour, chondrocytes became rounded and the nucleus contained more condensed chromatin (panel b). After 12 hours, multiple vacuoles, swelling of rough endoplasmic reticulum and clustering of swollen mitochondria were visible (panel c). Inset: arrows demonstrate swollen mitochondria. Longer incubations of 24 to 48 hours led to the formation of apoptotic bodies and cell lysis (panels d to e). Treatment of IL-1β-stimulated primary chondrocytes with resveratrol and curcumin (both at 50 μM), however, inhibited the adverse effects of IL-1β (panels f-i), and after 48 hours of treatment (panel i) chondrocytes demonstrated large, flattened cells with numerous microvilli-like processes, mitochondria and endoplasmic reticulum comparable with control cultures. (b) To quantify apoptosis in these cultures, 100 cells from 20 microscopic fields were counted. The number of apoptotic cells was highest in cultures stimulated with IL-1β alone and rose steadily over the entire culture period. In contrast, treatment of IL-1β-stimulated cultures with resveratrol and/or curcumin inhibited the apoptotic effects of IL-1β and the number of apoptotic cells remained significantly lower over the entire culture period (*).