Opposite Regulation of IL-1β and Secreted IL-1 Receptor Antagonist Production by Phosphatidylinositide-3 Kinases in Human Monocytes Activated by Lipopolysaccharides or Contact with T Cells

Abstract

The unbalanced production of IL-1β 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-β. In this study, we addressed the question of PI3K involvement in the production of IL-1β 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-1β protein in both CEsHUT- and LPS-activated monocytes, the enhancement being drastically higher in the former. This was not due to changes in IL-1β mRNA steady-state levels or transcript stability, but to the involvement of PI3Ks in the repression of IL-1β secretion. The downstream PI3K effector, Akt, was implicated in this process. The present results demonstrate that PI3Ks are involved in the inhibition of IL-1β 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.

Glatiramer acetate increases IL-1 receptor antagonist but decreases T cell-induced IL-1β in human monocytes and multiple sclerosis

“…Monocytes (2 ϫ 10 6 cells/well/3 mL) were cultured in 6-well plates with the indicated stimulus for 3 h or 18 h. Total RNA was isolated and analyzed by quantitative real-time PCR as previously described (23).…”

“…HUT-78 cells (2 ϫ 10 6 cells/mL) were stimulated for 6 h by phytohemagglutinin (1 g/mL) and PMA (5 ng/mL). Plasma membranes of stimulated HUT-78 cells were prepared as previously described and solubilized in 8 mM CHAPS (23,44). CHAPS extract of membranes of stimulated HUT-78 cells was referred as to CE sHUT.…”

“…Studies of cell-cell interactions such as those occurring in T cell contact activation of human monocytes are usually complicated by the simultaneous presence of at least 2 viable cell types. To obviate this problem, and possible interferences caused by the fact that target cells are potentially phagocytic, isolated membranes from stimulated HUT-78 cells were solubilized with CHAPS and used as a stimulus, referred to as CE sHUT (23). As shown in Fig.…”

Interleukin-1β production in human monocytes/macrophages is differentially regulated by MEK1 upon sterile and infectious inflammatory conditions

“…Previous works demonstrated that CE sHUT and LPS induce IL-1β and sIL-1Ra production in human monocytes [23,24]. Since the levels of cytokine production varied between different monocyte preparations (i.e., blood donors), the results below are presented as percentages of the cytokine production measured in the absence of inhibitor.…”

“…In parallel, LPS was used as a prototypical infectious stimulus. Using these models, we previously demonstrated that phosphatidylinositide-3 kinase δ (PI3Kδ) regulate IL-1β and sIL1Ra expression in opposite ways in human monocytes activated by LPS or contact with T cells, dampening the production of pro-inflammarory cytokines in LPS-activated monocytes, but inducing it in contact-activated monocytes [23,24]. Therefore, inhibition of PI3Ks could exacerbate inflammatory response to pathogens.…”