摘要
AIM: To investigate the effects of mammalian target of rapamycin(mT OR) inhibition on liver regeneration and autophagy in a surgical resection model.METHODS: C57BL/6 mice were subjected to a 70% partial hepatectomy(PH) and treated intraperitoneally every 24 h with a combination of the m TOR inhibitor rapamycin(2.5 mg/kg per day) and the steroid dexamethasone(2.0 mg/kg per day) in phosphate bufferedsaline(PBS) or with PBS alone as vehicle control. In the immunosuppressant group, part of the group was treated subcutaneously 4 h prior to and 24 h after PH with a combination of human recombinant interleukin 6(IL-6; 500 μg/kg per day) and hepatocyte growth factor(HGF; 100 μg/kg per day) in PBS. Animals were sacrificed 2, 3 or 5 d after PH and liver tissue and blood were collected for further analysis. Immunohistochemical staining for 5-Bromo-2'-deoxyuridine(Brd U) was used to quantify hepatocyte proliferation. Western blotting was used to detect hepatic microtubule-associated protein 1 light chain 3(LC3)-Ⅱ protein expression as a marker for autophagy. Hepatic gene expression levels of proliferation-, inflammation- and angiogenesisrelated genes were examined by real-time reverse transcription-polymerase chain reaction and serum bilirubin and transaminase levels were analyzed at the clinical chemical core facility of the Erasmus MC-University Medical Center.RESULTS: m TOR inhibition significantly suppressed regeneration, shown by decreased hepatocyte proliferation(2% vs 12% Brd U positive hepatocyte nuclei at day 2, P < 0.01; 0.8% vs 1.4% at day 5, P = 0.02) and liver weight reconstitution(63% vs 76% of initial total liver weight at day 3, P = 0.04), and furthermore increased serum transaminase levels(aspartate aminotransferase 641 U/L vs 185 U/L at day 2, P = 0.02). Expression of the autophagy marker LC3-Ⅱ, which was reduced during normal liver regeneration, increased after mT OR inhibition(46% increase at day 2, P = 0.04). Hepatic gene expression showed an increased inflammation-related response [tumor necrosis factor(TNF)-α 3.2-fold upregulation at day 2, P = 0.03; IL-1Ra 6.0-fold upregulation at day 2 and 42.3-fold upregulation at day 5, P < 0.01] and a reduced expression of cell cycle progression and angiogenesis-related factors(HGF 40% reduction at day 2; vascular endothelial growth factor receptor 2 50% reduction at days 2 and 5; angiopoietin 1 60% reduction at day 2, all P ≤ 0.01). Treatmentwith the regeneration stimulating cytokine IL-6 and growth factor HGF could overcome the inhibitory effect on liver weight(75% of initial total liver weight at day 3, P = 0.02 vs immunosuppression alone and P = 0.90 vs controls) and partially reversed gene expression changes caused by rapamycin(TNF-α and IL-1Ra levels at day 2 were restored to control levels). However, no significant changes in hepatocyte proliferation, serum injury markers or autophagy were found.CONCLUSION: mT OR inhibition severely impairs liver regeneration and increases autophagy after PH. These effects are partly reversed by stimulation of the IL-6 and HGF pathways.
AIM: To investigate the effects of mammalian target of rapamycin(mT OR) inhibition on liver regeneration and autophagy in a surgical resection model.METHODS: C57BL/6 mice were subjected to a 70% partial hepatectomy(PH) and treated intraperitoneally every 24 h with a combination of the m TOR inhibitor rapamycin(2.5 mg/kg per day) and the steroid dexamethasone(2.0 mg/kg per day) in phosphate bufferedsaline(PBS) or with PBS alone as vehicle control. In the immunosuppressant group, part of the group was treated subcutaneously 4 h prior to and 24 h after PH with a combination of human recombinant interleukin 6(IL-6; 500 μg/kg per day) and hepatocyte growth factor(HGF; 100 μg/kg per day) in PBS. Animals were sacrificed 2, 3 or 5 d after PH and liver tissue and blood were collected for further analysis. Immunohistochemical staining for 5-Bromo-2'-deoxyuridine(Brd U) was used to quantify hepatocyte proliferation. Western blotting was used to detect hepatic microtubule-associated protein 1 light chain 3(LC3)-Ⅱ protein expression as a marker for autophagy. Hepatic gene expression levels of proliferation-, inflammation- and angiogenesisrelated genes were examined by real-time reverse transcription-polymerase chain reaction and serum bilirubin and transaminase levels were analyzed at the clinical chemical core facility of the Erasmus MC-University Medical Center.RESULTS: m TOR inhibition significantly suppressed regeneration, shown by decreased hepatocyte proliferation(2% vs 12% Brd U positive hepatocyte nuclei at day 2, P < 0.01; 0.8% vs 1.4% at day 5, P = 0.02) and liver weight reconstitution(63% vs 76% of initial total liver weight at day 3, P = 0.04), and furthermore increased serum transaminase levels(aspartate aminotransferase 641 U/L vs 185 U/L at day 2, P = 0.02). Expression of the autophagy marker LC3-Ⅱ, which was reduced during normal liver regeneration, increased after mT OR inhibition(46% increase at day 2, P = 0.04). Hepatic gene expression showed an increased inflammation-related response [tumor necrosis factor(TNF)-α 3.2-fold upregulation at day 2, P = 0.03; IL-1Ra 6.0-fold upregulation at day 2 and 42.3-fold upregulation at day 5, P < 0.01] and a reduced expression of cell cycle progression and angiogenesis-related factors(HGF 40% reduction at day 2; vascular endothelial growth factor receptor 2 50% reduction at days 2 and 5; angiopoietin 1 60% reduction at day 2, all P ≤ 0.01). Treatmentwith the regeneration stimulating cytokine IL-6 and growth factor HGF could overcome the inhibitory effect on liver weight(75% of initial total liver weight at day 3, P = 0.02 vs immunosuppression alone and P = 0.90 vs controls) and partially reversed gene expression changes caused by rapamycin(TNF-α and IL-1Ra levels at day 2 were restored to control levels). However, no significant changes in hepatocyte proliferation, serum injury markers or autophagy were found.CONCLUSION: mT OR inhibition severely impairs liver regeneration and increases autophagy after PH. These effects are partly reversed by stimulation of the IL-6 and HGF pathways.
基金
Supported by Erasmus MC Grant and the Liver Research Foundation(SLO) Rotterdam
