Prolonged liver
ischemia followed by reperfusion (I/R) causes functional and structural damage to liver cells, resulting in
necrosis and apoptosis.
c-jun N-terminal kinase 1/
stress-activated protein kinase 1 (JNK(1)/SAPK(1)) is activated during I/R and participates in the onset of the apoptosis program. Excessive blood loss during surgery can hinder postoperative recovery. Intermittent portal triad clamping (PTC) is better tolerated than prolonged continuous
ischemia. This study was designed to demonstrate that intermittent
ischemia could improve postischemic survival rates by a decrease of JNK(1)/SAPK(1) and
caspase 3 activation, which were involved in the apoptosis process. Rats were subjected to intermittent 1-hour
ischemia (15-minute
ischemia/5-minute reperfusion, 4 times), followed by 220-minute reperfusion, or to continuous
ischemia (1 hour), followed by 240-minute reperfusion. Mortality rates were assessed on day 7. Serum
aspartate transaminase (AST),
alanine transaminase (ALT), and
lactate dehydrogenase levels (LDH) were measured 6 hours after
ischemia. This study was completed in primary cultured isolated rat hepatocytes, subjected to the same continuous or intermittent hypoxic conditions. The activation status of JNK(1)/SAPK(1) was evaluated by immunoprecipitation or Western blotting experiments. Apoptosis was assessed by measuring
caspase activation and by
terminal deoxynucleotidyl transferase-mediated dUTP
biotin nick end labeling (TUNEL) reaction. Eighty percent of the intermittent-
ischemia group was alive 7 days after surgery and serum
enzyme levels were significantly decreased. Intermittent
hypoxia or
ischemia did not lead to JNK(1)/SAPK(1) activation, but at least 3
hypoxia-reoxygenation (H/R) sets were necessary to inhibit
kinase activation. Consequently,
caspase 3 activation and apoptosis were dramatically reduced. Intermittent
ischemia is a powerful, protective way to reduce I/R damage of the liver, by reduction of JNK(1)/SAPK(1) activation associated with a down-regulation of
caspase 3 activity, which leads to inhibition of hepatocyte apoptosis.