Zinc regulates expression of IL-23 p19 mRNA via activation of eIF2α/ATF4 axis in HAPI cells
- 255 Downloads
Zinc (Zn2+) is considered to be one of the factors aggravating brain damage after cerebral ischemia. Since Zn2+ activates microglia, immune cells in the brain, this metal is proposed to modulate neuroinflammatory responses in the post-ischemic brain. Interleukin (IL)-23 is a heterodimeric cytokine composed of the p19 subunit unique to IL-23 and the p40 subunit common to IL-12. IL-23 has been shown to play a critical role in the progression of ischemic brain injury. However, whether Zn2+ participates in the expression of IL-23 in microglia remains unknown. In this study, we examined the effect of Zn2+ on IL-23 p19 mRNA expression using rat immortalized microglia HAPI cells. Exposure to Zn2+ dose- and time-dependently induced the expression of IL-23 p19 mRNA in HAPI cells. Inhibitors of MAPK and NF-κB pathways failed to suppress this induction. Interestingly, we found that Zn2+ stimulated the phosphorylation of eIF2α and promoted the nuclear accumulation of activating transcription factor 4 (ATF4). Treatment with salubrinal, an eIF2α dephosphorylation inhibitor, enhanced Zn2+-induced ATF4 accumulation and IL-23 p19 mRNA expression. In addition, reporter assay using the IL-23 p19 promoter region revealed that ATF4 directly transactivated IL-23 p19 promoter and that dominant-negative ATF4 suppressed Zn2+-induced activation of IL-23 p19 promoter. Taken together, these findings suggest that Zn2+ up-regulates expression of the IL-23 p19 gene via the eIF2α/ATF4 axis in HAPI cells.
KeywordsZinc IL-23 Microglia Activating transcription factor 4 eIF2α Phosphorylation
This work was supported by a Grant-in-Aid for Scientific Research (C) from the Japan Society for the Promotion of Science (to H.H.; No. 26460630).
- Cua DJ, Sherlock J, Chen Y, Murphy CA, Joyce B, Seymour B, Lucian L, To W, Kwan S, Churakova T, Zurawski S, Wiekowski M, Lira SA, Gorman D, Kastelein RA, Sedgwick JD (2003) Interleukin-23 rather than interleukin-12 is the critical cytokine for autoimmune inflammation of the brain. Nature 421:744–748CrossRefPubMedGoogle Scholar
- Ho Y, Samarasinghe R, Knoch ME, Lewis M, Aizenman E, DeFranco DB (2008) Selective inhibition of mitogen-activated protein kinase phosphatases by zinc accounts for extracellular signal-regulated kinase 1/2-dependent oxidative neuronal cell death. Mol Pharmacol 74:1141–1151PubMedCentralCrossRefPubMedGoogle Scholar
- Hua F, Ma J, Ha T, Xia Y, Kelley J, Williams DL, Kao RL, Browder IW, Schweitzer JB, Kalbfleisch JH, Li C (2007) Activation of Toll-like receptor 4 signaling contributes to hippocampal neuronal death following global cerebral ischemia/reperfusion. J Neuroimmunol 190:101–111PubMedCentralCrossRefPubMedGoogle Scholar
- Shichita T, Hasegawa E, Kimura A, Morita R, Sakaguchi R, Takada I, Sekiya T, Ooboshi H, Kitazono T, Yanagawa T, Ishii T, Takahashi H, Mori S, Nishibori M, Kuroda K, Akira S, Miyake K, Yoshimura A (2012) Peroxiredoxin family proteins are key initiators of post-ischemic inflammation in the brain. Nat Med 18:911–917CrossRefPubMedGoogle Scholar