Effect of ischemia-reperfusion on Na+, K+-ATPase expression in human liver tissue allograft: image analysis by confocal laser scanning microscopy.
We have analyzed the effect of ischemia-reperfusion on expression of hepatic Na+,K+-ATPase on bile canalicular (BCM) and basolateral membranes (BLM) in human liver allografts using confocal laser scanning microscopy imaging. Na+, K+-ATPase, an integral membrane enzyme, plays a key role in the physiology and structure of hepatocytes, where it maintains the electrochemical gradients for Na+ and K+ across the cell membrane. The concentrations of these ions as well as their gradients regulate the active transport across the plasma membrane for bile acid and water from sinusoidal to canalicular membranes. In addition, Na+,K+-ATPase is also involved in cellular structure because of its close relationship with submembrane microfilaments and its implication in tight junction assembly. Therefore, Na+,K+-ATPase appears as an indicator of tissue viability and hepatic functionality during liver transplantation. Its localization and its function in BCM are still controversial. As in previous studies, we found an enzyme expression in both BLM and BCM. We show that ischemia induced a decrease in Na+,K+-ATPase expression only in BCM. This result could be explained by the differences in biochemical membrane environment between basolateral and bile canalicular Na+,K+-ATPase. Membrane lipid fluidity, which is more elevated in BLM than in BCM, could protect the enzyme during ischemia. After reperfusion, Na+,K+-ATPase expression was strongly decreased in both BCM and BLM. This alteration following reperfusion is probably due to multiple factors: direct alteration of the enzyme catalytic subunit and modification of its environment and membrane lipid fluidity by free radicals and changes in ATP levels and ionic distribution. This important decrease in Na+,K+-ATPase expression of both BLM and BCM could disturb not only hepatic secretory function but also cellular volume and structure during the postoperative period.
Benkoel
Liliane
L
INSERM U 559, Faculté de Médecine, 27 boulevard Jean Moulin, 13385 Marseille Cedex 05, France.
Dodero
Frank
F
Hardwigsen
Jean
J
Mas
Eric
E
Benoliel
Anne-Marie
AM
Botta-Fridlund
Danielle
D
Le Treut
Yves Patrice
YP
Chamlian
Albert
A
Lombardo
Dominique
D
D000328:Adult; D000704:Analysis of Variance; D015415:Biomarkers / Q000032:analysis; D001707:Biopsy, Needle; D002102:Cadaver; D015331:Cohort Studies; D005260:Female; D022781:Hepatocytes / Q000648:ultrastructure*; D006801:Humans; D007150:Immunohistochemistry; D007511:Ischemia / Q000378:metabolism / Q000473:pathology*; D008099:Liver / Q000098:blood supply*; D016031:Liver Transplantation / Q000473:pathology*; D008297:Male; D018613:Microscopy, Confocal; D008875:Middle Aged; D011336:Probability; D012016:Reference Values; D015427:Reperfusion Injury / Q000378:metabolism / Q000473:pathology*; D012680:Sensitivity and Specificity; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis / Q000378:metabolism*; D046509:Tissue Culture Techniques; D014019:Tissue Donors; D014184:Transplantation, Homologous / Q000473:pathology
D015415:Biomarkers; D000254:Sodium-Potassium-Exchanging ATPase