title: Cadmium-induced DNA synthesis and cell proliferation in macrophages: the role of intracellular calcium and signal transduction mechanisms.
abstract: Cd(2+) exposure increases the risk of cancer in humans and animals. In this report, we have studied the effect of Cd(2+) on signal transduction and Ca(2+) mobilization in murine macrophages. At micromolar concentrations, Cd(2+) significantly increased cell division as judged by [3H]thymidine uptake and cell counts. Cd(2+)-treated cells continued to proliferate even after more than 4 weeks in culture. Cd(2+) (1 microM) treatment induced a 1.5- to 2-fold increase in cytosolic free Ca(2+), [Ca(2+)](i), which was transitory and/or oscillatory. The sources of this Ca(2+) included both inositol 1,4,5-trisphosphate (IP(3))-sensitive and -insensitive stores. Macrophage treatment with 1-(6-((17beta-3-methoxyestra-1,2,5(10)-triene-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122), an inhibitor of phosphatidylinositol-specific phospholipase C (PLC), decreased Cd(2+)-induced formation of IP(3) in a concentration-dependent manner (K(d) about 2 microM). This caused a concomitant, partial decrease in the effect of Cd(2+) on [Ca(2+)](i). Cd(2+) itself crosses the macrophage membrane in part via L-type Ca(2+) channels, but it also interacts with a cell surface membrane protein(s) coupled to a pertussis toxin-sensitive G protein. Use of selective inhibitors of signal transduction and the quantitation of the levels of phosphorylated MAPK/ERK-activating kinase-1 (MEK1), extracellular signal-regulated kinase-1 (ERK1), and p38 mitogen-activated protein kinase (MAPK) suggests that the effects of Cd(2+) are mediated by the p21(ras)-dependent MAPK, but not the phosphoinositide 3 (PI 3)-kinase signalling pathway. The effect of activating these pathways includes increased availability of the transcription factor NFkappaB as well as activation of the early genes c-fos and c-myc.
authors.affiliation: Department of Pathology, Duke University Medical Center, Box 3712, Durham, NC 27710, USA.
authors.forename: Uma Kant
authors.initials: UK
authors.lastname: Misra
authors.forename: Govind
authors.initials: G
authors.lastname: Gawdi
authors.forename: Gomal
authors.initials: G
authors.lastname: Akabani
authors.forename: Salvatore Vincent
authors.initials: SV
authors.lastname: Pizzo
mesh_terms: D000818:Animals; D002104:Cadmium / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002274:Carcinogens, Environmental / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004261:DNA Replication; D004305:Dose-Response Relationship, Drug; D007700:Kinetics; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D054801:Phosphoinositide Phospholipase C; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D013936:Thymidine / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D002274:Carcinogens, Environmental; D016328:NF-kappa B; D016760:Proto-Oncogene Proteins c-fos; D016271:Proto-Oncogene Proteins c-myc; D002104:Cadmium; D004247:DNA; D010738:Type C Phospholipases; D054801:Phosphoinositide Phospholipase C; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D002118:Calcium; D013936:Thymidine