Table 3. Effect of C8 on PGE₂ secretion by articular chondrocytes incubated with different IL-1β concentrations.

	C8 inhibitory effect (%inhibition)
IL-1β (ng/mL)	C8 at 0.31 µM	C8 at 4.96 µM
1	25*	68***
0.5	60*	67*
0.25	67	65

Chondrocytes were untreated or treated for 20 h with IL-1β (1-, 0.5-, or 0.25-ng/mL) alone or 1 h after the addition of C8 (0.31- or 4.96-µM) in DMEM with 2% FCS. PGE₂ concentration was determined in conditioned culture medium, and protein concentration was determined in whole-cell protein extracts. The PGE₂ concentration was normalized relatively to whole cell protein concentration (pg PGE₂/µg proteins). The means of PGE₂ concentrations from 3 independent determinations were calculated and the anti-IL-1β inhibitory effect of C8 was determined with the formula %inhibition  = 100−100×[(mean PGE₂ in IL-1β+C8 condition)/(mean PGE₂ in IL-1β condition)]).

*P<0.05,

***P<0.001 between IL-1β- and IL-1β+C8-treated groups.