title: Effect of remifentanil on mitochondrial oxygen consumption of cultured human hepatocytes.
abstract: During sepsis, liver dysfunction is common, and failure of mitochondria to effectively couple oxygen consumption with energy production has been described. In addition to sepsis, pharmacological agents used to treat septic patients may contribute to mitochondrial dysfunction. This study addressed the hypothesis that remifentanil interacts with hepatic mitochondrial oxygen consumption. The human hepatoma cell line HepG2 and their isolated mitochondria were exposed to remifentanil, with or without further exposure to tumor necrosis factor-α (TNF-α). Mitochondrial oxygen consumption was measured by high-resolution respirometry, Caspase-3 protein levels by Western blotting, and cytokine levels by ELISA. Inhibitory κBα (IκBα) phosphorylation, measurement of the cellular ATP content and mitochondrial membrane potential in intact cells were analysed using commercial ELISA kits. Maximal cellular respiration increased after one hour of incubation with remifentanil, and phosphorylation of IκBα occurred, denoting stimulation of nuclear factor κB (NF-κB). The effect on cellular respiration was not present at 2, 4, 8 or 16 hours of incubation. Remifentanil increased the isolated mitochondrial respiratory control ratio of complex-I-dependent respiration without interfering with maximal respiration. Preincubation with the opioid receptor antagonist naloxone prevented a remifentanil-induced increase in cellular respiration. Remifentanil at 10× higher concentrations than therapeutic reduced mitochondrial membrane potential and ATP content without uncoupling oxygen consumption and basal respiration levels. TNF-α exposure reduced respiration of complex-I, -II and -IV, an effect which was prevented by prior remifentanil incubation. Furthermore, prior remifentanil incubation prevented TNF-α-induced IL-6 release of HepG2 cells, and attenuated fragmentation of pro-caspase-3 into cleaved active caspase 3 (an early marker of apoptosis). Our data suggest that remifentanil increases cellular respiration of human hepatocytes and prevents TNF-α-induced mitochondrial dysfunction. The results were not explained by uncoupling of mitochondrial respiration.
authors.affiliation: Department of Intensive Care Medicine, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland.
authors.forename: Siamak
authors.initials: S
authors.lastname: Djafarzadeh
authors.forename: Madhusudanarao
authors.initials: M
authors.lastname: Vuda
authors.forename: Jukka
authors.initials: J
authors.lastname: Takala
authors.forename: Stephan M
authors.initials: SM
authors.lastname: Jakob
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D019069:Cell Respiration / Q000187:drug effects / Q000502:physiology; D042967:Electron Transport Complex I / Q000037:antagonists & inhibitors / Q000378:metabolism; D042963:Electron Transport Complex II / Q000037:antagonists & inhibitors / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000037:antagonists & inhibitors / Q000378:metabolism; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D051550:I-kappa B Kinase / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D010766:Phosphorylation; D010880:Piperidines / Q000494:pharmacology*; D000077208:Remifentanil; D015398:Signal Transduction / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D006993:Hypnotics and Sedatives; D009292:Narcotic Antagonists; D010880:Piperidines; D014409:Tumor Necrosis Factor-alpha; D009270:Naloxone; D000255:Adenosine Triphosphate; D042963:Electron Transport Complex II; D003576:Electron Transport Complex IV; D051550:I-kappa B Kinase; D053148:Caspase 3; D042967:Electron Transport Complex I; D000077208:Remifentanil