COX-2 degradation by μ-calpain in vitro. Control cells were treated with LPS/IFN for 24 h to induce COX-2. Extracts were then mixed with the indicated units of porcine μ-calpain, in calpain reaction buffer, incubated 30 min, and then denatured for western blotting. A representative blot of COX-2 is shown. Bars represent the average COX-2 signal intensity ± SE of 3 independent cultures for each point, as a percent of the value without added calpain.