ZVAD reduced COX-2 protein expression in monocytes but not in macrophages. Macrophages and monocytes were obtained from Donor 1 and Donor 2 and were left untreated (lane 1) or were incubated with LPS at 20 ng/ml in the absence (lane 2) or in presence of ZVAD (lane 3) for 12 h. Cells were lysed in 1% NP40 and proteins were analyzed by SDS-PAGE (12 and 16 µg protein per lane for monocytes and macrophages, respectively) and Western Blotting with Abs against COX-2 (panels 1 and 3 from the top) or with β-actin as loading control (panels 2 and 4 from the top). Densitometry was performed on developed films and percent reduction of COX-2 protein expression in LPS-treated monocytes in the presence of ZVAD was calculated relative to the expression of COX-2 in monocytes treated with LPS alone.