Induction of cyclooxygenase-2 synthesis by ligation of the macrophage α2-macroglobulin signalling receptor

We have studied the induction of cyclooxygenase-2 (COX-2) in macrophages consequent to ligating the alpha (2)-macroglobulin (alpha M-2) signalling receptor (alpha 2MSR) with receptor-recognized forms of alpha M-2 (alpha M-2*). Macrophage stimulation with alpha M-2* increased total cellular and nuclear COX-2 two- to threefold. The maximal increase in COX-2 occurred at a ligand concentration of 50-100 pM and after 2 h. Modulation of intracellular Ca2+ levels or incubation of [S-35] methionine-labelled macrophages with actinomycin D, prior to treatment with alpha M-2*, markedly reduced the induction of total cellular and nuclear COX-2. Protein kinase C (PKC) or phospholipase A(2) (PLA(2)) inhibition in alpha M-2*-stimulated macrophages or inhibition of the p21(ras)-dependent mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI 3-kinase) signalling pathways also significantly reduced alpha M-2*-induced total cellular and nuclear COX-2 expression. Thus, COX-2 induction is dependent on cPLA(2) activity, Ca2+ mobilization, and PKC activity and requires participation of both the p21(ras)-dependent MAPK and PI 3-kinase signalling pathways. COX-2 activation may mediate alpha M-2*-induced mitogenesis, which we have previously observed in this and other cell types. (C) 2001 Elsevier Science Inc. All rights reserved.