Research Papers: Immunology:
Hepatic TLR4 signaling is activated by LPS from digestive tract during SARA, and epigenetic mechanisms contribute to enforced TLR4 expression
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Guangjun Chang1, Su Zhuang2, Hans-Martin Seyfert3, Kai Zhang1, Tianle Xu1, Di Jin1, Junfei Guo1 and Xiangzhen Shen1
1 College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China
2 College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China
3 Leibniz Institute for Farm Animal Biology, Dummerstorf, Germany
Xiangzhen Shen, email:
Keywords: subacute ruminal acidosis, LPS translocation, liver, TLR4 signaling, epigenetic mechanisms, Immunology and Microbiology Section, Immune response, Immunity
Received: August 13, 2015 Accepted: September 30, 2015 Published: October 19, 2015
Subacute ruminal acidosis (SARA) is known to trigger a systemic inflammatory response that is possibly caused by the translocation of lipopolysaccharides (LPS) from the gastrointestinal tract into the bloodstream. The aim of this study is to investigate this causal relationship between the increases of circulating LPS and liver inflammation. Here we found that SARA goats exhibited significantly increased LPS concentrations in both the rumen and portal vein. The livers of these goats exhibited increased mRNA concentrations of pro-inflammatory genes that indicated inflammation. Meanwhile, the occurrence of liver inflammation was further validated by the enhanced protein expression of those cytokines in the livers of SARA goats. These increased expressions of detected pro-inflammatory genes were likely mediated by enforced TLR4 signaling because SARA increased the concentrations of TLR4 mRNA and protein in the liver and the abundance of both the NF-kB-p65 factor and its active phosphorylated variant. We also verified that the enhanced TLR4 expression was accompanied by chromatin decompaction and demethylation of the proximal TLR4 promoter. Hence, epigenetic mechanisms are involved in the enforced expression of immune genes during SARA, and these findings open innovative routes for interventions via the modulation of these epigenetic mechanisms.
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