“…To inhibit A-Smase, we used imipramine, which induces proteolysis of the enzyme (Hurwitz et al, 1994;Grassmé et al, 1997;Jensen et al, 1999), and D609, a potent inhibitor of the phosphatidylcholine-specific phospholipase C, an enzyme known to be involved in A-SMase activation by TNF-␣, and other stimuli, through generation of diacylglycerol (Mü llerDecker, 1989;Schü tze et al, 1992;Wiegmann et al, 1994;Grassmé et al, 1997). Inhibition of N-SMase was obtained using two specific, direct inhibitors (i.e., scyphostatin and manumycin A) (Tanaka et al, 1997;Arenz et al, 2001). We tested the specificity of these compounds in our cell model.…”