BETA-AMYLOID-INDUCED IL-1-BETA RELEASE FROM AN ACTIVATED HUMAN MONOCYTE CELL-LINE IS CALCIUM-DEPENDENT AND G-PROTEIN-DEPENDENT

The proinflammatory cytokine, interleukin-l (IL-I) is elevated in the Alzheimer's disease (AD) brain [1-3]. Studies from our laboratory have demonstrated that beta-amyloid (A beta) 1-42, fibrillar A beta 1-40 a nd A beta 25-35 induce the release of IL-1 beta from activated THP-1 c ells, a human monocyte cell line [4,9]. A beta also is chemotactic for primary rodent microglia and peritoneal macrophages [5]. We hypothesi ze that A beta is a chemokine and induces these responses by interacti on with chemotactic receptors. If this is true, then these A beta-indu ced responses should be calcium-dependent and require activation of pe rtussis toxin-sensitive G-proteins. To test this hypothesis, THP-1 cel ls were grown in culture with lipopolysaccharide (LPS) and incubated w ith A beta 1-42 (5 mu M) in the presence and absence of a calcium chel ator, an inhibitor of intracellular calcium mobilization, a calcium ch annel blocker, or pertussis toxin, a bacterial endotoxin which uncoupl es G proteins from receptors by catalyzing the ADP ribosylation of cys teine near the carboxy-terminus of the alpha subunit [6]. The media wa s collected and IL-1 beta present in the media was measured using an E LISA. Treatment of LPS-activated THP-1 cells with A beta 1-42 signific antly elevated IL-1 beta released into the media as previously shown. Addition of ethylene glycol-bis (beta-aminothyl ether) N,N,N',N'-tetra acetic acid (EGTA) (0.5 mM), a calcium chelator, to the media blocked A beta-induced IL-1 beta release, but had no effect on LPS-activated T HP-I cell release of IL-1 beta. The presence of 3,4,5-trimethoxybenzoi c acid 8-(diethyl amino)-octyl ester (TMB-8), an inhibitor of intracel lular calcium mobilization, as well as nickel chloride, a non-specific calcium channel blocker, in the media also inhibited A beta-induced I L-1 release from LPS-activated THP-1 cells. IL-1 beta release from act ivated THP-1 monocytes incubated with TMB-8 and nickel chloride withou t A beta remained at baseline values. Pretreatment of THP-1 monocytes with pertussis toxin for 4 h, followed by LPS activation and incubatio n with A beta, antagonized the release of IL-1 beta from these cells, but did not alter IL-1 beta release from activated THP-1 monocytes. Th ese data suggest that A beta-induced IL-1 beta release from these cell s is calcium-dependent and requires the activation of specific G-prote ins. These findings are consistent with known second messengers that a re activated following stimulation of chemotactic receptors. (C) 1997 Elsevier Science Ireland Ltd.