Opposite regulation of IL-1 beta and secreted IL-1 receptor antagonist production by phosphatidylinositide-3 kinases in human monocytes activated by lipopolysaccharides or contact with T cells

The unbalanced production of IL-1 beta and its natural, specific inhibitor, the secreted IL-1R antagonist (sIL-1Ra), plays an important role in chronic/sterile inflammation. Relevant to this condition is direct cellular contact with stimulated T cells which is a potent inducer of cytokine production in human monocytes/macrophages. We previously demonstrated that activation of PI3Ks is a prerequisite of the transcription of the sIL-1Ra gene in human monocytes activated by IFN-beta. In this study, we addressed the question of PI3K involvement in the production of IL-1 beta and sIL-1Ra in monocytes activated by cellular contact with stimulated T cells (mimicked by CHAPS-solubilized membranes of stimulated T cells (CEsHUT)), and a crude preparation of LPS, to compare stimuli relevant to chronic/sterile and acute/infectious inflammation, respectively. In monocytes activated by either CEsHUT or LPS, the inhibition of PI3Ks abrogated sIL-1Ra transcript expression and sIL-1Ra production, demonstrating that PI3Ks control the induction of sIL-1Ra gene transcription. In contrast, PI3K inhibition increased the production of IL-1 beta protein in both CEsHUT- and LPS-activated monocytes, the enhancement being drastically higher in the former. This was not due to changes in IL-1 beta mRNA steady-state levels or transcript stability, but to the involvement of PI3Ks in the repression of IL-1 beta secretion. The downstream PI3K effector, Akt, was implicated in this process. The present results demonstrate that PI3Ks are involved in the inhibition of IL-1 beta secretion and in the induction of sIL-1Ra production in human blood monocytes by controlling different mechanisms in conditions mimicking chronic/sterile (CEsHUT) and acute/infectious (LPS) inflammation.