Stimulation and release of interleukin-1 from peritoneal macrophages of the mouse

Abstract

Lipopolysaccharide (LPS) caused a concentration-dependent increase of released and cell-associated interleukin-1 (IL-1) in resident peritoneal macrophages from the mouse. LPS was about 30 times more potent at stimulating the level of cell-associated IL-1 than it was at stimulating the release of IL-1. Human recombinant tumour necrosis factor-α (TNF-α) and the calcium ionophores A23187 and ionomycin induced a concentration-dependent increase of cell-associated IL-1 but failed to cause release of IL-1 at concentrations producing maximal stimulation of cell-associated IL-1. The phorbol ester, 4β-phorbol dibutyrate, stimulated the release of IL-1 from mouse macrophages but failed to induce an increase in cell-associated IL-1. Substance P, neurokinin A, neurokinin B, calcitonin gene-related peptide and platelet-activating factor did not increase the released or cell-associated IL-1 in mouse macrophages. These agents also failed to alter released or cell-associated IL-1 stimulated by LPS, 1 μg ml⁻¹. It appears that a calcium signal is sufficient for the transcription and translation of IL-1 mRNA but does not result in the secretion of biologically active forms of IL-1. Our data also indicate that different intracellular signals may control the release and the cell accumulation of IL-1. We conclude that inflammatory mediators may independently increase either the release of, or the cell accumulation of IL-1.