Ischemic preconditioning enhances hepatocyte proliferation in the early phase after ischemia under hemi-hepatectomy in rats.
BACKGROUND
Ischemia/reperfusion (I/R) injury is an important barrier to liver surgery and transplantation because it impairs remnant liver/reduced-size-graft regeneration. Ischemic preconditioning (IPC), as an effective measure to overcome I/R injury, has been shown to enhance the regenerative capacity of hepatocytes. However, investigations have always focused on regeneration in the late phase after reperfusion. This study aimed to investigate whether IPC enhances hepatocyte proliferation in the early phase after reperfusion and possible underlying mechanisms.


METHODS
A total of 90 rats were divided into three groups: hemi-hepatectomy alone (PHx group), 60 minutes of ischemia plus hemi-hepatectomy (I/R group), and a cycle of 10 minutes of alternating I/R prior to 60 minutes of ischemia plus hemi-hepatectomy (IPC group). Each group was divided into five subgroups sacrificed after 0.5, 2, 6, 12 or 24 hours (n=6/subgroup). Subsequently, serum concentrations of alanine aminotransferase (ALT), aspartate aminotransferase (AST), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) were measured; caspase-3 and proliferating cell nuclear antigen (PCNA) proteins were also determined by Western blotting. Furthermore, PCNA was detected by immunohistochemistry to identify the expression site.


RESULTS
Serum ALT and AST levels after 2-24 hours of reperfusion in the PHx and IPC groups were remarkably decreased compared to the I/R group, and the serum TNF-alpha was relatively lower. A significant increase of serum IL-6 levels was found in the PHx and IPC groups compared with the I/R group at each time point. Furthermore, PCNA expression was remarkably increased in the IPC group after 6-12 hours of reperfusion, and in the earlier 0.5 and 6 hours time points after reperfusion have shown the massive PCNA-positive hepatocytes. At the same time, the expression of liver p-JNK was higher in the IPC group in the early phase after reperfusion than that of the I/R group and its expression was consistent with the PCNA.


CONCLUSIONS
IPC can initiate hepatocyte proliferation in the early phase after ischemia under hemi-hepatectomy, and may be associated with p-JNK expression and triggered by TNF-alpha/IL-6 signals.
Department of General Surgery, First Affiliated Hospital, Zhejiang Chinese Medical University, Hangzhou 310003, China.
Li-Ming
LM
Jin
Shui-Fang
SF
Jin
Yuan-Xing
YX
Liu
Lin
L
Zhou
Hai-Yang
HY
Xie
Sheng
S
Yan
Xiao
X
Xu
Shu-Sen
SS
Zheng
D000818:Animals; D053148:Caspase 3 / Q000032:analysis; D049109:Cell Proliferation; D006498:Hepatectomy; D022781:Hepatocytes / Q000502:physiology*; D015850:Interleukin-6 / Q000502:physiology; D007511:Ischemia / Q000473:pathology*; D019194:Ischemic Preconditioning; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008099:Liver / Q000098:blood supply*; D008297:Male; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology
D015850:Interleukin-6; D018809:Proliferating Cell Nuclear Antigen; D014409:Tumor Necrosis Factor-alpha; D048031:JNK Mitogen-Activated Protein Kinases; D053148:Caspase 3