Matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) produced by monocytes are believed to be involved in the migration of these cells through the basement membrane and the ensuing destruction of connective tissue in chronic inflammatory lesions. Because monocytes encounter a variety of cytokines at these sites, we examined the effect of cytokines either alone or in combination on the production of monocyte MMPs and TIMP-1. TNF-α, granulocyte-macrophage-CSF (GM-CSF), or IL-1β when added individually enhanced the endogenous levels of 92-kDa gelatinase (MMP-9) and TIMP-1 but failed to induce interstitial collagenase (MMP-1). However, GM-CSF, when added with either TNF-α or IL-1β, induced MMP-1 and synergistically enhanced MMP-9 and TIMP-1. Th2 cytokines, such as IL-4, inhibited the induction of MMPs and TIMP-1 by TNF-α, GM-CSF, and IL-1. Cytokine stimulation of MMP-1 was due, at least in part, to an increase in the release of arachidonic acid and PG E 2 (PGE 2), because inhibition of MMP-1 by indomethacin could be reversed by exogenous PGE 2. In contrast to MMP-1, cytokine stimulation of MMP-9 and TIMP-1 was unaffected by indomethacin. The PGE 2-independent induction of monocyte MMP-9 and TIMP-1 by these cytokines differed from stimulation of MMP-9 and TIMP-1 by LPS, which is in large part PG-dependent. In addition, LPS stimulated higher levels of MMP-1 whereas cytokines induced higher levels of MMP-9 and TIMP-1. This is the first demonstration that monocyte MMP-1 can be induced by cytokines and that MMP-1, MMP-9, and TIMP-1 are differentially regulated by cytokines through PG-dependent and-independent mechanisms.