Differential regulation of soluble interleukin 1 release and membrane expression by pharmacologic agents.

Membrane IL-1 (mIL-1) expression was compared with release of soluble IL-1 (sIL-1) by C3H/HeNCrl mouse peritoneal macrophages. Selective antagonists of protein kinase C (PKC) (H-7) and calmodulin (W-7) in combination inhibited LPS-induced mIL-1 and sIL-1 production, suggesting a role for these activation pathways in IL-1 induction. Low levels of A23187, when combined with OAG (a direct activator of PKC), stimulated mIL-1 expression in the absence of sIL-1 release. Induction of mIL-1 by LPS was inhibited by PGE2 and dibutyryl cAMP, but higher concentrations were required to inhibit mIL-1 expression compared with sIL-1 release. LTB4 alone did not induce mIL-1 or sIL-1 production. LTB4 did enhance LPS-induced mIL-1 expression but not sIL-1 release. These results indicate that mIL-1 expression and sIL-1 release are differentially regulated. Membrane IL-1 is induced by lower levels of certain stimuli and is less effectively inhibited than is sIL-1 release. This differential regulation is further evidence to support the existance of membrane IL-1.