title: Inhibition of TXA synthesis with OKY-046 improves liver preservation by prolonged hypothermic machine perfusion in rats.
abstract: OBJECTIVE
  We previously reported that hypothermic machine perfusion (HMP) for liver preservation is feasible, but hepatic microcirculatory dysfunction and significant liver damage remain major obstacles in its application when the preservation is extended to 24 h. The underlying injury mechanism is not well understood. The present study sought to investigate the role of thromboxane A(2) (TXA(2)) in the pathogenesis of liver injury after prolonged HMP.
  
  
  METHODS
  Livers isolated from Sprague-Dawley rats were subjected to continuous machine perfusion with University of Wisconsin (UW) solution at a flow rate of 0.4 mL/min/g liver at 4 degrees C for 24 h. A specific TXA(2) synthase inhibitor, OKY-046 (OKY), was added to UW solution during the preservation period and to the Krebs-Henseleit buffer during reperfusion. The performance of the livers after preservation was evaluated using an isolated liver perfusion system with Krebs-Henseleit buffer at a flow rate of 15 mL/min at 37 degrees C for 30 min.
  
  
  RESULTS
  Prolonged HMP induced a significant release of TXA(2) into the portal circulation as indicated by markedly increased levels of TXB(2) in the perfusate during reperfusion (at 30 min, 1447.4 +/- 163.6 pg/mL vs 50.91 +/- 6.7 pg/mL for control). Inhibition of TXA(2) synthesis with OKY significantly decreased releases of TXA(2) (69.8 +/- 13.4 pg/mL) concomitant with reduced lactate dehydrogenase (LDH) releases (at 30 min, HMP + OKY: 144.9 +/- 27.9 U/L; HMP: 369.3 +/- 68.5 U/L; simple cold storage or SCS: 884.4 +/- 80.3 U/L), decreased liver wet/dry weight ratio (HMP + OKY vs SCS and HMP: 3.6 +/- 0.3 vs 4.4 +/- 0.1 and 3.9 +/- 0.2, respectively) and increased hyaluronic acid uptake (at 30 min, HMP + OKY vs SCS, HMP: 33.1 +/- 2.9% vs 13.9 +/- 3.6%, 18.6 +/- 2.4%, respectively). Liver histology also showed significant improvement in tissue edema and hepatocellular necrosis with OKY compared with HMP without OKY.
  
  
  CONCLUSIONS
  The results demonstrate that TXA(2) is involved in the development of hepatocellular injury induced by HMP, and inhibition of TXA(2) synthesis during preservation and reperfusion protects liver hepatocytes and sinusoidal endothelial cells from injuries caused by prolonged HMP.
authors.affiliation: Department of Biology, University of North Carolia at Charlotte, Charlotte, North Carolina 28223, USA.
authors.forename: Hongzhi
authors.initials: H
authors.lastname: Xu
authors.forename: Charles Y
authors.initials: CY
authors.lastname: Lee
authors.forename: Mark G
authors.initials: MG
authors.lastname: Clemens
authors.forename: Jian X
authors.initials: JX
authors.lastname: Zhang
mesh_terms: D000818:Animals; D003080:Cold Temperature; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006820:Hyaluronic Acid / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008099:Liver / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology / Q000601:surgery; D008297:Male; D008689:Methacrylates / Q000494:pharmacology*; D009926:Organ Preservation / Q000379:methods; D019188:Organ Preservation Solutions / Q000494:pharmacology; D010477:Perfusion; D017082:Portal Pressure; D051381:Rats; D017207:Rats, Sprague-Dawley; D015424:Reperfusion; D013928:Thromboxane A2 / Q000378:metabolism*; D013930:Thromboxane-A Synthase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013997:Time Factors
chemical_list: D004791:Enzyme Inhibitors; D008689:Methacrylates; D019188:Organ Preservation Solutions; D013928:Thromboxane A2; D006820:Hyaluronic Acid; D007770:L-Lactate Dehydrogenase; D013930:Thromboxane-A Synthase; C034364:ozagrel