SILICA-INDUCED NUCLEAR FACTOR-ĸB ACTIVATION : (INVOLVEMENT OF REACTIVE OXYGEN SPECIES AND PROTEIN TYROSINE KINASE ACTIVATION)

다국어 초록 (Multilingual Abstract)

Nuclear Factor-ĸB(NF-ĸB) is a multiprotein complex that may regulate a variety of inflammatory cytokines involved in the initiation and progression of silicosis. The present study documents the ability of in vitro silica exposure to induce DNA-binding activity of NF-ĸB in mouse macrophages(RAW264.7 cells) and investigates the role of reactive oxygen species(ROS) and/or protein tyrosine kinase in this activation. In vitro exposure of mouse macrophages to silica(100㎍/㎖) resulted in a 2-fold increase in ROS production, measured as the generation of chemiluminescence(CL), and caused activation of NF-ĸB. Silica-induced CL was inhibited 100% by superoxide dismutase(SOD) and 75% by catalase, while NF-ĸB activation was inhibited by a variety of antioxidants(Catalase, SOD, sodium formate, α-tocopherol, and pyrrolidine dithiocarbamate). Further evidence of the involvement of ROS in NF-ĸB activation is that 1 mM H₂O₂ enhanced NF-ĸB/DNA binding and that this activation was inhibited by catalase. Specific inhibitors of protein tyrosine kinase, such as herbimycin A, genistein and AG-494, prevented NF-ĸB activation in silica-treated cells. Genistein and AG-494 also prevented NF-ĸB activation in H₂O₂-treated cells. In contrast, inhibitiors of protein kinase A or C, such as H89, staurosporin, calphostin C, chelerythrine, and H7 had no inhibitory effect on this response. The results suggest that ROS play a role in silica-induced NF-ĸB activation in macrophages and that phosphorylation events mediated by tyrosine kinase may be involved in this activation.