Raphael A Seidel1, Thierry Claudel2, Franziska A Schleser3, Navin K Ojha4, Matthias Westerhausen5, Sandor Nietzsche6, Christoph Sponholz3, Frans Cuperus7, Sina M Coldewey3, Stefan H Heinemann4, Georg Pohnert8, Michael Trauner2, Michael Bauer9. 1. Department of Anesthesiology and Intensive Care Medicine/Center for Sepsis Control and Care, Jena University Hospital, Germany; Institute of Inorganic and Analytical Chemistry, Bioorganic Analytics, Friedrich Schiller University Jena, Germany. 2. HansPopper Laboratory of Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Austria. 3. Department of Anesthesiology and Intensive Care Medicine/Center for Sepsis Control and Care, Jena University Hospital, Germany. 4. Center for Molecular Biomedicine, Department of Biophysics, Friedrich Schiller University Jena & Jena University Hospital, Germany. 5. Institute of Inorganic and Analytical Chemistry, Inorganic Chemistry I, Friedrich Schiller University Jena, Germany. 6. Electron Microscopy Center, Jena University Hospital, Germany. 7. HansPopper Laboratory of Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Austria; Pediatric Gastroenterology and Hepatology, Center for Liver, Digestive, and Metabolic Diseases, University Medical Center Groningen, The Netherlands. 8. Institute of Inorganic and Analytical Chemistry, Bioorganic Analytics, Friedrich Schiller University Jena, Germany. 9. Department of Anesthesiology and Intensive Care Medicine/Center for Sepsis Control and Care, Jena University Hospital, Germany. Electronic address: michael.bauer@med.uni-jena.de.
Abstract
BACKGROUND & AIMS: Biliverdin and bilirubin were previously considered end products of heme catabolism; now, however, there is evidence for further degradation to diverse bioactive products. Z-BOX A and Z-BOX B arise upon oxidation with unknown implications for hepatocellular function and integrity. We studied the impact of Z-BOX A and B on hepatic functions and explored their alterations in health and cholestatic conditions. METHODS: Functional implications and mechanisms were investigated in rats, hepatocytic HepG2 and HepaRG cells, human immortalized hepatocytes, and isolated perfused livers. Z-BOX A and B were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in acute and acute-on-chronic liver failure and hereditary unconjugated hyperbilirubinemia. RESULTS: Z-BOX A and B are found in similar amounts in humans and rodents under physiological conditions. Serum concentrations increased ∼20-fold during cholestatic liver failure in humans (p<0.001) and in hereditary deficiency of bilirubin glucuronidation in rats (p<0.001). Pharmacokinetic studies revealed shorter serum half-life of Z-BOX A compared to its regio-isomer Z-BOX B (p=0.035). While both compounds were taken up by hepatocytes, Z-BOX A was enriched ∼100-fold and excreted in bile. Despite their reported vasoconstrictive properties in the brain vasculature, BOXes did not affect portal hemodynamics. Both Z-BOX A and B showed dose-dependent cytotoxicity, affected the glutathione redox state, and differentially modulated activity of Rev-erbα and Rev-erbβ. Moreover, BOXes-triggered remodeling of the hepatocellular cytoskeleton. CONCLUSIONS: Our data provide evidence that higher-order heme degradation products, namely Z-BOX A and B, impair hepatocellular integrity and might mediate intra- and extrahepatic cytotoxic effects previously attributed to hyperbilirubinemia. LAY SUMMARY: Degradation of the blood pigment heme yields the bile pigment bilirubin and the oxidation products Z-BOX A and Z-BOX B. Serum concentrations of these bioactive molecules increase in jaundice and can impair liver function and integrity. Amounts of Z-BOX A and Z-BOX B that are observed during liver failure in humans have profound effects on hepatic function when added to cultured liver cells or infused into healthy rats.
BACKGROUND & AIMS:Biliverdin and bilirubin were previously considered end products of heme catabolism; now, however, there is evidence for further degradation to diverse bioactive products. Z-BOX A and Z-BOX B arise upon oxidation with unknown implications for hepatocellular function and integrity. We studied the impact of Z-BOX A and B on hepatic functions and explored their alterations in health and cholestatic conditions. METHODS: Functional implications and mechanisms were investigated in rats, hepatocytic HepG2 and HepaRG cells, human immortalized hepatocytes, and isolated perfused livers. Z-BOX A and B were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in acute and acute-on-chronic liver failure and hereditary unconjugated hyperbilirubinemia. RESULTS: Z-BOX A and B are found in similar amounts in humans and rodents under physiological conditions. Serum concentrations increased ∼20-fold during cholestatic liver failure in humans (p<0.001) and in hereditary deficiency of bilirubin glucuronidation in rats (p<0.001). Pharmacokinetic studies revealed shorter serum half-life of Z-BOX A compared to its regio-isomer Z-BOX B (p=0.035). While both compounds were taken up by hepatocytes, Z-BOX A was enriched ∼100-fold and excreted in bile. Despite their reported vasoconstrictive properties in the brain vasculature, BOXes did not affect portal hemodynamics. Both Z-BOX A and B showed dose-dependent cytotoxicity, affected the glutathione redox state, and differentially modulated activity of Rev-erbα and Rev-erbβ. Moreover, BOXes-triggered remodeling of the hepatocellular cytoskeleton. CONCLUSIONS: Our data provide evidence that higher-order heme degradation products, namely Z-BOX A and B, impair hepatocellular integrity and might mediate intra- and extrahepatic cytotoxic effects previously attributed to hyperbilirubinemia. LAY SUMMARY: Degradation of the blood pigment heme yields the bile pigment bilirubin and the oxidation products Z-BOX A and Z-BOX B. Serum concentrations of these bioactive molecules increase in jaundice and can impair liver function and integrity. Amounts of Z-BOX A and Z-BOX B that are observed during liver failure in humans have profound effects on hepatic function when added to cultured liver cells or infused into healthy rats.
Authors: Kevin A Strauss; Charles E Ahlfors; Kyle Soltys; George V Mazareigos; Millie Young; Lauren E Bowser; Michael D Fox; James E Squires; Patrick McKiernan; Karlla W Brigatti; Erik G Puffenberger; Vincent J Carson; Hendrik J Vreman Journal: Hepatology Date: 2020-02-05 Impact factor: 17.425
Authors: Marcel Ritter; Vincensius S P Oetama; Daniel Schulze; Katrin Muetzlaff; Anja K Meents; Raphael A Seidel; Helmar Görls; Matthias Westerhausen; Wilhelm Boland; Georg Pohnert Journal: Chemistry Date: 2020-04-28 Impact factor: 5.236