Coordinating Role of RXRalpha in Downregulating Hepatic Detoxification during Inflammation Revealed by Fuzzy-Logic Modeling

Coordinating Role of RXRalpha in Downregulating Hepatic Detoxification during Inflammation Revealed by Fuzzy-Logic Modeling
Keller R, Klein M, Thomas M, Drager A, Metzger U, Templin MF, Joos TO, Thasler WE, Zell A, Zanger UM
PLoS Comput Biol. 2016 Jan 4;12(1):e1004431. doi: 10.1371/journal.pcbi.1004431. eCollection 2016 Jan.

During various inflammatory processes circulating cytokines including IL-6, IL-1beta, and TNFalpha elicit a broad and clinically relevant impairment of hepatic detoxification that is based on the simultaneous downregulation of many drug metabolizing enzymes and transporter genes. To address the question whether a common mechanism is involved we treated human primary hepatocytes with IL-6, the major mediator of the acute phase response in liver, and characterized acute phase and detoxification responses in quantitative gene expression and (phospho-)proteomics data sets. Selective inhibitors were used to disentangle the roles of JAK/STAT, MAPK, and PI3K signaling pathways. A prior knowledge-based fuzzy logic model comprising signal transduction and gene regulation was established and trained with perturbation-derived gene expression data from five hepatocyte donors. Our model suggests a greater role of MAPK/PI3K compared to JAK/STAT with the orphan nuclear receptor RXRalpha playing a central role in mediating transcriptional downregulation. Validation experiments revealed a striking similarity of RXRalpha gene silencing versus IL-6 induced negative gene regulation (rs = 0.79; P<0.0001). These results concur with RXRalpha functioning as obligatory heterodimerization partner for several nuclear receptors that regulate drug and lipid metabolism.