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Am J Physiol Gastrointest Liver Physiol (January 8, 2009). doi:10.1152/ajpgi.90502.2008
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Submitted on August 19, 2008
Revised on December 29, 2008
Accepted on December 29, 2008

Transcriptional Regulation of IL-6 in Bile Duct Epithelia by Extracellular ATP

Jin Yu, Nina Sheung, Elwy M. Soliman1, Carlo Spirli2, and Jonathan A. Dranoff1*

1 Yale University School of Medicine
2 Yale University

* To whom correspondence should be addressed. E-mail: jonathan.dranoff{at}yale.edu.

The inflammatory cytokine IL-6 is essential for cell survival after liver injury. Bile duct epithelia (BDE) markedly upregulate IL-6 release after liver injury, but the mechanisms regulating this have not been defined. Purinergic signals induce multiple potent downstream effects in BDE, so the goals of this study were to determine whether extracellular ATP regulates BDE IL-6 transcription and to identify the molecular mechanisms regulating this process. Effects on extracellular nucleotides on IL-6 transcription in primary rat bile duct epithelia were assessed. The relative effects of cAMP and cytosolic calcium were determined using agonists and antagonists. The role of the cAMP response element (CRE) was determined by site-directed mutagenesis. We found that ATP potently upregulated IL-6 mRNA, and that the pharmacologic profile for IL-6 upregulation was most consistent with the newly identified P2Y11 receptor. This occurred in a cAMP-dependent and calcium-dependent fashion. The effect of cAMP and calcium agonists on IL-6 promoter activity was synergistic, and mutation of the IL-6 CRE blocked upregulation by ATP. Taken together, these data show that extracellular ATP acts through a mechanism involving a rat P2Y receptor functionally related to the P2Y11 receptor, cAMP and calcium signals, and that the IL-6 promoter CRE to upregulate transcription of IL-6 in BDE. Since IL-6 has such critical importance in the liver, it is likely that this pathway is of great relevance to the understanding of hepatic response to injury.







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