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标题：Lack of mitochondrial topoisomerase I (TOP1mt) impairs liver regeneration
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作者：Salim Khiati ; Simone A. Baechler ; Valentina M. Factor 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：36
页码：11282-11287
DOI：10.1073/pnas.1511016112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceThe liver is rich in mitochondria and has an exceptional regenerative capacity after partial hepatectomy or transplantation, viral infections, or chemical injuries; however, relatively little is known about the genetic factors for mitochondrial DNA (mtDNA) replication during liver regeneration. Here, we show that liver regeneration is markedly reduced in mice lacking mitochondrial topoisomerase I (TOP1mt). This defect is linked with reduced production of mtDNA and defective mitochondrial functions during acute energy demand for liver regeneration. Additionally, TOP1mt KO primary hepatocytes from CCl4-treated mice showed reduced and damaged mitochondria, decreased O2 consumption, and ATP production. Together with mtDNA depletion and regeneration experiments with ethidium bromide, these results demonstrate that Top1mt is required for mtDNA synthesis and appropriate liver regeneration. The liver has an exceptional replicative capacity following partial hepatectomy or chemical injuries. Cellular proliferation requires increased production of energy and essential metabolites, which critically depend on the mitochondria. To determine whether Top1mt, the vertebrate mitochondrial topoisomerase, is involved in this process, we studied liver regeneration after carbon tetrachloride (CCl4) administration. TOP1mt knockout (KO) mice showed a marked reduction in regeneration and hepatocyte proliferation. The hepatic mitochondrial DNA (mtDNA) failed to increase during recovery from CCl4 exposure. Reduced glutathione was also depleted, indicating increased reactive oxygen species (ROS). Steady-state levels of ATP, O2 consumption, mtDNA, and mitochondrial mass were also reduced in primary hepatocytes from CCl4-treated KO mice. To further test whether Top1mt acted by enabling mtDNA regeneration, we tested TOP1mt KO fibroblasts and human colon carcinoma HCT116 cells and measured mtDNA after 3-d treatment with ethidium bromide. Both types of TOP1mt knockout cells showed defective mtDNA regeneration following mtDNA depletion. Our study demonstrates that Top1mt is required for normal mtDNA homeostasis and for linking mtDNA expansion with hepatocyte proliferation.
关键词：liver regeneration ; mitochondrial topoisomerase I ; cell proliferation ; mitochondrial DNA replication ; mitochondrial homeostasis