RESUMO
Objective To identify the role of autopahgy in the protective mechanism of heme oxygenase 1(HO-1) against hepatic ischemia/reperfusion (I/R) injury.Methods Forty healthy male Sprague-Dawley (SD) rats were randomly (random number table) divided into five groups (n =8 in each group),namely sham group,model group,cobalt protoporphyrin (CoPP) group,zinc protoporphyrin (ZnPP) group and 6-amino-3-methylpurine (3-MA) group.Partial hepatic I/R model was established by clamping the pedicles of left and median lobes for 1 hour and reopening for 6 hours in rats,and the rats in sham group were only received celiotomp without hepatic I/R.In the CoPP group,CoPP (a HO-1 inducer,5 mg/kg) was administered i.p 24 hours before I/R.In the ZnPP or 3-MA group,besides pretreatment with CoPP,the rats were given ZnPP (a HO-1 inhibitor,25 mg/kg) or 3-MA (an autophagy inhibitor,30 mg/kg) i.p 1 hour before I/R.Serum alanine aminotransferase (ALT) was determined with automatic biochemistry analyzer.The hepatic pathological scores (PS) were determined under light microscope using hematoxylin-eosin (HE) staining.The hepatocyte apoptosis index (AI) was assessed with terminal dexynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining.Autophagosomes in liver tissue were counted under electron microscope.The mRNA expressions of HO-1,caspase-3,Beclin-1 and Atg-5 in the liver were determined by reverse transcription-polymerase chain reaction (RT-PCR).The HO-1 activity was also measured by the generation of bilirubin with the method of double-wave spectrophotometry.Results Compared with the sham group,the level of serum ALT significantly increased in the I/R group (U/L:560.3±73.6 vs.49.1 ± 13.8,P ＜ 0.01),HE staining showed a severe hepatic injury (PS:12.0±2.0 vs.1.3±0.9,P ＜ 0.01),TUNEL staining showed a higher hepatocytes apoptosis and the expression of caspase-3 significantly increased [AI:(19.38±3.07)％ vs.(3.25±1.28)％,caspase-3 mRNA (2-△△CT):4.62±0.40 vs.1.05±0.15,both P ＜ 0.01].However,there was no significant difference in the expression of HO-1 and the genes associated with autophagy between the two groups.In the CoPP group,the hepatic injury was blunted compared with that in the I/R group [ALT (U/L):223.3 ± 34.4 vs.560.3 ± 73.6,PS:5.6 ± 2.3 vs.12.0 ± 2.0,AI:(11.38± 2.39)％ vs.(19.38 ± 3.07)％,caspase-3mRNA (2-△△CT):2.42±0.33 vs.4.62±0.40,all P ＜ 0.01].HO-1 was induced in the CoPP group and autophagy was also increased significantly after I/R when compared with those in the I/R group [HO-1 mRNA (2-△△CT):3.01 ±0.71vs.1.14 ± 0.20,HO-1 activity (pmol ·mg-1 · h-1):259 ± 37 vs.113 ± 26,the number of autophagosomes:8.75 ± 0.87 vs.1.25±0.71,Beclin-1 mRNA (2-△△CT):2.85±0.28 vs.1.15±0.11,Atg-5 mRNA (2-△△CT):2.44±0.25 vs.1.14±0.12,all P ＜ 0.01].In the ZnPP group,the activity of HO-1 was much lower than that in the CoPP group,and as a result autophagy was decreased and liver injury was increased.In the 3-MA group,although there was no difference in the activity of HO-1 compared with that in the CoPP group,autophagy was inhibited,and the protective effect of CoPP was eliminated.Conclusion HO-1 could regulate the level of autophagy during liver I/R,and in turn autophagy might mediate the protective effects of HO-1 against liver I/R injury.