beta-Amyloid-induced IL-1 beta release from an activated human monocyte cell line is calcium- and G-protein-dependent.
The proinflammatory cytokine, interleukin-1 (IL-1) is elevated in the Alzheimer's disease (AD) brain. Studies from our laboratory have demonstrated that beta-amyloid (A beta) 1-42, fibrillar A beta 1-40 and A beta 25-35 induce the release of IL-1 beta from activated THP-1 cells, a human monocyte cell line. A beta also is chemotactic for primary rodent microglia and peritoneal macrophages. We hypothesize that A beta is a chemokine and induces these responses by interaction with chemotactic receptors. If this is true, then these A beta-induced responses should be calcium-dependent and require activation of pertussis toxin-sensitive G-proteins. To test this hypothesis, THP-1 cells were grown in culture with lipopolysaccharide (LPS) and incubated with A beta 1-42 (5 muM) in the presence and absence of a calcium chelator, an inhibitor of intracellular calcium mobilization, a calcium channel blocker, or pertussis toxin, a bacterial endotoxin which uncouples G proteins from receptors by catalyzing the ADP ribosylation of cysteine near the carboxy-terminus of the alpha subunit. The media was collected and IL-1 beta present in the media was measured using an ELISA. Treatment of LPS-activated THP-1 cells with A beta 1-42 significantly elevated IL-1 beta released into the media as previously shown. Addition or ethylene glycol-bis (beta-aminothyl ether) N,N,N'N'-tetraacetic 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 THP-1 cell release of IL-1 beta. The presence of 3,4,5-trimethoxybenzoic acid 8-(diethyl amino)-octyl ester (TMB-8), an inhibitor of intracellular calcium mobilization, as well as nickel chloride, a non-specific calcium channel blocker, in the media also inhibited A beta-induced IL-1 release from LPS-activated THP-1 cells. IL- 1 beta release from activated THP-1 monocytes incubated with TMB-8 and nickel chloride without A beta remained at baseline values. Pretreatment of THP-1 monocytes with pertussis toxin for 4 h, followed by LPS activation and incubation 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. These data suggest that A beta-induced IL-1 beta release from these cells is calcium-dependent and requires the activation of specific G-proteins. These findings are consistent with known second messengers that are activated following stimulation of chemotactic receptors.
Lorton
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Hoover Arthritis Research Center, Sun Health Research Institute, Sun City, AZ 85372, USA.
D016229:Amyloid beta-Peptides / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002460:Cell Line; D003470:Culture Media / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008934:Mitogens / Q000494:pharmacology; D009000:Monocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009532:Nickel / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology*; D037342:Pertussis Toxin; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D016229:Amyloid beta-Peptides; D002121:Calcium Channel Blockers; D003470:Culture Media; D007375:Interleukin-1; D008070:Lipopolysaccharides; D008934:Mitogens; D010446:Peptide Fragments; D010566:Virulence Factors, Bordetella; C075222:amyloid beta-protein (1-42); D004533:Egtazic Acid; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; C022838:nickel chloride; D009532:Nickel; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D002118:Calcium