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Phytosterols Synergize With Endotoxin to Augment Inflammation in Kupffer Cells but Alone Have Limited Direct Effect on Hepatocytes

Gregory Guthrie, Bryan Tackett, Barbara Stoll, Camilia Martin, Oluyinka Olutoye, Douglas G. Burrin
Journal of Parenteral and Enteral Nutrition 2017 v.20 no.10 pp. 1-12
ABC transporters, Kupffer cells, agonists, bacteria, bile acids, bile salts, endotoxins, enteral feeding, hepatocytes, in vitro studies, in vivo studies, inflammation, interleukins, lipopolysaccharides, liver, liver diseases, neonates, parenteral feeding, phytosterols, piglets, soybean oil, synergism
Introduction: Phytosterols are implicated in the development of parenteral nutrition–associated liver disease. A newly proposed mechanism for phytosterol-mediated parenteral nutrition–associated liver disease is through phytosterol-facilitated hepatic proinflammatory cytokine release following exposure to intestinally derived bacteria. Whether the proinflammatory effects are liver cell specific is not known. Aim: To determine if phytosterols cause inflammation in hepatocytes or Kupffer cells independently or require costimulation by lipopolysaccharide (LPS). Methods: In an in vivo study, neonatal piglets on parenteral nutrition for 11 days received an 8-hour infusion of LPS. In the in vitro studies, neonatal piglet Kupffer cells and hepatocytes were treated with media, media + 1% soy oil, or media + 1% soy oil + 100µM phytosterols. After 24-hour incubation, cells were treated with farnesoid X receptor (FXR) agonist obeticholic acid or liver X receptor (LXR) agonist GW3965 and challenged with LPS or interleukin 1ß. Results: LPS administration in piglets led to transient increases in proinflammatory cytokines and suppression of the transporters bile salt export pump and ATP-binding cassette transporter G5. In hepatocytes, phytosterols did not activate inflammation. Phytosterol treatment alone did not activate inflammation in Kupffer cells but, combined with LPS, synergistically increased interleukin 1ß production. FXR and LXR agonists increased transporter expression in hepatocytes. GW3965 suppressed proinflammatory cytokine production in Kupffer cells, but obeticholic acid did not. Conclusions: LPS suppresses transporters that control bile acid and phytosterol clearance. Phytosterols alone do not cause inflammatory response. However, with costimulation by LPS, phytosterols synergistically maximize the inflammatory response in Kupffer cells.