Submitted to: Journal of Innate Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2008
Publication Date: 10/10/2008
Citation: Kogut, M.H., Genovese, K.J., He, H., Kaiser, P. 2008. Flagellin and lipopolysaccharide up-regulation of IL-6 and CXCLi2 gene expression in chicken heterophils is mediated by ERK1/2-dependent activation of AP-1 and NF-kappaB signaling pathways. Innate Immunity. 14:213-222.
Interpretive Summary: During the first week of life after hatching, the immune system of the baby chick is not very good at fighting bacterial infections such as Salmonella. We do not know the reason for this problem. The objective of this experiment was to look at a specific white blood cell of the chicken (called the heterophil) and determine whether the cells’ internal machinery is controlled by the same chemicals reactions or not. We found that the various parts of the cells’ machinery are controlled by totally different chemical processes that are independent of each other. Therefore, the cell can control different parts of its internal machinery at different times without using other parts of the machinery. The results of this experiment are important to the pharmaceutical industry in the United States because it shows that we can stimulate different parts of the baby chick’s cells of the immune system without affecting other parts. Thus, it is possible to help the immune response without causing damage to the chick. It may be possible to develop new drugs that can increase the chick’s immune system and provide protection against infections such as Salmonella.
Technical Abstract: The Toll-like receptor agonists, flagellin (FLG) and lipopolysaccharide (LPS), stimulate chicken heterophils to induce the expression and secretion of pro-inflammatory cytokines by a mechanism involving the triggering of differential MEK-ERK signaling cascades. However, the translocation and activation of transcription factors potentially involved in the control of cytokine gene expression remains unknown. Herein, we examined the effects of FLG and LPS on the activation of the transcription factors NF-'B and AP-1 and their role in regulating heterophil activation leading to cytokine gene expression. Treatment of heterophils with either FLG or LPS induced a significant increase in DNA binding by the NF-'B family members p50, c-Rel, and RelB. Likewise, FLG and LPS induced a significant increase in DNA binding by the AP-1 family members c-Jun and JunD. The activation of both NF-'B and AP-1 was inhibited following treatment of heterophils with specific inhibitors of ERK1/2 (U0126), NF-'B (Bay 11-7086), and AP-1 (Tanshinone IIA). Likewise, the up-regulation of gene expression of the pro-inflammatory cytokine, IL-6, and the inflammatory chemokine, CXCLi2, were inhibited when heterophils were treated with the same specific inhibitors. Taken together these data demonstrate that although FLG (Rap1àB-RafàMEKàERK) and LPS (RasàRaf-1àMEKàERK) stimulate differential MEK-ERK signaling pathways, the up-regulation of expression of IL-6 and CXCLI2 was mediated by ERK1/2-dependent activation of both NF-'B and AP-1.