Effects of resveratrol and curcumin on IL-1β-induced inhibition of collagen type II and Sox-9 production in chondrocytes. To evaluate the effects of resveratrol and curcumin on IL-1β-stimulated chondrogenic inhibition in primary chondrocytes, whole cell lysates (500 ng protein per lane) were probed with antibodies to (a) collagen type II (panel I), as the most abundant cartilage-specific extracellular matrix protein, and (b) the chondrogenic-specific transcription factor Sox-9 (panel I). Cultures were treated with 10 ng/ml IL-1β, 50 μM resveratrol, 50 μM curcumin, 50 μM resveratrol and 50 μM curcumin, or were pre-treated with 50 μM resveratrol, 50 μM curcumin, 50 μM resveratrol and 50 μM curcumin for 4 hours and then co-treated with 10 ng/ml IL-1β, or left untreated for 24 hours. Untreated cultures had strong (a) collagen type II and (b) Sox-9 and stimulation with IL-1β alone greatly reduced collagen type II as well as Sox-9 production. However, pre-treatment of the cultures with resveratrol, curcumin or a combination of both inhibited the adverse effects of IL-1β and the chondrocytes produced large quantities of collagen type II and Sox-9 at levels similar to control cultures. This was confirmed by quantitative densitometry (a, panel II and b, panel II). The mean values and standard deviations from three independent experiments are shown. White, grey and solid bars represent different molecular forms of collagen type II. Synthesis of the housekeeping protein β-actin remained unaffected.