Zinc-suppressed inflammatory cytokines by induction of A20-mediated inhibition of nuclear factor-kappaB.

摘要

OBJECTIVE: Chronic generation of inflammatory cytokines and reactive oxygen species are implicated in atherosclerosis, aging, cancers, and other chronic diseases. We hypothesized that zinc induces A20 in premonocytic, endothelial, and cancer cells, and A20 binds to tumor necrosis factor (TNF)-receptor associated factor, and inhibits Ikappa kinase-alpha (IKK-alpha)/nuclear factor-kappaB (NF-kappaB), resulting in downregulation of TNF-alpha and interleukin-1beta (IL-1beta). METHODS: To test this hypothesis, we used HL-60, human umbilical vein endothelial cells, and SW480 cell lines under zinc-deficient and zinc-sufficient conditions in this study. We measured oxidative stress markers, inflammatory cytokines, A20 protein and mRNA, A20-FRAF-1 complex, and IKK-alpha/NF-kappaB signaling in stimulated zinc-deficient and zinc sufficient cells. We also conducted antisense A20 and siRNA studies to investigate the regulatory role of zinc in TNF-alpha and IL-1beta via A20. RESULTS: We found that zinc increased A20 and A20-tumor necrosis factor-receptor associated factor-1 complex, decreased the IKK-alpha/NF-kappaB signaling pathway, oxidative stress markers, and inflammatory cytokines in these cells compared with zinc-deficient cells. We confirmed that zinc-induced A20 contributes to downregulation of TNF-alpha and IL-1beta by antisense and short interfering RNA A20 studies. CONCLUSION: Our studies suggest that zinc suppresses generation of NF-kappaB-regulated inflammatory cytokines by induction of A20.